III B.

Tech I Semester Supplementary Examinations, MAY 2010

DATA COMMUNICATION SYSTEMS
(Common to CSE, IT)
Time: 3 Hours Max Marks: 80
Answer Any FIVE Questions
All Questions Carry Equal Marks
*****
_
1. (a) What is an open system? Explain, in detail, about open systems
interconnection.
(b) Explain, in detail, about quadrature amplitude modulation and trellis
code modulation. [8 + 8 M]
2. (a) What is a metallic transmission line? Explain the five types of metallic
transmission line losses.
(b) State Snell’s law for refraction and outline its significance for optical
fiber cables. [8 + 8 M]
3. (a) What do you understand by companding? Compare analog companding
and digital companding.
(b) A PCM-TDM system multiplexes 24 voice-band channels. Each sample
is encoded into 7-bits., and a framing bit is added to each frame. The
sampling rate is 9000 samples per second. Determine the line speed in bps.
[8 + 8 M]
4. (a)What is a radio wave? What are the optical properties of radio waves?
Explain all the details of how they relate to radio wave propagation?
(b) What are the three modes of terrestrial propagation of electromagnetic
waves? Explain. [8 + 8 M]
5. (a) Compare the operation of a cordless telephone and a standard telephone.
(b) What considerations are addressed by facility parameters? Compare
phase hits and phase jitter. [8 + 8 M]
6. (a) What is N-AMPS cellular telephone system? Explain the operation of
NAMPS
cellular telephone system.
(b) List the basic parameters of GSM and describe, briefly, the GSM radio
subsystem. [8 + 8 M]
7. (a) What is a SYN character? Compare and contrast synchronous and
asynchronous serial data formats. For the following sequence of bits over the
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Code No: V3124/R07
time from left to right, identify the ASCII- encoded character, the start and
stop bits, and the parity bits (assume an even parity and two stop bits):
11111101000001011110001000
(b) What is high speed modem synchronization? What are the purposes of
scrambler and descrambler circuits? Illustrate with an example. [8 +8 M]
8. (a) What is a line discipline of a data link protocol? Illustrate an
enquiry/acknowledgement (ENQ/ACK) line discipline with an example.
(b) Compare synchronous data link control (SDLC) and high level data link
control (HDLC). Describe the HDLC operational modes. [8 +8 M]
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Code No: V3124/R07
III B. Tech I Semester Supplementary Examinations, MAY 2010
DATA COMMUNICATION SYSTEMS
(Common to CSE, IT)
Time: 3 Hours Max Marks: 80
Answer Any FIVE Questions
All Questions Carry Equal Marks
*****
1. (a) What is meant by a layered protocol? Why are protocol layered? Explain.
(b) What is meant by M-ary encoding? Explain higher-than-binary encoding
with an example. [8 + 8 M]
2. (a) What is a transverse electromagnetic wave? Explain with a neat diagram.
(b) What is an optical fiber mode? Explain the three practical types of
optical fiber modes. [8 + 8 M]
3. (a) What is the relationship between dynamic range and the number of bits
in a pulse code modulation (PCM) code? For a PCM system with the
minimum dynamic range: 46dB, determine minimum number of bits used in
the PCM code.
(b) What is superframe and extended superframe time division multiplexing
(TDM) format? Explain each with an example. [8 + 8 M]
4. (a) What is meant by a free space path loss of an electromagnetic wave?
Give the mathematical equation in decibel form. Determine, in dB, the free
space path loss for a frequency of 6 GHz traveling a distance of 50km.
(b) What is a satellite multiple accessing arrangement? List and describe, in
detail with neat diagrams, the three forms of satellite multiple accessing
arrangements. [8 + 8 M]
5. (a) What is a paging system? Describe, in detail with a neat block diagram,
how a paging system works.
(b) What is meant by transmission line conditioning? Compare C-type and
D-type line conditioning. [8 + 8 M]
6. (a) What are the three primary subsystems of GSM? Describe, in detail, the
GSM system architecture.
(b) Explain, in detail with neat diagrams, the CDMA traffic channels.
[8+ 8 M]
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Code No: V3124/R07
7. (a) What is a Hamming code? For a 12-bit data string of: 101100010010,
determine the number of Hamming bits required, arbitrarily place the
Hamming bits into the data string, determine the logic condition of each
Hamming bit, assume an arbitrary single –bit transmission error, and prove
that the Hamming code will successfully detect the error.
(b) Explain the terms: bits per second (bps), baud, probability of error, bit
error rate with an example each. [8 + 8 M]
8. (a) What is the difference between synchronous and asynchronous data link
protocols? Explain, with a neat frame format, how the XMODEM protocol
works.
(b) What is an invert-on zero encoding? Obtain the non return-to-zero
inverted (NRZI) encoding to the data stream: 1 0 0 1 1 1 0 0 1 0 1 0 1 0 0 0 1
0 1 1 1 0 0 0 1 1 1 [8 + 8 M]
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Code No: V3124/R07
III B. Tech I Semester Supplementary Examinations, MAY 2010
DATA COMMUNICATION SYSTEMS
(Common to CSE, IT)
Time: 3 Hours Max Marks: 80
Answer Any FIVE Questions
All Questions Carry Equal Marks
*****
1. (a) What is the difference between the communication of data and
communication of information?
