Quality of Person-to-Person Services in the Third
Generation Partnership Project Architecture
Hanna Heiskanen
Supervisor: Professor Raimo Kantola
Instructor: Niclas Svahnström, M.Sc.
July 24, 2016
hanna.heiskanen@teliasonera.com
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
July 24, 2016
hanna.heiskanen@teliasonera.com
2
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
July 24, 2016
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3
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
July 24, 2016
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4
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
IMS
Internet
PS domain
CS domain
UTRAN
GERAN
Access networks
User
Equipment
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WLAN
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
Home
HSS
I-CSCF
S-CSCF
SGSN
GGSN
Other
OtherIP/IMS
IP/IMS
network
network
P-CSCF
Serving PS Domain
Access
Access
Network
Network
July 24, 2016
Core Network Component
IMS Component
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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
Throughput
GPRS Up to 21.4 kbit/s per TSL
EGPRS Up to 59.2 kbit/s per TSL
UTRAN Up to 2 Mbit/s
WLAN Up to 54 Mbit/s (shared)
July 24, 2016
Latency
600 ms, with extended UL TBF 420 ms
600 ms, with extended UL TBF 420 ms
200 ms
3-10 ms
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Coverage
Country
Country
Large cities
Hot spot
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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
Speech
Video stream
July 24, 2016
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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
Access
Accessnetwork
network
UE 3
UE 2
PoC server
UE 1
Presence
server
IMS
GLMS
July 24, 2016
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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
July 24, 2016
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Motivation for QoS
• VoIP requires low delays and cannot
tolerate much jitter
VoIP
Streaming
Browsing
Best effort RAB
• If all the services are treated the same
way, some end up suffering while others
might even settle for less
Internet access
MMS
• 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
July 24, 2016
• 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
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VoIP
Guaranteed bit rate conversational RAB
Streaming
Guaranteed bit rate streaming RAB
Browsing
Interactive RAB
MMS
Background RAB
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Examples of Performed Measurements (1/3)
Performance of AMR VoIP in UTRAN
USB
Laptop
with ttcp+
UTRAN
UTRAN
USB
• Delay spikes are caused by
retransmissions at RLC layer
Laptop
with ttcp+
AMR 4.75 kbit/s AMR 12.2 kbit/s
Average end-to-end delay
185 ms
397 ms
Minimum end-to-end delay
132 ms
348 ms
Maximum end-to-end delay
565 ms
771 ms
Standard deviation of delay
46 ms
59 ms
Average packet loss rate
0.26 %
0.14 %
July 24, 2016
• The QoS requirements for VoIP are barely
fulfilled when using the highest coding
modes
hanna.heiskanen@teliasonera.com
• 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
12
Examples of Performed Measurements (2/3)
PoC in EGPRS
• Sawtooth pattern caused by
the release and set up of TBFs
70
1.60
1.60
60
• Extended UL TBF would solve
this problem
1.40
1.40
50
1.20
1.20
1.00
1.00
40
0.80
0.80
30
0.60
0.60
20
0.40
0.40
10
0.20
0.20
0
Packet number
Packet delay (in seconds)
1.80
1.80
delay
DL
UL
• PoC requires that the end-toend delay is less than 1.6
seconds
• Only one talk burst did not
fulfill this requirement
0
10
10
11
11
12
12
13
13
14
14
15
15
16
16
17
17
18
18
19
19
20
20
21
21
22
22
Time (in seconds)
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13
Examples of Performed Measurements (3/3)
The effect of WMM class voice (VO)
45
Laptop generating
VO stream
AP
Server
Interarrival delay (ms)
35
802.11g WLAN
Four laptops
generating BE streams
VO
BE
BE
BE
BE
40
30
25
20
15
10
5
Time (min:sec)
• 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
July 24, 2016
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14
9:
30
8:
50
7:
30
8:
10
6:
50
6:
10
4:
50
5:
30
4:
10
3:
30
2:
10
2:
50
1:
30
0:
50
0:
10
0
Conclusions and Future Work
GPRS
AMR VoIP
Not possible
EGPRS Not possible
UTRAN ROHC, unacknowledged RLC,
conversational class
WLAN WMM or IEEE 802.11e
with QoS class voice
Video Sharing
Not possible
PoC
SigComp, interactive class,
allocation/retention priority 1,
traffic handling priority 1
As in GPRS
As in GPRS
Not recommended
streaming class,
allocation/retention priority 1
WMM or IEEE 802.11e
WMM or IEEE 802.11e
with QoS class background
with QoS class video
• 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
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15
Questions?
Thank you!
The Nordic and Baltic
telecommunications leader
July 24, 2016
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