Log-distance path loss model β visualize RSSI and coverage radius across environments and frequencies. Adjust TX power, antenna gain, cable loss, and environment to see real-time coverage circles and a path loss table.
| Distance (m) | Path Loss (dB) | RSSI (dBm) | Quality |
|---|---|---|---|
| 5 | 69.6 | -32.6 | Excellent |
| 10 | 78.0 | -41.0 | Excellent |
| 20 | 86.4 | -49.4 | Excellent |
| 30 | 91.4 | -54.4 | Excellent |
| 50 | 97.6 | -60.6 | Excellent |
| 75 | 102.5 | -65.5 | Excellent |
| 100 | 106.0 | -69.0 | Excellent |
| 150 | 110.9 | -73.9 | Good |
| 200 | 114.4 | -77.4 | Good |
| 300 | 119.4 | -82.4 | Acceptable |
| 500 | 125.6 | -88.6 | Acceptable |
The RF Propagation & Coverage Simulator uses the log-distance path loss model to visualize signal strength as a function of distance across multiple environments and frequencies, displaying color-coded coverage circles and a detailed path loss table. RF engineers use it to quickly compare propagation characteristics between frequency bands, optimize DAS and BDA designs, and estimate coverage radii for different deployment scenarios.
The log-distance path loss model used in this simulator is: PL(d) = PL(d0) + 10Β·nΒ·log10(d/d0) + ΞPL_freq, where d0 = 1 m is the reference distance, n is the path loss exponent specific to the environment, and ΞPL_freq is a frequency-dependent offset applied to the reference path loss. RSSI(d) = TX Power + Antenna Gain β Cable Loss β PL(d). Coverage radius at a target RSSI threshold is solved as: d = 10^((TX Power + Antenna Gain β Cable Loss β PL(d0) β ΞPL_freq β RSSI_target) / (10Β·n)).
The propagation exponent n ranges from 2.0 for free space to 4.5 for dense indoor NLOS environments. The frequency offset accounts for the higher reference path loss at higher frequencies β 2.4 GHz WiFi has 8 dB more path loss at 1 m than 450 MHz UHF. Shadowing margin is not included in this simulator β add 6β10 dB to achieve 90% location probability in indoor NLOS environments.
The log-distance model is documented in IEEE 802.11 channel models (IEEE 802.11-03/940r4) for indoor WLAN planning and in 3GPP TR 25.996 for UMTS spatial channel models. ITU-R M.2135 provides the reference models used for IMT-Advanced evaluation. For public safety communications, APCO ANS 3.103.2 and TIA-TSB-88 reference propagation exponents of 3.0 to 3.5 for general in-building planning. NFPA 1221 coverage calculations use an equivalent model with environment-specific parameters for each building type.
The propagation exponent n is the most sensitive parameter in the model β underestimating n by 0.5 can overestimate coverage radius by 30β50% in dense environments. Use n = 3.8 to 4.5 for concrete high-rise buildings, n = 2.8 to 3.2 for open-plan offices with light drywall partitions, and n = 2.0 to 2.5 for large warehouses and open factory floors. No shadowing margin is included in this simulator. For 90% location probability coverage design, add a shadowing margin of 8Β·Ο dB where Ο is the standard deviation of the log-normal shadowing component (typically 6β10 dB for indoor NLOS). For reliable NFPA 1221 compliance, design to β85 dBm rather than the β95 dBm minimum to allow for shadowing uncertainty.
Select the frequency band and environment type from the dropdowns. Use the TX Power, Antenna Gain, and Cable + Connector Loss sliders to model your specific system configuration (use the EIRP Calculator for exact values). The coverage circle diagram updates in real time showing the radius at β70, β85, and β95 dBm RSSI thresholds. The System Summary panel shows EIRP and coverage radii at each threshold. The Path Loss & RSSI table gives exact values at specific distances from 5 to 500 m. Use the β95 dBm circle radius as the input to the Antenna Coverage Radius Calculator to determine antenna spacing for a multi-antenna DAS layout.
Hospitals typically use n = 3.5 to 4.0 due to thick concrete walls, lead shielding in imaging rooms, and mixed construction. For ICU and imaging areas with additional electromagnetic shielding, n can approach 4.5. Critical areas like operating rooms and basement labs often require dedicated antennas rather than relying on propagation from the main corridor antenna grid.
5 GHz has 6.6 dB more free-space path loss at a given distance than 2.4 GHz, due to the smaller effective antenna aperture at higher frequencies. Additionally, 5 GHz signals attenuate more rapidly through walls and partitions β a single drywall partition adds approximately 6 dB at 5 GHz versus 3 dB at 2.4 GHz. The combination of higher FSPL and increased penetration loss results in roughly half the indoor coverage radius at 5 GHz.
The log-distance model provides a good median path loss estimate, but individual measurement locations can vary by Β±10 to 15 dB due to multipath and shadowing effects. For planning purposes, the model is accurate to within 3β5 dB for the median signal level. For compliance testing and walk-test planning, actual measurements are always required β the model is a design tool, not a substitute for site measurement.
Building penetration loss is the additional attenuation when a signal passes through an exterior wall from outside to inside (or vice versa). Typical values: glass curtain wall 2β6 dB, brick exterior 8β12 dB, concrete 15β25 dB, metallic glass (low-E coated) 20β30 dB. For DAS systems, the signal source is inside the building and penetration loss only applies to donor antenna calculations β the log-distance model used here assumes propagation within the building from an interior antenna source.
Determine the coverage radius at β85 dBm (providing 10 dB margin above the NFPA β95 dBm threshold). The coverage area per antenna is Ο Γ rΒ². Divide the total floor area by this per-antenna coverage area to get the minimum antenna count. Add 20β30% additional antennas for geometry efficiency (rectangular floors, corners, and corridors). Verify the final design using the NFPA 1221 Coverage Simulator.
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