基于高频段卫星动态信道预约的自适应QoS切换算法

未来高频段卫星网络将为固定和移动用户提供多媒体通信业务,而为移动用户提供无线多媒体业务的一个最关键的问题是保证端到端连接的业务质量。该文提出了一种基于高频段卫星动态信道预约的自适应QoS切换算法,并与其它切换方式进行了性能比较。     

移动通信网络的服务质量

移动用户需要通过移动通信网络接入因特网的多 媒体业务。但是在移动通信网络中，用户的移动性、带宽紧缺和传输链路易产生差错等因素对无线网络服务质量（QoS)的提供增加了许多难题。从2．5G和3G移动通信系统的核心网络和无线接入网络两个方面对端到端QoS的提供进行了详细分析，并简要地讨论了未来移动无线网络端到端QoS中一些有待解决的问题。     

基于移动IPv6技术的无线城域网QoS研究

重点介绍了无线城域网中有关IPv6的QoS保证机制．为了提供端到端的QoS保证．除了需要在无线空中接口采用业务分类的动态业务流管理机制外．还需要在IPv6核心网络中采用能提供QoS保证的移动路由管理机制。并对各种支持移动性的InterServ、DiffServ和MPLS等QoS保证机制进行了研究和比较，建议在基于移动IPv6技术的无线城域网中采用扩展的MPLS机制进行核心网的QoS保证。     

基于3GPP2框架的无线移动网络的RSVP扩展研究

本文讨论了面向固定网络设计的RSVP协议应用于无线移动网络需要解决的问题,并针对3GPP2框架下的无线移动网络提出了一种RSVP扩展方案.该方案采用隧道预留技术建立端-端主动预留,为数据连接提供服务质量保证;采用移动预测和被动预留技术在移动节点可能进入的蜂窝内提前预留无线资源,提高切换成功的概率;通过采用主动切换技术减小预留路径调整的时间,进一步提高通信的连续性.     

EV-DO系统支持差异化服务的QoS应用研究

EV-DO系统是专门针对移动多媒体应用进行优化的无线传输技术.本文概述了EV-DO Rev A系统的QoS机制及端到端QoD体系架构,分析了EV-DO系统为不同用户、不同业务提供差异化服务的QoS需求,探讨了EV-DO系统支持差异化服务的端到端QoS技术及应用,并指出了进一步改进分组调度算法和速率控制技术以优化无线资源管理,从而满足用户公平性、不同用户和业务的QoS要求.     

移动自组网基于动态蜂窝的QoS路由协议

本文为移动自组网提出了一个基于动态蜂窝的QoS路由协议，它利用移动跟踪技术实现了一个分布式动态蜂窝生成协议；采用一个多Qos路由探测算法选择一条能够最大满足QoS要求的路由，并在这条路由上建立端．端主动资源预留；使用移动预测和被动资源预留技术预测源结点和目的结点可能进入的蜂窝集合，并在这些蜂窝集合与目的结点和源结点之间提前进行端．端被动资源预留；融合蜂窝动态检测技术与QoS路由修补技术自动发现和修补断裂的QoS路由．由于该路由协议模仿了固定蜂窝网络中的操作，所以，大大改善了QoS路由的性能．仿真结果表明：在满足QoS条件下，它明显提高了包传输率，减轻了路由负载．     

MPLS在移动IP网络中的应用

移动通信网络和IP网络的融合推动了电信产业的发展。在一个统一的IP网络平台上传输话音、数据、视频、图像将是大势所趋。目前针对移动用户的服务质量(QoS)要求,也正面临着很大的挑战。在移动IP网络中,由于用户的频繁移动使得端到端的QoS保证和移动切换(handoff)管理更加复杂。多协议标签交换(MPLS)技术作为借鉴了面向连接网络的优越性和实现流量工程的重要技术,为网络提供了较好的QoS保证。文章介绍了MPLS技术是如何应用在移动IP网络中,解决了诸如认证、QoS、流量工程等问题。     

