Bit Soft-Output Algorithm for Dual N-ary Orthogonal Spread Spectrum System
双多进制正交扩频系统的比特软值输出算法

Focusing on Turbo-coded dual N-ary orthogonal spread spectrum system, this paper proposes an algorithm for computing bit soft metric based on Maximum a Posteriori Probability (MAP) criterion, and then presents a simplified MAP algorithm. Meanwhile, the fixed-point and float-point performances are simulated and compared with several existing algorithms. It is shown that MAP algorithm greatly improves the whole system performance; the simplified MAP algorithm with L = 3 outperforms the dual-maxima algorithms 0.4dB without extra cost in complexity..