The International Congress on Electrocardiology
will be held in Lund in 2010, June 3-5, at Akademiska Föreningen. The Department of Electrical and Information Technology is one of the responsible for organizing the congress, and Prof. Leif Sörnmo is the conference president.
Licentiat seminar Kristin Persson
On Friday February 5, 2010, 10.15am in E:2311, Kristin Persson will present her Licentiate thesis "Retrieval of equivalent currents by the use of an integral representation and the extinction theorem – radome applications". Professor Ari Sihvola, of Helsinki University of Technology, Finland, will be the thesis reviewer.
Master Thesis Presentation
Mosse Rodbay presents his Master Thesis "Investigation of Anonymous Communications" Friday 27/11 2009 at 13:15 in E:3139.
Anonymous communications on the Web is a grey zone which provides means of protection, allowing the freedom of speech and fighting regimes that force great censorship on its people. The major trend today with increased legislation, regulation and supervision are all becoming a threat to the freedom that is the very core of the Internet. This has sparked an increased demand for anonymity. This master thesis will investigate logical overlay networks used for secure communications.
These will be evaluated and discussed. Threats like traffic analysis will be discussed and the performance will be evaluated. Lastly the limits of these networks will be discussed in order allow users of these systems to gain insight of their privacy.
Licentiate Seminar Vanja Plicanic Samuelsson
On Wed November 18, 10.15am in E:2311, Vanja Plicanic will present her Licentiate thesis "Performance Characterization of Compact Multiple Antenna Terminals". Dr Jon Wallace of Jacobs University Bremen, Germany will be the thesis reviewer.
IEEE AESS Distinguished Lecture by Paul E. Gartz. September 16, 10.15 in E:2311.
Title: The New Role of Systems-of-Systems and Professional Societies in Advancing Scandinavia and Global Business and Research.
Digital and IT technologies have re-carved the way the world works and have penetrated almost every product made and service offered. The more recent globalization of the use of the internet and web have further enabled these products and services to link and interoperate with one another on a global scale.
The terrorist incidents in the US on 2001-09-11 (so called “911”) and the potential for “cyber-terrorism” have also had a profound effect on the need for better interoperability of intelligence information and coordinated planning and response that links domestic agencies with military ones.
These needs and realities of increased interoperability of “systems”, humans and organizations has given rise to a larger scale, higher level concept to assure all the interoperability’s are conceived and implemented in more optimal and even human-friendly manners called “Systems-of-Systems” or SoSs. As in any higher level system, the SoSs set a new context, framework and set of requirements and architectural standards for all the “smaller” products (systems also) and services (systems also). They will also surface new research topics, new business opportunities across all levels of systems and even governmental opportunities to set policies to take advantage of the SoS concepts even if not called that. A good example is the current healthcare reform debate in the US.
This talk will introduce the SoS concepts, show some examples and discuss the unique role tha professional, non-profit organizations and human networks can provide.
About the Author
IEEE: In IEEE, Paul has presidency positions in two IEEE business units called “IEEE Organizational Units”. He is Past President of the Aerospace and Electronic Systems Society (AESS) and current President of the IEEE Systems Council. Systems Council address large-scale, integrated, systems-of-systems (SoSs) of “national or global significance”. He is currently expanding Systems Council into an “integrated team of IEEE and other societies” for this purpose. Earlier he re-organized AESS to expand globally and created new Directors for each major population and economic center in the world and chartered them to address the needs of their regions. They will be offered dual positions in Systems Council for the same purpose.
Boeing: In Boeing, Paul’s career spans defense, commercial and civil large-scale systems, more than half of which were world firsts. He is currently overall Systems-of-Systems Architect for Boeing’s “GoldCare”, a new, e-based global business for airplane maintenance. Previously, he, was Chief Architect for Boeing’s new GEOSS venture, Head Airplane Architect for “Connexion-by-Boeing”, a new, global, satellite-based, wide-band SoS business and earlier yet led Boeing’s 1st commercial systems engineering groups on programs, advanced theory, new methods and tools and technically led development teams for all modern, major commercial transport programs.