针对移动视频流介于UMTS和WiMAX网络间的切换方案

下一代移动网络(NGMN)倾向于融合多个无线接入技术(RATs)来为用户提供无处不在的访问服务。而作为一个无处不在系统,能够有一个解决方案来支持日益流行的视频应用程序也是至关重要的。由于移动视频应用程序的高带宽要求和对延迟敏感的特点,如何让移动视频应用程序在不同的RATs之间进行无缝切换并保证服务质量(QoS)是我们面临的一个挑战。为了加快实现在异构网络中提供无缝视频流服务,通过运用IEEE 802.21规定的媒体独立信息服务的服务器提出了一种移动端发起-网络端控制的移动网络切换方案。仿真结果表明,该方案在丢包率、延迟和峰值信噪比等方面提高了性能。     

CME20为用户提供的业务

ＣＭＥ２０为用户提供的业务俞珑爱立信蜂窝移动设备ＣＭＥ２０在我国有很大市场。本文主要介绍由ＣＭＥ２０所提供的业务。一、电信业务１．话音这是任何一个蜂窝系统所必备的最基本业务，即允许一个移动用户（手机或车台）与另一个移动用户或有线用户完成双向通话功能。...     

移动IP网络电话的一种实现方式

本文介绍了移动节点快速切换链路时在移动节点和基站之间的QoS保证以及在移动IP上提供端到端的QoS机制，通过在网络中实现QoS的服务来防止传输延迟，抖动和话音分组的丢失，满足IP电话业务对于实时性的要求。     

DiffServ resource allocation for fast handoff in wireless mobileInternet

The next-generation wireless networks are evolving toward a versatile IP-based network that can provide various real-time multimedia services to mobile users. Two major challenges in establishing such a wireless mobile Internet are support of fast handoff and provision of quality of service (QoS) over IP-based wireless access networks. In this article, a DiffServ resource allocation architecture is proposed for the evolving wireless mobile Internet. The registration-domain-based scheme supports fast handoff by significantly reducing mobility management signaling. The registration domain is integrated with the DiffServ mechanism and provisions QoS guarantee for each service class by domain-based admission control. Furthermore, an adaptive assured service is presented for the stream class of traffic, where resource allocation is adjusted according to the network condition in order to minimize handoff call dropping and new call blocking probabilities     

Handoff Performance Improvement with Latency Reduction in Next Generation Wireless Networks

The next generation (NG) wireless networks are expected to provide mobile users with the real-time multimedia services. High sensitivity to time constraints like delay and jitter is one of the important characteristics of the multimedia traffic. In order to maintain a certain quality of service (QoS) level, the handoff latency should be minimized. Furthermore, if the new cell is not ready at the actual handoff time, the handoff call may be even forced terminated. Hence, the handoff preparation latency directly affects the performance of the cellular networks in terms of QoS support and the handoff blocking probability. In this paper, we present the expected visitor list (EVL) method to achieve reduced handoff blocking probability and maintain a certain QoS level in the network by minimizing handoff preparation latency. The handoff signaling decomposition is introduced to make the neighbor cells aware of the resource demands and QoS requirements of the mobile terminal before the actual handoff time. The obtained information about the prospective active mobile terminal is stored in an EVL entry at the neighbor cells. The call admission control (CAC) with QoS-provisioning is run against each EVL entry. According to the CAC result, the network preparation algorithms are executed and the results are stored in the entry. No resource reservation or allocation is performed in advance, and the varying network conditions are reflected to validity and admission status of the entries. The results of handoff preparation algorithms stored in the EVL entry are activated at the actual handoff time and hence the handoff latency is minimized. Performance evaluation through mathematical analysis and extensive simulation experiments show that the EVL method reduces handoff latency and hence handoff call blocking probability significantly without introducing high overhead.Özgür B. Akan received the B.S. and M.S. degrees in electrical and electronics engineering from Bilkent University and Middle East Technical University, Ankara, Turkey, in 1999 and 2001, respectively. He received the Ph.D. degree in electrical and computer engineering from the Broadband and Wireless Networking Laboratory, School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, in 2004. He is currently an Assistant Professor with the Department of Electrical and Electronics Engineering, Middle East Technical University. His current research interests include sensor networks, next-generation wireless networks, and deep space communication networks.Buyurman Baykal received his B.Sc. (High Hons.) degree in Electrical and Electronics Engineering from Middle East Technical University in 1990; M.Sc. (Distinction) and Ph.D. degrees in 1992 and 1995 from Imperial College of Science, Technology and Medicine. Dr. Baykal has research and teaching interests in speech processing, signal processing for telecommunications, and communication networks. He has extensive experience both in the theory and applications of adaptive signal processing techniques to communication applications such as acoustic echo cancellation, noise reduction, channel equalization and digital receiver design through self-conducted research and industry-funded research projects. He conducts research and implementation work on low bit rate speech coding and content based indexing of audio signals. He is also involved in communication network research with particular interest in ATM/IP design aspects, wireless networks and network management issues. Dr. Baykal is an Associate Editor of Computer Networks (Elsevier Science), Sensor Letters (American Scientific Publishing), a past Associate Editor of the IEEE Transactions on Circuits and Systems Part II—Analog and Digital Signal Processing (TCAS-II). He authored and co-authored over 50 technical papers.     

