Title: Systems and methods for reducing satellite feeder link bandwidth/carriers in cellular satellite systems
Abstract: Information content is nonidentically mapped between service link carriers and feeder link carriers at a cellular satellite. A reduced number of satellite feeder link carriers compared to the number of satellite service link carriers and/or a reduced total bandwidth of the satellite feeder link carriers compared to the satellite service link carriers thereby may be obtained.
Patent Number: 6,937,857 Issued on 08/30/2005 to Karabinis
| Inventors:
|
Karabinis; Peter D. (Cary, NC)
|
| Assignee:
|
Mobile Satellite Ventures, LP (Reston, VA)
|
| Appl. No.:
|
328062 |
| Filed:
|
December 23, 2002 |
| Current U.S. Class: |
455/428; 455/13.3; 455/429; 455/12.1 |
| Intern'l Class: |
H04Q 007/20 |
| Field of Search: |
455/111,121,133,132,134,17,427,428,429,430,426.1,553.1,552.1,414.1,418
370/319-326,431,435,530-535
445/553,426,552
|
References Cited [Referenced By]
U.S. Patent Documents
| 5073900 | Dec., 1991 | Mallinckrodt.
| |
| 5339330 | Aug., 1994 | Mallinckrodt.
| |
| 5446756 | Aug., 1995 | Mallinckrodt.
| |
| 5511233 | Apr., 1996 | Otten.
| |
| 5612703 | Mar., 1997 | Mallinckrodt.
| |
| 5613193 | Mar., 1997 | Ishikawa et al.
| |
| 5638374 | Jun., 1997 | Heath.
| |
| 5724345 | Mar., 1998 | Guarneri et al.
| |
| 5832379 | Nov., 1998 | Mallinckrodt.
| |
| 5835857 | Nov., 1998 | Otten.
| |
| 5878329 | Mar., 1999 | Mallinckrodt.
| |
| 5903549 | May., 1999 | von der Embse et al.
| |
| 5940753 | Aug., 1999 | Mallinckrodt.
| |
| 5995832 | Nov., 1999 | Mallinckrodt.
| |
| 6052560 | Apr., 2000 | Karabinis.
| |
| 6108561 | Aug., 2000 | Mallinckrodt.
| |
| 6150977 | Nov., 2000 | Wilcoxson et al.
| |
| 6317583 | Nov., 2001 | Wolcott et al.
| |
| 6341213 | Jan., 2002 | Wu.
| |
| 6366776 | Apr., 2002 | Wright et al.
| |
| 6377561 | Apr., 2002 | Black et al.
| |
| 6442148 | Aug., 2002 | Adams et al.
| |
| 6449461 | Sep., 2002 | Otten.
| |
| 6522865 | Feb., 2003 | Otten.
| |
| 2002/0122408 | Sep., 2002 | Mullins.
| |
| 2003/0022625 | Jan., 2003 | Otten et al.
| |
| 2003/0149986 | Aug., 2003 | Mayfield et al.
| |
Other References
International Search Report, PCT/US03/17614, Aug. 19, 2003.
Written Opinion, PCT/US03/17614, Apr. 9, 2004.
|
Primary Examiner: Maung; Nay
Assistant Examiner: Lee; John J.
Attorney, Agent or Firm: Myers Bigel Sibley & Sajovec
Parent Case Text
CROSS-REFERENCE TO PROVISIONAL APPLICATION
This application claims the benefit of provisional Application No. 60/383,688,
filed May 28, 2002, entitled Systems and Methods for Reducing Satellite Feeder
Link Bandwidth in Satellite Cellular Systems, assigned to the assignee of the present
application, the disclosure of which is hereby incorporated herein by reference
in its entirety as if set forth fully herein
Claims
1. A cellular satellite communications method comprising:
packing at a cellular satellite, information from a plurality of return service
link carriers having a total aggregate return service link bandwidth into at least
one return feeder link carrier having a total return feeder link bandwidth that
is less than the total aggregate return service link bandwidth; and
unpacking at the cellular satellite, information from at least one forward feeder
link carrier having a total forward feeder link bandwidth into a plurality of forward
service link carriers having a total aggregate forward service link bandwidth that
is greater than the total forward feeder link bandwidth.
2. A cellular satellite commutations method according to claim 1,
wherein the packing comprises packing at the cellular satellite, information
from the plurality of return service link carriers into fewer return feeder link
carriers; and
wherein the unpacking comprises unpacking at the cellular satellite, information
from a plurality of forward feeder link carriers into more forward service link
carriers.
3. A cellular satellite commutations method according to claim 1:
wherein the packing comprises packing at the cellular satellite, information
from the plurality of return service link carriers to fill the return feeder link
carrier; and
wherein the unpacking comprises unpacking at the cellular satellite, information
from at least one forward feeder link carrier that is filled, into more forward
service link carriers.
4. A cellular satellite communications method according to claim 1:
wherein the packing campuses loading slots in TDMA frames of a return feeder
link carrier from TDMA frames of a plurality of return service link carriers that
are not fully loaded.
