Understanding Analog and Digital Communication Systems

QUESTION

BANK

PREPARED BY

PARTHIBAN. S.
ASSISTANT PROFESSOR
DEPARTMENT
OF
ELECTRONICS AND COMMUNICATION ENGINEERING AND TECHNOLOGY

SUBJECT DETAILS:

SUBJECT CODE / NAME : CS2204 / ANALOG & DIGITAL COMMUNICATION
(Regulation 2008)
DEPARTMENT: COMPUTER SCIENCE AND ENGINEERING
YEAR / SEMESTER : II / III

PREPARED BY: PARTHIBAN. S., ASST. PROF., VRS COLLEGE OF ENGG. AND TECHNOLOGY, VILLUPURAM

SYLLABUS
CS2204 ANALOG AND DIGITAL COMMUNICATION LTPC
3 10 4
UNIT I FUNDAMENTALS OF ANALOG COMMUNICATION 9
Principles of amplitude modulation, AM envelope, frequency spectrum and bandwidth, modulation index
and percent modulation, AM Voltage distribution, AM power distribution, Angle modulation - FM and PM
waveforms, phase deviation and modulation index, frequency deviation and percent modulation, Frequency
analysis of angle modulated waves. Bandwidth requirements for Angle modulated waves.
UNIT II DIGITAL COMMUNICATION 9
Introduction, Shannon limit for information capacity, digital amplitude modulation, frequency shift keying,
FSK bit rate and baud, FSK transmitter, BW consideration of FSK, FSK receiver, phase shift keying – binary
phase shift keying – QPSK, Quadrature Amplitude modulation, bandwidth efficiency, carrier recovery –
squaring loop, Costas loop, DPSK.
UNIT III DIGITAL TRANSMISSION 9
Introduction, Pulse modulation, PCM – PCM sampling, sampling rate, signal to quantization noise rate,
companding – analog and digital – percentage error, delta modulation, adaptive delta modulation, differential
pulse code modulation, pulse transmission – Intersymbol interference, eye patterns.
UNIT IV DATA COMMUNICATIONS 9
Introduction, History of Data communications, Standards Organizations for data communication, data
communication circuits, data communication codes, Error control, Error Detection, Error correction, Data
communication Hardware, serial and parallel interfaces, data modems, Asynchronous modem, Synchronous
modem, low-speed modem, medium and high speed modem, modem control.
UNIT V SPREAD SPECTRUM AND MULTIPLE ACCESS TECHNIQUES 9
Introduction, Pseudo-noise sequence, DS spread spectrum with coherent binary PSK, processing gain, FH
spread spectrum, multiple access techniques – wireless communication, TDMA and CDMA in wireless
communication systems, source coding of speech for wireless communications.
TUTORIAL: 15
TOTAL: 45 +15=60

TEXT BOOKS:
1. Wayne Tomasi, “Advanced Electronic Communication Systems”, 6/e, Pearson Education, 2007. (Unit I,
II, III and IV)
2. Simon Haykin, “Communication Systems”, 4th Edition, John Wiley & Sons., 2001. (Unit V)

REFERENCES:
1. H.Taub,D L Schilling ,G Saha ,”Principles of Communication”3/e,2007.
2. B.P.Lathi,”Modern Analog And Digital Communication systems”, 3/e, Oxford University Press, 2007.
3. Blake, “Electronic Communication Systems”, Thomson Delmar Publications, 2002.
4. Martin S.Roden, “Analog and Digital Communication System”, 3rd Edition, PHI, 2002.
5. B.Sklar,”Digital Communication Fundamentals and Applications”2/e Pearson Education 2007.


UNIT I
FUNDAMENTALS OF ANALOG COMMUNICATION
Principles of amplitude modulation, AM envelope, frequency spectrum and bandwidth, modulation
index and percent modulation, AM Voltage distribution, AM power distribution,
Angle modulation - FM and PM waveforms, phase deviation and modulation index, frequency
deviation and percent modulation, Frequency analysis of angle modulated waves. Bandwidth requirements
for Angle modulated waves.

