Abstract:  For Turbo decoding on the additive white Gaussian noise (AWGN) channel, the optimal algorithm in term of bit error rate (BER) is symbol by symbol maximum a posteriori (MAP) algorithm. In order to reduce the computational complexity and to implement the MAP decoding algorithm, a number of simplified MAP-based methods have been proposed recently, e.g. the Log-MAP algorithm, the Max Log-MAP algorithm and the linear Max Log-MAP algorithm. This paper introduces the basic principle of MAP-based turbo decoding. In addition, by the means of the so called correction function, these simplified MAP-based approaches are categorized and compared, while the performance and sensitivity to the signal to noise ratio (SNR) offsets of those simplified algorithms are also theoretically investigated. Further, all the results are verified with a number of computer simulations. By considering both the performance and the computational cost, Turbo decoding algorithm selection suggestion as well as a practical and easy parameter configuration are proposed.