Abstract:
An optimized integrated high capacity digital satellite trunking network, otherwise known as the Multipurpose Wideband Communications System (MPWCS) and method to link multiple earth stations in the same or different satellite antenna transponder footprints using uplink frequency to select the downlink footprint. The configuration of the network eliminates the need to reconfigure the transponder based on the desired downlink footprint. The invention integrates wideband receivers and hybrid signal combiners on the satellite along with an appropriate uplink and downlink frequency plan to provide the ability to reconfigure connectivity between uplink and downlink footprints based on uplink frequency selection. Certain configurations allow single hop connectivity between all transponder antenna footprints for all users within those footprints of the geostationary satellite. The system uses the full power and bandwidth of the constituent communications satellites for all services without dividing the power or bandwidth among multiple networks.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to the field of satellite communication. More specifically the present invention is an optimized integrated high capacity digital satellite trunking network system, otherwise known as the Multipurpose Wideband Communications System (MPWCS) and method for linking multiple earth stations in the same or different antenna transponder footprints of the same satellite at the greatest efficiency in use of power and bandwidth, thereby eliminating the need to reconfigure the satellite transponder based on the desired downlink footprint. 
     BACKGROUND OF THE INVENTION 
     Geostationary satellites provide flexible communication relay service using earth stations and satellite transponders, with satellites supporting point-to-multi-point relay service between earth stations. Satellite operators typically lease transponder capacity based upon power, bandwidth, connectivity, and coverage desired by lessees. The leasing of power, bandwidth, connectivity and coverage of the satellite in a non-optimum manner due to the sharing between different user networks results in less than the maximum satellite power and bandwidth being utilized. Further, networks have been historically developed by separate organizations responsible for provision of space segment and earth segment leading to a complex definition of interfaces and less than the highest efficiency in the total capacity which can be derived from the satellite orbit and frequency spectrum which has been assigned. Depending on a number of satellite design parameters (e.g. uplink and downlink frequencies, antenna type, antenna boresight, antenna size, and transmitter power of the satellite) the effective “earth footprint” of a satellite transponder has geographic limits. The geographic limits of the transponder footprint constrain the type of relay service that may be provided. 
     For two users that are within the same satellite transponder footprint who desire to establish a communication link, a usual and simple form of simplex service requires that the transmitting user point its earth terminal antenna at the relay satellite and transmit on an uplink frequency. Using a satellite antenna whose receive footprint includes the earth station location of the transmitting user, the satellite transponder receives the uplink frequency, translates the frequency to a downlink frequency, amplifies the signal and then re-transmits the translated and amplified signal through the same satellite antenna used to receive the signal. The downlink signal can be received by any earth terminal that is within that satellite antenna footprint. Depending on the downlink frequency, and the previously mentioned physical characteristics of the satellite, the downlink footprint may be as small as a few hundred miles in diameter or up to several thousand miles in diameter. For two users who are within the same satellite antenna footprint, this form of relay service is very effective. 
     For two users who are not within the same satellite antenna footprint, but are within the satellite antenna footprint of another antenna on the same satellite, other techniques are used. One technique involves providing an electronic “cross-strap” between two antennas/transponders on the same satellite. In this arrangement, the uplink signal from the earth transmitting station is received by one satellite antenna and the signal is translated and amplified for re-transmission by another satellite antenna, whose footprint includes the desired receiver. Using this technique, two users who are physically distant from each other and are each within small and different satellite antenna footprints of the same satellite may use a single satellite for relay service. 
     The problem with cross-strapping is the tied transponders remain dedicated to each other for as long as the strap remains in place. Thus, all of the signals received by the tied receiving transponder are directed to the tied downlink transponder and to the antenna associated with that transponder. If the uplink transponder and downlink transponder are not fully utilized, strapping results in unused satellite capacity and inefficient use of resources. 
     Various attempts have been made to address different aspects of these problems. Examples include U.S. Pat. No. 5,615,407 to Barkats, U.S. Pat. No. 4,720,873 to Goodman et al., U.S. Pat. No. 5,283,639 to Esch et al., U.S. Pat. No. 5,081,703 to Lee, U.S. Pat. No. 5,276,904 to Mutzig et al., U.S. Pat. No. 5,455,823 to Noreen et al., U.S. Pat. No. 5,633,891 to Rebec et al., U.S. Pat. No. 5,424,770 to Schmelzer et al., and U.S. Pat. No. 5,303,393 to Noreen et al. 
