Abstract:
A space segment for a radioterminal communications system includes a satellite having service link antennas of different sizes that are configured to communicate with at least one radioterminal. The service link antennas of different size may serve different sized geographic areas, which may at least partially overlap. Analogous radioterminal communications methods also are provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of provisional Application No. 60/538,299, filed Jan. 22, 2004, entitled Satellite With Different Size Service Link Antennas and Radioterminal Communication Methods Using Same, the disclosure of which is hereby incorporated herein by reference in its entirety as if set forth fully herein. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to radioterminal communications systems and methods, and more particularly to terrestrial and satellite radioterminal communications systems and methods.  
       BACKGROUND OF THE INVENTION  
       [0003]     Satellite radioterminal communication systems and methods are widely used for communicating among radioterminals and/or among radioterminals and wire-line terminals. As is well known to those having skill in the art, a satellite radioterminal communication system includes a space segment, which includes one or more satellites and one or more gateways. The satellite(s) communicate with radioterminals over a plurality of service links and communicate with the gateway(s) over one or more feeder links using one or more antennas at the satellite(s).  
         [0004]     As used herein, the term “radioterminal” includes cellular and/or satellite radioterminals with or without a multi-line display; Personal Communications System (PCS) terminals that may combine a radioterminal 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. As used herein, the term “radioterminal” also includes any other radiating user device/equipment/source that may have time-varying or fixed geographic coordinates, and may be portable, transportable, installed in a vehicle (aeronautical, maritime, or land-based), or situated and/or configured to operate locally and/or in a distributed fashion at any other location(s) on earth and/or in space. A “radioterminal” also may be referred to herein as a “radiotelephone,” “terminal” or “wireless user device”.  
         [0005]     These radioterminals can include satellite-only radioterminals and/or multi-mode satellite/terrestrial radioterminals. The multi-mode satellite/terrestrial radioterminals may be configured to communicate with an ancillary terrestrial network using one or more satellite frequencies.  
         [0006]     Satellite radioterminal communications systems and methods that may employ terrestrial reuse of satellite frequencies are also described in U.S. Pat. No. 6,785,543 to Karabinis, entitled Filters For Combined Radiotelephone/GPS Terminals, and Published U.S. patent application Nos. US 2003/0054761 to Karabinis, entitled Spatial Guardbands for Terrestrial Reuse of Satellite Frequencies; US 2003/0054814 to Karabinis et al., entitled Systems and Methods for Monitoring Terrestrially Reused Satellite Frequencies to Reduce Potential Interference; US 2003/0054762 to Karabinis, entitled Multi-Band/Multi-Mode Satellite Radiotelephone Communications Systems and Methods; US 2003/0153267 to Karabinis, entitled Wireless Communications Systems and Methods Using Satellite-Linked Remote Terminal Interface Subsystems; US 2003/0224785 to Karabinis, entitled Systems and Methods for Reducing Satellite Feeder Link Bandwidth/Carriers In Cellular Satellite Systems; US 2002/0041575 to Karabinis et al., entitled Coordinated Satellite-Terrestrial Frequency Reuse; US 2002/0090942 to Karabinis et al., entitled Integrated or Autonomous System and Method of Satellite-Terrestrial Frequency Reuse Using Signal Attenuation and/or Blockage, Dynamic Assignment of Frequencies and/or Hysteresis; US 2003/0068978 to Karabinis et al., entitled Space-Based Network Architectures for Satellite Radiotelephone Systems; US 2003/0153308 to Karabinis, entitled Staggered Sectorization for Terrestrial Reuse of Satellite Frequencies; and US 2003/0054815 to Karabinis, entitled Methods and Systems for Modifying Satellite Antenna Cell Patterns In Response to Terrestrial Reuse of Satellite Frequencies, US 2004/0121727 to Karabinis, entitled Systems and Methods For Terrestrial Reuse of Cellular Satellite Frequency Spectrum In A Time-Division Duplex Mode, US 2004/0192293 to Karabinis, entitled Aggregate Radiated Power Control For Multi-Band/Multi-Mode Satellite Radiotelephone Communications Systems And Methods, US 2004/0142660 to Churan, entitled Network-Assisted Global Positioning Systems, Methods And Terminals Including Doppler Shift And Code Phase Estimates, and US 2004/0192395 to Karabinis, entitled Co-Channel Wireless Communication Methods and Systems Using Nonsymmetrical Alphabets, all of which are assigned to the assignee of the present invention, the disclosures of all of which are hereby incorporated herein by reference in their entirety as if set forth fully herein.  
