They start with the WiFi to TV distance at 20 or less feet. What else you have may be of higher WiFi performance than the TV. Usually folk rearrange the devices or get a wired connection.
I have a Samsung 8300 TV that is a few months old. Recently, it cannot stay connected to the internet (Wireless.) To reconnect I must reset the Smart Hub which is obviously a time consuming process. This is happening way too frequently. Sometimes the TV goes off line in a few minutes. Sometimes 24 hours. I have multiple wireless devices on this network and they all work fine.
Why is this happening???

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic