Characteristics of closed loop power control algorithms for a cellular DS/CDMA system.

The authors consider the performance of a reverse link DS/CDMA system with fast closed loop power control algorithms. For power control purposes, the received signal-to-interference ratio (SIR) must be measured. A simple proc edure is proposed for estimating received SIR which does not need much cali bration. The result shows that the BER performance is sensitive to the feed back delay or the inverse of the power control updating frequency. The powe r control mechanism is effective provided that the power control command up dating frequency is ten times higher than the Doppler frequency. A step-siz e of 2 dB for the single step-size power control algorithm is found to be o ptimal for the mobile unit's velocity, which is uniformly distributed in th e range 0-100 km/h. It was also found that the BER performance is very sens itive to the power control command channel error rate in the range 10(-1)-1 0(-2) This suggests that the system designer should concentrate on minimisi ng this error to improve the overall performance. Lastly, if a multiple ste p-size power control algorithm is to be implemented, two power control comm and bits would perform better than one, three, or more bits in a mobile cha nnel environment.