http://hdl.handle.net/2117/217 Fri, 24 May 2013 09:38:22 GMT 2013-05-24T09:38:22Z webmaster.bupc@upc.edu Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació no http://hdl.handle.net/2117/16702 Title: Performance assessment & synergic operation of algorithmic solutions enabling opportunistic networks– D4.2 Authors: Demestichas, Panagiotis; Pérez Romero, Jordi; Sallent Roig, José Oriol; Bouali, Faouzi; Ferrús Ferré, Ramón Antonio; Karvounas, Dimitrios; Georgakopoulos, Andreas; Stavroulaki, Vera; Tsagkaris, Kostas; Riaz, Maryam; Bourdellès, Michel; Vahid, Seiamak; Gebert, Jens; Fuchs, Rolf; Moreno, Oscar; Matinmikko, Marja; Sarvanko, Heli; Boskovic, Dragan; Tosic, M.; Alnwaimi, Ghassan; Rakotoharison, Lanto; Panaitopol, Dorin; Bagayoko, Abdoulaye; Mouton, Christian; Lee, Haeyoung; Shariat, Shahin Abstract: Deliverable D4.2 del projecte europeu OneFIT http://hdl.handle.net/2117/16702 Demestichas, Panagiotis; Pérez Romero, Jordi; Sallent Roig, José Oriol; Bouali, Faouzi; Ferrús Ferré, Ramón Antonio; Karvounas, Dimitrios; Georgakopoulos, Andreas; Stavroulaki, Vera; Tsagkaris, Kostas; Riaz, Maryam; Bourdellès, Michel; Vahid, Seiamak; Gebert, Jens; Fuchs, Rolf; Moreno, Oscar; Matinmikko, Marja; Sarvanko, Heli; Boskovic, Dragan; Tosic, M.; Alnwaimi, Ghassan; Rakotoharison, Lanto; Panaitopol, Dorin; Bagayoko, Abdoulaye; Mouton, Christian; Lee, Haeyoung; Shariat, Shahin no Deliverable D4.2 del projecte europeu OneFIT http://hdl.handle.net/2117/18800 Title: Efficient margin adaptive scheduling for MIMO-OFDMA systems Authors: Moretti, Marco; Pérez Neira, Ana Isabel Abstract: In this paper we address the problem of margin adaptive scheduling in the downlink of an orthogonal frequency division multiple access (OFDMA) multiple-input multiple-output (MIMO) system. Optimal resource allocation in MIMO systems requires the joint optimization of: a) linear transmit and receive spatial filters, b) channel assignment and c) power allocation. This problem is not convex and its complexity becomes thus intractable already for small sets of users and subcarriers. To reduce the complexity of the problem at hand, we propose a novel heuristic strategy that partitions the users in different groups according to their average channel quality and addresses the original problem by solving a succession of lower-complexity allocation problems. The spatial dimension is employed to prevent multiple access interference from hindering the performance of the sequential allocation. To further reduce the complexity burden we introduce a linear programming formulation in combination with a waterfilling-based strategy to allocate channels and power to the groups of users. Numerical results and evaluation of the computational complexity show that, though suboptimal, in most cases the proposed algorithm manages to exploit in an original way the inherent multi-user diversity of multi-carrier systems to ease the task of resource allocation with a very limited performance loss from the theoretic optimum. http://hdl.handle.net/2117/18800 Moretti, Marco; Pérez Neira, Ana Isabel no Allocation problems, Channel allocation, Channel Assignment, Channel quality, Heuristic strategy, Joint optimization, Linear programming formulation, Margin adaptive, MIMO-OFDMA, Multi carrier systems, Multiple-input-multiple-output systems, Multiuser diversity, Numerical results, OFDMA, Optimal resource allocation, Orthogonal frequency division multiple access, Performance loss, Power allocations, Spatial dimension, Spatial filters, Sub-carriers, MIMO systems, Mobile telecommunication systems, Multiple access interference, Optimization, Resource allocation, Scheduling, Frequency division multiple access In this paper we address the problem of margin adaptive scheduling in the downlink of an orthogonal frequency division multiple access (OFDMA) multiple-input multiple-output (MIMO) system. Optimal resource allocation in MIMO systems requires the joint optimization of: a) linear transmit and receive spatial filters, b) channel assignment and c) power allocation. This problem is not convex and its complexity becomes thus intractable already for small sets of users and subcarriers. To reduce the complexity of the problem at hand, we propose a novel heuristic strategy that partitions the users in different groups according to their average channel quality and addresses the original problem by solving a succession of lower-complexity allocation problems. The spatial dimension is employed to prevent multiple access interference from hindering the performance of the sequential allocation. To