SINR and Delay Analyses in Two-Way Full-Duplex SWIPT-Enabled Relaying Systems

We first investigate the accumulated loopback self-interference (ALSI) under amplify-and-forward (AF) protocol in two-way full-duplex (TWFD) relaying systems with simultaneous wireless information and power transfer (SWIPT). We analyze how SWIPT affects ALSI and establish the condition for ALSI to converge when there is no energy buffer. Unlike ALSI in TWFD relaying without SWIPT (Chang et al. , 2019), ALSI in TWFD relaying with SWIPT always converges and does not grow unbounded. In addition, we study the delay performance in such a system under AF and decode-and-forward (DF) protocols. In AF protocol, the condition for successful signal transmissions is provided. When that condition is met, the received signals at the relay can always get through the channels but experience delays. Otherwise, the outage event occurs. In DF protocol, the best-effort scenario (having no energy buffer) and the QoS scenario (having energy buffer) are discussed. The probability of successful transmissions and the distribution of the delay in both scenarios are derived. Simulation results of DF protocol show that the best-effort scenario is suitable for the delay-tolerant service and the QoS scenario is suitable for the delay-sensitive service. Furthermore, AF protocol is more suitable for the service with less QoS demanding.