Practical Turbo Receiver Design for Throughput-Efficient Relay ARQ Transmissions over Broadband Cooperative MIMO Channels

In this paper, we investigate practical turbo receiver design for throughput-efficient relay ARQ transmissions over broadband cooperative MIMO channels. Our setup is comprised of three multi-antenna nodes: a source, a destination, and a relay node operating under the amplify-and-forward half-duplex relaying mode. To attain higher system average throughput, we adopt a two-slot transmission strategy where the ARQ mechanism is activated on top of the amplify-and-forward protocol. We derive a soft subpacket combiner allowing the destination node to jointly perform subpacket combining (over both time slots and multiple ARQ rounds) and frequency domain MMSE filtering. Its computational load is then smoothly relaxed via a recursive implementation alleviating the memory requirements when the number of ARQ rounds increases. Simulation results show that the proposed transmission strategy along with turbo reception at the destination side achieves significant average throughput performance gain compared with conventional ARQ-based cooperative relaying.