Performance of two-path successive relaying in the presence of inter-relay interference

Abstract

Half-duplex constraint refers to the inability of a radio to transmit and receive signals simultaneously due to the hardware limitation. In cooperative communication, half duplex constraint requires orthogonal time or frequency channel use between source transmission phase and relay transmission phase. This limits the spectral efficiency of conventional relaying to half of the performance of direct transmission without relay. Two-path successive relaying has been proposed to relax this half-duplex constraint by allowing nonorthogonal transmission, where the source transmits new message continuously in every time slot. In twopath successive relaying, two relays are scheduled to assist the transmission alternately. However, the interrelay interference degrades the performance significantly since the two relays are not operating in orthogonal channel. Majority of the existing literature neglects the inter-relay interference and over estimates the performance of two-path successive relaying. The main objective of this paper is to investigate the actual interference limited performance of two-path successive relaying compared to conventional half-duplex relaying in terms of ergodic capacity. We consider several channel and system conditions to identify the optimal scheme in respective conditions. The results show that the two-path successive relaying is not always optimal if compared to the conventional half-duplex relaying in interference limited scenario.