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Dwight Borses MTS, Field Applications Engineering National Semiconductor, Irvine,CA Feb 25, 2002

IEEE Orange County Computer Society Joint Meeting with IEEE OC ComSig Chapter Wireless LAN Instrumentation, Scientific, Medical Band. Dwight Borses MTS, Field Applications Engineering National Semiconductor, Irvine,CA Feb 25, 2002.

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Dwight Borses MTS, Field Applications Engineering National Semiconductor, Irvine,CA Feb 25, 2002

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  1. IEEE Orange County Computer SocietyJoint Meeting withIEEE OC ComSig ChapterWireless LANInstrumentation, Scientific, Medical Band Dwight Borses MTS, Field Applications Engineering National Semiconductor, Irvine,CA Feb 25, 2002

  2. The IEEE ("eye-triple-E") The Institute of Electrical and Electronics Engineers, Inc., helps advance global prosperity by promoting the engineering process of creating, developing, integrating, sharing, and applying knowledge about electrical and information technologies and sciences for the benefit of humanity and the profession. • Local volunteers needed!

  3. Points to Ponder • Standards - so many to choose from • Cellular/PCS - both a competitor and a complement to WLAN • DECT – up-banded applications for proprietary applications • UWB – yet another contender • FSO – Light based wireless

  4. Wireless Technologies: Short Distance

  5. 802.11 InfraredA real standard that sort of died

  6. Wireless Technologies: Long Distance

  7. Data Migration Path to 3G WWAN 3G Fixed access at 2Mbps 2 M 384 K 144 K 64 K 14.4 K 9.6 K 3G Phase II IS-2000 Rel A (3XRTT) Packet Data / Voice / Video 3G Phase I IS-2000 Rel 0 (1XRTT) Packet Data Subscriber Data Rate 2.5G IS-95B Packet Data 2G IS-95-A Circuit Switched + QNC 1G Analogue Cellular 1999 2000 2001 2002 2003 2004 2005 2006

  8. 2.4GHz ISM Band

  9. ISM Band Inhabitants (Besides 802.11)Frequency & Modulation Spec’s

  10. Comparing Different WLAN Technologies

  11. 5 GHz Unlicensed National Information Infrastructure

  12. IEEE 802 Framework

  13. 802.11 StandardsOverview IEEE 802.11 802.11a 802.11b 802.11d 802.11e 802.11f 802.11g 802.11h 802.11i

  14. 802.11 Standards • Original 802.11, circa 1999 • FHSS, DSSS, IR • 1 & 2 Mbps • Wired Equivalent Privacy (WEP) • SNMP v2 for remote management • 802.11b (shortly after 802.11) • DSSS • 1, 2, 5.5 & 11 Mbps, Complementary Code Keying (CCK)

  15. 802.11 Standards • 802.11a (Approved same time as .11b) • 6, 9, 12, 18, 24, 36, 48, 54 Mbps • Only 6, 12, 24 Mbps support is mandatory • 5 GHz UNII band (not universally free)

  16. 802.11 Standards • 802.11c (completed, subsumed into d) • Bridge operation • 802.11d (ongoing) • Specs for other regulatory domains • 802.11e (ongoing) • QoS (Security moved to 802.11i (May 2001)) • 802.11f (ongoing) • Inter Access Point interoperability

  17. 802.11 Standards • 802.11g (ongoing) • High-speed extension to 802.11b, > 20Mbps • Just approved! • 802.11h (ongoing) • improvement to 802.11a, w.r.t. power and spectrum management • 802.11i (ongoing) • Security enhancements

