地空数据传输系统中单载波频域预均衡技术

在频率选择性瑞利慢衰落信道条件下,提出了一种适用于地空传输系统上行链路的单载波频域预均衡方法。在此基础上设计了预均衡系统模型,地面端将下行链路中的导频信号与本地导频信号对比进行信道状态估计,利用获得的信道状态信息对上行链路信号进行预均衡处理,然后在机载接收端对上行链路信号进行再均衡。基于迫零准则和最小均方误差准则,分析了该方法的信号处理流程,计算得到预均衡系数。通过仿真实验,对比分析了不同均衡方案的误码性能,结果表明:单独在地面发送端进行预均衡,会出现误码率平台效应;而预均衡之后在机载接收端进行再均衡的方法,在误码率为10-5的情况下,与采用线性均衡结构的传统单载波频域均衡方法相比有2~3dB的性能增益。

A Method of Single Carrier Frequency Domain Pre-equalization in Ground-to-air Data Transmission System

In this paper, a method of single carrier frequency domain pre-equalization suitable for air-ground communication system uplink is brought forward under the condition of frequency-selective Rayleigh slow fading channel. A model of pre-equalization system is designed on the basis of this method. In the model, the downlink pilot signal is compared with the local one to perform channel condition estimation on ground station, and then the pre-equalization of uplink signal is processed by utilizing the acquired channel condition information. Finally, the uplink signal equalization is conducted on airborne receiver. The signal processing procedures of the method are analyzed and the coefficient of the pre-equalization are obtained based on zero-forcing criterion and minimum mean square criterion. By comparing the BER performance of different equalization schemes, the simulation results show that the error-floor effects will arise when pre-equalization is implemented only on ground transmitter; whereas, when bit error rate is 10-5, a 2 to 3 dB gain in performance is expected by the equalization made again on airborne receiver after ground pre-equalization in comparison with the former single carrier frequency equalization method with a linear equalization structure.