For the uplink of a radio-on-fiber system or an electromagnetic field sensor, a resonant type optical modulator array connected with antennas can effectively convert a micro/millimeter-wave to a light wave. We designed and fabricated 10 GHz band resonant modulators and micro-strip antennas. And we demonstrated the simultaneous operation of four modulators using power received by micro strip antennas connected to each modulator. We confirmed that the optical phase change induced by the received power could be proportionally increased with the number of arrays.

It is widely believed to take exponential time to find a solution of a system of random multivariate polynomials because of the NP-completeness of such a task. On the other hand, in most of multivariate public key cryptosystems proposed so far, the computational complexity of cryptanalysis is polynomial time due to the trapdoor structure. In this paper, we introduce a new concept, piece in hand (soldiers in hand) matrix, which brings the computational complexity of cryptanalysis of multivariate public key cryptosystems close to exponential time by adding random polynomial terms to original cryptosystems. This is a general concept which can be applicable to any type of multivariate public key cryptosystems for the purpose of enhancing their security. As an implementation of the concept, we propose the linear PH matrix method with random variables. In 2003 Faugere and Joux broke the first HFE challenge (80 bits), where HFE is one of the major variants of multivariate public key cryptosystem, by computing a Grobner basis of the public key of the cryptosystem. We show, in an experimental manner, that the linear PH matrix method with random variables can enhance the security of HFE even against the Grobner basis attack. In what follows, we consider the strength of the linear PH matrix method against other possible attacks.

In this paper, we propose an adaptive data transmission scheme for DS/CDMA packet radio communication systems in bandlimited indoor multipath fading channels. We first analyze the relationship between the code rate and the processing gain (defined as the number of chips per coded bit) in maximizing the normalized throughput in connection with the channel state of the indoor multipath fading channels. One observation made is that the maximum throughput with BPSK modulation is attained when the code rate is chosen as low as possible irrespective of the channel state, and the processing gain is increased (decreased) as the channel becomes worse (better). The other observation made is that when DPSK modulation is employed, there exists an optimal combination of the code rate and the processing gain in maximizing the normalized throughput for each channel state. Based on these observations, we propose to adapt the processing gain and/or code rate according to the fading conditions in order to maximize the normalized throughput. We analyze the performance of the proposed scheme and compare it with the non-adaptive data transmission scheme. Our results show that the adaptive transmission scheme yields a significant performance improvement over the nonadaptive scheme, and increasing the adaptation level is more effective as the channel gets worse, but the 3-state adaptation seems to be practically optimum.

The most time consuming operation to verify a signature with the Elliptic Curve Digital Signature Algorithm is a multi-scalar multiplication with two scalars. Efficient methods for its computation are the Shamir method and the Interleave method, whereas the performance of those methods can be improved by using general base-2 representations of the scalars. In exchange for the speed-up, those representations require the precomputation of several points that must be stored. In the case of two precomputed points, the Interleave method and the Shamir method provide the same, optimal efficiency. In the case of more precomputed points, only the Interleave method can be sped-up in an optimal way and is currently more efficient than the Shamir method. This paper proposes a new general base-2 representation of the scalars that can be used to speed up the Shamir method. It requires the precomputation of ten points and is more efficient than any other representation that also requires ten precomputed points. Therefore, the proposed method is the first to improve the Shamir method such that it is faster than the Interleave method.

A novel PND (PMOS-NMOS-Depletion MOS) technology for a single poly gate non-volatile memory cell design has been reported for the first time. This technology features memory cell design with a differential cell architecture which enables to provide the higher performance for the key specifications such as programming time, erasing time, and endurance characteristics. This memory cell consists of 3-Transistors, PMOS, NMOS, and Depletion MOS transistors (hereafter PND). The DMOS in this cell is used for the tunneling device in the erasing operation, while the NMOS and the PMOS are used for the tunneling device and the coupling capacitor in the programming operation, respectively. The proposed PND design can allow lower applied voltage of the erase-gate (EG) and control-gate (CG) in the erasing and the programming operations so that the endurance characteristics can be improved because the DMOS suppresses the potential of floating-gate (FG) and hence the effective potential difference between the EG and the FG can be increased in the erasing operation. Based on the measured data, it can be expected that the erasing speed of the PND cell can be 125-fold faster than that of our previously reported work (PN type). Therefore, high performance and high reliability CMOS non-volatile memory without any additional process can be realized using this proposed PND technology.

