Adaptive routing algorithms, which dynamically select the route of a packet, have been widely studied for interconnection networks in massively parallel computers. An output selection function (OSF), which decides the output channel when some legal channels are free, is essential for an adaptive routing. In this paper, we propose a simple and efficient OSF called minimal multiplexed and least-recently-used (MMLRU). The MMLRU selection function has the following simple strategies for distributing the traffic: 1) each router locally grasps the congestion information by the utilization ratio of its own physical channels; 2) it is divided into the two selection steps, the choice from available physical channels and the choice from available virtual channels. The MMLRU selection function can be used on any type of network topology and adaptive routing algorithm. Simulation results show that the MMLRU selection function improves throughput and latency especially when the number of dimension becomes larger or the number of nodes per dimension become larger.

This paper presents an attempt to make rational active adversary passive using mechanism design. We propose a secure Generalized Vickrey Auction (GVA) scheme where the procedure executed by a bidder affects neither the prices nor the allocation of the bidder. Therefore, a bidder does not have an incentive to be an active adversary.

In this paper, we propose an adaptive multistage fuzzy-based partial parallel interference cancellation (FB-PPIC) multiuser detector for multi-carrier direct-sequence code-division multiple-access (MC-CDMA) communication systems over frequency selective fading channels. The partial cancellation tries to reduce the cancellation error in parallel interference cancellation (PIC) schemes due to the wrong interference estimations in the early stages and thus outperforms the conventional PIC (CPIC) under the heavy load for MC-CDMA systems. Therefore, in this paper, the adaptive cancellation weights are inferred from a proposed multistage fuzzy inference system (FIS) to perform effective PPIC multiuser detection under time-varying frequency selective fading channels in MC-CDMA systems. Simulation results show that the proposed adaptive four-stage FB-PPIC scheme outperforms both CPIC and constant weight PPIC (CW-PPIC) schemes, especially in near-far environments.

The Multi-Point Relay (MPR) of the Optimized Link State Routing protocol reduces the flooding overhead compared with classic flooding. To select MPR nodes, HELLO messages are used. In dense population environments, the overhead of HELLO messages is critical because the HELLO messages carry all adjacent node IDs in the classical manner. Consequently, wireless bandwidth is consumed for data communications. One solution for this problem is to compress HELLO messages using a differential technique. However, few, if any, studies have applied a differential technique to HELLO messages. We introduce the novel Differential HELLO technique to reduce the overhead of the HELLO messages. The Differential HELLO technique consists of two kinds of compression methods: Chronological Compression and Topological Compression. In addition, the inconsistency problems of the 1-hop node information in adjacent nodes caused by packet loss are discussed. As solutions to the inconsistency problems, No Compression Acknowledgement (NC-ACK) and HELLO Information Forecast (HIF) have been examined. Our simulation has taken the efficiency of the Differential HELLO technique into consideration. The HELLO message overhead was reduced to 29.1 IDs from 75.8 IDs using the Differential HELLO technique at a packet loss rate of 10-4 under random node arrangement. This result reveals that the Differential HELLO technique reduces the classic HELLO overhead by 38%. In environments with lower packet-loss rates, the Differential HELLO technique promises to offer even better performance.

In this paper, we study trellis properties of the tensor product (product code) of two linear codes, and prove that the tensor product of the lexicographically first bases for two linear codes in minimal span form is exactly the lexicographically first basis for their product code in minimal span form, also the tensor products of characteristic generators of two linear codes are the characteristic generators of their product code.

This letter presents an image rectification scheme that can be used by any image watermarking algorithms to provide robustness against rotation, scaling and translation (RST) transformations.

The investigation presents a low cost and low insertion loss X-band dual mode bandpass filter (BPF) based on inexpensive commercial FR4 substrate. The proposed filter at a central frequency f0 of 11.3 GHz has high filter performance filter with a fractional bandwidth of 14%, the insertion loss of -2.7 dB, and two transmission zeros. The designed procedures are presented in this letter and the fabricated filter verifies the proposed designed concept.

Given a graph G, we give a fast algorithm for approximating the vertex connectivity κ of G. Our algorithm delivers a minimum vertex cut of G if κ δ/2, and returns a message "κ > δ/2" otherwise, where δ denotes the minimum degree of G. The algorithm runs in O(n2(1 + min {κ2, κ/δ)) time and O(n + m) space, where n and m denote the numbers of vertices and edges in G, respectively.

