Improved Power Control Algorithm For TD-SCDMA System

The third generation mobile telecommunication system adopts code division multiple access (CDMA) technology. The CDMA system is an interference-limited system, so all the technologies, which could improve the performance of resisting interference, can enlarge its capacity. In CDMA system, power control technology is one of the key technologies, it not only can overcome the near-far effect, but also can reduce the multiple access interference, in order to enlarge the capacity.Power control technology in TD-SCDMA system is studied in this paper. To overcome the problem, that conventional power control algorithm is not able to track deep fading timely, one new adaptive step-size algorithm for controlling the transmitted power of the mobile station in TD-SCDMA system is presented. The new algorithm is based on the measure of the signal to interference ratio(SIR)being able to eliminate the effect of deep fading and fast fading. It adopts Kalman filtering method to estimate the channel fading, meanwhile introduces a memory unit to record previous power control command, then generates instruction to decide next power control step-size. The simulation results show that the new algorithm has excellent performances in power control when deep fading occuring, the difference between received signal power value and expectation value is decreased, the conditional interrupt probability is reduced, the SIR in system is increased, the emissive power is decreased, the standard deviation of power control error is also reduced.