A rotate-forward relaying protocol for relay node with own broadcasting information

A rotate-forward (RF) relaying protocol is proposed when relay node has its own information to broadcast. In RF protocol, the source node with two transmitter antennas transmits its signals in a way as Alamouti space-time code, and the relay node rotates the received signals using its own transmission bits and forwards them to the destination node, where the transmitted signals in source are selected from the recently-proposed uniquely factorable constellation pairs. Without loss of generality, we assume both relay node and destination node are equipped with one antenna. A modified maximum likelihood (ML) decoder can be used to decode the source signal and the relay signal. For reducing the complexity, a hard-decision-based zero forcing algorithm is also proposed to realize the ML detection. Without any requirements for extra channel resources, the proposed protocol has great potentials when the source node broadcasts to lots of destination nodes and the relay node also has its own information to broadcast.