How to: Extend WLAN Range with Repeaters
February 05, 2009
You can extend the range of your access point (or Wi-Fi router) fairly simply by using a repeater. This tutorial offers an explanation of how repeaters work, how to install them, and recommends reliable products.
If youre having problems getting signal coverage out to all users, you can likely solve the problem by extending range with a repeater. Learn tips on how repeaters operate and how to install them.
Access points and Wi-Fi routers play a dominant role in 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 doesnt 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 a distant user to act as a relay point for frames traveling back and forth between the user and the access point.
Its 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 arent supported across all wireless LAN vendors. The 802.11 standard wasnt 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 manufacturers installation instructions when setting up a repeater. In addition, consider the following tips:
- Initially set up 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. Theres 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 repeaters 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 its 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.
- For more on extending range, read "DD-WRT Tutorial 2: Extend Range with WDS," "DD-WRT Tutorial 5: Wireless Repeater," and "Affordable, Powerful Range Extension."
Jim Geier provides independent consulting services and training to companies developing and deploying wireless networks for enterprises and municipalities. He is the author of a dozen books on wireless topics.