Patent Publication Number: US-RE42261-E

Title: Wireless communications systems and methods using satellite-linked remote terminal interface subsystems

Description:
Notice: More than one reissue application has been filed for the reissue of U.S. Pat. No.  6 , 856 , 787 . The reissue applications are application Ser. No.  11 / 431 , 160  ( the present application ) , application Ser. No.  12 / 266 , 713   ( a first divisional of the present application )  and application Ser. No.  12 / 329 , 137   ( a second divisional of the present application ). 
     CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority to U.S. Provisional Application Ser. No. 60/356,264 entitled “WIRELESS COMMUNICATIONS SYSTEMS AND METHODS USING SATELLITE-LINKED REMOTE TERMINAL INTERFACE SUBSYSTEMS,” filed Feb. 12, 2002, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to wireless communications apparatus and methods, and more particularly, to wireless communications system and methods using satellite and terrestrial components. 
       FIG. 1  illustrates a conventional terrestrial wireless communications system  100 , and more particularly, a system conforming to the GSM standards. The system  100  includes a mobile switching center (MSC)  110 , a base station controller (BSC)  120 , and at least one base transceiver station (BTS)  130 . The BTS  130  includes radio transceivers that communicate with cellular terminals  50 , while the BSC  120  manages radio resources for one or more BTSs and provides a connection between the BTSs and the MSC  110 . The MSC  110  typically acts like a telephone switching node, and typically provides additional functions related to registration and mobility management for the cellular terminals  50 . The MSC  110  is typically coupled to a public switched telephone network (PSTN)  10 , which provides communications links between the cellular terminals  50  served by the wireless system  100  and other terminals (e.g., landline telephones). It will be appreciated that other wireless communications systems may provide similar functionality, but may, for example, use other groupings of functions referred to by different nomenclature. 
     Cellular satellite communications systems and methods are also widely used to provide wireless communications. Cellular 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 radiotelephones or other types of cellular terminals. The overall design and operation of cellular satellite communications systems and methods are well known to those having skill in the art, and need not be described further herein. 
     Hybrids of satellite and terrestrial systems may also be used. For example, as is well known to those having skill in the art, terrestrial networks can enhance cellular satellite communications system availability, efficiency and/or economic viability by terrestrially reusing at least some of the frequency bands that are allocated to cellular satellite communications systems. In particular, it is known that it may be difficult for cellular satellite communications systems to reliably serve densely populated areas, because the satellite signal may be blocked by high-rise structures and/or may not penetrate into buildings. As a result, the satellite spectrum may be underutilized or unutilized in such areas. The use of terrestrial retransmission can reduce or eliminate this problem. 
     Moreover, the capacity of the overall system can be increased significantly by the introduction of terrestrial retransmission, since terrestrial frequency reuse can be much denser than that of a satellite-only system. In fact, capacity can be enhanced where it may be mostly needed, i.e., densely populated urban/industrial/commercial areas. As a result, the overall system can become much more economically viable, as it may be able to serve a much larger subscriber base. One example of terrestrial reuse of satellite frequencies is described in U.S. Pat. No. 5,937,332 to the present inventor Karabinis entitled Satellite Telecommunications Repeaters and Retransmission Methods. 
     SUMMARY OF THE INVENTION 
     According to some embodiments of the present invention, a wireless communications system includes a satellite gateway coupled to a communications network and operative to communicate with a communications satellite. The system further includes a terrestrial terminal interface subsystem operative to communicate with the satellite gateway via the communications satellite using a first radio interface and to communicate with wireless terminals over a geographic area using a second radio interface. For example, in some embodiments, the communications network comprises a wireless communications network, and the satellite gateway is configured to communicate with a base station controller of the wireless communications network, such that the terrestrial terminal interface subsystem may provide one or more satellite-linked terrestrial base stations. 
     In some embodiments, the terrestrial terminal interface subsystem comprises an interface converter operative to convert between the first and second radio interfaces. The interface converter may be operative to transfer information from a plurality of terrestrial wireless communications channels to a lesser number of satellite communications channels. The interface converter may also be operative to transfer information from a single satellite communication channel to a plurality of terrestrial wireless communications channels. 
     According to further embodiments of the present invention, the terrestrial terminal interface subsystem includes a satellite radio antenna and a terrestrial radio antenna co-located at a single terrestrial base station. The terrestrial terminal interface subsystem may also comprise a plurality of terrestrial base stations located at respective ones of a plurality of geographically distributed sites and served by a single satellite link. 
