Nakagami信道基于16APSK的加权信噪比估计算法

Weighted SNR estimation algorithm based on 16APSK in Nakagami channel

自适应编码调制(adaptive coded modulation,ACM)技术是一种提高无人机(unmanned aerial vehicle,UAV)数据链吞吐量性能的有效方法,信道估计的准确性是决定ACM系统性能的关键因素之一,直接影响UAV数据链的吞吐量性能。首先对Nakagami衰落信道进行分析建模,推导了信号经过衰落信道后的表示方法。其次对Nakagami衰落信道下基于多进制数字相位调制(multiple phase shift keying,MPSK)的信噪比(signal-tonoise ratio,SNR)估计算法进行推导和分析,仿真结果表明三阶矩(third-order moments,M3)SNR估计算法比传统的二阶矩四阶矩(second and fourth moments,M2M4)SNR估计算法具有更好的估计性能。最后,针对Nakagami衰落信道下的现有估计算法对非恒包络调制信号估计性能差的问题,提出了一种适用于非恒包络的16阶振幅移相键控(amplitude phase shift keying,APSK)信号的加权SNR估计算法,该算法利用接收信号的先验信息和信号的阶矩关系进行SNR估计,具有复杂度低,估计精度高等优势。理论分析与仿真结果表明:所提出的算法可以有效地对16APSK调制信号进行SNR估计,且相比于M2M4算法,利用M3信息进行信道估计的加权SNR估计算法具有更高的估计精度。

Adaptive coded modulation(ACM)is an effective method to improve the throughput performance of the unmanned aerial vehicle(UAV)data link.The accuracy of channel estimation is one of the key factors to determine the performance of the ACM system,which directly affects the throughput performance of the UAV data link.The Nakagami fading channel is analyzed and modeled,and the representation of the signal through fading channels is derived.Secondly,the signal-to-noise ratio(SNR)estimation algorithm based on multiple phase shift keying(MPSK)modulation for the Nakagami fading channel is deduced and analyzed.Simulation results show that the third-order moments(M3)estimation algorithm has a better performance compared with the traditional second and fourth moments(M2M4)SNR estimation algorithm.Finally,because the estimation performance of the non-constant envelope modulation signal is poor for the existing estimation algorithms in Nakagami fading channels,a weighted SNR estimation algorithm for16APSK high-order modulated signals for non-constant envelopes for channel estimation of UAV communication systems in Nakagami fading channels is proposed.The algorithm uses the prior information of the received signal and the order moment relation of the signal to estimate the SNR,which has the advantages of low complexity and high estimation accuracy.Simulation results show that the improved algorithm can estimate SNR of the16APSK modulation signal,and has good SNR estimation performance.Compared with the M2M4algorithm,the weighted estimation of the SNR estimation algorithm has higher estimation precision by using M3information.