A Robust Resource Allocation Scheme for Device-to-Device Communications Based on Q-Learning

One of the most effective technology for the 5G mobile communications is Device-to-device (D2D) communication which is also called terminal pass-through technology. It can directly communicate between devices under the control of a base station and does not require a base station to forward it. The advantages of applying D2D communication technology to cellular networks are: It can increase the communication system capacity, improve the system spectrum efficiency, increase the data transmission rate, and reduce the base station load. Aiming at the problem of co-channel interference between the D2D and cellular users, this paper proposes an efficient algorithm for resource allocation based on the idea of Q-learning, which creates multi-agent learners from multiple D2D users, and the system throughput is determined from the corresponding state-learning of the Q value list and the maximum Q action is obtained through dynamic power for control for D2D users. The mutual interference between the D2D users and base stations and exact channel state information is not required during the Q-learning process and symmetric data transmission mechanism is adopted. The proposed algorithm maximizes the system throughput by controlling the power of D2D users while guaranteeing the quality-of-service of the cellular users. Simulation results show that the proposed algorithm effectively improves system performance as compared with existing algorithms.     

Energy-Efficient Low-Complexity Algorithm in 5G Massive MIMO Systems

Energy efficiency (EE) is a critical design when taking into account circuit power consumption (CPC) in fifth-generation cellular networks. These problems arise because of the increasing number of antennas in massive multiple-input multiple-output (MIMO) systems, attributable to inter-cell interference for channel state information. Apart from that, a higher number of radio frequency (RF) chains at the base station and active users consume more power due to the processing activities in digital-to-analogue converters and power amplifiers. Therefore, antenna selection, user selection, optimal transmission power, and pilot reuse power are important aspects in improving energy efficiency in massive MIMO systems. This work aims to investigate joint antenna selection, optimal transmit power and joint user selection based on deriving the closed-form of the maximal EE, with complete knowledge of large-scale fading with maximum ratio transmission. It also accounts for channel estimation and eliminating pilot contamination as antennas M → ∞. This formulates the optimization problem of joint optimal antenna selection, transmits power allocation and joint user selection to mitigate inter-cell-interference in downlink multi-cell massive MIMO systems under minimized reuse of pilot sequences based on a novel iterative low-complexity algorithm (LCA) for Newton’s methods and Lagrange multipliers. To analyze the precise power consumption, a novel power consumption scheme is proposed for each individual antenna, based on the transmit power amplifier and CPC. Simulation results demonstrate that the maximal EE was achieved using the iterative LCA based on reasonable maximum transmit power, in the case the noise power is less than the received power pilot. The maximum EE was achieved with the desired maximum transmit power threshold by minimizing pilot reuse, in the case the transmit power allocation ρ_d = 40 dBm, and the optimal EE = 71.232 Mb/j.     

基于部分可观察马尔可夫决策过程的受控无线网络系统动态资源分配

研究了受控无线网络的动态资源分配。针对传统无线通信传输模型的局限性随着无线通信系统架构的发展日益凸显的问题,提出了一种引入反馈控制策略的受控无线网络模型。该模型结合部分可观察马尔可夫决策过程(POMDP),将用户接收功率与数据传输误码率作为反馈观测对象,对通信小区内基站天线开启数与用户接入数进行动态资源最优匹配。仿真结果表明,这种方法能够有效提升系统传输能效性与可靠性,降低传输误码率,改善系统资源动态匹配控制性能。     

基于FDMA系统的两跳中继网络的资源分配

首先介绍了一种可用于两跳中继网络的时分模式帧结构,然后基于该帧结构提出了一种资源分配算法.该算法包括两个步骤:第一个步骤是第一个时隙上的动态资源分配,第二个步骤是基站与中继站之间的最优化功率分配.两跳中继网络中下行存在三种链路:"基站-中继"链路、"基站-用户"链路和"中继-用户"链路,在系统资源有限的条件下,通过所提算法为这三种链路分配相应的带宽和功率,可以使得系统的吞吐量最大.仿真结果表明所提算法能够有效地提高系统的吞吐量.     

