This paper investigates an accurate channel estimation method using the common pilot channel (CPICH) in addition to a dedicated pilot channel (PICH) when the fading correlation between the dedicated PICH and CPICH is high, and clarifies the area in which the proposed channel estimation method is effective for adaptive antenna array transmit diversity (AAA-TD) in the forward link. Computer simulation results elucidate that although a more precise channel estimation is possible by using the primary-CPICH (P-CPICH) transmitted from an omni-directional antenna in addition to the dedicated PICH for the area where the distance, d, between a base station and a mobile terminal is longer than approximately 200 m, no improvement is obtained for the area where the value of d is shorter than approximately 200 m. Meanwhile, by employing the secondary-CPICH (S-CPICH) transmitted with several directional beams in addition to the dedicated PICH, the required average received Eb/N0 at the average BER of 10-3 is decreased by approximately 0.4 (0.2-0.4) dB compared to the channel estimation method using only the dedicated PICH regardless of the value of d when the number of antennas is 4 (8).

This paper considers a reconfiguration problem on a processor array model based on single-and-half-track switches, which is proposed for a fault tolerance technique at the fabrication time. The focus of this paper is to achieve the optimal reconfigurability, which means that whenever there exists a solution for successful reconfiguration, the designed method can find the solution. The paper consists of two parts. In the first part, we show two essential constraints that have been assumed in most of the previous studies, and make four reconfiguration classes that differ in the assumed essential constraints. Then, we present some inclusion relations among the four reconfiguration classes. As a result, it becomes clear that the most restrictive class including most of the previous methods never achieves the truly optimal reconfigurability. In the second part, we present a reconfiguration method based on sequential routing (RMSR). Although the worst-case time complexity of the RMSR is exponential in the number of processing elements, the reconfigurability of the RMSR is optimal within the most restrictive reconfiguration class. The effectiveness of the RMSR is shown by a computer simulation.

We demonstrated apertureless scanning near-field optical microscopy using a small protrusion (a simple 500-nm-diameter polystyrene particle) on a flat glass substrate as a probe. We designed a small sample stage to operate with the particle probe. It is a 40-µm-diameter circular stage, fabricated from an optical fiber by Hydrofluoric acid (HF) etching. In this paper, we present the first atomic force microscope and scanning near-field optical microscope images obtained with such a probe. We also discuss schemes for probe-sample distance control in this novel form of apertureless scanning near-field optical microscopy.

This paper evaluates the bit error rate (BER) performance of high rate data transmission such as at 64 and 384 kbits/s (kbps) with high quality (average BER is below 10-6) using turbo/convolutional coding associated with Rake time diversity, antenna diversity, and fast transmission power control (TPC) in multipath fading channels for W-CDMA mobile communications. Laboratory experiments using multipath fading simulators elucidate the superiority of turbo coding over convolutional coding when the channel interleaving length is 40 msec. The required average transmission power for the average BER of 10-6 using turbo coding is decreased by approximately 1.1-1.5 dB and 1.5-1.6 dB for 64 and 384 kbps data transmissions, respectively, compared to that using convolutional coding for a two-path Rayleigh fading channel with the fading maximum Doppler frequency of fD = 5-200 Hz. Furthermore, field experimental results elucidate that the required transmission power for the average BER of 10-6 employing turbo coding is decreased by approximately 0.6 dB and 2.0 dB compared to convolutional coding for 64 and 384 kbps data transmissions, respectively, without antenna diversity reception, while that with antenna diversity reception exhibits only an approximate 0.3-0.5 dB decrease. This decrease in improvement with antenna diversity reception indicates that in an actual fading channel in the field experiments, the impact of the error in path search for Rake combining and SIR measurement for fast TPC diminishes the performance improvement of the turbo coding due to a very low received signal power.

In this paper, we propose and describe a new synchronizer for the FFT timing applicable to multi-carrier spread-spectrum (MC-SS) communication systems. The performance of the synchronizer is evaluated in terms of false- and miss-detection probabilities in the presence of additive white Gaussian noise (AWGN) and Rayleigh fading.

