Detection with erasure for error-propagation mitigation in decode-and-forward relaying with general pulse amplitude-modulated/quadrature amplitude-modulated signals

In the research of decode-and-forward (DF) cooperative communications, it is often supposed that the included relay only transmits correctly decoded signals. This simplifies the analysis of DF cooperation. However, in practical circumstances, erroneous messages may be forwarded which makes the decision at the destination even worst. In this study, the authors formulate a special detection way, named `detection with erasure´, to make certain that the relay-forwarded signals are mostly correct. Specifically, whenever the decoded result at the relay falls into some preset `erasure regions´, the relay will not process and transmit it anymore. This effectively prevents the forwarding of erroneous messages. With general pulse amplitude-modulated or squared quadrature amplitude-modulated signals, the authors demonstrate that these erasure regions can be adjusted to minimise the end-to-end symbol error rate (SER). This detection scheme can be extended to be used in the DF cooperation employing multiple relays as well. Simulations reveal that in terms of the end-to-end SER performance, the proposed detection with erasure can outperform some signal-to-noise ratio threshold-based relaying approaches, and can perform quite similarly as compared with those decoding/combining methods realised at the destination with the advantage of less channel state information exchange.