  18. Wireless Data Standards Technology Comparison

  19. PANs, LANs, and Bluetooth

  20. Very High Speed60 GHz Range LAN 300GHz • 156MbpsMMAC(Japan) • 156MbpsMEDIAN (German) EHF(milli-wave) Frequency 19GHz range LAN10Mbps (ARIB) 30GHz High Speed5GHz Range LAN SHF(micro-wave) (1)IEEE 802.11a 6/12/24Mbps (2)HIPERLAN (ETSI BRAN)Type ½: 23.5/25Mbps (3)WATM (ATM Forum) 25Mbps Middle Speed 2.4GHz Range LAN 3GHz IEEE802.111Mbps/2Mbps UHF 1GHz UHF 300MHz IEEE802.11b5.5Mbps/11Mbps VHF Bandwidth 4Mbps/16MbpsToken RingIEEE 802.5 10MbpsEthernetIEEE 802.3 25/52/100MbpsATM-LAN(ATM Forum) 100MbpsFast EthernetIEEE 802.3u 156/622 MbpsATM-LAN(ATM Forum) 1000MbpsGigabit EthernetIEEE 802.3z, 802.3ab Wired LAN Full Range of Wireless LANs

  21. Data Rates and Range by Technology

  22. 802.11 – Infrastructure Architecture

  23. 802.11 - Layers and Functions

  24. Binary Phase Shift KeyingQuadrature Phase Shift Keying

  25. Quadrature Modulation

  26. Quadrature Amplitude Modulatoion

  27. IEEE 802.11 Direct Sequence Spread Spectrum DSSS

  28. AU 1 Freq. f7 AU 2 f6 f5 AU 3 f4 f3 AU 4 f2 f1 t1 t2 t3 t4 t6 Time t5 Frequency Hopping Spread Spectrum (FHSS) • Transmitted signal is “spread” over a wide range of frequencies (ISM 2.4-2.4835 GHz) • Transmission hops 8 to 30 times per second

  29. Complementary Code Keying This sequence 1 has 4 pairs of like elements with a separation of 1 and 3 pairs of unlike elements with a separation of 1

  30. Complementary Code Keying This sequence has 4 pairs of unlike elements with separation of 1 and 3 pairs of like elements.

  31. 802.11 Modulation Set

  32. Binary Phase Shift Keying

  33. IEEE 802.11a OFDM

  34. IEEE 802.11 DSSS

  35. CSMA/CD Carrier Sense, Multiple Access/Collision Detection For wire communication No control BEFORE transmission Generates collisions Collision Detection How? CSMA/CD

  36. CSMA/CA Carrier Sense, Multiple Access/Collision Avoidance For wireless communication Collision avoidance BEFORE transmission Pre-avoidance of collision Why avoidance on wireless? CSMA/CA

  37. Difference on energy/power for transmit and receive At maximum, transmission power is a million times larger than receiving Very hard to detect because of this difference Energy often matter on wireless environment Portable devices/terminals with batteries Collision Detection On Wireless?

  38. Decrease the possibility of contention/collision Backoff window Time to wait ot avoid collision Random backoff Use random length of time to wait Backoff

  39. IFS – Inter Frame Spacing • Defined length of time for control • To assure the control of multiple access • DIFS – Distributed Inter Frame Spacing • PIFS – Point Inter Frame Spacing • SIFS – Short Inter Frame Spacing • DIFS (MAX) > PIFS > SIFS (MIN)

  40. Backoff Time = Random() x aSlotTime Basic Access Method: CSMA/CA

  41. 802.11 - Competing Stations - Simple Version

  42. RTS : Request To Sent. CTS : Clear To Sent Duration/ID fields that define the period of time that the medium is to be reserved to transmit the actual data frame and the returning ACK frame RTS/CTS

  43. The NAV maintains a prediction of future traffic on the medium based on duration information that is announced in RTS/CTS frames prior to the actual exchange of data The duration information is also available in the MAC header of all frames sent during the CP other than PS-Poll Control frames Network Allocation VectorNAV

  44. RTS/CTS/Data/ACK and NAV

  45. Security

  46. Impractical to stop RF signals from propagating beyond your premises “Parking lot” attack, war-driving Poorly configured networks can be woefully exposed Hackers can be highly stealthy, guerilla warfare style That’s the reason for WEP Basic Security Concerns

  47. Wired Equivalent Privacy Shared 40/128 bit key Static, i.e. not designed to change often RC4 stream cipher Any AP/client can be configured to handle up to 4 keys Baseline Security Features

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