NTNs for 5G-Advanced and 6G

An effective NTN simulation starts with geometry—range, elevation, look angles, Doppler, and latency versus time—because those quantities drive nearly every downstream impairment. It then layers in propagation and loss, combining free-space effects with atmospheric losses (rain, gas, cloud/fog, scintillation) and computing availability statistics over the access window. Where fading or selectivity matters, standard-based NR NTN channel models (for example, TR 38.811 narrowband/TDL families) provide a consistent way to stress receivers. Finally, the model must represent arrays and beams. Steering limits, pointing errors, polarization, and interference across beams, especially with spectrum reuse, directly influence link quality and system capacity.

A practical MATLAB^® workflow typically begins with scenario and orbit modeling using satelliteScenario to generate access windows and time-varying geometry. Engineers then establish feasibility with static and time-varying link budgets using the Satellite Link Budget Analyzer app, including availability analysis framed by ITU‑R P.618 to size antennas/EIRP/G/T and evaluate band choices. Next, waveform and PHY studies combine 5G Toolbox™ with NR NTN channel models to evaluate synchronization robustness, channel estimation, BLER, and throughput under Doppler and delay dynamics. The workflow then adds beamforming and RF realism, including arrays, beam squint, quantization effects, and PA nonlinearity, and scales to system KPIs by abstracting link quality. This approach creates a path from algorithm design to lab and field test.

In NTN systems, link budgets determine feasibility and availability defines whether performance targets are met over time. Engineers typically close the link early using C/N₀, E_b/N₀, and margin targets tied to modulation and coding, then examine how those margins evolve over time as range, elevation, and pointing change throughout an access window. Atmospheric loss processes can dominate at certain bands and elevation angles. As a result, availability becomes a primary KPI. Design goals are often defined in terms of “percent of time meeting a target” under geometry and weather, which is especially critical for gateways and feeder links.

Evaluating NR NTN PHY performance requires end-to-end simulations that connect Doppler and delay effects to BLER and throughput. Teams typically run physical channel simulations using deployment-aligned NTN channel models (often framed by 3GPP TR 38.811) to capture Doppler-driven impairments and their impact on synchronization and channel estimation. Doppler mitigation strategies are modeled explicitly. This includes transmitter-side precompensation and receiver-side tracking so that residual CFO reflects realistic ephemeris and oscillator errors. Where procedure sensitivity matters, time-varying propagation delay is included to assess its impact on timing advance, HARQ behavior, and buffering. To translate these effects into performance metrics, a throughput reference workflow (for example, an NR NTN PDSCH throughput-style simulation) maps channel conditions to decoded BLER and throughput.

Beamforming in NTN systems must account for wide-angle steering, hardware constraints, and interference, not just main-lobe direction. Wide steering angles introduce scan loss and coverage variation, which directly affect link closure across the service area. In wideband systems, frequency-dependent effects such as beam squint can distort beam patterns and must be considered in array design and weighting. Practical implementation constraints also matter. Phase quantization, element variation, and calibration errors shape sidelobes and influence interference, especially when spectrum is reused across beams. Transmitter and receiver impairments further impact performance. Power amplifier nonlinearity, EVM, spectral regrowth, and receiver quantization all affect link quality and must be included to connect RF behavior to throughput. When multiple beams share spectrum, interference becomes a system-level constraint. Techniques such as null steering and interference mitigation are essential to maintain capacity, not just improve link gain. (See the webinar Beamforming for NTN Systems with MATLAB for an end-to-end engineering walkthrough.)

NTN teams often validate designs using a continuous-verification mindset: the same reference models used in simulation are reused during prototyping and tests. Practically, this means generating and analyzing waveforms in MATLAB, connecting to SDRs and RF instrumentation to validate impairment sensitivity and receiver robustness, and then using implementation workflows (including code generation and FPGA acceleration where applicable) to move algorithms toward real-time constraints while keeping the verification chain intact.

To extend beyond PHY without building a full satellite network stack, many teams start from scenario traces. Access intervals and time-varying geometry (elevation, Doppler, latency) drive a time series of link quality. Rather than re-running waveform processing for every packet, the PHY is abstracted by mapping C/N₀ or SINR to MCS/throughput curves derived from link-level studies. A discrete-event model can then represent queues, scheduling, handovers, gateway selection, and, where needed, ISL availability to compute latency/jitter, packet loss, and fairness. Because routing and traffic engineering are mission specific, scalable studies typically add the network behaviors that dominate design decisions first, then expand via scripted parameter sweeps and scenario automation.