Birmingham students get Wi-Fi freedom of speech

With one of the largest campuses in the UK, rolling out a quarter-of-a-million-pound wireless network at the University of Birmingham was always going to be a big challenge.

The university's IT department is covering every inch of the 250-hectare campus with a Wi-Fi network — inside buildings and out — to give its 36,000 students and staff access to information wherever they are. The project is due for completion by the end of the year and is set to deliver one of the country's largest wireless networks.

Upgrading the network
The network upgrade was the brainchild of John Turnbull, the university's head of networks, and Chris Lea, a senior network specialist at the institution. Faced with an ageing LAN infrastructure in 2002, Turnbull knew a major upgrade was essential to meet the demands of students used to wireless connectivity.

The existing LAN was not up to scratch, said Turnbull. It was based on four switches from 3Com — a vendor which backed out of the networking market, leaving behind many unhappy customers — arranged in an FDDI ring, trundling along at 100Mbps. Eight fibre links were required between each switch, consuming a hefty portion of the IT budget.

Two related initiatives were required to turn around the ailing network. At the beginning of the project in 2002, Turnbull upgraded the existing switches to allow them to accommodate 10Gbps blades. The increased bandwidth meant only one fibre link was required between each switch, which freed up 35 fibre pairs and 80 GBICs (gigabit interface converters) with a cost saving of £87,000.

The upgrade enabled the second initiative to take place: the now spare fibre could be used to form the backbone of a new network containing the Wi-Fi access points. Rolling out Wi-Fi would offer multiple advantages. Not only would it give students access to their network resources right across the campus, it would provide a backup network if ever the fixed LAN went down.

The fact that the Wi-Fi access points were on a separate network to the wireline LAN would also have a further advantage: raising the level of security. "I wasn't convinced of security at the access point," said Turnbull. "I was concerned about students coming in with laptops [harbouring] viruses and worms. We have a site firewall and building firewalls where there is sensitive data, but we would have been letting them on behind that firewall and the viruses could have spread to the rest of the network."

To mitigate that risk, Turnbull designed the Wi-Fi network to run in parallel with the fixed network, connecting at only two points through a firewall. In that way, if a virus were let loose on the wireless network, it couldn't affect anything on the fixed network. The wireless network could then be disconnected while the situation was resolved.

The division of the fixed and wireless networks also came in useful in another, unexpected way. The IT department was asked to intervene to help a senior visitor to the arts faculty who complained of suffering from electrosensitivity to Wi-Fi. The team was able to cut the Power-over-Ethernet supply to the relevant ports when the visitor arrived and restore it on her departure.

Virtual cells
The chosen topology was not the only clever design technique employed by the university. Turnbull said he chose to base the network on switches and access points from Foundry Networks, a much smaller vendor than market leader Cisco, but one with a considerable customer base in the UK.

One of the features of Foundry's access points is "virtual cell" technology, which helps to eliminate interference between access points. Normally, access points based on the 802.11g standard — which the University of Birmingham is using — are configured to work on one of three non-overlapping channels: 1, 6 and 11. There are two problems with this approach.

One problem is that, if two access points working on the same channel are located near each other, they will cause interference and, therefore, degradation in network performance. For access points working on different channels, there is a delay in handing off clients from one access point to the other while the client reassociates and gains a new IP address.

Virtual-cell technology gets around both of these issues by allowing all the access points to run on one channel; the access points don't interfere with each other because they are managed by a central mobility controller which gives times slots to each access point and client in which they can communicate. Because all the access points work on the same channel, they appear to the client as if they are one large access point, and so the handoff time is minimal.

"With virtual cell, the client just sees one access point," said Lea. "So there is effectively zero handoff between physical access points. For VoIP activity, this is absolutely invaluable."

VoIP is at the centre of the university's plans for the network. Turnbull's vision is that students should be able to make a voice call over the Wi-Fi network from...

...anywhere on campus. So, not only is fast roaming essential but also comprehensive network coverage, to stop calls dropping out.

To survey or not to survey?
Usually, organisations requiring blanket wireless coverage of a particular area would undertake a site survey to find out where the access points need to be located. It is all too easy to guess where to put access points and then discover the black spots when it's too late.

