基于FPGA的特征扩频卫星物联网链路设计与实现

Design and Implementation of Eigen-based Spread Spectrum Satellite IoT Link Based on FPGA

随着卫星通信与地面无线通信的发展,通信系统频谱共用问题日益突出。传统扩频方法通常将外部干扰视作均匀功率谱信号,但此类方法对卫星通信频谱的利用尚不充分。采用信号功率谱特征与干扰信号功率谱特征互补塑形的特征扩频系统,更符合实际卫星通信中噪声频谱非均匀和小信噪比(Signal to Noise Ratio, SNR)的情况。设计了特征扩频的扩频与解扩方案的现场可编程门阵列(Field Programmable Gate Array, FPGA)实现,借助成型的四相相移键控(Quadrature Phase Shift Keying, QPSK)通信链路,嵌入特征扩频模块对QPSK调制后的信号进行扩频幅度调制。在FPGA上实现了该方案,验证所完成的系统在发送端能正确对数据进行扩频处理,在接收端能识别扩频后的信号,并正确解析出来。该研究的结论有助于现代卫星通信中业务数据实现小信噪比和低误码率(Bit Error Rate, BER)传输。

With the development of satellite communication and terrestrial wireless communication,the problem of spectrum sharing in communication systems has become increasingly prominent.Traditional spread spectrum methods usually regard external interference as a uniform power spectrum signal,but such methods have not yet fully utilized the satellite communication spectrum.The proposed design adopts an Eigen-based spread spectrum system with signal power spectrum characteristics and interference signal power spectrum characteristics complementary to shape,which is more in line with the situation of non-uniform noise spectrum and small Signal to Noise Ratio(SNR)in actual satellite communications.The Field Programmable Gate Array(FPGA)implementation of the Eigen-based spread spectrum and despreading scheme is designed.With the help of the formed Quadrature Phase Shift Keying(QPSK)communication link,the eigen-based spread spectrum module is embedded to perform spread spectrum amplitude modulation on the QPSK modulated signal.Finally,the scheme is implemented on FPGA to verify that the completed system can correctly perform the spread spectrum processing on the data at the transmitting end,and the signal after spreading can be identified at the receiving end and parsed correctly.The conclusions of this research are helpful to realize small signal-to-noise ratio and low Bit Error Rate(BER)transmission of business data in modern satellite communications.