Uplink and downlink performance analysis of a structured coded NOMA in Cognitive Radio Networks

This study examines the uplink and downlink communication in a structured coded nonorthogonal multiple access (NOMA) in the context of cognitive radio networks (CRNs). Due to the ever-increasing demand for spectrum-efficient communication systems, NOMA has emerged as an effective approach to enhance spectral efficiency by allowing multiple users to share the same frequency resources. Furthermore, CRN also improves spectrum utilization by enabling dynamic spectrum access while primary users are present. This work presents a method that can maximize the spectral efficiency by combining NOMA and CRN mechanisms. The suggested system is evaluated in terms of throughput, spectral efficiency, and bit error rate (BER). The collected results show that the proposed strategy performs better in reducing data mistakes when two users access the spectrum at different signal-to-noise ratios (SNR), with a 7 dB improvement for 1st user and a 2.5 dB improvement for the 2nd user, respectively, in the downlink scenario. Next, the exact BER expressions for both coded and uncoded uplink NOMA systems are introduced. As a result, the proposed system demonstrates superior performance and needs only 11 dB to reach 1 × 10−6 of BER while the uncoded system cannot operate in this harsh environment and the BER is fixed at 0.25 dB.