Vorrichtung und Verfahren zur SISO Dekodierung

• Main Authors: ELNEKAVE, MARK, PISEK, ERAN, TOKAR, JACOB, TARRAB, MOSHE
• Format: Patent
• Language: German
• Published: 15.07.2004
• Edition: 7
• Subjects: BASIC ELECTRONIC CIRCUITRY; CODE CONVERSION IN GENERAL; CODING; DECODING; ELECTRICITY

A device and method for performing SISO (Soft In-Soft Out) decoding, particularly for turbo decoders, moving the forward-backward decoding approximation of MAP (Maximum a Posteriori probability) decoding. The method comprises the steps of: (a) providing a trellis representative of an output of a convolutional encoder, the convolutional encoder has a coding rate of R, the trellis having a block length T. (b) assigning an initial conditions to each starting node of the trellis for a forward iteration through the trellis. (c) computing a forward metric for each node, starting from the start of the trellis and advancing forward through the trellis and storing forward metrics of nodes of a plurality of starting stages of windows. (d) repeating stages d(1)-d(3) until all lambdas of the trellis are calculated; d(1) retrieving forward metrics of nodes of a starting stage of a window, the retrieved forward metrics were computed and stored during step (c). d(2) computing and storing forward metrics for each node, starting from a second stage of the window and ending at the ending stage of the window. d(3) computing backwards metrics for each node, starting from the ending stage of the window and ending at the starting stage of the window; wherein when backward metrics of nodes of a stage are computed and the forward metrics of the nodes of an adjacent stage were previously computed, the computation of backward metrics is integrated with the computation of lambda from the stage of the adjacent stage and a storage of the claculated lambdas in order to accelerate the decoding operation.