U.S. patent application number 14/166582 was filed with the patent office on 2015-01-08 for payload for a multibeam communication satellite of a hub-spoke system with receive and transmit switching pattern synchronized over a frame for flexible forward and return capacity allocation.
This patent application is currently assigned to ViaSat, Inc.. The applicant listed for this patent is ViaSat, Inc.. Invention is credited to Kenneth V. Buer, Mark J. Miller.
Application Number | 20150009891 14/166582 |
Document ID | / |
Family ID | 46634559 |
Filed Date | 2015-01-08 |
United States Patent
Application |
20150009891 |
Kind Code |
A1 |
Miller; Mark J. ; et
al. |
January 8, 2015 |
PAYLOAD FOR A MULTIBEAM COMMUNICATION SATELLITE OF A HUB-SPOKE
SYSTEM WITH RECEIVE AND TRANSMIT SWITCHING PATTERN SYNCHRONIZED
OVER A FRAME FOR FLEXIBLE FORWARD AND RETURN CAPACITY
ALLOCATION
Abstract
A method for conducting communications via a satellite includes
providing a hub-spoke spot beam group. The hub-spoke spot beam
group includes at least one fixed location spot beam illuminating a
location containing a gateway terminal and at least one fixed
location spot beam illuminating a location containing at least one
user terminal. The satellite comprises a pathway associated with
the hub-spoke spot beam group. At least one receive-side switch is
sequentially switched to connect an input of the pathway with
different spot beams within the hub-spoke spot beam group. At least
one transmit-side switch is sequentially switched to connect an
output of the pathway with different spot beams within the
hub-spoke spot beam group. Beam switching patterns support both
forward and return traffic within a frame.
Inventors: |
Miller; Mark J.; (San
Marcos, CA) ; Buer; Kenneth V.; (Gilbert,
AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ViaSat, Inc. |
Carlsbad |
CA |
US |
|
|
Assignee: |
ViaSat, Inc.
Carlsbad
CA
|
Family ID: |
46634559 |
Appl. No.: |
14/166582 |
Filed: |
January 28, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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PCT/US2012/048668 |
Jul 27, 2012 |
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14166582 |
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61513317 |
Jul 29, 2011 |
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61568569 |
Dec 8, 2011 |
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61568578 |
Dec 8, 2011 |
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61591810 |
Jan 27, 2012 |
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Current U.S.
Class: |
370/316 |
Current CPC
Class: |
H04B 7/18515 20130101;
H04L 49/252 20130101; H04B 7/18584 20130101; H04L 49/10 20130101;
H04W 88/16 20130101; H04B 7/18519 20130101 |
Class at
Publication: |
370/316 |
International
Class: |
H04B 7/185 20060101
H04B007/185 |
Claims
1. A method for conducting communications via a satellite
comprising: providing a hub-spoke spot beam group using at least
one directional antenna on the satellite, the hub-spoke spot beam
group comprising at least one fixed location spot beam illuminating
a location containing a gateway terminal and at least one other
fixed location spot beam illuminating a location containing at
least one user terminal; wherein the satellite comprises a pathway
associated with the hub-spoke spot beam group; sequentially
switching at least one receive-side switch to connect an input of
the pathway with different spot beams within the hub-spoke spot
beam group, according to a receive beam switching pattern;
sequentially switching at least one transmit-side switch to connect
an output of the pathway with different spot beams within the
hub-spoke spot beam group, according to a transmit beam switching
pattern; wherein the receive beam switching pattern and the
transmit beam switching pattern are synchronized over a frame to
establish both forward traffic and return traffic over the pathway
during the frame, the forward traffic being sent from the gateway
to the at least one user terminal, the return traffic being sent
from the at least one user terminal to the gateway; and wherein a
first fraction of time in the frame is used to support forward
traffic and a second fraction of time in the frame is used to
support return traffic, wherein the first and second fractions are
selected based on a desired ratio between forward and return
capacity.
2. The method of claim 1 wherein the receive beam switching pattern
and transmit beam switching pattern are repeated in each of a
plurality of consecutive frames.
3. The method of claim 1 wherein the location illuminated by the at
least one fixed location spot beam and containing the gateway
terminal also contains at least one user terminal.
4. The method of claim 1 wherein the satellite comprises a
plurality of pathways, each associated with a corresponding
hub-spoke spot beam group, wherein for each pathway and
corresponding hub-spoke spot beam group: at least one receive-side
switch is sequentially switched according to a receive beam
switching pattern, and at least one transmit-side switch is
sequentially switched according to a transmit beam switching
pattern, to establish both forward traffic and return traffic over
the pathway during the frame, and a first fraction of time in the
frame is used to support forward traffic and a second fraction of
time in the frame is used to support return traffic, wherein the
first and second fractions are selected based on a desired ratio
between forward and return capacity.
5. The method of claim 1 wherein the pathway associated with the
hub-spoke spot beam group comprises a receiver and a
transmitter.
6. The method of claim 5 wherein the receiver comprises a low noise
amplifier (LNA).
7. The method of claim 5 wherein the transmitter comprises a high
power amplifier (HPA).
8. A satellite communication system comprising: a gateway; at least
one user terminal; a satellite coupled to the gateway and the at
least one user terminal; wherein the satellite comprises: at least
one directional antenna and a pathway coupled to the at least one
directional antenna, the pathway associated with a hub-spoke spot
beam group comprising at least one fixed location spot beam
illuminating a location containing the gateway terminal and at
least one other fixed location spot beam illuminating a location
containing the at least one user terminal; at least one
receive-side switch coupled to an input of the pathway, the at
least one receive-side switch configured to perform sequential
switching to connect the input of the pathway with different spot
beams within the hub-spoke spot beam group, according to a receive
beam switching pattern; at least one transmit-side switch coupled
to an output of the pathway, the at least one transmit-side switch
configured to perform sequential switching to connect the output of
the pathway with different spot beams within the hub-spoke spot
beam group, according to a transmit beam switching pattern; wherein
the receive beam switching pattern and transmit beam switching
pattern are synchronized over a frame to establish both forward
traffic and return traffic over the pathway during the frame, the
forward traffic being sent from the gateway to the at least one
user terminal, the return traffic being sent from the at least one
user terminal to the gateway; and wherein a first fraction of time
in the frame is used to support forward traffic and a second
fraction of time in the frame is used to support return traffic,
wherein the first and second fractions are selected based on a
desired ratio between forward and return capacity.
