U.S. patent application number 12/904795 was filed with the patent office on 2011-02-10 for integrated or autonomous system and method of satellite-terrestrial frequency reuse using signal attenuation and/or blockage, dynamic assignment of frequencies and/or hysteresis.
This patent application is currently assigned to ATC Technologies, LLC. Invention is credited to Peter D. Karabinis, Rajendra Singh.
Application Number | 20110034166 12/904795 |
Document ID | / |
Family ID | 46278546 |
Filed Date | 2011-02-10 |
United States Patent
Application |
20110034166 |
Kind Code |
A1 |
Karabinis; Peter D. ; et
al. |
February 10, 2011 |
INTEGRATED OR AUTONOMOUS SYSTEM AND METHOD OF SATELLITE-TERRESTRIAL
FREQUENCY REUSE USING SIGNAL ATTENUATION AND/OR BLOCKAGE, DYNAMIC
ASSIGNMENT OF FREQUENCIES AND/OR HYSTERESIS
Abstract
A signal strength that is associated with a first wireless
communications channel is detected. Electromagnetic energy is
transmitted over the first wireless communications channel in
response to the signal strength being sufficiently weak. A
determination is made whether a handoff should be made to a second
wireless communications channel having a signal that is weaker than
a signal of the first wireless communications channel. Related
systems and methods are described.
Inventors: |
Karabinis; Peter D.; (Cary,
NC) ; Singh; Rajendra; (Alexandria, VA) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC
PO BOX 37428
RALEIGH
NC
27627
US
|
Assignee: |
ATC Technologies, LLC
|
Family ID: |
46278546 |
Appl. No.: |
12/904795 |
Filed: |
October 14, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11536481 |
Sep 28, 2006 |
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12904795 |
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10965303 |
Oct 14, 2004 |
7577400 |
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11536481 |
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10000799 |
Dec 4, 2001 |
6859652 |
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10965303 |
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09918709 |
Aug 1, 2001 |
6892068 |
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10000799 |
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60250461 |
Dec 4, 2000 |
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60222605 |
Aug 2, 2000 |
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60245194 |
Nov 3, 2000 |
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60250461 |
Dec 4, 2000 |
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Current U.S.
Class: |
455/427 |
Current CPC
Class: |
H04B 7/18563 20130101;
H04B 7/2041 20130101; H04W 16/14 20130101 |
Class at
Publication: |
455/427 |
International
Class: |
H04W 28/00 20090101
H04W028/00 |
Claims
1. A communications system comprising: at least one satellite that
is configured to provide wireless communications to subscriber
terminals in a service region using a set of frequencies; and at
least one base station that is configured to provide wireless
communications to subscriber terminals in the service region using
at least one frequency of the set of frequencies; wherein the at
least one satellite is configured to provide wireless
communications to subscriber terminals in the service region using
a first channel width and the at least one base station is
configured to provide wireless communications to subscriber
terminals in the service region using a second channel width that
is greater than the first channel width.
2. The communications system according to claim 1, wherein the
wireless communications that are provided by the at least one
satellite are devoid of spectrum spreading and wherein the wireless
communications that are provided by the at least one base station
comprise spectrum spreading.
3. The communications system according to claim 1, wherein the
wireless communications that are provided by the at least one
satellite comprise a power control that is responsive to the
wireless communications that are provided by the at least one base
station.
4. The communications system according to claim 1, wherein a
capacity that is associated with the wireless communications that
are provided by the at least one base station is responsive to the
wireless communications that are provided by the at least one
satellite.
5. A communications method comprising: configuring at least one
satellite to provide wireless communications to subscriber
terminals in a service region using a set of frequencies; and
configuring at least one base station to provide wireless
communications to subscriber terminals in the service region using
at least one frequency of the set of frequencies; wherein the at
least one satellite is configured to provide wireless
communications to subscriber terminals in the service region using
a first channel width and the at least one base station is
configured to provide wireless communications to subscriber
terminals in the service region using a second channel width that
is greater than the first channel width.
6. The communications method according to claim 5, wherein the
wireless communications that are provided by the at least one
satellite are devoid of spectrum spreading and wherein the wireless
communications that are provided by the at least one base station
comprise spectrum spreading.
7. The communications method according to claim 5, wherein the
wireless communications that are provided by the at least one
satellite comprise a power control that is responsive to the
wireless communications that are provided by the at least one base
station.
8. The communications method according to claim 5, wherein a
capacity that is associated with the wireless communications that
are provided by the at least one base station is responsive to the
wireless communications that are provided by the at least one
satellite.
9. A communications system comprising: at least one satellite that
is configured to provide wireless communications to subscriber
terminals in a service region using a set of frequencies; wherein
the set of frequencies comprises at least one frequency that is
also used by at least one base station to provide wireless
communications to subscriber terminals in the service region; and
wherein the at least one satellite is configured to provide
wireless communications to subscriber terminals in the service
region using a first channel width that is less than a channel
width that is used by the at least one base station to provide
wireless communications to subscriber terminals in the service
region.
10. The communications system according to claim 9, wherein the
wireless communications that are provided by the at least one
satellite are devoid of spectrum spreading and wherein the wireless
communications that are provided by the at least one base station
comprise spectrum spreading.
11. The communications system according to claim 9, wherein the
wireless communications that are provided by the at least one
satellite comprise a power control that is responsive to the
wireless communications that are provided by the at least one base
station.
12. The communications system according to claim 9, wherein a
capacity that is associated with the wireless communications that
are provided by the at least one base station is responsive to the
wireless communications that are provided by the at least one
satellite.
13. A communications method comprising: configuring at least one
satellite to provide wireless communications to subscriber
terminals in a service region using a set of frequencies; wherein
the set of frequencies comprises at least one frequency that is
also used by at least one base station to provide wireless
communications to subscriber terminals in the service region; and
wherein the at least one satellite is configured to provide
wireless communications to subscriber terminals in the service
region using a first channel width that is less than a channel
width that is used by the at least one base station to provide
wireless communications to subscriber terminals in the service
region.
14. The communications method according to claim 13, wherein the
wireless communications that are provided by the at least one
satellite are devoid of spectrum spreading and wherein the wireless
communications that are provided by the at least one base station
comprise spectrum spreading.
15. The communications method according to claim 13, wherein the
wireless communications that are provided by the at least one
satellite comprise a power control that is responsive to the
wireless communications that are provided by the at least one base
station.
16. The communications method according to claim 13, wherein a
capacity that is associated with the wireless communications that
are provided by the at least one base station is responsive to the
wireless communications that are provided by the at least one
satellite.
17. A communications system comprising: at least one base station
that is configured to provide wireless communications to subscriber
terminals in a service region using at least one frequency of a set
of frequencies that are used by at least one satellite to provide
wireless communications to subscriber terminals in the service
region; wherein the at least one base station is configured to
provide wireless communications to subscriber terminals in the
service region using a first channel width that is greater than a
channel width that is used by the at least one satellite to provide
wireless communications to subscriber terminals in the service
region.
18. The communications system according to claim 17, wherein the
wireless communications that are provided by the at least one
satellite are devoid of spectrum spreading and wherein the wireless
communications that are provided by the at least one base station
comprise spectrum spreading.
19. The communications system according to claim 17, wherein the
wireless communications that are provided by the at least one
satellite comprise a power control that is responsive to the
wireless communications that are provided by the at least one base
station.
20. The communications system according to claim 17, wherein a
capacity that is associated with the wireless communications that
are provided by the at least one base station is responsive to the
wireless communications that are provided by the at least one
satellite.
21. A communications method comprising: configuring at least one
base station to provide wireless communications to subscriber
terminals in a service region using at least one frequency of a set
of frequencies that are used by at least one satellite to provide
wireless communications to subscriber terminals in the service
region; wherein the at least one base station is configured to
provide wireless communications to subscriber terminals in the
service region using a first channel width that is greater than a
channel width that is used by the at least one satellite to provide
wireless communications to subscriber terminals in the service
region.
22. The communications method according to claim 21, wherein the
wireless communications that are provided by the at least one
satellite are devoid of spectrum spreading and wherein the wireless
communications that are provided by the at least one base station
comprise spectrum spreading.
23. The communications method according to claim 21, wherein the
wireless communications that are provided by the at least one
satellite comprise a power control that is responsive to the
wireless communications that are provided by the at least one base
station.
24. The communications method according to claim 21, wherein a
capacity that is associated with the wireless communications that
are provided by the at least one base station is responsive to the
wireless communications that are provided by the at least one
satellite.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 11/536,481, filed Sep. 28, 2006, entitled Integrated Autonomous
System and Method of Satellite-Terrestrial Frequency Reuse Using
Signal Attenuation and/or Blockage, Dynamic Assignment of
Frequencies and/or Hysteresis, which itself is a continuation of
U.S. App No. 10/965,303, filed Oct. 14, 2004, now U.S. Pat. No.
7,577,400, entitled Integrated or Autonomous System and Method of
Satellite-Terrestrial Frequency Reuse Using Signal Attenuation
and/or Blockage, Dynamic Assignment of Frequencies and/or
Hysteresis, which itself is a continuation of U.S. application Ser.
No. 10/000,799, filed Dec. 4, 2001, now U.S. Pat. No. 6,859,652,
entitled Integrated or Autonomous System and Method of
Satellite-Terrestrial Frequency Reuse Using Signal Attenuation
and/or Blockage, Dynamic Assignment of Frequencies and/or
Hysteresis, which itself claims priority from U.S. provisional App.
No. 60/250,461, filed Dec. 4, 2000, entitled System and Method of
Satellite-Terrestrial Frequency Reuse. U.S. application Ser. No.
10/000,799 is a Continuation-in-Part of U.S. application Ser. No.
09/918,709 filed on Aug. 1, 2001, entitled Coordinated
Satellite-Terrestrial Frequency Reuse, which itself claims priority
from U.S. provisional App. No. 60/222,605 filed on Aug. 2, 2000,
entitled System and Method of Satellite-Terrestrial Frequency
Reuse, U.S. provisional App. No. 60/245,194 filed Nov. 3, 2000,
entitled Coordinated Satellite-Terrestrial Frequency Reuse, and
U.S. provisional App. No. 60/250,461 filed Dec. 4, 2000, entitled
System and Method of Satellite-Terrestrial Frequency Reuse. All of
these applications are assigned to the assignee of the present
application, the disclosures of which are hereby incorporated
herein by reference in their entirety as if set forth fully
herein.
FIELD OF THE INVENTION
[0002] The present invention generally relates to frequency
assignment, reuse and/or sharing among communications systems
having both a terrestrial component and a satellite component and,
more particularly, to a satellite-terrestrial communication system
and method of operation thereof that provides frequency assignment,
reuse and/or sharing between autonomously operating or integrated
satellite and terrestrial components, that can optionally utilize
different communication protocols and/or air interfaces.
DESCRIPTION OF THE RELATED ART
[0003] FIG. 1 shows a prior art satellite radiotelephone system, as
shown in U.S. Pat. No. 6,052,586, incorporated herein by reference.
As shown in FIG. 1, a satellite radiotelephone system includes a
fixed satellite radiotelephone system 110 and a mobile satellite
radiotelephone system 130. The fixed satellite radiotelephone
system 110 uses a first satellite 112 to communicate with a
plurality of fixed radiotelephones 114a, 114b and 114c in a first
communication area 116.
[0004] Fixed satellite radiotelephone communication system 110
communicates with the plurality of fixed radiotelephones 114a-114c
using a first air interface 118 (e.g., at C-band). Control of the
fixed satellite system 110 is implemented by a feeder link 122
which communicates with a gateway 124 and the public switched
(wire) telephone network (PSTN) 126.
[0005] The feeder link 122 includes communication channels for
voice and data communications, and control channels. The control
channels are indicated by dashed lines in FIG. 1. The control
channels are used to implement direct communications between fixed
radiotelephones, as shown for example between radiotelephones 114a
and 114b. The control channels are also used to effect
communications between a fixed satellite radiotelephone 114c and a
mobile radiotelephone or a wire telephone via gateway 124 and PSTN
126. The feeder link 122 uses the same air interface or a different
air interface from the first air interface 118.
[0006] Still referring to FIG. 1, mobile satellite radiotelephone
system 130 includes a second satellite 132 that communicates with a
plurality of mobile radiotelephones 134a-134d which are located in
a second communication area 136. Mobile satellite radiotelephone
system 130 communicates with mobile radiotelephones 134 using a
second air interface 138 (e.g., at L-band or S-band).
Alternatively, the second air interface 138 may be the same as the
first air interface 118. However, the frequency bands associated
with the two air interfaces are different.
[0007] A feeder link 142 is used to communicate with other
satellite, cellular or wire telephone systems via gateway 144 and
PSTN 126. As with fixed satellite system 110, the feeder link 142
includes communication channels shown in solid lines and control
channels shown in dashed lines. The control channels are used to
establish direct mobile-to-mobile communications, for example,
between mobile radiotelephones 134b and 134c. The control channels
are also used to establish communications between mobile phones
134a and 134d and other satellite, mobile or wire telephone
systems.
[0008] As with the fixed satellite radiotelephone system 110, the
mobile satellite radiotelephone system 130 will generally
communicate with large numbers of mobile radiotelephones 134. The
fixed and mobile satellite radiotelephone system use a common
satellite.
[0009] Still referring to FIG. 1, a congested area may be present
in the mobile satellite radiotelephone system 130 where a large
number of mobile radiotelephones 134e-134i are present. As is also
shown in FIG. 1, this congested area may be in an overlapping area
128 between first communication area 116 and second communication
area 136. If this is the case, excess capacity from fixed satellite
radiotelephone system 110 is offloaded to mobile satellite
radiotelephone system 130.
[0010] Capacity offload is provided by at least one fixed
retransmitting station 150a, 150b, that retransmits communications
between the fixed satellite radiotelephone system 110 and at least
one of the mobile radiotelephones. For example, as shown in FIG. 1,
first fixed retransmitting station 150a retransmits communications
between satellite 112 and mobile radiotelephones 134e and 134f.
Second fixed transmitting station 150b retransmits communications
between the satellite 112 and mobile radiotelephones 134g, 134h and
134i.
[0011] The fixed retransmitting stations communicate with the
satellite 112 using first air interface 118. However they
communicate with the mobile radiotelephones using the second air
interface 138. Accordingly, from the standpoint of the mobile
radiotelephones 134e-134i, communication is transparent. In other
words, it is not apparent to the mobile radiotelephones 134e-134i,
or the users thereof, that communications are occurring with the
fixed satellite radiotelephone system 110 rather than with the
mobile satellite radiotelephone system 130. However, additional
capacity for the mobile satellite radiotelephone system 130 in the
congested areas adjacent the fixed retransmitting stations 150 is
provided.
[0012] As shown in FIG. 1, a mobile radiotelephone can establish a
communications link via the facilities of the fixed satellite
radiotelephone system, even though the mobile radiotelephone is
designed, manufactured and sold as a terminal intended for use with
the mobile satellite radiotelephone system. One or more operators
may offer both mobile and fixed telecommunications services over an
overlapping geographic area using two separate transponders in
separate satellites or within the same "hybrid" satellite, with one
transponder supporting mobile satellite radiotelephones and the
other supporting fixed satellite radiotelephones. As capacity "hot
spots" or congestion develops within certain spot beams of the
mobile radiotelephone system, the fixed system, with its much
higher capacity, can deploy fixed retransmitting stations to
relieve the capacity load of the mobile system.
[0013] FIG. 2A shows a seven-cell frequency reuse pattern used by
the mobile satellite radiotelephone system 130. Within each of the
relatively large mobile system cells, each typically being on the
order of 400-600 kilometers in diameter, frequencies used by
adjacent cells are locally retransmitted by the retransmitting
station at reduced, non-interfering power levels, and reused as
shown in FIGS. 2B and 2C, thus substantially increasing the
effective local capacity.
[0014] Accordingly, fixed retransmitting stations 150a, 150b,
located within the fixed system's footprint or coverage area,
receive signals from the fixed satellite and retransmit these
signals locally. In the reverse direction, the fixed retransmitting
stations receive signals from mobile radiotelephones 134e-i and
retransmit signals from the mobile radiotelephones to the fixed
satellite system 110. Frequency translation to bring the signals
within the fixed system's frequency band is provided.
[0015] The mobile radiotelephones 134e-i are ordinarily used with
the mobile satellite system 130. Accordingly, the fixed satellite
system 110 may need to be configured to support the air interface
used by the mobile satellite radiotelephone system. If different
air interfaces are used by the fixed and mobile satellite
radiotelephone systems, the fixed retransmitting stations 150a,
150b, can perform a translation from one air interface to the
other, for example, by demodulation and remodulation. The fixed
retransmitting station then becomes a regenerative repeater which
reformats communications channels as well as control channels.
However, if the mobile and fixed systems both use substantially the
same air interface, then the fixed retransmitting station can
function as a non-regenerative repeater.
[0016] However, in contrast to U.S. Pat. No. 6,052,586, the present
invention does not utilize in at least one embodiment frequency
translation between fixed and mobile systems. Also in contrast to
U.S. Pat. No. 6,052,586, the present invention optionally provides
autonomous or substantially autonomous operation between the
satellite and terrestrial components.
[0017] FIG. 3 is another prior art system as shown in U.S. Pat. No.
5,995,832, incorporated herein by reference. FIG. 3 provides an
overview of a communications system 310 showing the functional
inter-relationships of the major elements. The system network
control center 312 directs the top level allocation of calls to
satellite and ground regional resources throughout the system. It
also is used to coordinate system-wide operations, to keep track of
user locations, to perform optimum allocation of system resources
to each call, dispatch facility command codes, and monitor and
supervise overall system health. The regional node control centers
314, one of which is shown, are connected to the system network
control center 312 and direct the allocation of calls to ground
nodes within a major metropolitan region. The regional node control
center 314 provides access to and from fixed land communication
lines, such as commercial telephone systems known as the public
switched telephone network (PSTN). The ground nodes 316, under
direction of the respective regional node control center 314,
receive calls over the fixed land line network, encode them, spread
them according to the unique spreading code assigned to each
designated user, combine them into a composite signal, modulate
that composite signal onto the transmission carrier, and broadcast
them over the cellular region covered.
[0018] Satellite node control centers 318 are also connected to the
system network control center 312 via status and control land lines
and similarly handle calls designated for satellite links such as
from PSTN, encode them, spread them according to the unique
spreading codes assigned to the designated users, and multiplex
them with other similarly directed calls into an uplink trunk,
which is beamed up to the designated satellite 320. Satellite nodes
320 receive the uplink trunks, frequency demultiplex the calls
intended for different satellite cells, frequency translate and
direct each to its appropriate cell transmitter and cell beam, and
broadcast the composite of all such similarly directed calls down
to the intended satellite cellular area. As used herein, "backhaul"
means the link between a satellite 320 and a satellite node control
center 318.
