LMDS gets mesh: New architecture concept could prove more efficient

After a long stretch of technology emerging only in the point-to-multipoint arena, the local multipoint distribution service sector is beginning to spur new innovation. Radiant Networks plc, a start-up from the U.K., is one of those innovators. Radiant has developed LMDS equipment based on a mesh architecture, which involves installing a node at each customer site that can receive and transmit information.

"Now, when we install a node, the problem isn't whether you can see the base station but whether you can see another customer node," said Nadeem Siddiqui, commercial director for Radiant. "The probability of seeing another node is high."

Such an architecture could solve some coverage problems that current point-to-multipoint networks have. Once operators install point-to-multipoint base stations in a city, they can hope to establish line of sight w ith about 40% of potential customers, Siddiqui said. To improve that penetration to 60%, operators must use overlapping cells, which reduces spectral efficiency.

"Because base station sectors flood a region with radiation ... you transmit to places [where] you don't actually have customers," Siddiqui said. Radiant's mesh network transmits RF signals only where they are needed, which leads to a 50-fold capacity advantage over traditional point-to-multipoint systems, he said.

With Radiant's mesh architecture, when an operator achieves 1% penetration in an area, new customers have a 95% chance of being in the line of sight of another customer already being served, he said.

Each Radiant node can link to four other nodes. But "the amount of nodes doesn't drive the mathematics," Siddiqui said. "How we connect the nodes together is important."

If an operator has 10 nodes in a city, there may be thousands of ways to connect them. "We use algorithms to determine which is the best topology for the mesh," Siddiqui said.

The system automatically can change the configuration when service providers add new customers. Operators can reconfigure daily, which Radiant recommends they do overnight.

To date, most point-to-multipoint operators have targeted downtown business districts because they have a better chance of recouping their investment where a concentration of customers is seeking high-bandwidth connectivity. Although Radiant's mesh architecture is suitable for deployment in those downtown business districts, its backers hope that it will help open new markets for LMDS operators.

"We see Radiant coming into its own ... with small and medium-sized businesses and residential areas where coverage restraints become important," said John Lewis, an associate at ARC Associates, which invests in Radiant.

During the next couple of years, major cities will begin to become saturated with high-bandwidth local loop alternatives, including fiber and LMDS, Lewis said.

But by the time Radiant's product is commercially available - a year or so from now, said Siddiqui - residential demand will have increased.

Technologies such as DSL and cable modems may begin to struggle with providing super high bandwidth and coverage in those areas, Lewis said. Radiant believes that its product is more efficient than other options and will allow operators to offer more customers higher bandwidth services.

Operators also may be interested in using Radiant's system to fill in holes in downtown business districts that they currently cover using point-to-multipoint technology.

Radiant currently is demonstrating its mesh network in Cambridge, England, and expects its first customers to be in the U.S.