Lund Circuit Design Workshop
Lund Circuit Design Workshop
Theme: Circuit Design for the Wireless Future
September 9-10, 2009, at Grand Hotel and Faculty of Engineering, Lund University, Lund, Sweden.
Master Thesis presentation: Verification of Impedance Relations for Antennas using Experiment and Theory
Said Abushamleh presents his Master's Thesis. Mats Gustafsson has been the supervisor.
Time and place:
Friday 12 June at 1.15 PM in E:2311.
In this master thesis, an overview of sum rules for the antenna input impedance and admittance is presented. The sum rules relate the radiation resistance and conductance integrated over a very wide range of frequencies with the low frequency inductance and capacitance. They are particularly useful for small antennas that utilize their first resonance. By applying the concept of least squares and the norm equations on the admittance the low frequency capacitance and inductance are estimated. Numerical simulation was used to determine the antenna input impedance over a wide range of frequencies for dipole, loop, monopole, spherical helix, and butterfly antennas. Finally, measurements for dipole, loop, patch, butterfly, log-periodic, monopole, UWB, PIFA, PIFA with ceramic feeder, and a wave guide antenna were performed to measure the antenna input impedance over a wide range of frequencies and to estimate the low-frequency capacitance and inductance. The numerical simulations and the measurements show good agreement with the sum rules.
Licentiate seminar, Fredrik Lindqvist
Title: Estimation of Line Properties in the Copper Access Network
Date and Time: 2009-06-10, at 10:15
Place: Lecture hall E:2311 (Orangeriet) at the department of Electrical and Information Technology, Ole Römers väg 3, Lund University, Faculty of Engineering LTH
Reviewer: Dr. Bastiaan M. van den Heuvel, TNO Information and Communication Technology, Delft, Holland
F. Lindqvist: Estimation of Line Properties in the Copper Access Network ISSN 1654-790X, 2009.
Abstract: The copper access-network operators face the challenge of developing and maintaining cost-effective digital subscriber line (DSL) services that are competitive to other broadband access technologies. The way forward is dictated by the demand of ever increasing data rates on the twisted-pair copper lines. This forces a deployment of the DSL transceivers in cabinets closer to the customers with a joint expansion of the accompanying optical-fiber backhaul network. The equipment of the next generation copper network is therefore becoming more scattered and geographically distributed, which often leads to increased maintenance for the operator. Another challenge for the operators is to maintain high quality of service even when the signal-to-noise-ratio margin is reduced in favor of higher bit-rates, required by new services such as IP-TV and high-definition TV (HD-TV). Moreover, the emerging multi-user techniques for increasing the total throughput in the copper network utilize spectrum management, which relies on accurate information of the usually unknown crosstalk channels in the cable binders.
What these challenges have in common is the need of an efficient tool for estimating the properties and the states of the transmission lines. A viable solution is to use the already installed DSL transceivers for line qualification and monitoring, combined with rapid fault detection and localization, in order to prevent unnecessary and costly manual intervention.
This thesis addresses estimation of various kinds of line properties based on one-port or two-port measurements. For the purpose of line qualification and fault detection, the focus is on: low-order and causal cable modeling (Paper I), estimation of the characteristic impedance (Paper II), detection and localization of load coils (Paper III), and estimation of line topology (Paper IV). For the application of dynamic spectrum management (DSM), the focus is on: estimation of the crosstalk channels (Paper V) and the impact of estimation errors on the DSM performance (Paper VI). Finally, estimation of the echo transfer function for echo cancellation is addressed (Paper VII).
Wireless seminar: Should Coded Modulation Be Based on Nyquist Pulses? The Shannon Capacity Answer
Should Coded Modulation Be Based on Nyquist Pulses? The Shannon Capacity Answer
by John B Anderson, Electrical and Information Technology, LTH
Time and place:
Tuesday, 9 June 2009, at 3.15 PM in E:3139.
