The performance of an M-ary spread-spectrum multiple-access (M-ary/SSMA) scheme in the presence of carrier frequency offset is discussed in this paper. The influence of carrier frequency offset on the non-coherent reception of M-ary/SSMA signals is examined and it is shown that the carrier frequency offset degrades the performance remarkably, yet. this influence has a distinctive property. Making use of this property, we propose a new M-ary/SSMA scheme that can mitigate the influence of the carrier frequency offset. The scheme is based on the assignment of two distinctive Hadamard codes to in-phase and quadrature components of the transmitted signal. The effect of simultaneous transmission is evaluated in terms of bit-error-rate performance with the carrier frequency offset. As the result, it is observed that the satisfactory bit-error-rate performance can be achieved in the presence of carrier frequendy offset.

This paper presents a new blind identification method of nonminimum phase FIR systems and an adaptive blind equalization for PAM/QAM inputs without employing higher-order statistics. They are based on the observation that the absolute mean of a second-order white sequence can measure whether the sequence is higher-order white or not. The proposed methods are new alternatives to many higher-order statistics approaches. Some computer simulations show that the absolute mean is exactly estimated and the proposed methods can overcome the disadvantages of the higher-order statistics approaches.

For direct sequence spread spectrum systems, the performance of PN sequence acquisition can be significantly affected if data modulation is present. However, the data modulation often exists during the reacquisition of a PCS radio channel. This study proposes and analyzes two shemes which are designed to improve acquisition process for PN sequence under data modulation. Both designs are based upon a PN acquisition receiver with parallel I-Q matched filters. The first scheme employs a serial search strategy with verification mode. The second scheme, which is still based upon the same parallel acquisition receiver, employs the parallel search strategy. We show that the second scheme is capable of providing faster acquisition under data modulation than the first serial search scheme using the same number of I-Q matched filter. We believe it should become a very good alternative for the acquisition of data modulated PN sequences in personal communications.

This paper considers the evaluation of the acquisition performance for an access channel preamble based on the random access procedure of direct sequence code division multiple access (DS/CDMA) reverse link. The parallel acquisition technique that employs the single-dwell and multiple-dwell (double-dwell) detection schemes is investigated. The acquisition performance for two detection schemes is compared in terms of the acquisition probablity and the mean acquisition time. The parallel acquisition is done by a bank of N parallel I/Q noncoherent correlators. Expressions on the detection, false alarm, and miss probabilities of the single-dwell and multiple-dwell (double-dwell) detection schemes are derived for the multiple H1 cells and multipath Rayleigh fading channel. Comparing the single-dwell detection scheme with the multiple-dwell (double-dwell) detection scheme in the case of employing the parallel acquisition technique in the reverse link, the numerical results show that the single-dwell detection scheme provides a better performance.

ISM band has been approved for spread spectrum communication in radio LAN in Japan since December 1992. This frequency band extends from 2.474 GHz to 2.5 GHz with 26 MHz bandwide. In an indoor environment, the maximum observed delay spread is 100-200 ns in a room, it is too short to generate a selective fading, thus flat fading conditions are often observed. Serve as an alleviation, we propose a new system of multi-antenna in base station (BS) and single antenna in mobile station (MS). In this system, MS should have a simple structure for its small size and energy-saving.

The robust statistics has recently been adopted by the computer vision community. Various robust approaches in the computer vision research have been proposed in the last decade for analyzing the image motion from the image sequence. Because of the frequent violation of the Gaussian assumption of the noise and the motion discontinuities due to multiple motions, the motion estimates based on the straightforward approaches such as the least squares estimator and the regularization often produces unsatisfactory result. Robust estimation is a promising approach to deal with these problems because it recovers the intrinsic characteristics of the original data with the reduced sensitivity to the contamination. Several previous works exist and report some isolated results, but there has been no comprehensive analysis. In this paper robust approaches to the optical flow estimation based on the maximum likelihood estimators are proposed. To evaluate the performance of the M-estimators for estimating the optical flow, comparative studies are conducted for every possible combinations of the parameters of three types of M-estimators, two types of residuals, two methods of scale estimate, and two types of starting values. Comparative studies on synthetic data show the superiority of the M-estimator of redescending ψ-function using the starting value of least absolute residuals estimator using Huber scale iteration, in comparison with the other M-estimators and least squares estimator. Experimental results from the real image experiments also confirm that the proposed combinations of the M-estimators handle the contaminated data effectively and produce the better estimates than the least squares estimator or the least absolute residuals estimator.

