Scanning by remotes in multipoint-to-point communication using orthogonal frequency division multiplexing

Abstract

Systems and methods for scanning by remotes in multipoint-to-point communication using orthogonal frequency division multiplexing are provided. In one embodiment, a system comprises a host unit; and a plurality of remote units using a multiple access scheme to communicate at the same time with the host unit using orthogonal frequency division multiplexing (OFDM); wherein at least one remote unit scans a band of frequencies for a downstream signal from the host unit; wherein the host unit sends an adjustment signal to the at least one remote unit instructing the at least one remote unit to adjust the timing of transmissions from the remote unit to improve orthogonality of an OFDM waveform received at the host unit; and wherein the host unit allocates orthogonal tones within the OFDM waveform to the plurality of remote units.

1 . A multipoint-to-point, orthogonal frequency division multiplexed (OFDM) communication system comprising: 
 a plurality of remote units;    a host unit that includes a demodulator;    wherein each of the remote units transmits an upstream OFDM signal using a multiple access scheme to the host unit demodulator using at least one of a plurality of orthogonal tones within an OFDM waveform;    wherein the host unit receives the upstream OFDM signals from a plurality of the remote units, the tones of the upstream signals being substantially orthogonal when received at the host unit;    wherein portions of upstream OFDM signals from at least two of the remote units arrive at the host unit at the same time;    wherein the host unit demodulator demodulates said portions; and    wherein at least one remote unit scans a band of frequencies for a downstream signal from the host unit.    
     
     
         2 . The OFDM communication system of  claim 1  wherein the host unit sends an adjustment signal to the at least one remote unit instructing the at least one remote unit to adjust the timing of transmissions from the at least one remote unit to improve orthogonality of the OFDM waveform received at the host unit.  
     
     
         3 . The OFDM communication system of  claim 1  wherein the at least one remote unit scans for a downstream signal during initialization of the at least one remote unit.  
     
     
         4 . The OFDM communication system of  claim 1  wherein the at least one remote unit scans for a downstream signal from the host unit comprising an identification code associated with the remote unit.  
     
     
         5 . The OFDM communication system of  claim 1  wherein via the downstream signal the host unit assigns at least one frequency band comprising a subset of the plurality of orthogonal tones within the OFDM waveform to the at least one remote unit, from which subset the host unit subsequently allocates tones to the at least one remote unit for at least one of upstream and downstream communication between the host unit and the at least one remote unit.  
     
     
         6 . The OFDM communication system of  claim 5  wherein the host unit sends an adjustment signal to the at least one remote unit instructing the at least one remote unit to adjust the timing of transmissions from the at least one remote unit to improve orthogonality of the OFDM waveform received at the host unit.  
     
     
         7 . A system comprising: 
 a host unit;    a plurality of remote units using a multiple access scheme to communicate at the same time with the host unit using orthogonal frequency division multiplexing (OFDM);    wherein at least one remote unit scans a band of frequencies for a downstream signal from the host unit;    wherein the host unit sends an adjustment signal to the at least one remote unit instructing the at least one remote unit to adjust the timing of transmissions from the remote unit to improve orthogonality of an OFDM waveform received at the host unit; and    wherein the host unit allocates orthogonal tones within the OFDM waveform to the plurality of remote units.    
     
     
         8 . The system of  claim 7  wherein the at least one remote unit scans for a downstream signal during initialization of the at least one remote unit.  
     
     
         9 . The system of  claim 7  wherein the at least one remote unit scans for a downstream signal from the host unit comprising an identification code associated with the remote unit.  
     
     
         10 . The system of  claim 7  wherein via the downstream signal the host unit assigns at least one frequency band comprising a subset of the plurality of orthogonal tones within the OFDM waveform to the at least one remote unit, from which subset the host unit subsequently allocates tones to the at least one remote unit for at least one of upstream and downstream communication between the host unit and the at least one remote unit.  
     
     
         11 . The system of  claim 7  wherein the remote unit scans the band of frequencies for the downstream signal by successively listening for the downstream signal on each of the plurality of orthogonal tones within the frequency band.