Docstoc

wlan

Document Sample
wlan Powered By Docstoc
					Wireless LAN Technology

           Chapter 13
      Chapter 10 (Pahlavan)
Wideband local wireless networks
 WLAN
   Coverage area
   Data rate
   Batter consumption
   IEEE 802.11 and HIPERLAN
 WPAN
   IEEE 802.16, Bluetooth, HomeRF
 Data-oriented and voice-oriented MAC
History of LAN Industry
 WANs are offered as service
   Cost of infrastructure
   Coverage area
 LANs are sold as “end products”
   You own, no service charge
   Analogy with PSTN/PBX
LAN History-2
 Emerged to enable sharing of expensive resources
 such as printers & to ease wiring problems
 Early 1980s: Three standards are developed
   802.3 (Ethernet)
   802.4 (Token Bus)
   802.5 (Token Ring)
 Distinct PHY and MAC layers & topologies, but same
 management and bridging
 ~1985: Think coax      Thin coax   TP wiring
 Shorter segments, but ease of installation, lower
 cost, increased data rate
            500 m per segment                                                185 m per segment

                         Thick coax            Terminator              Thin coax with
                                       MAU                            BNC T-connector
         MAU          MAU
            AUI cable

                                                                          10 Mbps clients        Server


    10 Mbps clients
                                                            Thin Coax Cheaper-net Installation
                                      Server
Thick Coax Installation

                                               100 m UTP
MAU: Medium Attachment Unit
                                                             10BASE-T Repeater
AUI: Attachment Unit Interface
UTP: Unshielded Twisted Pair                                                Hub-and-Spoke Architecture

                                                                 Server




     Figure 10.1: Evolution of the LANs from thick to thin cable and then to star topology using TP.
Need for higher data rates
 Thick/Think/TP ~ 10Mbps
 Interconnect LANs in different buildings to
 share computing resources
 High speed multimedia applications
 Interconnect LANs
 FDDI (fiber distributed data interface): 100
 Mbps in mid-1980
 Mid-1990: 100 Mbps fast Ethernet (802.3)
 Mid-1990: 100VG-AnyLAN (802.12)
 Late-1990: Gigabit Ethernet (802.3)
Backbone Network


                                 Router




                   Figure 10.2: Hierarchical LANs
LAN History-3
 Mid 1990: ATM LAN (LANE) Emulation
 IEEE 802 Standards
  802.3, 802.4, 802.5 are wired LANs
  802.9: ISO Ethernet
  802.6: MAN
  802.11, 802.15, 802.16: Wireless local net
  802.14 Cable modem
  802.10 Security management
IEEE 802.10 Security




                                                                                                           Higher Layers
                       802 Overview and Architecture




                                                                                                  IEEE 802.2 Logical Link Control
                                                       IEEE 802.1 Management




                                                                                                          IEEE 802.1 Bridging

                                                                               802.3   802.4    802.5   802.6   802.9 802.11 802.12 802.14 802.15 802.16
                                                                               MAC     MAC      MAC     MAC     MAC    MAC    MAC    MAC    MAC    MAC



                                                                               802.3   802.4    802.5   802.6   802.9 802.11 802.12 802.14 802.15 802.16
                                                                                PHY     PHY      PHY     PHY     PHY   PHY    PHY    PHY    PHY    PHY




                                                                                               Figure 10.3: IEEE 802 Standard Series
WLAN Industry
 WLAN vs. WAN Cellular Networks
   Data rate (2 Mbps vs. 54 Mbps)
   Frequency band regulation (Licensing)
   Method of data delivery (Service vs. own)
Early Experiences
 IBM Switzerland
    Late 1970
    Factories and manufacturing floors
    Diffused IR technology
    Could not get 1 Mbps
 HP Labs, Palo Alto
    1980
    100 Kbps DSSS around 900 Mhz
    CSMA as MAC
    Experimental licensing from FCC
    Frequency administration was problematic, thus abandoned
 Motorola
    ~1985
    1.73 GHz
    Abandoned after FCC difficulties
What we learned
 Complexity and cost
 Bandwidth
 Coverage
 Interference
 Frequency administration
Unlicensed Bands
 FCC dilemma
   WLAN requires ~o(10 MHz)
   WWAN uses 2*25 MHz     tens of billions
 FCC solutions (mid 1980)
   Avoid 1-2 GHz, approve higher frequencies
   Motorola Altair (18-19 GHz)
   Release unlicensed frequency bands
     ISM bands (May 1985)
     Public vs private public use etiquette
Products, Bands, Standards
 By late 1980s, products with diff. tech.
   18-19 MHz licensed bands
   Spread spectrum technology in ISM bands
   IR
 802.4L 802.11
 Shoe-box sized APs (LAN extension)
 LAN WLAN did not materialize
More bands
 WINForum created to obtain more
 license from FCC
   20 MHz in PCS band
   10 for voice, 10 for data
   Rules (based on CSMA)
     Listen before talk
     Low transmit power
     Restricted duration
                     Three basic rules
     1. Listen before talk (or transmit) LBT Protocol
                2. Low transmitter power
          3. Restricted duration of transmissions




