In this paper, a cost-efficient LDPC decoder for DVB-S2 is presented. Based on the Normalized Min-Sum algorithm and the turbo-decoding message-passing (TDMP) algorithm, a dual line-scan scheduling is proposed to enable hardware reusing. Furthermore, we present the solution to the address conflict issue caused by the characteristic of the parity-check matrix defined by DVB-S2 LDPC codes. Based on SMIC 0.13 µm standard CMOS process, the LDPC decoder has an area of 12.51 mm2. The required operating frequency to meet the throughput requirement of 135 Mbps with maximum iteration number of 30 is 105 MHz. Compared with the latest published DVB-S2 LDPC decoder, the proposed decoder reduces area cost by 34%.

We report on the first terahertz emission from a novel dual grating gate plasmon-resonant emitter fabricated with InAlAs/InGaAs/InP material systems. The introduction of InP based heterostructure material systems, instead of the GaAs based ones, in order to improve the quality factor, has successfully enhanced the THz emission intensity and realized the spectral narrowing at room temperature.

This paper presents a method to monitor information of a large-sized multicast group that can follow the group's dynamics in real-time while avoiding feedback implosion by using probabilistic polling. In particular, this paper improves the probabilistic-polling-based approach by deriving a reference mean value as the reference control value for the number of expected feedback from the properties of a binomial estimation model. As a result, our method adaptively changes its estimation parameters depending on the feedback from receivers in order to achieve a fast estimate time with high accuracy, while preventing the possible occurrence of feedback implosion. Our experimental implementation and evaluation on PlanetLab showed that the proposed method effectively controls the number of feedback and accurately estimates the size of a dynamic multicast group.

The paper presents a systematic study of in-situ passivated AlN/GaN Metal Insulator Semiconductor Field Effect Transistors (MISFETs) with submicron gates. DC, high frequency small signal, large signal and low frequency dispersion effects are reported. The DC characteristics are analyzed in conjunction with the power performance of the device at high frequencies. Studies of the low frequency characteristics are presented and the results are compared with those of AlGaN/GaN High Electron Mobility Transistors (HEMTs). Small signal measurements showed a current gain cutoff frequency and maximum oscillation frequency of 49.9 GHz and 102.3 GHz respectively. The overall characteristics of the device include a peak current density of 335 mA/mm, peak extrinsic transconductance of 130 mS/mm, a maximum output power density of 533 mW/mm with peak power added efficiency (P.A.E.) of 41.3% and linear gain of 17 dB. The maximum frequency dispersion of transconductance and output resistance of the fabricated MISFETs is 20% and 21% respectively.

This paper proposes two novel frame resource allocation schemes: Mixed bidirectional allocation scheme and Offset allocation scheme. They improve system capacity and latency performance unlike the conventional time-division duplex relay scheme which divides the frame structure into time segments for the access zone and time segment for the relay zones as in IEEE802.16j (WiMAX) systems. Computer simulations confirm that the two proposed schemes outperform the conventional schemes in terms of throughput and latency. An evaluation of the offset allocation scheme confirms that it improves the total throughput by about 85%, and reduces latency by about 72%, compared to the conventional schemes.

In this letter, we present a real-time orientation estimation and motion tracking scheme using interacting multiple model (IMM) based Kalman filtering method. Two nonlinear filters, quaternion-based extended Kalman filter (QBEKF) and gyroscope-based extended Kalman filter (GBEKF) are utilized in the proposed IMM-based orientation estimator for sensor motion state estimation. In the QBEKF, measurements from gyroscope, accelerometer and magnetometer are processed; while in the GBEKF, sole measurements from gyroscope are processed. The interacting multiple model algorithm is used for fusing the estimated states via adaptive model weighting. Simulation results validate the proposed design concept, and the scheme is capable of reducing overall estimation errors in sensor motion tracking.

This paper proposes an interference avoidance technique that allows wireless device with similar frequency bands to be operated adjacent to each other for compact mobile wireless routers (MWRs). This MWR implements two devices of Wireless LAN (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX). The MWR connects WLAN terminals to the backbone network by using WiMAX-WLAN relay. Generally, different frequency channels are assigned for the wireless systems assign in order not to interfere among multiple systems. However, mutual system interference is generated if the space between each device is very close and if the frequency using each system is adjacent. To suppress this interference, this paper proposes a novel interference avoidance technique that leverages IEEE802.11n Power Save Multi-Poll (PSMP). First, we clarify the conditions that raise the issues of mutual interference by experiment. Simulations are conducted to show that the proposed scheme outperforms the conventional schemes. Finally, the effectiveness of the proposed scheme is shown by the computer simulation.

