Excitation of magnetostatic surface waves by slot line transducers is analyzed by using the integral kernel expansion method. The Fourier integral for the current density is derived in terms of an unknown normal component of the magnetic flux density in a slot region. The integral kernel is expanded into a series of orthogonal polynomials and then applying Galerkin's method to the resulting equation yields a system of linear equations for the unknown coefficients. Comparison of a numerical result by the present method with an experiment is in good agreement.

This paper proposes an adaptive transmission control scheme for code-division multiple-access (CDMA) cellular slotted-ALOHA systems. This scheme adaptively controls the target received power and the processing gain according to both channel load and location of the mobile station. The target received power of each mobile station is controlled so that the difference between the target received powers by distance becomes large under heavy load conditions. As the distance from the base station increases, the target received power becomes smaller. The processing gain of transmitted packets is concurrently controlled with their target received powers. The packets transmitted with low signal power are spread by a large processing gain in order to reduce the unfairness in packet reception. The radio channels with distance attenuation, shadowing, slow Rayleigh fading and imperfect power control are taken into consideration in order to evaluate the performance of this scheme in the case that mobile stations transmit short massages to the base station in cellular environments. Computer simulation validates the effectiveness of this scheme: the capture effect can be achieved under heavy channel loads, and therefore, throughput performance is improved. Detailed evaluation of throughput, packet reception probability and transmission complete probability is presented. The effect of movement of mobile stations is also discussed. Calculated results show that the proposed scheme has superior characteristics and thus can expand the allowable load area in the cellular environments with slow Rayleigh fading channels.

In this paper, a novel design method for bandpass filter with attenuation poles (BAP) is presented. The changed inverter element values due to inserting either capacitors or inductors can be optimized using the linear relationship between inverter element values of a conventional bandpass filter (BPF) and those of the BAP using the Touchstone program. A 1800-1825 MHz bandpass filter with attenuation poles for duplexers is designed and fabricated using coaxial dielectric resonators. The validity of this design approach is demonstrated by a computer simulation. The resonators are simulated equivalently as shorted lossy transmission lines. The measured results of center frequency, bandwidth, and attenuation pole frequencies closely agree with the design values.

The feasibility of a dynamic zone configuration technique has been investigated. To make it easy to implement this technique in wireless communication systems, a simplified method for determining a suitable weight vector by using the least squares (LS) methods was developed. Simulations showed that the developed system is more effective than the present omni-directional zone system. Moreover, combining dynamic zone configuration technique with dynamic channel assignment strategy reduced blocking rate, forced call termination ratio, and required transmission power.

Authentication protocols are necessary for the receiver of a message to ascertain its origin in a distributed environment. Since they exchange cryptographic messages at the beginning of communication, their security is an essential requirement. However, most of the protocols have suffered from several kinds of attacks. A replay attack is one kind of those attacks. Attackers could launch it easily by replaying an eavesdropped message. Moreover, there are many types of replay attacks while most of the formal methods are not capable of detecting them. [3] classified various kinds of replay attacks and proposed a taxonomy. Therefore, it is necessary to verify authentication protocols deliberately with such a taxonomy for a basis. In this paper, at first, we give a clear definition and several remarks on replay attacks. Secondly we review the taxonomy of replay attacks presented in [3], and comment on its minor mistake. Finally we examine on the basis of the taxonomy the password-based authentication protocol, K1P, which was proposed in our earlier papers for protecting weak secrets efficiently. As a result of the examination, we have found that three way mutual K1P shown in [2] was vulnerable to one of replay attacks. Therefore, we improve three way K1P on security against the replay attack. Improved three way K1P is secure against replay attacks as well as guessing attacks and therefore it may be useful for security services of various communication networks.

This study is aimed to explore a fast convergence method of blind equalization using higher order statistics (cumulants). The efforts are focused on deriving new theoretical solutions for blind equalizers rather than investigating practical algorithms. Under the common assumptions for this framework, it is found that the condition for blind equalization is directly associated with an eigenproblem, i. e. the lag coefficients of the equalizer can be obtained from the eigenvectors of a higher order statistics matrix. A method of blind phase recovery is also proposed for QAM systems. Computer simulations show that very fast convergence can be achieved based on the approach.

