D2D技术在LTE-A系统中的应用分析

由于移动通信技术的飞速发展,第三代的移动通信技术及设备已经从最开始的理论性逐渐的走向了商用。在整个移动通信的业界中,各大通信业的巨头们加大了对下一代无线通信网络的开发和探索,比如"3GPP"的长期演进(LTE),以及IEEE802.16m等方面的研究。不仅如此,对3GPP进行研究的同时,对LTE-A系统进行了更为深入详细的研究。对于这些系统而言,无论是系统的演进,还是系统的发展将"未来移动蜂窝网络(IMT-A)"作为主要的支持背景,在该范畴下展开的,如此众多的IMT-A系统,在小区蜂窝的网络背景下,允许支持Device-to-Device(D2D),其主要的目的是进一步的提高频谱利用率。文章主要针对D2D技术在LTE-A系统中的应用进行研究,首先介绍了D2D通信的原理及应用,然后对其仿真结果进行研究和分析,并提出展望,以期对D2D技术的良好应用,起到相应的参考帮助。     

D2D通信资源调度研究现状综述

终端直通技术(D2D)是一种终端在基站控制下直接进行通信而不需要基站转发的新型通信技术。D2D引入LTE-A蜂窝系统虽然可以带来吞吐量和频谱效率的提升,但是也会带来很大的干扰。综合近些年来的研究成果,合理的资源调度算法成为降低干扰,提升系统性能的关键。首先,描述了D2D通信技术引入LTE-A蜂窝网络后的系统干扰模型。然后,从模式选择、资源分配和功率控制三个方面综述了目前国内外文献关于资源调度算法的研究成果。     

D2D研究现状及发展前景

LTE Device to Device(D2D)Proximity Services(LTE终端直通近距离服务)即我们熟知的LTE-D2D(端到端)技术。2013年,D2D成为3GPP组织重点研讨技术之一,其标准化工作正在讨论完善之中。LTE-D2D是在LTE-A系统(辅助)控制或无网络基础设施的情况下,用户设备在授权频段上直接进行通信的技术。它的出现将在一定程度上缓解无线频谱资源匮乏的问题,并能够提升蜂窝系统频谱效率。文章对D2D通信的发展历程、场景和关键技术进行了介绍,最后展望D2D技术发展前景及在未来应用中的情况。     

LTE-A网络中D2D通信的资源分配算法研究

该文研究了D2D通信使用LTE-A网络上行链路的资源分配问题。首先将问题建模为混合整数非线性规划问题(MINLP),其次根据待接入用户对各信道的青睐程度计算特征值列表并形成相应联盟。在保证各用户服务质量(QoS)的情况下,利用最大加权二部图匹配(MWBM)方法为待接入网络用户寻找合适的资源及复用的组合。仿真结果表明,该算法打破了D2D用户在数据传输过程中一直处于专用或者复用模式的束缚,扩大了D2D用户对可选用的资源范围,与现有算法相比,可有效提高系统的总速率。     

LTE系统中引入D2D技术后的干扰研究

D2D(终端到终端)是一种在LTE(长期演进)通信系统中通过重用小区内蜂窝用户的资源来实现终端到终端通信的新型技术。在LTE中引入D2D后,资源调度也随之发生变化,不仅体现在资源块的使用上,也体现在相应的功率控制机制上。D2D技术在提高系统容量的同时,也带来了新的干扰问题——普通蜂窝通信模式与D2D模式的相互干扰。通过协调好系统内蜂窝通信与D2D通信之间的干扰,可以提高系统的总体性能。     

毫米波D2D通信上下行链路吞吐量优化方案

5G通信技术中终端直通(D2D通信)的功率分配是近期研究的热点,为了提升系统容量和频谱利用率,将毫米波与D2D通信技术结合,在此技术中,针对28GHz频段上行链路及下行链路蜂窝网络中的D2D资源分配进行了研究,将其系统总吞吐量达到最大化算法进行优化。首先,推导出每个D2D对所对应的准入集,其次,在考虑每个D2D对用户以及蜂窝用户功率控制情况下,分别求出上行链路及下行链路中的吞吐量,最后,在保证D2D对总吞吐量最大化前提下将蜂窝用户信道分配给D2D对。仿真结果表明,所提出的方案可以提高系统的吞吐量。     

