Airwave security in doubt

The security of Britain's £2.5bn police Tetra network, known as Airwave, was this week brought into question by analysts and communications experts from the Israeli army, which is investing in Tetra to provide tank phones for battlefield communications.

The security of Britain's £2.5bn police Tetra network, known as Airwave, was this week brought into question by analysts and communications experts from the Israeli army, which is investing in Tetra to provide tank phones for battlefield communications.

Brigadier general Moshe Markovitch, of the Israeli defence force communications branch, claimed that Tetra needed at least four channels to be secure. However, the UK's police force only plans to use one channel, except in densely populated areas.

Markovitch does not believe that the police can be sure that Airwave would not be jammed without additional channels to provide security. Tetra was designed to hop channels, increasing resilience when multiple transmission channels are used in the network.

Nigel Deighton, research director at Gartner, said that any radio system could be jammed, but that a Tetra network can switch to another channel, allowing communication to continue.

"The more channels and power you use, the more resilient your Tetra network becomes," he said. "It means that someone would have to block all channels, which would drive up the cost of jamming the network."

Ray Mason, implementation manager at BT Airwave, confirmed that Airwave would use multiple channels in built-up areas to provide the required coverage and capacity. "Non-dense areas will get fewer base stations and only one radio channel," he said.

When the radio frequencies from the base station are jammed, Tetra offers an alternative way of making contact. The technology does support Direct Mode, so that handsets can bypass base stations and communicate directly with each other.

However, the BT Airwave handsets do not automatically switch to Direct Mode, but keep looking for the network when they lose connection. If terrorists jammed the network, the police could mistake this for a quiet day, and not realise they should manually switch handsets to Direct Mode.

"We don't know of any terminals that automatically go to Direct Mode when they lose connection," said Mason. "They keep hunting for a signal, but you could presumably switch them manually."