Tune in, track down

2 min read

Researchers at University College London are developing a wireless system that could allow continuous, real-time radar-style detection and tracking of people or objects in any area with wireless network coverage.

Current target detection and tracking systems rely on co-operative targets, such as with RFID, which requires subjects to carry a tag, or have restricted coverage including systems using video surveillance, which may have their vision blocked by objects such as parked cars. Both also require the installation of high-cost equipment.

But according to UCL's researchers, WiFi-based tracking could be developed using low-cost wireless hardware. It would be able to be used indoors and outdoors and would allow monitoring to take place without the subject's knowledge or co-operation.

'The system could be deployed anywhere with a WiFi capability using the existing infrastructure,' said Dr Karl Woodbridge of UCL's Department of Electronic and Electrical Engineering. 'All you would have to do is to install a relatively simple receiver to build a detection system.'

Working prototype

The two-year project to develop the system is receiving about £400,000 in EPSRC funding and is due to be completed at the end of August 2009, by which time Woodbridge hopes to have produced a working prototype. This will demonstrate detection, tracking, location and imaging performance through the construction of a small network able to show the essential features of a security-type surveillance system. UCL is working with industrial project partner, Era Technology, which will help with testing the prototype and act as consultant to bring the product to market.

The technology will use WiFi and the longer-range WiMax system, which has a range of up to 25 miles. It should be able to provide comprehensive local area surveillance of public or military-controlled areas. In combination with video surveillance, this could be used to detect unusual behaviour and feed the information to a central intelligence-gathering unit to allow any perceived threat to be analysed.

The system is similar to radar devices in that it will use a WiFi or WiMax transmitter and a separate receiver to receive the signal waveforms being transmitted by this.

Woodbridge said there are still significant technological hurdles to be overcome. 'The signal received may come from both the transmitter and the target. However, the transmitter signal will be stronger as it has not been reflected,' he said.

'The waveforms are designed for communications not radar detection, so they aren't necessarily ideal for passive radar transmission. We will therefore have to develop a way to suppress the stronger signal as well as software that will be able to pinpoint the target.'

A previous, EPSRC-funded project allowed the group to prove that the system could work and basic target detection capability has already been established.

Researchers will look at the way the signal is changed by hitting a target and how it is changed depending on factors such as how the person is standing. They believe it may be possible to use this motion for identification and are also looking at the reflectivity of certain clothing materials.

Under investigation

The use of WiFi for positioning is already under investigation using relative radio strengths from base stations. These systems track active WiFi transmitters. 'Unlike video this technology can see through walls,' said Woodbridge. 'We will not be limited by line of sight.'

He said successful development of the technology would result in a major advance in local area detection, with many applications in security and passive monitoring. It would also complement ongoing research into co-operative local area detection and passive monitoring techniques such as those using mobile phone systems and RFID tagging.

Co-operative technologies such as RFID can be very accurate and cost-effective in controlled environments. However, it can be easy to fool them by removing the tag, and they also suffer from problems within crowded areas such as airport terminals. To improve their reliability, complementary sensing capabilities can be used but this can be costly, particularly when sensors must be deployed throughout an environment.

Meanwhile, private and commercial wireless networking applications are growing fast. As WiFi sensors are already deployed for other applications, their use for surveillance purposes means security services would face only a small extra cost to develop tracking technology.