5. A cellular satellite communications method according to claim 1:
wherein the packing comprises combining direct sequence spread return service
link carriers that are not fully loaded into one return feeder link carrier.
6. A cellular satellite communications method according to claim 1:
wherein the packing comprises combining direct sequence spread information from
return service link carriers that are not fully loaded into one return feeder link
carrier; and
wherein the unpacking comprises selectively routing direct sequence spread information
from a forward feeder link carrier to selected ones the forward service link carriers.
7. A cellular satellite communications method according to claim 1:
wherein the packing comprises selectively loading slots in TDMA frames of a return
feeder link carrier from TDMA frames of a plurality of return service link carriers
that are not fully loaded; and
wherein the unpacking comprises selectively routing slots in TDMA frames of a
forward feeder link carrier to TDMA frames of selected ones of the forward service
link carriers.
8. A cellular satellite communications method comprising:
packing at a cellular satellite, information from a plurality of return service
link carriers into a return feeder link carrier by selectively loading slots in
TDMA frames of a return feeder link carrier from TDMA frames of a plurality of
return service link carriers that are not fully loaded; and
unpacking at the cellular satellite, information from a forward feeder link carrier
into a plurality of forward service link carriers by selectively routing slots
in TDMA frames of a forward feeder link carrier to TDMA frames of selected ones
of the forward service link carriers;
wherein the unpacking comprises demodulating the forward feeder link carrier
and modulating the forward service link carriers at the satellite.
9. A cellular satellite communications method comprising:
packing at a cellular satellite, information from a plurality of return service
link carriers into a return feeder link carrier by selectively loading slots in
TDMA frames of a return feeder link carrier from TDMA frames of a plurality of
return service link carriers that are not fully loaded; and
unpacking at the cellular satellite, information from a forward feeder link carrier
into a plurality of forward service link carriers by selectively replicating TDMA
frames of a forward feeder link carrier to TDMA frames
0f selected ones
of the forward service link carriers.
10. A cellular satellite communications method according to claim 9 wherein the
selectively replicating further comprises:
reducing power in selected ones of the slots of the TDMA frames of the selected
ones of the forward service link carriers.
11. A cellular satellite communications method comprising:
packing at a cellular satellite, information from a plurality of return service
link carriers into a return feeder link carrier by combining direct sequence spread
information from return service link carriers that are not fully loaded into one
return feeder link carrier; and
unpacking at the cellular satellite, information from a forward feeder link carrier
into a plurality of forward service link carriers by selectively routing direct
sequence spread information from a forward feeder link carrier to selected ones
of the forward service link carriers;
wherein the selectively routing comprises demodulating the forward feeder link
carriers and modulating the forward service link carriers at the satellite.
12. A cellular satellite communications method comprising:
packing at a cellular satellite, information from a plurality of return service
link carriers into a return feeder link carrier by combining direct sequence spread
information from return service link carriers that are not fully loaded into one
return feeder link carrier; and
unpacking at the cellular satellite, information from a forward feeder link carrier
into a plurality of forward service link carriers by selectively replicating direct
sequence spread information from a forward feeder link carrier selected ones of
the forward service link carriers.
13. A cellular satellite communications method according to claim 12 wherein
the selectively replicating further comprises:
reducing power in selected direct sequence spread information of the selected
ones of the forward service link carriers.
14. A space segment according to claim 11 wherein the satellite is further configured
to pack information from the plurality of return service link carriers into fewer
return feeder link carriers, and to unpack information from the plurality of forward
feeder link carriers into more forward service link carriers.
15. A space segment for a cellular satellite communications system comprising:
a satellite that is configured to receive information from gateway over a plurality
of forward feeder link carriers, to transmit information the gateway over a plurality
of return feeder link carriers, to transmit information to a plurality of satellite
cells over a plurality of forward service link carriers and to receive information
from the plurality of satellite cells over a plurality of return service like carriers,
the satellite being further configured to pack information from the plurality of
return service link carriers into the plurality of return feeder link carriers;
wherein the satellite is further configured to unpack information from the plurality
of forward feeder link carriers into the plurality of toward service link carriers;
and
wherein the satellite is further configured to pack information from the plurality
of return service link carriers having a total aggregate return service link bandwidth
into at least one return feeder link carrier having a total return feeder link
bandwidth that is less than the total aggregate return service link bandwidth,
and to unpack information from at least one forward feeder link carrier having
a total forward feeder link bandwidth into the plurality of forward service link
carriers having a total aggregate forward service link bandwidth that is greater
than the total forward feeder link bandwidth.
16. A space segment according to claim 15 wherein the satellite is further the
configured from the plurality of return service link carriers to fill at least
one return feeder link carrier, and to unpack information from at least one forward
feeder link carrier that is filled, into more forward service links.
17. A space segment according to claim 15 wherein the satellite is further configured
to load slots in TDMA frames of a return feeder link carrier from TDMA frames of
a plurality of return service link carriers that are not fully loaded.
18. A space segment according to claim 15 wherein the satellite is further configured
to selectively load slots in TDMA frames of a return feeder link carrier from TDMA
frames of a plurality of service link carriers that are not fully loaded, and to
selectively route slots in TDMA frames of a forward feeder link carrier to TDMA
frames of selected ones of the forward service link carriers.
