Transmission mode switching for relay/RIS assisted device-to-device communication networks

Reconfigurable intelligent surface (RIS) is now envisioned as a promising strategy to enhance the performance of the traditional device-to-device (D2D) communication system. In this paper, taking the relay strategy into consideration, we propose a new mode selection scheme between three communication modes, including amplify-and-forward (AF) relay-assisted D2D communication mode, decode-and-forward (DF) relay-assisted D2D communication mode and RIS-assisted D2D communication mode, which always selects the mode with maximum achievable rate. The switching thresholds between three modes or any two modes are presented by closed-form expressions. The simulation result verifies the accuracy of the selection scheme and illustrates higher achievable rate performance under the proposed scheme.

I. Introduction

Device-to-device (D2D) technology is one of the critical technologies of 5G network, which can provide lager capacity and better service by sharing the time-frequency resources with cellular users. On the other hand, relay technology has emerged as a promising technique to show higher potential gains in ergodic achievable rate, outage performance, as well as spectrum efficiency of the wireless link. Great efforts have been spent on the investigation of relay-assisted D2D communication system [1] –[3].