http://hdl.handle.net/2117/3924 Sun, 26 May 2013 09:03:32 GMT 2013-05-26T09:03:32Z webmaster.bupc@upc.edu Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació no 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/2117/19268 Title: Special issue on power amplifier linearization Authors: Wood, John; Bertran Albertí, Eduardo Wed, 15 May 2013 16:33:00 GMT http://hdl.handle.net/2117/19268 2013-05-15T16:33:00Z Wood, John; Bertran Albertí, Eduardo no Guest editorial. Special issue on Power Amplifier linearisation http://hdl.handle.net/2117/19181 Title: A solution framework to provide management services for wireless communications in the digital home Authors: Ferrús Ferré, Ramón Antonio; Sallent Roig, José Oriol; Pérez Romero, Jordi; Agustí Comes, Ramon Abstract: The future digital home (DH) is envisioned as a place where a plethora of diverse personal and machine-to-machine communications will coexist to support different applications in areas such as information and entertainment, home automation, home health care and home security and management. Wireless technologies are usually the preferred solution to cope with DH communications for their ease of installation and use. However, expected capacity demand and the lack of coordination between an increasing number of diverse wireless devices in use within the DH is seriously challenging the performance and usability of wireless technologies. This article outlines a novel technical solution intended to enhance capacity and quality of DH wireless communications. The proposed solution establishes a radio-independent coexistence framework where key operational radio settings of DH devices are coordinately determined, and new spectrum sources other than traditional ISM bands can be exploited for DH communications. The addressed solution enables a business player to offer management services for DH wireless communications so that ordinary users can be relieved of complex management tasks likely to arise within the DH. The article discusses how potential management service providers could benefit from the proposed solution. Besides, the functional architecture of the proposed solution together with the set of procedures necessary for the management of the DH wireless communications are outlined. A realistic indoor scenario is presented as an illustrative use case to show how proper decision making logic in managing the DH could improve the efficiency by selecting the most suitable spectrum for in-house wireless communications. Finally, the main implementation issues are identified and discussed in order to outline a feasible roadmap. Mon, 13 May 2013 14:15:57 GMT http://hdl.handle.net/2117/19181 2013-05-13T14:15:57Z Ferrús Ferré, Ramón Antonio; Sallent Roig, José Oriol; Pérez Romero, Jordi; Agustí Comes, Ramon no The future digital home (DH) is envisioned as a place where a plethora of diverse personal and machine-to-machine communications will coexist to support different applications in areas such as information and entertainment, home automation, home health care and home security and management. Wireless technologies are usually the preferred solution to cope with DH communications for their ease of installation and use. However, expected capacity demand and the lack of coordination between an increasing number of diverse wireless devices in use within the DH is seriously challenging the performance and usability of wireless technologies. This article outlines a novel technical solution intended to enhance capacity and quality of DH wireless communications. The proposed solution establishes a radio-independent coexistence framework where key operational radio settings of DH devices are coordinately determined, and new spectrum sources other than traditional ISM bands can be exploited for DH communications. The addressed solution enables a business player to offer management services for DH wireless communications so that ordinary users can be relieved of complex management tasks likely to arise within the DH. The article discusses how potential management service providers could benefit from the proposed solution. Besides, the functional architecture of the proposed solution together with the set of procedures necessary for the management of the DH wireless communications are outlined. A realistic indoor scenario is presented as an illustrative use case to show how proper decision making logic in managing the DH could improve the efficiency by selecting the most suitable spectrum for in-house wireless communications. Finally, the main implementation issues are identified and discussed in order to outline a feasible roadmap. http://hdl.handle.net/2117/19149 Title: Distinguishing signatures of determinism and stochasticity in spiking complex systems Authors: Aragoneses Aguado, Andrés; Rubido, Nicolás; Tiana Alsina, Jordi; Torrent Serra, Maria del Carmen; Masoller Alonso, Cristina Thu, 09 May 2013 12:28:42 GMT http://hdl.handle.net/2117/19149 2013-05-09T12:28:42Z Aragoneses Aguado, Andrés; Rubido, Nicolás; Tiana Alsina, Jordi; Torrent Serra, Maria del Carmen; Masoller