To stop WiFi interference, start by repositioning your wireless router to a central, elevated location, away from walls, mirrors, and metal objects. Use a WiFi interference scanner like NetSpot to identify overlapping networks and choose the least crowded channel. If physical barriers are a problem, consider using Wi-Fi extenders or Powerline adapters to improve coverage in weak areas.

If there is physical interference with your WiFi signal, you can troubleshoot it by performing the following:

1. Estimate the very middle of your wirelessly covered area and put your router in it. See how that affects the signal.
2. Try setting up the router antenna vertically.
3. Put the router on an elevated surface, e.g. a desk.

Dense materials such as concrete, metal, and brick are the strongest blockers of Wi-Fi signals. Mirrors also create high levels of WiFi signal interference by reflecting and scattering radio waves. Positioning your router away from these materials can improve signal strength.