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Ieee 802.11 wireless lan

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Ieee 802.11 wireless lan

  1. 1. IIEEEEEE 880022..1111 WWIIRREELLEESSSS LLAANN V.Par thipan Assistant Professor ,Saveetha University
  2. 2.  LANs provide connectivity for interconnecting computing resources at the local levels of an organization  Wired LANs Limitations because of physical, hard-wired infrastructure  Wireless LANs provide Flexibility Portability Mobility Ease of Installation
  3. 3.  In response to lacking standards, IEEE developed the first internationally recognized wireless LAN standard – IEEE 802.11  IEEE published 802.11 in 1997, after seven years of work  Most prominent specification for WLANs  Scope of IEEE 802.11 is limited to Physical and Data Link Layers.
  4. 4.  Appliance Interoperability  Fast Product Development  Stable Future Migration  Price Reductions  The 802.11 standard takes into account the following significant differences between wireless and wired LANs: Power Management Security Bandwidth
  5. 5. IEEE 802.3 Carrier Sense IEEE 802.4 Token Bus IEEE 802.5 Token Ring IEEE 802.11 Wireless IEEE 802.2 Logical Link Control (LLC) PHY OSI Layer 1 (Physical) Mac OSI Layer 2 (Data Link)
  6. 6.  Medical Professionals  Education  Temporary Situations  Airlines  Security Staff  Emergency Centers
  7. 7.  In historical building and small office where cabling is not economical.  Supports nomadic access by providing a wireless link between a LAN hub and mobile data terminal with an antenna.  Creation of an adhoc n/ws. i.e peer to peer network with no centralized server that is set up temporarily to meet some immediate need.
  8. 8. CM 10 Mbps Ethernet switch UM Bridge Or Router Server 100 Mbps Ethernet switch Server
  9. 9.  Mostly a wireless Lan will be linked into a wired LAN. This is called LAN Extension.  Control Module is wireless LAN acts as an interface to a wired LAN  If all wireless end systems are within the range of a single control module, then it is called single cell wireless LAN.  If multiple control Module are present ,then it is multiple cell wireless LAN.  CM- control module uses polling or token passing scheme to regulate access from end systems.  Hubs or user module(UM), that control number of stations directly without a wired LAN, can also be a part of wireless LAN
  10. 10.  Wireless LAN requirement:-  throughput – should provide high capacity.  Number of nodes –should support many data.  Connectivity of backbone LAN.  Battery power consumption- use battery powered workstations , so when not using n/w, can be set to sleep mode to reduce power consumption.  Transmission robustness and security: Highly interference prone should provide reliable transfer.  coallocated network operation –Wireless LAN operating in same area may face interference.  License free operation – should provide wireless products without license for frequency based used.  Hand off (or) Roaming – mobile station can move from cell to another.  Dynamic configuration: automated addition or relocation of end systems without disruption to others.
  12. 12. WWLLAANN TTooppoollooggyy IInnffrraassttrruuccttuurree
  13. 13.  Access point (AP): A station that provides access to the DS.  Basic service set (BSS): A set of stations controlled by a single AP.  Distribution system (DS): A system used to interconnect a set of BSSs to create an ESS. DS is implementation-independent. It can be a wired 802.3 Ethernet LAN, 802.4 token bus, 802.5 token ring or another 802.11 medium.  Extended service set (ESS):Two or more BSS interconnected by DS  Portal: Logical entity where 802.11 network integrates with a non 802.11 network.
  14. 14.  Distribution service (DS) Used to exchange MAC frames from station in one BSS to station in another BSS  Integration service Transfer of data between station on IEEE 802.11 LAN and station on integrated IEEE 802.x LAN
  15. 15.  Association Establishes initial association between station and AP. Each station must send its identify to all others through AP  Re-association Enables transfer of association from one AP to another, allowing station to move from one BSS to another  Disassociation Association termination notice from station or AP
  17. 17.  Authentication Establishes identity of stations to each other  De-authentication Invoked when existing authentication is terminated  Privacy Prevents message contents from being read by unintended recipient.
