802.11i EAP-TLS认证机制

目前解决无线局域网通信安全的方法主要有认证和加密这两种,而EAP-TLS是目前应用最广泛的认证机制,802.11i EAP-TLS认证机制通过认证中心签发的证书对双方身份进行认证,同时在认证过程中产生并分配临时密钥,加强了无线局域网的通信安全.     

An implementation of IEEE 1588 protocol for IEEE 802.11 WLAN

Wireless Networks - Clock synchronization is one of the enabling technologies for Wireless Local Area Networks (WLAN). It is crucial to perform applications such as data fusion, location detection...     

一种改进的IEEE802．11协议

以网络方式获取信息并交流信息,已经成为现代信息社会的一个重要特征.传统网络设计和规划方法主要是靠经验,但随着无线局域网的不断发展,这样的方法已经不能适应网络的发展.通过设计一个无线校园网,采用OPNET Modeler的建模层次和建模方法[1],实现对IEEE802.11协议的模拟及优化,给出了使用OPNET进行网络仿真的步骤,对网络的性能指标进行了有效的测量,为设计及优化本校园无线网络提供了重要的依据.     

Rate adaptive protocol for multirate IEEE 802.11 networks

In this paper, a rate adaptive protocol AMARF (Adaptive Multirate Auto Rate Fallback) for multirate IEEE 802.11 networks is proposed. In AMARF, each data rate is assigned a unique success threshold, which is a criterion to judge when to switch a rate to the next higher one, and the success thresholds can be adjusted dynamically in an adaptive manner according to the running conditions, such as packet length and channel parameters. Moreover, the proposed protocol can be implemented by software without any change to the current IEEE 802.11 standards. Simulation result shows that AMARF yields significantly higher throughput than other existing schemes including ARF and its variants, in various running conditions.     

IEEE 802.11i研究综述

IEEE 802．11i标准可以为WLAN用户提供一种更加可靠的安全解决方式。文章介绍了其标准体系结构。分析了工作原理及机制。并与目前流行的宽带认证方式进行了比较。最后给出了在宽带接入网中实际应用的方案。     

Wireless LAN security and IEEE 802.11i

This article reviews wireless LAN security with a focus on the evolving new IEEE 802.11i standard. The major security enhancements in encryption and authentication defined by 802.11i are illustrated. In addition, the newly introduced key management in 802.11i is discussed. Because 802.11i incorporates IEEE 802.1X as its authentication enhancement, 802.1X with consideration of roaming users is depicted. Both intrasubnet and intersubnet roaming are illustrated.     

Security protocol for IEEE 802.11 wireless local area network

As Wireless Local Area Networks (WLANs) are rapidly deployed to expand the field of wireless products, the provision of authentication and privacy of the information transfer will be mandatory. These functions need to take into account the inherent limitations of the WLAN medium such as limited bandwidth, noisy wireless channel and limited computational power. Moreover, some of the IEEE 802.11 WLAN characteristics such as the use of a point coordinator and the polling based Point Coordination Function (PCF) have also to be considered in this design. In this paper, we introduce a security protocol for the IEEE 802.11 PCF that provides privacy and authentication, and is designed to reduce security overheads while taking into account the WLAN characteristics. We prove this protocol using the original and modified BAN logic.     

Optimal frame aggregation level for IEEE 802.11 PCF protocol

In this paper, we analyze the effect of the frame aggregation level on the PCF (Point Coordination Function) MAC performance in IEEE 802.11 wireless LANs and analytically derive the optimal frame aggregation level for maximizing the PCF MAC performance. For various values of unit data frame size and transmission error probability, we propose the optimal frame aggregation levels. By computer simulations, we show that the derived optimal frame aggregation level significantly enhances the PCF MAC performance in IEEE 802.11 wireless LANs.     

