D2D通信技术研究

首先描述了近距离通信的技术特点和应用场景,并与其他相关技术进行了比较,深入研究了近距离通信技术的网络架构,并从ProSe Direct Discovery、ProSe Communication两个方面详细研究了各功能实体间的接口及其功能,最后分析了该技术的发展现状以及未来趋势.     

3D手机的价值：持续性的3D体验

文章介绍了3D手机的概念和3D手机能为消费者带来的独特的视觉欣赏体验，分析了过去几年出现的3D手机的功能特点和它们无法流行的原因，在此基础上提出了评价3D手机价值的“3D占比值”的概念以衡量3D手机能为消费者带来的3D体验的深度和广度。     

毫米波D2D通信网络拓扑演化建模

D2D通信技术能显著提高通信系统的频谱效率,有效降低终端发射功率,在一定程度上缓解了无线通信系统频谱资源匮乏的问题。毫米波通信的窄波束则能有效抑制D2D对之间的相互干扰,从而实现一对多、多对多的通信链路,但其通信网络拓扑更加密集复杂。首先分析了毫米波D2D网络特性,然后提出了一种D2D网络拓扑演化模型,随之分析了其邻接矩阵、节点度、特征谱等网络特征,最后进行了仿真实现。仿真实验表明,所提模型能准确反映毫米波D2D网络的拓扑演化过程,揭示出D2D网络模型介于小世界网络模型和无标度网络模型之间。     

D2D技术在5G通信中的应用

移动通信从第一代仅仅能通话的模拟移动电话到如今4G以及成熟商用,移动互联网呈现飞速发展的模式下.当前时期,智能设备的大规模普及以及移动网络需求的急剧增长,对5G的无线通讯技术的更新需求也是显得十分迫切.在5G移动通信的研究过程中,主要有两点.一点是,对于传统的移动通信性能要加强,例如网络用户容量、频谱利用率都需要提供,因为日益减少的频谱资源使得频谱资源尤为宝贵;另外一点,多制式的通信模式给用户带来的使用体验和蜂窝网络的业务扩张是另外一个研究热点.对于5G通信中的"潜力"技术,设备到设备通信(Device-to-Device,D2D)可以提高整体性能,使得体验上升、应用拓展等潜力,因此是如今一大热点.本文即是对D2D在5G通信中的应用进行了探讨.     

3D产业现状及关键技术

从3D产业链角度出发,分析国内外3D产业的发展现状,逐一对3D内容制作、3D编解码、3D传输存储及3D显示技术等3D关键技术进行介绍,最后就目前制约3D电视产业发展的一些问题提出建议。     

Flash Papervision3D中3D Web应用程序设计

为了能将日益应用广泛的Papervision3D、能在Flash Player中播放的目的,采用较为新颖的3D引擎方法,做了三维到二维的转换、Flint粒子系统实验,实现了平滑拉近物体从远处拉近及喷泉的效果.通用开源Flash 3D渲染引擎中Papervision3D是基于ActionScript的开源项目,而Flash在3D领域的应用相对贫乏,在Flash Player中播放,则具备体积小、与用户交互能力强、效果逼真的3D Web应用程序特点.     

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。     

Study on adaptive modulation in D2D communications over Nakagami-m fading channel

A novel adaptive modulation based on nondata-aided error vector magnitude (NDA-EVM) was proposed to solve the problem of lower spectral efficiency in device to device (D2D) communication over Nakagami-m fading channel.The NDA-EVM was used to evaluate the channel quality.The relationship between NDA-EVM and symbol error ratio (SER) was derived according to the maximum likelihood method.Thereafter,the adaptive modulation mechanism of MQAM with the SER constraint was designed.Considering the joint effect of finite-length queuing and fading channel,the system packet loss rate and spectral efficiency was analyzed.Theoretical analysis and simulation experiments show that NDA-EVM based adaptive modulation accurately gives the modulation threshold and evaluates the relationship between QoS and packet loss rate,the proposed algorithm improves system spectral efficiency while maintaining low algorithm complexity,spectral efficiency improves by 0.752 bit·(s·Hz)^-1,compared with traditional algorithm.     

