Uplink Interference and Performance Analysis for Megasatellite Constellation

Satellite communications plays an important role in future Internet of Things (IoT) networks, and mega satellite constellations can further provide global coverage and high-quality services for IoT communications. In the mega constellation, large-scale satellites are launched to enhance the capacity. However, the dense distribution of satellites brings intra-constellation interference, limiting the performance. In order to evaluate the restriction of interference caused by system parameters such as the scale of constellation or the frequency reuse factor, we investigate uplink intra-constellation interference and performance of the mega satellite constellation. First, a multi-beam polar constellation with uplink spatial frequency reuse is assumed. Then, the interference model is constructed considering the antenna gain of interfering user terminals and multi-beam satellites, where the details of satellite-fixed frequency reuse scheme and coordinates of co-frequency cells are provided. To evaluate the performance, expressions of outage probability, ergodic capacity and sum ergodic capacity are driven. The analytical results disclose the impact of system design on the performance, and the accuracy of analysis results is obtained through extensive simulation evaluation. Results show that sum ergodic capacity achieves highest in the case of full frequency reuse for frequency limited constellation system, and it gets a linear growth at first but then keeps flat with a trend of fluctuating downward as scale increases, therefore, the impact of the scale should be considered when constructing mega constellations.