Disputation Deepak Dasalukunte
Datum: 2012-01-19, kl 10:15
Plats: E:1406, E-building, Ole Römers väg 3, Lund University, Faculty of Engineering
Opponent: Prof. Gerhard Fettweis. Technische Universität Dresden, Germany
Multicarrier Faster-than-Nyquist Signaling Transceivers: From Theory to Practice
ISSN 1654-790X, 2011.
Abstract: The demand for spectrum resources in cellular systems worldwide has seen a tremendous escalation in the recent past. The mobile phones of today are capable of being cameras taking pictures and videos, able to browse the Internet, do video calling and much more than an yesteryear computer. Due to the variety and the amount of information that is being transmitted the demand for spectrum resources is continuously increasing. Efficient use of bandwidth resources has hence become a key parameter in the design and realization of
wireless communication systems. Faster-than-Nyquist (FTN) signaling is one such technique that achieves bandwidth efficiency by making better use of the available spectrum resources at the expense of higher processing complexity in the transceiver.
This thesis addresses the challenges and design trade offs arising during the hardware realization of Faster-than-Nyquist signaling transceivers. The FTN system has been evaluated for its achievable performance compared to the processing overhead in the transmitter and the receiver. Coexistence with OFDM systems, a more popular multicarrier scheme in existing and upcoming wireless standards, has been considered by designing FTN specific processing blocks as add-ons to the conventional transceiver chain. A multicarrier system capable of operating under both orthogonal and FTN signaling has been developed. The performance of the receiver was evaluated for AWGN and fading channels. The FTN system was able to achieve 2x improvement in bandwidth usage with similar performance as that of an OFDM system. The extra processing in the receiver was in terms of an iterative decoder for the decoding of FTN modulated signals. An efficient hardware architecture for the iterative decoder reusing the FTN specific processing blocks and realize different functionality has been designed. An ASIC implementation of this decoder was implemented
in a 65nm CMOS technology and the implemented chip has been successfully verified for its functionality.
Ex-jobbspresentation: "A 90nm Digital Phase-Locked Loop based on a Multi-Delay Coarse-Fine Time to Digital Converter"
Ying Wu will present his Master's thesis "A 90nm Digital Phase-Locked Loop based on a Multi-Delay Coarse-Fine Time to Digital Converter" on Monday, December 19, at 10.15, in room E:2311.
Technology scaling and large-scale integration make the operating environment increasingly hostile for traditional analog design. In the area of frequency synthesis, Digital PLLs (DPLLs) provide an attractive alternative to conventional PLLs: their wide programmability allows for multistandard application, and a digital intensive design means easy reconfigurability and shorter design cycles. In this paper, a 5GHz digital frequency synthesizer achieving a low noise for wireless RF application is presented. This architecture uses a multidelay coarse-fine Time-to-Digital Converter (TDC) to achieve both the large detection range and fine resolution. A Digitally Controlled Oscillator (DCO) based on capacitive degeneration in LC-Tank is also implemented. The DCO achieves frequency quantization step of 300 Hz without any dithering. Simulated phase noise at 5 GHz carrier frequency is -125 and -151 dBc/Hz at 1 MHz and 20 MHz offset, respectively. The Digital phase-locked loop (DPLL) is realized in 90nm CMOS process and consumes 14mA from a 1.2V supply.
Ex-jobbspresentation: "Prediction of Intradialytic Hypotension using Photoplethysmography"
Erik Wallenborg will present his thesis
"Implementation and development of a gradient optimization method for antennas" on thursday 15/12 at 11.15 in E:2311.
Acute intradialytic hypotension is the most common complication during a hemodialysis treatment. In the doctoral dissertation "Signal Modeling and Detection in Nephrologic and Cardiac Applications" , a method for prediction of this complication using photoplethysmography is demonstrated. This thesis will implement and evaluate this method on a larger database. It will be shown that the database gathered at Lund University Hospital in 2010 can not be used for the prediction of acute intradialytic hypotension with this method. Because of this, the method itself could not be evaluated. It will also been shown that there are clear differences between the signals from the Nonin Medair Life Sense and the wireless Nonin 4100 sensor.
Seminar: "A General Formula for the Exact (Decoding) Bit Error Probability"
Rolf Johannesson will give a seminar, "A General Formula for the Exact (Decoding) Bit Error Probability", on Wednesday Dec. 14, at 10.15 - 11.00 in E:3139.
It is based on research carried out jointly with Irina Bocharova, Florian Hug, and Boris Kudryashov.
In 1995, Best et al. published a formula for the exact bit error probability for Viterbi decoding of the rate R=1/2, memory m=1 (2-state) convolutional encoder with generator matrix G(D)=(1 1+D) when used to communicate over the binary symmetric channel. Their formula was later extended to the rate R=1/2, memory m=2 (4-state) convolutional encoder with generator matrix G(D)=(1+D^2 1+D+D^2) by Lentmaier et al.
In this presentation, a different approach to the challenging problem of deriving a general formula for the exact bit error probability is described. A matrix recurrent equation, connecting the average information weight at the current and previous states of a trellis section of the Viterbi decoder, is derived and solved. The general solution of this matrix equation yields a closed form expression for the exact bit error probability. As special cases, the expressions obtained by Best et al. for the 2-state encoder and by Lentmaier et al. for the 4-state encoder are obtained. Our analytical expression is evaluated for various realizations of encoders, including rate R=1/2 and R=2/3 encoders, of as many as 16 states.
The important fact that the bit error probability is an encoder property, neither a generator matrix property nor a convolutional code property, is shown.
Finally, it is shown that it is straightforward to extend the approach to communication over the quantized additive white Gaussian noise channel.
Disputation Fredrik Lindqvist
Datum: 2011-12-12, kl 09:00
Plats: Room E:1406, E-building, Ole Römers väg 3, Lund University, Faculty of Engineering
Opponent: Dr Tomas Nordström. School of Information Science, Computer and Electrical Engineering, Halmstad University, Halmstad
Estimation and detection of transmission line characteristics in the copper access network
ISSN 1654-790X, No.34, 2011.
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. To meet this demand, a relocation of the DSL transceivers in cabinets closer to the customers are often necessary combined with a joint expansion of the accompanying optical-fiber backhaul network. The equipment of the next generation copper network are therefore becoming more scattered and geographically distributed, which increases the requirements of automated line qualification with fault detection and localization.