The completeness (i.e. confluent and terminating) property is an important concept when using a term rewriting system (TRS) as a computational model of functional programming languages. Knuth and Bendix have proposed a procedure known as the KB procedure for generating a complete TRS. A TRS cannot, however, directly handle higher-order functions that are widely used in functional programming languages. In this paper, we propose a higher-order KB procedure that extends the KB procedure to the framework of a simply-typed term rewriting system (STRS) as an extended TRS that can handle higher-order functions. We discuss the application of this higher-order KB procedure to a certification technique called inductionless induction used in program verification, and its application to fusion transformation, a typical kind of program transformation.

Accurate estimating or measuring the intake manifold absolute pressure plays an important role in automobile engine control. In order to achieve the real-time estimation of the absolute pressure, the high accuracy and high speed processing ability are required for automobile engine control systems. Therefore, in this paper, an analog method is discussed and a fully integrated analog circuit is proposed to simulate automobile intake systems. Furthermore, a novel behavioral macromodeling is proposed for the analog circuit design. With the analog circuit, the intake manifold absolute pressure, which plays an important role for the effective automobile engine control, can be accurately estimated or measured in real time.

Nowadays, MIMO systems are playing an important role in wireless communications. In this paper, we propose a spatial-temporal adaptive MIMO beamforming scheme for single carrier transmission in frequency-selective fading channels with the assumption of perfect channel state information (CSI) at both the transmitter and receiver. The transmit and receive weight vectors for detecting the preceding signal and the receive weight vectors for detecting the delayed signals of the preceding signal are designed by an iterative update algorithm. Based on minimum mean square error (MMSE) method, the delayed versions of the preceding signal are exploited to maximize the output signal to interference and noise ratio (SINR) instead of suppressing them at the receiver. The improvement of output SINR is useful for MIMO systems to enhance the high-quality communication in broadband wireless systems.

In this letter, we present a procedure to analyze the delay distribution of data traffic in CDMA systems supporting voice and delay-tolerant data services with a finite buffer. The queueing method using a buffer for a delay-tolerant traffic can be used to improve the system utilization or the availability of system resources. Under the first-come and first-serve (FCFS) service discipline, we present a numerical procedure for the formation of delay distribution that is defined as the probability that a new data call get a service within the maximum tolerable delay requirement, based on a two-dimensional Markov model.

In this paper, we propose an effective asynchronous datapath synthesis system to optimize statistical performance of asynchronous systems. The proposed algorithm is a heuristic method which simultaneously performs scheduling and resource binding. During the design process, decisions will be made based on the statistical schedule length analysis. It is demonstrated that asynchronous datapaths with the reduced mean total computation time are successfully synthesized for some datapath synthesis benchmarks.

This paper proposes new resource management schemes for multiple data streams in an orthogonal frequency and space division multiplex access (OFSDMA) system using Radio-on-Fiber (RoF) ubiquitous antennas. The proposed schemes classify the services into some classes in which the number of sub-carriers is dynamically assigned according to the requested data size. The computer simulation results show that the proposed schemes improve the number of users satisfying the required bit error rate (BER) level as well as the average throughput and also show that the RoF ubiquitous antennas can improve system capacity.

In this paper, we propose an integral-type T-S fuzzy control scheme to deal with the regulation problem of buck converters without current sensors. This current sensorless control of converters provides the output voltage to achieve zero steady-state error and is with high robust performance. The stability of the overall closed-loop system is rigorously analyzed by using Lyapunov's method. Based on an appropriate assumption, the separation principle can still succeed in the control problems. Hence, the controller and observer gains can be separately obtained by solving LMIs via Matlab's toolbox. The observer-based controller is realized with Simulink and digital signal processors (DSPs). The simulation and experimental results verify the feasibility of the proposed schemes and show the satisfactory performance for the power converters.

In this letter, the system capacity of multiuser diversity combined with spatial multiplexing schemes is analyzed. An analytic expression is derived for the ergodic system capacity with multiuser scheduling and dual multi-input multi-output (MIMO) systems by using a tight lower bound of the link capacity. The proposed analytic approach is verified through comparisons between analytic and simulated results, and is shown to make fairly precise predictions of the ergodic system capacity and the scheduling gains even when the numbers of antennas and users are small.

