Wi-Fi Repeater
The core functionality of the project rests with the ability to reach the Internet. We choose to use Wi-Fi because it provides the fastest wireless connection at the lowest price. A microwave based solution would be the ideal, but this type of equipment is expensive, more complicated to configure, and in many situations more power hungry than Wi-Fi based networking gear. In many less populated areas interference on Wi-Fi frequencies isn’t an issue and off the shelf Wi-Fi equipment is capable of operating up to 5 miles with line of sight.
We utilized two Linksys WRT54G routers running the DD-WRT firmware to achieve Internet connectivity. One router was located on the second floor of an RIT building .33 miles away from the communication node. The router in the office was connected to the Internet and used a 8dBi external omni directional antenna to broadcast the signal. The communication node’s router used a 19dBi parabolic directional antenna pointed at the router in the building. The wireless link passed through a set of trees, but the link still yield a reliable SNR of 20dB. The link stayed stable even during the worst of snow storms and provided speeds of around 5Mpbs.
The DD-WRT firmware provides many features not available with the standard Linksys firmware such as repeater mode. In repeater mode, the router takes a weak signal and then repeats it at a stronger signal. Additionally, version v24 of the DD-WRT firmware added virtual interface support. This means that instead of just repeating the signal, it was now possible to repeat the signal using a different SSID and add encryption. This allowed the project to have its own SSID, Wind Turbine, so those connecting knew that they were using the wind and solar powered communication node. The repeater mode also allowed Ethernet based clients to connect via the four port switch on the rear of the router. This allowed the power meter and VOIP which lack Wi-Fi connections to easily connect to the Internet.