Robotiker

An optical system for the transmission of digital
\nvideo broadcasting (DVB) signals is proposed and experimentally
\ndemonstrated. The transmission media comprises 1-mm
\ndiameter graded-index plastic optical fiber (GI-POF) with a
\nrelatively high bandwidth. The system is fully engineered
\nusing low-cost off-the-self components including a vertical-cavity
\nsurface-emitting laser, a silicon avalanche photodiode, POF connectors,
\nand all integrated radio frequency (RF) circuitry. The RF
\ndistribution of standard DVB-satellite second generation signals
\nin 950 2150 MHz and DVB-terrestrial signals in 470 790 MHz
\nover 25-m GI-POF is successfully demonstrated.

The use of sensors is very widespread in a lot of different environments and applications. Each situation needs a different solution and for that reason the use of a scalable and easily manageable sensor network is a must as applications are becoming increasingly complex. In many cases the perfect solution is the one based on a wireless sensor network; it provides flexibility, ease of management of the system and expandability. But in order to provide interoperability between different sensor manufacturers and to give a transparent and independent interface, the use of a standard is mandatory. This standard system is provided by the IEEE 1451 family of standard protocols. In this project a Bluetooth based sensor network has been implemented using the IEEE 1451 family of standard protocols. The goal of this network is to aid data acquisition from a number of sensors within a car, in order to monitor the wellbeing of the passengers and improve safety and comfort.

This paper addresses the sensor network scenario where several nodes sense a common information source S. When such sensors forward their correlated observations to a common shared receiver, it is necessary to combine the received information in order to obtain an estimation of S with high reliability. In this manuscript we propose the use of low-complexity concatenated Zigzag codes for the transmission of correlated sensors through orthogonal AWGN channels. In reception, a novel albeit simple correlation estimation procedure is integrated into the iterative decoding and data fusion algorithm, which is based on the Sum-Product Algorithm applied over the factor graph describing the system. Fundamental limits are also derived for the end-to-end probability of error. Simulation results verify that the Bit Error Rate (BER) performance of the proposed receiver is very close to the aforementioned fundamental limits, while requiring less decoding complexity than other capacity-approaching codes.

This work considers virtualization of the wireless medium as a mean to share common network physical infrastructure by different Virtual Operators (VO) based on a Time Division Multiple Access (TDMA) virtualization technique. We have developed a Wireless Medium Virtualization Framework (WMVF) to analyze the performance of a variable number of VOs (with one or more types of traffic) accessing to the same wireless medium through the same wireless node in a coordinated way. Extensive simulations have been carried out to assess the impact of wireless medium virtualization based on relevant parameters such as the type of traffic, the number of VOs and the specific wireless technology. Delay, jitter and the utilization of the network are the metrics used in this paper to show the potential and limitations of wireless virtualization as a way to increase network usage. This work has been carried out partially inside the European Project 4WARD (FP7 Project reference: 216041).

This paper presents an optimal voltage-balancing compensator for a specific modulation technique applied to a neutral-point-clamped converter. The technique uses two modulation signals per phase, and it is called double-signal pulsewidth modulation. It completely eliminates low-frequency oscillations in the neutral-point voltage. However, it does not provide natural voltage balancing; therefore, a compensation loop is required. The proposed control generates a feedback compensation signal that correctly modifies the three-phase modulation signals. The optimal compensation signal is calculated by a dynamic limiter according to the intrinsic limitations of the system related to the variability range of the modulation signals. It significantly improves the voltage balancing under all operating conditions of the converter. In addition, this compensation strategy does not increase the switching frequencies of the power devices. The algorithm is tested and verified using both simulation and experimentation.

Focusing on densely deployed wireless sensor networks, this paper presents a novel method for joint source-channel-network coding of distributed correlated sources through multiple access relay channels. In such networks, the role of intermediate sensors as relay nodes permits to achieve enhanced end-to-end error performance and increased spatial diversity in presence of channel fading. This paper addresses this scenario for a two source, single relay architecture by proposing a novel coding approach based on concatenated Zigzag codes, whose low complexity is specially suitable for energy-constrained autonomous systems. Joint decoding and estimation of the parameters defining the correlation between sensors is iteratively performed at the receiver side. Simulation results show that the proposed joint coding scheme attains significant energy gains with respect to traditional routing techniques, specially at high signal to noise ratios.

In order to be competitive, tourism intermediaries (i.e. travel agents, tour operators, etc.) require flexible and customizable solutions to adapt the wide variety of products and services on demand according to customers' preferences. In addition, tourism intermediaries need to provide added value to customers by mapping their preferences or wishes into a composition of specific market products and services offered by different suppliers, e.g. hotel supplier plus car rental service supplier plus flight supplier plus attraction supplier. This paper presents a platform where the combination of ontologies and semantic Web services (SWS) allows tourism intermediaries to seamlessly offer customized and diversified services and products that can rapidly satisfy market and end-users' demands. This platform includes an infrastructure to register, catalogue and discover services; a graphical tool for the composition of services; middleware to deploy and execute the composed services, and a Web 2.0-oriented interface generator.

This paper presents some modified topologies of the neutral-point-clamped converter. In all of them, the main change consists of adding a fourth leg, which is based on the flying-capacitor converter structure. The aim of this additional leg is to provide the converter with fault tolerance. Furthermore, during normal operation mode, this leg is able to provide a stiff neutral voltage. Consequently, the low-frequency voltage oscillations that appear at the neutral point of the standard three-level topology in some operating conditions no longer exist. As a result, the modulation strategy of the three main legs of the converter does not have to take care of voltage balance, and it can be designed to either achieve optimal output voltage spectra or improve the efficiency of the converter. Simulation and experimental results are presented to show the viability of this approach both under normal operation mode and in the event of faults.