Networks riot as cops scramble

Police officers using an early version of the terrestrial trunked radio system (Tetra) in their battle to quell the May Day protests may have caused interference to 802.11 wireless networks in West London.

Police officers using an early version of the terrestrial trunked radio system (Tetra) in their battle to quell the May Day protests may have caused interference to 802.11 wireless networks in West London.

A West End-based network manager claimed that interference from the massed handsets carried by so many police officers in one place brought down his wireless 802.11 network. It was not until police officers and their vans left that he got his network up and running again.

Although the handsets are not the same as those to be issued to officers as part of the Government's multi-billion pound Tetra system, it is possible that the new handsets may have similar frequency problems when massed together.

The Metropolitan Police used 6000 officers to control protests across London, equipped with trunked radios from Motorola, called Metradios.

A police spokesman confirmed that if interference had occurred, it was most likely caused by its radios, but added it was unaware of earlier interference issues.

The Metropolitan Police is running its own radio network and is scheduled to join the national police radio network, Airwave, which uses Tetra, in 2003. Metradios and Airwave radios are both trunked radios, but the first is a previous analogue generation, while the latter is a modernised digital version.

Nigel Deighton, research director at Gartner, said it was "perfectly feasible" that the interference was caused by the abundance of police radios in the neighbourhood.

He confirmed Metradios were analogue but said digital Tetra radios or GSM phones could have caused similar interference. "If the radio's system broadcasts with an intermediate frequency, which is close to the decoders in the wireless Lan, interference is possible," he said.

Deighton argued that 802.11 wireless Lans used the unlicensed public band 2.4Ghz and the equipment was not always checked to make sure it was immune to interference.

"Anyone can use it and you can't prevent eavesdropping or interference. This holds a security risk. Interference pollution is going to get worse before it gets better. Companies must prepare to migrate to 5Ghz," he said.