Wi-Fi range extenders are the wireless equivalent of repeaters in cabled systems. They are sometimes called “wireless repeaters.” Their task is to re-transmit a signal so it can travel further from its source. Range extenders are also known as wireless range expanders and wireless relay stations.
It is tempting to see a range extender as a second Wi-Fi router. They look similar and they both transmit a radio signal to carry data. However, they are very different inside. The range extender has none of the computing power of a Wi-Fi router. Its sole task it to repeat incoming signals. A router has to distribute temporary IP addresses, convert between MAC addresses and IP addresses (two different addressing systems for networks and the Internet) and forward data to anywhere in the world by maintaining a connection to the Internet. The range extender just parrots anything it hears.
Most Wi-Fi routers are “omni-directional,” which means they transmit in all directions, like a sphere of signals. A range extender does not extend the diameter of a router's footprint. It has its own circular footprint, which must overlap that of the router. This extends the footprint of the router in one direction. To extend the range in all directions, a series of range extenders would need to be placed north, south, east, west and above the router.
The range extender has to be within range of the router. The router's messages have to reach the relay and the relay's footprint has to reach the router. This means the extender should be placed just within the signal footprint of the router. A wireless device thus may be out of range of the router, but still be able communicate with it if it is in range of the wireless range extender.
Range extenders are not the best solution to expand router coverage. A range extender indiscriminately retransmits everything it receives, which means network traffic doubles within its signal footprint. Increased traffic causes congestion and slows down the network. A signal booster for the router would produce better results, because it does not require the signal to be repeated and it operates in all directions. Most household users have their wireless router by an external wall, which ends up putting half of their network beyond the outside wall. Simply moving the router to the middle of the building would double their wireless reach within the home, effectively matching the distances a range extender can achieve without increasing network traffic.