A Hop-by-Hop Relay Selection Strategy in Multi-Hop Cognitive Relay Networks

In this paper, a hop-by-hop relay selection strategy for multi-hop underlay cognitive relay networks (CRNs) is proposed. In each stage, relays that successfully decode the message from previous hop form a decoding set. Taking both maximum transmit power and maximum interference constraints into consideration, the relay in the decoding set which has the largest number of channels with an acceptable signal-to-noise ratio (SNR) level to the relays in the next stage is selected for retransmission. Therefore, relay selection in each stage only relies on channel state information (CSI) of the channels in that stage and does not require the CSI of any other stage. We analyze the performance of the proposed strategy in terms of endto-end outage probability and throughput, and show that the results match those obtained from simulation closely. Moreover, we derive the asymptotic end-to-end outage probability of the proposed strategy when there is no upper bound on transmitters’ power. We compare this strategy to other hop-by-hop strategies that have appeared recently in the literature and show that this strategy has the best performance in terms of outage probability and throughput. Finally it is shown that the outage probability and throughput of the proposed strategy are very close to that of exhaustive strategy which provides a lower bound for outage probability and an upper bound for throughput of all path selection strategies

Performance analysis of a hop-by-hop relay selection strategy in multi-hop networks

We propose and analyze a hop-by-hop relay selection strategy for multi-hop decode-and-forward (DF) cooperative relay networks. In this method, relay selection in each stage is based on the channel state information (CSI) to the relays in the following stage. More specifically, in each stage, relays that successfully receive and decode the message from the previous hop form the candidate set for relaying, and the best relay in this set is selected for retransmission to the next hop. As such, a central controller (CC) for the entire relay network is not required and this strategy can be implemented in a distributed manner. We analyze the performance of this method in terms of end-to-end outage probability and ergodic and effective ergodic capacities. Numerical results from analysis are shown to closely match those obtained from simulation. We also compare our results to those from existing relay selection strategies in the cases of perfect and imperfect CSI and demonstrate the advantages of the proposed method