[0019] User units 322 respond to signals of either satellite or
ground node origin, receive the outbound composite signal, separate
out the signal intended for that user by despreading using the
user's assigned unique spreading code, de-modulate, and decode the
information and deliver the call to the user. Such user units 322
may be mobile or may be fixed in position. Gateways 324 provide
direct trunks (i.e., groups of channels) between satellite and the
ground public switched telephone system or private trunk users. For
example, a gateway may comprise a dedicated satellite terminal for
use by a large company or other entity. In the embodiment of FIG.
3, the gateway 324 is also connected to that system network
controller 312.
[0020] All of the above-discussed centers, nodes, units and
gateways are full duplex transmit/receive performing the
corresponding inbound (user to system) link functions as well in
the inverse manner to the outbound (system to user) link functions
just described.
[0021] FIG. 4 is a block diagram of U.S. Pat. No. 5,995,832 which
does not include a system network control center 312. In this
system, the satellite node control centers 442 are connected
directly into the land line network as are also the regional node
control centers 444. Gateway systems 446 are also available as in
the system of FIG. 3, and connect the satellite communications to
the appropriate land line or other communications systems. The user
unit 322 designates satellite node 442 communication or ground node
450 communication by sending a predetermined code. Alternatively,
the user unit could first search for one type of link (either
ground or satellite) and, if that link is present, use it. If that
link is not present, use the alternate type of link.
[0022] U.S. Pat. No. 5,995,832 uses code division multiple access
(CDMA) technology to provide spectral utilization and spatial
frequency reuse. The system of U.S. Pat. No. 5,995,832 has a
cluster size of one. That is, each cell uses the same, full
allocated frequency band. This is possible because of the strong
interference rejection properties of spread spectrum code division
multiple access technology (SS/CDMA).
[0023] The specification of U.S. Pat. No. 5,995,832 also states
that in a spread spectrum system, the data modulated carrier signal
is modulated by a relatively wide-band, pseudo-random "spreading"
signal so that the transmitted bandwidth is much greater than the
bandwidth or rate of the information to be transmitted, and that
the "spreading" signal is generated by a pseudo-random
deterministic digital logic algorithm which is duplicated at the
receiver. In this regard, FIG. 7 of U.S. Pat. No. 5,995,832
discloses PRN generators 136, 166 in conjunction with wide band
multipliers 122, 148 that are associated with CDMA technology.
[0024] The system also determines the position of user units 322
through two-dimensional multi-lateration. Each CDMA mobile user
unit's transmitted spreading code is synchronized to the epoch of
reception of the pilot signal from its current control site,
whether ground or satellite node.
[0025] However, it has been determined that it is desirable to have
communication protocols other than CDMA be used in a
satellite-terrestrial system. It is also desirable to have a
satellite-terrestrial system that does not require frequency
translation between fixed and mobile systems. In addition, it is
also desirable to provide a satellite-terrestrial system that does
not require CDMA technology, and which utilizes a robust
satellite-terrestrial frequency assignment and/or reuse scheme in
which the satellite and terrestrial components can optionally
utilize different air interfaces, and optionally operate
independently of each other while either sharing a common or
different frequency band.
[0026] Further, it is also desirable to provide a
satellite-terrestrial system that utilizes a first frequency as a
downlink frequency between a satellite and a first fixed and/or
mobile user terminal and as an uplink frequency between a second
fixed and/or mobile user terminal and a terrestrial base
transceiver station (BTS), and a second frequency as an uplink
between the first fixed and/or mobile user terminal and the
satellite and as a downlink between the BTS and the second fixed
and/or mobile user terminal. Other advantages and features of the
invention are described below, that may be provided independently
and/or in one or more combinations.
[0027] It is also desirable to provide a satellite-terrestrial
system in which the space based and ground based components
function autonomously or substantially autonomously in which the
space based component can use a time division multiple access
(TDMA) air interface, and the ground based system can use either a
TDMA air interface or a CDMA air interface. In such a system, it is
further desirable to provide user units having a first plurality of
vocoders, each having a different data rate, and a second plurality
of vocoders, each having a different data rate, wherein a vocoder
in the first plurality is used when the subscriber terminal is
communicating with the space based system, and wherein a vocoder in
the second plurality is used when the subscriber terminal is
communicating with the ground based system.
SUMMARY OF THE INVENTION
[0028] It is one feature and advantage of the present invention to
provide a satellite-terrestrial communication system in which the
satellite and terrestrial components utilize different air
interfaces while facilitating efficient spectrum assignment, usage,
sharing, and/or reuse.
[0029] It is another optional feature and advantage of at least
some embodiments of the present invention to provide a
satellite-terrestrial communication system in which the satellite
and terrestrial components operate independently of each other
while sharing at least a portion, and optionally all, of a common
frequency band.
[0030] It is another optional feature and advantage of at least
some embodiments of the present invention to provide a
satellite-terrestrial communication system in which the satellite
and terrestrial components operate independently of each other
while utilizing discrete frequency bands.
[0031] It is another optional feature and advantage of at least
some embodiments of the present invention to provide a
satellite-terrestrial communications system and method of operation
thereof that minimizes interference between the satellite and
terrestrial components.
[0032] It is another optional feature and advantage of at least
some embodiments of the present invention to provide a
communication system utilizing at least two air interfaces having a
common area of coverage, wherein at least a portion of the
frequencies associated with a first air interface are assigned,
reused and/or shared by the second air interface.
[0033] It is still another optional feature and advantage of at
least some embodiments of the present invention to provide a
satellite-terrestrial communication system in which frequencies are
assigned, used and/or reused when signal strength is, for example,
attenuated and/or blocked by terrain and/or structures.
[0034] It is still another optional feature and advantage of at
least some embodiments of the present invention to provide a
satellite-terrestrial communication system that dynamically assigns
frequencies.
[0035] It is yet another feature and advantage of at least some
embodiments of the present invention to provide a
satellite-terrestrial communication system that utilizes hysteresis
and/or negative hysteresis in assigning, re-assigning and/or
reusing frequencies.
[0036] It is another optional feature and advantage of at least
some embodiments of the present invention to, for example, invert
the frequencies between the satellite system and an underlay
terrestrial system, whereby a first frequency is used, for example,
as a downlink frequency between a satellite and a first fixed
and/or mobile user terminal, and as an uplink frequency between a
second fixed and/or mobile user terminal and a BTS. In addition, a
second frequency is used, for example, as an uplink between the
first fixed and/or mobile user terminal, and the satellite and as a
downlink between the BTS and the second fixed and/or mobile user
terminal.
[0037] The present invention provides a system and method for
assigning, re-assigning, using and/or reusing channels for
terrestrial and/or satellite use. In one embodiment, a
satellite-terrestrial communication system and method is provided
for reusing one or more channels in a manner that minimizes
interference between the respective satellite and terrestrial
systems. The present invention can also be applied to multiple
satellite systems as well as, in addition to, or instead of,
terrestrial systems. The present invention optionally provides both
a terrestrial frequency assignment and/or reuse plan, and a
satellite frequency assignment and/or reuse plan.
[0038] Advantageously, the present invention provides a
satellite-terrestrial system and method that optionally uses a
reduction in signal strength caused by, for example, signal
attenuation, terrain blocking and/or blocking by man-made
structures to assign, use or reuse one or more channels. In one
embodiment, the channels having the weakest signal are reused
terrestrially in order to minimize interference.
[0039] Another embodiment determines that one or more of the
satellite channels detected by, for example, a subscriber terminal
or BTS are not being used. In this embodiment, any idle channels
are preferably used terrestrially first before any used (i.e.,
established) satellite channels are considered for terrestrial
reuse.
[0040] The satellite and terrestrial components can operate in an
integrated manner, or autonomously. For example, in an integrated
embodiment, the satellite and terrestrial components can share a
common network operations controller (NOC), mobile switching center
(MSC), and/or Radio Resource Manager (RRM). In an autonomous
embodiment, a separate NOC, MSC and/or RRM is provided for each of
the satellite and terrestrial components. For example, a RRM
associated with the terrestrial component can comprise or utilize,
for example, a suitable antenna operatively connected to a spectrum
analyzer and/or other signal detection means to search a band of
radio frequencies for the presence of radio signals, to determine
what frequencies are currently being utilized within a range or
ranges of frequencies of interest. The terrestrial RRM can
therefore determine, independently and without communication with a
RRM associated with the satellite component, or any other satellite
component equipment, what frequencies are not being used by the
system. Since the terrestrial RRM knows the frequencies used across
a range of frequencies of interest, as well as the frequencies used
by the terrestrial component, the terrestrial RRM can also
determine or deduce the frequencies that are currently being used
by the satellite component. Similarly, the satellite component
functions in substantially the same manner to, inter alia,
determine the frequencies currently being used by the terrestrial
component.
[0041] In the case of, for example, a single geosynchronous
satellite having multiple spot beams, the channels that are
reassigned terrestrially can be predetermined and/or computed
dynamically. In the case of multiple satellites, a predetermined
preference may optionally be provided where the subscriber
terminals communicate by using either the satellite system or the
terrestrial system.
[0042] In another embodiment, the present invention minimizes the
frequency reuse between the satellite and terrestrial networks by
utilizing channels for each system in an ordered manner. Channels
can be dynamically reassigned to maximize frequency separation and
thereby minimize any potential interference therebetween.
[0043] In another embodiment, the invention optionally uses
hysteresis so that there is a predetermined difference in signal
strength before allowing a subscriber terminal to transition back
and forth between channels associated with, for example, two
adjacent spot beams or BTSs. Similarly, the present invention
optionally uses negative hysteresis to keep channels assigned to,
for example, a BTS having a weaker signal strength rather than,
handing off to another channel having a stronger signal strength.
Negative hysteresis can also be used, for example, to facilitate a
desired loading of the respective satellite and/or terrestrial
networks, either individually or in combination with each
other.
[0044] In yet, another embodiment, the present invention uses a MSC
to coordinate frequency assignment and/or use between the satellite
and terrestrial components. The MSC determines which of the
channels are currently being used, and where. In this embodiment,
the MSC is operatively communicable with, for example, a base
station controller (BSC) which, in turn, informs one or more BTSs
which channels are currently in use by the satellite component.
When a channel goes in use on a satellite while the channel is
being used terrestrially, a determination is made whether a handoff
should be made to a channel having a weaker signal.
[0045] More particularly, at least one embodiment of the present
invention comprises a space based system comprising at least one
satellite. Each satellite, in turn, comprises at least one antenna
and establishes a first set of cells and transmits and receives GSM
based waveforms using at least a first portion of at least one
predetermined frequency band used by the first set of cells. In
addition, a ground based system comprises at least one base
transceiver station (BTS), each which can establish a second set of
cells and transmit and receive GSM based waveforms utilizing at
least a second portion of the one predetermined frequency band. The
space and ground systems function substantially autonomously and
use and/or reuse at least a portion of spectrum from at least one
predetermined frequency band to be used as at least one of an
uplink and downlink frequency channel from any of the frequencies
within the at least one predetermined frequency band. However, the
space based system and ground based system can utilize any air
interfaces. For example, in other embodiments, the space and ground
based systems can optionally utilize, for example, a code division
multiple access (CDMA) based air interface or derivatives thereof.
Similarly, the space based system can optionally utilize a CDMA
based air interface or derivative thereof, whereas the ground based
system can optionally utilize a GSM based air interface or
derivative thereof. In addition, the ground based system can
optionally utilize a CDMA based air interface or derivative
thereof, whereas the space based system can optionally utilize a
GSM based air interface or derivative thereof.
[0046] The system further comprises at least one subscriber
terminal that communicates with at least one of the space based
system and with the ground based system when located in at least
one of the first and second set of cells, as well as at least one
RRM that determines available communication links between the at
least one subscriber terminal and at least one of the space based
system and the ground based systems.
[0047] The at least one predetermined frequency band optionally
comprises at least one discrete space based system uplink portion
and at least one discrete space based system downlink portion,
wherein the ground based system uses and/or reuses at least a
portion of at least one of the uplink and downlink portions. Each
of the discrete portions are optionally associated with at least
one of a satellite spot beam and a subsection of a spot beam.
[0048] The at least one predetermined frequency band optionally
comprises at least one discrete space based system uplink portion,
at least one discrete space based system downlink portion, and at
least ground based system portion. Further, at least two cells of
the first set of cells in the space based system optionally utilize
a mutually exclusive portion of the first portion of the at least
one predetermined frequency band.
[0049] One or more frequencies in the first and second portion of
the at least one predetermined frequency band used by the space
based system and the ground based system are optionally
substantially the same or closely spaced.
[0050] Each of the subscriber terminals can optionally utilize at
least a first vocoder having a first data rate and at least a
second vocoder having a second data rate, wherein the first vocoder
is used when a subscriber terminal is communicating with the space
based system, and wherein the second vocoder is used when the
subscriber terminal is communicating with the ground based system.
The RRM optionally assigns and/or activates at least one of the
first and second vocoders in response to predetermined criteria
such as capacity demand, voice quality, and/or received signal
level.
[0051] The system can also optionally utilize at least one MSC that
is operatively connected to the space based system and the ground
based system that at assigns and/or activates a vocoder in response
to predetermined criteria such as capacity demand, voice quality,
and received signal level. The RRM can also optionally assign or
activate a different vocoder to a voice communications circuit in
response to the predetermined criteria such as capacity demand,
voice quality, signal strength, and received signal level having
changed substantially since assignment or activation of the at
least first and second vocoder being utilized.
[0052] The at least one predetermined frequency band can optionally
comprise first and second frequency bands, such that subscriber
terminals communicate with the ground based system by transmitting
at first frequencies within the first frequency band used as an
uplink of the space based system, and receive at second frequencies
within the second frequency band used as a downlink of the space
based system. In addition, the first and second frequencies used by
a cell of the space based system are optionally mutually exclusive
to third frequencies used by a cell of the ground based system
containing one or more of the subscriber terminals, within the cell
of the space based system.
[0053] The at least one predetermined frequency band can also
optionally comprise first and second frequency bands, such that
subscriber terminals communicate with the ground based system by
transmitting at first frequencies within a first frequency band
used as a downlink of the space based system, and receive at second
frequencies within a second frequency band used as an uplink of the
space based system. The first and second frequencies used by a cell
of the space based system are mutually exclusive to third
frequencies used by a cell of the ground based system containing
one or more of the subscriber terminals, within the cell of said
space based system.
[0054] The at least one predetermined frequency band can also
optionally comprise first and second frequency bands, such that
subscriber terminals communicate with the ground based system(s) by
transmitting at first frequencies within the first frequency band
used as the uplink of the space based system, and receive at
frequencies within the first frequency band used as the uplink of
the space based system. The first and second frequencies used by a
cell of the space based system are optionally mutually exclusive to
third frequencies used by a cell of the ground based system
containing one or more of the subscriber terminals, within the cell
of said space based system.
[0055] The at least one predetermined frequency band can also
optionally comprise first and second frequency bands, such that
subscriber terminals communicate with the ground based system(s) by
transmitting at first frequencies within the first frequency band
used as the downlink of the space based system, and receive at
frequencies within the first frequency band used as the downlink of
the space based system. The first and second frequencies used by a
cell of the space based system are optionally mutually exclusive to
third frequencies used by a cell of the ground based system
containing one or more of the subscriber terminals, within the cell
of the space based system.
[0056] The RRM(s) can optionally monitor which channels are
currently being utilized by the subscriber terminals. A MSC
operatively connected to one or more of the RRMs can optionally be
utilized, wherein one or more of the RRMs indicate to the MSC which
channels are currently being utilized by one or more of the
subscriber terminals. Each RRM, can be, for example, a spectrum
analyzer. Individual RRMs can optionally be utilized in connection
with each of the space based and ground based systems to, for
example, monitor inband interference and avoid using and/or reusing
channels that would cause levels of interference exceeding a
predetermined threshold. The RRMs can also optionally monitor at
least one of received signal quality and available link margin from
one or more of the subscriber terminals. The RRMs can also
optionally execute utilization of a different communications
channel when a quality measure of the existing communications
channel has fallen below a predetermined level or has fallen below
a predetermined link margin.
[0057] Each of the subscriber terminals can optionally comprise a
variable rate vocoder, or two or more vocoders each having a
different data rate. The vocoder data rate can be selected as
determined by predetermined criteria such as capacity demand, voice
quality, signal strength, and/or received signal level.
[0058] RRMs can optionally monitors inband interference and avoid
using channels containing levels of interference exceeding a
predetermined threshold, as well as monitor received signal quality
from subscriber terminals communicating with the space based system
and/or ground based system. RRMs can also optionally monitor
available link margin from subscriber terminals communicating with
the space based and/or ground based systems. The RRMs can also
optionally execute utilization of a different communications
channel when a quality measure of the existing communications
channel has fallen below a predetermined level or has fallen below
a predetermined link margin.
[0059] The system can optionally comprise a NOC operatively
connected to at least a MSC that assigns a channel to subscriber
units. The NOC maintains cognizance of the availability of
satellite and/or terrestrial resources, and optionally administers
at least one of reconfiguration, assignment and reuse of
frequencies within the predetermined frequency band to meet changed
traffic patterns or other predetermined conditions. The NOC is
optionally commonly shared between and operatively connected to the
space based and ground based systems. The NOC can also optionally
utilize past system traffic patterns in the reconfiguration,
assignment and/or reuse of the frequencies, as well as utilize at
least one of hysteresis and negative hysteresis in the
reconfiguration, assignment and/or reuse of the frequencies.
[0060] The space based system satellite can optionally have a
geostationary orbit, wherein the NOC dynamically assigns a channel
to a subscriber unit communicating with the space based system. The
dynamic assignment can optionally be performed on a call-by-call
basis, or be based on past and present usage. Dynamic assignment is
optionally performed by one or more base station controllers
operationally connected to the NOC.
[0061] A exemplary method in accordance with the present invention
assigns to a requesting subscriber unit a communication channel
commonly shared between a space based communication system and a
ground based communication system. The method comprises the steps
of configuring a first satellite spot beam, associated with the
space based system, having a plurality of communication channels
associated therewith, and configuring at least one terrestrial
cell, associated with the ground based system, that at least
partially geographically overlaps the first satellite spot beam. A
dual mode subscriber terminal requests a communication channel, and
at least one of the ground based system and the space based system
substantially autonomously determines channel availability and
assigns to the requesting dual mode subscriber unit at least one of
an unused channel and, for reuse with the dual mode subscriber
terminal, a used channel having a sufficiently weak signal
strength.