Alonso, Cristina no http://hdl.handle.net/2117/19143 Title: Weak measurements with orbital-angular-momentum pointer states Authors: Puentes, G.; Hermosa, N.; Pérez Torres, Juan Abstract: Weak measurements are a unique tool for accessing information about weakly interacting quantum systems with minimal back action. Joint weak measurements of single-particle operators with pointer states characterized by a two-dimensional Gaussian distribution can provide, in turn, key information about quantum correlations that can be relevant for quantum information applications. Here we demonstrate that by employing two-dimensional pointer states endowed with orbital angular momentum (OAM), it is possible to extract weak values of the higher order moments of single-particle operators, an inaccessible quantity with Gaussian pointer states only. We provide a specific example that illustrates the advantages of our method both in terms of signal enhancement and information retrieval. Wed, 08 May 2013 18:22:45 GMT http://hdl.handle.net/2117/19143 2013-05-08T18:22:45Z Puentes, G.; Hermosa, N.; Pérez Torres, Juan no Weak measurements are a unique tool for accessing information about weakly interacting quantum systems with minimal back action. Joint weak measurements of single-particle operators with pointer states characterized by a two-dimensional Gaussian distribution can provide, in turn, key information about quantum correlations that can be relevant for quantum information applications. Here we demonstrate that by employing two-dimensional pointer states endowed with orbital angular momentum (OAM), it is possible to extract weak values of the higher order moments of single-particle operators, an inaccessible quantity with Gaussian pointer states only. We provide a specific example that illustrates the advantages of our method both in terms of signal enhancement and information retrieval. http://hdl.handle.net/2117/18978 Title: Modeling the routing and spectrum allocation problem for flexgrid optical networks Authors: Velasco Esteban, Luis Domingo; Klinkowski, Miroslaw; Ruiz Ramírez, Marc; Comellas Colomé, Jaume Abstract: Flexgrid optical networks are attracting huge interest due to their higher spectrum efficiency and flexibility in comparison with traditional wavelength switched optical networks based on the wavelength division multiplexing technology. To properly analyze, design, plan, and operate flexible and elastic networks, efficient methods are required for the routing and spectrum allocation (RSA) problem. Specifically, the allocated spectral resources must be, in absence of spectrum converters, the same along the links in the route (the continuity constraint) and contiguous in the spectrum (the contiguity constraint). In light of the fact that the contiguity constraint adds huge complexity to the RSA problem,we introduce the concept of channels for the representation of contiguous spectral resources. In this paper, we show that the use of a pre-computed set of channels allows considerably reducing the problem complexity. In our study, we address an off-line RSA problem in which enough spectrum needs to be allocated for each demand of a given traffic matrix. To this end, we present novel integer lineal programming (ILP) formulations of RSA that are based on the assignment of channels. The evaluation results reveal that the proposed approach allows solving the RSA problem much more efficiently than previously proposed ILP-based methods and it can be applied even for realistic problem instances, contrary to previous ILP formulations. Wed, 24 Apr 2013 11:33:35 GMT http://hdl.handle.net/2117/18978 2013-04-24T11:33:35Z Velasco Esteban, Luis Domingo; Klinkowski, Miroslaw; Ruiz Ramírez, Marc; Comellas Colomé, Jaume no Flexgrid optical networks, Off-line routing, Spectrum allocation Flexgrid optical networks are attracting huge interest due to their higher spectrum efficiency and flexibility in comparison with traditional wavelength switched optical networks based on the wavelength division multiplexing technology. To properly analyze, design, plan, and operate flexible and elastic networks, efficient methods are required for the routing and spectrum allocation (RSA) problem. Specifically, the allocated spectral resources must be, in absence of spectrum converters, the same along the links in the route (the continuity constraint) and contiguous in the spectrum (the contiguity constraint). In light of the fact that the contiguity constraint adds huge complexity to the RSA problem,we introduce the concept of channels for the representation of contiguous spectral resources. In this paper, we show that the use of a pre-computed set of channels allows considerably reducing the problem complexity. In our study, we address an off-line RSA problem in which enough spectrum needs to be allocated for each demand of a given traffic matrix. To this end, we present novel integer lineal programming (ILP) formulations of RSA that are based on the assignment of channels. The evaluation results reveal that the proposed approach allows solving the RSA