Performance Analysis of Multi-Parametric Call Admission Control Strategies in Un-Buffered Multi-Service Cellular Wireless Networks

In this paper model of integrated voice/data cellular wireless networks (CWN) are investigated. The unified approximate approach to calculate the desired Quality of Service (QoS) metrics in an isolated cell of such networks under two multi-parametric call admission control (CAC) strategies is developed. One of them is based on the guard channels scheme while the second is based on a threshold scheme. Results of the numerical experiments are given and a comparison of QoS metrics under different CAC strategies is carried out.

A novel dynamic call admission control policy for wireless network

To address the issue of resource scarcity in wireless communication, a novel dynamic call admission control scheme for wireless mobile network was proposed. The scheme established a reward computing model of call admission of wireless cell based on Markov decision process, dynamically optimized call admission process according to the principle of maximizing the average system rewards. Extensive simulations were conducted to examine the performance of the model by comparing with other policies in terms of new call blocking probability, handoff call dropping probability and resource utilization rate. Experimental results show that the proposed scheme can achieve better adaptability to changes in traffic conditions than existing protocols. Under high call traffic load, handoff call dropping probability and new call blocking probability can be reduced by about 8%, and resource utilization rate can be improved by 2%-6%. The proposed scheme can achieve high source utilization rate of about 85%.

A NOVEL CALL ADMISSION CONTROL SCHEME IN CELLULAR/WLAN INTEGRATION AND PERFORMANCE ANALYSIS

In order to achieve the Quality of Service(QoS) provisioning and efficient resource utili-zation in cellular network and Wireless Local Area Network(WLAN) integration,an Integrated Ser-vice-Based Call Admission Control(ISB-CAC) scheme is proposed in this paper.The integrated network is modeled by using multi-dimensional Markov chains.The numerical analysis is presented to evaluate the important performance measures such as the blocking probability of originating calls,the dropping probability,and the average transfer time,etc.The steady-state probabilities of the multi-dimensional Markov chains are obtained by using an iterative approach,and the CAC pa-rameters are optimally designed.The analytical model is validated by the computer simulation.It is shown that compared with the conventional WLAN-First Call Admission Control(WF-CAC) scheme,the proposed ISB-CAC scheme not only provides better QoS for mobile users but also utilizes the bandwidth resources more efficiently.

Call Admission Control in HAP W-CDMA Cellular Systems

Among various radio sources which control different dependencies/functions, in this article, we will talk about the Call Admission Control (CAC), and we are supposed to confine our concentration on W-CDMA which is based on high raised platforms, since during the recent years remarkable amount of attention has been focused on platforms located in stratosphere layer [1]. Firstly, we study the capacity of uplink from HAP (High Altitude Platform) W-CDMA and we’ll work on estimation and power control defects in a new conversation added to current conversations. We’ll enhance the Call Admission Control (CAC) based on the side effects of power control defects and users’ stimulus and then compare the CAC which has been measured by using of momentary energy on bit in the spectral density form (Eb/N0). Then we examine the mentioned charts for two different criteria which the decision will be made by these criteria in order to decide if exchanged calls are to be admitted or not. The first criterion is based on the minimum of (Eb/N0) of the first row cells meanwhile the second criterion is based on the average of (Eb/N0) of first row-cells.

Unified Performance and Availability Model for Call Admission Control in Heterogeneous Wireless Networks

The system capacity of wireless networks varies temporally. This may be due to the dynamic allocation of the channels and also the mobility of the users. The change in capacity will create greater impact on the system performance parameters. This variation of capacity particularly poses a greater challenge to the research community to ensure the Quality of Service (QoS) as it affects the call blocking probability which is one of the important QoS parameters. This paper proposes a performance model for call admission control and the availability model for a heterogeneous wireless network environment. The proposed model is able to handle three types of traffic considered for the study includes conversation traffic, interactive traffic and background traffic. The unified performance-availability model is developed using the Stochastic Area Networks (SAN). The performance of both analytical models and the SAN based performance-capacity models are verified by taking the call blocking probabilities for all the three types of traffics.