This scenario is addressed in the first five papers of this dissertation where the focus is on estimation and detection of transmission line characteristics in the copper access network. The developed methods apply model-based optimization with an emphasis on using low-order modeling and a priori information of the given problem. More specifically, in Paper I a low-order and causal cable model is derived based on the Hilbert transform. This model is successfully applied in three contributions of this dissertation. In Paper II, a class of low-complexity unbiased estimators for the frequency-dependent characteristic impedance is presented that uses one-port measurements only. The so obtained characteristic impedance paves the way for enhanced time domain reflectometry (a.k.a. TDR) on twisted-pair lines. In Paper III, the problem of estimating a nonhomogeneous and dispersive transmission line is investigated and a space-frequency optimization approach is developed for the DSL application. The accompanying analysis shows which parameters are of interest to estimate and further suggests the introduction of the concept capacitive length that overcomes the necessity of a priori knowledge of the physical line length. In Paper IV, two methods are developed for detection and localization of load coils present in so-called loaded lines. In Paper V, line topology identification is addressed with varying degree of a priori information. In doing so, a model-based optimization approach is employed that utilizes multi-objective evolutionary computation based on one/two-port measurements.
A complement to transceiver relocation that potentially enhances the total data throughput in the copper access network is dynamic spectrum management (DSM). This promising multi-user transmission technique aims at maximizing the transmission rates, and/or minimizing the power consumption, by mitigating or cancelling the dominating crosstalk interference between twisted-pair lines in the same cable binder. Hence the spectral utilization is improved by optimizing the transmit signals in order to minimize the crosstalk interference. However, such techniques rely on accurate information of the (usually) unknown crosstalk channels.
This issue is the main focus of Paper VI and VII of this dissertation in which Paper VI deals with estimation of the crosstalk channels between twisted-pair lines. More specifically, an unbiased estimator for the square-magnitude of the crosstalk channels is derived from which a practical procedure is developed that can be implemented with standardized DSL modems already installed in the copper access network. In Paper VII the impact such a non-ideal estimator has on the performance of DSM is analyzed and simulated. Finally, in Paper VIII a novel echo cancellation algorithm for DMT-based DSL modems is presented.
Ex-jobbspresentation: "Implementation and development of a gradient optimization method for antennas"
Robin Johansson will present his thesis
"Implementation and development of a gradient optimization method for antennas"
on Fri 9/12 at 13.15 in E:2311.
Full-wave electromagnetic simulators today require a lot of computer power and hence it is very demanding to do simulations on antennas. This master thesis investigates a gradient shape optimization method that can reduce the number of simulations. The gradient sensitivity is an expression derived from Maxwell's equations and tells how the reflection coefficient varies with respect to geometry changes. The optimization algorithm is a steepest descent method with Armijo line search and the cost is the reflection coefficient defined over a certain frequency interval. The simulation program used is called HFSS and is an electromagnetic simulator that uses the finite element method. The optimization program is written in MatLab and the antenna models that are used are either made by me or borrowed from RUAG Space with perhaps a small modification.
Ex-jobbspresentation: "Beam position monitoring"
Rouhina Behpour and Elham Vafa will present their master thesis project "Beam position monitoring" on December 8, at 14.15 in E3139.
The project is done in collaboration with ESS.
This thesis is done in collaboration with European Spallation Source (ESS) in Lund, Sweden, which will be one of the largest accelerator research centers using the neutron scattering technique in the world. A particle accelerator is an instrument for accelerating charged particles by using electromagnetic fields to propel particles close to the speed of light. An important part of an accelerator is the Beam Position Monitoring system, BPM, that provides information about the beam position and cross section. The BPM system is usually composed of four button electrodes installed around the cavity wall. The main purpose of this thesis is to study the relations between induced BPM electrode voltages and the geometry and position of the proton beam, and to determine the accuracy and the stability of the system.
2011-12-01 Licentiat-seminarium Farzad Foroughi Abari
Low-complexity and filter-tap memory optimized channel estimation in multi-mode and multi-standard OFDM Systems
Datum: 2011-12-01, kl 10:15, Lecture hall E:1406, E-building, Ole Römers väg 3, Lund University, Faculty of Engineering
Discussion Leader: Maja Loncar, Renesas, Danmark
Communication over orthogonal pulses in frequency (e.g., OFDM) has become a dominant choice for the emerging high speed wireless standards. One of the main processing blocks in such systems is dedicated to combating and compensating for the fading frequency selective wireless channels. Thus, channel estimation is a crucial signal processing operation in modern wireless transceivers. To assist channel estimation, it is a common practice in wireless communications jargon to use pilots. Scattered pilots have been used in a number of existing state-of-the-art communications systems. For instance, LTE and DVB-H benefit from different forms of scattered pilots in their downlink transmission. Considering the very fact that it is desired to use low-complexity algorithms to address the channel estimation needs of the mobile terminals, a number of approaches to low-complexity estimators have been probed and discussed in this thesis. The focus of the work has been on developing algorithms with low hardware requirements in terms of processing elements as well as on-chip memory, when possible. In particular, it is shown how certain families of linear estimators can be manipulated into low-complexity variants which can be used as alternatives for channel estimation with a certain amount of performance degradation. Besides, the estimators have been tailored to the needs of two existing OFDM standards, i.e., LTE and DVB-H. In the event of co-integration of these standards, the innate analogy between them, in terms of OFDM system parameters and their respective pilot patterns, is exploited to reduce the overall hardware requirements for channel estimation purposes. For instance, it is shown that by exploiting the similarities in 2nd-order channel statistics, the employed channel estimators can be shared between LTE and DVB-H across their modes of operation. Furthermore, a certain strategy can be pursued for pilot pattern design in OFDM systems such that it is possible to reuse the designed estimators in multi-mode or/and multi-standard environments.
Disputation Ruiyuan Tian
Datum: 2011-11-29, kl 10:15
Plats: Lecture hall E:1406, E-building, Ole Römers väg 3, Lund University, Faculty of Engineering
Opponent: Professor Daniel Stancil. Department of Electrical and Computer Engineering, North Carolina State University, USA
Design and Evaluation of Compact Multi-antennas for Efficient MIMO Communications
ISBN 978-91-7473-186-6, 2011.
