Quality of Person-to-Person Services in the Third Generation Partnership Project Architecture

1. Quality of Person-to-Person Services in the Third Generation Partnership Project Architecture Hanna Heiskanen Supervisor: Professor Raimo Kantola Instructor: Niclas Svahnström, M.Sc. hanna.heiskanen@teliasonera.com

2. Contents • Background and research problem • Research methods • Overview of the Third Generation Partnership Project (3GPP) architecture • Overview of person-to-person services • Motivation for Quality of Service (QoS) • Examples of performed measurements • Conclusions and future work hanna.heiskanen@teliasonera.com

3. Background and Research Problem • The ultimate all-IP vision is that everything in mobile networks, including voice, will be carried in packet switched form using IP • The IP Multimedia Subsystem (IMS) allows for a portfolio of new services that can be roughly divided into person-to-person and content-to-person categories • Voice is – and remains – the most important type of application in mobile telecommunication but it will be increasingly combined with other content to deliver enriched person-to-person communication • So far, person-to-person services have covered voice, MMS and SMS • Push to Talk over Cellular (PoC), Video Sharing and rich call that allows the user to add other media to Voice over IP (VoIP) sessions are examples of emerging person-to-person services • The Problem: It is vitally important that the emerging person-to-person services perform in such a manner that the QoS is accepted by the end-user. Consequently, it is of great concern to the operator to ensure that the emerging person-to-person services achieve adequate level of QoS while the expensive network resources are utilized as efficiently as possible. However, • The QoS for these services has not been widely studied • The effect of these services on the underlying network is not known for sure • Most of the prior work is solely based on theoretical analysis, there are very few available measurement results hanna.heiskanen@teliasonera.com

4. Research Methods • Literature study • Identification of the challenges of the access networks of the 3GPP architecture • Overview of three chosen person-to-person services: Adaptive Multi-Rate (AMR) VoIP, PoC and Video Sharing • Analysis of service specific QoS requirements • Literature study based on 3GPP, OMA, ITU and IEEE specifications, IETF RFCs, several books, articles and conference proceedings. • Evaluation • Performance estimates for AMR VoIP, PoC and Video Sharing in the access networks of the 3GPP architecture • Comparing access network capabilities with service specific QoS requirements • Measurements • In live network and at laboratory circumstances • The feasibility of AMR VoIP, PoC and Video Sharing was concluded both based on evaluation and measurements • Recommendations for the implementation of these services, including QoS parameterization and required network features hanna.heiskanen@teliasonera.com

5. 3GPP Release 6 Architecture • Release 6 is the latest series of 3GPP specifications. The work on Release 6 was frozen in Spring 2005 • 3GPP Release 6 architecture is comprised of three domains: User Equipment (UE), Access Networks and Core Network • Release 6 officially encompasses two access networks: GERAN and UTRAN. Release 6 also enables interworking between 3GPP-defined networks and IEEE-defined WLAN, and therefore WLAN is regarded as the third access network of the 3GPP architecture • Core network consists of three domains: Circuit Switched (CS), Packet Switched (PS) and the IP Multimedia Subsystem (IMS) domains • This thesis focuses on PS services • CS domain was not studied • QoS in the 3GPP Release 6 architecture: • 3GPP TS 23.107, UMTS QoS (also applicable to GERAN) • 3GPP TS 23.207, End-to-end QoS (IMS specific) • IEEE 802.11e, WLAN QoS • WMM, WLAN QoS implemented by the industry consortium hanna.heiskanen@teliasonera.com

6. The IMS • The IMS was introduced in 3GPP Release 5 • The IMS aims to merge two of the most successful paradigms in communication: cellular networks and the Internet • The idea of the IMS is to enable IP multimedia services based on and built upon IETF protocols • The IMS is independent of the underlying access technology • Sessions are handled with Session Initiation Protocol (SIP) and Session Description Protocol (SDP) • The IMS presents the following benefits: • Centralized profile management e.g. QoS profiles • Evolved charging schemes, not just based on the amount of data or the duration of the session • End-to-end QoS and policy control • Possibility to offer services that are provided by a third party hanna.heiskanen@teliasonera.com

7. Challenges of the 3GPP Architecture • The wireless medium is always somewhat unpredictable. Due to the nature of the wireless medium, QoS violations cannot be totally avoided • GERAN presents challenges in terms of high latency and poor handover performance • With Network Assisted Cell Change (NACC), cell change takes approximately one second • Radio resources are released as soon as there is no data to be transmitted. The unnecessary release and set up of Temporary Block Flows (TBFs) causes additional delay – especially with bursty data. Delayed DL TBF and extended UL TBF aim to solve this problem by delaying the release of TBFs • Transmission protocols cause a overhead that cannot be compressed • Uncertainties whether to use GERAN A/Gb mode or Iu mode. For example, all QoS classes are not supported when using A/Gb mode • UTRAN brings considerable improvements both to throughput and latency. • Prior to data transmission, a Dedicated Channel (DCH) has to be set up. The establishment of a DCH consumes approximately 1.5 seconds • The latency in WLAN is low and the provided transmission rates are relatively high. However, WLAN covers only hot spot areas and it cannot be used e.g. to provide nationwide coverage hanna.heiskanen@teliasonera.com

