中继协作下认知NOMA网络性能分析

把非正交多址接入（NOMA）技术应用到认知网络中,提出基于中继协作的底层认知NOMA系统模型。在瑞利衰落信道下,考虑一个两跳的通信网络,认知中继同时接收来自主网络发射源和次网络发射源的信号,并采用串行干扰消除策略解码转发接收到的信号。次级网络通过为主网络提供中继解码转发服务,获得接入授权频段的机会;主网络通过贡献出授权频段,换取次级网络协作通信的机会,同时获得了优先解码权,保证了主网络通信的可靠性。推导了系统各个接收端的中断概率闭合表达式,并进行了MATLAB仿真。仿真结果表明:采用中继协作可以有效提升认知NOMA网络的中断概率性能。      

全双工认知NOMA网络下中继选择策略性能分析

本文把非正交多址接入(NOMA)技术与认知网络相结合,提出了一种基于多中继选择的认知NOMA网络模型。考虑了在瑞利衰落信道下,主网络借助次级网络中的全双工中继实现可靠通信,作为回报,次级网络允许接入授权频谱来传输次级信号。中继同时接收主次信号后,采用串行干扰消除技术(SIC)依次解码主次信号,并根据NOMA协议转发信号到主次用户端。推导了在两种中继选择策略下认知NOMA网络中断概率,并通过了蒙特卡罗仿真验证。仿真结果表明,两阶段中继选择策略和全双工技术能有效提高系统中断性能。      

Throughput enhancement of cognitive M2M networks based on NOMA for 5G communication systems

One of the promising technologies for 5G cellular networks is machine‐to‐machine (M2M) communications. We propose a cognitive radio network (CR) that includes a primary cellular system and a secondary cognitive system. The primary cellular system has a primary client (PC) and the secondary cognitive system has M2M clients which are called secondary clients (SCs). In a conventional system of CR network based on orthogonal frequency division multiple access (CR‐OFDMA), when the primary client (PC) is absent, only one SC can obtain the idle spectrum. But, the SC must leave the spectrum when detecting the existence of the PC. So, the spectrum usage of this system is very low. This paper proposes a cooperative CR network based on nonorthogonal multiple access (CCR‐NOMA) for spectrum sensing using energy detection (ED) to allow multiple SCs to share the same frequency at the same time, but are differentiated according to the power domain or code domain, to improve spectrum efficiency of 5G communications and the transmission performance of CR network at the absence and presence of the PC. To evaluate the channel sensing performance of the ED technique in CCR‐NOMA, we derived a closed‐form expression between the achievable throughput and sensing time for the CCR‐NOMA system. The same analysis for the case of CR‐OFDMA is reproduced for the sake of comparison. The analysis showed that the CR‐NOMA system for M2M communication outperforms the CR‐OFDMA system for M2M communication for the same noncooperative and cooperative spectrum sensing and physical layer parameters.     

Performance analysis of nonorthogonal multiple access‐based underlay cognitive relay network

This paper considers cooperative non‐orthogonal multiple access (NOMA) scheme in an underlay cognitive radio (CR) network. A single‐cell downlink cooperative NOMA system has been considered for the secondary network, consisting of a base station (BS) and two secondary users, ie, a far user and a near user. The BS employs NOMA signaling to send messages for the two secondary users where the near user is enabled to act as a half‐duplex decode‐and‐forward (DF) relay for the far user. We derive exact expressions for the outage probability experienced by both the users and the outage probability of the secondary system assuming the links to experience independent, nonidentically distributed Rayleigh fading. Further, we analyze the ergodic rates of both the users and the ergodic sum rate of the secondary network. The maximum transmit power constraint of the secondary nodes and the tolerable interference power constraint at the primary receiver are considered for the analysis. Further, the interference caused by the primary transmitter (PT) on the secondary network is also considered for the analysis. The performance of the proposed CR NOMA network has been observed to be significantly better than a CR network that uses conventional orthogonal multiple access (OMA) scheme. The analytical results are validated by extensive simulation studies.     

NOMA-D2D协作无线系统的物理层安全

针对未来海量用户设备接入的物理层安全（physical layer security，PLS）应用需求，提出了一种组合非正交多址接入（non-orthogonal multiple access，NOMA）、终端直通（device-to-device，D2D）与中继协作的NOMA-D2D协作无线系统PLS模型。该模型由采用发射天线选择（transmit antenna selection，TAS）的基站、分别作为基站和D2D发射端的NOMA远端蜂窝用户、D2D接收端以及被动窃听者组成，其中的D2D发射端承担基站的 NOMA 近端用户和解码转发中继两种角色。利用高斯—切比雪夫正交定理推导两种 TAS 方案下NOMA-D2D协作无线系统的安全中断概率、非零安全容量概率以及渐近安全中断概率的近似表达式。数值计算和仿真实验验证了NOMA-D2D协作无线系统PLS性能分析的准确性；在基站总功率恒定时增大分配给远端蜂窝用户的功率能有效提升NOMA-D2D协作无线系统的PLS性能。     