     In yet additional embodiments, the communications satellite is further operative to communicate with wireless terrestrial terminals without use of the terrestrial terminal interface subsystem. In particular, the terrestrial terminal interface subsystem or the satellite or both may communicate with wireless terminals. For example, in some embodiments, the communications satellite is operative to receive information intended for wireless terminals from the satellite gateway and to convey the received information to the wireless terminals without use of the terrestrial terminal interface subsystem, while the terrestrial terminal interface subsystem is operative to receive information from wireless terminals and to convey the received information to the communications network without use of the communications satellite. In this manner, for example, “receive only” terrestrial base stations may be used to provide uplinks from wireless terminals to a communications network, while downlinks are provided directly from the satellite to the wireless terminals. In other embodiments, the communications satellite is operative to receive information from wireless terminals without use of the terrestrial terminal interface subsystem and to convey the received information to the satellite gateway, while the terrestrial terminal interface subsystem is operative to receive information intended for wireless terminals from the communications satellite and to convey the received information to terrestrial terminals. In this manner, for example, “transmit-only” terrestrial base stations may be used to provide downlinks from a communications network to wireless terminals, while uplinks may be provided directly from the wireless terminals to the satellite. 
     According to some method embodiments of the present invention, communications between a communications network and a plurality of wireless terminals served by a terrestrial base station may be provided by conveying terminal communications between the communications network and the terrestrial base station via a communications satellite. The communication via the satellite can be bidirectional or unidirectional. 
     The present invention may be embodied in variety of forms, including, but not limited to, wireless communications systems, components of wireless communications systems, combinations of components of wireless communications systems, and wireless communications methods. For example, the present invention may be embodied as earth-based components and combinations thereof configured to interoperate with space-based components, as spaced-based components, and as combinations of earth-based and space-based components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a conventional terrestrial wireless communications system. 
         FIG. 2  is a schematic diagram illustrating a wireless communications systems and methods according to some embodiments of the present invention. 
         FIG. 3  is a schematic diagram illustrating a wireless communications system and methods according to further embodiments of the present invention. 
         FIG. 4  is a schematic diagram illustrating a terrestrial terminal interface subsystem and methods according to some embodiments of the present invention. 
         FIG. 5  is a schematic diagram illustrating a wireless communications system and methods according to further embodiments of the present invention. 
         FIG. 6  is a schematic diagram illustrating a wireless communications system and methods according to still further embodiments of the present invention. 
         FIG. 7  is a schematic diagram illustrating a wireless communications system and methods according to additional embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention now will be described more fully hereinafter with reference to the accompanying drawings, in which typical embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout. 
     As used herein, the term “cellular terminal” refers to wireless terminals including, but not limited to: radiotelephone terminals (“cell phones”) 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. These devices may be capable of wireless voice and/or data communications. 
       FIG. 2  conceptually illustrates a wireless communications system  200  according to embodiments of the present invention. The system  200  includes a satellite gateway  220  that is coupled to a communications network  210  (which may be a portion of the system  200  or an external network), which may include, but is not limited to, wireless network control components, such as BSCs and MSCs, and other gateways similar to the gateway  220 . The system  200  further includes one or more remote terrestrial terminal interface subsystems  240  that communicate with the gateway  220  via a satellite  230 . In particular, the terrestrial terminal interface subsystem  240  provides communications between cellular terminals  60  served by the terrestrial terminal interface subsystem  240  and the other portions  210  of the communications system  200  via the satellite  230  and the gateway  220 . 
     As shown, the terrestrial terminal interface subsystem  240  includes a satellite antenna  241  and a terrestrial antenna  243  that are connected to an interface converter  242 . The interface converter  242  is configured to receive information from cellular terminals  60  according to a first radio interface and to transmit the received information to the satellite  230  according to a second radio interface, and to receive information from the satellite  230  according to the second radio interface and to transmit the received information to the cellular terminals  60  according to the first radio interface. For example, the first radio interface may conform to a conventional standard, such as a GSM standard that uses Gaussian minimum shift keying (GMSK) modulation. The second radio interface may support a higher data rate using, for example, M-ary quadrature amplitude modulation (QAM), such that information received from or intended for cellular terminals  60  may be “concentrated” for transmission over the satellite link. In other embodiments, the first and second radio interfaces may be the same or substantially similar. 
     It will be appreciated that the interface converter  242  may include a variety of different components. For example, in embodiments described below with reference to  FIGS. 3 and 4 , the interface converter may be positioned at a remote base station and may include components to convert signals received over the satellite link into radio signals for transmission to cellular terminals, as well as components for performing complementary conversion of signals received from cellular terminals. In embodiments described below with reference to  FIG. 5 , the interface converter  242  may comprise components distributed among a remote BSC and base stations connected thereto. In such embodiments, the interface converter  242  may include, for example, components configured to convert between the satellite link signaling format and, for example, landline signaling formats used to communicate between the BSC and the base stations, as well as components for converting between the signaling format used for the links between the BSC and the base stations and the radio signaling format used to communicate with cellular terminals. 
