QoS restoration, a new approach to keep QoS of end-to-end ATM connections for failures is proposed. In a network with QoS restoration, each end-to-end connection's customer pre-defines the minimum QoS requirements such as minimum throughput. When a failure occurs, resources such as bandwidth of working connections are reallocated for restoration if they are dispensable to keep the minimum requirements along with the pre-assigned spare resources. This resource reallocation is done in a distributed manner and the result of the modification of a connection is notified to the customer of the connection to help him adjust the way of using it. The effect of the reallocation is mathematically evaluated. It is shown that the reallocation enables to achieve high restoration ratio with insufficient pre-assigned spare resources, such as to restore double-link failures with spare resources prepared for single-link failures, or even to restore single-link failures with no spare resources. It is also shown that pre-assigned spare resources can be reduced if the reallocation is considered in network design phase. The performance of the proposed distributed algorithm is evaluated with an event-driven simulator. The result shows that regardless of whether or not pre-assigned spare resources exist, a restoration ratio which is close to the theoretical maximum can be achieved. A proof-of-concept experimental system is developed by controlling commercial ATM switches via SNMP. The system shows it can effectively manage failures in WAN environment.

This letter proposes a modified synchronous acquisition method using code-orthogonalizing filters (COFs) in an asynchronous direct sequence (DS) / CDMA. Improvements on the average acquisition time for several conditions are shown.

To provide cellular data services with differentiated QoS, a shared resource scheme, based on the optimization theory and LaGrange λ-calculus was developed. This scheme can generate a fair schedule for a diverse mix of traffic with diverse QoS requirements in a limited radio spectrum. We define the acceptance indication, AI, as the QoS measurement for the shared resource scheme. The experimental results show that this approach outperforms other existing schemes.

We propose a unique word detection scheme having the correction of the phase ambiguity that remains in the output of a carrier recovery circuit for QPSK systems. The performance of the proposed scheme is analyzed by obtaining the probability generating function (PGF) for the output of the detector. The PGF is obtained from the z-transform of the probability density function (PDF) for each matched symbol with the reference symbol and by using the characteristics at this time that the random variables for matched symbols are independent and identically distributed. Then the total PGF for a unique word is obtained from powering the PGF for the individual symbol. From the total PGF, the length of a UW and the threshold value for detection can be obtained with a detection probability defined in a required system specification.

A new method of sequential control has been developed in order to increase the productivity and flexibility of production systems. This advanced sequential control (ASC) method is proposed for sequential control systems based on the autonomous decentralized system (ADS) architecture. The ADS defines the system software and message formats and makes it easy to expand the number of devices and software modules. The ASC method increases productivity because it minimizes the processing and adjustment times of production lines by adjusting the starting times of production processes automatically. Experimental evaluation results of the ASC method showed that it increases the productivity of production systems. It is also applied to an actual production system and the results are reported.

In synchronous CDMA system, the orthogonal spreading sequences are employed to reduce the multiple access interference. However, as the frequency selectivity of the propagation channel strengthens, the orthogonality among different users tends to diminish because of increasing inter-path interference. In this paper, various binary and nonbinary orthogonal sequences are discussed. In order to maintain the orthogonality among different users, a new concept of generalized orthogonality is defined and the corresponding sequences are presented, including binary, quadriphase and nonbinary code sequences. Based on a simplified synchronous CDMA system model, the related system performance is also analyzed and compared for different orthogonal and generalized orthogonal spreading sequences. Our analytical and simulation results show that the generalized orthogonal code sequences are indeed more robust in the multipath propagation channels, compared with the traditional orthogonal code sequences.

In this letter, the constant amplitude transmission for orthogonal multicode systems is discussed. In order to obtain the high power efficiency, we require the high power amplifier which has non-linear characteristic. The nonlinear distortion, however, may occur because of the multicode signals having large amplitude fluctuations. If we can achieve the constant amplitude transmission, the nonlinear distortion can be neglected. In this letter, I investigate the property of the information bit streams that can achieve the constant amplitude transmission and show that the bent sequences can achieve the constant amplitude transmission.

