3919925
Calculation of Loss Probability in a Finite Size Partitioned Buffer for Quantitative Assured Service
This paper proposes an approximate yet accurate approach to calculate the loss probabilities in a finite size partitioned buffer system for the achievement of a quantitative assured service in differentiated services networks. The input is modeled as a fractional Brownian motion (FBM) process including J classes of traffic with different packet loss requirements. A first-in first- out buffer partitioned with J-1 thresholds is used to provide J loss priorities. Heuristic expressions of the loss probabilities for all the J classes are derived, and validated by computer simulations. The proposed loss calculation technique is then extended to a general input process by using the recently proposed traffic substitution technique, where both long-range dependent and short-range dependent input sources are equivalent to a properly parameterized FBM. We also apply the loss calculation to admission control, where the partition thresholds are optimally configured for quality of service guarantee and maximal resource utilization. Computer simulation results demonstrate that resource allocation based on the accurate finite buffer loss analysis results in much more efficient resource utilization than that based on the classic large-buffer overflow approximation.
3921961
Call admission control for integrated on/off voice and best-effort data services in mobile cellular communications
This paper proposes a call admission control (CAC) policy for a cellular system supporting voice and data services, and providing a higher priority to handoff calls than to new calls. A procedure for searching the optimal admission region is given. The traffic flow is characterized by a three-dimensional (3-D) birth-death model, which captures the complex interaction between the on/off voice and best-effort data traffic sharing the total resources without partition. To reduce complexity, the 3-D model is simplified to an exact (approximate) 2-D model for voice (data). The mathematical expressions are then derived for the performance measures and for the minimal amount of resources required for quality-of-service (QoS) provisioning. Numerical results demonstrate that: 1) the proposed CAC policy performs well in terms of QoS satisfaction and resource utilization; 2) the approximate 2-D model for data traffic can achieve a high accuracy in the traffic flow characterization; and 3) the admission regions obtained by the proposed search method agree very well with those obtained by numerically solving the mathematical equations. Furthermore, computer simulation results demonstrate that the impact of lognormal distributed data file size is not significant, and may be compensated by conservatively applying the Markovian analysis results.
14894173
Gingko: correlating causal paths in distributed systems
Many large-scale systems are distributed systems of multiple communicating components. Finding causal paths of message traces between components throughout these systems is important to uncover runtime behaviors and identify the root cause of failures, but this "art" often hides in the heads of developers or domain experts. Our goal is to design tools and algorithms to help developers record this art into logs and help the modestly-skilled users and system administrators master it to make better use and management of distributed systems. In this paper, we present a methodology that automatically builds the causal paths of message traces by 1) an agreement with programmers on the style and content of logs produced by operational distributed systems they develop and 2) a correlation algorithm to build message causal paths with the clues from these logs. To validate this mechanism, we have implemented Gingko, a prototype providing a tool chain for users to gain better comprehensions of distributed systems and to debug them efficiently when errors happen.
201804
Analysis on Appearance Reasons of the Positive Feedback Traders
Positive feedback traders buy the asset when price is rising and sell it when price is falling. This type of speculation in short term causes the violent fluctuation for a given asset price, and make great influence to the stabilization of the financial market. The price reaction model under the influence of noise traders is established by considering the influence which the investment cost and information arrival rate make to the arbitrage and asset price. We analyze the reasons and conditions why positive feedback traders are born from quantitative analysis
26330758
Music Genre Classification Based on Multiple Classifier Fusion
Although researchers have made great progresses on music genre classification in recent years, the need for more accurate system is still not satisfied. In this paper, we propose a method for further reducing the classification error rate based on multiple classifier fusion. First of all, MFCCs and four features from MPEG-7 audio descriptor are extracted in every short time frame, and then a group of frames are gathered into a longer segment, in which mean and variance of these short time frames features are calculated. The segment is considered as the basic unit for training and testing module. Then random forest (RF) and multilayer perceptron neural network (MLP) are executed on such segment independently. Finally, a weighted voting fusion strategy is employed to fusion the result of the two classifiers on each segment, and the whole file decision is made by selecting the most frequently labeled genre over all the segments. Experiments showed that the approach is effective. The fusion result gets 12.4% relative reduction in error rate compared to our baseline system.
8141740
A Vector-Based Approach to Broadcast Audio Database Indexing and Retrieval
This paper proposes a novel framework to index and retrieve audio content from broadcast database that contains both speech and music. In this framework, we model the acoustic events using hidden Markov models, which are then used to decode the audio content. The decoding results in the form of acoustic token sequence and acoustic lattice are used to generate features for indexing and retrieval with the vector space model. Experiments were carried out on the TRECVID database and the results showed that the proposed framework is effective in audio information retrieval. The results also showed that the features generated from the acoustic lattice provide more accurate information than token sequence.
11153922
Enhancing security using legality assertions
Buffer overflows have been the most common form of security vulnerability in the past decade. A number of techniques have been proposed to address such attacks. Some are limited to protecting the return address on the stack; others are more general, but have undesirable properties such as large overhead and false warnings. The approach described in this paper uses legality assertions, source code assertions inserted before each subscript and pointer dereference that explicitly check that the referencing expression actually specifies a location within the array or object pointed at run time. A transformation system is developed to analyze a program and annotate it with appropriate assertions automatically. This approach detects buffer vulnerabilities in both stack and heap memory as well as potential buffer overflows in library functions. Runtime checking through using automatically inferred assertions considerably enhances the accuracy and efficiency of buffer overflow detection. A number of example buffer overflow-exploiting C programs are used to demonstrate the effectiveness of this approach.