1. Principles of amplitude modulation
1) Define modulation.
2) Define demodulation.
3) What is the need for modulation?
4) Define Amplitude modulation.
5) Give the explanation for AM envelope.
6) Illustrate the relationship among carrier, modulating and modulated signals using a neat diagram.
7) What is modulation index and percentage modulation in AM?
8) Explain in detail about Frequency spectrum of AM.
9) How will you calculate bandwidth from the given frequency spectrum.
2. Coefficient of Modulation and percent modulation
1) Define Coefficient of Modulation
2) Define percent modulation
3) Give the equations for Coefficient of Modulation and percent modulation and explain the terms
4) Give the formulae to calculate the peak amplitudes of upper and lower side frequencies
5) Write the equation for percent modulation in terms of Vmax and Vmin
3. AM Voltage distribution and AM power distribution
1) Give the expression for unmodulated carrier and amplitude modulated wave.
2) Write the expression for modulated signal in terms of using carrier, upper and lower side signals.
3) Write the formulas to find upper and lower side frequencies by using the carrier and message frequencies.
4) What is the expression for power in an unmodulated carrier?
5) Express the power of side bands in terms of peak power voltage and load resistance.
6) Write the expression for total power in an AM DSBFC envelope.
7) What will be the transmitted power in case of m=0?
8) How the total power is varied according to the modulation index.
9) Explain about the power in case of 100% modulation.
10) Write the expression for the total power of side bands.
4. Angle modulation
1) What are the forms of angle modulation?
2) What are the limitations (or) disadvantages of angles modulation?
3) What are the advantages of angles modulation?
4) Write the mathematical expression of angle modulated wave and explain the notations.
5) Define Direct frequency modulation.
6) Define Direct phase modulation.
7) Give explanation about phase deviation.
8) Give explanation about frequency deviation.
9) What is meant by Carrier rests frequency.
10) Define instantaneous phase deviation.
11) Define instantaneous phase.
12) Define instantaneous frequency deviation.
13) Define instantaneous frequency.
14) Explain about the deviation sensitivity of PM and FM and give the expressions.
5. FM and PM waveforms
1) Draw the wave form of FM and give the explanation.
2) Draw the wave form of PM and give the explanation.


3) Explain the frequency deviation characteristics in FM.
4) Explain the frequency deviation characteristics in PM.
5) Explain FM in terms of instantaneous frequency.
6) Explain PM in terms of instantaneous phase.
6. Phase deviation and modulation index
1) Write the general equation of angle modulation in terms of modulation index.
2) What is meant by peak phase deviation?
3) What is modulation index in PM?
4) What is meant by index of modulation?
5) Give the expression and derive the unit for modulation index of PM.
6) Give the expression and derive the unit for modulation index of FM.
7. Frequency deviation and percent modulation
1) Define frequency deviation.
2) Define carrier swing.
3) Write the equation for frequency deviation.
4) Write the three forms equation for FM in terms of K1, ∆f and m.
5) Express modulation index in terms of frequency deviation and modulating signal frequency.
6) How the PM and FM modulation indexes varies with modulating signal frequency?
7) How the percent modulation is calculated in angle modulation?
8. Frequency analysis of angle modulated waves
1) Frequency analysis of Angle modulation is complex, why?
2) How the side frequencies are related to the carrier frequency through modulating signal frequency?
3) Write one of the Bessel function identity used for angle modulation.
4) Express the angle modulation general equation in terms of Bessel function.
5) Write the first four terms of Bessel series.
6) Write the Bessel sets of frequency components resulted in angle modulation.
7) Write the Jn(m) equation to solve the amplitude of the side frequencies.
8) What if meant by first carrier null?
9) What if meant by second carrier null?
9. Bandwidth requirements for Angle modulated waves
1) Write the classification of angle modulated waveforms in terms in terms of indexes.
2) What is meant by narrowband FM?
3) What is quasi stationary approach?
4) How the low index modulation is related to amplitude modulation?
5) How will you calculate the minimum bandwidth from Bessel table?
6) Write Carson’s rule for bandwidth
7) Which one is accurate to calculate bandwidth among Bessel and Cason’s rules? Justify your answer.
Frequently asked questions… (Slanting style – Most important)
1. Distinguish between FM and PM by giving its mathematical analysis. (8m)
2. Discuss about the sets of side bands produced when a carrier is frequency modulated by a single frequency
sinusoid. (8m)
3. Explain the principles of amplitude modulation. (8m)
4. AM: Voltage distribution and power distribution
5. In an AM modulator, 500 KHz carrier of amplitude 20 V is modulated by 10 KHz modulating signal which
causes a change in the output wave of +_ 7.5 V. Determine:
(1) Upper and lower side band frequencies
(2) Modulation Index
(3) Peak amplitude of upper and lower side frequency
(4) Maximum and minimum amplitudes of envelope. (8m)
6. Write a note on frequency spectrum analysis of angle modulated waves. (8m)
7. Derive the relationship between the voltage amplitudes of the side band frequencies and the carrier and draw the
frequency spectrum. (8m)
8. Explain the band width requirements of angle modulated waves. (8m)


UNIT II
DIGITAL COMMUNICATION

Introduction, Shannon limit for information capacity, digital amplitude modulation, frequency shift
keying, FSK bit rate and baud, FSK transmitter, BW consideration of FSK, FSK receiver.
Phase shift keying – binary phase shift keying – QPSK, Quadrature Amplitude modulation,
bandwidth efficiency, carrier recovery – squaring loop, Costas loop, DPSK.