     What is needed is a satellite network that utilizes all of the available power and bandwidth of a satellite or a fleet of satellites and that permits communications to occur among users whether using the same or different communication protocols. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to create a satellite network optimized to use the full power and bandwidth of the constituent satellite, thereby providing highest capacity for operation of a digital trunking network based on the integration of the earth stations and satellite for maximum transmission efficiency. 
     It is a further objective of the present invention to create a high capacity satellite communications network where usage is measured by time (minutes-of-use) rather than by power or bandwidth leased by a party. 
     It is yet another objective of the present invention to create a global digital high capacity telecommunications network using the full power and bandwidth of multiple constituent satellites for any communications services within the field-of-view of the satellite network. 
     It is a further objective of the present invention to integrate multi-service satellite telecommunications using the full power and bandwidth of constituent satellites for all communications. 
     It is yet another objective of the present invention to provide voice, data, facsimile, video and general bit stream service using the full power and bandwidth of constituent satellites for all communications. 
     It is a further objective of the present invention to provide public switched telephone network services using the full power and bandwidth of constituent satellites for all communications. 
     It is yet another objective of the present invention to provide private branch exchange services to selected groups of users using the full power and bandwidth of constituent satellites for all communications. 
     It is a further objective of the present invention to provide overlay network services to selected groups of subscribers using the full power and bandwidth of constituent satellites for all communications. 
     It is yet another objective of the present invention to provide domestic and international telecommunications service using the full power and bandwidth of constituent satellites for all communications. 
     It is a further objective of the present invention to link telecommunication services of the present invention with other communications service providers and carriers. 
     It is yet another objective of the present invention to link telecommunication services of the present invention with other terrestrial telecommunications providers and carriers. 
     It is a further objective of the present invention to provide telecommunications services using the full power and bandwidth of constituent satellites for all communications when data being transmitted is either standard or non-standard telecommunications protocols such as but not limited to; ATM, frame relay, Internet, XDSL, IP, and/or mobile telecommunications protocols. 
     It is yet another objective of the present invention to provide protocol conversion between different standards of communications between countries and within a single country using multiple protocols. 
     It is still another object of the present invention to allow a user within the satellite antenna footprint of one satellite transponder to flexibly communicate with other users who are within the same or other satellite antenna footprints of a single satellite by using the uplink frequency to selectively select between users and satellite antenna downlink footprints without the need to reconfigure the satellite transponders. 
     It is another object of the present invention to provide this flexible communication capability for wideband high data rate communication. 
     An embodiment of the present invention, hereinafter referred to as MPWCS, generally comprises three spacecraft each of which is in a geosynchronous orbit at three orbital locations. Interacting with the three spacecraft are high-capacity digital earth stations. The digital modulation used is phased shift keying (PSK) and specifically 8-PSK modulation for highest bandwidth efficiency. The use of PSK dramatically increases the channel capacity in bits per Hz which can be carried within a given amount of bandwidth. 
     Relatively large diameter earth station antennas are used to maximize the efficiency with which satellite power is used, for example and without limitation 9 meter antennas are currently used. Further, each earth station has a relatively large high power amplifier to insure communication links are not uplink-power limited. For example and without limitation 350 watt amplifiers are currently used. Digital modems are used for all services to be supported by the system of the present invention. Compression technology is also used within the earth segment to take advantage of silent periods within a voice conversation, statistical utilization of speech activity among multiple voice channels and redundancy within individual voice channels to allow the available satellite communications bandwidth to be allocated to the largest number of voice channels consistent with maintaining high quality and consistent with meeting national and international standards where appropriate. 
     In a conventional satellite system, when a transponder is illuminated by multiple signals occupying different bands or channels, additional guard bands are imposed between the channels to minimize interference. The additional guard bands consume bandwidth thereby reducing the efficiency of the transponder utilization. In an embodiment of the present invention, a transponder is limited to a single carrier permitting the full bandwidth and power of the transponder to be utilized. In another embodiment, all of the transponders on the satellite are so limited thereby maximizing the power and bandwidth utilization of the satellite. 
     Finally, protocol conversion is implemented throughout the system so that communications using dissimilar protocols can be converted from one to another. This allows communication from regions or countries using dissimilar protocols to occur in a continuous and seamless manner. Taken together these characteristics result in a high-capacity satellite based digital trunking network. 