Next generation free electron lasers aim to generate x-ray pulses with pulse durations down to 30 fs, and possibly even sub-fs. Synchronization of various stages of the accelerator and the probe laser system to the x-ray pulses with stability on the order of the pulse width is necessary to make maximal use of this capability. We are developing an optical timing synchronization system in order to meet this challenge. The scheme is based on generating a train of short optical pulses, with a precise repetition frequency, from a mode-locked laser oscillator and distributed via length-stabilized optical fibers to points requiring synchronization. The timing information is embedded in the repetition frequency and its harmonics. A significant advantage of the optical synchronization system is that multiple mode-locked Ti:sapphire seed oscillators typically present in an accelerator facility can be replaced by the master mode-locked fiber laser. In this paper, we briefly review progress on the development of the synchronization system and then discuss the implementation of this new possibility. Several technical issues related to this approach are analyzed.

This paper proposes a two-dimensional self-matching receiver for Free Space Optics (FSO) communication system using chaotic spatial synchronization. This system is able to obtain the information of two-dimensional code from received pattern. This paper considers that proposed system is applied to two applications. The first application is image transmission. This paper shows that applying proposed system to image transmission enables to restore the desired image, which doesn't require strict alignment of receiver, and evaluates transmission optical power. The second application is Code Division Multiplexing (CDM). This paper shows that applying proposed system to CDM system enables to demodulate desired digital signals regardless of the uncertainty of received position. Moreover, the required transmission optical power and bit error rate performance are obtained by computer simulation.

Simultaneous all-optical frequency up/downconversion technique utilizing a single semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) for full-duplex WDM radio over fiber (RoF) applications is presented. Using this technique, error-free simultaneous upconversion and downconversion of RoF signals with a finite-length single mode fiber were experimentally demonstrated. The results show the potential of the proposed scheme for use in a cost-effective full-duplex WDM RoF link.

This paper introduces an adaptive GOP structure (AGS), which adaptively defines the GOP structure according to the time-varying temporal properties of video sequences, and thus improves the coding efficiency of the MPEG & ITU-T's Joint Scalable Video Coding (JSVC) scheme, the method proposed in this paper, which adaptively modifies the size of GOP based on the image characteristics of video sequence, improves the coding efficiency up to 0.77 dB compared to the JSVC JSVM (Joint Scalable Video Model).

Diseases of the gastro-intestinal tract are becoming more prevalent. New techniques and devices, such as the wireless capsule endoscope and the telemetry capsule, that are able to measure the various signals of the digestive organs (temperature, pH, and pressure), have been developed for the observation of the digestive organs. In these capsule devices, there are no methods of moving and grasping them. In order to make a swift diagnosis and to give proper medication, it is necessary to control the moving speed of the capsule. This paper presents a wireless system for the control of movements of an electrical stimulus capsule. This includes an electrical stimulus capsule which can be swallowed and an external transmitting control system. A receiver, a receiving antenna (small multi-loop), a transmitter, and a transmitting antenna (monopole) were designed and fabricated taking into consideration the MPE, power consumption, system size, signal-to-noise ratio and the modulation method. The wireless system, which was designed and implemented for the control of movements of the electrical stimulus capsule, was verified by in-vitro experiments which were performed on the small intestines of a pig. As a result, we found that when the small intestines are contracted by electrical stimuli, the capsule can move to the opposite direction, which means that the capsule can go up or down in the small intestines.

This paper deals with a design problem of an observer-based robust preview control system for uncertain discrete-time systems. In this approach, we adopt 2-stage design scheme and we derive an observer-based robust controller with integral and preview actions such that a disturbance attenuation level is satisfactorily small for allowable uncertainties.

We present theoretical foundations about error estimations of the global Krylov subspace techniques for multiple-inputs multiple-outputs (MIMO) Interconnect reductions. Analytical relationships between Lyapunov functions of the original interconnect network and those of the reduced system generated by the global Arnoldi algorithm will be developed. Under this framework, a new moment matching reduced network is proposed. Also, we will show that the reduced system can be expressed as the original network with some additive perturbations.