You would be looking at signal strength, noise and nearby networks. If there a lot of networks and they are using the same channel (or something close to yours) it would be best to change the channel on your router (refer to manual if unsure).
Make sure router is up to date. Distance between ATV and router is a factor as is the age of your router, placement of ATV and other WiFi devices or appliances in the area that use that same frequency.