This letter proposes a diffusion model that considers both mobility and multimedia based on the user population process to examine the effects of multimedia in mobile communications. As an application example of this model, the shared bandwidth that can be used by one user in packet communications is evaluated. In this model, the user speed and variation in the number of users in a cell are interrelated with respect to mobility. By examining the shared bandwidth behavior based on multimedia teletraffic characteristics, assuming that the number of simultaneously-communicating users within a cell have self-similarity, we found that shared bandwidth and its variance are not dependent on self-similarity but that variance in the shared bandwidth is dependent on user speed.

This paper presents two man-machine reliability models. A system consists of one machine unit, one operator, and one event detecting monitor. The machine unit has three states, normal, abnormal, and failed. The event detecting monitor may fail in two ways. If a machine unit becomes abnormal, the event detecting monitor sends a signal, and the operator takes necessary actions. If the operator fails in the action in the cause of human error, the machine unit goes down. The condition of the operator is classified into two types, good and bad. The time to repair, and the human error rate both depend on the condition of the operator. The MTTF is obtained by using a Markov model and numerical computation. Furthermore, the optimal operating period which minimizes the overall cost is decided by using computer methods. Some numerical examples are shown.

In this paper, we consider the Integrate-and-Fire Model (ab. IFM) with two periodic inputs. The IFM outputs a pulse-train which is governed by a one dimensional return map. Using the return map, the relationship between the inputs and the output is clarified: the first input determines the global shape of the return map and the IFM outputs various periodic and chaotic pulse-trains; the second input quantizes the state of the return map and the IFM outputs various periodic pulse-trains. Using a computer aided analysis method, the quantized return map can be analyzed rigorously. Also, some typical phenomena are confirmed in the laboratory.

In this paper, a general formula of disparity estimation based on Bayesian Maximum A Posteriori (MAP) algorithm is derived and implemented with simplified probabilistic models. The formula is the generalized probabilistic diffusion equation based on Bayesian model, and can be implemented into some different forms corresponding to the probabilistic models in the disparity neighborhood system or configuration. The probabilistic models are independence and similarity among the neighboring disparities in the configuration. The independence probabilistic model guarantees the discontinuity at the object boundary region, and the similarity model does the continuity or the high correlation of the disparity distribution. According to the experimental results, the proposed algorithm had good estimation performance. This result showes that the derived formula generalizes the probabilistic diffusion based on Bayesian MAP algorithm for disparity estimation. Also, the proposed probabilistic models are reasonable and approximate the pure joint probability distribution very well with decreasing the computations to O(n()) from O(n()4) of the generalized formula.

In this paper, the performance of some communication systems using chaos synchronization is evaluated and compared. A new channel model taking the attenuation, impedance mismatch and noise into account, is proposed for the performance evaluation. The evaluation of bit error rate is done for both ideal and non-ideal conditions using the channel model. It is confirmed that some chaos-based communication systems have a good performance compared with conventional analog communication schemes.

We have developed a new type of phase interpolation direct digital synthesizer (DDS) with a symmetrically structured delay generator. The new DDS is similar to a sine output DDS in that it produces lower spurious signals, but it does not require a sine look-up table. The symmetrically structured delay generator reduces the periodic jitter in the most significant bit (MSB) of the DDS accumulator. The symmetrical structure enables the delay generator to produce highly accurate delay timing and eliminates the need to adjust the circuit constants. Experimental results confirm frequency synthesizer operation in which the spurious signal level is reduced to less than that of the accumulator.

In this paper, the performance of dynamic channel assignment for cellular systems with an array antenna is evaluated assuming realistic beamformer. A new dynamic channel assignment algorithm is proposed to improve the performance by forming a directional beam pattern to cancel stronger co-channel interference with higher priority. Performance comparison is carried out by computer simulations. Conventional algorithm shows 2.7 fold capacity increase compared with an omni antenna system, whereas proposed algorithm shows around 3.3 fold capacity increase, at the point of 3 percent blocking probability. The simulation results also denote that a shorter reuse distance can be achieved by the proposed algorithm, which indicates a more efficient utilization of channel resource.

