In high-capacity optical WDM networks, the failure of a network component such as a fiber link may disconnect many optical lightpaths, leading to severe disruption in network services. Therefore it is imperatively important to provide fast and full protection against any failure in optical WDM networks. The method of pre-configured protection cycles (p-cycles) is very attractive for design of survivable optical networks. So far p-cycle approach has been extensively studied for design of survivable optical networks where traffic demand is static. In this paper, we first briefly describe our recently proposed p-cycle design heuristic and then show how to apply this heuristic to optical networks where traffic demand is dynamically changing. We consider three different strategies to configure dynamic p-cycles for dynamic traffic demands, and compare their performance in terms of blocking probability and computational time.

In this paper, a cycle-based network recovery method for optical mesh networks is studied. The study in this paper concentrates on improving two performance requirements on network recovery: efficient spare resource utilization, and robustness for multiple failures. The proposed method uses multiple ring-covers and performs distributed link restoration using preplanned logical cycles embedded in physical mesh topologies. This method provides fast and simple recovery operation by exploiting the characteristics of ring topology and also provides efficient resource utilization by using multiple backup paths per link to improve the sharability of overall spare resources in the networks. With this method, layered reliability can be provided to network services by enabling priority-based robustness against multiple failures. The performance results reveal the trade-off between the resource efficiency for single failure and the robustness for multiple failures, and show the preconfiguration of a few logical cycles per link can provide enhanced resource efficiency and priority-based hierarchical robustness.

This paper explores how to extend the dependency pair technique for proving termination of higher-order rewrite systems. In the first order case, the termination of term rewriting systems are proved by showing the non-existence of an infinite R-chain of the dependency pairs. However, the termination and the non-existence of an infinite R-chain do not coincide in the higher-order case. We introduce a new notion of dependency forest that characterize infinite reductions and infinite R-chains, and show that the termination property of higher-order rewrite systems R can be checked by showing the non-existence of an infinite R-chain, if R is strongly linear or non-nested.

Current centralized restoration schemes are unsuitable for the increase of scale and complexity of networks. A novel distributed network partition scheme is proposed in this paper. In this scheme, a large-scale network can be partitioned into some wheellike sub-networks with nuclear nodes. In wheellike sub-networks, ring links and spoke links could provide reciprocal safeguard. Based on such structure, different distributed restoration schemes can be combined for failure restoration. The proposed partition approach has been implemented through computer simulation, and it was tested on practical national-scale optical networks. The simulation result shows that this scheme is practicable and effectual.

One of the main disadvantage of multi-carrier CDMA (MC-CDMA) signals is the high peak power of the transmitted signals which limits their applications. To account for this issue, we provide a simple signal processing for reducing the high crest factor (CF) of MC-CDMA signals. Using this modified MC-CDMA signal, the high CF due to Walsh spreading sequences can be mitigated without explicit side information and degradation in the detection performance.

This paper proposes a scattered-pilot-OFDM reception scheme employing turbo inter-carrier interference (ICI) cancellation in the fast varying fading environments of mobile communications. In the OFDM transmission, the orthogonality among the subcarriers cannot hold due to large Doppler shift, and the OFDM signal suffers from severe degradation due to ICI. The proposed receiver carries out two modes: (i) a coherent detection (CD) mode, and (ii) a turbo ICI cancellation (TC) mode. Initially, the receiver performs the CD mode. When any decision errors are detected, it shifts from the CD mode to the TC one that carries out both the ICI cancellation and the channel estimation by using the decoder output (the log likelihood ratio). In addition, the iteration of the TC mode can improve the accuracy of the channel estimation and ICI cancellation ability. Computer simulations following specifications for the mobile reception mode in the digital terrestrial television broadcasting demonstrate that the receiver can effectively cancel ICI due to the fast varying fading, and that its average BER performance is much better than that of CD.

