Matthew Gast - 802.11n: A Survival Guide

In memory of Nicholas A. Jeremica

(December 5, 1977 - December 12, 2006)

And for Maria, Max, and Nicole,

who no doubt miss him even more than I do

Communications is changing our life in many ways. Our society is increasingly dependent on wireless communications technologies and the applications they support. In the same way that we cant understand how the folks who lived in 1800 managed without anesthesia, television, (insert favorite must-have technology here), our children wont understand how we managed to grow up without on-the-go email, social networking, (insert technology x[] here).

IEEE 802.11 is a fundamental component of todays wireless communications technology. We have seen a rapid penetration of this technology into the enterprise (replacing or augmenting wired networks), home (wireless routers) and public spaces (airports, hotels). It is now no longer an optional feature, but an end-user expectation. IEEE 802.11n is the current must-have standard for wireless LAN that provides increased throughput and supports new applications and usage models. This book describes the development and operation of the 802.11n communications protocol. It provides background for understanding the impact of various features and settings on network operation and deployment. It is recommended reading for networking professionals and those who are curious as to what goes on under the hood. I have known Matthew Gast through our work together in the IEEE 802.11 working grouphe as chair of 802.11REVmb and I as its technical editor. He writes clearly with a minimum of jargon and a maximum of relevant example usage. His personal experience of wireless LAN standards development, product development, and product deployment shines through. He has turned what might be a dry subject into a surprisingly easy read.[] So, throw another log on the fire, pour your favorite libation, put your feet up, and settle down to

People still move. Networks still dont.

A decade ago, I first wrote that people moved, and networks needed to adapt to the reality that people worked on the go. Of course, in those days, wireless LANs came with a trade-off. Yes, you could use them while moving, but you had to trade a great deal of throughput to get the mobility. Although it was possible to get bits anywhere, even while in motion, those bits came slower. As one of the network engineers I worked with put it, Weve installed switched gigabit Ethernet everywhere on campus, so I dont understand why youd want to go back to what is a 25-megabit hub. He underestimated the allure of working on the go.

In the rubble of the early 2000s Internet bust, wireless LANs were one of the first new technologies to cut through the gloom. As they gained in popularity, they morphed from an expensive toy to show off and became a must-have technology. My apartment had a wireless LAN very early, and I remember when I showed it off with pride. In the days of 2 Mbps 802.11 networks (or, if you were rich, an 11 Mbps 802.11b network!), all you had to do was beat the speed of your Internet link, which was not particularly hard.

What made 802.11n the next big step in the wireless revolution is that it was the first time that a wireless LAN delivered reasonable performance. Wireless LANs first took root in industries with highly mobile employees: hospital medicine, logistics, and education. Trading speed for mobility is a good exchange when you are on the move. It looks less attractive when you are relatively stable. 802.11n was the technology that buried the trade-off of speed for mobility. For the first time, it was possible to build a wireless network without compromise.

To build your network without wires, you dont have a choice: youre about to get familiar with 802.11n.