What are the methods of wireless transmission?

Wireless transmission methods include: 1. Video baseband transmission; 2. Optical fiber transmission; 3. Network transmission; 4. Microwave transmission; 5. Twisted pair transmission; 6. Broadband common cable transmission; 7. Wireless SmartAir transmission.

What are the wireless transmission methods?

1. Video baseband transmission

is the most traditional TV monitoring transmission method. The 0~6MHz video baseband signal is not processed in any way and is directly transmitted through coaxial cable (unbalanced). analog signal. Its advantages are: small loss of image signal in short-distance transmission, low cost, and stable system. Disadvantages: The transmission distance is short, and the high-frequency component is attenuated greatly above 300 meters, so the image quality cannot be guaranteed; one cable is required for one video signal, and another cable is required for transmitting control signals; its structure is a star structure, which requires a large amount of wiring and maintenance Difficult, poor scalability, suitable for small systems.

2. Optical fiber transmission

Common ones include analog optical transceivers and digital optical transceivers, which are the best solution for TV surveillance transmission over tens or even hundreds of kilometers. By converting video and control signals into Laser signals are transmitted in optical fibers. Its advantages are: long transmission distance, small attenuation, good anti-interference performance, and suitable for long-distance transmission. Its disadvantages are: it is not economical enough for monitoring signal transmission within a few kilometers; optical splicing and maintenance require professional technicians and equipment operation, high maintenance technical requirements, and it is not easy to upgrade and expand capacity.

3. Network transmission

is a monitoring transmission method that solves the problem of long distance and extremely dispersed points in urban areas. It uses MPEG2/4 and H.264 audio and video compression formats to transmit monitoring signals. The advantage is that the network video server is used as the monitoring signal uploading device. As long as there is an Internet network, remote monitoring software can be installed to monitor and control. Its disadvantages are: limited by network bandwidth and speed, ADSL can only transmit small, low-quality images; it can only transmit a few to a dozen frames of images per second, and the animation effect is very obvious and delayed, making it impossible to achieve real-time monitor.

4. Microwave transmission

is one of the solutions for monitoring and transmitting in places that are difficult to wire for several kilometers or even dozens of kilometers. Using frequency modulation or amplitude modulation, the image is loaded onto a high-frequency carrier and converted into high-frequency electromagnetic waves for air transmission. Its advantages are: low overall cost, more stable performance, eliminating wiring and cable maintenance costs; it can dynamically transmit broadcast-level images in real time, with good image transmission clarity and completely real-time; flexible networking, good scalability, and plug-in Ready to use; low maintenance. Its disadvantages are: due to the use of microwave transmission, the frequency band is above 1GHz. Commonly used ones are L-band (1.0~2.0GHz), S-band (2.0~3.0GHz), and Ku-band (10~12GHz). The transmission environment is an open space. If used in big cities, radio waves are relatively complex and relatively susceptible to external electromagnetic interference; microwave signals are transmitted in straight lines and cannot be blocked by mountains or buildings; if there are obstacles, relays need to be added to solve them. The Ku band is affected by the weather. It is more serious, especially in rainy and snowy weather, which will cause serious rain attenuation. However, there are also digital microwave video transmission products, which have much improved anti-interference capabilities and scalability.

5. Twisted pair transmission

(balanced transmission): It is also a type of video baseband transmission, which converts the 75Ω unbalanced mode into a balanced mode for transmission. It is a good solution for the transmission of surveillance images within 1Km, the electromagnetic environment is relatively complex, and the situation is better. The surveillance image signal is processed and transmitted in a balanced and symmetrical manner. Its advantages are: simple wiring, low cost, and strong resistance to common mode interference. Its disadvantages are: it can only transmit surveillance images within 1Km, and one twisted pair can only transmit one image, so it is not suitable for use in large and medium-sized surveillance; the twisted pair is fragile and has poor anti-aging ability, so it is not suitable for field transmission; double The high-frequency components transmitted by twisted wires are attenuated greatly, and the image color will be greatly lost.

6. Broadband common cable transmission

The video adopts AM modulation, audio frequency carrying, FSK data signal modulation and other technologies to integrate dozens of monitoring images, audio, control and alarm signals into " Bidirectional transmission in one coaxial cable. Its advantages are: it makes full use of the resource space of the coaxial cable, and thirty audio, video and control signals are transmitted bidirectionally in the same cable to achieve "one line communication"; it is simple to construct and maintain, and saves a lot of material costs and construction costs; frequency division Multiplexing technology solves the monitoring and transmission problems of dispersed long-distance transmission points and difficult wiring; the radio frequency transmission method only attenuates the carrier signal, and the image signal attenuation is relatively small. The brightness and chrominance transmission are synchronously nested to ensure that the image quality reaches about level 4; using 75Ω The coaxial unbalanced transmission method makes it have strong anti-interference ability, and the image quality can still be guaranteed in complex electromagnetic environment. Its disadvantages are: it uses weak signal transmission, and the system debugging technology requires high technical requirements. Professional instruments must be used. If there is a problem with one device in the trunk line, it may cause the entire system to have no image. In addition, the broadband modulation end needs to be powered by an AC220V AC power supply (but most monitoring All have the condition of AC220V AC power supply).

7. Wireless SmartAir transmission

SmartAir technology is a unique single-antenna mode gigabit wireless high-speed transmission technology in the communications industry. It uses multi-band OFDM air interface technology, TDMA's low-latency scheduling technology, and advanced wireless communication technologies such as low-density parity check code LDPC, adaptive modulation coding AMC and hybrid automatic repeat HARQ to achieve a transmission rate of 1Gbps.

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