7107822
Minimax disappointment criterion for video broadcasting
Users of media broadcasting services generally experience different grades of overall performance because of the non-uniform quality of their channel conditions. In order to provide all users equally satisfactory performance, we propose a new performance criterion named "minimax disappointment", based on layered service levels and the basic principle of joint source-channel coding. This criterion minimizes for all users the maximum value of performance degradation between the received performance and the expected optimal performance, given each user's individual channel situation. In support of this criterion, we develop two broadcasting systems and a gradient-based optimization scheme. Our systems achieve universally near-maximal performance for multiple user classes by providing layered service.
36682359
Ultrasound speckle reduction by directional median filtering
This paper presents a novel adaptation of the median filter to the problem of boundary-preserving speckle reduction in ultrasonic imaging. The technique involves applying a bank of oriented one-dimensional median filters to the image, and retaining at each point the largest value among all the filter bank outputs. The result is an operator which suppresses speckle noise while retaining the structure of the image, particularly the thin bright streaks, which tend to occur along boundaries between tissue layers. The technique is compared to a block median filter and an algorithm discussed by Loupas et al. (1989), and is shown to be far superior to the median filter, and noticeably better than the Loupas filter at enhancing thin lines.
17269099
Edge detection in ultrasound speckle noise
Presents a statistical approach to edge detection in ultrasound speckle, and uses actual noise statistics to derive an expression for an optimal detection rule. The authors compute the optimal detector for the special case of uncorrelated speckle, and an approximation to the optimal detector for the case when signal-to-noise ratio (SNR) is high. They also discuss a simple sub-optimal detection scheme, and show that its performance is close to that of the optimal uncorrelated speckle detection rule, and surpasses that of the high-SNR approximation except in the case of extremely high SNR, in which case they both perform equally well.<<ETX>>
27407130
Wavelet-based 2-D multichannel signal estimation
In this paper, we present a new wavelet-based estimator for 2-D multichannel signals. Estimation of a 2-D multichannel signal relies on the ability to decorrelate the signal in both space and channel. The new estimator we present uses a 2-D discrete wavelet transform to approximately decorrelate the signal in space, allowing for efficient estimation of both stationary and nonstationary signals. When channel correlation is unknown, but depends only on channel separation, the DFT may be utilized to decorrelate the channel efficiently. In contrast to the optimal estimation scheme, our new estimator does not require second-order signal statistics, making it well suited to many applications. In addition to providing vastly improved visual quality, the new estimator typically yields signal-to-noise ratio gains of over 12 dB.
9647930
Cross-layer adaptive video coding to reduce energy on general-purpose processors
Traditionally, video encoders have been designed assuming that the more redundancy is removed, the better the encoder. However, on current laptops, reducing the compression efficiency of the video encoder by reducing the number of instructions used to perform compression can actually reduce the total energy used to encode and transmit a sequence. The correct balance between computation and compression efficiency may change dynamically, motivating adaptive encoders. At the same time, recent general-purpose processors also employ energy-driven adaptations. For best gains, the adaptations in the hardware and application layers must be coordinated. From a system design viewpoint, this coordination must happen through minimal, well-defined interfaces. This paper develops (1) an adaptive video encoder for general-purpose processors that trades computational complexity for compression efficiency to minimize total system energy, and (2) a method for determining the best configuration for such an encoder when running on a processor that is also adaptive. Our adaptive processor employs recent energy saving techniques of dynamic voltage and frequency scaling and architectural adaptation. Using a detailed simulator, we show that our cross-layer adaptive application algorithm reduces energy significantly, when employed on a fixed or adaptive processor.
1963957
Fast and efficient searches for effective optimization-phase sequences
It has long been known that a fixed ordering of optimization phases will not produce the best code for every application. One approach for addressing this phase-ordering problem is to use an evolutionary algorithm to search for a specific sequence of phases for each module or function. While such searches have been shown to produce more efficient code, the approach can be extremely slow because the application is compiled and possibly executed to evaluate each sequence's effectiveness. Consequently, evolutionary or iterative compilation schemes have been promoted for compilation systems targeting embedded applications where meeting strict constraints on execution time, code size, and power consumption is paramount and longer compilation times may be tolerated in the final stage of development, when an application is compiled one last time and embedded in a product. Unfortunately, even for small embedded applications, the search process can take many hours or even days making the approach less attractive to developers. In this paper, we describe two complementary general approaches for achieving faster searches for effective optimization sequences when using a genetic algorithm. The first approach reduces the search time by avoiding unnecessary executions of the application when possible. Results indicate search time reductions of 62%, on average, often reducing searches from hours to minutes. The second approach modifies the search so fewer generations are required to achieve the same results. Measurements show this approach decreases the average number of required generations by 59%. These improvements have the potential for making evolutionary compilation a viable choice for tuning embedded applications.