Vertical handoffs in wireless overlay networks

No single wireless network technology simultaneously provides a low latency, high bandwidth, wide area data service to a large number of mobile users. Wireless Overlay Networks - a hierarchical structure of room-size, building-size, and wide area data networks - solve the problem of providing network connectivity to a large number of mobile users in an efficient and scalable way. The specific topology of cells and the wide variety of network technologies that comprise wireless overlay networks present new problems that have not been encountered in previous cellular handoff systems. We have implemented a vertical handoff system that allows users to roam between cells in wireless overlay networks. Our goal is to provide a user with the best possible connectivity for as long as possible with a minimum of disruption during handoff. Results of our initial implementation show that the handoff latency is bounded by the discovery time, the amount of time before the mobile host discovers that it has moved into or out of a new wireless overlay. This discovery time is measured in seconds: large enough to disrupt reliable transport protocols such as TCP and introduce significant disruptions in continuous multimedia transmission. To efficiently support applications that cannot tolerate these disruptions, we present enhancements to the basic scheme that significantly reduce the discovery time without assuming any knowledge about specific channel characteristics. For handoffs between room-size and building-size overlays, these enhancements lead to a best-case handoff latency of approximately 170 ms with a 1.5% overhead in terms of network resources. For handoffs between building-size and wide-area data networks, the best-case handoff latency is approximately 800 ms with a similarly low overhead. This revised version was published online in June 2006 with corrections to the Cover Date.     

Enabling seamless multimedia wireless access through QoS‐based bandwidth adaptation

Effective support of real‐time multimedia applications in wireless access networks, viz. cellular networks and wireless LANs, requires a dynamic bandwidth adaptation framework where the bandwidth of an ongoing call is continuously monitored and adjusted. Since bandwidth is a scarce resource in wireless networking, it needs to be carefully allocated amidst competing connections with different Quality of Service (QoS) requirements. In this paper, we propose a new framework called QoS‐adaptive multimedia wireless access (QoS‐AMWA) for supporting heterogeneous traffic with different QoS requirements in wireless cellular networks. The QoS‐AMWA framework combines the following components: (i) a threshold‐based bandwidth allocation policy that gives priority to handoff calls over new calls and prioritizes between different classes of handoff calls by assigning a threshold to each class, (ii) an efficient threshold‐type connection admission control algorithm, and (iii) a bandwidth adaptation algorithm that dynamically adjusts the bandwidth of an ongoing multimedia call to minimize the number of calls receiving lower bandwidth than the requested. The framework can be modeled as a multi‐dimensional Markov chain, and therefore, a product‐form solution is provided. The QoS metrics—new call blocking probability (NCBP), handoff call dropping probability (HCDB), and degradation probability (DP)—are derived. The analytical results are supported by simulation and show that this work improves the service quality by minimizing the handoff call dropping probability and maintaining the bandwidth utilization efficiently. Copyright © 2006 John Wiley & Sons, Ltd.     

Priority-determined multiclass handoff scheme with guaranteed mobile QoS in wireless multimedia networks

The provision of multiclass services is gaining wide acceptance and will be more ubiquitous in future wireless and mobile systems. The crucial issue is to provide the guaranteed mobile quality of service (QoS) for arriving multiclass calls. In multimedia cellular networks, we should not only minimize the dropping rate of handoff calls, but also control the blocking rate of new calls at an acceptable level. This paper proposes a novel multiclass call-admission-control mechanism that is based on a dynamic reservation pool for handoff requests. In this paper, we propose the concept of servicing multiclass connections based on priority determination through the combined analysis of mobile movement information and the desired QoS requirements of multimedia traffic. A practical framework is provided to determine the occurrence time of handoff-request reservations. In our simulation experiments, three kinds of timers are introduced for controlling the progress of discrete events. Our simulation results show that the individual QoS criteria of multiclass traffic such as the handoff call-dropping probability can be achieved within a targeted objective and the new-call-blocking probability is constrained to be below a given level. The proposed scheme is applicable to channel allocation of multiclass calls over high-speed wireless multimedia networks.     

