In this paper, a novel CMOS defuzzification circuit using dual-output current conveyors (DO-CCII) is introduced. The behaviour of the proposed circuit has been verified with PSPICE using the models for 1.2 µm MIETEC CMOS process. The proposed circuit offers high-speed operation and high accuracy because of using second generation current conveyors (CCII). The designed circuit is suitable for fuzzy logic controllers using center of gravity (COG) defuzzification method.

Wavelet packet modulation (WPM) using the discrete wavelet transform is a multiplexing transmission method in which data is assigned to wavelet subbands having different time and frequency resolutions. The WPM keeps data transmission throughput even in tone and impulse interference environments that cannot be achieved with conventional multiplexing methods such as TDM (Time division multiplexing) or OFDM (Orthogonal frequency division multiplexing). In this paper, we propose an effective multicarrier transmission method of WPM for wireless mobile communications. First, the transmission characteristics of WPM in fading environments are minutely investigated. Then, taking the advantage of the WPM and the OFDM that has an equalizing technique in multipath fading environments, we propose a multimode transmission method using them. The adaptive transmission in those fading and interference environments is achieved by using the multimode transmission. Their transmission performances are evaluated by computer simulations.

A novel ferroelectric-gate transistor with split-gate structure has been proposed and its read out characteristics have been analyzed. "Transistor-type" FeRAMs have a problem in degradation of readout current, i.e. when the readout voltage is applied at the gate, the current of readout operation is smaller than that of write operation. We demonstrate by SPICE simulation that the proposed split-gate structure ferroelectric-FET can overcome the problem.

In this paper, Pre-Rake scheme for pulse based Ultra Wideband impulse radio (UWB-IR) communications system is proposed considering a standardized UWB channel model from IEEE 802.15 SG3a, which is based on an extensive set of short-range indoor channel measurements. Two kinds of pulse waveforms are taken in account here, namely, Gaussian mono-pulse and newly designed Prolate Spheroidal Wave Functions (PSWF) pulses corresponding to FCC Spectrum Mask. The Pre-Rake scheme is shown to contribute to the low-power, cost-efficient UWB system designing as well as Rake combining gain. Instead of building a Rake receiver at the receiving side (e.g. portable unit), the transmitter (e.g. access point) can pre-combine the UWB signal before transmission in the forward link by estimating the channel impulse response from the reverse link. While the Pre-Raked signal is convolved with the estimated channel impulse response, the function of Rake combination at the receiver is automatically performed. Meanwhile, in order to defeat inter-pulse-interferences (IPI) caused by severe multipath fading conditions, adaptive guard-time scheme for consecutive pulses is proposed as well. Monte-Carlo simulations are carried out to compare the Pre-Rake with Rake results and show that Pre-Rake scheme is as good as Rake combining for both types of pulse waveforms. Then the mobile or portable unit with a conventional receiver can still achieve the diversity gain of Rake combination. Moreover, the effects of placing guard-time between pulses are also verified.

Recently, there have been a number of studies on wavelength division multiplexing (WDM) systems designed to increase transmission capacity and flexibility. This has in turn made it necessary to design the optical loss for optical fiber networks over a wide wavelength range. However, there is no general optical loss design method that allows us to employ for an optical fiber network over a wide wavelength range. In this paper, we propose a novel optical loss design and estimation method based on multiple regression analysis and statistical loss design technology for designing new optical fiber networks and for upgrading those that have already been installed. We show that the method can be used for highly accurate optical loss design and estimation from the O- to the L-band (1260 nm to 1625 nm), except for the E-band, by using easily obtainable optical loss values at wavelengths of 1310 and 1550 nm, which are usually used for communication. Moreover, we also show that the accuracy of our proposed method can be improved by selecting proper additional predictor wavelengths.

In this letter, we address the problem of how to measure the link quality in terms of signal-to-interference ratio (SIR) in rapidly time varying channels which are due to fast variation of the interference or the bursty nature of the traffic. We propose a new SIR estimation approach for the TD-CDMA system, that is based on a pre-selection tentative decision device which discards and selects the estimated symbol on the basis of MAP ratio. The simulation results show that the proposed SIR estimator works and is superior to other known estimators in rapidly time varying channels.

