A Secure Cooperative Sensing Protocol for Cognitive Radio Networks

Cognitive radio networks sense spectrum occupancyand manage themselves to operate in unused bands without disturbing licensed users. Spectrum sensing is more accurate if jointly performed by several reliable nodes. Even though cooperative sensing is an active area of research, the secureauthentication of local sensing reports remains unsolved, thus empowering false results. This paper presents a distributed protocol based on digital signatures and hash functions, and ananalysis of its security features. The system allows determining a final sensing decision from multiple sources in a quick and secure way.

Report on theorerical results of power generation and conversion

Experimental results of a new controller able to support bidirectional power flow in a full-bridge rectifier with boost-like topology are obtained. The controller is computed using port Hamiltonian passivity techniques for a suitable generalized state space averaging truncation system, which transforms the control objectives, namely constant output voltage dc-bus and unity input power factor, into a regulation problem. Simulation results for the full system show the essential correctness of the simplifications introduced to obtain the controller, although some small experimental discrepancies point to several aspects that need further improvement.

Hybrid model of a double-fed induction machine and back-to-back converter

This report details the port interconnection of two subsystems: a power electronics subsystem (a back-to-back AC/AC converter (B2B), coupled to a phase of the power grid), and an electromechanical subsystem (a doubly-fed induction machine (DFIM), coupled mechanically to a flywheel and electrically to the power grid and to a local varying load). Both subsystems have been essentially described in previous reports (deliverables D 0.5 and D 4.3.1), although some previously unpublished details are presented here. The B2B is a variable structure system (VSS), due to the presence of control-actuated switches: however from a modelling and simulation, as well as a control-design, point of view, it is sensible to consider modulated transformers (MTF in the bond-graph language) instead of the pairs of complementary switches. The port-Hamiltonian models of both subsystems are presents and coupled through a power-preserving interconnection, and the Hamiltonian description of the whole system is obtained; detailed bond-graphs of all the subsystems and the complete system are provided.

Energy-based modelling and simulation of the interconnection of a back-to-back converter and a doubly-fed induction machine

This paper describes the port interconnection of two subsystems: a power electronics subsystem (a back-to-back AC/CA converter (B2B), coupled to a phase of the power grid), and an electromechanical subsystem (a doubly-fed induction machine (DFIM). The B2B is a variable structure system (VSS), due to presence of control-actuated switches: however, from a modelling simulation, as well as a control-design, point of view, it is sensible to consider modulated transformers (MTF in the bond graph language) instead of the pairs of complementary switches. The port-Hamiltonian models of both subsystems are presented and, using a power-preserving interconnection, the Hamiltonian description of the whole system is obtained; detailed bond graphs of all subsystems and the complete system are also provided. Using passivity-based controllers computed in the Hamiltonian formalism for both subsystems, the whole model is simulated; simulations are run to rest the correctness and efficiency of the Hamiltonian network modelling approach used in this work.

On the inclusion of channel's time dependence in a hidden Markov model for blind channel estimation

In this paper, the theory of hidden Markov models (HMM) isapplied to the problem of blind (without training sequences) channel estimationand data detection. Within a HMM framework, the Baum–Welch(BW) identification algorithm is frequently used to find out maximum-likelihood (ML) estimates of the corresponding model. However, such a procedureassumes the model (i.e., the channel response) to be static throughoutthe observation sequence. By means of introducing a parametric model fortime-varying channel responses, a version of the algorithm, which is moreappropriate for mobile channels [time-dependent Baum-Welch (TDBW)] isderived. Aiming to compare algorithm behavior, a set of computer simulationsfor a GSM scenario is provided. Results indicate that, in comparisonto other Baum–Welch (BW) versions of the algorithm, the TDBW approachattains a remarkable enhancement in performance. For that purpose, onlya moderate increase in computational complexity is needed.

Probabilistic algorithms for blind adaptive multiuser detection

In this paper, two probabilistic adaptive algorithmsfor jointly detecting active users in a DS-CDMA system arereported. The first one, which is based on the theory of hiddenMarkov models (HMM’s) and the Baum–Wech (BW) algorithm,is proposed within the CDMA scenario and compared withthe second one, which is a previously developed Viterbi-basedalgorithm. Both techniques are completely blind in the sense thatno knowledge of the signatures, channel state information, ortraining sequences is required for any user. Once convergencehas been achieved, an estimate of the signature of each userconvolved with its physical channel response (CR) and estimateddata sequences are provided. This CR estimate can be used toswitch to any decision-directed (DD) adaptation scheme. Performanceof the algorithms is verified via simulations as well as onexperimental data obtained in an underwater acoustics (UWA)environment. In both cases, performance is found to be highlysatisfactory, showing the near–far resistance of the analyzed algorithms.

Blind channel estimation and data detection using hidden Markov models theory

In this correspondence, we propose applying the hiddenMarkov models (HMM) theory to the problem of blind channel estimationand data detection. The Baum–Welch (BW) algorithm, which is able toestimate all the parameters of the model, is enriched by introducingsome linear constraints emerging from a linear FIR hypothesis on thechannel. Additionally, a version of the algorithm that is suitable for timevaryingchannels is also presented. Performance is analyzed in a GSMenvironment using standard test channels and is found to be close to thatobtained with a nonblind receiver.