We clarify the effectiveness of receiver-side compensation in offsetting fiber Bragg grating (FBG) dispersion induced-electrical signal-to-noise ratio (SNR) degradation in a 10 Gb/s 8-channel wavelength-division multiplexing (WDM) 6,400 km transmission system. The receiver-side compensation greatly improves the SNR degradation. The allowable accumulated FBG dispersion is -400 1000ps/nm for the worst arrangement, a single FBG at the transmitter, which is about half the accumulated fiber dispersion permissible with receiver-side compensation.

In an orthogonal frequency division multiplexing (OFDM) system, the bit error performance is degraded in the presence of multiple propagation paths whose excess delays are longer than the Guard Interval (GI), because the orthogonality between subcarriers cannot be maintained. In this paper, we propose a new OFDM demodulation method with a variable-length effective symbol and a multi-stage inter-carrier interference (ICI) canceller, in order to improve the bit error performance in the presence of multipaths whose excess delays are longer than the GI. The influence of the inter-symbol interference (ISI) is eliminated by the variable-length effective symbol, and then the ICI component is reduced by the multi-stage ICI canceller. The principle of the proposed method is explained, and the performance of the proposed method is then evaluated by computer simulation. The results show that the proposed method improves the system availability under more various multipath fading environments without changing the system parameters.

To design a high-speed m-bit parallel inversion circuit over GF(2m), we study two variations for the repetition-operation of the numerical formula, AB2, in employing square-first and multiply-first type operations. From the proposed two variations, we propose four inversion architectures, adopting the multiplier and square in [10], as follows: simple duplication semi-systolic architecture for multiply-first inversion circuit (MFIC), m-bit parallel semi-systolic architecture for MFIC, simple duplication semi-systolic architecture for square-first inversion circuit (SFIC), and simplified m-bit parallel semi-systolic architecture for SFIC. Among them, performance of the simplified m-bit parallel semi-systolic architecture for SFIC is recommended for a high-speed applications to get a maximum throughput in the sense of small hardware-complexity, and low latency. When we implement the simplified 8-bit parallel semi-systolic architecture for SFIC over GF(28) by using 0.25 µm CMOS library, necessary are 2495 logic-gates and 1848 latches, and the latency is 56 and the estimated clock-rate is 580 MHz at 100% throughput.

In this letter, we propose a two-stage object-based error-concealment technique for MPEG-2 video transmitted in a burst-packet-loss environment. A burst packet loss typically destroys a large area of MPEG-2 coded video. In the first stage, the missing area is intra-picture estimated and concealed in terms of a region-based approach. In the second stage, irregular-moving objects with respect to the background are identified and compensated from the predictive picture. As compared with conventional concealment approaches, the proposed method achieves better PSNR performance and reduces the visual artifacts.

Using eigenstructure approach to form interference canceler is very sensitive to pointing error, especially when the interference number is overestimated. This Letter presents an effective technique to correct the pointing error by the projection matrix of noise subspace. Based on the corrected steering angle, a proper blocking matrix of the eigenstructure interference canceler can be obtained to suppress the leakage of desired signal. Therefore, signal cancellation does not occur, even the interference number is overestimated in constructing the interference subspace.

This paper describes the behavior of voids that were formed due to electromigration and diffusion in the interconnections of gold during a DC bias tests of GaAs ICs to current densities in the interconnections of 0.67 106 A/cm2 to 1.27 106 A/cm2 in the high temperature range of 230 to 260. We have found that the voids were formed at the centers in the cross sections of the interconnections and that gold is left around the voids, which means current still flows after the void formation. We have carefully observed the movement of the anode and cathode side edge of the voids during the tests and found that edges moved toward the cathode, in the direction opposite to the electron flow. This direction is constant. Also, the voids are extended, which means that the velocity of the cathode side edge is greater than that of the anode side edge. The velocity of the edges almost proportionally increased with the current density. The constant edge movement direction and the velocity of the edge dependence on the current density suggest that one of the causes of the edge movement is electromigration. The velocity of the edge depends on the distance between the anode side edge of the void and the through hole. The velocity increases in accordance with a decrease in the distance. This means that one of the causes of the edge movement is the diffusion of gold atoms by a concentration and pressure gradient. The GaAs IC failed at almost the same time as the voids appeared. It is important for reliability to prevent the formation of voids caused by electromigration and diffusion.