Figure 10.4 Unlicensed PCS Bands and their Spectrum Etiquette
Even more bands
 1992 HIPERLAN completed
 23 Mbps
 200 MHz, 5.15-5.35 & 17.1-17.3 GHz
 FCC responded by U-NII bands in 1997
 OFDM based WLANs
Shift in Marketing
 Early 1990’s expectation of LAN WLAN shift
 did not happen
 Two new directions
 1: Boost the power, directional antennas
   Cross-building interconnect
   Alternative (T1) were expensive
   Range is fairly good (Tens of kms)
 2: Reduce the size to PCMCIA card
   Targeted for notebooks
   Use SS, low power, unlicensed bands
                                       Building Cross-connect




                                                                        (b)
PCMCIA cards and
   Laptops
                                    Wired Backbone
     (c)




                              (a)                    Shoebox type LAN
                                                        Extension




                      Figure 10.5 Different forms of WLAN products
           (a) LAN-Extension (b) Inter-LAN Bridge (c ) PCMCIA cards for laptops
Shift in Marketing
 Horizontal vs. vertical integration
 Traditionally horizontal (end products)
 New vertical markets (solutions)
   Barcode industry
   Financial services
   Health care
   WCANs
 Horizontal markets now….
New Interest from Military
 Mid-1990
 InfoPAD
 BodyLAN
 SUO/SAS
Figure 10.7: Fusion of Computers and Communications in the
InfoPAD project at the University of California, Berkeley.
Figure 10.8: Body LAN or Wearable LAN
Figure 10.9: The urban/outskirts combat scenario for the SUO-SAS project
New Interest in EU
 Incorporate into cellular industry
 ATM-based vision
 HIPERLAN-2
Explosion in 2000
 Japan
   Small office sizes
   Laptops replacing PCs
 EU
   WLAN is seen part of the WWAN Cellular
   Unlicensed, high-data rate
 US
   Broadband Internet access
   Home networking
 Low-power personal networking devices
To fixed network


Connection
Point




         Intelligent Office                  Smart Home




TODAY!
Win $ 1000

             Ad hoc setup
                              WLAN                   Position Location


               Figure 10.11: Wireless Networks: 2000 and Beyond
Wireless Home Networking
        PSTN
                     Telephone
                     Wiring



                  Virtual connection
    Internet     Cable, xDSL,
                 Voiceband modem




                       Cable or
   Cable Net           Satellite




Figure 10.12: Today’s fragmented home access and distribution networks
12

10        Almost doubles each year
 8

 6                                                     No. of Homes

 4

 2

 0
 1998     1999   2000    2001   2002    2003   2004



        Figure 10.13: Growth of the home networking industry
Internet

             Broadband
            Home-Access



                                  Broadband Home-Distribution
                                  or Home Area Network (HAN)



 Figure 10.14: Two basic technologies needed for home networking
What is a HAN?
                                                                                   Location /
                                                                                   Navigation
                                            Phone appliances                       locating children and
                                            Standard phone                         pets
                                            Inter Comm                             navigating handicaps
                                            Cordless phone
Home Computing                                                 Entertainment
Desktop computer                                               Audio/Visual
Laptop                                                         appliances
Printer
                                        Security               Analog/Digital TV
Scanner                                 Systems                VCR / DVD
QuickCam                                Motion detectors       Camcorder
                                        Door pins              Stereo system
                   Smart appliances     System control         Speakers / Headphones
                   Oven(s)              unit
                   Fridge(s)            Camera                                   Utility metering
                   Washing machine(s)   Alarm                                    Electricity
                                                                                 Gas
                   PROGRAM
                                                                                 Fuel
                                                                                 Water




