Basic Introduction to wireless LAN

The local area network application well is not short, so common LAN environments include enterprises and campuses. With the increasing popularity of computer networks, more and more small local area networks are available. Looking back on the past and looking forward to this evening, wireless technology will bring new blood to the network environment. The basic concept of Wireless LAN is also introduced.

The basis of the wireless LAN is the traditional wired LAN, which is the extension and replacement of the wired LAN. It only enables wireless communication through wireless hubs, wireless access nodes, wireless bridges, wireless NICs, and other devices on the basis of a wired LAN. Like wired networks, wireless LAN also needs to transmit media. Only the transmission media used by the wireless LAN is not twisted pair wires or optical fiber cables, but infrared or radio waves, and most of them will be used later.

Wireless LAN basics-Infrared System

The infrared LAN uses infrared rays smaller than 1 micron wavelength as transmission media and has strong directionality. because it uses a spectrum lower than visible light as the transmission media, it is not restricted by the radio management department. Infrared signals require visual distance of the line of sight) transmission, and it is difficult to eavesdrop, and will not interfere with similar systems in neighboring areas. In practical applications, infrared rays have high background noise and are greatly affected by sunlight and environmental lighting. Generally, the emission power is high, infrared wireless LAN is currently a viable option for "networks with a performance-to-price ratio of over 100 Mbit/s.

Wireless LAN basics-radio waves

Radio waves are currently the most widely used as the transmission medium for wireless LAN. This is mainly because radio waves have a wide coverage and are widely used. When spread-spectrum communication is used, especially the direct sequence spread spectrum modulation method, has strong anti-interference and anti-fading ability because the transmit power is lower than the background noise. In this aspect, communication is very secure, which basically avoids eavesdropping and theft of communication signals and has high availability. On the other hand, the main frequency band used for wireless local areas is S GHz ~ GHz frequency range), which is also called ISMIndustry Science Medical) is an industrial Science Medical frequency band. This frequency band is not restricted by the US Federal Communications Commission and belongs to the industrial free radiation frequency band, it will not cause harm to human health. Therefore, radio waves have become the most common wireless transmission media in Wireless LAN.

Apart from the traditional LAN, one of the characteristics of the wireless LAN technology that is different from the wired access is that the standards are not uniform, and different standards have different applications. Currently, 802.11 of the most popular standards include 802.11a, 802.11b, and 802.11g), Bluetooth, and HomeRF family network.