problem much more efficiently than previously proposed ILP-based methods and it can be applied even for realistic problem instances, contrary to previous ILP formulations. http://hdl.handle.net/2117/18819 Title: A novel linear feature detector for SAR images Authors: He, Chu; Liao, Z.X.; Yang, Fang; Deng, Xinping; Liao, M.S. Abstract: A new linear feature detector for synthetic aperture radar (SAR) images is presented in this article by embedding a three-region filter into the wedgelet analysis framework. One of its main features is that it can detect linear features with a range of varying widths and orientations in the same image by changing the direction and size of the detector mask within a multiscale framework. In addition, this detector takes into account both statistical and geometrical characteristics to detect line segments directly instead of detecting target pixels. To show its effectiveness, the detector is applied to extract one of the most important linear features: roads. Results and comparisons with several multiscale analysis techniques as well as ratio correlation detector on DLR E-SAR images reveal its advantages. Tue, 16 Apr 2013 13:50:21 GMT http://hdl.handle.net/2117/18819 2013-04-16T13:50:21Z He, Chu; Liao, Z.X.; Yang, Fang; Deng, Xinping; Liao, M.S. no A new linear feature detector for synthetic aperture radar (SAR) images is presented in this article by embedding a three-region filter into the wedgelet analysis framework. One of its main features is that it can detect linear features with a range of varying widths and orientations in the same image by changing the direction and size of the detector mask within a multiscale framework. In addition, this detector takes into account both statistical and geometrical characteristics to detect line segments directly instead of detecting target pixels. To show its effectiveness, the detector is applied to extract one of the most important linear features: roads. Results and comparisons with several multiscale analysis techniques as well as ratio correlation detector on DLR E-SAR images reveal its advantages. http://hdl.handle.net/2117/18796 Title: Analysis of the hidden and exposed terminal effects in wireless networks with cooperative ARQ Authors: Alonso-Zarate, J.; Alonso Zárate, Luis Gonzaga; Kormentzas, Georgios; Verikoukis, Christos Abstract: Cooperative Automatic Retransmission Request (C-ARQ) schemes allow those users which overhear a transmission to act as spontaneous relays when a packet has been received with errors at destination. When these users assist a source-destination pair in the retransmission process, the area exposed to the original transmission increases in comparison with non-cooperative ARQ schemes. In addition, the extension of the transmission time, due to the retransmissions, increases the vulnerability of a transmission to the hidden terminal problem. The paper provides a performance analysis of the hidden and exposed terminal effects in an 802.11-based wireless network where a C-ARQ scheme is executed at the Medium Access Control (MAC) layer. The presented analysis is supported by computer-based simulations. Mon, 15 Apr 2013 14:15:59 GMT http://hdl.handle.net/2117/18796 2013-04-15T14:15:59Z Alonso-Zarate, J.; Alonso Zárate, Luis Gonzaga; Kormentzas, Georgios; Verikoukis, Christos no Cooperative Automatic Retransmission Request (C-ARQ) schemes allow those users which overhear a transmission to act as spontaneous relays when a packet has been received with errors at destination. When these users assist a source-destination pair in the retransmission process, the area exposed to the original transmission increases in comparison with non-cooperative ARQ schemes. In addition, the extension of the transmission time, due to the retransmissions, increases the vulnerability of a transmission to the hidden terminal problem. The paper provides a performance analysis of the hidden and exposed terminal effects in an 802.11-based wireless network where a C-ARQ scheme is executed at the Medium Access Control (MAC) layer. The presented analysis is supported by computer-based simulations. http://hdl.handle.net/2117/18578 Title: Analysis of energy efficient distributed neighbour discovery mechanisms for machine-to-machine networks Authors: Vazquez, Francisco; Alonso-Zarate, J.; Alonso Zárate, Luis Gonzaga; Dohler, Mischa Abstract: Energy efficiency is one of the main challenges of Machine-to-Machine (M2M) networks, since they aim at connecting devices with limited access to power sources and operate without human intervention. It has been shown in the past that the use of short-range cooperation between wireless devices equipped with multiple Radio Access Technologies (RATs) can achieve energy savings and extend the lifetime of cellular wireless networks. Devices with cellular connectivity can become temporary gateways to provide energy-constrained devices within the short-range cluster with access to the long range cellular infrastructure. To this end, the devices need to discover their neighbours using their short-range radio interface