A low power single frequency system can be used to create a wireless LAN connection with 10Mbps of bandwidth, but with a range limited to around 30m (100 feet) due to the low transmitter power. This range is severely reduced by obstructions, so it is best suited for an open area. Devices for this are often preconfigured, so they are easy to install. The systems have problems with EMI, due to many EMI sources producing low-frequency noise, and they are also susceptible to eavesdropping.
info from http://tutorials.findtutorials.com/read/category/recent/id/394 and http://ctdp.tripod.com/independent/networking/cert/netwireless.html