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  • LTE UE Power on Interview Questions Answers 1-10


    LTE UE Power on Interview Questions Answers

    Q01. In power on which Layer activate first?
    Ans. The NAS layer activate 1st when our mobile is switch on (power on).

    Q02. What is the 1st job RRC Layer performed during power on procedure?
    Ans. When, our UE is switch on, our UE NAS layer trigger a message to RRC layer to provide all the plmn list present in a geographical area. After that RRC Layer start scanning of all plmn’s and make a list and send it back to NAS layer. 

    Q03. How Physical Layer Scan all Frequencies and pick-up 1 frequency?
    Ans. When NAS layer select a plmn (available in plmn list), then it trigger a message towards RRC layer, RRC layer forward this message to Physical layer (via L1 Command) to searching best cell behalf of cell access and cell selection parameters available in SIB1.

    Q04. How UE select a Frequency?
    Ans. Once UE physical layer select a cell frequency behalf of priority (set by operators), after that UE will tries to guess middle frequency called as DC_frequency.

    Q05. What is cell selection and re-selection procedure in lte?
    Ans. When our UE is switch off it stored previous cell information eg: previous cell frequency, bandwidth info and TAC like that. So when UE is switch on it will tries with previous info based cell selection. But if it’s not present then it will find new cell which information's are present in SIB1.
    The Cell re-selection is based on parameters deviation so our UE try to find a next strong cell. so the formula is to do cell re-selection is
    Srxlev>0 and Squal>0
    where
    Srxlev=Qrxlevmeas-(Qrxlevmin+Qrxlevminoffset)-pcompensation
    Squal=Qqualmeas-(Qqualmin+Qqualoffset).

    Q06. How UE guess middle DC frequency of a Bandwidth?
    Ans. When UE pick a frequecy according priority it tries to guess bandwidth middle DC-frequecy. It happen in middle frequency the power value become 0db. So our UE know that this is middle part of bandwidth then applied Zadoff-chu angular varience formula.

    Q07. How NAS layer select PLMN if no.’s of PLMN information provided by RRC Layer?
    Ans. When RRC layer provide PLMN list to NAS layer, UE NAS layer applied security level parameters to, every PLMN present in a list. These security information present in USIM so that a USIM belongs to particular operators, it will select only that operator network without any fail.

    Q08. What is PSS, which sequence is using in PSS?
    Ans. PSS stands for Primary Synchronization Signal.
    PSS is a specialized occupied symbol in frame Structure and generated by Zadoff-chu Angular Varience.

    Q09. What kind of information PSS Carry?
    Ans. It provide Sector id of a cell  eg: 0,1, 2.

    Q10. What is the location of PSS in Type-1 Frame structure?
    Ans. PSS present in every Radio frame and Sub-frame no. 0 and 5 on 1st time slot (ts).
    And last OFDM symbol either Normal Cyclic or Extended Cyclic prefix.