Distributed power control with multiuser detection for asynchronous DS-CDMA networks subject to time-delays

Abstract

If transmission power is increased in a direct-sequence code-division multiple-access network, interference increases, thus reducing network capacity. In this paper, we address these opposite goals of reducing transmission power and increased network capacity by jointly considering power control and multiuser detection. Since propagation delay occurs inevitably during data communication, we present an analysis by considering also that the interference measurement is not available at the transmitter instantaneously but with some time-delay, something that is generally neglected in the literature. This framework is used to investigate the design of a distributed power control strategy enhanced with linear multiuser receivers in an asynchronous uplink channel, subject to multipath and quality of service constraints. Thus, a cross-layer solution that combines a Linear-Quadratic-Gaussian power control scheme with a linear multiuser receiver is proposed to compensate for the round-trip delay and the time-varying channel characteristics in the communication link. Simulation results are used to show the advantages of such scheme in terms of saving energy, increasing network capacity and robustness against propagation delays.