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  • Open Access


    Outage Behaviors of Active Intelligent Reflecting Surface Enabled NOMA Communications

    Zhiping Lu1, Xinwei Yue2,*, Shuo Chen2, Weiguo Ma1

    CMES-Computer Modeling in Engineering & Sciences, Vol.137, No.1, pp. 789-812, 2023, DOI:10.32604/cmes.2023.027663

    Abstract Active intelligent reflecting surface (IRS) is a novel and promising technology that is able to overcome the multiplicative fading introduced by passive IRS. In this paper, we consider the application of active IRS to non-orthogonal multiple access (NOMA) networks, where the incident signals are amplified actively through integrating amplifier to reflecting elements. More specifically, the performance of active/passive IRS-NOMA networks is investigated over large and small-scale fading channels. Aiming to characterize the performance of active IRS-NOMA networks, the exact and asymptotic expressions of outage probability for a couple of users, i.e., near-end user and far-end user are derived by exploiting… More >

  • Open Access


    Exploiting the Direct Link in IRS Assisted NOMA Networks with Hardware Impairments

    Ziwei Liu1, Xinwei Yue1,*, Shuo Chen1, Xuliang Liu2, Yafei Wang1, Wanwei Tang3

    CMES-Computer Modeling in Engineering & Sciences, Vol.136, No.1, pp. 767-785, 2023, DOI:10.32604/cmes.2023.025300

    Abstract Hardware impairments (HI) are always present in low-cost wireless devices. This paper investigates the outage behaviors of intelligent reflecting surface (IRS) assisted non-orthogonal multiple access (NOMA) networks by taking into account the impact of HI. Specifically, we derive the approximate and asymptotic expressions of the outage probability for the IRS-NOMA-HI networks. Based on the asymptotic results, the diversity orders under perfect self-interference cancellation and imperfect self-interference cancellation scenarios are obtained to evaluate the performance of the considered network. In addition, the system throughput of IRS-NOMA-HI is discussed in delay-limited mode. The obtained results are provided to verify the accuracy of… More >

  • Open Access


    Performance Analysis of RIS Assisted NOMA Networks over Rician Fading Channels

    Xianli Gong1, Chongwen Huang2,3,4, Xinwei Yue5, Zhaohui Yang2,4,6, Feng Liu1,*

    CMES-Computer Modeling in Engineering & Sciences, Vol.135, No.3, pp. 2531-2555, 2023, DOI:10.32604/cmes.2023.024940

    Abstract In this paper, we consider a downlink non-orthogonal multiple access (NOMA) network assisted by two reconfigurable intelligent surfaces (RISs) over Rician fading channels, in which each user communicates with the base station by the virtue of a RIS to enhance the reliability of the received signal. To evaluate the system performance of our proposed RIS-NOMA network, we first derive the exact and asymptotic expressions for the outage probability and ergodic rate of two users. Then, we derive the exact and asymptotic upper bound expressions for the ergodic rate of the nearby user. Based on asymptotic analytical results, the diversity orders… More >

  • Open Access


    Secrecy Outage Probability for Two-Way Integrated Satellite Unmanned Aerial Vehicle Relay Networks with Hardware Impairments

    Xiaoting Ren1, Kefeng Guo2,*

    CMES-Computer Modeling in Engineering & Sciences, Vol.135, No.3, pp. 2515-2530, 2023, DOI:10.32604/cmes.2023.024857

    Abstract In this paper, we investigate the secrecy outage performance for the two-way integrated satellite unmanned aerial vehicle relay networks with hardware impairments. Particularly, the closed-form expression for the secrecy outage probability is obtained. Moreover, to get more information on the secrecy outage probability in a high signal-to-noise regime, the asymptotic analysis along with the secrecy diversity order and secrecy coding gain for the secrecy outage probability are also further obtained, which presents a fast method to evaluate the impact of system parameters and hardware impairments on the considered network. Finally, Monte Carlo simulation results are provided to show the efficiency… More >

  • Open Access


    Outage Probability Analysis of Free Space Communication System Using Diversity Combining Techniques

    Hasnain Kashif*, Muhammad Nasir Khan

    CMC-Computers, Materials & Continua, Vol.73, No.3, pp. 6001-6017, 2022, DOI:10.32604/cmc.2022.031291

    Abstract Recently, free space optical (FSO) communication is gaining much attention towards the research community. The reason for this attention is the promises of high data-rate, license-free deployment, and non-interfering links. It can, however, give rise to major system difficulties concerning alignment and atmospheric turbulence. FSO is the degradation in the signal quality because of atmospheric channel impairments and conditions. The worst effect is due to fog particles. Though, Radio Frequency (RF) links are able to transmit the data in foggy conditions but not in rain. To overcome these issues related to both the FSO and RF links. A free space… More >

