Source Coding in Communications

Variable-length code words

Unique decodability

A prefix code is a code system with the 'prefix property' where no code word is a prefix of another.

<p>{a=0, b=110, c=10, d=111}</p> Signup and view all the answers

<p>Unique decoding and instantaneous decoding</p> Signup and view all the answers

<p>The prefix property requires that no code word in the system is a prefix of any other code word.</p> Signup and view all the answers

<p>Source encoding is the process of representing data generated by a discrete source efficiently in binary form. Two functional requirements of an efficient source encoder are: code words produced in binary form and uniquely decodable source code.</p> Signup and view all the answers

<p>The formula for entropy H(Y) for a source with statistically independent symbols is: H(Y) = -∑(P(y_j) * log_2(P(y_j))), where P(y_j) is the probability of symbol y_j.</p> Signup and view all the answers

<p>Code efficiency η is defined as (H(Y) / max[H(Y)]) * 100. It is calculated by dividing the entropy by the maximum entropy and multiplying by 100.</p> Signup and view all the answers

<p>The formula for the overall code length L in terms of the average code word length is: L = ∑(P(x_j) * l_j) bits/symbol, where l_j is the length of the code word for symbol x_j.</p> Signup and view all the answers

<p>Fixed-length code words have a constant length for each symbol in the source alphabet. For example, the code C(a) = 000, C(b) = 001, C(c) = 010, ..., C(g) = 110 uses fixed-length code words for symbols a to g.</p> Signup and view all the answers

<p>A source sequence is encoded using fixed-length code words by assigning the corresponding code word to each symbol and concatenating the code words together.</p> Signup and view all the answers