IEEE 802系列无线网络网状组网与移动切换技术综述

传统的无线区域网络在进行大规模应用时受制于网络灵活扩展和对快速移动的支持。IEEE 802的相关标准组正在致力于推动网状组网和快速移动性支持方面的技术进步,制定相关的技术标准。以802.11s、802.15.5和802.16/20为例讨论了基于无线局域网、无线个域网和无线城域网的网状网技术与移动性支持技术。介绍了无线区域网络的发展趋势和技术路线,为更好地推动无线多跳网络的研究与应用奠定基础。     

具有多网络自适应选择的无线宽带视频传输系统

针对移动信道带宽不稳定以及Wi-Fi热点覆盖有限等网络问题,提出了一种可自适应选择第二代移动通信网络(CDMA1X)、第三代移动通信网络(3G-EVDO)及无线局域网(WLAN)的多网络自适应无线视频传输的系统架构,并给出了多网络自适应选择的算法。该算法主要包括多网络的自适应接入、无线异构网络的动态切换以及无线同构网络的自适应选择传输。该方案可实现无线视频的高质量可靠传输。     

A survey on emerging broadband wireless access technologies

Wireless broadband technologies provide ubiquitous broadband access to wireless users, enabling services that were available only to wireline users. In this paper, we summarize emerging wireless broadband access technologies, ranging from WLANs to satellite communications. We explain the latest standards in the IEEE 802.11 and IEEE 802.16 families in detail. The MAC layer mechanisms of IEEE 802.11e, 802.11n, and 802.11s standards are explained as well as the point-to-multipoint and Mesh modes of IEEE 802.16. The recent mobility amendment to the WiMAX family, IEEE 802.16e, is also described. Though the earliest versions of some of these technologies date back to 1996 (such as IEEE 802.11) and some are obsolete (such as HiperLAN), they have been included in this survey for the sake of completeness.Wireless technologies can be categorized based on their coverage areas. IEEE 802.11 and ETSI HiperLAN standards are considered for wireless access in local areas. IEEE 802.16 and 802.22, ETSI HiperACCESS and HiperMAN, WiBro, and HAP technologies can be used to provide service in metropolitan areas. Lastly, IEEE 802.20 and satellite systems provide service as wide area networks. Since the aim of this survey is to summarize wireless broadband technologies for data services, technologies such as Wireless USB are excluded. 3G and 4G systems have also been excluded since they are covered in detail in [C. Smith, D. Collins, 3G Wireless Networks, second ed., McGraw-Hill Osborne Media, 2006; S.G. Glisic, Advanced Wireless Networks: 4G Technologies, Wiley Publishing, 2005].     

Interworking wireless mesh networks: Problems,performance characterization,and perspectives

Wireless broadband networks based on the IEEE 802.11 technology are being increasingly deployed as mesh networks to provide users with extended coverage for wireless Internet access. These wireless mesh networks, however, may be deployed by different authorities without any coordination a priori, and hence it is possible that they overlap partially or even entirely in service area, resulting in contention of radio resources among them. In this paper, we investigate the artifacts that result from the uncoordinated deployment of wireless mesh networks. We use a network optimization approach to model the problem as resource sharing among nodes belonging to one or different networks. Based on the proposed LP formulation, we then conduct simulations to characterize the performance of overlaying wireless mesh networks, with the goal to provide perspectives for addressing the problems. We find that in a system with multiple overlaying wireless mesh networks, if no form of inter-domain coordination is present, individual mesh networks could suffer from capacity degradation due to increased network contention. One solution toward addressing the performance degradation is to “interwork” these wireless mesh networks by allowing inter-domain traffic relay through provisioning of “bridge” nodes. However, if such bridge nodes are chosen arbitrarily, the problems of throughput sub-optimality and unfairness may arise. We profile the impact of bridge node selection and show the importance in controlling network unfairness for wireless mesh network interworking. We conclude that mesh network interworking is a promising direction to address the artifacts due to uncoordinated deployment of wireless mesh networks if it is supplemented with appropriate mechanisms.     

Protocols for mobility management in heterogeneous multi-hop wireless networks

Substantial works have recently been reported on the mobility management in single-hop wireless networks (e.g. cellular networks and WLAN hotspots), while there has been an increased interest in multi-hop communications. This has made mobility management in heterogeneous multi-hop wireless networks (HMWNs) really interesting so that both single-hop and multi-hop communication paradigms can be integrated. One of the main research challenges for 4G wireless systems is the identification of a mobility management technique that could integrate different wireless technologies such as WLANs, WMANs and WWANs, operating in infrastructure (single-hop) and infrastructureless (ad hoc or multi-hop) modes. In this article we envision a futuristic HMWN where heterogeneous networks, operating in single-hop and multi-hop modes are integrated to provide increased capacity and enhanced coverage for the users. We summarize various existing mobility management solutions and discuss why these schemes are not adequate for HMWNs, as well as highlighting our view of mobility management issues in HMWNs.     

