Image reconstruction/synthesis from nonuniform data and zero/threshold crossings

We address the problem of reconstructing functions from their nonuniform data and zero/threshold crossings. We introduce a deterministic process via the Gram-Schmidt orthonormalization procedure to reconstruct functions from their nonuniform data and zero/threshold crossings. This is achieved by first introducing the nonorthogonal basis functions in a chosen 2-D domain (e.g., for a band-limited signal, a possible choice is the 2-D Fourier domain of the image) that span the signal subspace of the nonuniform data. We then use the Gram-Schmidt procedure to construct a set of orthogonal basis functions that span the linear signal subspace defined by the nonorthogonal basis functions. Next, we project the N-dimensional measurement vector (N is the number of nonuniform data or threshold crossings) onto the newly constructed orthogonal basis functions. Finally, the function at any point can be reconstructed by projecting the representation with respect to the newly constructed orthonormal basis functions onto the reconstruction basis functions that span the signal subspace of the evenly spaced sampled data. The reconstructed signal gives the minimum mean square error estimate of the original signal. This procedure gives error-free reconstruction provided that the nonorthogonal basis functions that span the signal subspace of the nonuniform data form a complete set in the signal subspace of the original band-limited signal. We apply this algorithm to reconstruct functions from their unevenly spaced sampled data and zero crossings and also apply it to solve the problem of synthesis of a 2-D band-limited function with the prescribed level crossings

Evaluating indoor positioning systems in a shopping mall : the lessons learned from the IPIN 2018 competition

The Indoor Positioning and Indoor Navigation (IPIN) conference holds an annual competition in which indoor localization systems from different research groups worldwide are evaluated empirically. The objective of this competition is to establish a systematic evaluation methodology with rigorous metrics both for real-time (on-site) and post-processing (off-site) situations, in a realistic environment unfamiliar to the prototype developers. For the IPIN 2018 conference, this competition was held on September 22nd, 2018, in Atlantis, a large shopping mall in Nantes (France). Four competition tracks (two on-site and two off-site) were designed. They consisted of several 1 km routes traversing several floors of the mall. Along these paths, 180 points were topographically surveyed with a 10 cm accuracy, to serve as ground truth landmarks, combining theodolite measurements, differential global navigation satellite system (GNSS) and 3D scanner systems. 34 teams effectively competed. The accuracy score corresponds to the third quartile (75th percentile) of an error metric that combines the horizontal positioning error and the floor detection. The best results for the on-site tracks showed an accuracy score of 11.70 m (Track 1) and 5.50 m (Track 2), while the best results for the off-site tracks showed an accuracy score of 0.90 m (Track 3) and 1.30 m (Track 4). These results showed that it is possible to obtain high accuracy indoor positioning solutions in large, realistic environments using wearable light-weight sensors without deploying any beacon. This paper describes the organization work of the tracks, analyzes the methodology used to quantify the results, reviews the lessons learned from the competition and discusses its future

The IPIN 2019 Indoor Localisation Competition—Description and Results

IPIN 2019 Competition, sixth in a series of IPIN competitions, was held at the CNR Research Area of Pisa (IT), integrated into the program of the IPIN 2019 Conference. It included two on-site real-time Tracks and three off-site Tracks. The four Tracks presented in this paper were set in the same environment, made of two buildings close together for a total usable area of 1000 m 2 outdoors and and 6000 m 2 indoors over three floors, with a total path length exceeding 500 m. IPIN competitions, based on the EvAAL framework, have aimed at comparing the accuracy performance of personal positioning systems in fair and realistic conditions: past editions of the competition were carried in big conference settings, university campuses and a shopping mall. Positioning accuracy is computed while the person carrying the system under test walks at normal walking speed, uses lifts and goes up and down stairs or briefly stops at given points. Results presented here are a showcase of state-of-the-art systems tested side by side in real-world settings as part of the on-site real-time competition Tracks. Results for off-site Tracks allow a detailed and reproducible comparison of the most recent positioning and tracking algorithms in the same environment as the on-site Tracks