This letter presents a new approximation algorithm suitable for Taylor series expansion. The algorithm can effectively reduce the approximation error by using only a small number of terms in series expansion. The proposed algorithm can be more easily implemented and has better performance than the conventional Euler approximation algorithm. Also, the approximation performance of the proposed algorithm is compared with direct approaches, such as least-squares and Chebyshev approximation algorithm to show the relative advantages of the proposed algorithm. This letter also presents an application example of the proposed approximation algorithm in carrier recovery of OFDM (Orthogonal Frequency Division Multiplexing) modem.

This paper presents an active vision system for on-line traffic sign recognition. The system is composed of two cameras, one is equipped with a wide-angle lens and the other with a telephoto lens, and a PC with an image processing board. The system first detects candidates for traffic signs in the wide-angle image using color, intensity, and shape information. For each candidate, the telephoto-camera is directed to its predicted position to capture the candidate in a larger size in the image. The recognition algorithm is designed by intensively using built-in functions of an off-the-shelf image processing board to realize both easy implementation and fast recognition. The results of on-road experiments show the feasibility of the system.

A number of mobile hosts might be densely staying in an area caused by traffic congestions. The greater part of the mobile hosts will require commonly useful data, such as traffic information, parking information and other driving related information in such environment. Simultaneous data transmission broadcasts using a common link are regarded as a suitable means to distribute this location-dependent information. However, there is no guarantee that mobile hosts can finish receiving the information completely within a limited time. In this paper, we propose a data retransmission method for communications between a base station and mobile hosts and a data recovery processing method for use between base stations. The data retransmission method called "TOA" (The Order of Arrival) schedules retransmission data specified in the first NACK request received after retransmission processing. We have proposed "Advanced" Join system in which a base station makes consolidated join requests to a multicast group on behalf of mobile hosts. Applying the TOA method to resending in the Advanced Join system, data-receiving efficiency is higher than with the simple Advanced Join system and the absolute number of completed mobile host data reception is higher. Using the TOA method, even with the base station disposition rate of 50% the number of completed reception is higher than with the Advanced Join system at 80%. The proposed reliable multicasting system to the DSRC-based ITS network can realize an efficient base station arrangement in the ITS network infrastructure and contribute to the deployment of a superior ITS.

Fiber-optic access system integration is the key to providing various kinds of services to home users. The combination of ATM- and SCM-PON systems is essential to support a high-speed data service and analog/digital video distribution services. From this viewpoint, a frequency-division- multiplexing technique for digital baseband and subcarrier multiplexed signals is required to achieve system integration. However, system integration for these two access systems has not been fully investigated yet. The SCM-PON system, which uses a super wideband optical FM converter, will enable these two different kinds of access system (ATM and SCM) to be integrated. In this paper, we describe experimentally obtained results for frequency- division-multiplexed signals consisting of digital baseband and subcarrier- multiplexed signals. The experiments were carried out using a 622-Mb/s baseband signal and an FM-converted signal containing AM and 64QAM signals. The experimental results reveal that the inter-channel interference between the digital baseband and FM-converted signals restricts the number of subcarriers for AM and 64QAM. With an intermediate frequency of 3 GHz for the FM-converted signal, an FDM signal consisting of 622-Mb/s baseband, 30 carriers of 64QAM, and 11 carriers of AM was successfully transmitted.