When designing microwave amplifiers, it is the task to select values of the source (input generator) and load reflection coefficients for the transistor, to achieve certain amplifier performance requirements and ensure stability. For unconditionally stable transistors, simultaneous conjugate matching can be achieved using well-known design formulae. Under this condition, the gain is maximised, and the input and output ports are matched. On the other hand when the transistor is conditionally stable, source and load reflection coefficients are selected using graphical design methods, involving gain and stability circles. To eliminate the reliance on graphical techniques, this paper shows the derivation of explicit design formulae that ensure maximum gain for a minimum specified safety margin, with one port matched. In this work, the safety margin is the distance between the chosen source or load reflection coefficient and its respective stability circle. In a production environment, where the circuit and transistor parameters are subject to random variations, the safety margin therefore makes allowance for such variations. This paper shows that the design problem for conditionally stable transistors can be reduced from the selection of values for two complex variables (port terminations) to the selection of the value for just one scalar variable.

Multi-ary Trellis-Coded Modulation (TCM) schemes have been studied for use with digital radio communication systems. Among these TCM schemes, we have already reported the optimum signal constellation of a rate-3/4 trellis-coded (TC) 16-ary Amplitude and Phase Shift Keying (APSK) scheme and computed the minimum Euclidean distance: dfree. In this paper, we evaluate other performance parameters: Nfree and bit error rate (BER) over an additive white Gaussian noise channel, and further investigate the various signal constellations of rate-4/5 TC 32-APSK schemes. It is found that the BER performances of circular-type signal constellations are superior to that of rectangular-type in the TC 16-APSK, and a (24,8) circular type signal constellation is superior to other constellations in the TC 32-APSK.

CTL (Computation Tree Logic) model checking is a formal method for design verification that checks whether the behavior of the verified system is contained in that of the requirements specification. If this check doesn't pass, the CTL model checker generates a subset of fair states which belongs to the system but not to the specification. In this letter, we present an incremental method which successively modifies the latest verification result each time the design is modified. Our incremental algorithm allows the designer to make changes in terms of addition or subtraction of fair CTL formulas, or fairness constraints on acceptable behavior from the problem statement. Then, these changes are adopted to update the set of fair states computed earlier. Our incremental algorithm is shown to be better than the current non-incremental techniques for CTL model checking. Furthermore, a conclusion supported by the experimental results is presented herein.

One effective way to make a large-capacity mobile communication system is to use a microcellular system. One way to do this is to place the base station antennas lower than the surrounding buildings. This result in what is called a street microcellular system. We previously presented basic simulation results evaluating the performance of a different-sized cell combination algorithm (DCC) designed to avoid the problems due to an unbalanced distribution of traffic in street microcellular systems. In this paper, we present the results of simulations evaluating the performance of an improved active different-sized cell combination method (ADCC) that controls the transmission power of each base station.

This paper presents a method of calculating an interval including a bifurcation point. Turning points, simple bifurcation points, symmetry breaking bifurcation points and hysteresis points are calculated with guaranteed accuracy by the extended systems for them and by the Krawczyk-based interval validation method. Taking several examples, the results of validation are also presented.

This paper describes a defect detection method which automatically extracts defect information from complicated background LSI patterns. Based on a scanning electron microscope (SEM) image, the defects on the wafer are characterized in terms of their locations, sizes and the shape of defects. For this purpose, two image processing techniques, the Hough transform and wavelet transform, have been employed. Especially, the Hough Transform for circles is applied to non-circular defects for estimating the shapes of defects. By experiments, it has been demonstrated that the system is very effective in defect identification and will be used as an integral part in future automatic defect pattern classification systems.

A new IC interconnect transmission line parameter determination methodology and a novel fast simulation technique for non-uniform transmission lines are presented and verified. The capacitance parameter is a strong function of a shielding effect between the layers, while silicon substrate has a substantial effect on inductance parameter. Thus, they are taken into account to determine the parameters. Then the virtual straight-line-based per unit length parameters are determined in order to perform the fast transient simulation of the non-uniform transmission lines. It was shown that not only the inductance effect due to a silicon substrate but also the shielding effect between the layers are too significant to be neglected. Further, a model order reduction technique is integrated into Berkeley SPICE in order to demonstrate that the virtual straight-line-based per-unit-length parameters can be efficiently employed for the fast transient response simulation of the complicated multi-layer interconnect structures. Since the methodology is very efficient as well as accurate, it can be usefully employed for IC CAD tools of high-performance VLSI circuit design.