JNTU
JNTU B.Tech III SPREAD SPECTRUM COMMUNICATIONS Previous Question Paper (February - 2023 - R16)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, Answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
What is hybrid direct sequence?
Answer
A hybrid direct sequence system combines Direct Sequence Spread Spectrum (DSSS) with another spread spectrum technique, such as Frequency Hopping (FHSS), to provide enhanced security and interference rejection by leveraging the advantages of both modulation schemes.
Write the properties of PN sequence.
Answer
- Balance property: The number of 1s and 0s in a period differs by at most one.
- Run property: The distribution of runs of consecutive 1s or 0s follows specific statistical patterns.
- Correlation property: The autocorrelation function is periodic and has a sharp peak at zero shift, resembling white noise.
What is optimum delay discriminator?
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Discuss the function of PLL and VCO.
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What is multiple dwell energy detector?
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Discuss low pass implementation using matched filter.
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Write about multistage detector.
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Discuss interference cancellation.
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What are the error correction codes?
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Compare block codes and convolutional codes.
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Part B
Explain how PN sequences are generated.
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Explain the Direct Sequence Spread Spectrum (DSSS).
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Explain the slow and fast frequency hopping techniques.
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What is sequence generator? Explain about maximal length sequences.
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Explain non coherent delay lock tracking loop.
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Describe the code tracking loops for frequency hop systems.
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Discuss about Double Dither Non-Coherent Tracking Loop.
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Explain about tracking loop for arbitrary wide band signals.
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Explain the DSSS receiver using matched filter code acquisition.
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Discuss about the fixed integrator time detector.
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Explain the procedure to detect a signal in additive white Gaussian noise.
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Discuss about RASE synchronization system with neat block diagram.
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Explain in detail the CDMA multiple access technique.
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Discuss the Interference Analysis for Broadcast and Multiple Access Channels.
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What is wide band mobile channel? What is the role of CDMA in wide band channel?
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Explain linear suboptimal detection scheme.
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Discuss about Jamming margin in spread spectrum communications.
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Explain about convolutional coding with example.
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Discuss about the trellis representation for convolutional encoder.
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Compare the coded and un coded performance of FH/MFSK worst case partial band jamming.
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