Video Quality Evaluation for Wireless Transmission with Robust Header Compression Fourth International Conference on Information, Communications & Signal Processing Fourth IEEE Pacific-Rim Conference On Multimedia 15-18 December 2003, Meritus Mandarin Hotel, Singapore Seeling, Fitzek, Reisslein
Content Introduction & Motivation Header Compression Schemes Robust Header Compresion (ROHC) RFC3095 Video over ROHC Methodology and Testbed Setup Results Conclusion
Introduction Video services over wireless networks are gaining more and more interest Services are needed that convince customers to buy new equippment (e.g., 3GPP networks) 3GPP networks support video services such as the IMS and the MBMS entities Problem: Video services need much more bandwidth than voice calls, which makes them hard to sell
Motivation Video services are transmitted over IP networks using the RTP/UDP/IP protocols Video is encoded efficiently, but the protocol stack overhead is not The protocol overhead comprises a large portion of the traffic (even more for small video formats as for the mobile phones) Therefore: Compression of the protocol overhead needed
General Structure of Header Compressors Two entities: compressor and decompressor Compressor sends initial base Base is used by compressor and decompressor Compressor removes redundancy Decompressor adds removed information Proposed solution differ in a possible feedback channel Base Base Compressor N N* Decompressor N
IP Header Compression IP HC RFC2507 provides only rudimentary support for UDP with low compression CRTP has problems with high loss rates and delays (bandwidth-delay product) Overall: problems with previous header compression schemes over wireless links
Robust Header Compression (ROHC) RFC3095 General ROHC header compression scheme Single hop and stateful Dynamic state and context changes
Context states: Robust Header Compression (ROHC) RFC3095 No context: largest ROHC header for context establishment Static context: context for static parts exists Full context: all parts are within the established context
Robust Header Compression (ROHC) RFC3095 ROHC modes based on feedback availability Unidirectional mode (no feedback) Periodic context state updates Fallback to lower states upon minor changes Bi-directional optimistic mode Decompressor ACKs context changes NACK based context updates triggered by decompressor Bi-directional reliable mode Closest coupling between compressor / decompressor
Methodology Uncorrelated bit errors as recently found for UMTS channels Simulated with and without ROHC implementation O-Mode
Metrics Peak Signal to Noise Ratio (PSNR) for quality comparison PSNR = 10log 10 2 255 MSE Header Compression, total compression, and mean ROHC header size
Testbed Setup
PSNR Measurements PSNR calculation is standard metric for objective video quality measurements Freezing for lost frames VideoMeter tool for visualization
Netmeter Tool Bandwidth w/o ROHC Bandwidth with ROHC Header compression Overall compression
ROHC Results Table of Compression
Insights Protocol header compression can be achieved by using ROHC Higher compression ratios for smaller video formats and higher quantization Lower fraction of packets comprised of actual video data (i.e., payload) Lower error probability and state changes within ROHC
ROHC Results PSNR Figure
Conclusion ROHC is an efficient header compression scheme for multimedia in wireless environments Compression achieved depends on video format and video content Utilization of ROHC for multimedia streaming does not introduce additional losses in terms of perceived video quality (PSNR)
Q/A Thank you! patrick.seeling@asu.edu fitzek@acticom.de reisslein@asu.edu Am Borsigturm 42 13507 Berlin Germany www.acticom.de The only situation we recommend to be wired!
Related Work F.H.P. Fitzek, S. Hendrata, and M. Reisslein, "Header Compression Schemes for Wireless Internet Access", in Wireless Internet: Technologies and Applications, Series: Electrical Engineering & Applied Signal Processing Series, 2004 F.H.P. Fitzek, S. Hendrata, P. Seeling and M. Reisslein, "Video Quality Evaluation for Wireless Transmission with Robust Header Compression", Technical Report: acticom-03-003, acticom GmbH, Germany, July, 2003 P. Seeling, F.H.P. Fitzek, and M. Reisslein, "VideoMeter tool for YUV bitstreams", IEEE Network Magazine, software tools for networking, Vol.17, No. 1, January 2003 S. Rein, F.H.P. Fitzek, and M. Reisslein, "Voice Quality Evaluation for Wireless Transmission with ROHC", International Conference on Internet and Multimedia Systems and Applications (IMSA 2003), pages 461-466, August 13-15, 2003, Honolulu, USA