SATELLITE COMMUNICATIONS SYSTEMS AND METHODS USING SUBSTANTIALLY CO-LOCATED FEEDER LINK ANTENNAS

FIELD OF THE INVENTION

[0001 ] The present application claims the benefit of priority to United States Provisional Application Serial No. 60/706,823 filed August 9, 2005, the disclosure of which is hereby incorporated herein in its entirety by reference.

FIELD OF THE INVENTION

[0002] This invention relates to wireless communications systems and methods, and more particularly to satellite communications systems and methods.

BACKGROUND OF THE INVENTION

[0003] Satellite radiotelephone communications systems and methods are widely used for radiotelephone communications. Satellite radiotelephone communications systems and methods generally employ at least one space-based component, such as one or more satellites, that is/are configured to wirelessly communicate with a plurality of satellite radiotelephones and feeder link antennas.

[0004] A satellite radiotelephone communications system or method may utilize a single satellite antenna pattern (beam or cell) covering an entire service region served by the system. Alternatively or in combination with the above, in cellular satellite radiotelephone communications systems and methods, multiple satellite antenna patterns (beams or cells) are provided, each of which can serve a substantially distinct service region in an overall service region, to collectively provide service to the overall service region. Thus, a cellular architecture that is similar to that used in conventional terrestrial cellular radiotelephone systems and methods can be implemented in cellular satellite-based systems and methods.

[0005] Figure 1 is a schematic diagram that illustrates a satellite communications system 100 that includes a space based component 102, radioterminals Tl-TN, feeder link antennas 110-116 and a gateway processor 120. A network 130 (that may be a wireline and/or wireless network) is also illustrated as being connected to the satellite communications system 100 and may be part of the satellite communications system 100. The radioterminals Tl-TN can communicate (through the satellite 102 and feeder link antennas 110-116) with one another and/or

with other communications devices that are connected to the network 130. The satellite 102 receives information from the radioterminals Tl-TN through return service links, and transmits the information to the feeder link antennas 110-116 through return feeder links. The satellite 102 receives information from the feeder link antennas 110-116 through forward feeder links, and transmits the information to the radioterminals Tl-TN through forward service links. In some cases, such as, for example, in broadcasting, a single forward service link of the satellite may communicate information to more than one of the radioterminals Tl-TN. The forward feeder links and the return feeder links each use one or more feeder link carriers and/or channels of a feeder link band of frequencies.

[0006] To provide a relatively high aggregate signal spectrum from the satellite 102 to one or more satellite gateways (for processing such as, for example, ground-based beam forming), the satellite 102 can be configured to form return feeder link spot beams (antenna patterns) that are aligned with different ones of a plurality of feeder link antennas (i.e., gateway antennas), such as the feeder link antennas 110- 116, and can thereby "spatially multiplex" the return service link aggregate spectrum across the return feeder link spot beams to the feeder link antennas 110-116, thereby spatially reusing an available feeder link bandwidth. For example, when the satellite 102 is configured to provide to one or more satellite gateways an aggregate signal spectrum corresponding to, for example, 100 return service link antenna feed elements (of the satellite return service link antenna) with each return service link antenna feed element providing, for example, 20MHz of spectrum, the satellite 102 must be configured to provide an aggregate of 2 GHz (i.e., 20 x 100 MHz) of return feeder link spectrum to one or more gateways via one or more respective feeder link antennas, such as, for example, feeder link antennas 110-116, illustrated in Figure 1. The satellite 102 may be configured to provide the 2GHz aggregate spectrum while using only a 500 MHz feeder link bandwidth by forming four feeder link spot beams that are aligned with different ones of the four feeder link antennas 110-116, as illustrated in Figure 1. Because the four feeder link spot beams use the same frequencies within the 500 MHz feeder link spectrum, the feeder link antennas 110- 116 must be sufficiently spaced apart geographically to prevent or reduce a level of interference therebetween.

[0007] The satellite 102 may also reduce the feeder link bandwidth that is needed to support return service links using the techniques described in U.S. Patent

No. 6,937,857 to the present inventor, entitled Systems And Methods For Reducing Satellite Feeder Link Bandwidth/Carriers In Cellular Satellite 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. As described in the Abstract of this Patent Application Publication, information content is non-identically mapped between service link carriers and feeder link carriers at a satellite. A reduced number of feeder link carriers compared to the number of service link carriers and/or a reduced total bandwidth of the feeder link carriers compared to the service link carriers may thereby be obtained.

