U.S. patent application number 12/271381 was filed with the patent office on 2009-03-19 for terrestrial communications networks that transmit using circular polarization.
This patent application is currently assigned to ATC Technologies, LLC. Invention is credited to Peter D. Karabinis.
Application Number | 20090075645 12/271381 |
Document ID | / |
Family ID | 34108844 |
Filed Date | 2009-03-19 |
United States Patent
Application |
20090075645 |
Kind Code |
A1 |
Karabinis; Peter D. |
March 19, 2009 |
Terrestrial Communications Networks That Transmit Using Circular
Polarization
Abstract
A terrestrial communications network may be configured to
wirelessly communicate with a plurality of radiotelephones. The
terrestrial communications network may include a plurality of base
stations that are configured to wirelessly communicate with the
plurality of radiotelephones. Moreover, the plurality of base
stations may include at least one base station that is configured
to transmit information to at least one radiotelephone using a
circularly polarized antenna. Related methods are also
discussed.
Inventors: |
Karabinis; Peter D.; (Cary,
NC) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC
PO BOX 37428
RALEIGH
NC
27627
US
|
Assignee: |
ATC Technologies, LLC
|
Family ID: |
34108844 |
Appl. No.: |
12/271381 |
Filed: |
November 14, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10880023 |
Jun 28, 2004 |
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12271381 |
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60490638 |
Jul 28, 2003 |
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60492710 |
Aug 5, 2003 |
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Current U.S.
Class: |
455/422.1 |
Current CPC
Class: |
H04W 16/12 20130101;
H04W 16/30 20130101; H04B 7/18543 20130101 |
Class at
Publication: |
455/422.1 |
International
Class: |
H04W 4/00 20090101
H04W004/00 |
Claims
1. A terrestrial communications network that is configured to
wirelessly communicate with a plurality of radiotelephones, the
terrestrial communications network comprising: a plurality of base
stations that are configured to wirelessly communicate with the
plurality of radiotelephones, the plurality of base stations
including at least one base station that is configured to transmit
information to at least one radiotelephone using a circularly
polarized antenna.
2. A terrestrial communications network according to claim 1
wherein the at least one base station receives information from at
least one radiotelephone using a polarization diversity and/or a
space diversity antenna configuration.
3. A terrestrial communications network according to claim 1
wherein the at least one base station transmits information using a
FDM/FDMA, TDM/TDMA, CDM/CDMA and/or OFDM/OFDMA air interface
protocol and/or architecture.
4. A terrestrial communications network according to claim 1
wherein the at least one base station transmits information using
at least one frequency that is also used by a satellite system.
5. A terrestrial communications network according to claim 1
wherein the circularly polarized antenna is configured to transmit
using substantially Left-Hand Circular Polarization (LCHP).
6. A wireless communications method comprising: configuring a
plurality of base stations to wirelessly communicate with a
plurality of radiotelephones; configuring at least one base station
of the plurality of base stations with a circularly polarized
antenna; and transmitting information to at least one
radiotelephone using the circularly polarized antenna.
7. A method according to claim 6 further comprising: receiving
information at the at least one base station from at least one
radiotelephone using a polarization diversity and/or a space
diversity antenna configuration.
8. A method according to claim 6 wherein transmitting information
comprises: using a FDM/FDMA, TDM/TDMA, CDM/CDMA and/or OFDM/OFDMA
air interface protocol and/or architecture.
9. A method according to claim 6 wherein transmitting information
comprises: using at least one frequency that is also being used by
a satellite system.
10. A method according to claim 6 wherein the circularly polarized
antenna is a left-hand circularly polarized antenna.
11. A method according to claim 6 wherein transmitting information
to the at least one radiotelephone comprises transmitting
information to the at least one radiotelephone using the circularly
polarized antenna using substantially Left-Hand Circular
Polarization (LHCP).
Description
RELATED APPLICATIONS
[0001] This application claims the benefit of priority as a
divisional of U.S. application Ser. No. 10/880,023, filed Jun. 28,
2004, entitled Systems And Methods For Modifying Antenna Radiation
Patterns Of Peripheral Base Stations Of A Terrestrial Network To
Allow Reduced Interference which claims the benefit of: provisional
Application No. 60/490,638, filed Jul. 28, 2003, entitled Systems
and Methods for Modifying Antenna Radiation Patterns of Peripheral
Base Stations of an Ancillary Terrestrial Component to Allow
Reduced Interference; and of provisional Application No.
60/492,710, filed Aug. 5, 2003, entitled Additional Systems And
Methods For Modifying Antenna Radiation Patterns Of Peripheral Base
Stations Of An Ancillary Terrestrial Component To Allow Reduced
Interference. All of the above referenced patent applications are
assigned to the assignee of the present application, and the
disclosures of all of the above referenced patent applications are
hereby incorporated herein by reference in their entirety as if set
forth fully herein.
FIELD OF THE INVENTION
[0002] This invention relates to wireless communications systems
and methods, and more particularly to terrestrial cellular
communications systems and methods.
BACKGROUND
[0003] Satellite radiotelephone communications systems and methods
are widely used for radiotelephone communications. Satellite
radiotelephone communications systems and methods generally employ
at least one space-based component, such as one or more satellites
that are configured to wirelessly communicate with a plurality of
satellite radiotelephones.
[0004] A satellite radiotelephone communications system or method
may utilize a single antenna beam covering an entire area served by
the system. Alternatively, in cellular satellite radiotelephone
communications systems and methods, multiple beams are provided,
each of which can serve distinct geographical areas in the overall
service region, to collectively serve an overall satellite
footprint. Thus, a cellular architecture similar to that used in
conventional terrestrial cellular radiotelephone systems and
methods can be implemented in cellular satellite-based systems and
methods. The satellite typically communicates with radiotelephones
over a bidirectional communications pathway, with radiotelephone
communication signals being communicated from the satellite to the
radiotelephone over a downlink or forward link, and from the
radiotelephone to the satellite over an uplink or return link.
[0005] The overall design and operation of cellular satellite
radiotelephone systems and methods are well known to those having
skill in the art, and need not be described further herein.
Moreover, as used herein, the term "radiotelephone" includes
cellular and/or satellite radiotelephones with or without a
multi-line display; Personal Communications System (PCS) terminals
that may combine a radiotelephone with data processing, facsimile
and/or data communications capabilities; Personal Digital
Assistants (PDA) that can include a radio frequency transceiver and
a pager, Internet and/or intranet access, Web browser, organizer,
calendar and/or a global positioning system (GPS) receiver; and/or
conventional laptop and/or palmtop computers or other appliances,
which include a radio frequency transceiver. Radiotelephones may
also be referred to herein as "radioterminals" or simply
"terminals".
[0006] As is well known to those having skill in the art,
terrestrial networks can enhance cellular satellite radiotelephone
system availability, efficiency and/or economic viability by
terrestrially reusing at least some of the frequency bands that are
allocated to cellular satellite radiotelephone systems. In
particular, it is known that it may be difficult for cellular
satellite radiotelephone systems to reliably serve densely
populated areas, because the satellite signal may be blocked by
high-rise structures and/or may not penetrate into buildings. As a
result, the satellite band spectrum may be underutilized or
unutilized in such areas. The use of terrestrial retransmission of
all or some of the satellite band frequencies can reduce or
eliminate this problem.
[0007] Moreover, the capacity of the overall system can be
increased significantly by the introduction of terrestrial
retransmission, since terrestrial frequency reuse can be much
denser than that of a satellite-only system. In fact, capacity can
be enhanced where it may be mostly needed, i.e., in and/or
proximate to densely populated urban, industrial, and/or commercial
areas. As a result, the overall system can become much more
economically viable, as it may be able to serve a much larger
subscriber base. Finally, satellite radiotelephones for a satellite
radiotelephone system having a terrestrial component within the
same satellite frequency band and using substantially the same air
interface for both terrestrial and satellite communications can be
more cost effective and/or aesthetically appealing. Conventional
dual band and/or dual mode alternatives, such as the well known
Thuraya, Iridium and/or Globalstar dual mode satellite and/or
terrestrial radiotelephone systems, may duplicate some components,
which may lead to increased cost, size and/or weight of the
radiotelephone.
[0008] U.S. Pat. No. 6,684,057 issued Jan. 27, 2004, to the present
inventor Karabinis, and entitled Systems and Methods for
Terrestrial Reuse of Cellular Satellite Frequency Spectrum, the
disclosure of which is hereby incorporated herein by reference in
its entirety as if set forth fully herein, describes that a
satellite radiotelephone frequency can be reused terrestrially by
an ancillary terrestrial network even within the same satellite
cell, using interference cancellation techniques. In particular,
the satellite radiotelephone system according to some embodiments
of U.S. Pat. No. 6,684,057 includes a space-based component that is
configured to receive wireless communications from a first
radiotelephone in a satellite footprint over a satellite
radiotelephone frequency band, and an ancillary terrestrial network
that is configured to receive wireless communications from a second
radiotelephone in the satellite footprint over the satellite
radiotelephone frequency band. The space-based component also
receives the wireless communications from the second radiotelephone
in the satellite footprint over the satellite radiotelephone
frequency band as interference, along with the wireless
communications that are received from the first radiotelephone in
the satellite footprint over the satellite radiotelephone frequency
band. An interference reducer is responsive to the space-based
component and to the ancillary terrestrial network that is
configured to reduce the interference from the wireless
communications that are received by the space-based component from
the first radiotelephone in the satellite footprint over the
satellite radiotelephone frequency band, using the wireless
communications that are received by the ancillary terrestrial
network from the second radiotelephone in the satellite footprint
over the satellite radiotelephone frequency band.
