Soft-output turbo code decoder and optimized decoding method

A method of optimizing the performance of an iterating turbo code decoder including a plurality of serial constituent decoders, said method comprising the steps of:

• (a) establishing a limit for an output for at least one of said serial constituent decoders;
• (b) determining a first and a second number of said outputs approximately equaling said limit produced by a second one of said serial constituent decoders while performing a first iteration and a second iteration, respectively;
• (c) determining a third number of said outputs approximately equaling said limit produced by a first one of said serial constituent decoders while performing said second iteration;
• and
• (d) terminating operation of said turbo code decoder when said first, second, and third numbers of said outputs are substantially equal.

A method of optimizing the performance of an iterating turbo code decoder including a plurality of serial constituent decoders, said method comprising the steps of:

• (a) establishing a limit for an output for at least one of said serial constituent decoders;
• (b) determining a first number of said outputs approximately equaling said limit produced by a first of said serial constituent decoders while performing an iteration;
• (c) determining a second number of said outputs approximately equaling said limit produced by a last of said serial constituent decoders while performing said iteration;
• and
• (d) terminating operation of said turbo code decoder when said first and second numbers of said outputs are substantially equal.

An iterating turbo code decoder comprising:

• (a) a plurality of serial constituent decoders;
• (b) a comparator to compare a plurality of outputs of a constituent decoder to a threshold value for said outputs;
• (c) a counter to count a number of said outputs produced by said constituent decoder approximately equaling said threshold value;
• and
• (d) a decision unit to terminate operation of said turbo code decoder when said number of said outputs approximately equaling said threshold value is unchanged for successive iterations.

An iterating turbo code decoder comprising:

• (a) a plurality of serial constituent decoders;
• (b) a comparator to compare an output of one of said constituent decoders to a threshold value for said output;
• (c) a counter to count a first and second number of outputs produced, respectively, by a first one of said serial constituent decoders and a subsequent one of said serial constituent decoders approximately equaling said threshold value;
• and
• (d) a decision unit to terminate iteration by said turbo code decoder when said first number of said outputs is approximately equal to said second numbers of said outputs.

An iterating turbo code decoder comprising:

• (a) a plurality of serial constituent decoders;
• (b) a comparator to compare an output of one of said serial constituent decoders to a threshold value for said output;
• (c) a counter to count a number of said outputs approximately equaling said threshold value;
• (d) a memory to store a first, a second, and a third said number of said outputs approximately equaling said threshold value, said outputs produced, respectively, by a last a serial constituent decoder performing a first and a subsequent iteration and a first serial constituent decoder performing said subsequent iteration;
• and
• (e) a decision unit to terminate iteration by said turbo code decoder when said first, second, and third numbers of said outputs are approximately equal.