  Figure 10.15: Classification of home equipment demanding networked operation
Why do we need a HAN?
 LANs do not provide a good solution
   Applications diversity
   Number of users
   Bandwidth requirements
   Coverage area
   System administration
   Installation and maintenance
HAN Technologies
 TP phone lines
    Relatively good distribution
    Suitable for Ethernet connection
    Also used for phone and xDSL
 Cable from cable TV
    Poor distribution
    Used for multi-channel TV signal distribution
    Cable-modems are required
 Power lines
    Excellent distribution
    Line quality is poor
    Frequency selective channel & impulse noise
    Data-rate limitations and complex DSP
 Wireless
    Ideal
    Bandwidth, coverage, security, interference, reliability etc.
HPNA
 Ethernet compatible LAN over home phone
 lines
 Stand-alone adapter to connect to any device
 with 10Base-T interface to phone jacks
 Shares the medium through FDM
 Up converts the Manchester coding to HPNA
 band
 MAC layer is the same as 802.3
 Incorporates the legacy hardware and
 software
                                                   Network camera
                      Home Gateway                                                Laptop

 Internet



            Desktop                        telephone




                           Multimedia PC
Printer
                                               Webphone



                                                                    TV and Set-Up Box
   Camera
                      Scanner




              Figure 10.17 An example of a HPNA network
Figure 10.18: Phone line wirings shared among three technologies using FDM.
(a) POTS uses 20 Hz – 3.4 kHz (b) xDSL uses 25 kHz – 1.1 MHz, and
(c) HomePNA uses 2 MHz – 30 MHz
Power Line Modems
 1 Mbps type rates
 AM band is avoided
 Some use in smart appliances
 Interference, noise, multi-path, fading makes
 it a challenging medium
 FSK and QPSK is used for low-rates
 OFDM for high rates
 CSMA is used as MAC
Figure 10.16: (a) Typical Power line transfer function (b) Typical noise level in the
power lines
            Narrowband
            applications
                                         Wideband applications




                       AM radio




                 3 kHz - 148.5 kHz (EU) HF band (1 - 30 MHz)     frequency
                 9 kHz - 490 kHz (US)




Figure 10.19: Frequency bands for low- and high-speed data communications over power
                                        lines.
                        Electric Company
 Internet               Local Transformer
                       Meter reading
                       communications through outside AC
                       lines to the meter


                                     Head
                                                                 Control network
                                control/security                 on/off, light dimmer,
  xDSL modem
                                                                 HVAC control
Voice band modem
  Cable modem




                                                                                    Smart appliances
                                                                                    Sense other appliances on the
                                                                                    power lines, breakdown
                                                                                    alert, access through web
                                                                                    site, email
                   High speed
                   computing               Security systems                                             PROGRAM
                   Sharing Internet
                                           Sensors network
                   connection,
                                           through power lines
                   file transfer,
                   share printer




                       Figure 10.20: Power lines potential applications
                                 Home Server
                   Security

                                                HPNA
                 Cable,
                 xDSL,
Internet
                 v.90


                                               Home RF



                              Power Line
                   PROGRAM




           Figure 10.21: Evolving Home Area Networks (HAN)
   • Wireless
             • 802.16
                                                                     Digital
             • HIPER-ACCESS
                                                                   Broadcast
             • DBS                                                  Satellite
   • Wired
             • xDSL
             • Cable Modem




                                                                     Wireless
Hybrid Fiber-Coax Network                       PSTN




                Figure 10.23: Broadband home access alternatives
                                                     Grandma’s Brownies


HomeRF SWAP
                                                   3 cups flour
                                                   1 cup grated
                                                   chocolate
                                                   1 cup sugar
                                                   1 stick butter




                  Control Point

          USB                                                             Phone

                                                                          Cable
                Camera      Game Pad          Printer
   1394




     Stereo      Camcorder           VCR              TV
                     Multimedia (e.g. 1394)



                                                HomePNA




Figure 10.22: Vision of the Home RF group at IEEE 802.15.

				
DOCUMENT INFO
Shared By:
Stats:
views:23
posted:1/25/2012
language:
pages:45