Relay-volunteered multi-rate cooperative MAC protocol for IEEE 802.11 WLANs

In IEEE 802.11, the rate of a station (STA) is dynamically determined by link adaptation. Low-rate STAs tend to hog more channel time than high-rate STAs due to fair characteristics of carrier sense multiple access/collision avoidance, leading to overall throughput degradation. It can be improved by limiting the transmission opportunities of low-rate STAs by backoff parameters. This, however, may cause unfair transmission opportunities to low-rate STAs. In an attempt to increase overall throughput by volunteer high-rate relay STAs while maintaining fairness, we propose a new cooperative medium access control (MAC) protocol, relay-volunteered multi-rate cooperative MAC (RM-CMAC) based on ready to send/clear to send in multi-rate IEEE 802.11. In the RM-CMAC protocol, we show that the effect of hogging channel time by low-rate STAs can be remedied by controlling the initial backoff window size of low-rate STAs and the reduced transmission opportunity of low-rate STAs can be compensated by the help of volunteer high-rate relay STAs. We analyze the performance of RM-CMAC, i.e., throughput and MAC delay, by a multi-rate embedded Markov chain model. We demonstrate that our analysis is accurate and the RM-CMAC protocol enhances the network throughput and MAC delay while maintaining the fairness of low-rate STAs.     

A secure n-secret based client authentication protocol for 802.11 WLANs

Authentication has strong impact on the overall security model of every information system. Various authentication techniques are available for restricting the access of unauthorized users to the enterprise scale networks. IEEE 802.1X defines a secure and reliable authentication framework for 802.11 WLANs, where Extensible Authentication Protocol (EAP) provides the base to this architecture. EAP is a generic architectural framework which supports extensibility by incorporating the new and improved authentication schemes, which are based on different types of credentials. Currently there exist a number of EAP and Non-EAP methods with varying level of security and complexity. In this work, we have designed a new n-secret based authentication scheme referred here as Personal Dialogue Based Authentication, for the client authentication to the network. It is a Transport Layer Security (TLS) protected authentication protocol, which will be executed inside the secure TLS tunnel for providing the privacy and credential security to the wireless client. The developed authentication protocol has a reasonable set of features like; strong security, user privacy, simplicity and extensibility. For the formal analysis of the protocol we have used SPAN–AVISAP model checker on Ubuntu platform for validating the realization of the specified security goals. The experimental results obtained by simulation performed with the Automated Validation of Internet Security Protocols and Applications (AVISPA) tool shows that our protocol is efficient and secured.

     

Enhancing IEEE 802.11 MAC via a Sender-Initiated Reservation

The IEEE 802.11 MAC adopted a collision avoidance mechanism in which contending stations should wait a random backoff time before sending a frame. While the algorithm reduces the collision probability in general, a large number of stations may still experience heavy collisions thus decrease the throughput. In this paper, we propose a simple reservation scheme for enhancing the performance of multiple access in 802.11 MAC: when a transmitter sends a frame, if it has another frame to send in its output queue, it may reserve an additional time that is needed to send the next frame and receive an ACK for the frame. Thus a sender can occupy the medium for two data frames, while reducing the collision probability and improving channel utilization via the reservation. We develop a mathematical model to analyze the performance of proposed scheme, and perform simulations to evaluate its performance compared with the original MAC.     

A multichannel relay MAC protocol for IEEE 802.11 wireless LANs

One of the challenging issues in wireless LANs (WLANs) is improving the network throughput. One of the possible solutions for the issue is maximizing the number of concurrent transmissions. Although some protocols have been proposed to exploit transmission concurrency in WLANs, their performance depends on the degree of the interference among links. Also, it is hard to obtain interference information because of their dynamics. In this paper, we propose an enhanced medium access control (MAC) protocol for WLANs, named multichannel relay MAC (MRMAC), which is able to transmit multiple frames simultaneously without considering interference. To enable concurrent transmissions, MRMAC adopts the concept of frame relaying. Furthermore, MRMAC utilizes several nonoverlapping channels to eliminate interferences. Through extensive simulations, we found that MRMAC shows better performance than existing well‐known MAC protocols. Copyright © 2013 John Wiley & Sons, Ltd.     

IEEE802.11协议中关联业务的实现

本文着重分绍了802.11协议中关联/再关联的定义,以及关联业务的实现和实现所采用的工具库ACE.     

