Agustin de Dios, Adrian
Total activity: 69
Department
Department of Signal Theory and Communications
E-mail
adrian.agustinupc.edu
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  • Coordinated beamforming access for interfering half-duplex relay networks

     Torrellas Socastro, Marc; Agustin de Dios, Adrian; Vidal Manzano, Jose
    IEEE International Conference on Communications
    Presentation's date: 2013-06-09
    Presentation of work at congresses

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    This work deals with a relay-assisted cellular network, where the downlink communication is carried out in two orthogonal phases. In the first-hop transmission, multiple evolved Node Bs (eNB) transmit in a coordinated way to multiple half-duplex Relay Nodes (RNs). In the second-hop transmission, each RN assists a single User Equipment (UE) without precise channel knowledge. In the first hop, we consider two multiple- intput multiple-output (MIMO) access schemes: Interference Alignment (IA) and block diagonalization zero-forcing (ZF-BD) precoders for which power and transmission time to RNs are optimally allocated. Cell capacity and outage rates are evaluated and benchmarked to the case where network-MIMO (N-MIMO) coordinated transmission in used in the first hop

  • Degrees of freedom of the rank-deficient MIMO X channel

     Agustin de Dios, Adrian; Vidal Manzano, Jose
    IEEE Information Theory Workshop
    Presentation's date: 2013-09-12
    Presentation of work at congresses

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    The multiple-input multiple-output (MIMO) X channel with rank-deficient channels is considered. We characterize the total degrees of freedom (DoF) by defining an outer bound which is attained by the proposed precoding scheme. The total DoF are described in closed-form when all transmitters and receivers have M and N antennas, respectively. For an arbitrary number of antennas, the total DoF are obtained as solution of a linear programming problem. Results elucidate that, unlike point-to-point MIMO systems where DoF increase with the rank of the channel, the total DoF in a multipoint-to-multipoint MIMO system can increase up to a certain point if channels are rankdeficient. Hence, we corroborate the relevance of knowing the rank-deficiency in the MIMO X channel, a property already observed in the MIMO Interference channel.

  • Distributed inter-cluster interference management for CoMP-based cellular networks

     Lagen Morancho, Sandra; Agustin de Dios, Adrian; Vidal Manzano, Jose
    IEEE Global Communications Conference
    Presentation's date: 2013-12-12
    Presentation of work at congresses

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    This paper proposes distributed inter-cluster interference management procedures for 1 Coordinated Multi-Point (CoMP) Time Division Duplexing (TDD) cellular networks, in which a set of base stations (BSs), that form a cluster, cooperate in the downlink (DL) and uplink (UL) transmissions to communicate with a group of users while causing interference to users in neighbor clusters. In order to reduce the complications associated to the estimation of the interfering channels, we describe new iterative procedures based on channel reciprocity that avoid such estimation by exploiting the received signal in the UL, provided that transmit and receive filters in DL and UL are properly designed. Simulations show that proposed techniques attain significant DL and UL spectral efficiency gains. Furthermore, an analysis of imperfect channel state information (CSI) at both ends is included, evidencing the robustness of the proposed procedures. Considerations on convergence are included.

  • Network-MIMO for downlink in-band relay transmissions

     Lagen Morancho, Sandra; Agustin de Dios, Adrian; Vidal Manzano, Jose
    Eurasip journal on wireless communication and networking
    Date of publication: 2013-01-23
    Journal article

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    With the objective of improving the spectral efficiency and coverage homogeneity of wireless cellular systems in the downlink, we investigate how to take advantage of two promising transmission technologies envisioned in current standards: network-MIMO and relay stations (RSs). It is assumed that half-duplex RSs are deployed in a cellular system, where the duration of the relay-receive and the relay-transmit phases is fixed beforehand for all cells. In order to reduce the spectral efficiency loses associated to half-duplex relaying, we propose the use of base station (BS) cooperation under a network-MIMO precoding strategy based on block-diagonalization zero-forcing, and optimize radio resources under the convex performance criteria constrained by the per-BS power, modulation and coding schemes and the transmission rate in the relay-transmit phase. By applying convex optimization techniques, the optimal precoding strategy is derived and a suboptimal low complexity solution is also proposed. The obtained solutions are evaluated at system level and compared to other cooperative and non-cooperative BS-based schemes.