19. A space segment according to claim 15 wherein the satellite is further configured
to combine direct sequence spread return service link carriers that are not fully
loaded into one return feeder link carrier.
20. A space segment according to claim 15 wherein the satellite is further configured
to combine direct sequence spread information from return service link carriers
that are not fully loaded into one return feeder link carrier, and to selectively
route direct sequence spread information from a forward feeder link carrier to
selected ones of the forward service link carriers.
21. A space segment for a cellular satellite communications system comprising:
a satellite that is configured to receive information from a gateway over a plurality
of forward feeder link carriers, to transmit information the gateway over a plurality
of return feeder link carriers, to transmit information to plurality of satellite
cells over a plurality of forward service link carriers and to receive information
from the plurality of satellite cells over a plurality of return service link carriers,
the satellite being further configured to pack information from the plurality of
return service link carriers into the plurality of return feeder link carrier;
wherein the satellite is further configured to unpack information from the plurality
of forward feeder link carriers into the plurality of forward service link carriers;
wherein the satellite is further configured to selectively load slots in TDMA
frames of a return feeder link carrier from TDMA frames of a plurality of return
service link carriers that are not fully loaded, and to selectively route slots
in TDMA frames of a forward feeder link carrier to TDMA frames of selected ones
of the forward service link carriers; and
wherein the satellite is further configured to demodulate forward feeder link
carrier and modulate the forward service link carriers.
22. A space segment for a cellular satellite communications system comprising:
a satellite that is configured to receive information from a gateway over a plurality
of forward feeder link carriers, to transmit information to the gateway over a
plurality of return feeder link carriers, to transmit information to a plurality
of satellite cells over a plurality of forward service link carriers and to receive
information from the plurality of satellite cells over a plurality of return service
link carriers, the satellite being further configured to pack information from
the plurality of return service link carriers into the plurality of return feeder
link carriers;
wherein the satellite is further configured to unpack information from the plurality
of forward feeder link carriers into the plurality of forward service link carriers;
and
wherein the satellite is further configured to selectively load slots in TDMA
frames of a return feeder link carrier from TDMA frames of a plurality of return
service link carriers that are not fully loaded, and to selectively replicate TDMA
frames of a forward feeder link carrier to TDMA frames of selected ones of the
forward service link carriers.
23. A space segment according to claim 22 wherein the satellite is further configured
to reduce power in selected ones of the slots of the TDMA frames of the selected
ones of the forward service link carriers.
24. A space segment for a cellular satellite communications system comprising:
a satellite that is configured to receive information from a gateway over a plurality
of forward feeder link carriers, to transmit information to the gateway over a
plurality of return feeder link carriers, to transmit information to a plurality
of satellite cells over a plurality of forward service link carriers and to recieve
information from the plurality of satellite cells over a plurality of return service
link carriers, the satellite being further configured to pack information from
the plurality of return service link carriers into the plurality of return feeder
link carriers;
wherein the satellite is further configured to combine direct sequence spread
return service link carriers that are not fully loaded into one return feeder link
carrier; and
wherein the satellite is further configured to demodulate the return service
link carriers and modulate the return feeder link carrier.
25. A space segment for a cellular satellite communications system comprising:
a satellite that is configured to receive information from a gateway over a plurality
of forward feeder link carriers, to transmit information to the gateway over a
plurality of return feeder link carriers, to transmit information to a plurality
of satellite cells over a plurality of forward service link carriers and to receive
information from the plurality of satellite cells over a plurality of return service
link carriers, the satellite being further configured to pack information from
the plurality of return service link carriers into the plurality of return feeder
link carriers;
wherein the satellite is further configured to unpack information from the plurality
of forward feeder link carriers into the plurality of forward service link carriers;
wherein the satellite is further configured to combine direct sequence spread
information from return service link carriers that are not fully loaded into one
return feeder link carrier, and to selectively route direct sequence spread information
from a forward feeder link carrier to selected ones of the forward service link
carriers; and
wherein the satellite is further configured to demodulate the forward feeder
link carriers and modulate the forward service link carriers.
26. A space segment for a cellular satellite communications system comprising:
a satellite that is configured to receive information from gateway over a plurality
of forward feeder link carriers, to transmit information to the gateway over a
plurality of return feeder link carriers, to transmit information to a plurality
of satellite cells over a plurality of forward service link carriers and to receive
information from the plurality of satellite cells over a plurality of return service
link carriers, the satellite being further configured to pack information from
the plurality of return service link carriers into the plurality of return feeder
link carriers;
wherein the satellite is further configured to unpack information from the plurality
of forward feeder link carriers into the plurality of forward service link carriers;
and
wherein the satellite is further configured to combine direct sequence spread
information from return service link carriers that are not fully loaded into one
return feeder link carrier, and selectively replicate direct sequence spread information
from a forward feeder link carrier to selected ones of the forward service link
carriers.
27. A space segment according to claim 26 wherein the satellite is further configured
to reduce power in selected direct sequence spread information of the selected
ones of the forward service link carriers.
