Intelligent Handoff for Mobile Wireless Internet

This paper presents an intelligent mobility management scheme for Mobile Wireless InterNet – MWIN. MWIN is a wireless service networks wherein its core network consisting of Internet routers and its access network can be built from any Internet-capable radio network. Two major standards are currently available for MWIN, i.e., the mobile IP and wireless LAN. Mobile IP solves address mobility problem with the Internet protocol while wireless LAN provides a wireless Internet access in the local area. However, both schemes solve problems independently at different layers, thereby some additional problems occur, e.g., delayed handoff, packet loss, and inefficient routing. This paper identifies these new problems and performs analyses and some real measurements on the handoff within MWIN. Then, a new handoff architecture that extends the features of both mobile IP and wireless LAN handoff mechanism was proposed. This new architecture consists of mobile IP extensions and a modified wireless LAN handoff algorithm. The effect of this enhancement provides a linkage between different layers for preventing packet loss and reducing handoff latency. Finally, some optimization issues regarding network planning and routing are addressed.     

UWB技术在家庭和有线电视网络中的应用

UWE无线通信是近几年发展起来的一项十分有潜力的无线通信技术。由于其高性能、低成本的无线数据通信能力,成为实现无限个人局域网的富有竞争力的技术之一。在有线电视网络和家庭网络无线系统引入频谱利用率高效的UWB技术,可提供具有灵活性和移动性的宽带接入业务。依据超宽带技术的主要原理和特点,讨论了该技术在有线电视网络和家庭网络中应用的优势和实现,使得UWB技术具备了更广泛的应用。     

Wireless LANs and mobile networking: standards and futuredirections

The emerging widespread use of wireless LAN systems together with the users' desire for such systems to interoperate has created a requirement for standards. Many standards bodies are currently defining standards for wireless systems that relate to different layers of the networking protocol stack. Of these, two influential physical and data link layer standards, IEEE 802.11 and the European HIPERLAN, are described. The article then considers the network layer by discussing extensions that are being made to the widely used Internet protocol (IP) to deal with mobility (wired or wireless). The final standards that are discussed relate to wireless link management. The article concludes by speculating on future directions for wireless LAN systems     

Ad Hoc 网络中的路由机制

Ad Hoc网络是一种无中心式（分布式）的无线通信网络。它为局域内的移动或无线主机的互连提供了灵活的解决办法。由于其支持主机移动以及无中心的特点，合适的路由策略在Ad Hoc网络中是至关重要的。对Ad Hoc网络的路由机制进行了介绍和分析，并结合其分布式及对移动的支持提出了扩展的网络管理策略。     

A Flexible QoS-aware Service Gateway for Heterogeneous Wireless Networks

The integration of different types of wireless access networks, or heterogeneous wireless networks (HWN), is emerging. This article investigates in particular how a combination of UMTS (Universal Mobile Telecommunications System) cellular networks, wireless LAN ad hoc networks, and DVB-H (digital video broadcasting - handheld) broadcasting networks, called UWD networks for short, is constructed and managed to provide users with QoS-aware services. Given the complexity of the UWD networks, a novel policy-based service gateway is proposed. As a software framework sitting over and communicating with the UWD network, this UWD service gateway makes network management decision by reasoning over a set of predefined policies that describe the behaviors of the UWD network. Network variables such as bandwidth, delay, and mobility in policies are fuzzified using fuzzy control theory to make the service gateway (as well as the whole UWD network) more flexible and robust. Both the prototype implementation and the evaluation results indicate the feasibility and effectiveness of the system     

一种基于AP ESSID的智能流量控制方法

无线局域网作为3G的一个重要补充,以其灵活性和便捷性取得了巨大发展。但是由于无线局域网以微波传输的特性,与有线网相比其传输速率要低得多,充分有效利用有限的带宽资源使得流量控制在无线局域网中显得尤为重要。在Linux内核IP数据包过滤系统Ebtables的基础上,结合开源流量控制器TC,设计了一种基于扩展服务集标志符(ESSID)的智能流量控制方法,实现网络数据的识别和分类,保证网络流量的稳定和畅通。测试结果表明:该流量控制方法能对无线接入点(AP)中的无线局域网络进行有效的流量控制,保证无线网络资源的充分利用。     

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.     

