Ray-Tracing Channel Modeling for LEO Satellite-to-Ground Communication Systems

TL;DR

This work advances urban LEO satellite-to-ground channel modeling for 6G by integrating a GO/UTD-based ray-tracing framework with SGP4-derived orbital propagation and precise TEME-to-ECI/local-coordinate transformations. It computes time-varying path loss, RMS delay spread, and Doppler shifts within a defined transmission window, employing a model where $PL = PL_{fs} + PL_{rain}$ and Doppler shifts are given by a time-dependent expression $f_D(t)$ that accounts for satellite motion and geometry. Key contributions include a practical coordinate transformation pipeline from TLE/SGP4 data to local coordinates for ray-tracing, an explicit Doppler-shift formulation, and validation against 3GPP results and urban measurements (Cid2016TVT), demonstrating accurate blockage modeling and realistic multipath behavior in cityscapes. This framework enables high-fidelity design and optimization of LEO-ground links for urban 6G deployments, informing system planning with time-varying channel characteristics across the satellite pass.

Abstract

Based on the vision of global coverage for sixth-generation (6G) wireless communication systems, the low earth orbit (LEO) satellite-to-ground channel model for urban scenarios has emerged as highly important for the system design. In this paper, we propose an LEO satellite-to-ground channel model through shooting and bouncing rays (SBR) algorithm to analyze the channel characteristics. The orbit of LEO is modeled by the simplified general perturbations 4 (SGP4), and an accurate celestial model is applied to calculate the Doppler shift of multipath in a transmission time window of LEO satellite-to-ground communications. Channel characteristics of LEO satellite-to-ground communications such as the root-mean-square (RMS) delay spread, the Doppler shift, and the received power at different times are obtained. The simulation results show that the received power is only significantly noticeable in the transmission time window when the satellite is close to the receiver. Proposed model validates the effectiveness of ray-tracing in actual LEO satellite-to-ground communication scenarios and extends the calculation of the Doppler shift.

Figures (9)

• Figure 1: LEO satellite-to-ground communication scenarios.
• Figure 2: Flow chart of the LEO satellite-to-ground channel modelling method.
• Figure 3: LEO satellite orbital model in ray-tracing.
• Figure 4: Convert ECI to local coordinate.
• Figure 5: Geometric diagram of LEO satellite and ground terminal.