Showing papers by "Beijing University of Posts and Telecommunications published in 2009"

Execution Anomaly Detection in Distributed Systems through Unstructured Log Analysis

Abstract: Detection of execution anomalies is very important for the maintenance, development, and performance refinement of large scale distributed systems. Execution anomalies include both work flow errors and low performance problems. People often use system logs produced by distributed systems for troubleshooting and problem diagnosis. However, manually inspecting system logs to detect anomalies is unfeasible due to the increasing scale and complexity of distributed systems. Therefore, there is a great demand for automatic anomalies detection techniques based on log analysis. In this paper, we propose an unstructured log analysis technique for anomalies detection. In the technique, we propose a novel algorithm to convert free form text messages in log files to log keys without heavily relying on application specific knowledge. The log keys correspond to the log-print statements in the source code which can provide cues of system execution behavior. After converting log messages to log keys, we learn a Finite State Automaton (FSA) from training log sequences to present the normal work flow for each system component. At the same time, a performance measurement model is learned to characterize the normal execution performance based on the log mes-sages’ timing information. With these learned models, we can automatically detect anomalies in newly input log files. Experiments on Hadoop and SILK show that the technique can effectively detect running anomalies.

Mining spectrum usage data: a large-scale spectrum measurement study

Abstract: Dynamic spectrum access has been a subject of extensive research activity in recent years. The increasing volume of literature calls for a deeper understanding of the characteristics of current spectrum utilization. In this paper we present a detailed spectrum measurement study, with data collected in the 20MHz to 3GHz spectrum band and at four locations concurrently in South China. We examine the first and second order statistics of the collected data, including channel occupancy/vacancy statistics, channel utilization within each individual wireless service, and the temporal, spectral, and spatial correlation of these measures. Main findings include that the channel vacancy durations follow an exponential-like distribution, but are not independently distributed over time, and that significant spectral and spatial correlations are found between channels of the same service. We then exploit such spectrum correlation to develop a 2-dimensional frequent pattern mining algorithm that can accurately predict channel availability based on past observations.

An efficient two-party quantum private comparison protocol with decoy photons and two-photon entanglement

Abstract: Following some ideas of the quantum secret sharing (QSS) protocol (2008, Phys. Lett. A 372, 1957), we propose an efficient quantum private comparison (QPC) protocol for comparing information of equality with the help of a third party (TP). The protocol can ensure fairness, efficiency and security. The protocol is fair, which means that one party knows the sound result of the comparison if and only if the other one knows the result. The protocol is efficient with the help of the TP for calculating. However, the TP cannot learn any information about the players' respective private inputs and even about the comparison result and cannot collude with any player. The protocol is secure for the two players, that is, any information about their respective secret inputs will not leak except the final computation result. A precise proof of security of the protocol is presented. Applications of this protocol may include private bidding and auctions, secret ballot elections, commercial business, identification in a number of scenarios and so on.

Interference avoidance mechanisms in the hybrid cellular and device-to-device systems

Abstract: A hybrid system of cellular mode and device-to-device (D2D) mode is considered in this paper, where the cellular uplink resource is reused by the D2D transmission. In order to maximize the overall system performance, the mutual interference between cellular and D2D sub-systems has to be addressed. Here, two mechanisms are proposed to solve the problem: One is mitigating the interference from cellular transmission to D2D communication by an interference tracing approach. The other one is aiming to reduce the interference from D2D transmission to cellular communication by a tolerable interference broadcasting approach. Both mechanisms can work independently or jointly to synergy the transmission in the hybrid system for the efficient resource utilization. In the end, simulation is conducted to study the performance of the proposed schemes, which shows satisfying results.

A Dual Band Unequal Wilkinson Power Divider Without Reactive Components

Abstract: This paper presents an unequal Wilkinson power divider operating at arbitrary dual band without reactive components (such as inductors and capacitors). To satisfy the unequal characteristic, a novel structure is proposed with two groups of transmission lines and two parallel stubs. Closed-form equations containing all parameters of this structure are derived based on circuit theory and transmission line theory. For verification, two groups of experimental results including open and short stubs are presented. It can be found that all the analytical features of this unequal power divider can be fulfilled at arbitrary dual band simultaneously.