1. Introduction
1) Draw and explain the simplified Block diagram of an Electronic communication system.
2) Write the examples for the analog and digital signals (symbols).
3) List out some of the modulation techniques.
4) Differentiate digital communication and digital radio.
5) Differentiate digital communication and digital radio through block diagram.
2. Shannon limit for information capacity
1) State Information capacity theorem.
2) Define State Hartley’s Law.
3) Give the equation of Shannon limit for Information capacity.
3. Digital Amplitude Modulation
1) Write the expression for digital amplitude modulated signal.
2) Write OOK: On-Off Keying (Digital amplitude modulation).
3) What is meant by continuous wave?
4) What is the use of Amplitude modulated analog carriers.
5) Draw the diagrammatic representation for digital amplitude modulated signal.
4. Frequency shift keying, FSK bit rate and baud,
1) Write the mathematical expression of binary FSK with the explanation of its notations.
2) Draw the wave forms of binary FSK.
3) Rewrite the mathematical expressions of binary FSK for logical inputs 1 and 0.
4) Explain about the mark and space frequencies.
5) Define FSK Bit rate.
6) Define FSK Baud rate.
5. FSK transmitter
1) Draw the block diagram and waveforms of FSK Modulator or FSK transmitter.
2) What is meant by VCO and write about its contribution in FSK Transmitter?
3) What is meant by frequency deviation ∆f (in terms of vm(t)) and write its mathematical expression?
4) Draw the diagram for the FSK frequency Deviation and explain it.
6. BW consideration of FSK
1) Write the expression for frequency deviation ∆f (in terms of fm, fs) and explain it.
2) Derive the expression for bandwidth (in terms of ∆f) of FSK from fb, fs fm.
3) Give the relationship between highest fundamental frequency of the bin. modulating signal fa and bit rate fa.
4) Give the expression for the h-factor of FSK (in terms of ∆f and in terms of fm, fs) and state its notations.
7. FSK receiver
1) What are the types of FSK Receiver?
2) Draw the block diagram of Noncoherent FSK Receiver.
3) What is the work of BPF in Noncoherent FSK Receiver?
4) What is the work of Envelope detector in Noncoherent FSK Receiver?
5) What is the work of Comparator in Noncoherent FSK Receiver?
6) Draw the block diagram of Coherent FSK Receiver
7) Write about phase locked loop (PLL) / Demodulating binary FSK signals.
8) Explain the operation of PLL/FSK
9) Compare which is best among Binary FSK and PSK or QAM? Conclude your answer.
10) Write about Continuous-Phase FSK.


8. Phase shift keying
1) Define PSK.
2) Differentiate PSK and Conventional phase modulation.
9. Binary phase shift keying
1) Define BPSK
2) What are the other names of BPSK (Phase Reversal Keying or Biphase modulation)
BPSK transmitter
3) Draw the block diagram of BPSK transmitter.
4) What is the function of balanced modulator / Product modulator at transmitter?
5) What is the condition for balanced modulator to operate properly? (Digital I/p V > peak carrier voltage)
6) Write about the switching elements (Diodes) present in the transmitter during the binary input 1 (or 0)?
7) What is meant by Constellation diagram? (or) What is the difference between phasor diagram and
Constellation diagram?
8) Write the truth table of BPSK.
9) Draw the Constellation diagram of BPSK.
10) Draw the phasor diagram of BPSK
Bandwidth considerations of BPSK
11) Derive the expression for Bandwidth of BPSK.
M-ary Encoding
12) What is M-ary / Beyond binary/ Higher than binary encoding
BPSK Receiver
13) Draw the block diagram of BPSK receiver.
14) What is the function of balanced modulator / Product modulator at receiver?
15) What are the input signals of BPSK Receiver?
16) What is the function of LPF in receiver?
17) Derive the reproduction of Logic 1 (or 0) from +sin ωct ( or –sin ωct)
10. QPSK
1) Define QPSK
2) What are the other names of QPSK
3) Relate QPSK with M-ary. (M=4), Explain the term Quarternary.
4) What is the function of balanced modulator / Product modulator at transmitter?
5) Explain about the number of Input conditions and Output phases.
6) Explain about Dibits.
7) What is the relationship between input bit rate and output baud rate. (output baud rate = 1/2 input bit rate)?
QPSK transmitter
8) Draw the block diagram of QPSK transmitter.
9) Write about Bit splitter.
10) Write about I and Q channels?
11) What are the output signals of QPSK transmitter? (2 logics and 2 phase So 4 O/p’s, Write equations)
12) What is the function of balanced modulator at transmitter?
13) Write the truth table of QPSK.
14) Draw the Constellation diagram of QPSK.
15) Draw the Phasor diagram of QPSK.
Bandwidth considerations of QPSK
16) Derive the expression for Bandwidth of QPSK.
BPSK Receiver
17) Draw the block diagram of QPSK receiver.
18) What is the function of balanced modulator / Product modulator at receiver?
19) What are the input signals of QPSK Receiver?
20) What is the function of carrier recovery circuit? (i/p and o/p signals)
21) What is the function of Product detector at receiver?
22) What is the function of LPF in receiver?
23) Derive the reproduction of Logic 1 and 0 from -sin ωct + cos ωct.
24) What is offset QPSK?
• Similar questions for 8-PSK (Extra: 2-to-4 convertor) and 16-PSK (Extra: Quad bits)


