To estimate the impact of electromagnetic disturbances on multi-carrier wireless systems, a method for converting an amplitude probability distribution (APD) of disturbance measured at a frequency to be valid for another frequency is presented. The conversion uses two parameters, the receiver noise power of the APD measuring equipment and a scale factor that can be estimated from a measured disturbance spectrum. The method is based on the assumption that the difference in measurement frequency affects only the relative scale of the probability distribution of band-limited disturbance amplitude, and is applicable to disturbances of practically importance such as 1) continuous or pulse-modulated wideband Gaussian noise, 2) disturbance with a much narrower bandwidth than receiver bandwidth B, and 3) repetitive short pulses with similar waveforms with an interval much longer than 1/B. The validity of the proposed method is examined by measurements of actual disturbances.

A phase-retrieval method is applied to the quasioptical feed system of the offset Cassegrain antenna of the Superconducting Submillimeter-Wave Limb-Emission Sounder (JEM/SMILES) to be aboard the International Space Station for evaluating the beam alignment by estimating the phase pattern from the beam amplitude pattern measurements. As the result, the application of the phase retrieval method is demonstrated to be effective for measuring and evaluating the quasioptical antenna feed system. It is also demonstrated that the far-field radiation pattern of the antenna main reflector can be estimated from the phase-retrieved beam pattern of the feed system.

This paper proposes a new control scheme in which the base station (BS) controls terminal's transmit beamforming in time-division duplex (TDD)/multi-input multi-output (MIMO) systems. In the proposed scheme, the BS transmits pilot signals using appropriate downlink beams to instruct a terminal on target transmit beamforming. Using responses of the downlink pilot signals, the terminal can perform transmit beamforming close to the target one. Our theoretical investigation reveals that the BS can control multiple terminals' transmit beamforming simultaneously. Furthermore, an efficient signal processing at the terminal is investigated to obtain precise weight of transmit beamforming in noise environments. Numerical results show that the terminal can perform precise transmit beamforming close to the target one in noise environments. It is also shown that the amount of downlink control signalling in the proposed scheme is much less than that in codebook-based approach.

The MIMO system can meet the growing demand for higher capacity in wireless communication fields. So far, the authors have reported that, based on channel measurements, uncoded performance of narrowband MIMO spatial multiplexing in indoor line-of-sight (LOS) environments generally outperforms that in non-LOS (NLOS) ones under the same transmit power condition. In space-frequency coded MIMO-OFDM spatial multiplexing, however, we cannot expect high space-frequency diversity gain in LOS environments because of high fading correlations and low frequency selectivity of channels so that the performance may degrade unlike uncoded cases. In this letter, we present the practical performance of coded MIMO-OFDM spatial multiplexing based on indoor channel measurements. The results show that an LOS environment tends to provide lower space-frequency diversity effect whereas the MIMO-OFDM spatial multiplexing performance is still better in the environment compared with an NLOS environment.

Managing the performance at the flow level through traffic measurement is crucial for effective network management. With the rapid rise in link speeds, collecting all packets has become difficult, so packet sampling has been attracting attention as a scalable means of measuring flow statistics. In this paper, we firstly propose a method of estimating TCP flow rates of sampled flows through packet sampling, and then develop a method of detecting performance degradation at the TCP flow level from the estimated flow rates. In the method of estimating flow rates, we use sequence numbers of sampled packets, which make it possible to improve markedly the accuracy of estimating the flow rates of sampled flows. Using both an analytical model and measurement data, we show that this method gives accurate estimations. We also show that, by observing the estimated rates of sampled flows, we can detect TCP performance degradation. The method of detecting performance degradation is based on the following two findings: (i) sampled flows tend to have high flow-rates and (ii) when a link becomes congested, the performance of high-rate flows becomes degraded first. These characteristics indicate that sampled flows are sensitive to congestion, so we can detect performance degradation of flows that are sensitive to congestion by observing the rate of sampled flows. We also show the effectiveness of our method using measurement data.

Quantifying user satisfaction is essential, because the results can help service providers deliver better services. In this work, we propose a generalizable methodology, based on survival analysis, to quantify user satisfaction in terms of session times, i.e., the length of time users stay with an application. Unlike subjective human surveys, our methodology is based solely on passive measurement, which is more cost-efficient and better able to capture subconscious reactions. Furthermore, by using session times, rather than a specific performance indicator, such as the level of distortion of voice signals, the effects of other factors like loudness and sidetone, can also be captured by the developed models. Like survival analysis, our methodology is characterized by low complexity and a simple model-developing process. The feasibility of our methodology is demonstrated through case studies of ShenZhou Online, a commercial MMORPG in Taiwan, and the most prevalent VoIP application in the world, namely Skype. Through the model development process, we can also identify the most significant performance factors and their impacts on user satisfaction and discuss how they can be exploited to improve user experience and optimize resource allocation.

