一种新的衰落信道自适应Turbo码调制方法

针对衰落信道下频谱资源利用率较低的问题，提出了一种自适应T urbo码调制方法。该方法在一定平均辐射功率和通信误码率的约束下，以优化平均频谱效率为目标，将衰落信道划分为 N个相邻的衰落区域，并利用拉格朗日函数法求得了最优的衰落区域边界值。仿真结果表明：与同等复杂度的自适应网格编码调制方案相比，本文方法的平均频谱效率获得了将近2～3 dB的性能增益，与香农极限仅相差3 dB ；与非最优4衰落区域相比，最优4衰落区域有将近1 dB的性能增益。本文方法可显著提高无线通信系统的平均频谱效率。

New adaptive Turbo coded modulation method over fading channels

Considering the low spectrum resource utilization restricting high‐speed data transmission over fading channels ,this paper proposes an adaptive Turbo‐coded modulation to maximize the spectral efficiency of system . Fading channel is divided into N adjacent regions ,and Lagrange Multiplier is used to obtain the optimal switching thresholds under an average power constraint and bit‐error constraint . Numerical results show that the spectral efficiency of adaptive Turbo‐coded modulation has a 2~3 dB gain in performance with the same complexity of TCM scheme ,and within 3 dB of the fading Shannon limit ;comparing with the not optimized 4 fading regions and the optimal 4 fading regions ,nearly 1 dB performance gain can be obtained .The average spectral efficiency of wireless communication system can improve significantly .