In this letter, a method to construct good binary and quaternary error correcting codes, called complex Hadamard codes, based on a complex Hadamard matrix is presented. The related properties of the codes are analyzed. In addition, through the operation in Z4 domain, a new simplex soft-decision decoding algorithm for the complex Hadamard codes is also proposed.

This paper discusses real-time language recognition by 1-dimensional one-way cellular automata (OCAs) and two-way cellular automata (CAs), focusing on limitations of the parallel computation power. To clarify the limitations, we investigate real-time recognition of cyclic strings of the form uk with u {0,1}+ and k 2. We show a version of pumping lemma for recognizing cyclic strings by OCAs, which can be used for proving that several languages are not recognizable by OCAs in real time. The paper also discusses the real-time language recognition of CAs by prefix and postfix computation, in which every prefix or postfix of an input string is also accepted, if the prefix or postfix is in the language. It is shown that there are languages L Σ+ such that L is not recognizable by OCA in real-time and the reversal of L and the concatenation LΣ* are recognizable by CA in real-time.

Microwave circuits embedded in a multi-layer resin PCB are demonstrated using low loss resin materials. Resin materials for microwave frequencies were compared with conventional FR-4 with respect to dielectric and conductor loss factors, which proved that losses could be reduced drastically with the low loss material and design optimizations. Baluns, switches and BPFs were designed and fabricated to estimate microwave performances. Measured and simulated insertion losses of the circuits for 2.5 GHz band, were 0.3 dB for a switch, 0.4 dB for a balun and 2.0 dB for a 3-stage Chebyshev BPF. An integration of a switch, a BPF and two baluns was successfully implemented in a multi-layer PCB. Insertion losses of the fabricated integrated circuit were less than 3 dB with 0.1 dB additional loss compared with a sum of individual circuit losses. With estimated results of temperature characteristics and reliability as well as low loss performances, microwave circuits in resin PCBs can be considered as a viable candidate for microwave equipments.

This paper presents the definition and implementation design of a low power data bus encoding scheme dedicated to system on chip video architectures. Trends in CMOS technologies focus the attention on the energy consumption issue related to on-chip global communication; this is especially true for data dominated applications such as video processing. Taking into account scaling effects a novel coupling-aware bus power model is used to investigate the statistical properties of video data collected in the system bus of a reference hardware/software H.263/MPEG-4 video coder architecture. The results of this analysis and the low complexity requirements drive the definition of a bus encoding scheme called CDSPBI (Coupling Driven Separated Partial Bus Invert), optimized ad-hoc for video data. A VLSI implementation of the coding circuits completes the work with an area/delay/power characterization that shows the effectiveness of the proposed scheme in terms of global power saving for a small circuit area overhead.

A stability of the cascade two-stage Power-Factor-Correction converter is investigated. The first stage is boost PFC converter to achieve a near unity power factor and the second stage is forward converter to regulate the output voltage. Previous researches studied the system using linear analysis. However, PFC boost converter is a nonlinear circuit due to the existence of the multiplier and the large variation of the duty cycle. Moreover, the effect of the second stage DC/DC converter on the first stage PFC converter adds more complexity to the nonlinear circuit. In this issue, low-frequency instability has been detected in the two-stage PFC converter assuring the limitation of the prior linear models. Therefore, nonlinear model is proposed to detected and explain these instabilities. The borderlines between stable and unstable operation has been made clear. It is cleared that feedback gains of the first stage PFC and the second stage DC/DC converters are the main affected parts to the total system stability. Then, a simplified nonlinear model is provided. Experiment confirm the two models with a good agreement. These nonlinear models have introduced new PFC design scheme by choosing the minimum required output capacitor and the feedback loop design.

Leakage power is predicted to become dominant in the total operation power as the transistor technology gets advanced. Even in the current technology, dramatic increase of leakage power at elevated temperature is a big problem. Burn-in testing, which is typically performed at 125, is facing at difficulties such as throughput degradation or thermal runaway due to increase of leakage power. Reducing leakage power at operation time is essential to solve these problems. We propose a novel approach to make use of an enable signal of a gated-clock technique for reducing active leakage power. A sleep transistor is provided between combinational logic circuits and the ground, and is controlled by the enable signal. When state transitions do not occur in Finite-State-Machines (FSM's), the enable signal becomes low and the state flip-flops keep the data. At the same time, the sleep transistor is turned off so that combinational logic gates are electrically disconnected from the ground to reduce leakage. Simulation results have shown that the proposed scheme reduces active leakage power by 30-60% in 0.18 µm technology. The total power was reduced by 20% at the maximum at 125. It was also found that performance degradation was tolerable for burn-in testing.

