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Johansson, Peter
Publications (4 of 4) Show all publications
Muhammad, A., Johansson, P. & Forchheimer, R. (2009). Effect of Buffer Placement on Performance When Communicating Over a Rate-Variable Channel. Paper presented at ICSNC 2009. IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA
Open this publication in new window or tab >>Effect of Buffer Placement on Performance When Communicating Over a Rate-Variable Channel
2009 (English)In: / [ed] Eugen Borcoci, Michel Diaz, Cosmin Dini, Reijo Savola, IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA , 2009, p. 125-130Conference paper, Published paper (Refereed)
Abstract [en]

We compare the performance of two real-time multimedia communication systems for quality versus end-to-end delay. We develop an analytical framework for comparison when the systems use a deterministic time-varying channel. Moreover, we assess their performance for the Gilbert-Elliott channel model which alternates between a good and a bad state with time durations that are exponentially distributed. The goal of the paper is to select the best system with low average distortion while obeying a real-time constraint.

Place, publisher, year, edition, pages
IEEE, 345 E 47TH ST, NEW YORK, NY 10017 USA, 2009
Keywords
Buffers, Interactive systems, Source coding, Time-varying channel
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-68031 (URN)10.1109/ICSNC.2009.95 (DOI)000289709600022 ()978-1-4244-4772-5 (ISBN)
Conference
ICSNC 2009
Available from: 2011-05-06 Created: 2011-05-06 Last updated: 2012-11-22
Löfvenberg, J., Johansson, P. & Forchheimer, R. (2005). A Model for Mobility-Based Communication in Ad Hoc Networks. In: The Third Swedish National Computer Networking Workshop,2005.
Open this publication in new window or tab >>A Model for Mobility-Based Communication in Ad Hoc Networks
2005 (English)In: The Third Swedish National Computer Networking Workshop,2005, 2005Conference paper, Published paper (Other academic)
Abstract [en]

We introduce the concept of mobility-based communication in ad hoc networks, meaning that the packet transport is performed mainly by the nodes' movement. We outline a model for such networks, utilizing a stochastic model for the geographical location of the nodes. A test case is defined in which three strategies for packet forwarding are presented and evaluated.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-31642 (URN)17449 (Local ID)17449 (Archive number)17449 (OAI)
Available from: 2009-10-09 Created: 2009-10-09
Johansson, P. & Forchheimer, R. (2005). Source Coding Rate Control for Gilbert-Elliott Channel. In: RVK 05,2005 (pp. 543). Linköping: FOI
Open this publication in new window or tab >>Source Coding Rate Control for Gilbert-Elliott Channel
2005 (English)In: RVK 05,2005, Linköping: FOI , 2005, p. 543-Conference paper, Published paper (Refereed)
Abstract [en]

We consider the problem of choosing the rate for a source coder when transmitting lossy-compressed data in real-time over a channel with time-varying rate. The goal for the rate selection is to obtain a low average distortion while obeying a real-time constraint. We formulate the real-time constraint in terms of a limited buffer size. A few strategies for rate-control are suggested and evaluated for a Gilbert-Elliott type channel model. The results are also compared to a theoretical upper bound on performance for a rate-control algorithm working with constraints on buffer size.

Place, publisher, year, edition, pages
Linköping: FOI, 2005
Keywords
Rate-distortion, lossy compression, real-time communication
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-24189 (URN)3780 (Local ID)3780 (Archive number)3780 (OAI)
Available from: 2009-10-07 Created: 2009-10-07
Andersson, K., Johansson, P., Forchheimer, R. & Knutsson, H. (2002). Backward-forward motion compensated prediction. In: Proceedings of ACIVS 2002 (Advanced Concepts for Intelligent Vision Systems), Ghent, Belgium, September 9-11, 2002: . Paper presented at ACIVS 2002, Ghent, Belgium, September 9-11, 2002 (pp. 260-267).
Open this publication in new window or tab >>Backward-forward motion compensated prediction
2002 (English)In: Proceedings of ACIVS 2002 (Advanced Concepts for Intelligent Vision Systems), Ghent, Belgium, September 9-11, 2002, 2002, p. 260-267Conference paper, Published paper (Refereed)
Abstract [en]

This paper presents new methods for use of dense motion fields for motion compensation of interlaced video. The motion is estimated using previously decoded field-images. An initial motion compensated prediction is produced using the assumption that the motion is predictable in time. The motion estimation algorithm is phase-based and uses two or three field-images to achieve motion estimates with sub-pixel accuracy. To handle non-constant motion and the specific characteristics of the field-image to be coded, the initially predicted image is refined using forward motion compensation, based on block-matching. Tests show that this approach achieves higher PSNR than forward block-based motion estimation, when coding the residual with the same coder. The subjective performance is also better.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-24519 (URN)6651 (Local ID)6651 (Archive number)6651 (OAI)
Conference
ACIVS 2002, Ghent, Belgium, September 9-11, 2002
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2013-08-28
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