A multi-hop bidirectional relay selection scheme based on Viterbi algorithm

In this paper, we propose a low-complexity multihop bidirectional relay selection (RS) scheme to enable simultaneous information exchange between two sources. The proposed RS scheme draws on the analogy between the node distribution of the general multi-hop bidirectional relay network model and the trellis of a convolutional code, and applies the Viterbi algorithm in selecting a path to minimize the sum outage probability of two sources. Specifically, the multi-hop bidirectional relay network model is first mapped to a convolutional code trellis. The branch metric in the trellis is defined as the instantaneous SNR of the channel connecting two relays in two adjacent clusters. Therefore, the path metric, which is defined as the minimum of all the branch metrics along the path, approximately equals the equivalent SNR of the multi-hop bidirectional path. Then, the sliding window Viterbi algorithm is applied to select a path between two sources. Simulation results show that the proposed multi-hop bidirectional RS scheme achieves almost the same outage probability as the optimal multi-hop bidirectional RS scheme when the window size is sufficiently large.