Channel Estimation for DS-CDMA with Transmit Diversity over Frequency Selective Fading Channels

RAKE receivers for DS-CDMA communications over fading channels require the knowledge of instantaneous complex channel phasors for each of the multipath diversity branches (or RAKE fingers). If transmit diversity is employed by using N transmit antennas in the basestation, N such fading channels need to be estimated in the mobile receiver. In this paper, a channel estimation algorithm which estimates two fading channels in the case of dual TX diversity is presented, making use of known pilot symbols. The proposed scheme performs remarkably well in Rayleigh fading multipath environments with little additional complexity if compared to a scheme where only one channel needs to be estimated (i.e. no TX or RX diversity). The performance of the algorithm is assessed by means of computer simulations.