April 2005
Beginner to intermediate
670 pages
22h 56m
English
Content preview from 802.11 Wireless Networks: The Definitive Guide, 2nd EditionBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Chapter 13. 802.11a and 802.11j: 5-GHz OFDM PHY
Go West, young man, and grow up with the country!
— John B.L. Soule[57]
The 2.4 GHz ISM bands are crowded, and often choked with non-802.11 traffic. In an attempt to develop higher data rates, the 802.11 working group standardized a physical layer using unlicensed spectrum around 5 GHz. Large tracts of undeveloped spectrum were available for unlicensed use, and far fewer devices have used the spectrum.
802.11a was standardized in 1999, but it took a significant amount of time to bring products to market. 802.11a hardware finally hit the market in late 2001. Today, the best known manufacturer of 802.11a chipsets is Atheros Communications. In form and function, they look similar to any other wireless LAN card. Most are CardBus cards, although some additional form factors are used more widely now. The range of very high data rates is quite short, but generally, 802.11a has a comparable data rate to 802.11b at comparable distance.
Initially, 802.11a was designed for the 5-GHz Unlicensed National Information Infrastructure (U-NII) bands in the United States. With the success of 802.11a in the American market, other regulators developed rules to allow 802.11a. The 802.11 working group supported these efforts through 802.11h for Europe, which was discussed in Chapter 8, and 802.11j for Japan.
This chapter begins with a qualitative introduction to the basis of OFDM. When all the mathematical formalism is stripped away, OFDM is a method for chopping ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.