9. The satellite communication system of claim 8 wherein the
receive beam switching pattern and transmit beam switching pattern
are repeated in each of a plurality of consecutive frames.
10. The satellite communication system of claim 8 wherein the
location illuminated by the at least one fixed location spot beam
and containing the gateway terminal also contains at least one user
terminal
11. The satellite communication system of claim 8 wherein the
satellite comprises a plurality of pathways, each associated with a
corresponding hub-spoke spot beam group, wherein for each pathway
and corresponding hub-spoke spot beam group: at least one
receive-side switch is sequentially switched according to a receive
beam switching pattern, and at least one transmit-side switch is
sequentially according to a transmit beam switching pattern, to
establish both forward traffic and return traffic over the pathway
during the frame, and a first fraction of time in the frame is used
to support forward traffic and a second fraction of time in the
frame is used to support return traffic, wherein the first and
second fractions are selected based on a desired ratio between
forward and return capacity.
12. The satellite communication system of claim 8 wherein the
satellite further comprises one or more low noise amplifiers (LNAs)
each connecting an input of the at least one receive-side switch
with a different spot beam within the hub-spoke spot beam
group.
13. The satellite communication system of claims 8 wherein the at
least one receive-side switch is implemented as a plurality of
on-off controllable low noise amplifiers (LNAs), the on-off
controllable LNAs having inputs connecting with different spot
beams within the hub-spoke spot beam group and outputs combined
with at least one combiner, the at least one combiner having an
output connecting with the input of the pathway.
14. The satellite communication system of claim 8 wherein the
pathway associated with the hub-spoke spot beam group comprises a
receiver and a transmitter.
15. The satellite communication system of claim 14 wherein the
receiver comprises a low noise amplifier (LNA).
16. The satellite communication system of claim 14 wherein the
transmitter comprises a high power amplifier (HPA).
17. A communications satellite comprising: at least one directional
antenna; a pathway coupled to the at least one directional antenna,
the pathway associated with a hub-spoke spot beam group comprising
at least one fixed location spot beam illuminating a location
containing a gateway terminal and at least one other fixed location
spot beam illuminating a location containing at least one user
terminal; at least one receive-side switch coupled to an input of
the pathway, the at least one receive-side switch configured to
perform sequential switching to connect the input of the pathway
with different spot beams within the hub-spoke spot beam group,
according to a receive beam switching pattern; at least one
transmit-side switch coupled to an output of the pathway, the at
least one transmit-side switch configured to perform sequential
switching to connect the output of the pathway with different spot
beams within the hub-spoke spot beam group, according to a transmit
beam switching pattern; wherein the receive beam switching pattern
and transmit beam switching pattern are synchronized over a frame
to establish both forward traffic and return traffic over the
pathway during the frame, the forward traffic being sent from the
gateway to the at least one user terminal, the return traffic being
sent from the at least one user terminal to the gateway; and
wherein a first fraction of time in the frame is used to support
forward traffic and a second fraction of time in the frame is used
to support return traffic, wherein the first and second fractions
are selected based on a desired ratio between forward and return
capacity.
18. The communications satellite of claim 17 wherein the receive
beam switching pattern and transmit beam switching pattern are
repeated in each of a plurality of consecutive frames.
19. The communications satellite of claim 17 wherein the satellite
comprises a plurality of pathways, each associated with a
corresponding hub-spoke spot beam group, wherein for each pathway
and corresponding hub-spoke spot beam group: at least one
receive-side switch is sequentially switched according to a receive
beam switching pattern, and at least one transmit-side switch is
sequentially according to a transmit beam switching pattern, to
establish both forward traffic and return traffic over the pathway
during the frame, and a first fraction of time in the frame is used
to support forward traffic and a second fraction of time in the
frame is used to support return traffic, wherein the first and
second fractions are selected based on a desired ratio between
forward and return capacity.
20. The communications satellite of claim 17 further comprising one
or more low noise amplifiers (LNAs) each connecting an input of the
at least one receive-side switch with a different spot beam within
the hub-spoke spot beam group.
21-30. (canceled)
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] The present application is a continuation of International
Application No. PCT/US2012/048668, filed Jul. 27, 2012, which
claims benefit of priority of U.S. Provisional Application Nos.
61/513,317, filed Jul. 29, 2011; 61/568,569, filed Dec. 8, 2011;
61/568,578, filed Dec. 8, 2011; and 61/591,810, filed Jan. 27,
2012; the entire contents of which are incorporated herein by
reference in their entirety for all purposes.
FIELD OF THE INVENTION
[0002] The present invention relates generally to satellite
communication systems and, more particularly, to providing flexible
forward and return capacity allocation in a hub-spoke satellite
communication system.
BACKGROUND
[0003] Broadband internet access may be provided via
satellite-based communication systems. Systems have been fielded
which provide multi-Gbps capacity. The systems fielded to date have
fixed designs based on pre-defined allocation of capacity as a
function of geography, data flow direction, etc.
SUMMARY
[0004] Some embodiments of the present invention provide a high
capacity hub-spoke spot beam satellite architecture with increased
flexibility for allocating capacity both temporally and spatially
as well as between both forward and return traffic.