28. A satellite for a cellular satellite communications system comprising:
first means for receiving first information from a gateway over a first plurality
of forward feeder link carriers having a total forward feeder link bandwidth;
first means for transmitting the first information to a plurality of satellite
cells over a second plurality of forward service link carriers having a total aggregate
forward service link bandwidth, wherein the total forward feed link bandwidth is
less than the total aggregate forward service link bandwidth;
second means for receiving second information from the plurality of satellite
cells over a third plurality of return service link carriers having a total aggregate
return service link bandwidth; and
second means for transmitting the second information to the gateway over a fourth
plurality of return feeder link carriers having a total return feeder link bandwidth,
wherein the total return feeder link bandwidth is less than the total aggregate
return service link bandwidth.
29. A satellite according to claim 28 further comprising:
means for unpacking the first information from the first plurality of forward
feeder link carriers into the second plurality of forward service link carriers;
and
means for packing the second information from the third plurality of return service
link carriers into the fourth plurality of return feeder link carriers.
30. A satellite according to claim 28 wherein the means for unpacking comprises
means for routing TDMA slots from one of the forward feeder link carriers into
a plurality of the forward service link carriers, wherein the means for packing
comprises means for routing TDMA slots a plurality of the return service link carriers
into one of the return feeder link carriers.
31. A satellite according to claim 28 wherein the means for unpacking comprises
means for replicating TDMA slots from a of the forward feeder link carriers into
a plurality of the forward service link carriers, and wherein the means for packing
comprises means for routing TDMA slots from a plurality of the return service link
carriers into one of the return feeder link carriers.
32. A satellite according to claim 31 wherein the first means for transmitting
comprises means for transmitting the first information in at least some of the
slots at reduced power.
33. A satellite according to claim 28, further comprising:
first means for demodulating the first information from first plurality of forward
feeder link carriers;
first means for modulating the first information onto the second plurality of
forward service link carriers;
second means for demodulating the second information from the third plurality
of return service link carriers; and
fourth means for modulating the third information onto fourth plurality of return
feeder link carriers.
34. A satellite according to claim 28 wherein the means for unpacking comprises
means for routing direct sequence spread information from one of the forward feeder
link carriers into a plurality of the forward service link carriers, and wherein
the means for packing comprises means for routing direct sequence spread information
from a plurality of the return service link carriers into one of the return feeder
link carriers.
35. A satellite according to claim 28 wherein the means for unpacking comprises
means for replicating direct sequence spread information from one for the forward
feeder link carriers into a plurality of the forward service link carriers, and
wherein the means for packing comprises means for routing direct sequence spread
information from a plurality of the return service link carriers into one of the
return feeder link carriers.
36. A satellite according to claim 35 wherein the first means for transmitting
comprises means for transmitting the direct sequence spread information in selected
ones of the forward service link carriers at reduced power.
37. A satellite according to claim 35 in combination with a gateway that is configured
to generate the first plurality of forward feeder link carriers and to receive
the fourth plurality of return feeder link carriers.
38. A satellite according to claim 35 in combination with a plurality of wireless
terminals that are configured to receive the second plurality of forward service
link carriers and to generate the third plurality of return service link carriers.
39. A cellular satellite communications method comprising:
receiving first information from a gateway over a first plurality of forward
feeder link carriers having a total forward feeder link bandwidth;
transmitting the first information to a plurality of satellite cells over a second
plurality of forward service link carriers having a total aggregate forward service
link bandwidth, wherein the total forward feeder link bandwidth is less than the
total aggregate forward service link bandwidth;
receiving second information from the plurality of satellite cells over a third
plurality of return service link carriers having a total aggregate return service
link bandwidth; and
transmitting the second information to the gateway over a fourth plurality of
return feeder link carriers having a total return feeder link bandwidth, wherein
the total return feeder link bandwidth is less than the total aggregate return
service link bandwidth.
40. A method according to claim 39 comprising:
unpacking the first information from the first plurality of forward feeder link
carriers into the second plurality of forward service link carriers; and
packing the second information from the third plurality of return service link
carriers into the fourth plurality of return feeder link carriers.
41. A method according to claim 39 wherein unpacking comprises routing TDMA slots
from one of the forward feeder link carriers into a plurality of the forward service
link carriers, and wherein the packing comprises routing TDMA slots from a plurality
of the return service link carriers into one of the return feeder link carriers.
42. A method according to claim 39 wherein the unpacking comprises replicating
TDMA slots from one of the forward feed link carriers into a plurality of the forward
service link carriers, and wherein the packing comprises routing TDMA slots from
a plurality of the return service link carriers into one of the return feeder link carriers.
43. A method according to claim 42 wherein the transmitting the first information
comprises transmitting the first information a at least some of the slots at reduced power.
44. A method according to claim 39 further comprising:
demodulating the first information from the first plurality of forward feeder
link carriers;
modulating the first information onto the second plurality of forward service
link carriers;
demodulating the second information from the third plurality of return service
link carriers; and
modulating the third information onto the fourth plurality of return feeder link
carriers.
