The fact is that i-Burst base-stations — equipped with smart antennas and colocated with the base stations of a 2G network — can provide a throughput of one megabit (1m bits) per second, at about one-thirtieth of the cost of building a 3G network for the same area. Thus, i-Burst plugs the gap between 3G networks (long-range, but capable of 384 kilobits per second) and the popular WI-FI wireless-network standard used to connect laptops to the Internet (short-range, and capable of 11 megabits per second). At the moment, the i-Burst receiver is a brick-like object about the size of a video cassette that fits on to the lid of a laptop, and draws about as much power as a WI-FIPC-card. But ArrayComm's licensees, including Kyocera, a Japanese electronics conglomerate, expect to be able to produce i-Burst receivers as PC-cards.
ArrayComm is pushing i-Burst in three separate ways. The company has bought spectrum in Australia and plans to launch a commercial service there in 2003. Hanaro Telecom of South Korea plans to launch i-Burst as a wireless broadband service this summer. ArrayComm is also trying to persuade firms that operate cellular-network towers on behalf of wireless operators to install i-Burst equipment. In short, Dr Cooper hopes that i-Burst will cut two technological Gordian knots at the same time, providing fast mobile-data access, and also a wireless solution to the "last mile" problem of providing high-speed broadband access to the home.
A Relay Race
Proponents of mesh networks also believe that they have found a way around the last-mile problem. At the moment, there are two main ways to provide broadband connections to the home: use either the local cable-TV network or a digital subscriber-line (DSL) from the local telephone company. DSL supercharges ordinary phone lines to enable them to carry data at high speed.
But not every neighbourhood has cable access, and DSL works only for subscribers close to a telephone exchange. Worse, the roll-out of broadband has been held back by obstructive telecoms incumbents, regulatory obstacles and infighting. No wonder the idea of a fixed wireless broadband service, blanketing a neighbourhood with connectivity without the need to lay any cables, seems so seductive.
The mesh-networking approach, which is being pursued by several firms, does this in a particularly clever way. First, the neighbourhood is "seeded" by the installation of a "neighbourhood access point" (NAP) — a radio base-station connected to the Internet via a high-speed connection. Homes and offices within range of this NAP install antennas of their own, enabling them to access the Internet at high speed.
Then comes the clever part. Each of those homes and offices can also act as a relay for other homes and offices beyond the range of the original NAP. As the mesh grows, each node communicates only with its neighbours, which pass Internet traffic back and forth from the NAP. It is thus possible to cover a large area quickly and cheaply. For providing fixed-wireless access, the mesh approach is technically superior to the traditional "point-to-multipoint" radio approach in a number of ways. For one thing, it requires much less power. Rather than using high power to get around obstacles, mesh networks offer multiple paths from one node to another; with systems typically being self-configuring so that, like the Internet, traffic is sent by the quickest route. Also like the Internet, mesh networks are robust and can be scaled up easily.
Another drawback of point-to-multipoint systems, observes Dave Beyer of Nokia's wireless-routers division, is their need for tall antennas to get above the clutter and maximise their coverage. Unfortunately, they then run into the problem of interference with adjacent cells. Mesh networks, in contrast, can use rooftop antennas, since each node needs only to be able to communicate with its neighbours. Such systems use one-ten-thousandth of the transmission power. That, in turn, means they can use unlicensed spectrum.
A number of firms are now pushing mesh-network technology as the fastest and easiest way to provide broadband Internet access. Following a successful trial in Santa Rosa, California, Nokia's system, called RoofTop, is being rolled out by more than 50 operators, mainly small Internet service-providers (ISPs). The ISP installs an AirHead unit (Nokia's name for a NAP) to seed a neighbourhood, and a small, weatherproof pod with an omni-directional antenna is fixed to the outside of each subscriber's home or office. Each pod costs around $800 — less if produced in large quantities. Vista Broadband, which offers a broadband service using RoofTop technology in Santa Rosa, charges around $200 for installation, and then a monthly fee of $50.
SkyPilot, a mesh-networks start-up based in Menlo Park, California, is taking a similar approach. Its rooftop units use smart antennas to beam data back and forth, enabling frequencies to be reused more efficiently and increasing capacity. Duncan Davidson, the firm's boss, says the Internet/mesh approach has many advantages over the traditional circuit-based approach used in telephony. "The Internet architecture gets better with density [whereas] the phone system gets worse," he says.
The problem with the mesh approach, however, is how to get it off the ground. Who will build the NAPs to seed a neighbourhood? Unlike Nokia, which simply sells its RoofTop gear to ISPs, SkyPilot plans to help prime the pump itself, by setting up NAPs and allowing ISPs to resell access. This approach also has technical merit: multiple overlapping mesh networks are far less efficient than a network in which all the nodes can talk to each other. So it makes sense to have competition at the ISP level, rather than the infrastructure level.
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