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Fat AP and Cloud AP V200R008C00 CLI-based Configuration Guide

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Smart Roaming

Smart Roaming


Some terminals on networks have low roaming aggressiveness. As a result, they stick to the initially connected RUs regardless of whether they move far from the RUs, and have weak signals or low rates. The terminals fail to roam to neighboring RUs with better signals. They are called sticky terminals.

Sticky terminals may bring the following problems:
  • Poor service experience: The terminals stick to weak-signal RUs, causing a sharp decrease in the wireless channel rate.
  • Channel performance degradation: The terminals have poor signals or low rates, and frequent packet loss and retransmissions occur. As a result, the terminals occupy the wireless channels for a long time, which prevents terminals with good signals from using the wireless channel for enough time.

Smart roaming addresses the problems. After smart roaming is configured, the system actively steers the terminals to neighboring RUs with better signals.

Benefits of smart roaming:
  • Improved performance

    • Common coverage scenarios: The smart roaming function allows terminals with poor signals to roam to better RUs. The service experience of the terminals and overall wireless channel performance are therefore improved.
    • High-density coverage scenarios: Terminals usually have good signals in the scenarios but may not connect to the optimal RUs. The smart roaming function allows the terminals to associate with the optimal RUs, which greatly improves the wireless channel performance.
  • Traffic load balancing

    With smart roaming, each terminal associates with the nearest RU, enabling RUs to load balance traffic.


Figure 18-8 shows the implementation of smart roaming.
Figure 18-8  Smart roaming

  1. An RU collects terminal information, discovers neighboring RUs, and periodically reports the terminal and neighbor information to the central AP.

    Neighboring RUs can be discovered in the following modes:
    • The RU listens on Probe frames of terminals.
    • The RU periodically switches working channels to scan terminals.
    • If the Beacon report mechanism of the 802.11k protocol is used, terminals report the detected neighboring RUs.

    The central AP maintains a terminal neighbor table based on the information reported by RUs. The terminal neighbor table records the neighboring RUs of each terminal and the corresponding SNR.

  2. When STA_1 associates with RU_1, RU_1 collects the SNR and rate of STA_1 in real time and determines whether STA_1 is a sticky terminal. If STA_1 is a sticky terminal, RU_1 reports the terminal to the central AP.

    RU_1 considers STA_1 a sticky terminal if the RU detects that the signal strength of STA_1 remains lower than the threshold in a certain period.

    In Figure 18-8, STA_1 moves from Area1 to Area2. AP_1 detects that the signal strength of STA_1 is lower than the threshold in a specified period of time and considers STA_1 a sticky STA.

  3. After receiving the reported information, the central AP selects the optimal neighboring RU of STA_1 (RU_2) as the target RU to which STA_1 is to roam and delivers the target RU information to RU_1.

    The central AP determines the target RU to which a sticky terminal is to roam as follows:
    1. The central AP checks the terminal neighbor table and selects neighboring RUs whose SNR exceeds that of the RU currently associated with the terminal based on the specified threshold. The selected neighboring RUs are candidate RUs to which the terminal is to roam.
    2. Among all candidate RUs, the central AP selects the optimal RU based on the STA's SNR, rate and load balancing information, and then triggers terminal roaming.

    To prevent frequent terminal roamings due to terminal movements or signal fluctuations, terminal roaming is triggered only when the terminal is detected a sticky terminal for three consecutive times.

  4. RU_1 forces STA_1 to roam to RU_2 based on the BSS transition mechanism defined in the 802.11v protocol or the forced logout mode.

    After STA_1 is disassociated from RU_1, RU_1 rejects the access request from STA_1 for a short time to prevent the STA from associating with the weak-signal RU again.

  5. STA_1 roams to RU_2.

Due to individual differences, some terminals do not roam to RUs with better signals but stick to the initially associated RUs even if they are disconnected forcibly. These terminals may not initiate association requests if forced offline. The central AP will record these terminals unable to roam. When an "unable to roam" terminal is classified as a sticky terminal, the RU does not trigger roaming of the terminal in a specified period to prevent service interruption.

Updated: 2019-01-11

Document ID: EDOC1000176006

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