# Digital Communication 6

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