further reduce the complexity burden we introduce a linear programming formulation in combination with a waterfilling-based strategy to allocate channels and power to the groups of users. Numerical results and evaluation of the computational complexity show that, though suboptimal, in most cases the proposed algorithm manages to exploit in an original way the inherent multi-user diversity of multi-carrier systems to ease the task of resource allocation with a very limited performance loss from the theoretic optimum. http://hdl.handle.net/2117/19377 Title: Designing national IP/MPLS networks with flexgrid optical technology Authors: Velasco Esteban, Luis Domingo; Wright, Paul; Lord, Andrew; Junyent Giralt, Gabriel Abstract: We propose a two-step procedure to design flexgrid-based national networks. Locations are first partitioned into a set of metro areas interconnected through a flexgrid optical network. Next, each network is designed separately. Optimal results show a future large (>200 nodes) flexgrid core network inter-connecting small (~10 nodes) metro regions. Thu, 23 May 2013 08:06:25 GMT http://hdl.handle.net/2117/19377 2013-05-23T08:06:25Z Velasco Esteban, Luis Domingo; Wright, Paul; Lord, Andrew; Junyent Giralt, Gabriel no Flexgrid optical networks We propose a two-step procedure to design flexgrid-based national networks. Locations are first partitioned into a set of metro areas interconnected through a flexgrid optical network. Next, each network is designed separately. Optimal results show a future large (>200 nodes) flexgrid core network inter-connecting small (~10 nodes) metro regions. http://hdl.handle.net/2117/19372 Title: Implementation of the Direct Torque Control (DTC) in current model, with current starting limiter Authors: Mino Aguilar, Gerardo; Muñoz Hernández, German Ardul; Romeral Martínez, José Luis; Cortez, Liliana; Saynes Torres, J. Abstract: This paper presents the scheme of Direct Torque Control (DTC) for induction motor drives, where flux and torque of the motor are estimated by the IM current model. Its scheme requires the knowledge of speed, rotor time constant and inductive parameters of the motor. The results prove the excellent characteristics for torque response and efficiency, which confirm the validity of this control scheme. Due to the rapid response offered by the DTC, this causes a high star current inversor protections activating. To resolve this, is presents the implementation of a closed loop of current vector the optimum switching table that limits the current and put into operation to the DTC. Experimental tests demonstrate effectiveness. Wed, 22 May 2013 11:30:26 GMT http://hdl.handle.net/2117/19372 2013-05-22T11:30:26Z Mino Aguilar, Gerardo; Muñoz Hernández, German Ardul; Romeral Martínez, José Luis; Cortez, Liliana; Saynes Torres, J. no current limiter, current model, DTC This paper presents the scheme of Direct Torque Control (DTC) for induction motor drives, where flux and torque of the motor are estimated by the IM current model. Its scheme requires the knowledge of speed, rotor time constant and inductive parameters of the motor. The results prove the excellent characteristics for torque response and efficiency, which confirm the validity of this control scheme. Due to the rapid response offered by the DTC, this causes a high star current inversor protections activating. To resolve this, is presents the implementation of a closed loop of current vector the optimum switching table that limits the current and put into operation to the DTC. Experimental tests demonstrate effectiveness. http://hdl.handle.net/2117/19353 Title: A procedure to design wide-band electromagnetically-coupled stacked microstrip antennas based on a simple network model Authors: Anguera Pros, Jaume; Puente Baliarda, Carles; Borja, C. Abstract: It is well known that microstrip patch antennas have a poor bandwidth due to the small spacing between the patch and the ground plane. A stacked patch configuration has been demonstrated experimentally as a feasible solution, but little information on the design procedure is available. Here, a systematic design procedure based on a single network model is shown. Fri, 17 May 2013 16:31:23 GMT http://hdl.handle.net/2117/19353 2013-05-17T16:31:23Z Anguera Pros, Jaume; Puente Baliarda, Carles; Borja, C. no Antenna radiation patterns, electromagnetic coupling, microstrip antennas It is well known that microstrip patch antennas have a poor bandwidth due to the small spacing between the patch and the ground plane. A stacked patch configuration has been