基于资源分配和功率控制的D2D中继选择

为优化蜂窝用户通信与设备直传(D2D)中继通信共存下的同频干扰问题,满足蜂窝用户容量要求,提出了一种基于能效的联合资源分配和功率控制的D2 D中继选择算法.该算法首先对等效D2 D中继链路进行资源分配,减小算法复杂度的同时使得D2 D链路对蜂窝链路产生的干扰最小;然后以资源分配结果和功率控制算法为依据进行中继选择.该方案不仅考虑了D2 D中继链路的能效问题,而且还同时考虑到了对蜂窝链路的干扰问题.通过仿真验证,所提算法不仅能有效提升D2 D中继链路的能效值,同时降低了对蜂窝用户的干扰.     

过时CSI下全双工中继辅助D2D网络的物理层安全

中继辅助终端直通（devicetodevice,D2D）网络通过与蜂窝网络共享频谱提高D2D用户的频谱效率和蜂窝用户（cellular user,CU）的物理层安全性。为进一步改善其性能,可以在基站和D2D链路的中继节点采用天线选择以及在中继节点采用全双工技术。然而,由于存在反馈时延和移动性,用于蜂窝链路和所有D2D链路天线选择的信道状态信息（channelstateinformation,CSI）均可能是过时的,针对该场景下的物理层安全性和可靠性问题,提出一种主动窃听和过时CSI场景下基站和中继节点均采用发射天线选择的全双工中继辅助D2D网络安全模型,推导CU的中断概率、遍历容量、非零安全容量概率、安全中断概率、渐近安全中断概率的解析表达式。数值计算与仿真结果均表明,基站发射天线数、中继干扰天线数越多,CU的安全性能越好;过时的CSI会降低CU的中断性能和安全性能。     

D2D/蜂窝通信模式切换与联合功率控制方案

设备直连（Device-to-Device, D2D）通信技术通过复用蜂窝系统的频谱资源提高频谱利用率,但D2D的引入会给蜂窝系统带来干扰。如何合理地选择D2D/蜂窝通信模式并进行功率优化控制,成为减小D2D和蜂窝系统间干扰、提升网络性能的关键。本文考虑D2D用户复用蜂窝上行链路场景,提出了一种基于距离和联合功率控制的通信模式选择方案。在该方案中,D2D用户和蜂窝用户与基站距离的比值决定了D2D用户是否采用Underlay模式进行通信,进而在约束蜂窝用户和D2D用户发射功率的条件下实现D2D链路和蜂窝链路的联合功率控制,最终推导出能够最大化系统总吞吐量的最优用户功率分配方案。根据仿真结果,本文提出的联合功率控制方案能够在降低系统间干扰的同时有效提高D2D和蜂窝系统的总吞吐量,进而提高了系统的性能。      

中继协同D2D通信的能效优化

针对D2D中继通信中D2D设备电池容量受限问题,本文提出了一种逐步优化功率控制和中继选择从而最大化系统能量效率的方法。首先,在满足蜂窝链路最小数据速率的条件下,将功率控制问题建模为一个非线性规划问题,并求解出D2D发射机的最优发射功率;然后,分别利用发送节点与接收节点的邻域为半径建立节点均匀分布的球状模型;其次,基于路径损耗相似性对节点进行k-means迭代聚类,并得到路径损耗最小节点的质心;最后,将得到的质心作为中继节点进行D2D中继通信。仿真结果表明,在保证高质量通信的条件下,本文提出的优化方法能够最大化系统的能量效率。      

基于用户中断概率的D2D通信干扰协调与资源分配

在LTE系统中引入设备直传(D2D)通信技术,会因为D2D用户复用蜂窝用户资源进行通信而产生同频干扰.在现有的干扰协调与资源分配研究中,都需要基站获取各个通信链路的信道状态信息(CSI),但这样无疑会增加基站的信令负担.为减小干扰与基站的信令负担,提出了一种基于用户中断概率的干扰协调与资源分配算法,首先在保证蜂窝用户正常通信的情况下,通过限制D2D用户到基站间的距离来降低干扰;其次通过遍历所有蜂窝用户的频谱资源,选择能使D2D用户的总中断概率最低的频谱资源进行复用.仿真结果表明,所提算法能够在保证蜂窝用户正常通信的情况下,明显降低D2D用户的平均中断概率,同时还能够降低基站信令负担.     

