卫星数传OFDM信号的多普勒效应影响分析

正交频分复用(orthogonal frequency division multiplexing,OFDM)信号具有较高的频谱效率,有利于实现高速传输。在卫星对地高码率数据传输系统设计中,OFDM有助于解决带宽资源的问题,因此极富吸引力。但是,由于近地轨道(low earth orbit,LEO)星地链路的大动态特性,传输信号会遭受严重的多普勒效应影响。对于宽带OFDM信号而言,多普勒效应的表现形式更为复杂,不再仅仅是频率的偏移。分析宽带OFDM信号在LEO卫星对地数传链路中所受到的多普勒影响。首先,对卫星数传链路进行数学建模,并且推导出该大动态场景下的OFDM信号模型;之后,量化分析由于多普勒效应所产生的符号间干扰和载波间干扰。根据理论分析结果,给出OFDM体制在LEO星地数传应用中的设计要求和设计局限。

Analysis of Doppler effects on satellite data transmission of OFDM signals

Orthogonal frequency division multiplexing (OFDM) is a spectral efficient technique which benefits the high speed transmission. In the high rate satellite ground data transmission system design, OFDM is very attractive since it helps solving the bandwidth resource issue. However, with the large dynamic character of the low earth orbit (LEO) satellite ground link, the data transmission signal suffers significant Doppler effects. Moreover, Doppler effects appear more complex for wideband OFDM. Merely considering frequency shift is inadequate. In this paper, we analyze the Doppler effect for wideband OFDM signals in the LEO satellite ground data transmission scenario. The paper models the LEO satellite ground data transmission link, and deduces the OFDM signal model in this large dynamic environment. Then, inter symbol interference (ISI) and inter channel interference brought by Doppler effects are quantified. The theoretical results are employed to analyze the OFDM system design requirement and design limitation for LEO satellite ground data transmission application.