Configure SM to register under secondary AP when the primary AP is unavailable.

Configure SUBSCRIBER COLOR CODE RESCAN parameter – when the SM is not registered under its Primary AP.

To be able to communicate in a robust system of unlicensed noisy and crowded band, several innovative ideas need to be implemented. Radio synchronization, frequency reuse, automatic power adjustment of Subscriber Modules (SM's), frequency hopping are just a few examples to name. After implementing several noise mitigation techniques and approaches, it is recommended to get prepared for an extra mile by introducing redundancy for a worst-case scenario - when the Access Point (AP) may not be available due to noisy network or loss of Radio Frequency (RF) signal strength. To deal with such a scenario proactively, it is suggested to have the SM configured for at least one secondary AP in the system. Following is a high-level overview to provide the details for how to configure an SM so that it can register to a secondary AP when its primary AP is not available for any reason. For more detailed procedure, the Cambium Networks user guide can be consulted as an excellent resource.


  1. Configure the SM for the secondary AP color code - second best available AP (after primary AP) in the network, at Configure --> Radio GUI tab of the SM:



The secondary color code configured at the SM GUI above should match the color code of the secondary AP.

  1. Click on the “Save Changes” button at the SM GUI:

            There is no need to reboot the SM.

  1. Access Secondary AP GUI at Configuration --> Radio tab, to configure the “Subscriber Color Code Rescan (When not on a Primary Color Code)” parameter to a value between 0-43200 minutes:



  • “Subscriber Color Code Rescan” is the period in minutes that the subscriber will wait before rescanning when not registered under its primary AP.
  • Value of 0 means the parameter is disabled and not being used.
  • You may have maximum value of 43200 minutes, which is equal to 30 days.
  • A couple of packets are lost, every time SM rescans to reach back to its primary AP. Therefore, a very small value should be avoided unless it is desired for the SM to re-register back to its primary AP immediately.
  1. Click on the “Save Changes” button at the Secondary AP GUI:

            There is no need to reboot the Secondary AP.

  1. Configure the “Subscriber Color Code Wait Period for Idle” parameter to 0 at Configuration --> Radio GUI tab of the secondary AP:

 6. Click on the “Save Changes” button at the Secondary AP GUI:

            There is no need to reboot the Secondary AP.


  • Make sure to have “Subscriber Color Code Wait Period for Idle” value set to 0 to disable it. This parameter will be used in future software releases. It will be used in conjunction with “Color Code Rescan” parameter. Once the “Color Code Rescan” period expires, the subscriber will wait for the configured idle period before rescanning. When the idle period is set to zero (0), the rescan will occur immediately at the expiration of the timer set by “Subscriber Color Code Rescan” value.
  • A value of 0 means that the “Subscriber Color Code Wait Period for Idle” parameter is disabled. This parameter is not available at current software release and thus should be disabled by entering a value “0”.

Once the above configuration is set and for any reason primary AP reboots or loses signal, the SM will find its new home at secondary AP and will get registered there automatically. The timer set by the “Subscriber Color Code Rescan” value will show up on the SM GUI in red letters and will run backwards, as shown below as an example:

Timer image.PNG

At its expiry, the SM will automatically re-register to its primary AP – as soon as it is available. Otherwise, the timer will reset and the SM will continue to re-attempt at the expiry of the timer until the SM registers back to its primary AP automatically.


  • For SM to be registered with an AP, the following parameters should match at both (AP and SM) ends:
    • Frequency Carrier
    • Channel Bandwidth
    • Color Code
    • Airlink Security Encryption Setting (DES / AES). This parameter can be set at Configuration --> Security Tab at SM and AP, as shown below:

  • To check which AP the SM is registered under, go to Home --> Session Status GUI tab of the AP or look at the SM Home --> General Status GUI tab.


When “Subscriber Color Code Rescan” parameter is configured at the AP, any SM which is registered under this AP as a secondary AP, will move back to its Primary AP automatically, as soon as the rescan timer expires and the Primary AP is available. The “Subscriber Color Code Wait Period for Idle” should be set to zero (disabled for now).

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