Publication of the 802.11 standard was only the beginning of wireless LAN standardization efforts. Several compromises were made to get the standard out the door, and a great deal of work was deferred for later. The 802.11 working group conducts its business publicly, and anybody can view their web site at http://grouper.ieee.org/ groups/802/11/ to get an update on the progress of any of these revisions to 802.11. As standards development progresses, many task groups post detailed reports, including the results of votes on different proposals.
Revisions to the standard are handled by Task Groups. Task Groups are lettered, and any revisions inherit the letter corresponding to the Task Group. For example, the OFDM PHY was standardized by Task Group A (TGa), and their revision was called 802.11a.
In the time since the publication of the first edition of this book, several standards revisions have been approved. 802.11g put the number 54 on boxes throughout the world. 802.11h made the underlying technology of 802.11a suitable for use in Europe, and convinced the U.S. government to open up additional spectrum in a worldwide harmonized band. For now, 802.11i has put security concerns largely to rest, and replaced them with demands for AES-based encryption.
Several new standards are worthy of note. 802.11 continues to be a fertile ground for the development of new technology. As a sign of its maturity, it is getting close to rolling over to double letters for its task groups!
Task group E: quality of service extensions
Compared to their wired cousins, wireless networks have limited capacity. Task group E is developing standards to provide quality of service (QoS) by operating multiple queues and reserving the medium. To further provide service quality, 802.11e will define a new coordination function, the hybrid coordination function (HCF), with new means of accessing the network. It will also define the block acknowledgment protocol to reduce the fraction of network operations devoted to overhead.
802.11e is taking a great deal of time to produce. (Originally, it was dedicated to both QoS and security, before security was split off into Task Group I, which has now completed its work.) Rather than hold implementations for the final standard, the industry has selected a subset of the current drafts for interim standardization as Wi-Fi Multi-Media (WMM; see http://www.wi-fi.org/OpenSection/wmm.asp). WMM is to 802.11e as WPA was to 802.11i. Both are snapshots of a standard in process.
Task group K: radio resources
Mobile telephone networks make extensive measurements of the radio network to optimize its use of radio capacity. Many 802.11 products make some efforts to monitor radio quality, but there is no standard way of doing so. Task group K is developing a standard for use with 802.11 that will enable access points to collect radio statistics and make intelligent operating decisions based on them. New measurement types are defined to allow 802.11 stations to collect information on noise distribution, the number of hidden stations, and the load on any particular operating channel.
Task group N: high-throughput (100+ Mbps) MIMO PHY
Four complete proposals were initially received by TGn. However, two of the proposals have been withdrawn, leaving only the two described in Chapter 15. In standards-committee votes, TGnSync has been drawing slightly more support than WWiSE. The two standards are quite dissimilar, so expect a fair amount of horse-trading to create the final standard.
Products based on a TGn proposal cannot yet be called "draft 802.11n" since there is no official working draft standard at this time, and it is doubtful that a single proposal will have been selected by the time this book is in print. Products cannot label themselves "pre-N" without risking revocation of Wi-Fi certification. As a result, many products based on one proposal or the other are self-labeled as MIMO.
More distant standards
Task group P is developing extensions to 802.11 for use in automobiles, called Wireless Access in Vehicular Environments (WAVE). Cars move at much higher speed, necessitating handoff improvements. It also includes peer-to-peer networking capabilities to build a mesh between cars. Unlike many other forms of 802.11, it would use licensed spectrum. It is designed initially as a standard method of toll collection and download of safety information, although some observers think that it may eventually replace cellular communications.
Task group R is developing roaming protocols. 802.11i preauthentication is limited in that it does not reduce the computational workload of roaming. TGr is defining protocols that will enhance roaming by moving key material around the network. In the January 2005 meeting, several proposals were eliminated from further consideration, which is an important step in moving towards the final standard.
Task group S is developing mesh networking standards for use in multi-hop environments. Standards development is in a very early stage.
Task group U will modify 802.11 so that it will work with other network technologies. Its goal is similar in scope to the 802.21 working group. TGu modifies 802.11 as necessary to work with other network technologies such as third-generation cellular networks, while 802.21 works on a framework independent of any network technology.
802.1X was originally designed for use on wired networks. Its use on wireless networks has been subject to a number of ad hoc standards that are essentially implementation agreements, and the integration of wired access control on wireless networks was messy. 802.1X-2004 specified a new version of EAPOL, and clarified the operation of the two state machines. It has not yet been widely implemented, but it will almost assuredly come to the market soon.
As more users adopt many types of wireless technology, each with its own niche of range and distance, inter-network handoff between complementary networks has moved to the fore. For example, many mobile professionals use 802.11 networks while sitting in hot spots and high-speed cellular data while in the car. Transferring a session between two disparate network types is the focus of the IEEE 802.21 working group.
Introduction to Wireless Networking
Overview of 802.11 Networks
11 MAC Fundamentals
11 Framing in Detail
Wired Equivalent Privacy (WEP)
User Authentication with 802.1X
11i: Robust Security Networks, TKIP, and CCMP
Contention-Free Service with the PCF
Physical Layer Overview
The Frequency-Hopping (FH) PHY
The Direct Sequence PHYs: DSSS and HR/DSSS (802.11b)
11a and 802.11j: 5-GHz OFDM PHY
11g: The Extended-Rate PHY (ERP)
A Peek Ahead at 802.11n: MIMO-OFDM
Using 802.11 on Windows
11 on the Macintosh
Using 802.11 on Linux
Using 802.11 Access Points
Logical Wireless Network Architecture
Site Planning and Project Management
11 Network Analysis
11 Performance Tuning
Conclusions and Predictions