Abstract
In this paper, we propose a full-duplex orthogonal frequency-division multiplexing (OFDM) device-to-device (D2D) system in two-hop networks, where multiple full-duplex decode-and-forward (DF) relays assist the transmission from D2D user equipment (DUE) transmitter to DUE receiver. By such a transmission mechanism, the signal transmitted by the DUE transmitter does not need to go through a base station (BS). Meanwhile, due to the adoption of underlay D2D communication protocol, power control mechanisms are thereby necessary to be applied to mitigate the interference to conventional cellular communications. Based on these considerations, we analyze the outage performance of the proposed system, and derive the exact expressions of outage probabilities when bulk and per-subcarrier relay selection criteria are applied. Furthermore, closed-form expressions of outage probabilities are also obtained for special cases when the instantaneous channel state information (CSI) between BS and cellular user equipments (CUEs) is not accessible, so that a static power control mechanism is applied. Subsequently, we also investigate the outage performance optimization problem by coordinating transmit power among DUE transmitter and relays, and provide a suboptimal solution, which is capable of improving the outage performance. All analysis is substantiated by numerical results provided by Monte Carlo simulations. The analytical and numerical results demonstrated in this paper can provide an insight into the full-duplex relay-assisted OFDM D2D systems, and serve as a guideline for its implementation in next generation networks.
Highlights
W ITH a rapidly increasing demand of communication services in recent years, existing communication technologies relying on infrastructure, e.g. access point (AP) and base station (BS), will soon be insufficient to meet the requirements of ubiquitous communications in the near future [1]
The contributions of this paper are listed infra: 1) We propose a more practical system model combining relayassisted D2D communications, orthogonal frequency-division multiplexing (OFDM) systems, full-duplex transmissions and multicarrier relay selections, which suits the nature of generation networks
By two ideal conditions, the outage floors for the static power control mechanism can be derived in neat and closed forms, which clearly reveal the relations among outage performance and system parameters
Summary
W ITH a rapidly increasing demand of communication services in recent years, existing communication technologies relying on infrastructure, e.g. access point (AP) and base station (BS), will soon be insufficient to meet the requirements of ubiquitous communications in the near future [1]. Conventional D2D communications requiring a strong direct link between DUEs might not always be feasible in practice, as the direct link could be in deep fading and shadowing due to the existence of physical obstacles In this scenario, D2D communications will become impractical or require a huge amount of transmit power, which will result in severe interference to cellular communications and significantly degrade the overall system performance [8]. Cations and multicarrier paradigms and provide a comprehensive analysis, we propose a full-duplex orthogonal frequency-division multiplexing (OFDM) D2D system assisted by multiple relays and analyze its outage performance in this paper. The contributions of this paper are listed infra: 1) We propose a more practical system model combining relayassisted D2D communications, OFDM systems, full-duplex transmissions and multicarrier relay selections, which suits the nature of generation networks.
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