N-Rth dual best relays opportunistic cooperation schemes and performance analyses over nakagami-m fading channels

To overcome the performance loss caused by the Nth single best relay selection schemes, in this study, the authors present the N-Rth dual best relays selection schemes. In the proposed schemes, there are two relays selected out of the available relays to forward the received signals to the destination by using the decode-and-forward protocol. The statistical descriptions of instantaneous end-to-end received signal-to-noise ratios (SNR) are investigated over independent and non-identically distributed Nakagami-m fading channels. By using the appropriate mathematical proof, the authors firstly obtain the closed-form expressions to the probability density function and cumulative distribution function of instantaneous end-to-end SNR. Then, based on the derived results, the outage probability and average symbol error rate (SER) of the proposed N-Rth dual best relays selection schemes are investigated. The comparison analyses between the Nth schemes and the N-Rth schemes show that the proposed N-Rth dual best relays selection schemes can improve greatly the performance of opportunistic relaying systems such as outage probability and average SER. Especially, the proposed dual best relays selection scheme can obtain more outstanding improvement on SER.