Apodised chirped gratings based on InGaAsP/InP deep-ridge waveguides with vertical-groove surface gratings were fabricated. Reflectivity ripple and group delay ripple were reduced from around 4 dB to 1 dB and from around 5 ps to 2 ps, respectively, by apodisation over a wavelength range of around 20 nm.

We propose an iterative tuning process of blind/group-blind detector based on constant modulus property of digitally modulated signal. By adopting the iterative tuning process after applying blind/group-blind detectors, significant gains are attained compared to the original blind/group-blind detectors. The signal to interference and noise ratio (SINR) approaches to ideal MMSE detector even with reasonably small number of data samples.

In this letter, we propose a closed-form joint space-time channel and direction of arrival (DOA) blind estimation algorithm for space-time coded MC-CDMA systems equipped with a uniform linear array (ULA) at the base station in frequency-selective fading environments. We prove that the signal subspaces defined by the receive data covariance matrix can be determinately separated into an equivalent set of signal subspaces spanned by the space-time channel vector of an individual user. From these signal subspaces, the space-time channels of multiple users are estimated using the subspace method.

This paper focuses on SIMD processor synthesis and proposes a SIMD instruction set/functional unit synthesis algorithm. Given an initial assembly code and a timing constraint, the proposed algorithm synthesizes an area-optimized processor core with optimal SIMD functional units. It also synthesizes a SIMD instruction set. The input initial assembly code is assumed to run on a full-resource SIMD processor (virtual processor) which has all the possible SIMD functional units. In our algorithm, we introduce the SIMD operation decomposition and apply it to the initial assembly code and the full-resource SIMD processor. By gradually reducing SIMD operations or decomposing SIMD operations, we can finally find a processor core with small area under the given timing constraint. The promising experimental results are also shown.

Visibility culling techniques have been studied extensively in computer graphics for interactive walkthrough applications in recent years. In this paper, a visibility culling approach by exploiting hardware-accelerated occlusion query is proposed. Organizing the regular grid representation of input scene as an octree-like hierarchy, a 2-tier view frustum culling algorithm is to efficiently cull away nodes invisible from a given viewpoint. Employing the eye-siding number of nodes, we can quickly enumerate an occlusion front-to-back order and effectively maximize the number of parallelizable occlusion queries for nodes while traversing the hierarchy. As experimental results show, our approach improves the overall performance in the test walkthrough.

In the paper, we introduce TLM methodology focusing on IEEE 802.11 WLAN as a derivative system. Decomposing the entire system into several computation components, we analyzed the property of each transaction, resulting in the TLM. In the case of shared bus, the simulation results show the effect of communication architecture such as bus protocol and bus parameters on the system performance.

In this paper, we propose a new error feedback (EF) structure for 2-D separable-denominator digital filters described by a rational transfer function. In implementing two-dimensional separable-denominator digital filters, the minimum delay elements structures are common. In the proposed structure, the filter feedback-loop corresponding to denominator polynomial is placed at a different location compared to the commonly used structures. The proposed structure can minimize the roundoff noise more than the previous structure though the number of multipliers is less than that of previous one. Finally, we present a numerical example by designing the EF on the proposed structure and demonstrate the effectiveness of the proposed method.

In order to control a sound field using multiple sources and microphones, we must choose the optimum values of parameters such as the numbers of sources and microphones, the location of the sources and the microphones and the filter tap length. Because there is a huge number of possible combinations of these conditions, the boundary surface control principle can be useful as a basis of a design method of such a system. In this paper, a design method of sound field reproduction and active noise control based on the BSC principle are described and several example of its application are presented.

An algorithm for the sound projection using multiple sources is presented. The source strength vector is obtained by using a fast estimation approach instead of the conventional eigenvalue decomposition (EVD) method. The computation load is therefore greatly reduced, which makes the algorithm more efficient in practical applications.

This paper presents a semi-automatic algorithm for video object segmentation. Our algorithm assumes the use of multiple key video frames in which a semantic object of interest is defined in advance with human assistance. For video frames between every two key frames, the specified video object is tracked and segmented automatically using Learning Vector Quantization (LVQ). Each pixel of a video frame is represented by a 5-dimensional feature vector integrating spatial and color information. We introduce a parameter K to adjust the balance of spatial and color information. Experimental results demonstrate that the algorithm can segment the video object consistently with less than 2% average error when the object is moving at a moderate speed.

For multiple-channel active noise control (ANC) systems, distributed systems consisting of more than one controller are useful. In this paper, we propose a performance improvement algorithm for the distributed multiple-channel ANC system based on the simultaneous equations method. In the proposed algorithm, no estimation of error paths is required. This algorithm can provide good performance in canceling primary noises with auto-/cross-correlations and achieve stable noise reduction under a change of the error paths.

We proposed a fuzzy control scheme to implement the cycle-to-cycle control for restoring swing phase of gait using functional electrical stimulation (FES). We designed two fuzzy controllers for the biceps femoris short head (BFS) and the vastus muscles to control flexion and extension of the knee joint during the swing phase. Control capabilities of the designed fuzzy controllers were tested and compared to proportional-integral-derivative (PID) and adaptive PID controllers in automatic generation of stimulation burst duration and compensation of muscle fatigue through computer simulations using a musculo-skeletal model. Parameter adaptations in the adaptive PID controllers did not significantly improve the control performance of the PID controllers. The fuzzy controllers were superior to the PID and adaptive PID controllers under several subject conditions and different fatigue levels. These results showed the fuzzy controller would be suitable to implement the cycle-to-cycle control of FES-induced gait.

