Hybrid coupling scheme for UMTS and wireless LAN interworking

We propose a hybrid coupling scheme to support interworking between UMTS and WLAN networks. Under the Tight-coupled system, it is expected that WLAN users can also use UMTS services with guaranteed QoS and seamless mobility. However, the interworking is problematic. The capacity of UMTS core network nodes cannot accommodate the bulky data traffic from WLAN, since the core network nodes are designed to handle the small-sized data of circuit voice calls or short packets. The proposed coupling scheme differentiates the data paths according to the type of the traffic and can accommodate traffic from WLAN efficiently, with guaranteed QoS and seamless mobility. We compare the handover procedures of the proposed coupling strategy with those of the loose and tight coupled schemes. In addition, we analyze the delay based on signaling costs during vertical handover. It is shown that the handover latency decreases when the UMTS and WLAN are coupled in the proposed way.     

Designing VoIP session management over interworked WLAN-3G networks

In an all-IP internetworked heterogeneous environment, ongoing VoIP sessions from roaming users will be subject to frequent vertical handoffs across network boundaries. Ensuring uninterrupted service continuity for these handoff calls requires successful session management among the participating access networks. As such, a mobility-aware novel interworking network design (interconnecting UMTS and WLAN over an IP-based common platform) [1] is presented in this article that facilitates VoIP session management, including session establishment and seamless session handoff across different networks. For comparison purposes, VoIP session management is evaluated in terms of session establishment, handoff delays, transient packet loss, end-to-end traffic delays, and jitter value for different voice codecs, which demonstrate satisfactory and feasible results. In the event (e.g., network congestion, buffer overflow) that session continuity cannot be guaranteed (also known as outage) across network boundaries, this article proposes an algorithm that compensates the user by reducing the unit service charge of future sessions (governed by the outage period) through a noncooperative game-theory-based pricing mechanism.     

Seamless Handoff Scheme Based on Pre-registration and Pre-authentication for UMTS–WLAN Interworking

Interworking issues between Universal Mobile Telecommunication System (UMTS) and Wireless Local Area Network (WLAN) have become a great matter of interest as an increasing number of mobile internet users require broadband wireless access to IP services in the wide area. In this paper, we present a practical UMTS–WLAN interworking architecture based on 3GPP standards and propose a seamless handoff scheme that guarantees low delay and low packet loss during UMTS–WLAN handoff. For low handoff delay, the proposed handoff scheme performs pre-registration and pre-authentication processes before layer 2 handoff. Moreover, it uses packet buffering and forwarding functions in order to reduce packet loss during the handoff period. On the above basis, detailed signaling procedures are presented, together with system requirements when a mobile terminal moves from UMTS to WLAN and vice-versa. Numerical results show that the proposed scheme performs well with respect to signaling cost, handoff delay, and packet loss compared with conventional schemes.     

On the support of voice call continuity across UMTS and wireless LANs

In this paper, we address the architecture and the procedures that can enable voice call handover from UMTS to WLAN and we also study how efficiently the WLAN can support the voice calls transferred from UMTS. Our study is based on a practical simulation model that lets us quantify the maximum number of voice calls that can be handed over from UMTS to WLAN, subject to maintaining the same level of UMTS QoS and respecting some WLAN policies. In addition, several other voice call performance metrics are derived. Our results indicate that an IEEE 802.11e access point can support a limited number of voice calls handed over from UMTS, which depends primarily on the applied WLAN bandwidth sharing policy (i.e., how the bandwidth is shared between WLAN voice and data users) and the QoS requirements. The performance of the WLAN scheduling algorithm is also of paramount importance and in our study we consider the so‐called ARROW scheduler. Although the simulation results are derived for a specific bandwidth sharing policy, they can readily be scaled and provide practical upper bounds for the number of UMTS voice calls that can be seamlessly admitted to a WLAN access point. Copyright © 2007 John Wiley & Sons, Ltd.     

Interoperability criteria, mechanisms, and evaluation of system performance for transparently interoperating WLAN and UMTS-HSDPA networks

The main challenge in the development of future wireless communication systems is to provide users with a wide range of services across different radio access technologies through a single mobile terminal, while maintaining the minimum QoS requirements, and ideally with no limits on the coverage area, mobility or radio conditions. Thus, the need for seamless interworking between heterogeneous wireless communication systems consisting of multiple radio access technologies and overlapping networks emerges. In this article we address the main issues that arise while implementing the interoperability mechanisms between two different radio access networks, with emphasis on UMTS-HSDPA and WLAN (HIPERLAN/2). Two interoperability mechanisms are introduced and described in detail: initial user assignment (optimal network selection) and intersystem handover. Both mechanisms are activated via the optimization of a suitably defined cost function which takes into account all the appropriate system level parameters that trigger the interoperability process. Finally, we investigate the overall performance of the proposed mechanisms by means of a software simulation platform. A number of simulations have been carried out in order to demonstrate the performance enhancements achieved by the proposed mechanisms in terms of unsatisfied users, dropped handovers, and system throughput.     

