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WIRELESS LAN

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WIRELESS LAN

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  1. WIRELESS LAN Presented by Ching-Man Chong Tracy Tien Johnny Wong Zhong Wei Yu

  2. WIRELESS LAN WIRLESS LOCAL AREA NETWORK

  3. WIRELESS LAN • Introduction • Wireless Technology • Wireless LAN • Configuration • Differences between wired LAN vs wireless LAN • Cost-Benefit Study • Customer Considerations

  4. INTRODUCTION • Data communications system • Alternates wired LAN • Transmits and receives data over the air • Minimize the need for wired connections • Become more popular in general-purpose alternative of business customers. • Benefited several industries in productivity and mobility

  5. WHY WIRELESS? Advantages: • MOBILITY • INSTALLATION • COST • SCALABILITY

  6. MOBILITY • Real-time information access from anywhere at any time • Increases productivity and flexibility

  7. INSTALLATION • Fast and easy • No cable needed • No frustration with wiring • Go where wires cannot go

  8. COST • Short run • Initial investment is higher than wired LAN • Long run • Long-term costs is essentially lower than wired LAN • Long-term cost and benefits are very important in dynamic and ever-changing business environments

  9. SCALABILITY • Can be configured in different topologies to meet the specification of applications and installations • Can be easily changed from peer-to-peer networks (small # of users) to full infrastructure networks (thousands of users)

  10. IN THE REAL WORLD • Not a replacement for the wired infrastructure • Great complement to what currently exists • Examples • Doctors and nurses • more productive in delivering patients’ information and status instantly • Student • access the Internet to consult the catalog of the Library of Congress • Network managers • provide backup for mission-critical applications

  11. HOW IT WORKS • Use electromagnetic airwaves to communicate information • Data imposed on radio carrier (radio wave) • RF electromagnetic wave can easily pass through ordinary wall, it needs to implement with heavy concrete or metal screening.

  12. WIRELESS TECHNOLOGY

  13. WIRELESS TECHNOLOGY • Satellite-Based System • Geosynchronous Earth Orbiting (GEO) • Low Earth Orbiting (LEO) • Land-Based Network Access System • Wireless WAN • Wireless LAN

  14. GEO SATELLITES • Circle the earth from a height of 22,300 miles • 3 satellites can be used to provide worldwide coverage • used for: • television broadcasts, long distance telecommunications, and various science and military applications

  15. LEO SATELLITES • Orbit no higher than 500 miles above the earth • Travel the earth in a couple of hours • Multiple satellites needed • Allow access to very low-power devices

  16. WIRELESS WAN • Provide nationwide or citywide coverage • Example: Ricochet Micro-Cell Coverage in Washington D.C., San Francisco, and Seattle Source: http://dcs.umd.edu

  17. WIRELESS LAN • Wireless LAN Topology • 2 main components • Access Points • Adapters • Roaming • Wireless LAN Technology • Types • Standard • Configuration

  18. ACCESS POINTS • Connects to the wired network • single access point can support a small group of users within a range of several hundred feet Wireless Clients Connected to LAN via Access Point Source: http://dcs.umd.edu

  19. ADAPTERS • Users used wireless-LAN adapters to connect to access points • Implemented as : • PC cards in notebook computers • ISA or PCI cards in desktop computers • Integrated within hand-held computers

  20. ROAMING • Each access point can provide between 50,000 to 250,000 square feet of coverage • Example: Hospital Environment Source: http://dcs.umd.edu

  21. WIRELESS LAN TECHNOLOGY • Narrowband Technology • Spread Spectrum Technology • Frequency-Hopping Spread Spectrum Technology • Direct-Sequence Spread Spectrum Technology • Infrared Technology

  22. NARROWBAND TECHNOLOGY • Transmits and receives user information on a specific radio frequency • keeps the radio signal frequency as narrow as possible • Radio receiver filters out all radio signals except the ones on its designated frequency • Example: private telephone lines

  23. SPREAD SPECTRUM TECHNOLOGY • Mostly used in wireless LAN system • Trades of bandwidth efficiency for reliability, integrity, and security • Signal looks like background noise if not turned to the right frequency

  24. FREQUENCY-HOPPING SPREAD SPECTRUM TECHNOLOGY • Uses a narrowband carrier that changes frequency in a pattern known to both transmitter and receiver • Maintain a single logical channel

