How to Measure and Calculate Wall Attenuation for Custom Presets

1. Equipment Setup

Required Equipment:

• Wi-Fi Access Point (AP) configured to transmit on the desired channels.
• TamoGraph Site Survey running  with a supported Wi-Fi Adapter.
• Measuring Tape to ensure accurate placement.

AP Placement:

• Place the AP at a fixed position (preferably 12-15 meters from the test wall).
• Ensure the AP's antenna orientation is consistent for all measurements.

2. Measurement Procedure

Take signal strength readings (RSSI in dBm) at different locations, making sure to measure at various distances in front and behind the wall.

Step 1: Measure Free Space Path Loss (FSPL) Reference

• Stand at the same distance from the AP as the wall, but without any wall obstruction.
• Record the signal strength in free space (P_free).

Step 2: Measure in Front of the Wall

• Directly in front of the wall, measure signal strength at the same distance from the AP as the reference.
• Record the signal strength (P_front).
• Optionally, measure 2 meters in front of the wall and record signal strength (P_front_2m).

Step 3: Measure Behind the Wall

• Move to the other side of the wall and measure signal strength at the same distance behind the wall.
• Record signal strength (P_behind).
• 1 meter behind the wall: Take measurements at 1 meter behind the wall and record signal strength (P_behind_1m).
• 2 meters behind the wall: Measure 2 meters behind the wall and record signal strength (P_behind_2m).

3. Calculating Wall Attenuation

Formula 1: Basic Wall Attenuation

To calculate the signal loss caused by the wall:

Awall​=Pfront​−Pbehind​

This will give you the basic signal loss between front and back of the wall.

Formula 2: Normalized Attenuation (Considering FSPL)

To normalize the attenuation by factoring in free space loss:

Awall_normalized​=(Pfree​−Pbehind​)−(Pfree​−Pfront​)

This will give you the signal loss caused by the wall, normalized for free space.

Formula 3: Extended Wall Attenuation with Additional Readings

For additional measurements behind the wall, use the following formulas to calculate attenuation at different distances:

For 1m behind the wall:

Awall_1m​=Pfront​−Pbehind_1m​

For 2m behind the wall:

Awall_2m​=Pfront​−Pbehind_2m​

Normalized Attenuation for Extended Measurements:

To normalize attenuation for these additional readings behind the wall:

For 1m behind the wall:

Awall_normalized_1m​=(Pfree​−Pbehind_1m​)−(Pfree​−Pfront​)

For 2m behind the wall:

Awall_normalized_2m​=(Pfree​−Pbehind_2m​)−(Pfree​−Pfront​)

Options for Combining the Attenuation Results:

 - If you are certain in the reflection chosen for your customer material, the use the following formula:

Afinal​ = 0.5⋅Awall ​+ 0.3⋅Awall_1m​ + 0.2⋅Awall_2m​​​

This method works well for real-world conditions where signal loss isn't uniform.

$$-\; If$$the reflection value is an approximate guess, you might want to blend attenuation effects at 1m behind the wall for a more stable result:

Afinal​ = 0.7⋅Awall​+0.3⋅Awall_1m​​

4. Best Practices for Accurate Results

✔ Take multiple readings at each point and average them for better accuracy.
✔ Measure at the same height at all points to avoid discrepancies due to vertical angle.
✔ Ensure a clear line of sight between the AP and measurement points to avoid reflections.
✔ Use the same frequency band and channel for consistency in signal loss calculation.
✔ Avoid interference from other Wi-Fi devices by conducting the survey in less crowded times.