Question

Define the basic concept of channel coding, and enumerate two types of channel coding?

Answer 1

A way of encoding data in a communications channel that adds patterns of redundancy into the transmission path in order to lower the error rate. Such methods are widely used in wireless communications.

Channel coding is often used in digital communication systems to protect the digital information from noise and interference and reduce the number of bit errors. Channel coding is mostly accomplished by selectively introducing redundant bits into the transmitted information stream.

The channel codes can be classified into two types.

1.Block Codes and 2.Convolutional codes.

There are many differences between block codes and convolutional codes.

1. Block codes :- Block codes are based rigorously on finite field arithmetic and abstract algebra. They can be used to either detect or correct errors. Block codes accept a block of k information bits and produce a block of n coded bits. By predetermined rules, n-k redundant bits are added to the k information bits to form the n coded bits. Commonly, these codes are referred to as (n, k) block codes. Some of the commonly used block codes are Hamming codes, Golay codes, BCH codes, and Reed Solomon codes .

2. Convolutional codes :-this codes are one of the most widely used channel codes in practical communication systems. These codes are developed with a separate strong mathematical structure and are primarily used for real time error correction. Convolutional codes convert the entire data stream into one single codeword. The encoded bits depend not only on the current k input bits but also on past input bits. The main decoding strategy for convolutional codes is based on the widely used Viterbi algorithm.