STBC Technique for Improving Error Performance in Cooperative NOMA Systems Under Nakagami-$m$ Fading Channel

To meet the escalating demand for bandwidth and data rates, this paper introduces a cooperative model to enhance the quality of service (QoS) for users at the edge of a cell, aiming to support non-orthogonal multiple access (NOMA) scheme for future wireless communication systems. Although NOMA scheme is known for its high spectral efficiency, it has difficulty providing fair service to all users, especially those who are far from the base station (BS). To address this problem, the paper proposed a model that involves three user entities and a BS, where one user is located at a large distance from the others. The model employs a two-stage transmission mechanism: first, the BS sends a NOMA signal to all users. Next, the proximal users employ the space time block coding (STBC) technique to cooperatively retransmit the signal of the far user. To validate the effectiveness of the model, the Nakagami-m fading channel model is exploited. The simulation results obtained using the MATLAB tool show that the proposed model improves the symbol error rates (SER) for the cell edge user. This paper offers a strategic paradigm that opens up possibilities for improving QoS for future wireless communication networks.