Connected vehicle driving safety enhancement via dynamic communication channel selection

Vehicle-to-Vehicle communication can cogently improve traffic safety because it grants drivers better situational awareness and strengthens inter-cooperation among them. However, the current policy obliges the safety-critical messages, i.e., Basic Safety Messages (BSMs) and Event Safety Messages (ESMs), to be transmitted exclusively in one single channel over the Dedicated Short-Range Communication (DSRC) spectrum, which may incur severe channel congestions, intolerable communication delays, and higher accident probabilities. To alleviate the channel congestion, popular measures focus on adaptively adjusting the transmission parameters, e.g., packet generating rate. However, due to the narrow bandwidth of a single channel, these methods can hardly ensure timely delivery of critical safety-related messages when the density of DSRC-enabled vehicles becomes high. Instead of sticking to only one single channel, this paper applies a dynamic channel selection algorithm to thoroughly exploit the entire DSRC band resource and reduce the transmission delay. To demonstrate the effectiveness of the utilized algorithm, we conduct experiments under two representative scenarios, i.e., a cooperative adaptive cruise control scenario and a run-the-red-light scenario at an intersection. Experimental results show that the transmission delays of both the BSMs and the ESMs could be effectively reduced, yielding an improved vehicle platoon control accuracy, string stability, and collision avoidance performance.     

An efficient CMOS buffer for driving large capacitive loads

A CMOS class AB high-drive buffer suitable for driving large capacitive and moderate resistive loads is presented. The buffer, designed using 3-/spl mu/m technology, occupies only 100 mils/SUP 2/ of area and dissipates 1.5 mW of DC power from a /spl plusmn/2.5-V supply, yet it is capable of driving a 5000-pF capacitor at over 100-kHz clocking frequency. The buffer achieves good slew rate and fast settling by entering into a high-drive state during slewing and returning to a low-power wide-band state during the settling period. Unconditional stability is attained when C/SUB L//spl ges/100 pF and R/SUB L//spl ges/10 k/spl Omega/. Total harmonic distortion is below 0.5% for over 70% of the full supply range.     

A self-adjusting sinusoidal power source suitable for driving capacitive loads

A new self-adjusting current-fed push-pull parallel inverter (SA-CFPPRI) is presented and tested by simulation and experimentally. The power source includes a soft switching control circuitry and a controllable inductor. The SA-CFPPRI can drive a capacitive load at any frequency within the design range. It will maintain zero voltage switching of the main transistors and follow the input frequency signal even when the resonant elements and/or the load vary. Possible range of applications for the proposed power source is: piezoelectric transformers and motors, ac bus for a distributed power system and other loads that need to be fed by a sinusoidal waveform. The experimental results of the laboratory unit (160 Vrms at 93 kHz and nominal output power of 5W) verify the analytical analysis and proposed design procedure.     

Precision current and charge amplifiers for driving highly capacitive piezoelectric loads

Piezoelectric transducers are known to be highly capacitive loads that exhibit less hysteresis when driven with current or charge rather than voltage. Compliance feedback current and charge amplifiers are introduced. A secondary output voltage feedback loop is employed to prevent DC charging of capacitive loads and to compensate for any voltage or current offsets in the driver circuit. Low frequency bandwidths in the milliHertz range can be achieved.     

适用汽车智能驾驶的多光谱激光雷达波长选择可行性研究

在汽车智能驾驶系统中,激光雷达由于其独特的三维成像能力,成为场景探测感知传感器群组中不可或缺的组成部分。为提升单一波长激光雷达在物性探测分类和状态上的性能,借鉴多光谱探测具有物性探测能力的原理,论文对适用于汽车智能驾驶的多光谱激光雷达的波段选择进行了可行性研究,利用主成分分析法对智能驾驶中典型目标进行光谱计算及分析,结合激光光源特性以及光电探测器的特性,综合多光谱激光雷达波段选择方法和智能驾驶应用场景中典型目标地物光谱特性,以及商用激光雷达的可获得性,得出了适用汽车智能驾驶的多光谱激光雷达的波长可以选择808 nm、905 nm、1 064 nm、1 310 nm,并通过测试验证了多光谱激光雷达所选波长的有效性。     

High-energy (59 pJ) and low-jitter (250 fs) picosecond pulses from gain-switching of a tapered-stripe laser diode via resonant driving

High-energy (59 pJ), low-jitter (250 fs), high-extinction ratio (800), and short (14.5 ps FWHM) pulses were generated by gain-switching of a tapered stripe gain-guided laser diode (LD) via resonant driving. These characteristics are attributed to a stable single-mode near-field pattern, a single-lobe far-field pattern, and multilongitudinal modes associated with the tapered stripe LD under high driving current pulses. These pulses from a comb generator were enhanced mainly from reflection at the LD-transmission line impedance mismatch; the line length was adjusted for resonance with the reflection from the step recovery diode, further increasing the driving current.     

