With the rapid development of network technology and wireless technology, various network technologies and network products have emerged, and the application of wireless transmission technology has been accepted by various industries. As a special way of using wireless image transmission, it is gradually being favored by users. Wireless transmission occupies an important position in the emergency command system. So, what are the advantages of wireless transmission and the composition of transmission?
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First, wireless video transmission "point of the eye" emergency command system
Although the wireless mobile video transmission system accounts for a small proportion of the emergency command system support platform, it often plays a key role in the critical moment.
The wireless mobile video transmission system products of the emergency command system communication equipment are highly targeted. In addition to the communication command vehicle platform, they are also widely used in professional rescue vehicles, professional riot vehicles, helicopters, drones, various types of aircraft and robot platforms. Because the wireless transmission system development company has a thorough understanding of the application of the emergency command system and understand the professional application and needs of the users, the developed products are very suitable for the emergency command system, such as the multi-carrier adopted by Shenzhen Keweitai Company. The modulation technology system has inherent advantages, namely one-way transmission and zero-interference in the central receiving system. Unlike the two-way data transmission system, in the case of scarce radio resources and increasingly serious electromagnetic interference, this is an emergency command system that guarantees system integration. Reliability and practicality.
In the face of complex emergencies, it is necessary to consider not only the coordination and coordination of multi-sector communication tools, but also the interconnection and independence between systems. If a device interferes with other systems, it will destroy other systems and even The normal work of the entire emergency rescue platform, as long as a link is wrong, will be lost.
Second, the advantages of wireless monitoring highlight
The wireless transmission technology has the advantages of flexible and convenient networking, rapid opening and low maintenance cost, so there is a huge market for its application. However, with the rapid development of wireless transmission technology, its security issues have attracted more and more attention.
Low comprehensive cost: only one-time investment, no need to dig trenches, especially suitable for outdoor distances and renovated occasions; in many cases, users are often limited by geographical environment and work content, such as mountains and ports. The special geographical environment, such as open space, brings great inconvenience to the wired network and wired transmission wiring projects. The wired construction period will be very long or even impossible. At this time, the use of wireless monitoring can get rid of the constraints of the cable, and has the advantages of short installation period, convenient maintenance, strong capacity expansion, and rapid cost recovery.
Flexible networking: good scalability, plug and play, managers can quickly add new wireless monitoring points to the existing network, no need to lay networks for new transmissions, add equipment, and easily achieve remote wireless monitoring.
Low maintenance costs: Wireless monitoring and maintenance is maintained by the network provider, and the front-end equipment is a plug-and-play, maintenance-free system. Although wireless transmission equipment in the security market currently enhances its security through various mechanisms, many industry insiders have found that there are various security vulnerabilities in the confidentiality agreement. For example, he cannot guarantee the confidentiality and integrity of data. Implement identity authentication for the accessed user.
Third, wireless transmission technology analysis
1. Microwave of wireless transmission technology
It can be divided into analog microwave and digital microwave.
Analog microwave: In this way, the video signal is directly modulated on the channel of the microwave, and transmitted through the antenna. The monitoring center receives the microwave signal through the antenna, and then demodulates the original video signal through the microwave receiver. According to the introduction of Yuantiancheng Shichao Zhao, this monitoring method has no compression loss and almost no delay, so the video quality can be guaranteed, but it is only suitable for point-to-point single transmission, not suitable for scale deployment, and because there is no modulation and calibration process, Poor interference, almost impossible to use in the case of complex wireless signal environment. The lower the frequency of the analog microwave, the longer the wavelength, the stronger the diffraction ability, but it is very easy to interfere with other communication. Therefore, this method was used more in the 1990s and is rarely used at present.