Abstract: The use of multi-antenna systems with multiple-input multiple-output (MIMO) technology will play a key role in providing high spectrum efficiency for next generation mobile communication systems. This thesis offers valuable insights on the design of compact multi-antennas for efficient MIMO communications. In the course of the thesis work, several novel six-port antenna designs have been proposed to simultaneously exploit all six possible degrees-of-freedom (DOFs) by means of various antenna diversity mechanisms (Paper I & II). Moreover, the thesis also examines the potential of using uncoupled matching networks to adaptively optimize compact multi-antenna systems to their dynamic usage environments (Paper III). Furthermore, a simple and intuitive metric is proposed for evaluating the performance of MIMO antennas when operating in the spatial multiplexing mode (Paper IV). Last but not least, cooperation among multi-antenna systems at all three sectors of a given cellular base station is shown to deliver significant benefit at sector edges (Paper V). The thesis with five included research papers extend the understanding of MIMO systems from an antenna and propagation perspective. It provides important guidelines in designing compact and efficient MIMO antennas in their usage environments.
In Paper I, a fundamental question on the number of effective DOFs in a wireless channel is explored using two co-located six-port antenna arrays. The antenna elements of both arrays closely reproduce the desired characteristics of fundamental electric and magnetic dipoles, which can efficiently extract angle and polarization diversities from the wireless channel. In particular, one of the two array designs is by far the most electrically compact six-port antenna structure in the literature. Analysis of measured channel eigenvalues in a rich multi-path scattering environment shows that six eigenchannels are successfully attained for the purpose of spatial multiplexing.
To study the potential of implementing different diversity mechanisms on a practical multi-port antenna, Paper II builds on an existing dielectric resonator antenna (DRA) to provide a compact six-port DRA array that jointly utilizes space, polarization and angle diversities. In order to fully substantiate the practicality of the DRA array for indoor MIMO applications, the compact DRA array together with two reference but much larger arrays were evaluated in an office scenario. The use of the compact DRA array at the receiver is shown to achieve comparable performance to that of the reference monopole array due to the DRA array's rich diversity characteristics.
In Paper III, the study of uncoupled matching networks to counteract mutual coupling effects in multi-antenna systems is extended by allowing for unbalanced matching impedances. Numerical studies suggest that the unbalanced matching is especially effective for array topologies whose effective apertures can vary significantly with respect to the propagation channel. Moreover, it is also demonstrated that the unbalanced matching is capable of adapting the radiation patterns of the array elements to the dynamic propagation environment.
Paper IV introduces multiplexing efficiency as a performance metric which defines the loss of efficiency in decibel when using a multi-antenna prototype under test to achieve the same multiplexing performance as that of an ideal array in the same propagation environment. Its unique features are both its simplicity and the valuable insights it offers with respect to the performance impacts of different antenna impairments in multi-antenna systems.
In Paper V, intrasite cooperation among three 120°-sector, each with a cross-polarized antenna pair, is investigated in a measured urban macrocellular environment. The single-user capacity improvement is found to exceed 40% at the sector edges, where improvements are most needed. In addition, a simple simulation model is developed to analyze the respective impact of antennas and specific propagation mechanisms on the measured cooperative gain.
Ex-jobbspresentation: "Interactible video compression with motion compensation"
Daniel Borgehammar will present his Master thesis
"Interactible video compression with motion compensation"
on Tuesday November 22, 2011, at 15.15 in Room E:3139
Advisor: Irina Bocharova
Examiner: Rolf Johannesson
There exist various types of remote control software for mobile devices and smart phones. One problem they have in common is the lack of good image data compression. Typically, image compression standards such as JPEG and PNG are used to compress the image data, it works, but gives very low frame rates. Existing video compression standards are not used for remote control software, likely, in large part, because implementations are too specialized. It is easy enough grabbing image data from part of the screen and moving around the area you capture image data from, but when you try to do other things like zooming in and out you start to run into problems. The goal of this thesis is to develop a good method for image data compression, targeted specifically towards remote control applications. More specifically, this thesis explores the use of the wavelet transformation to compress the image data more efficiently than the commonly used JPEG and PNG standards. In addition, two wavelet based video compression methods are proposed to improve the compression further, while giving the flexibility the remote control software requires. The video compression methods show very competitive performance when compared to H.264.
2011-11-14 (-15) NORCHIP 2011
The Nordic Microelectronics event, November 14-15, 2011 will be held in Lund and is hosted by Lund University
The NORCHIP conference is the main microelectronics event of the Nordic countries. The annual IEEE CAS sponsored conference covers all areas of microelectronics, spanning from large digital systems to simple analog circuits. The wide scope of NORCHIP is intentional promoting cross-field collaboration. NORCHIP is a well established conference with representation from both academia and industry. Papers of the highest scientific and technical quality are presented together with selected invited speakers and pre-conference tutorial sessions.
Ex-jobbspresentation: "Comparative study of metrics for IPTV transport in the access network"
Patrik Björkqvist presenterar sin exjobbsrapport "Comparative study of metrics for IPTV transport in the access network"
fredagen den 11/11 10:15 i E:3139.
Stefan Höst och Jens A Andersson
Last few years, services such as Internet Protocol Television (IPTV) and Voice over Internet protocol (VoIP) have been in focus. Network operators see a huge potential in streaming real-time media over IP-networks and this lays the ground for so called paid services such as Video on Demand (VOD) as well as free services like YouTube and SVT Play. IPTV delivers content over a closed infrastructure that receives media from a particular provider using a set-top-box, or STB for short, in the home of customers. Services such as Internet TV (SVT Play, TV3 Play and YouTube for example), have the same look and feel as IPTV but are delivered over the open infrastructure of the internet, relying on the best-effort channel. The latter is called over-the-top or OTT , referring to the media going around the STB rather than through it. The benefit of such a service can be put into one word, flexibility, watch what you want, when you want and where you want. But these type of services have some drawbacks. Problems such as packet loss, delay and jitter in the network greatly affects the quality for the end-user. A significant problem for OTT-traffic in the access network are the old telephone cables used for the last mile to customers, this part of the network was not built for this kind of traffic and suffers from external disturbances in form of 50Hz power lines, crosstalk and radio frequency interferences. This paper aims to evaluate and compare different methods for classifying network traffic and how Quality-of-Service (QoS) parameters (packet loss, delay, jitter, out-of-sequence) on the IP level affect Quality-of-Experience (QoE) from a head-end to a receiver in a home network connected to an access network. A simulated IPTV transmission is done in this simulated network with and without an external disturbance signal injected to a pair in the same cable.