MODE-type algorithm for estimating damped, undamped, or explosive modes

We propose a new algorithm for estimating the parameters of damped, undamped, or explosive sinusoidal signals. The algorithm resembles the MODE algorithm, which is commonly used for direction of arrival estimation in the array signal processing field. It is derived as a natural approximation to an asymptotically (high-SNR) optimal parameter estimator and has excellent statistical accuracy. Nevertheless, it is computationally simple and easy to implement. Numerical examples are included to illustrate the performance of the proposed method.This work has been supported by the Swedish Research Council for Engineering Sciences (TFR).     

Sample selection for visual domain adaptation via sparse coding

Visual domain adaptation has attracted much attention and has made great achievement in recent years. It deals with the problem of distribution divergence between source and target domains. Current methods mostly focus on transforming images from different domains into a common space to minimize the distribution divergence. However, there are many irrelevant source samples for target domain even after the transformation. In order to eliminate the irrelevant samples, we develop a sample selection algorithm using sparse coding theory. We do the sample selection in a common subspace of source and target data to find as many as relevant source samples. In the common subspace, data characteristics are preserved by using graph regularization. Therefore, we can select the most relevant samples for our target image classification task. Moreover, in order to build a discriminative classifier for the target domain, we use not only the common part of source and target domains learned in the common subspace but also the specific part of target domain. The algorithm can be extended to handle samples from multiple source domains. Experimental results show that our visual domain adaptation method on the image classification tasks can be very effective for the state-of-the-art datasets.     

Partial iterative decoding for binary turbo codes via cross-entropy based bit selection

Near-capacity performance of turbo codes is generally achieved with a large number of decoding iterations. Various iteration stopping rules introduced in the literature often induce performance loss. This paper proposes a novel partial decoding iteration scheme using a bit-level convergence test. We first establish decoding optimality of windowed partial iteration for non-converged bits given that convergence has been achieved on window boundaries. We next present two criteria for testing bit convergence based on cross-entropy, and propose a windowed partial iteration algorithm. The overall complexity and memory requirements of the new algorithm are evaluated and compared with known algorithms. Simulations reveal that the proposed scheme suffers essentially no performance loss compared to full iterations, while reducing the decoding complexity. We also briefly discuss possible extensions of the proposed scheme to general iterative receivers.     

Adaptive quantization parameter selection for low-delay HEVC via temporal propagation length estimation

Rate Distortion Optimization (RDO) is employed in High-Efficiency Video Coding (HEVC) to enhance its coding efficiency. Owing to its coding complexity, RDO is traditionally performed within each frame with fixed quantization parameters (QPs), without fully considering the coding dependencies between the current frame and future frames within a temporal propagation chain. To improve the coding efficiency of HEVC, it is desirable to perform a global RDO among consecutive frames while maintaining a similar coding complexity. To address this problem, in this paper, temporal dependencies are first measured via a model for the energy of prediction residuals that enables the formulation of the global RDO in low-delay (LD) HEVC. Second, the notion of propagation length is introduced, which is defined as the impact length of the current frame on future frames. This length is estimated via offline experiments and used to propose two novel methods to predict the impact of the coding distortion of the current frame on future frames from previous frames of similar coding properties. Third, we apply these two methods to adaptively determine the Lagrangian multiplier and its corresponding QP for each frame in the LD configuration of HEVC. Experimental results show that, in comparison to the default LD HEVC, the first method can achieve, on average, BD-rate savings of 5.0% and 4.9% in low-delay-P (LDP) and low-delay-B (LDB) configurations, respectively, and the second can achieve, on average, BD-rate savings of 4.9% and 4.9% in the LDP and LDB configurations, respectively, all with insignificant increases in encoding time.     

Analysis, design, and resonant current control for a 1-MHzhigh-power-factor rectifier

Fundamental frequency analysis is used to examine the LCC series-parallel loaded resonant converter with a capacitive output filter when operating as a high-power-factor rectifier. Optimum values are identified for the Q factor and voltage conversion ratio such that zero-voltage switching is just maintained, while minimizing the resonant circuit conduction losses. A simple resonant current control loop is shown to provide an effective mechanism of active control, achieving a high-quality input current waveform over a wide load range. Results are presented from a 1 MHz 160 W prototype     

Adaptive off-time control for variable-frequency, soft-switchedflyback converter at light loads