Most coded modulations are based on linear modulation of orthogonal (Nyquist) pulses. Is this a good idea? Careful calculation of capacity is one way to look at this question. There are in fact two answers: When the signaling carries few bits/Hz-s (less than 2), the pulse shape does not matter much. When many bits/Hz-s are carried, as usual in coded modulation, the pulse should not be Nyquist. Faster than Nyquist (FTN) signaling is one way to achieve capacity. In fact, binary-alphabet FTN can have higher capacity than any scheme based on Nyquist linear modulation.
Seminar: Stochastic Routing for Delay Tolerant Networks
Time/place: June 4 2009, at 1.15 PM in E:2311.
IEEE Distinguished Lecturer Prof. Zygmunt J. Haas, Cornell University, Ithaca, NY, U.S.A
ABSTRACT: Broadcasting is a basic network operation, where a message is sent to all the nodes on a particular subnet. Many routing protocols are based on some variant of broadcasting. In fact, when the topology is unknown or constantly changing and on-demand routing is employed, such as is often the case in mobile ad hoc networks, broadcasting is the only approach for route discovery. Broadcasting is often implemented using flooding. Of course, the main disadvantage of flooding is its ineffective use of the network resources; the basic flooding technique “illuminates” every link in both directions, so that every node receives the communication the number of times equal to the number of its neighbors. Over the years, other techniques have been proposed to implement the broadcasting operation. For example, gossiping is one such a technique, where each node resends the message with some probability. In fact, flooding is a limiting case of gossiping, where the retransmission probability equals 1. Various other stochastic techniques have been proposed and optimized to implement efficient broadcasting, multicasting, and any casting. In this talk, we discuss the wealth of research in the area of stochastic routing. Especially, we concentrate on the use of stochastic routing as it applies to Delay Tolerant Networks (DTNs). DTNs are useful for applications with lenient requirements on message latency. Stochastic routing is especially well suited for Mobile DTNs. We demonstrate the operation of some of the stochastic routing schemes and discuss example applications. Furthermore, we compare the performance of the various stochastic routing techniques under various assumptions of network conditions.
Iqbal Hussain presents his Master's Thesis presentation "Rateless Coding for OFDM-Based Wireless Communications Systems". The work has been perfomed in cooperation with Lars Rasmussen and Mikael Skoglund at S3, KTH.
Time and place:
On Friday the 29th 15.15 in E2311
Performance of broadband wireless communication networks is limited by available resources such as frequency bandwidth and transmission power. Also, the time-varying features of wireless communication channels adversely affect performance. Transmission schemes, adapting to instantaneous channel characteristics can significantly improve performance. The block-fading channel is a good model for OFDM-based wireless communications systems in which the fading occurs in block wise manner. Raptor code is new emerging rateless code which has shown amazing performance over variety of channels. There is a constraint on the interleaving depth of OFDM-based system due to delay and maximum packet size. This non-ideal interleaving affects the maximum achievable diversity from the channel. We investigated the effect of correlation between fading blocks, which relates to the limited interleaving possible between carriers in an OFDM system, based on Raptor code. We investigated the performance of the Raptor code over correlated slowly fading channels and compared it with half rate standard (3,6) regular LDPC code, and to the ARQ systems using punctured LDPC codes for short block length. We also compared the performance of the Raptor code to the standard (3,6) regular LDPC code over Binary Erasure channel, Additive White Gaussian Noise channel, and fast fading Rayleigh chanel for short block length. Enormous simulations are performed to get insight for future reasearch.
Master Thesis presentation: Researching and developing a prototype logging tool for embedded devices
Gustaf Lundh presents his Master Thesis "Researching and developing a prototype logging tool for embedded devices".
Time and place:
Wednesday, May 27th at 1.15 PM in E3139
Since the complexity of mobile devices increases at a day-to-day basis, the debugging and log information becomes more complex and proportionally more important for the overall quality of the final consumer product. With the increased complexity of today’s devices, the task of evaluating real-time logging results becomes more time consuming and ineffective every day.
