Distributed power control in wireless communication systems

Energy efficiency is a measure of performance in wireless networks. Therefore, controlling the transmitter power at a given node increases not only battery operating life, but also overall system capacity by successfully admitting new links. It is essential to find effective means of power control in point-to-point, broadcasting and multicasting scenarios. Wireless networking presents formidable challenges and we consider the problem of unicast or point-to-point (peer-to-peer) communication in wireless networks in the presence of other nodes. We study the feasibility of admitting new links in an wireless network operating area while maintaining quality of service (QoS), in terms of signal-to-interference ratio (SIR), for each link. SIR is maintained by adjusting the transmitter power levels at each source for a given link. Distributed power control (DPC) is a natural choice for this purpose because, unlike centralized power control, DPC should be able to adjust the power levels of each transmitted signal using local measurements, so that in a reasonable time, all nodes/links maintain the desired SIR. We present a suite of DPC schemes using both state space and optimal control methodology in discrete-time. Further, we prove the convergence of the overall network with our algorithm using Lyapunov stability analysis in comparison with a well known DPC scheme (see Bambos, N. et al., IEEE ACM Trans. on Networking, p.583-97, 2000). We present simulation results and comparisons for point to point communications in an overlapping scenario.