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    ANR (Automatic Neighbour Relation)

    Actually before understand about ANR we have to clear little bit concept on neighbour cell scenario. What happened is every eNB attached the neighbour cell list inside SIBs. This is operator work to configure these details in system Info So There are two ways that network operator put this details inside the various cells.
    1.    Manually configuration: Its done manually by the Operator but here are some issue with it:
    a.    First operator need to provide special person to investigate it which is cost effective and also neighbour cells are changes time to time by shifting cells on demand
    2.    Automatic configuration : This is technique the eNB are used  for automatic configuration of neighbour cell which is known as Automatic neighbour request. Its a easier way of configuration. Procedure is as follows:
    a.    First N/W will send Measurement control Req to UE  for performing the measurement of cell around its geographical area and provide list to N/W that has sent Measurement control Req earlier.
    b.    N/W will decode the measurement report and update the neighbouring list according to the received report from UE.


    TAU(Tracking Area Update)

    TAU is a kind of report which sent by UE to eNB at a certain time, whenever the TAC(Tracking Area Code) is changed than TAU is needed not only that time there is some more condition when its needed.
    First the question is How UE get to know that TAC is changed? So our answer is this information is present in a SIB1.
    Now second question is when TAU report has to send?
    Actually we have something called TAI list which is already has provided by MME to UE at the time of registration. For more information Refer TAI.
    TAU trigger conditions:
    1.    Normal TAU is due to mobility i.e when UE enters in Tracking Area which is not included within the list of tracking areas with which the UE has registered.
    2.    Periodic TAU after T3412 timer Expires.
    3.    Reregistering the EPS after CSFB connection has been completed.

    4.    MME load balancing. 

    Jitendra Kumar

    Author & Editor

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