In this paper, an accurate and low-cost method for on-wafer noise figure measurement, specifically designed for low-noise amplifiers (LNAs), will be proposed. An experiment conducted on a 5 GHz LNA demonstrates that a good agreement can be reached between the measurement result of the proposed method and that of a commercial noise parameter measurement system.

High-frequency characteristics of SiGe heterojunction bipolar transistors with different emitter sizes are studied based on pulsed measurements. Because the self-heating effect in transistors will enhance the Kirk effect, as the devices operate in high current region, the measured cutoff frequency and maximum oscillation frequency decrease with measurement time in the pulsed duration. By analyzing the equivalent small-signal device parameters, we know the reduction of cutoff frequency and maximum oscillation frequency is attributed to the reduction of transconductance and the increase of junction capacitances for fixed base-emitter voltage, while it is only attributed to the degradation of transconductance for fixed collector current. Besides, the degradation of high-frequency performance due to self-heating effect would be improved with the layout design combining narrow emitter finger and parallel-interconnected subcells structure.

Recent advances in measurement techniques for microwave active devices and circuits are reviewed in this paper. The R&D activities have been devoted aggressively how to characterize nonlinear performance of high power devices and circuits. They are pulsed I-V, a variety of load-pull measurements, probing, sampling, and sensing techniques, supported by the recent significant advances in DSP (Digital Signal Processing), RF components, semiconductor devices, etc. The recent advances in vector network analyzers are of our great interest. They are (a) multi-port vector network analyzers for characterizing mixers, differential devices, packaged components, electronic package characterization, and multi-layer transmission lines, and (b) EO (Electro-Optic) modulated vector network analyzers for characterizing electronic performance of EO devices with the aid of EO modulators and photonic probes. In addition, probing, sampling, and sensing techniques have made great progress to directly measure electromagnetic field, time-domain voltage waveform, and temperature in small spot areas. In this paper, some topics related to these measurement techniques are briefly reviewed. Then the existing and future issues for characterization and measurement techniques of microwave active devices and circuits are discussed.

The maximum operating region of a SiGe HBT has been experimentally investigated by a direct microwave waveform measurement. Dynamic RF load lines are used as a probe to detect the limit of the RF operation. For the first time, it is found that SiGe HBTs operate beyond the conventional BVceo, while GaAs HBTs cannot survive at that voltage. The conventional BVceo limits the average Vc of the maximum load lines, but has no influence on the peak voltage. Another BVceo measured with a voltage generator is proposed to represent the irreversible avalanche breakdown instead of the conventional one. A pulsed breakdown measurement is also performed to reveal the time constant of the phenomena.

Currently, the IP infrastructure is widely available, which reduces the deployment and implementation cost of IP-based wireless networks. But, the corresponding researches on Quality of Service (QoS) in wireless mobile networks have not been done sufficiently. Although All-IP network has gotten the spotlight for both wired and wireless integrated networks, it has some unavoidable defects as it is based on best-effort IP transmission technologies. By focusing our attention on this point, we propose an Advanced QoS Provisioning Scheme (AQPS) that can provide satisfied QoS for multimedia applications based on accurate traffic measurements. With the AQPS, we consider 1xEV-DV system as a target system, extract QoS requirements for this system, and develop a corresponding QoS provisioning method using CDMA traffic measurement. The AQPS is designed to estimate delay parameters between a mobile station and a BTS (or repeater), verify whether the mobile station can support RSVP or not, operate a corresponding scheduler, and assign appropriate time slots based on traffic classes. One of the interesting results of this research is that the capability of distinguishing BTS' traffic from repeater's traffic helps save implementation cost of CDMA systems. The AQPS has been verified to outperform the existing system used in the current CDMA network and to efficiently manage network resources by computer simulations.

We propose a method for analyzing trade-off between an environment where a Java mobile code application is running and requirements for the application. In particular, we focus on the security-related problems that originate in low-level security policy of the code-centric style of the access control in Java runtime. As the result of this method, we get feasible requirements with respect to security issues of mobile codes. This method will help requirements analysts to compromise the differences between customers' goals and realizable solutions. Customers will agree to the results of the analysis by this method because they can clearly trace the reasons why some goals are achieved but others are not. We can clarify which functions can be performed under the environment systematically. We also clarify which functions in mobile codes are needed so as to meet the goals of users by goal oriented requirements analysis(GORA). By comparing functions derived from the environment and functions from the goals, we can find conflicts between the environments and the goals, and also find vagueness of the requirements. By resolving the conflicts and by clarifying the vagueness, we can develop bases for the requirements specification.

