Research Article Cancel-Decode-Encode Processing on Two-Way Cooperative NOMA Schemes in Realistic Conditions Thu-Thuy Thi Dao 1,2 and Pham Ngoc Son 1 1 Ho Chi Minh City University of Technology and Education, Ho Chi Minh City, Vietnam 2 Industrial University of Ho Chi Minh City, Ho Chi Minh City, Vietnam Correspondence should be addressed to Thu-Thuy Thi Dao; thuydtt.ncs@hcmute.edu.vn and Pham Ngoc Son; sonpndtvt@hcmute.edu.vn Received 28 July 2020; Revised 1 March 2021; Accepted 22 March 2021; Published 28 April 2021 Academic Editor: Alessandro Bazzi Copyright © 2021 Thu-Thuy Thi Dao and Pham Ngoc Son. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper considers the effects of perfect/imperfect successive interference cancellation (SIC) and perfect/imperfect ` information (CSI) in a multiple-relay two-way cooperative network using nonorthogonal multiple access (NOMA) and digital network coding (DNC). In this model, a relay is selected by maximizing estimated channel gains to enhance the decoding capacity of the nearer source and minimize the collection time of imperfect CSI. Spectrum utilization efficiency is enhanced two times by a mixture of the SIC and DNC techniques at the selected relay (called as the SIC-2TS protocol). The system performance is considered through analysis of the exact and asymptotic expressions of the system outage probabilities and throughput. The major thing is exposed as the proposed SIC-2TS protocol can reach the best performance at optimal positions of the selected relay. Besides, the system throughput of the proposed protocol outperforms a SIC-utilized two-way relaying scheme without the DNC (called as the SIC-3TS protocol) and a conventional two-way scheme (called as the CONV-4TS protocol) for all signal-to-noise ratio regions. Lastly, the validity of the analytical expressions is verified by the Monte Carlo simulation results. 1. Introduction Recently, wireless networks have rising challenges in enhanc- ing system throughput and spectrum efficiency owing to the increasing user devices and increasing various Internet of Things applications. A key technology for the fifth- generation wireless network to solve these challenges is NOMA technology because of its attainments to help grow spectral efficiency, enlarge connections, decrease access latency, and increase the users’ fairness [1–3]. Power domain NOMA uses the superposition coding to allocate different power levels for transmitted signals to the multiusers at the same time, frequency, and code domains. At receivers, the suc- cessive interference cancellation method is applied to decode the received signals [2, 3]. However, unexpected errors in decoding when using SIC still occur due to the complexity scale and error propagation, leading to the near user enduring a residual interference signal and the NOMA system perfor- mance impacted by this imperfect SIC (ipSIC) [3–6]. In [7], the authors investigated the reliability and security of the ambient backscatter NOMA systems, where the source was aimed at communicating with two NOMA users in the presence of an eavesdropper. The authors in [7] considered a more practical case that nodes and backscatter devices suffer from in-phase and quadrature-phase imbalance. Besides, cooperative communication has also been widely studied because its spatial diversity advantage helps to reduce fading, widen coverage, and increase communication pre- ciseness [6, 8–10]. In conventional cooperative communica- tions, relaying nodes apply the decode-and-forward (DF) method or the amplify-and-forward (AF) method to process their received and transmitted signals [6, 11]. The DF method is better because it decodes received signals at the relay, then reencodes them for forwarding to the destination so it does not amplify noises in received signals like the AF. Cooperative models show that the selection of the best- relaying devices, including partial relay selection and oppor- tunistic relay selection, is necessary to improve system Hindawi Wireless Communications and Mobile Computing Volume 2021, Article ID 8828443, 15 pages https://doi.org/10.1155/2021/8828443