At present, the ultra-high frequency mobile video wireless communication system has been widely used in the underground through the combination of ultra-high frequency (UHF) in the tunnel (tunnel) in the propagation characteristics. It is not only beneficial to wells staff on the bottom of the mobile device operating conditions have a more realistic and intuitive understanding, and image playback for the rescue work to start, but also played a supporting role.
Underground ultra high frequency (UHF) wireless video communication monitoring is divided into: wireless communication systems and positioning system. The former is based on mature urban wireless communications (PHS) technology; the latter is the use of radio frequency card (RFID) technology to monitor downhole mobile targets. Can achieve downhole operations personnel and transport vehicle location monitoring inquiries and a variety of practical alarm function.
● Wireless Communication Systems
Wireless communication system is mainly built on the PHS, it is the use of micro-cellular technology, the phone to digital wireless access to fixed telephone network, as a fixed telephone supplement and extension, make full use of fixed telephone network resources, also known as the wireless local . Through the phone or fixed unit, you can move or a fixed location to achieve the call and other data services. The system components shown in image 1, mainly by the base stations, mobile phones and public switched telephone network. System RF operating frequency is generally: 1900 ~ 1915MHz, belonging to the UHF range; where the phone's transmission power is about 10mW, underground base station transmit power of about 20mW. Wireless base station coverage is about 200m, ie a mobile phone base station radio coverage in wireless communication (Image 2 is a diagram of a spectrum analysis of the base station transmit signal) within 200m.
● Positioning System
Positioning system can be divided into two categories: one is the use of radio frequency (RFID) technology systems, and the other is based on the wireless network platform to achieve the tracking and positioning system. They are built on the basis of wireless digital communications, but the two systems to achieve the principle of different, so the results are inconsistent. At present most of the coal mine using radio frequency (RFID) technology to achieve underground personnel positioning system (see image 3).
Specific works: the use of RFID reader (reader station) as a fixed point of reference position, and underground through the communication cable and the control center interconnected, and then by reading the reader (reader station ) Within the scope of the miners to carry the RFID card (identification card), to determine the location of the miners.
Thus, UHF mobile video wireless communication system not only on the locomotive operating conditions have a more realistic and intuitive understanding of the information can also be seamlessly connected to the mine. At the same time, the system video playback function for the rescue work carried out, can also play a supporting role.