A framework design for the next-generation radio access system

Extensive use of the Internet and huge demands for multimedia services via portable devices require the development of packet-based radio access systems with high transmission efficiency. Advanced radio transmission technologies have recently been proposed to achieve this challenging task. However, few researches have been reported on the design of an integrated system that can efficiently exploit the advantages of these transmission technologies. This paper considers the design of a packet-based cellular system for next-generation radio access. We propose a novel system framework that can incorporate various advanced transmission technologies such as link adaptation, opportunistic packet scheduling, channel coding, and multiantenna techniques. For efficient use of these technologies together, we first investigate the interoperability between these technologies by proposing a so-called cause and effect analysis. Based on this investigation, we design a differentiated-segments-based orthogonal frequency-division multiplexing system, called DiffSeg, to accommodate heterogeneous operating conditions in a seamless manner. Simulation results show that the proposed DiffSeg system can provide a nearly optimum performance with flexible configuration in a wide range of wireless channel conditions.     

Beamforming for heterogeneous cloud radio access network

To overcome the problem that previous researches for heterogeneous cloud radio access network (H-CRAN) mainly focus on single macro cell,and only considered the intracell interference in the one macro cell,while the inter cell interferences among different macro cells are neglected,H-CRAN with multiple macro-cells was studied,and the objective was to maximize system sum-rate through jointly optimizing the beamforming vectors of macro base stations (MBS) and remote radio heads (RRH).Based on alternating optimization and Lagrangian dual method,a joint MBS and RRH beamforming algorithm was proposed.The original problem was first divided into two subproblems.Then,the two sub-problem were solved alternately to obtain the final solutions of the original problem.In addition,the closed expression solutions of the two sub-problem were derived based on Lagrangian dual method.The proposed algorithm was compared with some beamforming algorithms in the simulation.The experimental results demonstrate the proposed algorithm has a better performance in improving the sum-rate of H-CRAN.     

共用集群通信网的路应如何走

1 公众移动通信网与专用移动通信网的区别 移动通信从应用方面可划分为公众移动通信网和专用移动通信网。公众移动通信网俗称移动电话,是以为公众提供移动通信业务为目的而建立和经营的网络,供个人使用。专用移动通信网俗称集群电话,它是指某一业务部门如公安、铁路、交通、城市管理等部门作为生产调度、行政管理、抢险救灾、应急救援而建立的综合无线调度移动通信网络,供生产一线的专业人员使用。在专用移动通信网中,又可划分为两大类的集群移动通信网：一类是共用调度集群移动通信网(Public Access M0bile Radio),简称PAMR,另一类是专用集群移动通信网(Private Mobile Radio),简称PMR。共用调度集群移动通信网是指许多专业部门在同一覆盖区内共用频率、共用设备、集中管理和维护的移动通信网。专用集群移动通信网是指某一个部门,如国家安全、公安、军队、铁路等部门使用的集群移动通信系统。由于应用范围的不同,要求的网络结构、技术特性和使用功能是有区别的。     

一种改进的认知无线电频谱接入策略

认知无线电（Cognitive Radio）网络中,次用户在不干扰主用户的情况下即时接入检测到的空闲频谱以提高频谱资源的利用率。基于部分可观测马尔科夫决策过程的最优频谱接入算法计算复杂度较高,而基于贪婪算法的次优接入策略具有自私性,都不能有效的提高频谱利用率。本文提出一种新的频谱接入算法,该算法对贪婪算法的自私性进行了改进。由于贪婪算法只关注信道当前时隙的瞬时奖励值,导致最大奖励值相同的信道可能会有多个,因此给瞬时奖励值加上这些信道下一时隙的奖励值后重新选择,直至次用户选择出奖励值最大的一个信道。仿真结果表明,相比于传统的贪婪算法,改进算法虽然增加了一些计算复杂度,但有效提高了系统的吞吐量。     

一种针对超短波电台接入网的混合信道接入方案

为超短波电台接入网提供了一种混合信道接入方案,方案借鉴了民用接入技术的一些先进理念,并结合军用跳频电台网络的特殊业务应用需求,采用了一种静态TDMA、动态TDMA和频分多址FDMA的混合信道接入策略,实现了多用户多业务传输的QOS保障,满足了军用业务的特殊传输需求。     

云无线接入网络的下行链路能效的优化

在下行云接入网络(C-RANs)中,核心网络内基站处理单元(BBU)通过前向回传线路向远端无线电头端(RRH)传输数据,然后RRHs通过无线接入链路转发数据。目前,C-RANs的下行链路的能效是C-RANs的研究热点。为此,对C-RANs下行链路能效进行研究,其目的在于最大下行链路的能效。通过对联合用户分配(UA)、RRH激活、数据率分配和信号预编码约束,建立能效最大化表述式,再利用基于逐次凸二次规划的迭代算法求解混合整数非线性问题。仿真结果表明,提出的联合优化设计提高了C-RANs的能效。     