广东工业大学信息工程学院

广东工业大学信息工程学院成立于2000年4月，其前身为原电子与信息工程系和原机械电子工程二系的测量与控制专业。现设有“信息工程”和“测控技术与仪器”两个本科专业，拥有“电子电力与电力传动”与“测试计量技术与仪器”两个学科的硕士学位授予点。     

基于解码转发CR-NOMA协同系统物理层安全性能分析

分析了认知无线电（Cognitive Radio,CR）非正交多址（Non-orthogonal Multiple Access,NOMA）网络中的物理层安全性能。考虑到现有窃听者,支持NOMA的CR通过Nakagami-m信道以解码转发协作模式传输数据。为了分析CR-NOMA物理层安全性能,通过连接中断概率和安全中断概率的闭式表达式来评估CR-NOMA的安全性能。此外,通过蒙特卡罗模拟仿真以验证推导出的分析结果,并深入分析了参数对系统性能的影响。     

Optimal cooperative strategy based on quantum bat for cognitive radio of energy harvesting

In order to reduce energy consumption and improve spectral efficiency of the cognitive relay wireless communication system in 5G network,an optimal cooperative transmission strategy of information and energy was designed for cognitive relay radio with wireless energy harvesting.For the proposed optimal cooperative strategy,the maximal throughput formula and outage probability of secondary user were deduced.In order to resolve the derived maximum throughput equation,a quantum bat algorithm which was based on the optimization mechanism of quantum computing and bat algorithm was designed to solve the deduced equation,and the optimal cooperative transmission scheme for information and energy could be obtained.Simulation results show that the proposed optimal cooperative strategy not only can meet the information transfer demand of primary user,but also can realize the energy self-supply of the secondary user system and improve the communication quality of the secondary user.The proposed optimal cooperative strategy has a better performance than the cooperative strategy of existing cognitive relay radio for different simulation scenarios.     

Outage of cooperative NOMA with an energy harvesting relay in an underlay cognitive radio network

This paper analyzes the performance of a cooperative nonorthogonal multiple access (NOMA) in an underlay cognitive radio network aided by an energy harvesting relay. A secondary source transmits signal for two users, where a near user acts as a relay for the far user. The far user applies the selection combining (SC) approach on the signals which were relayed by the near user and received via direct path from the secondary source. We analytically derive the outage probability (OP) of each user separately, the overall system OP, and the throughput of the system. The impact of the power allocation coefficient of NOMA and energy harvesting parameters on outage is indicated. Further, the performance of the network is investigated with imperfection in successive interference cancellation (SIC), maximal ratio combining (MRC) at relay, and Nakagami-m fading. The results derived analytically are supported by simulation in MATLAB.     

基于传输中断概率的认知无线电系统性能分析

如何设计最优的频谱感知与传输框架是认知无线电技术的重要环节。考虑频谱接入过程中数据传输中断对认知网络性能影响的问题,提出了一种新的基于传输中断概率的频谱感知与传输模型,联合优化频谱感知和数据传输两个阶段,将问题建模为对主用户的干扰量约束条件下的非凸优问题,以最大化认知网络吞吐量为目标联合优化感知时间、传输速率,并通过数值计算方法对其进行求解与仿真。数值分析表明,引入传输中断概率后,在满足上述约束条件的同时,在保护主用户和认知网络吞吐量、传输时延之间有了更好的权衡。     

非理想SIC下全双工NOMA系统的安全性能分析

针对存在多个非共谋窃听者,研究了一种基于全双工中继和两阶段中继选择（TSRS）的非正交多址接入（NOMA）物理层安全通信方案。每个通信过程包含一个传输时隙,系统在每个时隙开始由TSRS策略选择最优中继,所选中继在从源节点接收NOMA叠加信号的同时,向两个目的节点转发上一时隙的再编码叠加信号,两个目的节点采用串行干扰消除（SIC）技术从中继叠加信号中解码获取各自的期望信号。推导了非理想SIC下系统安全中断概率的近似表达式,进行了蒙特卡洛（Monte-Carlo）仿真验证,同时分析了各仿真参数（SIC残余干扰系数、目标安全速率、中继规模等）与系统安全中断概率的关系。理论分析与模拟仿真的结果表明,全双工技术与TSRS的结合方案能有效提升系统的安全中断性能。将该方案应用于实际通信系统设计时,选择合适传输信噪比（SNR）、提高串行干扰消除能力或适当增加中继数量均可实现更好的保密性能。     

