Truncated power control in code-division multiple-access communications

Abstract

We analyze the performance of truncated power control in a code-division multiple-access (CDMA) communication system. This power control scheme compensates for propagation gain above a certain cutoff fade depth: below the cutoff level, data transmission is suspended. We assume a channel with fast Rayleigh fading and slow lognormal shadowing plus path loss, where truncated power control is applied to the shadowing plus path loss and a RAKE receiver combines the Rayleigh fading multipath components separated by more than a chip time. We find that truncated power control exhibits both a power and capacity gain. These performance improvements result from the fact that with truncated power control, less power is wasted compensating for deep fading, and mobiles on the cell boundaries cause less interference to adjacent cells. We find that truncated power control is most effective for channels with large power fluctuations or with large background noise.