Department of TCE
QUESTION BANK
ET452-SPREAD SPECTRUM TECHNIQUES
VIII Semester - ETE
UNIT I & II
Part A
1. What is a transmitted reference system?
2. What is a stored reference system?
3. How does a PN signal differ from a random signal?
4. What is maximal length PN sequence?
5. What is the expression for the autocorrelation function of a periodic waveform.
6. What are the important applications of spread-spectrum (SS) systems?
7. What are the modulation techniques used in DSSS systems?
8. What is meant by spreading a signal?
9. What are the modulation techniques used in FHSS systems?
10. Given, hopping bandwidth=400MHz and a frequency step size = 100Hz. What is
the minimum number of PN chips required for each frequency word?
11. Draw a diagram showing a time-hopping waveform.
12. Define chirp SS system
13. Draw a PN signal waveform.
14. Draw the auto-correlation function (ACF) of a PN sequence.
15. Draw a block diagram to generate a PN signal
Part B
1. Explain the advantages of spread spectrum systems in detail.
2. Explain with a neat block diagram, the basic spread spectrum technique.
3. Draw and describe the block diagram of a direct-sequence (DS)
transmitter/receiver.
4. Draw and describe the block diagram of a DS receiver.
5. Explain the generation of PN sequence using LFSR.
6. From fundamentals, derive the expression for processing gain for a spread
spectrum system.
7. Derive expression for variance at the correlator output of the receiver in a SS
system
8. Draw and describe the block diagram of a FH/MFSK system.
9. What are the advantages and disadvantages of (a) DS systems, (b) FH systems
10. What are the different properties of PN sequences? Explain
11. What is FFH? Explain FFH/MFSK demodulator in detail.
12. Compare Fast FH and slow FH system.
13. Explain FH/DS system in detail.
14. Explain TH/DS system in detail.
15. What is the advantage of hybrid Spread spectrum technique? Exlain the Chirp
system in detail.
UNIT III
Part A
1. What are the goals of an antijam communication system?
2. What is aim of the BLADES system?
3. What are frequency follower jammers?
4. How can we defeat repeat back jamming?
5. How can we mitigate partial band jamming?
6. How can we overcome multiple tone jamming?
7. Who is referred to as a broad band jammer?
8. Draw the partial band jammer waveform.
9. Draw the broad band jammer waveform.
10. Draw the stepped tone jammer waveform.
11. What is the need for synchronization in a spread spectrum system?
12. Define acquisition.
13. Define tracking.
14. Compare parallel search and serial search acquisition technique.
15. What is the advantage of TDL tracking.
Part B
1.
2.
3.
4.
5.
6.
7.
8.
9.
Explain the importance of the required J/S ratio
What is Anti Jam margin? Explain in detail.
What is Broad band Jamming? Explain.
What is Partial Band Noise jamming? Explain.
Explain Multiple tone jamming in detail.
What is Pulse jamming? Explain.
Expalin repeat back Jamming? How is it overcome.
Explain the BLADES system in detail.
Explain the various jammer waveforms used for jamming communication
systems.
10. What is acquisition? Explain with a neat block diagram a DS parallel search
acquisition technique.
11. What is acquisition? Explain with a neat block diagram a Frequency hopped
acquisition technique.
12. Explain in detail a Direct sequence serial search acquisition technique.
13. Explain Frequency hopping serial search acquisition.
14. What is sequential estimation? Explain the RASE method.
15. What is tracking? Explain the Delay locked loop for tracking DS signals.
16. Explain with a block diagram the Tau Dither tracking loop.
UNIT IV
Part A
1.
2.
3.
4.
5.
What is cipher text?
What is block cipher?
Mention a few symmetric block cipher algorithms.
What is AES?
What is the value of symmetric key in the Deffie Helman protocol if
g=7,p=23,x=3,and y=7?
6. Name the security services provided to a message.
7. What is message confidentiality?
8. What is message Integrity?
9. What is message Authentication?
10. What is message NonRepudiation?
11. What is a message digest?
12. What is MAC?
13. What is key management?
14. What is Key distribution centre?
15. What is a certification Authority?
Part B
1. Explain symmetric key and Asymmetric key cryptography.
2. Explain DES in detail.
3. Discuss the RSA algorithm for asymmetric key cryptography.
4. Explain the Deffie Helman key exchange algorithm.
5. Explain in detail message confidentiality using symmetric key cryptography.
6. Explain in detail message confidentiality using Asymmetric key cryptography.
7. Explain message integrity in detail.
8. Explain SHA-1 hash algorithm.
9. What are the necessary criteria to be satisfied for a hash function?
10. How is message authentication performed using MAC ? Explain.
11. Write short notes on Digital Signature.
12. What is message non-repudiation?Explain.
13. Explain the process of signing a digest in a digital signature.
14. What is symmetric key distribution? Explain KDC
15. Write short note on KERBEROS.
16. Explain public key distribution in detail.
UNIT V
Part A
1. What is code division multiple access?
2. What is multipath fading?
3. What is the effect of multipath fading?
4. What is the ISM band?
5. What is the full form of FCC and CFR?
6. What is FDMA?
7. What is TDMA?
8. What is CDMA?
9. Why CDMA is called interference limited system?
10. What is the advantage of CDMA over TDMA?
Part B
1. Explain with a block diagram CDMA transmitter and receiver.
2. Explain the CDMA receiver in detail. Draw the spectrum at input and output of
the receiver. Explain.
3. Explain with a block diagram how a spread spectrum system eliminates multipath
interference.
4. Explain the FCC Part 15 rules for spread spectrum operation.
5. What are the factors that influence the maximum number of users per cell?
Explain.
6. A CDMA system is interference limited. Explain in detail.
7. Write short note on capacity of a CDMA system.
8. Compare an interference limited system versus a dimension limited system.
9. Compare TDMA and CDMA.
10. Write a short note on IS-95 CDMA Digital cellular system.
11. Explain in detail the reverse channel of IS-95 system.
12. Explain in detail the forward link of IS-95 system.