     The present invention overcomes the disadvantages of the prior art through: a) integration of earth and space segments for maximum capacity and efficiency using the available satellite orbit and frequency allocations, and b) providing integrated digital service to users on an end-to-end basis from switching center to switching center location. Further, a combination of multiple antennas and transponders on the same satellite, are linked to hybrid signal combiners, wideband receivers, and hybrid signal splitters on the satellite that are able to use a contiguous portion of both the uplink and downlink frequency spectrum. In one embodiment, the present invention uses two transponders with wideband receivers and two 80 MHZ bandwidth portions of the frequency spectrum separated by 64 MHZ to allow a user to flexibly connect an 80 MHZ bandwidth signal between two satellite antenna footprints. 
     In another embodiment of the present invention, a multiplexer is also used to interconnect multiple transponders, allowing a user to select the downlink footprints of more than two transponders based on the uplink frequency. 
     These and other objects of the present invention will be apparent to those of ordinary skill in the art after review of the detailed description, the drawings, and the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A shows an overview of the present invention. 
     FIG. 1B shows satellite locations for satellites of the present invention. 
     FIG. 1C shows PSTN backbone service of the present invention. 
     FIG. 1D shows the present invention providing dedicated services. 
     FIG. 1E shows regional setup of the present invention. 
     FIG. 1 shows a signal flow diagram of the satellite transponder in one embodiment of the present invention. 
     FIG. 2 shows an example of the frequency allocation used in one embodiment of the present invention. 
     FIG. 3 shows an example of satellite antenna footprints in one embodiment of the present invention. 
     FIG. 4 shows an example of the uplink and downlink signals with users in the same satellite antenna footprint. 
     FIG. 5 shows an example of the uplink and downlink signals with users in different satellite antenna footprints. 
     FIG. 6 shows a signal flow diagram of the satellite transponders in another embodiment of the present invention. 
     FIG. 7 shows an example of the frequency allocation used in another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1A an overview of a single satellite and associated ground stations of the present invention are shown. Satellite  10  is stationed in a geosynchronous orbit thereby allowing the satellite to be stationary relative to a geographic location on the equator of the earth. The satellite communicates with earth station  12  which has a large diameter antenna designed to maximize efficiency of satellite communications. Connected to antenna  12  is a zone toll switch  14  which meters the usage of the satellite link and is the switch through which communications are made to various local public switched telephone networks, overlay networks, and private networks. The various local access switches  16 ,  18 , and  20  are connected to the zone toll switch  14  and provide the access to various individuals and organizations in the local access area. 
     Earth station  12  may, for example and without limitation, communicate with earth station  22  that also comprises a relatively large diameter earth station antenna, again maximizing the efficiency and use by the earth station of satellite power. Earth station  22  is further connected to another zone toll switch  24  also connected generally to another public switched telephone network zone. Once again access of local customers is through a series of local access switches  26 ,  28 , and  30 . 
     Referring to FIG. 1B the satellite field-of-view areas of the three satellites of the present invention and their orbital locations are shown. In general concept, and without limitation, the present invention requires three satellites for virtually worldwide coverage. The satellites are stationed each in a geosynchronous orbit over ground locations at the equator at 16 degrees West, 77 degrees East, and 167 degrees East Longitude. 
     Referring to FIG. 1C the public switched telephone network backbone service is shown. In general concept, and without limitation, four earth stations  32 ,  34 ,  36 , and  38  are shown. Again each earth station has a relatively large diameter antenna to maximize the efficiency of communications with the satellites of the present invention. Again each earth station has an associated zone toll switch  40 ,  42 ,  44 , and  46 . Further, trunk switches  48 ,  50 ,  52  and  54  are directly connected to each earth station antenna and provide the basis for switching and communications being sent and received over that segment of the digital trunking network. 
     The system of the present invention can also interact with the existing terrestrial backbone  56  thereby providing alternative communication means to the existing terrestrial backbone. Communications can thus be carried over the backbone  56  where appropriate or over the high-capacity digital satellite trunking network of the present invention. A transit switch  58  is also provided to allow communications with PSTN zones  60  and  62  which may be outside the zone of coverage of the present invention, that is, in regions not covered by the satellite footprint. 
