📍The Most Important Interview Questions in 4G-LTE.

●What does OFDMA Stand for?
OFDMA stands for Orthogonal Frequency Division Multiple Access, it's a technique in which we can access LTE network successfully

OFDMA is a Downlink Link access technique which means from the Base Station (eNodB) to the UE(handset) only.

●What is the SC-FDMA in LTE?
It starts for Single Carrier- Frequency Division Multiple Access is a Uplink access technique which means from the UE(handset) to the Base Station (eNodB), we use SC-FDMA in the Uplink to avoid the problem of High Peak to Average Power Ratio (PAPR)

● What does CSFB mean?
Stands for circuit switched fallback, this feature used as a first choice to run Voice call over LTE network, It is a mechanism that sends the user from 4G to 3G/2G (CS RAT) where it can successfully complete a CS Voice Call because there is no IMS registration

●What does VoLTE Service mean?
Stands for voice over LTE, as a scound choice to make voice call in 4G network
We have this feature when there is LTE coverage and IMS registration surly you can make call of LTE

●What is the IMS?
IMS stands for IP Multimedia Subsystem Cloud is a suite of features to build up voice services over 4G/5G and Wireless LAN

●What does SRVCC mean?
Stands for Single Radio Voice call Continuity, used as a solution for handing voice over LTE to 2G/3G networks when there is no LTE coverage, the voice calls on LTE network are meant to be packet switched calls which use IMS system to be made, to make it inter operable with existing networks, these calls are to be handed over to Circuit switched systems in GSM/WCDMA.

●What does CQI refer to?
It refers to Cell Quality Index it an indicator refers to SINR it has a range form 0(bad) to 15(best)

●What is the Rank indicator(RI)?
Number of different layers(Antenna) which the UE can use to decode the signal at the receiver side.

●What is the PMI?
Pre coding Matrix indicator
UE indicates to eNB, which precoding matrix should be used for downlink transmission to enhance the MIMO quality

●What is the ICIC concept in LTE Planning?
Stands for Inter-Cell Interference Coordination (ICIC), which reduces inter-cell interference(ICI) and improves the quality at the cell-edge.

It works as it dividers the Resource Blocks (RB), between 2 neighbouring eNodB, Cells to let them be separated in the frequency domain as well as in time domin by suing different RB in different sub frames.

●What are the types of handover in LTE?
Handover simply aims to maintain service continuity with better quality along with mobility
Intra-frequency LTE Handover
Inter-frequency LTE handover
Inter-RAT handover

●How handover preformed in LTE?
X2 Based handover
Which eNdB is going to handle the Handover decision via X2 interface between eNdBs nodes

S1 based handover
In this case the handover decision will be via MME through S1 interface between eNdB and MME node

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