[0009] United States Patent Application Publication No.
2003/0054761 A1, published Mar. 20, 2003 to the present inventor
Karabinis and entitled Spatial Guardbands for Terrestrial Reuse of
Satellite Frequencies, the disclosure of which is hereby
incorporated herein by reference in its entirety as if set forth
fully herein, describes satellite radiotelephone systems that
include a space-based component that is configured to provide
wireless radiotelephone communications in a satellite footprint
over a satellite radiotelephone frequency band. The satellite
footprint is divided into a plurality of satellite cells, in which
satellite radiotelephone frequencies of the satellite
radiotelephone frequency band are spatially reused. An ancillary
terrestrial network is configured to terrestrially reuse at least
one of the ancillary radiotelephone frequencies that is used in a
satellite cell in the satellite footprint, outside the cell and in
some embodiments separated therefrom by a spatial guardband. The
spatial guardband may be sufficiently large to reduce or prevent
interference between the at least one of the satellite
radiotelephone frequencies that is used in the satellite cell in
the satellite footprint, and the at least one of the satellite
radiotelephone frequencies that is terrestrially reused outside the
satellite cell and separated therefrom by the spatial guardband.
The spatial guardband may be about half a radius of a satellite
cell in width.
[0010] United States Patent Application Publication No. US
2003/0054815 A1, published Mar. 20, 2003 to the present inventor
Karabinis, and entitled Methods and Systems for Modifying Satellite
Antenna Cell Patterns in Response to Terrestrial Reuse of Satellite
Frequencies, the disclosure of which is hereby incorporated herein
by reference in its entirety as if set forth fully herein,
describes that space-based wireless radiotelephone communications
are provided in a satellite footprint over a satellite
radiotelephone frequency band. The satellite footprint is divided
into satellite cells in which satellite radiotelephone frequencies
of the satellite radiotelephone frequency band are spatially
reused. At least one of the satellite radiotelephone frequencies
that is assigned to a given satellite cell in the satellite
footprint is terrestrially reused outside the given satellite cell.
A radiation pattern of at least the given satellite cell is
modified to reduce interference with the at least one of the
satellite radiotelephone frequencies that is terrestrially reused
outside the given satellite cell.
SUMMARY
[0011] According to embodiments of the present invention, a
communications system may include a terrestrial network having a
plurality of base stations providing communications service for
radioterminals over a terrestrial network coverage area. The
plurality of base stations may include interior base stations
providing communications service for radioterminals in an interior
portion of the terrestrial network coverage area and peripheral
base stations providing communications service for radioterminals
at a peripheral portion of the terrestrial network coverage area.
Moreover, at least one of the peripheral base stations may provide
transmissions directed toward an interior portion of the
terrestrial network coverage area with greater power than
transmissions directed away from interior portions of the
terrestrial network coverage area.
[0012] The peripheral base stations and/or interior base stations
may define a portion of a perimeter of the terrestrial network
coverage area such that interior base stations of the terrestrial
network are located on one side of the perimeter and not on the
other side of the perimeter. In addition, the perimeter may be
closed surrounding interior portions of the terrestrial network
coverage area. Moreover, at least one of the interior base stations
may define a plurality of sectors surrounding the interior base
station(s), and transmissions may be directed from the interior
base station(s) to each of the sectors so that transmissions are
directed over a 360 degree pattern surrounding the interior base
station.
[0013] At least one peripheral base stations may define a plurality
of sectors surrounding the peripheral base station(s), and the
peripheral base station(s) may provide transmissions to at least
one sector directed substantially toward an interior portion of the
terrestrial network coverage area with greater power than toward
another sector directed substantially away from interior portions
of the terrestrial network coverage area. At least one peripheral
base station(s) may include directional transmission antenna(s) for
sector(s) directed substantially toward interior portions of the
terrestrial network coverage area but not for the sector(s)
directed substantially away from interior portions of the
terrestrial network coverage area. In addition, at least one
peripheral base station(s) may include directional receive
antenna(s) directed to at least one of the sectors surrounding the
peripheral base station(s). Moreover, at least one peripheral base
station(s) may have fewer transmit sectors, fewer transmit antenna
elements, different transmit antenna elements, and/or different
transmit gain patterns than at least one interior base station.
[0014] The communications system may also include a second
terrestrial network having a second plurality of base stations
providing communications service for radioterminals over a second
terrestrial network coverage area, and a no-service region may
separate the first and second terrestrial network coverage areas.
Accordingly, communications services may not be provided by base
stations of either of the first or the second terrestrial networks
in the no-service region.
[0015] In addition, the communications system may include a space
based network including at least one satellite. The space based
network may provide communications service for radioterminals in a
first satellite coverage area using at least a first frequency of a
satellite frequency band, and the space based network may provide
communications service for radioterminals in a second satellite
coverage area using at least a second frequency of the satellite
frequency band. Moreover, at least a portion of the terrestrial
network coverage area may be within the first satellite coverage
area, and an entirety of the terrestrial network coverage area may
be outside the second satellite coverage area. In addition, at
least one of the base stations of the terrestrial network may
provide communications service using the second frequency of the
satellite frequency band, and at least one of the base stations may
not provide communications to and/or from the radioterminals
receiving communications from the base stations, using the first
frequency of the satellite frequency band.
[0016] The space based network may transmit communications to
radioterminals in the first satellite coverage area using the first
frequency, and the space based network may transmit communications
to radioterminals in the second satellite coverage area using the
second frequency. Moreover, the at least one of the base stations
of the terrestrial network may transmit communications using the
second frequency. In addition, the space based network may receive
communications from radioterminals in the first satellite coverage
area using at least a third frequency. The space based network may
receive communications from radioterminals in the second satellite
coverage area using at least a fourth frequency, at least one of
the base stations of the terrestrial network may receive
communications using the fourth frequency, and at least one of the
base stations of the terrestrial network may not receive
communications from the radio terminals receiving communications
from the base stations of the terrestrial network, using the third
frequency.
[0017] The terrestrial network may also include a plurality of
receive-only base stations configured to receive communications
from radioterminals at the peripheral portion of the terrestrial
network coverage area. Accordingly, communications service for a
radioterminal may be provided by a receive-only base station
receiving communications from the radioterminal and by another base
station transmitting communications to the radioterminal.
[0018] According to additional embodiments of the present
invention, a communications system may include a terrestrial
network having a plurality of base stations providing
communications service for radioterminals over a terrestrial
network coverage area. The plurality of base stations may include
interior base stations providing communications service for
radioterminals in an interior portion of the terrestrial network
coverage area and peripheral base stations providing communications
service for radioterminals at a peripheral portion of the
terrestrial network coverage area. Moreover, at least one of the
peripheral base stations may be a receive-only base station that
does not transmit.
[0019] The peripheral base stations and/or interior base stations
may define a portion of a perimeter of the terrestrial network
coverage area such that interior base stations of the terrestrial
network are located on one side of the perimeter and not on the
other side of the perimeter. In addition, the perimeter may be
closed surrounding interior portions of the terrestrial network
coverage area. Moreover, at least one interior base station(s) may
define a plurality of sectors surrounding the interior base
station(s), and transmissions may be directed from at least one
interior base station(s) to each of the sectors so that
transmissions are directed over a 360 degree pattern surrounding at
least one interior base station(s). At least one peripheral base
station(s) may define a plurality of sectors surrounding the
peripheral base station(s), and at least one peripheral base
station(s) may include directional reception antenna(s) for at
least one of the sectors.
[0020] The communications system may also include a second
terrestrial network having a second plurality of base stations
providing communications service for radioterminals over a second
terrestrial network coverage area. Moreover, a no-service region
may separate the first and second terrestrial network coverage
areas such that communications services are not provided by base
stations of either of the first or the second terrestrial networks
in the no-service region. In addition, the communications system
may also include a space based network having at least one
satellite. The space based network may provide communications
service for radioterminals in a first satellite coverage area using
at least a first frequency of a satellite frequency band, and the
space based network may provide communications service for
radioterminals in a second satellite coverage area using at least a
second frequency of the satellite frequency band. Moreover, at
least a portion of the terrestrial network coverage area may be
within the first satellite coverage area, and an entirety of the
terrestrial network coverage area may be outside the second
satellite coverage area. In addition, at least one of the base
stations may provide communications service using the second
frequency of the satellite frequency band, and at least one of the
base stations may not provide communications to and/or from the
radioterminals receiving communications from the base stations,
using the first frequency of the satellite frequency band.
[0021] The space based network may transmit communications to
radioterminals in the first satellite coverage area using the first
frequency, and the space based network may transmit communications
to radioterminals in the second satellite coverage area using the
second frequency. Moreover, the at least one of the base stations
of the terrestrial network may transmit communications using the
second frequency. The space based network may receive
communications from radioterminals in the first satellite coverage
area using at least a third frequency, and the space based network
may receive communications from radioterminals in the second
satellite coverage area using at least a fourth frequency. In
addition, at least one of the base stations of the terrestrial
network may receive communications using the fourth frequency, and
at least one of the base stations of the terrestrial network may
not receive communications, from the radio terminals receiving
communications from the base stations, using the third
frequency.
[0022] According to still additional embodiments of the present
invention, a communications system may include a terrestrial
network having a plurality of base stations providing
communications service for radioterminals over a terrestrial
network coverage area. The plurality of base stations may include
interior base stations providing communications service for
radioterminals in an interior portion of the terrestrial network
coverage area and peripheral base stations providing communications
service for radioterminals at a peripheral portion of the
terrestrial network coverage area. In addition, at least one of the
peripheral base stations may be substantially disabled for
transmission away from interior portions of the terrestrial network
coverage area.