     Referring to FIG. 1D, other dedicated services which can be serviced by the present invention are shown. Satellite earth stations  64 ,  66 ,  68 , and  70  interact with the satellite of the present invention to provide the high-capacity digital satellite trunking network. Earth station  70  is linked in via its associated trunk switch  72  to various other gateways  74 . These gateways provide access to other private communications networks  76 . Transit hub  78  provides access to various other local destinations  80  via associated transit and termination units  82 . These other domestic destinations  80  may be outside the satellite footprint or simply not be directly connected to an individual earth station of the present invention. 
     Earth station  68  is connected via its associated trunk switch  84  to a terrestrial fiber-optic or copper transport network  86 . Individual private voice  88 , a private network  90 , or private data access  92  may be connected to this terrestrial network  86 . 
     This flexible connection to terrestrial fiber-optic or copper transport networks can be duplicated at any other ground station location. Accordingly, a second terrestrial network  94  may also have private voice  96 , private network  98 , private data  99 , connected to it. Thus, the present invention allows data, private networks or any other communications to be connected across broad geographic areas to other terrestrial fiber-optic copper or copper transport networks. 
     Referring to FIG. 1E a typical configuration at any given communication region of the present invention is shown. This is the type of installation that is associated with a ground station in communication with a satellite of the present invention. Earth station  150 , with its large diameter antenna is connected to a trunks switch multiplexer  152 . This multiplexer allows communications from a variety of different sources to be multiplexed and transmitted over the earth station to maximize utilization of bandwidth. A private network  168  may be directly connected to the trunk switch multiplexer. It should be noted that in this specific example no protocol conversion is needed between the private network or end-user and the trunk switch multiplexer. 
     However, the system of the present invention is capable of protocol conversion in situations where communications are originating from other countries, or other regions that simply use different protocols. For example, communications via toll switches  162 ,  164 , and  166  may occur from a given PSTN zone  160 . These communications are transmitted through a zone switch  158  to the earth station or over the terrestrial backbone. If the protocol is not the same, protocol converter  154  converts the incoming communications having a different protocol. Thereafter signals in communications are connected to the trunk switch multiplexer and are transmitted over the high-capacity digital satellite trunking network of the present invention. 
     Each regional earth station also incorporates a redundant call logger  156  which allows the transmission of billing information regarding utilization of the network to the hub station. This billing information is also transmitted at various times, and on a non-interference basis with communications being transmitted over the network. 
     Referring to FIG. 1, a signal flow diagram of the satellite transponders in one embodiment is illustrated. Two independently steerable satellite antennas  101 ,  103  are provided which can be boresighted to provide different earth footprints. The received signal from each satellite antenna is amplified by a low noise amplifier (LNA)  105 ,  107  prior to signal combination in a hybrid signal combiner  109 . The combined signal is then filtered  110  and input to a wideband receiver  111  where the uplink frequency is shifted or translated to the downlink frequency. The translated frequency is then split by a hybrid signal splitter  113  into two signal paths before each is amplified by a high power amplifier (HPA)  115 ,  117 . Each signal is then filtered  119 ,  121  and passed to the corresponding satellite antenna  101 ,  103  for re-transmission on the corresponding downlink frequency. 
     Referring to FIG. 2, an example of frequency allocation for one embodiment is illustrated. Two 80 MHZ uplink frequency bands  201 ,  203  are shown, with a 64 MHZ separation frequency band  205 . Two 80 MHZ downlink frequency bands  207 ,  209  are also shown, with a corresponding 64 MHZ separation frequency band  211 . The downlink frequency for antenna  101 , in FIG. 1, is the lower 80 MHZ band  207  (approximately 12.512 to 12.592 GHZ) while the downlink frequency for antenna  103  is the upper 80 MHZ band  209  (approximately 12.656 to 12.736 GHZ). 
     Referring now to FIG. 3, examples of satellite antenna footprints for different transponders are illustrated. The footprint for one antenna ( 101  in FIG. 1) covers one geographic area  301 , while the footprint of the other antenna ( 103  in FIG. 1) covers another geographic area  303 . Using this embodiment of the present invention, a first user, located within satellite antenna footprint  301 , can communicate with a second user also located in satellite antenna footprint  301 . Alternatively, a first user, located within satellite antenna footprint  301 , can communicate with a third user located in satellite antenna footprint  303 . 
     Referring now to FIG. 4, examples of the uplink and downlink signals are shown for users who are both in satellite antenna footprint  301  (FIG. 3) of satellite antenna  101  (FIG.  1 ). Here, the uplink signal is in the lower of the two 80 MHZ bands  201  (approximately 14.744 to 14.824 GHZ) and the downlink signal is also in the lower of the two 80 MHZ bands  207  (approximately 12.512 to 12.592 GHZ). 
