This paper conducts a comprehensive performance analysis of Cooperative Non-Orthogonal Multiple Access (NOMA) systems through the application of Extrinsic Information Transfer (EXIT) chart analysis, a tool widely used for visualizing the iterative decoding process in communication systems. The proposed system integrates Successive Interference Cancellation (SIC), Multi-User Detection (MUD), and spreading techniques to enhance the reliability and efficiency of data transmission. In this cooperative framework, the near user (NU), having stronger channel conditions, assists the far user (FU) by acting as a decode-and-forward relay. This cooperation significantly mitigates the limitations of traditional power-domain NOMA, such as unfair power distribution and high bit error rates for weak users. Simulation results highlight the superiority of the cooperative model over non-cooperative NOMA in terms of Bit Error Rate (BER) and system throughput, especially in low Signal-to-Noise Ratio (SNR) scenarios. The EXIT chart analysis is employed to assess the mutual information exchange between the MUD and channel decoders during iterative processing. The results demonstrate clear convergence behaviour, with the EXIT curves forming an open tunnel that reaches the optimal [1,1] point without intersection. This indicates error-free transmission and optimal performance. The findings confirm that cooperative NOMA, when analysed through EXIT charts, provides improved user fairness and effective power allocation.

Keywords : Cooperative NOMA, SIC, EXIT Chart, Multi-User Detection, Throughput Analysis, BER, User Fairness, Spreading Factor

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1. Elsaraf Z, Khan F, Ahmed Q. Code domain non-orthogonal multiple access techniques for 5G mobile communications. In: Emerging Technology Conference (EMiT19); 2019 Jan; Huddersfield, UK.
2. Huang T, Yuan J, Cheng X, Lei W. Design of degrees of distribution of LDS-OFDM. In: International Conference on Signal Processing and Communication Systems; 2015 Dec; Cairns, Australia. p. 1–6.
3. Wang P, Xiao J, Ping L. Comparison of orthogonal and non-orthogonal approaches to future wireless cellular systems. IEEE Veh Technol Mag. 2006 Sep;1(3):4–11.
4. Choi J. Power allocation for max-sum rate and max-min rate proportional fairness in NOMA. IEEE Commun Lett. 2016 Oct;20(10):2055–8.
5. Ding Z, Fan P, Poor HV. Impact of user pairing on 5G non-orthogonal multiple-access downlink transmissions. IEEE Trans Veh Technol. 2016 Aug;65(8):6010–23.
6. Choi J. Minimum power multicast beamforming with superposition coding for multiresolution broadcast and application to NOMA systems. IEEE Trans Commun. 2015 Mar;63(3):791–800.
7. Shin W, Vaezi M, Lee B, Love DJ, Lee J, Poor HV. Non-orthogonal multiple access in multi-cell networks: Theory, performance, and practical challenges. IEEE Commun Mag. 2017 Oct;55(10):176–83.
8. Men J, Ge J, Zhang C. Performance analysis of non-orthogonal multiple access for relaying networks over Nakagami-m fading channels. IEEE Trans Veh Technol. 2017 Feb;66(2):1200–8.
9. Liau QY, Leow CY. Successive user relaying in cooperative NOMA system. IEEE Wireless Commun Lett. 2019 Jun;8(3):921–4.
10. Laneman JN, Tse DNC, Wornell GW. Cooperative diversity in wireless networks: Efficient protocols and outage behavior. IEEE Trans Inf Theory. 2004 Dec;50(12):3062–80.
11. Ding Z, Krikidis I, Sharif B, Poor HV. Wireless information and power transfer in cooperative networks with spatially random relays. IEEE Trans Wireless Commun. 2014 Aug;13(8):4440–53.
12. Marcano AS, Christiansen HL. System-level performance of C-NOMA: A cooperative scheme for capacity enhancements in 5G mobile networks. In: 2017 IEEE 86th Vehicular Technology Conference (VTC-Fall); 2017; Toronto, Canada. p. 1–6.
13. Mei W, Zhang R. Cooperative NOMA for downlink asymmetric interference cancellation. IEEE Wireless Commun Lett. 2020 Jun;9(6):884–8.
14. Ojha S, Pandey AK. Close loop V/F control of voltage source inverter using sinusoidal PWM, third harmonic injection PWM and space vector PWM method for induction motor. Int J Power Electron Drive Syst. 2016;7:217–24.
15. Ojha S, Sharma C, Pandey AK. Comparative analysis of close loop three-level voltage source inverter using sinusoidal pulse width modulation and third harmonic injection method for different loads. In: 2017 Second International Conference on Electrical, Computer and Communication Technologies (ICECCT); 2017; Coimbatore, India. p. 1–6.
16. Sinha AP, Prasad H, Yadav VK, Singh AP, Ojha S. Navigating the EV revolution: COVID-19’s influence and recent developments in EVs. In: 2024 1st International Conference on Innovative Sustainable Technologies for Energy, Mechatronics, and Smart Systems (ISTEMS); 2024; Dehradun, India. p. 1–6.
17. Ojha S, Gupta R. Switching frequency formulation for predictive current control in grid-connected VSI. IETE J Res. 2022;69(11):8502–10.
18. Singh AP, Gupta R, Ojha S, Yadav VK. DC bus capacitor discharge during standstill and running condition in PMSM based EVs. In: 2023 11th National Power Electronics Conference (NPEC); 2023; Guwahati, India. p. 1–6.
19. Ojha S, Gupta R. Stabilization of DC-link voltage in single-phase AC/DC converter with power factor correction using predictive control algorithm. Int J Circ Theor Appl. 2023;51(11):5197–209.
20. Singh AP, Gupta R, Ojha S. DC link voltage balance and discharge in three-level NPC fed PMSM-powered EVs using external circuit. In: 2024 IEEE Region 10 Symposium (TENSYMP); 2024; New Delhi, India. p. 1–6.
21. Ojha S, Gupta R. Selective harmonic compensation in active power filter using nonlinear predictive current control method. In: Tripathi SM, Gonzalez-Longatt FM, editors. Real-time simulation and hardware-in-the-loop testing using Typhoon HIL. Singapore: Springer; 2023. (Transactions on Computer Systems and Networks).
22. Ojha S, Gupta R. Switching frequency calculation for predictive control method in active power filter application. In: 2022 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES); 2022; Jaipur, India. p. 1–6.

