Hybrid Log-MAP Algorithm for Turbo Decoding Over AWGN Channel
In Log-MAP turbo decoding, the complicated log exponential sum is often simplified with the Jacobian logarithm which consists of the max operation along with an exponential correction function. Although the Max-Log-MAP reduces the complexity of the Jacobian logarithm implementation by omitting the correction function, its performance is inferior to the exact Log-MAP algorithm. Hence, a simple approximation to the correction function is needed to complement the Max-Log-MAP algorithm. In this paper, a new suboptimal hybrid Log-MAP algorithm for decoding turbo code is proposed. It approximates the exact Log-MAP accurately and is simple for hardware implementation. The performance of the hybrid Log-MAP algorithm is shown to have the closest performance to the exact Log-MAP solution especially at low SNR.