11. Quadrature Amplitude modulation
1) What is Quadrature Amplitude modulation.
Eight QAM Transmitter
2) What is the difference between 8-PSK and 8-QAM? (Omission of Inverter between the C channel and the
Q Product modulator)
3) Draw the block diagram of 8-QAM
4) Write about Tribits.
5) Write about I, C and Q Channels.
6) Write about the input and outputs of 2-to-4 convertor at transmitter.
7) What is the function of linear summer?
8) Write the truth table of 8-QAM.
9) Draw the Constellation diagram of 8-QAM.
10) Draw the Phasor diagram of 8-QAM.
Bandwidth considerations of 8-QAM
11) Derive the expression for Bandwidth of 8-QAM.
8-QAM Receiver
12) Draw the block diagram of 8-QAM receiver.
13) Write about the input and outputs of 2-to-4 convertor at receiver.
16-QAM Receiver
• Questions Similar as 8-QAM.
12. Bandwidth efficiency
1) Define bandwidth efficiency / Information density.
2) What is the use of bandwidth efficiency calculation?
3) Give the expression for bandwidth efficiency.

13. Carrier recovery – squaring loop, Costas loop
1) Explain the process of carrier recovery / Phase referencing.
2) What is meant by absolute phase encoding?
3) What are the methods of carrier recovery?
4) What is meant by squaring loop carrier recovery? (Block diagram, Derivation and Explanation)
5) What is meant by Costos loop carrier recovery? (Block diagram and Explanation)
6) What is meant by remodulator carrier recovery? (Block diagram and Explanation)
14. DPSK
1) Define differential phase shift keying.
2) Draw block diagram of DPSK transmitter.
3) Write about XNOR circuit.
4) Draw block diagram of DPSK receiver.
5) Draw timing sequence of DPSK.

1. What is known as Binary phase shift keying? Discuss in detail the BPSK transmitter and Receiver and also
obtain the minimum double sided Nyquist bandwidth. (16m)
2. Discuss the principle of operation of FSK transmitter and receiver (8m)
3. Write a note on QPSK transmitter and receiver. (16m)
4. What is the need for carrier Recovery? Explain the Costas loop method (or any one ) of carrier recovery. (8m)
5. Illustrate the concept of 8-QAM transmitter with the truth table. (8m)
6. Write a note on DPSK. (8m)
7. Describe the basic principles of PCM system. (8m)
8. What is companding? Explain in detail. (16m)


UNIT III
DIGITAL TRANSMISSION

Introduction, Pulse modulation, PCM – PCM sampling, sampling rate, signal to quantization noise
rate, companding – analog and digital – percentage error,
Delta modulation, adaptive delta modulation, differential pulse code modulation, pulse transmission –
Intersymbol interference, eye patterns.

1. Introduction
1) What are the advantages of Digital Transmission?
2) What are the disadvantages of Digital Transmission
2. Pulse modulation
1) Define Pulse modulation.
2) What are the four predominant methods of Pulse modulation?
3) Define PWM.
4) Define PPM.
5) Define PAM. (Intermediate form of modulation with PSK, QAM and PCM)
6) Define PCM.
7) Draw the waveforms of PWM, PPM, PAM and PCM.
8) Applications of PWM, PPM, PAM and PCM.
3. PCM
1) Define PCM / PCM Codec.
2) Draw the block diagram a Simple (One-way Only) PCM system.
3) What is the function of Sample and Hold Circuit?
4) What is the function of ADC (Analog to Digital Converter)?
5) What is the function of Parallel to Serial Converter?
6) What is the function of Regenerative repeater?
7) What is the function of Serial to Parallel Converter?
8) What is the function of DAC (Digital to Analog Converter)?
4. PCM sampling
1) What is the need for sampling? (Analog i/p Samples Series of pulses Digital Binary PCM Code)
2) How the Sample and hold circuit helps for the accurate function of ADC?
3) What are the types of sampling?
4) What is meant by Natural sampling?
5) What is meant by Flat top sampling?
6) Differentiate Natural sampling and Flat top sampling
7) Which sampling method is being preferred mostly? Why?
8) What is meant by Aperture error? (Caused by Flat top sampling)
9) What is the function of FET in S&H Circuit?
10) What is the function of Q1 and C1 in S&H Circuit? (or) What are the Sample and Hold Copmonents?
11) Explain Aperture (or) Acquisition time.
12) Define Storage time.
13) What is meant by Aperture Distortion?
14) Write about the Z1 and Z2 in S&H Circuit.
15) Write the combination of components acting as Capacitive voltage-divider network. (FET series with C1: if
FET is OFF)
5. Sampling rate
1) State Nyquist Sampling theorem.
2) Write the mathematical expression for Minimum sampling rate (fs).
3) What is meant by Heterodyning or Non linear mixing?
4) Draw and explain the Frequency domain representation of output spectrum from S&H Circuit.
5) What do you meant by Aliasing Effect (or) Fold-over distortion? How it can be removed?(Using Anti
aliasing filters or Anti fold-over filter)


