Distributed denial-of-service attacks on public servers have recently become more serious. The most effective way to prevent this type of traffic is to identify the attack nodes and detach (or block) attack nodes at their egress routers. However, existing traceback mechanisms are currently not widely used for several reasons, such as the necessity of replacement of many routers to support traceback capability, or difficulties in distinguishing between attacks and legitimate traffic. In this paper, we propose a new scheme that enables a traceback from a victim to the attack nodes. More specifically, we identify the egress routers that attack nodes are connecting to by estimating the traffic matrix between arbitral source-destination edge pairs. By monitoring the traffic variations obtained by the traffic matrix, we identify the edge routers that are forwarding the attack traffic, which have a sharp traffic increase to the victim. We also evaluate the effectiveness of our proposed scheme through simulation, and show that our method can identify attack sources accurately.

A comparison among the possible nonlinear photonic interactions for scalable nanometer networks and quantum gates as well as for coherence retention in solids is made theoretically, and then numerical plottings are given, on the basis of the dipole length estimated from our µ-PL (microphotoluminescence) spectra of GaAs/AlGaAs coupled quantum dots (QDs) having a pair of 0.3 meV splittings. Furthermore, prospective device concepts based on these nonlinear multipolar interactions are given.

A passive optical network (PON) that provides fiber to the home (FTTH) services is a fundamental access network topology in Japan. An optical fiber line monitoring and testing system is essential if we are to improve service reliability and reduce the maintenance costs of optical access networks. PONs have optical splitters in their optical fiber lines. It is difficult to find a fault in an optical fiber line equipped with an optical splitter by using a conventional optical fiber line testing system, which uses optical time-domain reflectometer (OTDR) in a central office (CO), because Rayleigh backscattering from the branched fibers accumulates in the OTDR trace. This paper describes a newly developed optical fiber line testing method that employs bi-directional OTDRs with two wavelengths at branched fiber regions in a PON to locate a fault precisely. Optical fiber line testing is conducted by two OTDRs that are installed in a CO and on a customer's premises, respectively. The OTDR in the CO has a U-band maintenance wavelength. We present two kinds of maintenance wavelength allocation for OTDRs on a customer's premises, which are in the U-band and C-band respectively. An OTDR whose maintenance wavelength is in the U-band enables us to test in-service PON lines simply by filtering the U-band wavelength. For the maintenance wavelengths in the C-band, we can use a cost-effective conventional OTDR to test the PON from the customer's premises on condition that we clarify the peak pulse power limit and dynamic range. We describe the test procedures for both cases. We also clarify the insertion loss design for an optical filter in the CO when using the U-band to provide the maintenance wavelength and the criteria for in-service line testing when the using C-band to provide the maintenance wavelength. To confirm the feasibility of our approach, we demonstrate a bi-directional OTDR method using the U-band and the C-band, and the test procedure, which successfully detected fault locations in branched fiber regions. We also describe the use of packet loss measurements to investigate the effect of in-service line testing with an OTDR in the C-band on data communication quality.

In order to support decision making, text classification is an important tool. Recently, in addition to term frequency and inverse document frequency, term distributions have been shown to be useful to improve classification accuracy in multi-class classification. This paper investigates the performance of these term distributions on binary classification using a centroid-based approach. In such one-against-the-rest, there are only two classes, the positive (focused) class and the negative class. To improve the performance, a so-called hierarchical EM method is applied to cluster the negative class, which is usually much larger and more diverse than the positive one, into several homogeneous groups. The experimental results on two collections of web pages, namely Drug Information (DI) and WebKB, show the merits of term distributions and clustering on binary classification. The performance of the proposed method is also investigated using the Thai Herbal collection where the texts are written in Thai language.

Service differentiation is one of the key issues in the current Internet. In this paper, we focus on a recent proposal for proportional loss rate differentiation which employs a single FIFO queue, an AQM algorithm for computing the packet drop probability, and a counter-based packet dropping routine for achieving the intended proportional loss rate differentiation among classes. It is first shown that, when the target dropping probability of a class is large, the counter-based packet dropping routine may yield a significant amount of error between the target and measured drop probabilities for the class, and subsequently, fails to maintain the loss rate ratios between classes as intended. To avoid this problem, a new compensatory packet dropping routine is developed in this paper. Then, a series of simulation experiments are conducted using the ns-2 simulator to assess the performances of the two dropping routines under various congestion conditions and quality spacings between classes. The simulation results show that, unlike the counter-based dropping routine, the proposed compensatory dropping routine is effective in keeping the loss rate ratios between classes closely on target regardless of the degree of congestion and quality spacing between classes, while the two dropping routines perform similarly in terms of throughput and queueing delay in the bottleneck link. In addition, such robustness of the proposed routine is achieved without any additional control parameter or computational effort compared to the counter-based routine.