As the software of the handset increases in size, number of features, complexity and functionality; more and more logging-information is available to the tester and the developer for evaluation and analysis. To keep the developing process from overflowing in logging-information, an intuitive log tool-support is needed, adapted to the needs of the organization.
A study will be done in order to evaluate how relevant log-information is triggered, found and reviewed during a regular testing and development process. This study will evaluate and research the possibilities to enhance the methods of working with a large flow of information and find suited methods of presenting the continuous flow of text data.
This master thesis is consequently a study of existing methods and tools, for presentation of logging information and communication with the mobile device. In this thesis, research will be done towards methods of extracting and presenting data in a new and improved way. Emphasis will be put on making the handset log reviewing process easier and more productive. E.g. focus will be on the cognitive areas of information finding in the large amounts of available information. Some additional focus will be put on the communication with the mobile device, ergo the execution of routines that triggers the important log-information.
Implementation wise, a basic prototype (e.g. demonstrator) will be developed to showcase the suggested changes. This tool will also allow the testers and developers to evaluate the changes in the user interface. The result of this evaluation will be compiled, presented and compared to the previous evaluation made about the already existing tool.
As a conclusion; the main focus areas of the thesis will be on the improved design suggestions and thereby partly the implementation of the suggested changes (the demonstrator).
The research and development will take place on site at Sony Ericsson Mobile Communications AB (FGO Local Communication) in Lund. This study will provide a base for a new in-house developed logging tool, which will increase efficiency and decrease time consumption for analyzing logs within the software development organization.
Master Thesis presentation: A high-speed Digitally Controlled DCDC Converter for Mobile Phone Applications
Zhang Ruiyi and Jianfeng Cai will present their Master Thesis "A high-speed Digitally Controlled DCDC Converter for Mobile Phone Applications". The project was conducted at Ericsson/Research in Lund.
Time and place:
Tuesday May 26th at 10:15 in 2311 (Orangeriet).
The DC/DC converter has become a standard component in power management modules of mobile phone systems. In active mode the DC/DC converter provides various output for different functional units. For example, step-up converters are used to generate a higher voltages to drive backlight white LED or RGB LED and memory works under a lower voltage, which is generated by a step-down converter.When the mobile phone is switched to standby mode, the power dissipation caused by leakage current can not be neglected. Supply voltage is a variable that can be set to a low level in order to dramatically decrease leakage current. This thesis explores DC/DC converter design techniques, a DC/DC converter for low power design is presented as a possible application.
The primary design challenges for low voltage DC/DC converters are summarized.Theory and loss analysis for a conventional buck converter is presented. A high speed PWM generator is described with specifications requirements imposed by full integration. To design a converter with efficiency as high as possible, it is necessary to optimize all parameters which include switching frequency selection, switching transistor sizing and LC implementation. Bonding wire and nonlinear capacitor such as MOSFET gate capacitors are used to replace the traditional onchipinductor and capacitor due to Q factor and capacitor size consideration.
Simulation results are reported on the prototype DC/DC converter which successfully demonstrate the theoretical analysis and circuit design. To evaluate the complete system, linearity, efficiency characteristic and output voltage property are fully simulated. The focus throughout is on loss analysis under different switching frequency trying to find the relationship between loss components and frequency.Comparisons with other architectures for low power applications are presented.
Master Thesis presentation: Developing a Capacitive Biosensor Towards an Embedded System
Mattias Jönsson presents his Master's Thesis "Developing a Capacitive Biosensor Towards an Embedded System".
Time and place:
Thursday, May 28, at 10.15 in E:3139.
The work has been a cooperation between
- Dept. Electrical and Information Technology
- Dept. of Biotechnology, and
- Nohau, http://www.nohau.se/
Talk by Eberhart Fetz
Professor Eberhard Fetz will visit the Neuronano Research Center and give a talk which should be of great interest. Already 40 years ago in a couple of pioneering studies published in Science Fetz analysed the relationship between behaviour and the activity in single neurones during learning. Over the years he has contributed greatly to the understanding of how the nervous system encodes information and how it controls movements. Still very much at the forefront of these research fields he focuses on the neural control of prostheses and the latest technological developments in brain-computer interfaces.Check out the link below and don't miss this opportunity!
