An HMM-based call admission control policy for supporting QoS in wireless cellular networks

The multimedia services are getting to become the major trend in next-generation cellular networks. Call admission control (CAC) plays the key role for guaranteeing the quality of service (QoS) in cellular networks. The goal which keeps both the call dropping probability (CDP) and call blocking probability (CBP) below a certain level is more difficult owing to user indeterminate mobility. In this paper, the Hidden Markov Models (HMMs) concept which is suitable for solving a dynamic situation is introduced and applied to the call admission control policy. The prediction of user mobility can be modeled and resolved as the decoding problem of the HMMs. According to the prediction result, the proposed CAC method can reserve appropriate bandwidths for a handoff call beforehand. Thus, the call dropping probability can be kept below a lower level. Moreover, the call blocking probability is not sacrificed too much since the proposed method can reserve the suitable bandwidths in the appropriate cells but not reserve stationary ones which are always adopted by traditional CAC methods. Therefore, the proposed method not only can satisfy both CDP and CBP issues, but also improve the system utilization.     

一种支持宽带无线多媒体网络QoS的动态呼叫接纳策略

在无线网络中,小区微型化的趋势使得呼叫切换发生的频率越来越高,迫切需要一种有效的呼叫接纳控制策略,对有限的无线带宽资源进行分配,以保证切换时的QoS,同时使带宽利用率最高。传统的预留带宽策略(GC,guard channel scheme)由于其固有的静态特征而不能适应流量模式的变化。最近,人们发现采用动态的随机控制策略能适应流量模式的变化,而且能使精度和稳定性大大提高。但将这种策略应用于多业务环境依然十分困难,挑战来自于多类呼叫的QoS要求、流量模式、切换率的多样性和宽带条件下的实时可计算性。在文[3]中,我们建立了一个随机控制模型,可以在宽带条件下实时地进行多业务接纳控制,但由于没有考虑复杂的边界条件,控制精度受到影响。本文,我们在考虑边界条件的情况下,求解该随机问题,并采用一种有效的数值方法,使计算复杂度大大降低,保证了计算的实时性。最后得到的多业务动态接纳控制策略具有较高的控制精度和良好的可计算性。仿真结果显示该策略能稳定地满足多业务QoS对呼叫中断概率的严格限制,同时又能保证信道的高利用率。     

Part 2: Traffic control in Multimedia Networks An efficient algorithm for multimedia call-admission control

This paper presents a call admission control (CAC) algorithm for multimedia communication systems with diverse bit-rate media sources. The proposed algorithm for making bandwidth allocation decisions is based on bounding the probability of demand for excess bandwidth and the loss (or blocking) probability. Recursion formulas for calculating these probabilities are derived. An algorithm based on these probabilities executes quickly enough so that the response time to a bandwidth request is acceptable.     

基于IP的无线接入网络性能研究

全IP化是未来通信系统发展的必然趋势。为了体现IP传榆的优势，基于IP的无线接入网络（IP RAN）的性能和传输效率是必须考虑并正视的问题。本文分析了IP RAN可能存在的性能瓶颈，并从拥塞控制的角度对呼叫接入控制和负载均衡两种性能改善策略进行对比。针对基站与网络控制器的IP RAN传输，提出一种改进的负载均衡方案，引入小区业务度的概念，并以此参量为基础，动态调整呼叫与RNC的连接关系。该方案更有效的利用了网络资源，改善系统性能。     

对一种新的基于实测的无线网络呼叫接入控制算法的性能研究

本文对一种新的基于实测的呼叫接入控制算法进行了仿真分析。研究结果表明预测算法均方差很小,同时不同多媒体业务的切换阻塞率和在总允许接入呼叫数中所占比例,在业务负载低于系统容量时满足要求;而在高负载情况下,性能出现分化,其中高带宽业务的服务质量下降更快。     

基于T—S模糊神经网络的ATM网络业务量智能控制

ATM网络的业务量控制是ATM网络中的关键技术之一。在充分考虑了模糊神经网络的学习功能后,提出了利用T－S模糊神经网络算法对ATM网络进行呼叫接纳控制。仿真结果表明,该方法提高了网络对呼叫的实时处理能力,又增加了网络资源的利用率。     

异构无线网络中基于效用的呼叫接纳控制及流量均衡策略

目前国内外对于异构无线网络中联合呼叫接纳控制和流量均衡策略的研究大多停留在网络层以上,即认为不同的网络具有不同的覆盖面积和网络容量,而没有考虑不同网络在物理层和链路层的具体特性.本文在对UMTS和WLAN底层特性分析的前提下,结合应用层为用户设定的效用函数,利用跨层信息提出了一种新的联合呼叫接纳控制及流量均衡策略.仿真结果表明该策略可以使异构无线网络中所有呼叫的效用总和最大.     