[0005] In accordance with an embodiment of the invention, a method
for conducting communications via a satellite may include providing
a hub-spoke spot beam group using at least one directional antenna
on the satellite. The hub-spoke spot beam group may include at
least one fixed location spot beam illuminating a location
containing a gateway terminal and at least one other fixed location
spot beam illuminating a location containing at least one user
terminal. The satellite may include a pathway associated with the
hub-spoke spot beam group. At least one receive-side switch may be
sequentially switched to connect an input of the pathway with
different spot beams within the hub-spoke spot beam group according
to a receive beam switching pattern. At least one transmit-side
switch may be sequentially switched to connect an output of the
pathway with different spot beams within the hub-spoke spot beam
group according to a transmit beam switching pattern. The receive
beam switching pattern and the transmit beam switching pattern may
be synchronized over a frame to establish both forward traffic and
return traffic over the pathway during the frame. The forward
traffic may be sent from the gateway to the at least one user
terminal, and the return traffic may be sent from the at least one
user terminal to the gateway. A first fraction of time in the frame
may be used to support forward traffic, and a second fraction of
time in the frame may be used to support return traffic. The first
and second fractions may be selected based on a desired ratio
between forward and return capacity.
[0006] In an embodiment, the receive beam switching pattern and
transmit beam switching pattern may be repeated in each of a
plurality of consecutive frames.
[0007] In another embodiment, the location illuminated by the at
least one fixed location spot beam and containing the gateway
terminal may also contain at least one user terminal.
[0008] In another embodiment, the satellite may include a plurality
of pathways each associated with a corresponding hub-spoke spot
beam group. For each pathway and corresponding hub-spoke spot beam
group, at least one receive-side switch may be sequentially
switched according to a receive beam switching pattern, and at
least one transmit-side switch may be sequentially switched
according to a transmit beam switching pattern, to establish both
forward traffic and return traffic over the pathway during the
frame. A first fraction of time in the frame may be used to support
forward traffic, and a second fraction of time in the frame may be
used to support return traffic. The first and second fractions may
be selected based on a desired ratio between forward and return
capacity.
[0009] In yet another embodiment, the pathway associated with the
hub-spoke spot beam group may include a receiver and a transmitter.
In some embodiments, the receiver may include a low noise amplifier
(LNA). In other embodiments, the transmitter may include a
high-power amplifier (HPA).
[0010] In accordance with another embodiment of the invention, a
satellite communication system may include a gateway, at least one
user terminal, and a satellite coupled to the gateway and the at
least one user terminal. The satellite may include at least one
directional antenna and a pathway coupled to the at least one
directional antenna. The pathway may be associated with a hub-spoke
spot beam group comprising at least one fixed location spot beam
illuminating a location containing the gateway terminal and at
least one other fixed location spot beam illuminating a location
containing the at least one user terminal. The satellite may also
include at least one receive-side switch coupled to an input of the
pathway. The at least one receive-side switch may be configured to
perform sequential switching to connect the input of the pathway
with different spot beams within the hub-spoke spot beam group
according to a receive beam switching pattern. The satellite may
also include at least one transmit-side switch coupled to an output
of the pathway. The at least one transmit-side switch may be
configured to perform sequential switching to connect the output of
the pathway with different spot beams within the hub-spoke spot
beam group according to a transmit beam switching pattern. The
receive beam switching pattern and transmit beam switching pattern
may be synchronized over a frame to establish both forward traffic
and return traffic over the pathway during the frame. The forward
traffic may be sent from the gateway to the at least one user
terminal, and the return traffic may be sent from the at least one
user terminal to the gateway. A first fraction of time in the frame
may be used to support forward traffic, and a second fraction of
time in the frame may be used to support return traffic. The first
and second fractions may be selected based on a desired ratio
between forward and return capacity.
[0011] In an embodiment, the satellite may further include one or
more LNAs each connecting an input of the at least one receive-side
switch with a different spot beam within the hub-spoke spot beam
group.
[0012] In another embodiment, the at least one receive-side switch
may be implemented as a plurality of on-off controllable LNAs. The
on-off controllable LNAs may have inputs connecting with different
spot beams within the hub-spoke spot beam group and outputs
combined with at least one combiner. The at least one combiner may
have an output connecting with the input of the pathway.
[0013] In accordance with another embodiment of the invention, a
communications satellite includes at least one directional antenna
and a pathway coupled to the at least one directional antenna. The
pathway may be associated with a hub-spoke spot beam group
comprising at least one fixed location spot beam illuminating a
location containing a gateway terminal and at least one other fixed
location spot beam illuminating a location containing at least one
user terminal. The communications satellite may also include at
least one receive-side switch coupled to an input of the pathway.
The at least one receive-side switch may be configured to perform
sequential switching to connect the input of the pathway with
different spot beams within the hub-spoke spot beam group according
to a receive beam switching pattern. The communications satellite
may also include at least one transmit-side switch coupled to an
output of the pathway. The at least one transmit-side switch may be
configured to perform sequential switching to connect the output of
the pathway with different spot beams within the hub-spoke spot
beam group according to a transmit beam switching pattern. The
receive beam switching pattern and transmit beam switching pattern
may be synchronized over a frame to establish both forward traffic
and return traffic over the pathway during the frame. The forward
traffic may be sent from the gateway to the at least one user
terminal, and the return traffic may be sent from the at least one
user terminal to the gateway. A first fraction of time in the frame
may be used to support forward traffic, and a second fraction of
time in the frame may be used to support return traffic. The first
and second fractions may be selected based on a desired ratio
between forward and return capacity.
[0014] In accordance with yet another embodiment of the invention,
a communications satellite may include a hub-spoke spot beam group
using at least one directional antenna on the satellite. The
hub-spoke spot beam group may include at least one fixed location
spot beam illuminating a location containing a gateway terminal and
at least one other fixed location spot beam illuminating a location
containing at least one user terminal. The satellite may include a
pathway associated with the hub-spoke spot beam group. The
communications satellite may also include a means for connecting an
input of the pathway with different spot beams within the hub-spoke
spot beam group according to a receive beam switching pattern, and
a means for connecting an output of the pathway with different spot
beams within the hub-spoke spot beam group according to a transmit
beam switching pattern. The receive beam switching pattern and
transmit beam switching pattern may be synchronized over a frame to
establish both forward traffic and return traffic over the pathway
during the frame. The forward traffic may be sent from the gateway
to the at least one user terminal, and the return traffic may be
sent from the at least one user terminal to the gateway. A first
fraction of time in the frame may be used to support forward
traffic, and a second fraction of time in the frame may be used to
support return traffic. The first and second fractions may be
selected based on a desired ratio between forward and return
capacity.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In some of the drawings a sub-label is associated with a
reference numeral and follows a hyphen to denote one of multiple
similar components. When reference is made to a reference numeral
without specifying an existing sub-label, it is intended to refer
to all such similar components.
