Downlink Interference Analysis of Large-Scale Non-Geostationary Orbit Constellation Based on Fibonacci Grid Method

With the increasing number of satellites, the downlink interference between non-geostationary orbit (NGSO) constellation systems is becoming more prominent. Interference-to-noise ratio (I/N) is an important evaluation index to measure the level of mutual interference, and its probability distribution is usually obtained by extrapolating the satellite orbit position and counting the time proportion of different I/N values. However, the traditional propagation method has the problems of long simulation time and low calculation efficiency. This paper proposes a new method to calculate the I/N of large-scale non-geostationary orbit constellation. By modeling large-scale constellation as uniformly distributed in space, Fibonacci grid method is used to calculate satellite position coordinate. In addition, equivalent number of satellites is defined to take into account the number of visible satellites at different latitudes. The expression of I/N is derived, and the probability distribution of I/N is obtained. On this basis, the effect of parameters of the constellations and the latitude of Earth Station on the I/N distribution is analyzed. The numerical results of the proposed method and the orbit propagation method is similar, and the calculation speed of the former is obviously faster than that of the latter.