A BARE-DIE SIC-BASED ELECTRO-THERMALLY CO-DESIGNED WIRE-BONDLESS HIGH-FREQUENCY DC-DC CONVERTER

The current technological status of switch-mode power converters requires a paradigm shift to enable a substantial enhancement in power density. The emergence of wide-bandgap (WBG) devices such as Silicon Carbide (SiC) MOSFETs o↵ers the possibility to achieve high power-density by enabling higher switching frequency and higher temperature operation. This dissertation addresses the following shortcomings of conventional designs: 1) High values of commutation loop inductances and parasitic capacitances which prohibit fast, reliable and efficient switching performance, 2) inadequate thermal design capable of handling very high heat-fluxes (exceeding hundreds of W/cm2), which naturally stem from highly compact design and high allowable losses of the SiC devices, and 3) decoupled and sequential electrical and thermal designs, which leads to sub-optimal electro-thermal performance. As a solution to these challenges, this dissertation investigates two design strategies: 1) a novel switch module structure with low parasitics, and 2) a novel planar transformer structure with integrated leakage inductance and cooling system. Both approaches result in enhanced thermal performance, optimized through simultaneous electro-thermal co-design. A common key highlight of the proposed solutions is the high degree of integration realized by use of sub-components that integrate both electrical and thermal performance. This will save real estate by reducing component count and by lessening electrical and thermal burdens. In the first part of this dissertation, a detailed electrical characterization of a novel, wire-bondless, three-dimensional (3D), half-bridge switch module using bare-die SiC MOSFETs is presented. The switch assembly features the use of electro- thermally multi-functional components, simultaneously serving as bus-bars and heat sinks. A highly compact composition with embedded decoupling capacitors and gate driver components is realized with vertical loop structures for both power and gate drive circuits. Besides, the wire-bondless structure enables double-sided cooling, which significantly improves the thermal performance. 3D finite element analysis simulations and experiments demonstrate that the proposed switch module can achieve extremely low values of parasitic loop inductances (Lloop,power = 1.35 nH, Lloop,gate = 5.1 nH at a parasitic oscillation frequency of 100 MHz) as well as high thermal performance without entailing significant layout capacitances and resistances. The second part of this dissertation proposes an electro-thermal design optimization method of a high-frequency planar transformer with an integrated leakage inductance and thermal management system. Aiming at the use in a high-frequency (>500 kHz) dual-active-bridge (DAB) converter, an optimal leakage inductance selection process is explored based on highly accurate analyses of the DAB converter operation for maximizing the efficiency. Effect of design variables like the number of turns of the transformer and cooler height on the transformer’s electrical parameters such as leakage inductance, ac resistance and parasitic capacitance is further analyzed in detail. The dependence of converter efficiency on these parameters is estimated using realistic simulations and analyses, and potential trade-o↵s of the design are investigated. Thermal modeling is used to evaluate the thermal performance of different designs. Based on a combination of the analyses, optimal designs are identified, which simultaneously ensure good electrical and thermal performance. Finally, a compact DAB converter is designed based on the investigated components, operating at a switching frequency of 500 kHz. Robust gate-driver circuitry and auxiliary parts are also developed to tolerate such high switching frequency as well as high dv/dt. The optimal design processes, operation strategies and analytical models are validated through diverse experiments on 3.3 kW dc-dc converter operation. As a result of the investigations, the converter achieves zero-voltage-switching over various load conditions with satisfactory high-frequency waveforms and a peak efficiency of 98%. The converter’s operation at high power is validated through a designed loss-emulation test corresponding to 8.4 kW operation

Fully Integrated Hybrid Voltage Regulator for Low Voltage Applications

A novel hybrid regulator topology is proposed to alleviate the weaknesses of existing hybrid topologies. Contrary to the dominant existing practice, a switched-capacitor converter and a resistorless LDO operate in a parallel fashion to supply current and regulate the output voltage. The proposed topology targets a fully integrated regulator without using any inductors and resistors. The primary emphasis is on maximizing power efficiency while maintaining sufficient regulation capability (with ripple voltage less than 10% of the output voltage) and power density. The first implementation of the proposed topology operates in a single frequency mode. Simulation results in 45 nm technology demonstrate a power efficiency of approximately 85% at 100 mA load current with an input and output voltage of, respectively, 1.15 V and 0.5 V. The worst case transient response time is under 20ns when the load current varies from 65 mA to 130 mA. The worst case ripple is 22 mV while achieving a power density of 0.5 W/mm2. This single-frequency hybrid voltage regulator is useful (due to its fast and continuous response and high power efficiency) when the output load current is relatively constant at a certain nominal value. However, the performance is degraded when the load current varies significantly beyond the nominal current since the current provided by switched-capacitor converter is constant. The second implementation of the proposed hybrid regulator topology partially alleviates this issue by employing two different frequencies depending on the load current. This design is also implemented in 45 nm technology. It is demonstrated that the power efficiency is maintained within 60% to 80% even though the load current varies by more than 100 mA. The power density remains the same (0.5 W/mm2). The simulation results of the proposed topology are highly competitive with recent work on integrated voltage regulators

