Cisco aironet 1522 Design And Deployment Manual page 17

Frequency depends on the regulatory domain in which the access point is installed. For additional
Note
information, refer to the
http://www.cisco.com/en/US/docs/wireless/access_point/channels/lwapp/reference/guide/lw_chp2.html
Table 3
Frequency Band Terms
UNII-1
UNII-2
UNII-2 Extended
ISM
1. UNII refers to the Unlicensed National Information Infrastructure.
2. ISM refers to Industrial Science and Mechanical.
Dynamic Frequency Selection
Previously, devices employing radar operated in frequency sub-bands without other competing services.
However, controlling regulatory bodies are attempting to open and share these bands with new services
like wireless mesh LANs (IEEE 802.11).
To protect existing radar services, the regulatory bodies require that devices wishing to share the newly
opened frequency sub-band behave in accordance with a protocol named Dynamic Frequency Selection
(DFS). DFS dictates that to be compliant, a radio devices must be capable of detecting the presence of
radar signals. When a radio detects a radar signal, it is required to stop transmitting to for at least 30
minutes to protect that service.The radio then selects a different channel to transmit on but only after
monitoring it. If no radar is detected on the projected channel for at least one minute then the new radio
service device may begin transmissions on that channel.
The process for a radio to detect and identify a radar signal is a complicated task that sometimes leads
to incorrect detects. Incorrect radar detections can occur due to a large number of factors, including due
to uncertainties of the RF environment and the ability of the access point to reliably detect actual
on-channel radar.
The 802.11h standard addresses DFS and Transmit Power Control (TPC) as it relates to the 5 GHz band.
DFS is to avoid interference with radar and TPC is used to avoid interference with satellite feeder links.
DFS is mandatory in the US for frequency bands 5250 to 5350, and 5470 to 5725. DFS and TPC are
Note
mandatory for these same bands in Europe. (See
Table 4
Cisco Aironet 1520, 1130, 1240 Series Wireless Mesh Access Points, Design and Deployment Guide, Release 6.0
OL-20213-01
Channels and Power Levels
Frequency Band
Description
1
Regulations for UNII devices operating in
the 5.15 to 5.25 GHz frequency band.
Indoor operation only,
Regulations for UNII devices operating in
the 5.25 to 5.35 GHz frequency band.
DFS and TPC are mandatory in this band.
Regulations for UNII-2 devices operating
in the 5.470 to 5.725 frequency band.
2
Regulations for UNII devices operating in
the 5.725 to 5.850 GHz frequency band.
provides a summary of those regulatory domains that require DFS support.
document at:
Model Support
1130, 1240
1130, 1240, 1522
1130, 1240, 1522
1130, 1240, 1522, 1524
Figure 8.)
Mesh Network Components
17