Realistic Simulation of 5G/6G NTN RF Systems and Transmission Channels

Commercial 5G deployments began in 2018, with steady expansion of terrestrial networks across urban and suburban regions. Despite this progress, large geographic areas — particularly rural, remote, maritime, and airborne environments — remain underserved by terrestrial infrastructure. This persistent coverage gap has accelerated interest in extending 5G through Non-Terrestrial Networks (NTN), positioning NTN as a critical enabler of truly global connectivity. NTN is especially well suited for enhanced mobile broadband, massive IoT, and direct-to-device services beyond the reach of traditional cellular networks.

NTN has evolved into an umbrella term encompassing multiple network types that rely on non-terrestrial platforms. These include satellite communication networks, High-Altitude Platform Systems (HAPS), and air-to-ground networks. Satellite-based NTNs span Low-Earth Orbit (LEO), Medium-Earth Orbit (MEO), and Geostationary Earth Orbit (GEO) systems. In recent years, global momentum has strongly shifted toward LEO constellations, driven by their ability to deliver lower latency, higher capacity, and broadband-class user experiences at scale.

The satellite ecosystem has played an active role in 3GPP standardization, culminating in the formal integration of NTN into the 5G framework starting with Release 17 and continuing through Release 18. These releases define key aspects of NTN operation, including physical-layer adaptations, protocols, system architecture, radio resource management, RF requirements, and supported frequency bands. Standardized deployment scenarios now cover satellite-based systems as well as high-altitude platforms such as balloons, airships, and uncrewed aerial vehicles operating in the stratosphere. Early commercial implementations have primarily focused on satellite NTNs with transparent payloads, however, regenerative payloads with on-board baseband processing capabilities have started to emerge as part of 3GPP Release 19.

Achieving robust NTN performance requires early validation of gateway infrastructure, airborne platforms, and user equipment — including handheld devices and very small aperture terminals — through system-level simulation. This is particularly critical for phased-array antennas and broadband power amplifiers employing digital predistortion (DPD), where nonlinearities, memory effects, antenna coupling and beamforming accuracy, and Doppler effects must be jointly analyzed. These challenges intensify as the industry transitions toward 6G, with higher carrier frequencies, ultra-wide bandwidths, larger antenna arrays, and tighter energy-efficiency constraints. As a result, NTNs are widely viewed as one of the key use cases shaping 6G system design.

High-fidelity virtual analysis has therefore become indispensable. Engineers must adopt shift-left design methodologies to accelerate development and reduce risk, using simulation-driven digital twins to evaluate performance across RF, baseband, antenna, and network domains. The ability to model realistic impairments, dynamic channels, and end-to-end KPIs at scale is now a prerequisite for delivering reliable NTN solutions. In an increasingly competitive landscape, success hinges on leveraging advanced simulation to explore complex 5G and pre-6G NTN scenarios and unlock the full potential of global, space-enabled wireless connectivity.

This solution brief explores the key RF link design and channel modeling challenges associated with 5G/6G NTN and demonstrates how to simulate an end-to-end link between the gateway, satellite, and user equipment in a transparent or regenerative payload architecture. Using Keysight SystemVue, the workflow enables high-fidelity analysis of propagation effects, RF impairments, and link performance to support early-stage validation and optimization of NTN designs.