Monolithic Implementation of Turbo Codes

One of the key aspects of turbo codes is that they use soft-input and soft-output values in the decoding stage. Thus no information is discarded until the algorithm has iteratively converged to a solution, at which time a hard decision is taken. The soft-input soft-output concept refers to infinite quantized or analog values in a natural form. This research work proposes CMOS integrated circuit implementations of both the encoding and the decoding algorithms. In particular it explores an all-analog decoder implementation that will naturally exploit the continuous nature of the received signals.The proposed analog decoder is based on the additive soft-input soft-output algorithm that can be naturally mapped into a multiple input floating gate transistors implementation. By taking advantage of the symmetric structure of the trellis generated by convolutional codes, every node in the trellis can have a direct analog counterpart that will mathematically solve the decoding algorithm in the analog domain.