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Fat AP and Cloud AP V200R008C00 CLI-based Configuration Guide

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Huawei uses machine translation combined with human proofreading to translate this document to different languages in order to help you better understand the content of this document. Note: Even the most advanced machine translation cannot match the quality of professional translators. Huawei shall not bear any responsibility for translation accuracy and it is recommended that you refer to the English document (a link for which has been provided).
Radio Calibration

Radio Calibration


On a WLAN, the 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. Radio calibration can dynamically adjust channels and power of APs to ensure that the APs work in a way that optimizes 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 11-1.

    For channels supported in different countries, see the Country Code & Channel Compliance Table. You can obtain this table at Huawei technical support website.
    Figure 11-1  Channels on the 2.4 GHz frequency band

    The 5 GHz frequency band has even richer spectrum resources. In addition to 20 MHz channels, APs working on the 5 GHz frequency band support 40 MHz and 80 MHz channels, as shown in Figure 11-2.
    Figure 11-2  Channels
    • Two neighboring 20 MHz channels are bundled into a 40 MHz channel. One of the two 20 MHz channels is the primary channel, and the other the auxiliary channel. The primary channel is used for transmission of the management and control packets, and the auxiliary channel for other packets, including the data packets.
    • Two neighboring 40 MHz channels are bundled into an 80 MHz channel. In an 80 MHz channel, one 20 MHz channel is selected as the primary channel. The other 20 MHz channel making up the 40 MHz channel with the primary channel is called the auxiliary 20 MHz channel. The 40 MHz channel not containing the primary channel is called the auxiliary 40 MHz channel.

    Figure 11-3 shows an example of 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 11-3  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 can 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 with 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. Power adjustment works according to the following:
    • When an AP is added to the network, the transmit power of neighboring APs decreases, as shown in Figure 11-4. The area of the circle around an AP represents the AP's coverage area after transmit power adjustment. When AP4 is added to the network, the transmit power of each AP decreases automatically.
    Figure 11-4  Transmit power of APs decreases

    • When an AP goes offline or fails, power of neighboring APs increases, as shown in Figure 11-5.
    Figure 11-5  Transmit power of APs increases


Radio calibration is implemented as follows:
  1. After radio calibration is enabled, the AP periodically implements neighbor probing.
  2. The AP periodically implements neighbor probing.
  3. The device executes radio calibration algorithms to adjust AP power and working channels.

    The radio calibration algorithm includes the Dynamic Channel Allocation (DCA) algorithm and Transmit Power Control (TPC) algorithm.

Updated: 2019-01-11

Document ID: EDOC1000176006

Views: 118817

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