[0008] As used herein, the term "radioterminal" includes a cellular and/or satellite radioterminal with or without a multi-line display; Personal Communications System (PCS) terminals that may combine a radioterminal with voice, facsimile and/or data communications capabilities; Personal Digital Assistants (PDA) that can include a radio frequency transceiver and/or a pager, Internet/Intranet access, Web browser, organizer, calendar and/or a global positioning system (GPS) receiver; and/or laptop and/or palmtop computers or other data processing devices, which include a radio frequency transceiver. A radioterminal also may be referred to herein as a "radiotelephone," a "mobile terminal," or simply as a "terminal". As used herein, the term(s) "radioterminal," "radiotelephone," mobile terminal," and/or "terminal" also include(s) any other communications device, equipment and/or source that may have time- varying or fixed geographic coordinates and/or may be portable, transportable, installed in a vehicle (aeronautical, maritime, or land-based) and/or situated and/or configured to operate locally and/or in a distributed fashion over one or more terrestrial and/or extra-terrestrial location(s). Furthermore, as used herein, the term "space-based component" or "space-based system" includes one or more satellites at any orbit (geostationary, substantially geostationary, substantially medium earth orbit, substantially low earth orbit, substantially elliptical earth orbit, etc.) and/or one or more other objects and/or platforms (e. g., airplanes, balloons, unmanned vehicles, space crafts, missiles, etc.) that has/have a trajectory above the earth at any altitude.

SUMMARY

[0009] Some embodiments of the present invention are directed to a satellite communications system that includes a plurality of feeder link antennas, that may be

ground-based feeder link antennas, a primary satellite, and one or more auxiliary satellites. The feeder link antennas are substantially co-located relative to one another. The primary satellite is configured to receive information over a plurality of return service links from radioterminals, to communicate a first portion of the information over at least one return feeder link directly to a first one of the feeder link antennas, and to communicate a second portion of the information across at least one inter-satellite link. The auxiliary satellites are spaced apart and separate from the primary satellite and from one another, and configured to receive the second portion of the information from the primary satellite via the at least one inter-satellite link, and to communicate the second portion of the information over at least one return feeder link to at least one second feeder link antenna.

[0010] Accordingly, the primary satellite can distribute an aggregate signal spectrum (or aggregate signal bandwidth) associated with the return service links and/or the receive service link antenna feed elements of the primary satellite over the return feeder link(s) of the primary satellite to the first feeder link antenna and over the return feeder link(s) of the auxiliary satellite(s) to the at least one second feeder link antenna.

[0011 ] Some other embodiments of the present invention are directed to related methods of communicating in a satellite communications system, primary satellites, auxiliary satellites, and satellite communications equipment that may be, in some embodiments, ground-based satellite communications equipment. According to embodiments of the invention, the auxiliary satellite(s) may be devoid of any service link antennas that enable the auxiliary satellite(s) to communicate directly with radioterminals.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate certain embodiment(s) of the invention, hi the drawings:

[0013] Figure 1 is a schematic diagram illustrating a conventional satellite communications system in which a satellite relays information between radioterminals and a plurality of widely spaced apart feeder link antennas;

[0014] Figure 2 is a schematic diagram illustrating a satellite communications system and methods in which a plurality of satellites relay information between radioterminals and a plurality of substantially geographically co-located feeder link antennas according to various embodiments of the present invention;

[0015] Figure 3 is a more detailed block diagram of the satellite communications system and methods of Figure 2 for communicating information from the radioterminals through a primary satellite and a plurality of auxiliary satellites to the feeder link antennas according to various embodiments of the present invention;

[0016] Figure 4 is a more detailed block diagram of the gateway processor and methods of Figure 2 for reducing interference in the feeder link signals; and

[0017] Figure 5 is a more detailed block diagram of the satellite communications system and methods of Figure 2 for communicating information from the feeder link antennas through the primary satellite and the auxiliary satellites to the radioterminals according to various embodiments of the present invention.

DETAILED DESCRIPTION

[0018] Specific exemplary embodiments of the invention now will be described with reference to the accompanying drawing. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. Furthermore, "connected" or "coupled" as used herein may include wirelessly connected or coupled.