Monday May 25th, 15:00-16:30 - NRC Seminar
Prof. Eberhard E. Fetz, University of Washington
Applications of recurrent brain-computer interfaces
Segerfalk Lecture Hall, BMC A-House
Mingle 15:00-15:30, Lecture 15:30-16:30
PhD thesis defence Ali Hamidian
Date: 2009-05-20, at 10:15
Place: Lecture hall E:1406 at the department of Electrical and Information Technology, Ole Römers väg 3, Lund University Faculty of Engineering
Opponent: Professor Khaldoun Al Agha. Paris-Sud University, France
Supporting Internet Access and Quality of Service in Distributed Wireless Ad Hoc Networks
ISSN 1654-790X, 2009.
Abstract: In this era of wireless hysteria, with continuous technological advances in wireless communication and new wireless technologies becoming standardized at a fast rate, we can expect an increased interest for wireless networks, such as ad hoc and mesh networks. These networks operate in a distributed manner, independent of any centralized device. In order to realize the practical benefits of ad hoc networks, two challenges (among others) need to be considered: distributed QoS guarantees and multi-hop Internet access. In this thesis we present conceivable solutions to both of these problems. An autonomous, stand-alone ad hoc network is useful in many cases, such as search and rescue operations and meetings where participants wish to quickly share information. However, an ad hoc network connected to the Internet is even more desirable. This is because Internet plays an important role in the daily life of many people by offering a broad range of services. In this thesis we present AODV+, which is our solution to achieve this network interconnection between a wireless ad hoc network and the wired Internet. Providing QoS in distributed wireless networks is another challenging, but yet important, task mainly because there is no central device controlling the medium access. In this thesis we propose EDCA with Resource Reservation (EDCA/RR), which is a fully distributed MAC scheme that provides QoS guarantees by allowing applications with strict QoS requirements to reserve transmission time for contention-free medium access. Our scheme is compatible with existing standards and provides both parameterized and prioritized QoS. In addition, we present the Distributed Deterministic Channel Access (DDCA) scheme, which is a multi-hop extension of EDCA/RR and can be used in wireless mesh networks. Finally, we have complemented our simulation studies with real-world ad hoc and mesh network experiments. With the experience from these experiments, we obtained a clear insight into the limitations of wireless channels. We could conclude that a wise design of the network architecture that limits the number of consecutive wireless hops may result in a wireless mesh network that is able to satisfy users? needs. Moreover, by using QoS mechanisms like EDCA/RR or DDCA we are able to provide different priorities to traffic flows and reserve resources for the most time-critical applications.
Master Thesis Presentation: Implementing a free of charge system for handling recommendations on a mobile device
Mikael Halén presents his master thesis Wednesday May 20th at 15.15 in E:2347a.
Recommendation systems that exist today put little value in one single per-son’s thoughts. Instead their systems are based on that great numbers put in their recommendations, making one alternative stand out. However, the value of all these users weigh lightly compared to one single close friends recommendation.
This master’s thesis focuses on building a free of charge system for a mobile device that shares and receives recommendations that are high in value. Two applications have been built, one implementing using JavaME and the other using Symbian. The work has taken place at The Astonishing Tribe (TAT) and has taken use of their graphics engine Cascades.
Master Thesis presentation: Improved Receivers for Intersymbol Interference Channels
Behrooz Kamary Aliabadi presents his Master Thesis "Improved Receivers for Intersymbol Interference Channels". Location and time: E:3139 at 15.15. Abstract: The project studies efficient Viterbi receivers for decoding intersymbol interference (ISI) that has very narrow bandwidth. The focus is on algorithms with reduced computation. Several schemes are investigated. One breaks the data state into two parts, corresponding to the high energy ISI taps and the long low-energy tail. This breakdown is accomplished by converting the incoming channel data to a minimum phase model. The M-algorithm is applied on top of this technique. By combining these three ideas, a receiver of very low complexity is created.