  • Wireless technologies for isolated rural communities in developing countries based on cellular femtocell deployment

     Muñoz Medina, Olga; Vidal Manzano, Jose; Pascual Iserte, Antonio; Agustin de Dios, Adrian; Fernandez Rubio, Juan-antonio
    Participation in a competitive project

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  • MCS and sub-band selection for downlink interference coordination in LTE-A Femtocells

     Muñoz Medina, Olga; Agustin de Dios, Adrian; Vidal Manzano, Jose
    IEEE Vehicular Technology Conference
    Presentation's date: 2012-09
    Presentation of work at congresses

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    This paper proposes a decentralized algorithm for interference coordination in LTE-A networks, based on the exchange of information (pricing) at control plane level. In our approach, every user equipment (UE) report the maximum modulation and coding scheme (MCS) that can be used within several sets (sub-bands) of available resource blocks, along with a parameter (cost) that measures the MCS degradation due to the transmission from an interfering neighbor. Through the exchange of pricing messages, the higher costs are distributed to the dominant interferers; and the selection of the MCS and operational sub-band is based on the current link conditions along with the received pricing messages. We evaluate the algorithm in a cellular area covered by a macro base station (MBS) and multiple active femtocells. We also measure the degradation due to the quantization of the exchanged cost values. The results demonstrate significantly enhanced performance as compared to the non-coordinated case.

  • Downlink coordinated radio resource management in cellular networks with partial CSI

     Calvo Page, Eduard; Muñoz Medina, Olga; Vidal Manzano, Jose; Agustin de Dios, Adrian
    IEEE transactions on signal processing
    Date of publication: 2012-03
    Journal article

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    We explore decentralized coordination of sectored cellular networks to adapt the usage of downlink resources to the instantaneous network conditions. The transmission frame consists of an orthogonal bandwidth usage phase, where sectors perform FDMA and power control over an agreed frequency chunk, and a shared bandwidth usage phase where each sector performs FDMA over the full available bandwidth without power control (interference is not controlled in this phase by any means). Decentralized network utility maximization with global optimality guarantee is enabled by fixing this structure of the transmission frame, which does not cause significant network-wide losses. Thus, the ability to better balance the resources gained from coordination generates some slack that can be used to either i) provide higher-quality access, ii) increase the number of active users, or iii) reduce deployment and maintenance costs by operating larger cells.

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    FREEDOM D3.3 - Cooperative schemes in the femto-based networks  Open access

     Agustin de Dios, Adrian; Vidal Manzano, Jose; Pescosolido, L.; Barbarossa, S.; Kammoun, M.; Sarkiss, M.
    Date: 2012-01
    Report

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    We investigate cooperative transmission schemes that can be applied to joint deployments of femto-access points (FAPs) and macro base stations (MBS) by exploiting backhaul communication links between nodes at the data-plane level. First, we study the effects of some hardware impairments, such as time misalignment and carrier offset compensation, on cooperation performance. Additionally, we look into the MIMO X channel as a general framework that subsumes all possible types of cooperative communication between two sources and two destinations (broadcast, interference or multiple access channels), assuming full channel state information at the transmitters. Since FAPs have a delay constrained backhaul the cooperation of multiple FAPs becomes sensitive to random delays at the sources. In this regard we have provided two solutions: a) appropriate delay-tolerant cooperative space-time coding and decoding schemes and b) specific cooperative schemes for critical delay applications.

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    FREEDOM - D42 Design and evaluation of effective procedures for MAC layer  Open access

     Mach, P.; Becvar, Z.; Bestak, R.; Neruda, M.; Roux, P.; Hariyanto, H.; Ari Wibowo, F.X.; Agustin de Dios, Adrian; Muñoz Medina, Olga; Vidal Manzano, Jose; Carfagna, A.
    Date: 2012-01
    Report

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    The implementation of femtocells introduces many technical challenges that must be solved in order to fully exploit their potentials. This deliverable primarily focuses on control procedures for radio resource management addressing the most critical issues. To utilize radio resources of femtocell efficiently, a novel routing of data among user s served by the same femtocell is proposed. Furthermore, spectrum-efficient technique for power control, scheduling (both at radio side and backhaul side and multicast/broadcast services transmissions are designed. Additionally, novel authorization approaches and femtocells’ identification technique are proposed while taking in consideration the scalability of the system. This document designs and specifies the control plane procedures to ensure effective coordination among femtocells and macrocell designed in WP3. Finally, cross-layer optimization issues are addressed here by means of optimal femtocells’ power allocation derivation using the Game Theory framework.

  • Distributed computing, storage and radio resource allocation over cooperative femtocells

     Muñoz Medina, Olga; Agustin de Dios, Adrian; Pascual Iserte, Antonio; Vidal Manzano, Jose; Lagen Morancho, Sandra; Torrellas Socastro, Marc
    Participation in a competitive project

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  • Network-MIMO backhauling for QOS-constrained relay transmission

     Vidal Manzano, Jose; Agustin de Dios, Adrian; Lagen, Sandra; Valera, Eduard; Muñoz Medina, Olga; García Armada, Ana; Sánchez Fernández, Matilde
    IEEE International Conference on Acoustics, Speech and Signal Processing
    Presentation's date: 2011-05
    Presentation of work at congresses

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    A relay station (RS)-based cellular system deployment is considered, where multiple base stations (BS) cooperate in the BS-RS in-band transmission for the downlink. With the joint optimization of the resources allocated to the wireless backhaul and to the RS-MS access, it is possible to exploit the benefits of networked-MIMO along with combating the pathloss and shadowing effects, and thus obtain significantly enhanced spectral efficiency and coverage homogeneity. The problem is shown to be convex under conventional QoS objective functions. Suboptimal low complexity solutions are also proposed and evaluated.

