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See detailCooperative transmission in cloud RAN considering fronthaul capacity and cloud processing constraints
Ha, Vu Nguyen UL; Le, Long Bao; Dao, Ngoc-Dung

in 2014 IEEE Wireless Communications and Networking Conference (WCNC) proceedings (2014, September 06)

We investigate the cooperative transmission design for the cloud radio access network (C-RAN) considering fronthaul capacity and cloud processing constraints. Specifically, we consider the joint ... [more ▼]

We investigate the cooperative transmission design for the cloud radio access network (C-RAN) considering fronthaul capacity and cloud processing constraints. Specifically, we consider the joint transmission scheme where the baseband signals and precoding vectors are processed and calculated by the cloud, which are delivered over the fronthaul links to the remote radio heads (RRHs) to form the RF signals for being transmitted to the users. We formulate the joint optimization problem for precoding design and allocation of RRHs, fronthaul capacity, and BBU processing resources to minimize the total transmission power subject to QoS constraints of the users. We present both optimal exhaustive search algorithm and two low-complexity algorithms to solve the resource allocation problem where the first one can achieve the Pareto optimality and the second one can determine an efficient solution with pretty low complexity. Numerical results confirm the excellent performance of the proposed low-complexity algorithms. [less ▲]

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See detailExtended Load Model for Point Fitted Insulating Glass Units
Thibolt, Mike; Odenbreit, Christoph UL

Scientific Conference (2014, September 03)

An insulating glass unit (IGU) reacts to a change in temperature or barometric pressure with a change of its cavity’s gas pressure. This leads to the so called “climate loading” of the glass panes, which ... [more ▼]

An insulating glass unit (IGU) reacts to a change in temperature or barometric pressure with a change of its cavity’s gas pressure. This leads to the so called “climate loading” of the glass panes, which can be considered in the structural analysis for each pane as an external load, acting on both adjacent glass panes. In addition, an external loading onto the exterior pane, like a wind- or snow load, is distributed to all glass panes of the IGU due to mechanical coupling effects of the encapsulated gas between the panes. Glass breakage and/or demolished edge bonds may be caused. In this paper, an extension of an existing load model for linear supported IGUs to IGUs with point fittings is presented. The extended load model considers beyond the coupling of the two panes via the encapsulated gas, the abolition of the pinned edges’ frame condition, which is replaced by (a) the coupling of the free edges via the edge bond and (b) the insertion of the point fittings. [less ▲]

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See detailInternalizing and externalizing behaviour: Subjective experiences in different classroom situations
Zurbriggen, Carmen UL; Venetz, Martin

Scientific Conference (2014, August)

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See detailSubgroups of problematic behaviour among students of primary school from teacher perspective: A latent profile analysis
Venetz, Martin; Zurbriggen, Carmen UL; Liesen, Christian

Scientific Conference (2014, August)

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See detailA vision based aerial robot solution for the IARC 2014 by the Technical University of Madrid
Pestana, Jesus; Sanchez Lopez, Jose Luis UL; Suarez-Fernandez, Ramon et al

Scientific Conference (2014, August)

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See detailEducational context and occupational aspirations: The role of academic tracking
Zurbriggen, Carmen UL; Kronig, Winfried; Venetz, Martin

Scientific Conference (2014, July)

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See detailZur Bedeutung von Peers für das akademische Selbstkonzept
Zurbriggen, Carmen UL

Scientific Conference (2014, June)

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See detailComputer vision based general object following for GPS-denied multirotor unmanned vehicles
Pestana, Jesus; Sanchez Lopez, Jose Luis UL; Saripalli, Srikanth et al

in 2014 American Control Conference (2014, June)

The motivation of this research is to show that visual based object tracking and following is reliable using a cheap GPS-denied multirotor platform such as the AR Drone 2.0. Our architecture allows the ... [more ▼]

The motivation of this research is to show that visual based object tracking and following is reliable using a cheap GPS-denied multirotor platform such as the AR Drone 2.0. Our architecture allows the user to specify an object in the image that the robot has to follow from an approximate constant distance. At the current stage of our development, in the event of image tracking loss the system starts to hover and waits for the image tracking recovery or second detection, which requires the usage of odometry measurements for self stabilization. During the following task, our software utilizes the forward-facing camera images and part of the IMU data to calculate the references for the four on-board low-level control loops. To obtain a stronger wind disturbance rejection and an improved navigation performance, a yaw heading reference based on the IMU data is internally kept and updated by our control algorithm. We validate the architecture using an AR Drone 2.0 and the OpenTLD tracker in outdoor suburban areas. The experimental tests have shown robustness against wind perturbations, target occlusion and illumination changes, and the system's capability to track a great variety of objects present on suburban areas, for instance: walking or running people, windows, AC machines, static and moving cars and plants. [less ▲]

