Path search performance and its parameter optimization of pilot symbol-assisted coherent rake receiver for W-CDMA mobile radio

In DS-CDMA (including W-CDMA), a received signal can be resolved into multiple paths to be Rake combined. An important design problem of the Rake receiver is how to accurately search the paths with a sufficiently large signal-tointerference plus background noise power ratio (SIR). This paper investigates the performance of a coherent Rake receiver using pilot symbol-assisted channel estimation with fast transmit power control, and thereby optimizes three key parameters: the total averaging period, Targ, consisting of a combination of coherent summation and power summation; each period of the summations for measuring the average power delay profile; and pathselection threshold M from the generated power delay profile. We used a path search algorithm, which searches the paths that have A/ times greater average signal power than the interference plus background noise power measured in the average power delay profile generated using time-multiplexed pilot symbols. It was clarified by both simulation and laboratory experiments that when A/ = 4, Tal-g = 50-100 msec, and the number of slots for coherent accumulation R = 2, the required average transmit E(,/No for obtaining the average DER of 10~3 is almost minimized with and without antenna diversity for both ITU-R Vehicular-B and average equal power L-path delay profile model, in which each path suffered independent Rayleigh fading. The paper also shows that based on the field experiments, the path search algorithm with optimized path-selection parameters is robust against actual dynamic changes in the power delay profile shape.