[0023] The peripheral base stations and/or the interior base
stations may define a portion of a perimeter of the terrestrial
network coverage area such that interior base stations of the
terrestrial network are located on one side of the perimeter and
not on the other side of the perimeter. Moreover, the perimeter may
be closed surrounding interior portions of the terrestrial network
coverage area.
[0024] At least one of the peripheral base stations may have fewer
transmit sectors, fewer transmit antenna elements, different
transmit antenna elements, and/or different transmit gain patterns
than at least one of the interior base stations. Moreover, at least
one of the interior base stations may transmit and receive
communications, and at least one of the peripheral base stations
may be a receive-only peripheral base station. The communications
system may also include a second terrestrial network having a
second plurality of base stations providing communications service
for radioterminals over a second terrestrial network coverage area.
In addition, a no-service region may separate the first and second
terrestrial network coverage areas such that communications
services may not be provided by base stations of either of the
first or the second terrestrial networks in the no-service
region.
[0025] The communications system may also include a space based
network having at least one satellite. The space based network may
provide communications service for radioterminals in a first
satellite coverage area using at least a first frequency of a
satellite frequency band, and the space based network may provide
communications service for radioterminals in a second satellite
coverage area using at least a second frequency of the satellite
frequency band. At least a portion of the terrestrial network
coverage area may be within the first satellite coverage area, and
an entirety of the terrestrial network coverage area may be outside
the second satellite coverage area. Moreover, at least one of the
base stations may provide communications service using the second
frequency of the satellite frequency band, and at least one of the
base stations may not provide communications to and/or from the
radioterminals receiving communications from the base stations,
using the first frequency of the satellite frequency band.
[0026] At least one of the peripheral base stations may provide
transmissions directed toward an interior portion of the
terrestrial network coverage area with greater power than
transmissions directed away from interior portions of the
terrestrial network coverage area. At least one of the peripheral
base stations may be a receive-only base station that does not
transmit.
[0027] According to yet additional embodiments of the present
invention, methods of providing communications for radioterminals
may include providing communications service for radioterminals at
an interior portion of a terrestrial network coverage area using
interior base stations. Communications service may be provided for
radioterminals at a peripheral portion of the terrestrial network
coverage area using peripheral base stations. More particularly, at
least one of the peripheral base stations may provide transmissions
directed toward an interior portion of the terrestrial network
coverage area with greater power than transmissions directed away
from interior portions of the terrestrial network coverage
area.
[0028] According to more embodiments of the present invention,
methods of providing communications for radioterminals may include
providing communications service for radioterminals at an interior
portion of a terrestrial network coverage area using a plurality of
interior base stations. Communications service may be provided for
radioterminals at a peripheral portion of the terrestrial network
coverage area using a plurality of peripheral base stations wherein
at least one of the peripheral base stations is a receive-only base
station that does not transmit.
[0029] According to still more embodiments of the present
invention, methods of providing communications for radioterminals
may include providing communications for radioterminals at an
interior portion of a terrestrial network coverage area using a
plurality of interior base stations. Communications may be provided
for radioterminals at a peripheral portion of the terrestrial
network coverage area using a plurality of peripheral base stations
wherein at least one of the peripheral base stations is
substantially disabled for transmission away from interior portions
of the terrestrial network coverage area.
[0030] According to yet more embodiments of the present invention,
a communications system may include a plurality of interior
down-link transmitters configured to transmit communications to
radioterminals located in interior portions of a terrestrial
network coverage area. A plurality of interior up-link receivers
may be configured to receive communications from radioterminals
located in the interior portions of the terrestrial network
coverage area. In addition, a plurality of peripheral up-link
receivers may be configured to receive communications from
radioterminals located in a peripheral region of the terrestrial
network coverage area adjacent the interior portions of the
terrestrial network coverage area, wherein at least a portion of
the peripheral region is outside an engineered coverage area of any
down-link transmitters of the communications system.
[0031] Some embodiments of the present invention provide an
Ancillary Terrestrial Component (ATC) that is configured to
wirelessly communicate with a plurality of radioterminals using at
least one satellite radiotelephone frequency over an ATC service
area. The ATC includes a plurality of base stations that are
configured to wirelessly communicate with the plurality of
radioterminals using at least one satellite radiotelephone
frequency. The plurality of base stations includes at least one
interior base station that is located in an interior portion of the
ATC service area, and at least one peripheral base station that is
located at a periphery of the ATC service area. In some
embodiments, at least one peripheral base station has fewer
transmit sectors, fewer transmit antenna elements, different
transmit antenna elements and/or different transmit gain patterns
than at least one interior base station. In other embodiments, at
least one interior base station is at least one transmit and
receive interior base station, and the ATC further includes at
least one receive-only peripheral base station. Thus, systems and
methods are provided for modifying antenna radiation patterns of
peripheral base stations of an ancillary terrestrial component,
compared to interior base stations, to allow reduced
interference.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a diagram illustrating portions of a terrestrial
network according to first embodiments of the present
invention.
[0033] FIG. 2 is a diagram illustrating portions of a terrestrial
network according to second embodiments of the present
invention.
[0034] FIG. 3 is a diagram illustrating a terrestrial network
according to third embodiments of the present invention.
[0035] FIG. 4 is a diagram illustrating satellite and terrestrial
communications networks sharing a satellite frequency band
according to fourth embodiments of the present invention.
[0036] FIG. 5 is a diagram illustrating a terrestrial network
according to fifth embodiments of the present invention.
[0037] FIG. 6 is a diagram illustrating satellite and terrestrial
communications networks sharing a satellite frequency band
according to sixth embodiments of the present invention.
DETAILED DESCRIPTION
[0038] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings, in which
embodiments of the invention are shown. This invention may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein. Rather,
these embodiments are provided so that this disclosure will be
thorough and complete, and will fully convey the scope of the
invention to those skilled in the art. Like numbers refer to like
elements throughout.
[0039] It will be understood that although the terms first, second,
etc. are used herein to describe various elements, these elements
should not be limited by these terms. These terms are only used to
distinguish one element or embodiment from another element or
embodiment. Thus, a first element or embodiment below could be
termed a second element or embodiment, and similarly, a second
element or embodiment may be termed a first element or embodiment
without departing from the teachings of the present invention. As
used herein, the term "and/or" includes any and all combinations of
one or more of the associated listed items. Moreover, as used
herein, "substantially the same" band means that the bands
substantially overlap, but that there may be some areas of
non-overlap, for example at the band ends. Moreover, "substantially
the same" air interface(s) means that the air interfaces are
similar but need not be identical. Some changes may be made to one
air interface (i.e., a satellite air interface) relative to another
(i.e., a terrestrial air interface) to account for different
characteristics that may exist between the terrestrial and
satellite communications environments. For example, a different
vocoder rate may be used for satellite communications compared to
the vocoder rate that may be used for terrestrial communications
(i.e., for terrestrial communications, voice may be compressed
("vocoded") to approximately 9 to 13 kbps, whereas for satellite
communications a vocoder rate of 2 to 4 kbps, for example, may be
used). In addition or in alternatives, different forward error
correction coding, different interleaving depth, and/or different
spread-spectrum codes may be used, for example, for satellite
communications compared to the coding, interleaving depth, and/or
spread spectrum codes (i.e., Walsh codes, long codes, and/or
frequency hopping codes) that may be used for terrestrial
communications.
[0040] Moreover, as used herein, a "substantially southern" or a
"substantially northern" direction means a direction that includes
a component in a southern or northern direction, respectively. For
example, a southwestern direction may be a substantially southern
direction.
[0041] Satellite systems that may operate co-frequency (also
referred to as co-channel) with at least some frequencies of a
satellite system containing an Ancillary Terrestrial Component
(ATC) may receive co-frequency (co-channel) interference from the
co-frequency (co-channel) operations of the ATC. To reduce the
level of co-frequency (co-channel) interference that may be
generated by an ATC, the ATC base stations may be engineered with X
dB (e.g., 18 dB) of in-building penetration signal margin, such as,
for example, X dB of in-building penetration return-link signal
margin. This signal margin may enable an ATC radioterminal (i.e., a
radioterminal that is communicating with an ATC) to operate even
when it is subjected to X dB of structural signal attenuation and
may also facilitate a reduction of the radioterminal's output
signal power when the radioterminal is being subjected to less than
X dB of structural signal attenuation. In the limit, as the
radioterminal is not being subjected to any structural signal
attenuation (the radioterminal is entirely in the clear) the signal
power that the radioterminal may radiate in order to communicate
with a base station may be reduced by as much as X dB (e.g., 18 dB)
relative to maximum. This can reduce the level of interference that
may be sensed by a co-frequency (co-channel) satellite system.
[0042] As used herein, the term Ancillary Terrestrial Component
(ATC) may refer to one or more terrestrial base stations in a
terrestrial network of base stations providing communications
service for radioterminals over a terrestrial network coverage area
(also referred to as an ATC service area). For example, the term
Ancillary Terrestrial Component may refer to a single terrestrial
base station, with a plurality of such terrestrial base stations
providing service for radioterminals over a coverage area of a
terrestrial network (referred to as an Ancillary Terrestrial
Network (ATN)).