Performance of multiantenna multicarrier direct-sequence code division multiple access using orthogonal variable spreading factor codes-assisted space?time spreading in time-selective fading channels

A downlink (base-to-mobile) multicarrier direct-sequence code-division multiple-access (MC DS-CDMA) system employing multiple antennas at both the base station and each of the mobile terminals is investigated, when communicating over fast time-varying fading channels resulting in time-selective fading. In the considered multiantenna MC DS-CDMA, space-time spreading (STS) based on the family of orthogonal variable spreading factor (OVSF) codes is proposed in order to achieve the time diversity because of the time-selective fading, in addition to the transmit/receive diversity. In this contribution, the closed-form expressions for the single-user bit-error rate (BER) are derived, in order to gain insight into the achievable BER performance of the multiantenna MC DS-CDMA. The BER performance of the multiantenna MC DS-CDMA system is investigated, when communicating over correlated time-selective Rayleigh fading channels. The study and performance results show that the multiantenna MC DS-CDMA using OVSF codes-assisted STS constitutes a high-efficiency downlink space-time transmission scheme. It is capable of achieving the full diversity provided by the time- selective fading and multiple transmit/receive antennas. Furthermore, the proposed multiantenna MC DS-CDMA is capable of achieving a self-balance between the time diversity achieved and the multiuser interference suppression capability, when using low-complexity correlation detection.     

An Optimized Algorithm for Resource Allocation for D2D in Heterogeneous Networks

With the emergence of 5G mobile multimedia services, end users’ demand for high-speed, low-latency mobile communication network access is increasing. Among them, the device-to-device (D2D) communication is one of the considerable technology. In D2D communication, the data does not need to be relayed and forwarded by the base station, but under the control of the base station, a direct local link is allowed between two adjacent mobile devices. This flexible communication mode reduces the processing bottlenecks and coverage blind spots of the base station, and can be widely used in dense user communication scenarios such as heterogeneous ultra-dense wireless networks. One of the important factors which affects the quality-of-service (QoS) of D2D communications is co-channel interference. In order to solve this problem of co-channel interference, this paper proposes a graph coloring based algorithm. The main idea is to utilize the weighted priority of spectrum resources and enables multiple D2D users to reuse the single cellular user resource. The proposed algorithm also provides simpler power control. The heterogeneous pattern of interference is determined using different types of interferences and UE and the priority of color is acquired. Simulation results show that the proposed algorithm effectively reduced the co-channel interference, power consumption and improved the system throughput as compared with existing algorithms.     

Capacity analysis for a multiuser cross-layer downlink model in the presence of fading and interference

A system model that employs beamforming at the physical (PHY) layer and different scheduling algorithms at the medium access control (MAC) layer is used in a downlink environment where two users are served simultaneously. The effect of the scheduling algorithms on the system performance is assessed in terms of total system capacity. The scheduling algorithms considered, choose users either randomly, or on the basis of their instantaneous signal-to-noise ratio (SNR) and/or their angular location around the base station. A semi-analytical framework for the capacity analysis is also presented. The results obtained from the numerical model are shown to be consistent with those based on the semi-analytical framework. It is shown that explicitly taking into consideration at the MAC layer the angular location of mobile users around the base station along with instantaneous SNR for the selection of users that are served simultaneously leads to an improved system capacity. This improvement is the result of reduced interference that simultaneously served users cause on each other. The results show that joint addressing of the PHY and MAC layer issues in an integrated cross-layer framework is important for achieving maximal system performance     

Adaptive opportunistic fair scheduling in power-controlled code division multiple access systems

The authors treat the multiuser scheduling problem for practical power-controlled code division multiple access (CDMA) systems under the opportunistic fair scheduling (OFS) framework. OFS is an important technique in wireless networks to achieve fair and efficient resource allocation. Power control is an effective resource management technique in CDMA systems. Given a certain user subset, the optimal power control scheme can be derived. Then the multiuser scheduling problem refers to the optimal user subset selection at each scheduling interval to maximise certain metric subject to some specific physical-layer constraints. The authors propose discrete stochastic approximation algorithms to adaptively select the user subset to maximise the instantaneous total throughput or a general utility. Both uplink and downlink scenarios are considered. They also consider the time-varying channels where the algorithm can track the time-varying optimal user subset. Simulation results to show the performance of the proposed algorithms in terms of the throughput/ utility maximisation, the fairness, the fast convergence and the tracking capability in time-varying environments are presented.     

基于基站间合作的下行干扰协调方法及其性能评估

从基站间合作的角度研究了蜂窝系统下行多小区干扰协调问题.引入了合作虚拟小区的概念,并提出了三扇区合作虚拟小区规划方案和双扇区合作虚拟小区规划方案.所提方案在实现小区间干扰协调的同时,还可使系统实现同频组网和无缝切换.仿真结果显示,与传统的频率复用方式相比,合作虚拟小区方案能很好地平衡小区内不同位置频谱效率的分布,改善边缘用户的性能.其中,双扇区合作方案可使系统中断概率比频率复用方式(1,3,3)下降5%以上,而且其扇区吞吐量与频率复用方式(1,3,1)相当.     

