Interworking of heterogeneous access networks and QoS provisioning via IP multimedia core networks

Moving towards packet networks, where IP will have a prominent role, constitutes nowadays a widely accepted perception of future communications, the first instance of which has begun to materialise with the IP multimedia core network subsystem (IMS). By specification, IMS is the first implementation towards reaching converged communications which allows users to communicate with video, audio and multimedia content, via any fixed, mobile and wireless access network type, with controllable QoS. To enable IMS communications across heterogeneous networks, incorporating UMTS, WLAN and fixed IP access points, 3GPP and ETSI’s TISPAN currently work on schemes for controlling bandwidth allocation at the service level by employing logical interfaces that carry SIP messages. This article analyzes how interconnection between such heterogeneous networks may be performed on real platforms. In this effort, special attention is paid to the way the various interconnection possibilities can affect end-to-end QoS provisioning.     

Optimization of QoS parameters using scheduling techniques in heterogeneous network

Multimedia applications in wireless communication have been increased in recent years. A variety of wireless access technologies is introduced for various needs. The abundant increase in mobile computing devices and different networking systems leads to the support of user’s mobility on heterogeneous network. In general, the roaming users migrate between two different wireless technologies and their service must be supported by vertical handover (HO). Since the roaming users expect a rapid handover experience while switching from one wireless network to another, the handover operation must be enhanced by the networks. Various wireless technologies such as wireless LAN, Worldwide Interoperability for Microwave Access (WiMAX), and the 3G Partnership Project (3GPP) are interlaced to support many wireless services in rural, urban, and global scenarios. Moreover, quality of service (QoS) has become more significant in many applications where wireless network resources are utilized. In this paper, a handover management scheme is proposed for QoS enhancement in roaming users between WiMAX and WLAN by subscribers of networks belonging to the 3GPP standards. The proposed algorithms genetic queuing, proportionally fair queuing, and WiMAX aware load balancing are analyzed in the scheduling process during handover. The simulation is implemented using NS–2 and the experimental results are obtained for the proposed algorithms and compared with the standard scheme.     

Bandwidth Aggregation-Aware Dynamic QoS Negotiation for Real-Time Video Streaming in Next-Generation Wireless Networks

In next generation wireless networks, Internet service providers (ISPs) are expected to offer services through several wireless technologies (e.g., WLAN, 3G, WiFi, and WiMAX). Thus, mobile computers equipped with multiple interfaces will be able to maintain simultaneous connections with different networks and increase their data communication rates by aggregating the bandwidth available at these networks. To guarantee quality-of-service (QoS) for these applications, this paper proposes a dynamic QoS negotiation scheme that allows users to dynamically negotiate the service levels required for their traffic and to reach them through one or more wireless interfaces. Such bandwidth aggregation (BAG) scheme implies transmission of data belonging to a single application via multiple paths with different characteristics, which may result in an out-of-order delivery of data packets to the receiver and introduce additional delays for packets reordering. The proposed QoS negotiation system aims to ensure the continuity of QoS perceived by mobile users while they are on the move between different access points, and also, a fair use of the network resources. The performance of the proposed dynamic QoS negotiation system is investigated and compared against other schemes. The obtained results demonstrate the outstanding performance of the proposed scheme as it enhances the scalability of the system and minimizes the reordering delay and the associated packet loss rate.     

公用IPv6网络承载服务SLA监测研究

分析了NGI中网络承载服务sIA(NSLA)的应用需求,针时NSLA可能的应用场合及IPv6特点定义了适用于NSLA的QoS参数:IP分组传送延迟(IPTD)、IP分组延迟变化(IPDV)、IP分组传送失败率(IPFR)和IP分组吞吐能力(IPTC),其中IPTC能有效刻画公用IP网段集维持业务流量模式的能力.分组识别和时钟同步是IPv6网络NSLA监测的两个关键问题.文中给出了分组识别的解决思路;为降低对同步的要求、支持较低成本的NSLA监测,除IFFD外其余参数均可容忍出入测量点之间存在有限的时钟不同步.此外,综合应用特点、用户感知、IPv6协议等因素,讨论了面向应用NSLA的QoS参数设定.最后设计了一个包括采集器、前端机、分析机、原始数据库和结果库等部件的NSLA监测系统,采用ON-OFF系统抽样方式被动监听自然流量,在各部件的协作下可实现各QoS参数的测量.     

