LANCOM Systems Support KnowledgeBase - Support Information
Document No: 1404.1610.5851.RHOO

WLAN Band Steering with LANCOM access points
Description:

The IEEE 802.11 standard contains virtually no criteria by which a WLAN client should select the access point for a connection. While there are, for example, general guidelines for the preference given to an access point with a higher RSSI value (i.e. the received signal strength), WLAN clients do not, in practice, adhere strictly to these definitions or the general guidelines. If both 2.4GHz and 5GHz are used to broadcast an SSID, there is normally no way of influencing the client as regards the preferred frequency band.

There are several, sometimes highly advanced, criteria for steering. One of these criteria relates to the wireless frequency ranges used for client communication. Modern dual-band WLAN clients are expected to prefer the 5GHz frequency band over the (now) overcrowded 2.4GHz band. Band Steering is the term given to purposefully assigning a WLAN client to a particular frequency band or range.

This document describes how WLAN Band Steering operates and how you set up the feature in the configurations of LANCOM access points.

WLAN Band Steering is a component of the LANCOM Active Radio Control (ARC) Database 'SP Knowledgebase', View '03. Edit Documents\by Responsible, Status', Document 'LANCOM Active Radio Control (ARC)'.




Requirements:

  • LANCOM dual-radio access point or LANCOM WLAN controller

Procedure:

In LANconfig you can use Configuration -> Wireless LAN -> Band Steering to enable and manage the LANCOM access point's Band Steering feature.
  • Band steering activated: Activates or deactivates this function.
  • Preferred frequency band: Specifies the frequency band to which the LANCOM access point steers WLAN clients.
    Possible values are:
    • 2.4 GHz: The device steers clients to frequency band 2.4 GHz.
    • 5 GHz: The device steers clients to frequency band 5 GHz.
  • Probe request ageout time: The time for which the LANCOM access point steers the WLAN client to the preferred frequency band. The default value is 120 seconds.



How WLAN Band Steering works:

For the process of WLAN Band Steering, the LANCOM access point maintains a list of all WLAN clients that it can "see" after receiving a probe request from each of them. In combination with the radio frequency on which the WLAN client sends the probe request, this list is one of the bases used by the access point to decide whether or not to respond to the request.

    Information:

    If a WLAN client has too low a transmit strength when SSIDs are reported, the WLAN client may not receive any probe responses at all on the preferred frequency band. In this case, it is important to ensure that the access point does not suppress probe responses on the less favored frequency band.

    This is controlled by the minimal client signal strength setting to be found in LANconfig in the menu Configuration -> Wireless LAN -> General -> Logical WLAN settings -> Network -> Minimal client signal strength.



    With a value set for the minimal client signal strength, the effect is as follows:
    • If a probe request with an appropriate SSID or a placeholder SSID is received, a response is only sent if it has at least the minimum signal strength. If not, it is discarded.
    • If an authentication or registration request is received, which is below the configured signal strength, it will be rejected. Please note that this situation is rare, since the probe requests of such clients usually go unanswered anyway, and a client can only have found this access point using a passive search of its radio beacon.

    This value is specified as a percentage. This specifies the ratio of the signal and noise levels (SNR). A percentage value of 100% infers an SNR of 64 dB, smaller percentage values are correspondingly lower. The default value is 0 and with this value, no WLAN clients are ignored.