Power control in fading broadcast channels with random arrivals and QoS constraints

Throughput regions of fading broadcast channels with random data arrivals in the presence of quality-of-service (QoS) requirements is studied when power control is employed at the transmitter. Two source models with random arrivals, namely discrete Markov source and Markov fluid source, are considered. It is assumed that superposition coding with power control is performed at the transmitter with interference cancellation at the receivers. By utilizing the effective capacity of time-varying wireless transmission channels and effective bandwidth of random arrivals, the maximum average arrival rates that can be supported in the fading broadcast channel with QoS guarantees are identified and the throughput is characterized. Optimal power control policies that maximize the weighted combination of the average arrival rates are investigated in the two-user case. In particular, optimality conditions are determined and an algorithm for optimal power control is proposed for different source arrival models. Impact of source burstiness, power adaptation, the use of different transmission strategies (e.g., superposition coding and time-division multiplexing) on the throughput regions and sum-rates are investigated.