A FCM-Based Peer Grouping Scheme for Node Failure Recovery in Wireless P2P File Sharing

Abstract: An effective node failure recovery scheme is very important in wireless peer-to-peer (P2P) file sharing networks. Most of the existing failure recovery protocols are based on backup path mechanism, in which a new path will be used if the original one breaks. However, due to the limited resources in wireless environments, the maintenance of backup paths is expensive. Moreover, the time spending on path switch may be unacceptable long. In this paper, we propose a novel peer grouping scheme to select a qualified peer from a group to replace the failed node. The main criteria in deciding the backup node is derived with the help of recent advances in fuzzy cognitive maps (FCM). Several influential factors are considered, including energy, movement, lingering time and security, with further investigation on their respective contributions to node failure risk. We compare the performance of the proposed scheme with that of traditional path redirection and multi-path backup algorithms. The FCM-based peer grouping scheme has significant improvement in failure recovery time and file transfer time.

Mean-variance analysis of the newsvendor model with stockout cost

Abstract: Note: Pre-published version entitled: A Note on Mean-variance Analysis of the Newsvendor Model with Stockout Cost.

Mobility Change in Two Types of Metamorphic Parallel Mechanisms

Abstract: This paper presents a new joint coined as the rT joint and proposes two types of metamorphic parallel mechanisms assembled with this rT joint. In the first type, the mechanism changes its topology by turning the rT joints in all limbs into different configurations. This change in mobility is completed by two cases illustrated by a 3(rT)PS metamorphic parallel mechanism having variable mobility from 3 to 6 and a 3(rT)P(rT) parallel mechanism having various configurations including pure translations, pure rotations, and mobility 4. In the second type, a central strut with the rT joint is added in a parallel mechanism. The variable mobility of the mechanism results from the topological change of the central (rT)P(rT) strut. This is illustrated in a 3SPS-1 (rT)P(rT) metamorphic parallel mechanism, which changes its mobility from 4 to 5. It is demonstrated in mobility analysis that the change in local mobility of each limb results in the change in the platform mobility that a metamorphic process can be achieved. This particular analysis leads to advancement of improved Grubler-Kutzbach criterion by introducing the local mobility factor in the mobility analysis.

Secure quantum private comparison

Abstract: We propose a two-party quantum private comparison protocol using single photons, in which two distrustful parties can compare whether their secrets are equal with the help of a third party (TP). Any information about the values of their respective secrets will not be leaked out even with a compromised TP. Security is also discussed.

Face recognition using SURF features

Abstract: The Scale Invariant Feature Transform (SIFT) proposed by David G. Lowe has been used in face recognition and proved to perform well. Recently, a new detector and descriptor, named Speed-Up Robust Features (SURF) suggested by Herbert Bay, attracts people's attentions. SURF is a scale and in-plane rotation invariant detector and descriptor with comparable or even better performance with SIFT. Because each of SURF feature has only 64 dimensions in general and an indexing scheme is built by using the sign of the Laplacian, SURF is much faster than the 128-dimensional SIFT at the matching step. Thus based on the above advantages of SURF, we propose to exploit SURF features in face recognition in this paper.

Technologies and standards forTD-SCDMA evolutions to IMT-advanced

Abstract: The current TD-SCDMA commercialization in China brings about many issues concerning the implementation of TD-SCDMA technology, the market, and its applications. In order to make TD-SCDMA successful, evolution from the current TD-SCDMA standards to international mobile telecommunications-advanced are anticipated. TD-SCDMA standards and technologies will take a home-made evolution path in China, aiming at a smooth migration to the next-generation mobile communication system. This article provides a brief description of the evolution strategies of both the standards and key technologies, in which the evolution is divided into three phases. The state of the art of TD-SCDMA evolution is surveyed, and its technologies and standards in different evolution phases are characterized. Single- and multi-carrier high-speed packet access is specified in the first evolution phase for guaranteeing the high transmission bit rate of packet services. Meanwhile, broadcast services are supported, and the HSPA evolution is also incorporated in this phase. Long term evolution is defined in the second evolution phase for approaching similar performance as mobile WiMAX, where channel-reciprocity- based multiple antenna techniques are utilized. The last phase is the revolution to the IMT-Advanced system and becoming one alternative standard in beyond 3G systems, which is based on the evolution of TD-LTE. The difference of standardizations between 3GPP and local standard releases are introduced. Some challenging work and open issues in different evolution phases are discussed as well.

