System and method for contention based tones in a multipoint-to-point orthogonal frequency division multiplexing system

Abstract

Systems and methods for round-trip-delay adjustment in a multipoint-to-point orthogonal frequency division multiplexing (OFDM) system are provided. In one embodiment, a method for a remote unit to request bandwidth in an Orthogonal Frequency Division Multiplexing (OFDM) multi-point to point system comprises: transmitting a signal from a remote unit having a request for bandwidth to a host unit on a first tone, the signal from the remote unit configured to combine with a signal from at least one other remote unit on a different tone to form a coherent OFDM waveform; determining when a collision has occurred on the first tone between the signal transmitted by the remote unit and a signal from at least one other remote unit; and when a collision occurs, re-transmitting the request for bandwidth on the first tone.

1 . A system comprising:
 a first remote unit for communicating with a multipoint-to-point host unit using an orthogonal frequency division multiplexing waveform comprising a plurality of orthogonal carriers modulated using an inverse Fourier transform, the first remote unit programmed to transmit at least one symbol representing a request for bandwidth allocation on a first carrier of the plurality of orthogonal carriers; and   a second remote unit for communicating with the multipoint-to-point host unit using an orthogonal frequency division multiplexing waveform comprising a plurality of orthogonal carriers modulated using an inverse Fourier transform, the second remote unit programmed to transmit at least one symbol representing a request for bandwidth allocation on the first carrier of the plurality of orthogonal carriers;   wherein the second remote unit is further programmed to determine when a collision has occurred on the first carrier of the plurality of orthogonal carriers between transmissions from the first remote unit and transmissions from the second remote unit.   
     
     
         2 . The system of  claim 1 , wherein the second remote unit is further programmed to retransmit the request for bandwidth allocation after a collision is determined. 
     
     
         3 . The system of  claim 2 , wherein the second remote unit is further programmed to delay retransmission of the request for bandwidth allocation based on an exponential back-off procedure. 
     
     
         4 . The system of  claim 1 , wherein the inverse Fourier transform is based on one of an inverse Fast Fourier Transform (FFT) and an inverse Discrete Fourier Transform (DFT). 
     
     
         5 . A method for an orthogonal frequency division multiplexing multipoint-to-point communications system, the method comprising:
 establishing communication between a first remote unit of a plurality of remote units and a host unit, the plurality of remote units communicatively coupled to the host unit in a multipoint-to-point configuration;   transmitting up to a plurality of tones from the first remote unit, the up to a plurality of tones modulated with upstream information using orthogonal frequency division multiplexing;   determining when bandwidth is needed for an upstream transmission to the host unit from the first remote unit;   transmitting a request for bandwidth to the host unit from the first remote unit on a first tone of the plurality of tones, the request for bandwidth from the first remote unit configured to combine with a signal from at least one other remote unit on a different tone to form a coherent OFDM waveform; and   determining when a collision has occurred on the first tone between the request for bandwidth transmitted by the first remote unit and a signal from at least one other remote unit.   
     
     
         6 . The method of  claim 5 , further comprising:
 delaying retransmission of the request for bandwidth based on a back-off procedure.   
     
     
         7 . The method of  claim 5 , further comprising:
 delaying retransmission of the request for bandwidth allocation based on an exponential back-off procedure.   
     
     
         8 . The method of  claim 5 , wherein spacing between tones of the coherent OFDM waveform is based on a reciprocal of a symbol period. 
     
     
         9 . The method of  claim 5 , further comprising:
 retransmitting the request for bandwidth after a collision occurs.   
     
     
         10 . A method for a remote unit to request bandwidth in an Orthogonal Frequency Division Multiplexing (OFDM) multi-point to point system, the method comprising:
 transmitting a signal from a remote unit having a request for bandwidth to a host unit on a first tone, the signal from the remote unit configured to combine with a signal from at least one other remote unit on a different tone to form a coherent OFDM waveform;   determining when a collision has occurred on the first tone between the signal transmitted by the remote unit and a signal from at least one other remote unit; and   when a collision occurs, re-transmitting the request for bandwidth on the first tone.   
     
     
         11 . The method of  claim 10 , further comprising:
 delaying retransmission of the request for bandwidth based on a back-off procedure.   
     
     
         12 . The method of  claim 10 , further comprising:
 delaying retransmission of the request for bandwidth based on an exponential back-off procedure.   
     
     
         13 . The method of  claim 10 , wherein spacing between tones of the coherent OFDM waveform is based on a reciprocal of a symbol period.