Analysis of secrecy outage performance for full duplex NOMA relay systems with appearance of multiple eavesdroppers

Full-duplex (FD) relay systems including a transmit antenna selection and a non-orthogonal multiple access (NOMA) methods are analyzed under presence of multiple eavesdroppers. A channel state information of both the considered system and eavesdroppers is assumed to be outdated and eavesdroppers eavesdrop information signals independently. A closed-form of secure outage probability (SOP), secrecy throughput of every user is derived to evaluate the secrecy performance, and the mathematical analysis approach is verified by the Monte-Carlo simulation. Furthermore, the Golden-Section Search algorithm is proposed to find the maximum of the secrecy throughput of the considered FD-NOMA system. Numerical results indicate that there exists the SOP floor in the considered system and it is constrained by the channel gain of near user. Moreover, there is the optimal signal to interference plus noise ratio value which minimizes the SOP of the system regardless of the number of eavesdroppers. In comparison with half-duplex NOMA model, the SOP of FD-NOMA model is better.

     

Exploiting secure performance in power domain–based multiple access: Impacts of relay link/direct link and secure analysis

A new design of secure nonorthogonal multiple access (NOMA) deployed together with cooperative relaying network is investigated in two modes including direct link and relay link. This paper proposes a mathematical analysis under secrecy considerations of a downlink two‐user NOMA systems. In particular, physical layer security of NOMA is studied in two specific metrics to achieve secure performance analysis such as the secrecy outage probability (SOP) and probability of strictly positive secrecy capacity (SPSC). It should be further explored the situation as the illegal user which is assumed to be eavesdropper at the information level, it attempts to decode the information intended to legal users while NOMA scheme is employed for legal users. The transmission techniques of NOMA equipping relaying architecture (dual‐hop transmission) have proposed due to improving the spectrum efficiency greatly compared with the traditional single‐hop networks. Finally, this study shows the advantages of NOMA over the traditional orthogonal multiple access in the studied problems analytically and numerical analysis is further provided. As important achievement, new exact and closed‐form expressions of the SOP and SPSC are derived, and they will be confirmed by simulation, ie, Monte Carlo simulations are performed to verify the proposed analytical results. Ultimately, the effects of some critical factors are studied on secure performance through these simulation results.     

非正交多址接入系统中的联合中继选择和用户配对算法

针对多用户NOMA中继系统,文中提出了一种联合中继选择和用户配对算法。该算法首先利用最小距离准则选择最优次级用户与主用户配对,然后进行最优中继选择来改善系统中断性能。根据系统模型的分析,推导了系统中断概率的准确表达式,并分析了高信噪比条件下的渐近中断性能。系统分集阶数的研究说明了所提NOMA中继系统相比于传统单中继NOMA系统的优越性。最后,蒙特卡洛仿真结果验证了理论分析的正确性。     

Cooperative Hybrid Spectrum Sharing: A NOMA-based Approach

Non-orthogonal multiple (NOMA) access using successive interference cancellation and cognitive radio are two promising techniques for enhancing the spectrum efficiency and utilization for future wireless communication systems. This paper presents a NOMA-based cooperative hybrid spectrum sharing protocol for cognitive radio networks. A two phase decode-and- forward (DF) relaying scheme in a multi-relay scenario is considered. Each secondary transmitter is grouped into one of the two clusters: a non-cooperative cluster (NCC) and a cooperative cluster (CC). The cluster head (CH) of the CC working as the best DF relay for the primary system is permitted to transmit its own signal superimposed on the primary signal using a NOMA approach in exchange for cooperation. On the other hand, the CH of the NCC transmits in parallel with the primary system satisfying a predefined peak transmit power and peak interference power constraints that guarantee a given primary quality of the service requirement. It is demonstrated that the performances of both the primary and secondary systems increase with the increasing number of secondary nodes. The simulation and theoretical results affirm the efficacy of the proposed protocol compared to the traditional overlay and underlay models in terms of the outage probability and the ergodic capacity.     

Outage analysis of SWIPT‐based full‐duplex cognitive NOMA downlink system over Nakagami‐m fading channels

Cognitive nonorthogonal multiple access (NOMA) technique allows multiple users to share the same time and same frequency resources to fulfil the reliability and spectral efficiency requirements of 5G communication standards. In this paper, simultaneous wireless information and power transfer (SWIPT)–based full‐duplex cognitive NOMA downlink system is proposed. In this system, secondary source (SS) serves as a relay to far primary user as there is no direct link from the primary source. NOMA technique is used at SS to transmit information to far primary user and secondary user. The time switching mechanism is adopted at SS for harvesting energy and information decoding. Analytical closed‐form expressions are derived for the outage probabilities of both primary and secondary users. Outage analysis is carried out in Nakagami‐ fading environment in the presence of self‐interference at SS. In addition to that, the optimal harvesting time to maximize the instantaneous throughput of the far primary user is also derived. Numerical results are plotted to validate the derived expressions. It is inferred that the outage probability of the proposed system depends on the fading environment, harvesting parameters, and self‐interference at SS.     

