Amazon.co.uk Review
The only significant detail that's been excluded has to do with security--a notorious weak point of 802.11x LANs. The authors cover the feeble-but-widely-used Wired Equivalent Privacy (WEP) authentication protocol in detail, and devote another whole chapter to 802.1x, which is an emerging authentication scheme based on Extensible Authentication Protocol (EAP). The author has considerable skill in communicating information graphically, and does a great job of using graphs to show how communications frequencies shift over time and how conversations among access points and network nodes progress over time. This is indeed an authoritative document. --David Wall
Topics covered: How IEEE 802.11a and 802.11b wireless networks (also known as WiFi networks) work, and how to configure your own. The framing specification is covered well, as are authentication protocols and (in detail) the physical phenomena that affect IEEE 802.11x radio transmissions. There's advice on how to design a wireless network topology, and how to go about network traffic analysis and performance improvement. --This text refers to an alternate Paperback edition.
Review
Major Keary, Book News 2002 No. 10
Craig Pfeifer, slashdot.org, July 1, 2002
Ben Rothke, unixreview.com, July 2002
Joel Snyder, Network World, August 2002
Joel Snyder, Network World, August 2002
Danny Kalev, IBM developerworks, Sept 2002
Tim Higgins, Smallnetbuilder,com, Feb 2003
Product Description
As we all know by now, wireless networks offer many advantages over fixed (or wired) networks. Foremost on that list is mobility, since going wireless frees you from the tether of an Ethernet cable at a desk. But that's just the tip of the cable-free iceberg. Wireless networks are also more flexible, faster and easier for you to use, and more affordable to deploy and maintain.
The de facto standard for wireless networking is the 802.11 protocol, which includes Wi-Fi (the wireless standard known as 802.11b) and its faster cousin, 802.11g. With easy-to-install 802.11 network hardware available everywhere you turn, the choice seems simple, and many people dive into wireless computing with less thought and planning than they'd give to a wired network. But it's wise to be familiar with both the capabilities and risks associated with the 802.11 protocols. And 802.11 Wireless Networks: The Definitive Guide, 2nd Edition is the perfect place to start.
This updated edition covers everything you'll ever need to know about wireless technology. Designed with the system administrator or serious home user in mind, it's a no-nonsense guide for setting up 802.11 on Windows and Linux. Among the wide range of topics covered are discussions on:
- deployment considerations
- network monitoring and performance tuning
- wireless security issues
- how to use and select access points
- network monitoring essentials
- wireless card configuration
- security issues unique to wireless networks
From the Publisher
About the Author
Matthew Gast works in the Office of the CTO at Trapeze Networks, where he leads the development of open wireless network standards and their application to the Trapeze architecture. He is a member of the IEEE 802.11 working group, and serves as chair of 802.11 Task Group M. As chair of the Wi-Fi Alliance's Wireless Network Management marketing task group, he is leading the investigation of certification requirements for power saving, performance optimization, and location and timing services. Matthew also chairs the Security Technical task group, which is extending Wi-Fi protected Access (WPA) certification to incorporate newly-developed security mechanisms so that it remains the strongest form of protection available for Wi-Fi networking. In 2007, Matthew was a founder of the OpenSEA Alliance, a group organized to support the development of open-source network security solutions. He currently serves on the engineering steering committee, the organization's board of directors, and as its corporate secretary. Matthew's most recent book, 802.11 Wireless Networks: The Definitive Guide (O'Reilly Media), now in its second edition, is the top selling reference work in the field and has been translated into six languages.
Excerpted from 802.11 Wireless Networks the Definitive Guide by Matthew Gast. Copyright © 2005. Reprinted by permission. All rights reserved.
802.11 task group N (TGn) has an interesting goal. Most IEEE task groups focus on increasing the peak throughput, making data fly as fast as possible during the time it is being transmitted. TGn’s goal is to achieve 100 Mbps net throughput, after subtracting all the overhead for protocol management features like preambles, interframe spacing, and acknowledgments. Although the goal is 100 Mbps net throughput, the final proposal seems certain to blow past that number, and offer many times that throughput in maximum configurations. There are two roads to 100 Mbps: improve the efficiency of the MAC, increase the peak data rate well beyond 100 Mbps—or both.