多业务IP网络呼叫接纳控制模型和算法

呼叫接纳控制(CAC)是多业务IP网络QoS的关键技术。文章主要研究在采用多协议标记交换(MPLS)传送机制的区分服务(DiffServ)网络中引入带宽代理(BB)资源管理实体条件下的呼叫接纳控制模型和算法。文章在分析比较三类常用呼叫接纳控制技术的基础上,提出了基于参数模型和网络测量相结合的控制模型,给出了该模型的核心控制算法,设计了算法实现流程,并在ns-2.26上进行了仿真实验。仿真结果表明,该文提出的控制模型和算法既能确保各类业务所需的QoS,又能有效地提高网络资源利用率。     

CDMA系统中考虑相邻小区干扰基于QoS的CAC算法

CDMA网络用户的数量日益增加,无线资源相对有限,用户对服务质量的要求也越来越高,呼叫接纳控制是解决这系列问题的关键技术之一。该文提出了基于QoS(服务质量)考虑相邻小区干扰的呼叫接纳控制算法,以高斯模型引入相邻小区的干扰,以不同业务的中断概率要求为判决门限来实现对于不同业务的QoS的保证。可以看到该算法对于系统干扰源的考虑更加全面,更加符合实际的网络环境;同时也满足了无线用户日益提高的QoS要求,这无疑是移动通信服务更加人性化的一种体现。     

Power-based multi-cell call admission control scheme for wideband-CDMA systems

Wideband code division multiple access (WCDMA) systems are interference-limited. When a WCDMA system operates at nearly full capacity, admitting a new user may affect the stability of the system. Therefore, the proper call admission control (CAC) is crucial and should balance between quality of service (QoS) requirements for the new user as well as for the existing users and the required high capacity. In this paper, we investigate this trade-off in the uplink direction using a power-based multi-cell admission control (MC-AC) algorithm. Multimedia services are considered with different QoS requirements in this algorithm. Different traffic scenarios are also considered. Simulation results reveal that the proposed MC-AC algorithm has many advantages over single-cell admission control (SC-AC) in terms of the overall stability of the system and the total system throughput.     

一种提高无线网络语音通话数量的方法

语音通话(Voice over IP)已经成为无线局域网中的一种重要的应用,并且近年来得到了越来越广泛的关注.分析了无线局域网所能支持的语音通话的最大数量,并在网络仿真器NS2上建立了IEEE 802.11语音通话的仿真模型根据仿真分析结果,提出一种自适应传输间隔接入控制方法,提高了IEEE 802.11无线局域网支持语音通话的数量.在自适应传输间隔接入控制方法中,基站(Base Station)通过监测网络冲突概率,自适应的改变网络中语音通话的传输间隔,使网络始终工作在非饱和状态.仿真实验结果表明,提出的白适应传输间隔接入控制方法不仅能够保证IEEE 802.11无线局域网中语音通话的质量,还可以增加网络所能支持语音通话的数量.     

An auction mechanism for allocating the bandwidth of networks to their users

We present a mechanism for auctioning bandwidth on a network-wide basis to end users or ISPs that will utilize it for the same time period. This mechanism consists of a set of simultaneous multi-unit descending-price (i.e. Dutch) auctions, one per link of the network. The per unit prices of bandwidth at the various links are asymmetric, thus reflecting the asymmetry of demand for these links. A user can be instantly allocated bandwidth over a certain path, by simultaneously bidding for the quantity desired at all relevant auctions. This winner determination rule is complemented by a payment rule of the VCG (Vickrey–Clarke–Groves) type, which provides users with the incentive to bid truthfully, thus simplifying bidding. Also, the mechanism enables the auctioneer to use his prior information on market demand anticipated and its spreading among the various links in order to set effectively the auction’s parameters. We argue that our mechanism attains nearly efficient allocation of the network’s bandwidth (i.e. the resulting social welfare is close to the respective maximum for the quantity decided to be sold by the auctioneer), while it is simple, scalable and applicable to real networks, even for auctioning the capacity of links owned by multiple providers and then splitting the revenue among them. Alternatively, the mechanism offers the provider the opportunity to optimize his revenue, rather than the social welfare. Since our mechanism’s computational complexity is low it can serve as a fast, practical, and near-optimal solution to a generally NP-hard optimization problem.     

A new scheme for traffic estimation and resource allocation for bandwidth brokers

This paper is motivated by the concern of a multi-service network provider who plans to offer quality of service guarantees to users. A bandwidth broker acts as the resource manager for each network provider. Neighboring bandwidth brokers communicate with each other to establish inter-domain resource reservation agreements. Conventional approaches for resource allocation rely on pre-determined traffic characteristics. If allocation follows the traffic demand very tightly, the resource usage is efficient but leads to frequent modifications of the reservations. This would lead to increased inter-bandwidth-broker signaling in order to propagate the changes to all the concerned networks. Contrarily, if large cushions are allowed in the reservations, the modifications are far spaced in time but the resource usage becomes highly inefficient. In this paper, a new scheme for estimating the traffic on an inter-domain link and forecasting its capacity requirement, based on a measurement of the current usage, is proposed. The method allows an efficient resource utilization while keeping the number of reservation modifications to low values.     

