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WiFiArea — Indoor Wi-Fi Coverage Simulator

A WinForms application that visualizes, as a heatmap, the received-power distribution from multiple indoor Wi-Fi access points (APs) across an office made up of a corridor and several rooms.

The propagation models and building-material transmission losses are based on ITU-R recommendations:

• Distance loss: ITU-R P.1238-13 (09/2025), eq. (2) L = 20log10(f) − 28 + N·log10(d)
• Wall transmission / reflection loss: ITU-R P.2040-4 (09/2025) — material electrical constants and single-layer slab transmission/reflection coefficients
• Diffraction loss: ITU-R P.526 single knife-edge approximation J(ν)
• Antenna pattern: ITU-R F.1336-5 empirical patterns (omni / directional), or an .ant file

In addition to the direct wave, it combines first-order reflections off walls and diffraction at the edges of apertures (windows/doors).

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1. Running

Requirements

• .NET 8 SDK or later
• Windows (the UI is WinForms; the WiFiArea.Core calculation layer is OS-independent, and its tests run on non-Windows too)

dotnet build WiFiArea.sln

dotnet run --project WiFiArea.Desktop -- config/office-sample.json

If you omit the argument, the app walks up from the working directory and opens config/office-sample.json automatically.

Screen controls

Action	Effect
Wheel	Zoom (anchored at the cursor)
Drag	Pan
Double-click / Home	Fit to view
F5	Reload the config and recalculate
Ctrl+O	Open a config
Ctrl+S	Save the current view as PNG

The status bar shows the value under the cursor (received power, loss, and number of paths).

Buildings and antennas are not edited in the GUI. Edit the config file in a text editor and press F5 to reload.

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2. Writing the config

config/office-sample.json is a practical example (one corridor + six rooms + four APs). It is JSON but tolerates line comments // and trailing commas.

2-1. Overall

{
  "schema": "wifiarea-site-1",     // fixed; used for the compatibility check
  "site":      { ... },            // building extent and environment
  "materials": [ ... ],            // material definitions (referenced by id from walls/apertures)
  "walls":     [ ... ],            // walls (line segments + apertures)
  "rooms":     [ ... ],            // rooms (for display only; not used in the calculation)
  "antennas":  [ ... ],            // APs
  "calc":      { ... },            // calculation settings
  "display":   { ... }             // display settings
}

2-2. site

Key	Meaning
name	Building name (shown in the title bar and the right pane)
environment	office / corridor / industrial / conferenceRoom; used for the coefficient lookup when a site-general model is selected
extent	Calculation/drawing range { "x0":0, "y0":0, "x1":24, "y1":14 } [m]
ceilingHeightM	Ceiling height [m]; used for input validation

2-3. materials

Specifying ituMaterial + thicknessMm computes the transmission loss from the material constants in ITU-R P.2040-4 Table 3. Specifying lossOverrideDb uses that fixed value instead (e.g. to substitute a measured value).

{ "id": "concrete", "displayName": "Concrete wall 180mm",
  "ituMaterial": "Concrete", "thicknessMm": 180, "color": "#555555" }

Available ituMaterial values (the P.2040-4 Table 3 material classes):

Vacuum / Concrete / Brick / Plasterboard / Wood / Glass / Clear Acrylic / Ceiling board / Chipboard / Plywood / Marble / Floorboard / Vinyl tile / Carpet tile / Asphalt concrete / Metal

Each material has a valid frequency range; using a frequency outside it is an error (coefficients are not extrapolated). For example, Floorboard is only defined at 50 GHz and above, so it cannot be used in the Wi-Fi bands.

2-4. walls / rooms

A wall is a line segment + material; apertures (windows, doors, openings) are given as intervals measured from the wall's start point.

{ "id": "W-C-S1", "from": [0, 6], "to": [18, 6], "material": "partition",
  "apertures": [
    { "type": "door", "start": 2.6, "length": 0.9, "material": "wood-door" }
  ] }

Rooms are for display only and are not used in the calculation.

