Hybrid Adaptive Channel Estimation in WCDMA Downlink Systems

Abstract

The receiver performance of DS-CDMA systems is significantly affected by the accuracy of channel estimate. In WCDMA downlink systems, the channel information can be estimated using a common pilot channel (CPICH). Since this pilot signal is transmitted to all users in the cell with constant power, we consider the improvement of channel estimate by additionally using power-controlled data signal in the dedicated physical channel (DPCH). Since decision errors are unavoidable in the DPCH decoding process, we combine the channel estimate from the CPICH and DPCH, considering the DPCH data decision error. For further improvement of channel estimate, we also employ an adaptive channel estimation filter (CEF). Numerical results show that the proposed channel estimator outperforms the conventional pilot channel aided estimator, particularly when the channel condition becomes worse