This paper is to investigate the application of fuzzy c-means clustering to the direct identification of coherent synchronous generators in power systems. Because of the conceptual appropriateness and computational simplicity, this approach is essentially a fast and flexible method. At first, the coherency measures are derived from the time-domain responses of generators in order to reveal the relations between any pair of generators. And then they are used as initial element values of the membership matrix in the clustering procedures. An application of the proposed method to the Taiwan power (Taipower) system is demonstrated in an attempt to show the effectiveness of this clustering approach. The effects of short circuit fault locations, operating conditions, data sampling interval, and power system stabilizers are also investigated, as well. The results are compared with those obtained from the similarity relation method. And thus it is found that the presented approach needs less computation time and can directly initialize a clustering process for any number of clusters.

Educational websites contain rich knowledge components on a web page. Detecting student attention on web pages fulfills the recommendation of adequate knowledge components to students based on students' current interests. Previous studies have shown the application of learner attention in intelligent learning systems. This study proposes a methodology to analyze student on-line mouse movement patterns that indicate student attentions. The methodology can be combined with learning systems that implement pedagogical models such as inquiry-based learning and problem-solving learning activities. The feasibility and effectiveness of the proposed methodology have been evaluated by student mouse movements in problem-solving scenarios.

In this paper, the packet error rate (PER) of IEEE 802.15.4 under the interference of a saturated IEEE 802.11b network is evaluated using an analytic model when IEEE 802.15.4 and IEEE 802.11b coexist. The PER is obtained from the bit error rate (BER) and the collision time, where the BER is obtained from the signal-to-interference-plus-noise ratio. The analytic results are validated using simulations.

Recently we proposed a new waveband MUX/DEMUX that uses two concatenated cyclic AWGs. We analyse and formulate connection arrangements of the waveguides connecting the two AWGs. The port utilization of the device is shown to be 100% with bi-directional input fibers.

We propose in this paper a SOM-like algorithm that accepts online, as inputs, starts and ends of viewing of a multimedia content by many users; a one-dimensional map is then self-organized, providing an approximation of density distribution showing how many users see a part of a multimedia content. In this way "viewing behavior of crowds" information is accumulated as experience accumulates, summarized into one SOM-like network as knowledge is extracted, and is presented to new users as the knowledge is transmitted. Accumulation of multimedia contents on the Internet increases the need for time-efficient viewing of the contents and the possibility of compiling information on many users' viewing experiences. In the circumstances, a system has been proposed that presents, in the Internet environment, a kind of summary of viewing records of many viewers of a multimedia content. The summary is expected to show that some part is seen by many users but some part is rarely seen. The function is similar to websites utilizing "wisdom of crowds" and is facilitated by our proposed algorithm.

In this letter, we present a modified printed folded λ/2 dipole antenna design for Digital Video Broadcasting (DVB) applications in UHF band (470-862 MHz). The arms of dipole are meandered to yield an asymmetrical structure. Wideband operation is obtained by increasing dipole-area. The impedance matching of the dipole structure is obtained by inserting some slots on the dipole-arms. This antenna combines omni-directional radiation pattern and wide bandwidth in an easy-to-fabricate structure. The experimental results of the constructed prototype are presented.

With the rapid rise in the demand for location related service, communication devices such as PDAs or cellar phones must be able to search and manage information related to the geographical location. To leverage location-related information is useful to get an in-depth perspective on environmental circumstances, such as traffic conditions or weather information. To handle the large number of information and queries communication devices generate in the current ubiquitous environment, some scalable mechanism must be required. DHTs and some overlay networks supporting range search are proposed. However, these overlay networks can not process queries of geographical region search. In this paper, we propose a overlay network called "Mill" which can efficiently manage information related to the geographical location. In DHT based overlay networks, each node has responsibility to manage a part of the whole hash table. DHTs provide scalable systems and support fast search. However, DHTs are not good at solving geographical search (range search), because hash function only supports exact match. In the Mill network, each node manages a part of ID-space calculated by "Z-ordering," which represents squire surface of the earth. This structure of ID-space enables to process region queries easily and fast. And Mill supports any scale of region search. We evaluate proposed system by using traffic infomation generator called "HAKONIWA." Simulation results show that the performance of Mill is good as well as other DHT systems. In addtion, Mill provedes more efficient region search than other overlay networks supporting range search.

To meet users' multi-service requests under dynamic and heterogenous environment with high-assurance, the Autonomous Network-Based Integration System based on Faded Information Field (FIF) has been proposed, which permits to actively integrate the correlated information services according to the current situation of the system. However, the increase in the total number of users' requests and changes in users' preferences cause the unbalancing load in the system and the overload in the locality. In this paper, based on the autonomous access distribution in the locality, a new approach of autonomous correlated services access is proposed to reduce the load of the system and achieve the adaptability and timeliness of correlated services utilization. We proved the effectiveness of the proposed technology through the simulation and the results show that the system can improve the average response time not only for joint requests of correlated services, but also for separate requests of each service under changing environments.

