Robust power control of CDMA cellular radio systems with time-varying delays

Power control is an important factor to increase communication link quality and system capacity in the direct-sequence code-division multiple access (DS-CDMA) cellular radio systems. The Smith prediction filter can achieve the unbiased asymptotic tracking about a desired target signal to interference noise ratio (SINR) under the fixed round-trip delay. However, it is sensitive to the variation of round-trip delay. In order to track the desired SINR with the time-varying round-trip delay, a multiple-mode Smith prediction filter, which combines the multiple Smith predictors with a likelihood function, is proposed for the power control of CDMA systems. The proposed scheme can compensate for the unknown time-varying round-trip delay. Simulation results show that the performance of the proposed multiple-mode power control method is robust to time-varying round-trip delay in the CDMA cellular radio systems.