Date Added: Feb 2012
In this paper, the authors consider the half-duplex Cooperative Multiple-Access Channel (CMAC) with frequency-selective block-fading. Each link employs an Orthogonal Frequency Division Multiplexing (OFDM) system, where modulated symbols are drawn from a finite constellation set. They first obtain the diversity order of the CMAC, as a function of the time sharing variables of the users and the rates of the codes. To achieve this rate-diversity tradeoff, they use the principle of network coding where messages of the two sources are jointly encoded. Both separate and joint network-channel coding approaches are considered. Specifically, they design multiple turbo codes that minimize the outage probabilities of these approaches.