5G System Learning - Scheduled Synchronization of Status Reports

Compared to previous generations of technology, 5G (NR) has higher requirements for timing and synchronization accuracy. This is because the network needs synchronization to achieve functions such as carrier aggregation, Mass MIMO, and TDD (Time Division Duplex); key technologies such as enhanced boundary clocks, PTP (Precise Time Protocol), and TSN (Time Sensitive Networking) can meet its accuracy requirements; regarding timing and synchronization status reports, 3GPP defines them in TS38.413 as follows:

I. Timing Synchronization Status Report The purpose of the timing synchronization status report process in the 5G system is to enable NG-RAN nodes to provide RAN timing synchronization status information to the AMF in accordance with TS 23.501 and TS 23.502; the timing synchronization status report process uses signaling not associated with the UE. The successful report operation process is shown in Figure 8.19.2.2-1, where:

The NG-RAN node initiates the process by sending a TSCTSF timed synchronization status report message, indicated by the routing ID IE, to the AMF.

II. The purpose of the timed synchronization status report is to enable the AMF to request the NG-RAN node to start or stop reporting RAN timed synchronization status information as specified in TS 23.501 and TS 23.502. The successful synchronization status report operation process is shown in Figure 8.19.1.2-1 below. The reporting process uses non-UE associated signaling; where:

AMF initiates this process by sending a timing synchronization status request message to the NG-RAN node.

• If the RAN TSS request type IE contained in the timing synchronization status request message is set to "start", the NG-RAN node should start RAN TSS reporting for the TSCTSF indicated by the route ID IE.
• If the RAN TSS request type IE is set to "stop", the NG-RAN node should stop reporting the TSCTSF indicated by the route ID IE.

III. The scheduled synchronization status report operation failed, as shown in Figure 8.19.1.3-1, where:

If an NG-RAN node is unable to report the timing synchronization status, the process should be considered a failure and a "Timing Synchronization Status Failed" message should be returned.