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**Digital Communications MCQs – ****Error Detection & Channel Coding ****MCQs ( Digital Communications ) MCQs**

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**Error Detection & Channel Coding MCQs ( Digital Communications ) MCQs – Digital Communications MCQs**

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# Error Detection and Correction 1

**1. In layering, n layers provide service to**

a) n layer

b) n-1 layer**c) n+1 layer**

d) none of the mentioned**Answer: c****Explanation: In layering n layer provides service to n+1 layer and use the service provided by n-1 layer.****2. Which can be used as an intermediate device in between transmitter entity and receiver entity?**

a) IP router

b) Microwave router

c) Telephone switch**d) All of the mentioned****Answer: d****Explanation: IP router, microwave router and telephone switch can be used as an intermediate device between communication of two entities.****3. Which has comparatively high frequency component?**

a) Sine wave

b) Cosine wave**c) Square wave**

d) None of the mentioned**Answer: c****Explanation: Square wave has comparatively high frequency component in them.****4. Which has continuous transmission?**

a) Asynchronous**b) Synchronous**

c) Asynchronous & Synchronous

d) None of the mentioned**Answer: b****Explanation: Synchronous has continuous transmission where as asynchronous have sporadic transmission.****5. Which requires bit transitions?**

a) Asynchronous**b) Synchronous**

c) Asynchronous & Synchronous

d) None of the mentioned**Answer: b****Explanation: Synchronous transmission needs bit transition.****6. In synchronous transmission, receiver must stay synchronous for**

a) 4 bits

b) 8 bits**c) 9 bits**

d) 16 bits**Answer: c****Explanation: In synchronous transmission, receiver must stay synchronous for 9 bits.****7. How error detection and correction is done?**

a) By passing it through equalizer

b) By passing it through filter

c) By amplifying it**d) By adding redundancy bits****Answer: d****Explanation: Error can be detected and corrected by adding additional information that is by adding redundancy bits.****8. Which is more efficient?**

a) Parity check**b) Cyclic redundancy check**

c) Parity & Cyclic redundancy check

d) None of the mentioned**Answer: b****Explanation: Cyclic redundancy check is more efficient than parity check.****9. Which can detect two bit errors?**

a) Parity check**b) Cyclic redundancy check**

c) Parity & Cyclic redundancy check

d) None of the mentioned**Answer: b****Explanation: CRC is more powerful and it can detect various kind of errors like 2 bit errors.****10. CRC uses**

a) Multiplication

b) Binary division**c) Multiplication & Binary division**

d) None of the mentioned**Answer: c****Explanation: CRC uses more math like multiplication and binary division.**

# Error Detection and Correction 2

**1. Which needs re-sending of signal?**

a) Error correction**b) Error detection**

c) Error correction & detection

d) None of the mentioned**Answer: b****Explanation: Error detection needs re-sending of data.****2. Which needs more check bits?****a) Error correction**

b) Error detection

c) Error correction & detection

d) None of the mentioned**Answer: a****Explanation: Error correction needs more check bits where as error detection needs less check bits.****3. Which gets less affected by noise?**

a) Error correction**b) Error detection**

c) Error correction & detection

d) None of the mentioned**Answer: b****Explanation: Error detection is less affected by noise.****4. Which is used to protect privacy of the information?**

a) Compression coding

b) Source coding**c) Cipher coding**

d) None of the mentioned**Answer: c****Explanation: Cipher coding is used to provide privacy for the information.****5. Digital signals are easy for**

a) Storage

b) Handling

c) Time dilation**d) All of the mentioned****Answer: d****Explanation: Digital signals have ease of handing, storage and time dilation.****6. Which are forward error correcting codes?**

a) Block codes

b) Convolutional codes**c) Block & Convolutional codes**

d) None of the mentioned**Answer: c****Explanation: Block codes and convolutional codes are examples of forward error correcting codes.****7. Which operates on continuous stream of data?**

a) Block codes**b) Convolutional codes**

c) Block & Convolutional codes

d) None of the mentioned**Answer: b****Explanation: Convolutional codes operates on a continuous stream of data.****8. Which is more complex?**