Six complete proposals were made to the group creating the eventual 802.11n, but support has coalesced around two main proposals, from groups named TgnSync and WWiSE (short for "World-Wide Spectrum Efficiency"). Both camps have chipmakers. Atheros, Agere, Marvell, and Intel are part of TGnSync; Airgo, Broadcom, Conexant, and Texas Instruments are the core of WWiSE. However, quite a few manufacturers of electronic devices that might use 802.11 (Cisco, Nokia, Nortel, Philips, Samsung, Sanyo, Sony, and Toshiba) have also become part of the effort, and they are disproportionately represented in TGnSync.
At a very high level, both proposals are similar, though they differ in the emphasis on increasing peak data rates versus improving efficiency. Each of them makes use of multiple-input/multiple-output (MIMO) technology in several configurations and provides for backwards compatibility with installed systems in the same frequency band. Both support operation in the current 20 MHz channels, with provisions to use double-width 40 MHz channels for extra throughput.
As the standards war is fought across the globe at IEEE meetings, a "pre-N" access point has already hit the streets, based on Airgo’s chipset. Purchasing it well before the standards process is underway is a roll of the dice. When most "pre-G" products were brought to market, the task group had begun to work in earnest on a single proposal. TGn is currently in the "dueling proposal" stage right now, and there is no guarantee that an early device will be firmware upgradeable to the final 802.11n standard. 802.11nis likely to be the last chance to standardize a PHY this decade. Developing a standard is as much political engineering as technical engineering. IEEE rules require that a proposal get a 75% supermajority vote before becoming the basis for a standard. As this book went to press, TGnSync was garnering a clear majority of support, but was still falling short of the necessary 75%. I expect that features from competing proposals will be incorporated into the working document to bring the vote count to the necessary level. As a result, this chapter describes both of the main competing proposals. Although TGnSync will probably be the basis for the 802.11n specification, some horse trading will likely result in a few WWiSE features being incorporated.
This chapter describes both the WWiSE and TGnSync proposals. The final standard will have some resemblance to both of them, and will likely pick and choose features from each. Fortunately, many basic concepts are shared between the two. As you read this, keep in mind that the proposals themselves may have changed quite a bit since the drafts upon which this chapter was based were written.
Common Features
Although the two proposals are different, there is a great deal of similarity between the two. Practically speaking, some features are required to reach the goal of 100 Mbps throughput.
Multiple-Input/Multiple-Output (MIMO)
Up until 2004, 802.11 interfaces had a single antenna. To be sure, some interfaces had two antennas in a diversity configuration, but the basis of diversity is that the "best" antenna is selected. In diversity configurations, only a single antenna is used at any point. Although there may be two or more antennas, there is only one set of components to process the signal, or RF chain. The receiver has a single input chain, and the transmitter has a single output chain.
The next step beyond diversity is to attach an RF chain to each antenna in the system. This is the basis of Multiple-Input/Multiple-Output (MIMO) operation.* Each RF chain is capable of simultaneous reception or transmission, which can dramatically improve throughput. Furthermore, simultaneous receiver processing has benefits in resolving multipath interference, and may improve the quality of the received signal far beyond simple diversity. Each RF chain and its corresponding antenna are responsible for transmitting a spatial stream. A single frame can be broken up and multiplexed across multiple spatial streams, which are reassembled at the receiver. Both the WWiSE and TGnSync proposals employ MIMO technology to boost the data rate, though their applications differ.
* MIMO is pronounced "MyMoe." I attended a symposium in which a standards committee attendee described the standardization vote on the acronym’s pronunciation.
MIMO antenna configurations are often described with the shorthand "YxZ," where Y and Z are integers, used to refer to the number of transmitter antennas and the number of receiver antennas. For example, both WWiSE and TGnSync require 2x2 operation, which has two transmit chains, two receive chains, and two spatial streams multiplexed across the radio link. Both proposals also have additional required and optional modes. I expect that the common hardware configurations will have two RF chains on the client side to save cost and battery power, while at least three RF chains will be used on most access points. This configuration would use 2x3 MIMO for its uplink, and 3x2 MIMO on the downlink.
