Regression analysis that incorporates measurement errors in input variables is important in various applications. In this study, we consider this problem within a framework of Gaussian process regression. The proposed method can also be regarded as a generalization of kernel regression to include errors in regressors. A Markov chain Monte Carlo method is introduced, where the infinite-dimensionality of Gaussian process is dealt with a trick to exchange the order of sampling of the latent variable and the function. The proposed method is tested with artificial data.

This paper describes the circuit design and measured performance of a high-speed digital-to-analog converter (DAC) for the next generation of coherent optical communications systems. To achieve high-speed and low-power operation, we used an R-2R current-steering architecture and devised timing alignment and waveform improvement techniques. A 6-bit DAC test chip was fabricated with InP HBT technology, which yields a peak ft of 175 GHz and a peak fmax of 260 GHz. The measured differential and integral non-linearity (DNL and INL) are within +0.61/-0.07 LSB and +0.27/-0.52 LSB, respectively. The measured spurious-free dynamic range (SFDR) is 44.7 dB for a sinusoidal output of 72.5 MHz at a sampling rate of 13.5 GS/s, which was the limit of our measurement setup. The expected ramp-wave outputs at a sampling rate of 24 GS/s are also obtained. The total power consumption is as low as 0.88 W with a supply voltage of -4.0 V. This DAC can provide low-power operation and a higher sampling rate than any other previously reported DAC with a resolution of 5 bits or more.

A unipolar n-n heterostrucuture diode is developed in the InP material system. The electronic barrier is formed by a saw tooth type of conduction band bending which consists of a quaternary In0.52(AlyGa1-y)0.48As layer with 0 < y < ymax. This barrier is lattice matched for all y to InP and is embedded between two n+-InGaAs layers. By varying the maximum Al-content from ymax,1 = 0.7 to ymax,2 = 1 a variable barrier height is formed which enables a diode-type I-V characteristic by epitaxial design with an adjustable current density within 3 orders of magnitude. The high current density of the diode with the lower barrier height (ymax,1 = 0.7) makes it suitable for high frequency applications at low signal levels. RF measurements reveal a speed index of 52 ps/V at VD = 0.15 V. The device is investigated for RF-to-DC power conversion in UHF RFID transponders with low-amplitude RF signals.

In this paper, we propose a new differential MIMO single-carrier system with frequency-domain equalization (SC-FDE) aided by the insertion of cyclic prefix. This block transmission system not only inherits all the merits of the SISO SC-FDE system, but is also equipped with a differential space-time block coding (DSTBC) such as to combat the fast-changing frequency selective fading channels without the needs to estimate and then compensate the channel effects. Hence, for practical applications, it has the additional merits of decoding simplicity and robustness against high mobility transmission environments. Computer simulations show that the proposed system can provide diversity benefit as the non-differential system does, while greatly reducing the receiver complexity.

This paper considers an optimized limited feedback design for a multi-antenna system serving multiple users under different types of channels: Rayleigh distributed and line-of-sight distributed channels. Since the users are asymmetric, we propose an optimized feedback bandwidth allocation scheme for users under a total feedback rate constraint. The allocation scheme is designed according to the long-term channel type information of users, and thus it can be efficiently implemented. Numerical results verify the effectiveness of our proposed scheme.

To tackle the increasing testing power during built-in self-test (BIST) operations, this paper proposes a new test pattern generator (TPG). With the proposed reconfigurable LFSR, the reconfigurable Johnson counter, the decompressor and the XOR gate network, the introduced TPG can produce the single input change (SIC) sequences with few repeated vectors. The proposed SIC sequences minimize switching activities of the circuit under test (CUT). Simulation results on ISCAS benchmarks demonstrate that the proposed method can effectively save test power, and does not impose high impact on test length and hardware for the scan based design.

This paper proposes a robust state observer for multi-input multi-output LTI systems. Unknown inputs of polynomial form and high-frequency measurement noises are considered in the system model. The unknown inputs and the noises are not in the same form. Multiple integrations of both the observer error signal and the measurement output are used for the observer design. The existence condition of the proposed observer is shown to be the same as that of the proportional-integral (PI) observer. Computer simulations show the effectiveness of the proposed observer.

We fabricated and examined current limiting effect for InP Gunn diodes with stable depletion layer mode operation of diodes for high efficiency Gunn oscillators. Current limiting at the cathode was achieved by a shallow Schottky barrier at the interface. We discussed fabrication procedure, the results for negative differential resistance and rf tests for InP Gunn diodes. It was shown that the fabricated Gunn diodes have the output power of 10.22 dBm at a frequency of 90.13 GHz. Its input voltage and corresponding current were 8.55 V and 252 mA, respectively.