We present a method to identify stakeholders and their preferences about non-functional requirements (NFR) by using use case diagrams of existing systems. We focus on the changes about NFR because such changes help stakeholders to identify their preferences. Comparing different use case diagrams of the same domain helps us to find changes to be occurred. We utilize Goal-Question-Metrics (GQM) method for identifying variables that characterize NFR, and we can systematically represent changes about NFR using the variables. Use cases that represent system interactions help us to bridge the gap between goals and metrics (variables), and we can easily construct measurable NFR. For validating and evaluating our method, we applied our method to an application domain of Mail User Agent (MUA) system.

The single-hidden-layer feedforward neural networks (SLFNs) are frequently used in machine learning due to their ability which can form boundaries with arbitrary shapes if the activation function of hidden units is chosen properly. Most learning algorithms for the neural networks based on gradient descent are still slow because of the many learning steps. Recently, a learning algorithm called extreme learning machine (ELM) has been proposed for training SLFNs to overcome this problem. It randomly chooses the input weights and hidden-layer biases, and analytically determines the output weights by the matrix inverse operation. This algorithm can achieve good generalization performance with high learning speed in many applications. However, this algorithm often requires a large number of hidden units and takes long time for classification of new observations. In this paper, a new approach for training SLFNs called least-squares extreme learning machine (LS-ELM) is proposed. Unlike the gradient descent-based algorithms and the ELM, our approach analytically determines the input weights, hidden-layer biases and output weights based on linear models. For training with a large number of input patterns, an online training scheme with sub-blocks of the training set is also introduced. Experimental results for real applications show that our proposed algorithm offers high classification accuracy with a smaller number of hidden units and extremely high speed in both learning and testing.

This paper experimentally studies and models the angular-delay power spectrum density at the mobile station based on the site-specific measurement in a macrocell in urban area of Tokyo. The authors first show the azimuth power spectral density at the mobile station. It is decomposed into the "classes" which represent specific contributions within limited azimuth range, as well as the residual. The site-specific propagation mechanism of the classes are next discussed. Finally, the angular-delay PSD models of both classes and residual are proposed and verified. The analysis and modeling in this paper are antenna independent with the full polarimetric information. Consequently, the results are useful to evaluate the performance of arbitrary array antennas with mixed polarization. Due to the rare number of antenna-independent and full-polarimetric measurements, the significant contribution of the angular-delay PSD channel model can be expected.

This paper proposes a method to generate exceptional scenarios from a normal scenario written with a scenario language. This method includes (1) generation of exceptional plans and (2) generation of exceptional scenario by a user's selection of these plans. The proposed method enables users to decrease the omission of the possible exceptional scenarios in the early stages of development. The method will be illustrated with some examples.

This paper deals with a TM plane wave reflection and transmission from a one-dimensional random slab with stratified fluctuation by means of the stochastic functional approach. Based on a previous manner [IEICE Trans. Electron. E88-C, 4, pp.713-720, 2005], an explicit form of the random wavefield is obtained in terms of a Wiener-Hermite expansion with approximate expansion coefficients (Wiener kernels) under small fluctuation. The optical theorem and coherent reflection coefficient are illustrated in figures for several physical parameters. It is then found that the optical theorem by use of the first two or three order Wiener kernels holds with good accuracy and a shift of Brewster's angle appears in the coherent reflection.

This letter presents the first experimental results that confirm the restorability of Rayleigh backscatter traces from a single-mode fiber measured by using a coherent optical time domain reflectometer (OTDR) with a precisely frequency-controlled light source. Based on this restorability, we can measure the distributed strain and temperature along the fiber with a very high measurand resolution that is one to two orders of magnitude better than that provided by Brillouin-based techniques for a long length of fiber.

During software requirements analysis, developers and stakeholders have many alternatives of requirements to be achieved and should make decisions to select an alternative out of them. There are two significant points to be considered for supporting these decision making processes in requirements analysis; 1) dependencies among alternatives and 2) evaluation based on multi-criteria and their trade-off. This paper proposes the technique to address the above two issues by using an extended version of goal-oriented analysis. In goal-oriented analysis, elicited goals and their dependencies are represented with an AND-OR acyclic directed graph. We use this technique to model the dependencies of the alternatives. Furthermore we associate attribute values and their propagation rules with nodes and edges in a goal graph in order to evaluate the alternatives with them. The attributes and their calculation rules greatly depend on the characteristics of a development project. Thus, in our approach, we select and use the attributes and their rules that can be appropriate for the project. TOPSIS method is adopted to show alternatives and their resulting attribute values.