[0062] In accordance with the method, the space based system
optionally utilizes a time division multiple access (TDMA) air
interface, and the ground based system optionally utilizes a TDMA
air interface. In general, however, any first and second air
interfaces can be respectively utilized by the space based and
ground based systems. For example, the first air interface can
optionally be a GSM based air interface or a derivative thereof,
and the second air interface can optionally be a GSM based air
interface or a derivative thereof. Alternatively, the first air
interface can optionally be a GSM based air interface or a
derivative thereof, and the second air interface can optionally be
a CDMA based air interface or a derivative thereof. Similarly, the
first air interface can optionally be a CDMA based air interface or
a derivative thereof, and the second air interface can optionally
be a GSM based air interface or a derivative thereof. Further, the
first air interface can optionally be a CDMA based air interface or
a derivative thereof, and the second air interface can optionally
be a CDMA based air interface or a derivative thereof.
[0063] The method optionally further comprises the step of
increasing the output power of a subscriber terminal utilizing the
space based system as the composite signal strength of the
subscriber terminals utilizing the ground based system reaches a
predetermined threshold. The number of subscriber terminals
connections with the ground based system can optionally be
decreased as at least one of bit error rate, received signal
strength, available link margin, and voice quality reach respective
predetermined thresholds.
[0064] The method optionally further comprises the steps of
enabling a subscriber terminal to communicate at a plurality of
data rates, and selecting a data rate as determined by at least one
of capacity demand, voice quality, and subscriber terminal received
signal level. One or more subscriber terminals communicating with
the space based or ground based system can optionally utilize a
different data rate as determined by at least one of capacity
demand, and received signal level having changed substantially
since assignment or activation of the current channel.
[0065] The channel can optionally comprise first and second
frequency bands, such that the subscriber terminals communicate
with the ground based system by transmitting at first frequencies
within the first frequency band used as an uplink of the space
based system, and receive at second frequencies within the second
frequency band used as a downlink of the space based system.
Subscriber terminals can also communicates with the ground based
system by transmitting at first frequencies within a first
frequency band used as an uplink of the space based system, and
receive at second frequencies within a second frequency band used
as a downlink of the space based system. Subscriber terminal can
also optionally communicate with the ground based system by
transmitting at first frequencies within a first frequency band
used as the uplink of the space based system, and receive at first
frequencies within the first frequency band used as the uplink of
the space based system. In addition, subscriber terminals can also
optionally communicate with the ground based system by transmitting
at first frequencies within a first frequency band used as the
downlink of the space based system, and receive at first
frequencies within the first frequency band used as the downlink of
the space based system. Further, subscriber terminals can
optionally communicate with the ground based system by transmitting
at first frequencies within a first frequency band used as the
downlink of the space based system, and receive at first
frequencies within the first frequency band used as the downlink of
the space based system.
[0066] In accordance with the method, a first communication channel
associated with the space based system optionally comprises a first
frequency band used for uplink communication and a second frequency
band used for uplink communication, such that the ground based
system shares at least a common portion of the first and second
frequency bands in a terrestrial cell positioned outside of and
non-overlapping with the satellite spot beam.
[0067] In accordance with the method, at least one of the ground
based system and the space based system optionally autonomously
monitors inband interference and avoids using and/or reusing
channels that would cause levels of interference exceeding a
predetermined threshold. A different communications channel is
preferably utilized when a quality measure of the existing
communications channel has fallen below a predetermined level.
[0068] In accordance with the method, at least one of the space
based system and the ground based systems autonomously monitor at
least one of received signal quality and available link margin from
a subscriber terminal. A different communications channel is
preferably utilized when at least one of received signal quality
and available link margin has fallen below a predetermined link
margin.
[0069] The method optionally further comprises the step of
arranging for at least one of channel reconfiguration and reuse of
frequencies to meet changed traffic patterns. Past system traffic
patterns, hysteresis and/or negative hysteresis can optionally be
utilized in determining the reconfiguration and reuse of
frequencies.
[0070] In accordance with the method, the communication channel is
optionally assigned to the subscriber unit in accordance with a
predetermined channel assignment scheme.
[0071] Also in accordance with the present invention, a method of
making a telephone call using at least one of a space based system
and a ground based system comprises the steps of dialing by a user
using a subscriber terminal a telephone number within an area of a
first terrestrial cell having at least partial overlapping
geographic coverage with at least a satellite spot beam, wherein
the terrestrial cell and the spot beam share a common set of
frequencies. At least one of the ground based system and the space
based system substantially autonomously determines channel
availability in response to the dialing, and assign a channel to
the requesting subscriber terminal.
[0072] In another embodiment, the system in accordance with the
present invention comprises a cellular-configured dual mode
communications system comprising a space based system comprising a
first set of cells, and a ground based system comprising a second
set of cells. Embodiments of the present invention contemplate that
the space and ground systems can function in an integrated manner
or substantially autonomously, each embodiment optionally using
spectrum from, for example, the same set of frequencies in at least
one predetermined frequency band and/or different sets of
frequencies in one or more discrete bands, optionally dedicated to
a particular system.
[0073] In at least some embodiments, two cells of the space based
system use a mutually exclusive portion of the at least one
predetermined frequency band. The space based system can optionally
utilize a TDMA air interface, and the ground based system can also
utilize a TDMA air interface. The TDMA air interfaces can be a
standard GSM air interface or a derivative and/or similar system
thereof. In general, however, the space based and ground based
systems can utilize any first and second air interfaces. For
example, the space based system can utilize a GSM based air
interface or a derivative thereof, and the ground based system can
utilize a CDMA based air interface or a derivative thereof. In
addition, the space based system can utilize a CDMA based air
interface or a derivative thereof, and the ground based system can
utilize a CDMA based air interface or a derivative thereof.
Further, the space based system can utilize a GSM based air
interface or a derivative thereof, and the ground based system can
utilize a CDMA based air interface or a derivative thereof.
[0074] The at least one predetermined frequency band can optionally
comprise at least one of a discrete space based system uplink
portion and a discrete space based system downlink portion. The
ground based system can optionally utilize at least a portion of at
least one of the uplink and downlink portions, wherein each of the
discrete portions are optionally associated with at least one of a
satellite spot beam and a subsection of a spot beam.
[0075] The at least one predetermined frequency band further
optionally comprises a discrete ground based system portion,
wherein at least two cells of said space based system optionally
utilize a mutually exclusive portion of the at least one
predetermined frequency band.
[0076] The system further comprises at least one subscriber
terminal communicating with the space based system and with the
ground based system. The at least one predetermined frequency band
used by the space based system and the ground based system are
optionally substantially the same.
[0077] Subscriber terminals comprise having means for communicating
with the space based system and with the ground based system
optionally include a first plurality of standard vocoders, each
having a different data rate, and a second plurality of standard
vocoders, each having a different data rate. A vocoder in the first
plurality can be used when a subscriber terminal is communicating
with the space based system, and a vocoder in the second plurality
can be used when a subscriber terminal is communicating with the
ground based system. The subscriber terminals can also utilize a
variable rate vocoder.
[0078] The system can also include a RRM that assigns a vocoder or
other functionally similar device in response to predetermined
criteria such as capacity demand, voice quality and/or received
signal level. The RRM can optionally assign a different vocoder to
a voice communications circuit in response to predetermined
criteria such as capacity demand and/or received signal level
having changed substantially since assignment of the vocoder
utilized.
[0079] Subscriber terminals can optionally communicate with the
ground based system by transmitting at frequencies within a
frequency band used as an uplink of the space based system, and
receiving at frequencies within a frequency band used as a downlink
of the space based system. In another embodiment of the present
invention, the subscriber terminals communicate with the ground
based system by transmitting at frequencies within a frequency band
used as a downlink of the space based system, and receiving at
frequencies within a frequency band used as an uplink of the space
based system. The subscriber terminals can also optionally
communicate with the ground based system by transmitting at
frequencies within a frequency band used as an uplink of the space
based system, and receiving at frequencies within a frequency band
used as the uplink of the space based system. Further, the
subscriber terminals can optionally communicate with the ground
based system by transmitting at frequencies within a frequency band
used as the downlink of the space based system, and receive at
frequencies within a frequency band used as the downlink of the
space based system. In each of the above embodiments of the present
invention, the frequencies used by a cell of the space based system
can optionally be mutually exclusive to those used by a cell of the
ground based system, containing one or more of subscriber
terminals, within the cell of the space based system.
[0080] At least some embodiments of the system in accordance with
the present invention can utilize one or more RRMs that monitor
which channels are currently being utilized by each or any of one
or more subscriber terminals. A first RRM can be utilized in
connection with the ground based system, and a second RRM can be
utilized in connection with the space based system. In at least
some embodiments of the present invention, the one or more RRMs
monitor inband interference and avoid using and/or reusing channels
that would cause levels of interference exceeding a predetermined
threshold. The one or more RRMs can optionally monitor subscriber
terminal received signal quality, available link margin and/or
utilization of a different communications channel when a quality
measure of the existing communications channel has fallen below a
predetermined level and/or has fallen below a predetermined link
margin. The one or more RRMs also monitor inband interference and
avoid using channels containing levels of interference exceeding a
predetermined threshold, and/or monitor available link margin from
subscriber terminals communicating with at least one of the space
based system and the ground based system. In accordance with at
least some embodiments of the present invention, the one or more
RRMs can also execute utilization of a different communications
channel when a quality measure of the existing communications
channel has fallen below a predetermined level or has fallen below
a predetermined link margin.
[0081] The RRM(s) can optionally monitor which channels are
currently being utilized by the subscriber terminals. A MSC
operatively connected to one or more of the RRMs can optionally be
utilized, wherein one or more of the RRMs indicate to the MSC which
channels are currently being utilized by one or more of the
subscriber terminals. Each RRM, can be, for example, a spectrum
analyzer. Individual RRMs can optionally be utilized in connection
with each of the space based and ground based systems to, for
example, monitor inband interference and avoid using and/or reusing
channels that would cause levels of interference exceeding a
predetermined threshold. The RRMs can also optionally monitor at
least one of received signal quality and available link margin from
one or more of the subscriber terminals. The RRMs can also
optionally execute utilization of a different communications
channel when a quality measure of the existing communications
channel has fallen below a predetermined level or has fallen below
a predetermined link margin.
[0082] The system can optionally comprise a NOC operatively
connected to at least a MSC that assigns a channel to subscriber
units. The NOC maintains cognizance of the availability of
satellite and/or terrestrial resources, and optionally administers
reconfiguration, assignment and/or reuse of frequencies within the
predetermined frequency band to meet changed traffic patterns or
other predetermined conditions. The NOC is optionally commonly
shared between and operatively connected to the space based and
ground based systems. The NOC can also optionally utilize past
system traffic patterns in the reconfiguration, assignment and/or
reuse of the frequencies, as well as utilize at least one of
hysteresis and negative hysteresis in the reconfiguration,
assignment and/or reuse of the frequencies.
[0083] The space based system satellite can optionally have a
geostationary orbit, wherein the NOC dynamically assigns a channel
to a subscriber unit communicating with the space based system. The
dynamic assignment can optionally be performed on a call-by-call
basis, or be based on past and present usage. Dynamic assignment is
optionally performed by one or more base station controllers
operationally connected to the NOC.
[0084] In another embodiment, the system in accordance with the
present invention comprises a space based system comprising a first
set of cells, and a ground based system comprising a second set of
cells, wherein at least a portion of the second set of cells share
at least a portion of a common geographic area and have overlapping
coverage with the first set of cells, the space and ground systems
function substantially autonomously and each use at least a portion
of commonly shared spectrum from at least one predetermined
frequency band.
[0085] The at least one predetermined frequency band optionally
comprises at least one discrete space based system uplink portion,
and at least one discrete space based system downlink portion. The
ground based system optionally utilizes at least a portion of at
least one of the uplink and downlink portions. Each of the at least
one discrete uplink and downlink portions are optionally associated
with at least one of a satellite spot beam and a subsection of a
spot beam. Further, at least two cells of the space based system
use a mutually exclusive portion of the at least one predetermined
frequency band.
[0086] The first and second air interfaces can optionally be, for
example, TDMA air interfaces, such as GSM or a derivative thereof.
However, in general, the space based system can utilize a first air
interface (e.g., GSM or CDMA, or derivatives thereof), and the
ground based system can utilize a second air interface (e.g., GSM
or CDMA, or derivatives thereof).
[0087] The system further optionally comprises at least one
subscriber terminal communicating with the space based system and
with said ground based system. The subscriber terminals can
optionally utilize a first vocoder having a first data rate and a
second vocoder having a second data rate, wherein first vocoder is
used when a subscriber terminal is communicating with the space
based system, and wherein a second vocoder is used when a
subscriber terminal is communicating with the ground based
system.
[0088] The system further optionally comprises a RRM operatively
connected to the space based system and the ground based system,
wherein the RRM optionally assigns and/or activates at least one of
the first and second vocoders in response to, for example, capacity
demand, voice quality, and/or received signal level.
[0089] The system further optionally comprises at least one MSC
operatively connected to the space based system and the ground
based system that selectively assigns a vocoder in response to
predetermined criteria such as capacity demand, voice quality,
and/or received signal level. The RRM also optionally assigns
and/or activates a different vocoder to a voice communications
circuit in response to the predetermined criteria such as capacity
demand, voice quality, signal strength, and/or received signal
level having changed substantially since assignment or activation
of the at least first and second vocoder being utilized.
[0090] The at least one predetermined frequency band optionally
comprises first and second frequency bands, and the subscriber
terminals optionally communicate with the ground based system by
transmitting at first frequencies within the first frequency band
used as an uplink of the space based system, and receive at second
frequencies within the second frequency band used as a downlink of
said space based system.
[0091] The subscriber terminals can also optionally communicate
with the ground based system by transmitting at first frequencies
within a first frequency band used as a downlink of the space based
system, and receive at second frequencies within a second frequency
band used as an uplink of the space based system. The subscriber
terminals can also optionally communicate with the ground based
system by transmitting at first frequencies within the first
frequency band used as the uplink of the space based system, and
receive at second frequencies within the second frequency band used
as the uplink of the space based system. Further, the subscriber
terminals can also optionally communicate with the ground based
system by transmitting at first frequencies within the first
frequency band used as the downlink of the space based system, and
receive at second frequencies within the second frequency band used
as the downlink of the space based system.
[0092] The system further optionally comprises at least one RRM
that monitors which channels are currently being utilized by each
of one or more subscriber terminals. The system further optionally
comprises a MSC operatively connected to one or more of the RRMs,
wherein one or more of the RRMs indicates to the MSC which channels
are currently being utilized by the subscriber terminals. The RRM
independently and autonomously identifies which channels are being
used by the ground based system as being the difference between all
of the frequencies being used by the system and the frequencies
being used by said space based system. The RRM also independently
and autonomously identifies which channels are being used by the
space based system as being the difference between all of the
frequencies being used by the system and the frequencies being used
by said ground based system.
[0093] The system also optionally comprises a MSC operatively
connected to one or more of the RRM(s), wherein one or more of the
RRM(s) indicate to the MSC which channels are currently being
utilized by each of one or more subscriber terminals. The RRM(s)
can be, for example, a spectrum analyzer.
[0094] First and second RRMs can also be utilized, wherein a first
RRM is utilized in connection with the ground based system, and
wherein a second RRM is utilized in connection with the space based
system. The first and second RRMs monitor inband interference and
avoid using and/or reusing channels that would cause levels of
interference exceeding a predetermined threshold. The RRMs also
monitor at least one of subscriber terminal received signal quality
and available link margin, and also optionally execute utilization
of a different communications channel when a quality measure of the
existing communications channel has fallen below a predetermined
level and/or has fallen below a predetermined link margin. The RRMs
further optionally monitor available link margin from subscriber
terminals communicating with at least one of the space based system
and the ground based system.
[0095] The system optionally further comprises a NOC operatively
connected to at least a MSC that assigns a channel to subscriber
units. The NOC maintains cognizance of the availability of at least
one of satellite and terrestrial resources and administers
reconfiguration, assignment and/or reuse of frequencies within said
predetermined frequency band to meet changed traffic patterns or
other predetermined conditions. The NOC is optionally commonly
shared between and operatively connected to the space based system
and the ground based system. The NOC optionally utilizes past
system traffic patterns in the reconfiguration, assignment and/or
reuse of the frequencies, and also optionally utilizes hysteresis
and/or negative hysteresis in the reconfiguration, assignment
and/or reuse of the frequencies.
[0096] The system can optionally utilize a satellite having a
geostationary orbit, wherein the NOC dynamically assigns a channel
to a subscriber unit communicating with the space based system and
the satellite. The dynamic assignment is optionally performed on a
call-by-call basis, or based on past and present usage. Further,
the dynamic assignment is optionally performed by one or more base
station controllers operationally connected to the NOC, such that
the dynamic assignment optionally maximizes bandwidth separation of
frequencies used by the space based system and the ground based
system.
[0097] Further, in an embodiment wherein the spade based and ground
based systems function substantially autonomously and each use one
or more mutually exclusive predetermined frequency bands, a method
in accordance with the present invention is provided for initiating
a call between a subscriber terminal and at least one of the space
based system and the ground based system. The method comprises the
steps of a subscriber terminal transmitting to the system a signal
indicating whether it is a single or dual mode terminal. The system
determines, based on at least the transmitted signal, whether the
subscriber terminal is a single mode or a dual mode terminal. For a
dual mode subscriber terminal, the system at least one of assigns
to the ground based system for use with the dual mode subscriber
terminal an unused space based system channel, using in the ground
based system an unused ground based system channel, reusing in the
ground based system a channel used by the space based system having
a substantially weak signal relative to the dual mode subscriber
terminal, and using in the space based system a channel assigned to
the space based system. For a single mode subscriber terminal, an
available channel is used in the space based system having an
acceptable signal strength.
[0098] Further, in a cellular communications system in which the
space based system and the ground based system share and commonly
use at least a portion of a predetermined frequency band, and in
which the space based and ground based systems function
substantially autonomously, a method is provided for initiating a
call between a subscriber terminal and at least one of the space
based system and the ground based system. The method comprises the
steps of a subscriber terminal transmitting to the system a signal
indicating whether it is a single or dual mode terminal. The system
determines whether the subscriber terminal is a single mode or a
dual mode terminal. For a dual mode subscriber terminal, the system
at least one of uses an unused channel to establish communication
between the ground based system and the dual mode subscriber
terminal, reuses in the ground based system a channel used by the
space based system having a substantially weak signal relative to
the subscriber terminal to establish communication between the
ground based system and the dual mode subscriber terminal, and
reuses in the ground based system a channel used by the ground
based system having a substantially weak signal relative to the
subscriber terminal to establish communication between the ground
based system and the dual mode subscriber terminal. For a single
mode terminal, the space based system uses an available channel
having an acceptable signal strength.