6) Define dynamic Range (DR).
7) Derive the expression for Dynamic range.
8) Define Code efficiency.

6. Signal-to-Quantization Noise Rate (SQR)
1) Define SQR
2) When the worst possible signal voltage-to-quantization noise will occur.
3) Write the mathematical expressions for SQR.
7. Companding – analog and digital
1) Define companding?
Analog companding
2) Draw the block diagram for the PCM system with Analog companding.
3) Write about block(s): BPF at Txr., Analog compressor, Sample and Hold Circuit, ADC, Parallel-to-Serial
Convertor, Serial-to-parallel Convertor, DAC, Hold circuit, Analog expandor, BPF at Rxr.
4) What are the methods of Analog companding? (A-law and µ-law)
5) Write the compression characteristic for µ-law.
6) Write the compression characteristic for A-law.
Digital Companding
7) Draw the block diagram for the PCM system with Digital companding.
8) Write about block(s): BPF at Txr., Sample and Hold Circuit, ADC, Digital compressor, Parallel-to-Serial
Convertor, Serial-to-parallel Convertor, Digital expandor, DAC, Hold circuit, BPF at Rxr.
9) What is 13-segment compression?
10) Define Percentage error.

8. Delta modulation PCM (uses single bit binary code to achieve digital transmission)
1) Write about Delta modulation
2) What is the algorithm for Delta modulation
Delta modulation Transmitter
3) Draw the block diagram of Delta modulation Transmitter.
4) What is the function of sample and hold circuit.
5) What is the function of up/down counter
6) What is the function of DAC in Delta modulation PCM
7) How the steps change value and clock frequency (sample rate) are related?
Delta modulation Receiver
8) Draw the block diagram of Delta modulation receiver.
9) What are the problems associated with Delta modulation.
10) Write about Slope overload and how it could be rectified?
11) Write about Granular noise and how it could be rectified?

9. Adaptive delta modulation
1) What is the need for Adaptive delta modulation?
2) What is Adaptive delta modulation?
3) What is the algorithm for an adaptive delta modulator?

10. Differential pulse code modulation
1) What is the need for Differential pulse code modulation (DPCM) – (to overcome the transmission of
several identical (redundant) PCM codes, in speech txn.)
2) Draw the block diagram of Differential pulse code modulation (DPCM) transmitter.
3) Write about differentiator / subtractor in Differential pulse code modulation (DPCM) transmitter.
4) Draw the block diagram of Differential pulse code modulation (DPCM) receiver.
5) Write about Adder / Integrator in Differential pulse code modulation (DPCM) receiver.

11. Pulse transmission
1) Draw the waveform ‘from a bandlimited communications channel’ (or) ‘typical response of a bandlimited
filter’ and explain its terms (First pulse, Second pulse, Major lobe, Secondary lobes or ringing tails)


2) Draw the spectrum of square pulse with duration 1/T.
3) Give the expression for the output frequency spectrum corresponding to a rectangular pulse. (f(ω)) and give
the Nyquist rate

12. Intersymbol interference (ISI)
1) Define intersymbol interference. (overlap of ringing tails)
2) What are the effects of ISI? (Cross talk)
3) How ISI can be removed?
4) What are the causes of ISI? (Timing inaccuracies, Insufficient bandwidth, Amplitude distortion, Phase
distortion)
5) How the causes of ISI could be rectified? (Timing inaccuracies, Insufficient bandwidth, Amplitude
distortion, Phase distortion)

13. Eye patterns
1) What is the purpose using Eye pattern?
2) Which block plays major role in regeneration of original pulses? (Decision circuit in repeater)
3) What is meant b eye pattern or eye diagram?
4) Draw and explain the eye diagram of ternary signals.
5) Draw the eye diagram measurement setup.
6) Explain the terms – Decision times, Crosshairs.
7) Write about eye opening.
8) Define and give the mathematical equation of ISI degradation.
9) What is Data transition jitter

