In this paper we analyze the characteristics of tapered multimode interference (MMI)-based coherent lightwave combiners, and theoretically confirm that the stable and clear multimode interference images exist in the tapered MMI combiners. We present the output characteristics of 21 tapered MMI-based coherent lightwave combiners under various structures, which are useful to optimally design the combiners. In order to extend the combiner to a multi-port (N1, N > 2) configuration, a new structure with the border shapes of two tangent arcs is proposed, by which we show an output power imbalance of about 0.5 dB between different input ports of an 81 tapered coherent lightwave combiner. Due to the advantages of no end-facet reflection, easy extension to a multi-port configuration, high tolerance for fabrication errors and a compact size, the tapered MMI structure is a good candidate as a coherent lightwave combiner used in large-scale photonic integrated circuits.

We present an approach and a web-based system implementation for modeling shapes using real distance functions. The system consists of an applet supporting the HyperFun modeling language. The applet is extended with primitives defined by Euclidean distance from a point to the surface of the shape. Set-theoretic operations (union, intersection, difference) that provide an approximation of the Euclidean distance to a shape built in a constructive way are introduced. Such operations have a controllable error of the exact Euclidean distance to the shape and preserve C1 continuity of the overall function, which is an important condition for further operations and applications. The proposed system should help model various shapes, store them in a concise form, and exchange them easily between different entities on a network. The applet offers also the possibility to export the models defined in the HyperFun language to other formats for raytracing or rapid prototyping.

This paper proposes an extension field named TypeII AOPF. This extension field adopts TypeII optimal normal basis, cyclic vector multiplication algorithm, and Itoh-Tsujii inversion algorithm. The calculation costs for a multiplication and inversion in this field is clearly given with the extension degree. For example, the arithmetic operations in TypeII AOPF Fp5 is about 20% faster than those in OEF Fp5. Then, since CVMA is suitable for parallel processing, we show that TypeII AOPF is superior to AOPF as to parallel processing and then show that a multiplication in TypeII AOPF becomes about twice faster by parallelizing the CVMA computation in TypeII AOPF.

A novel via chain structure for failure analysis at 65 nm-node fixing OPC using inner and outer via chain dummy patterns has been proposed. The inner dummy is necessary to localize failure site in 200 nm pitch via chain using an optical beam induced resistance change method. The outer dummy protects via chain pattern from local flare and optical proximity effects. Using this test structure, we can identify the failure point in the 1.2 k and 15 k via chain fabricated by Cu/low-k single damascene process. This test structure is beneficial in the application to the 65 nm-node technologies and beyond.

Self-stabilization is a theoretical framework of non-masking fault-tolerant distributed algorithms. In this paper, we investigate a self-stabilizing distributed approximation for the minimum k-dominating set (KDS) problem in general networks. The minimum KDS problem is a generalization of the well-known dominating set problem in graph theory. For a graph G = (V,E), a set Dk V is a KDS of G if and only if each vertex not in Dk is adjacent to at least k vertices in Dk. The approximation ratio of our algorithm is , where Δ is the maximum degree of G, in the networks of which the minimum degree is more than or equal to k.

A compromising technique is proposed for deterring clients from cheating by robot players in skill-based real-time network games. This technique is to inject a fair random noise into the manual input for a real-time game modeled as a chaotic dynamical system. The fair random noise is determined by means of the bit commitment protocol so that neither host nor client can control the noise in their favor. A scenario possibly plotted by a robot player for its victory may be spoiled by slight noise injection because of the sensitivity of chaotic systems to the input. The noise injection brings a luck-based factor into a skill-based game. In this sense, the technique proposed in this paper is not a solution but a compromise for the inherent problem of robot players with the skill-based network games. An example implementation of pinball is presented.

This paper reports on the suitability of the SUSAN filter for the removal of artifacts that result from quantization errors in wavelet video coding. In this paper two extensions of the original filter are described. The first uses a combination of 2-D spatial filtering followed by 1-D temporal filtering along motion trajectories, while the second extension is a pure 3-D motion compensated SUSAN filter. The SUSAN approach effectively reduces coding artifacts, while preserving the original signal structure, by relying on a simple pixel-difference-based classification procedure. Results reported in the paper clearly indicate that both extensions efficiently reduce ringing that is the prevalent artifact perceived in wavelet-based coded video. Experimental results indicate an increase in perceptual as well as objective (PSNR) decoded video quality, which is competitive with state-of-the-art post-processing algorithms, especially when low computational demands of the proposed approach are taken into account.

The fairness algorithm of the Resilient Packet Ring IEEE 802.17 standard suffers from throughput degradation under an unbalanced overload. This letter proposes an enhanced fairness algorithm using a valuable piece of information, represented by the transit buffer length, about congestion alleviation on a congested node, under which the throughput degradation can be completely improved.

