A framework for seamless roaming across cellular and wireless local area 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 for a variety of services. This awareness has led to research activities directed toward intersystem and global roaming, and can be noticed in numerous products like multimode handsets, interworking gateways, and ongoing standards and research work on intersystem roaming. The authors of this article proposed a global mobility management framework to support seamless roaming across heterogeneous wireless networks. In this article we provide details on the use of the framework to support roaming across cellular and wireless local area networks. Highlights of the framework include a robust architecture for mobility management for varying user mobility spans, provisioning for QoS mapping, intersystem message translation, and mechanisms in the WLAN to support user-subscribed services. Performance aspects related to handoff delays, data redirection, and processing overheads are presented and discussed. Performance comparison of intersystem roaming between cellular and WLAN with and without the framework is presented.     

Evaluation of Interoperability Criteria and Mechanisms for Seamless Inter-Working Between UMTS-HSDPA and WLAN Networks Enhanced with MIMO Techniques

This article proposes criteria and mechanisms that achieve seamless inter-working between the multi-radio access technologies that will compose the fourth-generation (4G) wireless mobile environment. We address the problem of incorporating system interoperability in order to provide the user with seamless mobility across different radio access technologies; namely we focus on inter-working UMTS-High Speed Downlink Packet Access (HSDPA) and WLAN networks, as these two networks are believed to be major components of the 4G wireless network. Interoperability results in providing the user with a rich range of services across a wide range of propagation environment and mobility conditions, using a single terminal. Specifically, the article aims at defining the criteria and mechanisms for interoperability between the two networks. Our approach considers the use of Cost functions to monitor the essential parameters at the system level in order to trigger an interoperability procedure. Initial user assignment and inter-system handover are considered the incidents that initiate the interoperability algorithm execution. The overall objective of this work is to assess the performance of our developed interoperability platform and to optimize system performance by guarantying a minimum QoS requirement and maximizing network capacity.     

A new signaling protocol for intersystem roaming in next-generationwireless systems

In next-generation wireless systems, one of the major features that is different from the current personal communication service systems is the seamless global roaming. The mobile subscribers will be allowed to move freely across different networks while maintaining their quality of service for a variety of applications. To meet this demand, the signaling protocol of mobility management must be designed, supporting location registration and call delivery for roaming users who move beyond their home network. A new signaling protocol is proposed, emphasizing the active location registration for ongoing services during the mobile subscribers' movement. Another important goal of this new protocol is to reduce the overhead caused by mobility management so that the signaling traffic load and consumption of network resources can be reduced. The new protocol efficiently reduces the latency of call delivery and call loss rate due to crossing wireless systems with different standards or signaling protocols. The numerical results reveal that the proposed protocol is effective in improving the overall system performance     

无线通信网络的移动性管理

未来无线通信网络的两个最重要的研究问题就是宽带和无缝漫游，而移动性管理是实现网络间无缝漫游的关键难题之一。本对移动性管理涉及的各个方面进行了简要的概述，首先介绍了移动性管理的分类和它对协议层次的影响，接着介绍了移动性管理的一般性框架和主要的协议特点，最后介绍了一些关键的研究问题和研究热点。     

Enabling Heterogeneous Mobility in Android Devices

The fast growing of mobile Internet users with the ability of using a wide diversity of access technologies such as Wi-Fi, WiMAX and UMTS/LTE, and the increasing proliferation of mobile devices with heterogeneous network interfaces, require versatile mobility mechanisms providing seamless roaming across those access technologies. Mobility agents such as Mobile IP and Fast MIPv6 are common, however, these solutions still have limitations when dealing with multiple link-layer technologies. In this context, the emerging standard IEEE 802.21 provides a framework which enables mobile agents and network operators to improve the handover process in heterogeneous networks. In this context, this paper presents and discusses the design and implementation of a mobility-aware solution for an Android device, using the IEEE 802.21 framework. A modified Android user terminal is proposed to improve the handover process, assuming a make-before-break approach. Resorting to an experimental testbed, the obtained results show that the proposed solution is an effective contribution to successfully accomplish seamless mobility of Android-based devices operating in 3G and Wi-Fi networks.     