2-5. antennas

{ "id": "AP1", "name": "AP-01 (corridor west)", "position": [6.0, 7.0], "heightM": 2.6,
  "frequencyMHz": 2412, "txPowerDbm": 17.0, "cableLossDb": 0.0,
  "azimuthDeg": 0, "tiltDeg": 0,
  "antenna": { "mode": "omni", "gainDbi": 3.0 } }

antenna.mode	Required fields	Pattern
omni	gainDbi	F.1336-5 omni pattern (uniform in azimuth, dipole-like in elevation)
directional	gainDbi, hpbwHDeg	F.1336-5 Recommends 3; hpbwVDeg is auto-derived from the empirical formula if omitted
file	patternFile	.ant file (path relative to the config)

Do not use omni for a ceiling-mounted AP. The F.1336 omni pattern is dipole-like, so the antenna-axis direction (straight down) is a null: directly under the AP is −8 dBi while the horizontal direction is +3 dBi, which cancels the distance falloff and flattens the distribution. Real ceiling APs radiate into the lower hemisphere, so specify a pattern such as the bundled config/patterns/ceiling-ap.ant (maximum straight down, −6 dB at the horizon, −20 dB straight up) in file mode. omni is appropriate for a pole-mounted vertical rod antenna whose axis is vertical and which radiates in the horizontal plane.

• azimuthDeg is measured clockwise with +y as 0° (the same convention as a true-north bearing).
• tiltDeg is positive for downtilt. A ceiling-mounted omni AP has a vertical antenna axis, so it is 0 (set it only when aiming a directional antenna downward).

2-6. calc / display

{ ...,
  "colormap": "RdYlGn",             // Turbo (blue→red) / RdYlGn (green→red) / Grayscale
  "thresholdsDbm": [-65.0, -75.0]   // legend threshold lines; the first is the basis for the coverage ratio
}

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3. What is being calculated

For each grid point, the received power is the sum of the powers of every path arriving from each AP. When there are multiple APs, the maximum (best server) among them is taken.

Path	Description
Direct wave	The straight line joining Tx and Rx; the transmission loss of each penetrated wall is added
First-order reflection	The reflection point is found by the image method on the wall face; reflection coefficients come from the P.2040 slab coefficients. Metal walls reflect almost losslessly (|R|≈1)
Diffracted wave	The aperture edge is treated as a vertical knife edge; from the path difference Δ, ν = √(2Δ/λ) and J(ν) are applied

The received power of each path is:

Prx = Pt − feed loss + Gtx(3D) + Grx − L_distance − Σ L_wall − L_extra   [dBm]

L_extra is the reflection or diffraction loss. Paths are combined by a simple power sum (incoherent combination); phase is not modeled. Fine interference fringes do not appear, but this is more practical for viewing the average distribution.

Effect of reflection and diffraction

The bottom-right of the sample is a server room enclosed by metal-panel walls (with one wooden door). Toggling "Reflection" and "Diffraction" in the toolbar lets you compare against the direct-wave-only result.

Direct wave only	Direct + first-order reflection + diffraction
The server room drops to around −70 dBm, and the aperture shadow is cut sharply into a fan shape	Waves wrapping around the door edge, plus waves reflected off the corridor wall and entering through the door, bring it up to around −55 dBm, and the boundary becomes smoother

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4. Development

Project	Description
WiFiArea.Core	OS-independent geometry, materials, and propagation engine
WiFiArea.Desktop	Windows WinForms UI
WiFiArea.Desktop.Tests	Tests for the drawing transforms and color scales
tools/FormPreview	A verification harness that captures the screen to PNG

dotnet test WiFiArea.sln

After changing the UI, capture and visually check it:

dotnet run --project tools/FormPreview -- --config config/office-sample.json --out shots/main.png --size 1440x900

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5. License and sources

This software is under the MIT License.

The propagation models and building-material electrical constants are based on the following ITU-R recommendations. The implementation uses only the coefficients needed in the indoor Wi-Fi bands (1–100 GHz) this app targets; obtain the full text and complete tables from the ITU website.

Recommendation	What is used
ITU-R P.1238-13 (09/2025)	Indoor basic transmission-loss eqs. (1)(2), site-general coefficients, the guideline for the distance power coefficient N, floor penetration loss
ITU-R P.2040-4 (09/2025)	Building-material electrical-constant models, single-layer slab reflection/transmission coefficients (ABCD-matrix method)
ITU-R P.526	Single knife-edge diffraction approximation J(ν)
ITU-R F.1336-5	Empirical antenna radiation patterns

This software has not been approved or endorsed by the ITU. The results are simplified predictions and do not guarantee the actual radio environment. Verify with field measurements when designing or operating radio equipment.