Introducing a mathematical model of image noise, we formalize the problem of fitting a line to point data as statistical estimation. It is shown that the reliability of the fitted line can be evaluated quantitatively in the form of the covariance matrix of the parameters. We present a numerical scheme called renormalization for computing an optimal fit and at the same time evaluating its reliability. We also present a scheme for visualizing the reliability of the fit by means of the primary deviation pair and derive an analytical expression for the reliability of a line fitted to an edge segment by using an asymptotic approximation. Our method is illustrated by showing simulations and real-image examples.

In conventional trellis coded modulation (TCM), higher-ary modulation scheme combining with a convolutional code is employed not to expand the transmitted bandwidth. This forces the system to be attended with signal constellation expansion and increasing the average signal power. As the solutions to avoid signal constellation expansion, TCM systems using totally overlapped signal sets (TO-TCM and RU-TCM) were proposed. These schemes can realize a coded modulation system without signal constellation expansion and achieve more coding gain compared with the conventional TCM. However, a problem that the systems with totally overlapped signal sets might be catastrophic has been remained. In this paper, we propose a novel TCM system using partially overlapped signal sets of non-equiprobable signaling (PO-TCM-NE). This scheme employs the partially overlapped signal constellation to control increasing signal points, and to avoid catastrophic error propagation. The non-equiprobable signaling is employed to reduce average signal power. Coding gain of the proposed PO-TCM-NE is considerably improved in consequence the average signal power is reduced much lower than that of other TCM systems with equiprobable signaling.

The independence number of one-order graph associated with a linear code is formulated. The formulation is represented by the parameters of the generator matrix.

An individual identification system is developed. In this system, we unify profile curve identification and full face image identification to obtain more successful recognition rate. In profile cruve identification process, the P-type Fourier descriptor is made use of. In full face image identification process, mosaic density values are made use of. A combination of the two processes shows higher recognition rates than those obtained by each single process.

This paper presents an O(mn log n) time algorithm for an approximate string matching problem, in which a pattern string may contain variable length don't care characters. This problem is important for searching DNA sequences or amino acid sequences.

For mobile/personal satellite systems, an ARQ protocol with low transmitter/receiver complexity as well as high throughput performance in a long Round-Trip-Delay (RTD) and even in a bad channel condition is required. In this paper, a new Selective-Repeat (SR) ARQ with multicopy retransmission is proposed and a performance on an AWGN channel is analyzed. The proposed scheme can be viewed as a modified version for SR + Stutter (ST) Scheme 2 [6]. The basic idea of the strategy is to repeat only erroneous blocks stored in the vN block transmitter buffer multiple times, when v consecutive retransmissions in SR mode are received in error, where N denotes RTD in blocks. Numerical analysis and simuration results in the case of N block transmitter/receiver buffer show that the proposed scheme presents better performance than SR + ST scheme 2 of 2N block buffer, especially that the robustness in the high BER region is remarkable.

We propose an access timing controlled derectdetection optical code-division multiple-access (ATC-CDMA) system with pulse position modulation (PPM) signaling to improve the performance of direct-detection optical CDMA systems with PPM signaling without narrowing the chip width. In the ATC-CDMA system, each user is allowed to access the network Tu times out Tt times according to the scheduled access timing pattern, and the number of users accessing the network simultaneously is decreased; the effect of the channel crosstalk is thus reduced. We analyze the performance of the proposed system under the assumption of Poisson shot noise model for the receiver photodetector including the noise due to the detector dark currents. We compare the performance of the ATC-CDMA system using PPM signaling with that of a conventional CDMA system using PPM signaling under a fixed bit rate, almost the same chip width and a constraint on the transmitted energy per pulse. It is shown that the ATC-CDMA system has better performance than the conventional CDMA system. Moreover, it is shown that the ATC-CDMA system with fewer slots per symbol and lower access timing probability to the network has better performance at the fixed bit rate and the chip width. Therefore, controlling an access timing of each user to the netwark is shown to be more effective for improving the bit error probability performance than the pulse position multiplicity with the increase in the number of slots per symbol under the constraint on the bit rate and the chip width on direct-detection optical CDMA systems with PPM signaling.

In many actual applications of the adaptive filtering, input signals as well as output signals often contain observation noises. Hence, it is necessary to develop an adaptive filtering algorithm to such an errors-in-variables (EIV) model. One solution for identifying the EIV model is a total least squares (TLS) algorithm based on a singular value decomposition of an off-line processing. However, it has not been considered to identify the EIV IIR system using an adaptive TLS algorithm of which stability has been guaranteed during adaptation process. Hence we propose a normalized lattice IIR adaptive filtering algorithm for the TLS parameter estimation. We also show the effectiveness of the proposed algorithm under noisy circumstances through simulations.

