Understanding STA Steering

Overview

As good WLAN service experience for users is increasing, STA association with proper APs becomes important. The STA steering function allows STAs with poor service experience to associate with proper APs based on the WLAN environment, improving STA service experience.

The STA steering function integrates band steering, load balancing, and smart roaming.

• Before STA association, Probe packets are suppressed to steer STAs to preferentially access the 5 GHz radio.
• After STA roaming, the target AP selection algorithm is used to consider the dual-band capability of STAs, AP load, and AP signal quality to steer STAs to optimal APs.

STA Steering

STA steering before association

During STA association, an AP parses multi-band information carried in Probe Request packets from STAs to determine whether a STA supports dual bands. Then the AP suppresses the 2.4 GHz radio for dual-band STAs so that these STAs preferentially access the 5 GHz radio. For details, see Band Steering.

STA steering after association

• Periodical load balancing

  1. The AC sorts APs by load.
  2. Based on the sorting result, load balancing is performed for APs in descending order of load.
  3. The AC searches for the neighboring AP list of a STA and determine the target AP based on the algorithm.
  4. The STA is steered to the target AP.

  For details, see AP-based Load Balancing.

• Sticky STA steering

  When a STA is determined as a sticky STA, it is steered using smart roaming. For details, see Smart Roaming.

• Periodical identification

  The AC periodically traverses online STAs and selects those that have been online for more than 10 minutes. Then the AC determines whether optimal APs exist for these APs. If so, the AC instructs the APs to steer APs.

Neighboring AP List of a STA

Before steering a STA, the AC needs to determine the target AP, which is selected from the neighboring AP list of the STA. Therefore, the AC needs to collect, store, and maintain the neighboring AP lists of STAs.

Neighboring AP information can be obtained based on Probe packet collection or Beacon Report measurement.

• Probe packet collection: APs scan channels, collect STA information (through Probe frames and management frames), and periodically report the collected information to the AC. The AC then generates a neighboring AP list.

• Beacon Report measurement: An STA supporting 802.11k can serve as a measurement STA to obtain AP list information from other STAs on a specific channel or a specified channel group. Then the STA sends the measurement result to the associated AP that periodically reports the information to the AC.

  Measurement can be performed in one of the following modes:

  • Active: The measurement STA sends Probe frames to other STAs to obtain AP information returned by the STAs.
  • Passive: The measurement STA only obtains AP information returned by the STAs, without sending Probe frames.
  • Beacon table: The measurement STA directly obtains AP information on other STAs.

During STA association, an AP parses the supported channels IE field from the request packet and reports the parsed information to the AC. The AC records channels supported by different STAs. When guiding a STA to be steered, the AC selects an appropriate AP for the STA based on the supported channels to ensure that the STA can still properly use wireless services after being steered.

STA Steering Mode

When a STA meets steering conditions, it is steered.

• The STA steering mode depends on whether the STA supports 802.11v. If so, the AP steers the STA in BTM mode. If not, it is the AP steers the STA in Deauthentication mode.
• Before sending BTM or Deauthentication messages, the AP notifies neighboring APs so that they suppress STA Probe or Authentication frames.
• STAs with voice and video services running are not steered.
• After a STA goes online again or roams, it is not steered within 5 minutes.