An Improved Stochastic Decoding Algorithm of LTE Turbo Codes

Turbo codes are widely used in many communication systems, and decoding algorithm is studied intensively. Most decoding algorithms are Max-Log-MAP based, which performs arithmetic computation in logarithm domain. In recent years, stochastic turbo decoding has been proposed as a potential high parallel scheme. Stochastic decoding is carried on in probability domain, and probability computations are done by logical operation of stochastic bit streams. In this paper, stochastic decoding is improved in three ways: firstly, use OR gate instead of multiplexer or Taylor expansion in exponential domain for probability adding operation, where data distribution of turbo decoding process is utilized; secondly, a direct intra parallel streams barrel shifter is used to break correlation of division results; thirdly, random initialization instead of zero initialization for flip-flop is used to shorten warming up time of decoding stages. Simulations show that these improvement methods reduce decoding complexity: it costs less hardware resources and decoding cycles/time. Stochastic decoding also shows scalable and flexible characteristics in the Software Defined Radio (SDR) scenario.