A low-voltage class-AB CMOS output stage with a tunable quiescent current control circuit is presented. It is based on a complementary common source. The quiescent current is detected by a compact circuit and can be adjusted by means of a control current without need to modify the transistor dimensions. The minimum supply voltage can be down to one threshold voltage plus two saturation voltages. It is suitable to drive low resistive loads. Simulation results are provided that are in agreement with expected characteristics.

This paper presents the new switching converter model used for analyzing the generation mechanism of ringing ground leakage (GL) current, generated during the transient, at switch on/off of any switching converter. By applying the Norton model, the proposed new model of switching converter can be formulated. The ringing GL current is evaluated at the switching on/off of the unbalanced (half-bridge converter) and the balanced converter (full-bridge converter) for bidirectional D.C. motor drive used as an example. It is concluded that the measured and simulated results of the generated GL current agree well with the numerical analysis results, analyzed by the proposed new model of switching converter, in terms of the minimum or maximum peak currents and the ringing frequency.

The error diffusion filter in this paper is optimized with respect to the ideal blue noise pattern corresponding to a single tone level. The filter coefficients are optimized by the minimization of the squared error norm between the Fourier power spectra of the resulting halftone and the blue noise pattern. During the process of optimization, the binary pattern power spectrum matching algorithm is applied with the aid of a new blue noise model. The number of the optimum filters is equal to that of different tones. The visual fidelity of the bilevel halftones generated by the error diffusion filters is evaluated in terms of a weighted signal-to-noise ratio, Fourier power spectra, and others. Experimental results have demonstrated that the proposed filter set generates satisfactory bilevel halftones of grayscale images.

A reaction cut is a set of chemical reactions whose deletion blocks the operation of given reactions or the production of given chemical compounds. In this paper, we study two problems ReactionCut and MD-ReactionCut for calculating the minimum reaction cut of a metabolic network under a Boolean model. These problems are based on the flux balance model and the minimal damage model respectively. We show that ReactionCut and MD-ReactionCut are NP-hard even if the maximum outdegree of reaction nodes (Kout) is one. We also present O(1.822n), O(1.959n) and o(2n) time algorithms for MD-ReactionCut with Kout=2, 3, k respectively where n is the number of reaction nodes and k is a constant. The same algorithms also work for ReactionCut if there is no directed cycle. Furthermore, we present a 2O((log n)) time algorithm, which is faster than O((1+ε)n) for any positive constant ε, for the planar case of MD-ReactionCut under a reasonable constraint utilizing Lipton and Tarjan's separator algorithm.

A monolithic modulator driver IC based on InP HBTs with a new circuit topology -- called a functional distributed circuit (FDC) -- for over 80-Gb/s optical transmission systems has been developed. The FDC topology includes a wide-band amplifier designed using a distributed circuit, a digital function designed using a lumped circuit, and broadband impedance matching between the lumped circuit and distributed circuit to enable both wider bandwidth and digital functions. The driver IC integrated with a 2:1 multiplexing function produces 2.6-Vp-p (differential output: 5.2 Vp-p) and 2.4- Vp-p (differential output: 4.8 Vp-p) output-voltage swings with less than 450-fs and 530-fs rms jitter at 80 Gb/s and 90 Gb/s, respectively. To the best of our knowledge, this is equivalent to the highest data rate operation yet reported for monolithic modulator drivers. When it was mounted in a module, the driver IC successfully achieved electro-optical modulation using a dual-drive LiNbO3 Mach-Zehnder modulator up to 90 Gb/s. These results indicate that the FDC has the potential to realize high-speed and functional ICs for over-80-Gb/s transmission systems.

This letter presents a theoretical analysis of the Parallel Iterative Matching (PIM)'s dynamics with multiple iterations used in an input-buffered packet switch. In our approach, by carefully categorizing all unmatched patterns into several representative patterns after each iteration, probabilities of accumulated matched pairs in a recursive manner are successfully obtained. Numerical evaluations of the analytical formulas are performed.

We fabricated a 2:1 multiplexer IC (MUX) with a retiming function by using 1-µm self-aligned InP/InGaAs/InP double-heterojunction bipolar transistors (DHBTs) with emitter mesa passivation ledges. The MUX operated at 120 Gbit/s with a power dissipation of 1.27 W and output amplitude of 520 mV when measured on the wafer. When assembled in a module using V-connectors, the MUX operated at 113 Gbit/s with a 514-mV output amplitude and a power dissipation of 1.4 W.

