Method and apparatus for ifdma receiver architecture

Abstract

A method and receiver for processing a composite signal in a wireless communication system is provided. The method includes receiving a composite signal within a channel bandwidth, wherein the composite signal comprises one or more symbol streams from a plurality of communication units. The method also includes sampling the composite signal at a sampling rate, wherein the sampling rate comprises one of equal to a symbol rate of the composite signal or larger than the symbol rate of the composite signal. In addition, the method includes selecting a symbol sampling phase for each of the symbol streams from a plurality of communication units. The symbol streams from each of the communication units are aligned to produce an aligned composite signal by separating the symbol streams for each of the plurality of communication units and orthogonal recombining the symbol streams for each of the plurality of communication units based on the selected symbol sampling phase for each of the plurality of signals. The symbol streams are also separated based on the aligned composite signal.

What is claimed is: 
     
         1 . A method comprising:
 receiving a composite signal within a channel bandwidth, wherein the composite signal comprises one or more symbol streams from a plurality of communication units;   sampling the composite signal at a sampling rate, wherein the sampling rate is equal to or larger than a symbol rate of the composite signal;   selecting a composite signal sampling phase for the composite signal;   determining a channel estimate of the one or more symbol streams of the signal for at least a subset of the plurality of communication units at the selected sampling phase; and   separating the one or more symbol streams from each of the communication units in the at least subset of the plurality of communication units based on one or more of the composite signal, the channel estimates, differing frequency components for the one or more communication units, the selected sampling phase for the composite signal and equalizing the signals of the composite signal using the channel estimates.   
     
     
         2 . The method of  claim 1 , wherein selecting the composite signal sampling phase further comprises selecting the composite signal sampling phase based on at least one of a channel estimate, a channel signal to noise ratio (SNR), a channel Signal to Interference-plus-Noise Ratio (SINR), and a channel link quality metric estimate. 
     
     
         3 . The method of  claim 1 , wherein selecting the composite signal sampling phase comprises selecting a pre-determined sampling phase. 
     
     
         4 . The method of  claim 1 , wherein equalizing comprises performing one or more of a frequency domain equalization, time-domain equalization, decision feedback equalization, iterative equalization, inter-symbol interference (ISI) cancellation, turbo equalization and maximum likelihood sequence estimation. 
     
     
         5 . The method of  claim 1 , wherein separating the one or more symbol streams further comprises separating, after detecting the one or more symbol streams in a frequency-domain using a communication unit-specific repetition factor and a modulation code. 
     
     
         6 . The method of  claim 1 , wherein separating the one or more symbol streams further comprises using a communication unit-specific subcarrier mapping and DFT size. 
     
     
         7 . The method of  claim 1  further comprising generating channel state information, generating log-likelihood ratios for the one or more symbol streams and decoding the one or more symbol streams. 
     
     
         8 . An apparatus comprising:
 a receiver for receiving a composite signal within a channel bandwidth, wherein the composite signal comprises one or more symbol streams from a plurality of communication units.   a sampler for sampling the composite signal at a sampling rate, wherein the sampling rate is one of equal to a symbol rate of the composite signal or larger than the symbol rate of the composite signal;   a selector for selecting a composite signal sampling phase for the composite signal;   an estimator to determine the channel estimate of one or more symbol streams for one or more of the plurality of communication units at the selected sampling phase for the composite signal;   a separator for separating the one or more symbol streams for one or more the plurality communication units using one or more of the composite signal, the channel estimates, different frequency components from the one or more communication units, selected sampling phase for the composite signal, and   an equalizer for equalizing the one or more symbol streams using the channel estimates.