Goal-oriented analysis and use case analysis are well known requirements analysis methods and are putting into practice. Roughly speaking, goal-oriented methods are suitable for eliciting constraints to a system and use case analysis methods elicit concrete system behavior. Thus these methods are complementary and their integration into a new method allows us to get a more powerful requirements elicitation method. This paper proposes a new method where both of the methods are amalgamated. In our method, constraints to the system are refined by goal-oriented style, while system behavior are described with hierarchical use cases. Since a use case is made relate to goals during our elicitation processes, the decomposition of goals and use cases are complementally supported. Furthermore we applied our method to a couple of development projects and assessed its effectiveness.

Feature point tracking over a video sequence fails when the points go out of the field of view or behind other objects. In this paper, we extend such interrupted tracking by imposing the constraint that under the affine camera model all feature trajectories should be in an affine space. Our method consists of iterations for optimally extending the trajectories and for optimally estimating the affine space, coupled with an outlier removal process. Using real video images, we demonstrate that our method can restore a sufficient number of trajectories for detailed 3-D reconstruction.

Scenarios that describe concrete situations of software operation play an important role in software development and especially in requirements engineering. Scenario details should vary in content when described from different viewpoints, but this presents a difficulty, because an informal scenario from one viewpoint can not easily be transformed into a scenario from another viewpoint with consistency and assurance. This paper describes (1) a language for describing scenarios in which simple action traces are embellished to include typed frames based on a simple case grammar of actions, and (2) a method to accomplish the transformation between scenarios from different viewpoints based on the scenario description language.

In this paper, we introduce the following m-layered hard constrained convex feasibility problem HCF(m): Find a point u m, where 0:=H (a real Hilbert space), i: = arg min gi(i-1) and gi(u):=wi,jd 2(u,Ci,j) are defined for (i) nonempty closed convex sets Ci,jH and (ii) weights wi,j > 0 satisfying wi,j=1 (i {1,,m}, j {1,,Mi}. This problem is regarded as a natural extension of the standard convex feasibility problem: find a point u Ci, where Ci H (i {1,, M}) are closed convex sets. Unlike the standard problem, HCF(m) can handle the inconsistent case; i.e., i,j Ci,j = , which unfortunately arises in many signal processing, estimation and design problems. As an application of the hybrid steepest descent method for the asymptotically shrinking nonexpansive mapping, we present an algorithm, based on the use of the metric projections onto Ci,j, which generates a sequence (un) satisfying limn d(un,3) = 0 (for M1 = 1) when at least one of C1,1 or C2,j's is bounded and H is finite dimensional. An application of the proposed algorithm to the pulse shaping problem is given to demonstrate the great flexibility of the method.

In this letter, the concept of cross-entropy is introduced for unsupervised polarimetric synthetic aperture radar (SAR) image classification. The difference between two scatterers is decomposed into three parts, i.e., the difference of average scattering characteristic, the difference of scattering randomness and the difference of scattering matrix span. All these three parts are expressed in cross-entropy formats. The minimum cross-entropy principle is adopted to make classification decision. It works well in unsupervised terrain classification with a NASA/JPL AIRSAR image.

In this paper, first, we consider how to illustrate the effect of background noise to the measurement of room acoustics under a background noise of arbitrary distribution type. Two kinds of estimation methods are proposed to evaluate a proper reverberation time of a room by observing real unrefined decay curves, which can not realize smoothly a sufficient decay of 60 dB in a low frequency region, especially under a contamination of background noise. In the first method, an observation equation is derived from a stochastic model by means of well-known Sabine's differential equation, which is approximately rewritten in a matched form of difference equation especially to preserve its original physical meaning and functional linearity on the reverberation parameter. The effect of background noise is eliminated by employing a generalized state estimation algorithm based on Bayes' theorem. In the second one, after reflecting the effect of background noise in an observation equation of measuring model, a well-known mutual information criterion is introduced to estimate a reverberation time especially based on the basic property of statistical independency between signal and background noise. Finally, the effectiveness of the proposed methods are experimentally confirmed too by applying it to the actual measurement of a reverberation time in the actual living situation of room contaminated by a background noise. The proposed methods are, however, some technique using actively the higher order correlation beyond a linear one, and so they are methodology-trials which should coexist with other techniques.

We have shown that a photonic sensor can be used as an electric-field probe for planar near-field measurements of X-band antennas. Because an antenna on the photonic sensor is small (about 0.1 λ) compared to the wavelength, the photonic sensor can directly measure the amplitude and the phase of the electric field close (about 0.3 λ) to the apertures of antennas without disturbing the electric field to be measured. Therefore we can obtain the antenna pattern by transforming the measured electric field without probe compensation. To verify the merits of the photonic sensor, we have evaluated the antenna patterns of a standard gain horn antenna and a microstrip array antenna at 9.41 GHz. Comparing the results obtained using the photonic sensor with those obtained using the conventional open-ended waveguide probe and other methods, we have shown that the antenna patterns agree with each other within 1 dB over wide ranges of directivity.

