GSM Interview Preparation Guide
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GSM Technology frequently Asked Questions by expert members with experience in GSM. These interview questions and answers on GSM Technology will help you strengthen your technical skills, prepare for the interviews and quickly revise the concepts. So get preparation for the GSM Technology job interview

15 GSM Technology Questions and Answers:

1 :: What is the GSM?

GSM, which stands for Global System for Mobile communications,
reigns as the world’s most widely used cell phone technology.
Cell phones use a cell phone service carrier’s GSM network by
searching for cell phone towers in the nearby area.

The origins of GSM can be traced back to 1982 when the Groupe
Spécial Mobile (GSM) was created by the European Conference of
Postal and Telecommunications Administrations (CEPT) for the
purpose of designing a pan-European mobile technology.
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2 :: I know that the main function of bts is to air interface signaling. But why?

mobile station is normally mobile in nature which is an
advantage over pstn network . and in order to provide
connection to mobile station we use radio resource (air)...
in order to provide interface between mobile and bss . bts
is used.. a bts is responsible to cover a small geographical
area called cell...
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3 :: Explain What is the deference between Rx Lev Sub and Rx Lev Full?
What you mean by Link Budget?

Rx_Level_Full is measured when DTX is off & Sub is when DTX
is on.
RX Lev Full: Its is nothing but the Mobile transmit the
measurment report(SACCH multiframe) for every 480ms. this
multiframe containes 104 TDMA frames, in 104 TDMA frames 4
TDMA frames for Decode the BSIC and remaining 100 TDMA
frames for Average measurment of serving cell and
neighbouring cell.This average measurment of 100 TDMA frames
are RX Lev Full

RX Lev Sub: DTX is a discontinouse trasmission, When the
mobile conversation 40% of the time either Trasmitter or
Receive is idle. When DTX is ON, DTX will switch off the
Trasmitter or Receiver when they is no speech Pulses. only
few TDMA frames will trasmit, the average of this TDMA
frames is called RX Lev Sub, give you proper measurment of
RX level
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4 :: Tell me What is the difference between FER and BER?

Error ratios used in conjunction with GSM speech channels:
· Frame Erasure Rate, FER, is defined as the amount of swept speech frames (260 bits each)
divided by the amount of transmitted speech frames. The speech frame is swept if even one of
its most important 50 bits is observed not to be correct. The three parity bits following the 50
class Ia bits are used for error detection.
· Bit Error Rate, BER, is the ratio of erroneously received bits to all received bits. It is
important to notice that BER is evaluated before channel decoding, i.e. after equaliser. BER is
used for defining the RXQUAL value
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5 :: Explain what is the relation between RXLEV [0 to 63] and rxlev [-110 to -47]?

Rx level 0 to 63 is GSM unit. While -110 to -47 is dbm
Rxlevel unit of GSM. When we will add 110 to Rxlevel
[dbm],it will get convert into GSM unit 0 to 63.
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