In a turbo code decoder (100, 100B), likelihood information for redundant parts of a received symbol sequence are used to update the redundant parts of the received symbol sequence for use by the decoder (100, 100B). The redundant likelihood update unit (101) comprises a first compare and update unit (204.sub.1) and a second compare and update unit (204.sub.2). The respective compare and update units (204) compare the likelihood information for their respective redundant part of the received symbol sequence with the original respective redundant part of the received symbol sequence, and obtain updated likelihood information for their respective redundant parts of the received symbol sequence.