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Wireless Networking. WiFi 802.11b/g/a Bluetooth 3G PCS 802.11s Mesh. WiFi 802.11b/g/a. Introduction RF Bands 802.11b WLAN IN-BUILDING WLAN BUILDING-BUILDING Equipment Site Survey Security Future. INTRODUCTION. What is a Wireless LAN?. Ethernet.

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Wireless Networking


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    Presentation Transcript
    1. Wireless Networking • WiFi 802.11b/g/a • Bluetooth • 3G PCS • 802.11s Mesh

    2. WiFi 802.11b/g/a • Introduction • RF Bands • 802.11b • WLAN IN-BUILDING • WLAN BUILDING-BUILDING • Equipment • Site Survey • Security • Future

    3. INTRODUCTION

    4. What is a Wireless LAN? Ethernet 10/100 Mbps Shared Bandwidth (CSMA/CD) Hub/ Switch Internet Ethernet 11 Mbps Shared Bandwidth (CSMA/CA) Access Point

    5. In-Building WLANs WLAN Product Categories Building-to-Building WLANS

    6. Wireless Bridging LAN-to-LAN connectivity Wireless Networking Mobile user connectivity Two Different Implementations of Wireless LAN Technology

    7. High-Speed Access Anywhere, Anytime Ethernet Everywhere At Home At School On the Road At Work Environments Solutions and Building Blocks Wireless Switches Security Access Ethernet Technologies Layer 3 Switched Ethernet Wireless Ethernet 10/100 Ethernet Gigabit Ethernet Long-Reach Ethernet

    8. Local Area Network (LAN) Wireless LAN (WLAN) as an extension to wired LAN Hub Hub Access Point Server Switch Internet Work Group Bridge

    9. Typical WLAN Topologies Wireless “Cell” Wireless “Cell” Channel 1 Channel 6 LAN Backbone Access Point Access Point Wireless Clients Wireless Clients

    10. Wireless Repeater Topology Wireless Repeater “Cell” Channel 1 LAN Backbone Channel 1 Access Point Access Point Wireless Clients

    11. Work Group BridgeApplication Access Point Hub WGB Server

    12. RF BANDS

    13. 902-928 MHz 26 MHz 2.4 – 2.4835 GHz 83.5 MHz (IEEE 802.11) 5 GHz (IEEE 802.11) HyperLAN HyperLAN2 ISM Unlicensed Frequency Bands Short Wave Radio FM Broadcast Infrared wireless LAN AM Broadcast Television Audio Cellular (840 MHz) NPCS (1.9GHz) Extremely Low Very Low Low Medium High Very High Ultra High Super High Infrared Visible Light Ultra- violet X-Rays

    14. 900 MHz vs. 2.4 GHz vs. 5 GHz 900 MHz band 2.4 GHz band 5 GHz band Global market IEEE 802.11 Higher data rates (10+ Mbps) Global market IEEE 802.11 Higher data rates (20+Mbps) Greater range than 2.4 GHz band ( for in- building LANs) PROs Much less Range than 900 MHz or 2.4 GHz Higher cost RF components Large antenna required Maximum data rate 1 Mbps Limited bandwidth Crowded band Less range than 900 MHz (for in-building LANs) CONs

    15. What Is Spread Spectrum RF Technology? • Data sent over the air waves • Two-way radio communications (half duplex) • Cisco designs and manufactures its own radios • Same radio frequency for sending & receiving (transceiver) • No licensing required for Cisco Aironet Wireless products

    16. 802.11b

    17. IEEE 802.11 Standard • IEEE 802.11 became a standard in July 1997 • Infrared • RF • Two RF technologies defined: • Direct sequence spread spectrum - 1 Mbps and 2 Mbps • Frequency hopping spread spectrum - 1 Mbps and 2 Mbps • IEEE 802.11b became a standard in September 1999 • Only one RF technology defined- DSSS at 5.5 Mbps & 11 Mbps • 802.11 defines a high-performance radio • 802.11 promises “true” vendor interoperability (over the air)

