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Definition of radio network for weak current engineering equipment
I understand the species in Shanghai electricity engineering wireless LAN
There are many types of wireless networks, such as weak total package wireless LAN, wireless wide area network, wireless Internet now GPRS and CDMA 1X, is really your wireless unlimited, as long as there is a mobile phone signal where access to the Internet, but because the price is expensive, and the user group is not widely.
So today I share with you only belong to a wireless network, wireless LAN English ELV engineering company, Wireless Local Area Networks is the name, abbreviation is WLAN, it is the use of radio frequency (Radio, Frequency, RF) of local area network technology, so the weak electric engineering wireless network can use simple architecture allows users to access through it, achieve the ideal free to receive information.
- HomeRF
HomeRF is primarily designed for home networks, a combination of IEEE 802.11 and DECT (digital cordless telephony) standards, designed to reduce the cost of voice data. HomeRF also uses spread spectrum hormones, operating in the 2.4GHz band, and can support 4 high-quality voice channels simultaneously.
The application of type WLAN
There are two main types of WLAN applications. One is the whole network with wireless communication, in this way, AP is not required, this is called independent WLAN, when not in use of AP, each user can directly via wireless Internet, but this way is the communication distance between users is closer, and when the number of users more when the performance will be relatively poor.
The second is the wireless communication as a supplement and extension of wired communication, this is called non independent WLAN, in this case, a plurality of AP connected to the wired network through a cable, so that wireless users can access any part of the network.
The weak construction of wireless local area network advantage
Usually computer network transmission media rely mainly on copper or fiber optic cable, LAN cable form. Unfortunately, the wired network is limited by wiring in some occasions, and the wiring and routing works are large, the lines are easy to damage, and the nodes cannot be moved. Especially when the phase of the distance from the node link, dedicated communication line wiring construction difficulty, high cost, time consuming is large, it is difficult to imagine, a serious bottleneck to the rapidly expanding Internet demand, the emergence of WLAN can be a good solution to the existing wired network the problem.
The technical advantages
The use of WLAN electromagnetic wave transmitting and receiving data in the air, without wires, now 802.11a and 802.11g most high-speed transmission rate has reached 54Mbps, fully meet the needs of video and multimedia, office more be nothing difficult. But in a sense, it is the way the cable network as a supplement and extension (still limited bandwidth), the Internet computer has mobility, can solve the problem of cable network connectivity quickly and easily.
Compared with the long wiring network construction project, WLAN is more simple, only need to install one or more access points (Access Point) equipment, we can establish a local area network covering the entire building, the construction period is greatly reduced, saving and efficiency of the cost increase is obviously.
Some of the more important the concept of micro unit and wireless roaming
Radio waves are known to decay as they spread, so that the range of communication within the AP can only be limited to a certain range, and this range is called micro units.
In addition, when the network has more than one AP, the micro unit between each other will have a certain range of coincidence, so the wireless user can move covering the entire region of WLAN wireless network card will automatically monitor the near maximum signal strength AP, and through the AP to send and receive data, maintain uninterrupted network connection. This is the wireless roaming, roaming wireless and mobile phone similar to roam in different base stations, only temporarily not so much AP let us move in the global scope.
The spread spectrum technology
The reason for WAPI's enforcement is that the country calls it more secure, but wireless networks are inherently safer than wired networks and use military technology, such as spread spectrum. Spread spectrum technology was originally broadband wireless communication technology used in the field of military communications, the use of the technology enables wireless transmission of data is more complete and reliable, and ensure that the transmission data in different frequency bands without mutual interference.
The direct sequence spread spectrum
Using high bit rate spread spectrum sequences, the spectrum of the signal is extended at the transmitter, and the same spread spectrum sequence is used for despreading at the receiver, and the spreading spread spectrum signal is reduced to the original signal.
The frequency hopping spread spectrum
Frequency hopping technology is quite different from direct sequence spread spectrum (DSSS) technology. It is another kind of spread spectrum technology. The frequency hopping carrier frequency is controlled by a pseudo random code, and its frequency varies continuously according to the random frequency in its operating bandwidth. The frequency of the receiver also varies according to the random law and remains consistent with the transmitter.
The wireless network to the human body is affected?
Health is the capital of revolution, radiation will have a great impact on the human body, and all day in radio waves, whether it will affect the human body? I believe this is a lot of consumers are more concerned about the problem, you know, some time ago fried hot mobile phone will cause cancer, is believed to have caused a panic.
Relatively speaking, the transmission power of wireless network equipment is much more green, only 60-70mW, while the mobile phone is as high as 200mW. The most important thing is that the signal of wireless network is not as direct as that of mobile phone