Electronic Engineering MCQ Question Papers: ENTC, IT Interview Placement

Subject: Digital Communication 6

**Part 6: List for questions and answers of Digital Communication**

** **

**Q1. For M equally likely messages, M>>1, if the rate of information R > C, the probability of ****error is**

**a) Arbitrarily small**

**b) Close to unity**

**c) Not predictable**

**d) Unknown**

** **

**Q2. For M equally likely messages, M>>1, if the rate of information R = C, the probability of ****error is**

**a) Arbitrarily small**

**b) Close to unity**

**c) Not predictable**

**d) Unknown**

** **

**Q3. The negative statement for Shannon’s theorem states that**

**a) If R is greater than C, the error probability increases towards Unity**

**b) If R is less than C, the error probability is very small**

**c) Both a & b**

**d) None of the above**

** **

**Q4. According to Shannon Hartley theorem,**

**a) The channel capacity becomes infinite with infinite bandwidth**

**b) The channel capacity does not become infinite with infinite bandwidth**

**c) Has a trade off between bandwidth and Signal to noise ratio**

**d) Both b and c are correct**

** **

**Q5. The capacity of a binary symmetric channel, given H(P) is binary entropy function is**

**a) 1 – H(P)**

**b) H(P) – 1**

**c) 1 – H(P)2**

**d) H(P)2 – 1**

** **

**Q6. The channel capacity is**

**a) The maximum information transmitted by one symbol over the channel**

**b) Information contained in a signal**

**c) The amplitude of the modulated signal**

**d) All of the above **

** **

**Q7. For M equally likely messages, the average amount of information H is**

**a) H = log10M**

**b) H = log2M**

**c) H = log10M2**

**d) H = 2log10M**

** **

**Q8. The capacity of Gaussian channel is**

**a) C = 2B(1+S/N) bits/s**

**b) C = B2(1+S/N) bits/s**

**c) C = B(1+S/N) bits/s**

**d) C = B(1+S/N)2 bits/s**

** **

**Q9. The probability density function of a Markov process is**

**a) p(x1,x2,x3…….xn) = p(x1)p(x2/x1)p(x3/x2)…….p(xn/xn-1)**

**b) p(x1,x2,x3…….xn) = p(x1)p(x1/x2)p(x2/x3)…….p(xn-1/xn)**

**c) p(x1,x2,x3……xn) = p(x1)p(x2)p(x3)…….p(xn)**

**d) p(x1,x2,x3……xn) = p(x1)p(x2 * x1)p(x3 * x2)……..p(xn * xn-1)**

** **

**Q10. Orthogonality of two codes means**

**a) The integrated product of two different code words is zero**

**b) The integrated product of two different code words is one**

**c) The integrated product of two same code words is zero**

**d) None of the above**

** **

**Q11. The Golay code (23,12) is a codeword of length 23 which may correct**

**a) 2 errors**

**b) 3 errors**

**c) 5 errors**

**d) 8 errors**

** **

**Q12. The minimum distance for unextended Golay code is**

**a) 8**

**b) 9**

**c) 7**

**d) 6**

** **

**Q13. The prefix code is also known as**

**a) Instantaneous code**

**b) Block code**

**c) Convolutional code**

**d) Parity bit **

** **

**Q14. Run Length Encoding is used for**

**a) Reducing the repeated string of characters**

**b) Bit error correction**

**c) Correction of error in multiple bits**

**d) All of the above**

** **

**Q15. For hamming distance dmin and number of errors D, the condition for receiving invalid ****codeword is**

**a) D = dmin + 1**

**b) D = dmin – 1**

**c) D = 1 – dmin**

**d) D = dmin**

** **

**Q16. For hamming distance dmin and t errors in the received word, the condition to be able ****to correct the errors is**

**a) 2t + 1 = dmin**

**b) 2t + 2 = dmin**

**c) 2t + 1 = 2dmin**

**d) Both a and b**

** **

**Q17. Parity check bit coding is used for**

**a) Error correction**

**b) Error detection**

**c) Error correction and detection**

**d) None of the above**

** **

**Q18. Parity bit coding may not be used for**

**a) Error in more than single bit**

**b) Which bit is in error**

**c) Both a & b**

**d) None of the above**

** **

**Q19. For a (7, 4) block code, 7 is the total number of bits and 4 is the number of**

**a) Information bits**

**b) Redundant bits**

**c) Total bits- information bits**

**d) None of the above **

** **

**Q20. Interleaving process permits a burst of B bits, with l as consecutive code bits and t ****errors when**

**a) B = 2tl**

**b) B = tl**

**c) B = tl/2**

**d) B = tl **

** **

**Part 6: List for questions and answers of Digital Communication**

** **

**Q1. Answer: b**

** **

**Q2. Answer: a**

** **

**Q3. Answer: a**

** **

**Q4. Answer: d**

** **

**Q5. Answer: a**

** **

**Q6. Answer: a**

** **

**Q7. Answer: b**

** **

**Q8. Answer: d**

** **

**Q9. Answer: a**

** **

**Q10. Answer: a**

** **

**Q11. Answer: b**

** **

**Q12. Answer: c**

** **

**Q13. Answer: a**

** **

**Q14. Answer: a**

** **

**Q15. Answer: b**

** **

**Q16. Answer: d**

** **

**Q17. Answer: b**

** **

**Q18. Answer: c**

** **

**Q19. Answer: a**

** **

**Q20. Answer: d**