Strong roaming authentication technique for wireless and mobile networks

When one considers the broad range of wirelessly connected mobile devices used today, it is clear that integrating such network‐enabled devices into secure roaming over wireless networks is of essential importance. Over the years, many authentication protocols have been suggested to address this issue. Among these protocols, the recently proposed privacy‐preserving universal authentication protocol, Priauth, exceeds the security and efficiency of other authentication techniques. This paper studies the existing roaming authentication protocols and shows that they are not strong enough to provide secure roaming services in three aspects. Further, using Priauth as an example, we propose efficient remedies that fix the weaknesses. The experimental results show that the proposed approaches are feasible in practice. Copyright © 2012 John Wiley & Sons, Ltd.     

Packet telephony support for the IEEE 802.11 wireless LAN

Packet telephony is one of the most promising applications in the Internet. In this paper, we propose a modified MAC protocol supporting voice traffic over the IEEE 802.11 WLAN. The proposed scheme adapts the power-saved mode of the IEEE 802.11 specifications in such a way that it approaches the TDM access mode carrying voice traffic, and is compatible with the IEEE 802.11 standard. Simulation results show that the proposed scheme does not degrade the performance of the IEEE 802.11 WLAN using the DCF and also provides good voice quality     

Route selection in IEEE 802.11 wireless mesh networks

This paper addresses the problem of route selection in IEEE 802.11 based Wireless Mesh Networks (WMNs). Traditional routing protocols choose the shortest path between two routers. However, recent research reveals that there can be enormous differences between links in terms of quality (link loss ratio, interference, noise etc) and therefore selecting the shortest path (hop count metric) is a poor choice. We propose a novel routing metric—Expected Link Performance (ELP) metric for wireless mesh networks which takes into consideration multiple factors pertaining to quality (link loss ratio, link capacity and link interference) to select the best end-to-end route. Simulation based performance evaluation of ELP against contemporary routing metrics shows an improvement in terms of throughput and delay. Moreover, we propose an extension of the metric called ELP-Gateway Selection (ELP-GS) which is an extension meant for traffic specifically oriented towards the gateway nodes in the mesh network. We also propose a gateway discovery protocol which facilitates the dissemination of ELP-GS in the network. Simulation results for ELP-GS show substantial improvement in performance.     

A survey of QoS enhancements for IEEE 802.11 wireless LAN

Quality‐of‐service (QoS) is a key problem of today's IP networks. Many frameworks (IntServ, DiffServ, MPLS etc.) have been proposed to provide service differentiation in the Internet. At the same time, the Internet is becoming more and more heterogeneous due to the recent explosion of wireless networks. In wireless environments, bandwidth is scarce and channel conditions are time‐varying and sometimes highly lossy. Many previous research works show that what works well in a wired network cannot be directly applied in the wireless environment. Although IEEE 802.11 wireless LAN (WLAN) is the most widely used IEEE 802.11 wireless LAN (WLAN) standard today, it cannot provide QoS support for the increasing number of multimedia applications. Thus, a large number of 802.11 QoS enhancement schemes have been proposed, each one focusing on a particular mode. This paper summarizes all these schemes and presents a survey of current research activities. First, we analyze the QoS limitations of IEEE 802.11 wireless MAC layers. Then, different QoS enhancement techniques proposed for 802.11 WLAN are described and classified along with their advantages/drawbacks. Finally, the upcoming IEEE 802.11e QoS enhancement standard is introduced and studied in detail. Copyright © 2004 John Wiley & Sons, Ltd.     

无线局域网 IEEE802.11 高性能局域网统一信息系统

无线局域网标准 IEEE802.11是第一代无线局域网标准之一。 1990年 IEEE802标准化委员会成立 802.11无线局域网 (WLAN)标准工作组。 802.11无线局域网标准工作组任务为研究 1Mbit/s和 2Mbit/s数据速率、工作在 2.4GHz开放频段的无线设备和网络发展的全球标准,并于 1997年 6月公布了该标准。该标准定义物理层和媒体访问控制 (MAC)规范,允许无线局域网及无线设备制造商建立互操作网络设备。 　　IEEE 802.11标准中物理层定义了数据传输的信号特征和调制。在物理层中,定义了两种 RF传输方法和一种红外线传输方法。在该标准中, RF传输采用扩频方法,即采用了跳频扩频 (FHSS)和直接序列扩频 (DSSS)两种方法,工作在 2.4000GHz～ 2.4835GHz频段。     

Optimal frequency assignment for IEEE 802.11 wireless networks

The performance of wireless local area networks (WLANs) is based on the performance of the corresponding access points (APs). Nowadays, network engineers tend to manually assign data channels (frequencies) for each AP. They only use channels 1, 6, and 11 because no interference exists between these channels. But it will be far more efficient if all 11 channels are used. Therefore, the channel allocation problem becomes a major challenge when deploying WLANs. In this paper, we assume that the location of each AP is known. Our objective is to optimally assign a frequency for each AP such that the throughput is maximized and the interference between the various APs is minimized. We also consider a realistic scenario where the APs are not in line of sight of each other, but on the other hand there are different barriers that separate them. We formulate the problem using integer linear programming (ILP) in order to obtain the optimal frequency assignment (OFA). Then, we propose two efficient heuristic algorithms to achieve the same results. Finally, we evaluate the performance of all techniques and make a comparison between them. Copyright © 2008 John Wiley & Sons, Ltd.     

