Portsmouth's Online Real Time Traveller Portal project, designed to encourage the use of public transport by displaying in real time the updated arrival times for the city's buses at 36 bus stops, is the largest intelligent transportation system in the world to be based on mobile mesh networking.
Mesh networking, developed by the US military for battlefield communications, avoids the need for a central hub, which can be both a single point of failure and a bottleneck, by making each node in the network capable of receiving, transmitting and passing on (hopping) messages to and from any other node in the network by dynamically routing an optimal path through the nodes.
For John Domblides, team leader for the project, mesh networking also has one other key advantage over traditional GPRS wireless or copper wire networks. Once the network is installed there are no further charges for data passed across it.
"The mesh radio technology cost just under £600,000 of the portal's total budget of £3.5m, £1.5m of which came from the Department of Transport's Transport Direct Initiative and £2m from the council's Local Transport Plan settlement," he said.
"Although we could not have done it without the DoT funding, we are already saving potentially £70,000 a year in charges on our wire traffic, and our monthly GPRS bill should stabilise at around £1,000," and that is before the mesh network is fully rolled out, Domblides added.
At the moment, the portal is using a hybrid mesh/GPRS system. GPRS is still needed for communicating with buses that travel beyond the limits of the mesh - about three square miles - and until all city buses are equipped with the ruggedised PCs with the Meshnetworks PCMCIA card, as well as the current GPS location card and GPRS modem, due by the end of the year. The buses do not communicate directly with bus stops, but to central AVL servers, which sort the incoming data and send what is relevant to each of the 36 stops and nine kiosks via the mesh.
Portsmouth is keen to capitalise on the mesh, far beyond the project. The network is also already being used by the Isle of Wight ferry company to provide real-time information on ferry information signs, and over the next three weeks the city's Urban Traffic Control data network, which controls traffic signals across the city, will migrate to the mesh network at three test locations.
A raft of applications can be run over the network, without any further communications charges. Public-access touch screens at the bus shelters and kiosks offer services such as weather forecasts, job vacancy lists or houses for sale by area, e-mail and games. The technology could be used for other applications such as field workers using voice over IP on PDAs to replace mobile phones, video streaming and for libraries and schools to provide low-cost 6Mbyte bandwidth access to the internet.
Portsmouth's recipe for success
- Go for a best-of-breed implementation, and use global suppliers. Portsmouth's bus shelters were built in Turkey, radio technology came from Meshnetworks in the US, the Telenor on-bus PCs from Denmark, the bus shelter screens and intelligence from Cityspace in the UK
- Use consultants who are communications experts. It is crucial they understand network implementation
- Do not leave third parties in charge. Portsmouth oversaw all the integration and had project management responsibility
- Try to get suppliers to work together. Telenor and Meshnetworks had to write bespoke software so that the XP drivers and firmware could be updated remotely. So they had to trust one another enough to give access to their proprietary intellectual property
- Accept the pros and cons of being a reference site. Because the suppliers were building the system from scratch, Portsmouth had to wait for things such as bespoke software, but we got a lot more for our money . The council was able to identify specific requirements that other prospective purchasers would require and get them from day one at no extra cost.
- Halt the project rather than implement the wrong kit. Portsmouth was going to use the CE platform for the bus PCs, because it was cheaper, but it is not expandable enough. It was a major decision to upgrade to the XP platform when already into the contract and the spec had to be rewritten, which cost time, but made it future-proof
- Expect hold-ups from telecoms and power companies. You have to accept that they will promise the earth but delivery will be delayed. Place orders as soon as you can.