Performance Analysis and Optimum Power Allocation for Packet Decode-and-Forward Cooperative Relaying System

Despite the very substantial body of research on the performance analysis of cooperative relay systems, most studies focus on either the symbol error ratio (SER) or outage behavior. This paper first analyzes the asymptotic average packet error probability (PEP) of uncoded packet cooperative relay system for DF (Decode-and-Forward) schemes in the high signal-to-noise ratio (SNR) region. In particular, the effect of packet length on optimum power allocation r_opt is studied. It is found, with a symmetrical links assumption, the optimum power allocation ratio is in the region of 1/2<;;r_opt<;;(3-√3)/2 regardless of modulation scheme; and when packet length becomes large enough, the optimum r_opt value converges to (3-√3)/2.