Coverage Heatmap Estimator
Estimate indoor cell radius, cell area and AP count from EIRP, target RSSI, wall losses and a path-loss exponent.
Inputs
Cell Radius at Target RSSI
12.6m
Effective Area per AP
327m²
Access Points to Cover the Floor
6
Usable Link Budget
77.0dB
Cell Size Assessment
Typical enterprise cell size
Step by step
Values used
AP EIRP = 20 dBm; Frequency = 5,500 MHz; Target RSSI at the cell edge = -67 dBm; Walls between AP and cell edge = 1 walls; Loss per wall = 5 dB; Shadow-fade margin = 5 dB; Path-loss exponent = 2.70; Floor area to cover = 1,800 m²
Coverage Heatmap
PL(d) = 20·log10(f_MHz) − 27.56 + 10·N·log10(d_m), inverted for d at a link budget of EIRP − target RSSI − wall losses − fade margin.
Cell Radius at Target RSSI
= 12.6 m
Effective Area per AP
= 327 m²
Access Points to Cover the Floor
= 6
Usable Link Budget
= 77.0 dB
Cell Size Assessment
= Typical enterprise cell size
How it works
The one-slope indoor model anchors path loss at a one-metre reference and then grows it by 10·N decibels per decade of distance. Solving it for distance at the point where received power equals the target RSSI gives the cell radius; multiplying the circle area by 0.65 accounts for overlap and non-circular real-world cells. Predictive designs live or die on the path-loss exponent and wall losses — assume free space indoors and you will deploy half the APs you need, then re-survey after go-live.
Formula
Coverage Heatmap
PL(d) = 20·log10(f_MHz) − 27.56 + 10·N·log10(d_m), inverted for d at a link budget of EIRP − target RSSI − wall losses − fade margin.
- N
- Path-loss exponent: 2 in free space, 2.7–3.5 in offices, 4+ through dense structure
- 27.56
- Constant that reduces free-space loss to a one-metre reference
Frequently Asked Questions
How is Coverage Heatmap calculated?
PL(d) = 20·log10(f_MHz) − 27.56 + 10·N·log10(d_m), inverted for d at a link budget of EIRP − target RSSI − wall losses − fade margin. The one-slope indoor model anchors path loss at a one-metre reference and then grows it by 10·N decibels per decade of distance. Solving it for distance at the point where received power equals the target RSSI gives the cell radius; multiplying the circle area by 0.65 accounts for overlap and non-circular real-world cells.
Why does Coverage Heatmap matter?
Predictive designs live or die on the path-loss exponent and wall losses — assume free space indoors and you will deploy half the APs you need, then re-survey after go-live.
What values do I need to enter?
This calculator takes 8 inputs: AP EIRP, Frequency, Target RSSI at the cell edge, Walls between AP and cell edge, Loss per wall, Shadow-fade margin, Path-loss exponent, Floor area to cover. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.