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W&M 2009 – 4th generation wireless – building for the future

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Transcript

  • 1.
    • 4th Generation Wireless
    • Building for the Future
    Dave Crowder – Senior Systems Engineer
  • 2. Agenda
    • Evolution of Wireless
    • The Challenges of Ordinary Wireless
    • Business Benefits and Cost Savings of 4th Generation Architectures
    • 4th Generation Wireless and 802.11n
  • 3. Evolution of Wireless Controller Controller AP AP AP AP AP Pre-standard AP Autonomous Centralized Microcell Centralized Virtual Cell AP Fourth Generation Third Generation Second Generation First Generation
  • 4. Challenges of Ordinary Wireless
    • Co-channel interference
    • Contention for shared medium
    • Clients control association
    • Lack of QoS / Fairness
  • 5. Co-Channel Interference Signal Strength Distance There are 3 non-overlapping channels in 2.4GHz (Ch 1, 6, 11) -68dBm -95dBm 54Mbps 1Mbps x x x x x x
  • 6. Contention for Shared Medium Number of Contenders (Devices in interference range ) 20 Total Bandwidth at Peak 3 Baseband + Protocol overhead Peak Aggregate Throughput in Single Cell Environment
    • Contention Limits Throughput and User Density in Traditional 802.11 Networks
    • Peak aggregate capacity with 3 or fewer contending stations
    • Very limited user density
      • Capacity drops precipitously with ~10 contending stations
      • Effective lack of connectivity with 20 stations
    • CSMA (Ethernet and 802.11) designed for low contention and low load
    • Contention penalty in 802.11 is even worse because there is no collision detection; all transmissions must be acknowledged
    Standard CSMA Curve Contention Loss
  • 7. Clients control association
  • 8. Airtime Fairness and QoS ‘ g’ client ‘ g’ client ‘ g’ client
  • 9. Airtime Fairness and QoS ‘ g’ client ‘ b’ client ‘ g’ client
  • 10. Challenges of Ordinary Wireless
    • Co-channel interference
    • Contention for shared medium
    • Clients control association
    • Lack of QoS / Fairness
  • 11. 4 th Generation Wireless
  • 12. 4 th Generation Wireless
    • Optimised coverage
    • No co-channel interference
    • Ease of deployment and upgrade
  • 13. 4 th Generation Wireless Number of Contenders (Devices in interference range ) 20 Total Bandwidth at Peak 3 Baseband + Protocol overhead Peak Aggregate Throughput in Single Cell Environment 100+ simultaneous connections per access point Standard CSMA Curve Contention Loss
  • 14. 4 th Generation Wireless
  • 15. 4 th Generation Wireless ‘ g’ client ‘ b’ client ‘ g’ client
  • 16. 4 th Generation Wireless ‘ b’ client ‘ g’ client ‘ g’ client
  • 17. 4 th Generation Wireless ‘ b’ client ‘ n’ clients
  • 18. 4 th Generation Wireless- Summary
    • Ease of deployment, upgrade and maintenance (lowest TCO)
    • Optimal throughput, even with dense deployments
    • Seamless roaming
    • Multi-application QoS / Legacy client support
  • 19. 4 th Generation and 802.11n
    • Benefits of 802.11n :
    • Improved network throughput
    • Improved (but less predictable) coverage
    • Opportunities from 802.11n :
    • Access layer connection
    • Substitute for desktop cabling?
  • 20. 4 th Generation and 802.11n *2.4 GHz 165 UNI I UNI II UNI III Unavailable Frequencies Channel Selection Options for 802.11abgn
    • Only 3 x40-Mhz channels in 5Ghz range (11a)
    • Only 1 x40-Mhz channel in 2.4 Ghz Range (11 b/g)
    Available Spectrum 20MHz 802.11abg Choices 40MHz 802.11n Choices 64 64 11* 11* 11* 11* 1, 6* 1, 6* 1, 6* 1, 6* 157, 161 149, 153 157, 161 149, 153 60, 64 60, 64 52, 56 52, 56 44, 48 44, 48 36, 40 36, 40 36 40 44 48 52 56 60 64 149 153 157 161
  • 21. 4 th Generation and 802.11n
    • Initial planning and optimization difficult
    • Fixing coverage holes requires re-planning and “domino effect” of changing channel plans
    • Not possible to fix co-channel interference issues in multi-floors
    X Office Floor Office Floor Current Technology 4 th Generation Solution
    • No channel planning needed
    • Deploy APs based on rule-of-thumb (e.g. 80 feet in office cubes)
    • Any coverage holes easily fixed without re-planning
    • Packet-access-level coordinated AP mitigates co-channel interference
    Traditional WLANs
  • 22. Meru Networks
    • Fastest Growing Wifi Vendor
    • Leading 4 th Generation Wifi Vendor
    • Gartner’s “most visionary”
    • Thousands of deployments worldwide
    • Hundreds of UK deployments (education, healthcare … )
  • 23. Thank You Dave Crowder – Senior Systems Engineer http://www.merunetworks.com

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