Subject 2018 Question Paper — Government College of Engineering and T…
The 2018 Subject previous year question paper (Government College of Engineering and Technology, Jammu), with every question and its marks.
- University: Government College of Engineering and Technology, Jammu
- Course: ELECTRONICS AND COMM. ENGG.—COURSE NO. PEC-501 (Digital Communication)
- Branch: ELECTRONICS AND COMM. ENGG.
- Year: 2018
- Paper: end-term
- Duration: 180 minutes
- Total marks: 100
Instructions
- Attempt five questions in all, selecting at least two questions from each Section.
Questions
Section A
- Q1. (a) Explain the geometrical representation of M energy signals as linear combination of N orthogonal basis functions with necessary diagrams and expressions. [15] (b) For the bit stream 10101011, draw the data formats for : (i) UniPolar NRZ (ii) Differential Manchester. [5] [20 marks]
- Q2. (a) For a bit stream 110110100, sketch the output of BASK, BPSK, DPSK and BFSK transmitters. Assume $f_s = f_b$ for first three cases and $f_L = f_b$ and $f_H = 2 f_b$ for last. [10] (b) Explain with the help of example why error always occur in pairs in DEPSK ? [10] [20 marks]
- Q3. (a) With aid of block diagram and waveforms, explain working of QPSK transmitter. [15] (b) Compare OQPSK and QPSK system. [5] [20 marks]
- Q4. (a) What is the difference between multiplexing and access technique ? [5] (b) Give features of TDMA and CDMA. What is the advantage of CDMA over other access techniques ? [15] [20 marks]
Section B
- Q5. (a) Briefly explain the applications of direct sequence spread spectrum. [10] (b) What is PN sequence ? Explain the generation of maximum length sequence. What are the properties of maximum length sequence ? [10] [20 marks]
- Q6. Explain how Acquisition and Tracking is achieved in FHSS system. [20] [20 marks]
- Q7. A Discrete Memoryless Source (DMS) X has four symbols $x_1$, $x_2$, $x_3$, $x_4$ with probabilities $P(x_1) = 0.1$, $P(x_2) = 0.1$, $P(x_3) = 0.6$, $P(x_4) = 0.2$. The source emits one of four symbols once every milliseconds. Calculate : (i) The information content of each of these symbols. [10] (ii) The total entropy and information rate. [10] [20 marks]
- Q8. (a) Define Hamming weight, Hamming distance and minimum distance. For a Hamming distance of 7, how many errors can be detected and corrected ? [5] (b) Determine Shannon-Fano code for the following messages with their probability as : $P(x_1) = 0.05$, $P(x_2) = 0.15$, $P(x_3) = 0.25$, $P(x_4) = 0.15$, $P(x_5) = 0.3$ and $P(x_6) = 0.1$. [15] [20 marks]