Analysis of Service Quality in 3G Mobile Networks

1. Analysis of Service Quality in 3G Mobile Networks Heidi Lagerström Supervisor: Professor Heikki Hämmäinen Instructors: M.Sc. Sami Vesala & M.Sc. Katja Koivu

2. Contents • Introduction to the study • Background, research problem, research methods • Quality of Service (QoS) in UMTS Networks • Measuring service quality • Defining Key Performance Indicators (KPI) • Case study

3. Background • UMTS introduces new real time services to mobile networks, such as video telephony. • These real time services require QoS guarantees to function properly. • For operators to maintain satisfactory service quality constant network monitoring is needed. • Network measurements are based on correctly defined KPIs for each service. • Operators’ possibilities to utilise QoS in practice have not been widely researched. • Key Performance Indicators have not been defined for the new services from the end-user perspective.

4. Research problem How should service quality be measured in 3G networks and how the QoS mechanisms can be used to affect the service quality perceived by subscribers. Objectives: • What are the KPIs that measure service quality, from end user perspective, in 3G networks for the key services (AMR voice, video telephony, video streaming, web browsing and e-mail)? • What are the QoS mechanisms in Release 99 and how can they be used to improve service quality?

5. Research methods • Literature study • 3GPP, ETSI, ITU specifications • Several books and publications • Interviews • Network equipment vendors: Ericsson, Nokia • Operators: Elisa • Several other radio network experts • Case study • Field measurements for two operators in live networks

6. Contents • Introduction to the study • Background, research problem, research methods • Quality of Service (QoS) in UMTS Networks • Measuring service quality • Defining Key Performance Indicators (KPI) • Case study

7. Why do we need QoS? • UMTS networks support services with very different performance requirements • Real-time services require performance guarantees • Customer acceptance closely tied to service quality • Optimal usage of network resources • Radio resources scarce • Cost-effectiveness • Return of investment • Service and user differentiation • Meet different needs of customers (e.g. business vs. consumer) • Support different services (real-time vs. best effort) • Competitive advantage!

8. QoS Traffic Classes • Demanding • Delay • Jitter • Demanding • Bit rate • Jitter • Tolerant • Delay and bit rate can vary • Integrity • Easiest • Delay and bit ratecan vary • Integrity

9. QoS Profile Attributes Depends on operator’s QoS strategy Depends on the QoS strategy and UE/RNC capabilities

10. Conversational RAB Streaming RAB Interactive RAB, THP/ARP = 1 Interactive RAB, THP/ARP = 3 Video telephony Background RAB Streaming Push-to-talk Web browsing MMS QoS Differentiation • Each service gets the treatment it requires according to the QoS profile • Network resources are shared according to the service needs • Network resources can be used more efficiently

11. ATM QoS Gn Iu Gn Inter-PLMN Backbone NT UE Node B RNC 3G-SGSN 3G-GGSN UTRAN Different channel types PS Domain DiffServ on transport level IP (ATM QoS for CS) Firewall Diffserv on transport level IP External IP (Internet) Diffserv in Gi IP TE QoS Mechanisms PDP context with the requested QoS capabilities RRM • Different QoS techniques in different parts of the network • Appropriate QoS must be provided in every network so that the user can experience good service quality

12. Conversational RAB Streaming RAB Interactive RAB, THP/ARP = 1 Interactive RAB, THP/ARP = 3 Application server Node B Background RAB 3G GGSN 3GSGSN RNC HLR Operators’ QoS Strategy User profiles are stored in HLR. Each user can have several user profiles, which correspond to different services and are mapped to different bearers according to the operator’s strategy. • Operators can practise user differentiation by giving each user set of QoS profiles, which he/she is entitled to use • Operators can practise service differentiation by mapping each service to the bearer that meets its requirements • Meet the needs of different customers • Offer each service the quality it requires • Optimise network resource usage

13. Contents • Introduction to the study • Background, research problem, research methods • Quality of Service (QoS) in UMTS Networks • Measuring service quality • Defining Key Performance Indicators (KPI) • Case study

14. Customer feedback Network Performance Monitoring  Optimisation Performance statistics from application server Network statistics from different counters and interfaces E2E service quality, QoE Application server Node B 3G GGSN 3GSGSN RNC UTRAN Core nw External nw Measuring network performance

15. Defining the right KPIs • Different services have different quality requirements • KPIs must be defined separately for each of the key services • KPI categories • Service Accessibility • Service Integrity • Service Retainability • With inadequate performance indicators and monitoring • Hidden problems in network performance and user perceived quality of service • Poorly defined indicators may show better quality than in the reality • Incorrect formulas and counters • Unreasonable measurement periods (too much averaging etc.)

