# Theoretical Wi-Fi decay

Is there a way to (theoretically at least) calculate the decay on bandwith of a Wifi related to the streght signal? For example, I know that I can theoretically expect 54Mbps of a 802.11g at 100%, which will be the bandwith expected at a 30% of signal? is it lineal? is it the same?

I could not find any source for this, but considering the error replay involved, I guess it should be possible to calculate something like this. Anybody knows?

It's not nearly as simple as you probably think it is.

1. Calculate the freespace loss:

``````20 * (log(d) + log(f) + 1.62)
``````

Where d is the distance in meters, f is the frequency in kHz.

2. Lookup the transmit strength of endpoint A, subtract the freespace loss, add the antenna gain at each end, add endpoint B's receive sensitivity, subtract a link budget (maybe 5 for small space WiFi, 10 for open environments, and 20+ for "dense" situations).

3. Itterate the #2 calculation for various speeds and modulations. High end equipment will have the exact specs for a wide variety of configurations. Low end stuff publishes less information.

4. For configurations where the final calculation comes out positive, it should work. Negative numbers should not work.

• Nice, this is the information I was looking for, thanks :) – lithiium Jun 2 '14 at 23:29