6.2.13 Handling of Small data rate control

Small data rate control is applicable only to NB-N1 mode and WB-N1 mode.

Small data rate control controls the maximum number of uplink user data messages including uplink exception data reporting sent by the UE in a time interval for the PDU session in accordance with 3GPP TS 23.501 [8]. The UE shall limit the rate at which it generates uplink user data messages to comply with the small data rate control policy. The NAS shall provide the indicated rates to upper layers for enforcement. The indicated rates in a NAS procedure applies to the PDU session the NAS procedure corresponds to, and the indicated rates are valid until a new value is indicated or the PDU session is released.

If the UE indicates support for CIoT 5GS optimizations, the network may provide the small data rate control parameters to the UE and may provide the small data rate control parameters for exception data to the UE if and only if the small data rate control parameters is provided to the UE. Small data rate control parameters and small data rate control parameters for exception data can also be provided to the UE in S1 mode as specified in 3GPP TS 24.301 [15].

If an allowed indication of additional exception reports is provided with the small data rate control parameters and:

• the additional small data rate control parameters for exception data is provided and the limit for additional rate for exception data reporting is not reached; or
• the additional small data rate control parameters for exception data is not provided,

the UE is allowed to send uplink exception reports even if the limit for the small data rate control has been reached.

During a PDU session release procedure, if the small data rate control was applied to the PDU session that is being released, the network may store the small data rate control status for the released PDU session as specified in 3GPP TS 23.501 [8].

If:

• the UE indicates support for CIoT 5GS optimizations; and
• the small data rate control status was stored for the PDU session and is still valid,

the network may provide the remaining small data rate control status as initial small data rate control parameters to the UE and initial small data rate control parameters for exception data to the UE during a subsequent PDU session establishment procedure.

If received during the establishment of a PDU session, the UE shall apply the initial small data rate control parameters and the initial small data rate control parameters for exception data for the duration of the validity period. When the validity period expires the small data rate control parameters and the small data rate control parameters for exception data shall be applied (see 3GPP TS 23.501 [8]).

NOTE 1: The HPLMN can discard or delay user data that exceeds the limit provided for small data rate control.

Upon inter-system change from N1 mode to S1 mode, the UE shall store the current small data rate control status for PDU sessions to be transferred from N1 mode to S1 mode as specified in 3GPP TS 23.501 [8].

NOTE 2: How long the UE stores the current small data rate control status is implementation specific.

Upon inter-system change from S1 mode to N1 mode, the UE shall use the stored small data rate control status, if any, to comply with the small data rate control policy for PDU sessions transferred from S1 mode to N1 mode as specified in 3GPP TS 23.501 [8], if the validity period of the stored small data rate control status has not expired.