Ex-jobbpresentation: "Linearization of a Wireless Receiver Front-End in 65 nm CMOS"
Anders Nejdel will present his Master´s thesis: "Linearization of a Wireless Receiver Front-End in 65 nm CMOS" on Wednesday November 2, Time 10.15 in E:2349 (E-building), LTH.
The front-end linearity is of key interest in modern radio communications and with the ever-increasing number of wireless applications used on a daily basis, more ways of improving the linearity are needed. In this thesis a wireless receiver front-end has been designed and simulated in the STM 65nm CMOS process with the main focus of increasing the linearity in the LNA. This was accomplished by employing a positive feedback network, in the LNA, biased in sub-threshold and with distortion cancellation by feed forward to current bleeding transistors. Monte Carlo simulations showed that mismatches can be countered by varying the bias point of the feedback transistors and the LNA can achieve an IIP3 of approximately +10 dBm. In order to verify the function of the LNA in a front-end receiver system, the complete receiver designed in the thesis also consists of an LO prescaler, two bootstrapped passive mixers and output buffers. Post layout simulations with extracted parasitics have been carried out and the system has been taped out in order to verify the function of the proposed linearity improvement technique.
Disputation: Ruiyuan Tian
Ruiyuan Tian will defend his PhD thesis on 29 Nov 2011 in E:1406, starting at 10.15 am. The opponent will be Prof. Daniel D. Stancil of North Carolina State University. The thesis title is “Design and Evaluation of Compact
Multi-antennas for Efficient MIMO Communications”.
The use of multi-antenna systems with multiple-input multiple-output (MIMO) technology will play a key role in providing high spectrum efficiency for next generation mobile communication systems. This thesis offers valuable insights on the design of compact multi-antennas for efficient MIMO communications. In the course of the thesis work, several novel six-port antenna designs have been proposed to simultaneously exploit all six possible degrees-of-freedom (DOFs) by means of various antenna diversity mechanisms (Paper I & II). Moreover, the thesis also examines the potential of using uncoupled matching networks to adaptively optimize compact multi-antenna systems to their dynamic usage environments (Paper III). Furthermore, a simple and intuitive metric is proposed for evaluating the performance of MIMO antennas when operating in the spatial multiplexing mode (Paper IV). Last but not least, cooperation among multi-antenna systems at all three sectors of a given cellular base station is shown to deliver significant benefit at sector edges (Paper V). The thesis with the five included research papers extend the understanding of MIMO systems from an antenna and propagation perspective. It provides important guidelines in designing compact and efficient MIMO antennas in their usage environments. In Paper I, a fundamental question on the number of effective DOFs in a wireless channel is explored using two co-located six-port antenna arrays. The antenna elements of both arrays closely reproduce the desired characteristics of fundamental electric and magnetic dipoles, which can efficiently extract angle and polarization diversities from wireless channels. In particular, one of the two array designs is by far the most electrically compact six-port antenna structure in the literature. Analysis of measured channel eigenvalues in a rich multi-path scattering environment shows that six eigenchannels are successfully attained for the purpose of spatial multiplexing. To study the potential of implementing different diversity mechanisms on a practical multi-port antenna, Paper II builds on an existing dielectric resonator antenna (DRA) to provide a compact six-port DRA array that jointly utilizes space, polarization and angle diversities. In order to fully substantiate the practicality of the DRA array for indoor MIMO applications, the compact DRA array together with two reference but much larger arrays were evaluated in an office scenario. The use of the compact DRA array at the receiver is shown to achieve comparable performance to that of the reference monopole array due to the DRA array’s rich diversity characteristics. In Paper III, the study of uncoupled matching networks to counteract mutual coupling effects in multi-antenna systems is extended by allowing for unbalanced matching impedances. Numerical studies suggest that unbalanced matching is especially effective for array topologies whose effective apertures can vary significantly with respect to the propagation channel. Moreover, it is also demonstrated that unbalanced matching is capable of adapting the radiation patterns of the array elements to the dynamic propagation environment. Paper IV introduces multiplexing efficiency as a performance metric which defines the loss of efficiency in decibel when using a multi-antenna prototype under test to achieve the same multiplexing performance as that of an ideal array in the same propagation environment. Its unique features are both its simplicity and the valuable insights it offers with respect to the performance impacts of different antenna impairments in multi-antenna systems. In Paper V, intrasite cooperation among three 120◦-sector, each with a cross-polarized antenna pair, is investigated in a measured urban macrocellular environment. The single-user capacity improvement is found to exceed 40% at the sector edges, where improvements are most needed. In addition, a simple simulation model is developed to analyze the respective impact of antennas and specific propagation mechanisms on the measured cooperative gain.
Ex-jobbspresentation: "Dynamic analysis of Android Applications"
Patrik Lantz will present his Master´s thesis: "Dynamic analysis of Android Applications" on monday, October 31, at 13.15-14.00 in E:3139 (E-building).
The number of malicious Android applications is increasing and currently there are analysis tools available that perform static analysis of application packages. In this thesis project, an Android application sandbox is implemented by modifying the Android framework and kernel to provide dynamic analysis of an application's behavior. An analysis is presented in a formatted output, much like in the traditional sandboxes. In addition to a text-based report, visualization is generated to interpret more complex samples in terms of in what temporal order the operations occur in and a treemap visualization is used to classify the similarities between analyzed packages. The operations that are of special interest to monitor cover: file and socket operations, sending SMS, initiating phone calls and detecting information leaks via the following channels: write operations on sockets, sent SMS and read and write operations related to files.
2011-10-28 11:e årets elevkonferens InfoCom
Fredag 28/10 hålls elevkonferensen InfoCom2011
Konferensen är avslutningen på kursen Kommunikationssystem, som är C-programmets först tillämpade kurs. Kursen är obligatorisk för förstaårsstudenterna, och konferensen är en del av studenternas examination.
Omkring 130 gymnasielever kommer att delta som åhörare. Gästerna kommer från Borgarskolan i Malmö, John Bauer-gymnasiet i Hässleholm och Polhemsskolan i Lund.
Alla intresserade av kommunikationsteknik, både dagens och framtidens, är välkomna till Kårhusets Hörsal (09.00-12.00) och E:B (13.30-16.00).
Jens A Andersson
Ex-jobbspresentation: “FPGA based Synthesizable Test Bench”
Mirza Jameel Baig will present his Master´s thesis: “FPGA based Synthesizable Test Bench” on monday, October 24, at 13.15-14.00 in E:2349.