Seminar: Multi-scale topics of electromagnetic research at NLR
Welcome to a seminar by Harmen Schippers! Title: Multi-scale topics of electromagnetic research at NLR Time and place: Friday May 15, 14.15, E:2311 (Orangeriet) Harmen Schippers is with the Dutch National Aerospace Laboratory (NLR), which is an independent technological institute, that carries out applied research on behalf of the aviation and space sectors. NLR performs research to develop new technologies for aviation and space travel, not only from a scientific perspective, but also for the application of this research in industrial and governmental sectors. NLR employs a staff of about 750 people. NLR supports Dutch government policy, assists the Dutch military and uses its own research to enhance the innovative capacity of private businesses. NLR is a non-profit organization that carries out market-oriented and socially-relevant studies.. Abstract: NLR’ Avionics department is involved in projects for development of an advanced conformal airborne antenna for satellite communication, and for development of magnetic radar absorbing structures. Both research projects involve multi-scale topics. The advanced conformal antenna consists of an array of stacked-patch antenna elements. The modelling of a single antenna element is on a smaller scale than the entire conformal antenna. Modelling aspects and measurements of a prototype antenna will be presented. The modelling of magnetic radar absorbing particles in composite structures requires knowledge about magnetic properties of microscopic fillers, an estimate of the dielectric properties of the composite with magnetic particles, and modelling of the structure. This will be explained for a structure consisting of a honeycomb coated by magnetite paint.
Seminar: CT Delta-Sigma Modulators
Thursday, April 30th at 10.00-12.30, in E:2311 (Orangeriet). Maretin Andersson is giving a a seminar on CT Delta-Sigma Modulators. Part 1 (60 min) presents basic concepts such as quantization, oversampling, noise shaping, and CT modulator implementation. Part 2 (40 min) presents the research results from the journal papers published this year on clock phase-noise sensitivity in CT Modulators.
Parabolic Synthesis Methodology Implemented on the Sine Function
Erik Hertz and Peter Nilsson, “Parabolic Synthesis Methodology Implemented on the Sine Function”, in Proceedings of the 2009 International Symposium on Circuits and Systems (ISCAS’09), Taipei, Taiwan, May 24-27, 2009
Hardware Architecture of an SVD Based MIMO OFDM Channel Estimator
Johan Löfgren, Peter Nilsson, and Ove Edfors, “Hardware Architecture of an SVD Based MIMO OFDM Channel Estimator”, in Proceedings of the 2009 International Symposium on Circuits and Systems (ISCAS’09), Taipei, Taiwan, May 24-27, 2009
PhD thesis defence Andres Alayon Glasunov
Date: 2009-03-18, at 10:15
Place: Lecture Hall E:1406, E-building, Ole Römers väg 3, Lund University Faculty of Engineering
Opponent: Prof. Michael A. Jensen. Department of Electrical and Computer Engineering
A. A. Glasunov:
On the Antenna-Channel Interactions: A Spherical Vector Wave Expansion Approach
ISSN 1654-790X, No.16, Electrical and Information Technology, 2009.
