In ATM Network, the VBR (Variable Bit Rate) service category is used to accommodate TCP/IP traffic. In an international ATM network with large propagation delay, higher TCP throughput can be obtained by use of window scale option. In order to accommodate TCP traffic with window scale option effectively, it is required to select appropriate values of VBR parameters, i. e. SCR (Sustainable Cell Rate) and MBS (Maximum Burst Size), and to evaluate the impact of UPC (Usage Parameter Control) function on TCP throughput. We have studied those technical issues for the conventional TCP, but the results cannot be applied to TCP traffic with the window scale option due to the TCP terminal performance and the large window size. In this paper, we proposed VBR parameter determination method for TCP with the window scale option and evaluated the values in each condition. These results show that the determined MBS is much smaller than the burst length of TCP segments especially using low performance TCP terminals. Furthermore, we also discuss some experimental results of TCP throughput degradation due to UPC function. It shows that the throughput of TCP with large window size is degraded when the SCR and MBS values used in ATM switch are smaller than the determined values.

Space Division Multiple Access (SDMA) will form an important part of the new Wideband Code Division Multiple Access (WCDMA) standard that will realize the Universal Mobile Telephone System (UMTS). This paper addresses a few issues of importance when SDMA techniques are used in a cellular CDMA system. Firstly, a brief overview of SDMA techniques are presented followed by a theoretical analysis of a SDMA/CDMA system. The analysis is focused on a single cell, multipath Rayleigh fading scenario with imperfect power control. As system performance measure Bit Error Rate (BER) is used to investigate the influence of user location, number of antennas and power control error. An important parameter in a SDMA system is the antenna array element spacing. In our analysis a Uniform Linear Array (ULA) is considered and a measure is defined to determine the optimal antenna element spacing in a CDMA cellular environment. Normally the mobile users in a cell are assumed to be uniformly distributed in cellular performance calculations. To reflect a more realistic situation, we propose a novel probability density function for the non-uniform distribution of the mobile users in the cell. It is shown that multipath and imperfect power control, even with antenna arrays, reduces the system performance substantially.

An enhanced priority reservation algorithm for ATM multicast switches with a one-shot scheduling scheme is proposed. This algorithm is an input reservation method in which priority is selected among input ports considering the number of rejected copy requests and the blocked age of head-of-line (HOL) cells. The operation procedure of the proposed algorithm is described, and the average cell-delay and throughput performance is evaluated by simulation. The simulation results show that the proposed algorithm yields better performance than the conventional algorithms.

An associative memory model with a forgetting process a la Mezard et al. is investigated for a piecewise nonmonotonic output function by the SCSNA proposed by Shiino and Fukai. Similar to the formal monotonic two-state model analyzed by Mezard et al. , the discussed nonmonotonic model is also free from a catastrophic deterioration of memory due to overloading. We theoretically obtain a relationship between the storage capacity and the forgetting rate, and find that there is an optimal value of forgetting rate, at which the storage capacity is maximized for the given nonmonotonicity. The maximal storage capacity and capacity ratio (a ratio of the storage capacity for the conventional correlation learning rule to the maximal storage capacity) increase with nonmonotonicity, whereas the optimal forgetting rate decreases with nonmonotonicity.

We have proposed a highly scattering optical transmission (HSOT) polymer for use as a high efficiency light source medium. This polymer contains specified internal microscopic heterogeneous structures for controlling light-transmission properties. An LCD backlighting system having a new light pipe made of this polymer has twice the brightness of the conventional one. A light scattering phenomenon inside the HSOT polymer was quantitatively analyzed by a ray tracing simulation based on the Mie scattering theory and the Monte Carlo method. The illumination of the backlight which is optimized by using the simulation program has enough uniformity of intensity and color because of specified multiple light scattering phenomena inside the HSOT polymer. We propose the new backlighting system having fewer components and twice efficiency of the conventional one.

A 14. 4-in. diagonal EL display with 640128 pixels has been developed in red/green multicolor structures by using a new phosphor layer consisting of Zn1-xMgxS:Mn and ZnS:Mn. The display is designed for 240 Hz-frame rate, enabling the luminance to be improved by a factor of two. In addition, the contrast ratio is strongly enhanced by optimizing the black background structure and color filters. Improved characteristics make it possible for the EL panel to meet the requirements for the public information display taking advantages of high-reliability, crisp image and wide-viewing angle. Furthermore, the possibility of full-color EL displays will be described on the basis of "color by white" approach.