[0099] Further, in a cellular communications system comprising a
space based system comprising a first set of cells, and a ground
based system comprising a second set of cells, in which at least a
portion of the second set of cells share a common geographic area
and have at least a portion of overlapping geographic coverage with
the first set of cells, and in which the space based and ground
based systems function substantially autonomously and each use one
or more mutually exclusive predetermined frequency bands, a method
is provided for executing a handoff from a first base station
associated with the ground system to at least one of a second base
station associated with the ground based system and a satellite.
The method comprises the steps of determining whether a received
signal strength indication (RSSI) between the subscriber terminal
and the second base station is satisfied. A subscriber terminal
transmits to the system a signal indicating whether it is a single
or dual mode terminal. The system determines, based on at least the
transmitted signal, whether the subscriber terminal is a single
mode or a dual mode terminal. For a dual mode subscriber terminal,
when the second base station has an acceptable RSSI, the system at
least one of reassigns to the second base station for communication
with the dual mode subscriber terminal at least one of an unused
space based system channel and an unused ground based system
channel, and reuses by the second base station for communication
with the dual mode subscriber terminal a channel used by the space
based system having a substantially weak signal relative to the
subscriber terminal. For a single mode subscriber terminal, the
subscriber terminal uses a channel associated with the space based
system having an acceptable signal strength.
[0100] Further, in a cellular communications system comprising a
space based system comprising a first set of cells, and a ground
based system comprising a second set of cells, in which the space
based system and the ground based system share and commonly use at
least a portion of a predetermined frequency band, the space based
and ground based systems functioning substantially autonomously, a
method is provided for executing a handoff from a first base
station associated with the ground system to at least one of a
second base station associated with the ground based system and a
satellite. The method comprises the steps of determining whether a
received signal strength indication (RSSI) between the subscriber
terminal and the second base station is satisfied. A subscriber
terminal transmits to the system a signal indicating whether it is
a single or dual mode terminal. The system determines, based at
least one the transmitted signal, whether the subscriber terminal
is a single mode or a dual mode terminal. For a dual mode
subscriber terminal, when the second base station has an acceptable
RSSI, the system at least one of reassigns to the second base
station for communication with the dual mode subscriber terminal an
unused system channel, and reuses by the second base station for
communication with the dual mode subscriber terminal a channel used
by the space based system having a substantially weak signal
relative to the subscriber terminal. For a single mode subscriber
terminal, the subscriber terminal uses at least one of an unused
channel and a used channel having a sufficiently weak signal
strength relative to the subscriber terminal.
[0101] Further, in a cellular communications system comprising a
space based system comprising a first set of cells, and a ground
based system comprising a second set of cells, in which at least a
portion of the second set of cells share a common geographic area
and have at least a portion of overlapping geographic coverage with
the first set of cells, the space based and ground based systems
functioning substantially autonomously and each using one or more
mutually exclusive predetermined frequency bands, a method is
provided for executing a handoff from a first satellite spot beam
associated with the space based system to at least one of a second
satellite spot beam associated with the space based system and a
base station associated with the ground based system. The method
comprises the steps of determining whether a received signal
strength indication (RSSI) between the subscriber terminal and the
second satellite spot beam is satisfied. A subscriber terminal
transmits to the system a signal indicating whether the subscriber
terminal is a single mode or a dual mode terminal. The system,
based on at least the transmitted signal, determines whether the
subscriber terminal is a single mode or a dual mode terminal. For a
dual mode subscriber terminal, when the base station has an
acceptable RSSI, the system at least one of assigns to the base
station for communication with the dual mode subscriber terminal an
unused space based system channel associated with the second spot
beam, reuses by the base station for communication with the dual
mode subscriber terminal a channel used by the second spot beam
having a substantially weak signal strength relative to the dual
mode subscriber terminal, and reuses by the base station for
communication with the dual mode subscriber terminal a channel used
by the ground based system having a substantially weak signal
strength relative to the dual mode subscriber terminal, and uses by
the base station for communication with the dual mode subscriber
terminal an unused ground based system channel having sufficient
signal strength. For a single mode subscriber terminal, a channel
associated with a second spot beam of the space based system having
a acceptable signal strength is utilized.
[0102] Further, in a cellular communications system comprising a
space based system comprising a first set of cells, and a ground
based system comprising a second set of cells, in which the space
based system and the ground based system share and commonly use at
least a portion of a predetermined frequency band, the space based
and ground based systems functioning substantially autonomously and
each using at least a portion of spectrum from at least a portion
of one predetermined frequency band, a method is provided for
executing a handoff from a first satellite spot beam associated
with the space based system to at least one of a second satellite
spot beam associated with the space based system and a base station
associated with the ground based system comprises the steps of
determining whether a received signal strength indication (RSSI)
between the subscriber terminal and the second base station is
satisfied. The subscriber terminal transmits to the system a signal
indicating whether the subscriber terminal is a single or a dual
mode terminal. The system determines based on at least the
transmitted signal whether the subscriber terminal is a single mode
or a dual mode terminal. For a dual mode subscriber terminal, when
the base station has an acceptable RSSI, the system at least one of
reassigns to the base station for communication with the dual mode
subscriber terminal an unused system channel, and reuses by the
base station for communication with the dual mode subscriber
terminal a channel used by the space based system having a
substantially weak signal relative to the dual mode subscriber
terminal, reuses by the base station for communication with the
dual mode subscriber terminal a channel used by the ground based
system having a substantially weak signal relative to the dual mode
subscriber terminal. For a single mode subscriber terminal, at
least one of an unused channel associated with the second spot beam
and a used channel having a sufficiently weak signal strength
relative to the subscriber terminal is utilized.
[0103] Another embodiment of the system comprises a space based
system comprising means for establishing a first set of cells and
transmitting and receiving GSM based waveforms using at least a
first portion of at least one predetermined frequency band used by
the first set of cells. A ground based system comprises means for
establishing a second set of cells and transmitting and receiving
GSM based waveforms utilizing at least a second portion of the one
predetermined frequency band, the space based and ground based
systems functioning substantially autonomously and at least one of
using and reusing at least a portion of spectrum from at least one
predetermined frequency band. At least one subscriber terminal
communicates with at least one of the space based system and with
the ground based system when located in at least one of the first
and second set of cells. Means for determining available
communication links between the at least one subscriber terminal
and the space based system and the ground based system is also
provided.
[0104] The at least one predetermined frequency band optionally
comprises at least one discrete space based system uplink portion
and at least one discrete space based system downlink portion,
wherein the ground based system uses and/or reuses at least a
portion of at least one of the uplink and downlink portions. Each
of the discrete portions are optionally associated with at least
one of a satellite spot beam and a subsection of a spot beam.
[0105] The at least one predetermined frequency band optionally
comprises at least one discrete space based system uplink portion,
at least one discrete space based system downlink portion, and at
least one ground based system portion.
[0106] At least two cells of the first set of cells in the space
based system optionally use a mutually exclusive portion of the
first portion of the at least one predetermined frequency band.
Further, one or more frequencies in the first and second portion of
the at least one predetermined frequency band used by the space
based system and the ground based system are optionally
substantially the same or closely spaced.
[0107] The at least one subscriber terminal optionally comprises at
least a first vocoder having a first data rate and at least a
second vocoder having a second data rate, wherein the first vocoder
is used when the subscriber terminal is communicating with the
space based system, and wherein the second vocoder is used when the
subscriber terminal is communicating with the ground based
system.
[0108] The means for determining available communication links
optionally at least one of assigns and activates at least one of
the first and second vocoders in response to predetermined criteria
such as capacity demand, voice quality, and/or received signal
level. The means for determining available communication links
further optionally assigns or activates a different vocoder to a
voice communications circuit in response to the predetermined
criteria such as such as voice quality, signal strength, and/or
received signal level having changed substantially since assignment
or activation of the first or second vocoder being utilized.
[0109] The at least one predetermined frequency band optionally
comprises first and second frequency bands, and the subscriber
terminals communicate with the ground based system by transmitting
at first frequencies within the first frequency band used as an
uplink of the space based system, and receiving at second
frequencies within the second frequency band used as a downlink of
the space based system.
[0110] The first and second frequencies used by a cell of the space
based system are optionally mutually exclusive to third frequencies
used by a cell of the ground based system containing one or more of
the subscriber terminals, within the cell of the space based
system.
[0111] The at least one predetermined frequency band optionally
comprises first and second frequency bands, wherein the subscriber
terminals communicate with the ground based system by transmitting
at first frequencies within a first frequency band used as a
downlink of the space based system, and receiving at second
frequencies within a second frequency band used as an uplink of the
space based system.
[0112] The first and second frequencies used by a cell of the space
based system are optionally mutually exclusive to third frequencies
used by a cell of the ground based system containing one or more of
the subscriber terminals, within the cell of said space based
system.
[0113] The at least one predetermined frequency band optionally
comprises first and second frequency bands, wherein the subscriber
terminals communicate with the ground based system by transmitting
at first frequencies within the first frequency band used as the
uplink of the space based system, and receives at frequencies
within the first frequency band used as the uplink of the space
based system.
[0114] The first and second frequencies used by a cell of the space
based system are optionally mutually exclusive to third frequencies
used by a cell of the ground based system containing one or more of
the subscriber terminals, within the cell of the space based
system.
[0115] The at least one predetermined frequency band optionally
comprises first and second frequency bands, wherein subscriber
terminals communicate with the ground based system by transmitting
at first frequencies within the first frequency band used as the
downlink of the space based system, and receives at frequencies
within the first frequency band used as the downlink of the space
based system.
[0116] The first and second frequencies used by a cell of the space
based system are optionally mutually exclusive to third frequencies
used by a cell of the ground based system containing one or more of
the subscriber terminals, within the cell of said space based
system.
[0117] The means for determining available communication links
comprises first and second means for determining available
communication links, wherein a first means for determining
available communication links is utilized in connection with the
ground based system, and wherein a second means for determining
available communication links is utilized in connection with the
space based system.
[0118] The system further optionally comprises means for
maintaining cognizance of the availability of at least one of
satellite and terrestrial resources and administering
reconfiguration, assignment and/or reuse of frequencies within the
predetermined frequency band to meet changed traffic patterns or
other predetermined conditions. The means for maintaining
cognizance is optionally operatively connected to at least a MSC
that assigns a channel to subscriber units.
[0119] In another embodiment, a cellular communications system in
accordance with the present invention comprises a space based
system comprising means for establishing a first set of cells and
transmitting and receiving GSM based waveforms using at least a
first portion of at least one predetermined frequency band used by
the first set of cells. A ground based system comprises means for
establishing a second set of cells and transmitting and receiving
code division multiple access (CDMA) waveforms utilizing at least a
second portion of the one predetermined frequency band to be used
as at least one of an uplink and downlink frequency channel from
any of the frequencies within the at least one predetermined
frequency band. One or more subscriber terminals communicate with
at least one of the space based system and with the ground based
system when located in at least one of the first and second set of
cells. The system also comprise means for determining available
communication links between the subscriber terminals and the space
based system and/or the ground based system.
[0120] The first portion of the at least one predetermined
frequency band optionally comprises at least one discrete space
based system uplink portion and at least one discrete space based
system downlink portion, wherein the first portion is a subset of
the second portion. Each of the discrete portions are optionally
associated with at least one of a satellite spot beam and a
subsection of a spot beam.
[0121] The first portion of the at least one predetermined
frequency band comprises at least one discrete space based system
uplink portion, at least one discrete space based system downlink
portion, and a ground based system portion. At least two cells of
the first set of cells in the space based system optionally use a
mutually exclusive portion of the first portion of the at least one
predetermined frequency band. Further, one or more frequencies in
the first and second portions of the at least one predetermined
frequency band are optionally substantially the same or closely
spaced.
[0122] The subscriber terminals optionally comprise a first vocoder
having a first data rate and a second vocoder having a second data
rate, wherein the first vocoder is used when the subscriber
terminal is communicating with the space based system, and wherein
the second vocoder is used when the subscriber terminal is
communicating with the ground based system.
[0123] The means for determining available communication links
further optionally at least one of assigns and activates at least
one of the first and second vocoders in response to predetermined
criteria such as capacity demand, voice quality, and/or received
signal level.
[0124] The system further optionally comprises means for at least
one of assigning and activating a vocoder in response to
predetermined criteria comprising, for example, capacity demand,
voice quality, and/or received signal level.
[0125] The means for detecting available communication links
optionally further assigns or activates a different vocoder to a
voice communications circuit in response to the predetermined
criteria such as capacity demand, voice quality, signal strength,
and received signal level having changed substantially since
assignment or activation of the at least first and second vocoder
being utilized.
[0126] The system further optionally comprises means for
maintaining cognizance of the availability of at least one of
satellite and terrestrial resources and administering
reconfiguration, assignment and/or reuse of frequencies within the
predetermined frequency band to meet changed traffic patterns or
other predetermined conditions. The means for maintaining
cognizance is optionally operatively connected to at least a mobile
switching center that assigns a channel to subscriber units. The
means for maintaining cognizance optionally utilizes hysteresis
and/or negative hysteresis in the reconfiguration, assignment
and/or reuse of the frequencies.
[0127] There has thus been outlined, rather broadly, the more
important features of the invention in order that the detailed
description thereof that follows may be better understood, and in
order that the present contribution to the art may be better
appreciated. There are, of course, additional features of the
invention that will be described hereinafter and which will form
the subject matter of the claims appended hereto.
[0128] In this respect, before explaining at least one embodiment
of the invention in detail, it is to be understood that the
invention is not limited in its application to the details of
construction and to the arrangements of the components set forth in
the following description or illustrated in the drawings. The
invention is capable of other embodiments and of being practiced
and carried out in various ways. Also, it is to be understood that
the phraseology and terminology employed herein are for the purpose
of description and should not be regarded as limiting.
[0129] As such, those skilled in the art will appreciate that the
conception, upon which this disclosure is based, may readily be
utilized as a basis for the designing of other structures, methods
and systems for carrying out the several purposes of the present
invention. It is important, therefore, that the claims be regarded
as including such equivalent constructions insofar as they do not
depart from the spirit and scope of the present invention.
[0130] Further, the purpose of the foregoing abstract is to enable
the U.S. Patent and Trademark Office and the public generally, and
especially the scientists, engineers and practitioners in the art
who are not familiar with patent or legal terms or phraseology, to
determine quickly from a cursory inspection the nature and essence
of the technical disclosure of the application. The abstract is
neither intended to define the invention of the application, which
is measured by the claims, nor is it intended to be limiting as to
the scope of the invention in any way.
[0131] These together with other objects of the invention, along
with the various features of novelty which characterize the
invention, are pointed out with particularity in the claims annexed
to and forming a part of this disclosure. For a better
understanding of the invention, its operating advantages and the
specific objects attained by its uses, reference should be made to
the accompanying drawings and descriptive matter in which there is
illustrated preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0132] FIG. 1 is a prior art diagram of a satellite radiotelephone
system;
[0133] FIGS. 2A, 2B and 2C are prior art schematic diagrams of
frequency reuse in the satellite radiotelephone system shown in
FIG. 1;
[0134] FIG. 3 is a diagram showing an overview of the principal
elements of a prior art communications system;
[0135] FIG. 4 is an overview block diagram of another embodiment of
the prior art communications system shown in FIG. 3;
[0136] FIG. 5 is an exemplary high level block diagram of a system
that can use and/or be used to produce the frequency reuse schemes
in accordance with the present invention;
[0137] FIG. 6a is an exemplary illustration of how a base
transceiver station can enhance network coverage, particularly in
an area having no line of sight path (or reduced line of sight
path) with a satellite;
[0138] FIG. 6b shows, for an embodiment of the present invention
using a single satellite, exemplary satellite uplink and downlink
frequency bands commonly used by and shared with the terrestrial
system;
[0139] FIG. 6c shows, for an embodiment of the present invention
using two or more satellites, exemplary satellite uplink and
downlink frequency bands commonly used by and shared with the
terrestrial system;
[0140] FIG. 6d shows, for an embodiment of the present invention
using a single satellite, exemplary satellite uplink and downlink
frequency bands;
[0141] FIG. 6e shows, for an embodiment of the present invention
using two or more satellites, exemplary satellite uplink and
downlink frequency bands;
[0142] FIG. 6f shows two frequency bands, each having channels that
can be utilized by the satellite and/or terrestrial components;
[0143] FIG. 6g shows a single frequency band with channels that can
be utilized by the satellite and/or terrestrial components;
[0144] FIG. 7a is an exemplary high level block diagram
illustrating an integrated satellite-terrestrial system that can
use and/or be used, for example, to produce the frequency reuse
schemes in accordance with the present invention;
[0145] FIG. 7b is an exemplary high level block diagram
illustrating an integrated satellite-terrestrial system, utilizing
a radio resource manager, that can use and/or be used, for example,
to produce the frequency reuse schemes in accordance with the
present invention;
[0146] FIG. 7c is an exemplary high level block diagram
illustrating a satellite-terrestrial system having autonomous
satellite and terrestrial components that can use and/or be used,
for example, to produce the frequency reuse schemes in accordance
with the present invention;
[0147] FIGS. 8a, 8b, 8c and 8d show exemplary embodiments of the
present invention pertaining to how uplink and downlink frequencies
can be utilized in the satellite and terrestrial components;
[0148] FIG. 9 is an exemplary schematic showing how link margins
can be affected when utilizing different air interfaces for the
satellite and terrestrial components;
[0149] FIG. 10 shows an exemplary seven cell satellite spot beam
pattern that can be used in connection with the present
invention;
[0150] FIG. 11 is an exemplary schematic showing how terrain
blockage can affect assignment of frequencies;
[0151] FIG. 12a shows an exemplary flow diagram of an overall
system method, including assignment and reuse of channels based on
signal strength, in accordance with the present invention;
[0152] FIG. 12b shows an exemplary flow diagram of a second overall
system method, including assignment and reuse of channels based on
signal strength, in accordance with the present invention;
[0153] FIG. 13 is a high level flow diagram illustrating the static
and dynamic channel assignment features of the present
invention;
[0154] FIG. 14 shows an exemplary flow diagram of call
initialization when terrestrial mode is preferred while using
common or partially overlapping frequency bands as shown, for
example, in FIGS. 6b, 6c, 6f and 6g;
[0155] FIG. 15 shows an exemplary flow diagram of call
initialization when terrestrial mode is preferred while using
discrete satellite and terrestrial frequency bands as shown, for
example, in FIGS. 6d and 6e;
[0156] FIG. 16 shows an exemplary flow diagram of base
station-to-base station or base station-to-satellite handoff while
using common or partially overlapping frequency bands as shown, for
example, in FIGS. 6b and 6c;
[0157] FIG. 17 shows an exemplary flow diagram of base
station-to-base station or base station-to-satellite handoff while
using discrete satellite and terrestrial frequency bands as shown,
for example, in FIGS. 6d and 6e;
[0158] FIG. 18 shows an exemplary method of satellite-to-base
station or satellite-to-satellite handoff while using common or
partially overlapping frequency bands as shown, for example, in
FIGS. 6b and 6c;
[0159] FIG. 19 shows an exemplary method of satellite-to-base
station or satellite-to-satellite handoff while using discrete
satellite and terrestrial frequency bands as shown, for example, in
FIGS. 6d and 6e; and
[0160] FIGS. 20a and 20b, taken together, show an exemplary method
of inverse assignment of the channels.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
[0161] FIG. 5 shows an exemplary high level block diagram of a
standard system 500 that can be used to implement the frequency
assignment, reuse and/or reassignment, and other features of the
present invention. The telemetry, tracking and command (TT&C)
facility 502 is used to control and monitor the one or more
satellites 516 of the system 500.