     As also shown in  FIG. 2 , the remote terrestrial terminal interface subsystem  240  may serve as part of an ancillary terrestrial component of the wireless communications system  200 , e.g., may function as a base station of an ancillary terrestrial network (ATN) of a satellite mobile communications system in a manner similar to that of the terrestrial base stations described in a United States Provisional Patent Application entitled “SYSTEMS AND METHODS FOR TERRESTRIAL REUSE OF MOBILE SATELLITE SPECTRUM,” U.S. Pat. No. 60/322,240, filed Sep. 14, 2001, and U.S. Patent Application entitled “SYSTEMS AND METHODS FOR TERRESTRIAL RE-USE OF MOBILE SATELLITE SPECTRUM,” U.S. Ser. No. 10/074,097, filed Feb. 12, 2002, the disclosure of each of which is incorporated herein by reference in its entirety. In particular, cellular terminals  60  may be operative to communicate with the system  200  directly through the satellite  230 , or may indirectly communicate with the system  200  via the remote terrestrial terminal interface subsystem  240 . It will be understood, however, that the present invention is also applicable to systems and methods in which communications between cellular terminals  60  and the satellite  230  are limited to communications via terrestrial terminal interface subsystems such as the remote terrestrial terminal interface subsystem  240 , i.e., without direct communication between the cellular terminals  60  and the satellite  230 . 
       FIG. 3  illustrates a “repeater” configuration for a wireless communications system  300  according to further embodiments of the present invention. The system  300  includes an MSC  312  and a BSC  314  that communicate with a remote terrestrial terminal interface subsystem, here a remote terrestrial base station  340 , via a “repeater” including a gateway  320  and a satellite  330 . The remote terrestrial base station  340  includes a first concentrator/deconcentrator  342  that sends and receives signals to and from the satellite  330  via a satellite antenna  341  over, for example, an L-band satellite link using, for example, M-ary quadrature amplitude modulation (QAM). The first concentrator/deconcentrator  342  converts signals received over the satellite link to, for example, GSM-format signals transmitted to cellular terminals via a terrestrial antenna  343  using GMSK modulation, and converts GSM format signals from the cellular terminals to M-ary QAM signals that are transmitted to the satellite  330 . The gateway  320  includes a second concentrator/deconcentrator  322  that performs conversion functions complementary to those of the first concentrator/deconcentrator  342 . 
     It will be appreciated that the satellite link through the satellite  330  may generally support a higher data rate than radio links to individual cellular terminals, due to, for example, a less obstructive radio signal propagation environment and/or less interference and/or higher available transmit power. The concentrator/deconcentrator  342 ,  322  takes advantage of this higher data rate capability by combining information received from or intended for terminals in a signal formatted according to a higher data rate signaling format for transfer through the satellite link. 
       FIG. 4  illustrates a remote terrestrial base station  400  that may be used with a wireless communication system, such as the communications system  300  of  FIG. 3 , according to further embodiments of the present invention. The base station  400  includes a satellite antenna  401  and a terrestrial antenna  402 . Signals received from a satellite  80  via the satellite antenna  401  are processed by a bandpass filter  405  and a low noise amplifier (LNA)  410 . The signal produced by the LNA  410  is processed by a demodulator &amp; regenerator component  415  to recover information in a format, e.g., a bitstream or other datastream, suitable for remodulation and transmission to a cellular terminal  70 . The demodulator &amp; regenerator component  415  may, for example, produce decoded datastreams that correspond to GSM carriers that are to be transmitted from the terrestrial antenna  402 . As shown, the demodulator &amp; regenerator component  415  may be operatively associated with an interference reducer, such as a decision feedback canceller  420 , that cancels interference in the signals received by the satellite antenna  401 , e.g., interference generated by transmissions from the terrestrial antenna  402 . For example, an interference reducer along the lines described in the aforementioned U.S. Ser. No. 60/322,240 and U.S. Ser. No. 10/074,097 may be used. 
     The information recovered from the demodulator &amp; regenerator component  415  may then be reformatted and remodulated by a modulator component  425 . The remodulated signal is then filtered and amplified by a filter  430  and a power amplifier  435  to produce a signal for transmission to the cellular terminal  70  via the terrestrial antenna  402 . Power information obtained by the demodulator &amp; regenerator component  415  may be used by a modulator component  475  to control the power of a signal transmitted to the satellite  80 . 