Extensions for Internet QoS paradigms to mobile IP: a survey

Mobile IP has been chosen as the core mobility management mechanism for wireless LANs, 3G cellular networks, and, most recently, aeronautical networks. It is viewed as a key element in providing a universal roaming solution across different wireless access technologies. However, mobile IP in its basic form inherits the IP incapability to provide QoS guarantees. This results in mobile IP's lack of support for seamless intradomain mobility. This article surveys extensions that have been proposed to enhance the QoS functionality of mobile IP. It gives a brief overview of mobile IP and Internet QoS paradigms, and describes their general shortcomings with regard to QoS and mobility, respectively. It then discusses the extensions that have been proposed in the literature and provides a qualitative comparison.     

LTE移动性管理研究

无线网络中的移动性是指对终端位置的改变而保证持续接入服务,并保持与之通信的能力。移动性管理就是为用户和终端提供相应的功能以保证异构网络的漫游和服务的无缝移动,并使用户与网络的联系达到最佳状态。针对未来数据业务具有高速、突发性的特点,LTE核心网发生了很大的变化,主要是采取了扁平化结构。在这种系统架构下怎样为用户提供更好的服务,LTE移动性管理成为目前该领域研究工作的重点。     

A new architecture for 3G and WLAN integration and inter-system handover management

WLAN has strong potential to provide a perfect broadband complement to the 3G wireless systems. This has raised much interest in their integration. In this paper, a novel architecture using the Network Inter-operating Agent (NIA), and Integration Gateway (IG) is proposed to integrate the 3G systems and WLANs of various providers that may not necessarily have direct service level agreement (SLA) among them. The proposed architecture is scalable as it eliminates the need for the creation of bilateral SLA among the 3G and WLAN operators. In addition, inter-system handover (ISHO) protocols using the concept of the dynamic boundary area is proposed to support seamless roaming between 3G and WLAN. The dynamic boundary area is determined based on the speed of the user and WLAN cell size. The ISHO procedures are initiated when a mobile user enters the boundary area of the WLAN and are completed before the user leaves the coverage area of the serving WLAN. This ensures that the roaming from WLAN to 3G is transparent to the applications. The performance evaluation shows that the proposed boundary area based ISHO algorithm outperforms the existing 3G/WLAN ISHO algorithms. Shantidev Mohanty (SM’04) received his B. Tech. (Hons.) degree from the Indian Institute of Technology, Kharagpur, India and the M.S. degree from the Georgia Institute of Technology, Atlanta, Georgia, in 2000 and 2003, respectively, both in electrical engineering. He is currently a graduate research assistant with the Broadband and Wireless Networking Laboratory and a Ph.D. candidate at the School of Electrical and Computer Engineering, Georgia Institute of Technology. His current research interests include wireless networks, mobile communications, mobility management, ad-hoc and sensor networks, and cross-layer protocol design. From 2000 to 2001 he worked as a mixed signal design engineer for Texas Instruments, Bangalore, India. He worked as a summer intern for Bell Labs, Lucent Technologies, Holmdel, New Jersey, during the summers of 2002 and 2003 and for Applied Research, Telcordia Technologies, Piscataway, New Jersey, uring the summer of 2004.     

A New Access Control Solution for a Multi-Provider Wireless Environment

The fundamental goal in future 4G mobile multi-service networks is to provide an efficient mobile computing environment. We presume that future terminals will be equipped with multiple heterogeneous wireless interfaces. We want to enable each user to seamlessly move between different providers networks. Besides seamless roaming, a key consideration is also devoted to quality-of-service provision. In this article, we propose a model and an architectural framework for supporting quality of service in the context of interconnected multi-provider wireless systems. The proposed integrated COPS-based management and RADIUS-based access control architecture will allow providers to offer multimedia services while optimizing the use of the underlying network resources. We suggest new concepts and protocols to provide solutions to these challenges and describe the French national research project named MMQoS aiming on building such future networks.     

