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In automatic retransmission request (ARQ) based systems, L time retransmissions are allowed. The achieved performance of such systems is closely related to the channel dynamics during different retransmissions. In this paper, we present a generalized dynamic channel model which covers both long term, and short term static channel as the special cases. We then analyze the diversity multiplexing trade off (DMT) for ARQ based non cooperative communication and ARQ based opportunistic cooperative communication (OCC) over Nakagami-m channels. The analysis in this paper studies the impact of channel dynamics on the DMT performance for non cooperative and cooperative systems. In the analysis we consider two non cooperative communication systems including random user selection (RUS), and best user selection (BUS). We show that depending on channel dynamic conditions, while all the studied schemes enjoy the time diversity gain, BUS exploits multi-user diversity gain in its DMT performance. Also, DMT performance of OCC is significantly high due to cooperative diversity gain. In particular, we show that for RUS and OCC, as the channel dynamics conditions are changing from long term to short term. The DMT performance is significantly improved until the performance is maximized in the case of short term static channels, however, this DMT behavior is different for BUS. Two retransmission approaches including packet combining (PC) and packet accumulating (PA) are also studied and their impacts on DMT performance are analyzed for cooperative and non-cooperative schemes.
Date of Publication: January 2011