Hybrid Demodulate-Forward Relay Protocol for Two-Way Relay Channels

Abstract

Abstract-Two-Way Relay Channel (TWRC) plays an important role in relay networks, and efficient relaying protocols are particularly important for this model. However, existing protocols may not be able to realize the potential of TWRC if the two independent fading channels are not carefully handled. In this paper, a Hybrid DeModulate-Forward (HDMF) protocol is proposed to address such a problem. We first introduce the two basic components of HDMF -direct and differential DMF, and then propose the key decision criterion for HDMF based on the corresponding log-likelihood ratios. We further enhance the protocol so that it can be applied independently from the modulation schemes. Through extensive mathematical analysis, theoretical performance of the proposed protocol is investigated. By comparing with existing protocols, the proposed HDMF has lower error rate. A novel scheduling scheme for the proposed protocol is introduced, which has lower length than the benchmark method. The results also reveal the protocol's potential to improve spectrum efficiency of relay channels with unbalanced bilateral traffic.

Performance analysis for non‐orthogonal multiple access (NOMA)‐based two‐way relay communication

“…This entails expensive radio frequency chains to mitigate the existing coupling effects in the transceiver [27,28]. Furthermore, AF relaying leads to noise amplification during the cooperation process [28][29][30]. Moreover, AF necessitates global CSI acquisition at various terminals, adding to the complexity and communication latency.…”

“…However, while the three-phase protocol has a lower spectral efficiency, the two-phase scheme based on the AF relaying protocol leads to noise amplification at the receivers [28][29][30]. In addition, AF relaying also necessitates global CSI acquisition at the users, adding to the communication latency.…”

“…Although the expression in (28) contains an infinite summation, due to the presence of the factorial term in the denominator, the ergodic capacity expression of user u 2 in (28) can be tightly approximated as…”

Relaying for 5G: A novel low-error relaying protocol

“…The closed form of average symbol error rate can be found in [24] and is neglected in this short paper. Numerical results are provided in the next section.…”