    18. Interoperability • 802.11 covers RF connectivity, association processes, and modulation schemes • Does not cover AP-to-AP connectivity over the wired network, roaming, load balancing, or repeaters • These features are vendor specific and proprietary • Choose a single vendor for the wireless backbone

    19. Cisco Radio Technology • Direct Sequence Spread Spectrum (DSSS) • 2.4 GHz • One piece PCMCIA radio product • 1, 2, 5.5 and 11 Mbps • Fully 802.11 compliant at all speeds

    20. POWER Frequency not used Frequency not used 1 Sec TIME 1 Mw 100 Mw 1 Ms Mhz Mhz 22 2.402 GHz FREQUENCY 2.483 GHz Spread Spectrum Approaches Direct Sequence Frequency Hopping Both technologies are viable.

    21. Channels- 802.11 DS Channel 10 5 4 9 • (11) 22 MHz wide stationary channels • X “chips per bit” means each bit sent redundantly • 11 Mbps data rate • 3 non-overlapping channels • 3 Access Points can occupy same area 3 8 2 7 1 11 6 2400 2437 2483 Frequency

    22. Frequency Hopping 9 8 7 6 Time 5 • A total of 79 channels, available • Changes frequency (hops) at least every 0.4 seconds • Synchronized hopping required 4 3 2 1 2.400 GHz 2.483 GHz Frequency

    23. Frequency Hopping Direct Sequence 2.4835 GHz 3 2.4835 GHz Channel 11 2 Channel 6 Frequency Frequency 1 Channel 1 2.400 GHz 2.400 GHz DS vs. FH: A Summary on Interference Handling Time • FH system hops around interference • Lost packets are re-transmitted on next hop • Data may be decoded from redundant bits • Can move to an alternate channelto avoid interference

    24. Access Point Coverage 1Mbps DSSS 2 Mbps DSSS 5.5 Mbps DSSS 11 Mbps DSSS

    25. Moduation Profiles 1 Mbps DBPSK Diff Binary Phase Shift Keying2 Mbps DQPSK Diff Quad Phase Shift Keying 5.5 Mbps CCK Complementary Code Keying 11 Mbps CCK Complementary Code Keying Higher data rates use less reliable modulation profiles and require stronger received signal strength to operate properly. Tradeoff between speed and reliability. Minimal Required Signal Strength for Aironet 350: 1 Mbps -94 dBm 2 Mbps -91 dBm 5.5 Mbps -89 dBm 11 Mbps -85 dBm

    26. Scalability With Direct Sequence Blue = 11Mb Total Bandwidth=33Mb!!! Green = 11Mb Red = 11Mb

    27. Channel 1 Channel 11 Channel 6 Channel 11 Channel 6 Channel 6 Channel 1 Channel 11 Channel 1 Channel 11 Channel Setup Site Survey Channel Example

    28. Access Point Coverage & Data Rate Shifting Review 1 Mbps DSSS 2 Mbps DSSS 5.5 Mbps DSSS 11 Mbps DSSS

    29. 2 Mbps 2 Mbps 2 Mbps 2 Mbps 2 Mbps 5.5 Mbps 5.5 Mbps 5.5 Mbps 5.5 Mbps 5.5 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 5.5 Mbps 5.5 Mbps 5.5 Mbps 5.5 Mbps 5.5 Mbps 2 Mbps 2 Mbps 2 Mbps 2 Mbps 2 Mbps Multi-rate Implementation Site Survey Bandwidth Example

    30. 350 (100mW)Cell Size Comparison 100 milli-Watt client and Access Point range capabilities 11 Mbps DSSS 100-150 feet radius 5.5 Mbps DSSS 150-250 feet radius 2 Mbps DSSS 250-350 feet radius

    31. WLAN IN-BUILDING

    32. Scalability Requirements for WLANs • Robust roaming for seamless handoff between access point • Centralized user-based authentication • Dynamic WEP key distribution and management • Subnet roaming • Client support for all popular operating systems

