Ray-Optics Simulations of Outdoor-to-Indoor Multipath Channels at 4 and 14 GHz

Radio wave propagation simulations based on the ray-optical approximation have been widely adopted in coverage analysis for a range of situations, including the outdoor-to-indoor (O2I) scenario. This work presents O2I ray-tracing (RT) simulations utilizing a laser-scanned point cloud of the building interior. The simulated radio channels are compared to their measured counterparts at 4 and 14 GHz in terms of path loss, delay, and angular spreads. Validation of channel simulations for O2I cases is rare, and so far nonexistent for above-6-GHz bands. This work reveals the importance of a floor plan model in channel simulations; it is confirmed that path loss can be replicated with a mean error (ME) under 6 dB utilizing a simple interior path loss model instead of a detailed building interior model. Neglecting to model the interior results in high delay and angular spread errors. By modeling the interior, the RT simulations achieve relative ME of under 10% for delay and angular spreads and under 1.5 dB for path loss. Finally, the effects of multilayer insulating window on propagation simulations are reported. Noticeable variation of the penetration loss on a small change of the incident angle of a propagation path causes path gain changes up to 15 dB.