a) Encoding**b) Decoding**

c) Encoding & Decoding

d) None of the mentioned**Answer: b****Explanation: In the case of block codes, decoding is a complex method.****9. Which has better minimum distance?**

a) Check sum**b) Cyclic redundancy check**

c) Check sum & Cyclic redundancy check

d) None of the mentioned**Answer: b****Explanation: Cyclic redundancy check has better distances.****10. In symmetric key cryptosystem, who knows the key?**

a) Sender

b) Receiver**c) Sender & Receiver**

d) None of the mentioned**Answer: c****Explanation: In symmetric key cryptosystem, both sender and receiver knows the same key.**

# Codes and Coding Technique

**1. While recovering signal, which gets attenuated more?**

a) Low frequency component**b) High frequency component**

c) Low & High frequency component

d) None of the mentioned**Answer: b****Explanation: High frequency components are attenuated more when compared to low frequency components while recovering the signals.****2. Mutual information should be**

a) Positive

b) Negative**c) Positive & Negative**

d) None of the mentioned**Answer: c****Explanation: Mutual information can also be negative.****3. ASCII code is a****a) Fixed length code**

b) Variable length code

c) Fixed & Variable length code

d) None of the mentioned**Answer: a****Explanation: ASCII code is a fixed length code. It has a fixed length of 7 bits.****4. Which reduces the size of the data?****a) Source coding**

b) Channel coding

c) Source & Channel coding

d) None of the mentioned**Answer: a****Explanation: Source coding reduces the size of the data and channel coding increases the size of the data.**

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**5. In digital image coding which image must be smaller in size?**

a) Input image**b) Output image**

c) Input & Output image

d) None of the mentioned**Answer: b****Explanation: In digital image coding, output image must be smaller than the input image.****6. Which coding method uses entropy coding?**

a) Lossless coding**b) Lossy coding**

c) Lossless & Lossy coding

d) None of the mentioned**Answer: b****Explanation: Lossy source coding uses entropy coding.****7. Which achieves greater compression?**

a) Lossless coding**b) Lossy coding**

c) Lossless & Lossy coding

d) None of the mentioned**Answer: b****Explanation: Lossy coding achieves greater compression where as lossless coding achieves only moderate compression.****8. A code is a mapping from**

a) Binary sequence to dicrete set of symbols**b) Discrete set of symbols to binary sequence**

c) All of the mentioned

d) None of the mentioned**Answer: b****Explanation: A code is a mapping from discrete set of symbols to finite binary sequence.****9. Which are uniquely decodable codes?****a) Fixed length codes**

b) Variable length codes

c) Fixed & Variable length codes

d) None of the mentioned**Answer: a****Explanation: Fixed length codes are uniquely decodable codes where as variable length codes may or may not be uniquely decodable.****10. A rate distortion function is a**

a) Concave function**b) Convex function**

c) Increasing function

d) None of the mentioned**Answer: b****Explanation: A rate distortion function is a monotone decreasing function and also a convex function.**

# Interpolation

**1. Interpolation is done by**

a) Curve fitting

b) Regression analysis**c) Curve fitting & Regression analysis**

d) None of the mentioned**Answer: c****Explanation: Interpolating the value requires or is done by curve fitting and regression analysis.****2. Interpolation provides a mean for estimating functions**

a) At the beginning points

b) At the ending points**c) At the intermediate points**

d) None of the mentioned**Answer: c****Explanation: Interpolation provides a mean for estimating the function at the intermediate points.****3. Interpolation methods are**

a) Linear interpolation

b) Piecewise constant interpolation

c) Polynomial interpolation**d) All of the mentioned****Answer: d****Explanation: Some of the interpolation techniques are linear interpolation, piecewise constant interpolation, polynomial interpolation, spline interpolation etc.****4. Linear interpolation is****a) Easy**

b) Precise

c) Easy & Precise

d) None of the mentioned**Answer: a****Explanation: Linear interpolation is quick and easy but not precise.****5. Error is equal to**

a) Distance between the data points**b) Square of the distance between the data points**

