1.
Nopchinda, Dhecha, 1991
(författare)
mm-Wave Data Transmission and Measurement Techniques: A Holistic Approach
2019
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
The ever-increasing demand on data services places unprecedented technical requirements on networks capacity. With wireless systems having significant roles in broadband delivery, innovative approaches to their development are imperative. By leveraging new spectral resources available at millimeter-wave (mm-wave) frequencies, future systems can utilize new signal structures and new system architectures in order to achieve long-term sustainable solutions. This thesis proposes the holistic development of efficient and cost-effective techniques and systems which make high-speed data transmission at mm-wave feasible. In this paradigm, system designs, signal processing, and measurement techniques work toward a single goal; to achieve satisfactory system level key performance indicators (KPIs). Two intimately-related objectives are simultaneously addressed: the realization of efficient mm-wave data transmission and the development of measurement techniques to enable and assist the design and evaluation of mm-wave circuits. The standard approach to increase spectral efficiency is to increase the modulation order at the cost of higher transmission power. To improve upon this, a signal structure called spectrally efficient frequency division multiplexing (SEFDM) is utilized. SEFDM adds an additional dimension of continuously tunable spectral efficiency enhancement. Two new variants of SEFDM are implemented and experimentally demonstrated, where both variants are shown to outperform standard signals. A low-cost low-complexity mm-wave transmitter architecture is proposed and experimentally demonstrated. A simple phase retarder predistorter and a frequency multiplier are utilized to successfully generate spectrally efficient mm-wave signals while simultaneously mitigating various issues found in conventional mm-wave systems. A measurement technique to characterize circuits and components under antenna array mutual coupling effects is proposed and demonstrated. With minimal setup requirement, the technique effectively and conveniently maps prescribed transmission scenarios to the measurement environment and offers evaluations of the components in terms of relevant KPIs in addition to conventional metrics. Finally, a technique to estimate transmission and reflection coefficients is proposed and demonstrated. In one variant, the technique enables the coefficients to be estimated using wideband modulated signals, suitable for implementation in measurements performed under real usage scenarios. In another variant, the technique enhances the precision of noisy S-parameter measurements, suitable for characterizations of wideband mm-wave components.
2.
Lian, Mengke, et al.
(författare)
What Can Machine Learning Teach Us about Communications
2018
Ingår i: IEEE International Symposium on Information Theory - Proceedings. - 2157-8095. ; 15 January 2019
Konferensbidrag (refereegranskat) abstract
Rapid improvements in machine learning over the past decade are beginning to have far-reaching effects. For communications, engineers with limited domain expertise can now use off-the-shelf learning packages to design high-performance systems based on simulations. Prior to the current revolution in machine learning, the majority of communication engineers were quite aware that system parameters (such as filter coefficients) could be learned using stochastic gradient descent. It was not at all clear, however, that more complicated parts of the system architecture could be learned as well. In this paper, we discuss the application of machine-learning techniques to two communications problems and focus on what can be learned from the resulting systems. We were pleasantly surprised that the observed gains in one example have a simple explanation that only became clear in hindsight. In essence, deep learning discovered a simple and effective strategy that had not been considered earlier.
3.
del Aguila Pla, Pol, 1990-
(författare)
Inverse problems in signal processing : Functional optimization, parameter estimation and machine learning
2019
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Inverse problems arise in any scientific endeavor. Indeed, it is seldom the case that our senses or basic instruments, i.e., the data, provide the answer we seek. It is only by using our understanding of how the world has generated the data, i.e., a model, that we can hope to infer what the data imply. Solving an inverse problem is, simply put, using a model to retrieve the information we seek from the data.In signal processing, systems are engineered to generate, process, or transmit signals, i.e., indexed data, in order to achieve some goal. The goal of a specific system could be to use an observed signal and its model to solve an inverse problem. However, the goal could also be to generate a signal so that it reveals a parameter to investigation by inverse problems. Inverse problems and signal processing overlap substantially, and rely on the same set of concepts and tools. This thesis lies at the intersection between them, and presents results in modeling, optimization, statistics, machine learning, biomedical imaging and automatic control.The novel scientific content of this thesis is contained in its seven composing publications, which are reproduced in Part II. In five of these, which are mostly motivated by a biomedical imaging application, a set of related optimization and machine learning approaches to source localization under diffusion and convolutional coding models are presented. These are included in Publications A, B, E, F and G, which also include contributions to the modeling and simulation of a specific family of image-based immunoassays. Publication C presents the analysis of a system for clock synchronization between two nodes connected by a channel, which is a problem of utmost relevance in automatic control. The system exploits a specific node design to generate a signal that enables the estimation of the synchronization parameters. In the analysis, substantial contributions to the identifiability of sawtooth signal models under different conditions are made. Finally, Publication D brings to light and proves results that have been largely overlooked by the signal processing community and characterize the information that quantized linear models contain about their location and scale parameters.