to identify and select potential gateway candidates. Existing neighbour discovery mechanisms perform poorly in terms of delay and energy consumption to maintain, continuously at each device, complete neighbourhood information, and thus may not be suitable for energy-constrained M2M networks. In this paper, we focus on distributed neighbour discovery mechanisms that are initiated dynamically and spontaneously by a single device to discover only its single-hop neighbours. We formulate accurate delay and energy models of three discovery mechanisms based on frame slotted-ALOHA and contention tree algorithms, and compare their performance in terms of delay and energy consumption. Wed, 03 Apr 2013 14:15:55 GMT http://hdl.handle.net/2117/18578 2013-04-03T14:15:55Z Vazquez, Francisco; Alonso-Zarate, J.; Alonso Zárate, Luis Gonzaga; Dohler, Mischa no Energy efficiency is one of the main challenges of Machine-to-Machine (M2M) networks, since they aim at connecting devices with limited access to power sources and operate without human intervention. It has been shown in the past that the use of short-range cooperation between wireless devices equipped with multiple Radio Access Technologies (RATs) can achieve energy savings and extend the lifetime of cellular wireless networks. Devices with cellular connectivity can become temporary gateways to provide energy-constrained devices within the short-range cluster with access to the long range cellular infrastructure. To this end, the devices need to discover their neighbours using their short-range radio interface to identify and select potential gateway candidates. Existing neighbour discovery mechanisms perform poorly in terms of delay and energy consumption to maintain, continuously at each device, complete neighbourhood information, and thus may not be suitable for energy-constrained M2M networks. In this paper, we focus on distributed neighbour discovery mechanisms that are initiated dynamically and spontaneously by a single device to discover only its single-hop neighbours. We formulate accurate delay and energy models of three discovery mechanisms based on frame slotted-ALOHA and contention tree algorithms, and compare their performance in terms of delay and energy consumption. http://hdl.handle.net/2117/18576 Title: Uniplanar bandpass filters based on multimodal immitance inverters and end-coupled slotline resonators Authors: Contreras Lizarraga, Adrián Arturo; Ribó, Miquel; Pradell i Cara, Lluís; Blondy, Pierre Abstract: This paper presents the design and implementation of uniplanar bandpass filters that use end-coupled slotline resonators and a new kind of multimodal immitance inverter. These inverters are based on an asymmetric shunt-short-circuit coplanar waveguide (CPW) transition, and are modeled using a multimodal circuit model, which takes into account both fundamental modes of the CPW (the even and the odd modes). From this model, analytical design expressions for the inverters are obtained. These structures are used as input/output inverters of a new class of compact low-loss arbitrary-order easily reconfigurable uniplanar filters featuring half-wavelength and quarter-wavelength end-coupled resonators. A multimodal model is obtained for these filters, which allows an accurate analysis, design, and prediction of their behavior. By using these multimodal tools, three second- and fourth-order prototypes, and a second-order frequency-tunable prototype, were designed and implemented. The fourth-order filter has an insertion loss of 2.2 dB at 2 GHz with an out-of-band rejection better than 20 dB in an extremelywide frequency band. The frequency-tunable filter features a tuning range from 1 to 1.37 GHz with quasi-constant 3-dB bandwidth from 121 to 135 MHz. The measurements show a good agreement with the proposed multimodal model, thus validating the model and the design methodology. Wed, 03 Apr 2013 14:07:47 GMT http://hdl.handle.net/2117/18576 2013-04-03T14:07:47Z Contreras Lizarraga, Adrián Arturo; Ribó, Miquel; Pradell i Cara, Lluís; Blondy, Pierre no Bandpass filter, coplanar stripline (CPS), coplanar waveguide (CPW), multimodal circuit, out-of-band rejection, slotline, tunable filter, uniplanar circuits This paper presents the design and implementation of uniplanar bandpass filters that use end-coupled slotline resonators and a new kind of multimodal immitance inverter. These inverters are based on an asymmetric shunt-short-circuit coplanar waveguide (CPW) transition, and are modeled using a multimodal circuit model, which takes into account both fundamental modes of the CPW (the even and the odd modes). From this model, analytical design expressions for the inverters are obtained. These structures are used as input/output inverters of a new class of compact low-loss arbitrary-order easily reconfigurable uniplanar filters featuring half-wavelength and quarter-wavelength end-coupled resonators. A multimodal model is obtained for these filters, which allows an accurate analysis, design, and prediction of their behavior. By using these multimodal tools, three second- and