We analyze the average bit error probability (BER) performances of BPSK with pilot tone in the frequency-selective Rayleigh fading channel, which can be characterized by the delay power spectrum due to multipath fading. The analysis is based on the error probability conditioned on the receiver input envelope in order to investigate the diversity effects. With taking into consideration of predetection receiving filter characteristic, the average BER is evaluated by treating the normalized standard deviation (rms delay spread), τ0/T (T: digital symbol period), of the delay power spectrum, BT product of predetection filter and power distribution between BPSK signal and pilot tone as parameters. The results show that the optimum power distribution (kopt) can be determined mainly according to the ratio (α) of tone extracting filter bandwidth to predetection filter bandwidth provided that α is small. For fixed α, τ0/T and kopt corresponding to α, optimum BT product, which minimizes the error rate, exists and the value is dependent on signal energy per bit to noise power spectral density ratio (SNR), and is affected slightly by the delay power spectrum shapes. In this paper, one-sided exponential, Gaussian and double spike shapes are treated as delay power spectrum shapes. On the average BER characteristics due to delay spread with fixed α, BT and kopt corresponding to α, the delay power spectrum shape is of no importance for τ0/T0.06. For τ0/T0.06, in the case of double spike delay power spectrum, BER is less than that for the other two spectral shapes. By making use of the selection diversity with 2-branch and predetection filter with optimum BT product, SNR can be improved by 16dB at the average BER of 10-4.

The inverted slot line (ISL) has been propoaed for millimeter-wave LiNbO3 optical modulator. It is simple in structure, and capable of achieving the perfect velocity matching between carrier and modulating waves. The excellent performance of the ISL optical modulator has been demonstrated at 100 GHz, and the extension into the 50 GHz range is being expected. This paper addresses the analysis of the ISL based on the spectral domain approach. The major results obtained here are the demonstration of the perfect velocity matching not only at 10 GHz but also at 50 GHz, and the characterization of the ISL in terms of effective refractive index, characteristic impedance, overlap integral factor and transmission loss. The depth of optical phase modulation is also estimated at 50 GHz to show a promising performance in the millimeter-wave frequency range. The effective refractive index and the characteristic impedance are found to be theoretically predictable, but the field profile, the overlap integral factor and the transmission loss are not necessarily in good agreement with measurements. As a result of analysis, it can be concluded that the Y-cut substrate is superior to the Z-cut substrate in the following respects: 1. Coupling with the surface wave mode hardly occurs near the operating frequency range. 2. The perfect velocity matching can be attained with a larger spacing between the electrode and the ground plane. 3. The transmission loss is smaller. 4. The field intensity and the voerlap integral factor do not seem to be much deteriorated in the actual ISL.

This paper describes design considerations for high frequency active BPFs up to 100 MHz. The major design issues for high frequency active filters are the excess phase shift in the integrators and high power consumption of the integrators. Typical bipolar transistor based transconductors such as the Gilbert gain cell and the linearized transconductor with two asymmetric emitter-coupled pairs have been analyzed and compared. It has been clarified that the power consumption of the linearized transconductor can be much smaller than that of the Gilbert gain cell because of its high transconductance to working current ratio while maintaining a signal to noise ratio of the same order. A simple high-speed fully differential linearized transconductor cell is proposed with emitter follower buffers and resistive loads for excess phase compensation. A novel gyrator based transformation for the LC ladder BPF has been introduced. This transformation has resulted in a structure with simple capacitor-coupled active resonators which exactly preserves the original transfer function. A fourth order 10.7 MHz BPF IC was designed using the proposed transconductors. It was fabricated and has demonstrated the usefulness of the proposed approach. In addition, an experimental 100 MHz second order BPF IC with Q=14 has been successfully implemented indicating the potential of the proposed approach.

Complex filters are used to synthesize real filters in digital signal processing, but few in analog one. In this paper, we propose a leapfrog synthesis of complex analog filters. By shifting frequency response of an LCR network along the ω-axis, we have a complex filter with imaginary resistances, which is called an "LCRRi filter." The complex resonator is then used to simulate series- or parallel-arms of the LCRRi filter. We analyze nonideal properties of the complex resonator due to finite gain-bandwidth product of operational amplifiers and propose a compensation method to put a pole on correct location. Experimental results show good performance of the proposed method.

In this paper, some misconceptions about "multipath propagation" are discussed for those propagation engineers, who are not familiar with the close relationship between multipath propagation and a communication system in a mobile/portable radio communication environment. It is shown that believed facts about multipath propagation are not always true. Namely, it is well-known that multipath propagation is undesirable if a conventional sample-and-decision receiver is assumed. It is not well-recognized that it can be a desirable phenomenon if a sophisticated communication system uses adaptive equalization, anti-multipath modulation, or spread spectrum communication, for example. On the other hand, it is widely accepted that root mean square (rms) multipath delay spread is a good measure of bit-error-rate performance, i.e., as rms delay spread gets larger, bit-error-rate generally gets worse. However, it is pointed out that this is not always true, especially in propagation conditions with very long-delayed multipath signals. In short, it is the purpose of this paper to show examples that the facts believed to be true sometimes turn out to be false, unless we pay attention to both aspects of propagation and system design in the field of mobile/portable radio communications. In fact, for highly efficient communication systems design, propagation, antenna and system factors should be taken into account simultaneously.

