Figure 1 Basic components of WLAN
Source: J. Burrell
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2.2 WLAN TRANSMISSION TECHNOLOGIES
Wireless LANs are generally categorized according to the transmission technique in use. All available wireless LAN products fall into one of the categories below
• Infrared (IR) LANs: Infrared light does not penetrate opaque walls as a result, an individual cell of an IR LAN is limited to a single room. No licensing is required.
• Spread Spectrum LANs: Here, spread spectrum transmission technology is used, and inmost cases, the LANs operate in ISM (Industrial, Scientific, and Medical) bands so as to avoid licensing requirement as in the United States for example.
• Narrowband Microwave: This category of LANs operates at microwave frequencies. Some operate at frequencies that require FCC licensing, others operate at the unlicensed ISM bands, but they do not use spread spectrum.
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