fourth-order prototypes, and a second-order frequency-tunable prototype, were designed and implemented. The fourth-order filter has an insertion loss of 2.2 dB at 2 GHz with an out-of-band rejection better than 20 dB in an extremelywide frequency band. The frequency-tunable filter features a tuning range from 1 to 1.37 GHz with quasi-constant 3-dB bandwidth from 121 to 135 MHz. The measurements show a good agreement with the proposed multimodal model, thus validating the model and the design methodology. http://hdl.handle.net/2117/18425 Title: Gene expression data classification combining hierarchical representation and efficient feature selection Authors: Bosio, Mattia; Bellot Pujalte, Pau; Salembier Clairon, Philippe Jean; Oliveras Vergés, Albert Abstract: A general framework for microarray data classification is proposed in this paper. It pro- duces precise and reliable classifiers through a two-step approach. At first, the original feature set is enhanced by a new set of features called metagenes. These new features are obtained through a hierarchical clustering process on the original data. Two different metagene generation rules have been analyzed, called Treelets clustering and Euclidean clustering. Metagenes creation is attractive for several reasons: first, they can improve the classification since they broaden the available feature space and capture the com- mon behavior of similar genes reducing the residual measurement noise. Furthermore, by analyzing some of the chosen metagenes for classification with gene set enrichment analysis algorithms, it is shown how metagenes can summarize the behavior of func- tionally related probe sets. Additionally, metagenes can point out, still undocumented, highly discriminant probe sets numerically related to other probes endowed with prior biological information in order to contribute to the knowledge discovery process. The second step of the framework is the feature selection which applies the Improved Sequential Floating Forward Selection algorithm (IFFS) to properly choose a subset from the available feature set for classification composed of genes and metagenes. Considering the microarray sample scarcity problem, besides the classical error rate, a reliability measure is introduced to improve the feature selection process. Different scoring schemes are studied to choose the best one using both error rate and reliability. The Linear Discriminant Analysis classifier (LDA) has been used throughout this work, due to its good characteristics, but the proposed framework can be used with almost any classifier. The potential of the proposed framework has been evaluated analyzing all the publicly available datasets offered by the Micro Array Quality Control Study, phase II (MAQC). The comparative results showed that the proposed framework can compete with a wide variety of state of the art alternatives and it can obtain the best mean performance if a particular setup is chosen. A Monte Carlo simulation confirmed that the proposed framework obtains stable and repeatable results. Tue, 19 Mar 2013 18:10:53 GMT http://hdl.handle.net/2117/18425 2013-03-19T18:10:53Z Bosio, Mattia; Bellot Pujalte, Pau; Salembier Clairon, Philippe Jean; Oliveras Vergés, Albert no feature selection, hierarchical representation, LDA, metagenes, Microarray classification, Treelets A general framework for microarray data classification is proposed in this paper. It pro- duces precise and reliable classifiers through a two-step approach. At first, the original feature set is enhanced by a new set of features called metagenes. These new features are obtained through a hierarchical clustering process on the original data. Two different metagene generation rules have been analyzed, called Treelets clustering and Euclidean clustering. Metagenes creation is attractive for several reasons: first, they can improve the classification since they broaden the available feature space and capture the com- mon behavior of similar genes reducing the residual measurement noise. Furthermore, by analyzing some of the chosen metagenes for classification with gene set enrichment analysis algorithms, it is shown how metagenes can summarize the behavior of func- tionally related probe sets. Additionally, metagenes can point out, still undocumented, highly discriminant probe sets numerically related to other probes endowed with prior biological information in order to contribute to the knowledge discovery process. The second step of the framework is the feature selection which applies the Improved Sequential Floating Forward Selection algorithm (IFFS) to properly choose a subset from the available feature set for classification composed of genes and metagenes. Considering the microarray sample scarcity problem, besides the classical error rate, a reliability measure is introduced to improve the feature selection process. Different scoring schemes are studied to choose the best one using both error rate and reliability. The Linear Discriminant Analysis classifier (LDA) has been used throughout this work, due to its good