[0162] The terrestrial segment can use digital cellular technology,
consisting of or including one or more Gateway Station Systems
(GSS) 504, a Network Operations Center (NOC) 506, one or more
Mobile Switching Centers (MSC) 508, one or more Base Transceiver
Stations (BTS) 514, and a variety of mobile, portable, Personal
Digital Assistant (PDA), computer and/or fixed subscriber terminals
512. The subscriber terminals 512 can be equipped with a Subscriber
Identity Module (SIM) (not shown) or similar module that identifies
the individual subscriber terminal 512. The subscriber terminals
512 are generally handheld devices that provide voice, video and/or
data communication capability. Subscriber terminals 512 may also
have additional capabilities and functionality such as, for
example, paging. Equipping the subscriber terminals 512 with a SIM
module can allow the user to have access to the system 500 by using
any subscriber terminals 512 having an authorized SIM.
[0163] The MSC 508 preferably performs the switching functions of
the system 500, and also optionally provides connection to other
networks (e.g., Public Data Network (PDN) 517, and/or Public
Switched Telephone Network (PSTN) 518). Since the subscriber
terminals 512 do not know what channels are actually being used by
the satellite and/or terrestrial system, the MSC 508 in accordance
with at least one embodiment of the present invention optionally
identifies the channels that are in use and the channels that are
not in use. In another embodiment, the MSC 508 can receive updates
from each terrestrial and satellite control center and or one or
more radio resource managers (RRM) regarding which channels are in
use. The MSC 508 is preferably connected to a BSC 510 which, in
turn, is preferably connected to a BTS 514. Therefore, in at least
one embodiment of the present invention, the MSC 508, via one or
more RRMs, determines which channels are in use or not in use.
[0164] Subscriber terminals 512 are preferably providing signal
strength measurements and/or other measurements such as
interference level, of the satellites 516 to, for example, a BTS
514. It is preferred that the BSC 510 assign a channel to the
subscriber terminal 512. It is also preferred that the BSC 510
first assign to the subscriber terminal 512 a channel that is not
in use by the satellite. If all of the channels are in use, then
the BSC 510 selects, for example, the satellite channel having the
weakest signal strength relative to the subscriber terminal 512.
Alternatively, any standard algorithm can optionally be used to
determine a preferred channel to use.
[0165] BTSs 514 can be used in those areas where the satellite
signal is attenuated by, for example, terrain and/or morphological
features, and/or to provide in-building coverage. The BTSs 514 and
BSCs 510 generally provide and control the air interface to the
subscriber terminals 512. The BTSs 514 can optionally use any
standard wireless protocol that is very similar to that of the
satellites 516. Alternatively, BTSs 514 can use a first air
interface (e.g., CDMA), and the satellite 516 can use a second air
interface (e.g., GSM, or Global Mobile Satellite Systems (GMSS),
which is a satellite air interface standard which is developed from
GSM). The BSC 510 generally controls one or more BTSs 514 and
manages their radio resources. BSC 510 is principally in charge of
handovers, frequency hopping, exchange functions and control of the
radio frequency power levels of the BTSs 514.
[0166] NOC 506 can provide functions such as, for example,
monitoring of system power levels to ensure that transmission
levels remain within tolerances, and line monitoring to ensure the
continuity of the transmission lines that interconnect the BSC 510
to the BTS 514, that interconnect the MSC 508 to the PDN 517 and
that interconnect the PSTN 518, and the NOC 506 to other network
components. The NOC 506 can also monitor the satellite 516
transponders to ensure that they are maintained within frequency
assignment and power allocation tolerances. The NOC 506 also
ensures that communication resources are available and/or assigned,
reused and/or borrowed in a timely manner to, for example,
facilitate calls originating and/or transmitted to a subscriber
terminal 512. Finally, to effectuate, for example, the dynamic
channel assignment of the present invention, the NOC 506 generally
maintains cognizance of the availability of satellite and/or
terrestrial resources and arranges for any necessary satellite
reconfiguration and/or assignment and or reuse of frequencies to
meet changed traffic patterns. An exemplary NOC is described in
U.S. Pat. No. 5,926,745, incorporated herein by reference.
[0167] The system 500 will also have one or more satellites 516
that communicate with the GSS 504 and the subscriber terminals 512.
A typical GSS 504 will have an antenna to access the satellite 516.
On the uplink transmission path, the GSS 504 will generally have
upconverters that can translate the GSS 504 intermediate frequency
(IF) to the feeder link frequency. On the downlink transmission
path, the received signal is preferably amplified, and feeder link
frequencies are translated to the common IF.
[0168] The system 500 generally comprises satellite and terrestrial
components. Satellite components comprise, for example, TT&C
502, GSS 504, and satellite 516. Terrestrial components comprise,
for example, BSC 510 and BTSs 514. In the FIG. 5 embodiment, the
NOC 506, MSC 508 are shared by the satellite and terrestrial
systems. As will be discussed with regard to FIGS. 7a-7d, alternate
embodiments of the present invention provide, for example, separate
NOCs 506 and/or MSCs 508 for the satellite and terrestrial
components to facilitate autonomous or substantially autonomous
operation.
[0169] FIG. 6a is an exemplary BTS 514 frequency plan. The
nomenclature is provided as follows: [0170] f.sup.U.sub.1a and
f.sup.D.sub.1a [0171] superscripts U and D indicate uplink and
downlink, respectively; [0172] the numeric subscript (e.g., 1)
indicates the frequency band; and [0173] the letter subscript
(e.g., a) indicates the channel within the frequency band.
[0174] Users communicating on uplink 604 and downlink 602 would
use, for example, paired uplink and downlink channels
f.sup.U.sub.1a and f.sup.D.sub.1a, f.sup.U.sub.1b and
f.sup.D.sub.1b, f.sup.U.sub.1c and f.sup.D.sub.1c, etc.
Advantageously, in the present invention, different channels within
the same frequency band, or different frequency bands, are
optionally assigned, reused and/or reassigned in a non-pairwise
manner. For example, downlink 602 could be using f.sup.D.sub.1a,
whereas uplink 604 could be using f.sup.U.sub.1b. Similarly,
downlink 602 could be using f.sup.D.sub.1c, whereas uplink 604
could be using f.sup.U.sub.1d. These pairings are illustrative
only, insofar as numerous other non-pairwise uplink 604 and
downlink 602 combinations are available that can be used, for
example, within different terrestrial cells, within different areas
of a spot beam, and/or between different spot beams.
[0175] Further, suppose that f.sup.U.sub.2a and f.sup.D.sub.2a are
the uplink and downlink frequency bands associated with a second
domestic or foreign satellite system. Users of system 500
communicating on downlink 602 and uplink 604 could use, for
example, uplink and downlink frequencies f.sup.U.sub.1a and
f.sup.D.sub.2a, f.sup.U.sub.1c and f.sup.D.sub.2b, f.sup.U.sub.1b
and f.sup.D.sub.2c, etc. In general, the present invention
optionally uses one or more uplink and downlink channels that are
from different frequency bands and/or associated with a different
domestic and/or foreign satellite system.
[0176] FIG. 6b shows, for a single satellite system, illustrative
uplink 604 and downlink 602 frequencies/channels that can be used
with the satellite component. Each channel generally comprises a
control portion and a data or voice portion. As shown, and as will
be discussed in more detail with regard to FIGS. 8a-8c, the
satellite uplink 604 and downlink 602 frequencies, in accordance
with at least one embodiment of the present invention, are commonly
used and shared by the terrestrial component, and generally
comprise a range of separated frequencies (e.g., 1626.5-1660.5 MHz
for uplink, and 1525-1559 MHz for downlink). The present invention
is not limited, however, to sharing frequencies within a single
frequency band assigned and/or designated by, for example, a
government regulatory agency. The present system may also
therefore, share and/or reuse frequencies of other domestic,
foreign, and/or international satellite and/or terrestrial systems,
subject to, for example, national, foreign, and/or international
government regulatory approval.
[0177] Accordingly, as defined in connection with the present
invention, a frequency band comprises any set of frequencies, and
is not limited to a consecutive set or series of frequencies.
Further, a frequency band in alternative embodiments may comprise a
logical set of frequencies that may be assigned to different
communication systems, carriers, or in other predesignated
frequency bands. That is, for example, a frequency band in the
present invention may include frequencies that are assigned to
other frequency bands, for example, for different purposes. With
regard to FIG. 6b, individual channels 603, 605 are shown within
frequency bands 604, 602, respectively.
[0178] FIG. 6c shows, for a multiple satellite system, illustrative
uplinks 604a, 604b and downlinks 602a, 602b within the frequency
bands of the satellite system. FIG. 6c can equally be used to
provide different frequency bands associated with various spot
beams of a single satellite, and/or subparts or subsectors of a
single spot beam. As shown, the satellite uplink 604a, 604b and
downlink 602a, 602b frequencies, in accordance with at least one
embodiment of the present invention, are commonly used and shared
by the terrestrial system, and generally comprise a range of
separated frequencies (e.g., 1626.5-1643 MHz for satellite 1 uplink
604a, 1644-1660.5 MHz for satellite n uplink 604n, and 1525-1542
MHz for satellite 1 downlink 602a, and 1543-1559 MHz for satellite
n downlink 602n). Individual channels 607, 609 are shown within
uplink frequency bands 604a, 604b, respectively, and individual
channels 611, 613 are shown within downlink frequency bands 602a,
602b, respectively.
[0179] FIG. 6d shows an alternate embodiment of the frequency bands
of FIG. 6b in which the satellite frequencies 602c, 604c and the
terrestrial frequencies 602d, 604d are discrete. That is, in
contrast to the frequency bands shown in FIG. 6b, where satellite
and terrestrial frequencies comprise common frequency bands 602,
604, in FIG. 6d there is no sharing of satellite and terrestrial
frequencies within a common frequency band. Individual channels
611, 613, 615, and 617, are shown within frequency bands 602c,
602d, 604c, and 604d, respectively.
[0180] FIG. 6e shows an alternate embodiment of the frequency bands
of FIG. 6c in which the satellite frequencies 602e, 602f, 604e,
604f and terrestrial frequencies 602g, 604g are discrete. That is,
in contrast to the frequency bands shown in FIG. 6c, where
satellite and terrestrial frequencies comprise common frequency
bands 602a, 602b, 604a, 604b, in FIG. 6e there is no sharing of
satellite and terrestrial frequencies within a common frequency
band. Individual channels 619, 621, 623, 625, 627, and 629 are
shown within frequency bands 602e, 602f, 602g, 604e, 604f and 604g,
respectively. FIG. 6e can equally be used to provide different
frequency bands associated with various spot beams of a single
satellite, and/or subparts or subsectors of a single spot beam.
[0181] FIG. 6f shows an alternate embodiment of the frequency bands
of FIG. 6b. In FIG. 6f, frequency bands 606a, 606b each contain
channels that can be used for satellite uplink, satellite downlink
and/or terrestrially. FIG. 6g shows a single frequency band 608
that contains channels that can be used for satellite uplink,
satellite downlink and/or terrestrially.
[0182] FIG. 7a is an exemplary high level block diagram of a
satellite-terrestrial system that can use, for example, the
frequency assignment and/or reuse schemes in accordance with the
present invention. The system of FIG. 7a is at least partially
integrated in that the satellite component and the terrestrial
component each share a common NOC 506 and MSC 508 (wherein S-MSC
represents the satellite portion of the MSC 508, and T-MSC
represents the terrestrial portion of the MSC).
[0183] Although FIG. 7a illustrates a GSM architecture, the
satellite and terrestrial components comprising the system 500 of
the present invention are not limited to the use of a GSM system,
and can be deployed with all satellite (e.g., LEO, MEO, GEO, etc.)
and cellular terrestrial technologies (e.g., TDMA, CDMA, GSM, etc.,
or any combinations thereof).
[0184] An exemplary Home Location Register (HLR) 706 comprises a
database that stores information pertaining to the subscribers
belonging to the system 500. The HLR 706 also stores the current
location of these subscribers and the services to which they have
access. In an exemplary embodiment, the location of the subscriber
corresponds to the SS7 504 address of the Visitor Location Register
(VLR) 702 associated with the subscriber terminal 512.
[0185] An exemplary VLR 702 contains information from a
subscriber's HLR 706 in order to provide the subscribed services to
visiting users. When a subscriber enters the covering area of a new
MSC 508, the VLR 702 associated with this MSC 508 will request
information about the new subscriber to its corresponding HLR 706.
The VLR 702 will then have enough information in order to
administer the subscribed services without needing to ask the HLR
706 each time a communication is established. The VLR 702 is
optionally implemented together with a MSC 508, so the area under
control of the MSC 508 is also the area under control of the VLR
702.
[0186] The Authentication Center (AUC) 708 register is used for
security purposes, and generally provides the parameters needed for
authentication and encryption functions. These parameters help to
verify the user's identity.
[0187] In accordance with the present invention, and as disclosed
in U.S. Pat. No. 5,812,968, which in incorporated herein by
reference, a subscriber terminal 512 can optionally utilize a
standard variable rate vocoder (i.e., a voice encoder that at two
or more data rates codes/decodes, for example, human speech
into/from digital transmission) or multiple vocoders, each
transmitting at a different data rate to, for example, increase
effective system 500 bandwidth, voice or data quality, received
signal level, and/or link margin. As used herein, link margin is
defined as the difference between the signal-to-noise ratio
available to the receiver (e.g., subscriber terminal 512, BTS 514
and/or satellite 516) and the signal-to-noise ratio needed at the
receiver to achieve a specific performance (e.g., Bit Error Rate
(BER)).
[0188] For example, one or more of the subscriber terminals 512 can
have a variable rate vocoder used for both satellite and
terrestrial communication having data rates of, for example, 13.0
kbit/sec, 6.0 kbit/sec, 3.6 kbit/sec, 2.4 kbit/sec, and 2.0
kbit/sec. Alternatively, one or more of the subscriber terminals
512 can have, for example, a variable rate vocoder for terrestrial
communications, and a variable rate vocoder for satellite
communications. One or more of the subscriber terminals 512 could
also have a plurality of vocoders having different data rates and
used for terrestrial communication, and a plurality of vocoders
having different data rates and used for satellite communication.
The MSC 508 and/or the GSS 504 and BSC 510, for example, can also
utilize corresponding vocoders to coordinate data rate selection
and/or transition.
[0189] If the system 500 determines that system 500 channel usage,
or channel usage within a portion of the system 500, is reaching a
predetermined threshold (e.g., 90%), a control signal can be
transmitted to one or more subscriber terminals 512 directing usage
of a lower vocoder data rate. Thus if the subscriber terminal 512
was utilizing, for example, a vocoder having a 13.0 kbit/sec data
rate, the subscriber terminal 512 could now be directed to utilize,
for example, a vocoder having a 2.4 kbit/sec data rate, thereby
increasing the effective bandwidth of the system 500 (by permitting
additional calls). Use of a higher data rate can optionally resume
when channel usage falls below a predetermined threshold (e.g.,
60%).
[0190] Similarly, if the system 500 determines that the BER exceeds
a predetermined threshold (e.g., 10.sup.-3 for voice), the system
500 can transmit a control signal to one or more subscriber
terminals 512 directing usage of a lower vocoder data rate. Thus if
the subscriber terminal 512 was utilizing a vocoder having a 13.0
kbit/sec data rate, the subscriber terminal 512 could now be
directed to utilize a vocoder having, for example, a 2.4 kbit/sec
data rate, thereby reducing the bit error rate by effectively
increasing the available link margin. Use of a higher vocoder rate
can optionally resume when voice quality and/or link margin exceeds
a predetermined threshold.
[0191] Specifically, the satellite 516 or a BSC 510 could send a
control signal to, for example, the subscriber terminal 512,
optionally via MSC 508, indicating whether the signals received
from the subscriber terminal 512 are of a sufficient quality. For
example, a GSM-based Fast Associated Control Channel (FACCH)
signal, which is used for time critical signaling such as when
performing handovers, can be sent to a subscriber terminal 512 to
indicate that the signals received are not of sufficient quality. A
receiver unit (not shown), for example, within the subscriber
terminal 512 can in turn send a control signal to, for example, a
variable rate vocoder within the subscriber terminal 512 to cause
the vocoder to reduce the bit rate of the signal being transmitted
from the subscriber terminal 512 to the satellite 516.
[0192] Finally, the variable rate vocoder can be used to improve
the effective received signal level as determined by, for example,
received signal strength indication (RSSI), which is the measured
power of a received signal. The RSSI is a relative measure of
received signal strength for a particular subscriber terminal 512,
and can optionally be based on, for example, automatic gain control
settings. If the system 500 determines that the RSSI is below a
predetermined threshold, the MSC 508, for example, can transmit a
control signal to one or more subscriber terminals 512 to utilize a
lower vocoder data rate. Thus, if one or more of the subscriber
terminals 512 was utilizing a data rate of 13.0 kbit/sec, the
subscriber terminal(s) 512 could now utilize a data rate of 2.4
kbit/sec, thereby increasing the effective link margin.
[0193] FIG. 7b is an exemplary high level block diagram
illustrating another embodiment of the satellite-terrestrial system
that utilizes a radio resource manager (RRM) 720. The RRM 720 is
preferably communicable with GSS 504, with the BSCs 510 (not
shown), with the MSC 508, and/or with one or more BTSs 514. The RRM
720 is preferably used to determine channels currently in use, and
to optionally monitor inband interference to avoid, for example,
using channels expected to cause unacceptable levels of
interference (e.g., a level of interference exceeding a
predetermined threshold as defined, for example, by BER). The RRM
720 can also optionally be used to monitor received signal quality
and available link margin, and execute, for example, an intra-beam
and/or intra-band hand-over of the communications channel when a
quality measure thereof has fallen below a predetermined level
and/or has exhausted a predetermined amount of link margin.
