as per 3gpp 28.552, V15.3
18.104.22.168.3 DL F1-U Packet Loss Rate
a) This measurement provides the fraction of PDCP SDU packets which are not successfully received at the gNB-DU). It is a measure of the DL packet loss on the F1-U interface. The measurement is optionally split into subcounters per QoS level (mapped 5QI or QCI in NR option 3).
c) This measurement is obtained as: 1000000* Number of missing DL GTP sequence numbers (TS 29.281), representing packets that are not delivered to lower layers, of a data radio bearer, divided by Total number of UL GTP sequence numbers (also including missing sequence numbers) of a bearer, starting from the sequence number of the first packet delivered by gNB-CU-UP to gNB-DU until the GTP sequence number of the last packet. Separate counters are optionally maintained for mapped 5QI (or QCI for NR option 3).
- why is division by “total number of UL GTP Seq number” is mentioned while it is DL packet loss rate?
- When NRUP loss is already being detected and reported in DL data delivery status and same can be used as F1-U Packet Loss Rate, why 3GPP is adding another measurement w.r.t GTP Seq. Number.