全IP 4G无线网络中的关键问题

第四代移动通讯系统的特点是:多种接入网络和基于IP的传输技术.不同的接入技术使用户在选择服务时有了极大的灵活性,而服务也具有不同的QoS支持、商务类型和服务提供商.在考虑QoS和AAAC的同时,实现向最优网络进行无缝切换不仅要求无缝换手协议,而且要求智能换手决定策略.本文介绍了全IP结构的第四代移动通讯系统的特点和关键技术以及未来的问题和研究方向.     

Design and analysis of a frame-oriented dynamic bandwidth allocation scheme for triple-play services over EPONs

Ethernet Passive Optical Networks (EPONs) are regarded as an important technology for current access networks. However, EPONs perform poorly in differentiated service environments, and may therefore fail to meet the Quality of Service (QoS) demands of emerging triple-play services (i.e. Voice over IP, video and BE traffic). Accordingly, the present study proposes a novel Dynamic Bandwidth Allocation (DBA) scheme, designated as Frame-Oriented Interleaved Polling with Adaptive Cycle Time (FIPACT), to improve the differentiated QoS capability of EPON networks. In the proposed scheme, the Optical Line Terminal (OLT) divides the time domain of the upstream network bandwidth into a contiguous series of fixed-length frames. Within each frame, each Optical Network Unit (ONU) is guaranteed sufficient network resources to transmit a specific quota of each triple-play service. In this manner, the proposed DBA scheme can satisfy the differentiated QoS requirements of triple-play services. Therefore, based on the M/G/1 queueing analysis framework of multiuser cyclic polling systems, this study develops an analytical framework to derive the closed-form expressions for FIPACT mean packet delay. The simulation results validate the analytical results and confirm the efficiency and effectiveness of the proposed DBA scheme.     

Issues in emerging 4G wireless networks

Researchers and vendors are expressing a growing interest in 4G wireless networks that support global roaming across multiple wireless and mobile networks. With this feature, users will have access to different services, increased coverage, the convenience of a single device, one bill with a reduced total access cost, and more reliable wireless access even with the failure or loss of one or more networks. 4G networks will also feature IP interoperability for seamless mobile Internet access and bit rates of 50 Mbps or more. Because deployment of 4G wireless technology is not expected until 2006 or even later, developers will hopefully have time to resolve issues involving multiple heterogeneous networks     

Access and service convergence over the mobile internet – A survey

Next generation heterogeneous wireless networks are expected to interwork with Internet Protocol (IP)-based infrastructures. Conventional network services operate like silos in that a specific set of services are offered over a specific type of access network. It is desirable for users to be able to roam between fixed and mobile networks that employ different access technologies. Therefore, mobility management with quality of service (QoS) support is of particular importance and one of the driving forces of convergence. Since service providers often provide more than one service to their subscribers, it is important to facilitate convergence of network charging architecture through a common charging framework. One of the main issues of IP-based convergence is security and privacy. This requires coordination of different security policies in diverse networks that have different security levels and capabilities. The business case for migration to an IP-based platform motivates operators to deliver more powerful services for customers as well as a better user experience. This paper provides an overview of converged mobile Internet architectures and their implications on QoS, charging/billing and security, as well as emerging business models for telecommunication services.     

自相似流量下包丢失的尺度特性

IP网络上的设备故障与流量拥塞经常导致网络数据丢包现象,研究网络上丢包行为的特性对于拥塞控制机制的设计、网络性能分析和服务质量保证都具有重要意义。文章基于ON/OF模型构造了具有长相关性包到达过程的链路流量,研究了在单路复用网络模型上的丢包特性,分析了丢包过程中体现的长相关特性,以及流量长相关性、缓冲区大小、输出链路速率因素与其长相关特性的关系。     

无线Mesh网络中VOIP的QoS性能分析

针对VoIP(Voice over IP)业务在无线Mesh网上进行传输时存在服务质量(QoS)需求难以保证、带宽利用率低的问题,介绍了VoIP的QoS影响因素,分析了端到端时延、时延抖动和丢包率等几个重要参数,并对VoIP在无线Mesh网中的传输性能进行了论述。提出了基于无线Mesh网络的QoS保证机制,可以为端到端的数据传输公平的分配带宽,并能在保证QoS下实现大规模的实时任务的多跳转发。仿真试验表明能有效降低端到端时延,有着更好的QoS性能。     

OmniCon: a Mobile IP‐based vertical handoff system for wireless LAN and GPRS links

