OFDM系统时频二维信道估计研究

针对短波信道时变色散的特点,设计了OFDM系统信道估计所需的时频二维棱形插入导频图案,并根据时频域两方向导频插入的稀疏程度,选择了二维插值的方法和插值次序,另外,提出了改进的变换域DFT信道估计算法.该算法通过适当选取变换域补零的位置,有效减小了非整数倍采样间隔信道时延引入的能量泄露,并滤除了噪声的影响.最后,在短波多径环境下仿真算法的性能,并与常用频域插值算法和维纳滤波方法进行了对比.仿真结果表明：改进方法的增强了算法对多径延迟分布的鲁棒性,提高了信道估计精度,同时还保持了较低的计算复杂度.

Time-frequency 2-D Channel Estimation Method for OFDM Systems

Aiming at the character of time-varying and dispersive HF channel, a time-frequency two-dimension diamond pilot pattern which is needed during OFDM channel estimation step, is designed. The two-dimension interpolation methods and order are chosen by the sparse degree of pilot in time domain and frequency domain. In addition, an improved channel es- timation method based on transform domain DFI＂ is proposed. The energy leakage of channel impulse response caused by non-integer-sample space can be decreased effectively by properly choosing the zero-padding position and the effect of noise can also be removed. Finally, simulation analysis and comparison of the algorithm with conventional frequency-domain inter- polation and Wiener estimation approaches in shortwave multipath environment demonstrate that the improved algorithm im- proves the robustness for multipath delay, achieves channel estimation accuracy and ensures low complexity at the same time.