Network survivability is one of the most pivotal issues in optical WDM networks. In particular, if a conduit is cut, approximately 16 terabits per millisecond can be lost in recent technology. A huge loss even by a single conduit failure fatally damages the performance and operation of the whole network. In this paper, we propose a new heuristic algorithm, called the Generalized Minimum-Cost (GMC) selection algorithm, to choose a pair of working and backup path which firstly minimizes total number of required wavelengths of working and backup path and secondly distributes lightpath request traffic into whole network links, if there are several pairs to require the same number of minimum wavelengths, in order to achieve load-balancing effect. GMC selection algorithm contains several formulas to get Working and Backup path Reservation Cost (WBRC) which can be obtained through heuristic GMC function. By using WBRC, our GMC selection algorithm achieves superior performance compared to the current Combined Min-Cost (CMC) selection algorithm and random selection algorithm in terms of the amount of wavelength consumption and blocked lightpath requests, especially on the relatively less-connected New Jersey LATA and 28-node US networks. Furthermore, we suggest a maximum number of non-blocked lightpath requests against single link failure in simulated networks for network operators to consider acceptable maximum traffic on their networks, so that they can provide 100% restoration capability in a single link failure without lightpath request blocking. We also analyze the complexity of the GMC selection algorithm and verify that the complexity of the GMC selection algorithm is lower than that of the CMC selection algorithm if the number of lightpath requests is sufficiently large.

This paper proposes a new framework to produce humanoid animations for simulating human tasks. Natural working movements are generated via management of motion capture data with our simulation package. An extensible middleware controls reactive human behaviors, and all processes of simulation in a cyber factory are controlled through XML documents including motions, scene objects, and behaviors. This package displays simulation using Web3D technology and X3D specifications which can supply a common interface for customizing cyberworlds.

One of the important problems in overlay multicast is how to deal with node failures and ungraceful leavings. When a non-leaf end host fails or leaves the multicast session, all downstream nodes will be affected. In this paper, we adopt the proactive approach, which pre-calculates a candidate node (called parent-to-be) for each node to connect to in case its current parent dies. The goal is to recover the overlay multicast tree quickly so that the disruption of service to those affected nodes is minimized. We combine the local parent-to-be locating and global parent-to-be locating schemes together, in order to take advantage of less interference in the local scheme and the flexibility of the global scheme. The quality of the recovered tree is improved while the responsiveness of the proactive approach is maintained.

In this paper, a new 2-antenna transmit diversity, called orthogonal space-time spreading transmit diversity (OSTSTD) combined with delay transmission, is proposed. At the transmitter, N data symbols to be transmitted are spread using N different orthogonal space-time spreading codes (each represented by NN matrix) and are transmitted from two transmit antennas after adding different time delays. At the receiver, 2-step space-time despreading is carried out to recover the N transmitted data symbols. The first step recovers the N orthogonal spatial channels by taking the correlation between the received space-time spread signal and the time-domain spreading codes. The second step recovers the N transmitted data symbols using minimum mean square error (MMSE) despreading. The average bit error rate (BER) performance in a Rayleigh fading channel is evaluated by computer simulation. It is confirmed that the OSTSTD provides better BER performance than the Alamouti's space-time transmit diversity (STTD) at the cost of transmission time delay.

In the cellular mobile communication systems, co-channel interference and Rayleigh fading degrade the transmission performance. Adaptive Array Antenna (AAA) can suppress interference and, at the same time, can cope with multi-path fading by using a wide antenna spacing resulting in low correlation of received signals in each antenna element. A feedback-type AAA was proposed for frequency division duplexed (FDD) systems, where mobile station measures channel characteristics and feed-backs them to the base station. In this paper, we extend the system by introducing 2-branch diversity reception at a mobile station, and study the influence of antenna element spacing at the base station and control delay time on bit error rate performance under a realistic propagation model.

Most of commercial websites provide customers with menu-driven navigation and keyword search. However, these inconvenient interfaces increase the number of mouse clicks and decrease customers' interest in surfing the websites. To resolve the problem, we propose an information retrieval assistant using a natural language interface in online sales domains. The information retrieval assistant has a client-server structure; a system connector and a NLP (natural language processing) server. The NLP server performs a linguistic analysis of users' queries with the help of coordinated NLP agents that are based on shallow NLP techniques. After receiving the results of the linguistic analysis from the NLP server, the system connector interacts with outer information provision systems such as conventional information retrieval systems and relational database management systems according to the analysis results. Owing to the client-server structure, we can easily add other information provision systems to the information retrieval assistant with trivial modifications of the NLP server. In addition, the information retrieval assistant guarantees fast responses because it uses shallow NLP techniques. In the preliminary experiment, as compared to the menu-driven system, we found that the information retrieval assistant could reduce the bothersome tasks such as menu selecting and mouse clicking because it provides a convenient natural language interface.