One of the important techniques in communication system design is the composition of service and protocol specifications. In this paper, we have presented a new approach to the composition technique based on the weak bisimulation concept. The main objective is to combine service specifications and protocol specifications individually and simultaneously. The composition technique can maintain the equivalence between the composed service and protocol specifications. LOTOS language terms are utilized to describe the communication specifications. The application on the asynchronous model is presented. Moreover, a support system of the composition technique is developed and presented in this paper.

We show that the necessary and sufficient condition for the existence of a balanced bowtie decomposition of the symmetric complete multi-digraph is n 5 and λ(n-1) 0 (mod 6). Decomposition algorithms are also given.

To improve the DS-CDMA signal transmission performance in a frequency-selective fading channel, the frequency-domain equalization (FDE) can be applied, in which simple one-tap equalization is carried out on each subcarrier component obtained by fast Fourier transform (FFT). Equalization weights for joint FDE and antenna diversity combining based on maximal ratio combining (MRC), zero-forcing (ZF), and minimum mean square error (MMSE) are derived. The conditional bit error rate (BER) is derived for the given set of channel gains in a frequency-selective multipath fading channel. The theoretical average BER performance is evaluated by Monte-Carlo numerical computation method using the derived conditional BER and is confirmed by computer simulation. Performance comparison between DS- and multi-carrier (MC)-CDMA both using FDE is also presented.

Direct manipulation by hand is an intuitive and simple way of positioning objects in an immersive virtual environment. However, this technique is not suitable for making precise adjustments to virtual objects in an immersive environment because it is difficult to hold a hand unsupported in midair and to then release an object at a fixed point. We therefore propose an alternative technique using a virtual 3D gearbox widget that we have designed, which enables users to adjust values precisely. We tested the technique in a usability study along with the use of hand manipulation and a slider. The results showed that the gearbox was the best of the three techniques for precise adjustment of small targets, in terms of both performance data and subject preference.

This paper presents experimental results of a future road-to-vehicle communications system with handover function. The proposed handover scheme, based on the current Dedicated Short Range Communication System (DSRC) standard (ARIB STD-T75) in Japan, maintains the continuity of data transmissions over multiple radio zones by transferring received and remaining data between base stations located along the roadside. Moreover, a link connection/disconnection method is newly proposed to avoid repetition of link connection and disconnections around the cell entrance and to actualize smooth handover between cells. The proposed method determines the link connection and disconnection timing by measuring the received signal strength and observing the results of CRC (Cyclic Redundancy Code) error checks of the control channel. By applying the proposed method to mobile stations (MS) in the DSRC system, the communication link between the MS and the base station (BS) can be smoothly connected. Field experiments were conducted to evaluate the performance and validity of the proposed methods using actual equipment. Experimental results show that the proposed methods perform a smooth link connection between cells and achieve a very short handover processing delay of less than 42 milliseconds.

In 2002, Hwang and Yeh showed that Peyravian-Zunic's password authentication schemes are not secure and proposed an improvement by using the server public key. Since applying the server public key results in the additional burden, we propose secure password authentication schemes without using the server public key in this paper.

A deniable authentication protocol is used to identify the source of a received message for a receiver, but the receiver is unable to prove to a third party the source of the received message. Recently, Fan et al. proposed a deniable authentication protocol based on Diffie-Hellman algorithm. In this paper, we show that Fan et al.'s protocol does not possess the deniable property as they claimed. A cheating receiver can prove the source of the received message to a third party. In addition, we also present a modification of Fan et al.'s protocol to overcome the security flaw.

