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IEEE 802.11a uses Orthogonal Frequency Division Multiplexing (OFDM), a
new encoding scheme that offers certain benefits over a spread spectrum in
channel availability and data rate. The 802.11a uses OFDM to define a total of 8
non-overlapping 200 MHz channels across the 2 lower bands; each of these is
divided into 52 subcarriers and each carrier is approximately 300 KHz wide. By
comparison, 802.11b uses only 3 non-overlapping channels.
IEEE 802.11a Channel Allocations