[0043] Cellular and PCS systems are routinely deployed in urban
areas with significant in-building signal penetration margins,
typically ranging between 15 to 20 dB. Engineering an ATC with X dB
(e.g., 18 dB) of structural attenuation signal margin may be
accomplished by using one of a plurality of established statistical
design methodologies that are known to those skilled in the art. In
accordance with an example of such a design methodology and as an
initial step, the link budget of a base station, and corresponding
radioterminal equipment, may be calculated and balanced,
bi-directionally, by taking into account some or all relevant base
station, radioterminal, and/or propagation environment parameters
such as the maximum Effective Isotropic Radiated Power (EIRP) of
the base station and radioterminal equipment, the propagation
exponent factor appropriate for the ATC environment, signal
attenuation due to multipath fading, receiver sensitivities of base
station and radioterminal, base station and/or radioterminal
antenna gain and diversity reception gain factor, etc., including a
signal loss of X dB (e.g., 18 dB) due to structural attenuation.
The bi-directionally balanced link budget can identify an estimate
of the service radius of a base station. At this service radius a
radioterminal may communicate with a base station, with certain
probability of success, subject to the assumed link budget
parameter values and propagation impairments including the effect
of one or more signal attenuating structures that may, in the
aggregate, impose X dB (e.g., 18 dB) of additional signal
attenuation beyond that imposed by the propagation loss (as
defined, for example, by the conventional Cost 231-Hata model) and
multipath fading loss. It follows that when a radioterminal is not
subject to any signal attenuating structures, it can, subject to
closed-loop power control, radiate at a reduced signal power level
that averages X dB (e.g., 18 dB) lower than its maximum.
[0044] An ATC service area may comprise an ensemble of ATC base
stations that may be engineered and deployed based on the above
design principles. In such an environment, as an active
radioterminal migrates from one ATC base station service area to
another, the system may continue to provide service to the
radioterminal via the ATC base station that can nominally provide
the highest signal quality and/or strength to that radioterminal.
As such, a radioterminal that is transitioning from the service
area of one ATC base station to another and is operating outside
the influence of any signal attenuating structures may, on average,
continue to radiate at a reduced signal power level of X dB (e.g.,
18 dB) less than its maximum.
[0045] According to some embodiments of the present invention, in
the proximity of a perimeter of an ATC service area, the ATC may be
configured to reduce, completely avoid and/or substantially
minimize serving radioterminals that may be beyond the engineered
service area of a base station and may thus radiate a higher level
of power. This may be accomplished, according to some embodiments,
by configuring and/or orienting the antenna elements of a base
station to substantially illuminate only certain directions that,
according to a link budget, may satisfy the X dB (e.g., 18 dB)
structural attenuation signal margin configuration design of an
ATC. Thus, for example, at least one ATC base station proximate to
a perimeter of an ATC service area may be configured with a reduced
(fewer) number of sectors, reduced (fewer) antenna elements and/or
different antenna elements, and may thus not be capable of
providing service in at least one direction, to substantially the
same radius as in another direction.
[0046] Thus, as shown in FIG. 1, an ATC includes a plurality of
base stations that are configured to wirelessly communicate with a
plurality of radioterminals using at least one satellite
radiotelephone frequency. The plurality of base stations include at
least one interior base station 10, that is located at an interior
portion of the ATC service area, and at least one peripheral base
station 20 that is located at a perimeter 30 of the ATC service
area. As shown in FIG. 1, at least one peripheral base station 20
has fewer sectors, fewer antenna elements, different antenna
elements and/or different gain patterns than at least one interior
base station 10. For example, as shown in FIG. 1, at least some of
the interior base stations 10 have complete 360.degree. coverage
using, for example, three sectors, whereas at least one of the
peripheral base stations 20 have a reduced number of sectors, such
as one or two sectors.
[0047] It will be understood by those having skill in the art that,
although FIG. 1 depicts a single row of peripheral base stations 20
adjacent the perimeter 30 of the ATC service area, more than one
row of peripheral base stations may be provided. It also will be
understood that, in some embodiments, only a single sector may be
provided for the perimeter base stations 20. In still other
embodiments, a complete set of sectors, such as three sectors, may
be provided, with reduced numbers of antenna elements, reduced
antenna gain, and/or reduced EIRP in one or more of the sectors,
compared to the interior base stations 10. Combinations of these
embodiments also may be provided. Moreover, each peripheral base
station need not include the same (reduced) number of sectors
and/or antenna elements, and not all peripheral base stations 20
need include fewer sectors, fewer antenna elements, different
antenna elements, and/or different (reduced) EIRP. In some
embodiments, the perimeter base stations 20 may communicate with an
interior base station 10. In other embodiments, the peripheral base
stations 20 may communicate with an ATC infrastructure.
[0048] In still other embodiments of the present invention, in lieu
of, or in combination with, the ATC configuration of FIG. 1, at
least one receive-only base station may be provided proximate to a
perimeter of an ATC footprint, that may have been engineered in
accordance with a link budget inclusive of X dB (e.g., 18 dB) of
structural signal attenuation, so as to maintain the emissions of a
radioterminal substantially in accordance with a reduced power
level criterion as the radioterminal continues to operate outside
of the engineered service footprint of the ATC.
[0049] Thus, as shown in FIG. 2, at least one peripheral ATC base
station may be a receive-only base station 40, which may include
the same number of sectors and/or receive antenna elements as the
interior ATC base stations 10 or, as shown in FIG. 2, may include
fewer sectors, fewer receive antenna elements and/or different
receive antenna elements compared to the interior ATC base stations
10. It also will be understood that, as with the reduced sector
and/or reduced antenna element peripheral base stations 20 of FIG.
1, the receive-only base stations 40 of FIG. 2 need not be
identical in their number of sectors and/or antenna elements, and
more than one row of receive-only base stations 40 may be provided.
Moreover, at least some of the receive-only base stations 40 may
communicate with an adjacent or non-adjacent interior ATC base
station 10 or may communicate with the ATC infrastructure.
Moreover, combinations of peripheral base stations 20 and 40 of
FIGS. 1 and 2 may be provided according to other embodiments of the
present invention.
[0050] Accordingly, embodiments of the present invention provide a
plurality of base stations that are configured to wirelessly
communicate with a plurality of radioterminals using at least one
satellite radiotelephone frequency. The plurality of base stations
include at least one interior base station that is located in an
interior portion of the ATC service area and at least one
peripheral base station that is located at a periphery of the ATC
service area. At least one peripheral base station has fewer
sectors, fewer antenna elements, different antenna elements,
different gain patterns, and/or different EIRP than at least one
interior base station. In other embodiments, at least one interior
base station is at least one transmit and receive interior base
station, and the ATC further includes at least one receive-only
peripheral base station.
[0051] Other embodiments of the present invention can configure at
least one peripheral base station 20 of an ATC, at the perimeter or
fringes 30 of an ATC service area to reduce or avoid serving
radioterminals that are beyond its engineered service footprint.
This may be accomplished in a variety of ways including orienting
some sectors of base stations to illuminate areas that are within
the ATC service footprint while disabling other sectors that may
illuminate areas away from the ATC service footprint. Such disabled
sectors can be configured as receive-only sectors. In some
embodiments, the signals that are received at a receive-only sector
may also be received by at least one other transmit and receive
sector and may be combined, using conventional techniques.
[0052] As such, a radioterminal that may be drifting away from the
core ATC service footprint, while continuing to communicate with a
base station by receiving on the side-lobes of an enabled sector,
may transmit back to that base station via the main lobe (or
substantially via the main lobe) of a receive-only sector that is
oriented toward it. In this configuration, the forward link to the
radioterminal generally will be a much weaker link than the return
link, and service to that radioterminal generally will terminate
due to forward link "breakage" before the radioterminal is at a
distance that may require it to radiate maximum or near maximum
power. Thus, a sharp decrease in base station forward-link signal
power may be established at an edge of an ATC service area by
judiciously configuring the sectors of base stations 20 that are at
or near the edge.
[0053] The front-to-back EIRP ratio of an ATC base station antenna
may be, per the ATC Rules, approximately 25 dB (see 47 CFR 25.253
(e)). Thus, a base station that is located at (or near) the edge of
an ATC service footprint can have at least one of its (typically
three) sectors transmit-disabled. In other words, the sector(s)
that would have pointed away from the ATC service footprint can be
disabled in their ability to transmit. For such a base station, a
user who is in an un-served area (an area that would have been
served by one of the transmit-disabled sectors) generally will
experience significant forward-link signal attenuation (of the
order of 25 dB) relative to a user who is at the same distance from
the base station tower and within a transmit-enabled sector. With a
forward link disadvantage of approximately 25 dB, the base station
service radius in the direction of a receive-only sector may shrink
to less than two tenths of what it would have been otherwise. It
follows that, in some embodiments, a radioterminal that is within a
receive-only sector and outside the influence of any signal
attenuating structures may radiate, subject to closed-loop power
control, approximately 25 dB less than it would have radiated at
the edge of a symmetrically engineered ATC sector.
[0054] According to additional embodiments of the present
invention, as illustrated in FIG. 3, a terrestrial communications
network 100 may include a plurality of interior and peripheral base
stations 110a-h and 120a-o respectively providing communications
service for radioterminals 150 over a terrestrial network coverage
area. The interior base stations 110 provide communications service
for radioterminals 150 in an interior portion of the terrestrial
network coverage area, and the peripheral base stations 120 provide
communications service for radioterminals at peripheral portions of
the terrestrial network coverage area. More particularly, at least
one of the peripheral base stations 120 may provide transmissions
directed toward an interior portion of the terrestrial network
coverage area with greater EIRP (power) than transmissions directed
away from interior portions of the terrestrial network coverage
area. For example, at least one of the peripheral base stations may
have fewer transmit sectors, fewer transmit antenna elements,
different transmit and/or receive antenna elements, and/or
different transmit and/or receive gain patterns and/or parameters
than at least one of the interior base stations.
