Layered Multiplexed-Coded Relaying in Wireless Multicast Using QAM Transmissions

摘要

We propose layered multiplexed-coded decode-and-forward (LMDF) relaying for a wireless multicast network. Splitting the message into two layers, the source encodes them separately and maps them to a quadrature amplitude modulation (QAM) constellation to achieve superposition, thus allowing partial message recovery at the relay and the destinations. The key component of LMDF is multiplexed coding at the relay that enables each destination to divert all channel resources toward decoding the layers that remain unrecoverable from the source’s transmission. We derive information theoretic achievable rates for LMDF and consider network outage as a performance measure. For a setup with 15 users uniformly spread around the relay, simulations indicate that LMDF outperforms conventional unlayered DF by 1.7 dB and superposition coding-based DF by 1.1 dB, while the respective gains in outage rate at individual users are up to 48.6% and 31.4%.