The Ieee 802.11B Specification - Proxim Harmony 8550 Manual

The IEEE 802.11b Specification

In 1997, the Institute of Electrical and Electronics Engineers (IEEE) adopted the 802.11
standard for wireless devices operating in the 2.4 GHz frequency band. This standard
includes provisions for three radio technologies: direct sequence spread spectrum, fre-
quency hopping spread spectrum, and infrared. Devices that comply with the 802.11
standard operate at a data rate of either 1 or 2 Mbps.
In 1999, the IEEE created the 802.11b standard. 802.11b is essentially identical to the
802.11 standard except 802.11b provides for data rates of up to 11 Mbps for direct
sequence spread spectrum devices. Under 802.11b, direct sequence devices can operate
at 11 Mbps, 5.5 Mbps, 2 Mbps, or 1 Mbps. This provides interoperability with existing
802.11 direct sequence devices that operate only at 2 Mbps.
Direct sequence spread spectrum devices spread a radio signal over a range of frequen-
cies. The IEEE 802.11b specification allocates the 2.4 GHz frequency band into 14
overlapping operating Channels. Each Channel corresponds to a different set of frequen-
cies. See Appendix B to determine the center frequency used by each Channel.
If operating multiple 802.11b Access Points in the same vicinity, the distance between
the center frequencies must be at least 25 MHz to avoid interference. Note that the
Channels available to an 802.11b Access Point will vary from country to country.
In the United States, the 802.11b standard allocates 11 operating Channels for direct
sequence devices. Channels 1, 6, and 11 are independent and do not overlap with each
other. To avoid interference between 802.11b Access Points, Proxim recommends that
you configure the Access Points using only Channels 1, 6, and 11 (if available).
The 802.11b operating parameters are described in Chapter 5.
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