Punctured coding system for providing unequal error protection in a digital communication system

A coding system for error protecting a digital message to be transmitted from a transmitter to a receiver over a channel, comprising:

• a) a coding circuit for coding the digital message according to a predetermined code prior to transmission to produce codewords having significant message symbols, insignificant message symbols, and redundancy symbols, wherein the redundancy symbols error protect both the significant and insignificant message symbols;
• b) a puncturing circuit for puncturing .tau. insignificant symbols of each codeword prior to transmission so as to produce erasures in the codewords;
• c) a depuncturing circuit for depuncturing the punctured codewords after transmission to produce depunctured codewords, the depuncturing circuit including:
• 1) correction determination means for determining for each received punctured codeword if the punctured codeword is correctable, and
• 2) correction means for correcting the punctured codewords determined to be correctable so as to produce corrected depunctured codewords;
• and
• d) a decoding circuit for decoding the depunctured codewords.

A digital communication method comprising:

• a) receiving a digital message including message blocks of k message symbols where the message blocks have significant message symbols and insignificant message symbols;
• b) coding the digital message to produce code words corresponding to the message blocks, the code words having n code symbols, where n>k and each code word includes the message symbols of the corresponding message block and redundancy symbols;
• c) puncturing .tau. insignificant symbols of each code word to produce a punctured signal including punctured code words with each punctured codeword having .tau. erasures;
• d) transmitting the punctured signal over a channel;
• e) receiving the punctured signal transmitted over the channel, the received punctured signal including received punctured code words;
• f) determining for each received punctured code word if the code word is correctable;
• g) correcting the code words determined to be correctable.