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Experiences with Multimedia Streaming over 2.5G and 3G
Networks
J. Chesterfield, R. Chakravorty, J. Crowcroft, P. Rodriguez, S. Banerjee
Presented by Denny Iskandar
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1. Introduction
• What?– Evaluates performance of multimedia
streaming over wireless network.
• Why?– 2.5G and 3G technologies are being deployed
everywhere (Europe, America, and Asia)– Popularity of multimedia applications such as
videoconferencing, Voice over IP, and audio/video broadcasting
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1. Introduction
• Scope of experiment– Measurements from real networks:
• The effect of heterogeneity of network is captured by comparison across different network technologies: (GSM), GPRS, and UMTS.
• Describes the importance of cooperation between network and application using an application called vorbistreamer.
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Roadmap
1. Introduction
2. Network measurements
3. Application measurements
4. Conclusions Application layer
Presentation layer
Session layer
Transport layer
Network layer
Data link layer
Physical layer
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2. Network Measurements
• Multimedia traffic characterization– Assume layered organization of media– Bandwidth used ranges between a minimum
and a maximum target rate.
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Figure taken from paper.
2. Network Measurements
2.1 Propagation delay and jitter
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The figure is only an approximation.
2. Network Measurements
2.1 Propagation delay and jitter
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2. Network Measurements
2.1 Propagation delay and jitter– Compare with ITU recommendation for voice
communications: RTT ≤ 500 ms
GSM GPRS UMTSMean 1460 ms 220 ms 30 ms
Variance Not mentioned
80-500 ms 20-300 ms
Note: For GPRS, disabling ARQ reduces jitter at the cost of higher packet loss rate (around 3%).
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Figure taken from paper.
2. Network Measurements
2.2 Capacity variation
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Figure taken from paper.
2. Network Measurements
2.2 Capacity variation
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2. Network Measurements
2.3 Summary– Propagation delay and delay jitter are reduced
as link capacity increases.– GPRS should disable ARQ for multimedia
application.– Sub-packet error detection [1] improves
performance.
[1] J. Chesterfield, R. Chakravorty, S. Banerjee, P. Rodriguez and I. Pratt. Transport Level Optimisations for Interactive Media Streaming Over Wide-Area Wireless Networks. In WiOpt ’04, 2004.
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Figure taken from paper.
3. Application Measurements
• Use Vorbis codec– A layered codec, encodes data into a base
layer and enhancement layers
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3. Application Measurements
• Design of vorbistreamer– Implements IP-based data striping; this is
used to aggregate channel bandwidth.– Uses RTP as transport protocol.– Supports interactivity constraints from fully
interactive communication to one-way streaming.
– Uses Vorbis codec.
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3. Application Measurements
• Encoding techniques– For multimedia application, reliability is
disabled– Needs to add redundancy to multimedia data
to facilitate receiver-based repairs– Also involves interleaving of encoding blocks
to reduce the effect of error burst
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3. Application Measurements
3.1 Intra-packet redundancy (UEP)
Header Base layer EL1 EL2 ELn...
Vorbis frame
RLC packets
FEC1 FEC2frame1 n-2 frames
FEC blocks
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3. Application Measurements
• Things to note:– This “bucketing” is done at application layer,
the actual RLC packetization is done at link layer.
– Multiple layers in one packet to minimize header overhead.
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3. Application Measurements
3.2 Inter-packet redundancy
• Cross-packet coding– Sends parity data in separate packets than
the original data.
original data parity data
dThe greater d is:• The more effective recovery• The greater recovery delay
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3. Application Measurements
3.2 Inter-packet redundancy
• Cross-channel coding– From tests, it is more likely that error occurs to
A and B than to B and C
A B
C
channel 1
channel 2
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3. Application Measurements
3.3 Interleaving
• Intra-packet: change the order of frames in the same packet
• Inter-packet: change the order of packets in the same channel
• Inter-channel:5channel 1
channel 2
3 17
6 4 28
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Tables taken from paper.
3. Application Measurements
3.4 Comparison
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4. Conclusions
• The need for cooperation between network and application.
• Encoding and organization of multimedia data is important.
• Benefits from aggregating independent channels.
• Benefits from sub-packet error detection.
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5. Related works
[1] J. Chesterfield, R. Chakravorty, S. Banerjee, P. Rodriguez and I. Pratt. Transport Level Optimisations for Interactive Media Streaming Over Wide-Area Wireless Networks. In WiOpt’04: Modelling and Optimization in Mobile, Ad Hoc and Wireless Networks, 2004.
[2] R. Chakravorty, J. Chesterfield, P. Rodriguez and S. Banerjee. Measurement Approaches to Evaluate Performance Optimizations for Wide-Area Wireless Networks. In Passive and Active Network Measurement (PAM 2004) 5th International Workshop, 2004.