Getting Started

1. Build or load the building model and check floor names/heights and material assignments.
2. Set TX frequency, power, antenna/array settings and propagation options, then position TX and RX.
3. Run Ray Trace. The solver always traces the complete model; 3D view controls only filter what is displayed.
4. Use RX Power for receiver link-budget work and the 2D/3D heatmaps to inspect coverage.
5. Use Optimize RX Height, Optimize RX Position or Optimize TX Coverage for placement studies. Export CSV to retain the grid, simulation settings and any optimizer recommendations.

Point and RX Power

Point is the interpolated wideband-average received power from the 3D coverage grid. The coverage grid always sums ray power incoherently; it does not create carrier-phase nulls from voxel sampling. When multiple tones are requested, the heatmap is a power average over that frequency band rather than a centre-frequency-only map.

Probe is an independent receiver calculation. Unobstructed LOS, every first-order specular reflection (including straight-through transmission on either leg) and first-order edge diffraction are all evaluated analytically; higher-order ray paths are captured once per interaction path using a range-scaled ray reception sphere. A reception sphere collects roughly one ray per path however many rays are launched, so the higher-order contribution does not converge with ray count: expect a residual of a couple of dB on the coherent total which the quality preset does not remove, while LOS, first-order reflection and first-order diffraction are exact and repeatable. In coherent mode the RX total is a point sample of a fast-fading field and can move 20 dB over a few centimetres of probe travel; the incoherent summation mode is the stable quantity for planning margins. The selected RX Power Summation mode controls only the RX total-power combination (coherent multipath or incoherent path power), and Bandwidth/Subcarriers are averaged across the requested tones. The MIMO channel matrix H always remains a coherent complex path channel.

For a 1×1 link, RX Power is the receiver-port power and channel gain can be added directly to total TX power. For arrays, the main readout reports RX Element Power (average, minimum and maximum antenna-port power under equal independent TX-port allocation); it does not pretend that summing all array ports is one receiver link budget. Use the MIMO metric matching the modem strategy: equal-power gain for equal port power, dominant-mode gain for ideal single-stream beamforming, and the full eigenvalue spectrum for spatial multiplexing/capacity. Resolved-path count is shown so sparse deep-NLOS estimates remain visible.

MIMO & Antenna Arrays

Total TX Power is the total conducted power across the configured TX array. With equal allocation it is divided equally between active TX elements. TX/RX Element Peak Gain supplies the absolute dBi gain of each element while Isotropic/Dipole/Patch/Sector supplies the relative angular pattern; array or beamforming gain is not manually added to TX power.

Array spacing is specified in wavelengths at the centre frequency. Elements are placed at their exact continuous XYZ phase centres independently of the coverage-grid spacing: for example 0.5λ at 2.4 GHz is about 6.25 cm even with a 1 m heatmap grid. The heatmap is an incoherent spatial power estimator, while every TX-to-RX element coefficient in H(f) is a coherent sum of resolved paths at each requested tone.

Equal-Power MIMO Gain is normalized to total array TX power. Dominant Mode Gain is the largest eigenmode power gain and represents ideal single-stream precoding/combining. The MIMO Analysis window reports all eigenmode gains, effective rank (the primary spatial-richness indicator), condition number, best-SISO reference, spatial combining gain, per-mode SNR, per-mode capacity contribution, Ideal Shannon Capacity — Equal Power and Ideal TX-CSI Water-Filled Capacity with the optimized power allocation. Capacity uses 290 K thermal noise, the configured receiver Noise Figure and optional System/Implementation Loss; interference, coding/modulation limits and modem non-idealities are otherwise not included.

Diversity gain is an outage/fading statistic and is therefore not claimed from one deterministic channel realization. The tool reports deterministic Spatial Combining Gain instead. Delay metrics are power-weighted and referenced to the first direct arrival (including straight-through transmission), or first resolved arrival when no direct path exists. NTN metrics are calculated separately for each satellite; satellite flight-time differences are not building multipath. Significant excess delay uses paths within 20 dB of the strongest path. Coherence bandwidth is an approximation based on RMS delay spread. Array elements are ideal independent phase centres: mutual coupling, S-parameters, polarization mismatch, embedded-element patterns and RF-chain calibration errors are outside this propagation model.

NTN Satellite Mode

NTN Satellite is a licensed feature; all terrestrial Building TX → Building RX functionality remains free. It is covered by the RFConsult supporter licence, which unlocks every licensed feature across the whole site for a team of up to ten users at one site. Load the licence file once at rfconsult.uk/licence and it applies to this and every other tool in that browser. Complimentary licences may also be issued to RF Consult consulting clients. The licence is verified by the server whenever an NTN calculation is requested.

NTN Satellite mode treats the satellite as a far-field endpoint rather than extending the voxel grid hundreds of kilometres. Satellite azimuth/elevation defines a plane-wave direction at the building; range is referenced to the exterior plane touching the upstream building bounds and supplies free-space loss and propagation delay. Downlink uses satellite EIRP, while uplink uses the satellite receiver G/T. The building propagation remains reciprocal and includes roof/façade penetration, floors, ceilings, internal walls, reflection, transmission, first-order diffraction and diffuse scatter.

