Seg 2: Wifi history

  • In 1996, Lucent in America firstly launched to set up Wireless Ethernet Compatibility Alliance (WECA), which aimed at the wireless local area networks (WLAN).
  • In 1999, WECA was renamed as Wi-Fi alliance, which would design an approval standard again. In this case, the alliance presented a series of wireless networks technology 802.11 in wireless communication, such as 802.11b, 802.11a, 802.11g, 802.11n, and so on.
  • Wi-Fi alliance committed itself to generate the 802.11 products and to solve the compatible problems. Note that, 802.11 is not denoted the wireless network. It is just one of the wireless networks.
  • Wireless Local Area Network can be abbreviated as WLAN. By this wireless communication technology, all the computer devices, pda, mobile phone and other many connectable devices, could communicate with each other by the wireless networks. Furthermore, if we use the wireless communication networks, all of the devices can be connected each other with no cable. It is would be much more mobile and flexible. Fortunately, wifi is the kind of wireless networks technology.

    Figure 1-2 wireless communication networks

  • Difference between Wifi, bluetooth, and ZigBee: bluetooth (BLE) is one of the WPAN (Wireless Personal Area Networks) technology, while wifi belongs to WLAN (Wireless Local Area Networks) technology. The two technologies can provide the different wireless networks services. Moreover, there exists an entitative difference for the realization of the two technologies.
  • The effects of WIFI radiation on human body: general speaking, the transmission power is much weaker than that of the mobile phone. For example, the transmitted power is about 60~70mW, while for mobile phone, the power is 200mW or so. What is more, wireless cannot directly touch the people tissue, but mobile phone must. So, the power to body is less than 1mW, and thus can be ignored.

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