Abstract: This invention relates to decoding symbols in the form of modulated carriers which are encoded using orthogonal frequency divsion multiplexing. The modulated carriers are supplied to a decoder which is preferably a Viterbi decoder. The decoder symbols are then recoded and passed to a comparator where they are compared with the incoming modulated carriers to locate errors between each recoded symbol and the corresponding modulated carrier symbol. The error rate for each carrier is derived by a counter and the indications of error rate and the modulated carriers are used to address entries in a look up table from which a decoder decodes the symbols represented by the modulated carriers.

Abstract: The present invention relates to a method and apparatus in which a differentially coded signal having forward error correction added to the encoded data can be decoded with an improved bit error rate performanceApparatus for decoding a differentially encoded input signal having forward error correction added to the encoded data, the apparatus comprising: a differential decoder to receive the input signal and to decode the data in each differentially encoded signal interval thereof by reference to the data in a previous differentially encoded signal interval; error correcting means to correct errors in the decoded signal form the decoder; and means for supplying to the decoder the corrected data from each signal interval to act as a reference for decoding the data in a following signal interval.