[0194] The RRM 720 preferably has means for determining which
channels are being used by the system 500. For example, RRM 720 can
comprise or utilize, for example, a suitable antenna operatively
connected to a spectrum analyzer capable of searching, for example,
one or more frequency bands for the presence of radio signals, and
to determine what channels are currently being utilized within the
frequency band(s). Thus, by being able to monitor usage of one or
more of the frequency bands shown, for example, in FIGS. 6b-6e, the
RRM 720 can identify all of the channels allocated to the system
500 that are currently being used. Alternatively, the system 500,
via direct connection can inform the RRM 720 as to what channels
are in use. In this embodiment, the RRM 720 does not need to
monitor whether the channels are being used by either the satellite
or terrestrial component(s); the RRM 720 simply determines whether
a channel is currently in use or not in use.
[0195] As discussed with regard to the embodiment of the present
invention shown in FIG. 7a, the subscriber terminals 512 of the
embodiment shown in FIG. 7b can also utilize a variable rate
vocoder or multiple vocoders, each transmitting at a different data
rate to, for example, increase effective system 500 bandwidth,
voice quality, effective received signal level, and/or link margin.
The MSC 508 and/or the GSS 504 and BSC 510 (not shown), for
example, can also utilize corresponding vocoders to coordinate data
rate selection and/or transition.
[0196] If the system 500 determines that system channel usage, or
channel usage within a portion of the system 500, is reaching a
predetermined threshold (e.g., 90%), a control signal can be
transmitted to one or more subscriber terminals 512 directing usage
of a lower vocoder rate. Thus if the subscriber terminal 512 was
utilizing a vocoder having a 13.0 kbit/sec data rate, the
subscriber terminal 512 could now be directed to utilize, for
example, a vocoder having a 2.4 kbit/sec data rate, thereby
increasing the effective bandwidth of the system 500 (by permitting
additional calls utilizing a lower data rate). Use of a higher data
rate can optionally resume when channel usage falls below a
predetermined threshold (e.g., 60%).
[0197] Similarly, if the system 500 determines that voice quality
as determined by, for example, bit error rate exceeds a
predetermined threshold (e.g., 10.sup.-3 for voice), the system 500
can transmit a control signal to one or more subscriber terminals
512 directing usage of a lower vocoder data rate. Thus, if a
subscriber terminal 512 was utilizing a vocoder having a 13.0
kbit/sec data rate, the subscriber terminal 512 could now be
directed to utilize a vocoder having a 2.4 kbit/sec data rate,
thereby reducing the bit error rate. Use of a higher vocoder rate
can optionally resume when voice or data quality exceeds a
predetermined threshold.
[0198] Specifically, the satellite 516 or a BSC 510 (not shown),
for example, can send a signal to a subscriber terminal 512, via
MSC 508, indicating whether the signals received from the
subscriber terminal 512 are of a sufficient quality. For example, a
GSM-based FACCH signal, as previously discussed, can be sent to a
subscriber terminal 512 to indicate that the signals received are
not of sufficient quality. A receiver unit (not shown), for
example, within a subscriber terminal 512 can in turn send a
control signal to, for example, a variable rate vocoder within the
subscriber terminal 512 to cause the vocoder to reduce the bit rate
of the signal being transmitted from the subscriber terminal 512 to
the satellite 516.
[0199] Finally, the variable rate vocoder can be used to improve
effective received signal level as determined by, for example,
RSSI. In this case, if the system 500 determines that the RSSI is
below a predetermined threshold, the MSC 508, for example, can
transmit a control signal to one or more subscriber terminals 512
to utilize a lower vocoder data rate. Thus if the subscriber
terminal 512 was utilizing a data rate of 13.0 kbit/sec, the
subscriber terminal 512 could now utilize a data rate of 2.4
kbit/sec, thereby increasing effective RSSI and/or link margin.
[0200] FIG. 7c is an exemplary high level block diagram
illustrating another embodiment of an autonomous
satellite-terrestrial system in accordance with the present
invention. In this embodiment, the satellite and terrestrial
components each have their own RRMs 720a and 720b, MSCs 508a, 508b,
and NOCs 506a, 506b, respectively. As shown, the satellite and
terrestrial components also have their own respective VLRs 702a,
702b, HLRs 706a, 706b, and AUCs 718a, 718b. In alternate
embodiments, the VLRs 702a, 702b, HLRs 706a, 706b, and/or AUCs
718a, 718b can also be connected to, for example, the PSTN 518.
[0201] As discussed with regard to FIG. 5, the NOCs 506a, 506b
ensure that communication resources are available and/or assigned,
reused and/or borrowed in a timely manner. Thus, by advantageously
providing separate NOCs 506a, 506b, MSCs 508a, 508b, RRMs 720a,
720b, VLRs 702a, 702b, HLRs 706a, 706b, and AUCs 718a, 718b in this
embodiment, the satellite and terrestrial components, while sharing
and/or being assigned to at least a portion of a common frequency
band can operate independently of each other.
[0202] Since, as previously discussed, RRMs 720a, 720b can
determine the channels currently being utilized, RRM 720b can
therefore determine, independently and without communication with
RRM 720a or any other satellite component equipment, what channels
are not being used for satellite communication by the system 500.
For example, the RRMs 720a, 720b can comprise or utilize, for
example, a suitable antenna operatively connected to a spectrum
analyzer capable of searching a band of radio frequencies for the
presence of radio signals, to determine what frequencies are
currently being utilized within a range or ranges of frequencies of
interest. RRM 720b can therefore determine, independently and
without communication with RRM 720a associated with the satellite
component, or any other satellite component equipment, what
frequencies are not being used by the system for satellite
communication. Since the RRM 720b knows the frequencies used across
a range of frequencies of interest, as well as the frequencies used
by the terrestrial component, RRM 720b can also determine or deduce
the frequencies that are currently being used by the satellite
component. Similarly, the satellite component functions in
substantially the same manner to, inter alia, determine the
frequencies currently being used by the terrestrial component.
[0203] Similarly, RRM 720a could also use, for example, an antenna
in combination with frequency and/or spectrum analysis techniques
to determine, independently and without communication with RRM 720b
or any other terrestrial component equipment, what channels are
being used by the system 500 for terrestrial communications. Since
RRM 720a knows all of the channels used across a range of
frequencies of interest, as well as the channels used by the
satellite component, RRM 720a can identify the channels that are
currently being used by the terrestrial component.
[0204] As discussed with regard to the embodiment of the present
invention shown in FIGS. 7a and 7b, the subscriber terminals 512 of
the embodiment shown in FIG. 7c can also utilize a variable rate
vocoder or multiple vocoders, each transmitting at a different data
rate to, for example, increase effective system 500 bandwidth,
voice quality, received signal level, and/or link margin. The MSC
508a, 508b and/or the GSS 504 and BSC 510 (not shown), for example,
can also utilize corresponding vocoders to coordinate data rate
selection and/or transition.
[0205] If the system 500 determines that system 500 channel usage,
or channel usage within a portion of the system 500, is reaching a
predetermined threshold (e.g., 90%), a control signal can be
transmitted to one or more subscriber terminals 512 directing usage
of a lower vocoder data rate. Thus, if a subscriber terminal 512
was utilizing a vocoder having a 13.0 kbit/sec data rate, the
subscriber terminal 512 could now utilize, for example, a vocoder
having a 2.4 kbit/sec data rate, thereby increasing the effective
bandwidth of the system 500 (by permitting additional calls
utilizing a lower data rate). Use of a higher data rate can
optionally resume when channel usage falls below a predetermined
threshold (e.g., 60%).
[0206] Similarly, if the system 500 determines that voice or data
quality as determined by, for example, bit error rate exceeds a
predetermined threshold (e.g., 10.sup.-3 for voice), the system 500
can transmit a control signal to one or more subscriber terminals
512 directing usage of a lower vocoder data rate. Thus, if a
subscriber terminal 512 was utilizing a vocoder having a 13.0
kbit/sec data rate, the subscriber terminal 512 could now be
directed to utilize a vocoder having a 2.4 kbit/sec data rate,
thereby reducing the bit error rate. Use of a higher vocoder rate
can optionally resume when voice quality exceeds a predetermined
threshold.
[0207] Specifically, the satellite 516 or a BSC 510 (not shown) can
send a signal to the subscriber terminal 512, via MSC 508a or MSC
508b, respectively, indicating whether the signals received from
the subscriber terminal 512 are of a sufficient quality. For
example, a GSM-based FACCH signal, as previously discussed, can be
sent to a subscriber terminal 512 to indicate that the signals
received are not of sufficient quality. A receiver unit (not
shown), for example, within the subscriber terminal 512 can in turn
send a control signal to, for example, a variable rate vocoder
within the subscriber terminal 512 to cause the vocoder to reduce
the bit rate of the signal being transmitted from the subscriber
terminal 512 to the satellite 516 or to the BTS 514.
[0208] Finally, the variable rate vocoder can be used to improve
received signal level as determined by, for example, RSSI. In this
case, if the system 500 determines that the RSSI is below a
predetermined threshold, the respective MSC 508a, 508b, for
example, can transmit a control signal to one or more subscriber
terminals 512 to utilize a lower vocoder data rate. Thus, if a
subscriber terminal 512 was utilizing a data rate of 13.0 kbit/sec,
the subscriber terminal 512 could now utilize a data rate of 2.4
kbit/sec, thereby increasing the effective RSSI and/or link
margin.
[0209] FIGS. 8a, 8b, and 8c show exemplary embodiments of the
present invention pertaining to how uplink and downlink frequencies
can be utilized in or by the satellite and terrestrial components.
FIG. 8a shows a first exemplary embodiment where the satellite 516
downlink f.sub.1 is used, assigned and/or reused as the terrestrial
downlink f.sub.1. Similarly, the satellite uplink f.sub.2 is used
as the terrestrial uplink link f.sub.2. Interference with channels
typically may result when, for example, a subscriber terminal 512
has a direct line of sight path to one or more satellites, and also
has a communication link with a terrestrial BTS having the same or
nearby frequency.
[0210] The embodiment shown in FIG. 8b involves reversing the
satellite downlink f.sub.1 and satellite uplink f.sub.2 frequencies
to become the terrestrial uplink link f.sub.1 and terrestrial
downlink link f.sub.2 frequencies, respectively. As a result, there
will be two possible interference paths: (1) between the satellite
516 and BTS 514, as uplink to downlink interference on f.sub.1, and
as uplink to downlink interference on f.sub.2; and (2) between the
satellite subscriber terminals 512a and terrestrial subscriber
terminals 512b, as downlink to uplink interference on f.sub.1, and
as downlink to uplink interference on f.sub.2. Measures should be
taken to eliminate or substantially reduces both of these possible
interferences.
[0211] For example, to minimize these interferences, BTSs 514 that
have a substantially reduced gain in the geostationary arc (i.e.,
the elevation angle above the horizon from a base station to the
satellite) can be utilized. Within North America, the geostationary
arc typically varies from approximately 30.degree. to 70.degree.,
depending, for example, on the latitude of the base station. To
fully take advantage of this fact, it is preferred that the base
station antenna pattern have a null, and therefore significantly
reduced gain, in the geostationary arc portion of its vertical
pattern.
[0212] In addition, it is preferred that the BTSs 514 be optimally
or substantially optimally located and oriented to advantageously
utilize the horizontal gain pattern of the antenna. The benefits of
using this technique, for example, are that frequency reuse will be
maximized or substantially maximized, thereby enhancing the overall
capacity of the system, and further reducing or eliminating
interference.
[0213] In addition to the increased isolation provided by the
vertical antenna pattern, additional isolation can be obtained from
the horizontal antenna pattern. For example, preferably by
configuring BTSs 514 such that the azimuth to the satellite is
off-bore or between sectors, several additional dB of isolation can
typically be achieved. By keeping this configuration standard for,
say, a cluster of base stations, frequency reuse for the
terrestrial system can generally be increased.
[0214] Interference between satellite subscriber terminals 512a and
terrestrial subscriber terminals 512b is typically a problem when
the units are in relatively close proximity to one another. It is
preferred that such interference be substantially reduced or
eliminated by, for example, first detecting close proximity before
the assignment of a radio channel (i.e., during call
initialization), and secondly by providing a hand-off to a
non-interfering channel if close proximity occurs after the
assignment of a radio channel. For example, a relatively small
group of channels, called "transition channels", can be reserved
for single-mode terminals. The single mode terminals preferably use
transition channels while inside base station coverage. It is also
preferred that dual-mode terminals also use the transition channels
under certain circumstances. For example, after a dual mode
terminal scans channels for signal strength and interference, a
transition channel can be utilized if unacceptable levels of
interference are detected.
[0215] The embodiment shown in FIG. 8c involves using the satellite
system uplink f.sub.2 as both the terrestrial system downlink
f.sub.2 and uplink f.sub.2 frequencies using time division duplex
techniques. In alternate embodiments, the terrestrial downlink and
uplink frequencies are optionally discrete bands. For example,
downlink frequencies may comprise f.sub.2a, and uplink frequencies
may comprise f.sub.2b.
[0216] Finally, the embodiment shown in FIG. 8d involves using the
satellite system downlink f.sub.1 as both the terrestrial system
downlink f.sub.1 and uplink f.sub.1 frequencies using time division
duplex techniques. In alternate embodiments, the terrestrial
downlink and uplink frequencies are optionally discrete bands. For
example, downlink frequencies may comprise f.sub.1a, and uplink
frequencies may comprise f.sub.1b.
[0217] FIG. 9 is an exemplary schematic showing how link margins
can be affected when the satellite and terrestrial components use
different air interfaces simultaneously in overlapping areas of
coverage. FIG. 9 assumes that the satellite component uses GSM 902,
and that the terrestrial component uses CDMA 904. However, the
principles discussed herein with regard to FIG. 9 are generally
applicable to any air interface(s) that may be used with the
satellite and terrestrial components.
[0218] As shown, the GSM channel 902 can be a 200 kHz channel, and
the CDMA channel 904 can be a 1.25 MHz channel. If the satellite
component is using the GSM channel 902 and the terrestrial
component is not operating (i.e., the 1.25 CDMA channel is not
being used), there will be a noise floor A, and the subscriber
terminals 512 will provide output at power level 910. The link
margin can be increased by, for example, increasing power output
level 910, reducing noise floor A, or a combination thereof.
[0219] When the terrestrial system goes into use, the noise floor
is indicated by C, which generally corresponds to the aggregate
power output of the CDMA channel 904. In order to compensate for
the increased noise floor C and increase their link margin,
subscriber terminals 512 operating in the GSM/satellite mode will
provide output at power level 912 to overcome the higher noise
floor C. Accordingly, subscriber terminals will provide output at
912 to provide sufficient link margin.
[0220] Now, consider the situation in which subscriber terminals
512 are using the CDMA channel 904, but not the GSM channel 902. In
such a case, the terrestrial component will generally be able to
utilize all n COMA channels per carrier.
[0221] When the satellite component goes into use, subscriber
terminals 512 operating in the satellite mode will detect noise
floor C, assuming that subscriber terminals 512 are utilizing all n
COMA channels. Accordingly, subscriber terminals 512 operating in
the satellite mode will output at level 912, which appears as noise
to the subscriber terminals 512 operating in the terrestrial mode.
The terrestrial system will then gracefully degrade by, for
example, prohibiting, for a period of time, subscriber terminal 512
use of certain user codes n (e.g., channels) once the calls have,
for example, been terminated. The RRM 720 (or 720a) can determine
when additional calls can be established by considering, for
example, anticipated link margin on the call to be established.
[0222] FIG. 10 shows a single satellite 516 providing a first set
of cells 1-7 in the form of a seven cell pattern. A second set of
terrestrial cells 8-10 is also shown, each generally comprising or
operationally communicable with a BTS 514. FIG. 10 can use any of
the embodiments discussed with regard to FIGS. 7a-7d. Multiple
satellites and/or any number of cells and/or cell configurations
may be used.
[0223] Suppose a subscriber terminal 512 (not shown) positioned
within terrestrial cell 8 wishes to use a channel when all channels
are currently being used by the satellite 516. If all channels are
currently being used (see, e.g., FIGS. 6b-6g), the subscriber
terminal 512 will preferably measure and select the satellite
channel or channel that is busy with the weakest signal strength to
be reused terrestrially by the subscriber terminal 512. Selecting
the satellite channel with the weakest signal generally minimizes
the interference between the satellite 516 and the subscriber
terminal 512.
[0224] Generally, the channels associated with the spot beam most
geographically distant from the subscriber terminal 512 (in, for
example, terrestrial cell 8) have the weakest signal strength and
thus will cause the least interference.
[0225] Thus, with regard to terrestrial cell 8, the channels
associated with cells 7 and 2 are the furthest distance
(geographically), and will generally cause the least interference.
Channels selected from cells 3 and 6 will generally cause more
interference than those channels selected from cells 7 and 2,
channels selected from cells 5 and 4 will generally cause more
interference than channels selected from cells 3 and 6, and
channels selected from cell 1 will generally cause the most
interference. If there is an available channel that is not being
used (by either the satellite or terrestrial components), the
subscriber terminal 512 is preferably assigned an unused channel.
Once the call is setup, handover will be performed if interference
levels having, for example, a predetermined threshold are detected.
The above process may alternatively or in addition be used for
systems with overlapping satellite-satellite coverage and/or
overlapping terrestrial-terrestrial coverage.
[0226] As shown in FIG. 11, the present invention can also be
practiced with two or more satellites 516a, 516b, each having their
own respective spot beam 1104a, 1104b. The (two or more) satellites
516a, 516b will generally have different assigned frequency bands
and associated channels, as shown, for example, in FIG. 6c. Each
spot beam 1104a, 1104b can further comprise, for example, two or
more subareas or subsectors, each having their own frequency band
or portion thereof associated therewith.
[0227] When possible, subscriber terminal 512a (512a, 512b, 512c,
512d can represent a single terminal in four locations, or four
different subscriber terminals) preferably measures signal strength
of the signaling and/or traffic channels associated with each
satellite 516a, 516b, and with at least the BTS 514 of the
terrestrial cell (if any) that the subscriber terminal is
positioned in. The signaling channels are the control channels, and
the traffic channels are where, for example, voice conversations
take place. For example, when the subscriber terminal 512a is
positioned in terrestrial cell 1106, it will measure the strength
of signals from at least BTS 514a. However, when the subscriber
terminal 512a is, for example, on a cell boundary between
terrestrial cells 1106 and 1108, the subscriber terminal can
optionally measure the signal strength from, for example, BTS 514a
and BTS 514b, and optionally from other neighboring BTS(s) (not
shown). It is preferred that subscriber terminals 512 continuously
measure the signal strength of the satellite 516a, 516b and the
BTSs 514.
[0228] In general, when a channel is not in use by any
communication system covering a predetermined area, the subscriber
terminals 512 will preferably and generally select for use the
channel having the strongest signal strength or other criteria that
indicates a preferred communication channel such as band, capacity,
protocols, time of day, location, interference level, and the link.