45. A according to claim 39 wherein the unpacking comprises routing direct sequence
spread information from one of the forward feeder link carriers into a plurality
of the forward service link carriers, and wherein the packing comprises routing
direct sequence spread information from a plurality of the return service link
carriers into one of the return feeder link carriers.
46. A method according to claim 39 wherein the unpacking comprises replicating
direct sequence spread information from one for the forward feeder link carriers
into a plurality of the forward service link carriers, and wherein the packing
comprises routing direct sequence spread information from a plurality of the return
service link carriers into one of the return feeder link carriers.
47. A method according to claim wherein the transmitting the first information
comprises transmitting the direct sequence information in selected ones of the
forward service link carriers reduced power.
Description
FIELD OF THE INVENTION
This invention relates to wireless communications systems and methods, and more
particularly to cellular satellite communications systems and methods.
BACKGROUND OF THE INVENTION
Satellite communications systems and methods are widely used for wireless
communications of voice and/or data. Satellite 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 wireless terminals.
A satellite communications system or method may utilize a single antenna beam
covering
an entire service area served by the system. Alternatively, in cellular satellite
communications systems and methods, multiple beams are provided, each of which
can serve distinct geographical areas in the overall service area, to collectively
serve an overall satellite service area. 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 wireless terminals over a bidirectional communications
pathway, with communication signals being communicated from the satellite to the
wireless terminal over a downlink or forward link, and from the wireless terminal
to the satellite over an uplink or return link. The downlink and uplink may be
collectively referred to as service links.
The overall design and operation of cellular satellite 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 "wireless terminal" 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/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, for wireless voice and/or data communications.
Cellular satellite communications systems and methods may deploy hundreds
of cells, each of which corresponds to one or more spot beams, over their satellite
footprint corresponding to a service area. It will be understood that large numbers
of cells may be generally desirable, since the frequency reuse and the capacity
of a cellular satellite communications system or method may both increase in direct
proportion to the number of cells. Moreover, for a given satellite footprint or
service area, increasing the number of cells may also provide a higher gain per
cell, which can increase the link robustness and improve the quality of service.
The uplink and downlink communications between the wireless terminals and the
satellite may utilize one or more air interfaces, including proprietary air interfaces
and/or conventional terrestrial cellular interfaces, such as Time Division Multiple
Access (TDMA) and/or Code Division Multiple Access (CDMA) air interfaces. A single
air interface may be used throughout the cellular satellite system. Alternatively,
multiple air interfaces may be used for the satellite communications. See, for
example, U.S. Pat. No. 6,052,560, issued Apr. 18, 2000, entitled Satellite System
Utilizing a Plurality of Air Interface Standards and Method Employing the Same,
by the present inventor Karabinis. In general, regardless of the air interface
or interfaces that are used, each satellite cell generally uses at least one carrier
to provide service. Thus, the return service link and the forward service link
each uses one or more carriers to provide service.
The above description has focused on communications between the satellite and
the wireless terminals. However, cellular satellite communications systems and
methods also generally employ a bidirectional feeder link for communications between
a terrestrial satellite gateway and the satellite. The bidirectional feeder link
includes a forward feeder link from the gateway to the satellite and a return feeder
link from the satellite to the gateway. The forward feeder link and the return
feeder link each uses one or more carriers.
As is well known to those having skill in the art, the number of satellite cells
and the air interface or interfaces that are used may impact the bandwidth that
is used in the feeder link from the satellite gateway to the satellite and from
the satellite to the satellite gateway. For example, if a cellular satellite system
and method deploys 400 cells and uses a narrowband CDMA air interface to provide
communications between the satellite and the wireless terminals, each CDMA carrier
that is transported from the satellite gateway to the satellite may consume 1.25
MHz of feeder link spectrum. Assuming that traffic is such that only one carrier
per cell is used, then 400×1.25 MHz or 500 MHz of forward feeder link bandwidth
may be used. Moreover, if certain cells use more than one carrier and/or a Wideband
CDMA (W-CDMA) air interface standard is used, the feeder link bandwidth may increase further.
U.S. Pat. No. 6,317,583 to Wolcott et al. describes a telecommunications satellite
channelizer for mapping radio frequency (RF) signals between feeder links and mobile
link beams based on a predefined frequency plan. The mobile link beams define a
coverage area of a satellite. Each feeder link and mobile link beam comprises a
plurality of feeder subbands and mobile subbands are grouped to form feeder link
channels and mobile link channels. The channelizer includes at least one feeder
lead carrying a feeder link signal associated with a ground station. A feeder link
distribution network is connected to the feeder leads and maps RF signals in the
feeder links onto a plurality of distribution leads as divided feeder signals.
Channel multiplexers are connected to the distribution leads. Each channel multiplexer
includes a set of band pass filters, each of which passes RF signals in a subset
of feeder subbands corresponding to a single feeder channel in order to map a mobile
link channel and a feeder link channel onto one another based on a predefined frequency
plan. The channelizer groups or multiplexes signals from a plurality of feeders
into each beam. Fixed local oscillator up converters shift each composite mobile
channel to a common band allocated to all beams. The frequency plan is defined
such that beam handovers and ground station handovers may be performed without
a need for at least one of switching, retuning and resynchronization of the telecommunications
satellite and the mobile terminal. See the Wolcott et al. Abstract.