The soft switching of a flyback converter can be achieved by operating the circuit in the critical conduction mode. However, the critical-mode operation at light loads cannot be maintained due to a very high switching frequency and the loss of the output voltage regulation. A control which regulates the output down to the zero load and maintains soft switching at light loads is proposed. The proposed control scheme was implemented in the 380 V/19 V, 65 W flyback DC/DC converter     

Simple approximate formulas for input resistance, bandwidth, andefficiency of a resonant rectangular patch

Simple approximate formulas for the input resistance, bandwidth, and radiation efficiency of a resonant rectangular microstrip patch are derived. These formulas become increasingly accurate as the substrate thickness decreases. Because the formulas are derived from approximations of a rigorous Sommerfeld solution, they provide insight into the effect of the substrate parameters on the patch properties, in addition to providing approximate design equations     

Joint power allocation and beamforming with users selection for cognitive radio networks via discrete stochastic optimization

Cognitive radio is a promising technique to dynamic utilize the spectrum resource and improve spectrum efficiency. In this paper, we study the problem of mutual interference cancellation among secondary users (SUs) and interference control to primary users (PUs) in spectrum sharing underlay cognitive radio networks. Multiple antennas are used at the secondary base station to form multiple beams towards individual SUs, and a set of SUs are selected to adapt to the beams. For the interference control to PUs, we study power allocation among SUs to guarantee the interference to PUs below a tolerable level while maximizing SUs?? QoS. Based on these conditions, the problem of joint power allocation and beamforming with SUs selection is studied. Specifically, we emphasize on the condition of imperfect channel sensing due to hardware limitation, short sensing time and network connectivity issues, which means that only the noisy estimate of channel information for SUs can be obtained. We formulate the optimization problem to maximize the sum rate as a discrete stochastic optimization problem, then an efficient algorithm based on a discrete stochastic optimization method is proposed to solve the joint power allocation and beamforming with SUs selection problem. We verify that the proposed algorithm has fast convergence rate, low computation complexity and good tracking capability in time-varying radio environment. Finally, extensive simulation results are presented to demonstrate the performance of the proposed scheme.     

Modeling, analysis and design of resonant free power distribution network for modern microprocessor systems

This paper presents design-oriented analysis of the power distribution network (PDN) for high performance microprocessor systems to realize the resonant free, close to flat output impedance magnitude over a wide frequency range. Based on the frequency domain analysis, closed form design equations and parametric curves relating the system parameters are derived. A systematic method of estimating the optimum parameters of the decoupling capacitors used in a single or multistage PDN is described to realize the output impedance of specified magnitude for the noise-free, and critically damped voltage at the microprocessor core. The design examples and simulation results are discussed to demonstrate the application of the design equations and parametric curves.     

Circuit reliability simulator for interconnect, via, and contactelectromigration

A model for predicting Al interconnect and intermetallic contact/via electromigration time-to-failure under arbitrary current waveform is incorporated in a circuit electromigration reliability simulator. The simulator can (1) generate layout advisory for width and length of each interconnect, and the number of contacts and vias at each node in a circuit, and (2) estimate the overall circuit electromigration failure rate and/or cumulative percent failure as functions of time, temperature, voltage, frequency, and previous stress (e.g., burn-in)     

Optimization models for selection of programs, considering cost andreliability

The authors present two optimization models for decision support tools for selecting available programs in the market. Information on reliability and cost of the available programs are considered as basic criteria for the selection. These models apply to software packages that consist of several programs where each, upon execution, performs a different function as required by the user. The objective is to maximize the average reliability of the software package, considering the tradeoff between reliability and cost of the programs. In model one, redundancy of the programs is not considered; thus, the authors select one program for each function. In model two, redundancy is considered: thus, the authors identify the optimal set of programs for each function. They begin with a discussion of the underlying concepts that rationalize the composition of the models     

Optimization procedure for the design of ultrafast, highlyefficient and selective resonant cavity enhanced Schottky photodiodes

An expression of quantum efficiency for high-speed resonant-cavity-enhanced (RCE) Schottky photodiodes is derived. This expression includes the structural and the physical parameters of the photodetector and takes into account the parameters of the metallic Schottky mirror and the wavelength dependence of the reflectivities. The metal layer thickness sets the maximum achievable quantum efficiency as it decays exponentially with it. The antireflection coating layer, on the other hand, determines the photodetector selectivity and the optimum absorption layer thickness that maximizes its quantum efficiency. An algorithm for the design and optimization of RCE Schottky photodetectors has been developed. Theoretical values of 647 GHz and 129 GHz were obtained, respectively, for the carrier-transit time limited 3-dB bandwidth and bandwidth-efficiency product for an RCE Schottky photodetector with a 0.02 μm gold layer