[0055] More particularly, at least one interior base station(s) 110
may define a plurality of sectors surrounding the interior base
station, and at least one interior base station(s) 110 may direct
transmissions to all sectors surrounding the respective interior
base station(s) so that transmissions are directed over a 360
degree pattern surrounding the respective interior base station(s).
For example, one of the interior base stations may include
directional transmit antennas configured to provide transmissions
over a 120 degree sector, and the base station may include at least
three such directional antennas so that transmissions are directed
over three 120 degree sectors to cover a 360 degree pattern
surrounding the base station. In addition or in an alternative, one
or more interior base stations 110 may include omnidirectional
antennas and/or directional antennas. At least one of the interior
base stations may also be configured so that transmissions are
directed to a pattern of less than 360 degrees surrounding the at
least one interior base station. Transmission patterns and/or
sectors are not shown for the interior base stations 110 of FIG. 3
for the sake of clarity.
[0056] As discussed above, at least one of the peripheral base
stations 120 may provide transmissions directed toward an interior
portion of the terrestrial network coverage area with greater EIRP
(power) than transmissions directed away from interior portions of
the terrestrial network coverage area. More particularly, at least
one of the peripheral base stations may include one or more
directional transmit antennas each providing transmissions to a
sector, such as a 120 degree sector. Moreover, the directional
transmit antenna(s) on a peripheral base station 120 may be
oriented such that transmissions from the peripheral base station
120 are directed over a sector (or sectors) oriented substantially
toward interior portions of the terrestrial network coverage area
with greater EIRP (power) than is directed over a sector (or
sectors) oriented substantially away from interior portions of the
terrestrial network coverage area.
[0057] By way of example, the peripheral base stations 120 may
respectively include one or more directional transmit antennas
configured to provide transmissions to a respective 120 degree
transmit sector 121a-o or 122c or 122n. In the example of FIG. 3,
for the base stations 120a-b, 120d-m, and 120o, one or more
directional transmit antennas at each base station may be
configured to provide transmissions to radioterminals in a single
respective 120 degree sector 121a-b, 121d-m, and 120o. Moreover,
for the base stations 120c and 120n, directional transmit antennas
at each base station may be configured to provide transmissions to
radioterminals in two respective 120 degree sectors 121c, 122c,
121n, and 122n. Accordingly, the peripheral base stations 120a-o
may define a perimeter 125 (illustrated by the dotted line of FIG.
3) of the terrestrial network coverage area such that interior base
stations 110 are located on one side of the perimeter 125 and not
on the other side of the perimeter 125. As illustrated by the
dotted line of FIG. 3, the perimeter 125 may substantially follow
boundaries of sectors to which the peripheral base stations 120
transmit. The transmit sectors of the peripheral base stations may
define the peripheral portions of the terrestrial network coverage
area, and areas bounded by the peripheral portions may define the
interior portions of the terrestrial network coverage area.
[0058] In addition, the peripheral base stations 120a-o may include
directional receive antennas defining receive coverage sectors that
span a full 360 degree pattern surrounding each of the peripheral
base stations. For example, the peripheral base stations 120a-b,
120d-m, and 120o may include directional transmit antennas that
substantially transmit to a single respective 120 degree sector
121a-b, 121d-m, and 121o, without substantially transmitting to
sectors covering the remaining 240 degrees surrounding the base
station. Similarly, the peripheral base stations 120c and 120n may
include directional transmit antennas that substantially transmit
to two 120 degree sectors without substantially transmitting to the
remaining 120 degree sector surrounding the base station. The
peripheral base stations, however, may include directional receive
antennas configured to receive communications from radioterminals
in the sectors 121a-o and 122c and 122n to which the peripheral
base stations transmit as well as directional receive antennas
configured to receive communications from radioterminals in sectors
to which the peripheral base stations substantially do not
transmit. In an alternative or in addition, one or more of the
peripheral base stations may include one or more omnidirectional
receive antenna(s).
[0059] Accordingly, interior and exterior base stations 110 and 120
may provide communications services for radioterminals in a
coverage area and/or sector thereof using, for example, air
interface protocols and/or architectures such as FDM/FDMA
(frequency division multiplexed/multiple access), TDM/TDMA (time
division multiplexed/multiple access), CDM/CDMA (code division
multiplexed/multiple access), and/or OFDM/OFDMA (orthogonal
frequency division multiplexed/multiple access). Moreover, the base
stations of the terrestrial communications network 100 may employ a
frequency reuse and/or spreading code reuse pattern to increase an
efficiency of frequency usage and/or capacity and/or reduce
interference. For example, each base station may have a relatively
small coverage area and/or sector and adjacent base stations and/or
sectors may use different frequencies and/or spreading codes to
reduce interference therebetween.
[0060] Communications for a radioterminal 150a in an interior
portion of the terrestrial network coverage area may be provided by
an interior base station 110c as illustrated in FIG. 3. As the
radioterminal 150a changes position within the terrestrial network
coverage area during a communication such as a radiotelephone
conversation, communications services for the radioterminal 150a
may be handed off from one sector of base station 110c to another
sector of base station 110c, and/or to sectors of other interior or
peripheral base stations.
[0061] Communications for a radioterminal 150b in the peripheral
portion of the terrestrial network coverage area may be provided by
a peripheral base station 120g. As the radioterminal 150b is in the
sector 121g, to which transmit and receive antennas of the base
station 120g are directed, communications can be provided for the
radioterminal 150b within the sector 121g. Moreover, communications
services for the radioterminal 150b may be handed off from the base
station 120g to an adjacent interior or peripheral base station if
the radioterminal 150b moves from the sector 121g to a sector of
another base station.
[0062] As shown in FIG. 3, the sectors of peripheral base stations
may appear to have fixed boundaries defined by the transmit sectors
of the respective transmit antennas. As will be understood,
however, side lobes of the radiation patterns generated by the
directional transmit antennas of the peripheral base stations may
have sufficient energy to support acceptable link transmissions to
a radioterminal 150c outside the perimeter 125 of the terrestrial
network coverage area and outside the sector 121f of the peripheral
base station 120f. As discussed above, the peripheral base station
120f may include receive antennas, that may, for example, be
directional, supporting robust link reception of communications
from the mobile terminal outside sector 121f.
[0063] Accordingly, communications service for the radioterminal
150c may initially be provided by the base station 120f within
sector 121f, but the radioterminal 150c may then move outside the
sector 121f and away from the terrestrial network coverage area.
According to embodiments of the present invention, down-link
transmissions from the base station 120f to the radioterminal 150c
may continue to be provided by the directional antenna(s) servicing
the sector 121f, and the quality of the down-link communications
received by the radioterminal 150c may rapidly deteriorate. A
relatively high quality of up-link communications received by the
base station 120f from the radioterminal 150c, however, may be
maintained as the radioterminal 150c moves outside sector 121f,
because the base station 120f includes receive antennas covering a
full 360 degree pattern surrounding the base station 120f.
Accordingly, communications service for the radioterminal 150c will
most likely be terminated due to deterioration in the down-link
from the peripheral base station 120f to the radioterminal before
significant deterioration in the up-link from the radioterminal
150c to the base station 120f occurs which may cause the
radioterminal to radiate at, or near, maximum power.
[0064] By providing sectors outside the perimeter 125 wherein a
peripheral base station can receive via antennas operative in these
sectors up-link communications from a radioterminal without
transmitting communications to the radioterminal via antennas
operative in these sectors, communications with the radioterminal
may be terminated without causing the radioterminal to increase its
transmit power to a maximum, or near a maximum before termination.
More particularly, in a closed loop power control system, the base
station may request that the radioterminal increase its
transmission power as the signal strength and/or quality of
communications received by the base station decreases, and
similarly, the radioterminal may request that the base station
increase its transmission power as the signal strength and/or
quality of communications received by the radioterminal decreases.
Once the radioterminal 150c moves outside the sector 121f, a
strength and/or quality measure of base station transmissions
outside the sector 121f may decrease due to the directional nature
of the base station transmit antenna(s) and due to the limited
maximum EIRP (power) capability of the base station. The base
station, however, may not request any, or any significant, power
increases from the radioterminal because at least one base station
receive antenna is directed outside the perimeter 125. To increase
further the available return link margin between a radioterminal
and a base station and thus further reduce the transmit power of a
radioterminal, at least one antenna sub-system of a peripheral
and/or interior base station may be configured to receive in more
than one spatial orientation, such as in a vertical and horizontal
orientation (polarization diversity reception) and, in addition or
in an alternative, may also be configured with more than one
spatially distinct elements (space-diversity reception).
[0065] According to additional embodiments of the present
invention, one or more of the peripheral base stations 120a-o may
be located proximate to an airport, a navigable waterway, or other
region likely to include satellite communications terminals that
may be communicating with a satellite. For example, one or more
peripheral base stations 120a-o may be located proximate to a
boundary of an airport with at least one transmit sector of the
peripheral base station(s) proximate to the boundary of the airport
being directed away or substantially away from the airport and/or
having a reduced EIRP relative to other sectors. An area proximate
to an airport may also be served by configuring at least one base
station having at least one transmit sector whose antenna is
oriented to point and/or radiate substantially in a southern
direction. Providing communications service to an area proximate to
an airport with at least one base station sector that is oriented
to point and/or radiate in a substantially southern direction may
increase and/or maximize the antenna discrimination between a
satellite terminal (that may also be operative with its antenna
oriented in a substantially southern direction due to the location
of an orbital slot of a geostationary satellite) and the base
station sector. (It will be understood that a base station sector
that may be providing communications service to an area proximate
to an airport that is located below the earth's equator may be
oriented to point and/or radiate substantially in a northern
direction since relative to a satellite terminal that is located at
or near the airport (below the earth's equator) a geo-stationary
satellite orbital location may be at a northern or substantially
northern direction.)