Wireless LAN design alternatives

The authors have discussed several alternatives in wireless LAN design: media choice, operating frequency, operating mode, network topology, and access method. Although each technical choice presents both advantages and disadvantages, they argue that there is a design point that provides the best fit with present and future wireless LAN user needs. Considering all factors-including robustness, regulatory considerations, and interference avoidance-using a product based on the slow frequency-hopping spread spectrum, in the 2.4 GHz ISM band, relying on a base station remote station network topology and using a TDMA-based access method is the best way to meet the needs of radio-frequency wireless LAN users. The choices are many, but slow frequency-hopping at 2.4 GHz and TDMA-based medium access control provide the best mix of cost, range, interference, and performance     

无线局域网络解决方案

无线局域网以其可移动性、布线简便、组网灵活和成本低廉的特点,在各行各业中越来越受到人们的关注和广泛的应用。在互联网高速发展的今天,无域局域网作为有线网络的补充或替代,有着极大广阔的发展前景和市场潜力。介绍了当前最流行的3种不同的IEEE 802.11扩展标准的特性。讨论了无线局域网的5种拓扑结构。对于无线局域网的安全技术也进行了讨论。     

无线宽带通信系统及应用

无线通信正处于从窄带传输向宽带传输过渡的发展时期。苯文简单介绍无线局域网、宽带综合数字网、第三代移动通信系统和无线ATM网络几种无线宽带通信系统及其应用。     

Design and implementation of WAP‐based LAN segment management system using RMON MIB

Advances in LAN technology have enabled fast data transmission. However, without effective management of these resources, congestion of networks as well as waste of resources are inevitable. Therefore, it is necessary to supervise, report, and even control, if necessary, the network resource status so that the communication network can be effectively operated without service interruption by monitoring traffic among the hosts. Web‐based network management systems have been developed and applied for remote management without using specific applications. However, such web‐based network management systems have limited manager mobility and poor performance. To overcome such disadvantages, this paper proposes a network management system using wireless communication. Copyright © 2003 John Wiley & Sons, Ltd.     

Infoshare : Design and Implementation of Scalable Multimedia Signage Architecture for Wireless Ubiquitous Environments

Digital signage systems have found many interesting applications in the realms of advertising, entertainment and education. One of the most prevalent challenging issues faced by current Local Area Network (LAN) based Digital signage network architectures is that their difficulty in porting to wireless ubiquitous environments. While popularity of wireless LANs promotes such architectural improvement, Traditional thin/thick client based architectures suffer inefficiency and scalability issues introduced by use of proprietary signage content formats. Use of such content formats to store signage contents is less optimal since it could lead to content redundancy, difficulty in creating, managing signage contents and scalability issues. As a solution for this issue we propose a Smart Client based digital signage architecture that uses XAML (an XML based declarative GUI language) contents for expressing its signage displays. While Smart Clients can better tolerate communication disruptions which are quite frequent in wireless environments, use of XAML based open content format promotes use of simple tools and variety of devices for signage content creation and management over the Internet in a ubiquitous environment. We successfully applied this generic architecture to a prototype digital signage system called Infoshare and report its robustness in withstanding network disruptions. We evaluate the easiness of editing XAML based signage contents by comparing Infoshare with a popular LAN based digital signage system which uses proprietary content formats. We demonstrate scalability of Infoshare signage service in terms of hardware resources by deploying it in different hardware platforms.     

A wireless broadband ad-hoc ATM local-area network

We describe the theory, design and ongoing prototyping of a wireless ATM LAN/PBX capable of supporting mobile users with multi-Mb/s access rates and multi-Gb/s aggregate capacities. Our proposed LAN Consists of network nodes called Portable Base Stations (PBS) providing microcell coverage. The PBSs are designed to be low-cost, compact and high-speed and can be relocated conveniently. We employ a concept ofad-hoc networking in the layout of the PBS-to-PBS interconnection. That is, the PBSs can be distributed in an arbitrary topology to form a backbone network and can be reconfigured with relative ease. The PBS-to-PBS backbone links are high-speed (Gb/s) for supporting high system capacity. Although they can either be wired or wireless, our emphasis is on wireless implementations. The user-to-PBS links, on the other hand, are primarily for mobile access (e.g., 2–20 Mb/s) and therefore are wireless. Wired connections from stationary users to PBSs are also possible. Typical mobile users are assumed to be laptops or notebook computers. Services supported include conventional data applications (e.g., over TCP/IP or SPX/IPX) as well as multimedia (video, voice and data) applications with QoS (Quality-of-Service) guarantees. A wireless ATM concept is proposed so as to provide seamless internetworking with other wired ATM local and wide-area net-works. Algorithms and control in our network are highly distributed for simple implementations and ease of mobility management. A new wireless VP/VC concept and a Homing Algorithm are described to provide ATM cell routing and connections in the network. PBS hardware and software architectures are discussed. Call management, network management and signaling are designed for simplicity, high performance and modular implementations. A fast network restoration scheme is proposed to cope with the potential link or node failures in the ad-hoc network. Error control is addressed taking the unreliable wireless links into consideration. Finally, a prototyping project called BAHAMA (Broadband Ad Hoc ATM Anywhere) for demonstrating this network concept is briefly outlined.     

On the mobility/capacity conversion in wireless networks

Given a quality-of-service constraint, a wireless network has to sacrifice its capacity in order to support an increase in mobility. In other words, the network needs to convert some of its capacity into mobility. We develop an analytical model to evaluate the efficiency of the mobility/capacity conversion processes of several wireless networks. One practical implication of our results is that a network, if designed correctly, should have a free convertibility between the two.     