16. Example: Voice Services - CS

17. Example: Data Services - PS

18. Contents • Introduction to the study • Background, research problem, research methods • Quality of Service (QoS) in UMTS Networks • Measuring service quality • Defining Key Performance Indicators (KPI) • Case study

19. Measurement plan Tools: Nemo Outdoor, Optimi x-AppMonitor, Ethereal

20. AMR voice – Drive test statistics Shoud be ~100% Good > -10dB Good > -92dBm Good < 21dBm • Reasons for call failure: • Ec/N0 was not at adequate level • Call setup was unsuccessful (unsuccessful RACH procedure) • Look at L3 signalling

21. CPICH coverage – Ec/N0 Operator 1 According to Ec/N0 values both operators have good coverage. Couple of RED areas, which need to be further investigated! Operator 2 If large interference areas are generated, the problem could be minimised later by adjusting the antenna direction or height, or by down tilting the antenna or by slightly tuning the pilot power levels.

22. Data Connection Typical RTT in UMTS network is ~200ms, which enables good quality conversational PS services, such as VoIP.

23. Video streaming In mobile phone display ~60 kbps streaming bit rate produces good video quality.

24. Web browsing Sample web page 319 kB

25. Conclusions • In 3G networks QoS management is required • Real-time services require QoS guarantees • Need to support different kinds of services • With QoS mechanisms operators can use their network resources more efficiently and gain competitive advantage • To maintain and improve the network performance and user experienced service quality constant monitoring and performance follow-up is needed • Successful network measurements are based on correct KPI definitions • A combination of end-to-end field measurements, interface probes, network element counter statistics and customer feedback is required • The measurement results show that there are big differences in the performance of operators’ UMTS networks • Currently UMTS networks are not fully optimised  there is a clear need for optimisation! • Majority of 3G measuring equipment and terminals are still quite immature

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27. KPI Definitions

28. AMR Speech KPIs Parameters Service coverage Speech quality Service accessibility Codec usage Service access time Service retainability Trigger points Place a call Alerting message Speech interchange Intentional termination of session T2 T3 T1 T0 Channel request ALERTING Start of audio stream RELEASE

29. Video Telephony KPIs Parameters Speech quality Video quality Service coverage Video call setup success ratio Audio/video synchronisation Service accessibility Video call setup time Service retainability Service access time Trigger points Video call Request Alerting message Audio/video output Intentional termination of session T2 T3 T1 T0 Audio/video output starts Audio/video output ends RELEASE ALERTING / Call accepted Channel request

30. Video Streaming KPIs Parameters Video quality Service coverage Audio quality Streaming reproduction start failure Service accessibility Audio/video synchronisation Streaming reproduction start delay Service access time Streaming reproduction cut-off ratio Trigger points Stream Request Buffering message appears on player Stream reproduction Intentional termination of session T2 T3 T1 T0 RTP: payload 1st data packet BUFFERING Streaming reproduction starts – picture appears PLAY Video/audio stream ends RTSP TEARDOWN RTSP: SETUP

31. Web Browsing KPIs Parameters Service coverage Service accessibility Web page download time Service access time Service retainability Trigger points Service access Data transfer Intentional termination of session T2 T3 T1 T0 1st HTTP: GET HTTP: FIN/ACK Reception of last data packet Display data 1st TCP [SYN]

32. E-mail KPIs Parameters Service coverage Service accessibility Sending time Receiving time Service access time Service retainability Trigger points Service access E-mail sending E-mail download T2 T3 T4 T1 T0 Last data packet send TCP [FIN/ACK] IMAP: FETCH Body Last data packet received TCP [FIN/ACK] SMTP: 250 ACK (HELO) 1st TCP [SYN]