直升机卫星通信中高动态低信噪比突发解调

Burst Demodulation of High Dynamic and Low SNR Signals for Helicopter Satellite Communications

采用突发通信模式的低速直升机卫星通信链路同时存在周期性的旋翼遮挡和较大的多普勒动态,且需要工作在低信噪比下,这些特点对解调提出了很大挑战,需要研究高性能、低复杂度的突发解调方法。本文基于分散导频帧结构提出一种译码辅助解调方法。首先进行频偏分区预补偿,然后进行联合频率变化率估计的突发捕获,最后根据译码软输出目标函数,从多路译码输出中选择最优的一路作为最终结果。在给定的信道模型下,与无遮挡高斯白噪声(Additive white Gaussian noise,AWGN)信道下的理论性能相比,解调门限仅提高1.5 dB。与缝隙通信方式的典型性能相比,前向链路信噪比损失降低1.5 dB,返向链路信噪比损失增大0.2 dB。

For the low-speed helicopter satellite communication link with burst mode,there are periodic rotor blade blockage,large Doppler dynamics and low signal-to-noise ratio,which pose a huge challenge to demodulation.It is necessary to study the burst demodulation technology with high performance and low complexity.Based on the decentralized pilots frame structure,a code-aided demodulation method is proposed.First,different frequency offsets are pre-compensated by zones.Then,the burst acquisition of joint Doppler rate estimation is carried out.Finally,the best demodulation branch is selected according to the statistical characteristics of decoding soft output.The simulation results show that,under a given channel model,the demodulation threshold is only increased by 1.5 dB compared with the theoretical performance of unobstructed additive white Gaussian noise(AWGN)channel.Compared with the typical performance of slot transmission,the forward link loss is reduced by 1.5 dB and the return link loss is increased by 0.2 dB.