Number of NR-U DUD without any PDCP PDU sent over X2-U at gNB-CU

5G NR
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1

Hi Experts.

Can anybody explain what is this NR-U DUD?
“Number of NR-U DUD without any PDCP PDU sent over X2-U at gNB-CU”

2

It can be NR - User Plane DL User Data.

There are three types of frame format defined for the NR user plane protocol.

DUD – DL User Data (PDU Type0) – DUD message is added to every packet of the data sent in DL direction(CU to DU). This frame format is defined to allow the corresponding node to detect lost NR-U packets. The Transfer of Downlink User Data procedure is done to give specific sequence number details for NR-U. This happens when user data, containing a DL NR PDCP PDU, is moved from CU to DU. The CU will give each transferred NR-U packet a sequence number in order. The DU will check if any NR-U packet is lost and remember its sequence number after marking it as “lost.” This helps prevent NR PDCP HFN de-synchronization. If the Transfer of Downlink User Data procedure isn’t used, other methods should ensure NR PDCP HFN synchronization.

DL DATA DELIVERY STATUS (PDU Type 1) – This is sent DU to CU.
ASSISTANCE INFORMATION (PDU Type 2)