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2.5 802.11 Wi-Fi

2.5.1 Introduction

At the end of the 1990s the first devices appeared on the market using a new wireless local area network technology that is commonly referred to today as Wireless LAN or Wi-Fi. Wi-Fi is specified by the IEEE in the 802.11 standard. It is very similar to the 802.3 fixed line Ethernet standard and reuses all protocol layers down to layer 2, as shown in Figure 2.28. The major difference between the two protocols is on layer 1, where the fixed line medium access has been replaced with several wireless variants. Furthermore, some additional management features were specified that address the specific needs of wireless transmissions that do not exist in fixed line networks, such as network announcements, automatic packet retransmission, authentication procedures and encryption. Over the years, several physical layer standards were added to increase transmission speeds and to introduce additional features. Devices are usually backwards-compatible and support all previous standards to enable newer and older devices to communicate with each other.


  

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