自适应Turbo-QAM编码调制及其在平坦Nakagami衰落信道的吞吐量性能

Adaptive Turbo-QAM Coded Modulation and Its Throughput Performance in Flat Fading Nakagami Channels

本文提出了一种通用的自适应编码调制系统吞吐量性能分析方法 .基于各固定编码调制方式的误码率(BER)性能 ,使每种编码调制方案对应于一个信道平均信噪比 (SNR)范围 ,再应用拉格朗日函数法得到使自适应编码调制系统吞吐量性能最大的信噪比转换门限 ,可得到系统的平均吞吐量性能 .数值分析结果表明 ,相对于自适应M进制正交幅度调制 (MQAM) ,自适应Turbo编码MQAM系统吞吐量性能有显著提高 ,并且该性能受瞬时误码率要求的影响较小 .Nakagami信道中 ,在相同平均信道信噪比条件下 ,随着m的增大 ,系统吞吐量性能提高缓慢 .

A general analytical framework for system throughput performance of adaptive coded modulation is proposed. Each coded modulation scheme is assigned with a certain range of average channel signal to noise ratio (SNR) based on bit error rate (BER) performance of each fixed coded modulation scheme. With the method of Lagrange, the SNR switching thresholds for throughput maximization of adaptive system are derived and the average throughput performance of the adaptive system is obtained. It is shown in our numerical results that significant improvements of system throughput performance of the adaptive Turbo-coded MQAM modulation over adaptive MQAM modulation have been achieved and the throughput performance is insensitive to the instantaneous BER requirement. For the same average channel SNR in Nakagami channel, less improvement of the throughput performance is observed with the increase of m.