PHY Transceiver Design Based on NOMA Cognitive Radio

The exponential growth in wireless communication demands has intensified the need for efficient spectrum utilization. With spectrum resources becoming increasingly scarce, traditional access methods struggle to keep up with the ever-growing number of connected devices, especially in the context of Beyond 5G (B5G) and future 6G networks. This has led to a search for advanced technologies capable of improving spectrum efficiency, accommodating high-density user connections, and supporting diverse quality of service requirements. Cognitive Radio (CR) and Non-Orthogonal Multiple Access (NOMA) have emerged as promising technologies to address these challenges. CR allows dynamic access to underutilized spectrum by enabling secondary users to coexist with licensed primary users, while NOMA facilitates multiple users sharing the same frequency resources by assigning distinct power levels. When combined, CR and NOMA, forming CR-NOMA, leverage the strengths of both technologies, aiming to maximize spectrum efficiency and user access while minimizing interference. This thesis aims to
conduct a comprehensive analysis of the CR-NOMA system's effectiveness in mitigating spectrum scarcity and enhancing system performance. By integrating Cooperative Communication with CR-NOMA, it seeks to further boost efficiency and expand coverage, addressing key challenges encountered
in practical implementations. In real-world scenarios, system performance is often hindered by imperfections in Channel State Information (CSI) and Successive Interference Cancellation (SIC). This thesis thoroughly examines the extent to which these imperfections impact crucial performance metrics,
such as bit error rate (BER), and outage probability (OP), across a range of operating conditions, offering insights into optimizing CR-NOMA under realistic constraints. First, we investigate a simple underlay CR assisted NOMA downlink transmission over the Rayleigh fading channel. Exact closed form expressions of the OP, achieved data rate and throughput of two CR-NOMA users are derived. The performance is demonstrated using both analytical and simulation results and also the influence of interference temperature constraint (ITC) on the CR-NOMA system . Then, we investigate underlay CR-NOMA-based device-to-device (D2D) communications in the presence of Rayleigh fading channels. The study assumes a decode-and-forward (DF) mode, where nearby users act as helper users to assist distant users. We
derived the closed-form expressions for OP and throughput at the end users in three scenarios: perfect SIC and CSI, imperfect CSI, and imperfect SIC. Thereafter, we examine the BER performance of underlay Cooperative CR based NOMA (CCR-NOMA) systems. We derive exact closed-form expressions for BER at distant users under perfect and imperfect CSI conditions. These mathematical formulations are validated through Monte Carlo simulations. The results can be summarized as follows: The simple system model shows superiority compared to the traditional multiple access scheme and the performance of user utilizing SIC technology is better than that of user who do not utilize SIC in CR-NOMA. Additionally, the near user outperforms the far user in CR-OMA. We also found the best result at ITC=35 dB ,which is a key factor in the system performance. In CR-NOMA with D2D communication system , users employing SIC technology demonstrate superior performance compared to those who do not utilize SIC. Additionally, the OP performance of users employing CR-NOMA mode surpasses that of users using CR-OMA mode. The presence of imperfect CSI and imperfect SIC adversely affects the outage performance. Additionally, distant users utilizing the CCR-OMA protocol demonstrate better BER performance than those employing the CCR-NOMA protocol. The presence of imperfect CSI adversely affects BER performance. Moreover, the derived closed-form expressions for BER in the investigated system align well with Monte Carlo simulations. These findings provide valuable insights for optimizing the performance of CCR-NOMA systems in real-world scenarios.

The exponential growth in wireless communication demands has intensified the need for efficient spectrum utilization. With spectrum resources becoming increasingly scarce, traditional access methods struggle to keep up with the ever-growing number of connected devices, especially in the context of Beyond 5G (B5G) and future 6G networks. This has led to a search for advanced technologies capable of improving spectrum efficiency, accommodating high-density user connections, and supporting diverse quality of service requirements. Cognitive Radio (CR) and Non-Orthogonal Multiple Access (NOMA) have emerged as promising technologies to address these challenges. CR allows dynamic access to underutilized spectrum by enabling secondary users to coexist with licensed primary users, while NOMA facilitates multiple users sharing the same frequency resources by assigning distinct power levels. When combined, CR and NOMA, forming CR-NOMA, leverage the strengths of both technologies, aiming to maximize spectrum efficiency and user access while minimizing interference. This thesis aims to
conduct a comprehensive analysis of the CR-NOMA system's effectiveness in mitigating spectrum scarcity and enhancing system performance. By integrating Cooperative Communication with CR-NOMA, it seeks to further boost efficiency and expand coverage, addressing key challenges encountered
in practical implementations. In real-world scenarios, system performance is often hindered by imperfections in Channel State Information (CSI) and Successive Interference Cancellation (SIC). This thesis thoroughly examines the extent to which these imperfections impact crucial performance metrics,
such as bit error rate (BER), and outage probability (OP), across a range of operating conditions, offering insights into optimizing CR-NOMA under realistic constraints. First, we investigate a simple underlay CR assisted NOMA downlink transmission over the Rayleigh fading channel. Exact closed form expressions of the OP, achieved data rate and throughput of two CR-NOMA users are derived. The performance is demonstrated using both analytical and simulation results and also the influence of interference temperature constraint (ITC) on the CR-NOMA system . Then, we investigate underlay CR-NOMA-based device-to-device (D2D) communications in the presence of Rayleigh fading channels. The study assumes a decode-and-forward (DF) mode, where nearby users act as helper users to assist distant users. We
derived the closed-form expressions for OP and throughput at the end users in three scenarios: perfect SIC and CSI, imperfect CSI, and imperfect SIC. Thereafter, we examine the BER performance of underlay Cooperative CR based NOMA (CCR-NOMA) systems. We derive exact closed-form expressions for BER at distant users under perfect and imperfect CSI conditions. These mathematical formulations are validated through Monte Carlo simulations. The results can be summarized as follows: The simple system model shows superiority compared to the traditional multiple access scheme and the performance of user utilizing SIC technology is better than that of user who do not utilize SIC in CR-NOMA. Additionally, the near user outperforms the far user in CR-OMA. We also found the best result at ITC=35 dB ,which is a key factor in the system performance. In CR-NOMA with D2D communication system , users employing SIC technology demonstrate superior performance compared to those who do not utilize SIC. Additionally, the OP performance of users employing CR-NOMA mode surpasses that of users using CR-OMA mode. The presence of imperfect CSI and imperfect SIC adversely affects the outage performance. Additionally, distant users utilizing the CCR-OMA protocol demonstrate better BER performance than those employing the CCR-NOMA protocol. The presence of imperfect CSI adversely affects BER performance. Moreover, the derived closed-form expressions for BER in the investigated system align well with Monte Carlo simulations. These findings provide valuable insights for optimizing the performance of CCR-NOMA systems in real-world scenarios.