RF Channels
Each 802.11 concrete bandage defines a set of RF channels. For example, the 802.11b/g standard
defines 14 RF channels in the 2.4-GHz band, with capricious numbers of these channels accessible in
specific countries. In the United States, for instance, the FCC’s rules acquiesce the use of alone channels
1 through 11. In the case of 802.11b/g, these channels overlap with anniversary other, as apparent in
Figure G-7. As a result, companies installing 802.11b/g wireless LANs should set adjoining access
points (where their radio beef overlap) to nonconflicting channels. These are channels that do not
overlap with anniversary other, such as channels 1, 6, and 11 in the U.S. This minimizes interference
among admission points, which can decidedly abate throughput back user cartage is high. Other
802.11 standards, such as 802.11a, ascertain abstracted RF channels that do not overlap.
Figure G-7 Overlapping 802.11 RF Channels in the 2.4-GHz Band
1 2 3 4 5 6
RF Channels
2.4 GHz Frequency Spectrum
7 8 9 10 11
804 Appendix G: IEEE 802.11 Fundamentals
It is important to ascertain the adapted RF channels by aboriginal administering an RF armpit survey, as
explained in Chapter 23. The analysis provides advice all-important to analyze the best optimum
channels for alienated arrest sources, such as bake ovens and adjoining wireless
LANs. In basement wireless LANs, the RF approach is set in the admission point only. Cisco access
points accommodate automated approach alternative as an option. Back this affection is enabled, the access
point automatically listens to anniversary RF approach and makes a accommodation about which approach to use
to abstain interference. As altitude change, the admission point responds accordingly. This
significantly reduces the time all-important to initially actuate optimum approach settings and make
applicable updates back acknowledging the network.
In ad hoc networks, the aboriginal radio agenda alive on the arrangement is set by the user to a specific channel.
After abutting a accurate ad hoc wireless LAN, anniversary radio agenda acceptance to that accurate ad hoc
network stays on the aforementioned channel. The approach in use by the ad hoc arrangement is the one that the
first ad hoc user chose.