In this paper, to investigate the processing requirements at each node and offered network load of receiver-based and router-based protocols, we analyze the number of packet transmissions on each link until all receivers receive a packet for an arbitrary multicast-tree topology and packet loss probability considering the correlation between loss events of a packet for different receivers. In order to show the effectiveness of the analytical results, we demonstrate the numerical examples for various conditions. The numerical results show that local recovery protocols, especially router-based protocol can reduce the offered network load due to data packets and their acknowledgements, and can decentralize processing requirement of sending nodes effectively. Further, we reveal the influence of the locations of group senders on the performance of both protocols.

Among ITS applications, it is very important to acquire detailed statistics of traffic flows. For that purpose, vision sensors have an advantage because of their rich information compared to such spot sensors such as loop detectors or supersonic wave sensors. However, for many years, vehicle tracking in traffic images has suffered from the problems of occlusion effect and illumination effect. In order to resolve occlusion problems, we have been proposing the Spatio-Temporal Markov Random Field model(S-T MRF) for segmentation of Spatio-Temporal images. This S-T MRF model optimizes the segmentation boundaries of occluded vehicles and their motion vectors simultaneously by referring to textures and segment labeling correlations along the temporal axis as well as the spatial axis. Consequently, S-T MRF has been proven to be successful for vehicle tracking even against severe occlusions found in low-angle traffic images with complicated motions, such at highway junctions. In addition, in this paper, we define a method for obtaining illumination-invariant images by estimating MRF energy among neighbor pixel intensities. These illumination-invariant images are very stable even when sudden variations in illumination or shading effect are occurred in the original images. We then succeeded in seamlessly integrating the method for MRF energy images into our S-T MRF model. Thus, vehicle tracking was performed successfully by S-T MRF, even against sudden variations in illumination and against shading effects . Finally, in order to verify the effectiveness of our tracking algorithm based on the S-T MRF for practical uses, we developed an automated system for acquiring traffic statistics out of a flow of traffic images. This system has been operating continuously for ten months, and thus effectiveness of the tracking algorithm based on S-T MRF model was proven.

This paper presents a comprehensive investigation of three optical wavelength-division multiplexed (WDM) mesh network protection approaches, namely minimal cost, single link basis and disjoint path approaches. The operation of each approach is described and their performances are extensively evaluated and compared. Key aspects that are taken into the consideration and comparison of the designs include a spare capacity requirement, ease of operation and practical feasibility. A mathematical model based on integer linear programming is introduced to obtain a lower bound on the spare capacity requirement for full protection against all single link failures. Two heuristic algorithms have also been developed to perform wavelength resource allocation under both normal and failure conditions for both systems with and without wavelength conversion capability. It is shown that the minimal cost approach can accomplish the lowest extra cost requirement for protection, but this approach is considered not appropriate for practical applications due to complicated restoration and management. The single link basis scheme is on the other hand more practical and very cost efficient. For the disjoint path technique, the cost for spare capacity is generally slightly greater than that of the single link basis scheme. Its main advantages lie in the simple re-configuration and inherent protection against node failure for in-transit traffic. Finally, a new framework for obtaining a good spare capacity cost estimate of a mesh restorable network is presented.

This paper describes a novel mobile video monitoring system. The receiver is a PDA (Personal Digital Assistant) with a PHS (Personal Handy Phone system) card. The sender is a PC-based video encoding system, which is connected to an ISDN line by ISDN-TA. Functions such as camera selection, remote camera control and high-resolution snap shot are implemented. In this paper, details of the system are explained and a practicability assessment is performed. An experiment was conducted to measure the upward and downward transmission delay. From the results, the system performs consistently to a theoretical behavior. Furthermore, the performance of this system is quite practical for mobile video monitoring.

The objective of this paper is to evaluate the impacts of impulsive class-A noise, co-channel interference due to other piconet, Rician fading on the packet error rate (PER), and throughput performance in the Bluetooth scatternet. Simulation results illustrate the significant difference in performance between synchronous and asynchronous Bluetooth systems. The paper also provides the insights on how to design Bluetooth scatternet for minimal PER and maximum throughput performance.