[0019] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms "includes," "comprises," "including" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or

more other features, integers, steps, operations, elements, components, and/or groups thereof.

[0020] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0021] It will be understood that although the terms first and second are used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, a first radioterminal below could be termed a second radioterminal, and similarly, a second radioterminal may be termed a first radioterminal without departing from the teachings of the present invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. The symbol "/" is also used as a shorthand notation for "and/or".

[0022] As was explained with regard to Figure 1, a satellite can increase its return feeder link bandwidth by forming spot beams that are aligned with different ones of a plurality of widely spaced apart feeder link antennas. However, the need to establish and maintain geographic sites for the widely spaced apart feeder link antennas may represent additional expense and/or management burden for a satellite communications system operator. Accordingly, an alternate satellite communications system that allows a number of feeder link antenna sites to be reduced or minimized may be advantageous.

[0023] Figure 2 is a schematic diagram that illustrates a satellite communications system 200 and methods in accordance with some embodiments of the present invention. The satellite communications system 200 includes a Primary Satellite ("PS"), a plurality (e.g., three) of Auxiliary Satellites ("ASs"), a plurality (e.g., four) of Feeder Link Antennas ("FLAs"), a Gateway Processor ("GP"), a plurality of radioterminals Tl-TN, and a network 130. The feeder link antennas FLA0-FLA3, the gateway processor GP, and the network 130 may be collectively referred to as Ground-Based Equipment ("GBE"). However, it will be understood that, according to some embodiments of the invention, the feeder link antennas FLAO-

FL A3, the gateway processor GP and/or the network 130 may not be ground-based (e.g., any combination thereof may be maritime-based, aeronautically-based and/or space-based). In accordance with embodiments of the invention, the network 130 (that may be a wireline and/or wireless network), illustrated as being connected to the satellite communications system 100, may or may not be part of the satellite communications system 100. The radioterminals Tl-TN may be configured to communicate with the primary satellite PS by radiating substantially linearly- polarized electro-magnetic energy and/or arbitrarily-polarized electro-magnetic energy and the primary satellite PS may, in accordance with some embodiments of the invention, be configured to receive both substantially Left Hand Circularly Polarized (LHCP) electro-magnetic energy and substantially Right Hand Circularly Polarized (RHCP) electro-magnetic energy that arrives at the primary satellite PS over service link frequencies. Service link frequencies may be frequencies of an L-band, S-band and/or any other band of frequencies that may be used to provide service link communications. The primary satellite PS may be configured to transmit information to the radioterminals Tl-TN by radiating substantially LHCP and/or RHCP electromagnetic energy.

[0024] As illustrated in Figure 2, each of the auxiliary satellites AS1-AS3 is spaced apart from the primary satellite PS and from other ones of the auxiliary satellites AS1-AS3 by an amount that allows the feeder link antennas FLA0-FLA3, (that may be at or near the Earth), to be substantially co-located relative to one another while providing substantial discrimination/isolation therebetween in receiving/transmitting signals from/to the primary satellite PS and the auxiliary satellites AS1-AS3. For example, the feeder link antenna FLAO that communicates with the primary satellite PS may be oriented and configured to provide a substantially higher (or maximum) gain in a direction associated with the primary satellite PS while providing a substantially lower gain in other directions including directions associated with the auxiliary satellites AS1-AS3. The feeder link antenna FLAl that communicates with the auxiliary satellite ASl may be oriented and configured to provide a substantially higher gain in a direction associated with the auxiliary satellite ASl while providing a substantially lower gain in other directions including directions associated with the other auxiliary satellites AS2-AS3 and the primary satellite PS. The feeder link antenna FLA2 that communicates with the auxiliary satellite AS2 may be oriented and configured to provide a substantially

higher gain in a direction associated with the auxiliary satellite AS2 while providing a substantially lower gain in other directions including directions associated with the other auxiliary satellites ASl and AS3 and with the primary satellite PS. The feeder link antenna FLA3 that communicates with the auxiliary satellite AS3 may be oriented and configured to provide a substantially higher gain in a direction associated with the auxiliary satellite AS3 while providing a substantially lower gain in other directions including directions associated with the other auxiliary satellites AS2 and AS3 and with the primary satellite PS.