This paper conducts a comprehensive performance analysis of Cooperative Non-Orthogonal Multiple Access (NOMA) systems through the application of Extrinsic Information Transfer (EXIT) chart analysis, a tool widely used for visualizing the iterative decoding process in communication systems. The proposed system integrates Successive Interference Cancellation (SIC), Multi-User Detection (MUD), and spreading techniques to enhance the reliability and efficiency of data transmission. In this cooperative framework, the near user (NU), having stronger channel conditions, assists the far user (FU) by acting as a decode-and-forward relay. This cooperation significantly mitigates the limitations of traditional power-domain NOMA, such as unfair power distribution and high bit error rates for weak users. Simulation results highlight the superiority of the cooperative model over non-cooperative NOMA in terms of Bit Error Rate (BER) and system throughput, especially in low Signal-to-Noise Ratio (SNR) scenarios. The EXIT chart analysis is employed to assess the mutual information exchange between the MUD and channel decoders during iterative processing. The results demonstrate clear convergence behaviour, with the EXIT curves forming an open tunnel that reaches the optimal [1,1] point without intersection. This indicates error-free transmission and optimal performance. The findings confirm that cooperative NOMA, when analysed through EXIT charts, provides improved user fairness and effective power allocation.

Keywords : Cooperative NOMA, SIC, EXIT Chart, Multi-User Detection, Throughput Analysis, BER, User Fairness, Spreading Factor

🔒 This is a subscription article

Full text is available to subscribers and institutional members. Please choose an option below to access it.