demonstrated experimentally as a feasible solution, but little information on the design procedure is available. Here, a systematic design procedure based on a single network model is shown. http://hdl.handle.net/2117/19352 Title: Iterative network models to predict the performance of Sierpinski fractal antennas and networks Authors: Borja, C.; Puente Baliarda, Carles Abstract: Two simple, fast numerical models to predict the input parameters of antennas and networks whose topologies are that of the Sierpinski gasket and carpet fractal shape, are introduced. These models are based on the same recursive principle used to generate fractal structures. Fri, 17 May 2013 16:28:53 GMT http://hdl.handle.net/2117/19352 2013-05-17T16:28:53Z Borja, C.; Puente Baliarda, Carles no Two simple, fast numerical models to predict the input parameters of antennas and networks whose topologies are that of the Sierpinski gasket and carpet fractal shape, are introduced. These models are based on the same recursive principle used to generate fractal structures. http://hdl.handle.net/2117/19350 Title: ONU optimal gain and position of the distribution element in Rayleigh-limited WDM and TDM PONs with reflective ONU Authors: López Pastor, Eduardo Tommy; Lázaro Villa, José Antonio; Arellano Pinilla, Cristina; Polo Querol, Víctor; Prat Gomà, Josep Joan Abstract: The influence of the distribution element position in PONs is reported. Best Crosstalk-to-Signal ratio (C/S) is achieved if it is placed either in the ONU or OLT vicinity with optimum ONU gain depending of the MUX position Fri, 17 May 2013 14:55:56 GMT http://hdl.handle.net/2117/19350 2013-05-17T14:55:56Z López Pastor, Eduardo Tommy; Lázaro Villa, José Antonio; Arellano Pinilla, Cristina; Polo Querol, Víctor; Prat Gomà, Josep Joan no The influence of the distribution element position in PONs is reported. Best Crosstalk-to-Signal ratio (C/S) is achieved if it is placed either in the ONU or OLT vicinity with optimum ONU gain depending of the MUX position http://hdl.handle.net/2117/19341 Title: Real time 100 GHz MST imaging retina Authors: Alonso del Pino, María; Garg, V.; Garcia Guerra, Carlos Enrique; Romeu Robert, Jordi; Llombart, Nuria; Jofre Roca, Lluís Abstract: A real time tomographic imaging system at 100 GHz based on a retina and Modulated Scattered Technique (MST) is presented in this paper. It consists in applying a low frequency modulation to each probe of an array of antennas in order to coherently detect the electric field by a collector. This system just requires low frequency wiring and reduces the RF equipment necessary for each pixel for a planar surface. The aim of this paper is to analyze the performance of different tomographic imaging processes for the imaging system described. Fri, 17 May 2013 13:52:47 GMT http://hdl.handle.net/2117/19341 2013-05-17T13:52:47Z Alonso del Pino, María; Garg, V.; Garcia Guerra, Carlos Enrique; Romeu Robert, Jordi; Llombart, Nuria; Jofre Roca, Lluís no antenna design, imaging reconstruction, imaging system, MST, Real time, Retina, THz, tomography A real time tomographic imaging system at 100 GHz based on a retina and Modulated Scattered Technique (MST) is presented in this paper. It consists in applying a low frequency modulation to each probe of an array of antennas in order to coherently detect the electric field by a collector. This system just requires low frequency wiring and reduces the RF equipment necessary for each pixel for a planar surface. The aim of this paper is to analyze the performance of different tomographic imaging processes for the imaging system described. http://hdl.handle.net/2117/19340 Title: Stability of the MIRAS amplitude calibration Authors: Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Núria; Martín Neira, Manuel Abstract: Efficient methods to characterize and mitigate long-and short- term drifts in SMOS data have been developed after careful analysis of the external and internal calibration parameters and by accurate modeling of the individual receiver front-ends. A method to characterize this drift has been successfully developed and used to reduce the measured antenna temperature variations. Fri, 17 May 2013 13:43:19 GMT http://hdl.handle.net/2117/19340 2013-05-17T13:43:19Z Corbella Sanahuja, Ignasi; Torres Torres, Francisco; Duffo Ubeda, Núria; Martín Neira, Manuel no Radiometer calibration, Accurate modeling, Amplitude calibration, Antenna temperature, Internal calibration, Radiometer calibration, Receiver front-ends Efficient methods to characterize and mitigate long-and short- term drifts in