With regard to FIGS. 6b, 6c, 6f and 6g, any unused channel,
however, can be selected to accommodate, for example, network
loading considerations. This channel can be used to communicate
with a subscriber terminal 512 either by the satellite component
(e.g., 602, 602a, or 602b) or terrestrial component (e.g., 604,
604a, or 604b) of the system 500.
[0229] When all channels are in use, the subscriber terminal 512
will preferably select a channel (e.g., 615) currently being used
by the satellite 516 having the weakest signal strength, and use
that channel to communicate with a BTS 514 with which the
subscriber terminal 512 has the strongest signal.
[0230] FIG. 12a shows a first exemplary flow diagram of an overall
system method, including assignment and reuse of channels based,
for example, on signal strength, in accordance with the present
invention. FIG. 12a assumes that there are separate satellite and
terrestrial channels as shown, for example, in FIGS. 6d and 6e. At
decision step 2 a determination is made whether a terrestrial
channel is available. The determination can be made by a subscriber
terminal 512, a RRM 720, 720a, 720b, a BTS 514, or a NOC 508, 508a,
508b. For example, as previously described herein, the subscriber
can select a channel based on signal strength (and, for example,
based on the channel having an acceptably low interference level
and/or availability). Channel availability as determined by the RRM
720, 720a, 720 has been discussed with regard to FIGS. 7a-7d.
Similarly, as previously described herein, in at least one
embodiment of the present invention, the BTS 514, via the MSC 508
and the BSC 510, determines which channels are in use or not in
use. NOCs(s) 508, 508a, 508b, can maintain cognizance of the
availability of satellite and/or terrestrial resources and/or
arrange for reconfiguration, assignment and/or reuse of frequencies
to meet changed traffic patterns.
[0231] If it is determined that a terrestrial channel is available,
then an available channel is used terrestrially at step 20, and the
process ends. If a terrestrial channel is not available, a
determination is made at decision step 4 if a satellite channel is
available. If so, an available channel is used for satellite
communication at step 22, and the process ends. If a satellite
channel is not available, a determination is made whether the one
or more satellites are in a geosynchronous orbit at decision step
6.
[0232] If a geosynchronous orbit is utilized then, at decision step
8, a determination is optionally made whether channels are
dynamically assigned. If not, a predetermined satellite channel as
determined by the system is reused terrestrially at step 10.
[0233] If a geosynchronous orbit is not utilized, or if a
geosynchronous orbit with dynamically assigned channels is
utilized, or if the determination regarding orbits is not made at
all then, at decision step 14, a determination is made whether the
signal strength of the received satellite channel(s) currently in
use is too strong. If so, unacceptable interference would occur
between the satellite channel and that channel when it is reused
terrestrially, and the process begins again at decision step 2. If
the signal strength of the received satellite channel(s) is
acceptably weak so as to not cause unacceptable interference, a
determination is made at decision step 16 whether the signal
strength is considered noise. If so, at step 12, any noise channel
can be selected for terrestrial reuse. If the satellite channel is
not considered noise, then the non-noise satellite channel having
the weakest signal strength is selected for terrestrial reuse.
[0234] FIG. 12b shows a second exemplary flow diagram of an overall
system method, including assignment and reuse of channels based on
signal strength, in accordance with the present invention. FIG. 12b
assumes that any channel can be used for satellite communication,
terrestrial communication or, in the case of frequency reuse,
simultaneous satellite and terrestrial communication. FIGS. 6f and
6g show exemplary frequency band embodiments that can be used with
the method in accordance with FIG. 12b.
[0235] At decision step 52 a determination is made whether a
channel is available (i.e., not currently in use). As previously
discussed with regard to FIG. 12a, the determination can be made by
a subscriber terminal 512, a RRM 720, 720a, 720b, a BTS 514, a MSC
508, or a NOC 508, 508a, 508b. For example, as previously described
herein, the subscriber can select a channel based on signal
strength (and availability). Channel availability as determined by
the RRM 720, 720a, 720 has been discussed with regard to FIGS.
7a-7d. Similarly, as previously described herein, in at least one
embodiment of the present invention, the BTS 514, via the MSC 508
and the BSC 510, determines which channels are in use or not in
use. NOCs(s) 508, 508a, 508b, can maintain cognizance of the
availability of satellite and/or terrestrial resources and/or
arrange for reconfiguration, assignment and/or reuse of frequencies
to meet changed traffic patterns.
[0236] If it is determined that a channel is available, a
determination is made at decision step 54 whether terrestrial
coverage is available and, if so, a channel is assigned for
terrestrial use at step 72. If it is determined at decision step 4
that terrestrial coverage is not available, that at decision step
70, a determination is made whether satellite coverage is
available. If so, a channel is assigned for satellite communication
at step 74. If it is determined that satellite coverage is not
available, then the process returns to decision step 52. If at
decision step 52 a determination is made that a channel is not
available, then steps 56-78 are executed, as described with regard
to steps 6-18 of FIG. 12a. It should be understood that criteria
other than signal strength can be used in assigning channels, as
will be discussed, for example, with regard to FIG. 13.
[0237] Returning to FIG. 11, as discussed, when accessing (e.g.,
initiating communication with) a channel, the subscriber terminal
512a, if possible, determines the signal strength of the signaling
channel(s) from the satellite(s) 516a, 516b, as well as the
signaling channels of at least BTS 514a. In the case of subscriber
terminal 512a, terrain blockage 1102, for example, can affect
assignment of frequencies since subscriber terminal 512a can detect
very little, if any, signal from satellite 516a. It should be
understood that assignment and/or reuse of frequencies can also be
affected by, for example, man made structures and/or naturally
occurring phenomena such as foliage that can also partially or
completely block or obstruct a line of sight between a subscriber
terminal 512a and a satellite 516a, as well as by general signal
attenuation.
[0238] When there is no direct line of site between subscriber
terminal 512a and satellite 516a, little or no signal is "leaked"
from the subscriber terminal 512a to the satellite 516a. At the
same time, when there is coverage from terrestrial BTS 514a, the
BTS 514a can reuse a channel being used by satellite 516a to
communicate without interference, or substantially without
interference, with subscriber terminal 512a. In such a case,
interference between the satellite 516a and the subscriber terminal
512a is minimized since, when signal attenuation occurs in the
channel from the subscriber terminal 512a to the satellite 516a,
there also is a substantially equal attenuation of the signal from
the satellite 516a to the subscriber terminal 512a. Therefore, if
the subscriber terminal 512a detects a weak signal having, for
example, a predetermined signal strength from a satellite 516a,
there will also be a correspondingly weak signal from the
subscriber terminal 512a to the satellite 516a. Thus, terrestrial
reuse of a channel is preferred when the signal from the satellite
516a to the subscriber terminal 512a (and vice versa) is, for
example, the weakest, or defined by, for example, a predetermined
signal quality (e.g., RSSI and/or bit error rate).
[0239] In the embodiment shown in FIG. 7d, the RRM 720b, having
determined the frequencies currently being used by the satellite
component, can assign such channel for terrestrial reuse by a
subscriber terminal 512. In general, it is preferred that the
satellite having the channel with predetermined criteria such as
the weakest signal strength vis-a-vis subscriber terminal 512a or
other predetermined criteria is preferably selected for terrestrial
reuse.
[0240] Alternatively, if the subscriber terminal 512a does not have
coverage from a BTS 514, then terrestrial transmission cannot be
utilized, and the subscriber terminal 512a preferably uses the
satellite having the strongest signal (which is satellite 516b in
this case).
[0241] Subscriber terminal 512b has a direct line of sight to both
satellites 516a, 516b. Accordingly, the channel having the weakest
signal strength vis-a-vis subscriber terminal 512b will preferably
be selected for terrestrial reuse via, for example, BTS 514b. As
shown, although subscriber terminal 512c has a direct line of sight
to satellite 516a, the line of sight between subscriber terminal
512c and satellite 516b is blocked by terrain 1102. Accordingly,
the signals received from satellite 516b, assuming they can be
received, by subscriber terminal 512c, will be weaker than the
signals received by subscriber terminal 512c from satellite 516a.
Accordingly, the weakest channel from satellite 516b will
preferably be selected for terrestrial reuse by subscriber terminal
512c.
[0242] With regard to subscriber terminal 512d, there is a line of
sight to both satellites 516a, 516b. In this case, an available
(i.e., unused) channel having the strongest signal strength from
either satellite 516a, 516b is preferably selected for use since,
as shown, subscriber terminal 512d is not within a terrestrial cell
(e.g., 1106, 1108) and is thus not covered (or sufficiently
covered) by a BTS 514 to enable terrestrial communication.
[0243] Referring to FIG. 11, the present invention is also
applicable to a mobile satellite system (e.g., a Low Earth Orbit
(LEO) system) or in which a given geographical area is covered on a
dynamic basis by, for example, two or more satellites. For example,
in a mobile satellite system, at one point in time the spot beams
of satellites 516a, 516b could be 1104a, 1104b, respectively. At a
subsequent (or previous) time, the satellite 516a, 516b, spot beams
could cover an area as indicated by 1104c, 1104d, respectively.
[0244] In this scenario, a subscriber terminal 512 preferably
recognizes, for example, the signaling channels associated with
each respective spot beam 1104a, 1104b. In the case of overlapping
coverage of spot beams within a given geographic area, the
subscriber terminal 512 preferably makes measurements on multiple
signaling channels coming from multiple satellites 516a, 516b. When
all available channels are utilized or not available, subscriber
terminal 512 preferably selects for reuse the channel with the
weakest signal strength in that given area. It should be understood
that although only two spot beams 1104a, 1104b (corresponding to
satellites 516a, 516b, respectively) are shown, the subscriber
terminal 512 preferably measures the strength of, for example, the
signaling channels associated with any number of spot
beams/satellites.
[0245] When a subscriber terminal 512 is on the border or under the
influence, for example, of two or more spot beams 1104a, 1104b (or,
e.g., the border of spot beams 1 and 7 in FIG. 10), the subscriber
terminal 512 may have a tendency to transition back and forth
between respective channels associated with the two spot beams
1104a, 1104b and/or between coverage areas of the terrestrial and
satellite systems. In order to prevent such a back-and-forth
transfer between the channels associated with the respective spot
beams, the present invention advantageously utilizes hysteresis so
that there is, for example, a predetermined threshold (e.g., 2 dB)
difference in signal strength before allowing the subscriber
terminal 512 to make such a transition.
[0246] The present invention also optionally utilizes negative
hysteresis to, for example, balance the loading between the
satellite and terrestrial components and/or respective portions
thereof. For example, with regard to FIG. 10, consider the case
when a channel is being reused terrestrially, and the channels of
spot beam 7 are being used much more than the channels of spot beam
1. Even though the channels of spot beam 7 may have a weaker signal
strength than the channels of spot beam 1, subscriber terminals 512
may be directed to terrestrially reuse channels from spot beam 1
rather than spot beam 7 to, for example, better balance network
loading. It should be understood that negative hysteresis can also
be applied to a single satellite when the satellite contains
multiple frequency bands.
[0247] Negative hysteresis can also be used to balance loading
between two or more satellites 516a, 516b. For example, with regard
to FIG. 11, suppose satellite 516a has all or substantially all of
its channels used, and satellite 516b has none or very few of its
channels used. Then, even though the signal strength of channels
from satellite 516a may be stronger, it may be desirable to assign
a call to satellite 516b when, for example, RSSI is sufficient.
Now, suppose channels from satellite 516b have a stronger signal
strength (relative to one or more subscriber terminals 512), and
that fewer of its channels are being utilized. In such a case, it
may be desirable to terrestrially reuse channels from satellite
516b to, for example, balance network loading, even though the use
of such channels may result in higher interference.
[0248] FIG. 13 is a high level flow diagram of illustrating the
static and dynamic channel assignment features of the present
invention. As discussed in Channel Assignment Schemes for Cellular
Mobile Telecommunication Systems: A Comprehensive Survey, IEEE
Personal Communications Magazine, June 1996, I. Katzela and M.
Naghshineh, incorporated herein by reference, when channel
assignment schemes are classified based on separating co-channels
apart in space, three broad categories can be identified: fixed
channel allocation schemes (FCA), dynamic channel allocation
schemes (DCA), and hybrid channel allocation schemes (HCA). FCA
schemes partition the given serving area into a number of cells and
allocate the available channels to cells based on some channel
reuse criterion. DCA schemes pool together all the available
channels and allocate them dynamically to cells as the need arises.
Consequently, DCA schemes are capable of adapting to changing
traffic patterns. HCA schemes provide a number of fixed channels,
and a number of channels that can be dynamically allocated.
[0249] If the satellite 516 has a geosynchronous orbit, the angle
of arrival from all spot beams is almost the same. In such a case,
as indicated by decision step 1302, the pool of channels can either
be assigned to, for example, a sub area of a spot beam and/or a
terrestrial cell ahead of time (i.e., fixed assignment), or
assigned dynamically. In the case of a geosynchronous orbit, the
signal strength measured by a subscriber terminal 512 using either
a fixed or dynamic channel assignment scheme should be
substantially the same, since the geographical location of the GSSs
504 are fixed and the angle of arrival from a single satellite 516
from different spot beams is substantially the same. Optionally,
the GSS 504 can be used to collect measured signal strength
reported by the subscriber terminals 512. Even in the case, for
example, of a fast moving vehicle that is handing off, channel
assignment can be done by a BSC 520 since, if the angle of arrival
is fixed, then all the spot beams will behave substantially
identically.
[0250] If it is determined at decision step 1302 that a FCA scheme
is being used, then a preassigned channel is utilized at step 1304.
The NOC 508, 508a, 508b will generally determine whether a hybrid
method is utilized, although a BSC 510 in conjunction with a GSS
504 can also store such information. The present invention can
utilize either a uniform allocation, in which the same number of
channels are allocated to, for example, each cell or subcell, or a
non-uniform allocation, in which different numbers of channels can
be allocated to, for example, each cell or subcell.
[0251] If it is determined at decision step 1302 that channels are
assigned dynamically, a determination is made at decision step 1306
whether a hybrid method is utilized. If a strictly dynamic scheme
is being utilized then, a determination is made at decision step
1308 whether calls are allocated on a call-by-call basis. If so, a
subscriber terminal 512 can compute the signal strength of
available channels, and select the channel based on relative signal
strength. If it is determined at decision step 1308 that channels
will not be allocated on a call-by-call basis, channels may
optionally be allocated based on past and present usage patterns.
For example, consider a situation in which 60% of satellite
channels are currently utilized and 40% of terrestrial channels are
utilized. Without considering past usage patterns, it would be
desirable to allocate the call to a terrestrial channel, since a
higher percentage of terrestrial channels are available. However,
if data stored at a MSC 508, for example, indicates that
terrestrial channel usage in this cell it typically 80% (or 120%)
and satellite channel usage is typically 40% (or 20%), the system
500 may assign the call to a satellite channel, even though it
currently has a higher percentage of its channels being used since,
based on past data, it is expected that traffic patterns will
shortly return to their typical loads (e.g., 80% of terrestrial
capacity and 40% of satellite capacity).
[0252] Further, the system 500 can control dynamic channel
allocation associated with steps 1312 and 1314 in either a
centralized or distributed manner. In a centralized DCA scheme, the
MSC 508, for example, could maintain a centralized pool of channels
(e.g., frequency bands) and allocate channels to calls based on,
for example: the first available channel; to minimize blocking
probability; and/or to maximize system utilization by maximizing
channel reuse.
[0253] The system 500 could also utilize a distributed DCA scheme
in which channels could be allocated based on locally available
information available at, for example, each BTS 514. Some
variations of distributed schemes include: a) allocating the first
available channel; b) allocating the channel that minimizes
adjacent channel interference; and/or c) allocating the first
available channel that also meets some adjacent channel
interference criterion.
[0254] If it is determined at decision step 1306 that a hybrid
scheme will be utilized, the system preferably assigns a ratio of
fixed and dynamic channels to, for example, each cell, subcell or
area of coverage. The ratio of fixed to dynamic cells generally
determines the performance of the system. Optimal ratio is likely
to depend on a number of factors such as, for example, system
traffic load and/or system characteristics. At step 1316, channels
are preferably assigned in accordance with, for example, channel
and system 500 load balancing and/or received signal strength
considerations.
[0255] FIG. 14 is an exemplary flow diagram of the call
initialization process when the terrestrial mode is preferred and
the satellite and terrestrial components share a common portion of
a frequency band as shown, for example, in FIGS. 6b, 6c, 6f and 6g.
A user places a call, for example, after acquiring a control
channel, and depressing a send button on the mobile
phone/subscriber terminal 512, and requests a channel at step 1402.
At decision step 1404, a determination is made whether the
subscriber terminal 512 is a dual mode (satellite-terrestrial)
terminal. If the subscriber terminal 512 is dual mode, then signal
strength measurements are made, for example at a BTS 514 and/or a
GSS 504 of at least a portion of the available channels (if any)
that can be used terrestrially at step 1406, preferably with one or
more satellites 516 and one or more associated BTSs 514. If, as
determined at decision step 1408, a channel is available for
terrestrial use, a channel is assigned to the BTS 514 for
terrestrial communication at step 1410 and the call is deemed
successful at step 1414. If, as determined at decision step 1408,
all terrestrial channels are currently being used, a channel
currently being used by a satellite 516 is assigned to a BTS 514
for terrestrial reuse at step 1412, and the call is deemed
successful at step 1414. It is preferred that the channel currently
being used by a satellite 516 having the weakest signal strength be
assigned to a BTS 514 for terrestrial reuse.
[0256] If, at decision step 1404, the subscriber terminal indicates
that it is a single mode terminal (e.g., a satellite terminal), a
determination is made by, for example, NOC 506, 606a, MSC 508,
508a, and/or RRM 720, 720a, at decision step 1418 whether a channel
is available for satellite use. If so, a channel is assigned for
satellite use at step 1416, and the call is deemed to be
successfully established at step 1414. If, at decision step 1418, a
determination is made that a channel is not available for satellite
use, the subscriber terminal 512 and/or system 500 wait(s),
preferably for a predetermined time, before determining whether a
channel is available for satellite use at decision step 1418.
[0257] The method of FIG. 14 can be used not only for initial
selection of frequencies as discussed above, but also for handoffs
between channels when a subscriber terminal 512 travels, for
example, from one area or portion thereof of satellite or
terrestrial system coverage to another. As used herein, handoff
refers to reassignment of a call to a different channel as a result
of current channel degradation, and can be, for example,
intra-cell/intra-satellite and/or inter-cell/inter-satellite.
Channel degradation can occur, for example, as the subscriber
terminal distance from the serving BTS increases or as a result of
increase in co-channel interference. Handoff schemes are designed
to prefer handoff calls to new calls when allocating channels so as
to maintain an established connection (e.g., avoid dropping a
call), and are preferably compared based, for example, on the
probability of successful handoff calls and/or new call
blocking.
