1. IEEE 802.11 Overview Onno W. Purbo Onno@indo.net.id

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).