Suitable Combination of Direct Intensity Modulation and Spreading Sequence for LIDAR with Pulse Coding

In the coded pulse scanning light detection and ranging (LIDAR) system, the number of laser pulses used at a given measurement point changes depending on the modulation and the method of spreading used in optical code-division multiple access (OCDMA). The number of laser pulses determines the pulse width, output power, and duration of the pulse transmission of a measurement point. These parameters determine the maximum measurement distance of the LIDAR and the number of measurement points that can be employed per second. In this paper, we suggest possible combinations of modulation and spreading technology that can be used for OCDMA, evaluate their performance and characteristics, and study optimal combinations according to varying operating environments

Independent Biaxial Scanning Light Detection and Ranging System Based on Coded Laser Pulses without Idle Listening Time

The goal of light detection and ranging (LIDAR) systems is to achieve high-resolution three-dimensional distance images with high refresh rates and long distances. In scanning LIDAR systems, an idle listening time between pulse transmission and reception is a significant obstacle to accomplishing this goal. We apply intensity-modulated direct detection (IM/DD) optical code division multiple access (OCDMA) using nonreturn-to-zero on-off keying to eliminate the idle listening time in scanning LIDAR systems. The transmitter records time information while emitting a coded laser pulse in the measurement angle derived from the pixel information as the measurement direction. The receiver extracts and decodes the reflected laser pulses and estimates the distance to the target using time-of-flight until the pulse is received after being transmitted. Also, we rely on a series of pulses and eliminate alien pulses via several detection decision steps to enhance the robustness of the decision result. We built a prototype system and evaluated its performance by measuring black matte and white paper walls and assessing object detection by measuring a watering can in front of the black matte paper wall. This LIDAR system eliminated both shot and background noises in the reception process and measured greater distances with improvements in accuracy and precision

Outage probability analysis for DS-CDMA systems with call admission control scheme

In this letter, a more exact analysis scheme for outage probability is proposed for uplink of direct sequence code division multiple access (DS-CDMA) systems. In the previous works, the effect of call admission control (CAC) on signal to interference ratio (SIR) is considered to evaluate the performance of the outage probability for CDMA systems, however, the effect of CAC on system states is not accurately considered. In this letter, we first analyze the system states more exactly by taking the effect of CAC on CDMA system states into account. Then, the exact probability of the outage is derived according to the exact system states. The probability of the system states and the outage of the proposed approximation scheme are compared with the results of the traditional analysis schemes and the computer simulation. Compared with traditional analysis schemes, the numerical results of the proposed analysis scheme is more close to the computer simulation results. Copyright © 2006 The Institute of Electronics, Information and Communication Engineers.1

Indoor Positioning on Disparate Commercial Smartphones Using Wi-Fi Access Points Coverage Area

The applications of location-based services require precise location information of a user both indoors and outdoors. Global positioning system’s reduced accuracy for indoor environments necessitated the initiation of Indoor Positioning Systems (IPSs). However, the development of an IPS which can determine the user’s position with heterogeneous smartphones in the same fashion is a challenging problem. The performance of Wi-Fi fingerprinting-based IPSs is degraded by many factors including shadowing, absorption, and interference caused by obstacles, human mobility, and body loss. Moreover, the use of various smartphones and different orientations of the very same smartphone can limit its positioning accuracy as well. As Wi-Fi fingerprinting is based on Received Signal Strength (RSS) vector, it is prone to dynamic intrinsic limitations of radio propagation, including changes over time, and far away locations having similar RSS vector. This article presents a Wi-Fi fingerprinting approach that exploits Wi-Fi Access Points (APs) coverage area and does not utilize the RSS vector. Using the concepts of APs coverage area uniqueness and coverage area overlap, the proposed approach calculates the user’s current position with the help of APs’ intersection area. The experimental results demonstrate that the device dependency can be mitigated by making the fingerprinting database with the proposed approach. The experiments performed at a public place proves that positioning accuracy can also be increased because the proposed approach performs well in dynamic environments with human mobility. The impact of human body loss is studied as well