61206461
A wavelet-based approach to detect shared congestion
Per-flow congestion control helps endpoints fairly and efficiently share network resources. Better utilization of network resources can be achieved, however, if congestion management algorithms can determine when two different flows share a congested link. Such knowledge can be used to implement cooperative congestion control or improve the overlay topology of a P2P system. Previous techniques to detect shared congestion either assume a common source or destination node, drop-tail queueing, or a single point of congestion. We propose in this paper a novel technique, applicable to any pair of paths on the Internet, without such limitations. Our technique employs a signal processing method, wavelet denoising, to separate queueing delay caused by network congestion from various other delay variations. Our wavelet-based technique is evaluated through both simulations and Internet experiments. We show that, when detecting shared congestion of paths with a common endpoint, our technique provides faster convergence and higher accuracy while using fewer packets than previous techniques, and that it also accurately determines when there is no shared congestion. Furthermore, we show that our technique is robust and accurate for paths without a common endpoint or synchronized clocks; more specifically, it can tolerate a synchronization offset of up to one second between two packet flows.
241209
Transient behaviors of TCP-friendly congestion control protocols
We investigate the fairness, smoothness, responsiveness, and aggressiveness of TCP and three representative TCP-friendly congestion control protocols: GAIMD, TFRC, and TEAR. The properties are evaluated both analytically and via simulation by studying protocol responses to three network environment changes. The first environment change is the inherent fluctuations in a stationary network environment. Under this scenario, we consider three types of sending rate variations: smoothness, short-term fairness, and long-term fairness. For a stationary environment, we observe that smoothness and fairness are positively correlated. We derive an analytical expression for the sending rate coefficient of variation for each of the four protocols. These analytical results match well with experimental results. The other two environment changes we study are a step increase of network congestion and a step increase of available bandwidth. Protocol responses to these changes reflect their responsiveness and aggressiveness, respectively.
528361
Eliminating Bottlenecks in Overlay Multicast
Recently many overlay multicast systems have been proposed due to the limited availability of IP multicast. Because they perform multicast forwarding without support from routers, data may be delivered multiple times over the same physical link, causing a bottleneck. This problem is more serious for applications demanding high bandwidth such as multimedia distribution. Although such bottlenecks can be removed by changing overlay topology, a naive approach may create bottlenecks in other parts of the network. In this paper, We propose an algorithm that removes all bottlenecks caused by the redundant data delivery of overlay multicast, detecting such bottlenecks using a wavelet-based technique we recently proposed. In a case where the source rate is constant and the available bandwidth of each link is not less than the source rate, our algorithm guarantees that every node receives at the full source rate. Simulation results show that even in a network with a dense receiver population, our algorithm finds a tree that satisfies all the receiving nodes while other heuristic-based approaches often fail.
63258
A doubly distributed genetic algorithm for network coding
We present a genetic algorithm which is distributed in two novel ways: along genotype and temporal axes. Our algorithm first distributes, for every member of the population, a subset of the genotype to each network node, rather thana subset of the population to each. This genotype distribution is shown to offer a significant gain in running time. Then, for efficient use of the computational resources in the network, our algorithm divides the candidate solutions intopipelined sets and thus the distribution is in the temporal domain, rather that in the spatial domain. This temporal distribution may lead to temporal inconsistency in selection and replacement, however our experiments yield better efficiency in terms of the time to convergence without incurring significant penalties.
33372839
3-D Facial Expression Recognition-Synthesis on PDA Incorporating Emotional Timing
This paper describes a pipeline by which facial expression of the face is recognized and then 3-D facial animation is synthesized in the remote place based upon timing information of the facial. The system first detects a facial area within the given image and then classifies its facial expression into 7 emotional weightings. Such weighting information, transmitted to the PDA via a mobile network, is used for non-photorealistic facial expression animation. A cartoon-like shading is used to render a 3-D avatar that conveys a familiar and yet unique facial character, even without employing extensive polygons. It turns out that facial expression animation using emotional curves is more effective in expressing the timing of an expression comparing to the linear interpolation method. The emotional avatar embedded on a mobile platform has some potential in conveying emotion between peoples in Internet.
18865506
Watermarking of 3D Irregular Meshes Based on Wavelet Multiresolution Analysis
In this paper, we propose a robust watermarking method for 3-D triangle surface meshes. Most previous methods based on the wavelet analysis can process only semi-regular meshes. Our proposal can be applied to irregular as well as regular meshes by using recently introduced irregular wavelet analysis scheme. L2-Norm of the wavelet coefficients is modified in various multi-resolution levels to embed the watermark. We also introduced a vertex and face re-ordering process as pre-processing in both watermark embedding and extraction for the robustness against connectivity reordering attacks. In addition, our proposal employs blind watermark detection scheme, which can extract the watermark without reference of cover mesh model. Through the simulations, we prove that our approach is robust against connectivity reordering as well as various kinds of geometrical attacks such as lossy compression and affine transform.
8330560
Shape Comparison of the Hippocampus Using a Multiresolution Representation and ICP Normalization
It is known that deformation of the hippocampus shape is involved with several neurological diseases. In this paper, we propose a hybrid shape representation scheme, which consists of multiresolution skeletons, voxels and meshes for the shape analysis of the hippocampus. Initially, a hippocampal surface model is reconstructed from MRI and then it is placed into a canonical coordinate system, where the position, orientation and scaling are normalized. From the voxel representation of the hippocampus, multiresolution skeletons are extracted and Iterative Closest Point normalization is carried out. Then the shape similarity of two hippocampal models is computed with a hierarchical fashion. In addition, we have implemented a neural network based classifier to discriminate whether a hippocampal model is normal or not. Results indicate that the proposed hybrid representation and the skeleton-based normalization using ICP are very effective in 3D shape analysis of the hippocampus.
12348020
Using a clone genealogy extractor for understanding and supporting evolution of code clones
Programmers often create similar code snippets or reuse existing code snippets by copying and pasting. Code clones---syntactically and semantically similar code snippets---can cause problems during software maintenance because programmers may need to locate code clones and change them consistently. In this work, we investigate (1) how code clones evolve, (2) how many code clones impose maintenance challenges, and (3) what kind of tool or engineering process would be useful for maintaining code clones.Based on a formal definition of clone evolution, we built a clone genealogy tool that automatically extracts the history of code clones from a source code repository (CVS). Our clone genealogy tool enables several analyses that reveal evolutionary characteristics of code clones. Our initial results suggest that aggressive refactoring may not be the best solution for all code clones; thus, we propose alternative tool solutions that assist in maintaining code clones using clone genealogy information.