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DCCN 2016 - QoS to QoE

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The Path from QoS- to QoE-centric Management
of Modern Communication Systems

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DCCN 2016 - QoS to QoE

  1. 1. The Path from QoS- to QoE-centric Management of Modern Communication Systems Jiri Hosek, Ph.D. Youth School-Seminar, DCCN 2016 RUDN University, Moscow, November 24, 2016 *These slides are intended for educational purposes and include material published by WISLAB group as well as available openly on the Internet.
  2. 2. Lecture’s Content • Definition of network quality • Quality of Service (QoS) • Quality of Experience (QoE) • Subjective evaluation of modern mobile applications
  3. 3. Evaluation of Service Quality • Two main approaches how to measure the network service quality • Objective • View from the network perspective • Measuring of traffic parameters and their comparison with pre- defined values • Different services (applications) have different requirements • Subjective (Relative) • View of the end user • Difficult and time-consuming • MOS (Mean Opinion Score) • Substitution of subjective evaluation by mathematical model
  4. 4. MOS Scale • Used especially for multimedia transmissions • Numerical expression of the human user’s view on the quality of the network service
  5. 5. Key Network Traffic Parameters • Dominant measurable parameters of network traffic • Packet delay • How long the transmission takes • Packet delay variation (jitter) • Difference between the delay of two consequent packets • Packet loss • How many packets are lost during the transmission • Throughput • Transmission speed (b/s) • Key Performance Indicators (KPIs)
  6. 6. Uniform Network Traffic Treatment • As default option in all older network technologies • Seemingly fair approach • Each data unit is of the same priority • No possibility to prefer or defer any type of traffic • “Best-effort” treatment • No guarantees, just try
  7. 7. Differentiated Network Traffic Treatment • Characteristic for modern network technologies • Traffic classes • Different requirements on transmission parameters • Efficient operation of network services • Identification of data units of different services/flows • Guarantee of adequate treatment • 2 basic QoS support mechanisms • Integrated Service – IntServ • Differentiated Services – DiffServ
  8. 8. Differentiated Services – DiffServ • Offers different transmission parameters for different service types • Every data packet is processed individually • Fixed network resource sharing • QoS functions implemented in each router • Service guarantees • Service-class based
  9. 9. DiffServ – Traffic Classification and Policing • Traffic classification into an appropriate category • Usually based on fields of IP and TCP/UDP header • Differentiated Service CodePoint (DSCP) field in the IP packet header • Relative priorities • Identifies service classes • Traffic policing • Ensures, that the incoming traffic satisfies the declared parameters • Service Level Agreement – SLA • Network operator / end-user obligations
  10. 10. DiffServ – Packet Scheduling Techniques • Main packet scheduling mechanisms • First In First Out – FIFO queuing • No QoS prioritization • Priority Queuing – PQ • Fair Queuing – FQ • Weighted Fair Queuing – WFQ FIFO Priority Queuing
  11. 11. Application of DiffServ Mechanism • Each network node (router) is performing QoS functions individually • DiffServ routers • Edge router • Core router
  12. 12. Subjective Evaluation of Network Services • Customers are demanding constantly increasing quality of mobile services • Modern mobile (multimedia) applications are highly diverse • Specific requirements and user expectations • QoS-based evaluation and network control is not enough anymore • New investments for increasing network quality at all levels. • Quality of (user) Experience (QoE) • User eXperience (UX) • Influenced by many factors • Technical, socioeconomical, etc.