We propose a direct-sequence spread-spectrum multi-access (DS/SSMA) receiver that incorporates multipath diversity combining and multistage co-channel interference (CCI) cancellation. This receiver structure which is more resistant to the near/far problem essentially removes more and more of the CCI with each successive cancellation stage. With the assumption that perfect channel estimates have been obtained, we analyze the bit error rate (BER) performance of this system when received powers are unequal. Results show that the BER can approach that of a single-user case as the number of CCI cancellation stages increases.

In this paper, we study the performance of convolutional coding using an error-and-erasure correction Viterbi decoder for π/4-shift QDPSK mobile radio transmission. The receiver uses received signal envelope as channel state information to erase unreliable symbols instead of making explicit decision before decoding. The performance study is carried out over frequency-selective fading channel with additive white Gaussian noise, co-channel interference and propagation delay spread. The results show that decoding with symbol erasure can significantly improve the system transmission performance compared to decoding without symbol erasure.

Power-law decay of current for the application of step-function voltage observed for amorphous materials can be expressed by an admittance sa(0a1) of a linear diode using complex angular frequency s. It is shown that power-law decay can be interpreted as a superposition of exponential decays having fractally distributed relaxation times and simulated using RC networks. By use of a similar manner, admittance s-b (0b1) showing the relation of duality can be simulated using RL networks. According to these methods, we can synthesize the admittance involving non-integer exponents systematically.

In this paper, the effects of the grouping and the addressing methods on the accuracy and the response time in a visual search task were investigated. Four grouping conditions (4, 8, 16 and 32 groups) and four addressing methods (random, ordered, cartesian and polar) were selected in the experiment. For each combination of grouping and addressing methods, subjects repeated the search task 30 times. No remarkable differences of the percent correct were observed both among the levels of grouping and among the addressing methods. The mean response time increased with the increase of the number of groups. Moreover, the interaction between addressing methods and grouping for both percent correct and response time was clarified.

The robust finite settling time stabilization problem is considered for a multivariable discrete time plant with structured uncertainties. Finite settling time (FST) stability of a feedback system is a notion introduced recently for discrete time systems as a generalization of the dead-beat response. The uncertain plant treated in this paper is described by (E0+ΣKi=1qiEi)x(t+1)(A0+ΣKi=1qiAi)x(t)+(B0+ΣKi=1qiBi)u(t), and y(t)=(C0+ΣKi=1qiCi)x(t) where Ei, Ai, Bi and Ci (0iK) are prescribed real matrices and qi (1iK) are uncertain parameters restricted to prescribed intervals [qi, i]. It is shown in this paper that a controller robustly FST stabilizes such an uncertain plant, if, the uncertain plant satisfies some conditions, and the controller simultaneously FST stabilizes a finite set of plants. The result leads to a testable necessary and sufficient condition of the existence of a solution to the robust FST stabilization problem, and a systematic method of designing a robust FST stable feedback system, in the case where the plant contains only one uncertain parameter.

An integrator is quite a suitable active element for high-speed filters. The effect of its excess phase shifts, however, is severe in the case of high-Q filter realization. The deterioration due to the excess phase shifts cannot be avoided when only integrators are used as frequency-dependent elements like in leapfrog realization. This paper describes a design of second-order high-speed and high-Q filters with low sensitivity to excess phase shifts of integrators by adding a passive RC circuit. The proposed method can drastically reduce the effect due to the undesirable pole of an integrator, which is the cause of the excess phase shifts, compared to conventional filters using only integrators. As an example, a fourth-order bandpass filter with 5-MHz center frequency and Q=25 is implemented by the proposed method on a monolithic chip. The results obtained here show quite good agreement with the theoretical values. This demonstrates effectiveness of the proposed method and feasibility of high-speed and high-Q filters on a monolithic chip.

In general, the work on developing an expert system has relied on domain experts to provide all domain-specific knowledge. The method for acquiring knowledge directly from experts is inadequate in oriental medicine because it is hard to find an appropriate expert and the development cost becomes too high. Therefore, we have developed two effective methods for acquiring knowledge indirectly from sample cases. One is to refine a constructed knowledge base by using sample cases. The other is to train a neural network by using sample cases. To demonstrate the effectiveness of our methods, we have implemented two prototype systems; the Oriental Medicine Expert System (OMES) and the Oriental Medicine Neural Network (OMNN). These systems have been compared with the system with the knowledge base built directly by domain experts (OLDS). Among these systems, OMES are considered to be superior to other systems in terms of performances, development costs, and practicalness. In this paper, we present our methods, and describe our experimental and comparison results.