SUMMARY OF THE INVENTION
Some embodiments of the present invention nonidentically map information content
between a plurality of service link carriers and a plurality of feeder link carriers
at a cellular satellite. A reduced number of satellite feeder link carriers compared
to the number of satellite service link carriers and/or a reduced total bandwidth
of the satellite feeder link carriers compared to the satellite service link carriers
thereby may be obtained.
More specifically, some embodiments of the present invention pack information
from a plurality of return service link carriers into a return feeder link carrier
at a cellular satellite. In other embodiments, information also is unpacked from
a forward feeder link carrier into a plurality of forward service link carriers
at the cellular satellite. In some embodiments, information from the plurality
of return service link carriers is packed into fewer return feeder link carriers
and/or information from at least one forward feeder link carrier is unpacked into
more forward service link carriers, at the cellular satellite. In still other embodiments,
information from the plurality of return service link carriers having a total aggregate
return service link bandwidth is packed into one or more return feeder link carriers
having a total return feeder link bandwidth that is less than the total aggregate
return service link bandwidth and/or information from one or more forward feeder
link carriers having a total forward link bandwidth is unpacked into the plurality
of forward service link carriers having a total aggregate forward service link
bandwidth that is greater than the total forward feeder link bandwidth, at the
cellular satellite. In still other embodiments, information from the plurality
of return service link carriers is packed at the cellular satellite to fill at
least one return feeder link carrier and/or information from at least one forward
feeder link carrier that is filled is unpacked at the cellular satellite into more
forward service link carriers.
Embodiments of the invention may be used with TDMA, CDMA and/or other
air interfaces. When TDMA air interfaces are used, slots in TDMA frames of a return
feeder link carrier are loaded with TDMA frames of the return service link carriers
that may not be fully loaded. This loading may take place by demodulating the return
service link carriers, performing the slot loading and then modulating the return
feeder link carriers at the satellite. Alternatively, the satellite may use slot-level
synchronization without resorting to demodulation to extract the information-carrying
return service link TDMA slots and use them to load and pack the return feeder
link frames.
In other embodiments, slots in TDMA frames of a forward feeder link carrier are
selectively routed to TDMA frames of selected ones of the forward service link
carriers. This routing may take place by demodulating a forward feeder link carrier,
performing the selective routing and modulating the forward service link carriers.
Alternatively, the satellite may use slot-level synchronization (without resorting
to demodulation) to extract the information-carrying forward feeder link TDMA slots
and route them selectively to load the TDMA frames of the forward service link carriers.
In still other embodiments, TDMA frames of a forward feeder link carrier are
selectively
replicated at the satellite to TDMA frames of selected ones of the forward service
link carriers. In yet other embodiments, power in selective ones of the slots of
the replicated TDMA frames of the selected ones of the forward service link carriers
is reduced (or brought to zero), so that power may be conserved for the replicated
TDMA slots that are not needed in a particular forward service link.
In CDMA embodiments, direct sequence spread return service link carriers that
are not fully loaded are combined into one return feeder link carrier. As part
of the combining, in some embodiments, the return service link carriers are demodulated,
the combining is performed and the return feeder link carriers are then modulated
at the satellite. In some embodiments, demodulation of the direct sequence spread
return service link carriers may not be performed. Instead, shifting a plurality
of underloaded return service links to a common frequency and superimposing, with
or without time alignment, may be used to form a highly packed return feeder link
carrier which, after frequency translation to the return feeder band, may be transmitted
to the cellular satellite gateway(s).
In other embodiments, direct sequence spread information from a forward feeder
link carrier is selectively routed to selected ones of the forward service link
carriers. In some embodiments, the forward feeder link carrier may be demodulated
prior to the routing and the forward service link carriers may be modulated after
the routing. In still other embodiments, direct sequence spread information from
a forward feeder link carrier is selectively replicated to selected ones of the
forward service link carriers. In these embodiments, power in selected direct sequence
spread information of the selected ones of the replicated forward service links
may be reduced (and in some embodiments reduced to zero), to conserve power. Accordingly,
an identical mapping of the feeder link carriers to the service link carriers,
and vice versa, need not be provided, so that a reduced feeder link bandwidth and/or
number of carriers may be used.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2 are block diagrams of cellular satellite radiotelephone systems
and methods according to some embodiments of the present invention.
FIGS. 3 and 4 are schematic diagrams of cellular satellite radiotelephone systems
and methods according to some embodiments of the present invention.
DETAILED DESCRIPTION
The present invention now will be described more fully hereinafter with reference
to the accompanying figures, in which embodiments of the invention are shown. This
invention may, however, be embodied in many alternate forms and should not be construed
as limited to the embodiments set forth herein.