1. Describe the basic principles of PCM system. (8m)
2. Explain in detail the Delta modulation transmitter and Receiver. (10m)
3. Discuss the draw backs of delta modulation and explain the significance of adaptive delta modulator.
(6m)
4. Discuss about the causes of ISI. (8m)
5. What is companding? Explain in detail. (8m)
6. Write a note on DPSK. (8m)
7. ISI and Eye pattern (12m)


UNIT IV
DATA COMMUNICATIONS

Introduction, History of Data communications, Standards Organizations for data communication,
data communication circuits, data communication codes, Error control, Error Detection, Error correction.
Data communication Hardware, serial and parallel interfaces, data modems, Asynchronous modem,
Synchronous modem, low-speed modem, medium and high speed modem, modem control.

1. Introduction
1) Define data
2) Define datum
3) Define information
4) What is the need for data communication codes?

2. History of Data communications
1) Write about telegraph and Morse code.
2) Write about multiplexer.
3) Discuss about AT&T.

3. Standards Organizations for data communication
1) What is the need for the set up of Standards Organizations?
2) What are the different Standards Organizations? (Explain about – ISO, CCITT, ANSI, IEEE, EIA and
SCC)

4. Data communication circuits
1) Draw the basic block diagram of a data communications network.
2) Explain the blocks of a data communications network. (Host computer, transmission medium, secondary
station, Data Terminal Equipment -- DTE, Data Communications Equipment (or) MODEM -- DCE )
3) Compare Serial and Parallel transmissions and conclude which is better for in which conditions.
4) What are the other names of serial communication? (serial-by-bit)
5) What are the other names of parallel communication? (parallel-by-bit or serial-by-character)
6) Write about the different configurations of data communications. (Two point, Multi point)
7) What are the different topologies / architectures used in data communications?
8) What are the different transmission modes in data communications? (Simplex, Half duplex, Full duplex,
Full/Full Duplex)
9) Compare two-wire and four wire operation.

5. Data communication codes
1) Define Data communication codes.
2) What are the other names of Data communication codes? (Chr. Set, Chr. Codes, Symbol Codes, Chr.
languages)*
3) What are the different Data communication codes .
4) Write notes on Baudot Code.
5) Write notes on ASCII Code.
6) Write notes on EBCDIC Code.
7) Write notes on Bar Codes and its types.

6. Error control, Error Detection, Error correction,
1) What is the need for Error control?
Error detection
2) What is meant by Error detection?
3) What are the methods of Error detection? (Redundancy, Echoplex, Exact-count encoding, Parity (odd /
even), Checksum, Vertical (Parity) and Horizontal(or Longitudinal) (b0⊕b1⊕b2⊕…) redundancy checking,
Cyclic redundancy checking ())
4) Write about Vertical Redundancy check – Parity (odd / even)


5) Write about Horizontal(or Longitudinal) redundancy checking – Block, Block check sequence gerneration
by (b0⊕b1⊕b2⊕…), appending.
6) Write about cyclic redundancy checking – Block, Block check sequence generation by Long division,
appending, CRD-16.
Error detection
7) What is meant by Error detection?
8) What are the methods of Error detection?
9) What is Symbol substitution? (Replacing chr. by unique chr.)
10) What is Retransmission? (ARQ, overhead, Retransmission of error message)
11) What is Forward error correction (FEC)? (Only error correction scheme that detects and corrects, Hamming
code explanation)
12) How will you predict the number of hamming bits to be inserted?
13) What are the advantage and application of Forward error correction (FEC)?
7. Data communication Hardware
1) Draw the block diagram of multipoint data communications circuit.
2) Define Data communications link.
3) Differentiate Host (Primary) and Secondaries (remotes). [Host Mainframe comp.; Remotes Remote
computer terminals]
4) What is meant by a centralized network? [N/w made up or Host and secondaries]
5) What are elements of a primary station? [Mainframe comp., Line Control Unit, Data MODEM]
6) What are the functions of host? [Storing, processing, retransmitting, storing softwares for data base
management]
7) Write notes on DTE.
8) Write notes on DCE.
UART Transmitter
9) What are the primary functions of UART?
10) What is the purpose of Control word in UART?
11) Draw the block diagram of UART Transmitter.
12) Explain the blocks [Control register, transmit buffer registers - 2, parity generator, data-parity-and-stop bit
steering logic, timing generator, buffer empty logic circuit, Status word register, output circuit] and signals.
13) Draw and explain timing diagram of UART Transmitter.
UART Receiver
14) Draw the block diagram of UART receiver.
15) Explain the blocks [start bit verify, receive timing circuit, receive shift register – 2, parity checker, control
register, status word register] and signals.
16) Draw and explain timing diagram of UART Receiver.
USRT
17) USRT Tranceiver – Block diagram, Block and Signals explanation, and Control word tabulation.
8. Serial and parallel interfaces
Serial interfaces
1) What is the application of Serial interfaces? [Connecting Line Control Unit and MODEM]
2) Explain about RS232 Interface. [Electrical specifications, Driver, Terminator, Noise margin, functional
characteristics, EIA RS-232 pin functions]
3) Explain about RS-449 and RS-530 interface standards.
4) Explain about CCITT X.21.
Parallel Interface
5) What is meant by parallel transmission?
6) What is the advantage of parallel transmission?
Centronics Parallel Interface
7) Draw and explain the Control, data, status lines block diagram of Centronics Parallel Interface.
Control lines (strobe, auto feed, prime, select)
Status lines (Acknowledge, Paper out, error, busy, select)
8) Explain in detail about IEEE 488 Bus. [operating modes, IEEE 488 interface lines, Interface management
circuits]


