Division of wireless AP channels in WLAN

What is a channel?

Channel is commonly referred to as frequency, which determines the frequency range within which the wireless AP communicates.

Considering that there is a signal overlapping area between two adjacent wireless APs, in order to ensure that the signal channels used in this area cannot overlap each other, specifically, the wireless APs whose signals overlap each other must use different channels. Otherwise, it is easy to cause interference between the signals of each wireless AP, thereby causing the overall performance of the wireless network to decline.

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Channel division of 2.4G frequency band

The bandwidth of the 2.4G frequency band is 83Mhz, which is divided into 13 channels. Each channel has a bandwidth of 22Mhz, which means that these channels must overlap. The following is a 2.4G channel map:

2.4G channel map

5.8G frequency band channel division

The 5.8G frequency band is divided into 13 channels. The frequency band is not continuous. The frequency band range of channels 36-64 is 5.150GHz-5.250GHz, and the frequency band range of channels 149-165 is 5.725GHz-5.845GHz. The channel bandwidth is adjustable, and you can choose 20Mhz or 40Mhz. That means these channels must have overlapping parts. The following is a 5.8G channel map:

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2.4G and 5.8G frequency bands do not overlap channels

2.4G frequency band non-overlapping channel planning solution

Among the 13 channels in the 2.4G frequency band above, select (1, 6, 11), (3, 8, 13) or (1, 5, 9, 13). You can see that the three channels in each group do not overlap, as shown in the following figure:

5.8G frequency band non-overlapping channel planning solution

The channel bandwidth in the above-mentioned 5.8G frequency band is adjustable, and there is basically no overlap in the channels with a bandwidth of 20MHz. The planning gives priority to the use of this channel bandwidth.

Considerations for selecting the number of wireless APs to deploy and the AP frequency band

For ordinary open spaces with an area of ​​less than 150 square meters, such as hotel public lounges, small bars, cafes, conference rooms, western restaurants and other areas, when the number of users is expected to not exceed 30, placing one wireless AP in each place can meet the needs.

If the environment is large with many obstructions, deploying too many APs may lead to interference in the same frequency band, resulting in poor and unstable signals. If deploying too few APs, there may be incomplete coverage and signal blind spots. In this case, you can choose dual-band AP products for coverage.

The frequency bands of wireless APs are divided into 2.4GHz and 2.4GHz&5.8GHz. Compared with single-band, dual-band has the advantages of faster speed and lower interference. It can be said that it is more suitable for the present and the future. Of course, dual-band APs are also more expensive.

Correctly select the installation point of the wireless AP

The WiFi signal is transmitted in a circular manner with the wireless AP as the center and scattered horizontally in all directions. It can be reflected or changed direction when encountering obstacles such as walls.

Install a wireless AP in a single room. Try to place it in the center of the hall. It is best to place it on the ceiling of the hall. If you install two wireless APs, place them at two opposite corners of the hall.

Seamless roaming of APs

The seamless roaming function of AP is very important in networking in a larger environment. For example, when you connect to the wireless Internet at point A in a shopping mall, you walk to point B and find that there is another wireless AP providing coverage. At this time, it is very cumbersome to re-enter the password to connect to the wireless network, which involves the seamless roaming problem of wireless AP.

The wireless AP sends a detection signal every 100ms, and the user end can judge the quality of the network connection based on it, and then decide which wireless AP to connect to. When the terminal roams between multiple wireless APs, the new service wireless AP notifies the original service AP through a wired form that a new connection has been established. The roaming protocol of wireless AP is not included in 802.11, and IAPP (Inter access point protocol) is likely to become the standard roaming protocol.

Wireless AP transmission power

The transmit power of a wireless AP determines the strength and distance of the transmitted wireless signal. The greater the transmit power, the stronger the signal strength and the longer the transmission distance. If the user environment is relatively simple, select an AP with normal transmit power. If the environment is complex and there are many terminal access users, it is better to select a high-power AP.

Of course, the greater the power of the wireless AP, the greater the radiation, and the country also has regulations on the maximum transmission power of wireless devices.

Understand external distractions

It is important to note that some electronic devices using the same frequency band as the wireless AP will affect the signal of the wireless AP, including microwave ovens, anti-theft facilities (shopping mall door inspections), and other high-power electronic devices. Therefore, when deploying APs, they should be 1-2 meters away from interference sources.

When there is a concrete wall between the AP and the terminal, the effective transmission distance is less than 5 meters. When there is a wooden wall and a glass wall between them, the effective transmission distance is about 15 meters.

Other points to note

The site selection during deployment must meet the construction requirements, and the technical parameters of the wireless AP coverage radius must be understood. The wireless AP must be high temperature resistant, moisture-proof, and support PoE power supply. It must be centrally managed using an AC controller, and the channel settings of adjacent APs must also be different.