Three-phase overlay D2D communications in traffic-aware two-way cellular systems

In this paper, we propose a new reliable scheme for device-to-device (D2D) communications overlaying a traffic-aware two-way cellular system. The considered system comprises a pair of D2D users, a base station (BS), and a mobile user (MU). In the proposed scheme, both participating D2D users provide relay assistance to the cellular nodes (BS, MU), and in return, they are allowed to exchange their own information by utilizing the same licensed cellular spectrum. Hereby, two end-to-end bi-directional transmissions (cellular and D2D) can be realized in three-time phases. Moreover, we employ decode-and-forward (DF) relaying strategy at both relaying D2D users and selection combining (SC) scheme at both cellular nodes. For this set-up, we investigate the performance of both cellular and D2D links in terms of outage probability (OP) under Nakagami-m fading. Further, we obtain an expression of average system throughput (AST) to conduct fair comparison with the other existing schemes. Numerical and simulation analyses are performed to validate our analytical findings and to present useful insights into performance of cellular and D2D systems.