Establiment dels objectius prioritaris i dels criteris de selecció de projectes per a l'aplicació del programa Leader Plus de la Unió Europea a l'Alt Urgell

Els programes Leader de la Unió Europea tenen com a objectiu el desenvolupament de territoris rurals.La comarca catalana de l’Alt Urgell es va beneficiar anteriorment de l’aplicació del programa Leader 2en set municipis del sud de la comarca. L’actual convocatòria anomenada Leader Plus té en canvi unàmbit d’aplicació que afecta a la totalitat del territori de l’Alt Urgell.A més de l’àmbit territorial, també els objectius estratègics són diferents. Leader 2 pretenia corregir lesconseqüències negatives de la crisi industrial de Taurus. Per aquest motiu, el seu objectiu fonamentalconsistia en aturar la pèrdua de població del territori i va donar molta importància a la creaciód’ocupació i les inversions en la indústria. En canvi, el programa Leader Plus té com a objectiu bàsicestabilitzar la població i millorar el benestar econòmic en els nuclis rurals. Per aquesta raó prioritza lesinversions en sectors con el turisme o altres serveis que ajudin a millorar la qualitat de vida de les zonesrurals.Les conclusions d’aquest treball han servit com a referència per a la redacció de les bases que hauran deservir per a la determinació de quins tipus d’inversions es poden acollir a la iniciativa Leader Plus al’Alt Urgell i quines subvencions es poden concedir.

Disseny d’un circuit analògic reconfigurable

En l’actualitat, l’electrònica digital s’està apoderant de la majoria de camps de desenvolupament, ja que ofereix un gran ventall de possibilitats que permeten fer front a gran quantitat de problemàtiques. Poc a Poc s’ha anat prescindint el màxim possible de l’electrònica analògica i en el seu lloc s’han utilitzat sistemes microprocessats, PLDs o qualsevol altre dispositiu digital, que proporciona beneficis enlluernadors davant la fatigosa tasca d’implementar una solució analògica.Tot i aquesta tendència, és inevitable la utilització de l’electrònica analògica, ja que el mon que ens envolta és l’entorn en el que han de proporcionar servei els diferents dissenys que es realitzen, i aquest entorn no és discret sinó continu. Partint d’aquest punt ben conegut hem de ser conscients que com a mínim els filtres d’entrada i sortida de senyal juntament amb els convertidors D/A A/D mai desapareixeran.Així doncs, aquests circuits analògics, de la mateixa forma que els digitals, han de sercomprovats un cop dissenyats, és en aquest apartat on el nostre projecte desenvoluparà un paper protagonista, ja que serà la eina que ha de permetre obtenir les diferents senyals característiques d’un determinat circuit, per posteriorment realitzar els tests que determinaran si es compleix el rang de correcte funcionament, i en cas de no complir, poder concretar quin paràmetre és el causant del defecte

Cholesterol regulates Syntaxin 6 trafficking at the TGN-endosomal boundaries

Inhibition of cholesterol export from late endosomes causes cellular cholesterol imbalance, including cholesterol depletion in the trans-Golgi network (TGN). Here, using Chinese hamster ovary (CHO) Niemann-Pick type C1 (NPC1) mutant cell lines and human NPC1 mutant fibroblasts, we show that altered cholesterol levels at the TGN/endosome boundaries trigger Syntaxin 6 (Stx6) accumulation into VAMP3, transferrin, and Rab11-positive recycling endosomes (REs). This increases Stx6/VAMP3 interaction and interferes with the recycling of αVβ3 and α5β1 integrins and cell migration, possibly in a Stx6-dependent manner. In NPC1 mutant cells, restoration of cholesterol levels in the TGN, but not inhibition of VAMP3, restores the steady-state localization of Stx6 in the TGN. Furthermore, elevation of RE cholesterol is associated with increased amounts of Stx6 in RE. Hence, the fine-tuning of cholesterol levels at the TGN-RE boundaries together with a subset of cholesterol-sensitive SNARE proteins may play a regulatory role in cell migration and invasion.

Maltractament en les relacions de parella: estils de personalitat i simptomatologia d'un grup de dones maltractades

Aquest treball examina diverses circumstancies del maltractament en dones que arriben a diferents serveis assistencials públics de la província de Barcelona, la simptomatologia clínica que presenten i els seus estils de personalitat. 43 dones ateses en centres d'urgincies o cases d'acolliment completaren I'MCMI-II (de Millon, 1999), 1 'Escala d 'Ajustament Dihdic (dlSpanier, 1976), i una adaptació de llEntrevista Semiestructurada sobre Maltractament Domistic (Echebunía, Corral, Sarasua, Zubizarreta i Sauca, 1994). Els resultats indicaren que es tractava d'un conjunt de dones maltractades que es caracteritzaven per haver patit experiincies de maltractament greus en les seves relacions de parella, pel que fa a intensitat, duració, frequincia i extensió. S'obsemi que les dones que havien patit maltractament en la seva infantesa es diferenciaven de les que no, mostrant major gravetat psicopatoldgica. Els resultats obtinguts amb lfMCMI-II reflectien una prestncia relativament baixa de simptomatologia ansiosa i depressiva i un predomini dels estils esquizoides, dependents i evitatius de la personalitat, de manera que un dels primers objectius clínics pensem que hauria de ser contrarestar la tendincia al retraiinent emocional i a l'azllament social per afavorir la seva capacitat d'establir relacions interpersonals i socials en general. Es discuteixen els resultats obtinguts i s'apunten algunes consideracions clíniques i assistencials

Possibilitats del sistema Sofia com a sistema alternatiu i augmentatiu de comunicació

En aquest article s'explica, breument, quins són els sistemes alternatius i augmentatius de comunicació, es comenten els de major ús al nostre país i es presenta un sistema gràfic d'aparició recent, el sistema Sofia, que podria ser utilitzat com a tal perque es tracta d'un sistema grafic obert, amb possibilitats d'estructurar i generar llenguatge. Perd, per a aixo, caldria ensenyar-lo a usuaris reals i investigar-ne les possibilitats.