Power-control problems caused by fast fading in a direct-sequence multiple-access network

When power control is used in a cellular network, the base station attempts to either directly or indirectly track the received power of the desired signal from a mobile. As the fading rate increases, the tracking ability of a direct-sequence code-division multiple-access system deteriorates, and the power-control accuracy declines. It is shown that a large performance degradation occurs when the instantaneous signal level cannot be accurately measured, even when the channel-code interleaving is perfect. An alternative that is assumed by many authors is to measure a long-term-average signal level that averages out the fast fading effects. However it is shown that this approach is less viable than attempting to track the instantaneous signal level even if the latter results in large errors.