Wireless LAN load balancing with genetic algorithms

In recent years IEEE 802.11 wireless local area networks (WLANs) have become increasingly popular. Consequently, there has also been a surge in the number of end-users. The IEEE 802.11 standards do not provide any mechanism for load distribution and as a result user quality of service (QoS) degrades significantly in congested networks where large numbers of users tend to congregate in the same area. The objective of this paper is to provide load balancing techniques that optimise network throughput in areas of user congestion, thereby improving user QoS. Specifically, we develop micro-genetic and standard genetic algorithm approaches for the WLAN load balancing problem, and we analyse their strengths and weaknesses. We also compare the performance of these algorithms with schemes currently in use in IEEE 802.11 WLANs. The results demonstrate that the proposed genetic algorithms give a significant improvement in performance over current techniques. We also show that this improvement is achieved without penalising any class of user.     

Ws6603无线控制器在WLAN中的应用

基于IEEE802．11标准的无线局域网（WLAN）技术已经开始广泛应用于城域网和企业网。WLAN（Wireless Local Area Networks）在特定的场合（目前主要应用于：商务区、学校、机场、写字楼、高端住宅）可以代替其他有线接入方式作为网络接入最后1公里的解决方案。Ws6603是华为公司推出的无线接入控制器,位于整个网络的接入层,可以提供高速、安全、可靠的WLAN业务。     

The Security of Wireless Local Area Network

The Wireless Local Area Network (WLAN) is a new and developing technology and the security problem is always important in all networks; therefore, the security problems will be discussed in this article. The article firstly introduces the history of development of IEEE 802.11 and provides an overview of the Wireless LAN. The architecture of WLAN will be referred in next. Finally, the further of the wireless LAN will be prospected by this article.     

The changing usage of a mature campus-wide wireless network

Wireless Local Area Networks (WLANs) are now commonplace on many academic and corporate campuses. As “Wi-Fi” technology becomes ubiquitous, it is increasingly important to understand trends in the usage of these networks. This paper analyzes an extensive network trace from a mature 802.11 WLAN, including more than 550 access points and 7000 users over seventeen weeks. We employ several measurement techniques, including syslog messages, telephone records, SNMP polling and tcpdump packet captures. This is the largest WLAN study to date, and the first to look at a mature WLAN. We compare this trace to a trace taken after the network’s initial deployment two years prior.We found that the applications used on the WLAN changed dramatically, with significant increases in peer-to-peer and streaming multimedia traffic. Despite the introduction of a Voice over IP (VoIP) system that includes wireless handsets, our study indicates that VoIP has been used little on the wireless network thus far, and most VoIP calls are made on the wired network.We saw greater heterogeneity in the types of clients used, with more embedded wireless devices such as PDAs and mobile VoIP clients. We define a new metric for mobility, the “session diameter”. We use this metric to show that embedded devices have different mobility characteristics than laptops, and travel further and roam to more access points. Overall, users were surprisingly non-mobile, with half remaining close to home about 98% of the time.     

嵌入式Linux无线接入点的设计与实现

基于IEEE802.11b协议的无线局域网是数据通信里的新兴领域,它所提供的无线接入功能在很大程度上满足了用户在移动情况下对无线数据传输接入的需求。无线接入点作为无线局域网中的核心设备,性能的好坏直接影响网络的容量。本文论述了基于IEEE802.11b无线局域网的接入点的软件设计,重点介绍了软件系统中的PCMCIA子系统的结构及其移植。     

IEEE802．11n聚合机制的研究与性能分析

分析了IEEE802．11n无线局域网提高网络吞吐量的瓶颈,介绍帧聚合机制的原理,其中着重对A-MSDU和A-MPDU两种聚会机制的性能进行仿真,仿真结果表明采用聚合机制降低了网络额外开销,与未采聚会机制相比在网络利用率上有较大地提高,同时降低了网络时延,有效地提高了网络性能。     

基于无线局域网的室内覆盖分布系统模型

精确的覆盖预测及容量预估能降低运营商的综合设备成本及维护成本,从而提高无线局域网业务的整体有效性。该文通过多组实际测试数据对理论传播模型进行校正,获得接近室内实际使用环境下的2.4 GHz无线局域网的无线信号传播模型。采用理论推算以及实测数据相结合的方式预测容量模型。该文探讨的无线局域网协议仅包括IEEE802.11b。     

Network selection in a WiMAX–WiFi environment

The tremendous growth of wireless technologies has introduced the potential of continuous service adaptation to the users’ needs by giving them the ability to be able to select and access the proper network based on different criteria. Moreover, next generation wireless networks have been designed to provide support for multimedia services, with different traffic characteristics and different Quality of Service (QoS) guarantees. However, the expansion of Wireless Local Area Networks (WLANs) and Worldwide Interoperability for Microwave Access (WiMAX) networks poses new research era in the decision of the access network selection. In this paper, the existing access network selection schemes are classified into three categories: the network-centric, the user-centric and the collaborative schemes, and are analyzed respectively. Moreover, we propose a multicriteria access network selection algorithm applied in a WiMAX–WLAN environment, in order to facilitate the provision of high quality services and at the same time to satisfy different types of user Service Level Agreements (SLAs).     

