Design And Analysis On Relay Selection Scheme In Cooperative Communication

As an extension to multi-antenna technology, cooperative communication system has become a hot topic in the field of communication studies, which is expected to be one of the key technologies for improving spectrum utilization in the future mobile communications systems. The core idea of cooperative communication is to take advantage of the collaboration among a plurality of nodes in a wireless network system, in order to achieve a shared transmission path, thereby improving the throughput of the entire wireless network.The major efforts of this dissertation are focused on the relay technology of cooperative communication.It compares and analyzes several cooperative diversity protocols. Makes a detailed analysis and numerical simulation of their outage probabilities. The simulation analysis shows decode forwards protocol is more suitable for large number of relays than amplify and forward protocol. Coded cooperation protocol is even better since it can utilize the bandwidth effectively.It studies the impact of using outdated channel state information for opportunistic relay selection scheme over independent and identically distributed(IID) Rayleigh fading channels. Derives a closed form expression for the exact outage probability and makes simulation analysis for the scheme. The simulation analysis shows a serious decline in performance of the opportunity relay selection scheme when using outdated channel state information. The diversity of the system reduced to two regardless of the number of relays whereas full diversity is achieved for ideal CSI.It studies the effect of co-channel interference in the opportunity relay scheme under Rayleigh fading channels and a opportunity relay selection criterion with a signal-to-interference-plus-noise ratio(SINR)-based is proposed. The criterion defines the equivalent end-to-end SINR of the system as the minimum instantaneous SINR between the instantaneous SINR from source to relay and the instantaneous SINR from relay to destination It selects the relay which has the max end to end SINR as the best relay. It provides the outage probability of the SINR-based selection criterion and compare with the opportunity relay selection scheme with a SNR-based selection criterion. It derives the coding gains of both criteria over independent but not necessarily identically distributed(INID) Rayleigh fading channels and independent and identically distributed(IID) Rayleigh fading channels. The simulation analysis shows that the SNR-based opportunity relay selection scheme is more vulnerable to the interference at the relays than the interference at the destination and the SINR-based opportunity relay selection scheme is better which gains more benefits when more relays are used.