Channel equalization and noise reduction based on turbo codes

A new class of error control coding with binary parallel concatenated recursive systematic convolutional codes-turbo codes- and its an application over SAR (Synthetic Aperture Radar) image transmitting is presented in this paper. The remarkable coding gains achieved by turbo code have a great influence in various areas of digital communication, including cellular mobile, deep space communications and satellite communication. The basic idea is that two or more a posteriori probability decoders exchange soft information. One of the decoders calculates the a posteriori probability distribution of the information sequence and passes that information to the next decoder. The new decoder uses this information and computes its own version of the probability distribution. This exchange of information is called an iteration. After a certain number of iterations, a decision is made at the second decoder. For each iteration, the probability that we decode in favour of the correct decision will improve. At the last iteration, the hard decision is made using the soft decision of the last decoder.