Movement of the thighs is an important factor for studying gait cycle. In this paper, a hybrid hidden Markov model (HMM)/Kalman filter (KF) scheme is proposed to track the hip angle during gait cycles. Within such a framework, HMM and KF work in parallel to estimate the hip angle and detect major gait events. This approach has been applied to study gait features of different subjects and compared with video based approach. Experimental results indicate that 1.) the swing angle of the hip can be detected with simple hardware configuration using biaxial accelerometers and 2.) the hip angle can be tracked for different subjects within the error range of -5°+5°.

We extend a graph spectral method for extracting clusters from graphs representing pairwise similarity between data to hypergraph data with hyperedges denoting higher order similarity between data. Our method is robust to noisy outlier data and the number of clusters can be easily determined. The unsupervised method extracts clusters sequentially in the order of the majority of clusters. We derive from the unsupervised algorithm a semi-supervised one which can extract any cluster irrespective of its majority. The performance of those methods is exemplified with synthetic toy data and real image data.

In this study, we propose an adaptive handoff scheme with dynamic hysteresis value for cellular communications, which is based on distance between the mobile station and the serving base station. Performance is evaluated in terms of the expected number of handoffs, the expected handoff delay, standard deviation of handoff location, and the expected link degradation probability as well. Numerical results and simulations show that the proposed scheme outperforms the handoff schemes with static hysteresis levels. The effect of distance error is also discussed.

This paper presents a view independent video-based face recognition method using posterior probability in Kernel Fisher Discriminant (KFD) space. In practical environment, the view of faces changes dynamically. Robustness to view changes is required for video-based face recognition in practical environment. Since the view changes induce large non-linear variation, kernel-based methods are appropriate. We use KFD analysis to cope with non-linear variation. To classify image sequence, the posterior probability in KFD space is used. KFD analysis assumes that the distribution of each class in high dimensional space is Gaussian. This makes the computation of posterior probability in KFD space easy. The combination of KFD space and posterior probability of image sequence is the main contribution of the proposed method. The performance is evaluated by using two face databases. Effectiveness of the proposed method is shown by the comparison with the other feature spaces and classification methods.

The noise robustness of an audio fingerprinting system is one of the most important issues in music information retrieval by the content-based audio identification technique. In a real environment, sound recordings are commonly distorted by channel and background noise. Recently, Philips published a robust and efficient audio fingerprinting system for audio identification. To extract a robust and efficient audio fingerprint, Philips applied the first derivative (differential) to the frequency-time sequence of the perceptual filter-bank energies. In practice, however, the noise robustness of Philips' audio fingerprinting scheme is still insufficient. In this paper, we introduce an extension method of the audio fingerprinting scheme for the enhancement of noise robustness. As an alternative to frequency filtering, a type of band-pass filter, instead of a high-pass filter, is used to achieve robustness to background noise in a real situation. Our experimental results show that the proposed filter improves the noise robustness in audio identification.

From the viewpoint of a low-power pipeline ADC design, a comparison between two conventional power reduction techniques is discussed. The comparison shows that the amplifier sharing technique has an advantage in terms of the power reduction effect. To confirm the advantage, a test chip of 10-bit 80-MSPS ADC using the amplifier sharing technique is fabricated. The test chip dissipates 55 mW at 80 MSPS (Mega Sample Per Second).

This paper proposes a calibration method for catadioptric camera systems consisting of a mirror whose reflecting surface is the surface of revolution and a perspective camera as typified by HyperOmni Vision. The proposed method is based on conventional camera calibration and mirror posture estimation. Many methods for camera calibration have been proposed and during the last decade, methods for catadioptric camera calibration have also been proposed. The main problem with catadioptric camera calibration is that the degree of freedom of mirror posture is limited or the accuracy of the estimated parameters is inadequate due to nonlinear optimization. On the other hand, our method can estimate five degrees of freedom of mirror posture and is free from the volatility of nonlinear optimization. The mirror posture has five degrees of freedom, because the mirror surface has a surface of revolution. Our method uses the mirror boundary and can estimate up to four mirror postures. We apply an extrinsic parameter calibration method based on conic fitting for this estimation method. Because an estimate of the mirror posture is not unique, we also propose a selection method for finding the best one. By using the conic-based analytical method we can avoid the initial value problem arising from nonlinear optimization. We conducted experiments on synthesized images and real images to evaluate the performance of our method, and discuss its accuracy.

Hirose and Yoshida proposed an authenticated key agreement protocol based on the intractability of the Computational Diffie-Hellman problem. Recently, Hirose and Matsuura pointed out that Hirose and Yoshida's protocol is vulnerable to Denial-of-Service (DoS) attacks. And they proposed two key agreement protocols which are resistant to the DoS attacks. Their protocols are the first authenticated key agreement protocols resistant to both the storage exhaustion attack and the CPU exhaustion attack. In this paper we show that Hirose and Matsuura's DoS-resistant key agreement protocols and Hirose and Yoshida's key agreement protocol are vulnerable to impersonation attacks. We make suggestions for improvements.