  • Improved interference alignment precoding for the MIMO X channel

     Agustin de Dios, Adrian; Vidal Manzano, Jose
    IEEE International Conference on Communications
    Presentation's date: 2011-06
    Presentation of work at congresses

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    We derive a linear transmit precoding scheme based on interference alignment at the transmitters and zero-forcing at the receivers, for the MIMO X channel based on the Generalized Singular Value Decomposition (GSVD) that is able to attain the outer bound on the degrees of freedom (DoF) region for any antenna configuration, except when all terminals have one antenna. Additionally, the proposed scheme is able to enhance the transmission rate in terms of high SNR offset.

  • Network MIMO for downlink in-band relay transmissions with relaying phases of fixed duration

     Agustin de Dios, Adrian; Vidal Manzano, Jose; Lagen, Sandra; Valera, Eduard
    European Signal Processing Conference
    Presentation's date: 2011-08
    Presentation of work at congresses

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    A half-duplex relay station (RS)-based cellular system deployment is considered, where multiple base stations (BS) cooperate in the BS-RS in-band transmission for the downlink. The duration of the relay-receive and the relay-transmit phases are fixed beforehand, so that the interference induced by other cells is stationary during a transmission interval. With the optimization of the precoders and powers allocated to the wireless backhaul (relay-receive phase)and to the RS-MS access (relay-transmit phase), it is possible to exploit the benefits of network-MIMO (N-MIMO) along with combating the pathloss and shadowing effects thanks to the RSs. Consequently, an appealing significant enhanced spectral efficiency, power efficiency and coverage homogeneity are obtained. Results are benchmarked to the case where the relay phases are optimized.

  • Interference pricing for self-organisation in OFDMA femtocell networks

     Agustin de Dios, Adrian; Vidal Manzano, Jose; Muñoz Medina, Olga
    Future Network and MobileSummit
    Presentation's date: 2011-06
    Presentation of work at congresses

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  • Decentralized weighted sum rate maximization in MIMO-OFDMA femtocell networks

     Agustin de Dios, Adrian; Vidal Manzano, Jose; Muñoz Medina, Olga; Rodriguez Fonollosa, Javier
    IEEE Global Communications Conference
    Presentation's date: 2011-12
    Presentation of work at congresses

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    We propose a decentralized strategy for downlink interference management in overlaid MIMO femtocell-macrocell deployments operating in the same band under OFDMA access. The resource allocation, consisting of MIMO precoders at the macro base station (MBS) and femto access points (FAPs) and possibly the resource block (RB) assignment, is designed to maximize the Weighted Sum Rate (WSR) of the system. Being the overall problem non-convex, we propose to solve it in a decentralized way where each transmitter designs its resource allocation using interference prices exchanged with other transmitters (FAPs and MBS) by exploiting the wired backhaul connection. The problem includes a rate restriction per FAP that accounts for the limited bitrate provided by the Internet Service Provider (ISP) wired backhaul. Two efficient algorithms are provided for: 1) optimizing MIMO precoders and 2) optimizing both MIMO precoders and RB assignment. Numerical results compare decentralized strategies based on pricing exchange and on pure competition in dense FAP deployments.

  • Weighted sum rate maximization for the MIMO X channel through MMSE precoding

     Agustin de Dios, Adrian; Vidal Manzano, Jose
    IEEE International Symposium on Information Theory
    Presentation's date: 2011-08
    Presentation of work at congresses

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  • Coordinated MIMO precoding for power minimization in femtocell systems

     Muñoz Medina, Olga; Vidal Manzano, Jose; Agustin de Dios, Adrian; Pascual Iserte, Antonio; Barbarossa, Sergio
    IEEE Global Communications Conference
    Presentation's date: 2011-12
    Presentation of work at congresses

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  • Relay-assisted wireless networks

     Agustin de Dios, Adrian; Vidal Manzano, Jose; Muñoz Medina, Olga; Glisic, S
    Date of publication: 2011
    Book chapter

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  • Macrocelulas y Femtocelulas en Sistemas con Técnicas Avanzadas de Coordinación de la Interferencia y Cooperación

     Vidal Manzano, Jose; Rodriguez Fonollosa, Javier; Cabrera Bean, Margarita Asuncion; Fernandez Rubio, Juan-antonio; Pages Zamora, Alba Maria; Agustin de Dios, Adrian; Silva Pereira, Silvana; Garcia Ordoñez, Luis; Vila Valls, Jordi; Muñoz Medina, Olga
    Participation in a competitive project

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    FREEDOM Project. Interference coordination protocols in femto-based networks  Open access