[0016] FIG. 1 is a simplified diagram of a hub-spoke satellite
communication system in accordance with an embodiment of the
present invention;
[0017] FIG. 2 is a simplified block diagram of a pathway coupled to
a receive-side switch and a transmit-side switch in accordance with
an embodiment of the present invention;
[0018] FIG. 3 is a simplified block diagram of two pathways each
coupled to a receive-side switch and a transmit-side switch to
provide beam switching in accordance with an embodiment of the
present invention;
[0019] FIGS. 4A-4G are simplified diagrams providing examples of
flexible allocation of capacity in accordance with an embodiment of
the present invention;
[0020] FIG. 5 is a simplified block diagram of pathways each
coupled to a receive-side switch and a transmit-side switch to
provide beam switching in accordance with another embodiment of the
present invention; and
[0021] FIG. 6 is a simplified map of a portion of North America
that provides an example of spot beam coverage areas in accordance
with an embodiment of the present invention.
DETAILED DESCRIPTION
[0022] Reference will now be made to the exemplary embodiments
illustrated in the drawings, and specific language will be used
herein to describe the same. It will nevertheless be understood
that no limitation of the scope of the invention is thereby
intended. Alterations and further modifications of the inventive
features illustrated herein, and additional applications of the
principles of the inventions as illustrated herein, which would
occur to one skilled in the relevant art and having possession of
this disclosure, are to be considered within the scope of the
invention.
[0023] In describing the present invention, the following
terminology will be used: The singular forms "a," "an," and "the"
include plural referents unless the context clearly dictates
otherwise. Thus, for example, reference to an item includes
reference to one or more items. The term "ones" refers to one, two,
or more, and generally applies to the selection of some or all of a
quantity. The term "plurality" refers to two or more of an item.
The term "about" means quantities, dimensions, sizes, formulations,
parameters, shapes and other characteristics need not be exact, but
may be approximated and/or larger or smaller, as desired,
reflecting acceptable tolerances, conversion factors, rounding off,
measurement error and the like and other factors known to those of
skill in the art. The term "substantially" means that the recited
characteristic, parameter, or value need not be achieved exactly,
but that deviations or variations, including for example,
tolerances, measurement error, measurement accuracy limitations and
other factors known to those of skill in the art, may occur in
amounts that do not preclude the effect the characteristic was
intended to provide. Numerical data may be expressed or presented
herein in a range format. It is to be understood that such a range
format is used merely for convenience and brevity and thus should
be interpreted flexibly to include not only the numerical values
explicitly recited as the limits of the range, but also interpreted
to include all of the individual numerical values or sub-ranges
encompassed within that range as if each numerical value and
sub-range is explicitly recited. As an illustration, a numerical
range of "about 1 to 5" should be interpreted to include not only
the explicitly recited values of about 1 to about 5, but also
include individual values and sub-ranges within the indicated
range. Thus, included in this numerical range are individual values
such as 2, 3 and 4 and sub-ranges such as 1-3, 2-4 and 3-5, etc.
This same principle applies to ranges reciting only one numerical
value (e.g., "greater than about 1") and should apply regardless of
the breadth of the range or the characteristics being described. A
plurality of items may be presented in a common list for
convenience. However, these lists should be construed as though
each member of the list is individually identified as a separate
and unique member. Thus, no individual member of such list should
be construed as a de facto equivalent of any other member of the
same list solely based on their presentation in a common group
without indications to the contrary. Furthermore, where the terms
"and" and "or" are used in conjunction with a list of items, they
are to be interpreted broadly, in that any one or more of the
listed items may be used alone or in combination with other listed
items. The term "alternatively" refers to selection of one of two
or more alternatives, and is not intended to limit the selection to
only those listed alternatives or to only one of the listed
alternatives at a time, unless the context clearly indicates
otherwise. The term "coupled" as used herein does not require that
the components be directly connected to each other. Instead, the
term is intended to also include configurations with indirect
connections where one or more other components may be included
between the specified components.
[0024] FIG. 1 is a simplified diagram of a hub-spoke satellite
communication system 100 in accordance with an embodiment of the
present invention. The satellite communication system 100 includes
a satellite 105 linking a gateway terminal 115 with one or more
user terminals 130. The satellite communication system 100 may use
a number of network architectures consisting of space and ground
segments. The space segment may include more than one satellite
while the ground segment may include a large number of user
terminals, gateway terminals, network operations centers (NOCs),
satellite and gateway terminal command centers, and the like. These
elements are not shown in the figure for clarity.
[0025] The gateway terminal 115 is sometimes referred to as a hub
or ground station. The gateway terminal 115 may service
communication links 135, 140 between the gateway terminal 115 and
the satellite 105. The gateway terminal 115 may also schedule
traffic to the user terminals 130. Alternatively, the scheduling
may be performed in other parts of the satellite communication
system 100 (e.g., at one or more NOCs and/or gateway command
centers--neither of which are shown in this embodiment).
[0026] The gateway terminal 115 may also provide an interface
between a network 120 and the satellite 105. The gateway terminal
115 may receive data and information from the network 120 that is
directed the user terminals 130. The gateway terminal 115 may
format the data and information for delivery to the user terminals
130 via the satellite 105. The gateway terminal 115 may also
receive signals carrying data and information from the satellite
105. This data and information may be from the user terminals 130
and directed to destinations accessible via the network 120. The
gateway terminal 115 may format this data and information for
delivery via the network 120.
[0027] The network 120 may be any type of network and may include,
for example, the Internet, an IP network, an intranet, a wide-area
network (WAN), a local-area network (LAN), a virtual private
network (VPN), a public switched telephone network (PSTN), a public
land mobile network, and the like. The network 120 may include both
wired and wireless connections as well as optical links. The
network 120 may connect the gateway terminal 115 with other gateway
terminals that may be in communication with the satellite 105 or
with other satellites.
[0028] The gateway terminal 115 may use one or more antennas 110 to
transmit forward uplink signals 135 to the satellite 105 and to
receive return downlink signals 140 from the satellite 105. The
antenna 110 shown in FIG. 1 includes a reflector with high
directivity in the direction of the satellite 105 and low
directivity in other directions. The antenna 110 may be implemented
in a variety of alternative configurations and include operating
features such as high isolation between orthogonal polarizations,
high efficiency in the operational frequency bands, low noise, and
the like.
[0029] In some satellite communication systems there may be a
limited frequency spectrum available for transmission.
Communication links 135, 140 between the gateway terminal 115 and
the satellite 105 may use the same, overlapping, or different
frequencies compared to the communication links 145, 150 between
the satellite 105 and the user terminals 130. In some embodiments,
the gateway terminal 115 may be located away from the user
terminals 130, which enables frequency re-use. In other
embodiments, the user terminals 130 may be located near the gateway
terminal 115.
[0030] The satellite 105 may be a geostationary satellite that is
configured to receive and transmit signals. The satellite 105 may
receive the forward uplink signals 135 from the gateway terminal
115 and transmit corresponding forward downlink signals 150 to the
user terminals 130. The satellite 105 may also receive return
uplink signals 145 from the user terminals 130 and transmit
corresponding return downlink signals 140 to the gateway terminal
115.
[0031] The satellite 105 may include one or more fixed directional
antennas for reception and transmission of the signals 135, 140,
145, 150. A directional antenna may include a fixed reflector with
one or more feed horns for each spot beam. The feed horns may be
employed for receiving uplink signals 135, 145 and transmitting
downlink signals 140, 150. The fixed feed of a directional antenna
is in contrast to a more complex phased-array antenna that includes
a number of phase combiners connected to a number of antenna
elements.
[0032] Contours of a spot beam may be determined in part by the
particular antenna design and depend on factors such as location of
feed horn relative to a reflector, size of the reflector, type of
feed horn, etc. Each spot beam may generally have a conical shape
(typically circular or elliptical) that extends between the antenna
and earth, illuminating a spot beam coverage area for both transmit
and receive operations. A spot beam coverage area generally
corresponds to an intersection between a spot beam and the earth's
surface and may illuminate terminals that are not on the earth
surface such as airborne user terminals, etc. In some embodiments,
directional antennas may be used to form fixed location spot beams
(or spot beams that are associated with substantially the same spot
beam coverage area over time). This is in contrast to dynamic
phased-array antennas that may be used to almost instantly change
spot beam locations and their associated spot beam coverage areas.
The directional antenna may be repointed, typically by mechanical
means, but not fast enough to allow capacity flexibility as
discussed herein.
[0033] The satellite 105 may operate in a multiple spot-beam mode,
receiving and transmitting a number of signals in different spot
beams. In the embodiment shown in FIG. 1, the gateway 115 and the
user terminals 130 may be within the same or different spot beams.
Each spot beam may use a single carrier (i.e., one carrier
frequency), a contiguous frequency range, or a number of frequency
ranges.
[0034] The satellite 105 may include a number of non-regenerative
pathways (represented as K pathways in this embodiment). Each of
the K pathways may be allocated as a forward pathway or a return
pathway at any given instant in time. The uplink signals 135, 145
received by the satellite 105 may be directed along one or more of
the pathways before being transmitted as downlink signals 140,
150.
[0035] The signals are not demodulated and re-modulated as in a
regenerative or processing satellite architecture. Instead, signal
manipulation by a non-regenerative satellite is generally limited
to functions such as frequency translation, polarization
conversion, filtering, amplification, and the like.
[0036] The forward downlink signals 150 may be transmitted from the
satellite 105 to one or more of the user terminals 130. The user
terminals 130 may receive the forward downlink signals 150 using
antennas 127. In one embodiment, an antenna and a user terminal
together include a very small aperture terminal (VSAT) with the
antenna measuring approximately 0.75 meters in diameter and having
approximately 2 watts of power. In other embodiments, a variety of
other types of antennas 127 may be used to receive the forward
downlink signals 150 from the satellite 105. Each of the user
terminals 130 may include a single user terminal or a hub or router
coupled to other user terminals. Each of the user terminals 130 may
be connected to various consumer premises equipment (CPE) such as
computers, local area networks, internet appliances, wireless
networks, and the like.
[0037] The user terminals 130 may transmit data and information to
a destination accessible via the network 120. The user terminals
130 may transmit the return uplink signals 145 to the satellite 105
using the antennas 127. The user terminals 130 may transmit the
signals according to a variety of physical layer transmission,
modulation and coding. In various embodiments, the physical layer
techniques may be the same or different for each of the links 135,
140, 145, 150.
[0038] FIG. 2 is a simplified block diagram of a pathway coupled to
a receive-side switch (Rx SW) and a transmit-side switch (Tx SW) in
accordance with an embodiment of the present invention. This
pathway may correspond to one of the K pathways shown in FIG. 1. In
general, the pathway may provide for conversion of uplink signals
received by the satellite into downlink signals. The pathway may
include one or more of the components shown within the dotted box
in FIG. 2. These components include an LNA, a down converter, a
filter, and an HPA. In some embodiments, the pathway may simply
include a receiver and a transmitter. The receiver may include only
an LNA but may alternatively include frequency conversion (e.g., a
down converter), filtering, and the like. The transmitter may
include only an HPA but may also include frequency conversion
(e.g., a down converter), filtering, and the like. In some
embodiments, the components that are included within the pathway
may be arranged in a different configuration than that shown in
this embodiment. The specific components included in a pathway and
the configuration of those components may depend on the particular
application.