(b) What is the difference between electrical noise and thermal noise? For an
electronic device operating at 17oC with a bandwidth of 10 kHz, determine
the thermal noise power in watts and dBm. [8 + 8 M]
2. (a) What is a transmission line? Compare balanced and unbalanced
transmission lines.
(b) What is an optical communication system? Explain an optical fiber
communication system with a neat block diagram. [8 + 8 M]
3. (a) What is pulse code modulation (PCM) line speed? For single-channel
PCM system with a sample rate, fs = 6000 samples per second and a 7-bit
compressed PCM code , determine the line speed.
(b) What is a T carrier system? What is a fractional T carrier? Describe, in
detail, the various T carrier systems. [8 + 8 M]
4. (a) What is a radio wave? What are the optical properties of radio waves?
Explain all the details of how they relate to radio wave propagation?
(b) What is meant by a free space path loss of an electromagnetic wave?
Give the mathematical equation in decibel form. Determine, in dB, the free
space path loss for a frequency of 6 GHz traveling a distance of 50km.
[8 + 8 M]
5. (a) What is a telephone set? Describe, in detail with a neat diagram, the
various functional components of a standard telephone set.
(b) What is the difference between dB and dBm? Determine: (i) the power
levels in dBm for signal levels of 10mW and 0.5mW (ii) the difference
between the two power levels in dB. [8 + 8 M]
6. (a) Explain the classifications of CDMA radiated power. Determine the
transmit power for a CDMA mobile unit that is receiving a signal from the
base station at -100dBm.
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Code No: V3124/R07
(b) What is a digital cellular system? List the advantages of a digital cellular
system. [8 + 8 M]
7. (a) Compare longitudinal and cyclic redundancy checking. Determine the
block check character (BCC) for the following polynomials:
Data polynomial, G(x) = x8 + x5 + x2 + x0
Generating polynomial, P(x) = x5 + x4 + x1 + x0.
(b) What is modem synchronization? What are its functions? Compare cable
modems and standard voice band modems. [8 + 8 M]
8. (a) What is a synchronous data link control(SDLC)? Describe, in detail, the
various fields of the SDLC frame format.
(b) What is the transparency mechanism used with SDLC? Illustrate with an
example. [8 + 8 M]
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Code No: V3124/R07
III B. Tech I Semester Supplementary Examinations, MAY 2010
DATA COMMUNICATION SYSTEMS
(Common to CSE, IT)
Time: 3 Hours Max Marks: 80
Answer Any FIVE Questions
All Questions Carry Equal Marks
*****
1. (a) Compare peer-to-peer client/server network and dedicated client/server
network
(b) What is a signal-to-noise power ratio? For a circuit with a signal power
of 100W and a noise power of 0.002mW, determine the signal-to-noise
power ratio in absolute and dB values. [8 + 8 M]
2. (a) What is a plenum cable? Compare plenum and non-plenum cables.
(b) What is a laser? Explain, in detail, the four types of
lasers. [8 + 8 M]
3. (a) What do you understand by signal voltage-to-quantization noise voltage
ratio? Give its relationship to resolution, dynamic range, and the maximum
number of bits in a pulse code modulation (PCM).
(b) Compare wavelength division multiplexing (WDM) and dense wave
division multiplexing (D-WDM); and also list the advantages and
disadvantages of WDM. [8 + 8 M]
4. (a) What are the three modes of terrestrial propagation of electromagnetic
waves? Explain.
(b) What is a satellite multiple accessing arrangement? List and describe, in
detail with neat diagrams, the three forms of satellite multiple accessing
arrangements. [8 + 8 M]
5. (a) Explain, briefly, how caller ID operates and when it is used. Interpret the
following hex code for a caller ID message(start and stop bits are not
included in the hex codes):
04 12 31 31 32 37 31 35 35 37 33 31 35 37 33 36 31 30 35 33 xx
(b) What is a crosstalk? What are the three types of crosstalk in telephone
systems? Compare near-end crosstalk and far-end crosstalk. [8 + 8 M]
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Code No: V3124/R07
6. (a) What is a GSM cellular telephone system? Describe the services offered
by GSM.
(b) What is meant by false handoff? What are the four types of handoffs
possible with N-AMPS? Compare macro cellular system and digital cellular
system. [8 + 8 M]
7. (a) What is POSTNET? What is POSTNET bar code? Determine the check
character for the POSTNET nine-digit ZIP + 4 numbers: 13424-7654.
(b) What is a modem? Compare synchronous and asynchronous modems.
Explain the four types of modem operational modes. [8 + 8 M]
8. (a) What is a data link protocol? List and describe, in detail, the three data
link protocol functions. (b) What are the three frame formats used with
synchronous data link control (SDLC)? What the purposes are of: the ns bit
sequence, nr bit sequence, P bit and F bit?