[0066] The at least one transmit sector of the peripheral base
station(s) proximate to the airport being directed away or
substantially away from the airport and/or configured to radiate
substantially in a southern direction may also have a reduced EIRP
value relative to other base station sectors of the same or other
base stations. At least one transmit sector of the peripheral
and/or interior base stations(s) proximate and/or distant to the
airport may also be configured with a Left-Hand Circularly
Polarized (LHCP) antenna to further maximize a discrimination
between the antenna systems of the at least one transmit sector and
a satellite terminal that is configured with a Right-Hand
Circularly Polarized (RHCP) receive antenna. Accordingly,
interference with satellite communications terminals (aeronautical
or other) that may be operating at or near the airport resulting
from base station transmissions can be reduced or eliminated. The
interior base stations can thus be located on a first side of the
perimeter 125, and the peripheral base stations 120a-o may be
located such that the airport is on a second side of the perimeter
125.
[0067] In another example, one or more peripheral base stations
120a-o may be located proximate to a navigable waterway with at
least one transmit sector of the peripheral base station(s)
proximate to the navigable waterway being directed away or
substantially away from the navigable waterway and/or pointed in a
southern or substantially southern direction. Providing
communications service to an area proximate to a navigable waterway
(in the northern hemisphere) with at least one base station sector
that is oriented in a southern or substantially southern direction
and/or is configured to radiate in a southern or substantially
southern direction may increase and/or maximize the antenna
discrimination between a satellite terminal (that may also be
operative with its antenna oriented in a substantially southern
direction due to an orbital slot location of a geostationary
satellite) and the base station sector. (It will be understood that
a base station sector that may be providing communications service
to an area proximate to a waterway that is located below the
earth's equator (in the southern hemisphere) may be oriented to
point and/or radiate substantially in a northern direction since
relative to a satellite terminal that is located at or near the
waterway (below the earth's equator) a geo-stationary satellite
orbital location may be at a northern or substantially northern
direction.).
[0068] The at least one transmit sector of the peripheral base
station(s) proximate to the navigable waterway being directed to
radiate away or substantially away from the navigable waterway
and/or being directed to radiate in a southern or substantially
southern direction may also have a reduced EIRP value relative to
other base station sectors of the same or other base stations. At
least one transmit sector of the peripheral and/or interior base
station(s) proximate and/or distant to the navigable waterway may
also be configured with a Left-Hand Circularly Polarized (LHCP)
antenna to further maximize a discrimination between the antenna
systems of the at least one transmit sector and a satellite
terminal that is configured with a Right-Hand Circularly Polarized
(RHCP) antenna. Accordingly, interference with satellite
communications terminals at or proximate to the navigable waterway
that may be operative, for example, on boats and/or ships in the
navigable waterway, resulting from peripheral and/or interior base
station transmissions can be reduced or eliminated. The interior
base stations can thus be located on a first side of the perimeter
125, and the peripheral base stations 120a-o may be located such
that the navigable waterway is on a second side of the perimeter
125.
[0069] According to some embodiments of the present invention, the
terrestrial network 100 may be ancillary to a space based
communications network providing radiotelephone communications
using a satellite radiotelephone frequency band. Moreover, base
stations of the terrestrial network 100 may reuse at least one
frequency of the satellite frequency band, and the space based
communications network may provide communications for
radioterminals when outside the terrestrial network coverage area.
Accordingly, as the radioterminal 150c moves away from the
perimeter 125, communications with the radioterminal 150c may be
handed off to the space based network and/or to an alternate
terrestrial communications network such as a cellular and/or PCS
terrestrial communications network.
[0070] The sharing of frequencies of a satellite frequency band
between a space based communications network and a terrestrial
communications network is discussed, for example, in the following
U.S. patent and U.S. patent publications. Satellite radioterminal
communications systems and methods that may employ terrestrial
reuse of satellite frequencies are described, for example, in U.S.
Pat. No. 6,684,057 to Karabinis, entitled Systems and Methods for
Terrestrial Reuse of Cellular Satellite Frequency Spectrum; and
Published U.S. Patent Application Nos. US 2003/0054760 to
Karabinis, entitled Systems and Methods for Terrestrial Reuse of
Cellular Satellite Frequency Spectrum; US 2003/0054761 to
Karabinis, entitled Spatial Guardbands for Terrestrial Reuse of
Satellite Frequencies; US 2003/0054814 to Karabinis et al.,
entitled Systems and Methods for Monitoring Terrestrially Reused
Satellite Frequencies to Reduce Potential Interference; US
2003/0073436 to Karabinis et al., entitled Additional Systems and
Methods for Monitoring Terrestrially Reused Satellite Frequencies
to Reduce Potential Interference; US 2003/0054762 to Karabinis,
entitled Multi-Band/Multi-Mode Satellite Radiotelephone
Communications Systems and Methods; US 2003/0153267 to Karabinis,
entitled Wireless Communications Systems and Methods Using
Satellite-Linked Remote Terminal Interface Subsystems; US
2003/0224785 to Karabinis, entitled Systems and Methods for
Reducing Satellite Feeder Link Bandwidth/Carriers In Cellular
Satellite Systems; US 2002/0041575 to Karabinis et al., entitled
Coordinated Satellite-Terrestrial Frequency Reuse; US 2002/0090942
to Karabinis et al., 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; US 2003/0068978 to Karabinis et al., entitled
Space-Based Network Architectures for Satellite Radiotelephone
Systems; US 2003/0143949 to Karabinis, entitled Filters for
Combined Radiotelephone/GPS Terminals; US 2003/0153308 to
Karabinis, entitled Staggered Sectorization for Terrestrial Reuse
of Satellite Frequencies; and US 2003/0054815 to Karabinis,
entitled Methods and Systems for Modifying Satellite Antenna Cell
Patterns In Response to Terrestrial Reuse of Satellite Frequencies.
All of the above referenced patent publications and patent are
assigned to the assignee of the present invention, and the
disclosures of all of these patent publications and patent are
hereby incorporated herein by reference in their entirety as if set
forth fully herein.
[0071] As shown in FIG. 4, a plurality of terrestrial
communications networks 100a-d (for example, as discussed above
with respect to FIG. 3) may be separated by no-service regions such
that communications services are not provided by base stations of
any of the terrestrial communications networks 100a-d in the
no-service regions. Moreover, a space-based network including at
least one satellite 210 may provide communications service for
radioterminals outside coverage areas of terrestrial communications
networks 100a-d and within satellite coverage areas 212a-e (such as
radioterminals 150i-m) using frequencies of a satellite frequency
band.
[0072] Frequencies of the satellite frequency band may be reused
among the satellite coverage areas 212a-e such that, for example,
the same frequencies of the satellite frequency band may not be
reused to provide communications service in overlapping satellite
coverage areas. Moreover, frequencies of the satellite frequency
band may be reused within the terrestrial networks 100a-d such
that, for example, the same frequencies may not be reused in a
satellite coverage area and in a terrestrial network located in the
satellite coverage area. For example, the space-based network may
provide communications service for radioterminals in satellite
coverage area 212a (such as radioterminal 150i) using at least a
first frequency of the satellite frequency band, and the
space-based network may provide communications for radioterminals
in satellite coverage area 212b (such as radioterminal 150m) using
a second frequency of the satellite frequency band. In addition,
the terrestrial network 100d (or at least a portion thereof) is
within the first satellite coverage area 212a, and the terrestrial
network 100d is outside the satellite coverage area 212b.
Accordingly, at least one base station of the terrestrial network
100d may provide communications service for radioterminals in a
coverage area thereof (such as radioterminal 150h) using the second
frequency of the satellite frequency band, and none of the base
stations of the terrestrial network 100d may provide communications
service using the first frequency of the satellite frequency
band.
[0073] Similarly, base stations of terrestrial networks 100a-b may
provide communications service for radioterminals in a coverage
area thereof (such as radioterminals 150e-f) using frequencies of
the satellite frequency band other than frequencies used by the
space based network to provide communications service over
satellite coverage area 212b. Moreover, base stations of
terrestrial network 100c may provide communications service for
radioterminals in a coverage area thereof (such as radioterminal
150g) using frequencies of the satellite frequency band other than
frequencies used by the space based network to provide
communications service over satellite coverage area 212e.
[0074] More particularly, the satellite frequency band may include
down-link frequencies and up-link frequencies. Down-link
frequencies may be used by the base stations of the terrestrial
network(s) and by the satellite(s) of the space based network to
transmit communications to radioterminals. Up-link frequencies may
be used by the base stations of the terrestrial network(s) and by
the satellite(s) of the space based network to receive
communications from radioterminals. Accordingly, base stations of
terrestrial network(s) may share a satellite frequency band with
the space based network, but base stations of the terrestrial
network(s) may not transmit on frequencies that are received by the
space based network. Accordingly, base stations of the terrestrial
networks sharing frequencies of the satellite frequency band may
not interfere with frequencies received by the space based network.
For example, the space based network may transmit communications to
radioterminals in the satellite coverage area 212a using a first
frequency of the satellite frequency band, the space based network
may transmit to radioterminals in the satellite coverage area 212b
using a second frequency of the satellite frequency band, and at
least one base station of the terrestrial network 100d may transmit
communications using the second frequency of the satellite
frequency band.