Abstract: The main focus of this thesis is the analysis of the interactions between antennas and channels where electromagnetic fields play a central role. Our goal has been to devise a general framework to enable a clear separation of the properties of the propagation channel from the influence of the antennas at the same time as it provides a common ground for a joint characterization of their properties. For this we have taken help of two tools: 1) a solution to Maxwell's equations, i.e., a spherical vector wave (svw) multi-modal expansion of the electromagnetic field and 2) the scattering matrix representation of an antenna that provides a full description of all its properties as a transmitting, receiving or scattering device. These tools offer a natural characterization of the polarizational, directional, and spatial properties of multiple-input multiple-output (MIMO) antenna systems. In this thesis we first show that under some assumptions the propagation channel and the antenna are equivalent. The equivalence is in the sense that the impact of the channel cross-polarization ratio (XPR) and the antenna effective cross-polarization discrimination (XPD) on the mean effective gain (MEG) of an antenna are symmetrical. We also find bounds on the MEG in a wireless channel. Then we provide closed form expressions for the covariance of the field multi-modes as a function of the Power Angle Spectrum (PAS) and the channel XPR. A new interpretation of the MEG of antennas in terms of field multi-modes is also provided where the maximum MEG is obtained by conjugate mode matching between the antennas and the channel. We also show the (intuitive) result that the optimum decorrelation of the antenna signals is obtained by the excitation of orthogonal spherical vector wave modes. The cross-correlation coefficient between signals at two antenna branches (ports) in the presence of spatially selective interference and additive white gaussian noise is also investigated showing that spatial interference can also be readily modeled in terms of the svw mode expansion. We further devise a correlation model for co- and cross-polarized field components and introduce the concept of mode-to-mode channel mapping, the M-matrix, between the receive and transmit antenna modes. The M-matrix maps the modes excited by the transmitting antenna to the modes exciting the receive antennas and vice versa. The covariance statistics of this M-matrix are expressed as a function of the double-directional power-angular spectrum (PAS) of co- and cross-polarized components of the electromagnetic field. We finally derive physical limitations on the interactions of antennas exciting TM or TE modes (but not both) and wireless propagation channels. Rather than maximizing antenna gain in a single direction we obtain physical limitations on the antenna gain pattern, which is directly translated to more condensed parameters, i.e. the instantaneous effective gain Gi and the mean effective gain Ge if instantaneous realizations or correlation statistics of the expansion coefficients of the electromagnetic field are known, respectively. The obtained limitations are on the maximum of Gi/Q and Ge/Q, which establish a trade-off between link gain and the antenna quality factor Q.
PhD thesis defence Shurjeel Wyne
Date: 2009-03-17, at 10:15
Place: Lecture Hall E:1406, E-building, John Ericssons väg 4, Lund University, Faculty of Engineering
Opponent: Professor Ernst Bonek. Vienna University of Technology, Vienna, Austria
Characterization of Single- and Multi-antenna Wireless Channels
ISSN 1654-790X No. 15, 2009.
Abstract: The wireless propagation channel significantly influences the received signal, so that it needs to be modeled effectively. Extensive measurements and analysis are required for investigating the validity of theoretical models and postulating new models based on measurements. Such measurements, analysis, and modeling are the topic of this thesis. The focus of the included contributions are Multiple-Input Multiple-Output (MIMO) propagation channels and radio channels for sensor network applications. Paper I presents results from one of the first MIMO measurements for a double-directional characterization of the outdoor-to-indoor wireless propagation channel. Such channels are of interest for both cellular and wireless LAN applications. We discuss physical aspects of building penetration, and also provide statistics of angle and delay spreads in the channel. The paper also investigates the coupling between DOD and DOA and the two spectra are found to have non-negligible dependence. We test the applicability of three analytical channel models that make different assumptions on the coupling between DODs and DOAs. Our results indicate that analytical models, that impose fewer restrictions on the DOD to DOA coupling, should be used preferrably over models such as the Kronecker model that have more restrictive assumptions. Paper II presents a cluster-based analysis of the outdoor-to-indoor MIMO measurements analyzed in Paper I. A subset of parameters of the COST 273 channel model, a generic model for MIMO propagation channels, are characterized for the outdoor-to-indoor scenario. MPC parameters are extracted at each measured location using a high-resolution algorithm and clusters of MPCs are identified with an automated clustering approach. In particular, the adopted clustering approach requires that all MPC parameters must be similar in order for the MPCs to form a cluster. A statistical analysis of the identified clusters is performed for both the intra- and inter-cluster properties. Paper III analyzes the spatial fading distribution for a range of canonical sensor deployment scenarios. The presented results are relevant to communicating within, and between, clusters of nodes. Contrary to the widely accepted assumption in published literature that the channel is AWGN at a small-enough distance, our measurements indicate that values of the Rice factor do not, in general, increase monotonically as the Tx-Rx distance is reduced. A probability mixture model is presented, with distance dependent parameters, to account for the distance dependent variations of the Rice factor. A simulation model that includes small- and large-scale fading effects is presented. According to the modeling approach, a sensor node placed anywhere within the spatial extent of a small-scale region will experience the channel statistics applicable to that region. Paper IV presents results characterizing a radio channel for outdoor short-range sensor networks. A number of antennas are placed on the ground in an open area and time-variation of the channel is induced by a person moving in the vicinity of the nodes. The channel statistics of both the LOS path and the overall narrowband signal are non-stationary. We investigate the stationarity interval length to be used for small-scale analysis. Our analysis of the various measured links shows that the Rx signal strength is significantly influenced by a moving person only when the person blocks the LOS path. We present a generic approach for modeling the LOS blockage, and also model the time-variant Doppler spectrum of the channel's scattered components.
