An improved macroblock level rate control algorithm for MPEG-4 video object coding

2005 International Symposium on Intelligent Signal Processing and Communication Systems (ISPACS 2005), Hong Kong, 13-16 December 2005This paper presents an improved macroblock (MB) level rate control algorithm for MPEG-4 object coding. Motivated by the statistical analysis of the coding of MBs and VOPs for typical sequences, a refined quadratic rate-distortion model is proposed in the new MB rate control algorithm. The basic idea is to exploit the statistical coding property of a group of MBs coded by an identical QP rather than an individual MB to do the modeling, thereby producing more stable quantization parameter to improve the estimation and coding performances. In addition, some improved measures which explore the new model for coding the MBs in a VOP are incorporated. Simulation results show that the proposed algorithm can achieve the much smoother bit rate and better picture quality in terms of PSNR than the MPEG-4 VM18 algorithm for the tested sequences. © 2005 IEEE.published_or_final_versio

Sustained slow-scale oscillation in higher order current-mode controlled converter

Author name used in this publication: Chi K. Tse2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

A semi-discrete model and its approach to a solution for a wide moving jam in traffic flow

This paper investigates the analytical and numerical solutions to wide moving jams in traffic flow. Under the framework of the Lagrange coordinates, a semi-discrete model and a continuum model correlate with each other, in which the former model approaches the latter as the increment ΔM in the former model vanishes. This implies that the solution to a wide moving jam in the latter model, which can be analytically derived using the known theory, can be conceivably taken as an approximation to that of the former model. These results were verified through numerical simulations. Because a detailed understanding of the traffic phase "wide moving jam" is very important for the further development of Kerner's three-phase traffic theory, this study helps to explain the empirical features of traffic breakdown and resulting congested traffic patterns that are observed in real traffic. © 2011 Elsevier B.V. All rights reserved.postprin

Symbol-timing estimation in space-time coding systems based on orthogonal training sequences

Space-time coding has received considerable interest recently as a simple transmit diversity technique for improving the capacity and data rate of a channel without bandwidth expansion. Most research in space-time coding, however, assumes that the symbol timing at the receiver is perfectly known. In practice, this has to be estimated with high accuracy. In this paper, a new symbol-timing estimator for space-time coding systems is proposed. It improves the conventional algorithm of Naguib et al. such that accurate timing estimates can be obtained even if the over-sampling ratio is small. Analytical mean-square error (MSE) expressions are derived for the proposed estimator. Simulation and analytical results show that for a modest oversampling ratio (such as Q equal to four), the MSE of the proposed estimator is significantly smaller than that of the conventional algorithm. The effects of the number of transmit and receive antennas, the oversampling ratio, and the length of training sequence on the MSE are also examined. © 2005 IEEE.published_or_final_versio

Load/Price Forecasting and Management of Demand Response for Smart Grids: Methodologies and Challenges

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Object-based coding for plenoptic videos

A new object-based coding system for a class of dynamic image-based representations called plenoptic videos (PVs) is proposed. PVs are simplified dynamic light fields, where the videos are taken at regularly spaced locations along line segments instead of a 2-D plane. In the proposed object-based approach, objects at different depth values are segmented to improve the rendering quality. By encoding PVs at the object level, desirable functionalities such as scalability of contents, error resilience, and interactivity with an individual image-based rendering (IBR) object can be achieved. Besides supporting the coding of texture and binary shape maps for IBR objects with arbitrary shapes, the proposed system also supports the coding of grayscale alpha maps as well as depth maps (geometry information) to respectively facilitate the matting and rendering of the IBR objects. Both temporal and spatial redundancies among the streams in the PV are exploited to improve the coding performance, while avoiding excessive complexity in selective decoding of PVs to support fast rendering speed. Advanced spatial/temporal prediction methods such as global disparity-compensated prediction, as well as direct prediction and its extensions are developed. The bit allocation and rate control scheme employing a new convex optimization-based approach are also introduced. Experimental results show that considerable improvements in coding performance are obtained for both synthetic and real scenes, while supporting the stated object-based functionalities. © 2006 IEEE.published_or_final_versio

MOTSA TOF-MRA using multi-oblique-stacks acquisition (MOSA)

One of the intrinsic advantages of current TOF MRA techniques is their insensitivity to in-plane blood flow or turbulent flow, causing hypointense signal or discontinuity in blood vessels in MRA images. To overcome this problem, a multi-oblique-stacks acquisition (MOSA) technique is proposed to improve the visualization of in-plane blood flows in MRA. The results showed that TOF-MRA obtained from MOSA was improved as compared to that of conventional MOTSA for the same amount of scan time.published_or_final_versio

Timing estimation and resynchronization for amplify-and-forward communication systems

This paper proposes a general framework to effectively estimate the unknown timing and channel parameters, as well as design efficient timing resynchronization algorithms for asynchronous amplify-and-forward (AF) cooperative communication systems. In order to obtain reliable timing and channel parameters, a least squares (LS) estimator is proposed for initial estimation and an iterative maximum-likelihood (ML) estimator is derived to refine the LS estimates. Furthermore, a timing and channel uncertainty analysis based on the CramrRao bounds (CRB) is presented to provide insights into the system uncertainties resulted from estimation. Using the parameter estimates and uncertainty information in our analysis, timing resynchronization algorithms that are robust to estimation errors are designed jointly at the relays and the destination. The proposed framework is developed for different AF systems with varying degrees of timing misalignment and channel uncertainties and is numerically shown to provide excellent performances that approach the synchronized case with perfect channel information. © 2006 IEEE.published_or_final_versio

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Erroneous results from SPICE simulations of switching converters : a dynamical system viewpoint

Author name used in this publication: Chi K. TseRefereed conference paper2005-2006 > Academic research: refereed > Refereed conference paperVersion of RecordPublishe