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A massive wireless LAN (WLAN) has gone live in a Swedish port that is acting as stopover for the prestigious around-the-world Volvo Ocean Race.

The WLAN at the Skeppsbron quay in the old town of Stockholm was constructed by DataCom, a Meru Networks distributor in Stockholm. The WLAN covers almost an entire kilometre, and has a capacity of 200Mbit/s.

"It was quite difficult to build," said Datacom CEO Ralf Aspholm. "That said, we are quite familiar with this type of thing, but we have not had to contend with all the problems at the same time."

One of the obstacles was user load, with an estimated 500,000 people expected to attend the event (depending on the weather), and make use of the free (but secure) network, without effecting the performance of the other networks within the WLAN.

"Within this WLAN, we have about 10 or 12 separate WLANs," Aspholm told Techworld. It seems that these additional networks that operate within the Skeppsbron quay WLAN, are set aside for the race teams, media, sponsor tents, and other event-specific ‘hot spots'.

Datacom also had to contend with over 100 wireless networks that already existed within the local vicinity, and the fact that the Skeppsbron quay is crowded with tall, wide buildings, which can have a major impact on radio signals.

Aspholm told Techworld it took Datacom roughly 600 man hours to build the WLAN, and they had very limited time and access to the site to construct it. To ensure reliable coverage, Datacom mounted 22 access points on bridges and other areas, including floating decks that could rise as much as 50cms, depending on the tide. The WLAN also uses a Meru MC3025 controller.

The general public have been given free online access for a couple of hours, and in order to ensure performance, other access points will automatically take over if one access point fails or is swamped.

"The challenge is to provide a predictable and dependable WLAN for the 14 day event," said Bo Ericson, vice president for Meru in Sweden. "Another challenge was to know how many people are coming, but you can never know that."

"Meru and Datacom had to ensure different service levels for different areas of the WLAN and decide which networks were business-critical, where service had to be guarantee," Ericson said. "We can tune areas of the network, and lower the capacity elsewhere," he added.

"In the neighbourhood, there were also more than one hundred WLANS, and we had to ensure we did not disturb anyone else," he said. "Another challenge came from the fact that Skeppsbron is a port, and a large ship coming in can change the radio environment."

Ericson said that the WLAN has a sub 3 millisecond handover to a new access point. "The client only sees one channel, and the controller and access point makes the decision to move the users to a new access point," he said. "The roaming option in the client device (i.e. mobile phone or laptop) doesn't start, because it doesn't need to. We handle the channels in a different way. It is not the cell phone or laptop deciding on the roaming, the infrastructure does it for them."

"Bandwidth is a limited resource, and radio is a shared infrastructure, but we take away a lot of collisions in the area," he said, likening it to an air traffic control system.

The WLAN used a firewall from Clavister to ensure people didn't use the WLAN to "step into wrong websites, and to keep it all 'safe and sane'".

The race runs from 14th to 25th June.

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