Auckland wireless net lures Asians

A firm planning a large wireless network around downtown Auckland is already claiming interest from Asia and the Pacific islands in its distance-boosting technology.

RoamAD, which plans to roll out a ubiquitous, multipoint-to-multipoint network in Auckland's CBD and inner suburbs by Christmas, has attracted inquiries from as far away as Cambodia, Fiji and Pakistan, according to chief executive Paul Stoddart.

RoamAD's proprietary solution allows wireless local area networks based on 802.11b, also known as Wi-Fi, to be extended to create networks up to 150 square km, rather than the traditional several hundred metres. The network, of which a three square km demonstration version is up and running in downtown Auckland, is based on a star grid topography. In a departure from the traditional "network hotspot" model, it isn't reliant on an incumbent carrier providing a terrestrial circuit to which the wireless operator connects the hotspot.

"The thing about our network is that you don't have to rely on established infrastructure," says Stoddart.

RoamAD's network design breaks the boundaries of traditional Wi-Fi LANs by means of its radiofrequency engineering, Stoddart says.

"The engineers designed it so that there are four to eight points of presence in each of the eight 45-degree sectors of the network and the sectors are overlapping, providing ubiquitous coverage."

He claims building a RoamAD network from scratch will cost $3.5 million at the most and operating costs will be low compared to those of larger mobile networks.

The novelness and potential cheapness of the approach has attracted media attention in the US and UK.

Stoddart doesn't see the RoamAD model as a competitor to the likes of Telecom's CDMA1X service, Mobile Jet-Stream or GPRS-based cellular services.

"We're looking to cover metropolitan areas, not the countryside."

Network access cards that can seamlessly switch a laptop from CDMA or GPRS to Wi-Fi are another essential factor in the RoamAD model, with users able to switch to the RoamAD network when they get to a city's CBD.

Wi-Fi access points advertise signals in 11 different channels within the 2.4GHz range and Stoddart says the network access cards in users' laptops "are always looking for the next best advertised signal, because the sectors overlap".

The RoamAD model is multipoint to multipoint, not point to multipoint or point to point, as are most other Wi-Fi installations. Stoddart claims the hand-over from one access point to the other is achieved in three milliseconds, compared with 240ms for transfers from one GPRS cell to another. There is no boosting of the signal by directional antennas, as happens when point to point Wi-Fi connections are stretched over several kilometres, he says.

Wi-Fi is notorious for interference problems and Stoddart says RoamAD's engineers have addressed the issue by way of SMT (site management tool), proprietary software developed in-house and present at every point of presence on the network.

"If someone erects a spurious signal, there's 100MHz and 11 channels, and if the signal my card is associated with is disturbed it will be seamlessly handed over to a different access point in a different channel."

He says the network has been engineered "in anticipation of a rising noise floor", meaning it can cope with increasing levels of interference.

SMT also handles quality of service by controlling packet re-tries, a common source of congestion in wireless networks, and the network's security.

Around 50 organisations, mainly existing and potential stakeholders in RoamAD's parent company, Auckland-based Nomad Communications, are using the trial network, Stoddart says.

RoamAD networks will have a speed limit of 330kbit/s, a far cry from the 11Mbit/s theoretical and approximately 6Mbit/s practical limits of conventional Wi-Fi local area networks and even Telecom's more limited terrestrial JetStream, but faster than Telecom's Mobile JetStream and Vodafone's GPRS.

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