Thank you for simplified explanation. In inter gNB HO, shouldn't the eNB HO also occur. You explained such that only gNB is changing, how will new gNB communicate with EPC through the old eNB because most probably after the HO, old eNB coverage will be very bad.
eNB to eNB mobility will be based on LTE handover events. It is possible that gNB is using a higher frequency which has lower coverage while eNB anchor is using a low frequency band with much higher coverage such that the eNB anchor also covers the second gNB as well
In case of Inter SgNB HO, UE will move to the target SgNB and data transfer start. What about the Anchor node(if target SgNB is 5KM away and moving towards SgNB), Anchor LTE node will be the same or its also going to be change with the target SgNB
Anchor does not need to be changed in inter-sgNb HO as long as a valid X2 link exists between the anchor and the new gNB. If the target gNB is at a distance which is greater than cell radius of that gNB then the UE will fail at RACH.
Thanks a lot, Very informative. I have a (question)request as I am trying to understand how the resources are managed within cells of same gNB. You have shown the spCellConfigCommon info for the second RRC Reconfig message. It will be helpful if you can share the same for the first one (where you just showed the measurement related info). This will clear how the resources are shared between two cells of the same gNB.
can u share some insights on inter gnb mobility where anchor is also different . in this video the anchor was common for both of them. would appreciate if you can throw some light on that as well.
Yes, the LTE eNB will know the target NR Cell details as all control plane information flows through the LTE eNB and the LTE eNB is the one that will inform the UE to move the target NR Cell via RRC Reconfiguration. Now, how the LTE eNB gets this information, that is via SgNB Change Required message.
Very well explained. Just 1 query. If during A3, the difference of RSRP between 2 gnodeb is just 1 dB, will it still attempt to handover because its just 1 dB better ? Or there is any parameter which restricts it to have minimum difference of levels between 2 gnodeB?
The A3 offset + hysteresis are the relevant parameters. For example, If A3+Hyst is 4dB then the handover will only happen when the target is better than the source by 4dB or more!
Very well done thanks brother, one question, what if the eNB also need to be changed so that the UE triggers A3 for LTE leg and 5G leg? "Let's say both have similar coverage e.g. NR700 + LTE800. Thanks
The process which starts first should be completed first. However, this should be implementation specific but I would say that LTE HO should be prioritized as LTE carries the control plane.
Content is very beautifully narrated, Thanks for such videos. One query , Will Endc attempt pegged here also when Menb requested gnb addition during inter pscell HO ?
Thank you Very informative. In case of HO from LTE cell A NR cell A to LTE cell B NR cell A, i.e, NR cell remain stationary, how does the LTE cell B get NR cell A info. What will be the additional messaging?
Sorry, somehow, I missed your comment. There are generally two implementations for this. One releases the NR cell and then re-adds it at the target cell. The second implementation retains the NR Cell. This is done by adding the NR Cell Configuration in the LTE Handover Request message from CellA to CellB
In case of inter-gnb pscell change, the Sgnb addition is not triggered by new B1 measurements but by the A3 or A5 measurement report.Is it correct? No new B1 measurements are needed for the target gNB.Is it correct?Thank you
This depends on vendor's implementation. Both scenarios are possible, LTE to LTE HO can cause release of 5G resources and then re-add on the new LTE anchor cell after handover. The other scenario is that NR config is passed to the target LTE cell and in that case, it is more seamless and NR service is carried over to the target LTE Cell during LTE to LTE HO. I will do a detailed session on that too later!
ENDC = Eutran Nr Dual Connectivity The name comes from the fact that the handset/mobile is connected to both EUTRAN (4G) and NR (5G) at the same time - so Dual Connectivity
It is just the working as per 3GPP. In LTE, we used to subtract 140 and in 5G, we subtract 156. This helps in sending non-negative values in measurement reports.
good presentation only there is a mistake it think correct me if i wrong the last handover is a inter-gnb it should be A2- A5 not A3 ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-nZKN6R2OgFQ.html
No, A2 and A5 are used for Inter-Frequency Handovers. Over here, we are talking about Intra-Frequency handover. Note that Inter-gNB handover can be Intra-Freq or Inter-Freq.
