Analysis of the Characteristics of Low-Latitude GPS Amplitude Scintillation Measured During Solar Maximum Conditions and Implications for Receiver Performance
Analysis of the Characteristics of Low-Latitude GPS Amplitude Scintillation Measured During Solar Maximum Conditions and Implications for Receiver Performance
复制标题
太阳极大值条件下低纬度 GPS 振幅闪烁特征分析及对接收机性能的影响
作者：
Alison Oliveira Moraes;Fabiano Silveira Rodrigues;W. Perrella;E. R. Paula
电离层闪烁是由电离层电子密度不规则引起的电离层无线电信号相位和/或振幅的波动。例如，更好地了解闪烁模式对于更好地评估GPS接收机的性能非常重要。此外，闪烁还可用作遥感电离层不规则现象的工具。因此，电离层闪烁的研究不仅具有科学意义，而且具有技术意义。在过去的几年中，闪烁的分析方法和我们对闪烁对GPS接收机性能影响的理解取得了重大进展。在这项工作中，我们回顾了一些现有的闪烁分析方法，提出了一种替代方法，并将这些技术应用于幅度闪烁特性的综合研究。这项综合研究利用了在高太阳通量条件下，位于巴西o joss<s:1> dos Campos（23.2°S, 45.9°W, - 17.5°倾角）赤道异常附近的基于gps的闪烁监测仪进行的32天高速率（50 Hz）测量。闪烁模式的去相关时间（τ0）的变化是闪烁严重指数（S4）的函数。我们发现τ0的值随着S4的增大有减小的趋势，证实了前人的研究结果。此外，我们发现，至少在这次活动中进行的测量中，τ0的平均值（对于固定的S4指数值）作为当地时间的函数变化不大。我们的研究结果还表明，当S4≥0.7时，τ0对GPS载波环路性能有显著影响。文中还提出了一种考虑衰落持续时间的计算周跳概率的方法。该方法的结果表明，在强闪烁情景（S4接近1，τ0接近0.2 s）中，周期滑移的概率为38%。最后，我们给出了在我们的一组测量中观察到的单个振幅衰减的分析结果。这一分析表明，使用C/N0阈值在30 dB-Hz及以上的GPS接收机的用户会受到低纬度闪烁的显著影响。
Ionospheric scintillations are fluctuations in the phase and/or amplitude of trans-ionospheric radio signals caused by electron density irregularities in the ionosphere. A better understanding of the scintillation pattern is important to make a better assessment of GPS receiver performance, for instance. Additionally, scintillation can be used as a tool for remote sensing of ionospheric irregularities. Therefore, the study of ionospheric scintillation has both scientific as well as technological implications. In the past few years, there has been a significant advance in the methods for analysis of scintillation and in our understanding of the impact of scintillation on GPS receiver performance. In this work, we revisit some of the existing methods of analysis of scintillation, propose an alternative approach, and apply these techniques in a comprehensive study of the characteristics of amplitude scintillation. This comprehensive study made use of 32 days of high-rate (50 Hz) measurements made by a GPS-based scintillation monitor located in São José dos Campos, Brazil (23.2°S, 45.9°W, −17.5° dip latitude) near the Equatorial Anomaly during high solar flux conditions. The variability of the decorrelation time (τ0) of scintillation patterns is presented as a function of scintillation severity index (S4). We found that the values of τ0 tend to decrease with the increase of S4, confirming the results of previous studies. In addition, we found that, at least for the measurements made during this campaign, averaged values of τ0 (for fixed S4 index values) did not vary much as a function of local time. Our results also indicate a significant impact of τ0 in the GPS carrier loop performance for S4 ≥ 0.7. An alternative way to compute the probability of cycle slip that takes into account the fading duration time is also presented. The results of this approach show a 38% probability of cycle slips during strong scintillation scenarios (S4 close to 1 and τ0 near 0.2 s). Finally, we present results of an analysis of the individual amplitude fades observed in our set of measurements. This analysis suggests that users operating GPS receivers with C/N0 thresholds around 30 dB-Hz and above can be affected significantly by low-latitude scintillation.