38
/
72
Moreover, 5 GHz channels do not overlap with each other.
As a result, the use of the 5 GHz
channels is most often the preferred choice when installing.
Channel
number
Frequency
range (MHz)
regional variant
NA
JP
EU
CN
36
5150 – 5170
X
X
x
40
5170 – 5190
X
X
X
44
5190 – 5210
X
X
X
48
5210 – 5230
X
X
X
149
5735 – 5755
X
X
153
5755 – 5775
X
X
157
5775 – 5795
X
X
161
5795 – 5815
X
X
165
5815 – 5835
X
X
Wi-Fi channel selection considerations
Wireless communication signals travel over the air. Therefore, two devices transmitting at the same
time, on the same frequency, and within range of one another, will interfere with each other. When the
interference is too strong, the packets transmitted by the Wi-Fi transmitter get so distorted that they
are no longer correctly understood by the receiver, and as a result these packets must be re-
transmitted. This causes a decrease in the actual data rate achieved between the transmitting and the
receiving Wi-Fi devices.
To limit the effect of interference between Wi-Fi devices, the 802.11 standard makes use of the
CSMA/CA and Clear-Channel Assessment (CCA) algorithms. Before sending a packet, the device
checks whether any other transmission is currently going on. If this is not case, the device can use the
channel and sends some packets. Otherwise, the device will do a random back-off and retry to access
the channel after a short period of time.
Even with the use of the CSMA/CA and CCA algorithms, the presence of too many Wi-Fi devices on
the same channel will have a negative impact on the maximum achievable data rate. Moreover, these
algorithms are inefficient against interferences coming from non-Wi-Fi devices or from Wi-Fi devices
operating on overlapping channels. Therefore, it is strongly recommended to select a Wi-Fi channel
with little to no congestion.
Site survey
Ideally, the selection of the Wi-Fi channel should be made after conducting a wireless site survey. This
site survey maps out the different sources of interference and the active RF systems.
Based on the results from the site survey, the least occupied channel can be found and selected for
each meeting room.