    33. WLAN Topologies Multiple AP’s with roaming Redundant WLAN Wireless Repeaters

    34. Rate Shifting • Survey performed at each data rate • Coverage cell for each rate mapped • Higher rates – shift to proper areas • Lower rates – overlap and frequency 2 Mbps 2 Mbps 2 Mbps 2 Mbps 2 Mbps 5.5 Mbps 5.5 Mbps 5.5 Mbps 5.5 Mbps 5.5 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 11 Mbps 5.5 Mbps 5.5 Mbps 5.5 Mbps 5.5 Mbps 5.5 Mbps 2 Mbps 2 Mbps 2 Mbps 2 Mbps 2 Mbps

    35. Wireless Office Maximum Coverage Auto Rate Negotiation Wireless Mobile Workers DiPole Antennas AP’s on Isolated LAN with PIX Class 1 1 6 11 1 Office 1 Office 2 Office 3 Office 4 Office 5 Office 6 Office 7 Office 8 850’ Hallway Office 9 Office 10 Office 11 Conference Room Break Room 11 1 6 11 2000’

    36. Indoor/Outdoor Coverage Maximum Coverage Auto Rate Negotiation Wireless for Mobile Workers DiPole Indoor, Patch Outdoor AP’s on Isolated LANwith PIX 11 1 6 Office 1 Office 2 Office 3 Office 4 850’ Hallway Break Room Conference Room 11 1 6 Building Courtyard 1000’ 1000’

    37. 1 11 6 1 6 1 11 6 Warehouse Design Sample Maximum Coverage Auto Rate Negotiation Cabling Available to Middle of Room High Gain Mast Mount Antennas 850’ 2000’

    38. WLAN BUILDING-TO-BUILDING

    39. Objectives • Upon completion of this chapter, you will be able to perform the following tasks: • Determine the feasibility of installing a wireless bridge link. • Explain why a wireless bridge may be a better solution than other alternatives. • Determine the maximum distance that can be achieved using wireless bridges with given antennas and extension cables. • Protect a wireless bridge installation against a lightning strike.

    40. Bridging Defined

    41. Wireless Bridge Alternatives Medium Drawbacks Monthly costs Phone lines Slow Installation costs Extra equipment needed (56K, T1) Installation costs Physical barriers may preclude Cable Inflexible FCC Licensing required Microwave Difficult installation High cost

    42. Point-to-Point Configuration Building A Building B Optional Antenna Optional Antenna 0 to 25 miles (line of sight) Bridge Ethernet

    43. Point-to-Multipoint Configuration Ethernet Building A Bridge Omni-directional Antenna Building B Building C Directional Antenna Directional Antenna

    44. Optional Antennas for Long Range 13.5dBi Yagi Distances over 6.5miles @ 2Mbps and 2miles @11Mbps 21dBi Solid Dish For distances up to 25+ miles @ 2Mbps 11.5miles @ 11Mbps Note: Distances include 50 feet of low loss cable and 10dB fade margin

    45. 340 Wireless Bridge How Fast? Max data rate 11 Mbps 2 Mbps Typical throughput 5.5 Mbps 1.4 Mbps How Far? (at MAX rate) 2 Miles 6.5 miles Yagi antenna Dish antenna 11.5+ Miles 25+ miles Common Questions

    46. Channel #1 Channel #6 Channel #11 Bridge Application: School District Richardson Elementary Yagi Weaver- Special Education Dish Roberts Middle School Dish High School 2 Bridges One 12dB omni One Dish Bode Elementary Yagi Lincoln Elementary Yagi Administration 2 Bridges One 12dB omni One Yagi Bolich Middle School Yagi Price Elementary Yagi Dewitt Elementary Yagi

    47. Bridge Ethernet Lightning • Static Electricity • Wind • Nearby Strikes

    48. 22 miles? Path Loss Considerations How far will it go?

    49. Calculations of Coverage Performance Coax Length 100ft? Towers needed to clear trees and other buildings Coax Length 150ft? Wants 11Mb datarate Distance =13miles

    50. Calculations of Coverage Performance