CBRS Alternate Channel Selection

Product: 3.6 GHz PMP 450x series CBRS Access Points.

Problem: CBRS Grant suspension due to DPA.


If more than the configured percentage of SMs are affected by CBRS DPA suspension, the AP triggers the channel hunting algorithm and selects a temporary channel. If on this channel several SMs more than the configured threshold do not reattach to the AP, or several SMs more than this configured threshold also experience a DPA suspension on the temporary channel, the AP will attempt to identify another temporary channel while still heartbeating the first temporary channel. This shall be repeated until either a channel is found that supports more than the ‘SM Percentage Threshold for Channel Change’ or a maximum of 6 grants for the AP is reached. At this point, a decision will be made on which channel is optimal, with the other grants relinquished.

To enable this, go to the Configuration>CBRS tab in the web interface.


For PMP 450m operators who wish to avoid rebooting, they can disable the ‘Reboot for Channel Bandwidth Change’ feature, leaving the ‘Alternate Channel Selection’ feature enabled, and hunting only to a channel of the same bandwidth in operation.

If the entire spectrum is suspended due to DPA, a channel hunt is triggered. If only part of the spectrum is suspended, in general, the AP shrinks the bandwidth to the remaining authorized grants. However, for a PMP 450m with ‘Reboot for Channel Bandwidth Change’ disabled, the AP remains suspended. If only part of the spectrum is suspended due to DPA on a PMP 450m AP. If the reboot flag is disabled, then the AP will trigger a channel hunt to the operating bandwidth only, rather than just waiting with the AP transmitter disabled until the DPA suspension clears.

For any other AP model, if part or all of the spectrum is terminated, the radio triggers a channel hunt.

When ‘Change Channel if Only SMs are Impacted’ is enabled, the AP automatically finds and moves to a new channel or decreases the bandwidth, when more than the ‘SM Percentage Threshold for Channel Change’ percentage of SMs have been impacted by termination or suspension, even though the AP itself has not been impacted. Not applicable to PTP configurations.

The ‘SM Percentage Threshold for Channel Change’ displays the percentage of SMs that need to be impacted by termination or suspension for the feature to be invoked, even though the AP itself has not been impacted. Note that the ‘Alternate Channel Selection’ feature must also be enabled for the AP to hunt for a new channel due to the ‘Change Channel if only SMs are Impacted’ feature. If an operator elects to run with ‘Alternate Channel Selection’ enabled but the ‘Change Channel if only SMs are impacted’ feature is disabled, the AP still performs automatic channel selection, but only in cases where the AP is directly impacted by terminations or suspensions. If the ‘Alternate Channel Selection’ feature is disabled, but the ‘Change Channel if only SMs are Impacted’ feature is enabled, if enough SMs are impacted by terminations or suspensions, the AP still reduces the bandwidth if authorized grants are available, but it will not hunt for a new channel.

When the ’Original Channel Restore Time’ feature is triggered via SM suspensions, the AP continues to heartbeat the original channels for itself and all the SMs, while operating on the temporary channels or reduced bandwidth for at least this length of a period after moving to these temporary channels or reducing bandwidth. When this timer expires, the AP can move back to the original channels and/or bandwidth if enough suspended SMs have become authorized on the original channels.

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