At present, the wireless network there are two major categories of application in security, one is the wireless monitoring terminal, the second is the wireless monitoring client. Through the wireless network and video monitoring technology, can derive a lot of industry applications of intelligent, highly efficient, such as public security emergency command, remote insurance fee, public transport intelligent dispatching and so on. Main problems facing the future, in fact, the increase in the number of terminals, the increasing of the industry users, how to more effectively use wireless network with limited resources. Solve this problem, need by means of technology and management, to provide customers with a better solution.

Wireless monitoring terminal

Wireless monitoring terminal, we will cable network can be understood as replacement for the wireless network of monitoring terminal. These terminals have one thing in common: some network monitoring needs urgently the scene, but due to the limitation of application environment, usually can't use cable network, such as car, ship, carrying a soldier, etc. This kind of demand in mobile scene monitoring, usually can realize real-time network through the wireless network. From a technical point of view, this kind of monitoring scenarios need to implement the following: 1. Wireless transmission optimization; 2. Hard disk shock; 3. Power supply high stability; 4. The host protection grade is high.

Common wireless monitoring terminal are car DVR, individual, wireless cameras, wireless encoder, etc., mainly used in mobile or temporary installation, deployment of the characteristics of convenient and flexible application. Wireless monitoring terminal has the following key technology.

Wireless transmission technology

Because the emergence of 3 g network, wireless monitoring in a certain extent, has been popular, but 3 g networks are able to provide the network bandwidth and stability, there is a certain gap compared with the traditional fixed network. Therefore, the optimization of wireless network transmission is the most critical technical points.

In the wireless video transmission, work need to do two aspects, one is through efficient coding compression algorithm, video stream will need compressed as much as possible, so as to adapt to the wireless network bandwidth. In general, the function of the wireless monitoring terminal has the double stream, is the main stream for local video, code flow for net. Due to the 3 g network uplink bandwidth in 500 KBPS to 800 KBPS, usually so single way need to compress video channel of stream around 128 KBPS to 256 KBPS. Wireless signal coverage, sector, on the other hand, the number of users, system noise distribution is uneven, and these factors as the user behavior change also can produce certain fluctuation. Therefore, wireless network optimization, even if many times the bandwidth of the network to provide is also relatively unstable, with some system factors.

Individual equipment transmission of real-time video and network on-demand video has a big difference, is the user perception of delay. When playing movies, for example, in order to guarantee the smooth, usually increase the cache for a period of time, and in the case of bandwidth to allow the cache will pile up. That is to say, in the process of the transport document, the user to see the video is already transfer to the client's video. It can ensure the smoothness, the user will not feel the time delay. But usually use individual users, both fluency requirements for video is very high, and to the real time requirement of the video is very high. In emergency command, such as application, usually is under 10 seconds to delay requirement. So, individual video system cache usually only use less than 3 seconds.

Therefore, simply by caching to deal with the network fluctuation was clearly not reality. In order to enhance the real-time and smoothness of the video, the video streaming must pass control algorithm, a real-time assessment of network bandwidth, to control the real-time streaming. In the case of low network bandwidth, control algorithm, through adjusting the parameters of the video transmission, video fluency.

General code flow control process is: monitoring - > computing - > control.

In the process of wireless video transmission is characterized by: the first step, synchronous monitoring wireless transmission condition; The second step, the access to the data statistics and calculation, it is concluded that the need to control the level (in rate Kbps); The third step, according to different levels to choose a different approach, switching channels, frame, smoking, etc.

Smoke the frame is controlled by the non-critical frame to ensure the normal order of the original video sequence can continue to play. As shown in figure 1.

Automatic control scheme and the bandwidth of the typical control model as shown in figure 2: bandwidth - = error code rate. High bandwidth, low bit rate, the error is big, the driver code rate regulator raising rate; Low bandwidth, high bit rate, great error in the negative, drive rate regulator lower code rate; Closed loop feedback system cycle error smaller and smaller, bandwidth material code rate.