Mobility Modeling and Performance Evaluation of Heterogeneous Wireless Networks

The future-generation wireless systems will combine heterogeneous wireless access technologies to provide mobile users with seamless access to a diverse set of applications and services. The heterogeneity in this inter-technology roaming paradigm magnifies the mobility impact on system performance and user perceived service quality, necessitating novel mobility modeling and analysis approaches for performance evaluation. In this paper, we present and compare three mobility models in two-tier integrated heterogeneous wireless systems, the independence model as a naive extension of the traditional cell residence time modeling techniques for homogeneous cellular networks, the basic Coxian model which takes into consideration the correlation between the residence time within different access technologies, and the extended-Coxian model for further improved estimation accuracy. We propose a general stochastic performance analysis framework based on application session models derived from these mobility models, applying it to a 3G-WLAN integrated system as an example. Our numerical and simulation results demonstrate the general superiority of Coxian-based mobility modeling over the independence model. Furthermore, using the proposed modeling and analysis methods, we investigate the impact of different parameters on system performance metrics such as network utilization time, handoff rates, and forced termination probability, for a wide range of user applications.     

Resource management for QoS support in cellular/WLAN interworking

To provide mobile users with seamless Internet access anywhere and anytime/ there is a strong demand for interworking mechanisms between cellular networks and wireless local area networks in the next-generation all-IP wireless networks. In this article we focus on resource management and call admission control for QoS support in cellular/WLAN interworking. In specific, a DiffServ interworking architecture with loose coupling is presented. Resource allocation in the interworking environment is investigated/ taking into account the network characteristics, vertical handoff, user mobility, and service types. An effective call admission control strategy with service differentiation is proposed for QoS provisioning and efficient resource utilization. Numerical results demonstrate the effectiveness of the proposed call admission control scheme.     

Challenges and Solutions to Adaptive Computing and Seamless Mobility over Heterogeneous Wireless Networks

Recent years have witnessed the rapid evolution of commercially available mobile computing environments. This has given rise to the presence of several viable, but non-interoperable wireless networking technologies – each targeting a niche mobility environment and providing a distinct quality of service. The lack of a uniform set of standards, the heterogeneity in the quality of service, and the diversity in the networking approaches makes it difficult for a mobile computing environment to provide seamless mobility across different wireless networks. Besides, inter-network mobility will typically be accompanied by a change in the quality of service. The application and the environment need to collaboratively adapt their communication and data management strategies in order to gracefully react to the dynamic operating conditions.This paper presents the important challenges in building a mobile computing environment which provides seamless mobility and adaptive computing over commercially available wireless networks. It suggests possible solutions to the challenges, and describes an ongoing research effort to build such a mobile computing environment.     

Hierarchical Mobile IPv6 Mobility Management in Heterogeneous 3G/WLAN Networks

The research and development of next generation networks results in continuously growing in heterogeneity of wireless systems. Those systems also offer users the increasing possibility of roaming between different networks, which undoubtedly needs seamless integration. As mobile users continue to expand their requirements for seamless roaming, a good handoff mechanism is necessary especially for cellular networks and wireless local area networks. The most critical problem faced in the handoff mechanism is that users may need immediate data transmission. However, immediate data transmission is always obstructed because handoff latency occurs. In this paper, we propose a Hierarchical Mobile IPv6 handoff scheme using active measurement-foreign mobility agent to measure the residual bandwidth of each access point (AP) for handoff decision. As a result, the proposed scheme prevents whole efficiency from being affected by the registration time and improves immediate data transmission. In addition, a dual-threshold of the received signal strength is used to avoid the ping-pong effect. Simulation results show that the proposed scheme outperforms the traditional Mobile IPv6 and enhanced multilayer Hierarchical Mobile IPv6.     

