Radio Calibration

Overview

On a WLAN, operating status of APs is affected by the radio environment. For example, adjacent APs using the same working channel interfere with each other, and a large-power AP can interfere with adjacent APs if they work on overlapping channels. The radio calibration function can dynamically adjust channels and power of APs to ensure that the APs work at the optimal performance.

• Channel adjustment

  On a WLAN, adjacent APs must work on non-overlapping channels to avoid radio interference. For example, the 2.4 GHz frequency band is divided into 14 overlapping 20 MHz channels, as shown in Figure 3-1.

  For channels supported in different countries, see the Country Code & Channel Compliance Table. You can search and obtain this table at https://support.huawei.com/enterprise.

  Figure 3-1 Channels in the 2.4 GHz frequency band
  
  

  Figure 3-2 shows the channel distribution before and after channel adjustment. Before channel adjustment, both AP2 and AP4 use channel 6. After channel adjustment, AP4 uses channel 11 so that it does not interfere with AP2.

  After channel adjustment, each AP is allocated an optimal channel to minimize or avoid adjacent-channel or co-channel interference, ensuring reliable data transmission on the network.

  Figure 3-2 Channel adjustment
  
  

  In addition to optimizing radio performance, channel adjustment can also be used for dynamic frequency selection (DFS). In some regions, radar systems work in the 5 GHz frequency band, which interfere with radio signals of APs working in the 5 GHz frequency band. The DFS function enables APs to automatically switch to other channels when they detect interference on their current working channels.

• Power adjustment

  An AP's transmit power determines its radio coverage area. APs with higher power have larger coverage areas. A traditional method to control the radio power is to set the transmit power to the maximum value to maximize the radio coverage area. However, a high transmit power may cause interference to other wireless devices. Therefore, an optimal power is required to balance the coverage area and signal quality.

  The power adjustment function helps dynamically allocate proper power to APs according to the real-time radio environment.

  • When an AP is added to the network, the transmit power of neighboring APs decreases. As shown in Figure 3-3, the area of the circle around an AP represents the AP's transmit power and coverage area. When AP4 is added to the network, transmit power of each AP decreases automatically.

  Figure 3-3 Transmit power of APs decreases
  
  

  • When an AP goes offline or fails, power of neighboring APs increases, as shown in Figure 3-4.

  Figure 3-4 Transmit power of APs increases
  
  

Implementation