Analysis of opportunistic two-path successive relaying in consideration of inter-relay interference

Two-path successive relaying (TPSR) improves spectral efficiency of relay under half-duplex constraint. However, when the relay pair is operating in non-orthogonal channels, the capacity of TPSR can be severely degraded by inter-relay interference (IRI). Relay selection has been proposed in the existing literature to mitigate the IRI. However, existing opportunistic TPSR (OSR) schemes limit the pool of potential relay pair choices. Eventually, the performance of existing OSR schemes is underestimated. This study proposes four OSR schemes to improve the achievable performance of OSR schemes in terms of ergodic capacity and outage probability. The proposed schemes select a pair of relays jointly from the N potential relays. This increases the pool of potential relay pairs quadratically. Acknowledging the fact that OSR is only good for certain operating conditions, adaptive schemes that dynamically switches between OSR and opportunistic half-duplex relaying (OHR) are proposed. The simulation results show that the proposed schemes outperform the existing OSR, OHR and full-duplex relaying schemes significantly. The asymptotic ergodic capacity analysis of the proposed schemes increases logarithmically with the quadratic of N. The diversity and multiplexing tradeoff analysis reveals that the proposed schemes achieve the full diversity and multiplexing gain given a large number of potential relays.