This paper proposes the dynamic resource assignment (DRA) scheme in the multi-carrier mesh-topology millimeter-wave (MMW) broadband entrance networks. In the DRA scheme, the radio path allocation and the frequency channel assignment techniques are deployed to maximize the network throughput. In the radio path allocation technique, the traffic load is distributed into the appropriate paths. On the other hand, the frequency channel assignment is performed based on the linear programming (LP) method. As the results, the proposed DRA scheme yields higher throughput performance than the conventional scheme using the random frequency channel assignment. In addition, the proposed scheme can guarantee the throughput performance when the number of frequency channels is 36 and the input load is no more than 9 Gbps. Moreover, the proposed scheme can yield the satisfaction sub-optimum throughput with the small computational complexity.

This paper proposes a bandwidth allocation algorithm and a demand accommodation algorithm guaranteeing utility max-min fairness under bandwidth constraints. We prove that the proposed algorithms can fairly split network resources among connections and achieve call admission control considering the fairness among different types of applications. We then formulate three different network design problems to maximize the total utility of all customers, the number of users accommodated in the network, and the average utility of the customers accommodated in the network. To solve the problems, we extend the conventional network design algorithms considering utility max-min fair share, and numerically evaluate and compare their performance. Finally, we summarize the best algorithms to design the utility max-min fair share networks considering the operation policy of network providers.

In mobile cellular networks it is crucial to be able to use the available radio spectrum as efficiently as possible while providing a certain level of Quality of Service (QoS) for the users. Emergence of miscellaneous services has dramatically increased the complexity of this problem by creating a heterogeneous traffic environment. In this paper an efficient resource allocation scheme between two real-time services with different bandwidth requirements has been proposed for cellular networks with multimedia offered traffic and highly mobile users, which combines classical intera-cell resource borrowing concept with a novel inter-cell resource-sharing scheme between diverse classes of traffic. By assuming the heterogeneous offered traffic to be a combination of audio and video traffic types, through extensive simulations it will be shown that HCBA-UCB is capable of significantly improving audio teletraffic performance of the system while preserving fairness in service provision, i.e. without imposing additional expenses upon video QoS performance.

Sensor networks, in which a large number of sensor nodes are connected with each other through communication networks, are potential to provide extensive new applications with various research and technical challenges and attracting much attention all over the world. In this paper we describe information and signal processing for sensor networks with emphasis on the concepts of collaboration and fusion as one of the most important issues for the sensor networks. We also review some basic aspects of sensor networks in terms of their features and the network architecture.

This paper presents novel algorithms for image restoration by state sharing methods with the stochastic model. For inferring the original image, in the first approach, a degraded image with gray scale transforms into binary images. Each binary image is independently inferred according to the statistical fluctuation of stochastic model. The inferred images are returned to a gray-scale image. Furthermore the restored image is constructed from the average of the plural inferred images. In the second approach, the binary state is extended to a multi-state, that is, the degraded image with Q state is transformed into n images with τ state and image restoration is performed. The restoration procedure is described as follows. The degraded image with Q state is prepared and is transformed into n images with τ state. The n images with τ state are independently inferred by the stochastic model and are returned to one image. Moreover the restored image is constructed from the average of the plural inferred images. Finally, the properties of the present approaches are described and the validity of them is confirmed through numerical experiments.

A readout circuit involving new two step current mode background suppression is studied for 2-dimensional long wavelength infrared focal plane arrays (LWIR FPA's). Buffered direct injection (BDI) and feedback amplifier structure are adopted for input circuit and background suppression circuit, respectively. The pixel circuit is simple and has very small skimming error less than 0.1%. Enough calibration range over 50% as well as long integration time over 1.75 ms can be obtained using this readout circuit.

The hardware implementation of a neural network model using stochastic logic has been able to integrate numerous neuron units on a chip. However, the limitation of applications occurred since the stochastic neurosystem could execute only discrete-time dynamics. We have contrived a neuron model with continuous-time dynamics by using stochastic calculations. In this paper, we propose the circuit design of a new neuron circuit, and show the fabricated neurochip comprising 64 neurons with experimental results. Furthermore, a new asynchronous updating method and a new activation function circuit are proposed. These improvements enhance the performance of the neurochip greatly.