论文标题
LEO-LEO光学卫星间链接的调制和信号处理
Modulation and Signal Processing for LEO-LEO Optical Inter-satellite Links
论文作者
论文摘要
我们研究了下一代超密集的低地轨道（LEO）星座上卫星间链接（ISL）相干光学通信的关键方面。最初，评估了QPSK，8-QAM和16-QAM调制格式，具有不同符号率（28 GBAUD，60 GBAUD和120 GBAUD）和通道编码方案（OFEC和楼梯代码）对内部和内部连接的通道编码方案（OFEC和楼梯代码）。我们为所有研究的集合提供SNR边缘，并确定不可行的操作点。我们表明，即使对于一流的连接，具有高阶调制格式的设置也可能是不可行的。此外，在某些Leo-Leo链接中，具有更健壮的通道编码技术（例如OFEC）的存在或不存在选择更健壮的通道编码技术（例如OFEC）的选择。接下来，我们表征了多普勒移位（DS）及其在两个不同拓扑中的邻次邻苯式连接的时间导数，以及任何对卫星对之间建立的一般连接。我们的结果表明，虽然最大多普勒生成的频移振幅可以大大高于光纤通信中通常的频率移动幅度，但时间导数值显着较低。最后，在极端的频率偏移幅度和衍生物的极端情况下，我们解决了全数字DS补偿，而典型的MTH-Power算法不够。为此，我们提出了一个现有两阶段方法的过滤版本，该方法将光谱变化与MTH-Power方法相结合。模拟结果表明，该方法为所有检查的情况提供了适当的解决方案。
We investigate key aspects of coherent optical communications on inter-satellite links (ISLs) for the next-generation ultra-dense low-Earth orbit (LEO) constellations. Initially, the suitability of QPSK, 8-QAM, and 16-QAM modulation formats with different symbol rates (28 GBaud, 60 GBaud, and 120 GBaud) and channel coding schemes (oFEC and staircase codes) for intra- and interorbital connections is evaluated. We provide SNR margins for all investigated sets and determine unfeasible operating points. We show that sets with higher-order modulation formats combined with high symbol rates can prove unfeasible, even for first-neighbor connections. Furthermore, the presence or absence of optical pre-amplification as well as the choice for a more robust channel coding technique, such as the oFEC, can be decisive in certain LEO-LEO links. Next, we characterize the Doppler shift (DS) and its time derivative for first-neighbor interorbital connections in two different topologies and for general connections established between any pairs of satellites. Our results reveal that while the maximum Doppler-generated frequency shift amplitude can be considerably higher than those typically found in fiber-optic communications, the time derivative values are significantly lower. Finally, we address all-digital DS compensation in extreme cases of frequency offset amplitude and derivative where the typical Mth-power algorithm is not sufficient. To this end, we propose a filtered version of an existing two-stage method combining spectral shifts with the Mth-power method. The simulation results indicate that this approach provides an appropriate solution for all examined cases.
