Layered Multiplexed-Coded Relaying: Design and Experimental Evaluation

We consider layered decode-forward (DF) cooperation in a relay-aided wireless multicast network. Splitting the source-message into two equal layers, we provide unequal power allocation to the individual layers through a simple mapping operation on a QAM constellation. The layering process thus allows the destinations to partially recover the message from the source's transmissions. At the relay, we propose a multiplexed-coded approach that, with a single transmission, caters for the disparity in the number of layers decoded at different destinations. In addition to simulations, we validate the performance gains of the proposed strategy through a system-level implementation using software-defined radios. Catering for real- world factors such as carrier and timing synchronization, we conduct over-the-air experiments in an indoor office environment and find that the proposed scheme can achieve a frame- error-rate that is 25% of that with conventional two-hop DF relaying.