Polarisation. Each satellite may carry one port (RHCP) or two co-located ports (RHCP + LHCP). A second co-located antenna is only worth having because a specular reflection reverses circular handedness: the direct path and every even-order reflection arrive with the transmitted handedness, while odd-order reflections arrive with the opposite one. The two ports therefore illuminate different parts of the multipath, and the channel columns differ. Without that bookkeeping a co-located antenna would be an exact duplicate, contributing nothing. The receiver is treated as RHCP, and Antenna XPD sets how much wrong-handed field it still accepts, which is what limits the rank achievable on a clean line-of-sight.

One or two satellites may be configured. Independent Links reports the satellites separately and does not invent coherent combining. Coordinated MIMO assumes ideal static time/frequency/phase coordination between satellite ports; the user-supplied relative phase defines Satellite 2's carrier reference. Doppler is not modelled because this tool is for static design and assumes the NTN network removes Doppler before modem processing.

In NTN mode the building-side antenna is an Nx × Ny matrix whose elements may be set individually to RHCP or LHCP from NTN Setup → RX Array Setup. Because a specular reflection reverses circular handedness, an element sees the even-order arrivals of a co-polar transmission and the odd-order arrivals of a cross-polar one, with the wrong-handed part suppressed by the configured antenna XPD. Mixing handedness across the matrix therefore produces genuinely different columns rather than duplicated ones. On an uplink the same grid applies to the building transmit array, since the building propagation is reciprocal.

The upper-floor ceiling remains present in NTN models. An enabled Roof is a separate exterior surface above the ceiling. Flat and pitched roofs use the selected roof material; pitched roofs use the entered angle and an automatic ridge along the longer building dimension. Default roof-tile material values are representative planning values only and should be replaced by measured/project construction data where available.

Diffraction

Edge diffraction is energy-conserving within the ray model: only illuminated ray tubes that reach a vertical wall edge can transfer the configured share of specular reflected power onto a Keller-cone edge path. Diffraction order is bounded independently from reflection depth; first-order diffraction is the validated default used to prevent unphysical recursive edge-branch explosion.

3D Viewing

Whole Building shows the full architectural height. Select a named floor or use the previous/next-floor arrows to isolate one storey. View Options can apply a lower/upper Z cut inside the selected building or floor range and can hide/show floors and ceilings. These are display filters only and never change the ray trace.

Optimisation

Receiver Placement has a shared Search Area: Current Room, Current Floor or Entire Building. Optimize RX Height keeps the current RX X/Y and searches valid heights in that scope; for Entire Building it can compare valid heights on different floors at the same X/Y. Optimize RX Position searches valid XYZ positions throughout the selected scope. Each selected candidate is then validated with the exact RX path calculation. Optimize TX Coverage performs a bounded maximin search over the chosen room, floor or building and validates finalists with the full propagation solver before recommending a TX XYZ.

Model Scope

Results are model predictions based on user-supplied frequency-independent material power coefficients, zero-thickness walls, no refraction or slab resonance, full-height window segments, bounded floor/ceiling planes and directive (cos⁵) scatter. A level’s floor and the ceiling of the level below it are one physical slab and take the lower level’s Ceiling Material. Material Absorption is derived as 1 − R − T rather than entered independently. Reported noise power is kTB + Noise Figure; System / Implementation Loss is applied to the signal when SNR is formed, not folded into the reported noise power. Site calibration remains appropriate where regulatory or safety margins require measurements.

The receiver is swept along a straight track while the transmitter, the building and (in NTN mode) the satellite stay put. Every sample re-solves the line-of-sight, first-order specular and first-order edge-diffraction paths exactly, so the channel evolves continuously and the resulting second-order statistics are meaningful. With higher-order multipath included, the second- and third-order paths are re-solved exactly at every sample too, by image theory.

Sampling. Level-crossing statistics are biased low if a fade is crossed between two samples. Measured against the Clarke closed form, the error stays within a few percent down to roughly −6 dB at λ/16, −10 dB at λ/32, −15 dB at λ/64, −20 dB at λ/128 and −25 dB at λ/256. The plots mark the depth below which the chosen rate under-samples.

Confidence. Second-order statistics converge with distance travelled in wavelengths, not with seconds: roughly one deep fade per wavelength, so the standard error on LCR is about 1/√N. Below 50 λ the curves are noisy.

Higher-order multipath is found and evaluated in two separate steps, because the ray launch is good at discovering which paths exist and bad at valuing them — reception spheres capture roughly one ray per path however many are launched. So the launch is used only to discover which sequences of surfaces reach the receiver, at the start, middle and end of the track; each sequence is then solved exactly at every sample by image theory. Mirroring the receiver through the sequence in reverse order of incidence unfolds the whole path into a straight line, so its length, delay, amplitude and Doppler are closed-form functions of receiver position. Nothing is frozen and nothing flickers.

This matters most in NTN mode, where the direct path arrives heavily attenuated through roof and floors, so the multipath is the channel. First-order bounces cannot supply the fading on their own: reflected in a horizontal surface a plane wave keeps its horizontal wavenumber, and a horizontal track senses only that, so floor and ceiling bounces arrive at exactly the direct path’s Doppler and never beat against it.

The full selected scope is shown unless the custom cut is enabled. View filtering never changes the ray trace.