Digital microwave: Digital microwave is the first encoding and compressing video signal, modulated by digital microwave channel, and then transmitted by antenna; the receiving end is reversed, the signal is received by the antenna, followed by microwave despreading and video decompression, and finally restored to analog The video signal is transmitted out, and this method is also widely used in the domestic market. The digital microwave has large scalability, and the communication capacity can be used for at least a dozen channels, and the construction is relatively easy, the communication efficiency is high, and the application is flexible. Digital microwave has the advantages that analog microwaves are incomparable, such as many monitoring points, multiple situations requiring relaying, complicated situations and many sources of interference.
To sum up, digital microwave has large capacity, strong anti-interference ability and good confidentiality. The same transmission power transmission distance is farther, less affected by terrain or obstacles, rich interface, strong expansion capability and so on. On the contrary, analog microwaves do not have these advantages, but they are cheaper.
2. Wireless transmission technology WiFi
The IEEE 802.11 standard defines the physical layer and media access control (MAC) specifications, the physical layer of which defines the signal characteristics and modulation of data transmission, operating in the 2.4000 to 2.4835 GHz band. IEEE802.11 is a wireless LAN standard originally developed by the IEEE. It is mainly used for wireless access in computers in difficult environments or in mobile environments. Since the transmission rate can only reach 2Mbps, the service is mainly used for data storage. take.
This series mainly includes IEEE802.11a/b/g/n wireless LAN standards, of which the IEEE802.11b standard, namely WiFi, is currently used more. This standard stipulates that the wireless LAN operating frequency band is 2.4GHZ?2.4835GHZ, and the transmission rate reaches 11Mbps, which is a supplement to IEEE802.11. According to the introduction of Yuantiancheng Shichao Zhao, WiFi products have better advantages in terms of bandwidth, anti-jamming, encryption, etc., and have powerful network management functions, providing a powerful means for large-scale networking under various applications. High-bandwidth video transmission is currently the most widely used wireless transmission technology. It is understood that WiFi signal radius can reach about 100 meters, can be used in the office or even the entire building, and the transmission speed is very fast.
However, some insiders pointed out that WiFi is a standard protocol, so users only need to take a wireless-enabled laptop or PDA into the WiFi-enabled area, and then they can access the Internet at high speed, which determines that the security is not very good. If the more sensitive image can not be used, in case of being stolen by others; in addition, its transmission distance is short and the flexibility is poor, so it does not have the capability of wide-area video surveillance.
Therefore, based on the requirements of the carrier level, the 802.11 standard develops an intelligent distributed technology architecture of the base station controller WiFi base station, which can realize large-scale networking of 100,000-level WiFi base stations and million-level terminals, and can be used in a wide range of areas. 802.11n is currently the highest wireless bandwidth standard. A single 802.11n base station can achieve 300 Mbps wireless bandwidth and 200 Mbps effective bandwidth. It can realize 200 D1/1 Mbps image transmission, which is superior to the most common 100 Mbps optical fiber transmission in the market.
In fact, 802.11 has the highest level encryption standard of WAPI/802.11i China and international, which can meet the high-density communication transmission requirements of military, financial, government, etc.; it has strict physical layer, MAC layer anti-interference, and reduces error. The rate-related protocol standard is the most robust standard system in the wireless standard.
3, 2G/3G wireless transmission technology
The transmission mode of 2G mainly includes two modes of CDMA and GSM. These two modes are lower in cost, have larger coverage, and have faster transmission speed. The theoretical transmission rate of CDMA is 153.6Kbps, which can reach 60~80Kbps in actual use. Therefore, in wireless monitoring, it is not obtained. Less favored by manufacturers. The GSM-based GPRS, although the coverage rate is higher than CDMA, but the transmission rate is slightly slower, so it is still in a disadvantage in use.
The mobile (TD-SCDMA), telecom (CDMA2000EVDO), and Unicom (WCDMA) operators' 3G technology access methods have been promoted by various operators since 2009. The product. The advantage of 3G highlighting is the high-speed downloading capability, and the ideal value can reach the transmission rate of 3Kbps~1G. However, because it is still in the promotion stage, it still needs further research on the transmission rate.
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