  18. 18. IEEE 802.11 MMEEDDIIUUMM AACCCCEESSSS CCOONNTTRROOLL  MAC layer covers three functional areas: Reliable data delivery Access control Security
  19. 19. MMAACC FFRRAAMMEE FFOORRMMAATT 2 2 6 6 6 2 6 0-2312 4 Frame Control Duration ID Addr 1 Addr 2 Addr 3 Sequence Addr 4 Control Frame CRC Body 802.11 MAC Header Bits: 2 2 4 1 1 1 1 1 1 1 1 Protocol Version Type SubType To DS Retry Pwr Mgt More Data WEP Order From More DS Frag Frame Control Field
  20. 20. MMAACC LLAAYYEERR FFRRAAMMEESS  Data Frames  Control Frames RTS,CTS,ACK and PS-POLL  Management Frames Authentication and De-Authentication Association, Re-Association, and Disassociation Beacon and Probe frames
  21. 21. IISS WWLLAANN SSEECCUURREE ?? The Parking Lot attack Man in the middle attack Freely available tools like Air Snort, WEP crack to snoop into a WLAN
  22. 22. PHYSICAL MMEEDDIIAA DDEEFFIINNEEDD BBYY OORRIIGGIINNAALL 880022..1111 SSTTAANNDDAARRDD  Frequency-hopping spread spectrum Operating in 2.4 GHz ISM band Lower cost, power consumption Most tolerant to signal interference  Direct-sequence spread spectrum Operating in 2.4 GHz ISM band Supports higher data rates More range than FH or IR physical layers  Infrared Lowest cost Lowest range compared to spread spectrum Doesn’t penetrate walls, so no eavesdropping
  23. 23. FREQUENCY HHOOPPPPIINNGG SSPPRREEAADD SSPPEECCTTRRUUMM  Signal is broadcast over seemingly random series of radio frequencies  Signal hops from frequency to frequency at fixed intervals  Receiver, hopping between frequencies in synchronization with transmitter, picks up message  Advantages Efficient utilization of available bandwidth Eavesdropper hear only unintelligible blips Attempts to jam signal on one frequency succeed only at knocking out a few bits
  24. 24. DIRECT SSEEQQUUEENNCCEE SSPPRREEAADD SSPPEECCTTRRUUMM  Each bit in original signal is represented by multiple bits in the transmitted signal  Spreading code spreads signal across a wider frequency band  DSSS is the only physical layer specified for the 802.11b specification 802.11a and 802.11b differ in use of chipping method 802.11a uses 11-bit barker chip 802.11b uses 8-bit complimentary code keying (CCK) algorithm
  25. 25. IEEE 880022..1111AA AANNDD IIEEEEEE 880022..1111BB  IEEE 802.11a – limited data rate Makes use of 5-GHz band Provides rates of 6, 9 , 12, 18, 24, 36, 48, 54 Mbps Uses orthogonal frequency division multiplexing (OFDM)  IEEE 802.11b 802.11b operates in 2.4 GHz band Provides data rates of 5.5 and 11 Mbps Complementary code keying (CCK) modulation scheme. Multiple carrier signals at different frequency sending some of the bits on each channel.
  26. 26. IEEE 802.11 standards : IEEE 802.11 a Multipath Effect(Multipath Fading) is simply a term used to describe the multiple Paths the radio wave may follow between transmitter and receiver
  27. 27. IEEE 802.11 standards : IEEE 802.11 a Orthogonal Frequency Division Multiplexing(OFDM) OFDM a digital multi-carrier modulation method. A large number of closely-spaced orthogonal sub-carriers are used to carry data. Although the principles and some of the benefits have been known since the 1960s, OFDM is popular for wideband communications today by way of low-cost digital signal processing components that can efficiently calculate the FFT.
  28. 28. IEEE 802.11 standards : IEEE 802.11 a Frequency = 5 GHz Maximum Speed = 54 Mbps Range = about 35 meters(Varies) Encoding Scheme = OFDM
  29. 29. IEEE 802.11 standards : IEEE 802.11 b Frequency = 2.4 GHz (ISM band) Maximum Speed =11 Mbps Range = about 38meters(Varies) Encoding Scheme = DSSS Modulation Technique= BPSK(1 Mbps), DQPSK(2 Mbps), CCK(5.5 Mbps,11Mbps)
  30. 30. FFUUTTUURREE OOFF WWLLAANN WLANs move to maturity Higher Speeds Improved Security Seamless end-to-end protocols Better Error control Long distances New vendors Better interoperability Global networking