We propose a method of face identification under various illumination conditions. Because we use image based method for identification, the accurate position of the face is required. First, face features are detected, and the face region is determined using the features. Then, by registering the face region to the average face, the horizontal position of the face is adjusted. Finally, the size of the face region is adjusted based on the distance of two eyes determined from all input frames. If the sizes of images for all faces are normalized into one size, the face length feature is lost in the normalized face image. The face is classified into three categories according to the face length, and the subspace is generated in each category so that the face length feature is preserved. We demonstrate the effectiveness of the proposed method by experiments.

To obtain large capacity, high quality mobile satellite communication systems in the future, we must use a multi-beam that can cope with extremely high levels of frequency reuse. This paper describes a novel resource allocation algorithm for multi-beam satellite communication systems that can dynamically adapt to maximum communication capacity without compromising quality. The algorithm combines two resource allocation schemes that enable it to contend with the ever-changing user distribution and inter-beam interference conditions. The first scheme optimizes the resources amongst beams. To minimize interference, the optimal constraint conditions are clarified when all clusters share and occupy the same bandwidth completely. These constraints are used in the optimization algorithm. The second scheme manages the various required resources and adapts them to the beam gain and interference levels at various user locations within a single beam. We propose a fixed power adaptive modulation scheme to obtain stable communications. This two-layered scheme can satisfactorily allocate multi-beam satellite resources to contend with the increasing communication capacity and still improve the quality.

A novel fabrication technology for lateral scale-down of sub-100-nm-gate InP-based HEMTs is presented. The fabricated device, whose structure features a reduced distance between the gate and ohmic metals of less than 100 nm, exhibits low ohmic resistances and improved DC and RF characteristics with good uniformity across a wafer. A fabricated 130-nm-gate lattice-matched InAlAs/InGaAs HEMT exhibits an extrinsic transconductance of 1.3 S/mm. This is 25% increase compared to that of a HEMT fabricated with our conventional process, which is explained by the reduction of RS. The average current-gain-cutoff-frequency (fT) of 261 GHz was obtained with a small deviation of 9.0 GHz. Uniform characteristics with high yield were also confirmed for HEMTs with shorter gates. The average fT of 290 GHz with a standard deviation of 9.3 GHz was obtained for 55-nm-gate HEMTs. The developed fabrication technology is promising for improving the electrical characteristics of sub-100-nm-gate InP-based HEMTs and for their integration.

Wavelength division multiplexing (WDM) technology offers the capability of building wide-area networks with high speed. Reconfigurability is a key feature of a WDM network that enables the network logical topology to change dynamically in response to the changing traffic patterns. There are two important issues involved in the reconfiguration of a network logical topology. One is how to determine the new logical topology corresponding to the current topology. It needs to consider a trade-off between the performance of the new target topology and the cost of the topology transition from the current topology to the new one. The other is how to determine the transition sequence from the current topology to the new one. It needs to control the disruption to the network as less as possible during the reconfiguration process. In this paper, we focus on the latter problem and propose several heuristic algorithms that reconfigure logical topologies in wide-area wavelength-routed optical networks. Our reconfiguration algorithms attempt to control the disruption to the network as less as possible during the reconfiguration process. For this purpose, a lightpath is taken as the minimum reconfiguration unit. The proposed algorithms are evaluated by using an NFSNET-like network model with 16 nodes and 25 links. The results show that very simple algorithms provide very small computational complexity but poor performance, i.e., large network disruption, and that an efficient algorithm provides reasonable computational complexity and very good performance. More complex algorithms may improve performance somewhat further but have unrealistically large computational complexity.

Point pattern matching (PPM) arises in areas such as pattern recognition, digital video processing and computer vision. In this study, a novel Genetic Algorithm (GA) based method for matching affine-related point sets is described. Most common techniques for solving the PPM problem, consist in determining the correspondence between points localized spatially within two sets and then find the proper transformation parameters, using a set of equations. In this paper, we use this fact that the correspondence and transformation matrices are two unitary polar factors of Grammian matrices. We estimate one of these factors by the GA's population and then evaluate this estimation by computing an error function using another factor. This approach is an easily implemented one and because of using the GA in it, its computational complexity is lower than other known methods. Simulation results on synthetic and real point patterns with varying amount of noise, confirm that the algorithm is very effective.

Micromobility management is a key issue for the deployment of broadband mobile communication services. The packet loss during handover and the handover latency need to be minimized to maintain the high quality of these services. We have previously proposed a mobility management scheme that addresses this issue in wide-area mobile networks that employed hierarchical multiple mobility management routers (Mobility Anchor Points or MAPs). Our scheme directs a Mobile Terminal (MT) to a suitable MAP to fully minimize packet loss during handover, and handover latency of the MTs. In our previous work, we confirmed the effectiveness of our scheme using a simple tree network. Actual networks however, always have densely meshed topologies to provide some redundancy for the elimination of single points of failure. In such networks, it is difficult to deduce the relationships between the MAPs, and this makes it difficult for our scheme to select a suitable MAP for an MT, because the selection is performed using both the MT's smoothed speed and the relationships existing between the MAPs located above the Access Router (AR), to which the MT is connected. In this paper, we propose a method to overcome this problem, by autonomously adjusting the selection criteria that are individually configured for use at a particular AR, and we evaluate this method using simulation experiments. The results show that our mobility management scheme works well in densely meshed networks using the proposed additional method.

