IRS and SWIPT-Assisted Full-Duplex NOMA for 6G umMTC

This paper proposes an intelligent reflecting surface (IRS) and simultaneous wireless information and power transmission (SWIPT) assisted full-duplex (FD) non-orthogonal multiple access (NOMA) transmission scheme for the ultra-massive machine type communications (umMTC) scenario in the envisioned sixth-generation (6G) and beyond wireless networks. In this work, SWIPT copes with the energy constraints of the battery-powered Internet of Things (IoT) devices in the umMTC scenario, while IRS is used as a helper to improve the efficiency of SWIPT, NOMA and FD transmission. Specifically, the proposed scheme considers a downlink transmission from a base station to a downlink user and simultaneous uplink transmissions from multiple IoT devices by harvesting energy from the downlink signals. Moreover, a resource allocation problem is formulated to maximize the uplink sum rate of the IoT devices by optimizing the transmit power of the base station, the power allocation coefficients, the IRS phase shifts, and the time-switching coefficient. Since it is difficult to obtain the optimal solution directly, an alternating optimization algorithm is proposed, where the Dinkelbach's method, a penalty-based method and successive convex approximation (SCA) technique are utilized. The superior performance of the proposed scheme compared to benchmark schemes is demonstrated by the provided numerical studies.