Description
Time Sensitive Communication Assistance Information (TSCAI) is a critical enabler for deterministic communications in 5G networks, specified within the 5G System architecture in TS 23.501 and related control plane specifications (e.g., TS 29.512, 29.513). It is not user data but rather control information that describes the temporal characteristics of an upcoming Time Sensitive Communication (TSC) data flow. The primary purpose of TSCAI is to bridge the knowledge gap between the application, which understands its own traffic generation pattern, and the network, which controls the transmission resources.
Architecturally, TSCAI is generated by an Application Function (AF) associated with the time-sensitive application, such as a manufacturing execution system or a robotic controller. This AF communicates with the 5G Core Network's Network Exposure Function (NEF) or directly with the Policy Control Function (PCF) via the N5/N7 interfaces. The PCF then incorporates this information into the PCC (Policy and Charging Control) rules that are provided to the Session Management Function (SMF). The SMF is responsible for setting up the appropriate QoS Flows for the PDU Session and, crucially, forwarding the relevant TSCAI to the (R)AN via the Access and Mobility Management Function (AMF) during PDU Session establishment or modification procedures.
How it works is predictive and proactive. A typical TSCAI container includes parameters such as the 'Periodicity' of critical packets (e.g., every 2ms), the 'Burst Arrival Time' (the expected time of the first packet in a burst relative to a time reference), and the 'Packet Delay Budget' for each packet. Upon receiving this information, the (R)AN node (gNB) can perform "time-aware scheduling." Instead of reacting to packets as they arrive in its buffer—which introduces unpredictable queuing delay—the scheduler can pre-allocate uplink grants or downlink resources at the precise radio frame/subframe that aligns with the expected packet arrival. This ensures the packet is transmitted with minimal waiting time. For downlink, the UPF can be instructed to forward packets to the RAN just in time for their scheduled transmission slot.
TSCAI's role is to transform the network from reactive to predictive for critical traffic. It allows the 5G system to meet the extreme bounds on latency and jitter required by industrial control loops. Without TSCAI, the RAN scheduler operates blindly, leading to potential deadline misses due to contention with other traffic. With TSCAI, the network can reserve a "deterministic lane" in the shared radio spectrum for each critical packet, making wireless behavior resemble that of a time-triggered wired network.
Purpose & Motivation
TSCAI was created to solve a fundamental challenge in supporting Time Sensitive Communications (TSC) over a shared, statistical multiplexing packet network like 5G. Even with advanced radio features for URLLC, the network scheduler cannot optimally prioritize traffic if it does not know *when* critical packets will arrive. Without this foreknowledge, packets may be queued behind other traffic, violating strict latency bounds. Previous approaches in mobile networks relied purely on QoS class identifiers (QCIs) and priority levels, which are reactive and insufficient for microsecond-level timing accuracy.
The specific problem TSCAI addresses is the unpredictability of packet arrival times from the network's perspective. In industrial automation, many control applications generate traffic in a perfectly periodic, predictable pattern (e.g., a sensor reading every control cycle). TSCAI allows the application to communicate this known pattern to the network infrastructure. This was motivated by the need for 5G to support IEEE Time-Sensitive Networking (TSN), where traffic is often scheduled in a time-aware manner based on a known schedule. For 5G to integrate as a TSN bridge, it needed a mechanism to receive and act upon such schedule information.
Its introduction in 3GPP Release 16 was a direct response to requirements from vertical industries participating in 3GPP. It enables a key paradigm shift: making the network "application-aware" for timing. This allows 5G to go beyond simply offering low average latency, to guaranteeing a maximum latency for each individual packet in a predictable stream, which is the cornerstone of reliable industrial wireless control.
Classification
Detected Changes Across Releases
from 3GPP Change RequestsSpecific changes extracted from the „Change history“ tables of 3GPP specifications (421 CRs across 6 releases). Complements the general historical overview above with the evidence-based evolution of this function.
In Release 15, the TSCAI (Time Sensitive Communication Assistance Information) function was newly introduced to support deterministic communication services with bounds on latency and reliability. This introduction included enhancements to CN assistance information and provided clarifications on its provisioning and handling. These foundational mechanisms enabled the 5G system to facilitate Time Sensitive Communication (TSC) for applications requiring guaranteed packet transport characteristics.
- Configuration information the UE may exchange with the SMF during the lifetime of a PDU Session TS 23.501CR0003
- Correction to handling of S-NSSAI mapping information TS 23.501CR0020
- Update on Traffic Detection Information TS 23.501CR0026
- Traffic mapping information that disallows UL packets TS 23.501CR0053
- CN assistance information enhancement TS 23.501CR0068
- 5G QoS fixes for URLLC services related attributes - PDB, PER, MDB, 5QI TS 23.501CR0087
+ 18 more changes
In Release 16, the TSCAI function was introduced to support Time Sensitive Communication by providing deterministic packet transport with bounded latency and high reliability. This enhancement specifically assists applications requiring strict QoS characteristics, such as those defined for industrial automation, by enabling the network to understand and meet the survival time and synchronization needs of time-sensitive services.
