Siemens IEEE802.11 - Manual (Page 15)

WLAN-IEEE802.11 Tutorial (Maximilian Riegel), 021018-wlan-tutorial.ppt Page 15 © Siemens, 2002
IEEE802.11 Architecture Overview
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One common MAC supporting multiple PHYs
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Two configurations
– “Independent” (ad hoc) and “Infrastructure”
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CSMA/CA (collision avoidance) with optional “point coordination”
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Connectionless Service
– Transfer data on a shared medium without reservation
– data comes in bursts
– user waits for response, so transmit at highest speed possible
– is the same service as used by Internet
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Isochronous Service
– reserve the medium for a single connection and provide a continues stream of bits, even
when not used
– works only when cells (using the same frequencies) are not overlapping.
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Robust against noise and interference (ACK)
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Hidden Node Problem (RTS/CTS)
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Mobility (Hand-over mechanism)
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Security (WEP)
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Power savings (Sleep intervals)