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| Blackfen School for Girls Chooses Meru’s Wireless Technology Blackfen School for Girls, in Sidcup, Kent, is a fast-expanding school with more than 1200 pupils, including a thriving mixed sixth form. It has more than 200 full time staff. All those staff and pupils can open a laptop and get on the Internet immediately, anywhere on the campus, thanks to a Meru wireless LAN, which has exceeded the expectations of the school's IT manager, Shaun Neighbour: "It's made a big difference - teachers can use online resources in the lessons, without having to cart the kids down to an IT suite." Blackfen has undergone a revolution, taking it beyond the old model of desktop computers in an IT suite, to a new world where technology is universally available, wherever it may be needed. To meet those needs, Neighbour first developed an enviable expertise in planning complex wireless networks - and then found that specialist distributor Siracom offered a radical solution from Meru that sidesteps wireless LAN limitations and makes RF channel planning unnecessary. Demand for technology in schools has increased, as all pupils routinely used computers in most of their subjects. It is no longer possible for every class to troop into a specially-furnished IT suite whenever it needs PCs or the Internet. Blackfen School has steadily invested in laptops for its pupils. The School currently has 140, which are stored in specialised "LapSafes" that can be wheeled into any room to create an on-demand computer lab. Each member of staff also has their own laptop, which they use for jobs such as taking the register. In 2003, Blackfen started using Wi-Fi; in the years since, its network grew and suffered all the problems of traditional wireless LAN technology, including: - interference between access points; - capacity limitations; - complex RF planning; - a need for continuous troubleshooting. "We started with two or three access points that roamed around [with the LapSafes]", says Neighbour. The £40 standalone devices, from D-Link, were taped to the top of the LapSafes, so when they reached the classroom they could be plugged in to provide a connection to the school network. It was a good solution in theory, but in 2003, laptops were slow, and so were access points, which then used the 802.11b standard: "With one 802.11b access point shared by twenty students, it took ten to fifteen minutes for pupils to log in. In a one hour lesson, that is not acceptable." To improve on that, Neighbour gradually expanded the network until fifty access points covered the whole school. But that didn't solve things: the network started to experience "co-channel interference", where signals from neighbouring access points overlap. Wi-Fi has a limited range of radio spectrum. There are thirteen possible Wi-Fi "channels", but they overlap, so access points in neighbouring rooms can't use adjacent channels without causing interference. There are only three channels guaranteed not to overlap, so most large Wi-Fi networks have to be carefully planned to distribute those channels across the floor plan of a building, adjusting the power and range of each access point to avoid interference. "It was quite interesting trying to organise which access point was on which channel - but once it went 3D and we had three-story buildings, channel planning was quite a puzzle", says Neighbour. He worked out the radio plan by hand, using massive colour-coded maps. He found three channels were not enough, so he researched: "I found a nice case study written by a US University that found you can just get away with five." As if that complexity weren't enough, Blackfen had a new building which turned out to have wire mesh in the walls. This played havoc with wireless transmission, so in that building every classroom needed a separate access point. Apart from the effort of design, the wireless network needed constant firefighting. The access points, set up so carefully, would reset themselves to factory settings, and interfere with each other, as well as turning off their encryption making the network insecure. "Resetting access points was a daily task", says Neighbour. "Half the wireless LAN decided to switch off encryption during one holiday." By 2005 a range of solutions were available which automated the interference problem, using a central switch to control and manage the channel plan. Blackfen's wired network used Hewlett-Packard switches, but HP's solution at the time wasn't suitable. A school nearby had invested in a Wi-Fi switch from Cisco, says Neighbour: "It looked like the next step." On paper the Cisco solution looked a good one. It increased coverage, gave more capacity by upgrading to the newer 802.11g standard, and centralised the security, management and channel planning tasks. The school had demonstrations from various Cisco resellers, and the technology seemed to work. The downside was the price. It cost £50, 000 - but what alternative was there? "It looked like a case of trying to find the budget, and justifying it", says Neighbour. At that point, Neighbour made contact with Siracom, a distributor specialising in converged networks. Siracom told him the Meru wireless LAN does away with the channel planning altogether. Instead of struggling to avoid overlaps, Meru's unique architecture puts all the access points on the same channel, and employs patented technology to deliver high performance and quality of service. "It turned everything we previously thought we knew about Wi-Fi on its head", says Neighbour. To convince him, Siracom lent Blackfen a switch and four access points. "We set it up in the difficult building, the one with wire mesh in the walls", he says. "We plugged all four Aps in, but we found we could get away with two for the entire floor." As well as giving good coverage, the LAN did things other networks couldn't, switching connections instantly between access points. "There was no cut off, even when we ran around streaming DVDs from a server", says Neighbour. "It all worked brilliantly." Without the need to plan radio channels, installation was dramatically simplified with the Meru WLAN. Meru access points simply replaced the D-Link devices, and were powered over the Ethernet using power injectors. The laptops can now log in as quickly as desktops connected to Ethernet, says Neighbour. "The laptops have never been used so much - they are a real viable alternative to carting the kids down to an IT suite. Staff know that five minutes after giving the laptops out the pupils are logged in and ready to go. The system has also supported Neighbour by simplifying admin. It has allowed him to set up separate wireless LANs on the same access point network, each with a different identifier (SSID) so staff and pupils can have their traffic kept separated, and voice devices and printers have networks tailored for their own characteristics. Overall, the Meru solution is more cost-effective than the Cisco alternative, so the school has been able to go ahead with 50 access points, and increase its coverage to provide a wireless LAN for the primary school that shares its site - with a separate SSID, of course. Unlike the Cisco offering, the Meru network also included a second back-up wireless switch for redundancy. write your comments about the article :: © 2008 Networking News :: home page |