Most wireless networks consist of heterogeneous nodes with diverse characteristics. These heterogeneous nodes have various moving characteristics such as speed and pausing time. Since conventional wireless routing schemes are designed for networks with homogeneous mobility, it is difficult to accomplish communication without degrading its quality, e.g., packet reachability and delay, in networks with heterogeneous mobility. In this paper, we propose efficient extensions of a proactive routing protocol to achieve sufficient communication quality in networks with heterogeneous mobility. The proposed extensions consist of three features, i.e., differential topology update, unidirectional movement notification and link quality based route calculation. Complementary actions among these functions can improve communication quality with acceptable control overhead. Simulation results reveal that the proposed scheme can achieve higher packet reachability and lower delay with low control overhead compared with existing routing schemes.

Content delivery network improves end-user performance by replicating Web contents on a group of geographically distributed sites interconnected over the Internet. However, with the development whereby content distribution systems can manage dynamically changing files, an important issue to be resolved is consistency management, which means the cached replicas on different sites must be updated if the originals change. In this paper, based on the analytical formulation of object freshness, web access distribution and network topology, we derive a novel algorithm as follows: (1) For a given content which has been changed on its original server, only a limited number of its replicas instead of all replicas are updated. (2) After a replica has been selected for update, the latest version will be sent from an algorithm-decided site instead of from its original server. Simulation results verify that the proposed algorithm provides better consistency management than conventional methods with the reduced the old hit ratio and network traffic.

The problem with traditional Brain Writing (BW) is that the users are restricted from viewing all sets of ideas at one time; and they are also restricted from writing down more than three ideas at a time. In this research we describe distributed experimental environment for BW which was designed to obtain better results and can thus eliminate the problems of traditional BW technique. The actual experimental system is an integration of three BW modes with mutually different features and characters. We conducted three different tests implementing this environment, and confirmed quality and quantity of ideas generated by three different groups. It was confirmed that unrestricted inputs are effective in generating a large quantity of ideas, whereas limiting the number of sharable/viewable ideas shows better tendency in some aspects. However, qualitative evaluation results were not confirmed as different functions show variant results. The evaluation of the functions that support viewing and sharing of ideas show that synergy is not always an advantage in generating ideas. The results of number of ideas in correlation with time show that 20 minutes time was appropriate to conduct BW in distributed environment.

This study introduces the fuzzy Lyapunov function to the fuzzy PID control systems, modified fuzzy systems, with an optimized robust tracking performance. We propose a compound search strategy called conditional linear matrix inequality (CLMI) approach which was composed of the proposed improved random optimal algorithm (IROA) concatenated with the simplex method to solve the linear matrix inequality (LMI) problem. If solutions of a specific system exist, the scheme finds more than one solutions at a time, and these fixed potential solutions and variable PID gains are ready for tracking performance optimization. The effectiveness of the proposed control scheme is demonstrated by the numerical example of a cart-pole system.

The averaged equation for an arbitrary number of oscillators coupled by nonlinear coupling scheme invented by S. Nagano, is derived. This system is invented as a model of uni-cellular slime amoeba. By using the averaged equation, we investigate the synchronization characteristics of five coupled oscillators and a large number of coupled oscillators. In particular, we present the statistical property of coupled oscillators in terms of coupling factor γ. We also investigate the effect of linear and nonlinear coupling terms for achieving synchronization, and confirm that the nonlinear coupling term plays an important role for strong synchronization than linear coupling term does.

The advanced-DFM (Design For Manufacturability) RAM provides the solution for the limitation of SRAM voltage scaling down and the countermeasure of the process fluctuations. The characteristics of this RAM are the voltage scalability (@0.6 V operation) with wide operating margin and the reliability of long data retention time. The memory cell consists of 2 Cell/bit with the complementary dynamic memory operation and has the 1 Cell/bit test mode for the accelerated screening against the marginal cells. The GND bitline pre-charge sensing scheme and SSW (Sense Synchronized Write) peripheral circuit technologies are also adopted for the low voltage and DFV (Dynamic Frequency and Voltage) controllable SoC which will be strongly required from the many kinds of applications. This RAM supports the DFM functions with both good cell/bit for advanced process technologies and the voltage scalable SoC memory platform.

The monitoring of performance in VoIP traffic has become vital because users generally expect VoIP service quality that is as high as that of PSTN services. A lightweight method of processing by extracting VoIP flows from Internet traffics is proposed in this paper. Estimating delay variations and the packet loss ratio using knowledge about specific features and the characteristics of VoIP flows, i.e., the inter-packet gap (IPG) which is constant in VoIP flows, is also proposed. Simulation with actual traffic trace is used to evaluate the method, and this revealed that delay variations (IPG variance) can be accurately estimated by monitoring only a few percentage of all flows. The proposed method can be used as a first-alert tool to monitor large amounts of flows to detect signs of degradation in VoIP flows. The method can be used by ISPs to estimate whether VoIP flow performance is adequate within their networks and at ingress from other ISPs.