Instructors: Amjad Soomro and Sai Shankar, Philips Research, USA

Since the adoption of IEEE 802.11 standard in 1999, it has been a remarkable success, which has seen its application range from data oriented computer communication to demanding multimedia applications such as voice and video. In response to growing applications and scarcity of limited unlicensed wireless spectrum, IEEE 802.11 has evolved over the years to use higher physical media transmission rates and cover additional unlicensed spectrum. The additional PHY layer protocols were developed to be compatible with the legacy IEEE 802.11 standard.

However, even as the wireless network was being widely deployed some weaknesses in the original MAC protocol got more scrutinized. For example, the WEP security mechanism in the protocol was shown vulnerable to attacks with the commonly available tools in as little as ten minutes. Secondly, in the European domains, there are some additional requirements on transmit power control and dynamic frequency selection which the original protocol did not address. Thirdly, looking at the future of networking real-time two-way and multimedia streaming applications took on increasing significance. While the IEEE 802.11 protocol was designed to provide good performance for data centric applications, the legacy MAC protocol did not provide mechanisms to ensure QoS for the applications served.

The IEEE 802.11 standard is an evolving standard as the legacy standard is continuously being amended to improve and address deficiencies mentioned above. This tutorial provides a comprehensive review of the current IEEE standard along with its amendments. Then it provides an in-depth look at the shape of the wireless network of tomorrow by covering the current work on the requirements of the future amendments of the protocol and the proposed means to address these.

First, the tutorial provides a review of the legacy MAC standard. The channel characteristics unique to wireless medium and the resulting effects on the protocol will be outlined. Then, mechanisms added in the standard to mitigate their harmful effects will be discussed.

Next the physical layer enhancement both in 2.4 GHz and 5 GHz bands, namely b, g and a, will be covered. The MAC-PHY interface will be presented and the main modulation blocks and their operation will be described. The mechanism for changing PHY rates and some practical aspects of link adaptation will be covered.

On the MAC side, protocol amendments related to: 1) geographical information, IEEE 802.11d; 2) inter access point protocol, IEEE 802.11f; and, 3) Dynamic frequency selection (DFS) and transmit power control (TPC), IEEE 802.11h, will be discussed in detail. The DFS and TPC amendment was driven by the European regulatory requirement that all LANs operating in 5 GHz be able to detect radars in operating band and be able to change operating channel and/or reduce transmit power when radars are detected. The mechanism added in the protocol could be considered as an example for upcoming spectrum agile radios technologies that are being discussed elsewhere.

IEEE 802.11 task group Œe¹ is working on an amendment to the protocol to address QoS needs of multimedia and real-time applications. Specifically, a hybrid coordination function (HCF) consisting of enhanced distributed contention access (EDCA) method and hybrid controlled contention access (HCCA) method are being proposed. Both mechanisms will be presented in detail and some published performance analysis will be presented.

IEEE 802.11 standards provides optional WEP security protection and the mechanism was thought to provide security equivalent to wired networks. However, under greater scrutiny vulnerabilities in this protocol were published which showed that it can be broken with commonly available equipment. IEEE 802.11i amendment to the standard provides enhancements to the security mechanism. This amendment will be covered in detail.

As the IEEE 802.11 protocol is being deployed in enterprise environments and commercial services are being offered over this technology, the need developed to measure and monitor the wireless environment in which the network is operating. In response, IEEE 802.11 task group k was formed to amend the standard to include mechanisms and protocols for radio resource measurement. Finally, a brief overview will be given of the scope of the work being conducted in study groups addressing wireless network management, fast roaming, ESS mesh networking, wireless access for vehicular environments and wireless performance prediction.

Amjad Soomro received his Ph.D degree from U. of Maryland at College Park in 1994 in electrical engineering. He is currently working as a Senior Member Research Staff ­ Project Leader, Wireless Communications and Networking, Philips Research, Briarcliff Manor, NY. He has been actively contributing in IEEE 802.11 standardization working group since 2000. He has made major contributions in IEEE 802.11k and IEEE 802.11e amendments. Prior to that he worked at Hewlett-Packard, Spokane Division from 1994-1999 where he developed and analyzed DSP algorithms for AMPS and GSM for HP8960 mobile phone/base station test equipment. He has 4 publications in international journals and over 30 patents pending related to LAN networking and optical communications. He was elected in Who's Who Amongst Students in American Universities and Colleges, in 1992.

Sai Shankar N received his PhD degree from the department of Electrical Communication Engineering from Indian Institute of Science, Bangalore, India in the area of ATM networks. In 1998, He was awarded the German Fellowship, DAAD, in the department of mathematics, University of Kaiserslautern, Gernany to work on queueing approaches in manufacturing. In 1999, he joined Philips Research, Eindhoven, the Netherlands, where he served as Research Scientist in the department of New Media Systems and Applications. He worked on various problems involving Hybrid, Fiber, Co-axial Cable (IEEE 802.14) Networks and IP protocols and provided efficient algorithms to improve protocol efficiency. In the year 2001 he joined Philips Research USA, Briarcliff Manor, NY and is working in the area of Wireless LANs. He is an active contributor of the wireless LAN standard and has submitted more than 15 proposals in shaping QoS related issues in the IEEE 802.11e. He is leading on proposals related to traffic specification in the 802.11e. He is also an active participant in the Ultra Wide Band (UWB) working group of IEEE 802.15.3 Multi-Band OFDM Alliance (MBOA) and is contributing in shaping the new MAC. Also Sai Shankar is a participant in IEEE 802.11n (High Throughput Study Group), a new standard that will define the wireless MAC that provides high throughput. Besides he is an IEEE Standards Association voting member. He was reviewer for ICICS 2001, Globecom 2001-2004, WCNC 2002-2004, ICME 2003, Infocom 2003-2004, VTC 2003-2004, special issue on WLANs in ACM Mobile Networks journal, IEEE Transactions on Multimedia and ACM Wireless Networks. He is the TPC member of IEEE Globecom 2004 organizing a workshop on mobile applications and also TPC member of workshop on Wireless LAN hotspots organized in conjunction with ACM Mobicom 2004. He is currently editing a book on ³Recent Trends in WLANs² that will be published by Wiley Interscience in Dec. 2004. He was the session chair of Networks performance evaluation session in IEEE ICICS 2001, Wireless Networks session, Chair and TPC member of 2nd New York Metro Area Workshop and the TPC member of 3rd New York Metro Area workshop. He is organizing a workshop on Broadband wireless Applications and services in California in conjunction with Broadnets 2004. He has authored more than 28 conference and journal papers, 11 accepted standard contributions and holds more than 25 patents.

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