     Agustin de Dios, Adrian; Muñoz Medina, Olga; Vidal Manzano, Jose; Goldhamer, M.; Rodriguez Fonollosa, Javier; Pastore, A.; Sardellitti, Stefania; Pescosolido, Loreto; di Lorenzo, Paolo; Barbarossa, Sergio; Baiocchi, Andrea; de Marinis, Enrico; Imponente, Giovanni; Pucci, Fabrizio; Rosi, Guido
    Date: 2011-11-28
    Report

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    This document looks into coordinated radio resource allocation algorithms in deployments of huge number of femto-access points (FAP) by exploiting the message exchange at control-plane level through the wired ISP backhaul link. The algorithms present in this document are based on decentralized cooperative strategies supported by Game Theory. Decentralized resource allocation algorithms based on price exchange have been derived under different criteria: guaranteeing a minimum rate with the minimum power, maximizing the weighted sum-rate of the system, maximizing the opportunistic throughput when there are different source of randomness like random link failures and noise quantization or when the activity of macro-users is not known by FAPs (coordinated channel sensing or modelling the activity). Additionally, a genetic-based resource allocation is investigated, providing centralized and decentralized algorithms, to which the Game Theory solutions are challenged. In all cases, the techniques derived require modifications of the current LTE-A standard which are identified. Finally, some of those algorithms have been evaluated in a Realistic corporate scenario elucidating the advantages of coordinated resource allocation techniques proposed.

    Postprint (author’s final draft)

  • Technoeconomic evaluation of cooperative relaying transmission techniques in OFDM cellular networks

     Moral, Antolín; Vidal Manzano, Jose; Pérez, Jorge; Agustin de Dios, Adrian; Marina, Ninoslav; Host-Madsen, Anders
    Eurasip journal on advances in signal processing
    Date of publication: 2011-02-27
    Journal article

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    We evaluate the costs in the deployment of a 4G relay-assisted network in the 2.6GHz band following a technoeconomic methodology that departs fromcell dimensioning based on spectral efficiency and outage capacity requirements. Different decodeand- forward relaying protocols are considered in the analysis, assuming a certain traffic load evolution over a period of ten years, different geotypes, and a progressive deployment of base stations and relay stations. Results show significant benefits for operators as well as reduction in the total radiated power.

  • MÉTODO Y SISTEMA PARA LA GESTIÓN DESCENTRALIZADA DE FEMTOCÉLULAS VECINAS

     Rodriguez Fonollosa, Javier; Agustin de Dios, Adrian; Vidal Manzano, Jose; Muñoz Medina, Olga
    Date of request: 2011-11-28
    Invention patent

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    Método y sistema para la gestión descentralizada de femtocélulas vecinas.

    El método comprende:

    - la comunicación, a una primera femtocélula desde una segunda femtocélula, de la siguiente información:

    i) la restricción de requerimientos de interferencia de un usuario activo de la segunda femtocélula, y

    ii) uno o más parámetros que caracterizan un canal radio físico definido desde la primera femtocélula hasta dicho al menos un usuario activo de la segunda femtocélula;

    - la autoconfiguración de los parámetros de transmisión de la primera femtocélula usando la información comunicada i) y ii).

    El sistema está configurado para implementar el método de la invención.

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    Performance of downlink schedulers with superposed or orthogonal transmissions  Open access

     Agustin de Dios, Adrian; Vidal Manzano, Jose; Muñoz Medina, Olga
    IEEE International Conference on Communications
    Presentation's date: 2010-05-26
    Presentation of work at congresses

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    This work looks into the extension of the proportional fair (PF) scheduler to the multi-user case, where the source is transmitting several messages under the superposition coding (SC) strategy in a Gaussian Broadcast channel. Jointly with the weighted sum-rate (WSR) scheduling criterion, we derive guidelines for 2-user pairing, based both on SNR and user priority. We compare superposition coding access with frequency division multiple access, while time division is obtained naturally as a result of the user pairing. Results elucidate that the 2-user SC PF always improves the single-user PF in terms of average throughput and delay reduction, and we compare its performance with the 3-user SC PF. Finally, the WSR shows throughput gains similar to the 2-user SC PF for certain configuration of the scheduler.

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    FREEDOM Project. Scenario, requirements and first business model analysis  Open access

     Vivier, G.; Agustin de Dios, Adrian; Vidal Manzano, Jose; Muñoz Medina, Olga; Barbarossa, Sergio; Pescosolido, Loreto; Omilipo, M; de Marinis, Enrico; Imponente, Giovanni; Lopatka, M; Roux, P; Kamoun, M; Becvar, Z; Mach, P; Corre, Y; Hariyanto, H; Widiawan, A.K.; Simamora, L
    Date: 2010-06-20
    Report

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    This deliverable is the first of FREEDOM project. It provides an outlook of the scenarios and assumptions widely shared in the wireless community when addressing femtocell deployment. It starts by providing scenarios as seen from the business perspective, and then they are further described with a more technical perspective. Both interference and mobility are addressed although from the review of foras and standardization bodies, the interference issues are more extensively considered. From these scenarios we derived a list of requirement that should be met by femto-cell systems. These requirements must drive the technical work in the other work-pacakges of FREEDOM. The report then captures the main assumptions for simulation in order to align the work from various WPs and partners around similar set of assumptions. A final section presents true business model from operator standpoint, highlighting the potential of massive femto-cell deployment.

