Yanqiu Chen, Xiaopeng Ji^*

CMES-Computer Modeling in Engineering & Sciences, Vol.136, No.1, pp. 531-553, 2023, DOI:10.32604/cmes.2023.024531 - 05 January 2023

Abstract Non-orthogonal multiple access technology (NOMA), as a potentially promising technology in the 5G/B5G era, suffers from ubiquitous security threats due to the broadcast nature of the wireless medium. In this paper, we focus on artificial-signal-assisted and relay-assisted secure downlink transmission schemes against external eavesdropping in the context of physical layer security, respectively. To characterize the non-cooperative confrontation around the secrecy rate between the legitimate communication party and the eavesdropper, their interactions are modeled as a two-person zero-sum game. The existence of the Nash equilibrium of the proposed game models is proved, and the pure strategy More >

Mohammad Al Mojamed^*

Computer Systems Science and Engineering, Vol.45, No.3, pp. 2953-2970, 2023, DOI:10.32604/csse.2023.032965 - 21 December 2022

Abstract Long Range Wide Area Network (LoRaWAN) has been developed to meet the requirements for the enormous device-to-device communication of Internet of Things (IoT) networks, which consist of a large number of participating devices spread over large coverage areas with low data rates and low power consumption. It supports communications in both directions, uplink, and downlink directions. However, the downlink communication in the current LoRaWAN raises the bottleneck issue at gateways due to the used gateway selection algorithm. This paper proposes a novel gateway selection algorithm based on the duty cycle time-off values for the existing gateways,… More >

Mohammed Abd-Elnaby^*

CMC-Computers, Materials & Continua, Vol.71, No.3, pp. 5099-5116, 2022, DOI:10.32604/cmc.2022.022020 - 14 January 2022

Abstract Non-orthogonal multiple access (NOMA) has been seen as a promising technology for 5G communication. The performance optimization of NOMA systems depends on both power allocation (PA) and user pairing (UP). Most existing researches provide sub-optimal solutions with high computational complexity for PA problem and mainly focuses on maximizing the sum rate (capacity) without considering the fairness performance. Also, the joint optimization of PA and UP needs an exhaustive search. The main contribution of this paper is the proposing of a novel capacity maximization-based fair power allocation (CMFPA) with low-complexity in downlink NOMA. Extensive investigation and… More >

Fahad Alraddady^*

Computer Systems Science and Engineering, Vol.42, No.2, pp. 535-544, 2022, DOI:10.32604/csse.2022.021746 - 04 January 2022

Abstract In this paper, the resource allocation problem for user pairing (UP) in downlink non-orthogonal multiple access (NOMA) systems is investigated. NOMA allows the use of one subcarrier for more than one user at the same time, thus increases the total capacity of the wireless communication system. However, users pairing is a challenging task in the NOMA systems, because a good channel quality subcarrier should be selected and allocated for the user to enhance the performance of NOMA systems. The proposed UP algorithm aims to enhance the sum rate of the paired users per subcarrier and… More >

Rao Muhammad Asif¹, Mustafa Shakir¹, Jamel Nebhen², Ateeq Ur Rehman³, Muhammad Shafiq^4,*, Jin-Ghoo Choi⁴

CMC-Computers, Materials & Continua, Vol.70, No.3, pp. 5889-5905, 2022, DOI:10.32604/cmc.2022.020777 - 11 October 2021

Abstract 5G technology can greatly improve spectral efficiency (SE) and throughput of wireless communications. In this regard, multiple input multiple output (MIMO) technology has become the most influential technology using huge antennas and user equipment (UE). However, the use of MIMO in 5G wireless technology will increase circuit power consumption and reduce energy efficiency (EE). In this regard, this article proposes an optimal solution for weighing SE and throughput tradeoff with energy efficiency. The research work is based on the Wyner model of uplink (UL) and downlink (DL) transmission under the multi-cell model scenario. The SE-EE… More >

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 - 20 August 2021

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 More >

Mohammed Abd-Elnaby^*

CMC-Computers, Materials & Continua, Vol.69, No.1, pp. 521-537, 2021, DOI:10.32604/cmc.2021.018351 - 04 June 2021

Abstract Non-orthogonal multiple access (NOMA) is one of the leading technologies for 5G communication. User pairing (UP) and power allocation (PA) are the key controlling mechanisms for the optimization of the performance of NOMA systems. This paper presents a novel UP and PA (UPPA) technique for capacity and fairness maximization in NOMA called (CFM-UPPA). The impact of the power allocation coefficient and the ratio between the channel gains of the paired users on the sum-rate capacity and the fairness in NOMA is firstly investigated. Then, based on this investigation, the PA and UP algorithms of the… More >

Park Chan-Yeob, Hyun-Ro Jae, Jun-Yong Jang, Song Hyoung-Kyu^*

CMC-Computers, Materials & Continua, Vol.68, No.1, pp. 137-148, 2021, DOI:10.32604/cmc.2021.016108 - 22 March 2021

Abstract Linear precoding methods such as zero-forcing (ZF) are near optimal for downlink massive multi-user multiple input multiple output (MIMO) systems due to their asymptotic channel property. However, as the number of users increases, the computational complexity of obtaining the inverse matrix of the gram matrix increases. For solving the computational complexity problem, this paper proposes an improved Jacobi (JC)-based precoder to improve error performance of the conventional JC in the downlink massive MIMO systems. The conventional JC was studied for solving the high computational complexity of the ZF algorithm and was able to achieve parallel… More >

Jun-Yong Jang¹, Won-Seok Lee¹, Jae-Hyun Ro¹, Young-Hawn You², Hyoung-Kyu Song^1,*

CMC-Computers, Materials & Continua, Vol.67, No.2, pp. 1729-1745, 2021, DOI:10.32604/cmc.2021.015424 - 05 February 2021

Abstract In this paper, a novel precoding scheme based on the Gauss-Seidel (GS) method is proposed for downlink massive multiple-input multiple-output (MIMO) systems. The GS method iteratively approximates the matrix inversion and reduces the overall complexity of the precoding process. In addition, the GS method shows a fast convergence rate to the Zero-forcing (ZF) method that requires an exact invertible matrix. However, to satisfy demanded error performance and converge to the error performance of the ZF method in the practical condition such as spatially correlated channels, more iterations are necessary for the GS method and increase… More >

Jianzhong Li¹, DexiangMei¹, Dong Deng¹, Imran Khan², Peerapong Uthansakul^{3, *}

CMC-Computers, Materials & Continua, Vol.65, No.2, pp. 1571-1590, 2020, DOI:10.32604/cmc.2020.011822 - 20 August 2020

Abstract Non-orthogonal multiple access (NOMA) is one of the key 5G technology which can improve spectrum efficiency and increase the number of user connections by utilizing the resources in a non-orthogonal manner. NOMA allows multiple terminals to share the same resource unit at the same time. The receiver usually needs to configure successive interference cancellation (SIC). The receiver eliminates co-channel interference (CCI) between users and it can significantly improve the system throughput. In order to meet the demands of users and improve fairness among them, this paper proposes a new power allocation scheme. The objective is More >