In this paper, we propose a full-duplex orthogonal frequency-divisionmultiplexing (OFDM) device-to-device (D2D) system in two-hop networks, wheremultiple full-duplex decode-and-forward (DF) relays assist the transmissionfrom D2D user equipment (DUE) transmitter to DUE receiver. By such atransmission mechanism, the signal transmitted by the DUE transmitter does notneed to go through a base station (BS). Meanwhile, due to the adoption ofunderlay D2D communication protocol, power control mechanisms are therebynecessary to be applied to mitigate the interference to conventional cellularcommunications. Based on these considerations, we analyze the outageperformance of the proposed system, and derive the exact expressions of outageprobabilities when bulk and per-subcarrier relay selection criteria areapplied. Furthermore, closed-form expressions of outage probabilities are alsoobtained for special cases when the instantaneous channel state information(CSI) between BS and cellular user equipments (CUEs) is not accessible, so thata static power control mechanism is applied. Subsequently, we also investigatethe outage performance optimization problem by coordinating transmit poweramong DUE transmitter and relays, and provide a suboptimal solution, which iscapable of improving the outage performance. All analysis is substantiated bynumerical results provided by Monte Carlo simulations. The analytical andnumerical results demonstrated in this paper can provide an insight into thefull-duplex relay-assisted OFDM D2D systems, and serve as a guideline for itsimplementation in next generation networks.
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