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Is it mandatory that X2 connection established between cell have single MME ?

0 votes

Is it mandatory that X2 connection established between cell have single MME ? ie If enb X is connected with mme 1 and other eNB Y is connected with MME2 then Is X2 possible between mme1 and mm2?

posted Sep 30, 2018 by Rakesh Kumar Suman

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2 Answers

+1 vote

If x2 is available between two eNBs and both eNBs are connected with different MMEs then S1 HO will be performed and data forwarding will be done via direct tunneling (via x2).

answer Oct 2, 2018 by Veer Pal Singh Yadav
Thanks for sharing your answer.
0 votes

If handover is being supported between any two eNodeBs over the X2 link, it is mandatory for both the eNodeBs to be connected to same MME in order to support the change data path direction from SGW to new eNodeB.
If handover is not mandatory for the X2 link then it is not necessary that both eNodeB should have connection with same MME.

answer Oct 1, 2018 by Harshita
Hi Harshita,
Thanks for response Harshita.  
How data path will impact If enb X is connected with MME 1 and other eNB Y is connected with MME2 There is X2 link between eNB1 and eNB2.
Since, mme can communicate with other mme through  s10 interface.

Please, explain in detail if possible
Hi Rakesh, I mentioned in my first sentence that if X2 handover is being supported between two eNodeBs then only it is required for both eNodeBs to be connected to same MME. The reason behind is "X2 handover signalling between eNodeBs is unknown to MME". If SGW is not updated with the new target eNodeB downlink tunnels, downlink data will keep delivering to source eNodeB which is incorrect. To update the downlink tunnels at SGW, target eNodeB sends "S1-AP Path switch request to MME" after handover completion. During the handover execution, forwarded tunnels will be used to forward data from source eNodeB to target eNodeB.
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+1 vote

In case of hub-and-spoke topology, X2 messaging can travel all the way back to an aggregation point, which may be co-located with EPC. In such scenario both X2 and S1 traverses same physical path (a.k.a X2 over S1). Please consider both Intra-MME and Inter-MME handover scenarios. Would X2 based handover in such a case yield advantage over S1 based handover. Thanks.

+3 votes

Consider Two ENB of two different operator can they establish X2-AP Connection if X2-AP Support is there ???

I guess it is possible as ECGI will give unique identification to them . (Though possibility of CGI is same) ...

is there any other scenario like x2AP- is not possible between them

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