Chapter 20. Faster Service: IEEE 802.11a

SOME OF THE MAIN TOPICS IN THIS CHAPTER ARE

Overview of the IEEE 802.11a Standard 302

Comparing 802.11a with 802.11b and 802.11g 306

IEEE 802.11a is a wireless networking specification that is designed to deal with the shortcomings of 802.11b networking. Although the rise of 802.11g networks clouded the prospects for 802.11a for awhile, many vendors have now recognized the benefits of using two separate wireless frequencies: 2.4GHz (802.11b/g) and 5GHz (802.11a).

IEEE 802.11b devices, which were the first to market (before the IEEE 802.11a standard was complete), were very popular for a short period, but they are limited for the most part to a maximum of 11Mbps bandwidth using radio frequencies in the 2.4GHz bandwidth. And, as with the subject of this chapter, you might not get the full bandwidth that the standard defines. This can depend on factors such as physical barriers to the radio frequencies and interference from other 2.4GHz devices. 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 by 802.11b hardware in the 2.4GHz bandwidth.

Note

The term wireless networking, used in this chapter as well as in Chapters 19, "IEEE 802.11g: Wi-Fi Pioneer"; 21, "The IEEE 802.11g Standard"; and 22, "Bluetooth Wireless Technology," 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.

Although 802.11a hardware has dropped in price relative to when it was introduced, it is still not nearly as inexpensive as 802.11b or its successor, 802.11g (which you will read about in the next chapter). Although IEEE 802.11a offers radio frequencies in the 5GHz band and data rates up to 54Mbps (about five times the maximum data rate of 802.11b), compatibility issues with existing 802.11b networks are among the major reasons that 802.11a networks are not as widespread as other 802.11-based networks.

Note

You might wonder, then, why IEEE 802.11b devices are so prevalent and inexpensive when compared to IEEE 802.11a. 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.