Wi‐Fi based hotspots offer mobile users broadband wireless Internet connectivity in public work spaces and corporate/university campuses. Despite the aggressive deployment of these hotspots in recent years, high‐speed wireless Internet access remains restricted to small geographical areas due to the limited physical coverage of wireless LANs. On the other hand, despite their lower throughput, cellular networks have a significantly wider coverage and are thus much more available. Recognizing that 2.5G or 3G cellular networks can effectively complement wireless LANs, we set out to develop a vertical handoff system that allows mobile users to seamlessly fall back to such cellular networks as the general packet radio service (GPRS) or 3G whenever wireless LAN connectivity is not available. The resulting handoff mechanism allows a network connection of a mobile node to operate over multiple wireless access networks in a way that is transparent to end user applications. In this paper, we present the design, implementation, and evaluation of a fully operational vertical handoff system, called OmniCon, which enables mobile nodes to automatically switch between wireless LAN and GPRS, based on wireless LAN availability, by introducing a simple extension to the existing Mobile IP implementation. We discuss the design issues in the proposed vertical handoff system for heterogeneous networks, including connection setup problems due to network address translation, and the disparity in link characteristics between wireless LANs and GPRS. A detailed performance evaluation study of the OmniCon prototype demonstrates its ability to migrate active network connections between these two wireless technologies with low handoff latency and close to zero packet loss. Copyright © 2006 John Wiley & Sons, Ltd.     

存在隐藏终端的IEEE802.11e多跳无线网络模型分析

首次将802.11e的接入机制放入多跳环境中进行仿真分析和定量研究。提出一种新的多跳环境下802.11e网络模型,结合M/G/1/K排队模型,定量分析在隐藏终端影响下802.11e网络的MAC层吞吐率、MAC时延和帧丢失率,研究802.11e在多跳环境下性能表现的内在原因。经过仿真实验结果与数值分析结果的对比,验证了分析模型的准确性;通过有(无)隐藏终端影响下MAC层性能的对比分析,指出了802.11e在多跳无线网络中支持QoS的局限性:受隐藏终端的影响,802.11e对不同接入等级的业务提供QoS区分的性能明显降级。因而有必要研究隐藏终端问题的解决方案,提高802.11e在多跳环境下的性能。     

End-to-End Security Across Wired-Wireless Networks for Mobile Users

ABSTRACT

Recent advances in mobile computing and wireless communication technologies are enabling high mobility and flexibility of anytime, anywhere service access for mobile users. As a result, network connections of such users often span over heterogeneous networking environments consisting of wired and wireless networking technologies. Both network heterogeneity and user mobility make the securing of data transmission over heterogeneous networks challenging and complex. In this paper, we focus on the challenge of providing secure end-to-end network transmissions to wireless mobile users. To minimize service interruption during ongoing secure sessions of mobile users, we present the design and implementation of an approach based on the well-known Internet Protocol Security (IPSec) standard. We conducted a performance evaluation of our implementation using a Voice over IP (VoIP) application over an actual network testbed. Our empirical performance results demonstrate a packet loss improvement of 17% to 34% (for various VoIP packet sizes) and a handoff delay improvement of almost 24% validating the high efficiency of our proposed approach.     

Performance analysis of multimedia based web traffic with QoS constraints

During the recent years, there has been a tremendous growth in the development and deployment of multimedia based networked applications such as video streaming, IP telephony, interactive games, among others. These applications, in contrast to elastic applications such as email and data sharing, are delay and delay jitter sensitive but can tolerate certain level of packet loss. A vital element of end-to-end delay and delay jitter is the random queueing delays in network switches and routers. Analysis of robust mechanisms for buffer management at network routers needs to be carried out in order to reduce end-to-end delay for traffic generated by multimedia applications. In this context, a threshold based buffer management scheme for accommodating multiple class multimedia traffic in network routers has been analysed. This technique effectively controls the allocation of buffer to various traffic classes according to their delay constraints. The forms of the joint state probabilities, as well as basic performance measures such as blocking probabilities are analytically established at equilibrium. Typical numerical experiments are included to illustrate the credibility of the proposed mechanism in the context of different quality of service (QoS) grades for various network traffic classes. This model, therefore, can be used as a powerful tool to provide a required grade of service to a particular class of multimedia based web traffic in any heterogeneous network.     

