By the tripod bridge technology (Shenzhen) Co., Ltd. Xiaobian for everyone to introduce a detailed about the wireless image transmission technology and applications:
   Wireless image transmission system from the application level is divided into two categories, one fixed point of the image monitoring transmission system, the second is the mobile video image transmission system.
Fixed point of the wireless image monitoring transmission system, mainly used in the closed-circuit monitoring of cable to achieve the occasion, such as the port terminal monitoring system, river water conservancy video and data monitoring, forest fire monitoring system, urban safety monitoring. The following frequency band from low to high on the different image transmission technology introduced.
1.1 - 2.4 GHz ISM band of a variety of image transmission technology
2.4 GHz image transmission equipment using spread spectrum technology, there are two ways of frequency hopping and direct expansion. Frequency hopping rate is low, the throughput rate of about 2 Mbit / s, anti-interference ability, but also can use different frequency hopping sequence to achieve multiplexing to increase capacity. Direct expansion mode has a higher throughput rate, but the anti-jamming performance is poor, and the use of multiple sets of systems with limited use.
2.4 GHz image transmission can be based on IEEE802.11b protocol, the transmission rate of 11 Mbit / s, remove the cost of transmission, the actual effective rate of 3.8 Mbit / s or so. Later developed IEEE802.11g standard, the maximum rate of 54 Mbit / s, the standard interoperability, point to point can transmit several MPEG-4 compressed image.
Applications in the 2.4 GHz band also Bluetooth technology, HomeRF technology, MESH, micro-cellular technology. With the gradual expansion of the scope of application, 2.4 GHZ this band is in full load working state, the speed of the problem, security issues, compatibility issues worthy of further study.
1.2 - 3.5 GHz band wireless access system
3.5 GHz wireless access system is a point-to-multipoint microwave communication technology, using FDD duplex mode, with 16QAM, 64QAM modulation, based on DOCSOS protocol. Its working frequency band is relatively low, the radio free space loss is small, the transmission rain attenuation performance is good, the access speed is high enough, and the equipment cost is relatively low. The system has a relatively good coverage, usually 5 km to 10 km, suitable for county-level units of low-cost, large area coverage of the application; also with WLAN, LMDS complement each other to form the size of the area with the , The density of users with dense multi-layer operation of the organic complementary mode. Now the problem is the lack of bandwidth, only up and down the 30 MHz, it is difficult to large-scale use.
1.3 - 5.8 GHz WLAN products
5.8 GHz WLAN products using orthogonal frequency division multiplexing technology, in this band of WLAN products based on IEEE802.11a protocol, the transmission rate can reach 54 Mbit / s. According to the WLAN transmission protocol, when the point-to-point application, the effective rate of 20 Mbit / s; point to six points, the effective transmission rate of each image is about 500 kbit / s, that is, the total amount of data For 3 Mbit / s or so. For the transmission of wireless images, basically solve the "high-definition digital images in the wireless network transmission" problem, making a wide range of 5.8 GHz band transmission of digital images become a reality, especially for urban security monitoring system.
WLAN transmission monitoring images, now more mature is the use of MPEG-4 image compression technology. This compression technology at 500 kbit / s rate, the compressed image resolution can reach 1CIF (352 × 288 pixels) ~ 2CIF. At the rate of 2 Mbit / s, the technology can transmit 4CIF (702 × 576 pixels, DVD resolution) sharpness of the image. Using MPEG-4 compression after the digital image, through the wireless channel transmission, with the corresponding software, it is easy to achieve network, intelligent digital urban security monitoring system.
The WLAN product in the 5.8 GHz band is not good, the point-to-point connection is not economical, is not suitable for small equipment, the technology cost is too high, and the 5.8 GHz band faces spectrum control in some areas.
1.4 - 5.8 GHz wireless transmission network
iMAX point-to-multipoint wireless access system is a typical wireless transmission network, with its strong non-line-of-sight ability, high capacity, long transmission distance, advanced encryption and QoS mechanisms and other excellent features, to provide users with an enhanced Type broadband wireless access solutions. Using excellent orthogonal frequency division multiplexing (OFDM), and receive high sensitivity -92dbm, to solve long-distance video transmission.
Broadband Fixed Wireless Access System in the 1.5--26 GHz Band
LMDS system is a typical 26 GHz wireless access system, using 64QAM, 16QAM and QPSK three modulation methods. LMDS has a greater bandwidth and two-way data transmission capabilities, can provide a variety of broadband interactive data and multimedia services, to solve the traditional local loop bottlenecks, to meet the high-speed broadband data, image communications and broadband Internet business needs. LMDS system coverage of 3 km to 5 km, for metropolitan area network. As the world of LMDS work band planning is different, so its poor compatibility, poor performance of poor rain, the cost is higher.
