The invention relates to the decoding of encoded data.
When data is moved from place to place, it is often the case that the transfer process will create errors in the data. Accordingly, it is common practice to encode data to mitigate the impact of errors introduced by a transfer process. Normally, encoded data has to be decoded in order to be put to its intended use. Both the encoding and decoding of data represent a processing burden. This burden can be quite heavy in the case of modern encoding schemes. The use of encoding schemes to protect against data transfer errors is widespread but such use is particularly heavy in the telecommunications industry, especially in the wireless communications sector.
There exists a wide range of data encoding techniques and complimentary data decoding techniques. In the wireless communications sector, convolutional encoding techniques are commonly used. Various techniques can be used for decoding a convolutionally encoded signal, such as the Viterbi algorithm, the MAP (maximum a posteriori probability) algorithm and the log-MAP algorithm. Convolutional encoding and Viterbi, MAP, log-MAP and max-log-MAP decoding algorithms will be well known to those skilled in the art of wireless telecommunications engineering but readers less familiar with the field can find an introduction to these subjects in the book entitled “Digital Communications”, by John G. Proakis, fourth edition, published by McGraw-Hill.
A paper by Gambe et at entitled “An Improved Sliding Window Algorithm for Max-Log-MAP Turbo Decoder and Its Programmable LSI Implementation” (IEICE Trans. Electron., Vol. E88-C, 3 Mar. 2005, pages 403 to 412) describes a sliding window approach to max-log-MAP turbo decoding in which certain metrics calculated in one turbo decoding iteration are carried over to provide window commencement metrics for a subsequent iteration.