Secrecy Performance of CCRN with an EHAF Relay under Source and Destination Jamming

In this paper, we investigate the secrecy performance of a cooperative cognitive radio network (CCRN) considering a single energy harvesting (EH) half‐duplex amplify and forward (AF) relay and an eavesdropper (EAV). Power is allocated to each node under cognitive constraints. Because of the absence of a direct wireless link, secondary source (SS) communicates with secondary destination (SD) in two time slots. The SD and the SS broadcast jamming signal to confuse the EAV in the first and in the second time slots, respectively. The relay harvests energy in the first time slot and amplifies and forwards the signal to SD in the second time slot. The EAV employs maximal ratio combining scheme to extract the information. We evaluate the performance in terms of secrecy outage probability (SOP) of the proposed CCRN. The approximate expression of SOP is obtained in integration form. Improvement in SOP is expected for the proposed CCRN because of the use of jamming signals. The secrecy performance of CCRN improves with increase in primary transmit power, peak transmit power of secondary nodes, channel mean power, and energy conversion efficiency but degrades with increase in threshold outage rate of primary receiver and threshold secrecy rate. A MATLAB‐based simulation framework has been developed to validate the analytical work.     

Wireless powered underlay cognitive radio network with multiple primary transceivers: Energy constraint,node arrangement,and performance analysis

This paper considers a cognitive radio–assisted wireless information and power transfer system consisting of multipair of transceiver in primary network and 2‐hop relaying link in secondary network. In this investigation, a decoded‐and‐forward–assisted relay node and power splitting protocol are deployed to obtain ability of wireless energy transfer. The relay node harvests energy from the radio frequency signals of the secondary transmitter and primary transmitters in data transmission to the destination by reusing the licensed spectrum resource. We propose 2 policies for wireless power transfer at the relay, namely, (1) multisource power transfer and (2) single‐source power transfer. To evaluate performance under energy harvesting regime, we derive the closed‐form outage probability expressions and achievable throughput of the secondary network in delay‐limited transmission mode. In addition, we investigate the impact of various system parameters including number of primary transceivers, primary outage threshold, and position arrangement of nodes in primary transceivers on the outage performance of the proposed scheme. Furthermore, we evaluate the system energy efficiency to show trade‐off metric of energy consumption and throughput. Performance results are presented to validate our theoretical derivation and illustrate the impacts of various system parameters. An important result is that the secondary network is more beneficial than harmful from the primary interference under power constraint and reasonable node location arrangement.     

非理想信道下基于人工噪声的密集异构蜂窝网安全传输方案

针对密集异构蜂窝网在非理想信道状态信息条件下的安全传输问题,该文分析了人工噪声对通信的可靠性和安全性的影响,在此基础上提出功率分配优化模型,在不同信道估计精度条件下给出了最优的功率分配因子。首先,考虑信道估计误差对合法信号传输以及人工噪声泄露的影响,推导了典型通信链路的连通中断概率和安全中断概率。然后,在安全性和可靠性约束条件下建立功率分配优化模型以最大化系统安全吞吐量,并通过K维联合搜索算法得到每层网络的最优功率分配因子。最后,仿真结果表明系统设置最优功率分配因子时,人工噪声方案可提升约15%的安全吞吐量。     

Secrecy outage performance analysis of MIMO underlay cognitive radio networks with delayed CSI and transmitter antenna selection

Cognitive radio network is an emerging solution to deal with spectrum scarcity and to utilize the radio spectrum in opportunistic and efficient manner. Secure data transmission is one of the important issues in these kind of networks. This work studies the secrecy outage performance of a multiple-input multiple-output underlay cognitive wiretap radio network system over Rayleigh fading channel with delayed channel state information. This work considers that the secondary transmitter is equipped with multiple antennas and confidential information is transmitted from to multiantenna receiver in the presence of multiantenna eavesdropper. Further, the transmit antenna selection scheme is considered at secondary transmitter to reduce the complexity of antenna selection and to make it more practicable. To improve the quality of signal, this work considers maximal ratio combining (MRC) at secondary receiver, while selection combining and MRC techniques are utilized at the eavesdropper. The closed form expression for exact, asymptotic, and intercept secrecy outage probability has been derived, and the simulation is done for the validation of analytical results. The derived results reveal deterioration of channel secrecy performance with outdated channel state information, and the eavesdropper with outdated channel state information has also an adverse effect. Moreover, the diversity order that can be achieved in underlay cognitive radio network with outdated channel state information is unity.