基于图着色的加权优先D2D资源分配算法研究

针对蜂窝用户与D2D用户所构成的异构网络系统中同频干扰问题,提出一种基于图着色的加权优先D2D资源分配算法.该算法不仅允许多个D2D用户复用一个蜂窝用户资源,而且能够实现简单功控.首先建立异构干扰图,对系统终端用户及干扰类型进行分类异构.然后计算着色优先级,考虑各种影响因子以提升算法的实用性.最后再由分配结果进行组内功率控制,以满足绿色通信的要求.仿真表明,该算法不仅可以降低系统用户接入损失率,提高系统吞吐量,而且还减少了功率消耗.     

An efficient resource optimization scheme for D2D communication

With the rapid development of wireless technologies, wireless access networks have entered their Fifth-Generation (5G) system phase. The heterogeneous and complex nature of a 5G system, with its numerous technological scenarios, poses significant challenges to wireless resource management, making radio resource optimization an important aspect of Device-to-Device (D2D) communication in such systems. Cellular D2D communication can improve spectrum efficiency, increase system capacity, and reduce base station communication burdens by sharing authorized cell resources; however, can also cause serious interference. Therefore, research focusing on reducing this interference by optimizing the configuration of shared cellular resources has also grown in importance. This paper proposes a novel algorithm to address the problems of co-channel interference and energy efficiency optimization in a long-term evolution network. The proposed algorithm uses the fuzzy clustering method, which employs minimum outage probability to divide D2D users into several groups in order to improve system throughput and reduce interference between users. An efficient power control algorithm based on game theory is also proposed to optimize user transmission power within each group and thereby improve user energy efficiency. Simulation results show that these proposed algorithms can effectively improve system throughput, reduce co-channel interference, and enhance energy efficiency.     

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.     

基于改进图着色的D2D资源分配和功率控制

针对蜂窝网络中D2D（Device-to-Device）用户复用蜂窝信道带来的同频干扰问题,提出了一种基于改进图着色的资源分配和功率控制算法。首先通过构建干扰图和候选集进行用户之间干扰关系建模,并定义指数型累积因子改进图着色算法,为D2D用户分配蜂窝信道;再采用基于信干噪比的闭环功率控制算法动态调整D2D用户发射功率,减小由于信道复用产生的干扰。仿真结果表明,与现有算法相比,所提算法能够有效提升系统吞吐量和D2D用户接入率,实现信道资源的合理分配。     

基于信干噪比的D2D通信功率控制与资源分配

为了优化长期演进(LTE)系统引入设备直传(D2D)通信后带来的同频干扰、系统边缘用户性能恶化问题,提出一种基于信干噪比(SINR)的多小区D2D通信资源分配方案,通过调整信干噪比阈值将部分蜂窝用户(CU)转化为D2D用户并释放频谱资源进而获得较佳的资源分配策略,同时提出一种基于小区间D2D竞争机制的配置算法有效降低小区间干扰.仿真表明,算法能够有效提升系统容量,并提升小区边缘D2D用户公平性.     

An interference cancellation scheme for D2D multi-link communication underlaying cellular network

Device-to-device (D2D) communication has attracted much attention in the field of mobile networks for local area connectivity due to its spectral efficiency, high bit rate support and low power consumption. A group of D2D capable devices, called a cluster, can be connected through multiple links by sharing common resources. This may however result in co-channel interference between them. In this paper, we propose a novel orthogonal precoding vector selection method for reducing co-channel interference and thus maximizing the achievable data rate for each device in the cluster. The proposed method can be employed for uplink and downlink transmissions of both cellular and D2D communications. The analysis of the proposed method is carried out for the case where the cellular channel resource is being shared by single and multiple D2D links. Initially, the results via simulations are compared with the theoretical analysis and the performance of the proposed method is evaluated and compared for different resource sharing modes. The results show that our proposed method enhance the system throughput when compared with the conventional precoding vector allocation method. Finally, the paper illustrates that the introduction of cluster head in a cluster can save battery life of devices.     

