On the spectrum efficiency of a cellular system based on multi-receiver, multiple access (MRMA)

Non-orthogonal multiple access (NOMA) has been considered a promising technique for the fifth generation (5G) mobile communication networks because of its high spectrum efficiency. In NOMA, by using successive interference cancellation (SIC) techniques at the receivers, multiple users with different channel gain can be multiplexed together in the same subchannel for concurrent transmission in the same spectrum. The simultaneously multiple transmission achieves high system throughput in NOMA. However, it also leads to more energy consumption, limiting its application in many energy-constrained scenarios. As a result, the enhancement of energy efficiency becomes a critical issue in NOMA systems. This paper focuses on efficient user clustering strategy and power allocation design of downlink NOMA systems. The energy efficiency maximization of downlink NOMA systems is formulated as an NP-hard optimization problem under maximum transmission power, minimum data transmission rate requirement, and SIC requirement. For the approximate solution with much lower complexity, we first exploit a quick suboptimal clustering method to assign each user to a subchannel. Given the user clustering result, the optimal power allocation problem is solved in two steps. By employing the Lagrangian multiplier method with Karush–Kuhn–Tucker optimality conditions, the optimal power allocation is calculated for each subchannel. In addition, then, an inter-cluster dynamic programming model is further developed to achieve the overall maximum energy efficiency. The theoretical analysis and simulations show that the proposed schemes achieve a significant energy efficiency gain compared with existing methods.

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A Novel User Grouping Algorithm for Downlink NOMA

10.21203/rs.3.rs-413432/v1 ◽

2021 ◽

Author(s):

Navideh Ghafouri Jeshvaghani ◽

Naser Movahhedinia ◽

Mohammad Reza Khayyambashi

Keyword(s):

Interference Cancellation ◽

Multiple Access ◽

Spectrum Efficiency ◽

System Capacity ◽

Substantial Impact ◽

User Grouping ◽

Radio Access ◽

Power Domain ◽

Rate Maximization ◽

Sum Rate

Abstract Non-orthogonal multiple access (NOMA) is one of the promising radio access techniques for resource allocation improvement in the 5th generation of cellular networks. Compared to orthogonal multiple access techniques (OMA), NOMA offers extra benefits, including greater spectrum efficiency which is provided through multiplexing users in the transmission power domain while using the same spectrum resources non-orthogonally. Even though NOMA uses Successive Interference Cancellation (SIC) to repeal the interference among users, user grouping has shown to have a substantial impact on its performance. This prformance improvement can appear in different parameters such as system capacity, rate, or the power consumption. In this paper, we propose a novel user grouping scheme for sum-rate maximization which increases the sum-rate up to 25 percent in comparison with two authenticated recent works. In addition to being matrix-based and having a polynomial time complexity, the proposed method is also able to cope with users experiencing different channel gains and powers in different sub-bands.

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Secrecy-Oriented Optimization of Sparse Code Multiple Access for Simultaneous Wireless Information and Power Transfer in 6G Aerial Access Networks

Wireless Communications and Mobile Computing ◽

10.1155/2021/9922043 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

Jingmin Zhang ◽

Xiaokui Yue ◽

Xuan Li ◽

Haofei Zhang ◽

Tao Ni ◽

...

Keyword(s):

Multiple Access ◽

Optimization Methods ◽

Access Networks ◽

Spectrum Efficiency ◽

Sparse Code ◽

Power Splitting ◽

Power Transfer ◽

Sixth Generation ◽

Successive Convex Approximation ◽

Iot Devices

This article focuses on the simultaneous wireless information and power transfer (SWIPT) systems, which provide both the power supply and the communications for Internet-of-Things (IoT) devices in the sixth-generation (6G) network. Due to the extremely stringent requirements on reliability, speed, and security in the 6G network, aerial access networks (AANs) are deployed to extend the coverage of wireless communications and guarantee robustness. Moreover, sparse code multiple access (SCMA) is implemented on the SWIPT system to further promote the spectrum efficiency. To improve the speed and security of SWIPT systems in 6G AANs, we have developed an optimization algorithm of SCMA to maximize the secrecy sum rate (SSR). Specifically, a power-splitting (PS) strategy is applied by each user to coordinate its energy harvesting and information decoding. Hence, the SSR maximization problems in the SCMA system are formulated in terms of the PS and resource allocation, under the constraints on the minimum rates and minimum harvested energy of individual users. Then, a successive convex approximation method is introduced to transform the nonconvex problems to the convex ones, which are then solved by an iterative algorithm. In addition, we investigate the SSR performance of the SCMA system supported by our optimization methods, when the impacts from different perspectives are considered. Our studies and simulation results show that the SCMA system supported by our proposed optimization algorithms significantly outperforms the legacy system with uniform power allocation and fixed PS.

