Logarithmic Bit-Significance Ratio: Definition, Calculation Rules and Examples

We motivate and discuss the logarithmic bit-significance ratio (S-value) which is a universal measure to quantify the significance of each bit in a digital communication system. Calculation rules for the S-values are given which, for instance, allow for the computation of the significances of parity bits when the significances of the data bits are given. The introduction of the S-value allows for the processing of soft-information, e.g., in encoding and modulation and can, hence, be interpreted as the transmitter-based counterpart of the well-established log-likelihood ratio (L-value) at the receiving end