     Referring to FIG. 5, examples of the uplink and downlink signals are shown for users who are in different satellite antenna footprints. In this example, the transmitting user is in the satellite antenna footprint  301  (FIG. 3) of antenna  101  (FIG.  1 ), while the receiving user is in the satellite antenna footprint  303  (FIG. 3) of antenna  103  (FIG.  1 ). Here, the uplink signal is in the upper of the two 80 MHZ band  203  (approximately 14.888 to 14.968 GHZ) and the downlink signal is in the upper of the two 80 MHZ bands  209  (approximately 12.656 to 12.736 GHZ). 
     Referring back to FIGS. 1 and 2, in this embodiment, both antennas ( 101 ,  103  in FIG. 1) and LNAs ( 105 ,  107  in FIG. 1) have sufficient bandwidth to pass both 80 MHZ bands ( 201 ,  203  in FIG. 2) in addition to a 64 MHZ band separation ( 205  in FIG. 2) into the hybrid signal combiner ( 109  in FIG.  1 ). This approximately 224 MHZ bandwidth output of the hybrid signal combiner ( 109  in FIG. 1) is processed by a wideband receiver ( 111  in FIG.  1 ), which performs a frequency translation from the uplink to downlink frequency. The translated frequency output of the wideband receiver is then split into two 80 MHZ downlink signals ( 207 ,  209  in FIG. 2) before amplification by two HPA&#39;s ( 115 ,  117  in FIG. 1) and transmission through the two antennas ( 101 ,  103  in FIG.  1 ). In this example, one transponder downlink antenna ( 101  in FIG. 1) uses the lower frequency band ( 207  in FIG. 2) of the two 80 MHZ bands, and the other transponder downlink antenna ( 103  in FIG. 1) uses the upper frequency band ( 209  in FIG. 2) of the two 80 MHZ bands. Both transponders are thus able to receive both 80 MHZ bands ( 201 ,  203  in FIG.  2 ). 
     Completing the example, a transmitting user in the satellite antenna footprint of one transponder ( 301  in FIG. 3) who wants to communicate with another receiving user also in the satellite antenna footprint of the same transponder ( 301  in FIG. 3) will uplink in the lower frequency band ( 201  in FIG. 4) of the two 80 MHZ uplink bands. When the uplink frequency is translated to the downlink frequency, the downlink frequency will also be in the lower frequency band ( 207  in FIGS. 2 &amp; 4) of the two 80 MHZ downlink bands. Alternatively, a transmitting user in the satellite antenna footprint of the first transponder ( 301  in FIG. 3) who wants to communicate with a second receiving user who is in the satellite antenna footprint of the second transponder ( 303  in FIG. 3) will uplink in the upper frequency band ( 203  in FIGS. 2 &amp; 5) of the two 80 MHZ uplink bands. When the uplink frequency is translated to the downlink frequency, the downlink frequency will now be in the upper frequency band ( 209  in FIGS. 2 &amp; 5) of the two 80 MHZ downlink bands. This will have the same effect as “cross-strapping” the two transponders would have in the traditional method of operation but without electrically tying the two transponders together. 
     Referring now to FIG. 6, the signal flow of another embodiment of the present invention is illustrated. This arrangement uses the transponder pair of the first embodiment  600  and adds another transponder pair  602  and further allows users to cross signals between the transponder pairs  604 . In this configuration, a multiplexer, IMUX  601 ,  603  is interposed in the signal path between the antenna  103 ,  605  and the low noise amplifiers  107 ,  607 . The IMUX provides an alternative signal path that allows signals to be crossed between the transponder pairs  600 ,  602 . After frequency splitting by the IMUX  601 ,  603 , the signal path is similar to the first embodiment. Specifically, the signal is amplified by an LNA  609 ,  611 , followed by a receiver  613 ,  615  which translates the uplink frequency to the downlink frequency. The frequency translated signals are then amplified by an HPA  617 ,  619  prior to another multiplex operation OMUX  621 ,  623  and final transmission by the respective antennas  103 ,  605 . 
