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.     

基于可变距离的车联网D2D通信连接选择

车联网是移动互联网的延伸,其中基站协作的D2D通信适用于车间交通消息的短距离无线传播.针对车辆快速移动导致的通信链路动态性,提出了一种基于可变距离的D2D连接选择方法.通过选择行车道及车间距离参数,估计D2D连接对的信道质量,推导了D2D连接选择的优先指数,并基于该优先指数建立D2D通信链路进行交通消息传播.仿真结果显示,所提方法在D2D连接的生存时间、传输效率方面得到提高,同时降低了D2D通信的中断概率,提升了车辆间通信可靠性.     

Dynamic resource allocation for Device‐to‐Device communication underlaying cellular networks

Future cellular networks such as IMT‐Advanced are expected to allow underlaying direct Device‐to‐Device (D2D) communication for spectrum efficiency. However, enabling D2D communication in a cellular network presents a challenge in resource allocation because of the potentially severe interference it may cause to the cellular network by reusing the spectrum with the cellular users. In this paper, we analyze the resource allocation problem in a single cell system when both cellular users and D2D users are present in the system. We first consider the scenario where cellular users and D2D users are allocated resource independently and propose an optimal algorithm and a heuristic algorithm, and then extend the methods to the scenario where cellular users and D2D users are allocated resource jointly. The number of permitted D2D pairs is selected as a performance measure because it is a more specific performance measure than spectrum efficiency. The proposed schemes maximize the number of permitted D2D communication pairs in a system meanwhile avoiding the strong interference from D2D links to the cellular links. Finally, the performance of the proposed methods is evaluated through the numerical simulation. The simulation results show that the proposed methods enhance the number of permitted D2D communication pairs significantly and that the performance of the proposed scheme for jointly allocation scenario is better than that of the proposed scheme for independently allocation scenario. Copyright © 2012 John Wiley & Sons, Ltd.     

DO‐Fast: a round‐robin opportunistic scheduling protocol for device‐to‐device communications

In this paper, we consider the distributed opportunistic scheduling problem for the Orthogonal Frequency Division Multiplexing OFDM‐based device‐to‐device (D2D) communications, where D2D links contend for access to the dedicated spectrum with limited assistance from cellular infrastructures. Particularly, a synchronous distributed opportunistic scheduling protocol under fairness constraints (DO‐Fast) is prompted. In DO‐Fast, a round‐robin strategy is integrated with the opportunistic scheduling to tackle the trade‐off between system throughput and access fairness. Moreover, without instantaneous channel state information at receivers, we incorporate a priority allocation scheme, where access priorities are assigned randomly in a local fashion. Consequently, DO‐Fast is robust against imperfect channel estimates and inaccurate channel state information ordering. In addition, the opportunistic strategy in DO‐Fast is distinguished from the existing ones in that efficient spatial reuse is exploited by allowing concurrent transmissions based on the signal‐to‐interference ratio scheduling criterion. Meanwhile, access opportunities are moderately granted for poor quality links by the round‐robin strategy for fairness considerations. We analyze and compare three practical scheduling strategies in terms of the access probability. We also evaluate access fairness through Jain's Index. It is shown via numerical and simulation results that DO‐Fast could achieve efficient spectrum utilization and guarantee the short‐term fairness. Copyright © 2014 John Wiley & Sons, Ltd.     

能量收集多跳D2D无线传感网络中的中继选择算法

针对无线功率传输技术的能量收集效率有限造成信噪比下降进而引发通信中断率增加的问题,在能量收集多跳D2D(Device to Device)无线传感网络中,提出一种基于改进K-means聚类的中继选择方法。首先,推导得到能量收集下的信噪比因子,使其作为K-means聚类特征。然后,利用最小欧氏距离原则得到距离聚类中心最近的实际节点的位置。最后,根据距离重排序得到中继节点,形成从源节点到目的节点的通信链路。仿真实验结果表明,相比最短路径算法和随机中继协作方案,所提出的改进算法链路信噪比更大,能够减小通信中断率,具有更好的中继性能。     

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/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。      

