What are the main sources of WIFI network interference?

There are 4 sources of interference:

1. Physical obstacles: brick walls, concrete etc …

Router models with the 2.4GHz frequency band pass through the materials more easily, so they offer greater coverage. However, they are more susceptible to interference.
The 5GHz frequency router is less sensitive to interference and is 2 times faster than the 2.4GHz band. On the other hand, it covers less distance.
A router that uses both bands dynamically provides better performance.

2. Sharing of airtime:

The more devices that request your WIFI network such as tablets, games console, smartphones, the more there will be a possible slowdown in performance on your devices remotely. Some routers send the WIFI signal to the devices one at a time (sharing).
In order to increase the bit rate and reduce the latency in an environment where there are different users connected simultaneously, a router with several antennas will be able to give good results because each antenna is able to manage the WIFI connection simultaneously.

3. Neighboring networks:

Have you ever noticed a slowdown in the performance of your WIFI network at certain times of the day (rush hour)? The more people on neighboring WIFI networks, the more likely there will be congestion. Several routers may end up on the same frequency channels.
Suggestion: Change the channel of your router (these frequency bands are open)
Routers that have a 2.4Ghz band offer a selection of 11 channels.
Routers that have a 5Ghz band offer a selection of 25 channels.

4. Domestic appliances: 

Microwave oven, electric garage doors, elevator motors, etc.
Observation:
Routers that have a 2.4Ghz band are susceptible to interference from the home appliances described above because they use substantially the same frequencies.
Routers that have a 5Ghz band are much less susceptible to interference because they do not use the same frequencies as your home devices.
The use of the 5Ghz band is recommended if you experience interference problems caused by household devices.

5. The quality of the antennas of your wireless devices : 

We have been able to demonstrate that the quality of the antennas of your wireless devices can play an important role in the quality of the WIFI signal. The relationship between antenna quality and distance can be critical to bandwidth performance.
To convince yourself, do a speed test with 2 different devices. Take a test at 3 meters and another at 10 meters and compare your results. The difference in the performance of your devices will be able to demonstrate the quality of the antenna compared to the two WIFI devices.