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IEEE 802.11 Overview Onno W. Purbo

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Presentation on theme: "IEEE 802.11 Overview Onno W. Purbo"— Presentation transcript:

1 IEEE 802.11 Overview Onno W. Purbo

2 Context Wireless Differences Power management Bandwidth Security addressing Presentation Physical Link Network Transport Session Application 802.3802.4802.5802.11 802.2 PHY MAC LLC OSIIEEE

3 Logical Link Control Services Upper Layer 802.2 802.11 Upper Layer 802.2 802.11 Unack Connectionless Connectionless Oriented Ack Connectionless

4 Topology Basic Service Set (BSS) Extended Service Set (ESS) BSS DS BSS AP

5 Independent BSS

6 Extended Service Set

7 Topology Characteristics Mobility No transitions BSS transition ESS transition (not guaranteed) Within ESS BSSs that are partially overlap BSSs that are physically disjoint BSSs that are physically collocated

8 Logical Architecture Service primitives Request Confirm Indication responds DSSSFHSSIR MAC LLC CSMA/CA 2.4GHz 1W 300 meter

9 802.11 services Station Services Authentication, deauthentication, privacy (WEP), MSDU delivery. Disrtibuted System Services Association, deassociation, distribution, integration, reassociation.

10 How does a station join a BSS? Scanning Passive Active Authentication Association

11 MAC Details CSMA/CA (time slot = 20 us) Distributed Coordination Function (DCF). Virtual carrier sense (RTS/CTS) Exponential random backoff algorithm. Priority Based Point Coordination Function (PCF). Segmentation & Reassembly.

12 Physical – DSSS details 2Mbps w/DQPSK or 1Mbps w/DBPSK 14 channels (11 channels for US). 5 plans – 3 max. non-overlapping channels.

13 Physical – FHSS details 1Mbps w/ 2 level GFSK 79 1Mbps channels (2.402 – 2.480 GHz) 78 sequences (3 sets of 26) Minimum hop rate = 2.5 hop/s Minimum hop distance = 6MHz

14 802.11 Future 802.11a High data rates 2.4GHz band: 5GHz band: 20 Mbps 802.11b High data rates 2.4GHz band: FH 4.5Mbps: DS 25.5Mbps WPAN Wearable Devices (30 feet, 1Mbps, 0.5 in3, lower power, low cost).

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