A STUDY ON PROBE-BASED MULTICAST ADMISSION CONTROL AND ENHANCEMENT

To provide scalable and simple Quality of Service(QoS) mechanism for multicast services, Probe-Based Multicast Admission Control (PBMAC) scheme was proposed. In this paper, PBMAC is studied and a so-called subsequent request problem is found in PBMAC, which degrades system performance significantly when the network traffic is heavily loaded. Based on the analysis on subsequent request problem, an Enhance PBMAC (EPBMAC) scheme is proposed, in which complementary probing is devised to solve the problem. Using a new metric of normalized requested equivalent link capacity, the performance of PBMAC and EPBMAC is analyzed and evaluated. Two implementations are proposed for incremental deployment. The paper finally introduces evaluation with packet-based simulations. Both analytical and simulation results show the significant improvement in performance.

MEASUREMENT-BASED ADMISSION CONTROL USING MULTIPLE TIME-SCALES TEST

A new measurement-based admission control algorithm to support Quality of Service(QoS) demand is proposed for soft real-time applications. In the algorithm, admission test is performed across Multiple Time-Scales (MTS) to accurately capture traffic fluctuation on various time-scales. By applying the QoS requirements directly to admission test, the MTS algorithm can properly meet the QoS target and maximize the bandwidth utilization.

Admission Control with Elastic QoS for Video on Demand Systems

In network service systems, satisfying quality of service (QoS) is one of the main objectives. Admission control and resource allocation strategy can be used to guarantee the QoS requirement. Based on partially observable Markov decision processes (POMDPs), this paper proposes a novel admission control model for video on demand (VOD) service systems with elastic QoS. Elastic QoS is also considered in resource allocation strategy. Policy gradient algorithm is often available to find the solution of POMDP problems, with a satisfactory convergence rate. Through numerical examples, it can be shown that the proposed admission control strategy has better performance than complete admission control strategy.

Dynamic resource management using bandwidth brokers

The admission control issue in the design of a centralized bandwidth broker model for dynamic control and management of QoS provisioning is studied. A two-phase differentiated flow treatment based dynamic admission control scheme under the centralized bandwidth broker model is proposed. In the proposed scheme, the flow requests are classified into two classes and get differentiated treatment according to their QoS demands. We demonstrate that this admission control scheme can not only improve the resource utilization but also guarantee the flows＇ QoS. Furthermore, the admission control is divided into two phases： edge admission control and interior admission control. During the interior phase, the PoQ scheme is adopted, which enhances the call processing capability of the bandwidth broker. The simulation results show that the proposed scheme can result in lower flow blocking probability and higher resource utilization. And it also reduces the number of QoS state accesses/updates, thereby increasing the overall call processing capability of the bandwidth broker.

Two-Level Cross-Talked Admission Control Mechanism for QoS Guarantee in 802.11e EDCA

This paper describes a two-level cross-talked admission control mechanism that guarantees quality of service （QoS） requirements for multimedia applications over wireless local area networks （WLANs）. An enhanced distributed channel access analytical model is used to compute the maximum number of admitted users according to the QoS requirements and the packet arrival characters. Then, some channel resources are reserved for handoff calls based on the maximum number of admitted users and the call-level traffic model. The channel utilization ratio is also measured to reflect the current system traffic load. The maximum number of admitted users and the channel utilization ratio are used for admission control for applications with QoS requirements in the call level and for rate control of best effort applications in the packet level using the p-nonacknowledgement scheme. Thus, the QoS requirements are statistically guaranteed while the system is efficiently utilized. Simulations validate the effectiveness of this mechanism to guarantee the QoS and bandwidth utilization.

Adaptive Call Admission Control Based on Reward-Penalty Model in Wireless/Mobile Network

A dynamic threshold-based Call Admission Control （CAC） scheme used in wireless/mobile network for multiclass services is proposed. In the scheme, each class＇s CAC thresholds are solved through establishing a reward-penalty model which strives to maximize network＇s revenue. In order to lower Handoff Dropping Probability （HDP）, the scheme joints packet and connection levels Quality of Service constraints, designing a bandwidth degradation algorithm to accept handoff calls by degrading existing calls＇ bandwidth during network congestion. Analyses show that the CAC thresholds change adaptively with the average call arrival rate. The performance comparison shows that the proposed scheme outperforms the Mobile IP Reservation scheme.

Joint admission control algorithm in access network

To deal with long probing delay and inaccurate probing results in the endpoint admission control method,a joint local and end-to-end admission control algorithm is proposed,which introduces local probing of access net-work besides end-to-end probing.Through local probing,the algorithm accurately estimated the resource status of the access network.Simulation shows that this algorithm can improve admission control performance and reduce users’average waiting time when the access network is heavily loaded.

