Relay-assisted transmission and radio resource management for wireless networks

The following paper presents an overview of the Ph.D Thesis1 presented in [1], which compiles all the research done during the period of time between 2004-2007. In that dissertation the relay-assisted transmission with half-duplex relays is analyzed from different points of view. This study is motivated by the necessity of finding innovative solutions to cope with the requirements of next generation wireless services, and with current radio technology. The use of relayed communications represents a change of paradigm of conventional communications, and requires the definition and evaluation of protocols to be applied to single or multiple-user relay communication. With the two fold goal of enhancing spectral efficiency and homogenize service in cellular communications, system design is investigated at physical (type of transmissions of the relay, decoding mode, ..) and upper layers (resource allocation, dynamic link control).

Cooperative Transmission and Radio Resources Management for Wireless Networks

Report for the scientific sojourn at the Multimedia Communications Laboratory, University of Texas at Dallas, USA, from September to December 2005. The cooperative transmission has been analyzed taking a broadcast relay channel which assumes a scenario with one source and multiple destinations. Moreover, in order to improve the performance in terms of mutual information, it has been considered that for each destination there is another nearby terminal (called relay) which will help to improve the performance of the destination. This scheme combines different types of channels considered in the information theory, such as the relay channel, broadcast channel and interference channel (if the relays transmit information intended only to its associated destination). In this work, the author has studied the optimal way to encode the signals for the different users, known as capacity region (i.e. related to radio resources management ), of the broadcast relay channel.

Preliminary study of cooperation in hybrid ad-hoc networks

In this paper, we present a first approach to evolve a cooperative behavior in ad hoc networks. Since wireless nodes are energy constrained, it may not be in the best interest of a node to always accept relay requests. On the other hand, if all nodes decide not to expend energy in relaying, then network throughput will drop dramatically. Both these extreme scenarios are unfavorable to the interests of a user. In this paper we deal with the issue of user cooperation in ad hoc networks by developing the algorithm called Generous Tit-For-Tat. We assume that nodes are rational, i.e., their actions are strictly determined by self-interest, and that each node is associated with a minimum lifetime constraint. Given these lifetime constraints and the assumption of rational behavior, we study the added behavior of the network.

Desenvolupament d'una aplicació web per a la recollida i classificació d'informació en entorns virtuals d'interacció síncrona

Treball final de carrera sobre el desenvolupament d'una aplicació web que comunica de manera síncrona a membres d'un grup i registra les converses generades en un log classificat per categoria.

Disseny i muntatge d'un mòdul d'entrades digitals per comunicació modbus

Actualment l’exigència i la competitivitat del mercat, obliguen les industries a modernitzar-se i automatitzar tots els seus processos productius. En aquests processos les dades i paràmetres de control són dades fonamentals a verificar. Amb aquest treball final de carrera, es pretén realitzar un mòdul d’entrades digitals, per tal de gestionar les dades rebudes d’un procés automatitzat. L’objectiu d’aquest TFC ha estat dissenyar un mòdul d’entrades digitals capaç de gestionar dades de qualsevol tipus de procés automatitzat i transmetre-les a un mestremitjançant un bus de comunicació Modbus. El projecte però, s’ha centrat en el cas específic d’un procés automatitzat per al tractament de la fusta. El desenvolupament d’aquest sistema, comprèn el disseny del circuit, la realització de la placa, el software de lectura de dades i la implementació del protocol Modbus. Tot el mòdul d’entrades està controlat per un microcontrolador PIC 18F4520. El disseny és un sistema multiplataforma per tal d’adaptar-se a qualsevol procés automàtic i algunes de les seves característiques més rellevants són: entrades aïllades multitensió, control de fugues, sortides a relé, i memòria externa de dades, entre altres. Com a conclusions cal dir que s’han assolit els objectius proposats amb èxit. S’ha aconseguit un disseny robust, fiable, polivalent i altament competitiu en el mercat. A nivell acadèmic, s’han ampliat els coneixements en el camp del disseny i de la programació.

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.

Hybrid turbo FEC/ARQ systems and distributed space-time coding for cooperative transmission

Cooperative transmission can be seen as a "virtual" MIMO system, where themultiple transmit antennas are in fact implemented distributed by the antennas both at the source and the relay terminal. Depending on the system design, diversity/multiplexing gainsare achievable. This design involves the definition of the type of retransmission (incrementalredundancy, repetition coding), the design of the distributed space-time codes, the errorcorrecting scheme, the operation of the relay (decode&forward or amplify&forward) and thenumber of antennas at each terminal. Proposed schemes are evaluated in different conditionsin combination with forward error correcting codes (FEC), both for linear and near-optimum(sphere decoder) receivers, for its possible implementation in downlink high speed packetservices of cellular networks. Results show the benefits of coded cooperation over directtransmission in terms of increased throughput. It is shown that multiplexing gains areobserved even if the mobile station features a single antenna, provided that cell wide reuse of the relay radio resource is possible.

Disseny i muntatge d'un mòdul d'entrades digitals per comunicació modbus

Actualment l’exigència i la competitivitat del mercat, obliguen les industries a modernitzar-se i automatitzar tots els seus processos productius. En aquests processos les dades i paràmetres de control són dades fonamentals a verificar. Amb aquest treball final de carrera, es pretén realitzar un mòdul d’entrades digitals, per tal de gestionar les dades rebudes d’un procés automatitzat. L’objectiu d’aquest TFC ha estat dissenyar un mòdul d’entrades digitals capaç de gestionar dades de qualsevol tipus de procés automatitzat i transmetre-les a un mestremitjançant un bus de comunicació Modbus. El projecte però, s’ha centrat en el cas específic d’un procés automatitzat per al tractament de la fusta. El desenvolupament d’aquest sistema, comprèn el disseny del circuit, la realització de la placa, el software de lectura de dades i la implementació del protocol Modbus. Tot el mòdul d’entrades està controlat per un microcontrolador PIC 18F4520. El disseny és un sistema multiplataforma per tal d’adaptar-se a qualsevol procés automàtic i algunes de les seves característiques més rellevants són: entrades aïllades multitensió, control de fugues, sortides a relé, i memòria externa de dades, entre altres. Com a conclusions cal dir que s’han assolit els objectius proposats amb èxit. S’ha aconseguit un disseny robust, fiable, polivalent i altament competitiu en el mercat. A nivell acadèmic, s’han ampliat els coneixements en el camp del disseny i de la programació.