LANCOM Support Knowledgebase Document No. 1404.1614.4940.RHOO - V1.40

Automatic radio-field (RF) optimization with LANCOM WLAN controllers



Description:

In larger installations with several access points it can be difficult to set a channel for every access point. With automatic radio-field (RF) optimization, the LANCOM WLAN controllers provide an automatic method of setting the optimum channels for access points that work in the 2.4-GHz band and 5-GHz band.

Automatic radio-field optimization is a component of LANCOM Active Radio Control (ARC) Database 'Anette Fries', View 'Calendar', Document 'Urlaub'.



Requirements:



RF optimization:

Selecting the channel from the channel list defines a portion of the frequency band to be used by an access point for its logical wireless LANs. The WLAN clients trying to connect to an access point have to use the same channel on the same frequency band. The 2.4-GHz band works with channels 1 to 13 (depending on the country) and the 5-GHz band works with channels 36 to 64.

On each of these channels, only one access point at a time can actually transfer data. In order to operate another access point within radio range with maximum bandwidth, each access point must use a separate channel—otherwise all of the participating WLANs would have to share a single channel's bandwidth.
    Informations:
    • With a completely empty channel list, the access points could automatically select channels which overlap in some areas, so reducing signal quality. Similarly, the access points might select channels which the WLAN clients cannot use due to the country settings.

      To direct access points towards certain channels, the non-overlapping channels 1, 6, 11 can be activated in the channels list.
    • You should ensure that APs transmitting in the 5-GHz band are set to the "indoor only" mode.
    • You can invoke optimization for a particular AP by entering its MAC address as a parameter for the action.

Procedure:

1) Right-click on the list of active access points or on a specific device, and in the context menu select Start automatic RF optimization.



2) RF optimization is then carried out in the following stages:
    1) The WLAN controller assigns the same channel to all access points. The selected channel is the one being used by the majority of access points.

    2) The access points carry out a background scan and report the results to the WLAN controller.

    3) Based on the devices found by the background scan, the WLAN controller sets an interference value for each access point.

    4) It then deletes the AP channel list for all access points. With the channel list now empty, each access point receives a configuration update with a new channel list for its respective profile.

    5) The WLAN controller disables the radio modules of all access points.

    6) The individual access points now go through the following sequence. This begins with the access point with the highest interference value being the first to select a channel.

    7) In the order of the interference values the WLAN controller enables the radio modules in the access points, which then start their automatic calibration. Each access point automatically searches for the best channel from the channel list assigned to it.

    To determine which channel is the best, the access point scans for interference in order to allow for the signal strengths and channels occupied by other access points. Because the former list in the WLAN controller's configuration was deleted, this is now the profile channel list.

    If the profile channel list is empty, then the access point has freedom of choice from the channels that are not occupied by other radio modules. The selected channel is then communicated back to the WLAN controller and entered into the AP channel list there. This means that the access point is given the same channel the next time it establishes a connection. The AP channel list has a higher weighting than the profile channel list.