System and Method for Multiple Access Control in a Communications System

Abstract

A satellite communications system ( 10 ) includes a hub ( 14 ), a satellite ( 32 ), and any number of remote terminals ( 16 ). Each remote terminal ( 16 ) includes a remote receiver ( 38 ), a monitor ( 40 ), and a network access controller ( 42 ). Each remote receiver ( 38 ) is configured to receive and down convert the system's entire spectrum of interest from which channels are accessed by the remote terminals ( 16 ). The monitors ( 40 ) independently perform FFT processes over this entire spectrum, but at a low frequency resolution which is no higher than needed to distinguish channels. Based on these spectral analyses, uplink/inbound channels are independently selected by the network access controllers ( 42 ) at each remote terminal ( 16 ). Remote terminals ( 16 ) immediately transmit data to the hub ( 14 ) as soon as they select an uplink/inbound channel.

1 : In a communications system, a method of accessing channels comprising:
 receiving a broadband signal occupying a predetermined portion of the electromagnetic spectrum and including a plurality of downlink channels;   identifying a portion of said spectrum of said broadband signal in which power is below a predetermined threshold;   translating said portion of said spectrum of said broadband signal in which power is below said predetermined threshold into an identity of an uplink channel; and   transmitting a communication using said uplink channel identified in said translating activity.   
     
     
         2 : A method as claimed in  claim 1  wherein each of said plurality of downlink channels occupies a different portion of the electromagnetic spectrum than is occupied by others of said plurality of downlink channels. 
     
     
         3 : A method as claimed in  claim 1  wherein:
 said communications system includes a plurality of remote terminals; and   said receiving, identifying, translating, and transmitting activities are independently performed at each of said plurality of remote terminals.   
     
     
         4 : A method as claimed in  claim 3  wherein said communications system includes fewer than 1000 remote terminals. 
     
     
         5 : A method as claimed in  claim 1  wherein said identifying activity comprises:
 sampling said broadband signal to form a block of samples;   performing a Fourier transform on said block of samples.   
     
     
         6 : A method as claimed in  claim 5  wherein said performing activity has a frequency resolution of between 1 KHz and 16 KHz. 
     
     
         7 : A method as claimed in  claim 1  wherein said transmitting activity accommodates burst and non-burst formats. 
     
     
         8 : A method as claimed in  claim 1  wherein said transmitting activity comprises:
 tuning a transmitter to said uplink channel identified in said translating activity; and   refraining from emitting a substantial transmission in any channel other than said uplink channel identified in said translating activity.   
     
     
         9 : A method as claimed in  claim 1  additionally comprising:
 detecting, after initiating said transmitting activity, a collision in said uplink channel identified in said translating activity; and   repeating said receiving, identifying, translating, and transmitting activities if said collision occurs.   
     
     
         10 : A method as claimed in  claim 1  wherein said broadband signal is broadcast by a satellite and said communication is transmitted to said satellite. 
     
     
         11 : A communications system comprising:
 a hub; and   a plurality of remote terminals wherein each of said remote terminals is configured to independently receive a broadband signal occupying a predetermined portion of the electromagnetic spectrum, to identify a portion of said spectrum of said broadband signal in which power is below a predetermined threshold, to translate said portion of said spectrum of said broadband signal in which power is below said predetermined threshold into an identity of an uplink channel, and to transmit toward said hub said uplink channel;   wherein each of said remote terminals includes a receiver and a monitor, each receiver is configured to sample said broadband signal to form a block of samples, and each monitor is configured to perform a Fourier transform on said block of samples.   
     
     
         12 : A communications system as claimed in  claim 11  wherein said communications system includes fewer than 1000 of said remote terminals. 
     
     
         13 : A communications system as claimed in  claim 11  wherein each of said remote terminals is further configured to detect a collision in said uplink channel by observing a downlink channel which occupies said portion of said spectrum of said broadband signal and to identify another uplink channel if said collision occurs.