Turbo-decoding without SNR estimation

Abstract—Theoretically, it is necessary to estimate the SNR when using a MAP or Log-MAP constituent decoder. The ef-fect of an SNR mismatch on the bit error rate performance of Turbo-codes and the design of good variance estimators have been addressed by several authors. In this letter, we study the SNR sensitivity of Turbo-decoding with Log-MAP and Max-Log-MAP constituent decoders, respec-tively, for AWGN and Rayleigh fading channels. Our theoretical and simulation results indicate that an estimation of the SNR is not necessary from a practical point of view. Our setup is aligned with decoder implementation aspects of future mobile communication systems. Index Terms—MAP decoding, mobile communication, Turbo-codes. I