     An example frequency allocation that corresponds to this other embodiment is illustrated in FIG.  7 . In addition to the technique of the first embodiment, using an orthogonal polarization, the uplink antenna ( 103  in FIG. 6) is able to receive and pass two 80 MHZ bands  701 ,  703 , with a 64 MHZ separation band  705 . These two 80 MHZ bands are received and translated to the downlink frequencies  707 ,  709  as in.the first embodiment. However, the bandwidth that is passed through the uplink antenna ( 103  in FIG. 6) to the IMUX ( 601 ,  603  in FIG. 6) also includes a 34 MHZ band  711  in addition to a 10 MHZ frequency separation band  713 . In this example, this 268 MHZ wideband signal (34+10+80+64+80 MHZ) is divided by the IMUX ( 601 ,  603  in FIG. 6) into two signal paths. One signal path, the upper 224 MHZ, is handled as in the first embodiment. The other signal path, the lower 34 MHZ  711 , is crossed to the other transponder pair ( 602  in FIG.  6 ). This 34 MHZ signal  711  (14.700 to 14.734 GHZ) is processed by the LNA ( 611  in FIG. 6) and the frequency is translated to the downlink frequency by a receiver ( 615  in FIG.  6 ). In the example, the 34 MHZ uplink frequency  711  is translated to the 34 MHZ downlink frequency  715  (11.057 to 11.091 GHZ) before it is amplified by the HPA ( 617  in FIG. 6) and multiplexed with other signals by the OMUX ( 621  in FIG. 6) and finally transmitted through the antenna ( 605  in FIG.  6 ). 
     The signal flow for transmission from the satellite antenna footprint of satellite antenna  605  to the satellite antenna footprint of satellite antenna  103  is similar to that from satellite antenna  103  to satellite antenna  605 . However, the example frequency allocation is different. Referring to FIG. 7, the uplink frequency  717  (approximately 15.216 to 15.247 GHZ) and the downlink frequency  719  (approximately 12.769 to 12.803 GHZ) are 34 MHZ wide. 
     For a transmitting user in the satellite antenna footprint of satellite antenna  605  who wants to transmit to a receiving user in the satellite antenna footprint of satellite antenna  625 , the uplink frequency will be  721  (approximately 15.130 to 15.180 GHZ) and the downlink frequency will be  723  (approximately 10.977 to 11.027 GHZ). A transmitting user in the satellite antenna footprint of satellite antenna  625  who wants to transmit to a receiving user in the satellite antenna footprint of satellite antenna  605 , the uplink frequency will be  725  (approximately 15.271 to 15.321 GHZ) and the downlink frequency  727  (approximately 11.121 to 11.171 GHZ). 
     Referring again to FIG. 1, the hardware to accomplish the present invention must have certain capabilities. The independently steerable satellite antenna  101 ,  103 , must each have sufficient pointing accuracy to track and maintain boresight at sufficient gain to provide the required performance. The low noise amplifier  105 ,  107  must have a flat response across the desired spectrum with sufficient gain to provide the required performance. The hybrid signal combiner  109  must be capable of receiving two signal sources and suitably combining them into a single composite signal (without adverse noise, attenuation or artifacts) sufficient-to provide the required performance. The filter  110  must have suitable cut-off and selectivity to provide the required performance. The wideband receiver  111  must be capable of translating the input signal frequency to the desired output signal frequency with sufficient gain to provide the required performance. The hybrid signal splitter  113  must be capable of dividing a single signal with specified bandwidth into multiple signals of specified bandwidth without adverse attenuation or artifact. The high power amplifiers  115 ,  117  must be capable of amplification across the input frequency spectrum with flat response. Finally, the filters  119 ,  121  must have suitable cut-off and selectivity to provide the required performance. 
     Referring again to FIG. 6, the hardware to accomplish the other embodiment of the present invention must have certain capabilities. The additional independently steerable satellite antenna  625 ,  605 , must each have sufficient pointing accuracy to track and maintain boresight at sufficient gain to provide the required performance. The input multiplexer, IMUX  601 ,  603  which is interposed in the signal path after the antenna  103 ,  605  must have sufficient bandwidth to provide the required performance. The low noise amplifier  107 ,  607 ,  609  and  611  must have a flat response across the desired spectrum with sufficient gain to provide the required performance. The wideband receiver  613 ,  615  must be capable of translating the input signal frequency to the desired output signal frequency with sufficient gain to provide the required performance. The high power amplifiers  617 ,  619  must be capable of amplification across the input frequency spectrum with flat response. Finally, the output multiplexer, OMUX  612 ,  623  must have bandwidth to provide the required performance. 