Through this kind of cycle control model and frame, smoking field algorithm, can effectively achieve the self-adjusting of video transmission.

For the seismic design of the hard disk

Because the monitoring terminal long-term application such as car, ship in turbulence, vibration and swing of bad environment, to ensure long-term, stable work, have higher request for reinforcement technology, especially the hard disk vibration strengthening technology is the key problem. On-board stainless steel wire rope of the main machine hard disk vibration damper. Use a stainless steel wire rope and two piece of plywood made of stainless steel wire rope around shock absorber, the rigidity and damping depends on the diameter of wire rope number, length, number of turns, winding way and tightness, damping characteristics related to the vibration isolator deformation.

Hard drive vibration failure cause analysis: hard work, high speed rotating disk, magnetic head, relying on the resistance of the air above the suspended in disk, servo drive head moving along the radial disk, implementation of disk read/write. In order to ensure that the head of disk records the sensitivity of the signal, the clearance between the disk and magnetic head is small, generally between 20 ~ 50 nm. Hard work head and disc distance is very small, vulnerable to the impact of the external environment.

On hard disk protection measures is to minimize the external shocks and hard disk resonance. Hard disk vibration strengthening technology principle is the use of vibration isolation materials to absorb external vibration energy, avoid the hard disk by a violent shock.

Wide power supply design

At present, the standard car battery are provided by the dc 12 v or 24 v power supply, the drive power can generally be stable in 12 ~ 16 v or 24 ~ 28 v, may also appear all sorts of high pressure during the burrs, so all kinds of vehicle electronic equipment power supply system should be equipped with a good performance. Car terminal to the wide isolated power supply, can automatically adapt to 6 ~ 36 v DC power input, and can filter up to 150 v DC high voltage burr, good all kinds of cars to meet the demand of the electric property.

Heat dissipation, dustproof design

Due to the special working environment, heat, dust, become an important factor to measure the performance of car DVR, common DVR use fan, window power dissipation structure is not suitable for car DVR. In a fully enclosed case, no fan is realized under the design requirements of good heat dissipation and dustproof performance: in the internal structure, to reasonable layout of PCB, according to the heat distribution situation to avoid heat congregation; On the equipment appearance, body fuselage adopts excellent aluminum materials, and cleverly integrated into the heat sink design concept, make the case that is equivalent to a large heat sink, under the condition of no fan, window could pass case internal heat in a timely manner to the external environment.

Wireless monitoring client

Nearly two years, with the development of smartphones, tablets, dongfeng, wireless monitoring client (also called mobile client) has been greatly development, all kinds of application software can be very convenient to download, this is the product of wireless network development and its main features and benefits is flexible and convenient.

Wireless monitoring client is in order to meet the needs of people anytime, anywhere monitoring, the main direction of development is mobile phone, tablet to the client.

Wireless client not only can be applied to the expert, leading the remote command, and can also make great efforts to promote the development of the civilian monitors. Due to previous shops monitor, family is unable to monitor through the network to realize remote viewing, greatly reduce application effect, can only as a basis for the later verification, the shops were stolen, the circumstance such as the old man ill cannot know in time. Through the wireless monitoring terminal, can in time connected to the Internet to check, for emergency response rapidly, not only have to verify for the accident, also can prevent the accident, to a certain extent reduce the accident loss.

Technically, client applications are generally more stable in the scenario, use the terminals such as mobile phone, tablet, wireless network downstream bandwidth is often greater than the upstream bandwidth, so in the transmission, shock, power supply, etc., technology difficulty is relatively small. But since the client often need to undertake the major business functions, is geared to the needs of the user's function. In terms of the design of the software function, need according to the characteristics of various industries, customized processing. The client often as powerful as it is hard to with PC client. In the future, the development of the business functions will be wireless monitoring client a key, is also one of the focuses of wireless monitoring for more industries.

4 g network has been in a number of key cities test, wait until 4 g licences officially released, when the national promotion of 4 g networks, wireless security will be on a new step. Believe in the near future, wireless monitoring will in many industries can replace wired monitoring.