Parity error correction for band-limited digital signals

An error correction technique for correcting and replacing an erroneous digital signal source sample sent by a transmitter to a receiver after ascertaining by parity check that the digital signal source sample received is erroneous, wherein the digital signal source sample has N bits, comprising the steps of:

• choosing M parity encoded bits which are used by the transmitter for parity, from said N bits in each said erroneous sample and producing M number of inverted test samples each with N bits, M being less than or equal to N, wherein each of said M inverted test samples is obtained by inverting a single one of the M bits and keeping all other N−1 bits unchanged;
• passing each of said M inverted test samples through a selected filter and obtaining a filtered output in each case, and for each of said M inverted test samples measuring a difference in value between each inverted test sample and its corresponding filtered output;
• selecting that value of the difference which is minimum, and choosing a corresponding inverted test sample with N bits for replacing the erroneous signal sample.

A method for correcting and replacing an erroneous digital signal sample from a band limited signal source received in a receiver after ascertaining by parity check that the digital signal sample is erroneous, wherein the digital signal sample has 14 bits compressed to N bits and expanded back to 14 bits as applicable, and wherein M bits are considered for parity check, N being equal to less than 14 and M being equal to or less than N, said method being implemented for error correction in a NICAM (Near Instantaneous Companded Audio Multiplexed) demodulator, and comprising the steps of:

• choosing M parity encoded bits from expanded samples of 14 bits in each said erroneous sample and producing M number of inverted test samples each with 14 bits, wherein each of said M inverted test samples is obtained by inverting a single one of the M bits and keeping all other remaining 13 bits unchanged;
• passing each of said M inverted test samples through a selected filter and obtaining a filtered output in each case, and for each of said M inverted test samples measuring a difference in value between each inverted test sample and its corresponding filtered output;
• selecting that value of the difference which is minimum, and choosing a corresponding inverted test sample with 14 bits for replacing the erroneous signal sample.