c) Half the distance between the data points

d) None of the mentioned**Answer: b****Explanation: Error is equal to square of the distance between the data points.****6. Which produces smoother interpolants?**

a) Polynomial interpolation

b) Spline interpolation**c) Polynomial & Spline interpolation**

d) None of the mentioned**Answer: c****Explanation: Polynomial interpolation and spline interpolation produces smoother interpolants.****7. Which is more expensive?****a) Polynomial interpolation**

b) Linear interpolation

c) Polynomial & Linear interpolation

d) None of the mentioned**Answer: a****Explanation: Polynomial interpolation is more expensive than linear interpolation.****8. Gaussian process is a _____ interpolation process.****a) Linear**

b) Non linear

c) Not an interpolation process

d) None of the mentioned**Answer: a****Explanation: Gaussian process is a non linear interpolation process.****9. Interpolation means****a) Adding new data points**

b) Only aligning old data points

c) Only removing old data points

d) None of the mentioned**Answer: a****Explanation: Interpolation is a method of adding new data points within the range of a discrete set of known data points.****10. Interpolation is a method of**

a) Interrelating**b) Estimating**

c) Integrating

d) Combining**Answer: b****Explanation: Interpolation is a method of estimating the value of the function.**

# Information and Coding

**1. Self information should be****a) Positive**

b) Negative

c) Positive & Negative

d) None of the mentioned**Answer: a****Explanation: Self information is always non negative.****2. The unit of average mutual information is****a) Bits**

b) Bytes

c) Bits per symbol

d) Bytes per symbol**Answer: a****Explanation: The unit of average mutual information is bits.****3. When probability of error during transmission is 0.5, it indicates that**

a) Channel is very noisy

b) No information is received**c) Channel is very noisy & No information is received**

d) None of the mentioned**Answer: c****Explanation: When probability of error during transmission is 0.5 then the channel is very noisy and thus no information is received.****4. Binary Huffman coding is a****a) Prefix condition code**

b) Suffix condition code

c) Prefix & Suffix condition code

d) None of the mentioned**Answer: a****Explanation: Binary Huffman coding is a prefix condition code.****5. The event with minimum probability has least number of bits.**

a) True**b) False****Answer: b****Explanation: In binary Huffman coding the event with maximum probability has least number of bits.****6. The method of converting a word to stream of bits is called as**

a) Binary coding**b) Source coding**

c) Bit coding

d) Cipher coding**Answer: b****Explanation: Source coding is the method of converting a word to stream of bits that is 0â€™s and 1â€™s.****7. When the base of the logarithm is 2, then the unit of measure of information is****a) Bits**

b) Bytes

c) Nats

d) None of the mentioned**Answer: a****Explanation: When the base of the logarithm is 2 then the unit of measure of information is bits.****8. When X and Y are statistically independent, then I (x,y) is**

a) 1**b) 0**

c) Ln 2

d) Cannot be determined**Answer: b****Explanation: When X and Y are statistically independent the measure of information I (x,y) is 0.****9. The self information of random variable is**

a) 0

b) 1**c) Infinite**

d) Cannot be determined**Answer: c****Explanation: The self information of a random variable is infinity.****10. Entropy of a random variable is**

a) 0

b) 1**c) Infinite**

d) Cannot be determined**Answer: c****Explanation: Entropy of a random variable is also infinity.****11. Which is more efficient method?**

a) Encoding each symbol of a block**b) Encoding block of symbols**

c) Encoding each symbol of a block & Encoding block of symbols

d) None of the mentioned**Answer: b****Explanation: Encoding block of symbols is more efficient than encoding each symbol of a block.****12. Lempel-Ziv algorithm is****a) Variable to fixed length algorithm**

b) Fixed to variable length algorithm

c) Fixed to fixed length algorithm

d) Variable to variable length algorithm**Answer: a****Explanation: Lempel-Ziv algorithm is a variable to fixed length algorithm.****13. Coded system are inherently capable of better transmission efficiency than the uncoded system.****a) True**

b) False**Answer: a****Explanation: Yes, the coded systems are capable of better transmission efficiency than the uncoded system.**