The new Internet has to provide the Quality of Services to converged multimedia services, in which each one may choose its own requirements. Managing such a dynamic network is not an easy task. A more intelligent and adaptive behavior is required from network management. We argue that agents are able to realize this task by dynamically adapting management mechanisms to the current network conditions. This article presents a Behavioral Multi-Agent-based model for QoS-enabled Internet. Based on this behavioral approach, we analyze network management mechanisms (or "elementary behaviors") in terms of performance and applicability profile. We use simulation to observe services performances when submitted to diverse QoS management elementary behaviors.

Lightning surges induced on subscriber lines in Kuala Lumpur, Malaysia, which is located in a tropical region, were observed at telecommunication centers. More than 100 surges per line were observed during a three-month period. Peak values, observed using a lightning surge counter, show that lightning surge current occurrences normalized by the number of thunderstorm days and number of subscriber lines closely agreed with data observed in temperate areas, e.g., Japan. Surge waveforms appearing at several points ranging from underground cable ducts to exchange equipment were observed using a wave memory system. The results show that lightning surge currents on the cables were larger than those on a wire, but the correlation between them was weak. Common and differential mode surge waveforms observed using the wave memory system were almost the same. These results will be useful in designing protection circuits for equipment used in tropical areas.

Simple genetic algorithm (SGA) is a population-based optimization method based on the Darwinian natural selection. The theoretical foundations of SGA are the Schema Theorem and the Building Block Hypothesis. Although SGA does well in many applications as an optimization method, it still does not guarantee the convergence of a global optimum in GA-hard problems and deceptive problems. As an alternative schema, therefore, there is a growing interest in a co-evolutionary system where two populations constantly interact and cooperate each other. In this paper we propose a schema co-evolutionary algorithm (SCEA) and show why the SCEA works better than SGA in terms of an extended schema theorem. The experimental analyses using the Walsh-Schema Transform show that the SCEA works well in GA-hard problems including deceptive problems.

We study relationships between the class of Boolean formulas called exclusive-or expansions based on monotone DNF formulas (MDNF formulas, for short) and the class of Horn DNF formulas. An MDNF formula f is a Boolean formula represented by f = f1fd , where f1 > > fd are monotone DNF formulas and no terms appear more than once. A Horn DNF formula is a DNF formula where each term contains at most one negative literal. We show that the class of double Horn functions, where both f and its negation can be represented by Horn DNF formulas, coincides with a subclass of MDNF formulas such that each DNF formula fi consists of a single term. Furthermore, we give an incrementally polynomial time algorithm that transforms a given Horn DNF formula into the MDNF representation.

A mathematical theory is proposed based on the concept of functional analysis, suitable for operation of network systems extraordinarily complicated and diversified on large scales, through connected-block structures. Fundamental conditions for existence and evaluation of system behaviors of such network systems are obtained in a form of fixed point theorem for system of nonlinear mappings.

Recently, Hwang and Li proposed a smartcard-based remote user authentication scheme. Later, Chan and Cheng showed that Hwang and Li's scheme is insecure against a kind of impersonation attack where a legitimate user can create another valid pair of user identity and password without knowing the secret key of the remote system. However, an assumption under Chan and Cheng's attack is that the attacker must be a legal user. In this paper, we further present a more fundamental and efficient impersonation attack on Hwang and Li's scheme. Using our attack, any users (including legal and illegal users) can easily get a specific legal user's password, impersonate this specific user to login to the remote system, and pass the system authentication.

IEEE 802.11 standard and the enhanced amendments have defined several transmission rates for mobile stations to transmit and receive data frames. With the characteristic of modulation schemes, a higher network throughput can be expected by using higher level modulation scheme, but frame error probability will also become higher. Doubtlessly, it is an open issue of selecting a proper modulation scheme for a pair of mobile stations in time-varying indoor environment. This paper proposes a safe multiple access-rates transmission (SMART) scheme to enhance the reliability of data transmission in IEEE 802.11 multi-rate infrastructure wireless networks. SMART scheme provides reliable transmission by reserving a retransmission period which immediately follows the transmitted frame and is estimated by a lower transmission rate according to the transmitted frame. The performance of SMART scheme is evaluated by analytical model and simulation experiment, which show that the proposed scheme is significantly better than the IEEE 802.11 standard under the real environment with asymmetric traffic load. An enhanced SMART (ESMART) scheme is also proposed especially to improve bandwidth waste for long packet length at access point (AP). The performance measurements, such as goodput, throughput, average access delay, and service rate, are obtained and compared for the different schemes.