characteristics, but the proposed framework can be used with almost any classifier. The potential of the proposed framework has been evaluated analyzing all the publicly available datasets offered by the Micro Array Quality Control Study, phase II (MAQC). The comparative results showed that the proposed framework can compete with a wide variety of state of the art alternatives and it can obtain the best mean performance if a particular setup is chosen. A Monte Carlo simulation confirmed that the proposed framework obtains stable and repeatable results. http://hdl.handle.net/2117/18353 Title: Determination of the overlap factor and its enhancement for medium-size tropospheric lidar systems: a ray-tracing approach Authors: Kumar, Dhiraj; Rocadenbosch Burillo, Francisco Abstract: The problem of overlap factor (OVF) computation and its near-range sensitivity for medium-size aperture ( f ∕ 10 , f ∕ 11 ) bi-axial tropospheric lidar systems using ray-tracing sim- ulation software is presented. The method revisits both detector and fiber optics coupling alter- natives at the telescope focal-plane along with the insertion of a field lens. A sensitivity analysis is carried out as a function of laser divergence, field lens, and detector/fiber positions, detector size, and the fiber ’ s core diameter and numerical aperture. The ray-tracing approach presented here is straightforward and a comparatively much simpler solution than analytical-based meth- ods. Parametric simulations are carried out to show that both approaches are coincident. Insertion of a field lens proves to be an elegant and low sensitivity solution for OVF enhancement, par- ticularly, in the near-range of the lidar Fri, 15 Mar 2013 15:03:19 GMT http://hdl.handle.net/2117/18353 2013-03-15T15:03:19Z Kumar, Dhiraj; Rocadenbosch Burillo, Francisco no The problem of overlap factor (OVF) computation and its near-range sensitivity for medium-size aperture ( f ∕ 10 , f ∕ 11 ) bi-axial tropospheric lidar systems using ray-tracing sim- ulation software is presented. The method revisits both detector and fiber optics coupling alter- natives at the telescope focal-plane along with the insertion of a field lens. A sensitivity analysis is carried out as a function of laser divergence, field lens, and detector/fiber positions, detector size, and the fiber ’ s core diameter and numerical aperture. The ray-tracing approach presented here is straightforward and a comparatively much simpler solution than analytical-based meth- ods. Parametric simulations are carried out to show that both approaches are coincident. Insertion of a field lens proves to be an elegant and low sensitivity solution for OVF enhancement, par- ticularly, in the near-range of the lidar http://hdl.handle.net/2117/18321 Title: Processing multidimensional SAR and hyperspectral images with binary partition tree Authors: Alonso González, Alberto; Valero, Silvia; Chanussot, Jocelyn; López Martínez, Carlos; Salembier Clairon, Philippe Jean Abstract: The current increase of spatial as well as spectral resolutions of modern remote sensing sensors represents a real opportunity for many prac tical applications but also generates important challenges in terms of image processing. In particular, the spatial correlation between pixels and/or the spectral correlation between spectral bands of a given pixel cannot be ignored. The traditional pixel-based representation of images does not facilitate the handling of these correlations. In this paper, we discuss the inter est of a particular hierarchical region-based representation of images based on binary partition tree (BPT). This representation approach is very flexible as it can be applied to any type of image. Here both optical and radar images will be discussed. Moreover, once the image representation is computed, it can be used for many different applications. Filtering, segmentation, and classifica- tion will be detailed in this paper. In all cases, the interest of the BPT representation over the classical pixel-based representa- tion will be highlighted Thu, 14 Mar 2013 19:10:03 GMT http://hdl.handle.net/2117/18321 2013-03-14T19:10:03Z Alonso González, Alberto; Valero, Silvia; Chanussot, Jocelyn; López Martínez, Carlos; Salembier Clairon, Philippe Jean no The current increase of spatial as well as spectral resolutions of modern remote sensing sensors represents a real opportunity for many prac tical applications but also generates important challenges in terms of image processing. In particular, the spatial correlation between pixels and/or the spectral correlation between spectral bands of a given pixel cannot be ignored. The traditional pixel-based representation of images does not facilitate the handling of these correlations. In this paper, we discuss the inter est of a particular hierarchical region-based representation of images based on binary partition tree (BPT). This representation approach is very flexible as it can be applied to any type of image. Here both optical and radar images will be discussed. Moreover, once the image representation is computed, it can