一种基于任务角色的云计算访问控制模型

数据安全问题是云计算推广的一大阻碍,主要来源于数据共享带来的安全问题和云服务提供商的超级特权导致的潜在危险。为此,分析云计算中数据存储和用户群体的特点,提出一种基于任务角色的云计算访问控制模型,对不同访问主体采取不同访问控制策略,以提供分级的安全特性,使云服务提供商不再享有超级特权。分析结果表明,该访问控制模型使得云端数据访问安全无须依赖于服务器的绝对可信,为云计算提供了更为可靠的安全特性。     

基于时频资源分配的认知无线中继网络物理层安全研究

提出了一种在认知无线中继网络物理层安全意义下的最优时频资源分配方案。在该方案中,主用户通过次用户的协作进行通信;作为回馈,允许次用户接入该频段传输信息。在次用户网络中,选择两个最优次用户,一个用作协作转发,一个用作协作干扰,同时在保证次用户网络传输速率的条件下,通过寻求系统的最优带宽分配因子、时隙分配因子以及次用户的协作功率,来最大化主用户的安全容量。仿真结果表明,提出的方案切实可行,能够显著提高主用户的安全容量。     

Heavy业务流的有效带宽及其基于测量的接纳控制算法

基于具突发性Heavy业务流的TES(Transform Expand Sample)模型,推导出一个计算Heavy业务流有效带宽的实用的公式,并由此公式求得的有效带宽,作为基于测量的接纳控制(MBAC)算法中新业务流所申请的带宽。仿真结果表明,采用该计算公式求得的有效带宽,MBAC算法可以取得更好的网络性能。     

Performance Analysis of Adaptive Admission Control Algorithms for Bandwidth Brokers

In this paper, we propose a novel architecture for the admission control module of a Bandwidth Broker entity that aims at achieving a satisfactory balance between maximizing the resource utilization for the managed network and minimizing the overhead of the module. We also describe, analyze and evaluate mechanisms which aim at solving the additional problems of fairly prioritizing resubmitted requests and efficiently handling requests which do not specify ending times. We use the well known network simulator ns-2, as well as a custom simulation environment in order to study the performance characteristics of the proposed mechanisms and compare them with various alternatives for the admission control module of a Bandwidth Broker. We provide the results of the experimental evaluations and the conclusions they lead us to for the relative importance of the proposed solution and the various alternatives, their advantages and drawbacks, and the environments for which each one is best suited.     

Key Technologies for SON in Next Generation Radio Access Networks

The aim of SON （self-organizing network） is to realize the autonomic function of the wireless network by self-configuration, self-optimization and self-healing, which reduces the human intervention and improves the user experience, Self-configuration is a process where newly deployed eNodeBs are configured by automatic installation procedures to get the necessary basic configuration for system operation. Self-optimization is a process that continuously monitors an environment and automatically optimizes various parameters when the environment changes. Self-healing is a process that detects and localizes failures, then fixes the problems automatically. This paper gives a comprehensive introduction to the SON functionalities and outlines the framework of self-configuration, self-optimization and self-healing. Some concrete algorithms are proposed for self-optimization and self-healing, which include capacity and coverage optimization and cell outage detection and compensation respectively. Simulation results in various scenarios are provided to evaluate the performance of the proposed algorithms.     

通用分组无线业务中基于测量的接纳控制算法

GPRS(generalpacketradioservice)通过使用类似于ATM中采用的QoS管理算法来为用户提供预留服务。许多学者的研究表明：基于测量的链接接纳控制算法与其他链接接纳控制算法相比,对GPRS网络具有更好的适应性和更高的效率。利用优先级队列的最坏延迟计算模型、等效漏桶近似和延迟标准化,在充分分析GPRS特性的基础上,提出了一种适合于GPRS的基于测量的接纳控制算法。通过仿真发现,该算法能在满足GPRS的QoS要求的同时获得80％的资源利用率。     

Designing for Semantic Access: A Video Browsing System

Users of browsing applications often have vague information needs which can only be described in conceptual terms. Therefore, a video browsing system must accept conceptual queries for preselection and offer mechanisms for interactive inspection of the result set by the user. In this paper, we describe a MM-DBMS that we extended with the following components: Our retrieval engine calculates relevance values for the results of a conceptual query by feature aggregation on video shot granularity to offer conceptual, content-based access. To reduce startup delays within sessions, our admission control module admits only complete browsing sessions, if required resources, which are heuristically predicted from query results, are available. In addition, our intelligent client buffer strategy employs the retrieval relevance values to enable flexible user interactions during browsing.