An extension of technology acceptance model: Analysis of the adoption of mobile data services in China

Abstract: Mobile data services are entering into all aspects of people's life and are expected to be an important revenue source of telecom carriers. Nevertheless, the acceptance pace of mobile data services is slower than the expected level projected by the telecommunication industry. This research investigated the reason that people use mobile data services in China. Combined with subscribers' experience factors, an extended technology acceptance model (TAM) for mobile data services was presented. The model was tested using data collected from 802 mobile subscribers. The findings of the study indicate that mobile voice service and innovation experience of mobile data services affect subscribers' consumption intention greatly; subscribers' perceived ease-of-use and brand experience influence subscribers' attitude towards mobile data services largely. Promotion of mobile data services is most effective when it is promoted with perfect voice service experience. Additionally, our findings suggest that mobile service carriers need to enhance their investments in mobile data services' R&D. Collaboration among the value chain members of mobile data services will promise cutting-edge new products and services. Using system methodology, a mobile data service infusion system model was constructed to explain the general adoption rules of mobile data services. The adoption of mobile data services in mobile logistics area was also discussed. Copyright © 2009 John Wiley & Sons, Ltd.

A Three-Section Dual-Band Transformer for Frequency-Dependent Complex Load Impedance

Abstract: In this letter, we propose a practical three-section dual-band transformer, which can terminate frequency-dependent complex load impedance at two arbitrary bands simultaneously. Analytical equations are derived to achieve the exact closed-form solutions. Numerical examples are examined to verify the validity. This three-section transformer can be utilized to match the complex load impedance with unequal values at two different frequencies, such as microwave amplifiers based on transistors, mixers, various kinds of antennas, and so forth.

A Generalized Dual-Frequency Transformer for Two Arbitrary Complex Frequency-Dependent Impedances

Abstract: The purpose of this letter is to propose a dual-frequency transformer for two arbitrary complex frequency- dependent impedances (ACF-DIs) and present a generalized T-junction power divider (T-JPD) operating at dual-band with arbitrary power-dividing ratios based on the proposed transformer. By the rigorous analysis of transmission line theory, the closed-form design equations for this generalized transformer are obtained. Using the analytical design method, a kind of generalized T-JPD can be designed to operate at two different frequencies with different power-dividing ratios. Furthermore, numerical examples are simulated and a microstrip T-JPD operating at 1 and 2.4 GHz with different power-dividing ratios (1.5 and 2 dB, respectively) is fabricated. Good agreements between the simulated and measured results can be observed.

Demonstration of a large-size real-time full-color three-dimensional display

Abstract: A large-size and full-color three-dimensional (3D) display system without the need for special eyeglasses is demonstrated. With a specially fabricated holographic functional screen with a size of 1.8×1.3 m2, the system including optimally designed camera-projector arrays and a video server can display the fully continuous, natural 3D scene with more than 1 m image depth in real time. We explain the operating principle and present experimental results.

Performance analysis of multiuser diversity in cooperative multi-relay networks under rayleigh-fading channels

Abstract: In multiuser cooperative relay networks, cooperative diversity can be obtained with the help of relays, while multiuser diversity is an inherent diversity in multiuser systems. In this letter, the performance analysis of multiuser diversity in cooperative multirelay networks is presented. Both the case of all relay participating and the case of relay selection are considered. We first derive asymptotic expressions of outage probability and symbol error probability for amplify-and-forward (AF) and decode-and-forward (DF) protocols with joint multiuser and cooperative diversity. Then, the theoretical analysis are validated by Monte Carlo simulations. Both the theoretical analysis and simulations show that a multiuser diversity order of K and a cooperative diversity order of M+ 1 can be achieved simultaneously for both AF and DF protocols (where K is the number of accessing users and M is the number of available relays). These demonstrate that the multiuser diversity can be readily combined with the cooperative diversity in multiuser cooperative relay networks.

Bound vector solitons and soliton complexes for the coupled nonlinear Schrödinger equations

Abstract: Dynamic features describing the collisions of the bound vector solitons and soliton complexes are investigated for the coupled nonlinear Schrodinger (CNLS) equations, which model the propagation of the multimode soliton pulses under some physical situations in nonlinear fiber optics. Equations of such type have also been seen in water waves and plasmas. By the appropriate choices of the arbitrary parameters for the multisoliton solutions derived through the Hirota bilinear method, the periodic structures along the propagation are classified according to the relative relations of the real wave numbers. Furthermore, parameters are shown to control the intensity distributions and interaction patterns for the bound vector solitons and soliton complexes. Transformations of the soliton types (shape changing with intensity redistribution) during the collisions of those stationary structures with the regular one soliton are discussed, in which a class of inelastic properties is involved. Discussions could be expected to be helpful in interpreting such structures in the multimode nonlinear fiber optics and equally applied to other systems governed by the CNLS equations, e.g., the plasma physics and Bose-Einstein condensates.