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See detailA system for the design and development of vision-based multi-robot quadrotor swarms
Sanchez Lopez, Jose Luis UL; Pestana, Jesus; de la Puente, Paloma et al

in 2014 International Conference on Unmanned Aircraft Systems (ICUAS) (2014, May)

This paper presents a cost-effective framework for the prototyping of vision-based quadrotor multi-robot systems, which core characteristics are: modularity, compatibility with different platforms and ... [more ▼]

This paper presents a cost-effective framework for the prototyping of vision-based quadrotor multi-robot systems, which core characteristics are: modularity, compatibility with different platforms and being flight-proven. The framework is fully operative, which is shown in the paper through simulations and real flight tests of up to 5 drones, and was demonstrated with the participation in an international micro-aerial vehicles competition3 where it was awarded with the First Prize in the Indoors Autonomy Challenge. The motivation of this framework is to allow the developers to focus on their own research by decoupling the development of dependent modules, leading to a more cost-effective progress in the project. The basic instance of the framework that we propose, which is flight-proven with the cost-efficient and reliable platform Parrot AR Drone 2.0 and is open-source, includes several modules that can be reused and modified, such as: a basic sequential mission planner, a basic 2D trajectory planner, an odometry state estimator, localization and mapping modules which obtain absolute position measurements using visual markers, a trajectory controller and a visualization module. [less ▲]

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See detailA Vision-based Quadrotor Swarm for the participation in the 2013 International Micro Air Vehicle Competition
Pestana, Jesus; Sanchez Lopez, Jose Luis UL; de la Puente, Paloma et al

in 2014 International Conference on Unmanned Aircraft Systems (ICUAS) (2014, May)

This paper presents a completely autonomous solution to participate in the 2013 International Micro Air Vehicle Indoor Flight Competition (IMAV2013). Our proposal is a modular multi-robot swarm ... [more ▼]

This paper presents a completely autonomous solution to participate in the 2013 International Micro Air Vehicle Indoor Flight Competition (IMAV2013). Our proposal is a modular multi-robot swarm architecture, based on the Robot Operating System (ROS) software framework, where the only information shared among swarm agents is each robot's position. Each swarm agent consists of an AR Drone 2.0 quadrotor connected to a laptop which runs the software architecture. In order to present a completely visual-based solution the localization problem is simplified by the usage of ArUco visual markers. These visual markers are used to sense and map obstacles and to improve the pose estimation based on the IMU and optical data flow by means of an Extended Kalman Filter localization and mapping method. The presented solution and the performance of the CVG UPM team were awarded with the First Prize in the Indoors Autonomy Challenge of the IMAV2013 competition. [less ▲]

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See detailSchulische Integration und Schulübergang. Ergebnisse einer Längsschnittuntersuchung
Venetz, Martin; Zurbriggen, Carmen UL

Presentation (2014, April)

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See detailAn approach toward visual autonomous ship board landing of a VTOL UAV
Sanchez Lopez, Jose Luis UL; Pestana, Jesus; Saripalli, Srikanth et al

in Journal of Intelligent and Robotic Systems (2014), 74(1-2), 113--127

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See detailEnergy-efficient coordinated transmission for cloud-RANs: Algorithm design and trade-off
Ha, Vu Nguyen UL; Le, Long Bao; Dao, Ngoc-Dung

in 2014 48th Annual Conference on Information Sciences and Systems (CISS) (2014, March 19)

In this paper, we consider the energy-efficient co-ordinated transmission design for downlink transmission in the cloud radio access network (Cloud-RAN) considering fronthaul capacity and user QoS ... [more ▼]

In this paper, we consider the energy-efficient co-ordinated transmission design for downlink transmission in the cloud radio access network (Cloud-RAN) considering fronthaul capacity and user QoS constraints. Specifically, we assume that baseband signals are processed in the cloud, which are delivered to remote radio heads (RRHs) equipped with multiple antennas over fronthaul links for transmissions to single-antenna users. The design amounts to determine the set of RRHs to serve each user as well as the precoding and power levels for downlink transmission while maintaining the fronthaul capacity and user QoS constraints. Toward this end, we study the two closely-related problems, namely pricing-based total power and fronthaul capacity tradeoff (PFT) and fronthaul-constrained power minimization (FCPM) problems. We employ the concave approximation and gradient search methods to solve the PFT problem for the given pricing coefficients, which capture the power and fronthaul capacity tradeoff. Then, we develop an efficient algorithm to address the FCPM problem by iteratively solving the PFT problem while intelligently updating the pricing coefficients. Numerical results confirm the excellent performance of the our proposed algorithms and illustrate underlying tradeoffs among total transmission power, fronthaul capacity, and cluster size. [less ▲]