USIM-based EAP-TLS authentication protocol for wireless local area networks

Due to the rapid growth in popularity of Wireless Local Area Network (WLAN), wireless security has become one of many important research issues. For the WLAN security, the IEEE 802.1X standard provides an authentication framework that is based on the Extensible Authentication Protocols (EAP). In the EAP framework, there are many authentication protocols that have been proposed, in which each authentication protocol has some strengths and weaknesses, respectively. Most EAP authentication protocols lack two features: identity protection and withstanding man-in-the-middle attacks. In this paper, we first propose a novel symmetric-key based certificate distribution scheme based on Universal Subscriber Identity Module (USIM) cards in a cellular network. The symmetric-key based certificate distribution scheme allows mobile subscribers to obtain temporary certificates from the corresponding cellular network. Combining the proposed certificate distribution scheme with the EAP-TLS (Transport Layer Security) protocol, we present a new EAP authentication protocol called USIM-based EAP authentication protocol. The new EAP authentication protocol combining with USIM cards is an extension of the EAP-TLS protocol and also follows the EAP framework in the IEEE 802.1X standard. Compared to other EAP authentication protocols, the proposed protocol provides mutual authentication, strong identity protection and roaming capability between the cellular network and the WLAN networks.     

无线局域网安全及防护技术分析

无线局域网（WLAN）技术已发展成为一种比较成熟的技术,得到了广泛应用,但由于无线网络的开放性,使其易于受到攻击,出现了很多安全方面的问题。在分析了无线局域网面临的一些威胁,提出了一些安全防范技术和措施让其更加安全可靠。     

无线局域网技术及其在家庭网络中的应用

无线局域网技术近年来产生了突飞猛进的发展,目前无线局域网技术所采用的技术标准主要有四种:IEEE802.11家族、蓝牙技术、红外线数据协会(IrDA)和HomeRF,其中IEEE802.11和蓝牙技术应用最为广泛。家庭网络是融合通信网络、控制网络和多媒体信息网络于一体的家庭信息化平台。该文从无线局域网技术及其最新发展入手,就无线局域网技术在家庭网络中的应用做出分析与比较。     

A survey of energy efficient MAC protocols for IEEE 802.11 WLAN

In recent years, IEEE 802.11 wireless local area networks (WLANs) have been widely deployed, and more and more mobile devices have built-in WLAN interfaces. However, WLAN employs the carrier sense multiple access with collision avoidance (CSMA/CA) medium access control (MAC) protocol, which consumes a significant portion of the energy resources of a mobile device. Hence, minimizing the energy consumption of the WLAN interface in mobile devices has recently attracted considerable interest in both academia and industry. This article provides a survey and an experimental study of the energy consumption issues and energy-efficient technologies of the MAC protocol in IEEE 802.11 WLAN.     

Analysis of temporal and throughput fair scheduling in multirate WLANs

The IEEE 802.11e Wireless Local Area Network (WLAN) provides controlled access features that can be used in conjunction with scheduling algorithms to provide guaranteed per-session services. However, the multirate operation of the WLAN complicates the design of scheduling and Quality of Service (QoS) provisioning algorithms. We propose a new solution based on Controlled Access Phase Scheduling (CAPS) framework, introduced for fixed rate WLANs in our earlier works, and employ a new fair central scheduler to achieve guaranteed fair services in a WLAN. We examine the fairness issues involved in designing such an algorithm and study several fair scheduling algorithms that can be used with CAPS. We present a modified start time fair queuing based scheduler as our choice and analyze its performance under dynamic and static multirate operation. The algorithm is then evaluated through several simulation experiments. We show that the enhanced CAPS is able to adapt to multirate environments and provide both temporal and throughput fair services in 802.11e WLANs.     

无线流媒体主动弃帧策略的仿真研究

仿真研究IEEE802.11g无线网络环境下实时流媒体的性能,在分析和探讨支持实时流媒体应用时无线网络性能瓶颈的基础上,提出一种改进策略--主动弃帧.仿真结果表明,这一策略显著改善了网络性能,为实时流媒体在WLAN上的应用提供更好的服务质量.     

Performance analysis of authentication and key distribution scheme for mobile multi-hop relay in IEEE 802.16j

Mobile multi-hop relay (MMR) network is known to be easy to install and convenient to manage because of its self-organizing and self-healing characteristics. However, MMR is vulnerable to security problems because of the same reason. In this paper, we propose a new hybrid authentication and key distribution algorithm for IEEE 802.16j MMR service. The proposed scheme uses centralized authentication when a mobile station or a relay station initially joins the MMR network and uses distributed authentication for hop-by-hop authentication between mobile nodes. We examine the procedure of the proposed scheme and its usefulness when applied to MMR networks. We also analyze the performance of the hybrid scheme. The proposed scheme can be used in any mobile multi-hop network as well as IEEE 802.16j MMR network.