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The Network Beacon Announcement scanning method

The Network Beacon Announcement scanning method. Dirk Kuijsten University of Amsterdam Dirk.Kuijsten@student.uva.nl Prof.dr. R.J. Meijer , UvA, TNO Telecom rmeijer@science.uva.nl. Outline. Introduction Network Beacon Announcement Time synchronization Results Analysis Conclusion

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The Network Beacon Announcement scanning method

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  1. The Network Beacon Announcement scanning method Dirk Kuijsten University of AmsterdamDirk.Kuijsten@student.uva.nlProf.dr. R.J. Meijer, UvA, TNO Telecomrmeijer@science.uva.nl D. Kuijsten, University of Amsterdam

  2. Outline • Introduction • Network Beacon Announcement • Time synchronization • Results • Analysis • Conclusion • Questions D. Kuijsten, University of Amsterdam

  3. Introduction • Current method’s disadvantages: • Non-directed search • STA Probe request: power intensive • Probe request medium access: • Interruption by client data transmissions • Not determined D. Kuijsten, University of Amsterdam

  4. Network Beacon Announcement • Current AP requests Beacons on other APs • AP transmits information to STA • Channel, other AP MAC address, Beacon time • Client performs passive scan • Beacon transmission time within a error margin defined by the time sync accuracy between the APs D. Kuijsten, University of Amsterdam

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  15. Time synchronization • Only between APs • Using NTP: <1ms possible on LAN networks • Or use external time source • Common backbone networks • CDMA / UMTS / Wi-Max • GPS, radio D. Kuijsten, University of Amsterdam

  16. Results • Reference implementation works on Linux • Scanning speed of around 5 ms • Possible speeds of 1 ms measured D. Kuijsten, University of Amsterdam

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  19. Analysis - Advantages • Simultaneous STA scans possible if AP sends NBA info in broadcast • Embed STA MAC in info to require STA to start scan • Other STAs are free to start scan • Passive scan • Other APs can use QoS to reserve the beacon frame transmission in advance: transmit time guaranteed • Old AP can know client state: buffer frames, IAPP proactive caching, pre-keying D. Kuijsten, University of Amsterdam

  20. Analysis - Disadvantages • More complex • Extra requirements for wired network • Simultaneous STA scans: for STAs that are free to start a scan: scanning/idle state unknown • STA can miss beacon if time sync error is large; time range could be defined dynamically • STA connection required before start scan D. Kuijsten, University of Amsterdam

  21. Analysis - Usage model • Voice Over WLAN usage models needed • Simulation of multiple handoffs: • 2 VOIP calls moving through the network • Performance of Network Beacon Announcement scan vs. other methods: • Loss of signal detection • Scanning speed • Overall higher layer latency • Number of lost packets D. Kuijsten, University of Amsterdam

  22. Conclusion • Fastest scan possible • Power efficient • Simultaneous scans • Network management with more client scans • Works on current hardware • Can be improved with new firmware • Can be improved with dedicated timing hardware (from external time sources) D. Kuijsten, University of Amsterdam

  23. Questions? D. Kuijsten, University of Amsterdam

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