45439748
Dynamic bandwidth allocation and buffer dimensioning for supporting video-on-demand services in virtual private networks
This paper focuses on the optimization of network bandwidth allocation and buffer dimensioning for transporting pre-stored MPEG video data from the source to the playback destination across virtual private network (VPN). This is one of the most important issues in the support of video-on-demand (VoD) service over VPN. This paper provides a novel scheme in the dynamic allocation of bandwidth to segments of video using the ABR mode. The dynamic bandwidth allocation mechanism is based on a new concept, called playback tunnel obtained from the traffic characteristics of the pre-stored MPEG video trace, to determine the optimum of transmission bandwidth as well as the optimum of buffer capacity to ensure that the playback buffer neither underflows nor overflows. The proposed scheme is tested with real-life MPEG video traces. The obtained results have shown its significant performance improvement in terms of the capacity of playback buffer, the start-up playback delay, network utilization and the network multiplexing gain.
205935860
An ATM cross-connecting node using optical CDMA
An asynchronous transfer mode (ATM) cross-connecting node is proposed based on direct sequence optical code division multiple access (DS-OCDMA). No buffering is necessary to facilitate switching because code conversion is instead emulating the switching function. The switch is also capable of limited dynamic bandwidth allocation. It is free from timing jitters and switching delay is significantly reduced. The switch provides a new approach to asynchronous cross-connection in the ATM core network, locally or over a wider area. The performance with the new proposed switch is evaluated using prime and modified prime OCDMA codes.
12649565
Optical nonlinear effects on the performance of IP traffic over GMPLS-based DWDM networks
With the introduction of Generalized multiprotocol label switching in the common control plane for optical crossconnects and electrical switching devices, the integration of IP and dense wavelength division multiplexing can be efficiently achieved. When IP traffic flows are directly mapped to optical channels without SDH inter-layer, the bursty nature of IP traffic may have significant effect on the performance of the optical channel. On the other hand, the nonlinear effects of the optical channel may also have significant effect on the performance at IP level. This paper focuses on the effect of fiber nonlinearities on the performance of IP traffic. Numerical results including IP packet error probability and high-order distribution functions of IP packet error are presented in terms of IP traffic load, input light signal power and the frequency space between the optical wavelengths. It is demonstrated that when IP traffic load is light in such systems, the effect of either four-wave mixing (FWM) or stimulated Raman scattering (SRS) is much less serious than the worst-case assumption, and the limitation on allowable power of input light is also relaxed. The obtained numerical results demonstrated that FWM and SRS are both sensitive to power level of input light and frequency spacing, but each in a unique way. Effort must be taken in system design to avoid improving the performance of one effect at the expense of deteriorating the other.
205934323
Effect of delay and delay jitter on voice/video over IP
Internet, especially in the situation when network has bursty background traffic. However, it is usually difficult to evaluate the statistics of delay and delay jitter in such bursty traffic environment due to their transient queuing nature. This paper focuses on the performance behavior of delay and delay jitter at IP packet level and also their effects on the performance of voice and video packet streams when they are multiplexed with bursty background traffic in IP routers. The performance analysis of delay and delay jitter is done using the transient queuing solution technique. The numerical results are presented in terms of probability density functions (pdfs) of delay and delay jitter, which focus on their effects on speech samples and video frames.
34513226
Incorporating priority scheme in IPv6 over ATM networks
An effective method to support multiple QoS classes in IPv6 over ATM networks is implemented by mapping of the priority field in IPv6 to the ATM cell. Such a scheme might not be necessary for simple congestion control in a network of equal capacity links; however, it might be important for multicasting to destinations reachable through a very diverse capacity network. When network congestion occurs, the cell loss requirements for different services can be satisfied by selectively discarding low priority cells. The results obtained show how the QoS can be affected by this field and how priority can be given for more important traffic in times of network congestion.
35154579
Incorporating priority scheme in IPv6 over ATM networks
An effective approach to support multiple QoS classes in IPv6 running over ATM networks is implemented by mapping the priority field of IPv6 into the ATM format. Such a scheme might not be necessary for simple congestion control in a network of equal capacity links, however, it might be important for multicasting to destinations reachable through a very diverse capacity network. When network congestion occurs, the cell loss requirements for different services can be satisfied by selectively discarding low priority cells. As the multi-priority scheme used in IPv6 is a ''differentiated service'' mechanism to enhance the QoS by best effort, its performance is certainly affected by the background traffic when these multi-priority traffic are multiplexed at the ATM level. This paper focuses on the performance with multi-priority scheme under different traffic conditions to determine the loss characteristics. The expected results are how QoS is affected and how priority can be given for more important traffic in the case of congested network.
