Experiences with Multimedia Streaming over 2.5G and 3G
Networks
J. Chesterfield, R. Chakravorty, J. Crowcroft, P. Rodriguez, S. Banerjee
Presented by Denny Iskandar
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
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.
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
2. Network Measurements
• Multimedia traffic characterization– Assume layered organization of media– Bandwidth used ranges between a minimum
and a maximum target rate.
Figure taken from paper.
2. Network Measurements
2.1 Propagation delay and jitter
The figure is only an approximation.
2. Network Measurements
2.1 Propagation delay and jitter
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%).
Figure taken from paper.
2. Network Measurements
2.2 Capacity variation
Figure taken from paper.
2. Network Measurements
2.2 Capacity variation
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.
Figure taken from paper.
3. Application Measurements
• Use Vorbis codec– A layered codec, encodes data into a base
layer and enhancement layers
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.
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
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
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.
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
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
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
Tables taken from paper.
3. Application Measurements
3.4 Comparison
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.
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.