We investigated collector current spreading in InGaAs single heterojunction bipolar transistors (SHBTs) having a collector thickness of 75 nm. SHBTs were fabricated with three different emitter widths -- 200, 400, and 600 nm -- and the highest cutoff frequency that was obtained was 468 GHz. The relationship between the current density at the highest cutoff frequency and the emitter width could not be used to estimate the current spreading because it was independent of the collector-base voltage. However, the relationship between the current density with the increase in the total collector-base capacitance and the emitter width indicates current spreading in the collector. The current spreading was estimated to be approximately 90 nm.

This paper considers the use of an antenna selection mechanism to reduce the cost of multiple analog transmit/receive chains in multiple-input multiple-output (MIMO) systems. With the optimal antenna selection scheme, radio-frequency chains can optimally connect with the best subset of transmitter and/or receiver antennas. However, the optimal antenna selection algorithm requires an exhaustive search of all possible combinations to find the optimum subset at the transmitter and/or receiver, thus resulting in high complexity. In order to reduce the computational load while still maximizing channel capacity, we introduce the simulated annealing (SA) method, an effective algorithm that solves various combinatorial optimization problems, to search the optimal subset. The simulation results show that the performance of the proposed SA method provides almost the same channel capacity as that of the optimal exhaustive search algorithm while maintaining low complexity.

An improved soft-input soft-output (SISO) minimum mean-squared error (MMSE) detection method is proposed for joint coding and precoding OFDM systems under imperfect channel estimation. Compared with the traditional mismatched detection which uses the channel estimate as its exact value, the signal model of the proposed detector is more accurate and the influence of channel estimation error (CEE) can be effectively mitigated. Simulations indicate that the proposed scheme can improve the bit error rate (BER) performance with fewer pilot symbols.

To increase both the capacity and the processing speed for input-queued (IQ) switches, we proposed a fair scalable scheduling architecture (FSSA). By employing FSSA comprised of several cascaded sub-schedulers, a large-scale high performance switches or routers can be realized without the capacity limitation of monolithic device. In this paper, we present a fair scheduling algorithm named FSSA_DI based on an improved FSSA where a distributed iteration scheme is employed, the scheduler performance can be improved and the processing time can be reduced as well. Simulation results show that FSSA_DI achieves better performance on average delay and throughput under heavy loads compared to other existing algorithms. Moreover, a practical 64 64 FSSA using FSSA_DI algorithm is implemented by four Xilinx Vertex-4 FPGAs. Measurement results show that the data rates of our solution can be up to 800 Mbps and the tradeoff between performance and hardware complexity has been solved peacefully.

A new deadbeat control scheme for linear systems with input constraints is presented. Input constraints exist in most control systems, but in conventional dead-beat control, logical strategy to handle it has not been studied enough. The proposed controller in this paper adjusts the number of steps for dead-beat tracking on-line, in order to achieve delayed deadbeat-tracking performance and satisfy any admissible input constraint. Increasing the number of steps for dead-beat tracking and formulating the corresponding degree of freedom into null-space vectors make it possible to obtain delayed dead-beat tracking, and minimize the inevitable delay, respectively. LMI feasibility problems are solved to numerically obtain the solution and minimize the unavoidable step-delay. As a result, calculation effort is reduced compared to LMI-optimization problem. The proposed schemes can be readily numerically implemented. Its practical usefulness is validated by simulation for 6-axis robot model and experimental results for DC-motor servoing.

In this paper, we propose a calculation method of gate delay for SSTA (Statistical Static Timing Analysis) considering MIS (Multiple Input Switching). In SSTA, statistical maximum/minimum operation is necessary to calculate the latest/fastest arrival time of multiple input gate. Most SSTA approaches calculate the distribution in the latest/fastest arrival time under SIS (Single Input Switching assumption), resulting in ignoring the effect of MIS on the gate delay and the output transition time. MIS occurs when multiple inputs of a gate switch nearly simultaneously. Thus, ignoring MIS causes error in the statistical maximum/minimum operation in SSTA. We propose a statistical gate delay model considering MIS. We verify the proposed method by SPICE based Monte Carlo simulations. Experimental results show that the neglect of MIS effect leads to 80% error in worst case. The error of the proposed method is less than 20%.

