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

Abstract

A method for an orthogonal frequency division multiplexing multipoint-to-point communications system is provided. The method includes 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, receiving information from the host unit to adjust a carrier frequency of tones transmitted by the first of remote unit, and adjusting the carrier frequency based on the received information from the host unit.

1 . 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;    receiving information from the host unit to adjust a carrier frequency of tones transmitted by the first of remote unit; and    adjusting the carrier frequency based on the received information from the host unit.    
     
     
         2 . The method of  claim 1 , wherein receiving information from the host unit to adjust the carrier frequency of tones transmitted by the first of remote unit further comprises: 
 receiving information from the host unit to adjust the carrier frequency of tones transmitted by the first remote unit 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 method of  claim 1 , further comprising: 
 locking a 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;    transmitting a reference signal to the host unit from the first remote unit; and    receiving a frequency adjustment command at the first remote unit, the frequency adjustment command based on an estimate of a frequency error in the reference signal.    
     
     
         4 . The method of  claim 1 , wherein transmitting up to a plurality of tones comprises wirelessly transmitting up to a plurality of tones.  
     
     
         5 . A method for an orthogonal frequency division multiplexing multipoint-to-point communications system, the method comprising: 
 receiving an orthogonal frequency division multiplexing waveform at a multipoint-to-point host unit, the orthogonal frequency division multiplexing waveform comprising a plurality of tones transmitted by the plurality of remote units; and    sending an adjustment command from the multipoint-to-point host unit to a first remote unit of the plurality of remote units, the information directing the first remote unit to adjust a carrier frequency of tones transmitted by the first of remote unit so that tones in the orthogonal frequency division multiplexing waveform are orthogonal when received at the multipoint-to-point host unit.    
     
     
         6 . The method of  claim 5 , wherein receiving the orthogonal frequency division multiplexing waveform at the multipoint-to-point host unit further comprises receiving a plurality of tones from more than one of the plurality of remote units.  
     
     
         7 . The method of  claim 5 , wherein receiving the orthogonal frequency division multiplexing waveform at the multipoint-to-point host unit further comprises receiving a plurality of tones from one of the plurality of remote units.  
     
     
         8 . The method of  claim 5 , further comprising adjusting 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.  
     
     
         9 . A method for an orthogonal frequency division multiplexing multipoint-to-point communications system, the method comprising: 
 receiving an orthogonal frequency division multiplexing waveform at a multipoint-to-point host unit, the orthogonal frequency division multiplexing waveform comprising a plurality of tones transmitted by a plurality of remote units; and    adjusting a carrier frequency of tones transmitted from at least one of the plurality of remote units based on the orthogonal frequency division multiplexing waveform.    
     
     
         10 . The method of  claim 9 , wherein adjusting the carrier frequency of tones transmitted from at least one of the plurality of remote units further comprises adjusting the carrier frequency of tones transmitted from at least one of the plurality of remote units so that the plurality of tones transmitted by the plurality of remote units are substantially orthogonal when received at the multipoint-to-point host unit.  
     
     
         11 . The method of  claim 9 , further comprising: 
 adjusting the carrier frequency of tones transmitted from the at least one of the plurality of remote units such that when any tones are transmitted from the at least one of the plurality of remote units and at least one other remote unit of the plurality of remote units, the tones are substantially orthogonal when received at the multipoint-to-point host unit.    
     
     
         12 . The method of  claim 9 , wherein receiving the orthogonal frequency division multiplexing waveform at the multipoint-to-point host unit further comprises receiving a plurality of tones from more than one of the plurality of remote units.  
     
     
         13 . The method of  claim 9 , wherein receiving the orthogonal frequency division multiplexing waveform at the multipoint-to-point host unit further comprises receiving a plurality of tones from one of the plurality of remote units.  
     
     
         14 . The method of  claim 9 , further comprising adjusting each of the plurality of remote units to achieve alignment of carrier frequencies within a predefined margin at the host unit of any upstream transmissions by the plurality of remote units.  
     
     
         15 . The method of  claim 9 , further comprising: 
 analyzing a signal from the at least one of the plurality of remote units;    generating an adjustment command at the multipoint-to-point host unit for adjusting the carrier frequency of the at least one of the plurality of remote units; and transmitting the adjustment command to the at least one of the plurality of remote units for use in adjusting the carrier frequency at the at least one of the plurality of remote units.