e requirements are broadly categoried as follows: Time alignment error limits between the PRTC/T-GM and the radio air interface Time alignment error limits between the PRTC/T-GM and the UNI of the virtualized DU and CU function As a best practice, it is recommended to have a common PRTC/T-GM for the virtualized DU and the RUs associated with that DU. As depicted in Table 10-17, the absolute time error budget between the PRTC and the RU antenna remains as +1.5 us; similarly, the time error requirement between the PRTC and the virtualized DU also must remain within the +1.5 us budget, keeping the network budget as +1.1 us. However, operators could have different deployment scenarios with vir- tualized DU architecture, as described in the sections that follow. Option 1 The RUs are directly connected to the DU, and the DU acts as a synchronization master to all con- nected RUs. As shown in Figure 10-33, this could have several options: The DU has a PRTC/T-GM directly connected to it. The DU is receiving clock from the network PRTC/T-GM using PTP and SyncE. Primary timing signal Relative TAE PRTC/T-GM Backup Local PRTC < 260 ns or 130 ns End application 1.5 us 1.5 us PRTC to DU Local PRTC to RU a) PRTC/T-GM is directly connected to DU Relative TAE PRTC/T-GM Primary timing signal < 260 ns or 130 ns End application + 1.5 us PRTC to RU b) DU is receiving clock over the network Figure 10-33 DU as Synchronization Master and Distributing Clock to Connected RUs In this option, the DU needs to support the SyncE or eSyncE clock definition according to ITU-T G.8262 or G.8262.1. In suboption (b), the DU needs to comply with the G.8275.1 PTP telecom pro- file with a minimum ITU-T G.8273.2 Class B performance as a T-BC clock. Option 2 The DU and RU are connected over multiple network hops, as shown in Figure 10-34: A centralized PRTC/T-GM distributes clock to the DU and RU as a primary reference The PRTC/T-GM is deployed on the network that connects the DU and RU. The centralized PRTC/T-GM is used as the backup timing source. (((p