NR-RLC-UM:ReorderingTImer

[nile]

Hi all,I am facing an issure regarding the "reordering window" when I execute the handover between gnbs throught X2 interface by nrhelper.

phenomenon:

After a handover, the protocol needs to re-"calibrate" its receive window. A slight difference in the calibration starting point—i.e., the sequence number of the last data packet before the handover—will lead to a difference in the right boundary of the window after calibration. This difference determines whether the formula VR(UH) > VR(UR) is satisfied, and thus decides whether the first subsequent data packet will trigger a reordering process that takes the duration of the ReordingTimer (likely a typo for "ReorderingTimer") or be accepted immediately. Is there any verifiable protocol content regarding this scenario?
thanks for your answer~

[Gabriel Ferreira]

Handover is not currently supported, so I have no idea how you managed to get to that point. :)

[nile]

Thank you for reply. Previously, I was testing handover on LTE, which also used the X2 interface. After switching to the NR module, I noticed that the same functions (AddX2Interface, HandoverRequest) are available in the nrHelper. By calling the callback functions of the RRC layer, I can also observe the UE handover between gNBs. 

[nile]

However, I did notice a strange observation: unlike in LTE where the link interruption time at the moment of handover varies, the NR module seems to have a fixed, ideal duration for this（4ms）. Could this be what was meant by "not supported" in your previous reply?：）

在2025年8月26日星期二 UTC+8 16:24:56<Gabriel Ferreira> 写道：

[Gabriel Ferreira]

I added these interfaces on nr-3.2, when porting upper layers from LTE. But handover was not tested, and I know for sure it should not work, because I'm working on it as we speak, and it does requires patches. Maybe you got it sort of functional, but I would not trust these results if I were you.