Half-Duplex Estimate-and-Forward Relaying:Bounds and Code Design

Abstract

We propose a coding scheme for half-duplex estimate-and-forward relaying. Our first contribution is to present an achievable rate for the estimate-and-forward protocol. We also derive the achievable rate for the special case of a Gaussian half-duplex relay channel. Guided by the information theoretic coding scheme for the aforementioned achievable rate, we propose a practical coding scheme. The proposed coding scheme incorporates several design choices to reduce receiver complexity without compromising performance. Binary LDPC codes are used in the source broadcast phase. Estimation is performed by scalar quantization of the received signal at the relay. Finally, a procedure similar to maximal ratio combining is used to aggregate direct and relayed signals at the destination. An important practical advantage of our scheme is that it does not require symbol level source-relay synchronization. The codes outperform direct and two-hop channel capacities, as well as decode-and-forward relaying when the relay-destination link is strong.