Analysis and Simulation for Spectrum Aggregation in LTE-Advanced System

Abstract: Spectrum aggregation (SA) is one of the potential LTE advanced technologies. The analysis and simulation for SA in LTE-Advanced system are addressed in this paper. We first analyze the system model of SA, and propose some evaluation methodologies for SA. Then the schedulers for SA with joint queue and disjoint queue are proposed. Finally, different traffic models are considered in the system level simulation to evaluate the performance gain of spectrum aggregation over deploying independent carriers on the eNode-B. The simulation results show that the SA technology can enhance the throughput, fairness and latency performance in LTE-Advanced system comparing with independent carrier scenario for different traffic models.

Multiuser Diversity in Multiuser Two-Hop Cooperative Relay Wireless Networks: System Model and Performance Analysis

Abstract: Cooperative communications significantly improve the performance of wireless networks with the help of relay nodes, whereas multiuser diversity (MUD) is a kind of diversity inherent in multiuser systems. In this paper, we present a framework to analyze the performance of MUD in the multiuser two-hop cooperative relay networks (TCRNs). Based on this framework, we derive tight closed-form expressions of outage probability and symbol error probability (SEP) for the amplify-and-forward (AF), fixed decode-and-forward (DF), and selective DF protocols with MUD. Both the theoretical analysis and simulations show that in multiuser TCRNs, MUD orders of 2K, K, and 2K can be achieved for AF, fixed DF, and selective DF, respectively (where K is the number of users).

Conservation laws, soliton solutions and modulational instability for the higher-order dispersive nonlinear Schrödinger equation

Abstract: In this paper, analytically investigated is a higher-order dispersive nonlinear Schrodinger equation. Based on the linear eigenvalue problem associated with this equation, the integrability is identified by admitting an infinite number of conservation laws. By using the Darboux transformation method, the explicit multi-soliton solutions are generated in a recursive manner. The propagation characteristic of solitons and their interactions under the periodic plane wave background are discussed. Finally, the modulational instability of solutions is analyzed in the presence of small perturbation.

A Dual-Frequency Transformer for Complex Impedances With Two Unequal Sections

Abstract: In this letter, a small dual-frequency transformer with two unequal sections for complex impedances is proposed. To design this transformer, two different groups of nonlinear equations and the corresponding solutions processes are obtained. The results of numerical examples show that two complex impedances can be matched at two different frequencies simultaneously. This proposed transformer can be regarded as the extension of small dual-frequency transformer in two sections for two resistances.

Analysis of vibroarthrographic signals with features related to signal variability and radial-basis functions.

Abstract: Knee-joint sounds or vibroarthrographic (VAG) signals contain diagnostic information related to the roughness, softening, breakdown, or the state of lubrication of the articular cartilage surfaces. Objective analysis of VAG signals provides features for pattern analysis, classification, and noninvasive diagnosis of knee-joint pathology of various types. We propose parameters related to signal variability for the analysis of VAG signals, including an adaptive turns count and the variance of the mean-squared value computed during extension, flexion, and a full swing cycle of the leg, for the purpose of classification as normal or abnormal, that is, screening. With a database of 89 VAG signals, screening efficiency of up to 0.8570 was achieved, in terms of the area under the receiver operating characteristics curve, using a neural network classifier based on radial-basis functions, with all of the six proposed features. Using techniques for feature selection, the turns counts for the flexion and extension parts of the VAG signals were chosen as the top two features, leading to an improved screening efficiency of 0.9174. The proposed methods could lead to objective criteria for improved selection of patients for clinical procedures and reduce healthcare costs.

Complex networks-based energy-efficient evolution model for wireless sensor networks

Abstract: Based on complex networks theory, we present two self-organized energy-efficient models for wireless sensor networks in this paper. The first model constructs the wireless sensor networks according to the connectivity and remaining energy of each sensor node, thus it can produce scale-free networks which have a performance of random error tolerance. In the second model, we not only consider the remaining energy, but also introduce the constraint of links to each node. This model can make the energy consumption of the whole network more balanced. Finally, we present the numerical experiments of the two models.

CAS algorithm-based optimum design of PID controller in AVR system

Abstract: This paper presents a novel design method for determining the optimal PID controller parameters of an automatic voltage regulator (AVR) system using the chaotic ant swarm (CAS) algorithm. In the tuning process of parameters, the CAS algorithm is iterated to give the optimal parameters of the PID controller based on the fitness theory, where the position vector of each ant in the CAS algorithm corresponds to the parameter vector of the PID controller. The proposed CAS-PID controllers can ensure better control system performance with respect to the reference input in comparison with GA-PID controllers. Numerical simulations are provided to verify the effectiveness and feasibility of PID controller based on CAS algorithm.