[0025] In some embodiments, both the primary satellite PS and the auxiliary satellites AS1-AS3 are in respective substantially geostationary orbits relative to Earth, and have at least about a 2° separation angle therebetween. In some other embodiments, a separation distance between the primary satellite PS and at least one of the auxiliary satellites AS1-AS3 and/or a separation distance between any two of the auxiliary satellites AS1-AS3, may be less or more than 2°. This separation distance can allow the substantially co-located feeder link antennas to provide a level of discrimination between the received/transmitted feeder link signals from/to the primary satellite PS and/or the auxiliary satellites AS1-AS3.

[0026] As used herein, "substantially co-located" feeder link antennas means that a distance between the feeder link antennas is not dictated by directional feeder link beams (antenna patterns) that are formed by a single satellite. Accordingly, the feeder link antennas FLA0-FLA3 can be spaced apart by any distance that is convenient to the satellite communications system operator, and may be spaced apart by about 30 meters or less, by about 300 meters or less, by about 3000 meters or less, or by any other distance based on the geographic site selection and management convenience of the operator. Thus, for example, an operator may mount the feeder link antennas FLA0-FLA3 within one or more acres of land which the operator may conveniently purchase/lease.

[0027] Figure 3 is a more detailed block diagram of the satellite communications system 200 and methods of Figure 2 for communicating information from the radioterminals Tl-TN through the primary satellite PS and the auxiliary satellites AS1-AS3 to the feeder link antennas FLAl -3 according to various embodiments of the present invention. The primary satellite PS is configured to receive return link information from the radioterminals Tl-TN through a plurality of return service links, and to transmit forward link information to the radioterminals Tl-

TN through a plurality of forward service links. The primary satellite PS transmits a portion of the return link information it receives from the radioterminals Tl-TN directly to the feeder link antenna FLAO through a return feeder link. The primary satellite PS also transmits another portion of the return link information to the auxiliary satellites AS1-AS3 through inter-satellite links. The auxiliary satellites AS1-AS3 transmit the received return link information through return feeder links to the associated feeder link antennas FLA1-FLA3.

[0028] Accordingly, the primary satellite PS distributes an aggregate signal spectrum (i.e., signal bandwidth) associated with the return service links on the return feeder link from the primary satellite PS to the feeder link antenna FLAO and on the return feeder links from the auxiliary satellites AS1-AS3 to the respective feeder link antennas FLA1-FLA3. For example, when an aggregate bandwidth associated with the return service links 302 yields 2 GHz of aggregate signal spectrum that must be transported from space to one or more satellite gateways (as may be the case, in some embodiments, in order to perform satellite antenna pattern forming at the one or more satellite gateways), the primary satellite PS may route 500 MHz of the aggregate signal spectrum through the return feeder link(s) 304a and route another 500 MHz of the aggregate signal spectrum to each of the auxiliary satellites AS 1-3 to be transported through their respective return feeder links 304b-d, and so that the return feeder links 304a-d each carry about one fourth of the aggregate signal spectrum that is associated with the return service links 302.

[0029] For example, as illustrated in Figure 3, the primary satellite can include a return service link receiver 310, an information spreader 312, a feeder link transmitter 314, and an inter-satellite link transmitter 316. The return service link receiver 310 receives information from the radioterminals Tl-TN across return service links 302, eight of which have been illustrated. The feeder link transmitter 314 transmits information across return feeder link(s) 304a to the feeder link antenna FLAO. The inter-satellite link transmitter 316 transmits information across inter- satellite link(s) 306 to selected ones of the auxiliary satellites AS1-AS3. The inter- satellite link(s) 306 may be Radio Frequency (RF) links, optical links and/or other types of wireless communications links.

[0030] The information spreader 312 distributes information associated with the return service links 302 across the return feeder link(s) 304a from the primary satellite PS to the feeder link antenna FLAO and across the inter-satellite link(s) 306

from the primary satellite PS to the auxiliary satellites AS1-AS3. For example, the information spreader 312 may route information associated with a first set of receive antenna feed elements and/or first set of frequencies of a receive service link antenna of the primary satellite PS to the feeder link transmitter 314 for transmission to the feeder link antenna FLAO, route information associated with a second set of receive antenna feed elements and/or second set of frequencies of the receive service link antenna of the primary satellite PS to the inter-satellite link transmitter 316 for transmission to the auxiliary satellite ASl, route information associated with a third set of receive antenna feed elements and/or third set of frequencies of the receive service link antenna of the primary satellite PS to the inter-satellite link transmitter 316 for transmission to the auxiliary satellite AS2, and route information associated with a fourth set of receive antenna feed elements and/or fourth set of frequencies of the receive service link antenna of the primary satellite PS to the inter-satellite link transmitter 316 for transmission to the auxiliary satellite AS 3.

