Efficient Design of Iterative Decoding Algorithm and Architecture for Channel Coding

Abstract

The demand for information exchange is ever increasing for most of the communication models. The communication systems are designed and developed for transmitting the information from source to a remote destination. The major purpose for designing the communication system is the accurate and error-free transmission of information between source and destination. The symbols produced by the information source are given to the source encoder. The source encoder assigns code words to the symbols. For each distinct symbol, there is a unique codeword.Errors may be introduced while transmitting these binary sequences over the channel due to noise and interference.At the receiver end, some sort of decoder is used to perform the reverse operation of source encoder. The channel decoder provides decoded output which is converted into a sequence of symbols. Errors may be introduced while transmitting the binary sequences over the channel due to noise and interference. Channel coding is done to avoid these types of errors. Some redundant binary bits are added to the input sequence by the channel encoder according to some pre-defined logic. The channel decoder at the receiver end reconstructs error-free accurate bit sequence, thus reducing the effects of channel noise and distortion. The error-control strategies are used by the channel encoder and decoder at the receiver to reduce the errors in the received signals. For example, forward error correction (FEC) or automatic repeat request (ARQ) techniques are used to correct errors and increase the reliability of the received signals. This thesis discusses the error control aspects of a communication system, in particular, the error-correcting Turbo codes and LDPC code. Turbo codes, introduced in 1993, are designed by combining two or more relatively simple component codes to achieve a large coding gain.