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.     

Policy-based QoS-management architecture in an integrated UMTS and WLAN environment

Strong demands for public wireless broadband services will require more capacity than even that can be,supplied by advanced mobile cellular systems like the Universal Mobile Telecommunication System. The increasing popularity of WLANs has prompted mobile network operators to consider their deployment in high-density usage areas like indoor/outdoor public hotspots to provide complementary broadband access to their UMTS networks. In order to provide consistent QoS control over an integrated UMTS and WLAN system, a policy-based multidomain QoS management architecture is proposed in this article. Different UMTS-WLAN interworking scenarios are discussed to illustrate the feasibility of the proposed architecture.     

HiperLAN/2与GPRS/UMTS网络的互联--全新的高速广域无线接入业务模式

本在介绍无线局域网HiperLAN／2标准及GPRS／UMTS网络的体系结构的基础上，对HiperLAN／2与GPRS／UMTS网络的互联进行了讨论。有两种不同的互联方式：紧耦合互联方式和松耦合互联方式，由于松耦合互联方式对GPRS／UMTS网络的影响最小，本重点对其安全性、移动性和QoS问题进行了讨论。     

UMTS-WLAN异构网络互联的方案研究

通用移动通信系统(UMTS)为移动数据用户提供了较广阔的覆盖范围,而无线局域网(WLAN)能在局部热点地区提供较高的接入带宽.两种网络的显著优势能够相互结合,为处于异构网络覆盖地区的用户提供网间无缝连接.本文总结了目前UMTS-WLAN互联的三种实施方案:移动IP、互联网关和仿真器.在分别介绍三种方案的体系架构、互联机制和切换流程后从互联层次、信令和数据流向、对现有网络的改造、安全认证机制及用户管理方式等不同层面分析三种方案的特点.     

基于媒体独立切换并提供QoS保证的跨UMTS和WiMAX无线异构网络的网络切换方案

The rapid growth and innovation of the various mobile communication technologies have caused a change in the paradigm of internet access. Wireless technologies such as WiMAX, WiFi and UMTS/LTE networks have shown great potential in dominating the wireless access markets. The existence of various access technologies requires a means for seamless internetworking to provide anywhere, anytime services without interruption in the ongoing session, especially in multimedia applications with rigid Quality of Services (QoS) requirements. The IEEE 802.21 Media Independent Handover (MIH) working group was formed to develop a set of mechanisms under a standard framework with the capability to support migration of mobile users across heterogeneous networks. Therefore, the implementation of handover is extremely important in the heterogeneous network environment. In order to guarantee various QoS requirements during handover execution especially in multimedia applications, in this paper we propose a novel MIH-based capacity estimation algorithm to execute handover with QoS provision supporting both horizontal and vertical handovers across UMTS and WiMAX networks. Simulation shows that the proposed mechanism achieves lower call dropping rate (highest approximate 3% ) and higher system throughput (average 92% ) than the basic handover method does.     

Interworking of IP multimedia core networks between 3GPP and WLAN

The 3GPP has specified the IP multimedia subsystem (IMS) for the provisioning of multimedia services in UMTS Release 5 and later. Interconnection at the service layer between 3GPP and LAN networks requires interworking between IMS and WLAN functionalities. Studying several interconnection scenarios and the main functionalities of IMS, this article analyzes how the interconnection of 3GPP and WLAN networks may be performed in order to support different levels of service interconnection. Special attention is paid to interconnection at the session negotiation level, using SIP (the base protocol of the IMS) to provide session negotiation with QoS and AAAC support.     

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 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.     

Vertical Handover Over Intermediate Switching Framework: Assuring Service Quality for Mobile Users

Ensuring quality of service (QoS) for the mobile users during vertical handover between IEEE 802.11 wireless local area networks (WLAN) and data network provided by Ultramodern Telecommunication Systems (UMTS) is one of the key requirements for seamless mobility and transfer of existing connections from one network to another. QoS fulfillment is a complex problem and requires participation of both the mobile users as well as the connection networks. The QoS assurance criteria for existing connections can be affected by fluctuations of data rates when a user moves from the high speed WLAN network to the low speed UMTS network, even in the presence of another WLAN network in its vicinity. This can happen if the alternate WLAN network is highly loaded. Therefore handover from a high speed network to a low speed network should be avoided, whenever possible. This paper proposes a QoS based handover procedure that prioritizes the existing connection over the new connections so that rate fluctuations due to handover can be avoided if there exist another WLAN network in the range of the mobile user. Whenever the possibility of handover is detected, a pre-handover bandwidth reservation technique is used to reserve bandwidth at the alternate WLAN networks to avoid QoS degradation. The proposed scheme is implemented in Qualnet network simulator and the performance is analyzed and compared with traditional handover techniques.     

