TABLE OF CONTENTS The fundamental principles behind binary convolutional turbo coding have been introduced, including the component codes, the interleaving, the trellis termination, the puncturing and the principle of iterative decoding. The central components of a turbo code encoder are the RSC encoders and the interleaver that links them in parallel by re-ordering the bits in the information sequence before they enter the second constituent encoder. Both optimal algorithms, MAP and Log-MAP and, suboptimal algorithms, Max-Log-MAP and SOYA depend on the tools, Log-likelihood Algebra, Soft channel output and the principle of iterative decoding algorithm. Turbo codes, due to their excellent error correcting capability, are being considered for the 3rd generation (3G) mobile communication standards, 3GPP, UTMS, and CDMA2000. Both parallel concatenation and serial concatenation were discussed and their decoding procedures were given.
The parallel concatenation is implemented by interleaving, i.e., re-ordering the information sequence before it is input to the second component encoder. The two most critical parts of a turbo code encoder are, thus the interleaver and the component encoders. Other essential aspects of a turbo encoder are trellis termination and puncturing. Trellis termination is an issue when dealing with data packets where truncation is necessary at some point of the trellis. Puncturing is the process of excluding bits from the outputs of the component encoders, so the concatenated transmitted sequence is a decimated version of the encoder output.