4.
Kersten, Anton, 1991, et al.
(författare)
Battery Loss and Stress Mitigation in a Cascaded H-Bridge Multilevel Inverter for Vehicle Traction Applications by Filter Capacitors
2019
Ingår i: IEEE Transactions on Transportation Electrification. - 2332-7782. ; 5:3, s. 659-671
Tidskriftsartikel (refereegranskat) abstract
In this paper, two types of filter capacitors of varying capacity, were connected to the battery packs of a cascaded H-Bridge single-star multilevel vehicle traction inverter, and their influence on the battery losses has been analyzed. The battery and capacitor simulation models used are experimentally verified in a down-scaled system. Different capacitor configurations were simulated for four drive cycle scenarios to determine the potentials for the mitigation of current pulse stresses and battery loss reduction with respect to the added weight. By adding capacitors corresponding to a weight of 4% of the initial battery storage, the peak current is reduced by 5%-20%, depending on the operating point from DC to a few kHz, and the battery losses are reduced by 10%. In comparison, it is demonstrated that adding supercapacitors is more beneficial for lower output frequencies, while adding electrolytic capacitors is better for higher output frequencies. Furthermore, the low-order voltage harmonics of the DC-rails between the converter and battery were reduced by 10%-30% for frequencies above 9 kHz, which decreases the potential of electromagnetic disturbances. In addition, during cold battery temperatures, when it is very important to avoid heavy cyclings, the loss reduction using the capacitors was 2.5 times larger than for nominal temperature.
5.
Kersten, Anton, 1991, et al.
(författare)
Fault Detection and Localization for Limp Home Functionality of Three-Level NPC Inverters with Connected Neutral Point for Electric Vehicles
2019
Ingår i: IEEE Transactions on Transportation Electrification. - 2332-7782. ; 5:2, s. 416-432
Tidskriftsartikel (refereegranskat) abstract
This paper deals with the detection of single battery or inverter switch faults during operation of a common and an active three-level neutral-point-clamped (NPC) inverter with a connected neutral point. Here, the main focus lies on the detection and localization of open-circuit faults of the inverter's switches. Therefore, a fault detection algorithm, using a current estimator, and two fault localization algorithms, a pulse pattern injection principle and an online adaption of the space vector modulation (SVM), are investigated and verified through simulations and experiments. Also, investigated is how the powertrain can be operated under a fault condition, so that the vehicle can drive with a limited maximum power using an adapted SVM, referred to as "limp home" mode, to the next service station. It is shown, that an active NPC inverter can cope with any single short or open-circuit fault of the inverter's switches without bringing the vehicle to standstill, whereas a generic NPC inverter loses controllability if an open-circuit fault at an inner switch occurs. Furthermore, both inverter types are able to be operated just with half of the dc-link voltage in case of a failure in one part of the battery.
6.
Theliander, Oskar, et al.
(författare)
LiFePO4 Battery Modeling and Drive Cycle Loss Evaluation in Cascaded H-Bridge Inverters for Vehicles
2019
Ingår i: ITEC 2019 - 2019 IEEE Transportation Electrification Conference and Expo. ; June 2019, s. 1-7
Konferensbidrag (refereegranskat) abstract
This paper deals with the modeling and parameterization of LiFeP04batteries when used in cascaded H-bridge multilevel inverter drive systems. Since the battery packs are intermittently conducting the motor currents, the battery cells are stressed with a dynamic current waveform containing a substantial amount of low order harmonic components in the range of a couple of kHz. Different battery models like a pure resistive or different RC networks are considered, to determine the battery losses. Measurements of the voltage drop for a pulsed current of variable frequency and magnitude are done to be able to determine the model parameters. The models are then verified against measurements on a battery pack placed in a small scale multilevel inverter operated at 6 different operating point that are representative for the operation of an electrified vehicle. It is shown that the dynamic model agrees very well with the measurements for all operating points analyzed with a maximum deviation of 4 %. The results are also compared with the commonly used resistive model which overestimates the losses with typically around 20 % for the evaluated points. Simulations of 4 full drive cycles are performed where it is stated that the resistive model always shows about 20 % more losses compared to the 3 time constant model.
7.
Pérez-Penichet, Carlos, et al.