存在隐藏终端的IEEE 802.11e多跳无线网络模型分析*

首次将802.11e的接入机制放入多跳环境中进行仿真分析和定量研究。提出一种新的多跳环境下802.11e网络模型,结合M/G/1/K排队模型,定量分析在隐藏终端影响下802.11e网络的MAC层吞吐率、MAC时延和帧丢失率,研究802.11e在多跳环境下性能表现的内在原因。经过仿真实验结果与数值分析结果的对比,验证了分析模型的准确性;通过有（无）隐藏终端影响下MAC层性能的对比分析,指出了802.11e在多跳无线网络中支持QoS的局限性：受隐藏终端的影响,802.11e对不同接入等级的业务提供QoS区分的性能明显降级。因而有必要研究隐藏终端问题的解决方案,提高802.11e在多跳环境下的性能。     

QoS management in heterogeneous home networks

An OSGi (Open Services Gateway Initiative) home gateway system manages the integration of heterogeneous home networks protocols and devices to develop ubiquitous applications. Wired and wireless heterogeneous home networks have different QoS concerns. For instance, jitter and latency are important concerns in web phones, while packet loss ratio is important in on-line video. This study adopts UPnP QoS specification version 1.0 to design an adaptive QoS management mechanism based on the RMD (Resource Management in DiffServ) architecture. This study monitors real-time network traffic, and adaptively controls the bandwidth, to satisfy the minimum but most important quality for each application in home network congestion. Simulation results indicate that the average jitter, latency and packet loss are reduced by 0.1391 ms, 0.0066 s, and 5.43%, respectively. The packet loss ratio is reduced by 4.53%, and the throughput is increased by 1.2% in high definition video stream; the packet loss ratio is reduced by 1.89% for standard definition video stream, and in VoIP (Voice over IP) the jitter and latency are reduced to 0.0407 ms and 0.0209 s, respectively.     

关于切换技术解决3G网络融合问题的综述

通过对无线通信网络的体系结构,运营方式,切换技术实现细节等方面的分析和研究,研究和探讨异构网络之间的切换技术,最终提出一个面向下一代无线通信网络的新型的基于IP的综合切换(Integrated Handover,IH)框架。IH技术的最终目标就是要解决移动通信网络中因网络异构、资源开销瓶颈等影响,成功地实现全球无线网络覆盖范围的低时延、高带宽、宽切换域、开销低和QoS保证的不同网络间顺畅的无缝切换。     

一种超3G通信系统的网络/小区智能选择方案

为提高超3G通信系统切换中网络／小区选择的准确性,提出一种网络／小区智能选择方案．这种方案综合考虑了超3G系统网络无线异构、接入技术不同和业务类型多样的特点,采用模糊多目标决策算法来选择最适合移动主机切换到的小区．实例分析和仿真结果证实,在不同的无线网络环境和业务类型下,此方案均能作出最合理的选择判断,所选小区相对于其他候选小区而言,能提供相对最优的切换后通信服务质量。     

An analytical evaluation of mobility management in integrated WLAN-UMTS networks

Ensuring uninterrupted service continuity for handoff calls in an all-IP inter-networked heterogeneous environment requires successful session management among participating access networks. As such, a mobility-aware novel interworking architecture is presented in this article that facilitates session management including session establishment and seamless session handoff across different networks. This framework conveniently enables any 3G cellular technology such as the Universal Mobile Telecommunications System (UMTS) to interwork with a given Broadband Wireless Access (BWA) technology such as the Worldwide Interoperability for Microwave Access (WiMAX) network or the Wireless Local Area Network (WLAN) under a common signaling platform. This framework exploits the IP Multimedia Subsystem (IMS) as a universal coupling mediator for real-time session negotiation and management. Next, a Queuing Theory based analytical model for evaluating the performance of vertical handoff management between these interworked 3rd Generation (3G) cellular networks and the WLANs is presented. The analysis includes vertical handoff performance measures such as delay, transient packet loss, jitter, and signaling overhead/cost. The latter part of this paper presents some results from OPNET based simulations for the verification of the analytical model and results.     

Performance analysis of adaptive buffer management mechanism using autoregressive based MPEG-4 encoded video traffic model

The burstiness of video traffic in future wired and wireless networks makes dynamic management of network resources more critical. This helps to meet stringent delay and loss requirements of video traffic and improves its Quality of Service (QoS). Since buffer management in queueing system plays an important role towards effective control of QoS for various types of applications, we have focused on its dynamic management. In this paper, we have proposed ADPBS scheme for priority queueing system. The performance of this scheme is analyzed with MPEG-4 encoded video sequence as input to the ADPBS queue. The simulation is carried out in MATLAB for various combinations of threshold control parameters, different traffic load and input traffic mix variations. The results of simulations indicate that dynamically controlled threshold in ADPBS contributes to significant reduction of packet loss of different priority classes as compared with static partial buffer sharing queue and first in first out queue based on threshold control parameters and the traffic type.