Coherent Signaling for Full-Duplex Relay Channel With Self-Interference

To improve the spectral efficiency (SE), coherent signaling is investigated for full-duplex relay channel (FDRC) in the presence of residual self-interference. First, we propose a novel coherent amplify-forward scheme and derive the SE achieved by both forward decoding and backward decoding. Condition on selecting forward/backward decoding is clearly given. Then, we elaborate the signal design for coherent decode-forward scheme and derive the optimal correlation coefficient for signaling. The optimal relay power that maximizes the SE is obtained in the closed form. Representative numerical results show that coherent signaling brings significant SE gain for FDRC.