D2D通信中干扰协调算法的研究

D2D(Device-to-Device,终端直通通信)技术是指用户可以直接进行通信而不用经过基站的一种终端直通通信技术,移动蜂窝使用终端直通通信技术能够增加蜂窝系统性能,然而却带来了较多的干扰以及加大了能量损耗.为了达到用户和基站间的相互干扰,增加频谱利用效率和能量利用效率,文章以D2D 用户和速率为优化目标提出了一种联合资源分配和功率控制的方法,用以达到高能效的终端直通通信.仿真结果表明:文章提出的联合信道分配和功率控制方案,能明显减少D2D用户与蜂窝系统受到的干扰,增加蜂窝频谱利用率以及D2D用户和速率.     

D2D通信中一种资源分配与功率控制结合的方案

以underlay方式工作的D2D(Device-to-Device)通信通过资源共享复用蜂窝网络中的资源,在提高系统资源利用率的同时,对已有蜂窝链路带来了同频干扰。为了减小因无线资源复用带来的干扰,提出了一种资源分配与功率控制相结合的方法。以最小化系统干扰为目的,通过在D2 D链路之间合理地分配资源,保证了蜂窝链路的通信质量;同时动态地调整D2 D链路的发射功率,在保证相应蜂窝链路干扰可控的情况下,合理提高了D2 D链路的通信质量。仿真结果表明,与现有方案相比,所提出的算法能够有效地提高D2 D通信与蜂窝用户共存场景下的系统性能。     

异构蜂窝网络中基于Stackelberg博弈的能效优化算法

设备到设备(Device To Device,D2D)通信允许移动终端无需通过基站而进行直接通信。为提高蜂窝系统能效,引入D2D通信共享频谱资源形成异构蜂窝网络。本文将D2D通信的能效优化问题转化为博弈收益最大化问题,并提出了一种基于Stackelberg博弈的分布式功率控制算法。针对系统模型中存在的跨层干扰以及层内干扰,该算法建立了干扰价格系数与D2D对发送功率之间的函数关系,并求解出给定干扰价格系数下D2D对最佳发送功率的闭合表达式。仿真结果表明所提算法能够在最大化基站端蜂窝用户收益的基础上有效提高D2D对的总能效。      

基于D2D通信系统中的一种跨层中继选择算法

在D2D通信系统与蜂窝网络共存的场景下,引入中继节点可有效提高D2D链路的吞吐量和D2D用户对蜂窝用户的干扰。文中基于译码转发模式,结合跨层协作通信的思想,提出了一种基于物理层和数据链路层的跨层中继选择算法。该算法结合物理层的信道状态信息和数据链路层的队列状态信息,两个参数进行最优中继节点的选择。并最终通过仿真验证表明,基于跨层中继选择算法可提高通信系统的吞吐量,同时降低了通信系统的平均时延和数据包错误率。     

一种复用蜂窝网络下行无线资源的D2D通信干扰抑制方法

由于蜂窝通信与D2D通信复用相同的小区下行资源,这两种通信方式之间的小区内干扰不能再被忽略。基站的发射功率要比UE的发射功率高出很多,同时实际的下行系统中,基站也不便对每个用户进行功率控制,因此功率控制干扰抑制方案在下行时的效果并不明显。本文从用户调度的角度出发．提出了一种适用于D2D通信复用蜂窝网络下行资源的干扰抑制方法。该方法充分利用的UE的空间隔离度,减少了两种通信模式之间的干扰,提升了整个蜂窝小区的吞吐量。     

