Chapter 21. Faster Service: IEEE 802.11a

SOME OF THE MAIN TOPICS IN THIS CHAPTER ARE

Overview of the IEEE 802.11a Standard

IEEE 802.11a is a wireless networking specification that has a future, but what that future will be is not yet known. You can expect in the future to see additional radio frequency bandwidths devoted to wireless networking, so the frequencies used by 802.11a may soon be superceded by other frequencies. Today the two main radio frequencies used for wireless LAN devices are the 2.4GHz and 5GHz frequencies. In the future, as wireless networking becomes an essential factor in everyday use, you will see newer encoding techniques in these bandwidths, as well as re-allocation of some current frequencies. Wireless networking has a great future, and I can only begin to speculate about the possibilities. The addition of the 2.4GHz spectrum to the 5GHz for wireless networks is indicative of this progress. Future expansion will depend on the addition of more radio frequencies, as well as new methods for modulating data on the available frequencies so that as time goes by, faster data rates are inevitable.

IEEE 802.11b devices, which were the first to market (before the IEEE 802.11a standard was complete) are very popular, but they are limited for the most part to about 11Mbps bandwidth using radio frequencies in the 2.4GHz bandwidth. And, as with the subject of this chapter, you may not get the full bandwidth that the standards define. This can depend on many factors, from barriers to the radio frequencies (because these are at the lower radio frequency spectrum). That is one advantage that the 5GHz spectrum gives you over the 2.4GHz spectrum. The 5GHz spectrum offers a larger bandwidth for wireless communications, and it uses a modulation technique that is superior to those used in the 2.4GHz bandwidth.

Note

The term wireless networking , used in this chapter as well as in Chapters 20, 22, and 23, refers to wireless methods for exchanging data over small distances to form a LAN. For transmitting data over longer distances (to create a WAN), another form of wireless networking is used: microwaves . This form of transmission has been in use for years by telephone companies, and more recently in campus networks where it is too costly to use copper or fiber- optic cables.

If it were not for a newer specification, IEEE 802.11g (which you will read about in the next chapter), one would think that as prices begin to drop over time, IEEE 802.11a would overtake the now-inexpensive 802.11b hardware. The increased bandwidth and declining costs should be a driving factor. 802.11a uses radio frequencies in the 5GHz band , and this enables it to provide a data rate of up to 54Mbps. That is almost five times the speed of 802.11b. There are a few other reasons why 802.11a might not get off to a speedy start, and these are discussed later in this chapter.

Note

You might wonder , then, why IEEE 802.11b (Wi-Fi) devices are so prevalent , and inexpensive, when compared to IEEE 802.11a (also known now as Wi-Fi 5 by a trade industry association). What was the reason that 802.11b-compatible hardware was the first to market?

The answer is simple. It took longer to develop the "a" standard than the "b" standard (people on a committee shouldn't argue so much). While the IEEE working group was still working on the 802.11a standard, 802.11b was finished, and manufacturers were anxious to start producing hardware for a new market: wireless networking.