System for multi-frame alignment

Abstract

A bidirectional communication system is provided. In one embodiment, a system comprises a host; and a plurality of remote units, wherein a plurality of tones is shared among the plurality of remote units in order to communicate with the host using orthogonal frequency division multiplexing, wherein the plurality of tones is shared in a manner that permits at least two of the remote units to transmit to the host at any one time using the plurality of tones. The host causes at least one remote unit to adjust a timing of symbols transmitted on at least one of the plurality of orthogonal tones in order to improve an alignment of multiframes received at the host.

1 . A system comprising: 
 a host; and    a plurality of remote units, wherein a plurality of tones is shared among the plurality of remote units in order to communicate with the host using orthogonal frequency division multiplexing, wherein the plurality of tones is shared in a manner that permits at least two of the remote units to transmit to the host at any one time using the plurality of tones; and    wherein the host causes at least one remote unit to adjust a timing of symbols transmitted on at least one of the plurality of orthogonal tones in order to improve an alignment of multiframes received at the host.    
     
     
         2 . The system of  claim 1 , wherein the host causes the at least one remote unit to adjust the timing of symbols transmitted on the at least one of the plurality of tones in order to align symbols of a first frame of the multiframes when received at the host.  
     
     
         3 . The system of  claim 1 , wherein the host generates information indicative of a transmission adjustment for the at least one remote unit and communicates 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 multiframes when received at the host.  
     
     
         4 . The system of  claim 1 , wherein the host generates information indicative of a transmission adjustment for the at least one remote unit and communicates the information to the at least one remote unit; and 
 wherein the at least one remote unit adjusts a phase of a superframe clock signal based on the information.    
     
     
         5 . The system of  claim 1 , wherein the host communicates a command to the at least one remote unit, wherein the at least one remote unit adjusts the timing of symbols transmitted therefrom in response to the command.  
     
     
         6 . The system of  claim 1 , wherein the host causes the at least one remote unit to adjust at least one of a carrier amplitude and a carrier frequency.  
     
     
         7 . The system of  claim 1 , wherein the system is used in a wireless network.  
     
     
         8 . A system comprising: 
 a host; and    a plurality of remote units;    wherein the host receives a plurality of upstream frames transmitted from the remote units on a plurality of tones using orthogonal frequency division multiplexing;    wherein a timing error for at least one remote unit is determined by the host; and    wherein at least one remote unit adjusts the manner in which symbols are transmitted therefrom based on the timing error to improve an alignment of a grouping of frames received at the host.    
     
     
         9 . The system of  claim 8 , wherein the grouping of frames is a multiframe.  
     
     
         10 . The system of  claim 8 , wherein the at least one remote adjusts the manner in which symbols are transmitted therefrom in response to a timing adjustment command sent to the at least one remote, wherein the timing adjustment command is related to the timing error.  
     
     
         11 . The system of  claim 8 , further comprising a distribution network coupled between the host and the plurality of remote units.  
     
     
         12 . The system of  claim 11 , wherein the distribution network comprises a wireless system.  
     
     
         13 . A host unit, comprising: 
 a multipoint-to-point modem providing multiple access for a plurality of remote units using an orthogonal frequency division multiplexing (OFDM) waveform;    wherein the multipoint-to-point modem performs a fast fourier transform to demodulate signals from a plurality of tones in the OFDM waveform; and    wherein the multipoint-to-point modem generates at least one command for at least one of the plurality of remote units to adjust a timing of symbols transmitted from the at least one of the plurality of remote units to the host unit to improve an alignment of multiframes received at the host unit.    
     
     
         14 . The system of  claim 13 , wherein the host generates the at least one command based on an alignment of symbols of a first frame of the multiframes received at the host.  
     
     
         15 . The host unit of  claim 13 , wherein the multipoint-to-point modem generates a timing delay adjustment for the at least one remote unit.  
     
     
         16 . The host unit of  claim 13 , wherein the multipoint-to-point modem generates the at least one command based on a signal received from the at least one of the plurality of remote units.  
     
     
         17 . The host unit of  claim 13 , wherein the host unit communicates over a distribution network with the plurality of remote units.  
     
     
         18 . The host unit of  claim 13 , wherein the host unit communicates over a wireless system with the plurality of remote units.  
     
     
         19 . The system of  claim 13 , wherein the host generates the at least one command based on an alignment of symbols of a first frame of the multiframes received at the host.