In CDMA system, the RAKE receiver is commonly used to attain diversity gain by taking advantage of the good correlation properties of the spreading codes. However, at low spreading gains the good correlation properties of the spreading codes are lost and the RAKE receiver performance is severely degraded by intersymbol interference (ISI) due to the interpath interference (IPI). In case of multi-code CDMA system, there are exist multi-code interference (MCI). In order to suppress ISI and MCI, a novel receiver based on soft-output viterbi algorithm (SOVA) equalization is proposed in this paper. The SOVA equalization is applied to symbol sequences after RAKE combining and MCI cancellation to effectively eliminate the ISI during transmission of high rate data in wideband DS-CDMA systems. Simulation results show that the proposed RAKE-SOVA receiver significantly outperform the traditional RAKE and RAKE-VA receivers.

This paper provides an overview of research in channel modeling for multiple-input multiple-output (MIMO) data transmission focusing on a radio wave propagation. A MIMO channel is expressed as an equivalent circuit with a limited number of eigenpaths according to the singular-value decomposition (SVD). Each eigenpath amplitude depends on the propagation structure not only of the path direction profiles for both transmission and reception points but also of intermediate regions. Inherent in adaptive control is the problem of instability as a hidden difficulty. In this paper these issues are addressed and research topics on MIMO from a radio wave propagation viewpoint are identified.

The supertask approach was proposed by Moir and Ramamthy as a means of supporting non-migratory tasks in Pfair-scheduled systems. In this approach, tasks bound to the same processor are combined into a single server task, called a supertask, which is scheduled as an ordinary Pfair task. When a supertask is scheduled, one of its component tasks is selected for execution. In previous work, Holman et al. showed that component-task deadlines can be guaranteed by inflating each supertask's utilization. In addition, their experimental results showed that the required inflation factors should be small in practice. Consequently, the average inflation produced by their rules is much greater than that actually required by the supertasks. In this paper, we first propose a notion of Transient Behavior Prediction for supertasks, which predicts the latest possible finish time of subtasks that belong to supertasks. On the basis of the notion, we present an efficient schedulability algorithm for Pfair supertasks in which the deadlines of all component tasks can be guaranteed. In addition, we propose a task merging process which combines the unschedulable supertasks with some Pfair tasks; hence, a newly supertask can be scheduled in the system. Finally, we propose the new reweighting functions that can be used when the previous two methods fail. Our reweighting functions produce smaller inflation factor than the previous work does. To demonstrate the efficacy of the supertasking approach, we present the experimental evaluations of our algorithm, which decreases substantially a number of reweights and the size of inflation when there are many supertasks in the Pfair-scheduled systems.

This paper focuses on the fatigue characteristics of the single crystal silicon (SC-Si) cantilever in relation with the critical design of micro electro-mechanical systems (MEMS). Development of MEMS actuators for optical communication usage is carried out successfully, for example, in optical switches and variable optical attenuators (VOA). In those devices, fatigue characteristics of the MEMS structure are crucial to its practical application. However, fatigue tests using real structures have not been carried out well. In this research, the fatigue life has been inspected at the actual device, under actual usage conditions for the first time. We obtained fracture rate λ from experimental results, and the value of Failure in Time (FIT) λ was about 0.3 FIT. This result indicates that these MEMS devices having enough reliability for practical usage.

This paper proposes a decentralized and asynchronous replica control method based on a fair assignment of the variation in numerical data that has weak consistency for loosely coupled database systems managed or used by different organizations of human activity. Our method eliminates the asynchronous abort of already committed transactions even if replicas in all network partitions continue to process transactions when network partitioning occurs. A decentralized and asynchronous approach is needed because it is difficult to keep a number of loosely coupled systems in working order, and replica operations performed in a centralized and synchronous way can degrade the performance of transaction processing. We eliminate the transaction abort by fairly distributing the variation in numerical data to replicas according to their demands and updating the distributed variation using only asynchronously propagated update transactions without calculating the precise global state among reachable replicas. In addition, fairly assigning the variation of data to replicas equalizes the disadvantages of processing update transactions among replicas. Fairness control for assigning the data variation is performed by averaging the variation requested by the replicas. A simulation showed that our system can achieve extremely high performance for processing update transactions and fairness among replicas.

Recently, various types of traffic have increased on the Internet with the development of broadband networks. However, it is difficult to guarantee QoS for each traffic type in current network environments. Moreover, it has been reported that bandwidth can be allocated to flows unfairly, and this can be an important issue for QoS guarantees. Therefore, we have proposed a flow-based queue management scheme, called Dual Metrics Fair Queueing (DMFQ), to improve the fairness and QoS per flow. DMFQ discards arrival packets by considering not only the arrival rate per flow but also the flow succession time. In addition, we have confirmed the effectiveness of DMFQ through several computer simulations. In this paper, we implement DMFQ with hardware for high-speed operation. Concretely, we propose the design policies and show the hardware design results.