Communication device and communication method

A communication device, which serves as a receiver using turbo codes as error-correction codes, comprising:

• a first decoder unit which extracts an information bit list of the two bits and a first redundant bit list from a received signal, and calculates the probability information of estimated information bits by using the results of the extraction and probability information that has been given as preliminary information (in some cases, not given);
• a second decoder unit which extracts the information bit list of the two bits and a second redundant bit list, and again calculates the probability information of estimated information bits by using the results of the extraction and the probability information from the first decoder unit to inform the first decoder unit of the results as the preliminary information;
• a first estimating unit which, based upon the results of the calculation processes of probability information by the first and second decoder unit that are repeatedly executed, estimates the information bit list of the original lower two bits for each of the calculation processes;
• an error correction unit which carries out an error checking process on the estimated information bit list by using an error correction code, and terminates the repeating process at the time when a judgment shows that the estimation precision exceeds a predetermined reference, as well as simultaneously carrying out an error-correction process on the estimated information bit list of the original lower two bits by using an error correction code;
• and
• a second estimating unit which hard-judges the other upper bits in the received signal so as to estimate an information bit list of the original upper bits.

A communication method, which uses turbo codes as error-correction codes, comprising:

• a turbo encoding step of carrying out a turbo encoding process on lower two bits in transmission data to output an information bit list of the two bits, a first redundant bit list generated in a first convolutional encoder having the information bit list of the two bits as an inout and a second redundant bit list generated in a second convolutional encoder to which the respective information bit lists that have been subjected to interleave processes are switched and input;
• a first decoding step of extracting the information bit list of the two bits and the first redundant bit list from a received signal, as well as calculating the probability information of estimated information bits by using the results of the extraction and probability information that has been given as preliminary information (in some cases, not given);
• a second decoding step of further extracting the information bit list of the two bits and the second redundant bit list, as well as again calculating the probability information of estimated information bits by using the results of the extraction and the probability information from the first decoding step to inform the first decoding step of the results as the preliminary information;
• a first estimating step of estimating the information bit list of the original lower two bits for each of the calculation processes, based upon the results of the calculation processes of probability information by the first and second decoding steps that are repeatedly executed;
• an error-correction step of carrying out an error checking process on the estimated information bit list by using an error correction code, and terminating the repeating process at the time when a judgment shows that the estimation precision exceeds a predetermined reference, as well as simultaneously carrying out an error-correction process on the estimated information bit list of the original lower two bits by using an error correction code;
• and
• a second estimating step of hard-judging the other upper bits in the received signal so as to estimate an information bit list of the original upper bits.