A.2 Deriving Retention Information for a Radio Link

25.4333GPPRelease 17TSUTRAN Iub interface Node B Application Part (NBAP) signalling

The Retention Information for an existing Radio Link shall be derived as follows:

– The latest received Allocation/Retention Priority IE for each transport channel shall be used.

NOTE: The Allocation/Retention Priority IE for a transport channel may have been received in
a) the procedure that establishes the first Radio Link for the Node B Communication Context in the Node B or
b) a procedure adding or modifying the transport channel.

– If the Priority Level IE in the Allocation/Retention Priority IE for one or more transport channels using the Radio Link is set to "no priority", the pre-emption vulnerability of the Radio Link shall be set to "not pre-emptable".

– If the Priority Level IE in the Allocation/Retention Priority IE for all the transport channels using the Radio Link is not set to "no priority", the retention priority of the Radio Link and the pre-emption vulnerability of the Radio Link shall be set according to the following:

– The retention priority for a Radio Link shall be set to highest priority level, given by the Priority Level IE in the Allocation/Retention Priority IE, for all transport channels that uses the Radio Link.

– If all transport channels that uses the Radio Link have the pre-emption vulnerability, given by the Pre-emption Vulnerability IE in the Allocation/Retention Priority IE, set to "pre-emptable", the pre-emption vulnerability of the Radio Link shall be set to "pre-emptable".
If one or more transport channels that uses the Radio Link have the value of the Pre-emption Vulnerability IE in the Allocation/Retention Priority IE set to "not pre-emptable", the pre-emption vulnerability of the Radio Link shall be set to "not pre-emptable".

The derived retention priority and pre-emption vulnerability are valid until they are changed, or until the Radio Link is deleted. When new transport channels are added to or deleted from the Radio Link or when existing transport channels are modified with regards to the Allocation/Retention Priority IE, the retention information shall be derived again according to above.