     Signals received from the cellular terminal  70  via the terrestrial antenna  402  are processed by a bandpass filter  455  and an LNA  460 . The signal produced by the LNA  460  is processed by a demodulator &amp; regenerator component  465  to recover information in a format suitable for remodulation and transmission to the satellite  80 . The demodulator &amp; regenerator component  465  may, for example, produce respective datastreams that correspond to respective GSM carriers received from the terrestrial antenna  402 . As shown, the demodulator &amp; regenerator component  465  may be operatively associated with an interference reducer, such as a decision feedback canceller  470 , that cancels interference in the signals received by the terrestrial antenna  402 , e.g., interference generated by transmissions from the satellite antenna  401 . For example, an interference reducer along the lines described in the aforementioned U.S. Ser. No. 60/322,240 and U.S. Ser. No. 10/074,097 may be used. 
     The information recovered from the demodulator &amp; regenerator component  465  is remodulated in a modulator component  475 , producing a remodulated signal corresponding to the multiple GSM carriers. This signal is then filtered and amplified by a filter  480  and a power amplifier  485  to produce a signal for transmission to the satellite  80  via the satellite antenna  401 . As described above with reference to  FIG. 3 , the signal may be conveyed via the satellite  80  to a gateway, which may include a complementary radio interface conversion architecture. Power information obtained by the demodulator &amp; regenerator component  465  may be used by the modulator component  425  to control the power of the signal transmitted to the cellular terminal  70 . 
       FIG. 5  illustrates an alternative configuration for a wireless communications and methods system  500  according to further embodiments of the present invention. The system  500  includes an MSC  510  that is linked via a gateway  520  and a satellite  530  to a remote terrestrial terminal interface subsystem, here shown as including a remote terrestrial base station controller  540  connected to base stations  550 . The remote BSC  540  is operative to control and communicate cellular terminal information with terrestrial base stations  550 . The remote BSC  540  and the gateway  520  include first and second interface converters  542 ,  522  that provide appropriate conversion between the signaling format(s) used by the MSC  510  and base stations  550  and the signaling format used by the satellite  530 . For example, the first and second interface converters  542 ,  522  may comprise respective concentrator/deconcentrator components. 
     It will be appreciated that the embodiments of  FIGS. 3-5  are provided as examples of possible system and method configurations, and that other configurations also fall within the scope of the invention. In particular, it will be understood that wireless network functionality described above may be distributed in other ways among network components such as satellites, BSCs, MSCs, and base stations. 
       FIG. 6  illustrates a wireless communications system  600  and methods according to still further aspects of the present invention. The system  600  includes one or more receive-only terrestrial base stations  620  that receive information from terminals  90  over return service links. Information received by the base station  620  is conveyed to a BSC  610  using, for example, landline and/or radio links (e.g., microwave or satellite links). Forward service links to the terminals  90  are provided via a satellite  640  and a satellite gateway  630  that are linked to the BSC  610 . The forward service links and the return service links to and from the terminals  90  may use the same frequency bands and/or signaling protocols (e.g., GSM data format with GMSK modulation), or may use respective different frequency bands and/or signaling protocols. It will be appreciated that embodiments of the present invention may use a structure complementary to that of FIG.  6 . For example, transmit-only base stations fed by conventional landlines (e.g., from a BSC) could be used to provide downlinks to terminals, while uplinks from terminals are provided via a communications satellite. 
       FIG. 7  illustrates another “repeater” configuration for a wireless communications system  700  according to further embodiments of the present invention. The system  700  includes an MSC  712  and a BSC  714  that communicates with a remote terrestrial terminal interface subsystem, here including a remote transmit-only terrestrial base station  740 , via a repeater including a gateway  720  and a satellite  730 . The remote terrestrial transmit-only base station  740  includes a deconcentrator  742  that receives signals from the satellite  730  and converts the signals received over the satellite link to, for example, GSM-format signals transmitted to cellular terminals  95 . The gateway  720  includes a concentrator  722  that performs conversion functions complementary to those of the deconcentrator  742 . The BSC  714  is also connected to one or more receive-only base stations  750  that receive signals from terminals  95  and convey information therein to the BSC  714  using, for example, conventional cable, fiber or terrestrial microwave links. A combination of the terrestrial transmit-only base station  740  and the receive-only base station  750  may be viewed as forming a satellite-linked terrestrial terminal interface subsystem. 
     In the drawings and foregoing description thereof, there have been disclosed exemplary embodiments of the invention. Terms employed in the description are used in a generic and descriptive sense and not for purposes of limitation, the scope of the invention being set forth in the following claims.