This paper discusses a cyclic prefixed single carrier frequency-domain equalization (SC-FDE) scheme with two types of transmit diversity. Firstly, we propose a SC-FDE system with space-frequency block coding (SFBC). The transmit sequence of the proposed system is designed to have spatial and frequency diversities, which is equivalent to the SFBC. The corresponding combining receiver is derived under a minimum mean square error (MMSE) criterion. It is shown that the proposed system significantly outperforms the SC-FDE system with space-time block coding (STBC) over fast fading channels, while providing lower computational complexity than orthogonal frequency division multiplexing (OFDM) combined with SFBC. We verify the performance of two-branch transmit diversity systems including the proposed one through bit error rate (BER) analysis. Secondly, as a scheme that combines STBC and SFBC, a space-time-frequency block code (STFBC) SC-FDE system is presented. Computer simulation results show that the proposed STFBC SC-FDE system has better immunity to the distortion caused by both fast fading and severe frequency selective fading, compared to the SC-FDE system with the STBC or the SFBC scheme. Complexity analysis is also conducted to compare their computational loads of the transceiver. It is shown that the proposed STFBC SC-FDE system has lower computational complexity than the STFBC OFDM system.

Intercarrier interference will cause the loss of subchannel orthogonality and increase the error floor in proportion to the Doppler frequency. In this paper, we firstly analyze the generation mechanism of intercarrier interference in OFDM. Then we propose an O(N log2N) complexity ICI equalizer for OFDM systems in the presence of double selective fading which is mainly bases on FFT operation. Simulation result shows that with only 6 iterations LCD-FFT can achieve better performance than the LS-equalizer. After 10 iterations LCD-FFT performs almost the same as MMSE equalizer.

An atmospheric visibility measurement system capable of quantifying the most common operating range of onboard exteroceptive sensors is a key parameter in the creation of driving assistance systems. This information is then utilized to adapt sensor operations and processing or to alert the driver that the onboard assistance system is momentarily inoperative. Moreover, a system capable of either detecting the presence of fog or estimating visibility distances constitutes in itself a driving aid. In this paper, we first present a review of different optical sensors likely to measure the visibility distance. We then present our stereovision based technique to estimate what we call the "mobilized visibility distance". This is the distance to the most distant object on the road surface having a contrast above 5%. In fact, this definition is very close to the definition of the meteorological visibility distance proposed by the International Commission on Illumination (CIE). The method combines the computation of both a depth map of the vehicle environment using the "v-disparity" approach and of local contrasts above 5%. Both methods are described separately. Then, their combination is detailed. A qualitative evaluation is done using different video sequences. Finally, a static quantitative evaluation is also performed thanks to reference targets installed on a dedicated test site.

If a logic circuit was specialized to a specific input, the derived circuit would be faster and smaller than the original. This study presents various designs of a key-specific AES encryption circuit. In our iterative design, 41% of the logic gates and 20% of RAM were reduced, while 24% more performance was derived. In our pipelined design, 54% of the logic gates and 20% of RAM were reduced, while 74% higher performance was achieved. The results on DES encryption circuits are also presented for comparison.

Accumulation of non-equilibrium longitudinal optical (LO) phonons (termed hot phonons) is considered as a possible cause for limitation of frequency of operation of GaN-based high-electron-mobility transistors (HEMTs). The experimental data on noise temperature of hot electrons at a microwave frequency as a function of supplied electric power is used to extract information on hot phonons: the hot-phonon lifetime, the equivalent hot-phonon temperature, the effective occupancy of hot-phonon states involved into electron-LO-phonon interaction. The possible ways for controlling the hot-phonon effect on electron drift velocity through variation of electron density, channel composition, and hot-phonon lifetime are discussed. The expected dependence of hot-electron drift velocity on hot-phonon lifetime is confirmed experimentally. A self-consistent explanation of different frequency behaviour of InP-based and GaN-based HEMTs is obtained from a comparative study of hot-phonon effects.

In this paper, we present a method for recognition of human activity as a series of actions from an image sequence. The difficulty with the problem is that there is a chicken-egg dilemma that each action needs to be extracted in advance for its recognition but the precise extraction is only possible after the action is correctly identified. In order to solve this dilemma, we use as many models as actions of our interest, and test each model against a given sequence to find a matched model for each action occurring in the sequence. For each action, a model is designed so as to represent any activity containing the action. The hierarchical hidden Markov model (HHMM) is employed to represent the models, in which each model is composed of a submodel of the target action and submodels which can represent any action, and they are connected appropriately. Several experimental results are shown.