基于大规模MIMO和D2D技术的混合网络能量效率研究

文章研究了基于大规模多输入多输出（multiple-input multiple-output,MIMO）和端到端（device-to-device,D2D）技术的双层混合网络及其能量效率,面向D2D用户（D2D user,DU）提出了无线能量采集方案。在该混合网络模型中,宏蜂窝基站由大规模MIMO天线阵列构成,D2D网络覆盖在宏蜂窝之上,与蜂窝网共享频谱。为了保证D2D通信,系统配置了由小规模MIMO天线构成的专用能量发射基站（power beacon,PB）,其通过迫零预编码向能量约束的D2D发射机传送能量;同时,为了提高网络的能量效率,DU还可以从附近蜂窝网用户（cellular user,CU）的射频（radio frequency,RF）干扰信号中采集能量。对此混合网模型和能量采集方案,文章通过假设网络中CU、DU以及PB的位置服从独立泊松点过程和利用随机几何分析方法,基于反功率控制方案得到了网络中任一D2D发射机通过采集足够能量来建立通信链路的概率,其以简单的积分形式给出。分析和数值结果表明,文章提出的无线能量采集方案由于PB的配置保证了D2D通信的可靠性;同时又因为充分利用了附近CU的RF干扰信号,有效提高了D2D用户采集足够能量的概率,节约了PB的能量,改善了系统的能量效率。      

D2D系统中带QoS约束的多天线选择及性能分析

本文研究了蜂窝直通通信（Device-to-Device,D2D）系统中基站端多天线选择问题,即在基站传输过程中选择多于一根天线进行传输。借助于次序统计的相关结论,本文分析了该D2D系统的整体性能。本文首先针对基站内的激活用户和D2D用户分别推导了概率密度函数和累积密度函数,进而得到了D2D系统的整体中断概率。基于推导结果,本文提出了一种基于服务质量（Quality of Service,QoS）约束的多天线选择方案来进一步提高基站端的能效,其中所需的天线数根据QoS约束和发送信噪比来确定。论文最后通过仿真验证了所做推导的正确性,以及展示了本文所提方案相对于最优天线选择的优势。      

裸眼3D视频教育应用价值分析

本文在介绍裸眼3D视频相关概念的基础上,通过介绍四种常见3D显示技术在教育中的应用情况及美国两个典型的裸眼3D视频教学实验案例,分析了裸眼3D视频在教育应用中的效果。进而总结了裸眼3D视频应用于教育的优势,论证了裸眼3D视频在教育中应用的价值所在。     

基于干扰对齐的D2D混合网络干扰管理研究

针对如何有效抑制蜂窝与D2D混合网络中的干扰问题,提出了一种基于干扰对齐的干扰协调策略。通过建立k对D2D用户(DUE)复用蜂窝用户(CUE)上行资源的干扰模型,并分别在发送端和接收端设计发送干扰抑制预编码,使得在某一接收端处的干扰均对齐在接收信号的零空间上,从而抑制区内和区间两大干扰。仿真证明,文中所提出的基于干扰对齐的功率分配方案,比其他算法能获得更大的系统总速率,从而最大化混合网络的自由度。     

Radio resource management scheme and outage analysis for network-assisted multi-hop D2D communications

In a cellular network it's very difficult to make spectrum resource more efficiently. Device-to-Device (D2D) technology enables new service opportunities, and provides high throughput and reliable communication while reducing the base station load. For better total performance, short-range D2D links and cellular links share the same radio resource and the management of interference becomes a crucial task. Here we argue that single-hop D2D technology can be used to further improve cellular networks performance if the key D2D radio resource management algorithms are suitably extended to support multi-hop D2D communications. Aiming to establish a new paradigm for the analysis and design of multi-hop D2D communications, We propose a radio resource allocation for multi-hop D2D routes based on interference avoidance approach in LTE-A networks. On top of that, we investigate the outage probability of D2D communication. We first introduce a new definition of outage probability by considering the maximum distance to be allowable for single-hop transmission. Then we study and analyze the outage performance of a multi-hop D2D route. We derive the general closed form expression of outage probability of the multi-hop D2D routes. The results demonstrate that the D2D radio, sharing the same resources as the cellular network, provide higher capacity compared to pure cellular communication where all the data is transmitted through the base station. They also demonstrate that the new method of calculation of D2D multi hop outage probability has better performance than classical method defined in the literature.     

A random access channel resources allocation approach to control machine-to-machine communication congestion over LTE-advanced networks

The Internet of Things (IoT) is becoming a reality, and one of the core elements to make this reality come true is machine-to-machine (M2M) communication. With the fast-growing rate in which devices are being deployed, communication among them has become crucial to support the development of IoT applications. The Long-Term Evolution-Advanced (LTE-A) is a potential access network for these M2M devices. However, the LTE-A inherited characteristics from older cellular network standards, which were designed for human-to-human (H2H) and human-to-machine (H2M) communication. Accordingly, supporting M2M communication poses some challenges to LTE-A, with a highlight of the congestion and overload problems in the radio access network (RAN) during the random access channel (RACH) procedure. Such a problem arises due to the large number of devices sending access-request messages to the network and the limited number of resources to satisfy this new demand. In this paper, we introduce a solution to mitigate the impact of M2M communication in the LTE-A network. Precisely, we model how to divide the random access resources into different types of devices as a bankruptcy problem. Then, we propose two solutions: (i) A game theory approach to formulate the bankruptcy problem as a transferable utility game, and (ii) an axiomatic method where some elements are considered for judging the amount of resources each class should receive. The simulation results show that our approaches present improvements in terms of energy efficiency, impact control of M2M over H2H accesses, and priority respect among the different classes of devices.     