    Postprint (author’s final draft)

  • FEMTOCELL-BASED NETWORK ENHANCEMENT BY INTERFERENCE MANAGEMENT AND COORDINATION OF INFORMATION FOR SEAMLESS CONNECTIVITY

     Muñoz Medina, Olga; Rodriguez Fonollosa, Javier; Agustin de Dios, Adrian; Fernandez Rubio, Juan-antonio; Vidal Manzano, Jose
    Participation in a competitive project

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    Downlink multi-cell radio resource management for coordinated base stations  Open access

     Muñoz Medina, Olga; Calvo Page, Eduard; Vidal Manzano, Jose; Agustin de Dios, Adrian
    IEEE Vehicular Technology Conference
    Presentation's date: 2009-04-28
    Presentation of work at congresses

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    Analytical resource optimization for DF relay-assisted transmission under HARQ  Open access

     Agustin de Dios, Adrian; Vidal Manzano, Jose; Muñoz Medina, Olga
    IEEE Vehicular Technology Conference
    Presentation's date: 2009-04-28
    Presentation of work at congresses

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    Under limited channel state information at the transmitter the communication suffers from the outage events produced by a data rate selection not supported by the current channel realization. Automatic repeat request (ARQ) protocols are a useful tool to deal with those outage events in delay-tolerant services. This work looks into how Automatic Repeat Request(ARQ) protocols are applied to the half-duplex relay-assisted transmission with a decode-and-forward (DF) relay. The exploitation of ACK feedback channels from destination and relay leads to two possible implementations: 1) only-source manages the retransmission procedure or 2) both source and relay control the retransmissions. We analyze both options under a chase-combining ARQ protocol with limited number of transmission rounds, providing integral expressions for the throughput. This study allows the optimization transmission rate and the amount of resources allocated for the relay transmission.

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    Adaptive bitrate and resource allocation for relay-assisted ARQ transmissions  Open access

     Agustin de Dios, Adrian; Vidal Manzano, Jose; Muñoz Medina, Olga
    IEEE International Conference on Communications
    Presentation's date: 2009
    Presentation of work at congresses

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    Automatic repeat request (ARQ) protocols deal with the situations where the selected data rate is not supported by the current channel realization. The inappropriate selection is motivated by the limited channel state information at the transmitter (CSIT). This work looks into how the ARQ protocols are applied to the half-duplex relay-assisted transmission with decode-and-forward relays by exploiting the ACK feedback channel of the terminals. Two implementations are tackled: 1) only the source or 2) source and relay manage the retransmissions under the pure-ARQ protocol. This work presents an analytical framework for the comparison of both options. The study allows the optimization of the bitrate and amount of resource allocated for the relay transmission phases.

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    Protocols and resource allocation for the two-way relay channel with half-duplex terminals  Open access

     Agustin de Dios, Adrian; Vidal Manzano, Jose; Muñoz Medina, Olga
    IEEE International Conference on Communications
    Presentation's date: 2009
    Presentation of work at congresses

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    The two-way relay channel (TWRC) describes the communication between two terminals sharing a common relay. In this work we compare different protocols for the TWRC with a half-duplex relay (forwarding and protocol I) and transmission schemes (Network Coding Relaying with random binning and XOR precoding), when the relay works in decode-and-forward and without channel state information at the transmitters. We provide the optimal resource allocation (in terms of phase duration, data rate and power allocation) when there is an individual or sum-average power constraint over the terminals. Closed-form solutions are derived whenever it is possible, while for others cases we show that the resource allocation can be formulated as a convex problem, which means that the solution can be obtained by low-complexity interior point methods.

  • Cooperative wireless networking beyond store-and-forward : Perspectives in PHY and MAC design

     Valentin, Stefan; Hermann, Lichte S; Holger, Karl; Guillaume, Vivier; Simoens, S; Vidal Manzano, Jose; Agustin de Dios, Adrian
    Wireless personal communications
    Date of publication: 2009-01
    Journal article

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  • RRM strategies in multihop and cooperative transmission

     Muñoz Medina, Olga; Vidal Manzano, Jose; Calvo Page, Eduard; Agustin de Dios, Adrian
    Date of publication: 2009-06-01
    Book chapter

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  • Relaying techniques for OFDM-MIMO systems

     Muñoz Medina, Olga; Vidal Manzano, Jose; Agustin de Dios, Adrian; Simoens, Sebastien; Calvo Page, Eduard; Hoshyar, Reza; Liu, Yajian
    Date of publication: 2009-06-01
    Book chapter

