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Wireless technology is currently dominating many industries, and surveillance is no exception. CCTV applications previously considered only possible by larger corporations and public service organisations, can now be used by the smallest of companies and even the domestic user. So it is no surprise to see why this technology is taking off at such a rate.

Evolving surveillance requirements has made traditional hard-wired systems difficult to implement, especially when the need for cameras in particular locations can change on a frequent basis. Local authorities and the police have found that CCTV displaces crime to fringe and rural areas and CCTV systems must therefore be flexible and capable of moving where they are most needed. Using hard-wired systems in this way is very costly and time consuming to install, as well as being difficult to keep up with everyday requirements.

Wireless CCTV creates any number of possible uses, providing a flexible and responsive system capable of dealing easily and efficiently with today's requirements.

Public order and nuisance incidents tend to recur in specific locations, such as a children's play area, park or street corner. A wireless CCTV camera can easily be deployed in these areas, acting as a deterrent to future incidents. As the offenders change to a different location in their endeavours to escape the cameras, so the location of the cameras move with them. Eventually, the offenders either give up or move out of the area.

Anti-social behaviour is more easily spotted. For example, the London Borough of Tower Hamlets uses mobile cameras located in parks and other key areas to assist the dog wardens to provide a clean and pleasant environment for the public.

Public safety concerns
Special events such as concerts and sports events can mean the convergence of thousands of people in one area, increasing concerns over public safety and the need for extra security. Wireless cameras can be placed in those areas considered most vulnerable, with the images transmitted back to a control centre. Alerts can be set up so that in the event of an incident taking place, police patrolling the area can be informed and then take any necessary action. Wireless cameras can also be strategically placed to ensure the safety of the celebrities, sportsmen etc themselves, when moving into and out of the venue. Remote areas may require coverage, such as a canal towpath, or in a country park where muggings are more likely. These types of location make it hard to use a hard-wired camera, and so a wireless system is the only viable option.

For example, the London Borough of Barking and Dagenham uses a wireless CCTV camera along a remote footpath that had become a particularly dangerous area. The previously reported levels of muggings and robberies have since been reduced to almost zero as a direct result of the camera being there.

Airports and harbours are key areas requiring the benefits of wireless CCTV systems. Ship, aircraft and airport perimeter security are all applications where wireless CCTV excels. Wireless cameras can be positioned on a ship to notify personnel of an approaching vessel, which can then be checked out to find if this presents a potential threat.

Aircraft can have cameras and PIRs positioned around them while they are parked on a stand, to ensure no one approaches it. In this way, it doesn't matter where the aircraft is within the airport since the relevant security can be provided. Perimeter security is also possible by positioning cameras at regular intervals around the airport.

Fly tipping is increasingly becoming an issue for local authorities. It does little to promote the area, is unsightly, unpleasant for those living near it and can be dangerous to the environment.

While the penalty for being caught is becoming harsher, this does not stop offenders from depositing white goods and other rubbish at all hours of the day and night. The only effective way to stop it is to police the area 24/7 or take measures to physically stop fly tipping from taking place.

Taking physical measures to stop vehicles from getting to hotspots may not be feasible, in which case wireless CCTV comes to the rescue. Not only do the cameras themselves act as a deterrent, offenders are caught on camera, leading to a likely conviction. The use of a wireless system means that as the fly tippers move locations, so too can the cameras.

Covert operations are another situation where wireless CCTV is of great benefit. Immediate deployment of a CCTV system is often essential in order to gain the intelligence required against a criminal, or where the police have received a tip-off about a pending crime.

Special police operations can make the most of wireless CCTV when specific operations require immediate deployment. For example, Kent Police carried out an operation in which wireless CCTV was used in conjunction with an Automatic Number Plate Recognition (ANPR) system for a day, to concentrate on catching suspect vehicles and those registered on a number of national databases. The camera was located on a bridge over a major road that was linked to a mobile unit in a lay-by a few hundred yards away.

Schools and colleges find wireless CCTV useful in locating missing students, stopping graffiti writing and other typical offences. By moving the cameras around the premises on an ad hoc basis, no particular area can become a haunt for regular activities. The CCTV system becomes the eyes and ears of the staff, reducing the need to patrol corridors and check nooks and crannies for irregular behaviour.

Wireless CCTV is useful for workplace observation. Hard-wired cameras can be difficult to install and make a mess of the existing décor.

It also makes it very apparent to employees that they are being watched – which can cause some discomfort. Wireless CCTV is more discreet and can be moved around in line with office moves and layout changes.

Testing for new hard-wired installations is made easy with wireless CCTV. By using it as a survey tool, the risks of costly errors by installing a camera in the wrong location are reduced.

N.B. The most important factor with a wireless system is to select the correct radio frequency and antenna, the combination of which will produce a reliable and successful system.

Frequency
The higher you move in the frequency spectrum, the more directional the radio signal becomes. This means the requirement for line of sight becomes more critical, and therefore frequencies in the range of 1 to 10 GHz, using both licensed and unlicensed frequencies, tend to be used for wireless rapid deployment systems. However, as the frequency increases, more bandwidth is available for additional video channels.

While lower frequencies have fewer channels available to them, they are more suitable for use within mobile equipment. Ranges depend on frequency, and power level ranges can be anything from 500 metres to 4 kilometres. The Radio Frequency (RF) power level is also an influencing factor because systems utilising lower power transmission will be more sensitive to RF interference and have less range.

There are two main types of frequency – licensed and unlicensed. A frequency that is license-exempt only requires that you stay within the Radio-communication Agency's specification. Alternatively a licence can be obtained from the radio licensing authority.

When planning a wireless installation it is useful to select a number of locations for the transmitter/ camera units and to test these sites at the required frequency. The choice of frequency will depend on a number of factors including the number of links, local frequency usage and its end use application. This means that when moving cameras around, the minimum effort is required for installation, which can take place in a matter of minutes.

Vast ranges of antennas are available including standard lower gain omni-directional, high gain (directional and omni-directional) and mag-mounted aerials for vehicular use.

The transmitting and receiving aerial polarisation must be matched, and the cable length limited. For example, at 2.4Ghz, 3m of RG-223 cable will reduce the gain of the system by 50 per cent.

Conclusion
Wireless CCTV will not eradicate the need for conventional CCTV systems, but will create a considerable extension with many more applications.

A major restriction is the limit on radio spectrum, which limits the number of live images that may be transmitted. However as equipment moves towards the digital domain this will improve.

The ability to utilise various transmission methods provides maximum flexibility and the use of interchangeable pods allows the operator to change transmission and select from many mediums such as radio, GSM / ISDN / PSTN, higher frequency microwave and infrared.

Petards Vision Limited, 8 Windmill Business Village, Brooklands Close, Sunbury-on-Thames, Middlesex TW16 7DY. Tel 01932 788 288.

Fax 01932 788 322. sally.weekes@petardsvision.com