What does a SAS triggered Suspension do and how does it affect my network?

The Domain Proxy service running on the Celona Edge interfaces with the SAS on behalf of all Celona APs at a site.

Celona Domain Proxy requests a grant to reserve spectrum based on availability returned from SAS. If the grant is authorized, the Access Points can transmit using the grant. A "suspension" is a response sent by SAS after a grant is authorized to stop it from transmitting temporarily. Celona Domain Proxy will, in this case, give up this grant and ask for a new one based on the new spectrum availability returned from SAS. The new Spectrum availability may be different due to the Incumbent activity that resulted in the suspension.

After a suspension, the FCC mandates that radios stop transmitting within 60 seconds of receiving the message. This will bring a part of the network down for approximately 120 seconds which is the time taken for a new grant to be authorized by SAS.

What are SAS Terminations, when do they occur, and how does it affect my network?

This Celona Domain Proxy service sends periodic heartbeat keep-alive requests to SAS for each AP's grant to utilize the CBRS spectrum.

If Celona Domain Proxy receives a SAS Termination in its 60-second heartbeat interval, the radios affected have to stop transmitting on that grant within 60 seconds of receiving the message. Domain Proxy asks for a new grant based on the new spectrum availability returned from SAS. A Termination could be received due to Incumbent Activity or a new PAL starting to operate in that location on the same channel the affected radios were using.

The difference between a Termination and a suspension in terms of SAS behavior is that when a grant is terminated, Domain Proxy has no choice but to ask for a new one immediately whereas if the grant is suspended with code: Interference Calculations Pending the current grant can get authorized again.

How long can DPA/Incumbent suspensions last?

Access Points deployed in a Dynamic Protection Area (DPA) suspension neighborhood, which are locations where incumbents/radar/Coastal Navy activity may exist before the deployment, are subject to a Suspension Pending Interference Calculations for 24 hours after they're brought up for the first time.

If a DPA is activated due to Incumbent activity in a region, the average suspension cycle lasts for approximately 2 hours. Celona Domain Proxy does not wait for this cycle to complete and changes grants for the affected radio immediately when the suspension is received.

What are SAS Sync/CPAS Interference Calculations? Is my network affected?

CPAS refers to Coordinated Periodic Activities among vendor SAS providers. During this process, the SASs exchange information and sync with the FCC CBRS database.

The SAS uses a "DPA move list" to keep track of which grants must be suspended during Incumbent activity. A grant might only get suspended if it’s on the move list and incumbent activity is detected.

During this CPAS cycle, DPA/suspension move lists might be re-calculated and grant resources may be re-assigned.

This means the following for your network:

  • During CPAS, SAS will not issue new grants. This is why Celona does not allow users to schedule a SAS Registration during the time interval 7 AM UTC–10 AM UTC each day.

Refer to the SAS Registration Scheduler document for additional information and a guide to scheduling your network downtime on CPI installation parameter edits or Access Point addition to a site.

  • During CPAS, SAS recalculates the DPA move lists, grants are either removed from the suspension list and authorized or terminated at the end of the CPAS cycle.

  • Sometimes, during the CPAS re-allocation of resources, the maximum power your Access Point is allowed to transmit at may be reduced. If this reduction is less than 3dB, Celona Domain Proxy will reduce the power. If the change in power from the originally authorized maximum Transmit power is greater than 3dB, Domain Proxy will ask for a new grant from SAS on another available channel with a greater available maximum transmit power.

I want to deploy my network near the US coast. Is my network prone to Suspensions due to Incumbent activity?

Unlike most incumbent users that constantly operate in a well-defined area, Naval Radar operations can happen at different places and times. SAS vendors use sensors on the coast to detect when the Navy is using a part of the CBRS band spectrum.

If SAS detects activity, it will send a DPA suspension for that frequency to all the APs operating entirely or partially on that frequency.

As per WinnForum rules, a DPA/ suspension neighborhood has the following sizes in distance from the coastline:

  • Category A Access Point: 150 km

  • Category B Access Point:

    • West coast: 150-200 km

    • East coast: 300-400 km

    • Gulf coast: 300-400 km

Actions by Celona Domain Proxy and Self-Organizing Network (SON) algorithm:

  • Celona Domain Proxy receives the list of available frequencies in the order of channel quality from SAS. The highest order of channel quality is determined by SAS based on factors like maximum Transmit power, channel usage by other customers, and Incumbent activity. Domain Proxy then picks the channel with the best quality and assigns channels optimally in the network to avoid Access Point to Access Point interference in the network.

  • If the top 50MHz of the CBRS spectrum [3.65 GHz - 3.7 GHz] is available to use, then this range of the spectrum is prioritized because Naval radars only use [3.55 GHz to 3.65 GHz] on the coast.

  • Celona Domain Proxy auto-recovers within 120 seconds after a suspension is received by asking for a new grant with the next best available frequency.

Can I subscribe to alerts on the Celona network that help me monitor these SAS events?

Celona network exposes SAS-initiated events in the form of alerts, which you can see in the below ways:

  • SAS Suspension/Termination events alert for a single Access Point can be viewed on the Access Points Details page -> Click on the Blue Celona icon on the Access Point Operation State card.

    • If an Access Point is brought transmit Down due to a SAS triggered suspension/termination, an alert will be visible with the time of the event and radio affected.

    • The Access Point will self-recover due to Celona Domain Proxy Auto-recovery

  • You can also subscribe to Celona Network Monitoring APIs to receive HTTPS-based push and Slack notifications for Celona Domain Proxy alerts. In this way, you can optimize your notification settings and subscribe to various events via REST APIs.

Did this answer your question?