An Error-Probability Upper Bound for Coherent Phase-Shift Keying with Peak-Limited Interference

An upper bound on the probability of error for coherent phase-shift-keyed (CPSK) systems operating in the presence of peaklimited interference is derived. Such a bound is particularly useful in analyzing the effect of co-channel and adjacent channel interference on CPSK systems. The bound is often tight enough to be employed as a system design tool, and is computationally simple to apply.     

Semi‐distributed resource management for underlay D2D communication with user's cooperation

Device‐to‐device (D2D) communication is a viable solution proposed by the Third Generation Partnership Project (3GPP) to handle the enormous number of devices and expected data explosion in 5G. It is competent in enhancing the system performances such as increased data rate, reduced delay, and less power consumption while maintaining a low load on the base station (BS). In this paper, channel assignment and power control scheme is proposed for underlay D2D system where one cellular channel is allowed to be shared among multiple D2D pairs. This will lead to enhanced spectral efficiency on the cost of additional interferences introduced among the D2D and cellular users (CUs). Our aim is to maximize the D2D throughput without degrading the performance of existing CU that is sharing the channel with D2D. This is achieved by maintaining a threshold signal‐to‐interference‐plus‐noise ratio (SINR) for each CU. A centralized channel assignment algorithm based on the well‐known two‐sided preference Gale‐Shapley algorithm is proposed, named as RAbaGS‐HR. Further, suboptimal distributed power control (DPC) algorithms are proposed for both uplink and downlink D2D. The novelty of the work lies in the facts that a channel is shared among multiple D2D users and the optimal power is calculated for all the users sharing the same channel under the full consideration of all kinds of interferences unlike most of the existing work that either assumed the fixed CU power or ignored the interferences among the D2D users. Numerical results show the efficacy of the proposed algorithms in terms of significant gain in throughput with a very low computational cost. In addition to this, the energy efficiency (EE) is also analyzed for different D2D user density, with respect to average circuit power consumption and D2D maximum transmit power.     

Interference management in dense inband D2D network using spectral clustering & dynamic resource allocation

Device-to-device (D2D) communication has emerged as a promising concept to improve resource utilization in fifth generation cellular networks. D2D network’s architectural capability to offload traffic from the backhaul network to direct links enables it to be used for internet of things (IoT) services. In a densely deployed setting of IoT devices, D2D network may experience critical interferences due to a limited number of spectral resources. To increase the overall signal-to-interference-plus-noise ratio (SINR) of the network while reducing the computational load on a macro base station, a novel decentralized interference management methodology is proposed for dense in-band D2D underlay LTE-A network. The proposed interference management scheme can decouple interference in a network into cross-cluster and intra-cluster interference and tackle with them separately. To mitigate the cross-cluster interference in a dense D2D network we propose dividing the densely deployed D2D user equipments (UEs) network into well-separated clusters using spectral clustering with modified kernel weights. The proposed spectral clustering scheme obtains well-separated clusters with regards to cross-cluster interference, that is, the UEs that offer maximum interference to each other are grouped into the same cluster. Thereafter, a dynamic resource allocation algorithm is proposed within each cluster to reduce the intra-cluster interference. The proposed dynamic resource allocation algorithm uses graph coloring to allocate resources in such a manner that after each spectrum allocation, a small cell base station updates the interference graph and assigns the next largest interference affected UE a spectrum resource that minimizes the overall intra-cluster interference the most. In conventional graph coloring, the adjacent UEs are allocated different spectrum resources without taking into consideration if the allocated spectrum resource might result in increased interference in the cluster. The simulation results show that the proposed clustering strategy considerably reduces the average cross-cluster interference as compared to other benchmark clustering algorithms such as K-means and KPCA. Moreover, the proposed resource allocation algorithm decreases the intra-cluster interference in the network resulting in the overall SINR maximization of the network.