Bandwidth-Efficient Partnering for Cooperative Diversity

This thesis presents two new techniques that enable a pair of cooperating partners (source nodes) to convey their data to a common destination. Both techniques employ bandwidth-efficient coded modulation and integrate relayinginto channel coding. The first technique is a form of bit-interleaved coded modulation (BICM) usinglow-density parity check (LDPC) codes. The signal labeling is based on set partitioning (SP), and is carried out in such a way that each partner's knowledge of the relayed data enables it to decode the other partner's data from a sparser subset of the original constellation, thereby enhancing the robustness of the partner-to-partner link. The second technique is a form of trellis coded modulation (TCM), in which 'local' and 'relayed' data are multiplexed together prior to encoding. The receiving partner employs trellis-pruning (TP), i.e., its knowledge of the relayed data helps to 'prune' the inappropriate edges from the code trellis, so the partner-to-partner link is enhanced. Moreover, the destination node also benefits from either SP (in the first technique) or TP (in the second technique) with high probability. Simulation results show that both of these approaches offer performance gain about 1.5 to 3 dB (at a frame error rate of 10^(-2)) over the conventional decode-and-forward time-sharing system in which local and relayed data are transmitted orthogonally.