Enabling Device-to-Device Transmission for NOMA-Aided Systems

Abstract

To utilize the close transmission, we assume that the device-to-device (D2D) link is activated to improve the performance of the far user. We consider two groups of users in the nonorthogonal multiple access- (NOMA)- aided wireless system. These features are necessary for massive connectivity in future wireless systems. The system performance also shows suitable performance at far distance users. To evaluate the performance in detail, we derive novel closed form expressions of outage probability. In practical situations impaired by channel uncertainty, it is necessary to evaluate the impact of channel error levels on outage probability. Our numerical results indicated that the transmit power at the base station and channel error level are the main impacts on system performance. Despite these impacts, our obtained numerical results demonstrated that the proposed scheme can still increase energy efficiency and achieve significant outage performance via many practical challenges.