1. WLAN network behavior under heavy load
May 2013
doc.: IEEE /xxxxr0
July 2013
WLAN network behavior under heavy load
Date:
Authors:
Veli-Pekka Ketonen (7signal)
Osama Aboul-Magd (Huawei Technologies)

2. July 2013
Abstract
This is background submission for HEW 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. July 2013
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-Pekka Ketonen (7signal Solutions)

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

5. Eye Location: Floor 1 –Learning Center
July 2013
Eye Location: Floor 1 –Learning Center
First Floor:
7signal Eye 1 2 6 5 3 4
Veli-Pekka Ketonen (7signal Solutions)

6. Off-peak Hours / On-peak Hours Comparison
July 2013
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-Pekka Ketonen (7signal Solutions)

7. 2.4 GHz band end-to-end Quality of experience
July 2013
2.4 GHz band end-to-end Quality of experience
Veli-Pekka Ketonen (7signal Solutions)

8. 2.4 GHz Attach Success Rate (Daily Average)
July 2013
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-Pekka Ketonen (7signal Solutions)

9. 2.4 GHz Attach Success Rate (One Week, hourly)
July 2013
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-Pekka Ketonen (7signal Solutions)

10. 2.4 GHz Downlink Throughputs, daily
July 2013
2.4 GHz Downlink Throughputs, daily
Weekend
Daily average values are on acceptable level
Veli-Pekka Ketonen (7signal Solutions)

11. 2.4 GHz Downlink Throughputs, hourly
July 2013
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 Mbit/s
At Mbit/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-Pekka Ketonen (7signal Solutions)

12. 2.4 GHz Downlink Throughput (2 Days), hourly
July 2013
2.4 GHz Downlink Throughput (2 Days), hourly
Throughput declines at 8:00 on weekdays and return after 16:00
At Mbit/s
Strong daily pattern and very low throughput values in some APs during the daytime
Veli-Pekka Ketonen (7signal Solutions)

13. 2.4 GHz Uplink Throughputs, daily
July 2013
2.4 GHz Uplink Throughputs, daily
Weekend
Daily average values mostly on acceptable level
Veli-Pekka Ketonen (7signal Solutions)

14. 2.4 GHz Uplink Throughputs, hourly
July 2013
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 Mbit/s
At Mbit/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-Pekka Ketonen (7signal Solutions)

15. 2.4 GHz Uplink Throughput (2 Days), hourly
July 2013
2.4 GHz Uplink Throughput (2 Days), hourly
Throughput declines at 8:00 on weekdays and return after 16:00
At Mbit/s
Like downlink, also uplink day time, hourly average thoughputs collapse remarkably, some of them to sub 1 Mbit/s level
Veli-Pekka Ketonen (7signal Solutions)

16. 2.4 GHz VoIP MOS Downlink Quality
July 2013
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-Pekka Ketonen (7signal Solutions)

17. 2.4 GHz VoIP MOS Uplink Quality
July 2013
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-Pekka Ketonen (7signal Solutions)

18. 2.4 GHz Downlink Jitter July 2013
Jitter increases significantly with the load
Veli-Pekka Ketonen (7signal Solutions)

19. 2.4 GHz Uplink Jitter July 2013 Uplink increases more than downlink
Jitter increases significantly with the load
Uplink increases more than downlink
Veli-Pekka Ketonen (7signal Solutions)

20. 2.4 GHz Downlink Packet Loss
July 2013
2.4 GHz Downlink Packet Loss
Target level 0.5%
Packet loss increases significantly with the load
Veli-Pekka Ketonen (7signal Solutions)

21. 2.4 GHz Uplink Packet Loss July 2013
Target level 0.5%
Packet loss increases significantly with the load
Uplink packet loss higher than downlink
Veli-Pekka Ketonen (7signal Solutions)

22. July 2013
2.4 GHz Latency
Target level 50ms
Latency increases significantly with the load
Veli-Pekka Ketonen (7signal Solutions)

23. 2.4 GHz data rates and retries
July 2013
2.4 GHz data rates and retries
Veli-Pekka Ketonen (7signal Solutions)

24. 2.4 GHz – Downlink Data Rates in Synthetic Eye tests
July 2013
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-Pekka Ketonen (7signal Solutions)

25. 2.4 GHz –Uplink Data Rates in Synthetic Eye Tests
July 2013
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-Pekka Ketonen (7signal Solutions)

26. AP 1076 2.4 GHz data rate usage Downlink (AP to client)
July 2013
AP GHz data rate usage Downlink (AP to client)
Undesirable low codecs
Low datarate usage from AP to clients
Veli-Pekka Ketonen (7signal Solutions)

27. AP 1076 2.4 GHz data rate usage Uplink (Client to AP)
July 2013
AP GHz data rate usage Uplink (Client to AP)
Undesirable low codecs
Low datarate usage from clients to AP
Veli-Pekka Ketonen (7signal Solutions)

28. 2.4 GHz AP Retransmissions towards clients
July 2013
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-Pekka Ketonen (7signal Solutions)

29. 2.4 GHz Client Retransmissions towards AP
July 2013
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-Pekka Ketonen (7signal Solutions)

30. 2.4 GHz Eye Retransmissions in Synthetic Tests, hourly
July 2013
2.4 GHz Eye Retransmissions in Synthetic Tests, hourly
High amount of retries in active tests
Veli-Pekka Ketonen (7signal Solutions)

31. Spectrum and interference
July 2013
Spectrum and interference
Veli-Pekka Ketonen (7signal Solutions)

32. 2.4 GHz Spectrum Graph July 2013
Bluetooth interference presence on busy hours
On off-peak hours the specturm graph shows an clean WLAN utilization
Bluetooth interference has negative impact on WLAN receiver performance at AP and client
Veli-Pekka Ketonen (7signal Solutions)

33. 2.4 GHz Average Spectrum (Busy Hours)
July 2013
2.4 GHz Average Spectrum (Busy Hours)
WLAN
Spectrum,
Ch 1
WLAN
Spectrum,
Ch 6
WLAN
Spectrum,
Ch 11
WLAN Average Spectrum on off-peak hours (On weekend)
Clear 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-Pekka Ketonen (7signal Solutions)

34. 2.4 GHz Max Spectrum (Busy Hours)
July 2013
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-Pekka Ketonen (7signal Solutions)

35. Radio enviroment, configuration and utilization
July 2013
Radio enviroment, configuration and utilization
Veli-Pekka Ketonen (7signal Solutions)

36. Radio channels at 2.4 Band July 2013
Well organized channel plan. No adjancent channel interference from other APs
Veli-Pekka Ketonen (7signal Solutions)

37. Channel allocation and changes
July 2013
Channel allocation and changes
No channel changes over the measurement period
Veli-Pekka Ketonen (7signal Solutions)

38. 2.4 GHz Number of SSID/MAC–pairs per channel
July 2013
2.4 GHz Number of SSID/MAC–pairs per channel
Rather well balanced 3 channel plan
Veli-Pekka Ketonen (7signal Solutions)

39. Number of Clients in ”Eduroam” 2.4 GHz APs
July 2013
Number of Clients in ”Eduroam” 2.4 GHz APs
On Busy Hour the usage is really high. AP shows over 50 clients at times
Number of concurrent active clients per Access point Radio should be lower to keep up a sufficiently good performance
Veli-Pekka Ketonen (7signal Solutions)

40. 2.4 GHz WLAN Traffic Utilization
July 2013
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
Frame GI GI GI GI
Frame
= 100% WLAN traffic utilization
Veli-Pekka Ketonen (7signal Solutions)