Impacts of air interface admission control and user mobility on UTRAN transport simulations

UMTS Terrestrial Radio Access Network (UTRAN) Transport Network Layer dimensioning has been of great interest among network researchers and planners due to the limit of Iub bandwidth. This paper investigates the potential impacts caused by Connection Admission Control (CAC) mechanism of the air interface and User Mobility (UM) on simulations carried out for the UTRAN transport network domain. Independent from the TNL CAC mechanism of the transport network which is in charge of Iub link bandwidth, the Radio CAC function deals with the highly non-linear resources needed for an attempted connection depending on its specific propagation and interference situation. The consideration of the air interface acting as bottleneck results into a less challenging amount of traffic for the transport domain. In addition, mobile user behaviors, e.g. UM, may dynamically change traffic load at the air interface, and in consequence affect Iub load, which has a very close correlation with cell load. In this work, a simulation model with Radio CAC mechanism and Handover strategies is implemented to study this correlation, and evaluate the UTRAN transport network performance given a limited radio capacity. The analysis on the impacts of the Radio CAC and UM are derived from qualitative simulations.     

QoS Provisioning with New Effective Bandwidth/Buffer Calculation Scheme in Wireless IP Networks

The huge commercial success of mobile telephony, the phenomenal growth of Internet users, the popularity of IP-based multimedia applications are the major driving forces behind third-generation (3G), ongoing Byond 3G (B3G), and forth-genertion (4G) evolution. 3G brought wired applications, both data and multimedia, into wireless environments. It operates on IP-based infrastructures to provide wider service access capability. To support and satisfy QoS (Quality of Service) of diverse IP-based multimedia applications, traffic management, such as Connection Admission Control (CAC) and resource allocation, becomes essential. CAC and resource allocation are computationally complex when combined with QoS guarantee for traffic with different characteristics. However, CAC and resource allocation are real-time traffic control procedures. Hence, processing load should be minimized to reduce delay. At the same time, network resources should be utilized efficiently to accommodate more users. However, reducing processing load and obtaining high resource utilization efficiency has been considered to be contradictory matter. In addition, CAC and resource allocation schemes which consider multiple QoS criteria – loss and delay – simultaneously have not been adequately studied. Simultaneous QoS consideration is important to satisfy stringent and diverse QoS requirements of multimedia traffic. In this paper, we propose a nobel effective bandwidth/buffer calculation method based on a virtual channel/buffer analysis scheme. We show that our method can achieve high resource utilization efficiency with reduced processing load. Moreover, we show that our scheme allows for simultaneous consideration of multiple QoS criteria, loss and delay.     

NOVEL MULTIMEDIA TRAFFIC MODELING BASED CAC SCHEME FOR CDMA COMMUNICATION SYSTEMS

As the radio spectrum is a very scarce resource, the Call Admission Control （CAC） is one of the most important parts in radio resource management. The Code Division Multiple Access （CDMA） based next generation wireless communications systems will support the transmission of multimedia traffic, such as voice, video and data, thus the CAC, which can support the multimedia traffic and guarantee the Quality of Service （QoS） of different traffic, has gained broad attention. In this paper, a novel multimedia traffic modeling method and a corresponding dynamic QoS based CAC are proposed. The analysis and simulation results show that the proposed CAC scheme can guarantee the QoS to different traffic demand, and improve the system performance significantly.     

Traffic modeling in packet switched networks for single links

To correctly model traffic in packet switched networks for single links with FC-FS discipline at each node, we introduce the influence of the phenomenon of short packets agglutinating behind long packets. It is then necessary to abandon the usual notions of local traffic sources and local G/G/1 queues in favor of the more realistic notion of traffic sources at the network input with local queues appearing as the consequence of a tandem queue whose parameters we define. The influence of the upstream transfer delay and the upstream network topology then appear. We compare theoretical results with those derived by traffic simulations.     

A Novel Analytical Framework for Integrated Cross-Layer Study of Call-Level and Packet-Level QoS in Wireless Mobile Multimedia Networks

We present a novel integrated analytical framework for analyzing the quality-of-service (QoS) performance measures in a wireless mobile multimedia network. The framework integrates physical, radio link, and network layer parameters and protocols to analyze the call-level and packet-level performances. In the network layer, call admission control (CAC) is responsible for deciding whether an incoming call can be accepted or not so that the performances of the ongoing calls do not deteriorate below the acceptable level. Also, an adaptive channel allocation (ACA) scheme is used to maximize the utilization of the radio resources. In the data link layer, queue management and error control are used for non-real-time loss-sensitive traffic. In the physical layer, a finite state Markov channel (FSMC) is used to model channel fading, and adaptive modulation is used for rate adaptation according to channel quality. Various call-level and packet-level QoS measures for real-time, non-real-time, and best-effort traffic are obtained. The analytical results are validated by extensive simulations. Examples of the applications of the presented analytical framework are also provided     

