Performance of user relay cooperative NOMA system with partial and imperfect CSI
Keywords:Cooperative Non-Orthogonal Multiple Access (NOMA), Imperfect Channel State Information (CSI), NOMA, Partial CSI, Relay Selection.
In this paper, we consider a cooperative non-orthogonal multiple access (NOMA) system with user relay under partial and imperfect channel state information (CSI). For a user cooperation, a relay is selected among near users using partial CSI to reduce the delay for the selection process. During the relay selection process, the channel errors caused by the imperfect CSI is considered. And selection combining is applied to the far user for spatial diversity. Outage probabilities of the relay and far user are derived separately in closed-form as a function of the channel errors. It is noticed that the max relay selection strategy is recommendable under fewer channel errors. However, as the channel errors increases, the performance of the relay with max selection degrades and finally approaches that of the randomly selected relay. It means the max relay selection strategy is not effective for the performance gain under high channel errors. Though the performance of the far user degrades as the channel errors increases, the degradation is less sensitive due to the selection combining. We noticed that the end-to-end outage probability with max relay selection is slightly increased with channel errors. However, the performance degradation is more sensitive with random relay selection. To demonstrate the accuracy of the developed analytical results, we showed Monte Carlo simulation results are perfectly matched with the analytical results.
 Saito Y, Kishiyama Y, Benjebbour A, Nakamura T, Li A, and Higuchi K, â€œNon-orthogonal multiple access (NOMA) for cellular future radio access,â€ Proceedings of Vehicular Technology Conference (VTC Spring), (2013), pp.1-5.
 Song L, Li Y, Ding Z, and Poor HV, â€œResource management in non-orthogonal multiple access networks for 5G and beyond,â€ IEEE Network, Vol. 31, No.4, (2017), pp.8-14. https://doi.org/10.1109/MNET.2017.1600287.
 Xu P, Yang Z, Ding Z, and Zhang Z, â€œOptimal relay selection schemes for cooperative NOMA,â€ IEEE Transactions on Vehicular Technology., to be appear in April 2018.
 Ding Z, Dai H, Poor HV, â€œRelay selection for cooperative NOMA,â€ IEEE Wireless Communications Letters, Vol.5, No.4, (2016), pp. 416-419. https://doi.org/10.1109/LWC.2016.2574709.
 Ding Z, Peng M, and Poor HV, â€œCooperative non-orthogonal multiple access in 5G systems,â€ IEEE Communications Letters, Vol.19, No.8, (2015), pp.1462-1465. https://doi.org/10.1109/LCOMM.2015.2441064.
 Liu Y, Ding Z, Elkashlan M, and Poor HV, â€œCooperative non-orthogonal multiple access with simultaneous wireless information and power transfer,â€ IEEE Journal on Selected Areas in Communications, Vol. 14, No. 4, (2016), pp. 938-953. https://doi.org/10.1109/JSAC.2016.2549378.
 Tourki K, Yang HC, Alouini MS, â€œAccurate outage analysis of incremental decode-and-forward opportunistic relaying,â€ IEEE Transactions on Wireless Communications, Vol.10, No.4, (2011), pp.1021-2015. https://doi.org/10.1109/TWC.2011.021611.100472.
 Lee S, Da Costa DB, and Duong TQ, â€œOutage probability of non-orthogonal multiple access schemes with partial relay selection,â€ Proceedings of Personal, Indoor, and Mobile Communications (PIMRC 2016), (2016), pp. 1-6.
 Fang F, Zhang H, Cheng J, and Leung VCM, â€œEnergy-efficient resource scheduling for NOMA systems with imperfect channel state information,â€ Proceedings of International Conference on Communications (ICC 2017), (2017), pp.1-5.
 Cai W, Chen C, Bai L, Jin Y, and Choi J, â€œUser selection and power allocation schemes for downlink NOMA systems with imperfect CSI,â€ Proceedings of Vehicular Technology Conference (VTC-fall 2016), (2016), pp. 1-5. https://doi.org/10.1109/VTCFall.2016.7881960.
 Wan D, Wen M, Ji F, Liu Y, and Huang Y, â€œCooperative NOMA systems with partial channel state information over Nakagami-m fading channels,â€ IEEE Transactions on Communications, Vol. 66, No. 3, (2017), pp. 947-958. https://doi.org/10.1109/TCOMM.2017.2772273.
 Sharma V, Premkumar K, and Swamy RN, â€œExponential diversity achieving spatio-temporal power allocation scheme for fading channels,â€ IEEE Transactions on Information Theory, Vol. 54, No. 1, (2008), pp.188-208. https://doi.org/10.1109/TIT.2007.911207.
 Kim NS, â€œEffect of SIC errors to cooperative NOMA systems,â€ Journal of the Institute of Internet, Broadcasting and Communication, Vol.17, No.5, (2017), pp.35-42.
 Kim NS, â€œOptimum power allocation of cooperative NOMA systems based on user relay,â€ Journal of the Institute of Internet, Broadcasting and Communication, Vol.17, No.5, (2017), pp.25-33. https://doi.org/10.7236/JIIBC.2017.17.1.25.
 Kim NS, â€œUtilization of max-min user relay in cooperative NOMA systems,â€ Journal of Telecommunications, Electronic and Computer Engineering, Vol. 10, No.1-4, (2018), pp.89-94.
 Goldsmith A, Wireless Communications, Cambridge University Press, (2005), pp. 46-47. https://doi.org/10.1017/CBO9780511841224.
 Vicario JL, Anton-Haro C, â€œAnalytical assessment of multi-user vs. spatial diversity trade-offs with delayed channel state information,â€ IEEE Communications Letters, Vol.10, No.8, (2006), pp.588-590. https://doi.org/10.1109/LCOMM.2006.1665119.
 Gradshteyn IS, Ryzbik IM, Table of integrals, series, and products, 6th ed., Academic Press, (2000), pp.689-1014.