基于Dec-POMDP的认知无线电网络频谱接入算法

针对认知无线电网络中认知用户（CR）的机会频谱感知及接入问题,提出了一种基于分布式部分可观测马尔科夫决策过程（Dec-POMDP）的多用户频谱接入算法。在该模型框架下,相邻CR用户通过交换接入策略,以区域策略梯度方向为基准,对各个CR用户的接入策略做出调整,从而得到最优联合接入策略。仿真结果表明：该算法有效降低了授权用户的容量损失,提高了空闲频谱的利用效率,能够更有效地做出接入决策。     

Multi-tier cooperative caching in fog radio access network

Aiming at the problem of reducing the load of the backward link in the edge buffer and fog wireless access network technology,a multi-tier cooperative caching scheme in F-RAN was proposed to further reduce the backhaul traffic load.In particular,by considering the network topology,content popularity prediction and link capacity,the optimization problem was decomposed into knapsack subproblems in multi-tiers,and effective greedy algorithms were proposed to solve the corresponding subproblems.Simulation results show that the proposed multi-tier cooperative caching scheme can effectively reduce the backhaul traffic and achieve relatively high cache hit rate.     

Planning and operating a fixed radio access network

The case for using radio in the local loop has been well documented, with obvious attractions for both developed and developing countries. Although trial systems of the various technologies exist in many countries throughout the world, operational networks are fewer in number. In June 1996, Ionica launched its service as a public telecommunications operator (PTO) in the UK, using radio in the local loop. This paper describes the experience gained in planning and operating that network. The importance of the access network in maintaining a truly competitive market is discussed. Radio propagation issues are considered, for these play a significant role in the strategic planning of the network, and then in its operational performance. The paper describes the special procedures, and the hardware and software systems, which are required for planning, building and managing the network     

Issues in packet radio network design

There are many design choices that must be made in the development of a packet radio network. There is usually no single correct choice, and the decisions are dependent on the environment that the network must work in, the requirements for performance and other functionalities, and the cost and other limitations, in addition, as new hardware and software technologies become available, the parameters governing the decisions change and often result in different selections. This paper outlines a number of design issues and choices available. The intent is to provide an overview of the design decisions that must be made so as to provide a context for the decisions made in a number of existing and developing packet radio networks. It is hoped that this will allow future designs to take advantage of both the wealth of experience available as well as new technologies. Three areas of design decisions are identified. The first area deals with the physical aspects of the network and concentrates on the radio connectivity and channel sharing. The second area deals with the automated management of the network and concentrates on issues such as link management and routing. The third area deals with the interface of the network to the users and some practical aspects of operating and maintaining a network.     

A dynamic spectrum access network based on cognitive radio

Dynamic spectrum access technologies based on Cognitive Radio (CR) is under intensive research carried out by the wireless communication society and is expected to solve the problem of spectrum scarcity. However, most enabling technologies related to dynamic spectrum access are considered individually. In this paper, we consider these key technologies jointly and introduce a new implementation scheme for a Dynamic Spectrum Access Network Based on Cognitive Radio (DSAN-BCR). We start with a flexible hardware platform for DSAN-BCR, as well as a flexible protocol structure that dominates the operation of DSAN-BCR. We then focus on the state of the art of key technologies such as spectrum sensing, spectrum resources management, dynamic spectrum access, and routing that are below the network layer in DSAN-BCR, as well as the development of technologies related to higher layers. Last but not the least, we analyze the challenges confronted by these mentioned technologies in DSAN-BCR, and give the perspectives on the future development of these technologies. The DSAN-BCR introduced is expected to provide a system level guidance to alleviate the problem of spectrum scarcity.     

Formal verification of a radio network random access protocol

In this paper, the random access procedure of Universal Mobile Telecommunications System network is investigated. We have proposed a model based on communicating timed automata that represents the main functions related to the random access procedure including the user equipment, the base station (node B or BTS), and the channel. Then, we have used computational tree logic formula to specify the proprieties to be verified. The model and the formulas serve as inputs to the model checker, which is used as a verification engine, ie, UPPAAL and SPIN. The formal verification approach shows that the protocol has several drawbacks that may not be detected by simulation.     

