Symbol alignment in multipoint-to-point orthogonal frequency division multiplexing communication

Abstract

A method is provided. The method includes sharing upstream bandwidth capacity among a plurality of remote units in a manner that permits at least two of the remote units to transmit to a host at any one time using the upstream bandwidth capacity, the upstream bandwidth capacity comprising a plurality of orthogonal tones generated using inverse fast Fourier transforms, and causing at least one remote unit to adjust the manner in which symbols are transmitted therefrom on at least one of the plurality of orthogonal tones in order to improve the alignment of symbols received at the host.

1 . A method comprising: 
 sharing upstream bandwidth capacity among a plurality of remote units in a manner that permits at least two of the remote units to transmit to a host at any one time using the upstream bandwidth capacity, the upstream bandwidth capacity comprising a plurality of orthogonal tones generated using inverse fast Fourier transforms; and    causing at least one remote unit to adjust the manner in which symbols are transmitted therefrom on at least one of the plurality of orthogonal tones in order to improve the alignment of symbols received at the host.    
     
     
         2 . The method of  claim 1 , wherein the symbols are transmitted from the at least one remote unit as frames, each frame comprising at least one symbol.  
     
     
         3 . The method of  claim 2 , wherein causing the at least one remote unit to adjust the manner in which symbols are transmitted therefrom on the at least one of the plurality of orthogonal tones in order to improve the alignment of symbols received at the host also improves the alignment of frames received at the host.  
     
     
         4 . The method of  claim 1 , further comprising generating information indicative of a transmission adjustment for the at least one remote unit and communicating the information to the at least one remote unit for use by the at least one remote unit in making the transmission adjustment based at least in part on the information in order to improve the alignment of the predetermined groupings of frames when received at the host.  
     
     
         5 . The method of  claim 1 , wherein causing the at least one remote unit to adjust the manner in which symbols are transmitted therefrom on the at least one of the plurality of orthogonal tones in order to improve the alignment of symbols received at the host comprises: 
 determining a phase shift associated with the receipt at the host of a first symbol transmitted from one of the plurality of remote units; and    causing the at least one remote unit to add a delay to the transmission of a second symbol therefrom, wherein the delay is related to the phase shift.    
     
     
         6 . The method of  claim 1 , wherein causing the at least one remote unit to adjust the manner in which symbols are transmitted therefrom comprises communicating a command to the at least one remote unit, wherein the at least one remote unit adjusts the manner in which symbols are transmitted therefrom in response to the command.  
     
     
         7 . The method of  claim 1 , wherein causing the at least one remote unit to adjust the manner in which symbols are transmitted therefrom on the at least one of the plurality of orthogonal tones comprises at least one of adjusting a carrier amplitude and a carrier frequency.  
     
     
         8 . The method of  claim 1 , wherein the method is used in a wireless network.  
     
     
         9 . A method comprising: 
 receiving at a host a plurality of upstream symbols transmitted from a plurality of remote units on a plurality of orthogonal tones using orthogonal frequency division multiplexing;    determining a symbol timing error for at least one remote unit; and    causing the at least one remote unit to adjust the manner in which symbols are transmitted therefrom based on the symbol timing error.    
     
     
         10 . The method of  claim 9 , wherein causing the at least one remote to adjust the manner in which symbols are transmitted therefrom comprises sending a symbol timing adjustment command to the at least one remote unit, wherein the at least one remote adjusts the manner in which symbols are transmitted therefrom based on the symbol timing adjustment command, wherein the symbol timing adjustment command is related to the symbol timing error.  
     
     
         11 . A method for a remote unit of a multi-point to point communication system, the method comprising: 
 modulating one or more tones of an orthogonal frequency division multiplexing waveform with the upstream information based on an inverse Fourier transform algorithm;    transmitting the one or more tones to a multi-point-to-point host unit;    receiving a symbol timing adjustment from the multi-point-to-point host unit; and    delaying transmission of symbols on the one or more tones based on the symbol timing adjustment.    
     
     
         12 . The system of  claim 11 , wherein transmitting the one or more tones to a multi-point-to-point host unit further comprises transmitting the one or more tones over a distribution network comprising a wireless system.