The thesis work is done in cooperation with Intel Mobile Communications, Dresden, Germany
This Master’s thesis aims at developing an FPGA Based Synthesizable Test Bench for verification of individual modules used in the LTE subsystem. Behavioral Simulation is one of the important processes in verification of design. But, the performance of the design cannot be verified in simulations because the stimulus is physical approximation of the actual physical environment. To improve the verification process of the design, FPGA Prototyping can be used which provides faster simulation speed i.e. more data can be processed covering more corner cases providing Realistic System Environment. In the initial section the top level synthesizable test bench is discussed. Then the individual modules in the top level are discussed in brief. The verification process of individual modules in the top level test bench is discussed in the preceding chapters. Functional verification of the synthesizable test bench as a whole with different DUT (Device under Test) is discussed in the next chapters. Finally the synthesis and timing results of the synthesizable test bench are discussed
Ex-jobbspresentation: "Audio över Ethernet med inbyggda system "
Erik Lundh and Emil Ohlsson will present their Master's thesis " Audio över Ethernet med inbyggda system " on Friday, October 21, at 13.15, in room E:3139.
Bertil Lindvall and Viktor Öwall
Audio over Ethernet using embedded systems. Today people are not satisfied with playing music on one system in one room. Instead they want to be able to play music in several rooms simultaneously using home entertainment systems. These systems are often complicated and/or expensive. This master thesis is about evaluating the different existing system and make a case study by implementing an Ethernet based sound card to be used with PulseAudio. PulseAudio is the audio mixer that is used in most modern GNU/Linux distributions, it act as a virtual layer between the sound card and the application playing the sound stream. This virtual layer can stretch over several computers via Ethernet and makes it possible for a computer to share its' sound card with other computers. The system to be implemented should be relatively simple and cheap, and use standard components, it should be connected to Ethernet and act as virtual sound card for PulseAudio. In this way it is possible to use the existing functionality of PulseAudio to control your audio stream. For smaller systems not requiring a lot of power, Power over Ethernet is an option making the system small and easy to connect only requiring an Ethernet cable. System components:– Hardware platform capable of Ethernet communication containing processor, A/Dconversion and audio output.– Software that makes the card a PulseAudio node. Thesis requirements:– Study and compare the different systems PulseAudio, DLNA, Sonos and Airplay.– Investigate implications of using Power over Ethernet.– Determine needed hardware requirements for the processor and audio parts.– Port necessary parts of PulseAudio for use in a embedded system. Optional:– Implement Power over Ethernet– Support for wireless network– Control of external units– User interface for Android/iPhone
Ex-jobbspresentation: Design of a Successive Approximation (SAR) ADC in a 65 nm CMOS Technology
Charles Arichandranadar Perumal will present his Master's thesis "Design of a Successive Approximation (SAR) ADC in a 65 nm CMOS Technology" on Wednesday, October 19, at 11.15, in room E:2311.
In the current technical era, the technology advancement leads most of the applications demanding for a reduction in the whole size of the system in terms of its space occupied in any device. Mobile applications are one of the apt scenarios for this category. Apart from the size reductions due to the technology advancement, it also calls in for the reduction in the power consumption.
The Data Converters section, besides being very power hungry, it is also usually extremely power hungry in comparison with the other blocks of any architecture and that’s why low power has also become a tough requirement in most of the systems. The total power consumption of the system being maintained in a low figure has almost become a mandatory specification in many applications.
The SAR Analog to Digital Converter architecture is chosen in this master thesis project, as it is one of the very successful moderate resolution achievable converter system present among all the data converter architectures. The schematic model of the entire system is implemented in Cadence system in order to fulfill the technical requirements of the project.
The SAR architecture is implemented in ST Microelectronics 65 nm technology and the power supply used is 1.2 volts. A differential configuration of the whole system is thoroughly studied and an equivalent single ended system is also studied, implemented and measured in this project. The differential architecture is studied in this project to learn the merits behind the differential architecture, which basically avoid the linearity and offset errors raised in the single ended architecture. The resolution for which the system is designed is 10 bits. The reference voltage maintained here is 600mV, which is half of the full-scale value.
Ex-jobbspresentation: "Characterization of RISC processors in the Sub-VT Domain"
On Oct 13 at 13:15 in E2311, Umair Siddiqui will present his Master thesis entitled "Characterization of RISC processors in the Sub-VT Domain"
Welcome, Joachim Rodrigues
Devices like medical implants and remote sensors etc, are required to operate with very low energy dissipation for longer battery-life. For such ultra-low energy devices, the subthreshold design is an essential design technique for reducing the energy dissipation of a circuit. An important aspect of this technique is the energy modeling of the design components (and if possible whole design) in subthreshold domain. This thesis presents the energy characterization of two 32-bit microprocessors, namely LEON-3 and Cortex-M0, in subthreshold domain. For this study, a high- level energy characterization model was used to analyze the energy dissipation and operating-frequency trends of these two microprocessors. The subthreshold designing can be combined with other energy saving techniques, like clock-gating, to further improve the energy efficiency of a design. In this thesis, the sub-threshold analysis is performed with and without clock-gating. The results from energy model show that by using a sub-threshold supply voltage and clock-gating, the energy dissipation of both microprocessors can be reduced to the order of pico joules (pJ). The subthreshold operation will reduce their clock frequency to almost 50 KHz, but most of the medical implants and remote sensors have relaxed throughput constraints.
2011-10-11 IVA-seminarium med Per Ödling
Seminariet kommer att handla om "Bredbandsindustrins utveckling och utmaningar" - en kväll fylld av spännande teknik och politik utlovas!
"Under de senaste decennierna har vi sett svenskt traditionellt näringsliv, inklusive telekomindustri, i relativ tysthet genomgå en högst dramatisk förvandling från att vara producenter av högkvalitativa varor till att leverera kundnära avancerade tjänster. Vad har detta inneburit för universiteten och forskningens villkor? Hur utvecklas relationen mellan universitet och näringsliv?
Seminariet behandlar bredbandsindustrins utveckling och utmaningar; likväl som presentatörens nyfunna insikter i hur beslut fattas i Stockholm och i Bryssel, vilka drivkrafter som finns hos olika delar av beslutsmaskineriet och hur detta kan stärkas."
