Performance Analysis Of Opportunistic Multi-Antenna Relay Selection In Cooperative Communication Networks

As a hot spot in wireless communication during the recent years, cooperative communication technology serves to mitigate wireless channel impairment, enhance communication reliability and increase transmission rate.According to whether instantaneous Signal-to-Noise Ratio (SNR) or average SNR can be exploited for relay selection, two opportunistic relay schemes, Opportunistic Multi-antenna Relay Selection (OMRS) and Average Best Relay Selection (ABRS) are proposed.Investigation is made upon the outage probability and error performance of OMRS and ABRS under aggregate power constraint in Amplify-and-Forward (AF) cooperative networks over Rayleigh fading channels, assuming are available at the relay node. The optimal relay is chosen based on the source-relay-destination end-to-end instantaneous SNR in OMRS, while ABRS selects relay based on the relay-destination average SNR. Ingonring the direct link between source and destination, the closed form expressions of outage probability of OMRS and ABRS are determined, and the expressions of error performance for binary phase shift keying (BPSK) modulation of OMRS and ABRS are given using the moment generating function (MGF) of the total SNR at the destination. Simulations are provided to verify the correctness of theoretical analysis. Compared with previous single-antenna Opportunistic Relaying (OR) scheme, OMRS brings remarkable performance improvement obtained from maximum ratio combining and beamforming, which proves that multiple antennas at the relays could provide more array gain and diversity order.Investigation is made upon the outage probability and error performance of OMRS and ABRS under aggregate power constraint in Decode-and-Forward (DF) relay networks over independent, non-identical, Nakagami-m fading channels, assuming multiple antennas are available at the relay node. OMRS chooses the optimal relay based on the relay-destination instantaneous Signal-to-Noise Ratio (SNR) from the decoding relay set, while ABRS selects relay based on the relay-destination average SNR from the decoding relay set. Considering the direct link between source and destination, the closed form expressions of outage probability and error performance for BPSK modulation of OMRS and ABRS are determined. It is observed that OMRS is outage-optimal among multi-antenna relay selection schemes and approaches the Beamforming scheme known as theoretical outage-optimal very closely. It also shows that the performance of ABRS in asymmetric channels is close to OMRS in the low and median SNR range.