<p>The present invention relates to a transmitter wherein channel estimation errors observed in unequal amplitude constellations in the additive noise and frequency equalization process in OFDM (Orthogonal frequency-division multiplexing) based multi-carrier systems are reduced by means of the channel and/or source coding performed by a generated dictionary, and a receiver which detects according to the said code dictionaries. A coding system is selected such that requirements on apriori probabilities for each constellation point are met by this code.</p>
