Summary
In this chapter, we've reviewed the basic building blocks of the 802.11 protocol and a bit of the history behind its creation.
To recap, the original 802.11 specification was ratified in 1997. It has three different physical layer definitions that operate at 1 and 2 Mbps: FHSS, DSSS, and IR. FHSS and DSSS (under the 1997 specification) operate at 2.4GHz. In 1999, 802.11b added DSSS support for 5.5 and 11 Mbps. Using DSSS at 2.4 GHz meant that 802.11b retained backwards compatibility with 802.11 cards (1997 spec) that used DSSS at 1 and 2 Mbps. 802.11a, however, achieved speeds of 54 Mbps using a different modulation technique called OFDM. 802.11a operates at 5 GHz, making it incompatible (but non-interfering) with 802.11b. In 2003, 802.11g ...
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