9. Data modems
1) Define MODEM or DCE or data set or dataphone.
2) What are the classifications of MODEM?
3) What are the modulation techniques used in MODEM?
Asynchronous modem
4) Application of Asynchronous modem.
5) Operating modes.
6) Low band channel and High band channel
7) Frequency division multiplexing
8) Answer channel
Synchronous modem
9) Application of Synchronous modem.
10) Synchronous modems are complicated then Asynchronous modems. Why? [B’coz of Clock and Carrier
recovery Ckts.]
MODEM Synchronization
11) How the MODEMs are synchronized? [By special, internally generated bit pattern called Training sequence
at transmit modem]
12) What the functions are of receive modem?
Low-speed modem, Medium and High speed modem
13) Write notes on Low-speed modem.
14) Write notes on medium and high speed modem [2400 bps, Training sequence, Clock Recovery, Adaptive
equalizers, Scrambler and Descrambler circuits]
15) Draw the scrambler and descrambler circuits.
16) Equalizers – To equalize Delay and Gain Characteristics – Types: Compromise equalizers [pre-
equalization], Adaptive equalizers [post-equalization]
17) Differentiate Low-speed modem and (medium and high speed modem).
Modem control – The AT Command Set
Write about
18) Dumb modems
19) Intelligent Modems
20) AT Command set (or) Hayes command set.
21) AT Command mode
22) AT on-line mode
23) CCITT Modem Recommendations
24) CCITT Modem Recommendations V.29
26) CCITT Modem Recommendations V.32bis and V.32terbo
28) CCITT Modem Recommendations V.42 and V.42bis
29) CCITT Modem Recommendations V.32 [V.fast]
30) CCITT Modem Recommendations V.34+

1. Write a note on data communication codes. (8m)
2. Describe the most common error detection techniques. (12m)
3. Briefly explain the three methods of error correction. (8m)
4. Explain in detail about Line control unit, DTE, DCE. (12m)
5. Discuss the function of a data modem. (6m)
6. Explain serial and parallel interfaces in detail. (16m)
7. Explain in detail the characteristics of IEEE 488 Bus. (10m)
8. Explain in detail about error detection and correction. (8m)
9. Write a note on low, medium and high speed modems. (8m)


UNIT V
SPREAD SPECTRUM AND MULTIPLE ACCESS TECHNIQUES

Introduction, Pseudo-noise sequence, DS spread spectrum with coherent binary PSK, processing
gain, FH spread spectrum.
Multiple access techniques – wireless communication, TDMA and CDMA in wireless
communication systems, source coding of speech for wireless communications.

1. Introduction
1) Define Spread spectrum modulation.
2) Discuss about bandwidth consideration in spread spectrum.
3) What is meant by multipath rejection?

2. Pseudo-noise sequence
1) What is Pseudo-Noise sequence?
2) Draw the block diagram of Pseudo-Noise sequence generator.
3) Give the mathematical expression for the Pseudo-Noise sequence generator output states.
4) Discuss the relationship between number of Flip-flops and number of possible states of shift
register.
5) Discuss: PN Sequence is periodic.
6) Explain the blocks of Pseudo-Noise sequence generator.
7) When did the PN sequence will be called as maximal-length sequence?
8) Discuss the properties of maximal-length sequence. [Balance property, Run property, Correlatoin
property]
9) Write the equation for Sampled spectrum of maximal-length sequences.
3. A Notion of Spread Spectrum
1) What is camouflaging the information signal? [Spread spectrum]
2) What is the purpose of using PN sequence? [Spreading code]
3) What is chopping?
4) Illustrate the waveforms of in the transmitter of baseband spread-spectrum system.
5) Block diagrams of transmitter, channel and receiver segments.
6) Equations of transmitter, channel and receiver segments.
4. Direct Sequence Spread Spectrum with coherent binary PSK, Processing gain
1) What is DSSS?
2) Draw the block diagram of DSSS transmitter?
3) What are the (2) modulations happening in the DSSS Txr.
4) Write about the inputs of the DSSS transmitter.
5) Draw the block diagram of DSSS receiver?
6) What are the (2) demodulations happening in the DSSS Rxr.
7) Write about the outputs of the DSSS transmitter.
8) Write the truth table for Phase modulation in DSSS.
9) Draw and explain the waveforms of DSSS
10) Write the equations for the Txr, Channel and Rxr. Segments.
11) Draw the model of DSSS BPSK System.
12) Synchronization: State about Acquisition and Tracking
13) What is meant by decision rule and search strategy.
5. FH Hop spread spectrum
1) Write about the frequency hopping.
2) Why we opt for Frequency hop spread spectrum?


