https://en.wikipedia.org/wiki/Wireless_repeater
Wireless repeater
A wireless repeater (also called wireless range extender) takes an existing signal from a wireless router or wireless access point and rebroadcasts it to create a second network. When two or more hosts have to be connected with one another over the IEEE 802.11 protocol and the distance is too long for a direct connection to be established, a wireless repeater is used to bridge the gap. It can be a specialized stand alone computer networking device. Also, some Wireless network interface controllers (WNIC)s optionally support operating in such a mode. Those outside of the primary network will be able to connect through the new "repeated" network. However, as far as the original router or access point is concerned, only the repeater MAC is connected, making it necessary to enable safety features on the wireless repeater. Wireless repeaters are commonly used to improve signal range and strength within homes and small offices.
Uses
- When there is no wireless hotspot in an area
- In an area with much interference.
- Interference can be caused by many environmental factors such as microwaves (such as from a microwave oven), metal appliances or metallic coating or an impeded line of sight.
- When the distance between the computer and the wireless access point or wireless router is too great for the internal wireless network interface card to receive the wireless signal.
- When networking in an environment with interference and multiple computers, networks or hubs
Drawbacks
Since only one wireless device can transmit at once, wireless transmissions are doubled (router to repeater and then repeater to client versus just router to client), and so:
- Wireless throughput is reduced by at least 50%.
- Wireless interference (e.g., with other networks on the same channel) is at least doubled.
- Potentially opens another security attack vector. Older devices don't always support WPA2-PSK so while the original network might be secure, the secondary one is potentially open.
Alternatives
Most wireless repeaters (or range extenders) are purpose built, but certain wireless routers can be flashed with custom firmware such as DD-WRT to give them a 'range extender' option.
A better option for extending wireless coverage is to configure a secondary box as a wireless access point, with a wired connection between a LAN port on this secondary box and a LAN port on the primary box (a router). If Ethernet wiring is not an option, an alternative is powerline networking -- AV500 technology is inexpensive and good.[vague] Wireless extender kits consisting of a powerline adapter module (connected to the wireless router) and a wireless extender module (integrated powerline networking and wireless access point) are available.
