Journal Articles - Engineering Technology - 2021

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Browsing Journal Articles - Engineering Technology - 2021 by Author "Anh-Tu Le"
  • Publication
    Improving Spectrum Efficiency in CR-NOMA over Rician Fading Channel Under Imperfection CSI
    ( 2021)
    Hung-Anh Tong
    ;
    Anh-Tu Le
    We present a downlink secondary network over Rician fading model since cognitive radio (CR) based non-orthogonal multiple access (NOMA) is adopted. Due to interference constraint, performance analysis of secondary destinations has further parameter to adjust performance as needed. We derive the closed-form expressions of outage probability for the case of two users in a group. Especially, we need to consider how system performance could be better in the case of imperfect channel state information. Then, we find main system parameters such as power allocation factor, condition of wireless channels as controlling factors of outage probabilities of two destinations. We perform Monte Carlo simulations to check the derived analytical expressions.
  • Publication
    On The Performance of NOMA with Bi-directional in Weibull-Channel
    ( 2021)
    Hung-Anh Tong
    ;
    Anh-Tu Le
    Fading is considered to be one of the major issues in wireless communications. The non-Orthogonal Multiple Access (NOMA) technique proved to be efficient enough to overcome the fading issues if utilized efficiently. Since the signals transmitted in NOMA are superimposed, with the help of Channel State Information (CSI), the Successive Interference Cancellation (SIC) technique is applied to separate each user's signal. A lot of researches have been going on to study the performance of the NOMA system in various fading channels such as Nakagami-m channel distribution, Rayleigh channel distribution, Rician fading channel distribution, etc. Very few studies were conducted on Weibull-channel distribution applied in the NOMA network. This letter studies performance of the Weibull-channel fading distribution applied in the NOMA network in presence of two users and the presence of a bi-directional communication link between the devices. The analytical expressions were obtained to study the performance efficiency of the system and extensive simulations were generated comparing the performance in various parameters.
  • Publication
    Secrecy Outage Probability of Reconfigurable Intelligent Surface-Aided Cooperative Underlay Cognitive Radio Network Communications
    ( 2021)
    Nhan Duc Nguyen
    ;
    Anh-Tu Le
    ;
    Munyaradzi Munochiveyi
    With the introduction of wireless communications in a diverse range of security-sensitive scenarios such as healthcare, Smart Cities, internet-of-things (IoT) infrastructure, nuclear power plants, so forth, it has become necessary to protect the wireless network against malicious eavesdroppers via physical layer security (PLS). We analyze and study the impact of an eavesdropper located in an underlay cooperative cognitive radio network (CRN). A reconfigurable intelligent surface is used to improve the secrecy outage probability of the proposed system. CRs resolve spectrum scarcity by enabling spectrum sharing. On the other hand, RIS is a planar surface device equipped with signal enhancing reflecting elements that enhance signals at desired users and suppress signal power at undesired eavesdroppers in PLS networks. Therefore, the integration of RIS in cooperative underlay CR networks can enable secure wireless communications. To this end, we derive closed-form secrecy outage probability (SOP) expressions for a network that consists of a primary destination, secondary source, secondary user and a passive eavesdropper. The obtained equations are verified via simulation.
  • Publication
    UAV Based Satellite-Terrestrial Systems With Hardware Impairment and Imperfect SIC: Performance Analysis of User Pairs
    ( 2021)
    Ngoc-Long Nguyen
    ;
    Si-Phu Le
    ;
    Anh-Tu Le
    ;
    Nhan Duc Nguyen
    ;
    Dinh-Thuan Do
    ;
    Miroslav Voznak
    We investigated the outage performance of non-orthogonal multiple access (NOMA) in satellite-terrestrial systems which contain hardware impairments. An unmanned aerial vehicle (UAV) was implemented to forward signals from a satellite to users on the ground. A two-user model was applied to achieve spectral efficiency. In practical, real-life scenarios, the UAV and ground users encounter issues with imperfect hardware. We examined the performance gap between two users experiencing practical problems such as hardware impairment and imperfect successive interference cancellation (SIC). To implement a practical scenario, Shadow-Rician fading was adopted in the satellite links, and Rician fading was employed in the terrestrial links for ground users. In the main results, we derived the closed-form expression of the outage probability, and to evaluate the system performance of two NOMA users, we obtained the approximate expressions for high signal-to-noise ratios (SNR). Finally, we produced Monte-Carlo simulations to verify the analytical expressions and demonstrate the effect of the main system parameters, such as the number of transmit antennas on the satellite, transmit SNR, and level of hardware impairment on the system performance metric