- New clause for URLLC supporting TS 23.501CR0810
- Introduction of indirect communication between NF services and implicit discovery TS 23.501CR0736
- Description of solution 2 in 23.725 for redundancy as an informational annex TS 23.501CR0754
- eSBA communication schemas related to general discovery and selection TS 23.501CR0799
- eSBA communication schemas related to UDM and UDR discovery and selection TS 23.501CR0800
- eSBA communication schemas related to SMF discovery and selection TS 23.501CR0801
+ 118 more changes
In Release 17, the TSCAI function was expanded to support Time Sensitive Communication (TSC) beyond just TSN, introducing a new architecture for AF-requested support of TSC and time synchronization. It also enhanced the system by introducing a UE-assistance operation and enabling the TSC Assistance container to be determined by the NEF. Furthermore, support for the TSCAI time domain was explicitly added, and PCC rules were updated to authorize with preliminary service information and include EAS IP replacement information.
- Introduction of the architectures for Time Sensing Communication other than TSN. TS 23.501CR2573
- Adding the usage of Redundant Transmission Experience analytics for URLLC service TS 23.501CR2581
- KI#3A - TSC Assistance container determined by NEF TS 23.501CR2619
- Service Assistance Information for 3GPP Advanced Interactive Service TS 23.501CR2653
- PMF extensions for sending UE-assistance data to UPF TS 23.501CR2647
- Introduction of UE-assistance operation TS 23.501CR2743
+ 72 more changes
In Release 18, the TSCAI function was enhanced to support the direct event notification of TSC management information, providing more dynamic updates. It also gained the capability for the provisioning of periodicity information at the service data flow level. Furthermore, updates were made to the Flow Description Information within the ChargeableParty and AsSessionWithQoS APIs to incorporate Time of Service and Traffic Class (ToSTC) parameters.
- Introduction of 5GS Information Exposure TS 23.501CR3887
- PIN communication configuration TS 23.501CR3897
- Assistance to Member Selection Functionality for Application Operation TS 23.501CR3910
- 5GS Assistance for Application AI/ML operation: General clause TS 23.501CR3968
- CN based MT communication capability indication TS 23.501CR4081
- SNPN broadcast system information and manual network selection for localized service TS 23.501CR4095
+ 85 more changes
In Release 19, the TSCAI function was enhanced to support the identification of PDU Set information for end-to-end encrypted traffic using connect-UDP, and to leverage PDU Set QoS information for DSCP marking over the N3/N9 transport network interfaces. Furthermore, support was introduced for delivering media-related information over N6 using an encapsulation protocol and for relaying multiplexed (S)RTP media information.
- Adding the NAT information exposure and Packet Inspection functionality in the UPF NF profile TS 23.501CR5420
- Introduction of new network function for energy related information, its definition and corresponding Architecture Reference Model TS 23.501CR5636
- Support of UE-Satellite-UE communication TS 23.501CR5583
- General description of relaying media related information over N6 using an encapsulation protocol TS 23.501CR5711
- Support PDU Set information identification based on MoQ for encrypted XRM traffic TS 23.501CR5632
- PDU Set Information Identification for end-to-end encrypted traffic using connect-UDP - architecture part TS 23.501CR5728
+ 94 more changes
In Release 20, the TSCAI function was enhanced to support energy-aware network selection by enabling N3IWF/TNGF reselection based on energy consumption information. Furthermore, it introduced the exposure of per-UE application ranking information via the Exposure Interface Function (EIF) to assist in TSC traffic prioritization. These additions provided new mechanisms for optimizing both energy efficiency and application performance for Time Sensitive Communications.
- N3IWF/TNGF reselection considering energy related information. TS 23.501CR6493
- KI#1: Per UE application ranking related information exposed by EIF TS 23.501CR6501
- Energy Consumption information exposure and policy control TS 23.501CR6508
- Support of UE-SAT-UE communication for non-IMS services TS 23.501CR6520
Explore further
Broader topics and technologies where TSCAI plays a role.
Defining Specifications
3GPP specifications that define or reference TSCAI, with the latest known release. Sourced from the 3GPP document catalog — see methodology.
| Specification | Title | Release |
|---|---|---|
| TS 23.501 vk00 | 5G System Architecture Stage 2 | Rel-20 |
| TS 29.122 vj40 | T8 Reference Point for Northbound APIs | Rel-19 |
| TS 29.512 vj40 | 5G Session Management Policy Control Service | Rel-19 |
| TS 29.513 vj40 | 5G PCC Signalling Flows & QoS Mapping | Rel-19 |
| TS 29.514 vj40 | 5G System; Policy Authorization Service; Stage 3 | Rel-19 |
| TS 29.522 vj40 | 5G NEF Northbound APIs Stage 3 | Rel-19 |
| TS 29.565 vj40 | Time Synchronization Function Services | Rel-19 |