8. Overview of Person-to-Person Services (1/2) • Difference between person-to-person and Peer-to-Peer (P2P) services:person-to-person services are characterized by user-created content while P2P services include also download of other content, such as files. P2P services are about connectivity without intermediaries, while person-to-person services include both direct P2P and intermediate server based connections between two persons or a group of persons • Three person-to-person services were studied in this thesis • AMR VoIP • PoC • Video Sharing • The AMR codec was originally developed and standardized by ETSI with GSM cellular systems in mind. Due to its flexibility and robustness, it is also suitable for real-time speech communication services over PS networks. AMR narrowband supports eight source rates from 4.75 kbit/s to 12.2 kbit/s and a low bit rate background noise-encoding mode • Video Sharingprovides a one-way, PS video stream in real time. Video Sharing is comparable to one-way video telephony hanna.heiskanen@teliasonera.com

9. Overview of Person-to-Person Services (2/2) • PoC is a walkie-talkie type of service that runs on top of PS mobile network. The voice connection is established and maintained by pushing a single button and only one user of a group can speak at a time • The first official PoC standard (OMA PoC) was finalized in March 2005 • Proprietary PoC systems are already in use hanna.heiskanen@teliasonera.com

10. QoS requirements for Person-to-Person services • VoIP cannot tolerate high delays or jitter. End-to-end delay has to be less than 400 ms, preferably under 150 ms. The effect of latency on the end-user satisfaction can be evaluated with the E-model • The bandwidth consumption of AMR VoIP is less than 40 kbit/s • PoC was designed from the beginning so that it would fit into one CS-1 GPRS timeslot. PoC media consumes approximately 8kbit/s • End-to-end delay of PoC talk burst should be less than 1.6 seconds • PoC data are characterized by a lot of signaling • Video Sharing is an asymmetric application that consumes at most 64 kbit/s • End-to-end delay of video transmission should be less than two seconds • These services require that sufficient bit rate is guaranteed even under the most demanding network conditions • Sufficient QoS should be guaranteed while the user is on the move hanna.heiskanen@teliasonera.com

11. Motivation for QoS • VoIP requires low delays and cannot tolerate much jitter • For MMS to be successful, it is important that messages are delivered with high reliability, while delivery time is short enough as long as it is below one minute • If all the services are treated the same way, some end up suffering while others might even settle for less • It would be worthwhile to use QoS mechanisms to divide the traffic into several classes • From the operator’s viewpoint, the benefit of providing QoS in mobile networks will not be the extra revenue collected from it. The emerging person-to-person services require better than just best effort treatment in order to fulfil their QoS requirements in a congested network hanna.heiskanen@teliasonera.com

12. Examples of Performed Measurements (1/3) • The QoS requirements for VoIP are barely fulfilled when using the highest coding modes • Delay spikes are caused by retransmissions at RLC layer • VoIP would tolerate packet loss rates of up to 3 % and the measured packet loss rate was low • The use of unacknowledged RLC mode (no retransmissions) would remove the delay spikes but the packet loss rate would be increased • The effect of overhead is emphasized because VoIP transmits 50 small packets per seconds Performance of AMR VoIP in UTRAN hanna.heiskanen@teliasonera.com

13. Examples of Performed Measurements (2/3) • Sawtooth pattern caused by the release and set up of TBFs • Extended UL TBF would solve this problem • PoC requires that the end-to-end delay is less than 1.6 seconds • Only one talk burst did not fulfill this requirement PoC in EGPRS hanna.heiskanen@teliasonera.com

14. Examples of Performed Measurements (3/3) The effect of WMM class voice (VO) • The use of QoS classes stabilizes the jitter of VoIP when the used AP is congested • This is important because VoIP is very intolerant of jitter hanna.heiskanen@teliasonera.com

15. Conclusions and Future Work • Mobility presents additional challenges • It is very difficult to guarantee sufficient service performance during handover in GERAN • Vertical handovers between different access networks (e.g. from UTRAN to WLAN) cause severe disruption • Themes for further research work • Measurements with conversational and streaming QoS class • Prioritization within streaming class using the allocation/retention priority attribute • The performance of AMR VoIP using unacknowledged RLC mode and RObust Header Compression (ROHC) • Lifetime packet discard hanna.heiskanen@teliasonera.com

16. Questions? Thank you! The Nordic and Baltictelecommunications leader hanna.heiskanen@teliasonera.com