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。     

On the performance of interference cancelation in D2D‐enabled cellular networks

Device‐to‐device (D2D) communication underlaying cellular networks is a promising technology to improve network resource utilization. In D2D‐enabled cellular networks, interference among spectrum‐sharing links is severer than that in traditional cellular networks, which motivates the adoption of interference cancelation (IC) techniques at the receivers. However, to date, how IC can affect the performance of D2D‐enabled cellular networks is still unknown. In this paper, we present an analytical framework for studying the performance of two IC methods, that is, unconditional IC and successive IC, in large‐scale D2D‐enabled cellular networks using the tools from stochastic geometry. To facilitate the interference analysis, we propose an approach of stochastic equivalence of the interference, which converts the two‐tier interference (interference from the cellular tier and D2D tier) to an equivalent single‐tier interference. Based on the proposed stochastic equivalence models, we derive the general expressions for the successful transmission probabilities of both cellular uplinks and D2D links in the networks where unconditional IC and successive IC are respectively applied. We demonstrate how these IC methods affect the network performance using both analytical and numerical results. Copyright © 2016 John Wiley & Sons, Ltd.     

D2D通信中联合链路共享与功率分配算法研究

针对D2D （Device-to-Device,D2D）通信过程中的资源分配问题,提出一种联合链路共享和功率分配算法.在保证系统内蜂窝用户服务质量（Quality of Service,QoS）需求的前提下,利用系统的信道状态信息,为D2D用户生成一个由蜂窝用户组成的通信链路的候选集合;在通信链路候选集合内使用凸优化方法得到D2D用户最优功率分配策略;最后利用（Kuhn-Munkres,KM）算法求解最大加权二部图匹配（Maximum Weight Bipartite Matching,MWBM）问题,为D2D用户选择最优的蜂窝用户进行资源共享.仿真结果表明该算法能有效的提升通信网络的吞吐量,可以为D2D用户选择最优的资源分配策略.     

一种5G异构云无线接入网络的D2D资源分配算法

为了解决设备对设备(Device-to-Device,D2D)资源共享带来的信号干扰问题,提出了一种5G异构云无线接入网络的D2D通信资源分配算法.在保证服务质量的前提下,将宏用户设备的频谱资源分配给D2D和中继用户设备,并且把资源分配问题看作一对一的匹配博弈.采用婚姻匹配理论,得到初始的匹配方案.在初始匹配的基础上,提出了一种遵循卡尔多-希克斯(Kaldor-Hicks)原则的资源交换策略,以提高系统的吞吐量.仿真结果表明,该资源分配算法收敛较快,与现有方案相比,能使系统吞吐量提升15％以上,能给系统用户带来约10％的增益,并且有较强抗信道干扰能力.     

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.     

An online resource allocation algorithm to minimize system interference for inband underlay D2D communications

This paper addresses the research question of total system interference minimization while maintaining a target system sum rate gain in an inband underlay device‐to‐device (D2D) communication. To the best of our knowledge, most of the state of the art research works exploit offline resource allocation algorithms to address the research problem. However, in Long‐Term Evolution (LTE) and beyond systems (4G, 5G, or 5G+), offline resource allocation algorithms do not comply with the fast scheduling requirements because of the high data rate demand. In this paper, we propose a bi‐phase online resource allocation algorithm to minimize the total system interference for inband underlay D2D communication. Our proposed algorithm assumes D2D pairs as a set of variable elements whereas takes the cellular user equipment (UEs) as a set of constant elements. The novelty of our proposed online resource allocation algorithm is that it incurs a minimum number of changes in radio resource assignment between two successive allocations among the cellular UEs and the D2D pairs. Graphical representation of the simulation results suggests that our proposed algorithm outperforms the existing offline algorithm considering number of changes in successive allocation for a certain percentage of sum rate gain maintaining the total system interference and total system sum rate very similar.     

