Optimum pilot-to-data power ratio for partial RAKE receiver in Nakagami-m 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 two types of power delay profile (PDP): uniform and exponential PDPs. The optimum PDR is derived via minimizing the upper bound of the probability of bit error. A closed-form expression for the optimum PDR is obtained for both CDM and TDM schemes with uniform PDP. For exponential PDP, we derive the condition satisfied by the optimum PDR and obtain it numerically. It is observed that the optimum PDR is noticeably affected by the decay factor, but not by the m-parameter. For exponential PDP, unlike for uniform PDP, the optimum PDR depends on the number of combined paths. We also show that the optimum PDR derived from the block-fading channel model performs favorably in the Jakes´ model.