Digital radio link handles video and data

Wood and Douglas has developed a novel digital body-mounted radio link system for security and military applications.

Wood and Douglas has developed a novel digital body-mounted radio link system for security and military applications.

The dVMo Manpack system (derived from digital video for moving objects) allows personnel on foot to simultaneously transmit high quality data including video, audio and a low-bitrate RS232 datastream.

The complete encoding and RF electronics of the Manpack is housed in a package that is physically similar to a videocassette case.

This level of integration would have been unthinkable until relatively recently.

Deployment will be particularly successful in city environments where there are high levels of radio related clutter that would normally make conventional video link reception "difficult".

The system is highly immune to multipath interference.

In fact it uses the very nature of these reflections to boost its operation.

The reception hardware can process the digital information from a number of receivers and chose the optimum image on a packet-by-packet basis.

This is known as intelligent diversity reception using packet switching.

Information from up to eight antenna sources can be simultaneously processed in this manner making the resultant images highly reliable.

To complement this technique the transmitter uses COFDM (coded orthogonal frequency division multiplexing) technology.

This is a system that sends the digital data by modulating many low-bitrate datastreams onto numerous narrowband radio channels of different and usually adjacent frequencies.

The result is that any interference caused by multipath reflections only affects a percentage of the data stream.

The dVMo can usually recreate any lost data by using error- correction techniques.

The design has successfully overcome the problem inherent with digital systems by reducing the video encoding delay to an exceptionally low 50ms.

This facility together with the small physical size makes the unit highly attractive for use on remotely controlled vehicles such as bomb disposal robots.

Such applications demand virtually real time images for their operators to be able to react quickly to circumstances.

Orders for dVMo hardware have already been received from UK and overseas security departments and the system is attracting considerable interest worldwide.

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