[0039] The receive-side switch may be used to control an input to
the pathway. The receive-side switch may be before a receiver of
the pathway along the signal path. The receive-side switch may
switch a number of beam feeds into the receiver. In this
embodiment, the receive-side switch may dynamically switch between
one of N user beam feeds or a gateway beam feed. Each of the N user
beam feeds may include signals from one or more user terminals
(e.g., user terminals 130 of FIG. 1). The gateway beam feed may
include signals from one or more gateway terminals (e.g., gateway
terminal 115 of FIG. 1). In some embodiments, the gateway beam feed
may sometimes include signals from user terminals that are located
within the same spot beam coverage area as the gateway terminal
(hence the designation "GW/U"). The set of beams that share a
pathway are called a hub-spoke spot beam group. Although only a
single gateway is shown in a hub-spoke spot beam group, in some
embodiments, more than one gateway may be used.
[0040] In a similar manner, the transmit-side switch may be used to
control an output from the pathway. The transmit-side switch may be
after a transmitter of the pathway along the signal path. The
transmit-side switch may switch a common signal between a number of
output beam feeds. The transmit-side switch may dynamically switch
between one of the N user beam feeds or the gateway beam feed.
[0041] As indicated in FIG. 2, the receive-side switch and the
transmit-side switch may be fast switches (capable of switching
rapidly, e.g., relative to a frame described further below) that
are controlled by a beam switch controller. The switches may
operate at radio frequency (RF) such as Ka band frequencies. In
some embodiments, ferrite switches may be used. Ferrite switches
may provide fast switching, low insertion loss (e.g., do not
adversely impact equivalent isotropically radiated power (EIRP) or
gain-to-noise-temperature (G/T)), and high power handling
capabilities. A single LNA is shown as part of the pathway. In
alternate embodiments, LNAs may be before the Rx switch. For
example, each receive feed in a hub-spoke spot beam group may have
an LNA. The switch may appear after the LNAs, or in one
alternative, a summer may combine the LNA outputs and the LNAs
themselves may be switched on and off to implement the switching
function.
[0042] Forward link operation may be obtained by connecting the
receive-side switch to the gateway beam feed and cycling the
transmit-side switch through the output switch positions. Return
link operation may be obtained by connecting the transmit-side
switch to the gateway beam feed and cycling the receive-side switch
through the input switch positions. Receive beam switching patterns
and transmit beam switching patterns may be used to determine the
input and output switch positions at specific times.
[0043] The fraction of time spent in each position may determine
the capacity provided to each beam. The capacity may be changed by
changing the fraction of time spent in each position. This provides
flexibility in allocating capacity between different beams both
temporally and spatially (e.g., temporally by changing capacity
allocation for a particular beam over time and spatially by
changing capacity allocation for a particular spot beam coverage
area over time).
[0044] Similarly, the fraction of time spent in the forward link
configuration may determine the capacity provided to the forward
direction, and the time spent in the return link configuration may
determine the capacity provided to the return direction. The
capacity ratio may be changed by changing the fraction of time
spent in each configuration. This provides flexibility in
allocating capacity between forward and return traffic.
[0045] Using the receive-side switch and the transmit-side switch,
the receive beam feeds (and their associated spot beams) may be
connected to the transmit beam feeds (and their associated spot
beams). Since there is only one pathway, only one of the receive
beam feeds may be connected to one of the transmit beam feeds at a
given instant in time. There will generally be more beam feeds (and
hence more spot beams) than pathways. A beam switching controller
may provide receive beam switching patterns (e.g., a receive
switching sequence) to the receive-side switch and transmit beam
switching patterns (e.g., a transmit switching sequence) to the
transmit-side switch. The switching pattern may be a set of switch
positions versus time during a frame. A frame may be a time during
which all active beams may be sequentially served (note that each
beam is not necessarily active in each frame). A frame may be
further segmented into a number of sequential slots that define
periods during which switch positions are unchanging. After each
slot the instantaneous beam positions may change or remain the same
for the next slot. The switching speed of the receive-side switch
and the transmit-side switch may be small relative to the slot
duration (e.g., less than 25% of a slot time).
[0046] The transmit and receive switching patterns may be
synchronized in time to provide sequential beam switching over the
pathway during a frame. The switching patterns may be stored in
memory at the beam switch controller and may be uploaded using an
uplink signal that may be either in-band or out-of-band with other
uplink signals. In some embodiments, the switching patterns may be
the same from frame-to-frame (repeated in each of a plurality of
consecutive frames), while in other embodiments the switching
patterns may be changed from frame-to-frame. In yet other
embodiments, a particular switching pattern may be used for a
particular time duration while another switching pattern may be
used for a different time duration (e.g., different times of the
day, different days of the week, or the like). Many variations,
modifications, and alternative switching patterns may be used
within the embodiments disclosed herein. Whether the switching
patterns remain the same or changes may depend on a desired
capacity allocation or a desired ratio between forward and return
capacity.
[0047] FIG. 3 is a simplified block diagram of two pathways each
coupled to a receive-side switch and a transmit-side switch to
provide beam switching in accordance with an embodiment of the
present invention. These pathways may correspond to two of the K
pathways shown in FIG. 1. Although not explicitly shown, each of
the pathways may include one or more of the same components as the
pathway shown in FIG. 2. The gateway beam feed may be associated
with a gateway terminal and user terminals in some embodiments. As
in the embodiment of FIG. 2, a beam switching controller (not
shown) may be employed. To the side of the satellite hardware is an
example map showing beam coverage areas A, B and GW/U.
[0048] In this embodiment, the first pathway (Pathway 1) is coupled
to a receive-side switch and a transmit-side switch that are each
associated with a user beam feed (A). The second pathway (Pathway
2) is coupled to a receive-side switch and a transmit-side switch
that are each associated with a user beam feed (B). The switches
may be fast switches as described previously. The user terminals
associated with each of the user beam feeds A, B may be serviced by
the same gateway terminal associated with a gateway beam feed
(GW/U).