Architecture,mobility management,and quality of service for integrated 3G and WLAN networks

Integration of 3G and wireless LAN (WLAN) becomes a trend in current and future wireless networks, and brings many benefits to both end users and service providers. In this paper, we provide a comprehensive survey on integration of 3G and WLAN. We discuss issues such as underline network architectures, integrated architectures, mobility management, and quality of service (QoS). We particularly study handoff QoS mapping and guarantee between 3G and WLAN, as well as how seamless voice/multimedia/data handoff becomes possible. Copyright © 2005 John Wiley & Sons, Ltd.     

IEEE 802.11 roaming and authentication in wireless LAN/cellular mobile networks

A wireless LAN service integration architecture based on current wireless LAN hot spots is proposed so that migration to a new service becomes easier and cost effective. The proposed architecture offers wireless LAN seamless roaming in wireless LAN/cellular mobile networks. In addition, a link-layer-assisted mobile IP handoff mechanism is introduced to improve the network/domain switching quality in terms of handoff delay and packet loss. An application layer end-to-end authentication and key negotiation scheme is proposed to overcome the open-air connection problem existing in wireless LAN deployment. The scheme provides a general solution for Internet applications running on a mobile station under various authentication scenarios and keeps the communications private to other wireless LAN users and foreign network. A functional demonstration of the scheme is given. The research results can contribute to rapid deployment of wireless LANs.     

A Framework for Seamless Roaming Across Heterogeneous Next Generation Wireless Networks

In the future, wireless and mobile users will have increased demands for seamless roaming across different types of wireless networks, quality of service guarantees and support of different types of services. This awareness has led to research activities directed towards inter-system and global roaming and can be noticed in the numerous products like multimode handsets, inter-working gateways and some ongoing standards and research work on signaling protocols for inter-system roaming. This article proposes a global mobility management framework. The framework is like an overlay network comprising of Inter-System Interface Control Units IICU to support inter-network communication and control for Location Management. The protocols and functions of this framework will be distributed and exist partly within the wireless networks and partly within the core-network. A hierarchy introduced among the IICUs will accommodate for the varying mobility coverage required by the mobile user. The IICU may be configured to perform various functions depending on its placement in the hierarchy of the framework. This approach aims to optimize across call set up delays, signaling traffic, database processing, handoff facilitation for seamless roaming and QoS mapping and negotiations as the user moves across different wireless networks. It avoids centralized database dependency with its associated single-point bottleneck and failures. We restrict our analysis of the framework to a 2-network and a 3-network roaming scenario. The presentation has been further restricted to cost and delay analysis of the location update and call delivery procedures. We have taken into account the signalling requirements when the mobile user roams across networks with and without an active call. Nirmala Shenoy is Associate Professor at the Information Technology department at RIT. She has several years of teaching and research experience while working in Germany, Singapore and Australia before she moved to USA. She is an avid researcher in the wireless networks area and has technically led several wireless network projects to success. She holds a Ph.D. in computer science from the University of Bremen, Germany, Masters in Applied Electronics and Bachelors in Electronics and Telecommunications Engineering both from Madras University in India. Professor Shenoy is interested in research in the area mobility management and modeling for wireless networks, Quality of service in wireless networks and the Internet.     

Multicasting streaming media to mobile users

Content distribution in general, and multicasting in particular, over a wired network to static hosts can be realized by placing proxies and gateways at several parts of the network. However, if the end hosts are mobile over heterogeneous wireless access networks, one needs to consider many operational issues such as network detection, handoff, join and leave latency, and desired level of quality of service, as well as caching and load balancing. This article surveys a set of protocols and technologies that offer multicast-based services for streaming multimedia in a mobile environment. It also brings forth some of the issues related to mobile content distribution in the wireless Internet that may be helpful during its deployment by application service providers.