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  • SPARKLE: Spectrum-Agile Network of Cooperative Relays With Efficient Interference Coordination

     Agustin de Dios, Adrian; Vidal Manzano, Jose
    Participation in a competitive project

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  • FREEDOM: Femtocell -Based Network By Interface Management And Coordination Of Information

     Muñoz Medina, Olga; Agustin de Dios, Adrian; Vidal Manzano, Jose
    Participation in a competitive project

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  • FREEDOM

     Muñoz Medina, Olga; Agustin de Dios, Adrian; Vidal Manzano, Jose
    Participation in a competitive project

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  • SPARKLE

     Agustin de Dios, Adrian; Muñoz Medina, Olga; Vidal Manzano, Jose
    Participation in a competitive project

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  • PROCESSAMENT DEL SENYAL EN COMUNICACIONS

     Rey Micolau, Francesc; Villares Piera, N. Javier; Vazquez Grau, Gregorio; Riba Sagarra, Jaume; Vidal Manzano, Jose; Cabrera Bean, Margarita Asuncion; Garcia Ordoñez, Luis; Rodriguez Fonollosa, Javier; Ramirez Javega, Francisco; Muñoz Medina, Olga; Matas Navarro, David; Font Segura, Josep; Silva Pereira, Silvana; Agustin de Dios, Adrian; Fernandez Rubio, Juan-antonio; Lamarca Orozco, M. Meritxell; Pages Zamora, Alba Maria; Sala Alvarez, Jose
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  • Amplify-and-forward cooperation under interference-limited spatial reuse of the relay slot

     Agustin de Dios, Adrian; Vidal Manzano, Jose
    IEEE transactions on wireless communications
    Date of publication: 2008-05
    Journal article

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  • Relay-Assisted Transmission and Radio Resource Management for Wireless Networks  Open access

     Agustin de Dios, Adrian
    Defense's date: 2008-05-29
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    La transmisión asistida por relay o transmisión cooperativa es una nueva técnica de diversidad espacial donde aparece un elemento nuevo (un relay o un usuario cooperativo) en la tradicional transmisión punto a punto (fuente a destino). Ahora en la comunicación intervienen tres enlaces: fuente-relay, relay-destino y fuente-destino. El relay, además de asistir a la fuente en la transmisión de un mensaje, permite combatir las degradaciones que puede sufrir el canal como el shadowing y el pathloss. Aunque esta técnica está basada en el trabajo realizado en los 70 por Van der Meulen, Cover y El Gamal, ha sido en los últimos años cuando se han vuelto a considerar el uso de relays. En realidad, la transmisión asistida por un relay puede verse como un sistema virtual multi-antena (virtual MIMO) donde las antenas están distribuidas en diferentes terminales. Sin embargo, al contrario de los sistemas multi-antena y debido a la limitación de la actual tecnología radio, el relay debe trabajar en modo half-duplex, ya que no puede transmitir y recibir simultáneamente en la misma banda. Este hecho, motiva que la transmisión deba realizarse en dos fases ortogonales en función del modo del relay (recibiendo datos - relay-receive phase o transmitiendo datos - relay-transmit phase). Estas fases pueden implementarse en el dominio de la frecuencia o el tiempo.Esta tesis investiga protocolos y estrategias para la transmisión asistida por relay para mejorar la eficiencia espectral y homogeneizar el servicio para todos los usuarios en un sistema de comunicación celular. La introducción del relay en la comunicación implica la redefinición de muchas técnicas y protocolos considerados en las comunicaciones punto a punto y en los sistemas multi-antena, situados en la capa física y/o superiores.En primer lugar se presentan los achievable rates obtenidos por la transmisión asistida por relay en función del rol del relay (amplifica y retransmite o decodifica y retransmite), el tipo de transmisión (siempre transmite, incremental o selectiva), los datos transmitidos por el relay (repite los símbolos recibidos o son independientes) y el tipo del protocolo half duplex. En función de los terminales activos en cada fase de la comunicación (fuente, destino o relay), existen hasta cuatro protocolos. Otro aspecto considerado es la asignación de recursos (resource allocation) para cada fase de la comunicación, la cual puede estar fijada de antemano o puede ser ajustada dinámicamente en función de los canales de los diferentes enlaces. En el caso de que todos los coeficientes del canal se conocieran perfectamente, los terminales podrían transmitir síncronamente, mejorando la comunicación gracias a la ganancia debida a técnicas de pre-codificación por medio de los autovectores del canal (con antenas distribuidas).Además dos técnicas de transmisión asistida por relay son evaluadas cuando existen múltiples relays por destino. Ambas dependen del tipo de mensajes transmitidos a cada relay (mensajes independientes o uno común). La asignación de recursos para ambas técnicas puede verse como un problema convexo.Tres escenarios resumen diferentes tipos de transmisión asistida por relay para múltiples fuentes y un solo destino: RMAC (Relay-assisted Multiple Access Channel), UC (User Cooperation) and MARC (Multiple Access Relay Channel). Su diferencia se basa en el tipo de relay half- duplex considerado. La transmisión puede hacerse síncrona o asíncronamente. Las fuentes y los relays están limitados en potencia y el acceso de ellos en cada fase de la comunicación pude hacerse por medio de TDMA (time division multiple access), FDMA (frequency division multiple access) or SC (superposition coding multiple access). La asignación de recursos puede ser formulada como un problema convexo en algunos casos y la solución óptima puede ser encontrada. Seguidamente la transmisión asistida por relay y duplexada en tiempo es aplicada a un sistema celular centralizado basado en TDMA en el downlink. Con el objetivo de mejorar la eficiencia espectral se propone el reuso espacial de un slot temporal para las transmisiones de los relays hacia sus respectivos destinos (slot de relay), generando interferencia para todos los restantes destinos activos. Un algoritmo de control de potencia basado en la teoría de juegos es propuesto para combatir la interferencia generada. Bajo esa configuración, un algoritmo de scheduling investiga las posibles ganancias debidas al multi-user gain y mide el overhead introducido.Otra forma de tratar con la interferencia es la de controlar el rate de nuestra transmisión (rate control management). Bajo ciertas condiciones es posible modelar la función de densidad de probabilidad de la potencia interferente. En ese caso, la fuente ajusta el rate para maximizar el throughput de la comunicación. Esta solución es extendida para el caso en el que cada destino es asistido por varios relays. Las dos soluciones propuestas son capaces de proporcionar mejores resultados que la transmisión directa, a pesar de la interferencia existente en el slot de relay. Finalmente, se investiga el control dinámico del enlace para la transmisión asistida por relay con dos diferentes tipos de conocimiento sobre el canal: conocimiento estadístico (statistical knowledge of the channel state) o conocimiento del canal instantáneo (actual information about the current channel state).Estos dos tipos de conocimiento derivan en diferentes estrategias a utilizar para seleccionar la modulación y el esquema de codificación (MCS). En el primer caso, los rates seleccionados no están adaptados al canal actual, por lo que el destino puede recibir erróneamente los mensajes. Los protocolos de retransmisión de mensajes (ARQ - automatic repeat request) son los encargados de asegurarse la correcta recepción y son redefinidos para la transmisión asistida por relay.. En este trabajo, se especifica los códigos espacio-tiempo distribuidos, la codificación en al fuente y el relay y la longitud de las retransmisiones. Cuando la fuente conoce algún parámetro del canal instantáneo puede adaptar el MCS para esa realización del canal. En ese caso se investiga la predicción del error en las transmisiones asistidas por relay, y con ello es posible diseñar el MCS para que maximice la cantidad de información transmitida para una probabilidad de pérdida de paquete o que maximice el throughput.