QoS enhancement in IEEE 802.11 wireless local area networks

A distributed medium access scheme called EDCF, which is adopted in an upcoming standard IEEE 802.11e to allow prioritized medium access for applications with QoS requirements, is described and discussed. Its performance is also evaluated via simulations.     

A novel performance analysis model for an IEEE 802.11 wireless LAN

This letter presents a novel analytic model that accurately evaluates the performance of a single-hop IEEE 802.11 wireless LAN (WLAN). By using a closed queuing network, we model an IEEE 802.11 WLAN system that consists of a fixed number of stations and derive the saturated throughput of the IEEE 802.11 distributed coordination function (DCF). The ns-2 simulation results show that our new analysis model is very accurate in evaluating the performance of the IEEE 802.11 DCF.     

Performance analysis of MAC layer protocols in the IEEE 802.11 wireless LAN

In recent years, WLANs (Wireless Local Area Networks) based on the IEEE 802.11 standard have been taken a growing interest and developed widely all over the world. CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) protocols are the most popular MAC (Medium Access Control) protocols for WLANs. The performance of CSMA/CA protocols over wireless channels has been investigated over the past years. In this paper, we obtain the probability distribution function of the MAC layer packet service time, and we present the comprehensive performance analysis of IEEE 802.11 MAC protocol by investigating the queue dynamics of a wireless station based on the MAC layer packet service time. We adopt an MMPP(Markov Modulated Poisson Process) as the input traffic model that describes well the bursty nature of Internet traffic. The analysis on the throughput and the delay performance has been carried out by using the MMPP/G/1/K queueing model. We have some numerical results that represent the system throughput and the queue dynamics including the mean packet waiting time and packet blocking probability.     

IEEE802.11无线局域网标准

介绍了IEEE802.11无线局域网技术规范.给出了ISM频段、扩频技术的背景及各国相应的标准、规范.描述了允许可证2.4GHzISM频段的直接序列扩频技术及IEEE802.11协议规范。     

A seamless handoff scheme for IEEE 802.11 wireless networks

The advance of computer network technologies such as IEEE 802.11 wireless local area network has made it possible for users to connect to Internet almost anywhere. A mobile node (MN) is likely to move between different base stations while running applications. The IETF has defined the Mobile IP (MIP) to allow MNs to maintain their communication uninterrupted while roaming across different IP subnets. However, the mechanisms defined in MIP may cause undesired connection disruptions or packet losses, which will significantly degrade the quality of real‐time applications. It is an important and challenging issue to support seamless handoff management. To achieve seamless handoff, we propose a unified scheme to address application quality degradation. Our main contribution is the concept and implementation of utilising buffering and resending method to eliminate the packet losses while keeping the end‐to‐end delay of real‐time traffic flow in an acceptable value. The NS‐2 simulation results show that our proposed scheme can significantly maintain application quality during layer‐2 and ‐3 handoffs. Copyright © 2011 John Wiley & Sons, Ltd.     

Modeling intra-flow contention problem in IEEE 802.11 wireless multi-hop networks

This letter proposes a new approach to model the intra-flow contention problem in multi-hop networks. The model takes into consideration of neighboring interference, hidden-node collision and multi-rate scenario. It can be easily used to do admission control or to calculate the end-to-end capacity of a given multi-hop route. Simulation results validate its accuracy.     

IEEE 802.11s wireless mesh networks: Framework and challenges

Wireless mesh networking based on 802.11 wireless local area network (WLAN) has been actively explored for a few years. To improve the performance of WLAN mesh networks, a few new communication protocols have been developed in recent years. However, these solutions are usually proprietary and prevent WLAN mesh networks from interworking with each other. Thus, a standard becomes indispensable for WLAN mesh networks. To meet this need, an IEEE 802.11 task group, i.e., 802.11s, is specifying a standard for WLAN mesh networks. Although several standard drafts have been released by 802.11s, many issues still remain to be resolved. In order to understand what performance can be expected from the existing framework of 802.11s standard and what functionalities shall be added to 802.11s standard to improve performance, a detailed study on the existing 802.11s standard is given in this paper. The existing framework of 802.11s standard is first presented, followed by pointing out the challenging research issues that still exist in the current 802.11 standard. The purpose of this paper is to motivate other researchers to develop new scalable protocols for 802.11 wireless mesh networks.     