PhD thesis defence Johan Kåredal
Date: 2009-02-12, at 10:15
Place: Room E:1406, E-building, John Ericssons väg 4, Lund University, Faculty of Engineering
Opponent: Professor Claude Oestges. Microwave Laboratory, Université catholique de Louvain (UCL), BELGIUM
Measurement-Based Modeling of Wireless Propagation Channels - MIMO and UWB
Series of licentiate and doctoral theses,Vol. No. 14,ISSN 1654-790X, 2009.
Abstract: Future wireless systems envision higher speeds and more reliable services but at the same time face challenges in terms of bandwidth being a limited resource. Two promising techniques that can provide an increased throughput without requiring additional bandwidth allocation are multiple-input multiple-output (MIMO) systems and ultra-wideband (UWB) systems. However, the performance of such systems is highly dependent on the properties of the wireless propagation channel, and an understanding of the channel is therefore crucial in the design of future wireless systems. Examples of such systems covered by this thesis are wireless personal area networks (papers I and II), vehicle-to-vehicle communications (paper III), board-to-board communications inside computers (paper IV) and sensor networks for industrial applications (paper V). Typically, channel models are used to evaluate the performance of different transmission and reception schemes. Channel modeling is the focus of this thesis, which contains a collection of papers that analyze and model the behavior of MIMO and UWB propagation channels. Paper I investigates the fading characteristics of wireless personal area networks (PANs), networks that typically involve human influence close to the antenna terminals. Based on extensive channel measurements using irregular antenna arrays, typical properties of PAN propagation channels are discussed and a model for the complete fading of a single link is presented. Paper II extends the model from paper I to a complete MIMO channel model. The paper combines the classical LOS model for MIMO with results from paper I by prescribing different fading statistics and mean power at the different antenna elements. The model is verified against measurement data and the paper also provides a parameterization for an example of a PAN scenario. Paper III presents a geometry-based stochastic MIMO model for vehicle-to-vehicle communications. The most important propagation effects are discussed based on the results from extensive channel measurements, and the modeling approach is motivated by the non-stationary behavior of such channels. The model distinguishes between diffuse contributions and those stemming from interaction with significant objects in the propagation channel, and the observed fading characteristics of the latter are stochastically accounted for in the model. Paper IV gives a characterization of UWB propagation channels inside desktop computer chassis. By studying measurement results from two different computers, it is concluded that the propagation channel only shows minor differences for different computers and positions within the chassis. It is also found out that the interference power produced by the computer is limited to certain subbands, suggesting that multiband UWB systems are more suitable for this type of applications. Paper V describes a UWB channel model based on the first UWB measurements in an industrial environment. Analyzing results from two different factory halls, it is concluded that energy arrives at the receiver in clusters, which motivates the use of a classical multi-cluster model to describe the channel impulse response. Parts of the results from this paper were also used as input to the channel model in the IEEE 802.15.4a UWB standardization work. In summary, the work within this thesis leads to an increased understanding of the behavior of wireless propagation channels for MIMO and UWB systems. By providing three detailed simulation models, two for MIMO and one for UWB, it can thus contribute to a more efficient design of the wireless communications systems of tomorrow.