Intelligence at the Edge #15


Rooftop’s wireless self-configuring technology bypasses local telcos.

David's smiling face

By David S. Isenberg                                                          amnetlogo

From America's Network, October 1, 1999

Nokia’s early September move to acquire Rooftop Communications may prove brilliant — if Nokia can manage radically disruptive technology. Regardless, Rooftop has convincingly demonstrated that the role of communications service provider is waning, and that self-configuring, self-service networks are close at hand.

Rooftop has produced a spread-spectrum radio plus packet router cleverly described by its trademark, "Unplug and Play." This device gives Internet service providers (ISPs) a link to customers that is not mediated by any infrastructure provider. In principle, the DSL-speed network formed by multiple devices could even run without an ISP, or with multiple ISPs — indeed, multiple ISPs would make such a network more robust.

Network architecture emerges as a multihop, multipoint network. Lauren Hipp, Rooftop’s EVP of marketing, calls it a "peer-to-peer distributed networking scheme, a routed mesh." Each device is both a customer’s access device and a network infrastructure node. Adjacent customers (up to a couple of miles apart) form a skein that is a natural extension of the Internet.

Take it home, Plug it in, Log on

In theory, customers will be able to buy a device, take it home, plug it in, and log onto the Internet. In practice, today’s installation issues include geography, roof rights, and how good a customer is with ladder, drill and screwdriver.

Each customer node needs a line of sight to at least one other node, and preferably to more than one. Unlike LMDS, a line of sight directly to a point of presence is not necessary — this is a benefit of multihop architecture. Even so, there are antenna placement issues; in the best case, the antenna can be placed in a window from which it can ‘see’ another node — but, more typically, rooftop is the name of the game. For longer distance hops, a directional antenna can be used.

While suburbs with one-story houses and many tall trees might never support a Rooftop network, Phoenix and Los Angeles are ideal environments. The San Francisco Bay Area already supports several beta nets. The world’s developing nations often provide ideal environments — there are pilot networks in Morocco and Guinea. "It is critical technology where there is no existing infrastructure," Hipp says.

                                                Adding customers improves network
                                                 throughput and robustness; a dense
                                                 net has many routes to the ISP’s

Adding customers improves throughput and robustness; a dense net has many alternate routes from a customer’s premises to the ISP’s ‘airhead.’ But slow acceptance is a palpable risk.

"The technology is promising, and looks scalable," says Bob Lucky, vice president of applied research at Telcordia. "But it could never get started because you need customers to create the mesh. I’d be afraid that one day the critical person between me and my ISP would say, ‘Sorry, I just got DSL, so I’m going off the air.’"

Hipp rebuts this thinking. "We have a lot of demand," she says, "and a jump-start promotion for interested ISPs. We’re aggressive about reaching the consumer marketplace. We have two priorities: cost and performance."

Cost and Performance

Today, Rooftop has two devices priced for small business: a $2,000 unit and a more sophisticated and powerful $5,000 device. Both, says Hipp, are on steep cost-reduction trajectories. They’re being redesigned for better integration. Increasing volume will help, and components are getting cheaper. "Radio technology is jumping onto the digital price curve," she says.

There’s room for improved performance, too. Each hop adds some 50 ms of latency. This limits the practical number of hops to three and it severely limits the quality of Internet telephony. But, Hipp says, "In the future, we think we can support telephony-quality voice. We haven’t tuned IROS [Rooftop’s proprietary Internet Radio Operating System] to optimize latency yet."

John Giannandrea of, a Silicon Valley ISP, is an early adapter of and testbed for Rooftop technology. He says that it gives new meaning to community networking. "The network grows organically," he says. "The ISP can get out of the business of planning network expansion."’s wireless customers include a gourmet restaurant, Global Village Cafe, whose owner (a former techie) wanted little to do with the incumbent telco. Other customers find a Rooftop installation easier than obtaining DSL — and DSL is more readily available in California than anywhere. Another factor is that Rooftop input/output is inherently symmetrical.

Will Rooftop pose an "Innovator’s Dilemma" for Nokia? The "wireless DSL" aspect may be a bit disruptive. But the radical disruption will come as it fulfills its potential to make local telcos obsolete. Will Nokia be able to capitalize on this, or will it "make sense" for it to limit or kill the product because it threatens its current customers, the world’s telcos?

David Isenberg can be reached at

Copyright 1999 Advanstar Communications.