实时DIS网络接口部件的设计与实现

计算机网络是分布交互仿真（ＤＩＳ）的关键支撑技术之一。ＤＩＳ的交互性和实时性对计算机网络的实时特性提出了很高的要求。本文简要介绍了ＤＩＳ的实时要求和网络提供实时性采用的措施，重点提出了支持实时传输的网络接口部件的结构，给出了硬件积木式和软件模块化设计的方法，并描述了各部分的功能和实现     

Utility‐based probabilistic call admission control for complete fairness in wireless networks

Resource reservation or the other prioritization strategies adopted by Call Admission Control (CAC) schemes in wireless networks lead to unfair resource allocation to users belonging to different service classes (SCs) due to high divergence among the respective call blocking probabilities (CBPs). In this paper, we propose dynamic optimization of probabilistic CAC (P‐CAC) schemes to assure CAC fairness among users of different SCs in wireless networks. The approach is based on users utility combined with fairness optimization, aiming at dynamically determining the probability value in the P‐CAC scheme. This optimal probability is adjusted to network ongoing traffic, CBPs of each SC, prioritization levels characterizing the SCs supported, and the users risk aversion, which reflects their behavior toward the perceived QoS. The existence and uniqueness of the optimal probability that leads to absolute fairness among the users of a wireless network are proven. Copyright © 2012 John Wiley & Sons, Ltd.     

Call admission control for QoS provisioning in 4G wireless networks: issues and approaches

This article presents a survey on the issues and the approaches related to designing call admission control schemes for fourth-generation wireless systems. We review the state of the art of CAC algorithms used in the traditional wireless networks. The major challenges in designing the CAC schemes for 4G wireless networks are identified. These challenges are mainly due to heterogeneous wireless access environments, provisioning of quality of service to multiple types of applications with different requirements, provisioning for adaptive bandwidth allocation, consideration of both call-level and packet-level performance measures, and consideration of QoS at both the air interface and the wired Internet. To this end, architecture of a two-tier CAC scheme for a differentiated services cellular wireless network is presented. The proposed CAC architecture is based on the call-level and packet-level QoS considerations at both the wireless and wired parts of the network. A performance analysis model for an example CAC scheme based on this architecture is outlined, and typical numerical results are presented.     

Connection admission control with picture-type dependent effectivebandwidths for VBR MPEG video traffic in ATM networks

The I-picture starting time distribution of variable bit rate (VBR) MPEG video sources may significantly affect the cell loss characteristics of ATM multiplexers. The authors propose a new connection admission control (CAC) method which can reflect this effect. For CAC, VBR MPEG video traffic is modelled as a composite sequence of three subsequences with different effective bandwidths according to their picture coding types. Experimental results show that the proposed method can fully reflect this effect due to the starting time distribution while also improving network utilisation significantly     

自相似业务合成流的建模及排队性能分析

近期起初网络流量分析表明很多信息源会产生在多时间尺度下具有自相似特性的信息流,据此人们采用模拟及分析的方法对此种业务流对ＡＴＭ交换机／复用器性能的进行了研究,发现了与传统短打关模型完全不同的排除生但是到２为止对于自相关信息流的复用问题尚未发现有要进行研究。而这个问题的解决对自相似业务流条件下的ＡＴＭ交换机／复用器性能分析,接入控制（ＣＡＣ）等都具有很重要的意义。本文基于临界时间尺度的概念对这个问题     

一种UMTS核心网中CAC算法

在通用移动通信系统(UMTS)中，无论在无线接入部分还是在核心网部分，QOS的保证都是关键性问题。呼叫准入控制(CAC)是QOS机制的重要组成部分，本文根据3GPP对UMTS业务种类的定义及相应的QOS分类，对UMTS核心网络的QoS准入控制问题进行了研究。基于排队论的思想，提出了一种基于综合排队机制的CAC算法，并对其进行了相应的性能分析和仿真实验，结果表明了本算法的有效性。     

Loss performance analysis for heterogeneous on-off sources withapplication to connection admission control

The bufferless fluid flow model (BFFM) is often used in the literature for loss performance analysis. We propose an efficient and effective means of investigating cell loss using the BFFM. We define the cell loss rate function (CLRF) and use it to characterize the loss performance of traffic sources in the BFFM. Stochastic ordering theory is used to study the CLRF. The introduction of the stochastic ordering theory not only simplifies the theoretical analysis but also makes it possible to extend the scope of applications and theoretical analysis presented. A cell loss upper bound for heterogeneous on-off sources is proposed. The proposed cell loss upper bound is tighter than those previously proposed in the literature. A connection admission control (CAC) scheme using online measurements is designed based on the cell loss upper bound. Extensive simulation is carried out to study the performance of the CAC scheme. Particular attention is paid to the impact of inaccuracies in user-declared traffic parameters on the performance of the CAC scheme. Simulation results indicate that the proposed CAC scheme can ensure QoS guarantee, is robust to inaccuracies in declared traffic parameters, and is capable of achieving high link utilization     

