Floating-gate analog implementation of the additive soft-input soft-output decoding algorithm

The soft-input soft-output algorithm is used to iteratively decode concatenated codes. To efficiently implement this algorithm, an additive form in the logarithmic domain is employed. A novel analog implementation using CMOS translinear circuits is proposed. A multiple-input floating-gate CMOS transistor working in the subthreshold region is used as the main translinear computing element. The proposed approach allows a direct mapping between the decoding algorithm and the circuit implementation. Experimental CMOS chip results are in good agreement with theoretical and simulation results.