(författare)
Poster abstract : Augmenting WSNs with interoperable 802.15.4 sensor tags
2017
Ingår i: SenSys 2017 - Proceedings of the 15th ACM Conference on Embedded Networked Sensor Systems. - New York, NY, USA : Association for Computing Machinery, Inc. - 9781450354592
Konferensbidrag (refereegranskat) abstract
The sensing capabilities of most sensor networks are fixed at the time of deployment. Adding new sensing capabilities to such networks is a costly and cumbersome process. We present Passive Sensor Tags, battery-free sensing devices that could be used to extend the sensing capabilities of an existing network. Sensor tags feature our new 802.15.4 receiver design which is suitable for micro-power operation, making battery-free tags possible. Because our tags can both transmit and receive 802.15.4 frames there is no need for any modification to the deployed hardware. We present preliminary measurements of transmission and reception range.
8.
Nielsen, Stig Anton, 1981
(författare)
Propositional architecture and the paradox of prediction
2015
Ingår i: Archidoct Vol. 4. - 2309-0103. ; 4, s. 72-85
Tidskriftsartikel (refereegranskat) abstract
What if we could predict trends, rising phenomena and future necessity in our build environment? If we could trace behaviors and forecast the needs for the future? If we had a tool for proposing architecture, that was able to point out potentialities and suggest additions, subtractions and modifications.If Architects had a tool to predict future demands, modification of the build environment could meet the changing behaviors and emerging phenomena in society. Research on existing building stock is reviewed in a context where prediction on complex indeterminate environments is possible. And an entirely new type of architectural tool is proposed, an algorithm for prediction.The algorithm, capable of making prediction in unstructured environments, is presented, and basis and idea of the algorithm is described in detail. The discussion focus on possible applications for this new tool, and the paradox of prediction is debated. Finally, improvements to the computational system are proposed.
9.
Jang, Jeong Keun, et al.
(författare)
Area-efficient scheduling scheme based FFT processor for various OFDM systems
2018
Ingår i: 2018 IEEE ASIA PACIFIC CONFERENCE ON CIRCUITS AND SYSTEMS (APCCAS 2018). - : IEEE. - 9781538682401 ; , s. 338-341
Konferensbidrag (övrigt vetenskapligt/konstnärligt) abstract
This paper presents an area-efficient fast Fouriertransform (FFT) processor for orthogonal frequency-division multiplexing systems based on multi-path delay commutator architecture. This paper proposes a data scheduling scheme to reduce the number of complex constant multipliers. The proposed mixed-radix multi-path delay commutator FFT processor can support 128-, 256-, and 512-point FFT sizes. The proposed processor was synthesized using the Samsung 65-nm CMOS standard cell library. The proposed processor with eight parallel data paths can achieve a high throughput rate of up to 2.64 GSample/s at 330 MHz.
10.
Cheng, Hei Victor
(författare)
Aspects of Power Allocation in Massive MIMO
2016
Licentiatavhandling (övrigt vetenskapligt/konstnärligt) abstract
The past decades have seen a rapid growth of mobile data trac, both in terms of connected devices and data rate. To satisfy the ever growing data trac demand in wireless communication systems, the current cellular systems have to be redesigned to increase both spectral eciency and energy eciency. Massive MIMO (Multiple-Input-Multiple-Output) is one solution that satisfy both requirements. In massive MIMO systems, hundreds of antennas are employed at the base station to provide service to many users at the same time and frequency. This enables the system to serve the users with uniformly good quality of service simultaneously, with low-cost hardware and without using extra bandwidth and energy. To achieve this, proper resource allocation is needed. Among the available resources, transmit power is one of the most important degree of freedom to control the spectral eciency and energy eciency. Due to the use of excessive number of antennas and low-end hardware at the base station, new aspects of power allocation compared to current systems arises. In the rst part of the thesis, a new uplink power allocation schemes that based on long term channel statistics is proposed. Since quality of the channel estimates is crucial in massive MIMO, in addition to data power allocation, joint power allocation that includes the pilot power as additional variable should be considered. Therefore a new framework for power allocation that matches practical systems is developed, as the methods developed in the literature cannot be applied directly to massive MIMO systems. Simulation results conrm the advantages brought by the the proposed new framework. In the second part of the thesis, we investigate the eects of using low-end ampliers at the base stations. The non-linear behavior of power consumption in these ampliers changes the power consumption model at the base station, thereby changes the power allocation. Two dierent scenarios are investigated and both results show that a certain number of antennas can be turned o in low load scenarios.