This paper presents a new design of spread spectrum signals with the minimally sufficient dimension from the view point of frequency diversity. Letting the signature signal duration and the bandwidth be denoted by T and B, respectively, we can nominally represent a signature signal of either Direct Sequence (DS) or MultiCarrier (MC) spread spectrum system as the sum of N=BT sinusoidal signal units with their frequencies separated by 1/T or its multiples. In our design,assuming the maximum expected channel delay spread σd « T as usual, one signature signal viewed in the frequency domain is made up of the minimum number K 2πσdB of sinusoidal signal units which are arranged so as there is placed at least one unit in coherence bandwidth 1/(2πσd) in which the fading channel transfer function has strong correlation. Although the signature signal does not make use of all the units in the given frequency domain as in the ordinary spread spectrum systems, but uses only skipped units, it can be shown that almost the same frequency diversity effect is attained. And it is also shown that the immunity to the external interfering signals is by no means inferior. If every L=N/K T/(2πσd) consecutive sinusoidal signal units are assigned to the K signal units of a signature signal, L different signature signals are simultaneously available mutually orthogonal when the synchronous demodulation is performed in the same T period. We call each of the orthogonal sinusoidal signal sets a Frequency Devision (FD) signal set. Now, CDMA can be independently realized on each of the L FD signal sets provided the operation is synchronous or quasi-synchronous with respect to the symbol demodulation (or signature) period. Partitioning the simultaneous users among the FD sets, it is possible to decrease the number of CDMA users to be processed, retaining the total number of simultaneous users. Owing to this effect, the multiple access performance for the FD/CDMA system is shown to be superior to that of the ordinary DS or MC/CDMA system, assuming matched filter reception based on the complete estimation of the channel characteristics for the both cases. The decrease of the number of CDMA users per FD set makes it practical for the receiver to employ multiple access interference cancellation and even the maximum likelihood detection. Curiously, any FD signal set can be represented in the time domain as L repetition of a sequence with its period equal to K in the number of 1/B duration time chips.

A novel adaptive algorithm based on pilot channel (PCA) for MMSE multiuser detection in downlink CDMA is proposed in this paper. This algorithm uses the information in pilot channel to compute the desired weight vector directly. Compared with conventional adaptive algorithms and blind algorithms, it does not require training sequences nor channel estimation. Analysis shows that the weight vector obtained by the PCA algorithm converges to the Wiener solution globally and its computational complexity is O(N2). Simulation results show that the PCA algorithm can adapt rapidly to the changing environment. The steady state performance can be enhanced by increasing the transmitted power in pilot channel, but is worse than that of conventional recursive least-square (RLS) algorithm in decision-directed mode. Also, performance of the adaptive MMSE detector is much better than that of conventional RAKE receiver.

This paper proposes the binary second-order recurrent neural networks (BSRNN) equivalent to the modified finite automata (MFA) and presents the learning algorithm to construct the stable BSRNN for inferring regular grammar. This network combines two trends; one is to transform strings of a regular grammar into a recurrent neural network through training with no restriction of the number of neurons, the number of strings, and the length of string and the other is to directly transform itself into a finite automaton. Since neurons in the BSRNN employ a hard-limiter activation functions, the proposed BSRNN can become a good alternative of hardware implementation for regular grammars and finite automata as well as grammatical inference.

Noncoherent detectors for use in acquiring data-modulated direct-sequence spread-spectrum (DS/SS) signals are considered in this paper. Taking data modulation and timing uncertainty into account and using the generalized maximum likelihood (GML) or maximum likelihood (ML) detection approaches, we derive optimal detectors in the sense of Bayes or Neyman-Pearson and propose various suboptimal detectors. A simple systematic means for their realization is suggested and the numerical performance of these detectors is presented. We also compare their performance with that of the noncoherent combining (NC1) detector that had been proposed to serve the same need. Numerical results show that even the proposed suboptimal detectors can outperform the NC1 detector in most cases of interest.

