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。      

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。     

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.     

蜂窝网络中全双工D2D通信功率控制

在蜂窝网络中,采用全双工传输的设备直通(D2D)通信可以共享蜂窝通信的信道资源,提升频谱利用率和系统吞吐量.针对单对全双工D2D用户复用单个蜂窝用户的上行信道资源时,用户之间会产生同频干扰的问题,提出了一种低复杂度的功率控制算法.该算法在保证全双工D2D用户和蜂窝用户(CU)的服务质量(QoS)的前提下,最大化全双工D2D链路的吞吐量.仿真结果表明,该算法能够提高全双工D2D链路的吞吐量;全双工D2D链路吞吐量取决于蜂窝用户的QoS要求、相对距离以及自干扰消除数量的限制.     

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。     

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.     

基于多智能体深度强化学习的D2D通信资源联合分配方法

设备对设备(D2D)通信作为一种短距离通信技术,能够极大地减轻蜂窝基站的负载压力和提高频谱利用率。然而将D2D直接部署在授权频段或者免授权频段必然导致与现有用户的严重干扰。当前联合部署在授权和免授权频段的D2D通信的资源分配通常被建模为混合整数非线性约束的组合优化问题,传统优化方法难以解决。针对这个挑战性问题,该文提出一种基于多智能体深度强化学习的D2D通信资源联合分配方法。在该算法中,将蜂窝网络中的每个D2D发射端作为智能体,智能体能够通过深度强化学习方法智能地选择接入免授权信道或者最优的授权信道并发射功率。通过选择使用免授权信道的D2D对(基于“先听后说”机制)向蜂窝基站的信息反馈,蜂窝基站能够在非协作的情况下获得WiFi网络吞吐量信息,使得算法能够在异构环境中执行并能够确保WiFi用户的QoS。与多智能体深度Q网络(MADQN)、多智能体Q学习(MAQL)和随机算法相比,所提算法在保证WiFi用户和蜂窝用户的QoS的情况下能够获得最大的吞吐量。     

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。     

蜂窝网络中D2D通信模式选择和信道分配算法

设备到设备(D2D)通信中,不合理的模式选择和信道分配方案会引入干扰,严重时不仅不能体现D2D通信优势,而且还将导致蜂窝用户传输速率下降。针对这一问题,文章提出了一种蜂窝网络中D2D模式选择和信道分配算法。仿真结果表明,新算法能够在有效的平衡蜂窝网络中D2D用户接入率和系统总吞吐量的同时,最小化用户之间的干扰。     

D2D通信中一种基于FFR的动态功率控制方案

工作在underlay方式下的D2D(device-to-device)通信利用资源复用共享蜂窝网络中的资源,在提高频谱资源利用率、降低移动终端功耗的同时,会给已有蜂窝网络带来干扰。在保证D2D用户和蜂窝用户的服务质量的前提下,研究了蜂窝用户和D2D用户的功率控制和资源分配问题。首先引入部分频率复用(FFR)实现蜂窝用户和D2D用户之间的资源划分和复用;然后以系统吞吐量最大化为原则,建立优化目标。结合部分功率控制(FPC)的基本思想,进而提出了一种动态功率控制(DPC)策略。仿真结果表明,所提出的方案能够有效地提高多小区系统的性能。     

Resource allocation and dynamic power control for D2D communication underlaying uplink multi-cell networks

Underlaying device-to-device (D2D) communication is suggested as a promising technology for the next generation cellular networks (5G), where users in close proximity can transmit directly to one another bypassing the base station. However, when D2D communications underlay cellular networks, the potential gain from resource sharing is highly determined by how the interference is managed. In order to mitigate the resource reuse interference between D2D user equipment and cellular user equipment in a multi-cell environment, we propose a resource allocation scheme and dynamic power control for D2D communication underlaying uplink cellular network. Specifically, by introducing the fractional frequency reuse (FFR) principle into the multi-cell architecture, we divide the cellular network into inner region and outer region. Combined with resource partition method, we then formulate the optimization problem so as to maximize the total throughput. However, due to the coupled relationship between resource allocation and power control scheme, the optimization problem is NP-hard and combinational. In order to minimize the interference caused by D2D spectrum reuse, we solve the overall throughput optimization problem by dividing the original problem into two sub-problems. We first propose a heuristic resource pairing algorithm based on overall interference minimization. Then with reference to uplink fractional power control (FPC), a dynamic power control method is proposed. By introducing the interference constraint, we use a lower bound of throughput as a cost function and solve the optimal power allocation problem based on dual Lagrangian decomposition method. Simulation results demonstrate that the proposed algorithm achieves efficient performance compared with existing methods.     

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。     

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.     

D2D communications with subchannel reusing for throughput‐guaranteed relay selection in LTE

Using full‐duplex relaying in device‐to‐device (D2D) communication, spectrum efficiency can be further improved as compared with traditional half‐duplex relaying. Due to the increasing demands for more system capacities and higher data rate, a throughput‐guaranteed and power‐aware relay selection mechanism is essential so that services can be successfully accomplished within tolerable power consumption. It is also imperative to prevent cellular users from interfering and preserve resources for more users at the same time. In current paper, we proposed an efficient relay selection scheme with subchannel reusing. Using the nonconflict group discovery algorithm, firstly, we divided D2D pairs into different groups based on the neighbor lists of all the devices. The D2D pairs in the same group were considered nonconflictive. By building a matrix that represents the power consumption of D2D transmission peers through relays, we proposed a group‐oriented relay selection scheme based on the Hungarian method allowing subchannel reuse over relay‐assisted D2D networks. Applying this mechanism, different D2D pairs are able to transmit messages at the same subchannel, whenever they are in the same group. Better throughput and spectrum usage than currently available relay selection schemes without subchannel reusing can be obtained. Particularly, more D2D pairs in high dense networks can be accommodated, and spectrum resources can be better preserved. The simulation results showed that our proposed mechanism can improve the total throughput by up to 35% as compared with an existing relay selection scheme without subchannel reusing, called as PRS‐D2D, when most D2D pairs are in a few groups.     

Research on the interference control and resource allocation in D2D communication

In order to solve the problem of interference caused by D2D users reuse cellular resources in cellular network,an algorithm of interference control and resource allocation of D2D communication in single cell cellular system was proposed.Firstly,an interference graph was constructed according to the interference between users in the system to find the reusable channel resource for D2D users.Then,the channel resource pre-allocation and the channel switching policy were performed for D2D users in sequence according to the preset D2D user priority.The simulation results show that the proposed algorithm can significantly improve the system throughput and the access rate of D2D users so that the system can achieve better performance in the presence of small or large number of D2D users.     

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.