Analysing and modeling of traffic play a vital role in designing and controlling of networks effectively. To construct a practical traffic model that can be used for various networks, it is necessary to characterize aggregated traffic and user traffic. This paper investigates these characteristics and their relationship. Our analyses are based on a huge number of packet traces from five different networks on the Internet. We found that: (1) marginal distributions of aggregated traffic fluctuations follow positively skewed (non-Gaussian) distributions, which leads to the existence of "spikes", where spikes correspond to an extremely large value of momentary throughput, (2) the amount of user traffic in a unit of time has a wide range of variability, and (3) flows within spikes are more likely to be "elephant flows", where an elephant flow is an IP flow with a high volume of traffic. These findings are useful in constructing a practical and realistic Internet traffic model.

Chemical sensor which can be used for a multi-purpose chemical measurement to detect various chemical substances with a small number of a sensor array was investigated. It was confirmed that chemical compounds adsorbed strongly and irreversibly on a platinum surface using conventional electrochemical methods and an instrumental surface analysis. The adsorbates were also analyzed by means of an electrochemical impedance spectroscopy under dynamic potential scan; measured impedance reflects CPE (constant phase element) properties of the electrode surface. The method provides a convenient technique for the surface analysis of adsorbing chemicals. The CPE response profile was modified through chemical adsorption/desorption and the interaction between the polarized surface and chemical substances. Consequently, various profiles depending on chemical substances were obtained and it had quantitative and qualitative information about chemicals interacting with the surface. The present method which does not require a specific electrochemical reaction can be applied for multi-purpose chemical sensors and also simple chemical analyses.

This paper describes an approach to feature extraction in speech recognition systems using kernel principal component analysis (KPCA). This approach represents speech features as the projection of the mel-cepstral coefficients mapped into a feature space via a non-linear mapping onto the principal components. The non-linear mapping is implicitly performed using the kernel-trick, which is a useful way of not mapping the input space into a feature space explicitly, making this mapping computationally feasible. It is shown that the application of dynamic (Δ) and acceleration (ΔΔ) coefficients, before and/or after the KPCA feature extraction procedure, is essential in order to obtain higher classification performance. Better results were obtained by using this approach when compared to the standard technique.

This paper proposes a new simulation algorithm for analyzing large power distribution networks, modeled as linear RLC circuits, based on a novel partial random walk concept. The random walk simulation method has been shown to be an efficient way to solve for voltages of small number of nodes in a large power distribution network, but the algorithm becomes expensive to solve for voltages of nodes that are more than a few with high accuracy. In this paper, we combine direct methods like LU factorization with the random walk concept to solve power distribution networks when voltage waveforms from a large number of nodes are required. We extend the random walk algorithm to deal with general RLC networks and show that Norton companion models for capacitors and self-inductors are more amenable for transient analysis by using random walks than Thevenin companion models. We also show that by nodal analysis (NA) formulation for all the voltage sources, LU-based direct simulations of subcircuits can be speeded up. Experimental results demonstrate that the resulting algorithm, called partial random walk (PRW), has significant advantages over the existing random walk method especially when the VDD/GND nodes are sparse and accuracy requirement is high.

Borrowing the notion of instantaneous frequency that was developed in the context of time-frequency signal analysis, an instantaneous frequency amplitude spectrum (IFAS) is introduced for estimating fundamental frequency of speech signal in both noiseless and adverse environments. We define harmonicity measure as a quantity that indicates degree of periodical regularity in the IFAS and that shows substantial difference between periodic signal and noise-like waveform. The harmonicity measure is applied to estimate the existence of fundamental frequency. We provide experimental examples to demonstrate the general applicability of the harmonicity measure and apply the proposed procedure to Japanese continuous speech signals. The results show that the proposed method outperforms the conventional methods with or without the presence of noise.

Checking the equivalence of two Boolean functions under permutation of the variables is an important problem in the synthesis of multiplexer-based field-programmable gate arrays (FPGAs), and the problem is known as Boolean matching. This paper presents an efficient breadth-first search technique for computing a canonical form--namely P-representative--of Boolean functions under permutation of the variables. Two functions match if they have the same P-representative. On an ordinary workstation, on the average, the method requires several microseconds to check the Boolean matching of functions with up to eight variables against a library with tens of thousands of cells.