Mobile ad hoc networks (MANETs) are starting to be used by armed forces and public safety organisations to enable connections to be provided to their users as and when required. They provide an alternative to costly satellite communications and, thanks to the management software that MANET propositions encompass, are fast and simple to deploy in the field.
Critically, MANETs can be formed from a wide range of typically available radio technologies including Wi-Fi, Bluetooth and the GSM cellular family. In addition they conform to a range of industrial, military and public safety standards.
‘The key advantage of a MANET is that it needs no fixed infrastructure, so if two or more devices are within range and wish to communicate, they can do so,’ explains Mark Hunter, director of the radio group at Plextek Consulting.
‘For example, when a fire engine is attending an incident, a commander will not know whether there is good coverage from the nearest base station within a burning building. Therefore, for communications at incidents, fire fighters use an ad-hoc network of handheld radios and telemetry devices that communicate directly with each other and not through a fixed base station.’
For Gab Yepes, the director of business development at network core software provider Quortus, the flexibility of MANET solutions is the attraction. ‘The software component can be ported into any application which is why it is so popular with public safety and military organisations,’ he says. ‘They can have a manpack or equipment in a vehicle or embed the software in a radio network. We can scale up so you can effectively have a replica of a public cellular network, all based on COTS hardware.’
There are many other examples within public safety where communication is needed in the absence of good network coverage, either directly with colleagues, or using a vehicle based device as a relay to communicate with the network. In the military, reliable terrestrial infrastructure for communications are normally not guaranteed to be available and so ad-hoc networks are the norm.
‘The advantages of MANETs for the primary user, such as a search and rescue organisation or a blue light service, that goes out of reach of a TETRA or mobile operator network, is that the network is constantly forming, breaking and reforming without any intervention from the user,’ says David Rees, the project manager for Secure Mobile IP Node at Airbus Defence and Space.
‘That means a paramedic, for example, can focus on their primary function. They just want communications to work, they don’t want to take special measures themselves.’
Janne Kolu, the director of channel emulator products at test firm Anite, sees increased military use of MANETs and is working to replicate in-service conditions to enhance the automated set up and operation capabilities of MANETs.
‘The system is dynamic and changing as the situation evolves in the field and there are certain configurations customers are looking for,’ he says. ‘Failure is not an option for military users so, compared to commercial systems like Wi-Fi, where trial and error is an option, everything has to be done quickly and work first time.’
Ad-hoc networks have clear advantages for peer to peer local communications, but complexities arise when information needs to travel across an ad-hoc network and is relayed via a number of devices. It becomes a multi-hop network.
‘The way it’s set up at the moment is with DLEP (Dynamic Link Exchange Protocol) compatible radios, which analyse the spectrum and capability and use that information to create the best network available,’ explains Rees.
‘A satellite link, for example, would only be used in an emergency, because the system finds the highest bandwidth, lowest cost link automatically. The big step forward for MANETs is the network aware routing and DLEP is the standard for that.’
‘We can also have policy based routing, so if there are a number of different organisations at an incident a hierarchy of who gets the bandwidth and when can be adhered to,’ adds Rees. ‘We also have the ability to differentiate and differently handle data for different organisations and security is integrated at the core of our solution.’
Anite’s Kolu also points out that users, especially in defence, are expecting more from their communications. ‘There are a lot of use cases for [MANET] systems,’ he says. ‘Soldiers in a plane or helicopter might take high definition images to share with troops, so that is quite bandwidth intensive.’
Resilience can be an issue and some ways to mitigate that can be counter-productive, warns Hunter. ‘There is a potential increase in resilience if these messages are able to propagate through the network using a number of different paths, because individual links can fail and yet the message arrive intact,’ he says.
‘However this can require many replicas of the original message to be transmitted within the network, quickly exhausting the available radio resource. A considerable amount of research effort has therefore been spent investigating routing strategies within mesh networks. This nevertheless remains a significant challenge,’ notes Hunter.
Chris O’Shea, system design authority for Secure Mobile IP Node at Airbus Defence and Space, thinks recent advances are removing some of the capacity issues and points out that few organisations ever have the need to support large numbers of users with MANETs.
‘There have been a lot of advances in terms of infrastructure and the equipment for individual vehicles and soldiers. If you have a lot of vehicles together it could get a bit congested, but you wouldn’t have 2,000 or 3,000 users in one location, they’d be spread out,’ he says, pointing out there can also be security benefits from MANETs’ capability to automatically switch between bearers.
‘Multi-bearer networks require different systems but there is a benefit to that because it stops you being jammed or blocked,’ he adds. ‘Having the ability to use four different systems, for example, means that the network can juggle amongst them, so the device switches over to the best available network automatically. You therefore get greater resilience than you would on a single mast network.’
MANETs, therefore, can offer compelling cost efficiency. ‘A MANET can simply take the form of software that runs on a phone or a laptop, so can be very low cost,’ says Hunter. ‘A MANET can be a very cost effective way to communicate as no infrastructure is required - but this is at the expense of the scalability and reliability of infrastructure based networks.’
Added to that, deployment is straightforward and should not require any specific configuration expertise for users on the ground. ‘We’re talking about pre-loaded configurations for well-defined requirements, so there is no room for misconfiguration,’ says Hunter. ‘If they’re back in base, reconfiguration is not complex, because it’s all software based.’