Seminariet kräver anmälan - men är gratis och även deltagare utanför IVA välkomnas!
Ex-jobbspresentation:“Implementation of Unrolled Newton-Raphson Hardware Architectures to determine the Inverse and Square Root"
On October 11, at 11:00-12:00 in E:3139:
Shamkrishna Mahankali will present his thesis “Implementation of Unrolled Newton-Raphson Hardware Architectures to determine the Inverse and Square Root”
Welcome, Peter Nilsson
In the era of Super-computers and Multicore-computers, everything comes down to speed. while operations such as addition, subtraction and multiplication does not consume many clock cycles, when it comes to division it is completely a different story. This thesis describes my Master Thesis project carried out at Faculty of Engineering, Lund University under supervision of Professor. Dr. Peter Nilsson. It gives detailed description of Newton-Raphson Algorithm and explains why it is feasible to implement division and square-root functions using this algorithm. A hardware implementation of its inverse and square root variants is discussed. The algorithm can be implemented in various ways; in this project we unroll the architecture and use independent hardware for each stage.
Ex-jobbspresentation: “Modeling Spatial Interference for Multiple Users in MIMO Channels”
On Tuesday 27/9 15.15 in E:2349 Zhinan Xu will present his thesis “Modeling Spatial Interference for Multiple Users in MIMO Channels” which is performed in cooperation with Forschungszentrum Telekommunikation Wien. You are all welcome to attend. At the moment there are no opponents, so contact me if you have any students interested.
For an interference-impaired multiple-input multiple-output (MIMO) channel, the severity of the interference is not only determined by the power ratio between intended signal and interference, but also by the degree of alignment between the eigenspaces of the their channel matrices. The focus of this thesis is to study the spatial compatibility by means of the channel receiver correlation matrices. First, the multi-user MIMO channel model is reviewed. We parameterize the multi-user MIMO channel model from real radio measurements. Several distinct distributions of spatial compatibility between intended and interfering transmissions are found for different types of movement. I evaluate and parameterize the multi-user MIMO channel model from the aspect of mutual information increase by providing the relationship between the eigenvalue structures of the receiver correlation matrices and the increase of mutual information. Furthermore, I evaluate and parameterize the model under interference from multiple users and find how the mutual information is affected by the eigenspace similarity between them. To better use the spatial resources, I propose a user grouping scheme for uplink multi-access channels using the newly-developed mutual information metric. Simulations show that this grouping scheme offers a gain in spectral efficiency and system throughput due to more efficient use of spatial resources.
2011-09-19: Ex-jobbspresentation: “V2X Communication to Enhance Active Safety Functionality”
Pradyumna Mahanta and Yilei Wang are going to present their M.Sc. thesis project entitled “ V2X Communication to Enhance Active Safety Functionality” on Monday, 19/9, at 10:15, in E:3139.
Long-Term-Evolution (LTE) and Wireless Access in Vehicular Environments (WAVE) are two technologies that can be used for vehicular communication. LTE is a standard which is considered as preliminary of next generation of mobile communication (4G). It offers a cellular infrastructure based solution (V2I) for safety function. WAVE provides another solution of vehicular communication for safety function with WLAN based ad-hoc networks (V2V). This master thesis work evaluates the performance of collision avoidance using LTE and WAVE based broadcast communication in urban and rural scenarios. The three main parameters compared are delay, packet loss rate and throughput. It also presents a comparative study of two technologies in supporting safety applications and reveals that they are complementary while combining together.
2011-09-08 (-09) Lund Circuit Design Workshop
@ Grand Hotel and Faculty of Engineering, Lund University
The workshop will offer an overview of the research activities in IC design at Lund University.
Additionally, invited presentations will be given by outstanding experts from academia and industry.
Disputation Andreas Axholt
Datum: 2011-09-07, kl 10:15
Plats: Lecture Hall E:1406, E-building at Faculty of Engineering
Opponent: Professor Bram Nauta. University of Twente, Enschede, Netherlands
Micro- and Millimeter Wave CMOS Beamforming Receivers
ISSN 1654-790X, No 33, 2011.
Abstract: The available bandwidth in wireless communication systems, such as the 802.11 family, is very limited. Together with the ever increasing data traffic, this causes problems. New possibilities are, however, available thanks to wide license-free bandwidth allocated at higher frequencies. Increased available bandwidth enables higher data rates in future radio systems that will be capable of Giga-bit/s communication applications. This creates new possibilities like transferring very large amounts of data in a short time between computers and their peripheral devices, wireless HD-video to and from smart phones, eliminating cables between video-source and video-projector, etc. The available bandwidth is, however, located at much higher frequencies than in current WiFi systems for private usage, that is, 2.4 and 5.8 GHz. This brings new challenges from both a system as well as a circuit perspective. Wave propagation at 60 GHz differs from 2.4 GHz and 5.8 GHz. The most substantial differences are the propagation loss and the small aperture of the millimeter wave antennas, which limit the possible communication distance between receiver and transmitter. Adopting beamforming transmitters focuses the transmitted energy into the desired direction, increasing the energy available at the receiver. Correspondingly, adopting beamforming receivers also increases the received signal energy by increasing the antenna gain. Beamforming is, therefore, a key technique in increasing communication distance. This thesis investigates CMOS beamforming receiver circuits and architectures for microwave and millimeter wave radio communication. Traditionally, III-V semiconductor technologies have been used for millimeter wave applications. Today, however, as the gate length of silicon CMOS devices has been continuously reduced thanks to advancements in IC fabrication, their maximum frequency of operation is also sufficient for millimeter waves. Several circuits have been designed and measured to validate new ideas. Among these circuits, five are included in the thesis. A chip with two fully-integrated phase-locked loops with digital phase control for beamforming receivers is presented in paper I, and an injection locked voltage controlled oscillator with phase control is presented paper II. A two channel 24 GHz receiver with beamforming implemented in the analog baseband is proposed in paper III, and a high-speed low-power inductor-less 24 GHz CML frequency divider is presented in paper IV, including an on-chip VCO for test purposes. Finally, in paper V a 60 GHz receiver with a digitally controllable phase using a phase-locked loop, based on the results of paper I, is presented. The circuit achieves a state-of-the-art phase control accuracy with a measured phase step error of less than 1 degree.
