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.
December 6, 2018

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
December 6, 2018

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
December 6, 2018

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
December 6, 2018

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 , UMTS QoS (also applicable to GERAN)
3GPP TS , End-to-end QoS (IMS specific)
IEEE e, WLAN QoS
WMM, WLAN QoS implemented by the industry consortium
December 6, 2018

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
December 6, 2018

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
December 6, 2018

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 Sharing provides a one-way, PS video stream in real time. Video Sharing is comparable to one-way video telephony
December 6, 2018

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
December 6, 2018

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
December 6, 2018

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
December 6, 2018

12. Examples of Performed Measurements (1/3)
Performance of AMR VoIP in UTRAN
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
December 6, 2018

13. Examples of Performed Measurements (2/3)
PoC in EGPRS
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
December 6, 2018

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
December 6, 2018

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
December 6, 2018

16. The Nordic and Baltic telecommunications leader
Questions?
Thank you!
The Nordic and Baltic telecommunications leader
December 6, 2018