  25. FREQUENCY-HOPPING SPREAD SPRECTRUM TECHNOLOGY (con’t) Source: www.wlana.com

  26. DIRECT-SEQUENCE SPREAD SPECTRUM TECHNOLOGY • Generates a redundant bit (chip) pattern for each bit to be transmitted • The longer the chip, the greater the probability that the original data can be recovered • To unintended receivers: • Viewed as low-power wideband noise • Rejected by most narrowband receivers

  27. DIRECT-SEQUENCE SPREAD SPECTRUM TECHNOLOGY (con’t) Source: www.wlana.com

  28. INFRARED (IR) TECHNOLOGY • Little used in commercial wireless LANs • Use very high frequencies • Inexpensive, but provide very limited range (3ft) • Typically used for personal area networks • Used only to implement fixed subnetworks

  29. WIRELESS STANDARD • IEEE 802.11 • represent the 1st standard for wireless LAN • standardize radio equipment and networks operating system for wireless LAN • Addresses for: • Physical (PHY) layer • Media Access Control (MAC)

  30. CONFIGURATION • Peer-to-peer network • Client and Access point • Multiple access points and roaming • Using an extension point • Using directional antennas

  31. PEER-TO-PEER NETWORK • Wireless adapter cards • Connect 2 PCs • Client access only to each other, not with a central server Source: http://www.proxim.com

  32. CLIENT & ACCESS POINT (AP) • Access point • Must be wired to the network • Extend the range of the network • Allow access from client-to-server and among each workstation • Real-world: each Access Point can accommodate from 15-50 client devices Source: http://www.proxim.com

  33. MULPTIPLE AP & ROAMING • In large facility, more than one AP might be needed to coverage the whole area • Access Point range: • Indoor = 500 ft; Outdoor = 1,000 ft Source: http://www.proxim.com

  34. EXTENTION POINT (EP) • EP can be connected to the network without wiring. • EP extend the range of the network by relaying signals from a client to an AP or another EP. Source: http://www.proxim.com

  35. DIRECTIONAL ANTENNAS • Extend the wireless networks between buildings • Antenna must be connected to an AP of the network Source: http://www.proxim.com

  36. PHYSICAL LAYER

  37. MEDIUM ACCESS CONTROL • A collision may occur when 2 stations transmit data simultaneously • Detects the collision and ignores the message • Each station that wants to transmit waits a random amount of time and then attempts to transmit again • The random transmission delays reduce the probability that the stations will transmit simultaneously again.

  38. DIFFERENCES BETWEEN WIRED LAN AND WIRELESS LAN

  39. WIRED vs. WIRELESS LAN WIRED • Wired • Link clients, printers, and network equipment using cables • Wireless • Basic building block is the Cell WIRELESS Source: www.breezecom.com

  40. WIRE vs. WIRELESS (con’t) • Bridging • Wired • Access point connects to the backbone of a wired Ethernet LAN via a simple cable • Wireless • can be mounted back-to-back with an access point • Able to link buildings that are miles apart Source: www.breezecom.com

  41. WIRED vs. WIRELESS (con’t) • Cells • Linked Cells (Wired) • user can walk from Cell A to overlap Cell B without interrupting a work session • Multi-cells (Wireless) • Position Access Points at different locations in the coverage areas with their directional antennas Source: www.breezecom.com

  42. WHEN DO YOU NEED WIRELESS LAN TECHNOLOGY?

  43. WHEN? • When you truly need mobility • When you plan to move or remodel soon • When set up a portable buildings for temporary use • When you don’t have time to configure and maintain a wiring scheme • When running cable is too expensive

  44. Cost-Benefit Study

  45. COST-BENEFIT STUDY • 89% successful implementation • 92% of respondents believe the definite economic and business benefit after installation • 92% continue to deploy wireless technology in their network • Payback was less than 1 year across all industries surveyed. Source: www.wlana.com

  46. COST/BENEFIT STUDY (con’t) • Economic Benefits • Payback Source: www.wlana.com

  47. COST/BENEFIT STUDY (con’t) • Broad cross-section of the representative industries with successful implementation of wireless LAN • Education: 23% • Healthcare: 23% • Manufacturing/Warehouse: 21% • Retail: 15% • Financial/Office Automation: 18% Source: www.wlana.com

  48. Wireless LAN Market

  49. WIRELESS LAN MARKET • Customer considerations • Range and coverage • Throughput • Compatibility • Interoperability • Interference and Coexistence • Licensing issues • Simplicity • Security • Cost • Major vendors • Scalability

  50. Customer Considerations