Patent ID: 7035354
Filing Date: 2006-04-25
Classification: H04L

Abstract:
1. A method for multi-user detection, comprising: receiving a complex input signal due to a superposition of waveforms encoding symbols in a real-valued constellation, which are transmitted respectively by a plurality of transmitters in a common frequency band; sampling the complex input signal at sampling intervals over the duration of an observation period to provide a sequence of complex samples; processing the sequence of complex samples to determine soft decision values corresponding to the symbols transmitted by the plurality of the transmitters in the observation period, while constraining the soft decision values to be real values; and projecting the soft decision values onto the constellation to estimate the transmitted symbols, wherein processing the sequence of complex samples comprises partitioning the samples into real and imaginary parts, and processing the real and imaginary parts separately to determine the soft decision values, and wherein the real and imaginary parts of the samples are related to the transmitted symbols by an expression having a form {overscore (x)}={overscore (s)}b+{overscore (n)}, wherein {overscore (x)} is a vector comprising real vector elements corresponding separately to the real and imaginary parts of the samples, b is a vector comprising real vector elements corresponding to the values of the symbols, {overscore (S)} is a matrix comprising columns corresponding to respective complex signatures of the plurality of the transmitters, the columns comprising real entries corresponding separately to the real and imaginary parts of the signatures, and {overscore (n)} is a vector comprising real vector elements corresponding separately to real and imaginary noise components in the samples, and wherein processing the sequence of complex samples comprises inverting the expression to determine the soft decision values of the elements of b.