An Improved Max-Log-MAP Algorithm for Turbo Decoding and Turbo Equalization

This paper proposes an improved Max-Log-maximum a posteriori (MAP) algorithm for turbo decoding and turbo equalization. The proposed algorithm utilizes the MacLaurin Series to expand the logarithmic term in the Jacobian logarithmic function of the Log-MAP algorithm. In terms of complexity, the proposed algorithm can easily be implemented by means of adders and comparators as this is the case for the Max-Log-MAP algorithm. In addition, simulation results show that the proposed algorithm performs very closely to the Log-MAP algorithm for both turbo decoding over additive-white-Gaussian-noise channels and turbo equalization over frequency-selective channels. Further, it is shown than even in a high-loss intersymbol-interference channel, the proposed algorithm preserves its performance close to that of the Log-Map algorithm, while there is a wide gap between the performance of the Log-MAP and Max-Log-MAP turbo equalizers