Linear precoding in W-CDMA systems based on S-CPICH channel estimation

In this article we analyze the impact of channel estimation by means of the secondary common pilot channel (S-CPICH) on linear preceding in W-CDMA systems. The pilot sequences on the S-CPICH are transmitted over a fixed grid of beams, causing a systematic channel estimation error at the receiver. Consequently, the adapted rake receiver coefficients will be corrupted due to the use of the S-CPICH, which will lead to an incoherent superposition of the signal components when conventional adaptive space time precoders are employed. Assuming partial channel state information (CSI) at the transmitter we show how the effect of S-CPICH based channel estimation can be reduced or even removed, resulting in an enhanced system performance.