2011-08-30 (-09-03) Ulrike Richter talar på EMBC
Ulrike Richter är inbjuden talare på "33rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC ’11)" som äger rum den 30/8–3/9, 2011. Hon kommer att presentera en nyutvecklad metod för att karaktärisera utbredningen av elektriska vågfronter vid förmaksflimmer. Föredraget har titeln "Propagation pattern analysis in intracardiac atrial fibrillation signals based on sparse modeling" med L. Faes och F. Ravelli (Trento) och L. Sörnmo som medförfattare.
2011-09-07 Disputation: Andreas Axholt
2011-06-20 First Scientific Meeting of COST Action IC1004
ALL IC1004 delegates as well as former COST Action 2100 participants are warmly invited to the First Scientific Meeting of COST Action IC1004, which will be held in Lund University, Lund, Sweden, between 20-21 June 2011. In addition, we are also pleased to welcome several external experts from CTIA who will be joining us for discussions on MIMO OTA test development.
Important deadlines for this Meeting are:
Registration to meeting:
6/6/2011 (those requesting TD number) or 13/6/2011 (all others)
Payment of registration fee online: 13/6/2011
Request for TD number: 6/6/2011
Submission of TD in pdf: 13/6/2011
2011-06-15 Licentiatavhandling: Peter Johannesson
"A Numerical Hybride Method for Microwave Applications, based on Hierarchical Basis Functions"
Den 15 juni kl 13.15 presenterar Peter Johannesson sin licentiatavhandling i sal E:2311, E-huset.
Handledare: Professor Anders Karlsson
Disputation Vanja Plicanic
Datum: 2011-06-14, kl 10:15
Plats: Lecture hall E:1406, E-building, Ole Römers väg 3, Lund University Faculty of Engineering
Opponent: Prof. Ernst Bonek. Vienna University of Technology, Wien, Austria
Characterization and Enhancement of Antenna System Performance in Compact MIMO Terminals
ISBN 978-91-7473-120-0, 2011.
Abstract: Co-band multiple-antenna implementation in compact user terminals is necessary for harvesting the full potential of diversity and multiple-input multiple-output (MIMO) technology in cellular communication systems. The recent worldwide deployment of Long Term Evolution (LTE), which requires the use of MIMO technology in the downlink, adds to the urgency of achieving both practical and optimal multiple-antenna systems in user terminals. Contrary to conventional understanding, an optimal multiple-antenna implementation does not only involve the design and placement of antenna elements in the terminals, but extends beyond the antenna elements and common antenna parameters to comprise interactions with the near field user and the propagation environment. Moreover, these interactions are non-static, which implies that the multiple-antenna system must adapt to the prevailing overall communication channel in order to assure the highest performance gains. This doctoral thesis aims to address several key issues in optimal multiple-antenna system design for compact multi-band MIMO terminals, with the first half (Papers I to III) focusing on the performance characterization of such terminals in the presence of user interaction and propagation channel, under the challenging constraint that the terminals are compact. The second half of the thesis (Papers IV to VI) considers two performance enhancement approaches suitable for compact MIMO terminals in realistic usage conditions. In particular, the potential benefits of harmonizing compact multiple-antenna systems with the propagation channel and user influence are determined with respect to reconfigurability in antenna patterns and impedance matching circuits. In Paper I, the diversity performance of internal multiple antennas with multi-band coverage in a mock-up with the size of a typical mobile handset is investigated in different user interaction scenarios. For comparison, a second mock-up with only one multi-band antenna is also evaluated in the same user cases. An ideal uniform propagation environment is assumed. The performance at frequency bands below and above 1 GHz are presented and analyzed in detail. Paper II extends the study in Paper I by evaluating the single-input multiple-output (SIMO) and MIMO capacity performance of the same antenna prototypes under the same user interaction scenarios and propagation environment. In Paper III, the impacts of gain imbalance and antenna separation on the throughput performance of a dual-dipole configuration are studied at frequencies below and above 1 GHz in a repeatable dynamic multi-path environment, using a live HSPA network. Since the compactness of a user terminal has implications on the antenna separation and gain imbalance of the multiple antennas, the focus is to gain knowledge on how these two factors affect the end user experience in practice. In Paper IV, three simple dual-antenna topologies implemented in compact smart phone prototypes of identical form factors are evaluated in MIMO channel measurements in noise-limited and interference-limited urban scenarios. Each dual-antenna topology is intentionally designed to provide a distinct set of antenna patterns. The goal is to investigate the potential of antenna system design as one of the key performance differentiators in real terminal implementations. Paper V extends the work in Paper IV by introducing user interaction to the same MIMO channel measurement setup. Furthermore, the focus of this paper is on the evaluation of both the average and local channel performances and their potential enhancements. Finally, Paper VI ascertains the potential capacity gains of applying uncoupled adaptive matching to a compact dual-antenna terminal in an indoor office environment, under a realistic user scenario. The performance gains are evaluated by means of extensive MIMO channel measurements at frequency bands below and above 1 GHz.
2011-06-10 Licentiatavhandling: Marco Munguia Mena
"Analysis of the Vascular Sounds of the Arteriovenous Fistula"
Den 10 juni kl 10.15 presenterar Marco Munguia Mena sin licentiatavhandling i sal E:2311, E-huset.
Handledare: Professor Leif Sörnmo
2011-05-18: The new DVB-T2 broadcasting standard and beyond
IEEE VT/COM Sweden Distinguished Industry Lecture av Erik Stare, Teracom.
Föreläsningarna hålls den 18 maj kl. 10 i E:A. Leif Wilhelmsson och Ove Edfors står för värdskapet.
With the main aim of offering more capacity for digital terrestrial HDTV services the DVB organisation has developed the new second generation standard for digital terrestrial TV (DVB-T2), which builds on the earlier DVB-T standard but offers improved functionality and performance. The DVB-T2 standard is currently in commercial use in several countries including the UK, Sweden and Finland. Compared to the existing DVB-T standard DVB-T2 allows for about 50% higher spectrum efficiency than DVB-T by using a more efficient FEC and modulation scheme and by reducing the overhead. DVB-T2 also allows for significantly more flexibility and a number of advanced options. One of these options is the concept of a Future Extension Frame (FEF), which will allow new systems to be time multiplexed with DVB-T2 on the physical layer. Examples of such new systems are T2-mobile (a new profile of DVB-T2) and DVB-Next Generation Handheld (DVB-NGH), currently under development in DVB. The use of FEFs will allow for a flexible mixture of several different standards in the same transmitted RF signal, which will ease the migration to new terrestrial standards and technologies.