Analysis of the integration of IEEE 802.11e capabilities in battery limited mobile devices

IEEE 802.11 wireless LANs (WLANs) is widely recognized as a complementary technology to cellular access networks in hot-spot areas due to its lower cost and higher data rates. Different interworking approaches are being studied, but one common element is considered by all of them: mobile devices can include capabilities for connecting through both access technologies, allowing the best option to be chosen depending on the availability at a specific moment. However, several challenges need to be addressed in order to achieve seamless integration of WLAN and cellular systems in such a mobile device. The IEEE 802.11e standard, which defines mechanisms to provide QoS in a WLAN, represents a basic step toward this integration, since it provides the means to support key applications such as voice over IP. The IEEE 802.11 power-save mode (PSM) is another necessary element for devices with severe battery limitations (e.g., cellular phones) in order to ensure reasonable battery duration. The resulting performance when both QoS and power-saving mechanisms are used together, however, is uncertain and requires further study. We analyze the implications of the interaction of the 802.11 PSM with 802.11e QoS mechanisms by determining if the desired QoS is still provided, detecting functionality conflicts, and quantifying the impact of the PSM upon the 802.11e QoS efficiency and system performance. The evaluation is performed via simulation.     

On designing issues of the next generation mobile network

Next generation mobile network (NGMN) is envisaged to support seamless mobility across disparate access technologies in a transparent manner. The success of NGMN design will depend on its ability to address key design issues, mainly architectural adaptation and modification of service continuity functions (i.e., mobility and resource management) that arise from such interoperability. The solutions presented in this article attempt to resolve these issues by considering an IP-based interworking framework that promotes evolution of individual networks and integration of new technologies     

Toward a generic "always best connected" capability in integrated WLAN/UMTS cellular mobile networks (and beyond)

The next generation of mobile communications, broadly referred to as 4G, is based on a heterogeneous infrastructure comprising different wireless (and wired) access systems in a complementary manner. 4G mobile users enjoys seamless mobility and ubiquitous access to applications in an always best connected (ABC) mode that employs the most efficient combination of available access systems. The ongoing commercialization of 3G cellular mobile networks and their upcoming enhancement with WLAN radio access provides a wireless platform suitable for the introduction of "ABC" capabilities. We analyze the implications of the "ABC" vision in a UMTS/WLAN network context, and reveal important issues that arise. Further on, we identify major requirements, point out the limitations of current UTMS/WLAN standards from an ABC viewpoint, and discuss key enabling technologies and research efforts. We formulate a generic application model for an ABC capability in the interworked UMTS/WLAN architecture and analyze its complexity proving that, in principle, being always best connected translates to a family of NP-hard problems. To complement our analysis, we present an object-oriented design of a real-time UML model for an ABC mobile system. Finally, we summarize the advantages of our ABC model and provide directions for future work.     

Services in interworking 3G and WLAN environments

Interworking WLANs and 3G mobile networks are expected to provide ubiquitous wireless communications at high data rates and a large variety of services with variable bandwidth and QoS requirements, across a wide range of propagation environments and mobility conditions, using dual mode terminals. The interworking of the two networks is a major step toward a new generation of wireless networks in which other radio technologies are also be integrated. In this article we present possible architectures that enable the interworking of 3G and WLAN networks. We then address the capabilities of various terminal types and describe future services in the interworking environment. Finally, we present market forecasts on terminal and service demand growth.     

Analysis of the evolution to an IP-based UMTS terrestrial radio access network

This article provides an overview of the various issues - and their solutions - the researchers faced when looking into the matter of introducing IP transport in the UMTS terrestrial radio access network. Starting with a synopsis of the framework provided by standardization (3GPP), we present more detailed solutions for several topics that were addressed in 3GPP such as the definition of an efficient protocol stack, the provisioning of QoS, and strategies for IP-ATM interworking. As a special case of the latter, the application of pseudo-wires as an innovative solution is put forward to allow interworking with dual-stacked nodes over an IP-only backbone.     

3GPP与WLAN互连的技术

主要介绍第三代移动通信合作计划(3GPP———3GPartnershipProject)与无线局域网(WLAN)互连的结构,3GPP用户可通过WLAN开展WLAN接入业务。在WLAN中,通过3GPP预约,使用客户识别模块(SIM)/用户服务识别模块(USIM)接入通用IC卡(UICC),使3GPP与WLAN终端互连。文中还介绍基于3GPP的WLAN接入认证授权、IEEE802.11i中的认证和密钥协定、3G-WLAN互连中的认证和授权、复用3GPP的归属位置注册器等,描述了用户数据如何选路和接入业务,最后介绍WLAN中基于3GPP的计费方法(预付费和后付费),以及如何对这些用户计费和对归属网络中基于IP的计费。