Network architecture and traffic transport for integrated wireless communications over enterprise networks

A novel network architecture based on the IEEE 802.6 metropolitan area networks (MAN) is proposed to integrate the wireless and wired segments of a regional enterprise network (REN) within a city. This architecture functions like a distributed switch for all types of services, reducing traffic congestion by sharing the high capacity link dynamically and facilitating signaling, mobility management, call processing and network management through its distributed functions, transport facilities and broadcasting capability. It also serves as a peripheral gathering network of REN traffic for transport over a wide area ATM/BISDN, enabling integration of an enterprise's regional networks into a global EN. Two major wireless applications, i.e., wireless PABX (WPABX) and wireless LAN (WLAN) are discussed to illustrate the advantages of this MAN‐based architecture. Although a REN is likely to support a wide range of different services, voice and data will continue to be the predominant traffic generated by WPABXs and WLANs, respectively, and are also representative of isochronous and asynchronous multimedia traffic carried by future wireless networks. We compare the traffic capacity of several voice transport alternatives under integrated (voice/data) network traffic with various data traffic loads, and study voice and data integration under three different integration schemes by simulations. Results indicate that the MAN‐based architecture is most effective employing queue arbitrated (QA) access for asynchronous traffic, pre‐arbitrated access for constant bit‐rate isochronous traffic, and the new reservation arbitrated (RA) access for variable bit‐rate isochronous traffic, under a scheme that permits full sharing between QA and RA traffic. This revised version was published online in July 2006 with corrections to the Cover Date.     

“无线局域网技术”课程的改革研究

随着计算机技术、网络通信的快速发展,无线网络正备受瞩目。在无线局域网离人们生活越来越近之时,社会对无线局域网技术人才的需求也越来越多。作为每年为社会输送大量人才的职业院校,应顺应时代发展要求,不断革新“无线局域网技术”的教学方式与内容,以此提高教学质量,培养出符合社会要求的无线局域网技术人才。因此,文章将对“无线局域网技术”课程的改革进行研究,旨在提升职业院校无线局域网技术人才的培养质量。     

新一代宽带无线局域网系统中的OFDM技术研究

无线局域网是一种高速的无线数据传输系统,其调制技术的选择非常关键。OFDM(正交频分复用)是一种无线环境下的高速传输技术,适合在多径传播和多普勒频移的无线移动信道中传输高速数据。他能有效地对抗多径效应,消除符号间干扰,对抗频率选择性衰落,而且信道利用率高。文中对OFDM技术在新一代宽带无线局域网无线接入系统中的应用进行了分析和研究。     

基于WLAN的无线校园网的设计与实现

随着IEEE 802.11无线局域网技术标准的不断推出以及基于这些标准的无线产品的出现,无线局域网的应用和普及已发展到了一个新阶段,基于WLAN的无线网络构建已成为组建无线校园网的主流技术,是有线校园网网络延伸的重要手段之一。结合东北石油大学无线校园网建设的工程实践,采用无线控制器＋＂瘦＂AP的无线网络解决方案,组建了基于WLAN的校园无线网络,并对相关的设计方法进行了详细说明。经过长期实践应用证明,该网络运行高速、稳定。     

Quality of Service and Mobility for the Wireless Internet

Our paper explores the issue of how to provide appropriate quality of service mechanisms closely integrated with flexible mobility management in wireless local area networks. We consider them as access networks of choice for the high performance Wireless Mobile Internet. We present a hierarchical QoS architecture that extends Differentiated Services (DiffServ) to mobile hosts in a wireless environment. Our approach is based on controlling several parameters of a wireless LAN cell: the limited geographical span to ensure the same high bit rate for all hosts, the constrained rate of traffic sources to limit the use of the channel in function of the required QoS and the limited number of active hosts to keep the load sufficiently low. The QoS management is coupled with mobility management at the IP level. We use a micro-mobility scheme implemented in the IPv6 layer with fast hand-offs between adjacent cells. Micro-mobility avoids address translation, traffic tunneling, and enables fast hand-offs. We give some details of experiments to show the quality of service differentiation over the 802.11b network.     

A nonpreemptive priority-based access control scheme for broadbandad hoc wireless ATM local area networks

The DQRUMA (distributed-queueing request update multiple access) protocol has been considered as an access protocol for the BAHAMA (broadband ad hoc wireless ATM local area network). However, it cannot support the service discipline of integrated multimedia traffic since it does not include any priority and access control policy. In this paper, we propose a nonpreemptive priority-based access control scheme for the DQRUMA protocol. Under such a scheme, modifying the CSMA/CA protocol in the contention period supports many levels of priorities such that user mobility (handoff) can be supported in BAHAMA. Besides, the proposed transmit-permission policy and adaptive bandwidth allocation scheme provide various QoS (quality-of-service) guarantees while maintaining high bandwidth utilization. Simulations show that it provides a good performance in ad hoc wireless ATM LAN environments