[0049] To reduce interference, the gateway beam feeds GW/U at each
pathway may use orthogonal polarizations and the uplink frequencies
may be different from the downlink frequencies. The uplink gateway
beam feed GW/U to Pathway 1 may use a left-hand polarization (L),
and the uplink gateway beam feed GW/U to Pathway 2 may use a
right-hand polarization (R). In this embodiment, the pathways
convert the polarization so that the downlink gateway beam feed
GW/U from Pathway 1 uses a right-hand polarization R, and the
downlink gateway beam feed GW/U from Pathway 2 uses a left-hand
polarization L. Due to the different polarizations and frequencies,
the spot beam associated with the gateway beam feed GW/U may
include both forward and return signals simultaneously.
[0050] In some embodiments, there may be two groups of user
terminals associated with the gateway beam feed GW/U. One group may
transmit using a left-hand polarization L and receive using a
right-hand polarization R. These user terminals may be serviced
through Pathway 1. Another group may transmit using a right-hand
polarization R and receive using a left-hand polarization L. These
user terminals may be serviced through Pathway 2.
[0051] The receive-side switch and the transmit-side switch coupled
to Pathway 1 may use switching patterns that are independent of
those used by the receive-side switch and the transmit-side switch
coupled to Pathway 2. This provides flexibility in allocating
capacity between each of the beam feeds (A, B, GW/U) both
temporally and spatially as well as between both forward and return
traffic.
[0052] FIGS. 4A-4G are simplified diagrams providing examples of
flexible allocation of capacity in accordance with an embodiment of
the present invention. The satellite communication system may use a
framed hub-spoke beam switched pathway access protocol, with time
slots like a Satellite Switched Time-Division Multiple Access
(SS/TDMA) scheme. Now, however, each time slot of the frame may
correspond to either forward link (gateway to user terminals) or
return link (user terminals to gateway) traffic from a transmitting
beam to a receiving beam--not just a single transmission from one
terminal to another.
[0053] During normal operation, continuous streams of frames are
typically used to facilitate the communications. In the embodiment
presented in FIG. 4A, a single hub-spoke beam switched frame is
shown that includes 64 time slots. FIGS. 4A-4G are presented merely
as examples, and embodiments of the present invention are not
limited to specific pathway access protocols or frame/slot
configurations. Multiple terminals may be serviced during each time
slot using multiplexing and multiple access techniques (e.g.,
Time-Division Multiplexing (TDM), Time-Division Multiple Access
(TDMA), Frequency-Division Multiple Access (FDMA), Multi-Frequency
Time-Division Multiple Access (MF-TDMA), Code-Division Multiple
Access (CDMA), and the like).
[0054] FIGS. 4B-4C provide examples of flexible allocation of
capacity during a frame. These figures provide visual
representations of the flexible allocation of capacity that may be
realized using the beam switching patterns described throughout
this specification. These examples refer specifically to the
pathways (Pathway 1, Pathway 2) and the beams (A, B, GW/U) shown in
FIG. 3.
[0055] FIG. 4B shows signals passing through Pathway 1 and Pathway
2 during a frame (Frame 1). The first 19 slots of Frame 1 over
Pathway 1 are occupied by signals that are received at the gateway
beam feed GW/U and transmitted to the gateway beam feed GW/U. These
are forward link signals from the gateway terminal associated with
the gateway beam feed GW/U that are destined for at least one user
terminal associated with the gateway beam feed
[0056] GW/U. During these 19 slots, the receive-side switch is in
an input switch position associated with the gateway beam feed
GW/U, and the transmit-side switch is in an output switch position
associated with the gateway beam feed GW/U.
[0057] The next 14 slots of Frame 1 over Pathway 1 are occupied by
signals that are received from the gateway beam feed GW/U and
transmitted to the gateway beam feed GW/U. These are return link
signals from at least one user terminal associated with the gateway
beam feed GW/U that are destined for the gateway terminal
associated with the gateway beam feed GW/U. During these 14 slots,
the receive-side switch is in the input switch position associated
with the gateway beam feed GW/U, and the transmit-side switch is in
the output switch position associated with the gateway beam feed
GW/U.
[0058] The next 12 slots of Frame 1 over Pathway 1 are occupied by
signals that are received from the user beam feed A and transmitted
to the gateway beam feed GW/U. These are return link signals from
at least one user terminal associated with the user beam feed A
that are destined for the gateway terminal associated with the
gateway beam feed GW/U. During these 12 slots, the receive-side
switch is in an input switch position associated with the user beam
feed A, and the transmit-side switch is in the output switch
position associated with the gateway beam feed GW/U.
[0059] The final 19 slots of Frame 1 over Pathway 1 are occupied by
signals that are received from the gateway beam feed GW/U and
transmitted to the user beam feed A. These are forward link signals
from the gateway terminal associated with the gateway beam feed
GW/U that are destined for at least one user terminal associated
with the user beam feed A. During these 19 slots, the receive-side
switch is in the input switch position associated with the gateway
beam feed GW/U, and the transmit-side switch is in and output
switch position associated with the user beam feed A.
[0060] Without going into the same level of detail as with Pathway
1, the first 12 slots of Frame 1 over Pathway 2 are occupied by
forward link signals that are received from the gateway beam feed
GW/U and transmitted to the user beam feed B. The next 15 slots of
Frame 1 over Pathway 2 are occupied by forward link signals that
are received from the gateway beam feed GW/U and transmitted to the
gateway beam feed GW/U. The next 21 slots of Frame 1 over Pathway 2
are occupied by return link signals that are received from the user
beam feed B and transmitted to the gateway beam feed GW/U. The
final 16 slots of Frame 1 over Pathway 2 are occupied by return
link signals that are received from the gateway beam feed GW/U and
transmitted to the gateway beam feed GW/U. For each of these
configurations, the receive-side switch and the transmit-side
switch associated with Pathway 2 are switched to the appropriate
input and output switch positions based on receive beam switching
patterns and transmit beam switching patterns.
