IEEE 802.11 Physical Layers

IEEE 802.11 Physical Layers
The 802.11 standard specifies several Physical layers. The initial standard approved in 1997
included frequency hopping and direct sequence spread spectrum, delivering data rates of 1
and 2Mbps in the 2.4GHz band. This initial release also defined an infrared Physical layer
operating at 1 and 2Mbps via passive ceiling reflection. The current 802.11 standard, released
in December 1999, added an 11Mbps, high-rate version direct sequence standard commonly
referred to as IEEE 802.11b. In addition, the current standard defines a Physical layer using
OFDM (orthogonal frequency division multiplexing) to deliver data rates of up to 54Mbps in
the 5GHz frequency band. Refer to Chapter 5, “IEEE 802.11 Physical (PHY) Layer,” for more
details on these standards As with the IEEE 802.3 standard, the 802.11 working group is considering additional PHYs as
applicable technologies become available.