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.
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.
46136838
IPv6 traffic with multi-class QoS in VPN
Abstract This paper focuses on the modeling and performance analysis for IPv6 traffic with multi-class QoS in virtual private networks (VPNs). The multi-class QoS is implemented on differentiated service basis using priority scheme of 4 bits defined in the packet header of IPv6. A VPN-enabled IP router is modeled as a tandem queuing system in which each output link consists of two parallel priority output queues. The high-priority queue is used to carry the delay sensitive traffic while the low-priority queue is used to carry the delay insensitive traffic. On the other hand, multiple thresholds are implemented in each queue, respectively, for packet loss priority control. The performance analysis is done using fluid flow techniques. The numerical results obtained from the analysis show that the differentiated service based on the priority schemes defined in IPv6 is able to effectively satisfy the multi-class QoS requirement for supporting multimedia services in VPN. The performance trade-off between the delay sensitive traffic and delay insensitive traffic in terms of traffic throughput, packet loss probability and end-to-end delay in VPN networks is presented.
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.
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.
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.
12034638
A block-based inter-band lossless hyperspectral image compressor
We propose a hyperspectral image compressor called BH which considers its input image as being partitioned into square blocks, each lying entirely within a particular band, and compresses one such block at a time by using the following steps: first predict the block from the corresponding block in the previous band, then select a predesigned code based on the prediction errors, and finally encode the predictor coefficient and errors. Apart from giving good compression rates and being fast, BH can provide random access to spatial locations in the image. We hypothesize that BH works well because it accommodates the rapidly changing image brightness that often occurs in hyperspectral images. We also propose an intra-band compressor called LM which is worse than BH, but whose performance helps explain BH's performance.
17414114
On the application of cross correlation function to subsample discrete time delay estimation
Cross correlation function (CCF) of signals is an important tool of multi-sensors signal processing. Parabola functions are commonly used as parametric models of the CCF in time delay estimation. The parameters are determined by fitting samples near the maximum of the CCF to a parabola function. In this paper we analyze the CCF for the stationary processes of exponential auto-correlation function, with respect to two important types of sensor sampling kernels. Our analysis explains why the parabola is an acceptable model of CCF in estimating the time delay. More importantly, we demonstrate that the Gaussian function is a better and more robust approximation of CCF than the parabola. This new approximation approach leads to higher precision in time delay estimation using the CCF peak locating strategy. Simulations are also carried out to evaluate the performance of the proposed estimation method for different sample window sizes and signal to noise ratios. The new method offers significant improvement over the current parabola based method.
9735559
Probabilistic analysis for combinatorial functions of moving points
We initiate a probabilistic study of configuration functions of moving points. In our probabilistic model, a particle is given an initiaf position and a velocity drawn independently at random from the same distribution D. We show that if n particles are drawn independently at random from the uniform distribution on the square, their convex hull undergoes El(logz n) combinatorial changes in expectation, their Voronoi diagram undergoes e(n312 ) combinatorial changes, and their closest pair undergoes El(n) combinatorial changes.
3730862
Distributed Resource Allocation in Stream Processing Systems
Distributed stream processing architecture has emerged as appealing solution to coping with the analysis of large amount of data from dispersed sources. A fundamental problem in such stream processing systems is how to best utilize the available resources so that the overall system performance is optimized. We consider a distributed stream processing system that consists of a network of cooperating servers, collectively providing processing services for multiple data streams. Each stream is required to complete a series of operations on various servers. We assume all servers have finite computing resources and all communication links have finite available bandwidth. The problem is to find distributed schemes to allocate the limited computing resources as well as the communication bandwidth in the system so as to achieve a maximum concurrent throughput for all output streams. We present a generalized multicommodity flow model for the above problem. We develop a distributed resource allocation algorithm that guarantees the optimality. We also provide detailed analysis on the complexity of the algorithm and demonstrate the performance using numerical experiments.
12946117
Searching One Billion Web Images by Content: Challenges and Opportunities
Although content-based image retrieval has been studied for decades, most commercial image search engines are still text-based. However, there is a growing demand for techniques to support content-based image search at Web scale. In this paper, we propose an ambitious goal to searching one billion Web images by content, and discuss the major challenges and opportunities. We also present several important applications that can be greatly benefited by techniques to enable Web-scale image search by content. These applications include image copyright infringement detection, street-side photo search, and searchbased image annotation. We believe that the insights presented in the paper are enlightening to researchers in this field, and any breakthrough we make in this space will lead to many impactful applications in the future.