Accordingly, while the invention is susceptible to various modifications
and alternative forms, specific embodiments thereof are shown by way of example
in the drawings and will herein be described in detail. It should be understood,
however, that there is no intent to limit the invention to the particular forms
disclosed, but on the contrary, the invention is to cover all modifications, equivalents,
and alternatives falling within the spirit and scope of the invention. Like numbers
refer to like elements throughout the description of the figures.
Some embodiments of the present invention may arise from a recognition that
an identical (i.e., one-to-one) mapping of the feeder link carriers to the service
link carriers (and vice versa) need not be provided. Rather, a nonidentical (i.e.,
not a one-to-one) mapping of information content between the service link carriers
and the feeder link carriers (and vice versa) may be provided. Thus, the information
that is transmitted between the satellite and the gateway via the feeder link(s)
may be packed to fill the feeder link carriers, so as to reduce or minimize the
number of feeder link carriers and/or the bandwidth that is used by the feeder
link(s). The information may be split or unpacked at the satellite, to provide
the desired satellite downlink spot beams with the desired information, and also
may be packed at the satellite, to allow the satellite uplink spot beams and the
information contained therein to be packed into a reduced number of carriers and/or
a reduced bandwidth on the feeder link(s).
FIGS. 1 and 2 are block diagrams of cellular satellite radiotelephone systems
and methods according to some embodiments of the present invention. More specifically,
FIG. 1 illustrates a reduction in the number of feeder link carriers and FIG. 2
illustrates a reduction in the aggregate bandwidth of the feeder link(s) according
to some embodiments of the present invention.
FIG. 1 illustrates packing
110 at a cellular satellite
100, information
from a plurality of return service link carriers
132a of a plurality
of return service links
130a, here shown as seven return service
link carriers
132a, which originate from wireless terminals
160,
into at least one return feeder link
140a comprising at least one
return feeder link carrier
142a, here four return feeder link carriers
142a, which are provided to one or more gateways
150, according
to some embodiments of the present invention. FIG. 1 also illustrates unpacking
120 at the cellular satellite
100 information from at least one forward
feeder link
140b, comprising at least one forward feeder link carrier
142b, here three forward feeder link carriers
142b,
which originate from gateway(s)
150, into a plurality of forward service
link carriers
132b of a plurality of forward service links
130b,
here eight forward service link carriers
132b, which are provided
to wireless terminals
160. Accordingly, as shown in FIG. 1, fewer return
feeder link carriers
142a then return service link carriers
132a
are used, and fewer forward feeder link carriers
142b than forward
service link carriers
132b are used. Thus, fewer feeder link carriers
may be used. It will be understood that the number of forward/return links and
carriers shown in FIGS. 1-4 are exemplary and are non-limiting. Moreover, equal
numbers of forward and return feeder link carriers and equal numbers of forward
and return service link carriers may be provided.
As will described in detail below, packing
110 may be provided by a first
receiver
111, a first demodulator
112, a first processor
113,
a first modulator
114 and a first transmitter
115 in some embodiments.
Unpacking
120 may be provided by a second receiver
121, a second
demodulator
122, a second processor
123, a second modulator
124,
and a second transmitter
125 in some embodiments. It also will be understood
that elements
111-
115 and
121-
125 are illustrated separately
for functional purposes, but some or all of the functions thereof may be combined
in some embodiments of the present invention.
FIG. 2 illustrates other embodiments of the present invention, where packing
210 of information is performed from a plurality of return service link
carriers that originate from wireless terminals
260 into a return feeder
link carrier that is provided to gateway
250, wherein the total return feeder
link bandwidth
240a is less than the total return service link bandwidth
230a, as indicated by the thickness of the return feeder link bandwidth
240a relative to the thickness of the aggregate return service link
bandwidth
230a. FIG. 2 also illustrates unpacking
220 at the
cellular satellite
200, information from a forward feeder link carrier that
is provided by the gateway
250, into a plurality of forward service link
carriers which interface with wireless terminals
260, wherein the total
forward feeder link bandwidth
240b is less than the total aggregate
forward service link bandwidth
230b, as indicated by the relative
thickness of the forward feeder link bandwidth
240b and the aggregate
forward service link bandwidth
230b of FIG.
2.
As will be described in detail below, packing
210 may be provided by a
first receiver
211, a first demodulator
212, a first processor
213,
a first modulator
214 and a first transmitter
215 in some embodiments.
Unpacking
220 may be provided by a second receiver
221, a second
demodulator
222, a second processor
223, a second modulator
224,
and a second transmitter
225 in some embodiments. It also will be understood
that elements
211-
215 and
221-
225 are illustrated separately
for functional purposes, but some or all of the functions thereof may be combined
in some embodiments of the present invention.
Conventionally, feeder link carriers are mapped onto satellite cells
upon arrival at the satellite, unaltered and/or without further processing that
may entail replication and/or adding or deleting information content. Because processing
may not be provided at the satellite, even though each carrier can support up to
L users simultaneously, where L is greater than 1, the feeder link bandwidth and/or
the number of carriers conventionally remains the same whether only one active
user per satellite cell or up to L active users per satellite cell are present.
Thus, in the example that was described above, 500 MHz bandwidth and 400 carriers
may be used conventionally on the feeder link even though one or more of the satellite
cells are operating with less than their maximum number of users.