WiMAX组网技术与解决方案

文章在介绍WiMAX标准、技术和相关应用的基础上,提出WiMAX组网需要考虑频率复用、认证计费和移动性管理3个主要因素.文章给出了固定应用和移动应用模式下的组网方案,探讨了WiMAX无线组网方式将经过的4个阶段:室外接入、室内接入、有缝漫游、无缝移动,认为WiMAX网络最终将融合到NGN和移动蜂窝系统中.     

Global roaming in next-generation networks

Next-generation mobile/wireless networks are already under preliminary deployment. Mobile/wireless all-IP networks are expected to provide a substantially wider and enhanced range of services. However, an evolutionary rather than revolutionary approach to the deployment of a global all-IP wireless/mobile network is expected. To support global roaming, next-generation networks will require the integration and interoperation of mobility management processes under a worldwide wireless communications infrastructure. In this article global roaming is addressed as one of the main issues of next-generation mobile networks. Apart from the physical layer connectivity and radio spectrum allocation plans, mobility in a hierarchical structured scheme is discussed. An all-IP wireless/mobile network combined with inherited mobility schemes of each network layer and Mobile IP extensions is proposed. In this respect the mobility management mechanisms in WLAN, cellular, and satellite networks are analyzed, and an all-IP architecture is described and an enhanced roaming scenario presented     

Efficient mobility management for vertical handoff between WWAN and WLAN

As we move toward next-generation all-IP wireless networks, we are facing the integration of heterogeneous networks, such as WWAN and WLAN, where vertical handoff is required. In vertical handoff between WWAN and WLAN, mobile hosts should be able to move freely across different networks while satisfying QoS requirements for a variety of applications. In order to achieve seamless handoff and maintain continuity of connection, we propose a novel mobility. management system that integrates a connection manager to detect network condition changes in a timely and accurate manner, and a virtual connectivity manager that uses an end-to-end principle to maintain a connection without additional network infrastructure support. A prototype system was built to test the effectiveness of the proposed system. Experiments show that seamless roaming between WLAN and WWAN can be achieved, and much better performance can be obtained than with the traditional scheme.     

A service level model and Internet mobility monitor

Mobility is gaining a tremendous interest among Internet users and wireless access networks are increasingly being installed to enable mobile usage. Internet mobility requires solutions to move between access networks with maintained network connectivity. Seamless mobility in turn means that the experience of using a service is unaffected while being mobile. Communication in next generation networks will use multiple access technologies, creating a heterogeneous network environment. Further, roaming between network service providers may take place. To enable mobile nodes to move between access networks within as well as between network service providers with minimal disruption, nodes should be able to maintain multiple active network connections. With the usage of multihomed nodes, seamless mobility can be achieved in already installed infrastructures, not providing mobility support. Mobility in heterogeneous access networks also requires network selections that scale for services. In this article we propose an architecture where application service providers and network service providers define service levels to be used by a mobile node and its user. The user selects a service and the service level from an application service provider. When performing access network selection, information received as part of an application service level will be used to find a network that supports the service required. The performance of available access networks will be monitored and considered when making the decision. Our proposed architecture provides solutions to move flows between interfaces in real-time based on network performance, quality of service signalling to correspondent nodes, and cancellation of flows to give way for more important traffic.     

Mobile information services enabled by mobile publishing (MIS-MP)

