We get asked this a lot and I think there is a lot of confusion between repeating a wireless network and “extending” it.
Netgear had a few products a while back that did the extending trick, but the issue with them is that they create a second SSID for devices to connect to. Devices that can properly repeat networks will maintain the same SSID and devices that do this particularly well will prevent your device from dropping a connection as they move between the repeating points.
The problem with using range extenders – as listed above is that your device will drop connection from the first network, then reconnect to the new SSID – this works OK, until your device realises the other network and then can’t quite figure out whether it should connect to the first SSID or the extended one then drops out.
There are two manufacturers that we have used for doing repeating wireless networks (there are a lot more than two manufacturers that are capable of this though).
The first is Apple – using an Apple Airport Extreme and an Apple Airport Express. The extreme provides the network that the Airport Express can then connect to and repeat. They are relatively simple to set up using the Airport Utility Tool – however, if you don’t have that they can not really be configured. This setup also allows some other nifty features such as Airplay and USB sharing.
The second is TP-Link. If you have any TP-Link Modems or routers you should be able to repeat them with one of these – a TP-Link WR702N – this nifty device can repeat your existing network and once its configure you can just go and plug it in somewhere that has signal and it will repeat happily. Another advantage of this device and the Airport Express is making connection to a wired device without running a cable to it. Both devices have LAN ports for connecting cabled devices, which can be very useful in apartment buildings or sites where you can’t really knock holes in walls.
We’ve found it best practice to have the main router doing DHCP then assigning the wireless repeaters outside of the DHCP range so that everything can continue talking over the network even back through the repeating points. Be aware though that the TP-LINK WR702N should have its firmware updated before you deploy it, as some of the older firmware versions had issues that caused settings to be wiped or reset.