Lossless and near-lossless source coding for multiple access networks

A multiple access source code (MASC) is a source code designed for the following network configuration: a pair of correlated information sequences {Xi}/sup (infinity)//sub i=1/ and {YI}/sup (infinity)//sub i=1/ is drawn independent and identically distributed (i.i.d.) according to joint probability mass function (p.m.f.) p(x, y); the encoder for each source operates without knowledge of the other source; the decoder jointly decodes the encoded bit streams from both sources. The work of Slepian and Wolf describes all rates achievable by MASCs of infinite coding dimension (n(longrightarrow)(infinity)) and asymptotically negligible error probabilities (Pe/sup (n)/(longrightarrow) 0). In this paper, we consider the properties of optimal instantaneous MASCs with finite coding dimension (n < (infinity) ) and both lossless (Pe/sup (n)/ = 0) and nearlossless (Pe/sup/ (n)(longrightarrow) 0) performance. The interest in near-lossless codes is inspired by the discontinuity in the limiting rate region at Pe/sup (n)/ = 0 and the resulting performance benefits achievable by using near-lossless MASCs as entropy codes within lossy MASCs. Our central results include generalizations of Huffman and arithmetic codes to the MASC framework for arbitrary p(x, y), n, and Pe/sup (n)/ and polynomial-time design algorithms that approximate these optimal solutions.