[0258] Following are exemplary principles on which handoffs can be
based: a) reserving some channels in each cell for handoff calls
(i.e., Guard Channel Scheme); b) queuing up candidate calls for
handoff (i.e., Handoff Queuing Scheme) with or without guard
channels; and c) queuing up new calls instead of handoff calls.
[0259] Since channels are set aside for handoff, the guard channel
scheme increases the probability of handoff calls. With a handoff
queuing scheme, calls are queued for handoff when the received
carrier power falls below a threshold. Queuing schemes can be, for
example, first-in-first-out or priority queuing schemes. Priority
can be based on, for example, how fast the threshold is being
reached.
[0260] For example, with regard to FIG. 10, if a subscriber
terminal 512 goes from cell 1 to, for example, cell 7, the
subscriber terminal 512 will scan the channels associated with each
cell, and preferably select first an open channel for terrestrial
use, if one is available. If no channel(s) is available, then the
subscriber terminal 512 takes signal strength measurements of the
channels, and preferably selects the channel having the weakest
signal strength (from the satellite 516 and relative to a
subscriber terminal 512) for terrestrial use.
[0261] FIG. 15 shows an exemplary flow diagram of call
initialization when terrestrial mode is preferred and discrete
satellite and terrestrial frequency bands are utilized as shown,
for example, in FIGS. 6d and 6e. As shown in FIG. 15, at step 1502
the user places a call and requests a channel.
[0262] At step 1504 the subscriber terminal transmits to the system
whether it is a single or dual mode (satellite-terrestrial)
terminal. The subscriber terminal can transmit this information on,
for example a signaling channel. For example, the subscriber
terminal can send a control signal upon powering up the unit to,
for example, a BTS 514 and/or satellite 516 indicating whether the
subscriber terminal is single mode or a dual mode terminal.
[0263] At decision step 1506, a determination is made by, for
example, the BTS 514 and/or BSC 510, based on the signal
transmitted at step 1504, whether the subscriber terminal is a
single mode or a dual mode terminal. If the subscriber terminal 512
is dual mode, then at step 1508 the system measures, for example,
the signal strength of the satellite 516 and BTS 514 channels
received by the subscriber terminal, and reports such measurements
to, for example, a BSC 510 and/or a MSC 508, 508a, 508b. For
example, in accordance with GSM technology, to initiate call setup,
a subscriber terminal sends a signaling channel request to the
system using a random access channel (RACH). The MSC 508, 508a,
508b, after considering signal strength measurements, informs the
subscriber terminal via a BTS 514 of the allocated signaling
channel using an access grant channel (AGCH). Then, the subscriber
terminal sends the call origination request via a standalone
dedicated control channel (SDCCH). The MSC 508, 508a, 508b, for
example, then instructs the BSC 510 to allocate a traffic channel
(TCH) for the call. Then, the subscriber terminal acknowledges the
traffic channel assignment using, for example, a fast associated
control channel (FACCH). Finally, both the subscriber terminal and
the BTS 514 tune to the traffic channel.
[0264] At decision step 1516, a determination is made whether a BTS
514 channel (i.e., terrestrial channel) is available. If so, a
determination is made at decision step 1526 whether a satellite
channel is available. If so, a request is made to utilize the
satellite channel terrestrially at step 1524, and the call is
deemed successful at step 1530. If, at decision step 1526, it is
determined by, for example, a MSC 508, 508a, 508b, that all
satellite channels are being used, the weakest signal is identified
at step 1534, a channel is assigned to the subscriber terminal 512
such that the subscriber terminal 512 reuses that satellite channel
terrestrially, and the call is deemed successful at step 1530.
[0265] If, at decision step 1516, a determination is made by, for
example, a MSC 508, 508a, 508b, that a BTS 514 channel is not
available, a determination is made at decision step 1520 whether a
satellite channel is available. If a satellite channel is
available, the call is deemed successful at step 1522. If a
satellite channel is not available, at step 1518 the subscriber
terminal 512 and/or system 500 waits, preferably for a
predetermined time, before taking additional measurements at step
1508.
[0266] If, at decision step 1506, the subscriber terminal 512 is
determined to be a single mode (e.g., satellite only) terminal, the
system measures, for example, the signal strength of the satellite
516 channels, and reports such measurements to, for example, the
MSC 508, 508a, 508b. At decision step 1512, a determination is made
whether a satellite channel is available. If a satellite channel is
available, the call is deemed successful at step 1530. If a
satellite channel is not available, at step 1528 the subscriber
terminal 512 and/or system 500 waits, preferably for a
predetermined time, before taking additional measurements at step
1514. As is the case with FIG. 14, the method described in FIG. 15
can be used both for initial selection of frequencies, as well as
handoffs between channels when a subscriber terminal travels, for
example, from one spot area or one terrestrial area to another.
[0267] FIG. 16 shows an exemplary flow diagram of base
station-to-base station or base station-to-satellite handoff when
the satellite and terrestrial components share a common portion of
a frequency band as shown, for example, in FIGS. 6b, 6c, 6f and 6g.
At step 1602, the system 500 and/or subscriber terminal 512 verify
that the RSSI or other signal strength indicator or criteria is
satisfied. Before establishing a call, the RSSI, for example,
should be high enough for the subscriber terminal 512 to establish
calls. As previously discussed, the RSSI is a relative measure of
received signal strength for a particular subscriber terminal 512,
and is typically measured in db/m (decibels/milliwatt).
[0268] At decision step 1604, a determination is made whether the
subscriber terminal 512 is a single mode or a dual mode terminal.
The subscriber terminal can transmit this information on, for
example, a signaling channel. For example, the subscriber terminal
can send a control signal upon powering up the unit to, for
example, a BTS 514 and/or satellite 516 indicating whether the
subscriber terminal is single mode or a dual mode terminal.
[0269] If it is determined at decision step 1604 that the
subscriber terminal is dual mode then, at decision step 1606, a
determination is made by, for example, a BSC 510 whether a
neighboring BTS 514 provides, for example, an acceptable RSSI.
Other criteria such as, for example, network loading and/or
balancing considerations, may also be used. If so, a request to
handoff to the neighboring BTS 514 is made at step 1608. At
decision step 1610, determination is made whether the BTS 514 has
capacity available. If so, a determination is made at decision step
1614 whether there is an available channel (not being used by the
satellite). If so, a request to handoff to the available channel is
made at step 1624, and the handoff is deemed successful at step
1626.
[0270] If, at decision step 1614, a determination is made that all
channels are being utilized, the weakest satellite signal is
preferably identified at step 1622. At step 1624, a request is made
to reuse the weakest satellite signal, and the handoff is deemed
successful at step 1626. If, at decision step 1610, it is
determined that there is no BTS 514 capacity available, one or more
subsequent requests are preferably made at step 1608, as determined
by decision step 1612.
[0271] If, at decision step 1606, a determination is made by the
BSC 510 and/or MSC 508, 508b that the neighboring BTS 514 does not
have, for example, an acceptable RSSI and/or does not, for example,
satisfy other handoff criteria (e.g., network loading), or if, at
decision step 1612 the maximum number of allowed handoff requests
has been made, a request to handoff to a satellite is made at step
1616. At decision step 1620, a determination is made by, for
example, MSC 508, 508a whether a channel is available and, if so,
the handoff is deemed successful at step 1626. If, at decision step
1620, a determination is made that a channel is not available, then
the subscriber terminal 512 and/or system 500 waits at step 1618,
preferably for a predetermined time prior to requesting another
handoff at step 1616.
[0272] If, at decision step 1604, a determination is made that the
subscriber terminal 512 is single mode (e.g., satellite only), then
a satellite handoff request is made at step 1616, after which
decision step 1620 is executed as discussed above.
[0273] FIG. 17 shows an exemplary flow diagram of base
station-to-base station or base station-to-satellite handoff while
using discrete satellite and terrestrial frequency bands as shown,
for example, in FIGS. 6d and 6e. At step 1702, the system 500
and/or subscriber terminal 512 verify that the RSSI and/or other
signal strength indicators or criteria are satisfied.
[0274] At decision step 1704, a determination is made whether the
subscriber terminal 512 is dual mode. The subscriber terminal can
transmit this information on, for example a signaling channel. For
example, the subscriber terminal can send a control signal upon
powering up the unit to, for example, a BTS 514 and/or satellite
516 indicating whether the subscriber terminal is single mode or a
dual mode terminal.
[0275] If it is determined at decision step 1704 that the
subscriber terminal is dual mode then, at decision step 1706, a
determination is made by, for example, a BSC 510 and/or MSC 508,
508b whether a neighboring BTS 514 provides an acceptable RSSI. If
so, a request to handoff to the neighboring BTS 514 is made at step
1708. At decision step 1710, a determination is made by, for
example, a BSC 510 and/or MSC 508, 508b whether there is a BTS 514
channel available. If so, a determination is made at decision step
1716 by, for example, MSC 508, 508a whether there is an available
satellite channel. If it is determined that a satellite channel is
available, a request to handoff to the satellite channel frequency
is made at step 1722, and at step 1724 the handoff is deemed
successful.
[0276] If, at decision step 1716, a determination is made by, for
example, MSC 508, 508a that all satellite channels are being
utilized, the weakest satellite signal vis-a-vis the subscriber
terminal is preferably identified at step 1728. At step 1726, a
request is made by, for example, MSC 508, 508a to reuse the weakest
satellite signal, and the handoff is deemed successful at step
1724. If, at decision step 1710, it is determined that a BTS 514
channel is not available, one or more subsequent requests are
preferably made at step 1708, as determined by decision step
1714.
[0277] If, at decision step 1706, a determination is made by, for
example, BSC 510 that the neighboring BTS 514 does not have an
acceptable RSSI, or if, as determined at decision step 1714, the
maximum number of handoff attempts has been made, a request to
handoff to a satellite channel is made at step 1712. At decision
step 1720, a determination is made by, for example, MSC 508, 508a
whether a satellite channel is available and, if so, the handoff is
deemed successful at step 1724. If, at decision step 1720, a
determination is made by, for example, MSC 508, 508a that a
satellite channel is not available, then the subscriber terminal
512 and/or system 500 wait(s) at step 1718, preferably for a
predetermined time, prior to requesting another handoff at step
1712.
[0278] If, at decision step 1704, it is determined that the
subscriber terminal 512 is a single mode (e.g., satellite only)
terminal, a request to handoff to a satellite channel is made at
step 1712, after which decision step 1720 is executed, as discussed
above.
[0279] The present invention also contemplates variations of the
method disclosed in FIG. 17. For example, although FIG. 17
describes a process of first using terrestrial mode communications,
and subsequently using satellite mode communications upon
exhausting terrestrial channels, FIG. 17 could also have first
preferred satellite mode communications, and subsequently use
terrestrial mode communication upon exhausting satellite
channels.
[0280] FIG. 18 shows an exemplary method of satellite-to-base
station or satellite-to-satellite handoff when the satellite and
terrestrial components share a common portion of a frequency band
as shown, for example, in FIGS. 6b, 6c, 6f and 6g. Upon determining
that handoff criteria (e.g., RSSI) is satisfied at step 1802, a
determination is made at decision step 1804 whether the subscriber
terminal 512 is dual mode. The subscriber terminal can transmit
this information on, for example a signaling channel. For example,
the subscriber terminal can send a control signal upon powering up
the unit to, for example, a BTS 514 and/or satellite 516 indicating
whether the subscriber terminal is single mode or a dual mode
terminal.
[0281] If it is determined at decision step 1804 that the
subscriber terminal is dual mode, a request to handoff to a BTS 514
is made at step 1806. At decision step 1814, a determination is
made whether the BTS 514 has capacity available and, if so, whether
there is an available channel at decision step 1816. If so, a
request to handoff to an available channel is made by, for example,
MSC 508, 508b at step 1808, and the handoff is deemed successful at
step 1810.
[0282] If, at decision step 1816, a determination is made by, for
example, MSC 508, 508a, 508b that all channels are being utilized,
the weakest satellite signal is preferably identified at step 1824.
At step 1826, a request by, for example, MSC 508, 508a, 508b, is
made to reuse the weakest satellite signal, and the handoff is
deemed to be successful at step 1810. If, at decision step 1814, it
is determined by, for example, BSC 510 that there is no available
BTS 514 capacity, a request to handoff to a satellite is made at
step 1822. At decision step 1828, a determination is made by, for
example, MSC 508, 508a whether satellite capacity is available and,
if capacity is available, the handoff is deemed successful at step
1830. If, at decision step 1828, a determination is made by, for
example, MSC 508, 508a that no satellite capacity is available,
then at step 1820 the subscriber terminal 512 and/or system 500
camps on one or more of the channels that can be used with a
satellite 516, preferably for a predetermined time, prior to
requesting another handoff at step 1806.
[0283] If a determination is made, as previously described, at
decision step 1804 that the subscriber terminal 512 is single mode
(e.g., a satellite terminal) then, at decision step 1812, a
determination is made by, for example, MSC 508, 508a whether there
is satellite capacity available. If satellite capacity is
available, the call is deemed successful at step 1830. If, at
decision step 1812 it is determined by, for example, MSC 508, 508a
that satellite capacity is not available, then at step 1818, the
subscriber terminal 512 and/or system 500 camps on one or more of
the satellite channels at step 1818, preferably for a predetermined
time, prior to again determining whether satellite capacity is
available at decision step 1812.
[0284] FIG. 19 shows an exemplary method of satellite-to-base
station or satellite-to-satellite handoff while using discrete
satellite and terrestrial frequency bands as shown, for example, in
FIGS. 6d and 6e. Upon determining that handoff criteria (e.g.,
RSSI) is satisfied at step 1902, a determination is made at
decision step 1904 whether the subscriber terminal 512 is dual
mode. The subscriber terminal can transmit this information on, for
example, a signaling channel. For example, the subscriber terminal
can send a control signal upon powering up the unit to, for
example, a BTS 514 and/or satellite 516 indicating whether the
subscriber terminal is single mode or a dual mode terminal.
[0285] If it is determined at step 1902 that the subscriber
terminal is dual mode then, a request to handoff to a BTS 514
channel is made at step 1906. At decision step 1916, a
determination is made by, for example, BSC 510 whether there is a
BTS 514 channel available. If so, a determination is made at
decision step 1918 by, for example, MSC 508, 508a, whether there is
a satellite channel not being used. If it is determined that a
satellite channel is available, a request to handoff to that
satellite channel is made at step 1908, and at step 1910 the
handoff is deemed successful.
[0286] If, at decision step 1918, a determination is made by, for
example, MSC 508, 508a that all satellite channels are being
utilized, the weakest satellite signal is preferably identified at
step 1926. At step 1928, the MSC 508, 508a reuses the satellite
channel having the weakest signal, and the handoff is deemed
successful at step 1910. If, at decision step 1916, it is
determined by, for example, BSC 510 that a BTS 514 channel is not
available, a request is made to handoff to, for example, an
adjacent spot beam or satellite at step 1924. For example, with
regard to FIG. 11, if subscriber terminal 512b requests a handoff
to satellite 516a and satellite 516a does not have any available
channels, subscriber terminal 512b can subsequently request a
handoff using satellite 516b. If, at decision step 1930 a
determination is made that an adjacent satellite (or spot beam) has
an available channel, the call is deemed successful at step 1912.
If, at decision step 1930 a determination is made that an adjacent
satellite (or spot beam) does not have an available channel then,
at step 1922, the subscriber terminal 512 camps on the current
channel, preferably for a predetermined time before returning to
step 1906.
[0287] If, at decision step 1904 it is determined, as previously
discussed, that the subscriber terminal 512 is a single mode (e.g.,
satellite only) terminal then, at decision step 1914, if a
determination is made that a channel from an adjacent spot beam or
satellite is available, the call is deemed successful at step 1912.
If it is determined at decision step 1914 that a channel from an
adjacent spot beam or satellite is not available, then the
subscriber terminal 512 or system 500 camps on the desired channel,
preferably for a predetermined time, after which decision step 1914
is repeated.
[0288] As shown in FIG. 20a, the present invention advantageously
and optionally implements an inverse assignment of the channels.
That is, in at least one embodiment of the present invention,
channels are assigned to the satellite component from one end of
the frequency spectrum, and channels are assigned to the
terrestrial component from the other end so that maximized spacing
of channels is used. FIG. 20a collectively represents the
respective downlink 602 and uplink 604 frequency bands of, for
example, FIG. 6b. For example, with regard to 602, 604 of FIG. 6a,
assume that the channels are arranged from 1, 2, 3, 4 . . . 98, 99,
100, from lower to higher frequency. The BTSs 514, for example,
could be assigned channels 100, 99, 98, etc. from higher to lower
frequencies, and the satellites can be assigned channels 1, 2, 3,
etc. from lower to higher frequencies. We have discovered that this
scheme advantageously reduces the chances of reuse. When no
channels remain for either satellite or terrestrial use then, as
previously discussed, the channel(s) having the weakest signal
strength is preferably reused terrestrially.
[0289] When there is a predetermined frequency closeness (e.g., a
BTS 514 is using channels 52 to 100, and a satellite 516 is using
channels 1 to 49), the present invention also enables transitioning
channels to avoid interference and/or reuse. For example, channel
49 may be handed off, for example, to channel 2, assuming channel 2
is available (as indicated by (2) in FIG. 20b). Similarly, BTS 514
channels may also be similarly handed off.
[0290] Accordingly, in this additional feature of inverse frequency
assignment, the MSC 508, 508a, 508b, for example, actively monitors
the active channels in ends of the systems (satellite/terrestrial,
satellite/satellite, terrestrial/terrestrial, etc.) and proactively
and/or dynamically re-assigns channels to maximize spacing between
the systems.
[0291] The many features and advantages of the invention are
apparent from the detailed specification, and thus, it is intended
by the appended claims to cover all such features and advantages of
the invention which fall within the true spirit and scope of the
invention. Further, since numerous modifications and variations
will readily occur to those skilled in the art, it is not desired
to limit the invention to the exact construction and operation
illustrated and described, and accordingly, all suitable
modifications and equivalents may be resorted to, falling within
the scope of the invention. While the foregoing invention has been
described in detail by way of illustration and example of preferred
embodiments, numerous modifications, substitutions, and alterations
are possible without departing from the scope of the invention as
described herein.
[0292] For example, one embodiment of the invention focused on
reusing or assigning terrestrial frequencies based on the status of
or signal strength of the satellite frequency. The present
invention is also applicable in the reverse. In addition, the
present invention is applicable to a plurality of satellite systems
and/or a plurality terrestrial systems having similar operational
characteristics as described herein. The present invention is
equally applicable to voice and/or data networks.
* * * * *