SMOS data have been developed after careful analysis of the external and internal calibration parameters and by accurate modeling of the individual receiver front-ends. A method to characterize this drift has been successfully developed and used to reduce the measured antenna temperature variations. http://hdl.handle.net/2117/19339 Title: Mathematical model of total cross-tied photovoltaic arrays in mismatching conditions Authors: Ramos Paja, Carlos Andres; Bastidas, Juan David; Saavedra Montes, Andres Julian; Guinjoan Gispert, Francisco; Goez, M. Abstract: This paper presents a mathematical procedure for modeling rectangular (N rows with M modules each) and non-rectangular photovoltaic (PV) arrays in Total Cross-Tied (TCT) configuration operating in uniform and mismatching conditions. The proposed model uses the simple single diode representation for each PV module; then each row of the TCT array is represented as an equivalent non-linear PV circuit with a bypass diode, which allows to represent the TCT array as one string of equivalent PV circuits. The inflection voltages (array voltages that turn off the bypass diodes) of the string are calculated in order to solve only the non-linear equation system related to the active equivalent PV circuits for calculating the array current for a given voltage. Such a strategy reduces the computational burden and improves calculation speed. A TCT array of 4×2 with deep mismatching conditions was implemented in PSIM software to validate the proposed model, obtaining a correlation between model predicted data and the circuital simulation. The accuracy and improved calculation speed of the proposed model allow its use altogether with reconfiguration techniques as well as to reduce the time of energetic evaluations of TCT arrays for PV planning. Fri, 17 May 2013 13:38:51 GMT http://hdl.handle.net/2117/19339 2013-05-17T13:38:51Z Ramos Paja, Carlos Andres; Bastidas, Juan David; Saavedra Montes, Andres Julian; Guinjoan Gispert, Francisco; Goez, M. no Array voltage, Bypass diodes, Calculation speed, Computational burden, Mathematical procedures, Nonlinear equation system, Photovoltaic arrays, PV modules This paper presents a mathematical procedure for modeling rectangular (N rows with M modules each) and non-rectangular photovoltaic (PV) arrays in Total Cross-Tied (TCT) configuration operating in uniform and mismatching conditions. The proposed model uses the simple single diode representation for each PV module; then each row of the TCT array is represented as an equivalent non-linear PV circuit with a bypass diode, which allows to represent the TCT array as one string of equivalent PV circuits. The inflection voltages (array voltages that turn off the bypass diodes) of the string are calculated in order to solve only the non-linear equation system related to the active equivalent PV circuits for calculating the array current for a given voltage. Such a strategy reduces the computational burden and improves calculation speed. A TCT array of 4×2 with deep mismatching conditions was implemented in PSIM software to validate the proposed model, obtaining a correlation between model predicted data and the circuital simulation. The accuracy and improved calculation speed of the proposed model allow its use altogether with reconfiguration techniques as well as to reduce the time of energetic evaluations of TCT arrays for PV planning. http://hdl.handle.net/2117/19338 Title: Resonant pulse-shaping power supply for radar transmitters Authors: Bell Rodriguez, Miguel Victoria Ramo; Roberg, Michael; Pack, Riley; Garcia Fernandez, Pablo; Alarcón Cot, Eduardo José; Popoviç, Zoya; Maksimovic, Dragan Abstract: The final radiofrequency power amplifier (PA) of a radar transmitter module is a large factor in system efficiency. Typical radar transmitter signals are frequency-modulated with constant-amplitude pulse envelopes in order to optimize efficiency, resulting in spectral broadening and power radiated outside of the radar frequency band. This paper demonstrates a PA with a dynamic power supply which enables high efficiency while reducing the spectral emissions. The resonant pulse-shaping power supply generates a raised-cosine pulse envelope waveform with efficiency greater than 90% and peak envelope power around 6 W. Measured results with a 2.14-GHz GaN power amplifier with an efficiency of 76% at peak power demonstrate over 67% transmitter efficiency. Fri, 17 May 2013 13:29:14 GMT http://hdl.handle.net/2117/19338 2013-05-17T13:29:14Z Bell Rodriguez, Miguel Victoria Ramo; Roberg, Michael; Pack, Riley; Garcia