Decode-and-forward relaying in cellular systems: Performance analysis and optimum power allocation

This paper considers a downlink cellular system with decode-and-forward (DF) protocol. The multiple-antenna base station uses maximum-ratio transmission to communicate with the single-antenna mobile station (MS) through direct link and a DF relay station, and the MS utilizes maximum-ratio combining to deal with the received signal. Our interest herein lies in performance analysis for this practical cellular system. We derive exact expressions for the outage probability and the symbol error rate (SER) in closed-form. Moreover, a simple asymptotic approximation and a tight lower bound are presented for the outage probability and the SER respectively, based on which we propose two optimum power allocation schemes as well. Simulation results are provided to validate the theoretical analysis.