Algorithms of adaptive mutual-invariant filtering of informational and accompanying signal parameters as well as maximum-likelihood decoding of signal-code structures are suggested that are optimal at a class of non-Gaussian additive interference. Effectiveness of the algorithm and the carrier synchronization system, realizing calculation of a phase error, is demonstrated on a concrete example. The synthesized algorithms can be applied to the design of high-speed modems through real communication channels with intersymbol interference, non-Gaussian additive interference, signal phase jumps and jittering.