[0031] The auxiliary satellites AS1-AS3 may each include an inter-satellite link receiver 320, an information relay 322, and a feeder link transmitter 324. The inter-satellite link receiver 320 receives information from the primary satellite PS across the inter-satellite links 306. The information relay 322 relays the received information, and may relay the received information substantially unchanged or add content, to the feeder link transmitter 324. The feeder link transmitter 324 transmits the information from relay 322 through an associated one of the feeder links 304b-d to an associated one of the feeder link antennas FLA1-FLA3. Because the auxiliary satellites AS 1-3 may be configured to serve primarily as information relays between the primary satellite PS and the feeder link antennas FLAl -3, they need not provide substantial on-board processing and, thereby, may be relatively simple and/or compact compared to the primary satellite PS. Furthermore, the auxiliary satellites AS 1-3 may be devoid of any service link antennas and may, therefore, be incapable of communicating directly with radioterminals. However, in some embodiments, one or more of the auxiliary satellites may be equipped with one or more service link antennas. Accordingly, it may be more efficient, less expensive and/or otherwise desirable to use a plurality of auxiliary satellites, according to embodiments of the present invention, rather than providing multiple, widely spaced apart, feeder link antennas as shown in Figure 1.

[0032] The feeder link transmitter 314 of the primary satellite PS and the feeder link transmitter 324 of each of the auxiliary satellites AS1-AS3 may use at least some of the same frequencies for the return feeder links 304a-d. Although the feeder link antennas FLA0-FLA3 are substantially geographically co-located, they can each discriminate/isolate among the feeder links 304a-d from a particular one of the auxiliary satellites AS1-AS3 or primary satellite PS with an acceptable level of interference because of the separation between any two of the primary satellite PS and the auxiliary satellites AS1-AS3.

[0033] The information spreader 312 may be configured to perform a static or dynamic routing of information associated with return service link antenna feed elements of the return service link antenna(s) of the primary satellite PS to return feeder links 304a-d. The information spreader 312 may dynamically vary the mapping in response to, for example, a utilization of the return service links 302 by the radioterminals Tl-TN. For example, the information spreader 312 may increase a bandwidth utilization of the return feeder links 304b-d from the auxiliary satellites AS1-AS3 to the feeder link antennas FLA 1-3 as the utilization of the return service links 302 increases, such as by offloading traffic to the auxiliary satellites AS 1-3 as the primary satellite PS return feeder link(s) 304a reach a threshold bandwidth utilization. The information spreader 312 may alternatively, or additionally, map information associated with the return service links 302 among the return feeder links 304a-d to obtain a balancing of bandwidth utilization or other desired bandwidth utilization characteristics.

[0034] The information spreader 312 may process information that is received from a plurality of the return service links 302, such as by interleaving the information, and may spread that information for transmission across a plurality, or all, of the return feeder links 304a-d. Interleaving the information across a plurality of the return feeder links 304a-d may increase a robustness measure associated with the return feeder links 304a-d. For example, by spreading information received from one of the return service links 302 and/or return service link antenna feed elements of the return service link antenna(s) of the primary satellite PS across all of the return feeder links 304a-d may allow the gateway processor GP, or other portion of the ground based equipment GBE, to reduce errors introduced by interference to one of the return feeder links 304a-d.

[0035] The gateway processor GP processes the return feeder link signals 304a-d from the feeder link antennas FL AO-FL A3 to extract the information from the radioterminals Tl-TN. Figure 4 is a block diagram of the gateway processor and methods of Figure 2 for reducing interference in the return feeder link signals from the feeder link antennas FL AO-FL A3 according to some embodiments of the present invention. The gateway processor GP may include a delay circuit 400, a correlator 420, an interference reducer 430, and a receiver 440. The delay circuit 400 may include a plurality (e.g., four) of adjustable delay elements 410-413, with each configured to delay a return feeder link signal from an associated one of the feeder link antennas FL AO-FL A3 by an amount that is controlled by the correlator 420. The correlator 420 correlates output signals of the adjustable delay elements 410-413 to determine timing offset(s) therebetween, and varies the delays caused by each of the adjustable delay elements 410-413 to time align the return feeder link signals. It will be understood that in accordance with some embodiments of the invention, the delay circuit 400 (or at least some of the delay elements 410-413) may not be required. For example, subject to a sufficiently compact co-location of the feeder link antennas FLA0-FLA3, the delay circuit 400 (or at least some of the delay elements 410-413) may not be required.

