Intelligent Omni-Surface-Assisted Cooperative Hybrid Non-Orthogonal Multiple Access: Enhancing Spectral Efficiency Under Imperfect Successive Interference Cancellation and Hardware Distortions
Non-orthogonal multiple access (NOMA) has emerged as a key enabler of massive connectivity in next-generation wireless networks. However, conventional NOMA studies predominantly focus on two-user scenarios, limiting their scalability in practical multi-user environments. A critical challenge in thes...
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2025-04-01
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| author | Helen Sheeba John Kennedy Vinoth Babu Kumaravelu |
| author_facet | Helen Sheeba John Kennedy Vinoth Babu Kumaravelu |
| author_sort | Helen Sheeba John Kennedy |
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| description | Non-orthogonal multiple access (NOMA) has emerged as a key enabler of massive connectivity in next-generation wireless networks. However, conventional NOMA studies predominantly focus on two-user scenarios, limiting their scalability in practical multi-user environments. A critical challenge in these systems is error propagation in successive interference cancellation (SIC), which is further exacerbated by hardware distortions (HWDs). Hybrid NOMA (HNOMA) mitigates SIC errors and reduces system complexity, yet cell-edge users (CEUs) continue to experience degraded sum spectral efficiency (SSE) and throughput. Cooperative NOMA (C-NOMA) enhances CEU performance through retransmissions but incurs higher energy consumption. To address these limitations, this study integrates intelligent omni-surfaces (IOSs) into a cooperative hybrid NOMA (C-HNOMA) framework to enhance retransmission efficiency and extend network coverage. The closed-form expressions for average outage probability and throughput are derived, and a power allocation (PA) optimization framework is proposed to maximize SSE, with validation through Monte Carlo simulations. The introduction of a novel strong–weak strong–weak (SW-SW) user pairing strategy capitalizes on channel diversity, achieving an SSE improvement of ∼0.48% to ∼3.81% over conventional pairing schemes. Moreover, the proposed system demonstrates significant performance gains as the number of IOS elements increases, even under imperfect SIC (iSIC) and HWD conditions. By optimizing PA values, SSE is further enhanced by at least 2.24%, even with an SIC error of 0.01 and an HWD level of 8%. These results underscore the potential of an IOS-assisted C-HNOMA system with SW-SW pairing as a viable solution for improving multi-user connectivity, SSE, and system robustness in future wireless communication networks. |
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| spelling | doaj-art-77d1433fd5df4eae90e9071e7a8b27a12025-08-20T02:09:14ZengMDPI AGSensors1424-82202025-04-01257228310.3390/s25072283Intelligent Omni-Surface-Assisted Cooperative Hybrid Non-Orthogonal Multiple Access: Enhancing Spectral Efficiency Under Imperfect Successive Interference Cancellation and Hardware DistortionsHelen Sheeba John Kennedy0Vinoth Babu Kumaravelu1Department of Communication Engineering, School of Electronics Engineering, Vellore Institute of Technology, Vellore 632014, Tamil Nadu, IndiaDepartment of Communication Engineering, School of Electronics Engineering, Vellore Institute of Technology, Vellore 632014, Tamil Nadu, IndiaNon-orthogonal multiple access (NOMA) has emerged as a key enabler of massive connectivity in next-generation wireless networks. However, conventional NOMA studies predominantly focus on two-user scenarios, limiting their scalability in practical multi-user environments. A critical challenge in these systems is error propagation in successive interference cancellation (SIC), which is further exacerbated by hardware distortions (HWDs). Hybrid NOMA (HNOMA) mitigates SIC errors and reduces system complexity, yet cell-edge users (CEUs) continue to experience degraded sum spectral efficiency (SSE) and throughput. Cooperative NOMA (C-NOMA) enhances CEU performance through retransmissions but incurs higher energy consumption. To address these limitations, this study integrates intelligent omni-surfaces (IOSs) into a cooperative hybrid NOMA (C-HNOMA) framework to enhance retransmission efficiency and extend network coverage. The closed-form expressions for average outage probability and throughput are derived, and a power allocation (PA) optimization framework is proposed to maximize SSE, with validation through Monte Carlo simulations. The introduction of a novel strong–weak strong–weak (SW-SW) user pairing strategy capitalizes on channel diversity, achieving an SSE improvement of ∼0.48% to ∼3.81% over conventional pairing schemes. Moreover, the proposed system demonstrates significant performance gains as the number of IOS elements increases, even under imperfect SIC (iSIC) and HWD conditions. By optimizing PA values, SSE is further enhanced by at least 2.24%, even with an SIC error of 0.01 and an HWD level of 8%. These results underscore the potential of an IOS-assisted C-HNOMA system with SW-SW pairing as a viable solution for improving multi-user connectivity, SSE, and system robustness in future wireless communication networks.https://www.mdpi.com/1424-8220/25/7/2283cooperative communicationintelligent omni-surfaces (IOSs)imperfect successive interference cancellation (iSIC)hardware distortions (HWDs)outage probabilitysum spectral efficiency (SSE) |
| spellingShingle | Helen Sheeba John Kennedy Vinoth Babu Kumaravelu Intelligent Omni-Surface-Assisted Cooperative Hybrid Non-Orthogonal Multiple Access: Enhancing Spectral Efficiency Under Imperfect Successive Interference Cancellation and Hardware Distortions Sensors cooperative communication intelligent omni-surfaces (IOSs) imperfect successive interference cancellation (iSIC) hardware distortions (HWDs) outage probability sum spectral efficiency (SSE) |
| title | Intelligent Omni-Surface-Assisted Cooperative Hybrid Non-Orthogonal Multiple Access: Enhancing Spectral Efficiency Under Imperfect Successive Interference Cancellation and Hardware Distortions |
| title_full | Intelligent Omni-Surface-Assisted Cooperative Hybrid Non-Orthogonal Multiple Access: Enhancing Spectral Efficiency Under Imperfect Successive Interference Cancellation and Hardware Distortions |
| title_fullStr | Intelligent Omni-Surface-Assisted Cooperative Hybrid Non-Orthogonal Multiple Access: Enhancing Spectral Efficiency Under Imperfect Successive Interference Cancellation and Hardware Distortions |
| title_full_unstemmed | Intelligent Omni-Surface-Assisted Cooperative Hybrid Non-Orthogonal Multiple Access: Enhancing Spectral Efficiency Under Imperfect Successive Interference Cancellation and Hardware Distortions |
| title_short | Intelligent Omni-Surface-Assisted Cooperative Hybrid Non-Orthogonal Multiple Access: Enhancing Spectral Efficiency Under Imperfect Successive Interference Cancellation and Hardware Distortions |
| title_sort | intelligent omni surface assisted cooperative hybrid non orthogonal multiple access enhancing spectral efficiency under imperfect successive interference cancellation and hardware distortions |
| topic | cooperative communication intelligent omni-surfaces (IOSs) imperfect successive interference cancellation (iSIC) hardware distortions (HWDs) outage probability sum spectral efficiency (SSE) |
| url | https://www.mdpi.com/1424-8220/25/7/2283 |
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