12937715
Improvement of Color Video Demosaicking in Temporal Domain
Color demosaicking is critical to the image quality of digital still and video cameras that use a single-sensor array. Limited by the mosaic sampling pattern of the color filter array (CFA), color artifacts may occur in a demosaicked image in areas of high-frequency and/or sharp color transition structures. However, a color digital video camera captures a sequence of mosaic images and the temporal dimension of the color signals provides a rich source of information about the scene via camera and object motions. This paper proposes an inter-frame demosaicking approach to take advantage of all three forms of pixel correlations: spatial, spectral, and temporal. By motion estimation and statistical data fusion between adjacent mosaic frames, the new approach can remove much of the color artifacts that survive intra-frame demosaicking and also improve tone reproduction accuracy. Empirical results show that the proposed inter-frame demosaicking approach consistently outperforms its intra-frame counterparts both in peak signal-to-noise measure and subjective visual quality
8791084
Collecting the internet AS-level topology
At the inter-domain level, the Internet topology can be represented by a graph with Autonomous Systems (ASes) as nodes and AS peerings as links. This AS-level topology graph has been widely used in a variety of research efforts. Conventionally this topology graph is derived from routing tables collected by Route Views or RIPE RIS. In this work, we assemble the most complete AS-level topology by extending the conventional method along two dimensions. First, in addition to using data from RouteViews and RIPE RIS, we also collect data from many other sources, including route servers, looking glasses, and routing registries. Second, in addition to using routing tables, we also accumulate topological information from routing updates over time. The resulting topology graph on a recent day contains 44% more links and 3% more nodes than that from using RouteViews routing tables alone. Our data collection and topology generation process have been automated, and we publish the latest topology on the web on a daily basis.
12511043
Real-time lossless compression of mosaic video sequences
This paper presents a simple, fast coding technique for lossless compression of mosaic video data. The design of a video codec needs to strike a balance between the compression performance and the codec throughput. Aiming to make the encoding throughput high enough for real-time lossless video compression, we propose a hybrid scheme of inter and intraframe coding. Interframe predictive coding is invoked only when the motion between adjacent frames is modest and a simple motion compensation operation can significantly improve the compression performance. Otherwise, still frame compression is performed to keep the complexity low. Experimental results show that the proposed scheme achieves higher lossless video compression ratio than existing methods such as JPEG-LS and JPEG-2000.
32712531
Some properties of 3-domination-critical graphs
Abstract A graph G is 3- γ -critical if its domination number γ is 3 and the addition of any edge decreases γ by 1. Wojcicka conjectured that every 3- γ -critical graph with minimum degree δ ⩾2 has a hamiltonian cycle. In this paper, we prove that if G is a 3- γ -critical connected graph of order n with minimum degree δ ⩾2, then (1) G is 1-tough; (2) the circumference of G is at least n −1.
636109
VizStruct: exploratory visualization for gene expression profiling
MOTIVATION
DNA arrays provide a broad snapshot of the state of the cell by measuring the expression levels of thousands of genes simultaneously. Visualization techniques can enable the exploration and detection of patterns and relationships in a complex data set by presenting the data in a graphical format in which the key characteristics become more apparent. The dimensionality and size of array data sets however present significant challenges to visualization. The purpose of this study is to present an interactive approach for visualizing variations in gene expression profiles and to assess its usefulness for classifying samples.


RESULTS
The first Fourier harmonic projection was used to map multi-dimensional gene expression data to two dimensions in an implementation called VizStruct. The visualization method was tested using the differentially expressed genes identified in eight separate gene expression data sets. The samples were classified using the oblique decision tree (OC1) algorithm to provide a procedure for visualization-driven classification. The classifiers were evaluated by the holdout and the cross-validation techniques. The proposed method was found to achieve high accuracy.


AVAILABILITY
Detailed mathematical derivation of all mapping properties as well as figures in color can be found as supplementary on the web page http://www.cse.buffalo.edu/DBGROUP/bioinformatics/supplementary/vizstruct. All programs were written in Java and Matlab and software code is available by request from the first author.