Abstract:
A broadband system wherein a mobile user terminal determines a cell set connection with a communications platform using location information provided by a navigation device on said mobile user terminal and a stored database containing a current cell topology for the communications platform.

Description:
[0001]    RELATED APPLICATIONS  
         [0002]    This application claims the benefit of earlier filed provisional patent application entitled “Methodology For Mobile User Terminals In Broadband Systems”, Serial No., 60/275,082, filed on Mar. 9, 2001. 
     
    
     
       TECHNICAL FIELD  
         [0003]    The present invention relates generally to point-to-point broadband systems and more particularly to bandwidth assignment in a point-to-point broadband system.  
         BACKGROUND OF THE INVENTION  
         [0004]    Broadband systems typically have access terminals with fixed, or relatively fixed, locations. Links to and from the satellite are tightly controlled and static. This arrangement does not support a mobile terminal. In prior art systems designed for mobile terminals, signals are routed based upon signal strength and without prior knowledge of the allocation of system resources.  
           [0005]    Generally, point-to-point systems do not track mobile terminals. The complexity associated with tracking and dynamically allocating routing mechanisms may overwhelm on-board processing capabilities or result in processing delays at the centralized network control center.  
         SUMMARY OF THE INVENTION  
         [0006]    It is an object of the present invention to allow a satellite containing multiple high-gain spot beams to provide point-to-point broadband service to or from a moving platform, such as a plane or a car. It is another object of the present invention to distribute bandpass capacity on a dynamic user defined basis.  
           [0007]    It is still another object of the present invention to alleviate the need for a spacecraft to track mobile user terminals for point-to-point applications. Yet another object of the present invention is to perform allocation of uplink spectrum and spot beams on a priority basis, as moving user terminals alter traffic patterns. A further object of the present invention allows a central processing facility or communications platform to allocate spectrum and spot beams.  
           [0008]    According to the present invention, a communications platform having a plurality of high-gain spot beams receives navigational information from a mobile user terminal. The mobile user terminal determines which of the spot beams downlink cells of the communications platform is the most appropriate for downlink to the mobile user terminal. The mobile user terminal maintains a database of the communications platform uplink and downlink geographic cell mapping to determine which cell set it is located within and which cell set it is transitioning into. It is possible to periodically update the cell mapping information stored in the mobile user terminal.  
           [0009]    It is an advantage of the present invention that it is not necessary for the communications platform to track a mobile user terminal for point-to-point applications. It is another advantage of the present invention that the communications platform does not need to be aware of the location of all of its user terminals.  
           [0010]    According to the present invention, the user terminal determines which uplink carrier and downlink cell will be used for transmission or reception. Therefore, it is a further advantage of the present invention that the need for onboard processing or centralized processing may be eliminated, increasing the flexibility and simplicity of the communications platform system.  
           [0011]    Other objects and advantages of the present invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    For a more complete understanding of this invention, reference should now be had to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention. In the drawings:  
         [0013]    [0013]FIG. 1 is a block diagram of the communications platform system of the present invention; and  
         [0014]    [0014]FIG. 2 is a flow diagram of the methodology of the present invention. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0015]    [0015]FIG. 1 is a block diagram of a communications platform system  10  according to the present invention. A communications platform  12 ,.shown as a satellite in FIG. 1, but which may also be a stratospheric platform or other platform, provides uplink  14  and downlink  16  capabilities between user terminals  18  and  20 . A user terminal  18 ,  20  may be any end user of satellite services, and may be fixed, or mobile, such as services to a plane, car, boat or other mobile vehicle as shown in FIG. 1.  
         [0016]    According to the present invention, the mobile user terminal  18 ,  20  is equipped with a navigational device  22 , such as a global positioning system (GPS) receiver. The navigational device  22  provides location information that is communicated by the mobile user terminal  18 ,  20  to the communications platform  12 . The location information provided to the mobile user terminal  18 ,  20  allows the terminal  18 ,  20  to determine which of the high gain spot beams of the communications platform  12  is most appropriate for the downlink and to determine which channel configuration is most appropriate for the uplink.  
