Pilot diversity channel estimation in power controlled CDMA systems

In this paper, we consider a channel estimator in CDMA systems, where there exist both common pilot channel (CPICH) symbols, which is not power controlled signal, and the dedicated pilot symbols, which is power-controlled. Our proposed channel estimator estimates the channel by combining the CPICH symbols and dedicated pilot symbols. We derive the maximal likelihood (ML) estimator and present the approximate ML, which can be readily used for fast and accurate on-line channel estimation. We also derive the Cramer-Rao lower bound (CRLB) of the proposed method and compare it with the CRLB of the method using the common pilot channel symbols only. End-to-end full downlink SPW simulations have been run and we confirm that the significant gain can be achieved with a proposed estimator in a power-controlled CDMA system. The resulting algorithms can be applied to open loop and closed loop transmit diversity cases as well as single antenna case.