터보 부호의 반복 복호를 조절하기 위한 stopping criteria 연구
(A) study on stopping criteria to control iterative decoding in turbo codes
v, 66 p.
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The term 'channel codes' of digital communication is used to identify codes to detect and/or correct errors occurring due to transmission distortion. Turbo codes were proposed in 1993, using new concept of parallel concatenated scheme. Its performance can approach to the Shannon's limit by using iterative decoding. The turbo codes are implemented with constructed two or more components of encoders, interleaver, and decoder. MAP decoding algorithm and iterative decoding method are used in turbo codes Turbo decoders have to perform a certain number of iterations. Iterative decoding can improve turbo codes performance. But any further iteration results in very little improvement. Threrfore proposed stopping cirteria for turbo decoding prevent unnecessary computations and decoding delay. In this thesis efficient stopping criteria are studied and a new stopping criterion method is proposed using soft-outputs difference of the second decoders. The performance of systems with the new stopping criterion is compared with the ones with soft-decision stopping cirterion in each of Gaussian and Rayleigh fading channels by using computer simulaion. Based on the results of computer simulation, it is verified that proposed stopping criterion has better performance than soft-decision stopping criterion for low SNR's.