A probabilistic approach for fair-efficient call admission control in wireless multiservice networks

The efficiency of call admission control (CAC) schemes in multiclass wireless networks should be evaluated not only with regard to the call blocking probability (CBP) achieved for every service class (SC) supported but also with regard to quality of service (QoS) and network efficiency criteria. In this article, four CAC schemes offering priority to SCs of advanced QoS requirements, based on guard channel policy, are studied and evaluated taking into account fairness and throughput criteria in addition to CBP. For the performance evaluation of the proposed CAC schemes and to examine fairness issues, two fairness indices are introduced along with a throughput metric. The analytical results, validated through extensive simulations, indicate that by appropriate selection of the CAC parameters satisfactory fairness and throughput are achieved while achieving low CBP.     

Performance of Reservation in Call Admission Control Schemes for Code-Division Multiple Access Systems with Nonuniform Traffic Distribution Among Cells

In this paper, we propose the reservation type call admission control (CAC) scheme to resolve the intercell unbalanced traffic problem. Differently from a conventional CAC scheme where the system resource is fully allocated to the local users in the home cell, the proposed CAC scheme reserves a small portion of the system resource for new calls occurring in the neighboring cells instead of fully allowing the local users in the home cell to occupy the system resource. As a result, the proposed CAC scheme improves the overall call blocking probability when the traffic is nonuniformly distributed among cells. More specifically, the proposed CAC scheme improves the overall call blocking probability by 15% when one cell has 67% more traffic than its surrounding cells.     

一种基于对策模型的ATM网络连接接纳控制策略

本文先简述了ATM网络进行连接接纳控制(Connection Admission Control:CAC)的主要方法,其中主要综述了基于动态带宽分配的CAC策略,而后从合作对策模型的角度讨论业务间共享链路资源的公平性问题,提出一种基于时延带宽积的业务收益函数形式,并通过遗传算法求解待优化的对策函数,以决定对呼叫请求的接入或拒绝。仿真结果表明此方法能够更好地保证不同带宽和服务质量要求的业务共享网络资源的公平性。     

基于功率谱密度分析的ATM连接允许控制研究

本文研究了ＡＴＭ网络中的多媒体实时突发业务流的功率谱密度特性，利用反映业务流相关特性的功率谱密度，设计了一个用于多媒体业务的ＡＴＭ连接允许控制方法，并给出了将人工神经网络技术应用于实现业务流的功率谱密度、负载强度与信元丢失概率之间映射的理论方法，增强了ＡＴＭ连接允许控制的智能特性。     

A connection admission control scheme based on game theoretical model in ATM networks

In this paper, the main schemes of connection admission control (CAC) in ATM networks are briefly discussed especially the principle of dynamic bandwidth allocation. Then the fair share of the bandwidth among different traffic sources is analyzed based on cooperative game model. A CAC scheme is proposed using the genetic algorithm (GA) to optimize the bandwidth-delay-product formed utilization function that ensures the fair share and accuracy of accepting/rejecting the incoming calls. Simulation results show that the proposed scheme ensures fairness of the shared bandwidth to different traffic sources.     

A call admission control for service differentiation and fairness management in WDM grooming networks

We investigate a call admission control (CAC) mechanism for providing fairness control and service differentiation in a WDM network with grooming capabilities. A WDM grooming network can handle different classes of traffic streams which differ in their bandwidth requirements. We assume that for each class, call interarrival and holding times are exponentially distributed. Using a Markov Decision Process approach, an optimal CAC policy is derived for providing fairness in the network. The Policy Iteration algorithm is used to numerically compute the optimal policy. Furthermore, we propose a heuristic decomposition algorithm with lower computational complexity and good performance. Simulation results compare the performance of our proposed policy with those of Complete Sharing and Complete Partitioning policies. Comparisons show that our proposed policy provides the best performance in most cases. Although this approach is motivated by WDM networks, it may be deployed to determine the optimal resource allocation in many problems in wireless and wired telecommunications systems.     

Soft QoS in Call Admission Control for Wireless Personal Communications

In wireless multimedia communication systems, call admission control (CAC) is critical for simultaneously achieving a high resource utilization efficiency and maintaining quality-of-service (QoS) to mobile users. User mobility, heterogeneous nature of multimedia traffic, and limited radio spectrum pose significant challenges to CAC. QoS provisioning to both new calls and handoff calls comes with a cost of low resource utilization. This paper proposes a CAC policy for a wireless communication system supporting integrated voice and dataservices. In particular, soft QoS (or relaxed target QoS) is incorporated in the CAC policy to make compromises among different objectives.Numerical results are presented to demonstrate that (a) in dealing with the dilemma between QoS satisfaction and high resource utilization, how the resource utilization efficiency can be increased by introducing soft QoS; and (b) in accommodating different types of traffic, how the QoS of low priority traffic can be improved by specifying soft QoS to high priority traffic.