Design of a lightweight authentication scheme for IEEE 802.11p vehicular networks

With the growing popularity of vehicle-based mobile devices, vehicular networks are becoming an essential part of wireless heterogeneous networks. Therefore, vehicular networks have been widely studied in recent years. Because of limited transmission range of wireless antennas, mobile vehicles should also switch their access points to maintain the connections as conventional mobile nodes. Considering the inherent characteristics of vehicular networks such as dynamic topology and high speed, the question of how to implement handoff protocol under real-time scenarios is very important. IEEE 802.11p protocol is designed for vehicular networks for the long distance transmission. To reduce handoff latency for 802.11p protocol, the authentication phase is waived during the handoff. However, security is also very important for wireless communications, and authentication can forbid access from malicious nodes and prevent wireless communications from potential attacks. Thus, in this paper, a lightweight authentication scheme is introduced to balance the security requirements and the handoff performance for 802.11p vehicular networks. In our scheme, the access points are divided into different trust groups, and the authentication process is completed in a group-based method. Once a vehicle is authenticated by an access point group, during the handoff within the same group, few extra authentication operations are needed. As a result, there is no extra overhead introduced to the authentication servers. Simulation results demonstrate that our authentication scheme only introduces small handoff latency and it is ideal for vehicular networks.     

Enhancing the CSMA/CA of IEEE 802.15.4 for better coexistence with IEEE 802.11

Wireless Networks - Wireless technologies are very often used simultaneously for different applications in the same deployment area. This is more and more the case with the massive use of the...     

Enhancing IEEE 802.11n WLANs using group-orthogonal code-division multiplex

The definition of the next generation of wireless networks is well under way within the IEEE 802.11 High Throughput Task Group committee. The resulting standard, to be called IEEE 802.11n, is expected to be a backward-compatible evolution of the successful IEEE 802.11a/g systems also based on multicarrier techniques. It can be anticipated that 802.11n systems will outperform its predecessors in terms of transmission rate and/or performance, mainly, due to the use of multiple antennae technology for transmission and reception. In this paper we propose to incorporate group-orthogonal (GO) code division multiplex (CDM) into the IEEE 802.11n specifications to further enhance its performance. It is shown how GO-CDM can take full advantage of the diversity offered by the multiple antennae and multicarrier transmission by using an iterative maximum likelihood (ML) joint detector. Furthermore, the use of GO-CDM does not compromise the backward compatibility with legacy systems.     

Performance analysis of the IEEE 802.11 MAC protocol for wireless LANs

Wireless local area networks (WLANs) are extremely popular being almost everywhere including business, office and home deployments. The IEEE 802.11 protocol is the dominating standard for WLANs. The essential medium access control (MAC) mechanism of 802.11 is called distributed co‐ordination function (DCF). This paper provides a simple and accurate analysis using Markov chain modelling to compute IEEE 802.11 DCF performance, in the absence of hidden stations and transmission errors. This mathematical analysis calculates in addition to the throughput efficiency, the average packet delay, the packet drop probability and the average time to drop a packet for both basic access and RTS/CTS medium access schemes. The derived analysis, which takes into account packet retry limits, is validated by comparison with OPNET simulation results. We demonstrate that a Markov chain model presented in the literature, which also calculates throughput and packet delay by introducing an additional transition state to the Markov chain model, does not appear to model IEEE 802.11 correctly, leading to ambiguous conclusions for its performance. We also carry out an extensive and detailed study on the influence on performance of the initial contention window size (CW), maximum CW size and data rate. Performance results are presented to identify the dependence on the backoff procedure parameters and to give insights on the issues affecting IEEE 802.11 DCF performance. Copyright © 2005 John Wiley & Sons, Ltd.     

An adaptive quorum-based energy conserving protocol for IEEE 802.11 ad hoc networks

The lifetime of a mobile ad hoc network (MANET) depends on the durability of the mobile hosts' battery resources. In the IEEE 802.11 Power Saving Mode, a host must wake up at every beacon interval, to check if it should remain awake. Such a scheme fails to adjust a host's sleep duration according to its traffic, thereby reducing its power efficiency. This paper presents new MAC protocols for power saving in a single hop MANET. The essence of these protocols is a quorum-based sleep/wake-up mechanism, which conserves energy by allowing the host to sleep for more than one beacon interval, if few transmissions are involved. The proposed protocols are simple and energy-efficiency. Simulation results showed that our protocols conserved more energy and extended the lifetime of a MANET.     

IEEE802.11标准MAC性能分析和一种改进方法

介绍了IEEE802.11标准MAC协议的功能,详细分析在网络站点数量增加的环境下,影响这个网络运行性能的主要因素是冲突的增加和空闲时间段所造成的无线信道资源的浪费。在此基础上,可以采用较容易实现的方法对MAC协议进行改进,以获得更好性能。