3) What is meant by FH Hop spread spectrum?
4) What are the types of Frequency Hopping? [Slow and Fast Frequency hopping]
5) What is Slow Frequency hopping?
6) What is Fast Frequency hopping?
7) Draw the block diagram of Frequency-hop spread M-ary frequency-shift keying transmitter.
[Write about M-ary FSK modulator, Frequency synthesizer, PN code generator, Mixer, BPF]
8) Draw the block diagram of Frequency-hop spread M-ary frequency-shift keying receiver.
[Write about M-ary FSK detector, Frequency synthesizer, Local PN code generator, Mixer, BPF]
9) Give the chip rate Rc in terms of hop rate Rh and symbol rate Rs.
10) Express the symbol energy-to-noise spectral density ratio.
11) Express processing gain in terms of Wc and Rs
Fast frequency hopping
12) Explain about the Fast frequency hopping
13) What are the two procedures followed in fast frequency hopping?
14) Draw the illustration of slow frequency hopping.
15) Draw the illustration of fast frequency hopping.

6. Multiple access techniques
1) What is meant by Multiple accessing
2) Discuss about FDMA.
3) Discuss about TDMA.
4) Discuss about CDMA.
5) Discuss about SDMA.
6) Compare FDMA, TDMA and CDMA.
7. Wireless communication
1) Discuss about Wireless communication
2) What are the factors to be considered in the evaluation of Wireless communication
Explain the terms
3) Cellular radio
4) Switching center
5) Base station
6) Hand over or Hand off
7) Frequency reuse
8) Cell splitting – macro cells, micro cells
9) Shift parameters
10) Co-channel cells
11) Propagation effects: (Multipath phenomenon, Constructive and destructive multipath phenomenon,
signal fading, Phasor representation of Constructive and destructive forms of multipath)
12) Illustrate how the envelope fades as two incoming signals combine with different phases.
13) Near- far problem in spread spectrum modulation
8. TDMA and CDMA in wireless communication systems
Write about
1) Up link and down link
2) Frequency division Duplexing.
3) Frame structure of GSM wireless communication system
4) Guard time
5) RAKE Rxr Block diagram and explanation [Diversity, Correlators, Delays, Adder, Integrator,
Decision device, Phase and gain adjustors (2 points)]
6) Maximum ratio combining principle
7) Linear combiner output equation


9. Source coding of speech for wireless communications
1) Linear predictive coding
2) Types of LPC
Multi-pulse Exited LPC
3) Multi-pulse Exited LPC transmitter [Synthesis filter, Excitation filter, Minimization of
perceptually weighted error] and Receiver [Synthesis filter, Excitation filter], Frames and sub
frames.
Code Exited LPC
4) Encoder [Synthesis filter, Gain factor, Excitation code book, Minimization of perceptually
weighted error].
5) Differentiate Multi-pulse Exited LPC and Code Exited LPC
6) Compare Multi-pulse Exited LPC and Code Exited LPC

1. What is a Pseudo noise sequence? What are the properties of Pseudo noise sequence? (8m)
2. With a block diagram explain, DS spread spectrum with coherent binary PSK. (10m)
3. Explain the principle of DS spread spectrum technique. (8m)
4. Describe the frequency hopping spread spectrum technique in detail. (10m)
5. Describe the application of CDMA in wireless communication system. (8m)
6. Explain the near- far problem in spread spectrum modulation? (6m)
7. Explain the basic principle of TDMA. (8m)
8. Discuss the methods of Source coding of speech for wireless communications (16m)

***
GENERAL INSTRUCTIONS:
1. Underline the two marks like question’s important terms if the topics wee asked as questions.
2. Prepare thoroughly the slanted questions of Frequently asked questions…
3. Prepare well at least the first half of each Unit (which is slanted) at the start of every unit.

***

*** STUDY WELL *** ∰ *** CLEAR THE SUBJECT *** ∰ *** ALL THE BEST ***


Understanding Analog and Digital Communication Systems

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