[0036] The interference reducer 430 generates interference correction signal(s) from the time aligned return feeder link signals that is indicative of interference caused by the return feeder link(s) 304a from the primary satellite PS to one or more of the return feeder links 304b-d received by the feeder link antennas FLAl -FL A3, and/or that is indicative of interference caused by one or more of the return feeder links 304b-d from the auxiliary satellites AS1-AS3 to the return feeder link(s) 304a received by the feeder link antennas FLAO. The interference reducer 430 also uses the interference correction signal(s) to reduce interference in at least one of the return feeder link signals from the feeder link antennas FLAO-FL A3. The receiver 440 can further process the return feeder link signals, including error correction decoding, to extract the information from the radioterminals Tl-TN, and can communicate the extracted information to the network 130 to allow the radioterminals Tl-TN to communicate with one another and/or with other communications devices that are connected to the network 130.

[0037] The gateway processor GP may carry out interference reduction using techniques described in provisional patent application Serial No. 60/662,053, entitled

Intra-System and/or Inter-System Reuse of Feeder Link Frequencies Including Interference Suppression Systems and Methods, filed March 15, 2005, the disclosure of which is hereby incorporated herein by reference in its entirety as if set forth fully herein.

[0038] Figure 5 is a more detailed block diagram of the satellite communications system and methods of Figure 2 for communicating information from the feeder link antennas FL AO-FL A3 through the primary satellite PS and the auxiliary satellites AS1-AS3 to the radioterminals Tl-TN according to various embodiments of the present invention. Information that is to be communicated from the ground based equipment GBE to the radioterminals Tl-TN can be communicated directly to the primary satellite PS through forward feeder links 504a and indirectly to the primary satellite PS via the auxiliary satellites AS1-AS3. The primary satellite PS can then retransmit information to the radioterminals Tl-TN through a plurality of forward service links 502. Accordingly, the primary satellite PS can utilize/process forward feeder link signals of each of the forward feeder links 504a-d to the primary satellite PS and auxiliary satellites AS1-AS3 to form an aggregate signal to serve the forward service links 502 associated with radioterminals Tl-TN.

[0039] Each of the auxiliary satellites AS1-AS3 can include an inter-satellite link transmitter 520, an information relay 522, and a feeder link receiver 524. The feeder link receiver 524 receives information from one of the feeder link antennas FLAl, FLA2, FLA3 through one or more forward feeder links 504b, 504c, 504d, respectively. The information relay 522 relays the received information, and may relay the received information substantially unchanged or modified/re-formatted, to the inter-satellite link transmitter 520. The inter-satellite link transmitter 520 transmits the information across the inter-satellite links 306 to the primary satellite PS.

[0040] The primary satellite PS can include a forward service link transmitter 510, an information combiner 512, a feeder link receiver 514, and an inter- satellite link receiver 516. The feeder link receiver 514 receives information directly from the feeder link antenna FLAO through one or more forward feeder links 504a. The inter- satellite link receiver 516 receives information transmitted by the auxiliary satellites AS1-AS3 through the inter-satellite links 306. The information combiner 512 routes the received information through selected ones of the forward service links 502 to the radioterminals T 1 -TN .

[0041] Although some embodiments of the present invention have been described in the context of a primary satellite that communicates through four auxiliary satellites to ground based equipment, it is to be understood that one or more primary and/or auxiliary satellites may be used according to various embodiments of the present invention. The number of auxiliary satellites may be selected based on a total aggregate bandwidth that is be supported by the service links between the primary satellite(s) and radioterminals and/or based on a total aggregate bandwidth that is allocated to the primary satellite(s) for return/forward feeder link communications. The auxiliary satellite(s) may not include forward and/or return service link antennas, thus reducing complexity, size, mass and/or cost associated with the auxiliary satellite(s), and may thus not be able to communicate directly with radioterminals.

In the drawings and specification, there have been disclosed typical embodiments of the invention and, although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being set forth in the following claims.