Wireless System of Video Surveillance
Complex of the equipment for video surveillance behind set of the dispersed objects
One of versions of systems of gathering of a video-information can consider video surveillance behind set of the dispersed objects.
The complex of the equipment is intended for video surveillance behind protected territories and objects. Signaling of video and a sound from points (items of surveillance) to posts of surveillance and further to the central station of protection is carried out by wireless way. In comparison with wire analogues, the system possesses a number of advantages:
- speed of expansion;
- mobility (presence of mobile transmitters allows to organize mobile posts of surveillance);
- the big radius of a zone of surveillance (up to 20 km for one post of surveillance and practically unlimited for a complex as a whole) allows to organize protection of extensive territories within the limits of one system;
- reliability at work in complex climatic conditions owing to the protected execution of many components of the complex working outside of premises;
- large quantity of channels - owing to use of several ranges of frequencies and modern methods of digital modulation, and also repeated use of frequencies due to a high orientation of antennas in a centimetric range, high efficiency of use of a frequency resource is reached. On each of posts of surveillance can act up to eight signals from points of surveillance, and the total of channels can reach several hundreds;
- efficiency of management owing to use of management by television cameras on a radio channel.
Examples of use
Owing to the listed advantages, our wireless complexes are successfully applied as to protection of complex objects, for example, warehouses, railway bridges, the enterprises, and the control of the objects located on significant distances from the dispatching center, and perimeters of protected territories. They also can be applied to surveillance over the complex technological processes which are carried out at once in several shops of the enterprise, borrowing significant territory, especially when presence of people is undesirable. Such complexes can be used, for example, for needs of security service of traffic for video surveillance over traffic on crossroads and under abnormal condition-dangerous sites of roads.
The basic components of a complex
The complex of the equipment of video surveillance consists of set of posts of video observation (figure 1), each of which receives a video information from several points of video surveillance which quantity corresponds to quantity of objects of supervision. On each of posts gathering and processing of the video information acting from separate points of surveillance (videocameras) which quantity can make from four up to eight is carried out.
After corresponding processing the video information from each of posts of surveillance on radio channels is sent in a direction of the central station of a complex where this information is processed and acts on monitors and devices of registration. The important component of a complex is the system of telecontrol which functions also are realized with use of a radio channels.The equipment of remote control carries out wireless telecontrol by television cameras to what the wireless network with time division of channels is applied. Thus, functionally equipment which is a part of a complex can be divided into the equipment:
processings and transfers on radio channels of the basic video information;
On an arrangement in space the equipment is subdivided as follows:
points (items) of surveillance (separate cameras) outdoor installation, analog signals from which act on transmitters L - band;
posts of video surveillance represent or small heated premises, or containers with thermostates in which the temperature in admissible for normal work of the equipment an interval is supported;
In figure the base structure of the equipment of the Complex which can change according to concrete a task in view is given.
Fig. 1 Structure of a complex of the equipment for video surveillance
Fig. 2. Point of video surveillance.
Into structure of a post enter:
- antennas L-band for receiving of signals from points of video surveillance;
- television cameras which can be in addition included to a post of video surveillance without preliminary transfer on a radio channel;
- the container (rack) in which receivers L-band are placed, the composer of a multichannel digital (analog FM) signal, connected directly to the container, modulator QPSK (FM) L-band;
- powerful upconverter L/Ku (Transmitter);
- the directed antenna of a L-band;
- the antenna of a meter range for remote control receiver (in figure it is not shown).
Fig. 3. Post of video surveillance.
- the receive antenna with the adapted diagram of an orientation to conditions of a problem (from directed with narrow diagram of orientation up to 360 deg. in a horizontal plane);
- the low noise converter C, X or Ku- ranges;
- the transmitting antenna of a meter range for remote control;
- receivers (tuners DVB), by quantity of accepted channels;
- devices of displaying and fixing of a video information;
- the powerful transmitter of system of remote control;
- the modem of remote control;
- a server of remote control;
- workplaces of operators.
The given structure can serve as a starting point for designing concrete system in which these or those components of a complex can be used.
Fig. 4. Central station
Opportunities for use of cameras with remote control are great owing to the fact that many manufacturers offer such cameras which have the mechanism of control, and also encoders and decoders of commands of the telecontrol transferred on wires. This wire systems can be transformed in wireless. For this purpose in system the modulator, the transmitter, the receiver and the demodulator should be added. It is possible to take advantage of already available encoder and decoder of commands of telecontrol without intervention in a design of the camera. We had been designed all devices of the given system which are necessary for signaling telecontrol in ranges VHF and UHF with frequency modulation. At remote control by a television camera the operator can be in a final point of reception of a video information, i.e. at the central station of video surveillance.
For transfer of a picture signal the two-level scheme of transfer is used. At the first stage the radio signal of standard DVB-T is transmitted from mobile point of video surveillance to a post of video surveillance. The receiver of a post of video surveillance should have one or the several (at receiving by principle Antenna Diversity) omni-directional antennas in which operative area the mobile point of video surveillance can move. Further this signal is transformed to a signal of standard DVB-S and transmitted to the central station of a complex. The workplace of the operator which structure includes a control panel a television camera and the transmitter of commands of telecontrol here can settle down. Range of action of system of telecontrol considerably surpasses range of action of mobile point of video surveillance, therefore there is no necessity to relay this signal by means of a post of video surveillance. The receiver of remote control should be placed inside of a post of video surveillance only in the event that it is necessary to control a television camera connected directly to a post of video surveillance.
The block diagram of mobile point of video surveillance is shown in figure. A power supply of all equipment is carried out from an onboard network (it can be strengthened by the additional battery). On a roof of the car are placed:
- camera of cupola type with the mechanism of control and the decoder of commands;
- power amplifier S-band;
- collinear transmitting antenna;
- stub antenna for receiving of signals of remote control.
Video signal from a television camera moves through a separate socket on the block of modulator COFDM in which it is digitized, compressed in conformity with standards MPEG-2 or MPEG-4AVC. Obtained TS modulates carrier with frequency 36,125MHz. Upconverter will convert modulated carrier in frequency S-band. Then this signal moves on the power amplifier which is located on a roof of the car. Strengthened by the power amplifier the signal is radiated by collinear antenna ANT1. The signal of remote control is received by antenna ANT2 and acts on the receiver which is located in interior of the car. Commands of control and a voltage of a power supply move on the camera through socket X2.
Block-diagram of mobile point of video surveillance