Cognitive Multi-User Multi-Relay Network: A Decentralized Scheduling Technique

To achieve a trade-off between the implementation complexity and reliability, in this work we develop a novel decentralized scheduling technique for the cognitive multi-user multi-relay network which operates on an incremental relaying mechanism. Considering asymmetric fading channels, the outage probability of the secondary network is derived under the proposed technique for both of the decode-and-forward (DF) and amplify-and-forward (AF) strategies. Monte-Carlo simulation comparisons between the proposed technique and benchmark schemes namely, two-stage with partial relay selection (TSWPRS) and two-stage with opportunistic relay selection (TSWORS) techniques, reveal that the geographical configuration of the network primarily defines the outage behavior of different scheduling techniques. In this regard, the proposed decentralized technique provides an acceptable outage performance for the realistic configurations, i.e., the relay links being stronger than the direct links. Findings demonstrate that the proposed technique under DF relaying strategy markedly outperforms the AF counterpart and therefore it is the preferable choice. Interestingly, the proposed technique under the DF strategy would outperform the TSWORS techniques if there are more users than relays which is impressive due to its lower complexity and relay activation rate. Moreover, the theoretical and Monte-Carlo results coincide in the provided examples which corroborates correctness of the theoretical analysis.