Cooperative diversity via set-partitioning in BICM: Outage analysis and frame interleaving

This paper considers cooperative diversity in the context of bandwidth-efficient modulation. Specifically, it analyzes a scenario in which high-order modulation - 16-QAM is used for illustration - is used in a way that enables two partners to cooperatively convey their data to a common destination. This approach uses set partitioning so that “relayed” data selects a sparse subset while “local” data selects the transmitted symbol from that subset. An outage probability analysis is presented that illustrates the advantage of this technique over the conventional time-sharing approach to cooperative diversity; for 16-QAM, coding gains range from 1.5 dB (for a spectral efficiency of η = 0.5 bits/symbol) to 3.2 dB (for η = 1.5). Then, a variation on this approach - in which codewords are spread out over multiple frames (and multiple channel realizations) - is examined and shown to provide a substantial gain at the cost of delay.