The video on demand (VOD) service can be implemented in a variety of ways called service policies. This paper investigates the characteristics of three distinct service policies, namely, on demand single cast, on demand multicast and phase multicast. The performance of the different service policies are evaluated and it was found that the on demand single cast policy is suitable for specialised viewing while phase multicast and on demand multicast can be used for broadcast video.
This paper develops \(\mathsf {Hercules} \) , a system for entity resolution (ER), conflict resolution (CR), timeliness deduction (TD) and missing value/link imputation (MI) in graphs. It proposes \(\mathsf {GCR^{+}\!s} \) , a class of graph cleaning rules that support not only predicates for ER and CR, but also temporal orders to deduce timeliness and data extraction to impute missing data. As opposed to previous graph rules, \(\mathsf {GCR^{+}\!s} \) are defined with a dual graph pattern to accommodate irregular structures of schemaless graphs, and adopt patterns of a star form to reduce the complexity. We show that while the implication and satisfiability problems are intractable for \(\mathsf {GCR^{+}\!s} \) , it is in PTIME to detect and correct errors with \(\mathsf {GCR^{+}\!s} \) . Underlying \(\mathsf {Hercules} \) , we train a ranking model to predict the temporal orders on attributes, and embed it as a predicate of \(\mathsf {GCR^{+}\!s} \) . We provide an algorithm for discovering \(\mathsf {GCR^{+}\!s} \) by combining the generations of patterns and predicates. We also develop a method for conducting ER, CR, TD and MI in the same process to improve the overall quality of graphs, by leveraging their interactions and chasing with \(\mathsf {GCR^{+}\!s} \) ; we show that the method has the Church-Rosser property under certain conditions. Using real-life and synthetic graphs, we empirically verify that \(\mathsf {Hercules} \) is 53% more accurate than the state-of-the-art graph cleaning systems, and performs comparably in efficiency and scalability.
In dynamic Magnetic Resonance Imaging (MRI), due to the limitation of imaging speed, it is commonly required to reconstruct the images from a reduced fourier encoded K-space sequence. This paper presents two temporal model based methods to estimate the un-acquired K-space data, called Adaptive K-space Updating (AKU) methods. The AKU reconstruction algorithms are directly applicable to the truncated K-space sequence generated by the well known Fourier Keyhole (FK) encoding scheme. The experimental study on the real MRI data shows that the proposed AKU methods can produce images with much lower reconstruction error than conventional FK method.
Examines the role of the loop/interpolation filter in the motion compensation loop of hybrid coders. Using the Wiener filtering concept and the statistical model developed by Chen and Pang (1992), the optimum filter that minimises the prediction error has been found. The result is expressed in an explicit form in terms of a correlation parameter, /spl rho/ and an inaccuracy parameter, /spl alpha/. It explains many current practices in MPEG and H.261 coders, as well as the leakage predictor, 3-tap versus 8-tap filters and other related issues. The analysis shows that minimum bit rate can only be achieved if the loop filter matches the statistical characteristic of the motion-compensated signal. Furthermore, since the motion noise characteristic could be very different in the horizontal and vertical direction for many sequences, the decision to deploy the optimum filter should be made separately in the two directions. The paper also derives the scalar loop filter in DCT domain. The scalar filter is sub-optimal, but it requires less computational load than the spatial domain filter (64 versus 484 multiplications per 8/spl times/8 block). Experiments show that it performs almost as efficiently as the optimum 3-tap spatial domain filter, thus ascertaining that its performance has not been significantly compromised by the scalar requirement. Experimental simulations on test sequences confirm the theoretical optimum results, and indirectly show that the simple statistical model used in the derivation is adequate.< >
Using a new sine-plane approach, an easy-to-use design procedure for microwave filters is developed. The design formulas are very simple and are valid for filters of wide bandwidths. Furthermore, the new design offers many advantages over other presently available designs.
This letter is aimed at establishing an equivalent LRC network for the cascaded ULC― and URC― networks. * Once the concept of equivalency is established, the wealth of classical synthesis theory of the LRC network can be inherited for the use of cascaded ULC― and URC― networks. Such application is demonstrated by using the continued fraction-expansion technique for the synthesis of cascaded ULC― or URC― network. This synthesis technique will be of particular interest in stepped-impedance transformer synthesis.
The aim of this paper is to analyze and compare the performance of trellis coded Space Time Transmit Diversity (STTD) scheme and trellis coded Time Switched Transmit Diversity (TSTD) scheme for CDMA system. In the first part of the paper we will derive an upper bound for the Frame Error Rate (FER) of both the schemes. We then use the expressions for the upper bound to present the design of trellis codes that are optimum in terms of FER. In the second part of the paper we provide numerical results that validate the design. We conclude with a comparison of both schemes under different channel conditions and multi-user interference.
An incoherent detection scheme based on frequency discrimination for minimum-shift keying (MSK) optical transmission systems is proposed to significantly extend the reach of uncompensated transmission distance. The receiver consists of dual narrowband optical filters in association with an optical delay line. This photonic front end operates based on frequency discrimination principles of matched filters, rather than relying on the phase of the optical carrier. Hence, its performance is less sensitive to the all-pass quadratic phase transfer function of the fiber transmission medium and is thus less susceptible to fiber chromatic dispersion. The photonic front-end optical receiver for 40-Gb/s optical MSK offers a dispersion tolerance of up to plusmn340 ps/nm for 1-dB power penalty at a bit-error rate of 10 -9 . This achievement is approximately five to seven times better than that of the existing value based on the Mach-Zehnder delay interferometer (MZDI) optical balanced receiver. Furthermore, the receiver is shown to be robust to polarization-mode dispersion.
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