In sharp contrast, some embodiments of the invention can pack
110,
210
the information from a plurality of return service link carriers
132a
into a return feeder link
140a that has a reduced number of carriers
142a compared to the sum of the carriers
132a in the
return service links
130a, and/or reduced bandwidth
240a
compared to the sum of the bandwidths
230a of all the return
links, and can unpack
120,
220 a forward feeder link
140b
to provide the desired satellite forward service links
130b.
FIG. 3 is a schematic diagram of cellular satellite systems and methods according
to some embodiments of the present invention. FIG. 3 illustrates a forward feeder
link
340 from a satellite gateway
350 to a satellite
300,
and the corresponding forward service links (downlinks)
330 from the satellite
to multiple satellite cells
360. However, it will be understood that similar
approaches may be used for the satellite return service links (uplinks) from wireless
terminals in the satellite cells
360 to the satellite
300 and the
corresponding return feeder link(s) from the satellite
300 to the satellite
gateway(s)
350.
Embodiments of FIG. 3 illustrate use of a CDMA air interface, and more
specifically illustrate CDMA carrier splitting on-board the satellite
300
to reduce or minimize feeder link bandwidth. Referring now to FIG. 3, assume that
there are λ active users, where λ≦L, distributed over N satellite
cells
360. According to some embodiments of the present invention, since
one carrier can serve up to L users, one carrier, in principle, can suffice to
serve the N cells
360 relative to the λ users. Thus, according to
some embodiments of the present invention, a single carrier may be used on the
feeder link
340 rather than N carriers. The number of feeder link carriers
and/or the feeder link bandwidth thereby may be less than the number of forward
service link carriers and/or aggregate forward service link bandwidth by a factor
of N, in this example.
Continuing with the above example, a single carrier serving all the λ
users may be provided to the satellite
300 from the gateway
350 via
the forward feeder link
340. However, since the users are distributed over
N different satellite cells
360, some embodiments of the present invention
may replicate the single carrier N times at the satellite, as illustrated in FIG.
3, and then distribute this carrier over each one of the N cells
360. Thus,
these embodiments may reduce the number of feeder link carriers and/or bandwidth
by a factor of N, but may increase the radiated service link power, since more
spreading codes than actually used in a particular cell may be transmitted to a
particular cell.
Other embodiments of the invention, as also illustrated in FIG. 3, may reduce
or eliminate the potential increase in power in the service links
330 between
the wireless terminals and the satellite
300, by demodulating the feeder
link carrier
340 at the satellite
300, with or without data regeneration,
before the forward service link carrier is transmitted over the N cells. Demodulation
can be used to separate or split the λ distinct direct sequence spread information
of the carrier, corresponding to the λ users. Once separated, the information
may be recombined as desired, and modulated to form appropriate carriers before
transmitting over the N downlinks
330 to the wireless terminals. Additional
radiated power overhead, therefore, may not be required.
Thus, in some embodiments of the present invention, the communications between
a plurality of wireless terminals and a satellite may be packed into a smaller
number of carriers and/or less bandwidth on the feeder link between the satellite
and the satellite gateway. The packed carrier(s) may be replicated for communication
with the satellite cells and/or may be unpacked at the satellite without replication,
so that only those communications that are used in a given cell will be transmitted
on the forward service links between the wireless terminals and the satellite.
Feeder link bandwidth thereby can be reduced or minimized. Moreover, feeder link
carrier unpacking at the satellite may be used to reduce or minimize the power
on the service links between the satellite and the wireless terminals. Power also
may be reduced, or brought to zero, for replicated spreading coded information
that is not needed by users of a particular service link.
Referring now to FIG. 4, other embodiments of the invention may be used
with TDMA air interfaces. FIG. 4 illustrates a forward feeder link
440 and
a plurality of forward service links
430. However, similar approaches may
be used for the return service links and the return feeder link(s). In FIG. 4,
a TDMA air interface is used for the service links, with an 8-slot (burst) frame
structure. It will be understood that other TDMA frame structures may be used.
Referring again to FIG. 4, each TDMA carrier may serve up to eight different
users, labeled A-H. These users may be in different satellite cells
460,
however. As illustrated in FIG. 4, in one example, users A, B, C, D and E may be
within one satellite cell. User F may be in another satellite cell and users G
and H may be in yet another satellite cell.
Conventionally, users A-H may be served by three different feeder
link carriers, represented by
480a,
480b and
480c,
that are not fully loaded. Conventionally, these three different feeder link carriers
are sent to the satellite from the gateway via the feeder link(s)
440.
In contrast, according to some embodiments of the present invention, one fully
loaded feeder link carrier
470 may be sent to the satellite
400 by
the satellite gateway
450, to serve all eight users. As shown in FIG. 4
at
470, the single, fully loaded carrier on the feeder link
440 may
contain eight slots A-H.
In some embodiments, the fully loaded feeder link carrier
470 may be transmitted
to each of the three satellite cells
460 shown in FIG.
4. This can
reduce the amount of processing that may be performed on the satellite
400,
at the potential expens