         [0017]    According to the present invention, the user terminal  18 ,  20  retains a database of the communications platform  12  uplink and downlink geographic cell mapping.  
         [0018]    The navigational device  22  provides location information that the user terminal  18 ,  20  incorporates into a header field of the uplinked packets or in a special information packet. The user terminal  18 ,  20  uses its known location and accesses its database of geographic cell mapping for the communications platform  12  to determine which cell set (uplink and downlink) it is contained within and which cell set it is transitioning into. For example, a sending mobile user terminal  18  will use its known location to determine which cell set it is contained within for uplinking information to the satellite and ultimately downlinking from the communications platform  12 . User terminal  20  uses its known location and database to determine a cell set so that the satellite  12  can downlink the data packets from mobile user terminal  18  to mobile user terminal  20 .  
         [0019]    In this regard, the communications platform  12  receives location information for the mobile user terminals and is therefore capable of anticipating new bandwidth and cell assignments as the user terminal transitions from one uplink/dowlink cell to another and will allow return messages to be routed to the proper downlink locations. However, it is not necessary for the communications platform  12  to be aware of the location of all of its users at any given time. It is only necessary to communicate location information during transmission in order for the satellite to know which cells are being used for uplink and to know where to transmit the uplinked data packets.  
         [0020]    [0020]FIG. 2 is a flow diagram of the method  100  according to the present invention. The system generally has at least one mobile user terminal  18 , and a communications platform (not shown in FIG. 2). Optionally, the system may include a network control center  24 . However, network control is not necessary as part of the system or method of the present invention.  
         [0021]    The mobile user terminal (MUT)  18  holds the cell topology  26  for the communications platform. This can be updated periodically  116  from the network control center  24  or by any known method. The mobile user terminal  18  also has navigational processing capabilities  102  to determine and communicate location information  104 , in the form of a position vector, to the communications platform and/or the optional control network  24 . The mobile user terminal will configure itself and request  106  uplink bandwidth as a function of its location and the database cell topology  24 .  
         [0022]    The bandwidth request  106  is processed  108  on board the communications platform and a bandwidth assignment  110  is determined and communicated  112  to the mobile user terminal  18  establishing an uplink connection with the communications platform.  
         [0023]    Ongoing mobile terminal to mobile terminal traffic is maintained because the source mobile user terminal  18  includes its current address information in the header. In this regard, the communications platform does not need to know the location of each of the mobile user terminals.  
         [0024]    In one embodiment of the present invention, the mobile user terminal  18 ,  20  may provide look ahead positional information  104  as to its estimated position in a predetermined time interval. It may also provide its current speed as well as a directional vector along with the positional information  104 . The estimated positional information may be contained with the uplink packet header or as a special information packet. Providing this information  104  to the optional network control  24  allows the network control center  24  to predict near term system performance and will allow destination terminals to establish a communications link at a later time.  
         [0025]    The optional ground-based network control center  24  is not necessary. However, the system of the present invention does not preclude the ability to have a centralized location to determine geographic cell assignment of a mobile user terminal given the uplinked information provided by the user terminal. Having the network control center  24  allows for greater centralized controls. The network control center introduces efficiencies in that there is less distribution processing required between the mobile user terminals and the communications platform.  
         [0026]    The ground-based network control center also maintains the network configuration  118  for the communications platform. Network updates are sent  120  to the communications network to assist in processing bandwidth requests and assignments.  
         [0027]    In yet another embodiment of the present invention the system will broadcast a message requesting a “lost” mobile user terminal to wake up and reply with a response if its destination cell is unknown or otherwise inoperative. The requested information may be relayed to a database in the network control center  24  where it can be accessed by other mobile user terminals that wish to establish a link with the “lost” terminal.  
         [0028]    The invention covers all alternatives, modifications, and equivalents, as may be included within the spirit and scope of the appended claims.