5.27.3 Support for TSC QoS Flows

TSC QoS Flows use a Delay-critical GBR resource type and TSC Assistance Information. TSC QoS Flows may use standardized 5QIs, pre-configured 5QIs or dynamically assigned 5QI values (which requires signalling of QoS characteristics as part of the QoS profile) as specified in clause 5.7.2. For each instance of Periodicity, within each Period (defined by periodicity value), TSC QoS Flows are required to transmit only one burst of maximum size MDBV within the 5G-AN PDB. Known QoS Flow traffic characteristics provided in the TSCAI may be used to optimize scheduling in the 5GS.

The following is applicable for the QoS profile defined for TSC QoS Flows:

1. The TSC Burst Size may be used to set the MDBV as follows:

The maximum TSC Burst Size is considered as the largest amount of data within a time period that is equal to the value of 5G-AN PDB of the 5QI. The maximum value of TSC Burst Size should be mapped to a 5QI with MDBV that is equal or higher. When integration with IEEE TSN applies, this 5QI also shall have a PDB value that satisfies the bridge delay capabilities (see clause 5.27.5 for more details) reported for the corresponding traffic class. For TSC QoS Flows, the Maximum Burst Size of the aggregated TSC streams to be allocated to this QoS Flow can be similarly mapped to a 5QI with MDBV value that is equal or higher. If interworking with a TSN network deployed in the transport network is supported, the maximum value of TSC Burst Size should be mapped to a 5QI with MDBV that is equal.

2. The PDB is explicitly divided into 5G-AN PDB and CN PDB as described in clause 5.7.3.4. Separate delay budgets are necessary for calculation of expected packet transmit times on 5G System interfaces. For the TSC QoS Flow, the5G-AN PDB is set to value of 5QI PDB minus the CN PDB as described in clause 5.7.3.4. The CN PDB may be static value or dynamic value and is up to the implementation of 5GS bridge.

3. When integration with IEEE TSN applies, the Maximum Flow Bitrate calculated by the TSN AF as per Annex I.1 may be used to set GBR. In this case, MBR is set equal to GBR.

4. ARP is set to a pre-configured value.

5. 5QI value is derived using QoS mapping tables and TSN QoS information as described in clause 5.28.4 in the case of integration with IEEE TSN network, or using QoS Reference parameters and Requested PDB, Burst Size, Priority parameters as described in clause 4.15.6.6 or clause 4.15.6.6a of TS 23.502 [3] in the case of AF requested Time Sensitive Communication.