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Robust Secure Beamforming Design for Cooperative Cognitive Radio Nonorthogonal Multiple Access Networks

Security and Communication Networks ◽

10.1155/2021/5526485 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Quanzhong Li ◽

Sai Zhao

Keyword(s):

Cognitive Radio ◽

Secure Communication ◽

Multiple Access ◽

Spectrum Efficiency ◽

Maximization Problem ◽

Artificial Noise ◽

Practical Case ◽

Secrecy Rate ◽

Worst Case ◽

Rank One

By the integration of cooperative cognitive radio (CR) and nonorthogonal multiple access (NOMA), cooperative CR NOMA networks can improve the spectrum efficiency of wireless networks significantly. Due to the openness and exposure of wireless signals, secure communication is an important issue for cooperative CR NOMA networks. In this paper, we investigate the physical layer security design for cooperative CR NOMA networks. Our objective is to achieve maximum secrecy rate of the secondary user by designing optimal beamformers and artificial noise covariance matrix at the multiantenna secondary transmitter under the quality-of-service at the primary user and the transmit power constraint at the secondary transmitter. We consider the practical case that the channel state information (CSI) of the eavesdropper is imperfect, and we model the imperfect CSI by the worst-case model. We show that the robust secrecy rate maximization problem can be transformed to a series of semidefinite programmings based on S-procedure and rank-one relaxation. We also propose an effective method to recover the optimal rank-one solution. Simulations are provided to show the effectiveness of our proposed robust secure algorithm with comparison to the nonrobust secure design and traditional orthogonal multiple access schemes.

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Joint Beamforming and Artificial Noise Optimization for Secure Transmissions in MISO-NOMA Cognitive Radio System with SWIPT

Electronics ◽

10.3390/electronics9111948 ◽

2020 ◽

Vol 9 (11) ◽

pp. 1948

Author(s):

Carla E. Garcia ◽

Mario R. Camana ◽

Insoo Koo

Keyword(s):

Cognitive Radio ◽

Mobile Networks ◽

Multiple Access ◽

Relaxation Method ◽

Spectrum Efficiency ◽

Artificial Noise ◽

Power Splitting ◽

Secondary Users ◽

Space Division Multiple Access ◽

Radio System

The integration of non-orthogonal multiple access (NOMA) in cognitive radio (CR) networks has demonstrated how to enhance spectrum efficiency and achieve massive connectivity for future mobile networks. However, security is still a challenging issue due to the wireless transmission environment and the broadcast nature of NOMA. Thus, in this paper, we investigate a beamforming design with artificial noise (AN) to improve the security of a multi-user downlink, multiple-input single-output (MISO) NOMA-CR network with simultaneous wireless information and power transfer (SWIPT). To further support power-limited, battery-driven devices, energy-harvesting (EH) users are involved in the proposed network. Specifically, we investigate the optimal AN, power-splitting ratios, and transmission beamforming vectors for secondary users and EH users in order to minimize the transmission power of the secondary network, subject to the following constraints: a minimum signal-to-interference-plus-noise ratio at the secondary users, minimum harvested energy by secondary users and EH users, maximum power at the secondary transmitter, and maximum permissible interference with licensed users. The proposed solution for the challenging non-convex optimization problem is based on the semidefinite relaxation method. Numerical results show that the proposed scheme outperforms the conventional scheme without AN, the zero-forcing-based scheme and the space-division multiple-access-based method.

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Design of Downlink Synchronization for Millimeter Wave Cellular System Based on Multipath Division Multiple Access

IEEE Transactions on Circuits and Systems I Regular Papers ◽

10.1109/tcsi.2020.2989467 ◽

2020 ◽

Vol 67 (9) ◽

pp. 3211-3223

Author(s):

Kang-Lun Chiu ◽

Pai-Hsiang Shen ◽

Bing-Ru Lin ◽

Wei-Han Hsiao ◽

Shyh-Jye Jerry Jou ◽

...

