Mesh networks solve distribution dilemmas

Wireless broadband networks could soon deliver digital services to homes and businesses.
The delivery of broadband digital services to the home is a global technology race with huge rewards for the winners. It is therefore not surprising that a company with an innovative wireless solution for the local loop has attracted one of the largest start-up venture-capital investments in Europe.

UK-based Radiant Networks has received $20 million in second-stage funding from a consortium fronted by Advent Venture Partners of the UK and Sandler Capital Management of the US. What these investors want is a slice of the wireless broadband local multipoint distribution service (or LMDS) market, which according to the US-based analysts Strategis Group will be worth $10 billion by 2003 and some $28 billion by 2008.
The profits could be big, but not before several technological hurdles are overcome. Radiant Networks believes it can solve many of the problems facing broadband operators by the use of mesh technology. Instead of a single base station transmitting to a number of local receiver units, mesh technology uses a network of receiver/transmitter local units. These units receive signals from one neighbour and pass them on to the next - forming a network of low-power transmitters that can cover large population centres.

Mesh networks have been tried before with narrowband systems, but what has got the venture capitalists excited is the belief that mesh technology may be the only high-bandwidth alternative to running fibre to every home. Indeed, Radiant believes it can deliver 25 Mbit/s - enough to supply video-on-demand services more economically than any other system.

"If you want to run broadband services such as video over a wireless system then you need to have 1 GHz of bandwidth, and you must be able to move terabits through your backbone infrastructure," explains Radiant founder Tim Jackson. "This means that you have to use technology that is up in the tens of gigahertz. In Europe, the 40 GHz band has been reserved for wireless broadband local loop or LMDS; in other parts of the world the 28 GHz [band] has been allocated. At these frequencies you have to have line of sight between the transmitter and the receiver." This is necessary to avoid diffraction and buildings and other obstructions absorbing the signal.

Jackson claims, "If you do the mathematics for a traditional point-to-multipoint system it works out that for full coverage you would have to cover a country with 50 m towers that are 1 km apart. Apart from the economics and the environmental impact there is also the problem of having to run fibre to each of these base-station towers."

Jackson's team hopes to produce a simple device for about $500 per household. The unit could be installed by a TV repairman and could create meshes covering cities or even countries. Only a fraction of the units must be wired to the broadband fibre network - the mesh handles distribution.

Mesh technology can create multiple paths from the interconnecting stations to an individual site. This not only makes the best use of available bandwidth but also creates resilience, because if one box is not working the system simply routes around it. Radiant believes that mesh technology uses the available bandwidth up to 50 times more efficiently than a traditional multipoint solution.

"You have to seed the network with a few nodes to begin with," says Jackson. "But the important thing is that the capacity of the network scales according to how many customers you have, which reduces the need for initial investment. We believe this will make the system very attractive to new entrants."

Bright sparks Radiant Networks started life four years ago when Jackson was managing director of design consultancy Plextek - Plextek engineers did much of the early work and eventually a separate company was spun off. Radiant now has 70 staff and aims for 100 by the end of this year. Plextek retains a financial interest in the company and still provides some design expertise.

Radiant is based in Cambridge, an ideal location. Jackson was able to exploit the pool of wireless talent in the area, plus the resources of local consultancies. He also needed to bring in fresh expertise in management as his own background was in running a consultancy rather than a product-based company. The post of chief executive officer was filled by Will Gibson, who had previously built and run his own data communications company. Alan Bates from Bell Cable Communications was brought in as non-executive chairman to take advantage of his contacts in the new carrier industry and the venture-capital community. Nadeem Siddiqui, former director and general manager of Ericsson's fixed broadband wireless business, was hired to be commercial director.

Radiant technology will receive its first commercial deployment early next year. The project involves UK-based FirstMark Communications Services, which already has a wireless local-loop licence in Germany, and is now bidding for one in the UK. Initially the individual units will be expensive, so the service will be aimed at small and medium-sized businesses.

Radiant has already passed several important commercial milestones. It has arranged technology trials with US-based Motorola, and signed a distribution agreement with Japan's Mitsubishi. The latter should see the first deployment of the technology in Tokyo by June 2001.

Jackson and his team have spent a year working on computer simulations, and are certain that they have defined all the properties of the mesh. The algorithms that control its exact configuration will be an important part of the system. This is crucial because a network of N nodes can have N! possible configurations - for example, a mere 10 nodes could operate in more than 3 million configurations.

To simplify network operation, the nodes are controlled from a central system rather than having individual "intelligence" and being left to configure themselves. The latter mode might open the door to chaotic effects and other unpredictabilities. A centrally controlled system should be stable, with new nodes being brought in by a reconfiguration signal.

Beyond the technical challenges, Radiant must also be able to deliver systems at the appropriate price point. Unfortunately, the market has historically been populated by high-value, low-volume military microwave trunking systems. In order to sell components for an affordable price, Radiant has developed modems and other systems that can be mass produced.

Although many larger companies are also developing this technology, Radiant can expect to come out of the exercise with a useful portfolio of intellectual property. Jackson says this is an important aspect of any business like Radiant.

Once the system is proven in a commercial deployment, Jackson predicts that Radiant will do business through a variety of models including licensing. He is emphatic that although manufacturing will be outsourced, there will be boxes out there with Radiant labels on them. Telecoms companies will buy components, while other customers will want an entire infrastructure. Either way Jackson will be happy. And if he manages to cover just one country with Radiant units, his venture-capital backers will be very pleased.

Source: WirelessWeb