[0075] Similarly, the space based network may receive
communications from radioterminals in the first satellite coverage
area 212a using a third frequency of the satellite frequency band,
and the space based network may receive communications from
radioterminals in the satellite coverage area 212b using a fourth
frequency of the satellite frequency band. Moreover, at least one
base station of the terrestrial network 100d may receive
communications from radioterminals using the fourth frequency of
the satellite frequency band, and none of the base stations of the
terrestrial network 100d may receive communications from
radioterminals that are communicating therewith using the third
frequency of the satellite frequency band (at least some of the
base stations of terrestrial network 100d may also be configured to
receive communications from radioterminals in the first satellite
coverage area 212a using the third frequency of the satellite
frequency band to communicate with the space based network).
[0076] A first radioterminal may thus transmit communications to a
peripheral base station of the terrestrial network 100d using the
fourth frequency and a second radioterminal in satellite coverage
area 212b may transmit to the space based network using the fourth
frequency. As discussed above with respect to FIG. 3,
communications between the first radioterminal and the terrestrial
network may be terminated without increasing a transmit power of
the first radioterminal to a maximum, or near maximum, level
because the peripheral base station provides transmissions directed
toward an interior portion of the coverage area of the terrestrial
network 100d with greater EIRP (power) than transmissions directed
away from interior portions of the terrestrial network 100d
coverage area. Accordingly, interference from the first
radioterminal with transmissions from the second radioterminal in
the satellite coverage area 212b to the space base network may be
reduced.
[0077] According to still additional embodiments of the present
invention, as illustrated in FIG. 5, a terrestrial communications
network 500 may include a plurality of interior and peripheral base
stations 510a-i and 520a-o providing communications service for
radioterminals 550 over a terrestrial network coverage area. The
interior base stations 510 provide communications service (both
transmitting down-link communications to radioterminals and
receiving up-link communications from radioterminals) for
radioterminals 550 in an interior portion of the terrestrial
network coverage area. In contrast, the peripheral base stations
520 may only receive up-link communications from radioterminals.
Stated in other words, at least one of the peripheral base stations
520 may be a receive-only base station.
[0078] More particularly, at least one of the interior base
stations 510 may define a plurality of sectors surrounding the at
least one interior base station, and the at least one interior base
station(s) 510 may direct transmissions to all sectors surrounding
the interior base station so that transmissions are directed over a
360 degree pattern surrounding the respective interior base
station. For example, one of the interior base stations may include
directional transmit antennas configured to provide transmissions
over a 120 degree sector, and the base station(s) may include at
least three such directional antennas so that transmissions are
directed over three 120 degree sectors to cover a 360 degree
pattern surrounding the base station. In addition or in an
alternative, one or more interior base stations 510 may include
omnidirectional antennas and/or directional antennas. At least one
of the interior base stations may also be configured so that
transmissions are directed to a pattern of less than 360 degrees
surrounding the at least one interior base station. Complete
transmission patterns and/or sectors are not shown for the interior
base stations 510 of FIG. 5 for the sake of clarity.
[0079] As discussed above, at least one of the peripheral base
stations 520 may be a receive-only base station(s). More
particularly, peripheral base stations may include one or more
receive antennas providing reception capability to at least one
sector, such as a 120 degree sector. Moreover, the receive
antenna(s) on a peripheral base station 520 may be oriented such
that reception for the peripheral base station 520 is directed over
a sector oriented substantially toward interior portions of the
terrestrial network coverage area with greater sensitivity than is
directed over a sector oriented substantially away from interior
portions of the terrestrial network coverage area. In an
alternative, a peripheral base station 520 may include receive
antennas directed over two or more sectors oriented substantially
toward interior portions of the terrestrial network coverage area,
and/or a peripheral base station 520 may include receive antennas
directed over a plurality of sectors covering a 360 degree pattern
surrounding the peripheral base station 520. An engineered boundary
of coverage areas of the interior base stations 510 may define a
perimeter 525 (illustrated by the dotted line of FIG. 5) of the
terrestrial network coverage area such that interior base stations
510 are located on one side of the perimeter 525 and not on the
other side of the perimeter 525. In an alternative or in addition,
one or more of the peripheral base stations may include one or more
omnidirectional receive antennas and/or one or more directional
receive antennas.
[0080] Accordingly, interior and exterior base stations 510 and 520
may provide communications services for radioterminals in a
coverage area and/or sector thereof using, for example, FDM/FDMA
(frequency division multiplexed/multiple access), TDM/TDMA (time
division multiplexed/multiple access), CDM/CDMA (code division
multiplexed/multiple access) architecture, and/or OFDM/OFDMA
(orthogonal frequency division multiplexed/multiple access).
Moreover, the base stations of the terrestrial communications
network 500 may employ a frequency reuse and/or spreading code
reuse pattern to increase an efficiency of frequency usage and/or
capacity and/or reduce interference. For example, each base station
may have a relatively small coverage area and/or sector and
adjacent base stations and/or sectors may use different frequencies
and/or spreading codes to reduce interference therebetween.
[0081] Communications service for a radioterminal 550a in an
interior portion of the terrestrial network coverage area may be
provided by an interior base station 510c as illustrated in FIG. 5.
As the radioterminal 550a moves within the terrestrial network
coverage area during a communication such as a radiotelephone
conversation, communications services for the radioterminal 550a
may be handed off from one sector of base station 510c to another
sector of base station 510c, and/or to sectors of other interior
and/or peripheral base stations. More particularly, a down-link for
transmissions to the radioterminal 510a and an up-link for
transmissions from the radioterminal may be provided by one or more
interior base stations as long as the radioterminal is within a
coverage area of one of the interior base stations.
[0082] As shown in FIG. 5, the engineered coverage areas of
interior base stations 510 may appear to have fixed boundaries
defined by the transmit sectors of the respective transmit
antennas. As will be understood, however, radiation patterns
generated by transmit antennas, such as by the transmit antennas of
the interior base station 510g, may have sufficient energy to
support transmissions to a radioterminal 550b outside the perimeter
525 of the terrestrial network engineered coverage area. As
discussed above, the peripheral base station 520g may include
receive antennas supporting robust link reception of communications
from the mobile terminal 550b outside the perimeter 525.
[0083] Accordingly, communications service for the radioterminal
550b may initially be provided by the interior base station 510g,
but the radioterminal 550b may then move outside the engineered
coverage area of interior base station 510g, outside the perimeter
525, and away from the terrestrial network engineered coverage
area. According to embodiments of the present invention,
transmissions from the base station 510g to the radioterminal 550b
may continue to be provided by the transmit antenna(s) of interior
base station 510g, and the quality of the communications received
by the radioterminal 550b may deteriorate. A relatively high
quality of communications received by the peripheral base station
520g from the radioterminal 550b, however, may be maintained as the
radioterminal 550b moves outside the engineered coverage area of
interior base station 510g. Accordingly, communications service for
the radioterminal 550b will most likely be terminated due to
deterioration in the down-link from the interior base station 510g
to the radioterminal 550b before significant deterioration in the
up-link from the radioterminal 550b to the base station 520g
occurs. (In an alternative, base station 520g and base station 510g
may be configured to combine their corresponding receptions from a
radioterminal such as their receptions from radioterminal 550b.)
Accordingly, down-link communications to the radioterminal 550b and
up-link communications from the radioterminal may be provided using
different base stations when the radioterminal 550b is outside the
engineered terrestrial network service perimeter 525.
[0084] By providing receive-only peripheral base stations outside
the perimeter 525 that can receive communications from a
radioterminal, communications with the radioterminal can be
terminated without causing the radioterminal to boost its transmit
power to a maximum, or a near maximum, level before termination.
More particularly, in a closed loop power control system, a
terrestrial network infrastructure such as, for example, a base
station (or base stations) may request that the radioterminal
increase its transmission power as the quality of communications
received by the infrastructure (base station or base stations)
decreases, and similarly, the radioterminal may request that an
infrastructure, such as, for example, a base station, providing
communications information to the radioterminal increase its
transmission power as the quality of communications received by the
radioterminal decreases. Once the radioterminal 550b moves
substantially outside the engineered coverage area of interior base
station 510g, and because the EIRP (power) from the base station
510g may be limited to a predetermined maximum, a strength and/or
quality measure of base station transmissions outside the
engineered coverage area thereof may decrease. An infrastructure of
the terrestrial communications network, however, such as base
station 510g, may not request any, or any significant, power
increases for transmissions from the radioterminal 550b that is
outside of the network's engineered limit(s) because receive
antennas from the base station 520g (and/or 510g) may be configured
to cover the areas outside of perimeter 525 not covered by transmit
and/or receive antennas of base station 510g in accordance with the
system's engineered limits and/or parameters. That is, for at least
some areas outside of perimeter 525 base station 510g on its own,
without aid of peripheral base station 520g, may not provide X dB
(i.e., 18 dB) of return-link structural attenuation margin.
[0085] According to additional embodiments of the present
invention, one or more of the peripheral base stations 520a-o may
be located proximate to an airport, a navigable waterway, or other
region likely to include satellite communications terminals. For
example, one or more peripheral base stations 520a-o may be located
proximate to a boundary of an airport with the peripheral base
station(s) being located between one or more of the interior base
stations 510a-i and the airport. Accordingly, interference with
satellite communications terminals in airplanes at the airport
resulting from base station transmissions of the terrestrial
network 500 can be reduced. The interior base stations 510a-i can
thus be located on a first side of the perimeter 525, and the
peripheral base stations 520a-o may be located such that the
airport is on a second side of the perimeter 525. Moreover, one or
more of the peripheral base stations may be between the perimeter
525 and the airport. In another example, one or more peripheral
base stations 520a-o may be located proximate to a navigable
waterway with one or more of the peripheral base stations 520a-o
being located between one or more of the interior base stations
510a-i and the waterway. Accordingly, interference with satellite
communications terminals on boats and/or ships in the navigable
waterway resulting from base station transmissions of the
terrestrial network 500 can be reduced. The interior base stations
can thus be located on a first side of the perimeter 525, and the
peripheral base stations 520a-o may be located such that the
navigable waterway is on a second side of the perimeter 525.