Ultrasonic distance measurement using the pulse-echo method is based on the determination of the time of flight of ultrasonic waves. The pulse-compression technique, in which the cross-correlation function of a detected ultrasonic wave and a transmitted ultrasonic wave is obtained, is the conventional method used for improving the resolution of distance measurement. However, the calculation of a cross-correlation operation requires high-cost digital signal processing. This paper presents a new method of sensor signal processing within the pulse-compression technique using a delta-sigma modulated single-bit digital signal. The proposed sensor signal processing method consists of a cross-correlation operation employing single-bit signal processing and a smoothing operation involving a moving average filter. The proposed method reduces the calculation cost of the digital signal processing of the pulse-compression technique.

For the success of a large deployment of UHF RFID, easy-to-use and low-cost engineering tools to facilitate the performance evaluation are demanded particularly in installations and for trouble shooting. The measurement of interrogation area is one of the most typical industrial demands to establish the stable readability of UHF RFID. Exhaustive repetition of tag position change with a read operation and a usage of expensive measurement equipment or special interrogators are common practices to measure the interrogation area. In this paper, a practical method to measure the interrogation area of a UHF RFID by using a battery assisted passive tag (BAP) is presented. After introducing the fundamental design and performances of the BAP that we have developed, we introduce the measurement method. In the method, the target tag in the target installation is continuously traversed either manually or automatically while it is subjected to a repetitive read of a commercial interrogator. During the target tag traversal, the interrogator's commands are continuously monitored by a BAP. With an extensive analysis on interrogator commands, the BAP can differentiate between its own read timings and those of the target tag. The read timings of the target tag collected by the BAP are recorded synchronously with the target tag position, yielding a map of the interrogation area. The present method does not entail a measurement burden. It is also independent of the choice of interrogator and tag. The method is demonstrated in a practical UHF RFID installation to show that the method can measure a 40 mm resolution interrogation area measurement just by traversing the target tag at a slow walking speed, 300 mm/sec.

The use of a formal method is a promising approach to developing reliable computer programs. This paper presents a formal method for anonymity, which is an important security property of communication protocols with regard to a user's identity. When verifying the anonymity of security protocols, we need to consider the presence of adversaries. To formalize stronger adversaries, we introduce an adversary model for simulation-based anonymity proof. This paper also demonstrates the formal verification of a communication protocol. We employ Crowds, which is an implementation of an anonymous router, and verify its anonymity. After describing Crowds in a formal specification language, we prove its anonymity with a theorem prover.

This paper presents a methodology for performing on-line voltage risk identification (VRI) in power supply networks using hyperrectangular composite neural networks (HRCNNs) and synchronized phasor measurements. The FHRCNN presented in this study integrates the paradigm of neural networks with the concept of knowledge-based approaches, rendering them both more useful than when applied alone. The fuzzy rules extracted from the dynamic data relating to the power system formalize the knowledge applied by experts when conducting the voltage risk assessment procedure. The efficiency of the proposed technique is demonstrated via its application to the Taiwan Power Provider System (Tai-Power System) under various operating conditions. Overall, the results indicated that the proposed scheme achieves a minimum 97 % success rate in determining the current voltage security level.

The advent of various quality-sensitive applications has greatly changed the requirements for IP network management and made the monitoring of individual traffic flows more important. Since the processing costs of per-flow quality monitoring are high, especially in high-speed backbone links, packet sampling techniques have been attracting considerable attention. Existing sampling techniques, such as those used in Sampled NetFlow and sFlow, however, focus on the monitoring of traffic volume, and there has been little discussion of the monitoring of such quality indexes as packet loss ratio. In this paper we propose a method for estimating, from sampled packets, packet loss ratios in individual TCP sessions. It detects packet loss events by monitoring duplicate ACK events raised by each TCP receiver. Because sampling reveals only a portion of the actual packet loss, the actual packet loss ratio is estimated statistically. Simulation results show that the proposed method can estimate the TCP packet loss ratio accurately from a 10% sampling of packets.

In a Cognitive Radio system, it is essential to recognize and avoid sources of interference signals. This paper describes a study on a location sensing scheme for interference signals, which utilizes multi-beam phased array antenna for cognitive wireless networks. This paper also elucidates its estimation accuracy of the interference location for the radio communication link using an OFDM signal such as WiMAX. Furthermore, we use the frequency spectrum of the received OFDM interference signal, to create a method that can estimate the propagation status. This spectrum can be monitored by using a software defined radio receiver.

Microwave measurement methods necessary to characterize copper-clad dielectric laminate substrates are reviewed to realize more precise design of planar circuits: that is, the balanced-type circular disk resonator method for the relative complex permittivity in the normal direction εrn and tan δn, the cavity resonator method and the cut-off waveguide method for one in the tangential direction εrt and tan δt, and the dielectric resonator method for the surface and interface conductivity of copper foil σs and σi. The measured results of the frequency and temperature dependences of these parameters are presented for a PTFE substrate and a copper-clad glass cloth PTFE laminate substrate.