On Optimal Control of Wireless Networks with Multiuser Detection, Hybrid ARQ and Distortion Constraints

We present a novel optimization framework based on stochastic control and Markov theory for wireless networks where users concurrently access the channel and implement retransmission-based error control. In order to let users transmit at the same time, we consider an interference mitigation, rather than a collision avoidance approach. Our focus is on the interaction between the stochastic processes modeling the various individual sources of the network. Due to retransmissions, transmission by a user does not only instantaneously interfere with other simultaneous communications, but also biases the future evolution of the stochastic processes describing the other users. We, thus, define a novel interference measure called process distortion, that takes this effect into account. We investigate the optimization of access and power control for a network with two groups of users where transmission by the second group is constrained by the process distortion generated to the first group. We present algorithms to solve the unconstrained and constrained infinite horizon average cost per stage problems modeling this scenario. We discuss in detail the application of this framework to cognitive networks.