Moreover, one or more of the peripheral base stations 520a-o may be
between the perimeter 525 and the waterway.
[0086] According to some embodiments of the present invention, the
terrestrial network 500 may be ancillary to a space based
communications network providing radiotelephone communications
using a satellite radiotelephone frequency band. Moreover, base
stations of the terrestrial network 500 may reuse at least one
frequency of the satellite frequency band, and the space based
communications network may provide communications for
radioterminals when outside the terrestrial network coverage area.
Accordingly, as the radioterminal 550b moves away from the
perimeter 525, communications with the radioterminal 550b may be
handed off to the space based network and/or to an alternative
terrestrial communications network such as a cellular and/or PCS
terrestrial communications network.
[0087] The sharing of frequencies of a satellite frequency band
between a space based communications network and a terrestrial
communications network is discussed, for example, in the following
U.S. patent and U.S. patent publications. Satellite radioterminal
communications systems and methods that may employ terrestrial
reuse of satellite frequencies are described, for example, in U.S.
Pat. No. 6,684,057 to Karabinis, entitled Systems and Methods for
Terrestrial Reuse of Cellular Satellite Frequency Spectrum; and
Published U.S. Patent Application Nos. US 2003/0054760 to
Karabinis, entitled Systems and Methods for Terrestrial Reuse of
Cellular Satellite Frequency Spectrum; US 2003/0054761 to
Karabinis, entitled Spatial Guardbands for Terrestrial Reuse of
Satellite Frequencies; US 2003/0054814 to Karabinis et al.,
entitled Systems and Methods for Monitoring Terrestrially Reused
Satellite Frequencies to Reduce Potential Interference; US
2003/0073436 to Karabinis et al., entitled Additional Systems and
Methods for Monitoring Terrestrially Reused Satellite Frequencies
to Reduce Potential Interference; US 2003/0054762 to Karabinis,
entitled Multi-Band/Multi-Mode Satellite Radiotelephone
Communications Systems and Methods; US 2003/0153267 to Karabinis,
entitled Wireless Communications Systems and Methods Using
Satellite-Linked Remote Terminal Interface Subsystems; US
2003/0224785 to Karabinis, entitled Systems and Methods for
Reducing Satellite Feeder Link Bandwidth/Carriers In Cellular
Satellite Systems; US 2002/0041575 to Karabinis et al., entitled
Coordinated Satellite-Terrestrial Frequency Reuse; US 2002/0090942
to Karabinis et al., 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; US 2003/0068978 to Karabinis et al., entitled
Space-Based Network Architectures for Satellite Radiotelephone
Systems; US 2003/0143949 to Karabinis, entitled Filters for
Combined Radiotelephone/GPS Terminals; US 2003/0153308 to
Karabinis, entitled Staggered Sectorization for Terrestrial Reuse
of Satellite Frequencies; and US 2003/0054815 to Karabinis,
entitled Methods and Systems for Modifying Satellite Antenna Cell
Patterns In Response to Terrestrial Reuse of Satellite Frequencies.
All of the above referenced patent publications and patent are
assigned to the assignee of the present invention, and the
disclosures of all of these patent publications and patent are
hereby incorporated herein by reference in their entirety as if set
forth fully herein.
[0088] As shown in FIG. 6, a plurality of terrestrial
communications networks 500a-d (as discussed above with respect to
FIG. 5) may be separated by no-service regions such that
communications services are not provided by base stations of any of
the terrestrial communications networks 500a-d in the no-service
regions. Moreover, a space-based network including at least one
satellite 610 may provide communications service for radioterminals
outside coverage areas of terrestrial communications networks
500a-d and within satellite coverage areas 612a-e (such as
radioterminals 550i-m) using frequencies of a satellite frequency
band.
[0089] Frequencies of the satellite frequency band may be reused
among the satellite coverage areas 612a-e such that, for example,
the same frequencies of the satellite frequency band are not reused
to provide communications service in overlapping satellite coverage
areas. Moreover, frequencies of the satellite frequency band may be
reused within the terrestrial networks 500a-d such that, for
example, the same frequencies are not reused in a satellite
coverage area and in a terrestrial network located in the satellite
coverage area. For example, the space-based network may provide
communications service for radioterminals in satellite coverage
area 612a (such as radioterminal 550i) using at least a first
frequency of the satellite frequency band, and the space-based
network may provide communications for radioterminals in satellite
coverage area 612b (such as radioterminal 550m) using a second
frequency of the satellite frequency band. In addition, the
terrestrial network 500d (or at least a portion thereof) is within
the first satellite coverage area 612a, and the terrestrial network
500d is outside the satellite coverage area 612b. Accordingly, at
least one base station of the terrestrial network 500d may provide
communications service for radioterminals in a coverage area
thereof (such as radioterminal 550h) using the second frequency of
the satellite frequency band, and none of the base stations of the
terrestrial network 500d may provide communications service using
the first frequency of the satellite frequency band.
[0090] Similarly, base stations of terrestrial networks 500a-b may,
for example, provide communications service for radioterminals in a
coverage area thereof (such as radioterminals 550e-f) using
frequencies of the satellite frequency band other than frequencies
used by the space based network to provide communications service
over satellite coverage area 612b. Moreover, base stations of
terrestrial network 500c may, for example, provide communications
service for radioterminals in a coverage area thereof (such as
radioterminal 550g) using frequencies of the satellite frequency
band other than frequencies used by the space based network to
provide communications service over satellite coverage area
612e.
[0091] More particularly, the satellite frequency band may include
down-link frequencies and up-link frequencies. Down-link
frequencies may be used by the base stations of the terrestrial
network(s) and by the satellite(s) of the space based network to
transmit communications to radioterminals. Up-link frequencies may
be used by the base stations of the terrestrial networks and by the
satellite(s) of the space based network to receive communications
from radioterminals. Accordingly, base stations of terrestrial
networks may share a satellite frequency band with the space based
network, but base stations of the terrestrial networks may not, for
example, transmit on frequencies that are received by the space
based network. Accordingly, base stations of the terrestrial
networks sharing frequencies of the satellite frequency band may
not interfere with frequencies received by the space based network.
For example, the space based network may transmit communications to
radioterminals in the satellite coverage area 612a using a first
frequency of the satellite frequency band, the space based network
may transmit to radioterminals in the satellite coverage area 612b
using a second frequency of the satellite frequency band, and at
least one base station of the terrestrial network 500d may transmit
communications using the second frequency of the satellite
frequency band.
[0092] Similarly, the space based network may receive
communications from radioterminals in the first satellite coverage
area 612a using a third frequency of the satellite frequency band,
and the space based network may receive communications from
radioterminals in the satellite coverage area 612b using a fourth
frequency of the satellite frequency band. Moreover, at least one
base station of the terrestrial network 500d may receive
communications from radioterminals that it is transmitting
communications to using the fourth frequency of the satellite
frequency band, and none of the base stations of the terrestrial
network 500d may receive communications from radioterminals that
are communicating therewith using the third frequency of the
satellite frequency band. (At least some of the base stations of
the terrestrial network 500d may also be configured to receive
communications from radioterminals in the first satellite coverage
area 612a using the third frequency of the satellite frequency band
to communicate with the space based network.)
[0093] A first radioterminal may thus transmit communications to a
peripheral base station of the terrestrial network 500d using the
fourth frequency and a second radioterminal in satellite coverage
area 612b may transmit to the space based network using the fourth
frequency. As discussed above with respect to FIG. 5,
communications between the first radioterminal and the terrestrial
network may be terminated without increasing a transmit power of
the first radioterminal to a maximum, or near maximum, level
because the peripheral receive-only base station provides at least
one receive antenna directed toward an interior portion of the
coverage area of the terrestrial network 500d such as to provide a
high-quality return link for the first radioterminal. Accordingly,
interference from the first radioterminal with transmission from
the second radioterminal in the satellite coverage area 612b to the
space base network can be reduced.
[0094] Moreover, elements of embodiments discussed above with
respect to FIGS. 3-6 may be combined. For example, the terrestrial
communications networks 100 of FIGS. 3 and/or 4 may include one or
more receive-only base stations configured to receive
communications from radioterminals outside the perimeter 125 (as
discussed above with respect to peripheral base stations 520 of
FIG. 5) thereby further enhancing up-link quality as compared to
down-link quality outside the perimeter 125. In addition or in an
alternative, a receive-only base station may be substituted for one
or more of the peripheral base stations 120 of FIGS. 3 and/or
4.
[0095] Similarly, the terrestrial communications networks 500 of
FIGS. 5 and 6 may include one or more base stations providing
transmissions directed toward an interior portion of the
terrestrial network coverage area with greater power than
transmissions directed away from interior portions of the
terrestrial network coverage area (as discussed above with respect
to peripheral base stations 120 of FIG. 3). For example, a
peripheral base station 120 as discussed above with respect to FIG.
3 may be substituted for one or more of the interior base stations
510a-b, 510d, 510e-g, or 510h-i along the perimeter 525. In
addition or in an alternative, a peripheral base station 120 as
discussed above with respect to FIG. 3 may be substituted for one
or more of the peripheral base stations 520 of FIG. 5.
[0096] In the drawings and specification, there have been disclosed
typical embodiments of the invention and, although specific terms
are employed, they are used in a generic and descriptive sense only
and not for purposes of limitation, the scope of the invention
being set forth in the following claims. Moreover, while particular
systems are discussed above with respect to the figures, analogous
methods are also included in the present invention.
* * * * *