A new construction of sequences having both a low peak factor (crest factor) and flat power spectrum is proposed. The flat power spectrum provides zero auto-correlation except for the case of zero shift. The proposed construction is based on a systematic scheme that does not require a search, and affords sequences of length 4n(2n+1) for an arbitrary integer n.

The problem of signal restoration in the presence of observation space noise has been tackled extensively. However, restoration of degraded signals in the presence of signal space noise leads to considerable complexity because it becomes difficult to distinguish between the original signal and the noise. In this paper, a partial projection filter has been devised for the restoration of signals degraded by both the signal space and the observation space noises. A closed form of the proposed filter has been derived and its performance has been verified experimentally.

The partial projection filter gives optimal signal restoration in the presence of both the signal space and the observation space noises. In this paper, the filter has been characterized from the point of view of its signal restoration and noise suppression capabilities. The filter is shown to suppress the noise component in the restored signal while retaining the signal component, thus maximizing the signal-to-noise ratio. Further, a digital implementation of the filter is presented in matrix form in contrast to its original operator based derivation, for practical applications.

In multicarrier code division multiple access (MC-CDMA) systems, the orthogonality among the spreading codes is destroyed because the channels exhibit frequency-selective fading and the despreading stage performs gain control; that is, inter-code interference (ICI) can significantly degrade system performance. This paper proposes an optimum spreading code assignment method that reflects our analysis of ICI for up and downlink MC-CDMA cellular systems over correlated frequency-selective Rayleigh fading channels. At first, we derive theoretical expressions for the desired-to-undesired signal power ratio (DUR) as a quantitative representation of ICI; computer simulation results demonstrate the validity of the analytical results. Next, based on the ICI imbalance among code pairs, we assign specific spreading codes to users to minimize ICI (in short, to maximize the multiplexing performance); our proposed method considers the quality of service (QoS) policy of users or operators. We show that the proposed method yields better performance, in terms of DUR, than the conventional methods. The proposed method can maximize the multiplexing performance of a MC-CDMA cellular system once the channel model, spreading sequence, and combining strategy have been set. Three combining strategies are examined at the despreading stage for the uplink, equal gain combining (EGC), orthogonality restoring combining (ORC), and maximum ratio combining (MRC), while two are considered for the downlink, EGC and MRC.

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.

In terms of the formulation of the optimality, image restoration filters can be divided into two streams. One is formulated as an optimization problem in which the fidelity of a restored image is indirectly evaluated, and the other is formulated as an optimization problem based on a direct evaluation. Originally, the formulation of the optimality and the solutions derived from the formulation are identical each other. However in many studies adopting the former stream, an arbitrary choice of a solution without a mathematical ground passes unremarked. In this paper, we discuss the relation between the formulation of the optimality and the solution derived from the formulation from a mathematical point of view, and investigate the relation between a direct style formulation and an indirect one. Through these analyses, we show that the both formulations yield the identical filter in practical situations.

This paper analyzes the timing of eyeblink during visual identification of katakana characters on a display, which were presented under the constraint of a restricted visual field (R.V.F.). Blinks frequently occurred when the subject slowly brought the R.V.F. near a feature point (e.g., terminal point, crossing point).

The present report introduces a new construction of sequences having both a low peak factor (crest factor) and a flat power spectrum. Since the proposed sequence has a flat power spectrum, its auto-correlation is zero except for the zero shift. The proposed construction uses a systematic scheme and no search method. The length of the proposed sequence is (2n+1)(4n+1) for an arbitrary integer n. The sequence construction presented herein provides a means for generating various sequences at the lengths required for such applications as system measurement (which requires uncorrelated test signals), and audio signal processing for sound production (for enhancing spatial imagery in stereo signals synthesized from mono sources).