Gd2O2S:Tb phosphor thin films have been prepared using the simple technique of electron beam evaporation for large area display applications. The photoluminescence and excitation spectra measurement of Gd2O2S:Tb phosphor thin films suggest that Tb3+ is incorporated into the Gd2O2S lattice at gadolinium sites. Relatively efficient electroluminescence is observed from a ZnS/Gd2O2S:Tb/ZnS sandwich cell.

A new or future system of mobile telecommunication is built by new digital technologies to provide an improved and more consistent quality of service for the customers. These digital systems can provide greater number of transmission channel allocation for their subscribers and security. On the digital communication system, distortion of transmitted signal should be eliminated as much as possible for high communication quality. However, the need to both minimize distortion of signal amplifiers and continue to provide good filtering protection can become difficult to achieve with conventional high power amplifiers and filters. In this paper, the application of high-Tc superconducting (HTS) power filters on such digital communication systems and recent progress of filter device developments for those are discussed.

A correction of the physical optics approximation by accounting for the presence of specific currents concentrated near shadow boundaries on the surface of a convex non-metallic scatterer is analysed by considering a canonical problem of diffraction of a plane electromagnetic wave incident normally to the axis of an infinite circular cylinder with impedance boundary conditions. The analysis focuses on the development of Fock-type asymptotic representations for magnetic field tangent components on the surface of the scatterer. The Fock-type representation of the surface field is uniformly valid within the penumbra region, providing a continuous transition from the geometrical optics formulas on the lit portion of the surface to the creeping waves approximation in the deep shadow region. A new numerical procedure for evaluating Fock-type integrals is proposed that extracts rapidly varying factors and approximates the rest, slowly varying coefficients via interpolation. This allows us to obtain accurate and simple representations for the shadow boundary currents that can be directly inserted into the radiation integral and effectively integrated. We show that accounting for the shadow boundary currents considerably improves the traditional PO analysis of the high-frequency electromagnetic fields scattered from smooth and convex non-metallic obstacles, particularly near the forward scattering direction.

This paper presents the subjective speech quality evaluation in terms of the Mean Opinion Score (MOS) and the relationship between BER and subjective speech quality in a GSM-based radio system. The results show that in certain environments (hilly terrain and rural areas), a SNR (or C/I) higher than 12 dB is required for acceptable speech quality. For an acceptable speech quality, a BER(c1) better than 10-2 is needed in a GSM-based system.

In GSM High Speed Circuit Switched Data (HSCSD), the data rate can be increased by using multiple time slots instead of single time slot. Multiple time-slot assignment results in high blocking rate. To accommodate more users, flexible resource allocation strategies have been proposed. Since GSM follows TDMA/FDMA, the channels (time slots) in a base station are segmented by frequency carriers. The base station must allocate the channels which belong to the same frequency carrier to individual requests. This Flexible Resource Allocation scheme for GSM (FRA-GSM) is contrastive to the scheme proposed in our previous studies where a base station may arbitrarily allocate idle channels in the base station to incoming requests. We define satisfaction indication SI as the measurement to compare the performance of these schemes. Experiment results indicate that FRA-GSM scheme has good performance when the user mobility is high, or when some cost factors are taken into account.

In this paper, we propose a new conference key distribution scheme and the supervision of a conference when users are in a level-based hierarchy. In a conference key distribution system, one message is transmitted to the participants from a chairman, a legitimate member can decrypt it and reveal the common session key. The proposed scheme can be implemented without using any tamper-proof hardware. For users in a level-based hierarchy, by applying the key distribution scheme, the higher priority users can derive the conference key and supervise the lower level users' communications. Further, the users in the same level who are not members of the conference or in lower levels can not expose the conference key. To break the common session key, a malicious user has to suffer from the difficulty of factorization and discrete logarithm problems.

We propose a method of reducing laser-clipping-induced distortion in a subcarrier multiplexed (SCM) optical-cable TV system. This scheme reduces amplitude peaks of the SCM signal by controlling the phases of video carriers to prevent the clipping which occurs when these peaks fall below the threshold of a laser-diode. It is experimentally shown that using this method reduces the bit error rate in an AM-VSB / QAM hybrid optical-transmission system.

In this paper, we present a method for evaluating the minimum free Chernov distance of trellis-codes for a discrete memoryless channels (DMC). In order to design an efficient trellis-code for the DMC, we need to evaluate the minimum free Chernov distance of the target code. However, the lack of the additive property of the Chernov distance prevents a conventional branch-and-bound search for evaluating the minimum distance. To overcome the difficulty, we present a lower bound on the Chernov distance with an additive property. The lower bound plays a key role in the minimum distance evaluation algorithm presented here. By using the proposed algorithm, we have derived the minimum free Chernov distance of some binary linear convolutional codes over Z-channel.

