RF Interview Ques Answer 1-10

Q00. Define RF? And use of RF in Wireless Technology?

Ans. RF stands for Radio frequency. It is a oscillation rate of electromagnetic radiation spectrum, or electromagnetic radio waves, from frequencies ranging from 300 GHz to as low as 9 kHz. With the use of antennas and transmitters, an RF field can be used for various types of wireless broadcasting and communications.

Q01. Why we need 4G if 3G working well?

Ans. As there are some limitation in 3G so fulfil those requirements we have a need of 4g :-

To increase the latency
To increase the bandwidth and throughput in technology.
Flexibility in using multiple freq bands.
Flat Architecture:Minimise the risk of single point of failure in the N/W.

Q02. What is the Limitation of 3G?

Ans. The limitation of 3G are:-

The maximum bit rate in 3G is 20 Mbps which is very much as compared to our non 3GPP.
The latency of user plane traffic is more than 30 ms and resource management procedure is above 100ms which is very high.
Heirarchial Architecture is the biggest drawback in 3G N/W, reason is if 1MSC goes down than all the network elements who come under that are stopped working.

Q03. What are the changes occurred in LTE architecture from 3G?

Ans. There are lot of changes occurred in 4G architecture from 3G:
LTE is only a PS domain network there is no CS domain.

Node B + RNC ==> eNB in LTE
HLR+AUC ==> HSS in LTE
MSC + VLR ==> MME in LTE

What-are-the-changes-occurred-in-LTE-architecture-from-3G

Q04. Difference between Bandwidth and Frequency?

Ans. Frequency is the number of oscillations ( data is convert into a signal in form of waves) in per seconds, Frequency unit is Hz. Whereas Bandwidth is the amount of data transferred at given unit of time. Bandwidth unit is Bits/sec
Freq formula Bandwidth formula
f=(1/t)Hz B=[f(max)-f(min)]bits/sec

Q05. Difference between band and bandwidth?

Ans. Band is a group of frequencies. Bandwidth is the amount of data transferred at given unit of time.

Q06. if 900 band have 5Mhz or 20Mhz bandwidth and 2300 band also have 5Mhz or 20Mhz bandwidth then what is effect on coverage would be happen?

Ans. As we know Coverage is depends upon bands, and lower bands coverage always greater than higher bands. for eg band 900 have more coverage than 2300 band, if we deploy 2 bandwidth like 5Mhz or 20Mhz then both bandwidth will have same coverage and they should belong to same band, the difference we got only in utilization of PRBs.

Q07. What is Throughput? How Throughput calculate in LTE?

Ans. Throughput is nothing but our DL and UL speed in LTE. And it is calculated by using the channel bandwidth, no. of subcarrier and Modulation techniques.
In lte we got 100 megabit/persec. The calculation formula is:-

Max. Bandwidth in lte==>20Mhz==>100PRBs
Resource elements in Normal cyclic prefix ==>84RE in 1 slot
Higher modulation in lte==>64QAM==>6bits per resource elements
0.5*2==>1 subframe==>1ms==>168RE
in lte 1 sec==>1000ms
formula is:-RE in subframe*PRB*Second*Modulation

Now calculate: 168*100*1000*6=100,800,000b/3==>100,800B/3==>100.8mbps

Q08. What are the Conditions of Handover in LTE?

Ans. There are 3 types of handover in LTE:

Intra Handover- when UE moves from 1 sector to another sector of same Tower is known as Intra handover.
Inter Handover- When UE moves form 1 tower to another tower than it is known as Inter handover.
Inter-RAT – When UE shift from LTE to UMTS and GSM than process is known as Inter RAT handover.
X2 handover happen between EnodeB to EnodeB.
S1 handover happen when both EnodeB don’t have X2 interface.

Q09. What is ANR?

Ans. ANR is a Automatic neighbour Relation present in eNB and use for Manually adding neighbor cells in network is indeed a very hectic process and prone to errors as well. While networks are becoming more and more complex, it is required to find an automatic and a more optimized way of adding neighbor cells.

Q10. What is interference and how it will overcome?

Ans. Interference is when same freq superimposed each other and totally corrupt the data signal waves.Interference may prevent reception although may loss the data. It can be overcome by proper optimisation tower cell by giving them proper azimuth, electrical and mechanical tilts.