Yu-Jin Na¹, Ji-Sung Jung¹, Young-Hwan You², Hyoung-Kyu Song^1,*

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 >

Lei Wang¹, Jian Liu¹, Changming Zhao^{2, 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 >

Yinghua Zhang^{1, 2}, Jian Liu^{1, *}, Yunfeng Peng¹, Yanfang Dong², Guozhong Sun², Hao Huang³, Changming Zhao^{4, 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 >

Jian Liu¹, Lei Wang¹, Changming Zhao^{2, 3, *}, Alan Yang⁴

CMC-Computers, Materials & Continua, Vol.63, No.1, pp. 119-130, 2020, DOI:10.32604/cmc.2020.06074

Abstract In this paper, we consider a three-hop relay system based on interference cancellation technique in Underlay cognitive radio (CR) network. Although underlay CR has been shown as a promising technique to better utilize the source of primary users (PUs), its secondary performance will be severely degraded. On one hand, by adapting the Underlay spectrum sharing pattern, secondary users (SUs) would observe the strict power constraints and be interfered by primary users. On the other hand, limited transmit power results in limited transmission range, which greatly degrade the secondary transmission capacity. To solve the problems above, we propose an interference cancellation… More >

Ruoyu Su^{1, 4}, Xiaojun Sun^{1, 3}, Fei Ding^{1, 2, *}, Dengyin Zhang^{1, 2}, Hongbo Zhu^{1, 2}, M. I. M. Wahab⁵

CMC-Computers, Materials & Continua, Vol.62, No.3, pp. 1387-1395, 2020, DOI:10.32604/cmc.2020.06864

Abstract Wireless communications have to face to several different security issues in practice due to the nature of broadcast. The information theory is well known to provide efficient approaches to address security issues in wireless communications, which attracts much attention in both industry and academia in recent years. In this paper, inspired by information theory, we study the outage probability of the opportunistic relay selection based on cognitive decode-and-forward relaying with the secrecy consideration. Specifically, the closed-form expression of the outage probability is proposed. Moreover, the asymptotic performance evaluation on the basis of the analytical results is investigated. The simulation results… More >

Lei Wang¹, Jian Liu^1,*, Alan Yang²

Journal of Information Hiding and Privacy Protection, Vol.1, No.3, pp. 119-133, 2019, DOI:10.32604/jihpp.2019.07296

Abstract In this paper, we study the state-dependent interference channel, where the Rayleigh channel is non-causally known at cognitive network. We propose an active secondary transmission mechanism with interference cancellation technique according to the ON-OFF status of primary network. the secondary transmission mechanism is divided into four cases according to the active state of the primary user in the two time slots. For these interference cases, numerical results are provided to show that active interference cancellation mechanism significantly reduces the secondary transmission performance in terms of secondary outage probability and energy efficiency. More >

Yinghua Zhang^1,2, Yanfang Dong², Lei Wang¹, Jian Liu^1,*, Yunfeng Peng¹, Jim Feng³

CMC-Computers, Materials & Continua, Vol.60, No.1, pp. 379-393, 2019, DOI:10.32604/cmc.2019.05790

Abstract In this paper, we propose a downlink cognitive non-orthogonal multiple access (NOMA) network, where the secondary users (SUs) operate in underlay mode. In the network, secondary transmitter employs NOMA signaling for downlink transmission, and the primary user (PU) is interfered by the transmission from SU. The expressions for the outage probabilities are derived in closed-form for both primary and secondary users in the presence of channel estimation error. Numerical simulation results show that the channel estimation error and the inter-network interference cause degradation of the downlink outage performance. Also the power allocation and the location have a significant impact on… More >