Distributed control of carrier frequency in multipoint-to-point orthogonal frequency division multiplexing communication

Abstract

A bidirectional communication system is provided. The system includes a first remote unit for communicating with a host unit using orthogonal frequency division multiplexing, the host unit communicatively coupled to a plurality of remote units in a multipoint-to-point configuration. The first remote unit is configured to transmit up to a plurality of tones, the up to a plurality of tones modulated with upstream information using orthogonal frequency division multiplexing. The first remote unit is configured to receive information from the host unit to adjust a carrier frequency of tones transmitted by the first remote unit, and is configured to adjust the carrier frequency based on the received information from the host unit.

1 . A bidirectional communication system, the system comprising: 
 a first remote unit for communicating with a host unit using orthogonal frequency division multiplexing, the host unit communicatively coupled to a plurality of remote units in a multipoint-to-point configuration;    wherein the first remote unit is configured to transmit up to a plurality of tones, the up to a plurality of tones modulated with upstream information using orthogonal frequency division multiplexing; and    wherein the first remote unit is configured to receive information from the host unit to adjust a carrier frequency of tones transmitted by the first remote unit, and is configured to adjust the carrier frequency based on the received information from the host unit.    
     
     
         2 . The system of  claim 1 , the first remote unit including a modulator for modulating up to a plurality of tones with upstream information using orthogonal frequency division multiplexing such that when any tones are transmitted from the first remote unit and at least one other remote unit of the plurality of remote units, the tones are substantially orthogonal when received at the host unit.  
     
     
         3 . The system of  claim 1 , the first remote unit further configured to transmit a reference signal to the host unit, and configured to receive a frequency adjustment command from the host unit, the frequency adjustment command based on an estimate of a frequency error in the reference signal.  
     
     
         4 . The system of  claim 3 , the first remote unit further comprising a clock, wherein the first remote unit is configured to lock the clock of the first remote unit to a frequency of a clock in the host unit based on one or more signals transmitted to the first remote unit from the host unit.  
     
     
         5 . The system of  claim 1 , further comprising a distribution network coupled between the host unit and the plurality of remote units.  
     
     
         6 . The system of  claim 5 , wherein the distribution network comprises one of a wireless system and a hybrid fiber/coax network.  
     
     
         7 . The system of  claim 1 , wherein the plurality of tones are transmitted concurrently from at least two of the plurality of remote units.  
     
     
         8 . A bidirectional communication system, the system comprising: 
 a host unit to communicate with a plurality of remote units using orthogonal frequency division multiplexing, the plurality of remote units communicatively coupled to the host unit in a multipoint-to-point configuration;    the host unit receiving an orthogonal frequency division multiplexing waveform, the orthogonal frequency division multiplexing waveform comprising a plurality of tones transmitted by the plurality of remote units;    the host unit configured to analyze at least a portion of the orthogonal frequency division multiplexing waveform to generate adjustment information for a first remote unit of the plurality of remote units; and    wherein the host unit is configured to transmit the adjustment information to the first remote unit, the information directing the first remote unit to adjust a carrier frequency of tones transmitted by the first of remote unit.    
     
     
         9 . The system of  claim 8 , further comprising a distribution network coupled between the host unit and the plurality of remote units.  
     
     
         10 . The system of  claim 9 , wherein the distribution network comprises one of a wireless system and a hybrid fiber/coax network.  
     
     
         11 . The system of  claim 8 , wherein the plurality of tones are transmitted concurrently from at least two of the plurality of remote units.  
     
     
         12 . The system of  claim 8 , wherein the host unit is configured to adjust each of the plurality of remote units to achieve carrier frequency alignment within a predefined margin at the host unit of any upstream transmissions by the plurality of remote units.  
     
     
         13 . A bidirectional communication system, the system comprising: 
 a multipoint-to-point host unit;    a plurality of remote units communicatively coupled to the multipoint-to-point host unit through an orthogonal frequency division multiplexing waveform;    wherein the multipoint-to-point host unit is configured to receive the orthogonal frequency division multiplexing waveform, the orthogonal frequency division multiplexing waveform comprising a plurality of tones transmitted by the plurality of remote units; and    wherein the multipoint-to-point host unit is configured to analyze and to adjust a carrier frequency of transmissions from at least one of the plurality of remote units based on the orthogonal frequency division multiplexing waveform to assist in achieving orthogonal tones in the orthogonal frequency division multiplexing waveform when received at the multipoint-to-point host unit.    
     
     
         14 . The system of  claim 13 , wherein the plurality of remote units are configured to modulate a plurality of tones with upstream information so that when the plurality of tones are transmitted from at least two of the plurality of remote units, the plurality of tones are substantially orthogonal when received at a multipoint-to-point host unit.  
     
     
         15 . The system of  claim 13 , wherein the plurality of tones are transmitted concurrently from at least two of the plurality of remote units.  
     
     
         16 . The system of  claim 13 , further comprising a distribution network coupled between the multipoint-to-point host unit and the plurality of remote units.  
     
     
         17 . The system of  claim 13 , wherein the distribution network comprises one of a wireless system and a hybrid fiber/coax network.