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WLAN network behavior under heavy load

WLAN network behavior under heavy load. Date: 2013-07-15. Authors:. Abstract. This is background submission for 802.11HEW SG in Genova July 15 th -19 th

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WLAN network behavior under heavy load

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  1. WLAN network behavior under heavy load Date: 2013-07-15 Authors: Veli-Pekka Ketonen (7signal)

  2. Abstract This is background submission for 802.11HEW SG in Genova July 15th-19th This material includes data from Avans University of Applied Sciences WLAN network in learning centre area. This material is based on a the trial report submitted to Avans University Purpose of this submission is to share information on current WLAN performance and behaviour under high load Veli-Pekka Ketonen (7signal Solutions)

  3. The key message • WLAN network engineers struggle today to maintain Quality of Experience and network performance on the required level • Maintaining the target level is difficult because: • There is no sufficient capability to assess the QoE network offers at certain time with meaningful metrics’ • There is no sufficient capability to set a target level and compare network delivery against that level • Without automating these capabilities, validating design & maintaining and operating WLAN networks continues to rely in manually made individual measurements. At the same time network QoE and behavior varies significantly every day, hour and minute Veli-PekkaKetonen (7signal Solutions)

  4. Avans University of Applied Sciences, Netherlands Trial Report Baseline Performance prior to Optimization March 21st, 2013 Veli-PekkaKetonen (7signal Solutions)

  5. Eye Location: Floor 1 –Learning Center First Floor: 7signal Eye 1 2 6 5 3 4 Veli-PekkaKetonen (7signal Solutions)

  6. 2.4 GHz Eduroam SLA Table Off-peak Hours / On-peak Hours Comparison Network performance is insufficient during weeks and especially during the daytime Weekend Busy-Hours (9:00–15:00) SLA Target limits Weekend • The following daily average metric’s do not meet target: Client attach success rate, Latency, FTP Throughputs DL/UL, VoIP MOS DL/UL scores Veli-PekkaKetonen (7signal Solutions)

  7. 2.4 GHz band end-to-end Quality of experience Veli-PekkaKetonen (7signal Solutions)

  8. 2.4 GHz Attach Success Rate (Daily Average) Target level 90% AP 1080 not accessible • At times, attach success rate seems to to drop to zero with for example AP001080, even though the radio is active and sending beacons. (This needs to be studied in more detail) Veli-PekkaKetonen (7signal Solutions)

  9. 2.4 GHz Attach Success Rate (One Week, hourly) Target level 90% Weekend Busy Hour effects on attach success rates • Attach success rate degrades significantly during high load • AP 1082 does allow Eye connections. (This needs to be studied in more detail) Veli-PekkaKetonen (7signal Solutions)

  10. 2.4 GHz Downlink Throughputs, daily Weekend • Daily average values are on acceptable level Veli-PekkaKetonen (7signal Solutions)

  11. 2.4 GHz Downlink Throughputs, hourly The DL throughput declines on average level to 1-7 Mbps on Busy Hours. Peak Hours are usually 11:00-12:00 At 13.00 0.52Mbit/s At 11.00 0.17Mbit/s • During the day time, hourly average thoughputs collapse remarkably, some of them to sub 1 Mbit/s level. This is likely insufficient level for end users. Veli-PekkaKetonen (7signal Solutions)

  12. 2.4 GHz Downlink Throughput (2 Days), hourly Throughput declines at 8:00 on weekdays and return after 16:00 At 11.00 0.17Mbit/s • Strong daily pattern and very low throughput values in some APs during the daytime Veli-PekkaKetonen (7signal Solutions)

  13. 2.4 GHz Uplink Throughputs, daily Weekend • Daily average values mostly on acceptable level Veli-PekkaKetonen (7signal Solutions)

  14. 2.4 GHz Uplink Throughputs, hourly The UL throughput declines on average level to 1-10 Mbps on Busy Hours. Peak Hours are 11:00-12:00 Very good performance when network is empty At 10.00 0.6Mbit/s At 12.00 1.1Mbit/s • During the day time, uplink hourly average thoughputs collapse remarkably, some of them to sub 1 Mbit/s level. This is likely insufficient level for end users. Veli-PekkaKetonen (7signal Solutions)

  15. 2.4 GHz Uplink Throughput (2 Days), hourly Throughput declines at 8:00 on weekdays and return after 16:00 At 11.00 0.74Mbit/s • Like downlink, also uplink day time, hourly average thoughputs collapse remarkably, some of them to sub 1 Mbit/s level Veli-PekkaKetonen (7signal Solutions)

  16. 2.4 GHz VoIP MOS Downlink Quality Target level for MOS 3.6 Downlink MOS declines on busy-hours but there are also some drops at times when there are no traffic on WLAN • During the day time, hourly average thoughputs degrade significantly Veli-PekkaKetonen (7signal Solutions)

  17. 2.4 GHz VoIP MOS Uplink Quality Target level for MOS 3.6 Uplink MOS declines clearly declines on busy hours • During the day time, hourly average thoughputs degrade significantly Veli-PekkaKetonen (7signal Solutions)