By modelling the quantization error as additive white noise in the transform domain, Wiener filter is used to reduce quantization noise for DCT coded images in DCT domain. Instead of deriving the spectrum of the transform coefficient, a DPCM loop is used to whiten the quantized DCT coefficients. The DPCM loop predicts the mean for each coefficient. By subtracting the mean, the quantized DCT coefficient is converted into the sum of prediction error and quantization noise. After the DPCM loop, the prediction error can be assumed uncorrelated to make the design of the subsequent Wiener filter easy. The Wiener filter is applied to remove the quantization noise to restore the prediction error. The original coefficient is reconstructed by adding the DPCM predicted mean with the restored prediction error. To increase the prediction accuracy, the decimated DCT coefficients in each subband are interpolated from the overlapped blocks.

Techniques for automatic program recognition, at the algorithmic level, could be of high interest for the area of Software Maintenance, in particular for knowledge based reengineering, because the selection of suitable restructuring strategies is mainly driven by algorithmic features of the code. In this paper an automated hierarchical concept parsing recognition technique, and a formalism for the specification of algorithmic concepts, is presented. Based on this technique, the design and development of ALCOR, a production rule based system for automatic recognition of algorithmic concepts within programs, aimed at support of knowledge based reengineering for high performance, is presented.

A novel fast KNN classification algorithm is proposed for pattern recognition. The technique uses one important feature, mean of the vector, to reduce the search space in the wavelet domain. Since the proposed algorithm rejects those vectors that are impossible to be the k closest vectors in the design set, it largely reduces the classification time and holds the classification performance as that of the original classification algorithm. The simulation on texture image classification confirms the efficiency of the proposed algorithm.

The classification time required by conventional multi-class SVMs greatly increases as the number of pattern classes increases. This is due to the fact that the needed set of binary class SVMs gets quite large. In this paper, we propose a method to reduce the number of classes by using nearest neighbor rule (NNR) in the principle component analysis and linear discriminant analysis (PCA+LDA) feature subspace. The proposed method reduces the number of face classes by selecting a few classes closest to the test data projected in the PCA+LDA feature subspace. Results of experiment show that our proposed method has a lower error rate than nearest neighbor classification (NNC) method. Though our error rate is comparable to the conventional multi-class SVMs, the classification process of our method is much faster.

We develop a non-concurrent single-failure occurring model, a restoration scheme based on adaptively-decided sub-lightpath rerouting algorithm is then proposed, which aims to achieve better service guaranty with less network status information.

Floating-point units (FPUs) are indispensable in processors, 3D-graphic engines, etc. To improve design productivity of these LSIs, FPU IPs are strongly desired. However, it is impossible to cover wide range of needs by an FPU IP, because there are various kind of options in specifications (e.g., operating frequency, latency, and ability of pipeline operation) and implementations (e.g., hardware algorithms). Thus, multiple IPs are needed even for the same functionality. In this paper, we propose to build an IP Library which consists of large number of FPU IPs with various kind of specifications and implementations, and which has catalogue data that shows not only specifications but also post-layout area and power dissipation of each IP. As the first step of the project, we have developed an IP Library targeted to Rohm 0.35 µm triple-metal process, which consists of 20 IPs for IEEE-754-standard single-precision floating-point division with 5 operating frequencies (50 MHz, 75 MHz, 100 MHz, 125 MHz, and 150 MHz), with two options whether pipelined or not, and with two hardware algorithms (the restoring method and the SRT method). We have also developed a catalogue for the IP Library, which shows post-layout area and power dissipation as well as specification of each IP. We have introduced two metrics "performance-area ratio (MFLOPS/mm2)" and "performance-power ratio (MFLOPS/W)" to afford a good insight into efficiency of implementations. From the catalogue data, the restoring method is, on the average, 1.4 times and 2.3 times better than the SRT method in terms of performance-area ratio and performance-power ratio, respectively. The developed catalogue is usable not only for selection of the optimal IP for a specific application, but also for quantitative analysis at the early stage of architecture design. It is also expected that the catalogue data based on an actual process technology is valuable for education.