Erik Stare was born in Väddö, Sweden, in 1959. He graduated in 1984 from the Royal Institute of Technology (KTH) in Stockholm with a Master of Science in Electrical Engineering and joined Ericsson where he worked as a sales engineer. In 1987 he joined the Radio Laboratory of Swedish Telecom (now Telia) where he worked with R&D related to HDTV and digital terrestrial TV.
Since 1992 he has worked at Teracom, mainly with R&D and standardisation related to digital terrestrial TV in general, DVB-T technology, mobile reception of DVB-T, IP-based hybrid networks using DVB-T and telecom systems, mobile TV using DVB-H and IP Datacast and most recently DVB-T2, T2-mobile and DVB-NGH. He has participated in a number of European projects under ACTS, IST and CELTIC (currently Celtic-Engines).
He participated in the Task Force which developed the DVB-T standard. In the DVB organization he chaired the work on the DVB-SFN specification and has also participated in a number of other DVB groups related mainly to DVB-T, DVB-H, DVB-T2 and DVB-NGH. He contributed actively to the standardisation of DVB-H, where he proposed one of the key technologies: MPE-FEC.
He also contributed actively to the second generation DVB terrestrial standard (DVB-T2), where he invented and proposed the new technology Time Frequency Slicing (TFS) as well as other technologies now in the DVB-T2 standard.
He is currently involved in the development of a mobile profile of the DVB-T2 standard as well as in the emerging DVB Next Generation Handheld (DVB-NGH) standard.
He holds two patents.
2011-03-30 Presentation av examensarbete: Hernrup
På onsdag den 30 mars presenterar Mikael Hernrup sitt examensarbete med titeln "Time dependent measurement system for nanowire transistor characterization" i E:3139.
2011-03-30 Presentation av examensarbete: Viswam & Liu
På onsdag den 30 mars, kl. 13.15, presenterar Vijay Viswam & Xiaodong Liu sitt examensarbete med titeln "Highly Linear Direct Conversion Receiver using Customized On-chip Balun" i E:3139. Exjobbet är utfört på Ericsson Research i Lund och handlett av Dr. Stefan Andersson.
STIMESI course: MEMSCAP MUMPs technologies
The department will host the STIMESI (Stimulation action on MEMS and SiP design) course MEMSCAP MUMPs® (Multi-User MEMS) technologies, March 1-4, 2011. Registration can be done using the STIMESI Course Booking System: http://www.stimesi.stfc.ac.uk
"MEMSCAP MUMPs technologies"
In the "MEMSCAP MUMPs technologies" course, attendees will study the technology processes called MUMPs and will get training on designing in these technologies using MEMS design tools like CoventorWare or SoftMEMS.
The Multi-User MEMS Processes, or MUMPs, is a well-established, commercial program that provides customers with cost-effective access to MEMS prototyping and a seamless transition into volume manufacturing. MEMSCAP offers three unique stand-alone, multi-mask MEMS processes in MUMPs: PolyMUMPs, SOIMUMPs, and MetalMUMPs. PolyMUMPs is a three-layer polysilicon surface and bulk micromachining process, with 2 sacrificial layers and one metal layer. SOIMUMPs is based on a Silicon-On-Insulator(SOI) wafer. MetalMUMPs incorporates all three major MEMS processes: LIGA-like, thick metal electroplating, as well as bulk and surface micromachining.
The first half of the course will provide attendees with an overview of each of the processes, as well as an introduction to the design kits and design rules. The second half of the course will consist of hands-on design exercises using either CoventorWare or SoftMEMS for design entry, system level simulation and finite element modeling.
Exjobbspresentation: "Sökmotorlösning för E-handel"
Razavi Babak, Siddhartha Pattni
2011-02-24 kl 15.15 E:3139
Utfört på Avensia AB
Tekniken inom e-handelssystem har utvecklas snabbt de senaste åren. Dessutom har konkurrensen och mängden information ökat i och med detta har det dykt upp nya krav på sökmotorer som används i samband med e-handelsystem. Det är viktigt att sökfunktionen i ett e-handelssystem tillfredsställer kundernas behov och eventuella brister kan leda till missnöje
Några av bristerna som uppstår är att man inte får träff på rätt sökfråga, får irrelevanta svar, viktar enligt felaktiga kriterier tex viktar på datum istället för försäljningstatistik och är inte konfigurerbar dvs att man inte kan ställa in sökresultatet om det behövs. Anledningen är att befintliga sökmotorer är skapade för att leta efter information på webbsidor medans e-handel kräver en sökmotor som letar efter produkter som har olika egenskaper som namn, pris osv.
Några av de viktigaste egenskaper som ställs på sökmotorn är att den kan konfigureras dvs det går att trimma in den efter frekvent förekommande sökfrågor. Sökmotorn skall snabbt svara på sökfrågor. Det skall finnas stöd för rankning/viktning tex efter användarbeteende, målgrupp och säljstatistik. Skall indexera upp relevant information från tex forum, bloggar, recensioner och omdömen. Dessa egenskaper är viktiga för att underlätta sökning för kunder och maximera försäljning.
Examensarbetet utförs i två faser dels att utreda och ta fram en kravspecifikation för sökmotorer anpassade för e-handel och vidare bestäms vilka kommersiella och öppen källkod sökmotorer som skall utvärderas. Sökmotorerna utvärderas utifrån kravspecifikationen som är sorterad enligt prioritetsordning. Resultatet av utvärderingen analyseras och för- och nackdelar hos de/den mest lämpade sökmotorerna presenteras.
Seminar Professor em. Kamil Sh. Zigangirov Wed. Feb. 23, 15.15-16.00, E:3139
Partially-Regular LDPC Codes with Linear Encoding Complexity and Improved Thresholds Dmitri K. Zigangirov, Institute for Problems of Information Transmission, Moscow, Russia, Kamil Sh. Zigangirov, University of Lund, Lund, Sweden, Daniel J. Costello, Jr., University of Notre Dame, Notre Dame, U.S.A. We consider an ensemble of systematic low-density parity-check (LDPC) codes of length N with linear encoding complexity, i.e., with complexity O(N). We call these codes partially-regular, since they can be considered as modifications of regular LDPC codes. Further, their thresholds on the binary erasure channel (BEC) are found to be significantly better than the thresholds of the corresponding regular LDPC codes.