基于OFDM-PON的媒质接入控制协议设计

在以太网无源光网络帧结构的基础上,针对正交频分复用无源光网络的特点,提出了一种适用于正交频分复用无源光网络的媒质接入控制协议.对多点控制协议、控制消息的结构、业务优先级等进行了设计,提出了一种提供服务质量保障的特殊情况下区别用户服务等级的动态带宽分配算法.该算法引入两级调度的机制,将带宽资源的分配分为不同优先级业务的调度和同类型业务下不同等级的光网络单元调度.文章对提出协议的时延、丢包率、吞吐量等方面的性能进行了仿真,仿真结果显示提出的媒质接入控制协议很好地实现了对各业务的服务质量保障,符合多业务接入对服务质量等的需求.

OFDMA中继蜂窝系统的接入控制策略

针对正交频分多址(OFDMA)2跳中继蜂窝系统,提出几种改进的用户接入中继的控制策略.采用启发式算法,以已接入用户的业务质量(QoS)指标、中继负载大小为约束条件,综合考虑用户对中继的选择、用户间竞争接入等情况,最大化每个中继上可减少使用的子载波数,从而有效提高资源利用率和系统容量.仿真结果验证了改进策略能进一步提高系统容量.

脑心健康管理师工作实践及培训研究进展

脑心健康管理师是卒中患者、高危及健康人群的专职管理师,其职责在于通过全面管理降低脑卒中发病率和复发率,提高我国卒中防控的水平。本文从脑心健康管理师的由来和发展、准入条件和培训现状、工作内涵和服务模式、不足与展望方面进行阐述,提出脑心健康管理目前存在的问题及不足。通过不断地持续改进,确保脑心健康管理师人才建设及团队的稳定性,以期为国内开展脑心健康管理、慢性病的研究及管理实践提供参考。

宽带OFDM系统支持实时分组业务的接纳控制策略

针对基于分组交换的宽带正交频分复用(OFDM)无线通信系统,提出了新的动态呼叫接纳控制策略.采用马尔可夫队列模型和维纳过程预测理论,分析了实时业务的分组等待时延与其接纳概率的关系.并利用此关系,得到了以分组等待时延和切换中断概率为约束条件的最大接纳概率.该策略满足系统实时业务用户连接层面和分组层面服务质量的同时达到系统带宽资源的最大化利用.仿真结果验证了所提策略的性能.

Diffserv中基于测量的准入控制

针对当前Internet只能提供传统的尽力而为(BestEffort)服务,不能提供QoS(QualityofService)的问题,IETF(InternetEngineeringTaskForce,Internet任务工程组)提出了几种解决方案,包括Intserv,Diffserv和MPLS。主要介绍了其中的Diffserv体系结构,并介绍在Diffserv中加入准入控制的几种方式。

区分服务网络基于测量的接纳控制方案的设计与应用

提出了一种分布式可扩展的接纳控制方案 ,其目的是为区分服务网络提供端到端服务质量 (QualityofSer vices,QoS)保证 ,该方案主要由以下部分构成 :(1)连接接纳控制协议 ,主要负责主机和网络节点以及网络节点和带宽代理之间的信息传送 ,实现对连接请求的串行操作 ;(2 )位于网络核心节点的可用带宽估计算法 ;(3)位于网络边缘节点的接纳控制算法 ;给出了该方案在视频传输方面的应用实例 ;利用多种网络拓扑结构和QoS指标评价该方案的性能 .实验结果表明该方案能准确地控制可接纳区域和提高网络资源的利用率 .

一种基于松弛时间的服务网格资源能力预留机制

通过资源能力预留为网格服务提供确定的QoS保证是实现服务网格QoS管理的基础和关键.针对确定性资源能力预留的“资源能力碎片”问题,提出了一种支持松弛时间的灵活资源能力预留机制,并设计了支持松弛时间的资源预留请求接纳控制算法.在CROWN的节点服务器上实现了该机制,并通过仿真实验进行性能评价.结果表明,和已有的确定型预留机制相比,支持松弛时间的资源能力预留机制,使资源能力调度具有更多的自主性,可显著地提高网格资源的综合利用效率.

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。