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。     

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.     

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。      

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。     

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。     

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.     

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。     

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.     

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。     

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。     

Deep reinforcement learning-based resource allocation for D2D communications in heterogeneous cellular networks

Device-to-Device (D2D) communication-enabled Heterogeneous Cellular Networks (HCNs) have been a promising technology for satisfying the growing demands of smart mobile devices in fifth-generation mobile networks. The introduction of Millimeter Wave (mm-wave) communications into D2D-enabled HCNs allows higher system capacity and user data rates to be achieved. However, interference among cellular and D2D links remains severe due to spectrum sharing. In this paper, to guarantee user Quality of Service (QoS) requirements and effectively manage the interference among users, we focus on investigating the joint optimization problem of mode selection and channel allocation in D2D-enabled HCNs with mm-wave and cellular bands. The optimization problem is formulated as the maximization of the system sum-rate under QoS constraints of both cellular and D2D users in HCNs. To solve it, a distributed multiagent deep Q-network algorithm is proposed, where the reward function is redefined according to the optimization objective. In addition, to reduce signaling overhead, a partial information sharing strategy that does not observe global information is proposed for D2D agents to select the optimal mode and channel through learning. Simulation results illustrate that the proposed joint optimization algorithm possesses good convergence and achieves better system performance compared with other existing schemes.     

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.     

Bio-inspired power control and channel allocation for cellular networks with D2D communications

With the tremendous increment of traffic in the next generation mobile networks, device to device (D2D) communication is proposed to relieve the traffic burden of the base station and improve the overall network capacity. It supports direct communications between devices and could reuse the resources of cellular users (CUs). Despite the advantages, D2D communications bring great challenges in interference management. In this paper, we study the power control and channel allocation problems in three scenarios: (1) one CU and one D2D pair; (2) one CU and multiple D2D pairs; (3) multiple CUs and multiple D2D pairs. The goal is to coordinate the mutual interferences and maximize the overall network capacity. We derive sufficient conditions to guarantee the efficiency of D2D communications in scenarios with one CU and one D2D pair. We propose the bio-inspired PSO-P power control algorithm for the scenarios with one CU and multiple D2D pairs, and the PSO-CP algorithm for the scenarios with multiple CUs and multiple D2D pairs to jointly assign channels and powers. Simulation results show that the proposed algorithms are efficient in improving the overall network capacity.

     

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.     

混合D2D蜂窝网络中基于模拟退火算法的资源调度策略

D2D通信是未来5G网络中一种近距离直通通信方式,在通信过程中,信息直接由发送端传给接收用户,而不需要经过基站的转发.在传统蜂窝网络中引入D2D通信可以极大地提升系统的总吞吐量、增大频谱资源的利用率以及降低发射终端的功耗.主要介绍了一种适用于混合D2D蜂窝网络中的资源分配方法,通过拉格朗日乘子法结合模拟退火算法实现频谱资源的分配,提出一种同时考虑信道容量和能耗的基于模拟退火算法的资源调度策略.本算法在维也纳仿真平台上经仿真验证,相比于传统贪婪优化算法,可以明显增大系统总吞吐量和频谱资源利用率.另外,算法中采用了分布式资源调度方法,D2D用户根据算法步骤自行搜索适合的目标信道并计算其发射功率,可以有效减少基站的信令开销.     

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.