Exploiting millimeter wave in non-orthogonal multiple access based full-duplex cooperative device-to-device communications system

The ever increasing demand for high data rate and spectral efficiency has led to the advent of the underutilized millimeter-wave (mmWave) frequency spectrum for fifth-generation and beyond (B5G) cellular networks. mmWave facilitates high throughput for short-range technologies such as device-to-device (D2D) communications by utilizing the carrier frequencies beyond 30 GHz. This paper proposes a mmWave assisted cooperative D2D (C-D2D) framework wherein a D2D transmitter (DT) acts as a full-duplex (FD) relay for cellular uplink transmission. In addition, DT employs non-orthogonal multiple access (NOMA) to transmit the superimposed cellular and D2D signal while utilizing power domain multiplexing. Successive interference cancellation is applied at the D2D receiver to decode the D2D signal. Further, we considered that each node is equipped with directional antennas to compensate for the impact of high propagation loss, and a sectored beamforming framework is used to model the antenna gain. The analytical expressions for the achievable rates and outage probabilities for cellular and D2D users with an optimal value of the power splitting factor have been derived to characterize the system performance. Our results include the impact of various system parameters such as half-power beamwidth, sidelobe gain, and residual self-interference constants on the cellular outage probability. We have also shown that our proposed model outperforms the recent work on the NOMA-aided FD C-D2D communications system by approximately 104 times in terms of cellular outage probability.