A framework for optical burst switching network design

We analyze optical burst switching (OBS) systems. The analysis leads to a framework which provides guidelines for OBS design. We identify conditions for OBS feasibility and the relationship between burst size, or equivalently burst assembly delay, and throughput, taking into consideration control packet processing and the number of available wavelengths per fiber     

无线网络控制器的一种设计方法

描述了第三代移动通信中的无线网络控制器的一种设计方法。从建立系统概念构架和业务模型开始，通过将业务模型应用到具体构架中而得到单板的设计边界条件，然后进行测试和评估，最后确定具体的软、硬件方案。该方法对于设计一个高性能、高质量、高效率的产品系统具有很好的借鉴意义。     

面向实时业务的认知无线网络 MAC 层频谱接入方案

摘 要：为满足认知无线网络中宽带业务实时传输的需求,提出低延迟的MAC层频谱接入方案,包括频谱感知调度与信道接入竞争两部分。在频谱感知阶段,认知用户选取最佳可用信道数实现感知与传输的延迟最小化;在信道接入竞争阶段,协议考虑频谱资源动态变化的特点,通过设计数据帧格式以及邻居节点协同侦听机制,减小信道冲突与“聋终端”的影响。理论与实验结果表明,与传统的认知无线网络MAC层协议相比,提出的接入方案数据传输延迟更短,同时在授权信道空闲率较大时吞吐量性能略优。     

典型部署策略下认知无线传感网的机会频谱接入方法

在典型规则拓扑模式及覆盖部署方式的传感网中探讨无冲突的认知频谱接入方法（包括频谱和时隙分配、协作频谱感知和感知结果汇报方案）,为数据采集提供高效的传输手段。提出对应网络环境下的次级用户的阻塞率和掉话率、各拓扑模式下的网络有效接收带宽和最大传输时延的分析模型。通过对几种拓扑模式的比较,表明Triangle的协作频谱感知效果最佳,而Square的有效接收带宽最佳;在完全覆盖部署方式下,Square和Triangle的传输时延较小,而多重覆盖部署方式下Square的时延最小。指出单个节点上的虚警概率对传输时延的影响不大,授权用户出现概率则对时延有明显影响,而选择较大的传输时隙/感知时隙比能显著降低时延。     

小区智能门禁管理系统设计

为了解决当前小区临时访客自由出入小区问题和车辆存在被盗的安全隐患,采用了RFID和GSM等相关技术,设计了车辆进出小区的智能管理系统;通过对实际需求的分析,所设计的系统主要包括2大部分：长期用户车辆出入管理,临时访客出入管理。其中,长期用户车辆管理是将射频卡和系统内信息核对,进行确认,并发短信通知用户;临时访客管理系统是为了减少管理人员工作量,以密码形式自由出入小区。经系统仿真证明,本系统设计良好,可以有较好的实用价值。     

A Markov Decision Process based flow assignment framework for heterogeneous network access

We consider a scenario where devices with multiple networking capabilities access networks with heterogeneous characteristics. In such a setting, we address the problem of efficient utilization of multiple access networks by devices via optimal assignment of traffic flows with given utilities to different networks. We develop and analyze a device middleware functionality that monitors network characteristics and employs a Markov Decision Process (MDP) based control scheme that in conjunction with stochastic characterization of the available bit rate and delay of the networks generates an optimal policy for allocation of flows to different networks. The optimal policy maximizes, under available bit rate and delay constraints on the access networks, a discounted reward which is a function of the flow utilities. The flow assignment policy is periodically updated and is consulted by the flows to dynamically perform network selection during their lifetimes. We perform measurement tests to collect traces of available bit rate and delay characteristics on Ethernet and WLAN networks on a work day in a corporate work environment. We implement our flow assignment framework in ns-2 and simulate the system performance for a set of elastic video-like flows using the collected traces. We demonstrate that the MDP based flow assignment policy leads to significant enhancement in the QoS provisioning (higher rate allocation, lower packet delays and packet loss rates) for the flows and better access network utilization, as compared to policies that allocate flows to different networks using greedy approaches or heuristics like average available bit rate on the networks.     

Telecommunication access network design with reliability constraints

In this paper, we study the problem of the design of telecommunication access networks with reliability constraints. These networks form an important part of the telecommunications infrastructure of large organizations, such as banks. Using data patterned after an actual bank network in the U.S., we formulate an optimization model for this problem which specifically takes into account the various cost, and discount structures offered by telecommunication carriers. We then develop dedicated solution procedures for obtaining solutions. Starting from a cluster solution, we then use perturbation techniques which we developed specifically for this problem within an overall simulated annealing solution algorithm. We show how to make the solution procedure more efficient by implicitly determining the values for many variables. We then report the results of our computational testing for a variety of problems. We compare our solution to a lower bound obtained using a linear programming relaxation. We show that substantial cost savings can be realized with our model, and solution procedure. Finally, we discuss which types of annealing steps in the simulated annealing algorithm are important.