Drain collapse in AlGaN/GaN HFET is analyzed using a two-dimensional device simulator. Two-step saturation is obtained, assuming hole-trap type surface states on the AlGaN surface and a short negative-charge-injected region at the drain side of the gate. Due to the surface electric potential pinning by the surface traps, the negative charge injected region forms a constant potential like in a metal gate region and it acts as an FET with a virtual gate. The electron concentration profile reveals that the first saturation occurs by pinch-off in the virtual gate region and the second saturation occurs by the pinch-off in the metal gate region. Due to the short-channel effect of the virtual gate FET, the saturation current increases until it finally reaches the saturation current of the intrinsic metal gate FET. Current collapses with current degradation at the knee voltage in the I-V characteristics can be explained by the formation of the virtual gate.

This work addresses the enormous efficiency and linearity potential of optimized AlGaN/GaN high-electron mobility transistors (HEMT) in conventional Doherty linear base-station amplifiers at 2.7 GHz. Supported by physical device simulation, the work further elaborates on the use of AlGaN/GaN HEMTs in high-speed current-switch-mode class-D (CMCD)/class-S MMICs for data rates of up to 8 Gbit/s equivalent to 2 GHz RF-operation. The device needs for switch-mode operation are derived and verified by MMIC results in class-S and class-D operation. To the authors' knowledge, this is the first time 2 GHz-equivalent digital-switch-mode RF-operation is demonstrated with GaN HEMTs with high efficiency.

This paper presents an asynchronous FPGA that combines 4-phase dual-rail encoding and LEDR (Level-Encoded Dual-Rail) encoding. 4-phase dual-rail encoding is employed to achieve small area and low power for function units, while LEDR encoding is employed to achieve high throughput and low power for the data transfer using programmable interconnection resources. Area-efficient protocol converters and their control circuits are also proposed in transistor-level implementation. The proposed FPGA is designed using the e-Shuttle 65nm CMOS process. Compared to the 4-phase-dual-rail-based FPGA, the throughput is increased by 69% with almost the same transistor count. Compared to the LEDR-based FPGA, the transistor count is reduced by 47% with almost the same throughput. In terms of power consumption, the proposed FPGA achieves the lowest power compared to the 4-phase-dual-rail-based and the LEDR-based FPGAs. Compared to the synchronous FPGA, the proposed FPGA has lower power consumption when the workload is below 35%.

This paper proposes a new multi-band received signal strength (MRSS) fingerprinting based indoor location system, which employs the frequency diversity on the conventional single-band received signal strength (RSS) fingerprinting based indoor location system. In the proposed system, the impacts of frequency diversity on the enhancements of positioning accuracy are analyzed. Effectiveness of the proposed system is proved by experimental approach, which was conducted in non line-of-sight (NLOS) environment under the area of 103 m2 at Yagami Campus, Keio University. WLAN access points, which simultaneously transmit dual-band signal of 2.4 and 5.2 GHz, are utilized as transmitters. Likewise, a dual-band WLAN receiver is utilized as a receiver. Signal distances calculated by both Manhattan and Euclidean were classified by K-Nearest Neighbor (KNN) classifier to illustrate the performance of the proposed system. The results confirmed that Frequency diversity attributions of multi-band signal provide accuracy improvement over 50% of the conventional single-band.

This paper presents a Pulse-Width Modulation (PWM) pre-emphasis technique which utilizes time-domain information processing to increase the data rate for a given bandwidth of interconnection. The PWM pre-emphasis method does not change the pulse amplitude as for conventional FIR pre-emphasis, but instead exploits timing resolution. This fits well with recent CMOS technology trends toward higher switching speeds and lower supply voltage. We discuss multiple-valued data transmission based on time-domain pre-emphasis techniques in consideration of higher-order channel effects. Also, a new data-dependent adaptive time-domain pre-emphasis technique is proposed to compensate for the data-dependent jitter.

A method has been developed for deriving the approximate global optimum of a nonlinear objective function. First, the objective function is expanded into a linear equation for a moment vector, and the optimization problem is reduced to an eigen analysis problem in the wave coefficient space. Next, the process of the optimization is expressed using a Schrodinger-type equation, so global optimization is equivalent to eigen analysis of the Hamiltonian of a Schrodinger-type equation. Computer simulation of this method demonstrated that it produces a good approximation of the global optimum. An example optimization problem was solved using a Hamiltonian constructed by combining Hamiltonians for other optimization problems, demonstrating that various types of applications can be solved by combining simple Hamiltonians.