  • Open Access


    NOMA-Based Cooperative Relaying Transmission for the Industrial Internet of Things

    Yinghua Zhang1,*, Rui Cao1, Lixin Tian1, Rong Dai2, Zhennan Cao2, Jim Feng3

    CMC-Computers, Materials & Continua, Vol.73, No.3, pp. 6513-6534, 2022, DOI:10.32604/cmc.2022.029467

    Abstract With the continuous maturity of the fifth generation (5G) communications, industrial Internet of Things (IIoT) technology has been widely applied in fields such as smart factories. In smart factories, 5G-based production line monitoring can improve production efficiency and reduce costs, but there are problems with limited monitoring coverage and insufficient wireless spectrum resources, which restricts the application of IIoT in the construction of smart factories. In response to these problems, we propose a hybrid spectrum access mechanism based on Non-Orthogonal Multiple Access (NOMA) cooperative relaying transmission to improve the monitoring coverage and spectrum efficiency. As there are a large number… More >

  • Open Access


    Lowest-Opportunities User First-Based Subcarrier Allocation Algorithm for Downlink NOMA Systems

    Mohammed Abd-Elnaby*, Sameer Alsharif, Hesham Alhumyani, Fahad Alraddady

    Intelligent Automation & Soft Computing, Vol.30, No.3, pp. 1033-1048, 2021, DOI:10.32604/iasc.2021.019341

    Abstract Non-orthogonal multiple access (NOMA) is one of the promising 5G technologies to improve spectral efficiency massive connectivity and cell-edge throughput. The performance of NOMA systems mainly depends on the efficiency of the subcarrier allocation algorithm. This paper aims to jointly optimize spectral efficiency (SE), outage probability, and fairness among users with respect to the subcarrier allocation for downlink NOMA systems. We propose a low-complexity greedy-based subcarrier allocation algorithm based on the lowest-opportunities user’s first precept. This precept is based on computing the number of opportunities for each user to select a subcarrier with good channel gain by counting the number… More >

  • Open Access


    Adaptive Relay Selection Scheme for Minimization of the Transmission Time

    Yu-Jin Na1, Ji-Sung Jung1, Young-Hwan You2, Hyoung-Kyu Song1,*

    CMC-Computers, Materials & Continua, Vol.69, No.1, pp. 1361-1373, 2021, DOI:10.32604/cmc.2021.018481

    Abstract As the installation of small cells increases, the use of relay also increases. The relay operates as a base station as well as just an amplifier. As the roles and types of relays become more diverse, appropriate relay selection technology is an effective way to improve communication performance. Many researches for relay selection have been studied to secure the reliability of relay communication. In this paper, the relay selection scheme is proposed for a cooperative system using decode-and-forward (DF) relaying scheme in the mobile communication system. To maintain the transmission rate, the proposed scheme classifies a candidate group considering the… More >

  • Open Access


    Analysis of Underlay Cognitive Radio Networks Based on Interference Cancellation Mechanism

    Lei Wang1, Jian Liu1, Changming Zhao2, 3, *, Alan Yang4

    CMC-Computers, Materials & Continua, Vol.63, No.1, pp. 401-416, 2020, DOI:10.32604/cmc.2020.06680

    Abstract In this paper, we investigate the performance of secondary transmission scheme based on Markov ON-OFF state of primary users in Underlay cognitive radio networks. We propose flexible secondary cooperative transmission schemewith interference cancellation technique according to the ON-OFF status of primary transmitter. For maximal ratio combining (MRC) at destination, we have derived exact closed-form expressions of the outage probability in different situations. The numerical simulation results also reveal that the proposed scheme improve the secondary transmission performance compared with traditional mechanism in terms of secondary outage probability and energy efficiency. More >

  • Open Access


    Performance Analysis of Relay Based NOMA Cooperative Transmission under Cognitive Radio Network

    Yinghua Zhang1, 2, Jian Liu1, *, Yunfeng Peng1, Yanfang Dong2, Guozhong Sun2, Hao Huang3, Changming Zhao4, 5

    CMC-Computers, Materials & Continua, Vol.63, No.1, pp. 197-212, 2020, DOI:10.32604/cmc.2020.07059

    Abstract This paper proposes a hybrid spectrum accessing mechanism by using NOMA-based cooperative transmission and beam-forming technology. In this mechanism, the secondary user employs spectrum-sensing technology to detect the existence of the primary user. If the primary user does not exist, the secondary source user directly transmits data to the destination user. If the primary user exists, the secondary source user finds the optimal relay according to certain selection principle before transmitting data to the destination user through the chosen relay node. For the signal receiving stage, the secondary user takes use of beam-forming technology to receive the signal from both… More >

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