An efficient software radio implementation of the UMTS turbo codec
- 13 November 2002
- proceedings article
- Published by Institute of Electrical and Electronics Engineers (IEEE)
Abstract
This paper addresses some critical implemen- tation issues involved in the development of a turbo de- coder, using the UMTS specification as a concrete example. The assumption is that the decoder is to be implemented in software rather than hardware, and thus a variable num- ber of decoder iterations is not only possible, but desirable. Three twists on the decoding algorithm are proposed: (1) A linear approximation of the correction function used by the max* operator which reduces complexity with only a negligible loss in BER performance; (2) A method for nor- malizing the backward recursion which yields a 12.5% sav- ings in memory usage; and (3) A simple method for halting the decoder iterations based only on the log-likelihood ra- tios.Keywords
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