Interplay of spectral efficiency, power and doppler spectrum for reference-signal-assisted wireless communication

Expressions relating spectral efficiency, power, and Doppler spectrum, are derived for Rayleigh-faded wireless channels with Gaussian signal transmission. No side information on the state of the channel is assumed at the receiver. Rather, periodic reference signals are postulated in accordance with the functioning of most wireless systems. The analysis relies on a well-established lower bound, generally tight and asymptotically exact at low SNR. In contrast with most previous studies, which relied on block-fading channel models, a continuous-fading model is adopted. This embeds the Doppler spectrum directly in the derived expressions, imbuing them with practical significance. Closed-form relationships are obtained for the popular Clarke-Jakes spectrum and informative expansions, valid for arbitrary spectra, are found for the low- and high-power regimes. While the paper focuses on scalar channels, the extension to multiantenna settings is also discussed.

Spectral efficiency in reference-signal-assisted low-power wireless communication

Expressions relating spectral efficiency, power and Doppler spectrum are derived for low-power Rayleighfaded wireless channels with proper complex signaling. Noside information on the state of the channel is assumed at the receiver. Rather, periodic reference signals are postulated inaccordance with the functioning of most wireless systems. In contrast with most previous studies, which relied on block-fading channel models, a continuous-fading model is adopted. This embeds the Doppler spectrum directly in thederived expressions thereby imbuing them with practical significance.

Optimum pilot overhead in wireless communication: a unified treatment of continuous and block-fading channels

The optimization of the pilot overhead in wireless fading channels is investigated, and the dependence of this overhead on various system parameters of interest (e.g., fading rate, signal-to-noise ratio) is quantified. The achievable pilot-based spectral efficiency is expanded with respect to the fading rate about the no-fading point, which leads to an accurate order expansion for the pilot overhead. This expansion identifies that the pilot overhead, as well as the spectral efficiency penalty with respect to a reference system with genie-aided CSI (channel state information) at the receiver, depend on the square root of the normalized Doppler frequency. It is also shown that the widely-usedblock fading model is a special case of more accurate continuous fading models in terms of the achievable pilot-based spectral efficiency. Furthermore, it is established that the overhead optimization for multiantenna systems is effectively the same as for single-antenna systems with thenormalized Doppler frequency multiplied by the number of transmit antennas.

Análisis y diseño de filtros apilados basados en resonadores acústicos

Durant els últims anys la demanda de filtres pas banda de ràdio freqüència, de reduïdes dimensions, lleugers i d'elevades prestacions destinats a sistemes de comunicacions inalàmbriques s'ha incrementat de forma significativa. Aquests sistemes principalment són els sistemes de telefonia mòbil de tercera generació UMTS y el sistema de navegació GPS. Els filtres actuals, basats en ressonadors SAW (Surface Acoustic Wave), tenen unes dimensions reduïdes però estan limitats en freqüència (3 GHz) i la seva tecnologia no és compatible amb les tecnologies estàndards de circuits integrats. Per aquestes raons s'espera que els filtres basats en ressonadors BAW (Bulk Acoustic Wave) substitueixin als SAW. Els dos tenen dimensions similars, però els filtres BAW poden funcionar a freqüències superiors a 3 GHz, poden treballar amb nivells de potència majors, i és important destacar el fet que la seva tecnologia és compatible amb les tecnologies estàndards de circuits integrats. La investigació en l'àmbit dels filtres BAW s'ha centrat en millorar els processos tecnològics i la qualitat dels materials, però s'ha treballat poc en l'adaptació de les tècniques sistemàtiques de disseny de filtres a les particularitats d'aquesta tecnologia, per tant el principal objectiu d'aquest treball és presentar mètodes sistemàtics per al disseny de filtres BAW, centrant-se en l'estudi d’estructures apilades.

Autoritat de certificació PKI amb serveis en línia

Autoritat de certificació (CA) per l'emissió de certificats digitals en una infraestructura de clau pública (PKI) amb una interfície web bàsica.

Monitorización de la temperatura de un CPD mediante una red de sensores inalámbricos

Con este proyecto se pretende que una organización sea más consciente del estado de sus máquinas y anticiparse a una situación de pérdida de información, parada de servicios o parada por sobrecalentamiento de servidores.

PGPWebmail : cliente de correo web con PGP

Trabajo Final de Carrera en desarrollo .NET: Aplicación web ASP.NET MVC cliente de correo electrónico con cifrado PGP y servicio web WCF que brinda funcionalidades de cifrado PGP.

