Access points and Wi-Fi routers play a dominate role for providing radio frequency (RF) coverage in wireless LAN deployments. In some situations, however, there may be coverage holes where users need access to the network. A wireless repeater may be a solution for extending the range of an existing access point (or Wi-Fi router) without adding more access points and corresponding cables.
A repeater simply regenerates radio signals in order to extend the range of a wireless LAN. The repeater doesn’t physically connect by wire to any part of the network. Instead, a repeater receives radio signals (802.11 frames) from an access point, wireless client device, or another repeater and retransmits the frames without changing the frame contents. This makes it possible for a repeater located between an access point and distant user to act as a relay point for frames traveling back and forth between the user and the access point.
As a result, wireless repeaters are an effective solution to overcome signal impairments such as RF attenuation. For example, repeaters provide connectivity to remote areas that would not typically have wireless network access. You may have one Wi-Fi router in a home or small office that doesn’t quite cover the entire area where users need connectivity, such as a basement or patio. The placement of a repeater somewhere between the covered and uncovered areas, however, will provide connectivity throughout the entire space. The wireless repeater fills in the coverage holes.
It’s very difficult to find wireless LAN devices sold with a repeater as its sole function. Linksys, though, currently has what they refer to as the Wireless-G Range Expander (WRE54G), which is specifically a repeater. Some wireless access points and most bridges also have built-in repeater functionality that you can optionally activate. For example, D-Link sells a wireless access point (WG602) that can be configured as a repeater, but it can also be used as an access point or bridge.
A problem with most repeaters (or access points that can be configured as repeaters) is that they aren’t supported across all wireless LAN vendors. The 802.11 standard wasn’t written with repeaters in mind. As a result, the best approach is to implement a repeater using the same vendor as your existing access points.
As with any equipment, be sure to follow the manufacturer’s installation instructions when setting up a repeater. In addition, consider the following are tips:
Initially setup the repeater at a location where there is very good known signal coverage. This keeps problems to a minimum when getting the repeater working for the first time.
Update firmware. Definitely do this before getting too far with the installation to ensure that the repeater has the latest firmware version. There’s no reason to wage battles with bugs that have already been fixed.
Configure IP addresses. Be certain that the IP address of the repeater is unique and falls within the range of IP addresses that your wireless network recognizes. In most cases, the default IP address will work, but check your existing access point to make sure. Also, set the subnet mask on the repeater to match the one that the network is set to. You may also have to configure the repeater’s gateway IP address to match the static IP address configured on the existing access point.
Configure the SSID. Set the SSID on the repeater to match the exact SSID of your existing network. If this is not done, the repeater will not work, unless the repeater has a feature that automatically scans for nearby access points and takes care of the configuration for you.
Configure the RF channel. Set the RF channel on the repeater to match the channel set in your existing access point. Similar to the SSID, the repeater will not work without the RF channel set the same as the access point.
All in all, wireless repeaters are an excellent way to increase the radio range of an existing wireless LAN, especially if it’s not practical to install an additional access point. A downside of using a wireless repeater, however, is that it will reduce throughput capacity of the wireless LAN by roughly fifty percent. A repeater must receive and retransmit each frame on the same RF channel, which effectively doubles the number of frames that are sent over the wireless LAN. This problem compounds when using multiple repeaters because each repeater will duplicate the number of frames sent. Thus, be sure to plan the use of repeaters sparingly.