Fernandez, Pablo; Alarcón Cot, Eduardo José; Popoviç, Zoya; Maksimovic, Dragan no pulse shaping methods, Pulsed power supplies, radar transmitters The final radiofrequency power amplifier (PA) of a radar transmitter module is a large factor in system efficiency. Typical radar transmitter signals are frequency-modulated with constant-amplitude pulse envelopes in order to optimize efficiency, resulting in spectral broadening and power radiated outside of the radar frequency band. This paper demonstrates a PA with a dynamic power supply which enables high efficiency while reducing the spectral emissions. The resonant pulse-shaping power supply generates a raised-cosine pulse envelope waveform with efficiency greater than 90% and peak envelope power around 6 W. Measured results with a 2.14-GHz GaN power amplifier with an efficiency of 76% at peak power demonstrate over 67% transmitter efficiency. http://hdl.handle.net/2117/19336 Title: Secondary control for reactive power sharing in droop-controlled islanded microgrids Authors: Micallef, A.; Apap, Maurice; Spiteri Staines, C.; Guerrero Zapata, Josep Maria Abstract: This paper focuses on the islanded operation of microgrids. In this mode of operation, the microsources are required to cooperate autonomously to regulate the local grid voltage and frequency. Droop control is typically used to achieve this autonomous voltage and frequency regulation. However, droop control has real and reactive power sharing limitations when there are mismatches between the microsources. This paper analyses the effect due to mismatches in the power line impedances connecting the source inverters to the microgrid. From the simulations results obtained, it was shown that the reactive power demand is unequally shared between the microsource inverters when there are mismatches between the power line impedances. To achieve equal reactive power sharing between the inverters, an external loop requiring low bandwidth communications was implemented in a central controller. Simulation results are presented showing the feasibility of the proposed solution in achieving reactive power sharing between the inverters connected to the microgrid. Fri, 17 May 2013 12:52:13 GMT http://hdl.handle.net/2117/19336 2013-05-17T12:52:13Z Micallef, A.; Apap, Maurice; Spiteri Staines, C.; Guerrero Zapata, Josep Maria no islanded operation, low bandwidth communication, microgrids, reactive power sharing This paper focuses on the islanded operation of microgrids. In this mode of operation, the microsources are required to cooperate autonomously to regulate the local grid voltage and frequency. Droop control is typically used to achieve this autonomous voltage and frequency regulation. However, droop control has real and reactive power sharing limitations when there are mismatches between the microsources. This paper analyses the effect due to mismatches in the power line impedances connecting the source inverters to the microgrid. From the simulations results obtained, it was shown that the reactive power demand is unequally shared between the microsource inverters when there are mismatches between the power line impedances. To achieve equal reactive power sharing between the inverters, an external loop requiring low bandwidth communications was implemented in a central controller. Simulation results are presented showing the feasibility of the proposed solution in achieving reactive power sharing between the inverters connected to the microgrid. http://hdl.handle.net/2117/19332 Title: CMOS fast transient low-dropout regulator Authors: Saberkari, Alireza; Alarcón Cot, Eduardo José; Shokouhi, Shahriar B. Abstract: In this paper a fast transient response CFA-based low-dropout regulator (LDO) is introduced. The circuit is stable for 0-100mA output load current and a 1μF output capacitor without any internal compensation. The CFA consists of a voltage follower with output local current-current feedback based on a level-shifted flipped voltage follower (LSFVF) which is instrumental to achieve high regulation and fast transient response. The inverting output buffer stage of the CFA together with current-mirror-based driving of the pass transistor results in high PSRR. Full transistor-level simulation results for an AMS 0.35μm CMOS process design reveal that the proposed LDO dissipates 58μA quiescent current at no-load condition and in worst case conditions has a current efficiency of 99.8%. For a 1μF output capacitor, the maximum output voltage variation to a 0-100mA load transient with rise and fall time of 10 