Cooperative MIMO precoding for the LTE-A D2D communications

In the current deployed 4G long term evolution-advanced (LTE-A) system, it adopts the precoding matrix to reduce the effect of the channel fading and improve the system capacity. Besides, a new technique of the device to device (D2D) communication enables the mobile devices using the LTE radio spectrum directly to communicate with each other. In this paper, two precoding selection methods are proposed for the multiple input multiple output (MIMO) D2D communications. The proposed methods adopt the subset and iterative concept to complete the precoding selection. Besides, a resource selection method is also provided for the D2D transmitter to select an appropriate spectrum resource among the nearby users served by the base station. Combined the resource selection with the proposed D2D precoding selection methods, both simulations and experiments demonstrate the excellent performance of the proposed methods.     

Performance evaluation of 3D video streaming services in LTE-Advanced networks

Due to the ever growing interest of 3-dimensional (3D) technology, together with the the widespread use of new generation smartphones, netbooks, and tablets, the idea to provide 3D multimedia services also to mobile users is attracting the attention of researchers worldwide. The emerging long term evolution-advanced (LTE-A) technology seems to have all the potential to offer such kind of services but no accurate studies have been yet conducted to demonstrate this assumption. To bridge this gap, we investigate herein how the LTE-A network configuration, the traffic load, and 3D video settings may influence to the quality of all services of all active flows. We consider a heterogeneous LTE-A network composed by macro and pico cells and a number of users uniformly distributed into the scenario, that receive at the same time 3D video streams, voice flows and best-effort applications. Moreover, several objective metrics, such as the ratio of lost packets, the peak signal to noise ratio, the Structural SIMilarity, the application goodput, and packet delays, have been evaluated to show the LTE-A effectiveness in delivering 3D videos in a realistic last generation mobile environment.     

在LTE蜂窝通信系统中实现设备到设备通信

基于蜂窝网络的设备到设备直通通信不但有助于提高频谱效率，而且为未来建立更广泛互联互通通信网络提供了基础。基于当前主流宽带蜂窝通信技术3GPPLTE／LTE-A，提出了在蜂窝通信网络中实现设备到设备通信的技术方案；同时，针对部分内容给出了数值仿真结果。为后续技术方案的进一步研究提供参考。     

面向5G通信网的D2D技术综述

在探讨D2D对通信技术未来发展的导向作用基础上,明确了影响D2D系统设计的多个因素,即D2D设备发现、资源分配、缓存技术、D2D-MIMO。从而勾画出基于D2D技术的光纤前传和软件定义网络实现数据/控制分离的扁平化5G架构,提出负责接入的下层宏/小基站蜂窝网和负责管理的上层网络云的管理机制。将D2D技术、SDN技术、边缘计算和物联网技术等关键技术引入未来移动通信网络已经成为研究领域的热点,针对与之相关的、未来大规模网络的移动性、QoS和大数据特性进行了讨论。     

UAV-assisted multi-hop D2D relaying for communication in large disaster area

An unmanned aerial vehicle (UAV)-assisted communication is a promising technique for enabling ground users in a non-functional area (NFA) or disaster area to communicate. All the base stations in the disaster area may be partially or fully damaged due to the natural calamity. Device-to-device (D2D) communication can be a viable solution for immediate connection between users in an NFA. We propose a UAV-assisted multi-hop D2D communication following a hybrid power-time switching (PTS) in this paper. Moreover, a D2D user of a cluster can communicate with another D2D user in a different cluster through UAVs. However, D2D users can harvest energy from their respective ad hoc energy stations and forward the information to the nearby D2D user following a hybrid PTS-based strategy. We propose a time frame for the same and show a node-based energy harvesting strategy. The expressions of outage probability, throughput, end-to-end energy consumption, and energy efficiency are developed for the Rician and Nakagami-m faded channel. The impact of several network parameters such as energy harvesting factor, energy harvesting efficiency, and fading parameter on the network performance is also indicated.     

D2D通信中Chief UE应用的研究

Chief UE的作用是辅助实现D2D通信与蜂窝网络通信更好地无缝切换并且提高通信的质量。对Chief UE的概念进行了详细描述,并且对于其在切换中的作用进行了相应的阐述和论证:在传统D2D通信的基础上,定义了其中一个性质稳定良好的UE为Chief UE,进行D2D连接的内部管理和通信,并且在需要切换时,能够进行通行保持直到整个通信切换的完成和结束。将具有Chief UE的D2D切换同不具有Chief UE的D2D切换进行了相应的对比和论述,以更好地论证Chief UE存在的必要性。