Date Added: May 2012
In this paper, transmission over multi-access fading channels under QoS constraints is studied in the low power regime. QoS constraints are imposed as limitations on the buffer violation probability. The effective capacity, which characterizes the maximum constant arrival rates in the presence of such statistical QoS constraints, is employed as the performance metric. The minimum received bit energy levels and wideband slope regions are characterized for different transmission and reception strategies, namely Time-Division Multiple-Access (TDMA), superposition coding with fixed decoding order, and superposition coding with variable decoding order.