基于人工噪声辅助的D2D异构蜂窝安全通信方法

A secure communication scheme based on artificial noise assisted from base station(BS)was proposed to improve the system secrecy rate of the D2D underlaying cellular.Firstly,the system secrecy rate was modeled.Then the BS with multi-antennas added artificial noise(AN)in cellular user’s signal as well as designed beam vectors of the desired signal and artificial noise to maximize system secrecy rate.In the end,a joint optimization scheme based on the fairness constraint was introduced to optimize beam vectors of the desired signal,the power allocation for BS’s information signal and AN and the D2D power control.Simulation results show that the system ergodic secrecy rate can be improved 2.7 bit·s^?1·Hz^?1more than the schemes based on SVD and zero-forcing at most.     

On selecting transmission mode for D2D transmitter in underlay cellular network with a multi-antenna base station

The Device-to-Device (D2D) communication underlaying cellular networks is considered in this study. The D2D transmitter in the D2D mode can directly transmit messages to a receiver, but it may interfere with the transmission of another cellular user who shares the same uplink channel. The transmitter can also operate in a cellular mode in which no interference to another cellular user occurs. We propose a mode selection scheme that aims to minimize the transmission power of the D2D transmitter subject to constraints on the minimum required data rate and maximum interference to other cellular users. The proposed scheme is based on bounds for transmission power and is less complex than the optimal scheme. Furthermore, it requires only a few statistics and does not need a fading channel distribution. The performance of the scheme is close to optimum when the number of Base Station (BS) antennas is large, and the mean absolute deviation of the fading terms is small. We verify this with numerical results of the Rician and Rayleigh fading channels by assuming that the BS antennas are independent. The simulation results for the two correlated BS antennas are presented herein.     

基于安全中断概率的D2D安全接入策略

针对D2D蜂窝系统通信安全性受资源限制的问题,考虑到蜂窝链路和D2D链路的同频干扰能够为两者带来安全增益,基于此,提出一种基于安全中断概率的D2D用户接入策略。首先理论分析了蜂窝用户和D2D用户的安全中断概率,并给出了基于安全中断概率最小化的D2D用户功率优化算法。在上述分析的基础上,选择安全中断概率最小的D2D用户接入复用蜂窝用户的无线资源,同时提高D2D通信链路和蜂窝上行链路的安全性。最后,仿真结果证明了所提算法的有效性。     

Secure opportunistic access control in D2D-enabled cellular network

The mutual interference between cellular links and D2D links can bring the secrecy gain to cellular users in D2D-enable cellular networks.To make full use of them,a cooperative secrecy transmission scheme was proposed based on wireless channels.The channel direction information and gains depict the interference from D2D links to cellular links and other D2D links in the proposed scheme.Firstly,only the D2D users which meet the limited interference conditions were accessed to cellular networks to ensure their reliable communications.It was assumed that legitimate users and eavesdroppers were independent two-dimensional homogeneous Poisson point processes (PPP) distribution.Then the security outage probability (SOP) was derived for cellular users and the connection outage probability (COP) for D2D users,and the impacts of interference thresholds were discussed on their performances.Next,an optimization model was given to minimize D2D users’ COP while ensuring the secrecy performance requirements of cellular users,thus achieving the optimal performance.Finally,simulation results verify the validity of the proposed scheme.     

异构云无线接入网场景下D2D通信资源共享与分配

针对异构云无线接入网中的前向链路受限问题,提出了一种基于干扰阈值的设备到设备(Device-to-Device,D2D)多用户分簇方案,并对系统信道和功率资源的分配进行优化。首先根据D2D用户之间的干扰级别,利用着色图理论对多用户进行分簇;然后,在满足D2D用户和蜂窝用户服务质量约束下,建立了基于D2D用户和速率最大化的资源分配模型,并进一步采用二分法对已分簇的D2D用户进行功率优化分配。仿真实验结果验证了所提方案相比传统方案,系统频谱利用率提高了55%以上。     

