Coupled with the availability of sub-US$100 router/access- point/firewall appliances, wireless networking became a simple reality in many homes and offices, where multiple computers and simultaneous computer users became the rule, not the exception. After 802.11b came 802.11a, which was five times faster, and then the now nearly universal 802.11g.

For the immediate future, a new refinement of that wireless technology promises to resolve many of the original concerns and offers even greater throughput and reliability. Called MIMO, short for multiple-input, multiple-output, it involves the use of two or more antennas on both transmitters and receivers.

MIMO magic

The magic of MIMO lies in its ability to take multipath reception, which used to be an unavoidable byproduct of radio communications, and convert it into a distinct advantage that actually multiplies transmission speed and improves throughput.

First, let's look at multipath radio reception. Say you're in a car in downtown Manhattan listening to the radio. You know that your car's antenna is receiving the direct signal from the station's transmitter. But your radio is also receiving additional signals of that same broadcast from many different directions, because buildings, wires, geographical features and other structures in the area between the sender and the receiver can reflect or refract those signals. The end result is that each of these additional signals arrives at your car radio via a different path (hence the term multipath) and also at a slightly different time, so that it's out of phase with the original and will randomly boost or cancel out parts of the signal.