Important Short Questions and Answers: Source and Error Control Coding

SOURCE AND ERROR CONTROL CODING

1. Define mutual information

It is defined as the amount of information transferred when Xi is transmitted and Yi is received. It is represented by I(Xi,Yi)

The average mutual information is defined as the amount of source information gain per received symbol

2. Define channel capacity

Channel capacity is defined as the maximum of the mutual information that may be transmitted through the channel

3. Define entropy

The entropy of a source is a measure of the average amount of information per source symbol in a long message.

4. Define linear block codes

A block code of length n and 2k code words is calleda linear (n, k) code if and only if its 2k code words form a k-dimensional subspace of the vector space of all the n-tuples over the field GF(2).

5. What is meant by variable length coding?

The message occurring frequently can be assigned short code words, whereas message which occur rarely are assigned long code word, such coding is called variable length coding.

6. Define source encoder

The efficient representation of data generated by a discrete source is known as source encoding. This device that performs this representation is called source encoder.

7. Define source encoding theorem

The discrete memory less source of entropy H(X), the average code word length

(L) for any distortion less source encoding is bounded.

8. Define code redundancy

It is the measure of redundancy bits in the encoded message sequence.

9. Mention the needs for encoding

To improve the efficiency of communication

To improve the transmission quality.

10. What are the advantages of Shannon fano coding

Reduced bandwidth

Reduced noise

It can be used for error detection and correction.

11. Define channel coding theorem

Channel coding theorem is applied for discrete memory less additive white gaussian noise channels

12. What are the types of error control method?

Error detection and retransmission

Error detection and correction

13. What are the objectives of cyclic codes

Encoding and syndrome calculations can be easily implemented by using simple shift register with feedback connection It is possible to design codes having useful error correction properties