Estimate-and-forward relaying for the Gaussian relay channel with coded modulation

In this work we consider the Gaussian relay channel with coded modulation at the transmitter and an orthogonal relay-destination link We investigate the application of the estimate-and-forward (EAF) scheme with different mappings at the relay to this scenario. We show that in certain situations a three-level quantization outperforms the Gaussian mapping, which is the common practice in this scenario. We conclude that for the coded modulation scenario Gaussian quantization is good at low source-relay SNR, decode-and-forward is superior at high source-relay SNR and at intermediate SNR, methods that combine elements of both schemes are superior to these individual assignments. Another observation is that as the source-relay SNR increases, the cardinality of the auxiliary random variable can be decreased.