Mobile users and devices want to discover and share a growing range of information as the processing and storage capabilities of mobile devices grow. For example, users want to discover nearby networks, and location-based or time-sensitive user information contents. A mobile device may want to discover neighboring networks and the parameters required to access these networks so that it can intelligently decide which networks to use next, and use its existing network connection to authenticate with selected neighboring networks before it moves into the coverage areas of the selected networks. This can significantly reduce handoff delays. Existing service discovery frameworks are not effective for such neighboring network discovery or for discovering dynamic, location- or time-sensitive user information contents. This paper describes and evaluates a new approach—Mobile Information Services enabled by Mobile Publishing (MIS-MP)—for real time collection, discovery, and sharing of network and user information. With MIS-MP, mobiles take full advantage of the wealth of information they can accumulate during their routine mobility and use of networks to help each other to discover the information they want when and where they want it. This is accomplished by mobiles publishing the information they collect about the networks they visited, and the user information contents they learned or used, to make the information available to other mobiles. This paper presents analytical models and simulation results to evaluate the feasibility and performance of MIS-MP. It also describes a testbed implementation of MIS-MP and some of the lessons we learned. Tao Zhang is Director of Mobile Networking Research Group at Telcordia Technologies, Piscataway, New Jersey, USA. He develops and directs research and advanced development programs in mobile networking and applications, including mobility and applications across heterogeneous radio networks, mobile information services, vehicular networking, mobile peer-to-peer applications, sensor networking and applications, and collaborative networking .Dr. Zhang’s work has led to several new commercial products. He co-authored the book “IP-Based Next Generation Wireless Networks” published by John Wiley & Sons in 2004. He initiated the International Conference on Collaborative Computing: Networking, Applications, and Worksharing (CollaborateCom), and has been serving in various roles for it. Dr. Zhang holds 4 U.S. patents, with over 25 more pending. He received the 2000 Telcordia CEO Award (for most exceptional teams and individuals who have achieved a significant business success) and 2002 SAIC’s Executive Science and Technology Council Publication Prize. Eric van den Berg received his Ph.D. in Applied Mathematics from Cornell University in 1999. After obtaining his degree, he joined Telcordia Technologies, where he is a Research Scientist in Applied Research Department. His research interests include traffic modeling and performance analysis of IP- and wireless networks. He received the 2000 Telcordia CEO Award (for most exceptional individuals and teams who have achieved a significant business success) and the 2002 SAIC Executive Science and Technology Council Publication Prize. Sunil Madhani is a Distinguished MTS with Motorola where he manages the IP Realization team in Mobile Device Technology Office. He aims at working on unconventional and disruptive IP technologies. His current research focus is on convergent networks, dynamic mobility management and fast handoff in secured/seamless wireless LAN/WAN roaming. His past research includes registration/configuration protocols in wireless environment, application layer mobility management, secured Mobile IP, managed DOS attack sensor and TCP/IP boosters. Sunil Madhani holds MS (2002) in Engineering Management & System from Columbia University and MS (1997) in Computer Science from State University of New York.     

4G网络的移动性

第四代移动通信系统(4G)是一个基于IP业务的无线网络集合。4G系统的目标是用户始终能连接上最佳网络,并实现无缝漫游。目前需解决网络移动性和网络体系结构问题,并验证二者的可行性。文章主要探讨与4G相关的网络移动性问题,并对未来工作提出展望。     

A distributed database architecture for global roaming in next-generation mobile networks

The next-generation mobile network will support terminal mobility, personal mobility, and service provider portability, making global roaming seamless. A location-independent personal telecommunication number (PTN) scheme is conducive to implementing such a global mobile system. However, the nongeographic PTNs coupled with the anticipated large number of mobile users in future mobile networks may introduce very large centralized databases. This necessitates research into the design and performance of high-throughput database technologies used in mobile systems to ensure that future systems will be able to carry efficiently the anticipated loads. This paper proposes a scalable, robust, efficient location database architecture based on the location-independent PTNs. The proposed multitree database architecture consists of a number of database subsystems, each of which is a three-level tree structure and is connected to the others only through its root. By exploiting the localized nature of calling and mobility patterns, the proposed architecture effectively reduces the database loads as well as the signaling traffic incurred by the location registration and call delivery procedures. In addition, two memory-resident database indices, memory-resident direct file and T-tree, are proposed for the location databases to further improve their throughput. Analysis model and numerical results are presented to evaluate the efficiency of the proposed database architecture. Results have revealed that the proposed database architecture for location management can effectively support the anticipated high user density in the future mobile networks.