To sum up, for the city digital monitoring system, the use of more than 2.4 GHz WLAN technology as a fixed point of image transmission is entirely feasible, but also the development trend.
Mobile video image transmission system
In addition to the need for fixed-point image monitoring, the demand for moving image transmission is also quite strong. Mobile video image transmission, widely used in public security command vehicles, traffic accident exploration vehicles, fire armed police field command vehicles and customs, oil, mining, water, electricity, finance, maritime, and other emergency, emergency command system, the main role is Live real-time image transmission back to the command center, so that the command center command and decision-makers such as immersive, improve the accuracy and timeliness of decision-making, improve work efficiency. Fu Shida on the mobile video image transmission using the public network and special technology for the two cases related to the introduction.
2.1 The use of CDMA, GPRS public mobile network transmission of images
CDMA wireless network mobile transmission technology has many advantages: good confidentiality, anti-interference ability, anti-multipath fading, the system capacity configuration flexibility, low cost of network construction. CDMA using MPEG-4 compression, MPEG-4 CIF format compression image, you can reach about 2 frames per second rate; if the image is adjusted to QCIF format, you can reach more than 10 frames per second. However, for the security system, the general use of low transmission frame rate to ensure the clarity of transmission, because only CIF above the image clarity can meet the needs of investigation and evidence collection. If you want to further improve the real-time transmission rate of live images, a simple scheme is to use multiple CDMA network card bundled with the way to improve the wireless channel transmission rate. Now the market has 2 to 3 network card bundled way to increase the cost of the network card is to increase equipment costs and the use of cost. With the continuous development of video compression technology, a single card on the 3 to 4 frames / sec image transfer rate can be achieved, if every second can transmit 3 to 4 frames CIF format images, to meet the general mobile public transport facilities Monitoring requirements.
GPRS is a GSM packet-based wireless packet switching technology that supports specific point-to-point and point-to-multipoint services to deliver data as a "packet". GPRS peak rate of more than 100 kbit / s, the network capacity is only allocated when required, this transmission is called statistical multiplexing. GPRS is the main advantage of always online and by traffic billing, no dial-up can always access the Internet, at any time to maintain contact with the network, resource utilization is high.
There is also a choice that is expected to be a 3G system, and now the world has entered the deployment phase, so far can achieve an effective rate of 384 kbit / s, it will bring the mobile video transmission system revolutionary progress. However, it should be noted that even if the rate increases a lot, do not think that all the mobile transport facilities can simultaneously transfer images back to the monitoring center, because the concept of the public network for the image transmission is almost impossible.
2.2 Dedicated image transmission technology for emergency emergencies
For some emergency command center image transmission system, often require the scene of the incident image back to the command center. Such as major natural disasters, floods, fire scenes, mass rallies and important security and security missions. Such emergency image transmission system should not use the public network transmission, it is best to use professional mobile image transmission equipment. But at present our country has not yet specialized planning frequency. There are several techniques that can be used for mobile video image transmission.
2.2.1 WiMAX
WiMAX is a point-to-multipoint broadband wireless access technology, WiMAX has adopted a series of new technologies such as dynamic adaptive modulation, flexible system resource parameters and multi-carrier modulation, and both high rate transmission capability (up to 70 Mbit / s ~ 100 Mbit / s) and better QoS and security control. WiMAX 802.16e coverage can reach 1 to 3 miles, mainly located in the mobile wireless metropolitan area network environment. However, 802.16e get enough global uniform frequency there is a certain degree of difficulty, and construction costs and equipment prices higher.
2.2.2 Wireless Grid (MESH) technology
Wireless "grid (MESH)" technology, you can achieve near-range high-speed data communications. Using the 2.4 GHz band, the effective bandwidth can reach 6 Mbit / s, this technology link design is simple, flexible networking, easy maintenance.
For fixed wireless image transmission can use low-cost WLAN technology products; for mobile video image transmission can use the public mobile network or dedicated wireless image transmission technology. Dingqiao technology hope that more counterparts can further focus on wireless image transmission issues to promote the development of the industry.

  Dingqiao Technology (Shenzhen) Co., Ltd. was established in 2016, has always been in the forefront of the electronics industry, has introduced a variety of customers to win the favor of new technology products. Product range of applications, such as: UAV, unmanned vehicles, unmanned vehicles, robots, construction supervision, security monitoring, automotive mobile TV and other fields. Tripod technology: Shenzhen wireless image transmission, high-definition map, Shenzhen communications products manufacturer, Shenzhen OFDM digital high-definition map transmission equipment;