Orthogonal frequency division multiplexing (OFDM) has been receiving a lot of attention in the field of broadcasting because of its ruggedness under multipath environments. One of important issues to realize high quality reception of OFDM signals is to correct frequency and timing offsets between the transmitter and receiver so that orthogonality of the carriers can be maintained. This paper discusses a frequency and timing period acquisition technique for OFDM systems. A new offset estimation technique is introduced that detects both the frequency and timing peirod offsets at the same time by using only one pilot symbol with its suitable frequency assignment. A pseudo noise (PN) sequence is also introduced to assign these frequencies of the pilot symbol so that the frequency acquisition range can be widened. Numerical examples are given to show the estimate variances of the proposed frequency and timing period estimator over both additive white Gaussian noise (AWGN) and multipath fading channels. Also the bit error rate (BER) performance for an open loop acquisition system is examined.

We propose a new QOS routing algorithm for finding a path that guarantees several quality of service (QOS) parameters requested by users, for ATM networks. It is known that a routing problem is NP-complete, if the number of additive QOS parameters, such as delay and cost, are more than or equal to two. Although a number of heuristic algorithms have been proposed recently to solve this problem, the appropriate choice of routing algorithms is still an open issue. In this paper, we propose a new heuristic routing algorithm, while being compliant with PNNI routing and signaling specification in the ATM Forum. The performance of algorithms is evaluated by simulation with a various network topologies and loading scenarios. This simulation results demonstrate that the proposed scheme improves the performance while reducing computational complexity.

We have studied liquid crystal (LC) alignment on UV-irradiated poly(vinyl cinnamate)(PVCi)films by using the texture observations and the anchoring energy measurements. Irradiation of the PVCi films with linearly-polarized UV light creates the optical anisotropy in the films, and the anisotropy can well align LCs perpendicular to the UV polarization. We discuss the LC alignment mechanisms and point out the important contribution from non-dimerized side chains of PVCi molecules. The anchoring energies on photo-processed PVCi films are shown to be smaller than those on conventional rubbed polyimide films. We propose a new method to generate pretilt angle on the photo-processed PVCi films, and successful results of pretilt angle generation are demonstrated. This method is applied to fabricate TN- and super-multidomain TN-LCDs, and the good electro-optical performance of the LCDs is confirmed.

A new ATM switch architecture, named shared multibuffering, features great advantages on memory access speed for a large switch, and overall size of buffer memories to achieve excellent cell-loss performance. We have developed a 622-Mb/s 88 shared multibuffer ATM switch with multicast functions and hierarchical queueing functions to accommodate 156-Mb/s, 622-Mb/s and 2.4-Gb/s interfaces. Implementation of the shared multibuffer ATM switch is described with respect to the four sorts of 0.8-µm BiCMOS LSIs and ATM switch boards. The switch board/type-1, with C1-LSI, allows to accommodate effectively 156-Mb/s and 622-Mb/s interfaces, which is suitable for an ATM access system. The switch board/type-2, with C2-LSI, can provide multicast functions and accommodate a 2.4-Gb/s interface. By using four switch boards, it is possible to apply them to a 2.4-Gb/s ATM loop system.

Amorphous silicon thin film transistors(a-Si TFTs) with a channel-etched structure were fabricated. The key technologies to realize these simple-process TFTs were 1) fabricating data lines and pixel electrodes of indium tin oxide(ITO); 2) carrying out tapered dry etching of plural layers of the a-Si and gate insulator silicon nitide; and 3) forming silicide layer to reduce the contact resistance between the phosphorousdoped a-Si and ITO. Excellent image quality, with a high contrast ratio of more than 100: 1, was obtained for video graphic array(VGA) mode TFT-LCDs using a dot inversion driving method. Furthermore, the transmission distribution was uniform with less than a 4.5% deviation on the whole display area although the ITO data line resistances were as large as 120 kΩ per line.

This paper concerns optimized facility design for VLSI production. The methods proposed are applicable in planning LSI production facilities with a good balance between the number of machines and the number of operators. The sequence in each processing step is analyzed in detail. A new algorithm based on the queueing model is developed for estimating the simultaneous requirements for the two kinds of resources, machines and operators. This estimation system can be applied to complicated fabrication schemes, such as batch processing, continuous processing, and mixed technologies. This methodology yields guidelines for ASIC LSI production system design.