This paper describes a task-oriented speech dialogue system based on spontaneous speech understanding and response generation (TOSBURG). The system has been developed for a fast food ordering task using speaker-independent keyword-based spontaneous speech understanding. Its purpose being to understand the user's intention from spontaneous speech, the system consists of a noise-robust keyword-spotter, a semantic keyword lattice parser, a user-initiated dialogue manager and a multimodal response generator. After noise immunity keyword-spotting is performed, the spotted keyword candidates are analyzed by a keyword lattice parser to extract the semantic content of the input speech. Then, referring to the dialogue history and context, the dialogue manager interprets the semantic content of the input speech. In cases where the interpretation is ambiguous or uncertain, the dialogue manager invites the user to confirm verbally the system's understanding of the speech input. The system's response to the user throughout the dialogue is multimodal; that is, several modes of communication (synthesized speech, text, animated facial expressions and ordered food items) are used to convey the system's state to the user. The object here is to emulate the multimodal interaction that occurs between humans, and so achieve more natural and efficient human-computer interaction. The real-time dialogue system has been constructed using two general purpose workstations and four DSP accelerators (520MFLOPS). Experimental results have shown the effectiveness of the newly developed speech dialogue system.

Optical interconnection is a rapidly expanding field of optical signal transmission, but it places some stringent requirements on optical devices. This paper introduces the current device characteristics of lasers and photodiodes and discusses the possibility of intra/inter wafer optical interconnection.

A high resolution iterative algorithm for estimating the direction-of-arrival of multiple wide band sources is proposed in this paper. For equally spaced array structure, two Unitary Transform based approaches are proposed in frequency domain for signal subspace processing in both coherent multipath and incoherent environment. Given a priori knowledge of the initial estimates of DOA, with proper spatial prefiltering to separate multiple groups of closely spaced sources, our proposed algorithm is shown to have high resolution capability even in coherent multipath environment without reducing the angular resolution, compared with the use of subarray. Compared with the conventional algorithm, the performance by the proposed algorithm is shown by the simulations to be improved under low Signal to Noise Ratio (SNR) while the performance is not degraded under high SNR. Moreover the computation burden involved in the eigencomputation is largely reduced by introducing the Pesudo-Hermitian matrix approximation.

The security problems of object-oriented database system are investigated and security level assignment constraints and an access control mechanism based on the multilevel access control security policy are proposed. The proposed mechanism uses the Trusted Computing Base. A unique feature of the mechanism is that security levels are assigned not only to data items (objects), but also to methods and methods are not shown to the users whose security level is lower than that of the methods. And we distinguish between the security level of a variable in a class and that in an instance and distinguish between the level of an object when it is taken by itself and it is taken as a variable or an element of another complex object. All of this realizes the policy of multilevel access control.

The performance of an enciphered B+-tree can be improved by the selective encryption of the components of the nodes in the tree. This paper suggests an approach to the selective encryption of nodes in a B+-tree and a method to substitute the plaintext search keys in order to increase the security of the tree. The method is based on structures in combinatorial block designs, and it allows for faster traversal of the tree, hence improving the overall speed of query responses. It also represents a trade-off between security and performance in that the substitution method affords less security compared to encryption. However, assuming the use of a secure cryptosystem with parameters which are kept secret, the encrypted state of the data pointers and data blocks still prevents an intruder from accessing the stored data. The method based on block designs has the advantage of requiring only a small amount of information being kept secret. This presents a considerable savings in terms of space used to hold security-related information.

A context-sensitive method to predict linguistic expressions in the next utterance in inquiry dialogues is proposed. First, information of the next utterance, the utterance type, the main action and the discourse entities, can be grasped using a dialogue interpretation model. Secondly, focusing in particular on dialogue situations in context, a domain-dependent knowledge-base for literal usage of both noun phrases and verb phrases is developed. Finally, a strategy to make a set of linguistic expressions which are derived from semantic concepts consisting of appropriate expressions can be used to select the correct candidate from the speech recognition output. In this paper, some of the processes are particularly examined in which sets of polite expressions, vocatives, compound nominal phrases, verbal phrases, and intention expressions, which are common in telephone inquiry dialogue, are created.

We show that, if NP language L has an invulnerable generator and if L has an honest verifier standard statistical ZKIP, then L has a 5 move statistical ZKIP. Our class of languages involves random self reducible languages because they have standard perfect ZKIPs. We show another class of languages (class K) which have standard perfect ZKIPs. Blum numbers and a set of graphs with odd automorphism belong to this class. Therefore, languages in class K have 5 move statistical ZKIPs if they have invulnerable generators.

This paper discusses the problems facing spoken dialogue processing and the prospects for future improvements. Research on elemental topics like speech recognition, speech synthesis and language understanding has led to improvements in the accuracy and sophistication of each area of study. First, in order to handle a spoken dialogue, we show the necessity for information exchanges between each area of processing as seen through the analysis of spoken dialogue characteristics. Second, we discuss how to integrate those processes and show that the memory-basad approach to spontaneous speech interpretation offers a solution to the problem of process integration. The key to this is setting up a mental state affected by both speech and linguistic information. Finally, we discuss how those mental states are structured and a method for constructing them.