The parameter may vary between vendors and can either be hardcoded or configurable, depending on the vendor’s implementation. If I recall correctly, Nokia also relies on DDDS for such cases. Let me illustrate this with an example to explain the concept of how this could be achieved.
Assume the DDDS period is 40 ms, and NR reports around 385 PDCP PDUs successfully delivered in sequence to the UE (based on the highest PDCP PDU Sequence Number). In contrast, LTE delivers around 192 PDUs in the same timeframe. For simplicity, let’s assume all packets are of the same size, 1300 bytes.
If packets are sent only in NR, using this assumption, the achievable throughput would be approximately 100 Mbps (based on the 385 delivered PDCP PDUs). However, if the implementation supports a split of 100/50, the throughput could reach around 150 Mbps. The same logic applies in reverse, depending on how the traffic is split.
In essence, throughput can be estimated by normalizing the delivered PDCP SNs over the DDDS periodicity, providing a basis for performance estimation.