Chapter 8

Wi-Fi Access for Ad Hoc Networks




8.1 Introduction

The Institute of Electrical and Electronics Engineers (IEEE) norm 802.11 is an international standard describing the characteristics of a wireless local area network (WLAN).

The name “wireless fidelity (Wi-Fi)” initially referred to the name of the certification delivered by the Wireless Ethernet Compatibility Alliance, the body charged with maintaining interoperability between materials conforming to the 802.11 norm.

Through misuse of terminology (and for marketing reasons), the name of the norm has now become confused with the name of the certification. A so-called “Wi-Fi” network is, in reality, a network that follows the 802.11 norm.

Thanks to Wi-Fi, it is now possible to create broadband wireless local networks. In practice, Wi-Fi allows portable computers, desktops, PDAs, and even peripherals to connect to a high-speed link (from 11 Mbps in 802.11b to 54 Mbps in 802.11a/g) within a radius of several dozen meters indoors (generally, between 20 and 50 m).

In a more open environment, the range can attain several hundred meters, or even, in optimal circumstances, tens of kilometers.

8.2. Wi-Fi network structure

The 802.11 norm defines the lower layers of the OSI model for a wireless link using electromagnetic waves, i.e.

– the physical layer (sometimes noted PHY layer), proposing different types of information coding;

– the data link layer, made up of two sublayers:

- the logical link control (LLC) sublayer; and ...

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