How can I set up access points that will communicate with each other and share an Internet connection? One access point will serve as the central node while the other will be the recipient with four computers stationed 400 meters apart.
This could be accomplished by using AP#1 in repeater mode, or by creating a wireless bridge connection between AP#1 and AP#2.
An AP operating in repeater mode cuts spectral efficiency in half by retransmitting everything that it hears. In your case, AP#1 would be set to repeater mode, and AP#2 would be set to root mode - the default mode for most APs. Whenever a client transmits a packet, AP#1 will receive and retransmit that packet on the same channel so that AP#2 can hear it. Whenever AP#2 transmits a packet, AP#1 will receive and retransmit that packet on the same channel so that the clients can hear it. This set-up is easy to accomplish but it will also perform poorly unless traffic is relatively light.
An AP operating in bridge mode also retransmits traffic, but it does so over a dedicated wireless distribution system (WDS) connection. This configuration is common in business WLANs that use dual-radio APs. In that case, one AP#1 radio would operate in root mode, interacting with clients, using 802.11b/g. The second AP#1 radio would operate in bridge mode, relaying traffic to AP#2, preferably over 802.11a. This solution is clearly more efficient, but dual-radio APs are also more expensive.
Alternatively, some consumer APs support "WDS-AP" mode -- that is, a combination of root mode and bridge mode, using a single radio.
Finally, a word about the 400 meters between AP#1 and AP#2: you're not likely to cover that distance without adding high-gain antennas.To learn more about high-gain antennas, read this expert response from Lisa Phifer.
This was first published in November 2007