information block not including the head part and the tail part is poor on the other hand the ber in the head part and the tail part each formed with m bits is better than the ber in the center part here m bits are proportional to code constraint length v further fig5 shows error characteristics per bit position in a fixed information block formed with k bits when turbo encoding scheme is employed in fig5 the horizontal axis indicates a bit position and the vertical axis indicates a bit error rate ber as shown in fig5 the ber of the bit position group formed with m bits in the head part of the fixed information block is good here m bits are proportional to code constraint length v on the other hand although the ber in parts other than the above head part is poorer than the ber in the head part the ber in certain bit positions is high here the certain bit positions showing higher ber correspond to the bit positions that are positioned within m bits in the head part of the fixed information block that is interleaved in interleaver 122 that is in the fixed information block immediately before being input into the convolutional encoder the head part and the tail part each formed with m bits tend to show better ber than the ber in the center part that is the difference of ber characteristics arises between the first codeword subsequence that is obtained based on the head part and the tail part and the second codeword subsequence that is obtained based on the center part not including the head part and the tail part of the fixed information block this is.