     An embodiment of the present invention is an optimized integrated high capacity digital satellite trunking network comprising a satellite comprising power and bandwidth, and having a plurality of transponders, a plurality of earth stations, the plurality of transponders and the plurality of earth stations constituting a communications network, means at each earth terminal for transmitting an uplink signal on an uplink frequency to one of the plurality of transponders on the satellite, and means at each earth terminal for receiving a downlink signal on a downlink frequency from one of the plurality of transponders. In this embodiment, each transponder translates an uplink signal to a downlink signal. The uplink signal may be translated to any downlink signal through use of a particular uplink frequency without modification or reconfiguration of the transponder means. In this embodiment, the full bandwidth and power of the satellite is used for the communications network. In an alternate embodiment, the optimized integrated high capacity digital satellite trunking network further comprises an uplink signal having a first center frequency and a downlink signal having a second center frequency such that the second center frequency is approximately 2.232. GHz less than the first uplink single center frequency. 
     In yet another embodiment, the optimized integrated high capacity digital satellite trunking network further comprises a signal combiner means on the satellite, a wideband receiver means on the satellite having a receiver bandwidth operating on the output of the signal combiner means, and a signal splitter on the satellite operating on the output of the wideband receiver means. In this embodiment, more than one of the uplink signals with the second center frequency are combined by the signal combiner means to create a hybrid signal with the second center frequency. The bandwidth of the wideband receiver means is at least as wide as the receiver bandwidth, and the signal splitter means converts the output signal of the wideband receiver means having the second center frequency to more than one downlink signal of the first bandwidth. 
     Another embodiment of the present invention is a method for providing an optimized integrated high capacity digital satellite trunking network comprising transmitting an uplink signal from a first of a plurality of earth stations on an uplink frequency to one of a plurality of transponders on a satellite having power and bandwidth characteristics, the plurality of earth stations and the plurality of satellite transponders constituting a communications network. The method further comprises receiving a downlink signal at a second of a plurality of earth stations on a downlink frequency from one of the plurality of transponders on the satellite and translating the uplink signal to the downlink signal using at least one of the plurality of satellite transponders. Using the method of this embodiment, the uplink signal may be translated to the downlink signal through use of a particular uplink frequency without modification or reconfiguration of the transponders. Additionally, the communications network uses the full power and bandwidth of the satellite. In an alternate embodiment, the method for providing an optimized integrated high capacity digital satellite trunking network further comprises translating the uplink signal having a first center frequency to the downlink signal having a second center frequency wherein the first center frequency is approximately a positive integer multiple, other than one, of the second center frequency. 
     In another embodiment of the present invention, in the method for providing an optimized integrated high capacity digital satellite trunking network, translating the uplink signal to the downlink signal comprises combining more than one uplink signal with a signal combiner means on the satellite, receiving the output of the signal combiner with a wideband receiver means, and splitting the output of the wideband receiver into more than one signal. In this embodiment, the uplink signals have a first center frequency and are combined to create a hybrid signal with the same first center frequency and the bandwidth of the wideband receiver is at least as wide as the first center frequency. Further, splitting the output of the wideband receiver means creates more than one downlink signal of a second center frequency which is less than the first center frequency. 
     Another embodiment of the present invention is an optimized integrated high capacity digital satellite trunking network comprising a first plurality of ground stations optimized to transmit communications in a first bandwidth, at least one communications satellite optimized to receive the communications from the plurality of ground stations in the first bandwidth, at least one communications satellite further transmitting the communications from the first plurality of ground stations in a second bandwidth and a second plurality of ground stations optimized to receive communications from the at least one communications satellite in the second bandwidth. The first plurality of ground stations, the second plurality of ground stations and the at least one communications satellite comprise a communications network. In this embodiment, the at least one communications satellite receives communications in only the first bandwidth and transmits communications in only the second bandwidth for optimizing power utilization of the at least one communications satellite. The communication network uses the full power and bandwidth of the at least one communications satellite. In an alternative embodiment, the at least one communications satellite comprises three communications satellites in geostationary orbit. By way of illustration and not as a limitation, the three communications satellites are respectively located at about 16 degrees West Longitude, at about 77 degrees East Longitude, and at about 167 degrees East Longitude. 
     An optimized integrated high capacity digital satellite trunking network has been described. Those skilled in the art will appreciate that minor variations may be made to the system described without departing from the scope of the invention as disclosed.