Obviously, in this guide, we will not show you very complicated mathematical calculations but we will show you, in simple words, how you can calculate the real coverage of the Wi-Fi modem by analyzing how the coverage changes according to the type of protocol used, how the signal is attenuated according to the type of obstacle that the Wi-Fi encounters and how to calculate the real coverage with a simple mathematical calculation.
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Different Wi-Fi protocols, different coverage
Let’s start with the simplest thing to understand, is the difference in coverage between the various Wi-Fi network protocols. Below we have collected the estimated coverage for all network protocols supported by a modern modem:
- Wi-Fi 6: also called IEEE 802.11axoperates on the 2.4 GHz and 5 GHz frequencies and provides maximum coverage of about 10 meters (with a bandwidth of 60 MHz).
- Wi-Fi 5: also called IEEE 802.11acoperates exclusively on the 5 GHz frequency and provides maximum coverage of about 15 meters.
- Wi-Fi 4: also called IEEE 802.11noperates on the 2.4 GHz and 5 GHz frequencies and provides maximum coverage of approximately 45 meters (on the 2.4 GHz frequency) or 20 meters (on the 5 GHz frequency).
As it is easy to guess, the fastest protocols (Wi-Fi 5 and Wi-Fi 6) are also those that have greater difficulty in getting through the home, since they use a frequency that is not very penetrating (5 GHz) and use channels with a width of the high band (60 MHz). In contrast, Wi-Fi 4 has excellent coverage on the 2.4 GHz frequency but it is more sensitive to interference from nearby networks and other electronic devices in our home.
For maximum coverage we will have to take advantage of Wi-Fi 4 in the areas farthest from the modem (to the detriment of the maximum achievable speed), leaving the fastest and most stable protocols (Wi-Fi 5 and Wi-Fi 6) for devices close to the modem (maximum 2 rooms).
Calculation of Wi-Fi signal attenuation
The values shown in the previous chapter do not take into consideration the attenuation of the signal which can generate a single wall, a brick wall, a reinforced concrete wall, a wooden door, or any obstacle between the modem and the device to be connected. Assuming that the maximum Wi-Fi signal obtainable by the modem is -30 dBm (or close values)let’s see together how much the signal is attenuated for each type of obstacle placed on the coverage area:
- Electric wires: -1,9 dBm
- Drywall: -2,43 dBm
- Wood’s door: -5,05 dBm
- Wall of bricks: -14,66 dBm
- Malta: -16,22 dBm
- Concrete wall or columns: -19,41 dBm
Doing two quick maths (additions) it is easy to verify that, with a simple brick wall and a wooden door, the -30 dBm signal (excellent signal) drops down to -49.71 dBm which corresponds to a coverage of 3 out of 4 notches on the device (good signal).
Each door or each wall we add increases the negative value of the coverage field, up to -90 dBm (signal loss due to a too weak network). This negative value is easier to achieve with 5 GHz networks.
Calculation of the real coverage of the Wi-Fi modem/router
But if we wanted to buy a Wi-Fi modem with excellent network coverage, which parameters should we look at? Unfortunately most of the parameters that allow obtaining the real coverage of the modem they are not shown by the manufacturers or are only available after careful Google searches.
To calculate the real coverage of the Wi-Fi modem/router we will have to derive the following parameters:
- The transmission power of the modem/router (expressed in dBm)
- Gain of the antenna or external or internal antennas (expressed in dBm)
Adding these values by 4000 square feet and dividing the obtained value by 42.7 we will obtain the maximum coverage of our modem (in feet, which we can convert to meters easily).
As a practical example, we can derive the transmission power of Fritz! Box modems from the dedicated page: it is equal to 23 dBm; together with it we can use it as a reference value for the antenna gain of 20 dBm (realistic value of all internal antennas). So let’s do two quick calculations:
23 dBm + 20 dBm + 4000 / 42,7 = 136,67 piedi -> 41,65 metri
Therefore, using a FRITZ! Box modem we will have maximum coverage of about 41.65 meters, a value very similar to that expected by the Wi-Fi protocols in the best-operating conditions! Obviously, the values will decrease if lower transmission powers or Wi-Fi antennas with lower gain are used; consequently, the coverage will increase on modems with external Wi-Fi antennas (although not by much, since the estimated gain is 23 dBm) and with transmission powers close to the legal limits (30 dBm).
In this guide, we have shown you what really affects the coverage of the Wi-Fi modem, which types of Wi-Fi protocols should be used to obtain real extended coverage and how to actually calculate the coverage of a Wi-Fi modem (always if we can find somewhere the real value on the transmission power and on the gain of the wireless antenna).
If a single modem is not sufficient to cover the whole house, we advise you to use the Wi-Fi Mesh to effectively extend network coverage or, alternatively, the Powerline Wi-Fi.
To learn more we can also read our guides to the best router for fiber and you have the best Wi-Fi 6 routers (IEEE 802.11ax).