  13. 13. QoE Key Questions and Goals (from network operator point of view) • How the key network parameters affect the quality of mobile service perceived by an end user? • How the type of application affects user‘s evaluation? • How long are end users willing to wait for specific mobile service and being still satisfied? • What are the “premium quality” and saturation thresholds for the specific service? • How to setup and control the mobile network to avoid the over-provisioning?
  14. 14. Experimental Study of QoE in Mobile Networks • The impact of following variables were investigated: • End-user device: • Smartphone Samsung Galaxy Nexus • Tablet Samsung Galaxy Tab 10.1 inch • Applications • Web browsing, file download (DL), file upload (UL) • YouTube video streaming • Network and content parameters • Bit rates (BR) in the range of 32kb/s to 16 Mb/s • Initial loading delay (connection establishment) in the range of 0 to 11 seconds • YouTube video resolution in the range of 320x180 to 1280x720 • Stalling effects with different duration and repetition • More than 200 test scenarios evaluated by almost 300 test participants
  15. 15. Experimental Study of QoE in Mobile Networks – Methodology • Laboratory environment • Completely controllable system • Test Methods: (rec. ITU-T P.800) • Absolute Category Rating (ACR): • Scaling: 5 grade MOS scale: • 1: Bad • 5: Excellent • Acceptability rating: • Question: Were you satisfied with tested quality? • Binary answer: YES or NO
  16. 16. Mobile QoE – Automatic Assessment Tool – User Interface Questionnaire:Demographic data:Briefing phase:
  17. 17. Web: Sample Results – Quality Rating • Web browsing, tablet
  18. 18. Web: Sample Results – Acceptability Rating • Web browsing, smartphone 0 10 20 30 40 50 60 70 80 90 100 0 200 400 600 800 1000 1200 Acceptability[%] BR [kbps] 0s 1s 3s 5s 7s 11s
  19. 19. Mobile Web QoE – Quality Thresholds • We specified 3.7 MOS as a quality threshold for “premium quality” service. • The saturation threshold refers to BR with zero initial loading delay and where quality rating is not more increasing or achieved maximum quality rating or 4.5 MOS. • This is very practical output in order to avoid quality overprovisioning. Scenario Notebook Smartphone Web 256 kbps 256 kbps File DL 4 Mbps 4 Mbps File UL 1 Mbps 1 Mbps Scenario Notebook Smartphone Web 512 kbps 256 kbps File DL 4 Mbps 8 Mbps File UL 4 Mbps 1 Mbps
  20. 20. Youtube: Sample Results (1) • Quality rating vs. Resolution • The subjective premium quality threshold (3.7 MOS) • Resolution [pixels]: 640 x 360 • Saturation threshold (4.5 MOS) • Resolution [pixels]: 854 x 480 Overprovisioning area
  21. 21. Youtube: Sample Results (2) • CDF of task’s leaving for infinity loading delay 50 % users wait more than 104 / 44 seconds
  22. 22. Youtube: Sample Results (3) • Acceptability rating results vs. single stalling duration – smartphone 1st level quality reduction 2nd level quality reduction
  23. 23. Youtube: Sample Results (4) • Quality rating results vs. multiple stalling – smartphone 1st level quality reduction 2nd level quality reduction
  24. 24. Web: Analytical User Experience Prediction • We need an adequate QoE prediction models based on given results of extensive QoE assessment. • Analytical tools (regression analysis) • Calculation of QoE value (MOS) for mobile data services based on input parameters: • Initial loading delay • Throughput (bit rate) a ccBRc ab MOS D      2 1 0 ~)(~1 )(
  25. 25. YouTube: Analytical User Experience Prediction MOS 𝐷, 𝑅 = 2,7 1+9,5𝑒 0,1𝐷+ 10,7 (0,01𝑅)2 𝑒−𝑁0,6 𝑆0,2 +1
  26. 26. Summary • Future-generation mobile services are more user- / service-oriented • QoS-centric evaluation and control of modern wireless networks is not enough • User-centric / application-centric approach needs to be implemented • Complex evaluation from network- and user-perspective as well • QoE modelling is very demanded research topic nowadays • Not easy task due to high heterogeneity of modern applications and their constant development • Models need to be updated as users’ expectations are growing • Standardization in QoE assessment for new mobile services is highly required
  27. 27. Thank you for your attention! Questions?

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