But the university declined to use site surveys beyond some initial in-building work and is instead relying on a more iterative approach for its outdoor coverage. "Traditionally, site surveying has been time-consuming," said Turnbull. "The traditional set-up is to survey so there's no interference."

Turnbull claimed that, between himself and Lea, they had a good feel for where the access points needed to be located.

The virtual-cell feature wasn't the only reason the university chose Foundry's technology; it calculated that the equipment outperformed that of Cisco.

"We wrote a tender, and Cisco, Foundry, Extreme, Nortel and a few others came back," said Turnbull. "We asked for a sample of equipment, which we rigorously tested in our lab. We blasted the network and found that Foundry network equipment, in terms of performance, outstripped Cisco and Extreme."

Turnbull added that he was further put off Cisco's equipment because the proposal the company had put forward was based on three different platforms. Cisco has, over its 24-year history, bought 126 companies, which means that, despite all its integration work, the company's products are still based on a wide range of operating systems and user interfaces. "Cisco suggested three switches from different families of products. The complexity of it would have been massive compared with what we got from Foundry," Turnbull said.

A phased approach
The university is adopting a two-phase approach to building its Wi-Fi network. In phase one, which is complete, Turnbull and Lea installed 300 access points in numerous academic buildings, libraries and coffee areas. Some of that wireless coverage propagates outside to areas such as the sports fields. Phase two, on which the duo are now embarking, will see current black spots filled in across the campus with a further 360 access points.

Once Turnbull and Lea have completed phase two, they will consider focusing their attention on upgrading the wireless network. Each access point currently supports the 802.11g maximum theoretical throughput of 54Mbps, which the duo believes is sufficient for the university's current needs. However, with an average of 20 students accessing the Wi-Fi network for the first time every week, they said they believed that could change in the future.

Most wireless-networking vendors have already started selling equipment based on the latest generation of Wi-Fi, 802.11n. 802.11n equipment promises a theoretical throughput of 300Mbps, as well as techniques for reassembling radio signals which have bounced off multiple surfaces. Although vendors have started selling the equipment, their kit is only based on a draft specification, not an international standard.

"In the short term, with virtual-cell technology and the ability to increase capacity by throwing in access points, we're covered for performance for some time to come," said Turnbull. "We need to be at the forefront, but it's not clear at the moment how 802.11n is going to be implemented."

One of Turnbull's concerns is over the power requirements of 802.11n access points. Currently the devices cannot be powered using standards-based Power over Ethernet over a single cable; the access points typically use 18.5W, while Power over Ethernet can supply only 15.4W. Given the uncertainty, Turnbull has gone to extraordinary lengths by installing two cables to every access point, in case the problem is not resolved.

The university's technical advancements won't stop there. The institution plans to make full use of the Wi-Fi network to stream live audio and video across its network from campus sports matches. It even has plans to stream live rugby across the SuperJanet academic network to halls of residence at the University of Warwick when the two teams meet next season.

With all these technical achievements, including the convergence of its fixed and mobile networks, the university, surprisingly perhaps, still maintains a separate, legacy voice network. Many universities have already converged their voice and data communications.

But Turnbull is in no rush. He said that trials with Microsoft's Office Communicator and mobile devices will more than suffice for the university's convergence efforts in the short term and it will be "two or three years" before anything changes on the fixed voice network.

With the increasing availability of Wi-Fi voice on campus, Turnbull said he sees little need to invest in fixed-line voice. "Wi-Fi phones raise the question of whether you need a fixed-line phone, " he said.

How the University of Birmingham's network measures up

• The Wi-Fi network is scheduled to cover 250 hectares by the end of the year at the university's main campus in Edgbaston. Satellite campuses in Selly Oak and Stratford-upon-Avon are also expected to benefit from Wi-Fi coverage
• The campus is so large that the switches have to be 2.5km apart
• Secure Wi-Fi access will be granted to 30,000 students and 6,000 staff, as well as visitors
• Each week, twenty students access the network for the first time
• The university has purchased 660 access points at a cost of around £250,000
• LAN cost savings of £87,000 have been achieved
• Over 45,000 ports have been connected using Category 6 copper
• A fibre backbone and four access points have been installed in the university's Great Hall, a listed building in which nothing can be attached to the walls