Future wireless/mobile system is expected to have heterogeneous wireless overlay networks for ubiquitous multimedia communication. In a such network environment, mobile users are likely to try to get attached to higher bandwidth network as bandwidth-hungry multimedia applications are increasing. However, the users have to perform vertical handoff to lower bandwidth network, as high bandwidth network become unavailable due to various reasons (such as its limited coverage, network congestion, etc.). In this paper, we discuss the problem of vertical handoff from a user's perspective. For this purpose, we formulate user satisfaction as a function of bandwidth utility and handoff latency. Then, we investigate the effect of call holding time, user movement probability, etc. on the satisfaction that a user derives from the use of network service for multimedia applications. In addition, based on the evaluation, we present an algorithm for selecting a wireless network, which maximizes the effective user satisfaction.

This paper deals with the decomposition of surface data into several fractal signal based on the parameter estimation by the Mean Likelihood and Importance Sampling (IS) based on the Monte Carlo simulations. The method is applied to the feature extraction of surface data. Assuming the stochastic models for generating the surface, the likelihood function is defined by using wavelet coefficients and the parameter are estimated based on the mean likelihood by using the IS. The approximation of the wavelet coefficients is used for estimation as well as the statistics defined for the variances of wavelet coefficients, and the likelihood function is modified by the approximation. After completing the decomposition of underlying surface data into several fractal surface, the prediction method for the fractal signal is employed based on the scale expansion based on the self-similarity of fractal geometry. After discussing the effect of additive noise, the method is applied to the feature extraction of real distribution of surface data such as the cloud and earthquakes.

In this letter, we study a hybrid Multimedia-on-Demand (MoD) system which provides broadcast, batch and interactive services. An analytical model for such an MoD system is provided. Numerical results show that with proper design, the system can provide better performance than those systems which only provide any subset of two services.

This paper presents the design of a novel method for improvement of the operation of distance relays during capacitive voltage transformer transients using artificial neural network. The proposed module uses voltage and current signals to learn the hidden relationship existing in the input patterns. Simulation studies are preformed and the influence of changing system parameters, such as fault resistance and source impedance is studied. Details of the design procedure and the results of performance studies with the proposed relay are given in the paper. Performance studies results show that the proposed algorithm decreases the effects of CVT transients and is fast and accurate.

Orthogonal modulation provides low probability of bit error, however its bandwidth efficiency is very low. Biorthogonal code may double the bandwidth efficiency, but its required bandwidth grows exponentially with the number of input bits as in orthogonal modulation. In this paper, we propose a multi-code biorthogonal code keying (MBCK) scheme that significantly reduces the signal bandwidth with the benefit from orthogonal waveform coding maintained. The system consists of multiple waveform coding blocks, and the sum of output codewords is transmitted. A problem with MBCK is that output signal is multi-level, which requires amplifier with high linearity. So it may not be an appropriate scheme for portable unit where power efficiency is highly important. We also propose a modified MBCK scheme that guarantees constant amplitude output. The transmitter of the proposed scheme contains a redundant waveform coder whose input is generated by encoding the information bits. Adding the codewords from all constituent waveform coding blocks, the composite signal has constant amplitude. It is also shown that the redundant bits are not only used to make constant amplitude signal but also used to improve the BER performance at the receiver.

In this paper, a complete X-tolerant test data compression solution is proposed for system-on-a-chip (SOC) testing. The solution achieves low-cost testing by employing not only selective Huffman vertical coding (SHVC) for test stimulus compression but also MISR-based time compactor for test response compaction. Moreover, the solution is non-intrusive, since it can tolerate any number of unknown states (also called X state) in test responses such that it does not require modifying the logic of core to eliminate or block the sources of unknown states. Furthermore, the solution achieves enhanced diagnosis capability over conventional MISR. The enhanced diagnosis requires the least hardware overhead by reusing the existing masking logic and achieves significant saving in diagnostic time. Experimental results for ISCAS 89 benchmarks as well as the evaluation of hardware implementation have proven the efficiency of the proposed test solution.

This paper discusses how to minimize the number of dissection lines regarded as wiring channels on a floorplan corresponding to a placement of n modules. In a floorplan (rectangular dissection), the number of dissection lines exceeds the number of rooms exactly by three. Since a floorplan obtained from a given module placement may have many empty rooms where no module is assigned, redundant wiring channels and wire bends may also be generated. Hence, in order to reduce redundant channels and wire bends, removal of empty rooms is required. For this purpose, we formulate a problem of obtaining a floorplan with the minimum possible empty rooms based on a given module placement. Then, we propose a method of removing as many redundant empty rooms as possible by merging dissection lines on a floorplan in O(n) time. The number of empty rooms in the resultant floorplan is reduced to n- or less.

Active integrated antenna techniques have high potential for giving smaller size, lighter weight, lower cost and higher efficiency, in particular to millimeter-wave circuit-antenna systems. This paper gives a review of active integrated antenna techniques with emphasis on beam steering and retrodirective antenna arrays. Various beam steering operations of integrated antenna oscillator arrays using locking phenomena are presented. Beam steering arrays of such type have the feature that phase shifters are not necessary in the arrays. Arrays with higher harmonic output radiation can enlarge the beam steering range. Arrays of locked active antennas which operate as self-oscillating mixers can be beam controllable receiving antennas.