and 100ns is only 2.5mV, and the PSRR is smaller than -58dB over the entire load current range. Fri, 17 May 2013 12:16:56 GMT http://hdl.handle.net/2117/19332 2013-05-17T12:16:56Z Saberkari, Alireza; Alarcón Cot, Eduardo José; Shokouhi, Shahriar B. no fast transient, level-shifted flipped voltage follower, low-dropout In this paper a fast transient response CFA-based low-dropout regulator (LDO) is introduced. The circuit is stable for 0-100mA output load current and a 1μF output capacitor without any internal compensation. The CFA consists of a voltage follower with output local current-current feedback based on a level-shifted flipped voltage follower (LSFVF) which is instrumental to achieve high regulation and fast transient response. The inverting output buffer stage of the CFA together with current-mirror-based driving of the pass transistor results in high PSRR. Full transistor-level simulation results for an AMS 0.35μm CMOS process design reveal that the proposed LDO dissipates 58μA quiescent current at no-load condition and in worst case conditions has a current efficiency of 99.8%. For a 1μF output capacitor, the maximum output voltage variation to a 0-100mA load transient with rise and fall time of 10 and 100ns is only 2.5mV, and the PSRR is smaller than -58dB over the entire load current range. http://hdl.handle.net/2117/19330 Title: Optimal linear correction in LMMSE estimation using moments of the complex inverse Wishart distribution Authors: Serra, Jordi; Nájar Martón, Montserrat Abstract: The conventional linear minimum mean square error esti- mator (LMMSE) suffers a severe performance degradation whenever the sample size is comparable to the observation dimension. In order to tackle this problem, we propose an optimal linear correction of the conventional LMMSE, which minimizes the average mean square error (MSE) by using the moments of the complex inverse Wishart distribution. Numerical simulations highlight that the proposed estimator dramatically outperforms the conventional LMMSE in the small sample size regime Fri, 17 May 2013 12:04:30 GMT http://hdl.handle.net/2117/19330 2013-05-17T12:04:30Z Serra, Jordi; Nájar Martón, Montserrat no Complex Inverse Wishart, LMMSE, Shrinkage, Small sample size The conventional linear minimum mean square error esti- mator (LMMSE) suffers a severe performance degradation whenever the sample size is comparable to the observation dimension. In order to tackle this problem, we propose an optimal linear correction of the conventional LMMSE, which minimizes the average mean square error (MSE) by using the moments of the complex inverse Wishart distribution. Numerical simulations highlight that the proposed estimator dramatically outperforms the conventional LMMSE in the small sample size regime http://hdl.handle.net/2117/19329 Title: Licensing open spectrum systems Authors: Vázquez, Miguel Angel; Pérez Neira, Ana Isabel; Lagunas Hernandez, Miguel A. Abstract: This paper studies how the spectrum regulation could change in the future open spectrum communication systems. Due to their huge success in short-range communication systems (WiFi, Zigbee, ...), broader area telecommunication providers might mimic the open spectrum philosophy to their systems. Nevertheless, current wireless open spectrum systems are not designed for wide areas and they do not provide QoS to their users. This work proposes an alternative to the nowadays open spectrum systems in order to fulfill those requirements. Optimal power transmission strategies are derived. Numerical results show the performance of our proposal. Fri, 17 May 2013 12:00:36 GMT http://hdl.handle.net/2117/19329 2013-05-17T12:00:36Z Vázquez, Miguel Angel; Pérez Neira, Ana Isabel; Lagunas Hernandez, Miguel A. no Numerical results, Optimal power, Short-range communication, Spectrum communications, Spectrum regulation, Spectrum systems, Telecommunication providers, Transmission strategies, Wide area This paper studies how the spectrum regulation could change in the future open spectrum communication systems. Due to their huge success in short-range communication systems (WiFi, Zigbee, ...), broader area telecommunication providers might mimic the open spectrum philosophy to their systems. Nevertheless, current wireless open spectrum systems are not designed for wide areas and they do not provide QoS to their users. This work proposes an alternative to the nowadays open spectrum systems in order to fulfill those requirements. Optimal power transmission strategies are derived. Numerical results show the performance of our proposal.