37
/
72
1
2401 – 2423
X
X
X
X
2
2406 – 2428
X
X
X
X
3
2411 – 2433
X
X
X
X
4
2416 – 2438
X
X
X
X
5
2421 – 2443
X
X
X
X
6
2426 – 2448
X
X
X
X
7
2431 – 2453
X
X
X
X
8
2436 – 2458
X
X
X
X
9
2441 – 2463
X
X
X
X
10
2446 – 2468
X
X
X
X
11
2451 – 2473
X
X
X
X
12
2456 – 2478
13
2461 - 2483
Table 2: Wifi channels in the 2.4 GHz frequency band
The 5 GHz U-NII band covers discontinued parts of the RF spectrum between 5.15GHz and 5.825GHz
and allows the use of unlicensed wireless systems. The U-NII band is divided into 4 different sub-
bands subjected to specific restriction (cf. Table 3).
Band
Frequency range
(MHz)
Number of
Wi-Fi
channels
Restriction
U-NII 1
5150 - 5250
4
Until recently
1
, limited to indoor
use only
U-NII 2
5250 – 5350
4
Requires use of radar detection
U-NII 2 extended
5470 – 5725
11
Requires use of radar detection
U-NII 3
5725 - 5825
4
Table 3 U-NII organization
Contrary to the channels defined on the 2.4 GHz band, the channels defined on the 5 GHz band do
not overlap each other.
As stated in Table 3, the U-NII 2 and U-NII2 extended sub-bands are also used by several radar
systems and can only be used by Wi-Fi access points using the Dynamic Frequency Selection (DFS)
and Transmit Power Control (TPC) algorithms. These two algorithms have been defined by the
IEEE802.11h standard and specify a set of procedures to detect and avoid interference with radar
systems operating in the U-NII 2 and U-NII 2 extended sub-bands.
Currently, the AirShare access points do not support DFS and TPC as specified in the IEEE 802.11h
standard and the list of the 5 GHz channels enabled for the different regional variants is displayed at
Table 4.
The 5 GHz band is much less used by non Wi-Fi devices than the 2.4 GHz band. Besides, many of the
older Wi-Fi devices only support the 2.4 GHz channels, meaning that the 5 GHz band is less crowded.