Improved Opportunistic Multipath Transmission for Bandwidth-Efficient Cooperative Communications

This paper presents an improved version of the opportunistic multipath (OM) proposed by Ribeiro et al. for cooperative communications. First, we generalize the OM scheme by using two groups of relays instead of using two relays for a source, so that inter-relay diversity can be achieved during the transmission between the two groups. Then, we propose a signal retransmission scheme for the relays based on the generalized OM (GOM) approach, where a relay in one group that fails to decode a symbol received from the source at the nth time slot can re-decode the symbol received from relays in the other group at the (n+2)th time slot and retransmit the correctly decoded symbol to the destination at the (n+3)th time slot. The proposed retransmission strategy retains the same data rate with only one time slot delayed to recover all the symbols, as compared with the original OM scheme. Computer simulation results show that both the proposed schemes effectively improve the system performance and that the retransmission strategy achieves better performance than the GOM scheme over poor channel links between one relay group and the destination.