An all-digital clock deskew buffer with variable duty cycles is presented. The proposed circuit aligns the input and output clocks with two cycles. A pulsewidth detector using the sequential time-to-digital conversion is employed to detect the duty cycle. The output clock with adjustable duty cycles can be generated. The proposed circuit has been fabricated in a 0.35 µm CMOS technology. The measured duty cycle of the output clock can be adjusted from 30% to 70% in steps of 10%. The operation frequency range is from 400 MHz to 600 MHz.

Orthogonal frequency division multiplexing (OFDM) has been adopted in the physical layer of IEEE802.11a WLAN standard. In this letter, an efficient diversity scheme is presented for better frequency synchronization in the OFDM-based WLAN. The diversity scheme utilizes a two-stage approach to effectively enhance the performance of frequency synchronization. Simulation results indicate that using the algorithm, the performance can significantly be improved in 802.11a WLAN systems.

The present letter deals with the blind equalization problem of a single-input single-output infinite impulse response (SISO-IIR) channel with additive Gaussian noise. To solve the problem, we propose a new criterion for maximizing constrainedly a fourth-order cumulant. The algorithms derived from the criterion have such a novel property that even if Gaussian noise is added to the output of the channel, an effective zero-forcing (ZF) equalizer can be obtained with as little influence of Gaussian noise as possible. To show the validity of the proposed criterion, some simulation results are presented.

To perform a comparative study, we experimented on two differential epitaxial structures, the conventional metamorphic high-electron-mobility-transistor (MHEMT) using the InAlAs/InGaAs/InAlAs structure and the InP-composite-channel MHEMT adopting the InAlAs/InGaAs/InP structure. Compared with the conventional MHEMT, the InP-composite-channel MHEMT shows improved breakdown performance; more than approximately 3.8 V. This increased breakdown voltage can be explained by the lower impact ionization coefficient of the InP-composite-channel MHEMT than that of the conventional MHEMT. The InP-composite-channel MHEMT also shows improved Radio Frequency characteristics of S21 gain of approximately 4.35 dB at 50 GHz, and a cutoff frequency (fT) and a maximum frequency of oscillation (fmax) of approximately 124 GHz and 240 GHz, respectively, were obtained. These are due to decreases in go and gm.

HfOxNy thin films formed by the electron cyclotron resonance (ECR) Ar/N2 plasma nitridation of HfO2 films were investigated for high-k gate insulator applications. HfOxNy thin films formed by the ECR Ar/N2 plasma nitridation (60 s) of 1.5-nm-thick HfO2 films, which were deposited on chemically oxidized Si(100) substrates, were found to be effective for suppressing interfacial layer growth or crystallization during postdeposition annealing (PDA) in N2 ambient. After 900 PDA of for 5 min in N2 ambient, it was found that HfSiON film with a relatively high dielectric constant was formed on the HfOxNy/Si interface by Si diffusion. An equivalent oxide thickness (EOT) of 2.0 nm and a leakage current density of 1.010-3 A/cm2 (at VFB-1 V) were obtained. The effective mobility of the fabricated p-channel metal-insulator-semiconductor field-effect transistor (MISFET) with the HfOxNy gate insulator was 50 cm2/Vs, and the gate leakage current of the MISFET with the HfOxNy gate insulator was found to be well suppressed compared with the MISFET with the HfO2 gate insulator after 900 PDA because of the nitridation of HfO2.

In this letter, we propose a combined scheme of minimum mean square error (MMSE) detection and successive interference cancellation (SIC) for multiuser space-time block coded orthogonal frequency division multiplexing (STBC-OFDM) systems. With the same complexity order, the proposed scheme provides significant bit error rate (BER) performance improvement over the linear MMSE multiuser detector.

Combined input-crosspoint buffered (CICB) switches relax arbitration timing and provide high-performance switching for packet switches with high-speed ports. It has been shown that these switches, with one-cell crosspoint buffer and round-robin arbitration at input and output ports, provide 100% throughput under uniform traffic. However, under admissible traffic patterns with nonuniform distributions, only weight-based selection schemes are reported to provide high throughput. This paper proposes a round-robin based arbitration scheme for a CICB packet switch that provides 100% throughput for several admissible traffic patterns, including those with uniform and nonuniform distributions, using one-cell crosspoint buffers and no speedup. The presented scheme uses adaptable-size frames, where the frame size is determined by the traffic load.

This paper proposes a low complexity composite CDMA system based on MIMO (Multiple-Input-Multiple-Output) processing and LDPC (low-density parity-check) codec based a CDMA system, which works well even if the complicated case of multipath, multiusers and short length LDPC codes. To explore the practical application, the mobile user in the composite CDMA systems is with only two antennas and adopts short length irregular LDPC codec, each user's data has been divided two LDPC encoded substreams being sent to two transmitter antennas at base station. Since the LDPC encoded substreams of reaching the mobile user are orthogonal to each other in space and time, the CDMA system performances (BER and SINR) can be improved much, but the multipath may ruin the orthogonalilty. To solve the problems, the paper provides the algorithms of main function modules of transmitter and receivers, gives a simple method to test the girth of LDPC codes, and analyzes the performance of MIMO-LDPC CDMA systems theoretically and experimentally. The simulation results show that the hybrid CDMA systems can have better performance than the conventional CDMA systems based on single transmitted antenna at a base station.

In this paper, we show the generalized method of the time-domain circuit simulation based on LIM. Our method is applicable to any structure of circuits by combination with the SPICE-like method. In order to show the validity and efficiency of our method, an example circuit is simulated and the proposed method is compared with the conventional ones.

