Advantages of using WiFi Access Points for making security cameras wireless
Using a WiFi based IP cameras and access points has several advantages over analog transmitters:

Better signal penetration
WiFi signals just like your home router have better penetration through obstructions without loss of video signal. That's why you can have your router on the ground floor and still watch Youtube on the second floor. Of course, the stronger the transmitter inside the router or AP, the farther it can transmit the signal. Since video sent over WiFi is a data signal, as long as there is signal penetration you will see a clear picture without interference lines.