Linear precoding for the downlink of multiple input single output coexisting wireless systems

Coexisting radio systems, often called cognitive radio (CR), have attracted much attention because of the lack of spectrum resources and the low usage statistics of existing spectrum allocations. Interference suppression and cancellation are seen as key technologies for enabling coexisting systems, and the application of multiple antennas might be one solution to tackle interference. Linear vector precoding for downlink of multiple input single output CR systems is addressed. The maximum ratio transmission, zero forcing, optimal interference-free, and optimal interference-constrained (IC) precoding algorithms in the sense of minimum mean squared error (MMSE) are presented. Then the authors compare and analyse these algorithms under different channel assumptions. The simulation results show that the proposed IC precoding algorithm can maximise the utilisation of multiple antennas and greatly improve the system performance.     

Effect of Spectrum Analyzer Filtering on Electromagnetic Dosimetry Assessment for UMTS Base Stations

While many different measurement techniques and simulation tools are available to assess electromagnetic exposure for second-generation mobile communications base stations, few works have tackled the problem for downlink third-generation (3G) universal mobile telecommunications system (UMTS) signals. In this paper, deep analyses of the effect of spectrum analyzer (SA) filtering on 3G/UMTS field measurement for electromagnetic compliance assessment are presented. A procedure for evaluating compliance of frequency-division duplex 3G/UMTS Node B to electromagnetic safety limits, avoiding the use of a code-domain analyzer, is also presented and discussed. Adequate SA settings for exposure compliance testing are proposed, and an important relationship between resolution and video bandwidths is found, which dominates analyzer settings effects on final 3G/UMTS exposure assessment results.     

大规模基站运维优化与车队规划研究

研究了考虑充电量决策的大规模基站断电运维的多车辆路径规划问题。目标是在运维能力有限的条件下最小化基站断电产生的损失和车辆运行成本的加权总和。分析了该问题区别于传统取送货问题的差异与难点,利用图论模型建立了动态多阶段车辆路径的混合整数规划模型,利用库存理论辅助基站充电量的决策并通过软时间窗口对车辆服务与路径规划进行约束,最后设计了基于局部最优插入和变邻域搜索的动态算法框架进行求解。基于中国铁塔公司真实数据生成的多个算例验证了该算法可以显著降低运维成本,并协助公司进行运维车队规模的规划。     

Efficient Algorithms for Cache-Throughput Analysis in Cellular-D2D 5G Networks

In this paper, we propose a two-tiered segment-based Device-to-Device (S-D2D) caching approach to decrease the startup and playback delay experienced by Video-on-Demand (VoD) users in a cellular network. In the S-D2D caching approach cache space of each mobile device is divided into two cache-blocks. The first cache-block reserve for caching and delivering the beginning portion of the most popular video files and the second cache-block caches the latter portion of the requested video files ‘fully or partially’ depending on the users’ video watching behaviour and popularity of videos. In this approach before caching, video is divided and grouped in a sequence of fixed-sized fragments called segments. To control the admission to both cache-blocks and improve the system throughput, we further propose and evaluate three cache admission control algorithms. We also propose a video segment access protocol to elaborate on how to cache and share the video segments in a segmentation based D2D caching architecture. We formulate an optimisation problem and find the optimal cache probability and beginning-segment size that maximise the cache-throughput probability of beginning-segments. To solve the non-convex cache-throughout maximisation problem, we derive an iterative algorithm, where the optimal solution is derived in each step. We used extensive simulations to evaluate the performance of our proposed S-D2D caching system.     

Optimized Evaluation of Mobile Base Station by Modern Topological Invariants

Due to a tremendous increase in mobile traffic, mobile operators have started to restructure their networks to offload their traffic. New research directions will lead to fundamental changes in the design of future Fifth-generation (5G) cellular networks. For the formal reason, the study solves the physical network of the mobile base station for the prediction of the best characteristics to develop an enhanced network with the help of graph theory. Any number that can be uniquely calculated by a graph is known as a graph invariant. During the last two decades, innumerable numerical graph invariants have been portrayed and used for correlation analysis. In any case, no efficient assessment has been embraced to choose, how much these invariants are connected with a network graph. This paper will talk about two unique variations of the hexagonal graph with great capability of forecasting in the field of optimized mobile base station topology in setting with physical networks. Since K-banhatti sombor invariants (KBSO) and Contrharmonic-quadratic invariants (CQIs) are newly introduced and have various expectation characteristics for various variations of hexagonal graphs or networks. As the hexagonal networks are used in mobile base stations in layered, forms called honeycomb. The review settled the topology of a hexagon of two distinct sorts with two invariants KBSO and CQIs and their reduced forms. The deduced outcomes can be utilized for the modeling of mobile cellular networks, multiprocessors interconnections, microchips, chemical compound synthesis and memory interconnection networks. The results find sharp upper bounds and lower bounds of the honeycomb network to utilize the Mobile base station network (MBSN) for the high load of traffic and minimal traffic also.     

Directional Antenna Intelligent Coverage Method Based on Traversal Optimization Algorithm

Wireless broadband communication is widely used in maneuver command communications systems in many fields, such as military operations, counter-terrorism and disaster relief. How to reasonably formulate the directional antenna coverage strategy according to the mobile terminal dynamic distribution and guide the directional antenna dynamic coverage becomes a practical research topic. In many applications, a temporary wireless boardband base station is required to support wireless signal communications between many terminals from nearby vehicles and staffs. It is therefore important to efficiently set directional antenna while ensuring large enough coverage over dynamically distributed terminals. The wireless broadband base station mostly uses two rotatable conical-polarized directional antennas with a coverage angle of 80 degrees. In this paper, we study this directional antenna coverage problem and propose a new solution by using three-dimensional coordinate transformation, provides wireless signal coverage schemes for point-to-point and point-to-region, determined the required horizontal rotation angle and pitch rotation angle of the directional antenna intelligent coverage, which lays the foundation for the performance of the wireless broadband communication in the maneuver command communication system.     

全复用多小区系统下行链路用户调度与功率分配

对全复用多小区系统下行链路用户调度与功率分配问题进行了研究,提出了一种半分布式的用户调度与功率分配方案.首先,各小区根据自身所辖用户的信道与干扰信息,采用最大信干噪比准则进行用户调度,然后各基站将所调度用户的信息上报给中央资源控制器,最后中央资源控制器基于最速下降法的思想,采用贪婪功率分配(GPA)算法为各用户分配相应的发射功率.所提方案利用小区之间的相互协作有效地弱化了小区间干扰,与现有方法相比获得了更好的吞吐量性能和更高的功率效率.     

Energy-Efficient Resource Optimization for Massive MIMO Networks Considering Network Load

This paper investigates the resource optimization problem for a multi-cell massive multiple-input multiple-output (MIMO) network in which each base station (BS) is equipped with a large number of antennas and each base station (BS) adapts the number of antennas to the daily load profile (DLP). This paper takes into consideration user location distribution (ULD) variation and evaluates its impact on the energy efficiency of load adaptive massive MIMO system. ULD variation is modeled by dividing the cell into two coverage areas with different user densities: boundary focused (BF) and center focused (CF) ULD. All cells are assumed identical in terms of BS configurations, cell loading, and ULD variation and each BS is modeled as an M/G/m/m state dependent queue that can serve a maximum number of users at the peak load. Together with energy efficiency (EE) we analyzed deployment and spectrum efficiency in our adaptive massive MIMO system by evaluating the impact of cell size, available bandwidth, output power level of the BS, and maximum output power of the power amplifier (PA) at different cell loading. We also analyzed average energy consumption on an hourly basis per BS for the model proposed for data traffic in Europe and also the model proposed for business, residential, street, and highway areas.     

IP组播路由协议的研究与实现

概述了组播路由协议，分析了协议独立的组播路由－稀疏模式（PIM－SM）的缺陷，提出多个会聚点（RPs)的PIM－SM的改进机制，多个RPs机制有效地提高了原有单个RP的PIM－SM协议的健壮性，有利于实现负载均衡、分类业务及提高系统的容错性能，并讨论多个RPs机制的开销问题。分析了PIM－SM实现细节和组播技术的前景。     

Investigation on wavelength multicasting technology based on XPM in a highly nonlinear fiber

All-optical wavelength conversion with multicasting is investigated in this paper, which is based on cross-phase modulation in a highly nonlinear fiber. With a pump-modulated light and only a single continuous-wave probe, wavelength multicasting is realized by appropriately controlling the powers of two beams. Our simulation work reveals that 10 multicast channels can be obtained with their Q factors being larger than six, if both pump and probe powers are properly selected. These wavelength channels of multicasting are positioned around the central wavelength of the probe on the blue-shifted and red-shifted sides. The central wavelength and the channel spacing can be affected by the wavelengths of the probe and the pump. The wavelength multicasting technique studied in this paper is simpler and can offer more multicast channels than that based on four-wave mixing.     

基于分布式资源管理的DiffServ组播策略

针对区分服务(DiffServ)和组播直接结合所产生的可扩展性问题、被忽视的预留子树问题和异构组播组问题,提出了一种基于分布式资源管理的区分服务组播策略(DMSBD).新方案采用由边界节点对DiffServ域内资源进行分布式管理的方式,申请加入组播组的新成员必须通过接纳控制审核才能享有合法的优先级,同时采用接收方驱动的思想建立一套服务质量请求信令机制,并通过使用重标记的方法使组播数据流的转发节点明确知晓新成员的服务质量请求.仿真结果表明该方案能够有效地解决或缓解区分服务和组播结合时所产生的几种问题.