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See detailFair Resource Allocation for OFDMA Femtocell Networks With Macrocell Protection
Ha, Vu Nguyen UL; Le, Long Bao

in IEEE Transactions on Vehicular Technology (2014)

We consider the joint subchannel allocation and power control problem for orthogonal frequency-division multiple-access (OFDMA) femtocell networks in this paper. Specifically, we are interested in the ... [more ▼]

We consider the joint subchannel allocation and power control problem for orthogonal frequency-division multiple-access (OFDMA) femtocell networks in this paper. Specifically, we are interested in the fair resource-sharing solution for users in each femtocell that maximizes the total minimum spectral efficiency of all femtocells subject to protection constraints for the prioritized macro users. Toward this end, we present the mathematical formulation for the uplink resource-allocation problem and propose an optimal exhaustive search algorithm. Given the exponential complexity of the optimal algorithm, we develop a distributed and low-complexity algorithm to find an efficient solution for the problem. We prove that the proposed algorithm converges and we analyze its complexity. Then, we extend the proposed algorithm in three different directions, namely, downlink context, resource allocation with rate adaption for femto users, and consideration of a hybrid access strategy where some macro users are allowed to connect with nearby femto base stations (FBSs) to improve the performance of the femto tier. Finally, numerical results are presented to demonstrate the desirable performance of the proposed algorithms. [less ▲]

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See detailDynamische Mathematik mit GeoGebra – Algebrafenster
Kreis, Yves UL

Speeches/Talks (2014)

Die Bildungsstandards in Mathematik für die Klassen begünstigen einen entdeckenden, problemorientierten Unterricht. Dynamische Mathematiksysteme (DMS) wie GeoGebra erlauben den Schüler/-innen sich mit ... [more ▼]

Die Bildungsstandards in Mathematik für die Klassen begünstigen einen entdeckenden, problemorientierten Unterricht. Dynamische Mathematiksysteme (DMS) wie GeoGebra erlauben den Schüler/-innen sich mit Fragestellungen auseinanderzusetzen und Hypothesen aufzustellen. Anschließend müssen diese natürlich noch immer mathematisch bewiesen werden; diese Beweise lehnen sich aber oft an den durchlaufenen Prozess der Schüler/-innen an und sind somit leichter verständlich. [less ▲]

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See detailDistributed Base Station Association and Power Control for Heterogeneous Cellular Networks
Ha, Vu Nguyen UL; Le, Long Bao

in IEEE Transactions on Vehicular Technology (2014)

In this paper, we propose a universal joint base station (BS) association (BSA) and power control (PC) algorithm for heterogeneous cellular networks. Specifically, the proposed algorithm iteratively ... [more ▼]

In this paper, we propose a universal joint base station (BS) association (BSA) and power control (PC) algorithm for heterogeneous cellular networks. Specifically, the proposed algorithm iteratively updates the BSA solution and the transmit power of each user. Here, the new transmit power level is expressed as a function of the power in the previous iteration, and this function is called the power update function (puf). We prove the convergence of this algorithm when the puf of the PC strategy satisfies the so-called “two-sided scalable (2.s.s.) function” property. Then, we develop a novel hybrid PC (HPC) scheme by using noncooperative game theory and prove that its corresponding puf is 2.s.s. Therefore, this HPC scheme can be employed in the proposed joint BSA and PC algorithm. We then devise an adaptation mechanism for the HPC algorithm so that it can support the signal-tointerference-plus-noise ratio (SINR) requirements of all users whenever possible while exploiting multiuser diversity to improve the system throughput. We show that the proposed HPC adaptation algorithm outperforms the well-known Foschini-Miljianic PC algorithm in both feasible and infeasible systems. In addition, we present the application of the developed framework to design a hybrid access scheme for two-tier macrocell-femtocell networks. Numerical results are then presented to illustrate the convergence of the proposed algorithms and their superior performance, compared with existing algorithms in the literature. [less ▲]

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See detailKurzfragebogen zur Erfassung der Dimensionen der Integration von Schülerinnen und Schülern (KFDI)
Venetz, Martin; Zurbriggen, Carmen UL; Eckhart, Michael

Scientific Conference (2014, January)

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See detailA general purpose configurable controller for indoors and outdoors gps-denied navigation for multirotor unmanned aerial vehicles
Pestana, Jesus; Mellado-Bataller, Ignacio; Sanchez Lopez, Jose Luis UL et al

in Journal of Intelligent and Robotic Systems (2014), 73(1-4), 387--400

Detailed reference viewed: 15 (0 UL)