Ús de Sensor Web Enablement per a gestió de dades marines i accés al servei d'observació de sensors a través de client Android

El present treball és un estudi de l'estat de Sensor Web Enablement (SWE) aplicat a l'àmbit marí d'investigació oceanogràfica. Per assolir aquest objectiu s'han avaluat les diferents solucions d'arquitectura de sistemes més adients a la problemàtica indicada i s'ha dissenyat un client de Sensor Observation Service (SOS) per plataforma mòbil Android que permeti consultar la descripció del sensor (SensorML) i conjunts d'observacions mitjançant estàndards oberts de SWE i peticions web (SOAP). Els dissenys anteriorment indicats han permès que quedés palès l'ampli ventall de possibilitats i avantatges que s'obtenen pel fet d'emprar SWE, ja que ens permet integrar fàcilment les dades proporcionades pels sensors i les pròpies descripcions dels sensors en diferents entorns, tal i com és el cas del disseny presentat en Android, a través d'estàndards oberts independents de les múltiples especificacions de cada fabricant, en un entorn, com és l'àmbit de la investigació marina on hi ha una gran heterogeneïtat de sensors i protocols.

Diseño comunicador inalámbrico

Informe para la empresa B&j Adaptaciones del diseño de comunicador inalámbrico

An empirical study of machine learning techniques applied to image watermarking

A study of how the machine learning technique, known as gentleboost, could improve different digital watermarking methods such as LSB, DWT, DCT2 and Histogram shifting.

Linear transceiver design in nonregenerative relays with channel state information

This paper deals with the design of nonregenerativerelaying transceivers in cooperative systems where channel stateinformation (CSI) is available at the relay station. The conventionalnonregenerative approach is the amplify and forward(A&F) approach, where the signal received at the relay is simplyamplified and retransmitted. In this paper, we propose an alternativelinear transceiver design for nonregenerative relaying(including pure relaying and the cooperative transmission cases),making proper use of CSI at the relay station. Specifically, wedesign the optimum linear filtering performed on the data to beforwarded at the relay. As optimization criteria, we have consideredthe maximization of mutual information (that provides aninformation rate for which reliable communication is possible) fora given available transmission power at the relay station. Threedifferent levels of CSI can be considered at the relay station: onlyfirst hop channel information (between the source and relay);first hop channel and second hop channel (between relay anddestination) information, or a third situation where the relaymay have complete cooperative channel information includingall the links: first and second hop channels and also the directchannel between source and destination. Despite the latter beinga more unrealistic situation, since it requires the destination toinform the relay station about the direct channel, it is useful as anupper benchmark. In this paper, we consider the last two casesrelating to CSI.We compare the performance so obtained with theperformance for the conventional A&F approach, and also withthe performance of regenerative relays and direct noncooperativetransmission for two particular cases: narrowband multiple-inputmultiple-output transceivers and wideband single input singleoutput orthogonal frequency division multiplex transmissions.

Determinants of Broadband Access: Is Platform Competition always the Key Variable to Success?

Previous studies have identified the rivalry among technological platforms as one of the main driving forces of broadband services penetration. This paper draws on data from the Spanish market between 2005 and 2011 to estimate the main determinants of broadband prices. Controlling for broadband tariffs features and network variables, we examine the impact of the different modes of competition on prices. We find that inter-platform competition has no significant effects over prices, while intra-platform competition is a key driver of the prices charged in the broadband market. Our analysis suggests that the impact of different types of competition on prices is critically affected by the levels of development of the broadband market achieved by the considered country

An energy efficient vertical handover decision algorithm

As wireless communications evolve towards heterogeneousnetworks, mobile terminals have been enabled tohandover seamlessly from one network to another. At the sametime, the continuous increase in the terminal power consumptionhas resulted in an ever-decreasing battery lifetime. To that end,the network selection is expected to play a key role on howto minimize the energy consumption, and thus to extend theterminal lifetime. Hitherto, terminals select the network thatprovides the highest received power. However, it has been provedthat this solution does not provide the highest energy efficiency.Thus, this paper proposes an energy efficient vertical handoveralgorithm that selects the most energy efficient network thatminimizes the uplink power consumption. The performance of theproposed algorithm is evaluated through extensive simulationsand it is shown to achieve high energy efficiency gains comparedto the conventional approach.