Since July 2012, the Shenzhen Metro Shekou Line and the Central Line train have been suspended due to interference with the signal system. Since November, due to the frequent occurrences, the general concern about the safe operation of the subway has been triggered. The preliminary conclusion of the investigation was that the passenger's WiFi interfered with the "vehicle-ground" communication of the subway signal system, causing the command abnormality to cause the train to stop. However, it is legal for a portable WiFi router to use the 2.4G band frequency. The same interference problem exists in wireless conference system applications. In recent years, the technology and application of wireless conference systems have developed rapidly, and it has become one of the important development trends of conference systems. The wireless conference system has the advantages of no need for wiring, real-time change to adapt to the layout of the venue, no need to damage the original decoration of the venue, convenient system maintenance, no need to worry about aging of the wire, and easy storage, so it is subject to high-end conference venues and large conference centers and administrative centers. Favor. The wireless conference system mainly includes an RF wireless conference system and an infrared wireless conference system. 1. RF wireless conference system The radio frequency refers to an electromagnetic wave having a frequency of 300 kHz to 30 GHz (3.0 x 105 to 3.0 x 1010 Hz). In the wireless application of the conference system, several ISM open frequency bands such as 433MHz, 2.4GHz, and 5GHz are mainly used, and the radio frequency wireless conference system based on WiFi (2.4GHz) technology is the most common. At present, Germany's Bosch (BOSCH), Germany's Beyerdynamic (Beyerdynamic), Belgium's Televic and other European brands and some Chinese brands have developed RF wireless conference system products. The advantage of the RF wireless conference system is that it is easy to install. A system requires only one wireless access point, which is not blocked by obstacles and has a large transmission distance (up to 30 meters or more). RF wireless conference system The biggest shortcoming of RF wireless conference system is that it is susceptible to radio interference. Today's radio interference is ubiquitous and it is difficult to predict that the broadcast equipment of aircraft and TV stations will cause interference to the RF system. The RF wireless conference system between adjacent conference rooms also May interfere with each other; frequency resources are also near no availability, and various wireless systems (including WiFi devices, Bluetooth devices, wireless walkie-talkies, cordless phones, wireless projectors, wireless mice, wireless keyboards, central control wireless touch screens, etc.) grab each other Resources, interfere with each other. At all professional exhibitions at home and abroad, all RF wireless conference systems cannot be demonstrated live, and it is because of its vulnerability. According to the relevant provisions of the State, "Notice on Adjusting the Limit of Transmit Power in the 2.4GHz Band and Related Issues" (No. [2002] No. 353), Article 2: 2.4GHz band as wireless LAN, wireless access system, Bluetooth technology equipment The shared frequency band of various radio stations such as point-to-point or point-to-multipoint spread spectrum communication systems. That is to say, 2.4 GHz is a non-licensed band (unlicense), and various types of radio communication equipment complying with technical requirements such as transmission power limitation and non-wireless communication equipment such as industry, science, and medical treatment can be used. Therefore, it is not difficult to understand the "Shenzhen Metro is forced to stop by WiFi" incident. Interference in other ISM open bands, such as 5 GHz systems, is also a matter of time. In addition, radio frequency has a wall-through property and cannot guarantee privacy. Even the use of data encryption technology can not be guaranteed, because eavesdroppers can use the same manufacturer's products to eavesdrop outside the conference room; and setting user passwords involves personnel management issues. Therefore, the radio frequency wireless conference system is mainly used in conference venues where the reliability and confidentiality requirements are not too high. Multiple sets of RF wireless conference systems should not be installed in the same building. Articles 4.2.5~4.2.7 of the current national standard GB 50799-2012 "Electronic Conference System Engineering Design Specification" also clearly stipulates: when installing multiple sets of wireless conference discussion systems in the same building, or near the venue When working with RF equipment in the same or similar frequency band as this system, it is not advisable to use the RF conference discussion system. When the wireless conference discussion system has confidentiality and anti-malicious interference requirements, an infrared conference discussion system should be adopted. When using the infrared conference discussion system, measures should be taken to prevent infrared leakage of doors and windows. RF mode: 2.4G signal passes through the wall, interferes with each other, and leaks 2. Infrared wireless conference system The infrared wireless conference system uses infrared rays with a wavelength of 830~950nm (3.16~3.61x1014Hz) as the transmission medium, while infrared rays have the characteristics of visible light transmission, and cannot penetrate opaque objects (such as conference room walls, blackout curtains, etc.), so it is well guaranteed. The confidentiality of the meeting. Moreover, the infrared wireless conference system is not subject to radio interference, and there is no interference between adjacent conference rooms. The problem of harmonic interference of energy-saving lamps in early years has also been solved. Therefore, the infrared method is very suitable for conference venue applications. In fact, in the simultaneous interpretation application of wireless mode, the infrared simultaneous interpretation system has already eliminated the radio-based simultaneous interpretation system. Infrared mode: the signal can't penetrate the wall, and the adjacent conference room will not interfere. The shortcomings of the infrared wireless conference system are mainly: the signal coverage of a single infrared transceiver is not large enough (the coverage radius is about 10 meters, the signal coverage can be increased by connecting multiple transceivers), and the infrared transceiver of a large conference site. The number and location of installations need to be calculated based on the physical environment of the site. Infrared wireless conference system can cascade multiple transceivers The infrared wireless conference system is divided into an analog infrared wireless conference system and a digital infrared wireless conference system. Japan's Iron Triangle (Audio-Technica), TOA and other brands launched an analog infrared wireless conference system, limited to analog audio technology, the sound quality can only achieve a frequency response of 200Hz ~ 4.5kHz (-3dB), signal-to-noise ratio of about 50dB. Nowadays, the digitalization of professional audio and video systems has become a development trend. The audio performance of the analog infrared transmission scheme has lagged far behind the system's supporting sound reinforcement system and audio and video processing system. Digital infrared wireless conference system adopts dirATC-digital infrared audio transmission and control technology, which has superior sound quality, and can reach 20Hz~20kHz (-3dB) frequency response and 80dB signal to noise ratio. It is an ideal wireless conference system solution. The digital infrared wireless conference system complies with the international standard IEC 61603-7 and is compatible with digital infrared simultaneous interpretation systems using the same international standards. The digital infrared wireless conference system was invented by Shenzhen Taidian (TAIDEN) in 2008. Digital infrared wireless conference system Digital Infrared/Analog Infrared Wireless Conference System Frequency Response Comparison There are more than ten conference rooms in China National Convention Center equipped with digital infrared wireless conference system. In the construction of the project, only digital infrared transceivers can be installed in each conference room (flowing infrared transceivers can also be used), and the conference unit can be needed. When the flow is used, the layout of the conference room can be freely changed, and the conference room can also be merged and split, and multiple conference rooms adjacent to each other up and down will not interfere with each other. China National Convention Center applies digital infrared wireless conference system 3, the conclusion Due to the particularity of the application of the conference system, security and reliability are the first principles of conference system design. With the increasing number of wireless products and their applications, radio conferencing systems based on radio frequency technology are inevitably subject to radio interference. It is hoped that all parties will pay full attention to the security and reliability of wireless conferencing systems. Dc Servo Motor,Dc Servo Motor Drive Kit,24V Dc Servo Motor High Torque,100W-200W Dc Servo Motors Jinan Keya Electron Science And Technology Co., Ltd. , https://www.keyaservo.com
Talking about the interference problem of wireless conference system from "Shenzhen subway is forced to stop by WiFi"
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