Dynamic bandwidth management in IEEE 802.11-based multihop wireless networks

In this paper, we propose a new protocol named dynamic regulation of best-effort traffic (DRBT) which supports quality of service (QoS) throughput guarantees and provides a distributed regulation mechanism for best-effort traffic in multihop wireless networks. By adapting dynamically the rate of best-effort traffic at the link layer, DRBT increases the acceptance ratio of QoS flows and provides a good use of the remaining resources through the network. Our protocol also provides an accurate method to evaluate the available bandwidth in IEEE 802.11-based ad hoc networks which is able to differentiate QoS applications from best-effort traffic. Through extensive simulations, we compare the performance of our proposal scheme with some others protocols like QoS protocol for ad hoc real-time traffic for instance.     

Avoiding collision with hidden nodes in IEEE 802.11 wireless networks

In wireless networks, collision is a major factor of performance degradation. In this letter, we propose a scheme for reducing collision in IEEE 802.11 networks. Each node can avoid collision by maintaining a disjoint set of time slots for transmission. Through simulation, we show that the proposed scheme is effective to reduce collision even in the presence of hidden nodes.     

Performance analysis and enhancements for IEEE 802.11e wireless networks

The IEEE 802.11 WLAN legacy standard cannot provide QoS support for multimedia applications. Thus, considerable research efforts have been carried out to enhance QoS support for 802.11. Among them, 802.11e is the upcoming QoS-enhanced standard proposed by the IEEE working group. This article describes in detail the new QoS features of 802.11e based on the latest version of the standard draft. We investigate the performance of 802.11e through computer simulations. Using simple examples, we show the effectiveness of adaptive schemes under the 802.11e framework.     

A single-chip dual-band tri-mode CMOS transceiver for IEEE 802.11a/b/g wireless LAN

A single-chip dual-band tri-mode CMOS transceiver that implements the RF and analog front-end for an IEEE 802.11a/b/g wireless LAN is described. The chip is implemented in a 0.25-/spl mu/m CMOS technology and occupies a total silicon area of 23 mm/sup 2/. The IC transmits 9 dBm/8 dBm error vector magnitude (EVM)-compliant output power for a 64-QAM OFDM signal. The overall receiver noise figure is 5.5/4.5 dB at 5 GHz/2.4 GHz. The phase noise is -105 dBc/Hz at a 10-kHz offset and the spurs are below -64 dBc when measured at the 5-GHz transmitter output.     

A 5-GHz CMOS transceiver for IEEE 802.11a wireless LAN systems

A 5-GHz transceiver comprising the RF and analog circuits of an IEEE 802.11a-compliant WLAN has been integrated in a 0.25-/spl mu/m CMOS technology. The IC has 22-dBm maximum transmitted power, 8-dB overall receive-chain noise figure and -112-dBc/Hz synthesizer phase noise at 1-MHz frequency offset.     

Design and implementation of a MAC controller for the IEEE802.11 wireless LAN

IEEE 802.11 wireless LANs have a tremendous market potential, as they support high data rates, work in the world-wide licence free 2.4 GHz ISM band and have high performance in terms of range and power consumption. Hence, the development of a communication processor that supports the IEEE 802.11 MAC functions has a significant potential, making very important the concept of having an ASIC ‘right from the first time’, in order to minimize development cost and to meet short time-to-market requirements. This paper presents the methodology of developing such a component with emphasis on the rapid prototyping approach. The chip architecture, which is based on an ARM processor core, is described in detail, focusing on the implementation of the protocol functions using custom hardware modules. Finally, the paper presents experimental results on the ASIC implementation.     

Sliding contention window (SCW): towards backoff range-based service differentiation over IEEE 802.11 wireless LAN networks

A number of works have tried to adjust the contention window in order to provide differentiated quality of service in IEEE 802.11-based wireless networks. By giving different service classes different CWs, the distribution of backoff intervals (chosen randomly, on the interval [O, CW]) will reflect the desired service classes. However, these protocols cannot deliver firm service guarantees while maintaining high network utilization, particularly under congested network conditions. In this article we propose a new MAC protocol featuring a sliding CW (SCW) for each network flow. The SCW dynamically adjusts to changing network conditions, but remains within a per-class predefined range in order to maintain a separation between different service classes. Each flow's SCW reacts based on the degree to which class-defined QoS metrics are satisfied. Simulation results show that compared to the enhanced distributed coordination function (EDCF) scheme of 802.11e, SCW consistently excels, in terms of network utilization, strict service separation, and service-level fairness.