D2D underlay massive MIMO hybrid networks with improved physical layer secrecy and energy efficiency

For us to meet the green and reliable communication requirement by the forthcoming fifth generation mobile networks, this paper focuses on a secrecy constrained device‐to‐device (D2D) underlay massive multiple‐input multiple‐output hybrid network, where the D2D user (DU) and cellular user (CU) links are exposed to passive malicious eavesdroppers. The D2D transmitters harvest the power from the signals of dedicated power beacons (PBs), but also the ambient radio frequency (RF) interference of CUs. The signals of PBs are known previously at the receivers of both the D2D and cellular users but are not known at eavesdroppers so that it can be regarded as an artificial noise. For the interested hybrid networks, we first present an energy‐harvesting scheme based on the inversion power control where the power received at the corresponding receiver is higher than the receiver's sensitivity. Then, by modeling the locations of network elements as Poisson point process and applying stochastic geometry, we derive the sufficient probability that a typical D2D transmitter harvests sufficient energy to establish communication links. Finally, with the derived sufficient probability, we evaluate the performance of the CUs and DUs in the achievable ergodic rate and the secrecy outage probability. Both the analytical and simulated results show that precious power of network is saved because of the ambient RF interference exploited, and the secrecy of both D2D and cellular links is improved simultaneously because of the signal of PBs modeled as artificial noises at CUs and DUs.     

Energy‐efficient resource allocation in D2D communications for energy harvesting–enabled NOMA‐based cellular networks

In this paper, we propose an energy‐efficient power control and harvesting time scheduling scheme for resource allocation of the subchannels in a nonorthogonal multiple access (NOMA)–based device‐to‐device (D2D) communications in cellular networks. In these networks, D2D users can communicate by sharing the radio resources assigned to cellular users (CUs). Device‐to‐device users harvest energy from the base station (BS) in the downlink and transmit information to their receivers. Using NOMA, more than one user can access the same frequency‐time resource simultaneously, and the signals of the multiusers can be separated successfully using successive interference cancellation (SIC). In fact, NOMA, unlike orthogonal multiple access (OMA) methods, allows sharing the same frequency resources at the same time by implementing adaptive power allocation. Our aim is to maximize the energy efficiency of the D2D pairs, which is the ratio of the achievable throughput of the D2D pairs to their energy consumption by allocating the proper subchannel of each cell to each device user equipment (DUE), managing their transmission power, and setting the harvesting and transmission time. The constraints of the problem are the quality of service of the CUs, minimum required throughput of the subchannels, and energy harvesting of DUEs. We formulate the problem and propose a low‐complexity iterative algorithm on the basis of the convex optimization method and Karush‐Kuhn‐Tucker conditions to obtain the optimal solution of the problem. Simulation results validate the performance of our proposed algorithm for different values of the system parameters.     

Secure content delivery over device‐to‐device communications underlaying cellular networks

Content delivery via device‐to‐device (D2D) communications is a promising technology for offloading the heavy traffic for future mobile communication networks. As security is a critical concern for the users, we focus on improving the secrecy capacity for content dissemination in D2D communications. In this work, we explore the inherent characteristics of wireless channels to prevent eavesdropping. Firstly, we propose a power control scheme to obtain the optimal transmission powers for the D2D links without violating secrecy requirement of cellular users. Then, we formulate the problem as a stochastic optimization problem, aiming at maximizing the secrecy capacity gain of D2D communications. By solving the expected value model for the stochastic optimization problem, the optimal D2D links are selected to realize maximal ergodic secrecy capacity gain. Specifically, a weighted conflict graph is formulated according to the protocol model. Thus, the optimization problem has been transformed to the maximum weighted independent set problem, which is solved by a greedy weighted minimum degree algorithm. Simulation results demonstrate that the content dissemination scheme with power control can bring high secrecy capacity gain to the network. Copyright © 2016 John Wiley & Sons, Ltd.