Posted by: Craig Mathias
802.11n, antennas, beamforming, cellular, MIMO, radio technology, wireless LANs, WLANs
I recently wrote about MIMO, discussing why it’s such a significant technology. But there’s another big term with equally far-reaching impacts – beamforming – and it’s time to introduce you to the other major leap forward in wireless. Like MIMO, beamforming has broad application, from wireless LANs to cellular. It’s starting to appear in low-cost 802.11n products that even a small mobile business can afford. And when you see what it can do, it will be hard to imagine that particularly WLAN products without beamforming will remain competitive.
First, the basics. Most radio antennas are omnidirectional in nature, meaning that they send signals in all directions when they transmit, and similarly can receive from any direction as well. This isn’t very efficient, as an omnidirectional antenna wastes energy sending it in a direction where the client isn’t, even though it’s possible for the transmitter and receiver to have a pretty good idea of each other’s whereabouts after just a few moments of communication. It would be nice, then, to focus the energy of the transmitter only in the direction it needs to go. As a bonus, the transmitter can even try a number of signal paths and use the best one at any given moment in time. The propagation of radio waves is statistical and non-linear, and, for that reason, the obvious straight line between the two endpoints might be far from the optimal solution.
So what beamforming does is to use two or more transmitters, each with their own antenna, all sending the same signal (remember, with MIMO, each antenna transmits a different signal) simultaneously. If one times each transmission carefully, the waves from one antenna will reinforce the waves from another. Adjusting this timing can literally steer the resulting radio beam formed by this activity, hence the term beamforming.
Thus beamforming allows two or more omnidirectional antennas to behave directionally. By focusing the energy where its needs to go, we can enhance range, throughput, and reliability. I’ve been testing beamforming systems for some time (see here for a brief article; I’ve got another longer piece coming shortly), and it really works. Again, like MIMO, this is a key technology, and one that’s coming to an access point (and cellular base station) near you.