1. Elsaraf Z, Khan F, Ahmed Q. Code domain non-orthogonal multiple access techniques for 5G mobile communications. In: Emerging Technology Conference (EMiT19); 2019 Jan; Huddersfield, UK.
2. Huang T, Yuan J, Cheng X, Lei W. Design of degrees of distribution of LDS-OFDM. In: International Conference on Signal Processing and Communication Systems; 2015 Dec; Cairns, Australia. p. 1–6.
3. Wang P, Xiao J, Ping L. Comparison of orthogonal and non-orthogonal approaches to future wireless cellular systems. IEEE Veh Technol Mag. 2006 Sep;1(3):4–11.
4. Choi J. Power allocation for max-sum rate and max-min rate proportional fairness in NOMA. IEEE Commun Lett. 2016 Oct;20(10):2055–8.
5. Ding Z, Fan P, Poor HV. Impact of user pairing on 5G non-orthogonal multiple-access downlink transmissions. IEEE Trans Veh Technol. 2016 Aug;65(8):6010–23.
6. Choi J. Minimum power multicast beamforming with superposition coding for multiresolution broadcast and application to NOMA systems. IEEE Trans Commun. 2015 Mar;63(3):791–800.
7. Shin W, Vaezi M, Lee B, Love DJ, Lee J, Poor HV. Non-orthogonal multiple access in multi-cell networks: Theory, performance, and practical challenges. IEEE Commun Mag. 2017 Oct;55(10):176–83.
8. Men J, Ge J, Zhang C. Performance analysis of non-orthogonal multiple access for relaying networks over Nakagami-m fading channels. IEEE Trans Veh Technol. 2017 Feb;66(2):1200–8.
9. Liau QY, Leow CY. Successive user relaying in cooperative NOMA system. IEEE Wireless Commun Lett. 2019 Jun;8(3):921–4.
10. Laneman JN, Tse DNC, Wornell GW. Cooperative diversity in wireless networks: Efficient protocols and outage behavior. IEEE Trans Inf Theory. 2004 Dec;50(12):3062–80.
11. Ding Z, Krikidis I, Sharif B, Poor HV. Wireless information and power transfer in cooperative networks with spatially random relays. IEEE Trans Wireless Commun. 2014 Aug;13(8):4440–53.
12. Marcano AS, Christiansen HL. System-level performance of C-NOMA: A cooperative scheme for capacity enhancements in 5G mobile networks. In: 2017 IEEE 86th Vehicular Technology Conference (VTC-Fall); 2017; Toronto, Canada. p. 1–6.
13. Mei W, Zhang R. Cooperative NOMA for downlink asymmetric interference cancellation. IEEE Wireless Commun Lett. 2020 Jun;9(6):884–8.
14. Ojha S, Pandey AK. Close loop V/F control of voltage source inverter using sinusoidal PWM, third harmonic injection PWM and space vector PWM method for induction motor. Int J Power Electron Drive Syst. 2016;7:217–24.
15. Ojha S, Sharma C, Pandey AK. Comparative analysis of close loop three-level voltage source inverter using sinusoidal pulse width modulation and third harmonic injection method for different loads. In: 2017 Second International Conference on Electrical, Computer and Communication Technologies (ICECCT); 2017; Coimbatore, India. p. 1–6.
16. Sinha AP, Prasad H, Yadav VK, Singh AP, Ojha S. Navigating the EV revolution: COVID-19’s influence and recent developments in EVs. In: 2024 1st International Conference on Innovative Sustainable Technologies for Energy, Mechatronics, and Smart Systems (ISTEMS); 2024; Dehradun, India. p. 1–6.
17. Ojha S, Gupta R. Switching frequency formulation for predictive current control in grid-connected VSI. IETE J Res. 2022;69(11):8502–10.
18. Singh AP, Gupta R, Ojha S, Yadav VK. DC bus capacitor discharge during standstill and running condition in PMSM based EVs. In: 2023 11th National Power Electronics Conference (NPEC); 2023; Guwahati, India. p. 1–6.
19. Ojha S, Gupta R. Stabilization of DC-link voltage in single-phase AC/DC converter with power factor correction using predictive control algorithm. Int J Circ Theor Appl. 2023;51(11):5197–209.
20. Singh AP, Gupta R, Ojha S. DC link voltage balance and discharge in three-level NPC fed PMSM-powered EVs using external circuit. In: 2024 IEEE Region 10 Symposium (TENSYMP); 2024; New Delhi, India. p. 1–6.
21. Ojha S, Gupta R. Selective harmonic compensation in active power filter using nonlinear predictive current control method. In: Tripathi SM, Gonzalez-Longatt FM, editors. Real-time simulation and hardware-in-the-loop testing using Typhoon HIL. Singapore: Springer; 2023. (Transactions on Computer Systems and Networks).
22. Ojha S, Gupta R. Switching frequency calculation for predictive control method in active power filter application. In: 2022 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES); 2022; Jaipur, India. p. 1–6.