An efficient finite element-integral equation method is presented for calculating scattered fields from conducting objects. By combining the integral equation solution with the finite element method, this formulation allows a finite element computational domain terminated very closely to the scatterer and thus results in the decrease of the resultant matrix size. Furthermore, we employ a new integral approach to establish the boundary condition on the finite element terminating surface. The expansion of the fields on the integration contour is not related to the fields on the terminating surface, hence we obtain an explicit expression of the boundary condition on the terminating surface. Using this explicit boundary condition with the finite element solution, our method substantially improves the computational efficiency and relaxes the computer memory requirements. Only one matrix inversion is needed through our formulation and the generation and storing of a full matrix is not necessary as compared with the conventional hybrid finite element methods. The validity and accuracy of the formulation are checked by some numerical solutions of scattering from two-dimensional metallic cylinders, which are compared with the results of other methods and/or measured data.

This paper describes subband-crosscorrelation analysis (SBXCOR) using two input channel signals. SBXCOR is an extended signal processing technique of subband-autocorrelation analysis (SBCOR) that extracts periodicities associated with the inverse of center frequencies present in speech signals. In addition, to extract more periodicity information associated with the inverse of center frequencies, the multi-delay weighting (MDW) processing is applied to SBXCOR. In experiments, the noise robustness of SBXCOR is evaluated using a DTW word recognizer under (1) a simulated acoustic condition with white noise and (2) a real acoustic condition in a sound proof room with human speech-like noise. As the results, under the simulated acoustic condition, it is shown that SBXCOR is more robust than the conventional one-channel SBCOR, but less robust than SBCOR extracted from the two-channel-summed signal. Furthermore, by applying MDW processing, the performance of SBXCOR improved about 2% at SNR 0 dB. The resultant performance of SBXCOR with MDW processing was much better than those of smoothed group delay spectrum (SGDS) and mel-filterbank cepstral coefficient (MFCC) below SNR 10 dB. The results under the real acoustic condition were almost the same as the simulated acoustic condition.

In the commonsense reasoning, priorities among rules are often required to be found out in order to derive the desired conclusion as a theorem of the reasoning. In this paper, first we present the bottom-up and top-down abduction procedures to compute skeptical explanations and secondly show that priorities of circumscription to infer a desired theorem can be abduced as a skeptical explanation in abduction. In our approach, the required priorities can be computed based on the procedure to compute skeptical explanations provided in this paper as well as Wakaki and Satoh's method of compiling circumscription into extended logic programs. The method, for example, enables us to automatically find the adequate priority w. r. t. the Yale Shooting Problem to express a human natural reasoning in the framework of circumscription.

Recently, Garcia and Stichtenoth proposed sequences of algebraic function fields with finite constant fields such that their sequences attain the Drinfeld-Vl bound. In the sequences, the third algebraic function fields are Artin-Schreier extensions of Hermitian function fields. On the other hand, Miura presented powerful tools to construct one-point algebraic geometric (AG) codes from algebraic function fields. In this paper, we clarify rational functions of the third algebraic function fields which correspond to generators of semigroup of nongaps at a specific place of degree one. Consequently, we show generator matrices of the one-point AG codes with respect to the third algebraic function fields for any dimension by using rational functions of monomial type and rational points.

For the realization of the very high-speed data transmission over wide area network, the HIPPI-ATM conversion for connecting two remote HIPPI end systems is specified by ANSI. Since the credit scheme is adopted for the flow control on the ATM part in the specification, the propagation delay influences the remarkable transfer throughput degradation with the longer distance between end systems. In this paper, two priority types of HIPPI bursts are proposed, which include the flag indicating the priority, high priority or low priority. We propose the hybrid scheme that the credit scheme is adopted only for sending the high priority HIPPI bursts and the source can send low priority HIPPI bursts without reserving buffers in the receiver. In order to confirm the effectiveness of the proposed scheme, we show the characteristics of transfer performance and low priority bursts loss ratio v. s. transmission distance by simulation. Furthermore, we introduce the implemental example of the proposed scheme in the MPEG video transmission application, and show it's good performance.

This paper describes a new architecture-based DSP processor, which consists of n n mesh multiprocessor for digital signal processing. A prototype chip, RCDSP9701 has been designed and implemented using a CMOS 0. 6 µm process. This architecture has better performance compare to the traditional microprocessor solution to Digital Signal Processing. The proposed method poses remarkable flexibility compare to ASIC (Application Specified Integrated Circuits) approach for Digital Signal Processing applications. In addition, the proposed architecture is fault tolerant and suitable for parallel computing applications. In this paper, an implementation into a silicon chip of the new architecture is presented to give a better understanding of our work.