17285109
Concurrent operations on priority queues
Among the fastest priority queue implementations, skew heaps have properties that make them particularly suited to concurrent manipulation of shared queues. A concurrent version of the top down implementation of skew heaps can be produced from previously published sequential versions using almost mechanical transformations. This implementation requires O(log n) time to enqueue or dequeue an item, but it allows new operations to begin after only O(1) time on a MIMD machine. Thus, there is potential for significant concurrency when multiple processes share a queue. Applications to problems in graph theory and simulation are discussed in this article.
26900731
A new organization for a perceptron-based branch predictor and its FPGA implementation
An unaltered rearrangement of the original computation of a neural based predictor at the algorithmic level is introduced as a new organization. Its FPGA implementation generates circuits that are 1.7 faster than a direct implementation of the original algorithm. This faster clock rate allows to implement predictors with longer history lengths using the nearly the same hardware budget.
413264
Phonetic Speaker Recognition with Support Vector Machines
A recent area of significant progress in speaker recognition is the use of high level features—idiolect, phonetic relations, prosody, discourse structure, etc. A speaker not only has a distinctive acoustic sound but uses language in a characteristic manner. Large corpora of speech data available in recent years allow experimentation with long term statistics of phone patterns, word patterns, etc. of an individual. We propose the use of support vector machines and term frequency analysis of phone sequences to model a given speaker. To this end, we explore techniques for text categorization applied to the problem. We derive a new kernel based upon a linearization of likelihood ratio scoring. We introduce a new phone-based SVM speaker recognition approach that halves the error rate of conventional phone-based approaches.
44981587
A Tool for Inference Detection and Knowledge Discovery in Databases
Latent dependencies and relationships between groups of attributes in databases can produce inference channels that pose serious security threats. This paper uses a powerful knowledge discovery formalism for modeling and identifying latent inference channels in relational databases. The inference discovery methodology supports the analysis of precise and imprecise inference in database schemes and extensions. An interactive graphical tool for aiding inference discovery in Oracle databases is described. This tool is useful for identifying compromising inference channels in databases with many hidden dependencies.
18506033
Evaluation of voting systems
T he recent spate of security issues and allegations of " lost votes " in the U.S. demonstrates the inadequacy of the standards used to evaluate our election systems. The current standards (the FEC Voting Systems Standards) along with the revision being developed by IEEE 1583 (see the article by Deutsch and Berger in last month's Communications) are poor from another perspective: they establish a single pass/fail threshold for all systems, thereby eliminating incentives for existing suppliers to improve their products and rendering the market unattractive to new entrants. Moreover, they fail to precisely define the properties that should be required of a voting system. Instead, the standards rely on specific designs that are more than 15 years old. These legacy designs handicap promising new approaches, such as the various voter-verified printing schemes. New systems are unnecessarily burdened, while their substantial advantages go unrecognized. A set of well-defined properties would encourage the development and commercialization of better voting systems, especially when combined with objective ways to measure performance with respect to those properties. The overall result would then resemble the quantitative federal ratings for automobiles , where features such as vehicle safety and fuel efficiency form a basis for Consumer Reports-style comparative tables. Similarly, specific performance rating guidelines for different aspects of voting systems would provide meaningful metrics upon which system developers could compete. Decision makers, both regulatory and purchasing, would then be free to establish their own minimums for these metrics. Such a rating system can thus cleanly disentangle the development of the technical evaluation process from the various political and regulatory processes. asked the technical community for assistance in determining a new standard. This community is no stranger to the area of voting system properties and standards: a number of authors have tried to characterize requirements , and, in 2002, the Workshop on Election Standards and Technology addressed similar issues. The performance properties for voting systems might include the following: integrity of the votes (both voter verification, " I can check that my vote was captured correctly " and public verification, " anyone can check that all recorded votes were counted correctly "); ballot secrecy (both voter privacy and resistance to vote selling and coercion); robustness (including resistance to denial of service attacks); usability and accuracy (including access for the disabled); and transparency (both of mechanism and election data). The inherent differences in system architectures can be characterized …