RRC Layer Interview Quetions and Answers 11-15

11. What are the reason/causes of RRC connection release? And release timer?

Ans The RRCConnectionRelease message is used to command the release of an RRC connection.

Signalling radio bearer: SRB1

RLC-SAP: AM

Logical channel: DCCH

Direction: E-UTRAN to UE

RRC Connection Release IEs

12. What is MIB and which channel carry the MIB? what information UE get after reading MIB? And size of MIB in Lte?

Ans MIB stands for Master Information Block. In LTE PBCH channel carry the MIB. After reading MIB ue get the information of System Frame No., Downlink Bandwidth Info, PHICH info,

In LTE MIB have 24bit size(Fixed).

§  3 bits for system bandwidth

§  3 bits for PHICH information,

§  1 bit to indicate normal or extended PHICH

§  2 bit to indicate the PHICH Ng value

§  8 bits for system frame number

§  10 bits are reserved for future use

§  Important point:- MIB new information is broadcast in every 40ms cycle and, next 3 system frame(10ms, 10ms, 10ms) carry same MIB information.

13. How many times System Information should be change? And Parameter responsible for count system information changed how many times?

Ans System information would be change when an operator changes some parameters in enb. So that System Info Value Tag (0..31). increment the value +1 to previous value present.

IMP:- This information present in SIB 1.

14. In connected state UE move from 1^st cell to 2^nd cell what are the minimum System Information, UE need to read while move to next cell?

Ans When UE move from 1^st cell to 2^nd cell if ue in connected state ue need to read only MIB, SIB1 and SIB2 only there is no need to read all SIBs information.

But in idle state UE will read all SIBs info include MIB info.

15. UE will 1^st read which system frame number to decode MIB Information?

Ans UE 1^st read System Frame No. (SFN==0) to read MIB information after that (SFN==1, SFN==2, SFN==3) broadcast repeat MIB information. (SFN==4) again new MIB information is broadcast. And follow same procedure previous define.