Is it possible to know from UE logs that which handover has been occurred either S1-based or X2-based ?

Question

How target enodeb will confirm if the incoming user is a genuine user or not?

Is there any IE exchanged during HO preparation phase? I am expecting that during X2 handover AS SECURITY INFO in UE context is very helpful? Is that or not?

Answer 1

There is no exchange of information transferred in RRCConnectionReconfiguration message used for handover. Handover in connection mode is completely taken care by eNodeB, i think UE wont be having any invisibility. But eNodeB will ask UE to camp on neighbor eNodeB based on measurement report and this will not give information about S1 or X2 handover.

Answer 2

hi,

To ascertain which HO has happened, we can use PLMN information to check which PLMN(MME) you are connected to.
-> PLMN information comes in the broadcast information in SIB1.
In the UE logs we can check the PLMN information when the UE is attached to source eNB and then
-> Check the PLMN information of the target eNB which we can check when UE has made the non contention based RACH, again in the SIB1 message.

Now two scenario can happen:
Scenario 1:
If the PLMN in SIB1 in source eNB is NOT same as that of target eNB then their MME is different.
Since MME is different so X2 HO cannot happen and in this case only S1HO can happen.

Scenario2:
If PLMN in SIB1 in source eNB is same as that of target eNB then their MME is different.
Here in this case we cannot identify from the UE logs.

Regards,

Harsh

Comments

I guess the scenario 1 will happen in case of network roaming , so i think in that case by UE display also Roaming Sign will be there.

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Hello Harsh,

Is it true that if PLMN is different then MME also has to be different ? What is the exact relations between PLMN and MME that you are pointing to?

And in your scenario 2 can you please check the statement again - "If PLMN in SIB1 in source eNB is same as that of target eNB then their MME is different" ?
 I think its not neccessary that MMEs will be different if PLMNs are same in target and source EnodeB

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One MME can support multiple PLMN so saying scenario 1 that the if PLMN changes->MME will change-> and hence it will be S1 handover is wrong.

Answer 3

I don't think so we can figure out the HO type is X2 or S1 from UE. It is purely eNB that decides the X2/S1 HO and can be checked from network logs(eNB).