Metro networks are based on SONET/SDH which uses the circuit switching technology. Circuit switching is inappropriate for the Internet traffic which is very bursty nature. Therefore, metro networks can become a bottleneck. In order to resolve this problem, the IEEE 802.17 working group has proposed the Resilient Packet Ring (RPR) technology. In order to provide fairness among stations in the RPR network, two types of RPR fairness mechanisms have been defined. However, the IEEE 802.17 RPR fairness mechanisms have the problem of inefficient use of the available bandwidth after the congestion at a node has been resolved. In this paper, we propose an improved bandwidth allocation in which, after the congestion resolution at a node, the node estimates the number of effective nodes transmitting traffic, measures the remaining bandwidth and fairly allocates the available bandwidth to effective nodes. To show the performance of our proposed mechanism, we have performed simulation and show that the proposed mechanism gives higher bandwidth utilization than the existing RPR fairness mechanisms.

The release of image processing techniques make image modification and fakery easier. Image fakery, here, is defined as a process to copy a region of source image and paste it onto the destination image, with some post processing methods applied, such as boundary smoothing, blurring, etc. to make it natural. The most important characteristic of image fakery is object copy and paste. In order to detect fake images, this letter introduces a blind detection scheme based on singular value decomposition (SVD). Experimental results also show the effectiveness of the proposed scheme.

A novel blind channel estimation scheme is proposed for OFDM systems employing PSK modulation. This scheme minimizes the number of possible channels by exploiting the constant modulus property, chooses a best fit over the possible channels by exploiting the finite alphabet property of information signals, and achieves competitive performance with low computational complexity. Results comparing the new scheme with the finite-alphabet based channel estimation are presented.

We propose a new group signature scheme which is secure if we assume the Decision Diffie-Hellman assumption, the q-Strong Diffie-Hellman assumption, and the existence of random oracles. The proposed scheme is the most efficient among the all previous group signature schemes in signature length and in computational complexity. This paper is the full version of the extended abstract appeared in ACISP 2005 [17].

Affine projection algorithms perform well for acoustic echo cancellation and adaptive equalization. Although these algorithms typically provide fast convergence, they are unduly complex when updating the weights of the associated adaptive filter. In this paper, we propose a new subband affine projection (SAP) algorithm and a facile method for its implementation. The SAP algorithm is derived by combining the affine projection algorithm and the subband adaptive structure with the maximal decimation. In the proposed SAP algorithm, the derived weight-updating formula for the subband adaptive filter has a simple form as compared with the normalized least mean square (NLMS) algorithm. The algorithm gives improved convergence and reduced computational complexity. The efficiency of the proposed algorithm for a colored input signal is evaluated experimentally.

In orthogonal frequency-division multiplexing (OFDM)-based wireless local area networks (WLANs), phase noise (PHN) and residual frequency offset (RFO) can cause the common phase error (CPE) and the inter-carrier interferences (ICI), which seriously degrade the performance of systems. In this letter, we propose a combined pilot symbol assisted and decision-directed channel estimation scheme based on the least-squares (LS) and the maximum-likelihood (ML) algorithms. Simulation results present that the proposed scheme significantly improves the performance of OFDM-based WLANs.

Recent studies of high quality, high resolution traffic measurements have revealed that network traffic appears to be statistically self similar. Contrary to the common belief, aggregating self-similar traffic streams can actually intensify rather than diminish burstiness. Thus, traffic prediction plays an important role in network management. In this paper, Least Mean Kurtosis (LMK), which uses the negated kurtosis of the error signal as the cost function, is proposed to predict the self similar traffic. Simulation results show that the prediction performance is improved greatly over the Least Mean Square (LMS) algorithm.

Recently, researches and developments for measuring and modeling of the human body have been receiving much attention. Our aim is to reconstruct an accurate shape of a human foot from multiple camera images, which can capture dynamic behavior of the object. In this paper, a foot-shape database is used for accurate reconstruction of human foot. By using Principal Component Analysis, the foot shape can be represented with new meaningful variables. The dimensionality of the data is also reduced. Thus, the shape of object can be recovered efficiently, even though the object is partially occluded in some input views. To demonstrate the proposed method, two kinds of experiments are presented: reconstruction of human foot in a virtual reality environment with CG multi-camera images, and in real world with eight CCD cameras. In the experiments, the reconstructed shape error with our method is around 2 mm in average, while the error is more than 4 mm with conventional volume intersection method.

The complexity of the optimal decoding for vector quantization (VQ) in code-division multiple access (CDMA) communications prohibits implementation. It was recently shown in [1] that a suboptimal scheme that combines a soft-output multiuser detector and individual VQ decoders provides a flexible tradeoff between decoder's complexity and performance. The work in [1], however, only considers an AWGN channel model. This paper extends the technique in [1] to a frequency-selective Rayleigh fading channel. Simulation results indicate that such a suboptimal decoder also performs very well over this type of channel.

In this paper, we describe a bootstrapped nMOS switch that is modified to reduce leakage current for nMOS reversible energy recovery logic (nRERL) [1]. Conventional bootstrapped switches are not suitable for nRERL because they have nonadiabatic loss due to leakage current that flows while boosted. Therefore, we lowered the gate voltage of the isolation transistor in each bootstrapped switch to reduce this leakage current. With detailed analysis and simulation, we determined the range of the bias voltage, in which the switches can transfer full-swing input signals. We implemented a simple 8-bit nRERL microprocessor into silicon and measured its energy consumption to confirm our analysis. For the supply voltage of 1.8 V and the operating frequency of 880 kHz, we found that the microprocessor consumed about 8.5 pJ/cycle for 1.3 V < Vbias <1.6 V, which was just about a half of its energy consumption when Vbias = 1.7 V.

We show that the necessary and sufficient condition for the existence of a balanced C4-trefoil decomposition of the complete multi-graph λKn is λ(n-1) ≡ 0 (mod 24) and n ≤ 10. Decomposition algorithms are also given.