[0061] FIG. 4C shows signals passing through Pathway 1 and Pathway
2 during a different frame (Frame 2). This frame may be adjacent to
Frame 1 in time or there may be any number of frames between Frame
1 and Frame 2. The first 12 slots of Frame 2 over Pathway 1 are
occupied by return link signals that are received from the user
beam feed A and transmitted to the gateway beam feed GW/U. The next
19 slots of Frame 2 over Pathway 1 are occupied by forward link
signals that are received from the gateway beam feed GW/U and
transmitted to the gateway beam feed GW/U. The next 19 slots of
Frame 2 over Pathway 1 are occupied by forward link signals that
are received from the gateway beam feed GW/U and transmitted to the
user beam feed A. The final 16 slots of Frame 2 over Pathway 1 are
occupied by return link signals that are received from the gateway
beam feed GW/U and transmitted to the gateway beam feed GW/U.
[0062] The first 17 slots of Frame 2 over Pathway 2 are occupied by
return link signals that are received from the user beam feed B and
transmitted to the gateway beam feed GW/U. The next 17 slots of
Frame 2 over Pathway 2 are occupied by forward link signals that
are received from the gateway beam feed GW/U and transmitted to the
gateway beam feed GW/U. The next 16 slots of Frame 2 over Pathway 2
are occupied by return link signals that are received from the
gateway beam feed GW/U and transmitted to the gateway beam feed
GW/U. The final 14 slots of Frame 2 over Pathway 2 are occupied by
forward link signals that are received from the gateway beam feed
GW/U and transmitted to the user beam feed B.
[0063] In comparing FIG. 4B with FIG. 4C, it can be seen that
capacity (as indicated by the fraction of time spent in each
position) is allocated differently between Frame 1 and Frame 2 for
each of the different pathways. FIGS. 4D-4E use pie charts to show
the change in allocation of forward and return traffic between
Frame 1 and Frame 2. FIG. 4D shows that for Pathway 1 more slots
are used for forward link signals during Frame 1 than during Frame
2. FIG. 4E shows that for Pathway 2 more slots are used for return
link signals during Frame 1 than during Frame 2.
[0064] FIGS. 4F-4G use pie charts to show the change in allocation
between forward link signals between Frame 1 and Frame 2 for the
user beam feeds. FIG. 4F shows that for Pathway 1 more slots are
used for forward link signals for the user beam feed A during Frame
1 than during Frame 2. FIG. 4G shows that for Pathway 2 more slots
are used for forward link signals for the gateway beam feed GW/U
during Frame 1 than during Frame 2.
[0065] These figures (particularly FIGS. 4D-4G) illustrate that the
fraction of time spent in each switch position may be changed
(e.g., from frame to frame, from time to time, or the like). This
may be done using the switching patterns (receive beam switching
patterns and transmit beam switching patterns) described
previously. This allows capacity to be flexibly allocated between
each of the beam feeds (feeds A, B, GW/U in this embodiment). Thus,
capacity may be flexibly allocated both temporally and spatially as
well as between both forward and return traffic.
[0066] FIG. 5 is a simplified block diagram of pathways each
coupled to a receive-side switch and a transmit-side switch to
provide beam switching in accordance with another embodiment of the
present invention. These pathways may correspond to the K pathways
shown in FIG. 1. Although not explicitly shown, each of the
pathways may include one or more of the same components as the
pathway shown in FIG. 2. The gateway beam feed may be associated
with a gateway terminal and user terminals in some embodiments. As
in the embodiment of FIG. 2, a beam switching controller (not
shown) may be employed. To the side of the satellite hardware is an
example map showing beam coverage areas A, B, C, D, E, F and
GW/U.
[0067] In this embodiment, the first pathway (Pathway 1) is coupled
to a receive-side switch and a transmit-side switch that are each
associated with user beam feeds (A, B, C). The second pathway
(Pathway 2) is coupled to a receive-side switch and a transmit-side
switch that are each associated with user beam feeds (D, E, F). The
switches may be fast switches as described previously. The user
terminals associated with each of the user beam feeds A, B, C, D,
E, F may be serviced by the same gateway terminal associated with a
gateway beam feed (GW/U). In FIG. 3, the communication capacity
from a single gateway is distributed by a pair of pathways to users
in 3 user beams (A, B, GW/U). In FIG. 5, a similar pair of pathways
are used to distribute the communication capacity from the gateway
to 7 user beams (A, B, C, D, E, F, GW/U) thus expanding the
coverage area without adding pathways or gateways. 4 additional
feeds are used for each of the transmit and receive antennas. Each
of the two receive switches handles 2 more inputs and each of the
two transmit switches handles 2 more outputs as compared to the
embodiment of FIG. 3.
[0068] FIG. 6 is a simplified map of a portion of North America
that provides an example of spot beam coverage areas in accordance
with an embodiment of the present invention. The spot beam coverage
areas may be the result of fixed location spot beams formed using
one or more directional antennas on a satellite. Some of the fixed
location spot beams illuminate locations that include gateway
terminals (indicated by a smaller dotted circle inside a larger
dotted circle). These locations may also include user terminals.
Other fixed location spot beams illuminate locations that include
only user terminals (indicated by larger dotted circles without
smaller dotted circles). As described above, capacity may be
flexibly allocated both temporally and spatially as well as between
both forward and return traffic between the spot beam coverage
areas shown on the map.
[0069] Embodiments of the present invention are not limited to the
examples shown or described herein. For example, embodiments of the
present invention may be used with any number of pathways, and
receive-side switches and transmit-side switches may be associated
with any suitable number of beam feeds, forming hub-spoke spot beam
groups of various sizes. Different pathways on a satellite may be
coupled to receive-side switches and transmit-side switches that
are associated with the same or a different numbers of beam
feeds.
[0070] Furthermore, features of one or more embodiments may be
combined with features of other embodiments without departing from
the scope of the invention. The specification and drawings are,
accordingly, to be regarded in an illustrative rather than a
restrictive sense. Thus, the scope of the present invention should
be determined not with reference to the above description, but
should be determined with reference to the appended claims along
with their full scope of equivalents.
* * * * *