A weighted interference estimation scheme for interface‐switching wireless mesh networks

The co‐channel interference problem in wireless mesh networks (WMN) is extremely serious due to the heavy aggregated traffic loads and limited available channels. It is preferable for mesh routers to dynamically switch channels according to the accurate estimation of co‐channel interference level in the neighborhood. Most developed interference estimation schemes, however, do not consider the impact of interface switching. Furthermore, the interference in wireless networks has been extensively considered as an all‐or‐nothing event. In this paper, we develop a weighted interference estimation scheme (WIES) for interface‐switching WMN. WIES takes a new version of multi‐interface conflict graph that considers the impacts of frequent interface switching as the interference relationship estimation scheme. Besides, WIES uses a weight to estimate the interference level between links. The weight utilizes two empirical functions to denote the impacts of the relative distance and characteristics of traffic loads in WMN. Extensive NS2 simulations show that WIES achieves significant performance improvements, especially when the interference level of the network is high. We also validate that the interference level of networks is affected by several system parameters such as the number of available channels and the ratio between interference range and transmission range. Copyright © 2008 John Wiley & Sons, Ltd.     

Energy‐efficient device‐to‐device communication using adaptive resource‐block allocation

Device‐to‐device (D2D) communication in the fifth‐generation (5G) wireless communication networks (WCNs) reuses the cellular spectrum to communicate over the direct links and offers significant performance benefits. Since the scarce radio spectrum is the most precious resource for the mobile‐network operators (MNOs), optimizing the resource allocation in WCNs is a major challenge. This paper proposes an adaptive resource‐block (RB) allocation scheme for adequate RB availability to every D2D pair in a trisectored cell of the 5G WCN. The hidden Markov model (HMM) is used to allocate RBs adaptively, promoting high resource efficiency. The stringent quality‐of‐service (QoS) and quality‐of‐experience (QoE) requirements of the evolutionary 5G WCNs must not surpass the transmission power levels. This is also addressed while using HMM for RB allocation. Thus, an energy‐efficient RB allocation is performed, with higher access rate and mean opinion score (MOS). Cell sectoring effectively manages the interference in the 5G networks amid ultrauser density. The potency of the proposed adaptive scheme has been verified through simulations. The proposed scheme is an essential approach to green communication in 5G WCNs.     

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.     

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.     

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.     

一种基于三维曲面变形的自由变形算法

在Dirichlet自由变形算法的基础上,针对Dirichlet自由变形方法不适合三维曲面变形的情况,提出了一种基于曲面两点之间最短距离的Dirichlet自由变形算法:算法将三维曲面上求两点之间最短距离问题转化为二维平面上求带权图最短路径问题,用三角面片的面积之和来表示Voronoi单元或部分Voronoi单元面积,并由此给出了一种适合由多边形表示的三维曲面的Voronoi图构造方法及Sibson邻居和Sibson坐标的计算方法;并且用该算法对人脸模型进行局部变换,进一步刻画特定人脸器官的细节特征,最终形成了个性化的三维人脸模型.     

A tractable analytical model for interference characterization and minimum distance enforcement to reuse resources in three‐dimensional in‐building dense small cell networks

In this paper, we address mainly 2 important issues, namely, characterizing co‐channel interference and enforcing a minimum distance between femtocell base stations (FCBSs) for reusing resources in FCBSs deployed in a 3‐dimentional multi‐floor building. Each floor is modeled as a group of square‐grid apartments, with one FCBS per apartment. We propose a simple yet reasonable analytical model by using planar‐Wyner model for intra‐floor interference and linear‐Wyner model for inter‐floor interference modeling in a 3‐dimensional multi‐floor building to derive a minimum distance between co‐channel FCBSs for optimization constraints, namely, link level interference, spectral efficiency, and capacity. As opposed to orthogonal resource reuse and allocation (ORRA) where resources are reused once, using the proposed model, we develop 2 strategies for reusing resources more than once, that is, non‐ORRA, within a multi‐floor building. An algorithm of the proposed model is developed by including an application of the model to an ultra‐dense deployment of multi‐floor buildings. With an extensive numerical analysis and system level simulation, we demonstrate the capacity outperformance of non‐ORRA over ORRA by manifold. Further, with a fairly accurate yet realistic estimation, we show that the expected spectral efficiency of fifth‐generation networks can be achieved by applying the proposed model to an ultra‐dense deployment of FCBSs.