Wireless LANs soon will start doubling or more in throughput and range if a smart antenna technology dubbed MIMO pans out as its backers anticipate.

Multiple-input-multiple-output, or MIMO (pronounced "my-moh" or "mee-moh"), has made its way into chipsets and could be in WLAN devices by year-end.

"Everybody is working on this," says Craig Mathias, principal with wireless consultancy Farpoint Group. "It's the most important radio technology for the next few years."

MIMO algorithms in a radio chipset send information out over two or more antennas. The radio signals reflect off objects, creating multiple paths that in conventional radios cause interference and fading. But MIMO uses these paths to carry more information, which is recombined on the receiving side by the MIMO algorithms.

Many WLAN vendors expect that some form of MIMO will be the basis of work just starting in the IEEE 802.11n Task Group, which is creating a specification for WLANs having at least 100M bit/sec throughput. The 3rd Generation Partnership Project, a collaboration of telecom standards groups, also is evaluating MIMO techniques for use in cellular networks.

Part of the enthusiasm for MIMO is based on the conviction that it can dramatically boost performance and range, and still handle existing 802.11a/b/g radios, with only a slight initial increase in price over those products.

The Holy Grail in radio technology is increased spectral efficiency, or how many bits per second per hertz pass through the air, Mathias says. MIMO doubles the spectral efficiency compared with that of current WLANs. The maximum data rate for 802.11g and 802.11a networks is 54M bit/sec, though actual throughput is closer to 20M to 30M bit/sec. Current MIMO techniques can boost raw WLAN throughput to 108M bit/sec, supporters say.

So far, the only company with MIMO chipsets is Airgo Networks. Former Stanford University researchers Greg Raleigh and V.K. Jones, who hammered out some mathematical proofs for MIMO and multipath, founded this Palo Alto radio chip designer.

One leading WLAN vendor has tested Airgo products for six months and has decided to use MIMO in products due out by year-end. "Our engineers found a 200% to 400% increase compared to the performance of other [802.11] products," says a vice president with this vendor who requested anonymity. "They found a 150% to 300% increase in range."