中文摘要：

针对快时变信道下无线通信频谱利用率降低的问题,提出一种基于非数据辅助的误差矢量幅度的自适应调制（NDA-EVM-AM,nondata-aided error vector magnitude based adaptive modulation）算法,选取NDA-EVM作为反映快时变信道变化的特征参量并给出不同调制阶数的统一计算模型,建立不同调制阶数NDA-EVM与误码率（BER）之间的关系并据此设计MQAM（multilevel quadrature amplitude modulation）调制阶数的快速调整机制。以高铁通信的快时变信道场景为例,数值仿真表明,相比DA-EVM（data-aided error vector magnitude）和信噪比估计,NDA-EVM估计具有最小均方根误差;NDA-EVM-AM算法可提高信道质量评估与调制阶数选择的准确性,相较于DA-EVM-AM（data-aided error vector magnitude based adaptive modulation）算法,调制阶数选择的正确率可提升7.9%,频谱利用率可提高0.53 bit·s（-1）·Hz（-1）;相较于SNR-AM（signal to noise ratio based adaptive modulation）算法,调制阶数选择的正确率可提升15.7%,频谱利用率可提高0.82 bit·s（-1）·Hz（-1）。

英文摘要：

A novel nondata-aided error vector magnitude based adaptive modulation（NDA-EVM-AM） was proposed to solve the problem of lower spectral efficiency over rapidly time-varying wireless channels.Namely,NDA-EVM was considered as a metric to reflect the rapid change of time-varying channels.The unified model to calculate different modulation order of NDA-EVM was analytically derived,with which the relationship between NDA-EVM and bit error rate（BER） for each modulation order was presented.Thereafter,the mechanism to adaptively select the modulation orders of multilevel quadrature amplitude modulation（MQAM） signals was designed to guarantee the predefined BER.Taking the two rapidly time-varying channels proposed for high-speed railway scenarios as examples,numerical results are conducted to verify the effectiveness of the proposed algorithm.It shows that NDA-EVM estimation has the lest root mean square error than data-aided error vector magnitude（DA-EVM） estimation and signal to noise ratio estimation.The proposed algorithm has better accuracy in aspects of channel quality estimation and modulation orders adjustment,Compared with conventional data-aided error vector magnitude based-adaptive modulation（DA-EVM-AM）,the accuracy improves by 7.9%,spectral efficiency improves by 0.53 bit·s（-1）·Hz（-1）,and compared with signal to noise ratio based-adaptive modulation（SNR-AM）,the accuracy improves by 15.7%,spectral efficiency improves by 0.82 bit·s（-1）·Hz（-1）.