Adjustment of a certain parameter in the course of performing a trajectory task such as drawing or gesturing is a common manipulation in pen-based interaction. Since pen tip information is confined to x-y coordinate data, such concurrent parameter adjustment is not easily accomplished in devices using only a pen tip. This paper comparatively investigates the performance of inherent pen input modalities (Pressure, Tilt, Azimuth, and Rolling) and Key Pressing with the non-preferred hand used for precision parameter manipulation during pen sliding actions. We elaborate our experimental design framework here and conduct experimentation to evaluate the effect of the five techniques. Results show that Pressure enabled the fastest performance along with the lowest error rate, while Azimuth exhibited the worst performance. Tilt showed slightly faster performance and achieved a lower error rate than Rolling. However, Rolling achieved the most significant learning effect on Selection Time and was favored over Tilt in subjective evaluations. Our experimental results afford a general understanding of the performance of inherent pen input modalities in the course of a trajectory task in HCI (human computer interaction).

This paper proposes a novel image inpainting method based on bandelet transform. This technique is based on a multi-resolution layer to perform image restoration, and mainly utilizes the geometrical flow of the neighboring texture of the damaged regions as the basis of restoration. By performing the warp transform with geometrical flows, it transforms the textural variation into the nearing domain axis utilizing the bandelet decomposition method to decompose the non-relative textures into different bands, and then combines them with the affine search method to perform image restoration. The experimental results show that the proposed method can simplify the complexity of the repair decision method and improve the quality of HVS, and thus, repaired results to contain the image of contour of high change, and in addition, offer a texture image of high-frequency variation. These repair results can lead to state-of-the-art results.

Three experiments were conducted in this study to investigate the human ability to control pen pressure and pen tilt input, by coupling this control with cursor position, angle and scale. Comparisons between pen pressure input and pen tilt input have been made in the three experiments. Experimental results show that decreasing pressure input resulted in very poor performance and was not a good input technique for any of the three experiments. In "Experiment 1-Coupling to Cursor Position", the tilt input technique performed relatively better than the increasing pressure input technique in terms of time, even though the tilt technique had a slightly higher error rate. In "Experiment 2-Coupling to Cursor Angle", the tilt input performed a little better than the increasing pressure input in terms of time, but the gap between them is not so apparent as Experiment 1. In "Experiment 3-Coupling to Cursor Scale", tilt input performed a little better than increasing pressure input in terms of adjustment time. Based on the results of our experiments, we have inferred several design implications and guidelines.

Input/Output (I/O) automata and the Temporal Logic of Actions (TLA) are two well-known techniques for the specification and verification of concurrent systems. Over the past few years, they have been extended to the so-called dynamic I/O automata and, respectively, Mobile TLA (MTLA) in order to be more appropriate for mobile agent systems. Dynamic I/O automata is just a mathematical model, whereas MTLA is a logic with a formally defined language. In this paper, therefore, we investigate how MTLA could be used as a formal language for the specification of dynamic I/O automata. We do this by writing an MTLA specification of a travel agent system which has been specified semi-formally in the literature on that model. In this specification, we deal with always existing agents as well as with an initially unknown number of dynamically created agents, with mobile and non-mobile agents, with I/O-automata-style communication, and with the changing communication capabilities of mobile agents. We have previously written a TLA specification of this system. This paper shows that an MTLA specification of such a system can be more elegant and faithful to the dynamic I/O automata definition because the agent existence and location can be expressed directly by using agent and location names instead of special variables as in TLA. It also shows how the reuse of names for dynamically created and destroyed agents within the dynamic I/O automata framework can be specified in MTLA.

A single-carrier multiple-input multiple-output (MIMO) system with frequency-selective channels suffers from the inter-symbol interference (ISI) and the co-channel interference (CCI). To eliminate both type of interference, we propose in this letter a hybrid two-stage decision-feedback equalizer (HTS-DFE), which performs the frequency-domain equalization (FDE) in the first stage and the layered serial interference-cancellation (SIC) in the second stage. Since the decision-feedback (DF) or noise-prediction (NP) architecture can be employed in FDE or SIC, the proposed equalizer actually can have four variations that achieve the same mean square error (MSE) under the assumption of perfect feedback. Further, we combine HTS-DFE with the decoded decision-feedback (DDF) scheme to mitigate the error-propagation encountered in the practice. Simulation results confirm that the proposed HTS-DFE can outperform the existing equalizers significantly.

Threshold-based ordered successive interference cancellation (OSIC) detection algorithm is proposed for per-antenna-coded (PAC) two-input multiple-output (TIMO) orthogonal frequency division multiplexing (OFDM) systems. Successive interference cancellation (SIC) is performed selectively according to channel conditions. Compared with the conventional OSIC algorithm, the proposed algorithm reduces the complexity significantly with only a slight performance degradation.