  18. 2.4 GHz Downlink Jitter • Jitter increases significantly with the load Veli-PekkaKetonen (7signal Solutions)

  19. 2.4 GHz Uplink Jitter • Jitter increases significantly with the load • Uplink increases more than downlink Veli-PekkaKetonen (7signal Solutions)

  20. 2.4 GHz Downlink Packet Loss Target level 0.5% • Packet loss increases significantly with the load Veli-PekkaKetonen (7signal Solutions)

  21. 2.4 GHz Uplink Packet Loss Target level 0.5% • Packet loss increases significantly with the load • Uplink packet loss higher than downlink Veli-PekkaKetonen (7signal Solutions)

  22. 2.4 GHz Latency Target level 50ms • Latency increases significantly with the load Veli-PekkaKetonen (7signal Solutions)

  23. 2.4 GHzdata rates and retries Veli-PekkaKetonen (7signal Solutions)

  24. 2.4 GHz – Downlink Data Rates in Synthetic Eye tests • High data rates used when there is no other traffic in WLAN. • During busy hours the data rates vary a lot and low values also used Veli-PekkaKetonen (7signal Solutions)

  25. 2.4 GHz –Uplink Data Rates in Synthetic Eye Tests • There is no big difference in UL direction with data rates when comparing off-peak hours and on-peak hours. Mainly good data rates in use. Veli-PekkaKetonen (7signal Solutions)

  26. AP 1076 2.4 GHz data rate usageDownlink (AP to client) Undesirable low codecs • Low datarate usage from AP to clients Veli-PekkaKetonen (7signal Solutions)

  27. AP 1076 2.4 GHz data rate usageUplink (Client to AP) Undesirable low codecs • Low datarate usage from clients to AP Veli-PekkaKetonen (7signal Solutions)

  28. 2.4 GHz AP Retransmissions towards clients Undesired behavior 10% limit for data traffic • High amount of retries reduce network capacity and daytime throughput Veli-PekkaKetonen (7signal Solutions)

  29. 2.4 GHz Client Retransmissions towards AP Undesired behavior 10% limit for data traffic • High amount of retries reduce network capacity and daytime throughput Veli-PekkaKetonen (7signal Solutions)

  30. 2.4 GHz Eye Retransmissions in Synthetic Tests, hourly • High amount of retries in active tests Veli-PekkaKetonen (7signal Solutions)

  31. Spectrum and interference Veli-PekkaKetonen (7signal Solutions)

  32. 2.4 GHz Spectrum Graph Bluetooth interference presence on busy hours On off-peak hours the specturm graph shows an clean 1-6-11 WLAN utilization • Bluetooth interference has negative impact on WLAN receiver performance at AP and client Veli-PekkaKetonen (7signal Solutions)

  33. 2.4 GHz Average Spectrum (Busy Hours) WLAN Spectrum, Ch 6 WLAN Spectrum, Ch 11 WLAN Spectrum, Ch 1 WLAN Average Spectrum on off-peak hours (On weekend) • Clear 1-6-11 WLAN channel deployment. During Busy Hours the energy level on adjacent channels is around -82 dBm • Average interference level is 20 dB lower on the interim channels during off-peak hours Veli-PekkaKetonen (7signal Solutions)

  34. 2.4 GHz Max Spectrum (Busy Hours) Bluetooth creates 1 MHz seperated spikes to spectrum WLAN Spectrum, Ch 1 WLAN Spectrum, Ch 6 WLAN Spectrum, Ch 11 • At times, Bluetooth interference is on same level than the received signal strength from WLAN Access Points Veli-PekkaKetonen (7signal Solutions)

  35. Radio enviroment, configuration and utilization Veli-PekkaKetonen (7signal Solutions)

  36. Radio channels at 2.4 Band Well organized 1-6-11 channel plan. No adjancent channel interference from other APs Veli-PekkaKetonen (7signal Solutions)

  37. Channel allocation and changes • No channel changes over the measurement period Veli-PekkaKetonen (7signal Solutions)

  38. 2.4 GHz Number of SSID/MAC–pairs per channel • Rather well balanced 3 channel plan Veli-PekkaKetonen (7signal Solutions)

  39. Number of Clients in ”Eduroam” 2.4 GHz APs On Busy Hour the usage is really high. AP001080 shows over 50 clients at times • Number of concurrent active clients per Access point Radioshould be lower to keep up a sufficiently good performance Veli-PekkaKetonen (7signal Solutions)

  40. 2.4 GHz WLAN Traffic Utilization Busy Hour WLAN utlization is on high level. This AP serves over 50 clients at times The 7signal WLAN air time utilization can show over 100% results if there are more packets in the air than properly GI separated (no –overlapping) packets allow • Air time is severly congested during busines hours • This limits available thoughputs significantly Beacon Frame GI GI GI GI Frame GI Frame = 100% WLAN traffic utilization Veli-PekkaKetonen (7signal Solutions)

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