A uniquely parsable grammar (UPG) introduced by Morita et al. is a kind of generative grammar, in which parsing can be performed without backtracking. It is known that UPGs and their three subclasses form the "deterministic Chomsky hierarchy. " In this paper, we introduce three kinds of normal forms for UPGs, i.e., Type-0, Type-1 and Type-2 UPGs by restricting the forms of rules to very simple ones. We show that the upper three classes in the deterministic Chomsky hierarchy can be exactly characterized by the three types of UPGs.

In this paper, visualized sound retrieval and categorization methods using a feature-based image search engine were evaluated aiming at efficient video scene query. Color-coded patterns of the sound spectrogram are adopted as the visualized sound index. Sound categorization experiments were conducted using visualized sound databases including speech, bird song, musical sounds, insect chirping, and the sound-track of sports video. The results of the retrieval experiments show that the simple feature-based image search engine can be effectively used for visualized sound retrieval and categorization. The results of categorization experiments involving humans show that after brief training humans can at least do rough categorization. These results suggest that using visualized sound can be effective method for an efficient video scene query.

This paper describes a new individual identification system employing a novel application of the PC/SS scheme. Since the proposed system requires no magnetic information, it is robust to various changes in environment. Moreover, it is applicable to contemporary identification systems as an officer identifies one's face with the card's portrait at immigration. In addition, cooperation with existing identification systems using magnetic information and this proposed system provides more secure identification. The proposed system embeds a cardholder-related information that forms a watermark generated by the modulating manner of the PC/SS scheme into cardholder's portrait printed on the card using a simple watermarking scheme also proposed in this paper. Experimental results show that the proposed system extracts embedded information correctly as its fundamental ability. Furthermore, various properties of this system have been investigated, and it has been found that the spatial resolution of scanners is the most dominant to the performance of the proposed system.

In this paper, the authors derived the distributions of the probability of detection and of false alarm in function of the decision threshold. An Optimized Threshold Decision (OTD) algorithm was proposed to decide the optimal threshold for reaching the best system performance in a given known channel noise. By applying this OTD algorithm, the multiple access capacity can thus be maximized.

In this letter, we propose a polarity decision carrier recovery algorithm that is useful for carrier acquisition in high order QAM. The PD (Phase Detector) output and its variance characteristic are mathematically derived and the simulation results are presented. The proposed algorithm shows enhanced acquisition performance especially for large frequency offset.

In this paper, we study macro/micro diversity techniques for code acquisition of a direct-sequence spread-spectrum signal in an indoor packet communication system. In the system discussed, the base station has several radio ports each with a cluster of antennas, and the terminal also has multiple antennas. The performance in the uplink of this system is analyzed under Lognormal shadowing and flat Rayleigh fading. The numerical results show great performance improvements by proposed diversity techniques. In addition, it is clarified that the mean acquisition time, which is often used as the measure of performance, is not suitable for packet radio systems as it underestimates the necessary preamble length for initial code acquisition.

Blind channel estimation algorithm which is applicable to the time-variant channel under frequency-selective fading is proposed. The condition on the blind channel identifiability using temporally and spatially oversampled data is shown. The proposed algorithm consists of two stages. At the first stage, the channel equalization matrix is estimated by taking account of the time-variant characteristics of the channel. At the second stage, the signals and the channel matrix are alternately estimated by using the finite alphabet property of the transmitted symbols. Periodical return from the second stage to the first makes the blind estimation algorithm feasible for the time-variant channel with fast fading. The simulation results confirm the fast convergence property and the effectiveness of the proposed algorithm in coping with the frequency-selective fading.

A "dual-ring" network configuration is proposed in wavelength-division multiplexing (WDM) metropolitan area network (MAN). In the proposed architecture, a "sub-ring" using two fibers is added to the existing metropolitan WDM ring for flexible and cost effective addition of new nodes.

We show some numerical results of computer simulations of secret key reconciliation (SKR) protocol "Cascade" and clarify its properties. By using these properties, we propose to improve the protocol performance on the number of publicly exchanged bits which should be as few as possible.