Market Realities

The market is where theory meets practice and, while MIMO in some form will eventually be part of the 802.11n standard, both types of MIMO are in products shipping today. Current MIMO gear is typically trumpeted as providing greater coverage area and better 802.11g throughput even if only the gateway or wireless adapter has MIMO built in. Reviewers have consistently found this to test true (click here for a review of Linksys' MIMO equipment).

Spatial multiplexing absolutely delivers higher throughput, but both a client computer and a gateway have to have that form of MIMO installed in order to achieve it. Otherwise, a MIMO gateway or adapter uses only a single signal at a time, similar to the Video54 and Atheros approach, which still offers a tremendous performance boost over single or dual antenna devices.

The bottom line for all these MIMO-based products is that they provide more speed raw speed not only when you're close to the MIMO router, but also at the far edges of the coverage area than 802.11g. David Henry, a product manager for WLAN equipment vendor Net gear, said that in a situation where 802.11g might deliver either no signal or a weak signal, their MIMO gateway could be pushing more than 10 Mbps to an adapter.

The overarching goal for MIMO is to have better speeds combined with coverage that spans an average home, allowing a single device to defeat dead spots. As Henry put it, consumers "want better range in their homes and they want higher speeds when they're at remote locations within their homes."

MIMO's current stumbling block is that range and speed comes with a price tag: early multiple-radio gear costs $150 or more for a single gateway in contrast to as little as $50 for an 802.11g Wi-Fi gateway; multiple antenna devices are much cheaper but still at a premium. Companies like Linksys are selling both MIMO and enhanced 802.11g gear side by side, making it an even tougher choice.

The only other option, at this point, is for consumers to use enterprise-class solutions to use standard equipment with expanded range. For instance, they could purchase multiple plain 802.11g gateways and connect them via Ethernet or using Wireless Distribution System. But Airgo's Raleigh contends that it was unlikely consumers could sort those more enterprise-like options out.

"I wouldn't say it's impossible for a consumer," Raleigh said. "The price is the same, but it's a hell of a lot harder to figure out."

Raleigh said their research and focus groups show that when people are presented with the total cost of ownership for a Wi-Fi-equipped laptop and their monthly DSL or cable modem bill, the extra $75 to $100 for a MIMO gateway suddenly seems much smaller.

The Road Ahead

So, for now, if you want greater speed and range, you are most likely to use non-standard equipment. It might be backward compatible with 802.11g, but is it forward compatible with 802.11n, when it is finally adopted?

The short answer: probably not. Because 802.11n incorporates a host of changes of which MIMO is just one, it's virtually impossible that any WLAN device sold today is future-proofed. Furthermore, it is unlikely that future firmware upgrades will make current equipment compatible with the eventual 802.11n standard.

This is one reason why some were rankled by Belkin's decision to call its Airgo-derived equipment "Pre-N." Some felt that the name implied an upgrade path.

Speaking about Airgo's chips, its CEO Raleigh said, "We're trying as best we can to make them firmware upgradeable. We're not promising that. It would not be fair at all to promise that." The best Airgo might be able to promise is backwards compatibility among its own gear, but not among generic 802.11n devices.

"Everybody is going to be forced to say it's upgradeable when you don't really know whether it is or not," Raleigh said. He said he wouldn't put his money on upgradeability until Task Group N nears a final draft of the spec, which is likely to be more than a year away.

Atheros CEO Craig Barratt put it more bluntly: "Because the MIMO modes are guaranteed not to be forward compatible, all of that equipment will have to be replaced."

Hooman Honary, a senior manager at Broadcom, said equally frankly, "Anything that goes out today is highly unlikely to be upgradeable." Neither Atheros nor Broadcom has a MIMO offering nor has disclosed their near-term plans.

Fundamentally, all current MIMO equipment can continue to deliver its improved throughput for 802.11g and its better range regardless of what ships in the future. But it's likely that equipment prices will rapidly drop while speeds and forward compatibility improve.

Atheros' Barratt said, "A number of the equipment companies in the space, they're prepared to introduce potentially multiple generations of incompatible MIMO products as they step towards the final N solution."

And that's the crux of the current situation: MIMO already delivers what it promises. But how will consumers react to devices that are superceded again and again on the road to N? Will consumers feel abandoned as MIMO moves from 100 Mbps to 200 Mbps to 600 Mbps with scattered, backwards but not forwards compatible detritus left behind? Only the unseen hand of the market knows.