Distributed Cochannel Control in Cellular Radio Systems Interference

Optimum transmitter power control schemes to minimize the outage probability due to cochannel interference have been investigated in (SI, (a. The main drawback of the previously proposed algorithms is that they would require reliable measurements of the gains in all radio paths in the system. In this paper, distributed power control algorithms that use only the signal-to-interference (C/I) ratios in those links actually in use, are investigated. An algorithm, that successfully approximates the behavior of the best known algorithms is proposed. The algorithm involves a novel distributed C/I-balancing scheme. Numerical results show that capacity gains in the order of 3-4 times can be reached also with these distributed schemes. Further, the effects of imperfect C/I estimates due to noise, vehicle mobility, and fast multipath fading are considered. Results show that the balancing procedure is very robust to measurement noise, in particular if C/I requirements are low or moderate. However, for required high C/I levels or for a rapidly changing path loss matrix, convergence may be too slow to achieve substantial capacity improvements.