         [0007]     For a given size of an antenna feed network (e.g., for a given number of antenna feed elements), as the antenna size (e.g., the reflector diameter) of a satellite antenna grows, the geographic area that can be served subject to a specified performance index (such as a specified satellite antenna gain over noise temperature (G/T)) generally becomes smaller. In order to increase the geographic area that can be served by a given satellite antenna size (subject to a specified satellite performance index) the size of the antenna feed network may have to be increased. This may be prohibitive, in some applications, where the size, mass and/or heat dissipation of a satellite has exceeded a certain limit. Growing the size of an antenna feed network may also require additional signal processing by the satellite payload which may further aggravate the size, mass and/or heat dissipation constraints of the satellite.  
       SUMMARY OF THE INVENTION  
       [0008]     Embodiments of the present invention provide a space segment for a radioterminal communications system that comprises a satellite having service link antennas of different sizes that are configured to communicate with at least one radioterminal. In some embodiments, the service link antennas of different size may serve different sized geographic areas, which may at least partially overlap. Analogous radioterminal communications methods also are provided. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  schematically illustrates satellites and satellite communication methods according to various embodiments of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0010]     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. In the drawing, like numbers refer to like elements. 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.  
         [0011]     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.  
         [0012]     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 will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.  
         [0013]     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 antenna below could be termed a second antenna, and similarly, a second antenna may be termed a first antenna 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”.  
         [0014]      FIG. 1  illustrates a satellite  10  having at least two service link  22  antennas—one larger than the other, according to some embodiments of the invention. The smaller antenna  12  (e.g., a reflector 9 meters in diameter) forms larger satellite beams (cells) on the ground and can thus serve a larger geographic area  16  (the area labeled as “secondary service area”) while using a smaller number of antenna feed network elements (radiators) compared to the number of antenna feed network elements that may be used by a larger antenna  14  to serve the same geographic area. The larger antenna  14  (e.g., a reflector 26 meters in diameter) forms smaller higher-gain satellite beams (cells) on the ground and provides service over a smaller geographic area  18  (the area labeled as “primary service area”) which can keep the number of its feed network elements smaller compared with a number of feed network elements that the larger antenna  14  may use to provide service over both the primary and secondary service areas.  
         [0015]     In some embodiments, the smaller antenna  12  and its feed network may be configured to provide service over both the secondary  16  and primary  18  service areas. Alternatively, the smaller antenna  12  and its associated feed network may be configured to provide service only over the secondary service area  16  and service to the primary service area  18  may be provided by the larger antenna  14  only. In yet other embodiments, the secondary service area  16  and the primary service area  18  may partially overlap, or the primary service area  18  may be contained within the secondary service area  16 , as shown in  FIG. 1 .  
         [0016]     The signal processing associated with the smaller antenna  12  and its feed network and/or the larger antenna  14  and its feed network (such as beam forming and/or signal channelization) may be operative on-board the satellite  10  (as per the Thuraya and/or Inmarsat-4 satellite configurations) and/or it may be operative on the ground such as at a satellite gateway or gateway(s)  20 , as described, for example, in U.S. Pat. Nos. 6,157,811; 5,848,060; 5,812,947; 5,631,898; 5,594,941 and/or 5,555,257 and/or in provisional Applications Nos. 60/572,164, entitled “Space-Based Networks and Methods with Ground-Based Beam Forming,” filed May 18, 2004; 60/583,218, entitled “Methods of Ground Based Beamforming and On-Board Frequency Translation and Related Systems,” filed Jun. 25, 2004; and ______ , “Adaptive Beam-Forming with Interference Suppression and Multi-User Detection in Satellite Systems with Terrestrial Reuse of Frequencies,” filed Jan. 5, 2005 (Attorney Docket No. 9301-152PR), all of which provisional applications are assigned to the assignee of the present invention, the disclosures of all of which are hereby incorporated herein by reference in their entirety as if set forth fully herein.  
         [0017]     In some embodiments, the smaller antenna  12  and its feed network are configured to serve a service area (primary  18  and secondary  16 , or just secondary  16 ) with the associated beam forming and/or channelization processor operative at the satellite  10 , while the larger antenna  14  and its feed network are configured to serve the primary service area  18  with its associated beam forming and/or channelization processor operative on the ground (e.g., at a satellite ground facility (gateway  20 ) or distributed between more than one satellite ground facilities (gateways  20 )). In some embodiments, the forward-link beam forming and/or channelization processor associated with a satellite antenna (larger  14  and/or smaller  12 ) and its corresponding feed network are operative at the satellite  10  while the return-link beam forming and/or channelization processor is operative on the ground  20 . In yet other embodiments, the smaller antenna  12  is configured to receive only Right Hand Circularly Polarized (RHCP) radiation and/or Left Hand Circularly Polarized (LHCP) radiation, and the larger antenna  14  is configured to receive both RHCP and/or LHCP radiation. The embodiments described in this paragraph also may be combined.  
         [0018]     In the drawing and specification, there have been disclosed 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.