    The relay-assisted or cooperative transmission is a relatively new class of spatial diversity technique where a new element comes up in the conventional source-destination or point-to point communication: an assisting relay or cooperating user. The relay assists to the source in transmitting a message to the destination and allows dealing with the channel impairments like shadowing and pathloss. Although the seminal works were issued in the 70's by van der Meulen, Cover and El Gamal, it has been during the last years when it has re-gained more attention by the researchers. In fact, the relay-assisted transmission can be seen as a virtual MIMO (Multiple Input Multiple Output) with distributed antennas. In contrast to MIMO systems, the transmission requires the use of additional channel resources because of the limitation of the current radio technology: the relay terminal is constrained to work in half-duplex mode, which motivates that the transmission must be carried out in two orthogonal phases (relay-receive and relay-transmit phase), duplexed in time or frequency domains.This dissertation investigates protocols and strategies for the relay-assisted transmission which improve the spectral efficiency and homogenize service in the cellular communication systems. The new element present in the communication, the relay terminal, imposes a redefinition of many techniques and protocols commonly used in the point-to-point and MIMO systems, which are placed at the physical and upper layers.First, achievable rates using the relay-assisted transmission are provided which depend on the role of the relay (amplify-and-forward or decode-and-forward), the type of the transmission (persistent transmission, incremental or selective relaying), the data transmitted by the relays (repetition or unconstrained coding) and the type of half-duplex protocol. There are up to four protocol definition depending on the activity of the terminals on each phase. An additional aspect addressed is the resource allocation for each phase, that is, either it is fixed beforehand (static) or it is adjusted dynamically (dynamic) as a function of the channel quality. For the single-user relay- assisted transmission the resources can be allocated based on the channel quality of the different links. Moreover, if there is complete channel state information about all channel coefficients, source and relay can transmit synchronously enhancing the transmission thanks to the (distributed) eigenvector precoding techniques.Two relay-assisted transmission techniques are evaluated when a destination is assisted by multiple relays. Both depend on the messages intended to each assisting relay (independent or common messaging). The resource allocation for both techniques is shown to be convex. Additionally, three different scenarios illustrate the multi-user relay-assisted transmission with a single destination and different types of half-duplex relays: RMAC (Relay-assisted Multiple Access Channel), UC (User Cooperation) and MARC (Multiple Access Relay Channel). The relay-assisted transmission can be done synchronously or asynchronously. The sources and relays are power limited and access in each phase of the communication by TDMA (time division multiple access), FDMA (frequency division multiple access) or SC (superposition coding multiple access). For those scenarios the allocation of transmitted power and time resources can be formulated as a convex problem under some circumstances, evaluating the optimal solution.Afterwards, the relay-assisted transmission duplexed in time is applied to a centralized cellular system based on TDMA in the downlink. The reuse of one time slot for the transmissions done from the relays to destinations (relay slot) is proposed to improve the spectral efficiency. This solution produces interference for all the destinations active in that time slot. A power control algorithm (at the relays) based on game theory is proposed to combat the generated interference. Under that configuration a scheduler algorithm explores the multi-user gain for the relay-assisted transmission, measuring the introduced overhead.Another way of dealing with the interference is by rate control management. Under some circumstances it is possible to model the probability density function (pdf) of the interfering power. In such a case, the source can tune the transmission rate in order to maximize the throughput. This solution is extended to the case where each destination is assisted by multiple relays. In spite of the interfering power, both proposed solutions are able to provide significant gains over the direct transmission.Finally, the dynamic link control of the relay assisted transmission is investigated under two different assumptions on the knowledge about the channel: statistical knowledge of the channel state and actual information about the current channel state. Both types of knowledge lead to different transmission strategies, in terms of selecting the modulation and coding scheme (MCS). Under the first case, the transmission rates are not adapted to the current channel realization and the destination can decode wrongly the messages. The Automatic Repeat reQuest (ARQ) protocols are redefined for the relayassisted transmission to cope with these events. In this work we specify the (distributed) space-time codes, the coding at the source and relay and the length of the retransmissions. When there is actual information about the channel state the MCS can be adapted to the current channel realization. In such a case, the link error prediction for the relay-assisted transmission is investigated, and thus the MCS can be designed for maximizing the information rate for a given probability of packet loss or maximizing the throughput.

