Microwave transmission Microwave transmission is the main method of wireless transmission. In monitoring image transmission, it is divided into: analog microwave transmission and digital microwave transmission, which are introduced as follows:
1. Analog microwave: There are mainly three frequency bands in the working frequency band, namely L-band, S-band and Ku-band. Generally, L-band and S-band can be used in places with relatively small interference. The cost is lower, and the general interference is more serious, or the environment The more complicated ones should be transmitted in the KU band. It is necessary to ensure that the two points on the scene are visible, and the video and audio transmission of the surveillance camera is carried out point-to-point. It cannot be used under obstruction. If it is blocked, ultrashort wave must be used. Although it has a certain degree of diffraction ability, the transmission distance is very short, and the cost is high. The analog microwave transmission adopts the analog frequency modulation method, which is affected by the environment and climate. If control is required, a wireless command control system must be added. The video system and the command system are separate. Two independent systems. If there are relatively few monitoring points and the transmission distance is relatively long, you can consider using it, but you must choose a suitable frequency band in accordance with the on-site environment, so as to ensure stable image transmission. Generally, the analog microwave needs to be equipped with lightning protection and waterproof work, otherwise the system will not work stably. Advantages of analog microwave: easy construction, simple installation, long-distance transmission. Disadvantages of analog microwave: debugging is troublesome, affected by the environment and climate, cannot transmit multiple signals at the same time, and it is easy to be struck by lightning.
2. Digital microwave is mainly composed of: wireless network bridge cooperates with codec (video server) to realize long-distance image transmission. Generally, point-to-point network is realized through network bridge, and the analog video image is converted into network signal through the encoder. , And then transmit the network signal through the wireless network bridge, and restore the network signal to the analog video signal through the decoder (hard decoding or soft decoding) at the back end, which can transmit video, audio, data, and transmitted images at the same time The number of channels and image quality depend on the bandwidth of the network. The advantages of digital microwave: it is less affected by the environment, supports relay, and can be transmitted over long distances. Disadvantages of digital microwave: troublesome debugging, affected by network bandwidth.
3. The image quality of the analog microwave surveillance camera is better than the digital microwave, but the analog microwave is easily affected by the environment and climate. Although the digital microwave has a small environmental impact, the wireless transmission bandwidth is limited, and it is difficult to transmit a large number of images. . Each has its own characteristics and can be selected in consideration of the engineering environment.
CDMA network transmission, the domestic CDMA network speed is relatively slow, currently only reach 2.5G, it is very difficult to transmit real-time continuous images through the current domestic CDMA network, basically only use the network to transmit pictures. If you want to transmit real-time video images, you must adjust the video to a small size or increase the network bandwidth. It will definitely be a trend to use network transmission in the future, because after all, it covers a wide area and is not limited by distance.
Satellite transmission, satellite transmission is mainly satellite positioning system, also known as GPRS system. It is also mainly affected by bandwidth. There are already many use of satellite positioning systems to understand the specific geographic location of the tracked target. Such as cash transport vehicles, mobile phone positioning and so on. In the future, if the bandwidth can be increased, it will be easy to feed back live images on it in real time, and it will have a wide range of applications.
Summarize
Only by understanding the characteristics of various transmissions and choosing the appropriate transmission method according to the actual situation of the project can you make your own project produce good results.
