User Cooperation Schemes in the Soft Handover Regions

This paper examines the effect of relay-assisted soft handover on the performance of the uplink communication in the third generation mobile networks. We focus on users which are traveling over two cell boundaries in a cellular infrastructure and operating over the same frequency band. We consider a scheme in which the relay is requested to cooperate only if the mobile source fails in its soft handover (SHO). In our study, we consider a regenerative relay in which the decision to cooperate is based on a signal-to-noise ratio (SNR) threshold at the base stations, and we consider the effect of the possible erroneously detected and transmitted data at the relay. We derive an expression for the end-to-end bit-error rate (BER) of binary phase-shift keying (BPSK) modulation and look at the optimal strategies which reduce the computational load and minimize the end-to-end BER at the destination for high SNR.