be used for many different applications. Filtering, segmentation, and classifica- tion will be detailed in this paper. In all cases, the interest of the BPT representation over the classical pixel-based representa- tion will be highlighted http://hdl.handle.net/2117/18290 Title: Sparse correlation matching-based spectrum sensing for open spectrum communications Authors: Lagunas Targarona, Eva; Nájar Martón, Montserrat Abstract: To deal with the current spectrum scarcity problem and exploiting the fact that exclusive access through tightly regulated licensing leads to idle spectrum, cognitive radio has been proposed as a way to reuse this underutilized spectrum in an opportunistic manner, i.e., allowing the use of temporarily unused licensed spectrum to secondary users who have no spectrum licenses. To protect the licensed users from the cognitive users ’ interference, the opportunistic user requires knowledge of the original license holder activity. In this article, a feature-based approach for spectrum sensing based on periodic non-uniform sampling is addressed. In particular, we face the compressed-sampling version of detecting predetermined spectral shapes in sparse wideband regimes by means of a correlation-matching procedure. Wed, 13 Mar 2013 19:36:35 GMT http://hdl.handle.net/2117/18290 2013-03-13T19:36:35Z Lagunas Targarona, Eva; Nájar Martón, Montserrat no To deal with the current spectrum scarcity problem and exploiting the fact that exclusive access through tightly regulated licensing leads to idle spectrum, cognitive radio has been proposed as a way to reuse this underutilized spectrum in an opportunistic manner, i.e., allowing the use of temporarily unused licensed spectrum to secondary users who have no spectrum licenses. To protect the licensed users from the cognitive users ’ interference, the opportunistic user requires knowledge of the original license holder activity. In this article, a feature-based approach for spectrum sensing based on periodic non-uniform sampling is addressed. In particular, we face the compressed-sampling version of detecting predetermined spectral shapes in sparse wideband regimes by means of a correlation-matching procedure. http://hdl.handle.net/2117/18289 Title: Determining building interior structures using compressive sensing Authors: Lagunas Targarona, Eva; Amin, Moeness; Ahmad, Fauzia; Nájar Martón, Montserrat Abstract: We consider imaging of the building interior structures using Compressive Sensing (CS) with applications to through-the-wall imaging and urban sensing. We consider a monostatic synthetic aperture radar imaging system employing stepped frequency waveform. The proposed approach exploits prior information of building construction practices to form an appropriate sparse representation of the building interior layout. We devise a dictionary of possible wall locations, which is consistent with the fact that interior walls are typically parallel or perpendicular to the front wall. The dictionary accounts for the dominant normal angle reflections from exterior and interior walls for the monostatic imaging system. Compressive sensing is applied to a reduced set of observations to recover the true positions of the walls. Additional information about interior walls can be obtained using a dictionary of possible corner reflectors, which is the response of the junction of two walls. Supporting results based on simulation and laboratory experiments are provided. It is shown that the proposed sparsifying basis outperforms the conventional through-the-wall CS model, the wavelet sparsifying basis, and the block sparse model for building interior layout detection. Wed, 13 Mar 2013 19:26:11 GMT http://hdl.handle.net/2117/18289 2013-03-13T19:26:11Z Lagunas Targarona, Eva; Amin, Moeness; Ahmad, Fauzia; Nájar Martón, Montserrat no We consider imaging of the building interior structures using Compressive Sensing (CS) with applications to through-the-wall imaging and urban sensing. We consider a monostatic synthetic aperture radar imaging system employing stepped frequency waveform. The proposed approach exploits prior information of building construction practices to form an appropriate sparse representation of the building interior layout. We devise a dictionary of possible wall locations, which is consistent with the fact that interior walls are typically parallel or perpendicular to the front wall. The dictionary accounts for the dominant normal angle reflections from exterior and interior walls for the monostatic imaging system. Compressive sensing is applied to a reduced set of observations to recover the true positions of the walls. Additional information about interior walls can be obtained using a dictionary of possible corner reflectors, which is the response of the junction of two walls. Supporting results based on simulation and laboratory experiments are provided. It is shown that the proposed sparsifying basis outperforms the conventional through-the-wall CS model, the wavelet sparsifying basis, and the block sparse model for building interior layout detection.