  • ICT-215282-ROCKET COORDINACIO

     Muñoz Medina, Olga; Vidal Manzano, Jose; Agustin de Dios, Adrian
    Participation in a competitive project

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  • Report on operational scenarios and simulation methodology

     Vidal Manzano, Jose; Muñoz Medina, Olga; Agustin de Dios, Adrian
    Date: 2008-08
    Report

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  • Enhancing 802.16 networks through infrastructure-based relays

     Muñoz Medina, Olga; Vidal Manzano, Jose; Agustin de Dios, Adrian; Calvo, Eduard; Alcón, Andreu
    17th ICT Mobile and Wireless Communications Summit (ICT 2008)
    Presentation of work at congresses

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  • Implementing cooperative wireless networks

     Valentin, Stefan; Lichte, Hermann; Karl, Holger; Simoens, Sebastien; vivier, guillaume; Vidal Manzano, Jose; Agustin de Dios, Adrian
    Date of publication: 2007-09-21
    Book chapter

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  • Implementing Cooperative Wireless Networks. Towards Feasibility and Deployment

     Vidal Manzano, Jose; Agustin de Dios, Adrian; Valentin, S; Lichte, H S; Karl, H; Simoens, S; Vivier, G
    Date of publication: 2007-09-30
    Book chapter

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  • Resource Management for Relay-Enhanced WiMax: OFDM and OFDMA

     Muñoz Medina, Olga; Vidal Manzano, Jose; Agustin de Dios, Adrian; Calvo Page, Eduardo; Alcón, Andreu
    Workshop Trends in Radio Resource Management
    Presentation's date: 2007-11-21
    Presentation of work at congresses

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  • Radio resources optimization for the half-duplex relay-assited multiple access gaussian channel

     Agustin de Dios, Adrian; Vidal Manzano, Jose
    8th IEEE Workshop on Signal Processing Advances in Wireless Communications
    Presentation of work at congresses

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  • Cellular deployment concepts for relay-based systems

     Vidal Manzano, Jose; Muñoz Medina, Olga; Agustin de Dios, Adrian
    Date: 2007-01
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  • Preliminary requirements for enhanced MAC protocols

     Muñoz Medina, Olga; Vidal Manzano, Jose; Agustin de Dios, Adrian
    Date: 2007-06
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  • Draft Specification for the enhanced WMAN and WLAN MAC Protocols

     Muñoz Medina, Olga; Vidal Manzano, Jose; Agustin de Dios, Adrian
    Date: 2007-11
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  • Detailed description of AAS and selected PHY techniques for relay/mesh based networks

     Agustin de Dios, Adrian; Vidal Manzano, Jose; Muñoz Medina, Olga
    Date: 2007-09
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