Ad hoc networks – bridging the gaps between wired and wireless

Ad hoc networks, that can be set up almost instantaneously in response to changing communication needs, could be the answer to plugging the various gaps in today’s wired and wireless infrastructures. With a WiFi-based ad hoc network, a taxi company could for example abandon traditional radio-dispatch technology and save thousands of euro in the process.

Under MobileMAN, a Future and Emerging Technologies (FET) initiative completed in December 2005, partners from five European countries investigated the potential offered by mobile ad hoc networks (MANETs).

Ad hoc networks – filling in the infrastructure gaps

“A network without a network, a MANET is based on wireless user devices, rather than being set up or managed by an external service provider,” says project coordinator Marco Conti of Italy's National Research Council (CNR) in Pisa. Ideally self-organising, such a network allows people with laptops, mobile phones and personal digital assistants (PDAs) to set up their own networks and run software on top.

If people are carrying suitable devices, such an ad hoc wireless network can be created anywhere within minutes. This has obvious benefits when coping with natural disasters or emergency situations, when existing communications infrastructures are often damaged or destroyed.

Such networks can also be used to establish links to the outside world from geographically remote areas. Best of all, wireless technologies such as Bluetooth or WiFi allow virtually cost-free communication between devices.

Complementing established infrastructures

However, the MobileMAN team concluded that ad hoc networking technology needs fine-tuning if it is to become a building block within future networks. If individuals are spaced too far apart or fail to cooperate – perhaps due to security concerns – the network will go down. Or links may disappear when user devices experience battery drain.

“Free it may be, but a citizens’ network will never offer the quality of service we are all used to with fixed or mobile-phone networks,” acknowledges Conti. “So we say that a MANET complements existing networks.”

As mobile ad hoc networks were mainly a theoretical concept before the project’s start, the partners had to create an innovative architecture. “We adopted a new approach to organising a network, with cross-layering,” says Conti. He calls this a form of context-awareness, enabling applications to adapt to their environment – for example by reducing the amount of information transmitted when a network suffers technical problems.

 At the Italian National Research Council campus in Pisa, Italy, the partners tested cross-layering on the prototype of a new peer-to-peer platform for MANET networks. They also conducted a large-scale test with 23 ‘nodes’ – volunteers running real applications on the MobileMAN network with their laptops and PDAs. The software modules for these devices were developed within the project.

Uses for ad hoc networks?

MobileMAN researchers also surveyed several groups of people to see how they would react to such a network, and how useful they would find it. Conti says the social aspect is important, because individuals’ willingness to use or be part of an ad hoc network will affect adoption of the technology.

Few users could immediately envisage innovative ways of using a MANET, underlining how unfamiliar these networks are. But some students felt it would be perfect for multiplayer gaming or passing on traffic information between car drivers on a highway.

 “We have proved the potential of a MANET in terms of the technology,” says Conti, pointing to the city taxi example. The project also identified current limitations, for instance to do with protocols for multi-hop networks.

However, Conti believes that ad hoc networking will soon be incorporated within hybrid (mesh) networks. “Instead of relying solely on user devices, one could cover a whole city with a mix of fixed infrastructure and MANETs at the boundaries,” he says.

In the long term, he foresees ad hoc networks being used in so-called opportunistic networks. Meanwhile, he is hoping to build and test a hybrid network within a new European project, calling on the routing protocols and other ideas culled from MobileMAN.

Contact:

Marco Conti
Institute for Informatics and Telematics (IIT)
National Research Council (CNR)
Via G. Moruzzi, 1
I-56124 Pisa
Italy
Tel: +39 050 315 3062
Fax: +39 050 315 2113
Email: marco.conti@iit.cnr.it

Source: Based on information from MobileMAN