On the Role of Estimate-and-Forward with Time-Sharing in Cooperative Communications

In this work we focus on the general relay channel. We investigate the application of estimate-and-forward (EAF) to different scenarios. Specifically, we consider assignments of the auxiliary random variables that always satisfy the feasibility constraints. We first consider the multiple relay channel and obtain an achievable rate without decoding at the relays. We demonstrate the benefits of this result via an explicit discrete memoryless multiple relay scenario where multi-relay EAF is superior to multi-relay decode-and-forward (DAF). We then consider the Gaussian relay channel with coded modulation, where we show that a three-level quantization outperforms the Gaussian quantization commonly used to evaluate the achievable rates in this scenario. Finally we consider the cooperative general broadcast scenario with a multi-step conference. We apply estimate-and-forward to obtain a general multi-step achievable rate region. We then give an explicit assignment of the auxiliary random variables, and use this result to obtain an explicit expression for the single common message broadcast scenario with a two-step conference.