Optimum Pilot-to-Data Power Ratio for Partial RAKE Receiver in Nakagami Fading Channels

In this paper, we study the problem of optimizing the pilot-to-data power ratio (PDR) for uplink code-division multiple access (CDMA) systems with partial RAKE (PRAKE) receivers. Both code-division multiplex (CDM) and time-division multiplex (TDM) reference-assisted schemes are considered. We assume Nakagami-m fading channel with uniform power delay profile (PDP) and that with exponential PDP. We derive the optinum PDR via minimizing the upper bound of the probability of bit error. For uniform PDP, we present a closed-form expression for the optimum PDR. For exponential PDP, we find the condition satisfied by the optimum PDR and obtain it numerically. For exponential PDP, unlike for uniform PDP, the optimum PDR depends on the number of combined paths. However, the effect of the number of combined paths on the optimum PDR is not significant.