Upon receiving a successful grant response, the CBSD sends a heartbeat request at every heartbeat interval to indicate to the SAS server that the spectrum is required.
The 7705 SAR-Hmc supports the following parameters in the heartbeat request:
CBSD ID
grant ID
grant renew — the node sets this parameter to TRUE when 1 h remains before either the grant timer expires or the heartbeat interval is longer than 30 min and two heartbeat requests can be sent before the grant timer expires. If either of these conditions cannot be met, this parameter is not included in the heartbeat request.
operation state — the node sets this parameter to GRANTED when a heartbeat response has not yet been received for the grant and to AUTHORIZED when a successful heartbeat response has been received.
The SAS sends a heartbeat response that contains the following parameters:
CBSD ID
grant ID
transmit expire time — the time that the CBSD must stop transmitting plus 60 s
grant expire time — the time the grant expires. When included in the grant response, the 7705 SAR-Hmc uses this value as the new grant expire time.
heartbeat interval — the maximum interval, in seconds, between two consecutive heartbeat requests. This value is used to set the heartbeat timer. If the value is changed by the SAS, the node uses the new value for this parameter.
response — an indication of whether the heartbeat request is approved
If the transmit timer expires before the CBSD receives a heartbeat response, the CBSD stops transmitting for the grant within 60 s of the timer expiry.
A heartbeat request is sent at every heartbeat interval. The heartbeat interval timer is set when the CBSD receives a grant response or a heartbeat response that includes a defined heartbeat interval. If no heartbeat interval is defined, the CBSD uses the default value of 30 s.
The 7705 SAR-Hmc disables the dynamic filter on the PDN router interface when the heartbeat response is the first successful response it receives after sending a grant request. Disabling the filter allows the router interface to operate normally and for any enabled SR OS features to operate.
If the heartbeat response includes a suspended grant message, the CBSD is no longer authorized to use the spectrum. The 7705 SAR-Hmc re-enables the dynamic filter on the PDN router interface to disable SR OS features and allow only SAS control messages over the interface.