Keyword(s):

Millimeter Wave ◽

Multiple Access ◽

Cellular System

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Spectrum Efficiency Enhancement in Dynamic Space Coded Multiple Access (DSCMA) System

Wireless Personal Communications ◽

10.1007/s11277-009-9682-7 ◽

2009 ◽

Vol 53 (2) ◽

pp. 253-267 ◽

Cited By ~ 1

Author(s):

Chee Kyun Ng ◽

Nor Kamariah Noordin ◽

Borhanuddin Mohd Ali ◽

Sudhanshu Shekhar Jamuar ◽

Mahamod Ismail

Keyword(s):

Multiple Access ◽

Spectrum Efficiency ◽

Efficiency Enhancement

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A Power-Domain NOMA Inspired Overlay Spectrum Sharing Scheme

10.31224/osf.io/vy3na ◽

2018 ◽

Cited By ~ 1

Author(s):

Fazlul Kader

Keyword(s):

Spectrum Sharing ◽

Multiple Access ◽

Spectrum Efficiency ◽

User Needs ◽

Sum Capacity ◽

Closed Form Solutions ◽

Sharing Scheme ◽

Power Domain ◽

Cooperative Spectrum Sharing ◽

Capacity Gain

Non-orthogonal multiple access (NOMA) and cooperative spectrum sharing (CSS) are integrated into this work to enhance both spectrum efficiency and utilization. An overlay spectrum sharing is proposed by exploiting NOMA in coordinated direct and relay transmission (CDRT) (termed as CSS-NOMA-CDRT). In CSS-NOMA-CDRT, a primary strong NOMA user is directly served by primary transmitter (PT), whereas a primary NOMA weak user needs the assistance of a relay to communicate with PT. Instead of using a dedicated relay, a secondary transmitter (ST) acts as a relay to forward the primary symbol to NOMA weak user and ST transmits own symbol to its receiver at the same time. The performance of the proposed CSS-NOMA-CDRT is evaluated along with closed-form solutions, in terms of ergodic sum capacity and outage probability. Through the analytical and Monte Carlo simulation results, it is demonstrated that CSS-NOMA-CDRT can obtain remarkable capacity gain as compared to the conventional NOMA-based CDRT.

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Time Switching Based Wireless Powered Relay Transmission with Uplink NOMA

Sensors ◽

10.3390/s21165467 ◽

2021 ◽

Vol 21 (16) ◽

pp. 5467

Author(s):

Zhihua Lin ◽

Shihua Cao ◽

Jianqing Li

Keyword(s):

Multiple Access ◽

Relay Node ◽

Base Station ◽

Spectrum Efficiency ◽

Transmission Model ◽

System Throughput ◽

Time Switching ◽

Power Domain ◽

End Node ◽

Save Energy

Non-orthogonal multiple access (NOMA) utilizes power domain multiplexing to improve spectrum efficiency compared with orthogonal multiple access (OMA). In the Internet of Things (IoT) uplink NOMA networks, if the channel between the far-end node and the base station is in deep fading, allocating larger transmitting power for this node cannot achieve higher spectrum efficiency and overall system throughput. Relay cooperative communication reduces the transmitting power at the far-end node but leads to extra energy expenditure at the relay node. Fortunately, simultaneous wireless information and power transfer (SWIPT) is advocated in energy-constrained IoT networks to save energy consumption. However, early works all focus on energy harvesting (EH) from one source node or one dedicated power supply station. In this paper, we propose a time switching based wireless powered relay transmission model with uplink NOMA where our EH technique can harvest energy from two simultaneously transmitting nodes. More importantly, by optimizing relay position more energy is harvested from the near-end node at the relay and relay signal attenuation to the destination is reduced as well. Furthermore, the closed-form expressions of outage probability and overall system throughput are derived, and numerical results prove that NOMA in our EH scheme achieves better performance compared to the traditional EH scheme and OMA by optimizing the position of the relay node, time switching factor and so on.

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Exploiting outage performance in device-to-device for user grouping

Indonesian Journal of Electrical Engineering and Computer Science ◽

10.11591/ijeecs.v24.i2.pp904-909 ◽

2021 ◽

Vol 24 (2) ◽

pp. 904

Author(s):

Dinh-Thuan Do ◽

Chi-Bao Le

Keyword(s):

System Performance ◽

Multiple Access ◽

Base Station ◽

Spectrum Efficiency ◽

Frame Structure ◽

Outage Performance ◽

User Grouping ◽

Numerical Result ◽

Device To Device ◽

New Form

The spectrum efficiency and massive connections are joint designed in new form of device-to-device for user grouping. A pair of users is implemented with nonorthogonal multiple access (NOMA) systems. Although NOMA benefits to such system in term of the serving users, device to device (D2D) faces the interference from normal cellular users (CUE). In particular, we derive exact formulas of outage probability to show system performance. In this article, we compare two schemes to find relevant scheme to implement in practice. The frame structure is designed with two timeslot related to uplink and downlink between the base station and D2D users. We confirm the better scheme in numerical result by considering the impacts of many parameters on outage performance.

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