Fabián García-Nocetti

Finding minimum transmission radii for preserving connectivity and constructing minimal spanning trees in ad hoc and sensor networks

Ad hoc networks are normally modeled by unit graphs, where two nodes are connected if and only if their distance is at most the transmission radius R, equal for all nodes. Larger than necessary values of R cause communication interference and consumption of increased energy, while smaller values may disable data communication tasks such as routing and broadcasting. It was recognized that the minimum value of R that preserves the network connectivity is equal to the longest edge in the minimum spanning tree. However, all existing solutions for finding R rely on algorithms that require global network knowledge or inefficient straightforward distributed adaptations of centralized algorithms. This article proposes to use the longest LMST (local minimum spanning tree, recently proposed message free approximation of MST) edge to approximate R using a wave propagation quasi-localized algorithm. The differences between exact and so approximated values of R are estimated for two and three-dimensional random unit graphs. Despite small number of additional edges in LMST with respect to MST (under 5%), they can extend R by about 33% its range on networks with up to 500 nodes. We then prove that MST is a subset of LMST and describe a quasi-localized scheme for constructing MST from LMST. It needs less than 7 messages per node on average (for networks up to 500 nodes). The algorithm eliminates LMST edges which are not in MST by a loop breakage procedure, which iteratively follows dangling edges from leaves to LMST loops, and breaks loops by eliminating their longest edges, until the procedure finishes at a single node (as a byproduct, this single node can also be considered as an elected leader of the network). This so elected leader also learns longest MST edge in the process, and may broadcast it to other nodes. We also describe an algorithm for updating MST when a single node is added to the network.

Reconfigurable fault tolerant PID networked control for magnetic levitation case study

Abstract Nowadays dynamic behaviour performed by a computer network system shows the needs to address it from the perspective of a control system. One strategy to be followed it is the real-time modeling. Having obtained a way to represent a computer network system, next stage is to how control approach can be affected and modified. In that respect, this paper proposes a control reconfiguration strategy from the definition of an automata considering computer network reconfiguration. Several stages are studied, how computer network takes place as well as how control techniques is modified.

Finding Minimum Transmission Radii for Preserving Connectivity and Constructing Minimal Spanning Trees in Ad Hoc and Sensor Networks

The minimum transmission radius R that preserves ad hoc network connectivity is equal to the longest edge in the minimum spanning tree. This article proposes to use the longest LMST (local MST, recently proposed message free approximation of MST) edge to approximate R using a wave propagation quazi-localized algorithm. Despite small number of additional edges in LMST with respect to MST, they can extend R by about 33% its range on networks with up to 500 nodes. We then prove that MST is a subset of LMST and describe a quazi-localized scheme for constructing MST from LMST. The algorithm eliminates LMST edges which are not in MST by a loop breakage procedure, which iteratively follows dangling edges from leaves to LMST loops, and breaks loops by eliminating their longest edges, until the procedure finishes at a single leader node, which then broadcasts R to other nodes.

Reconfigurable Fuzzy Takagi Sugeno Networked Control using EDF Scheduling in xPC Target

Nowadays dynamic behaviour performed by a computer network system shows the posibility to be addressed from the perspective of a control system. This paper discusses the use of Fuzzy Takagi Sugeno real time digital control with hardware-in-the-loop (HIL) magnetic levitator (maglev) using xPC Target. Here xPC Target is used as operating environment for real time processing and to connect a computer network system. In that respect, this paper proposes a control reconfiguration strategy from the definition of a Takagi-Sugeno approach, considering computer network reconfiguration. Several stages are studied, how computer network takes place as well as how control techniques are modified using Fuzzy Takagi- Sugeno Control.

HIGH PERFORMANCE COMPUTING OF TIME FREQUENCY DISTRIBUTIONS FOR DOPPLER ULTRASOUND SIGNAL ANALYSIS

Abstract Typical methods for signal analysis utilize the Fourier Transform-based algorithms to estimate the spectral response of a signal. This current practice suffers from poor frequency resolution when estimating non-stationary signals. This paper describes some alternative methods based on time-frequency distributions from a Cohens class point of view. Four distribution cases are evaluated: Wigner Ville, Choi Williams, Bessel and Born Jordan. Continuous and discrete distributions are presented for each case. Simplified discretised expressions for the implementation of distributions are formulated, these leading to a reduction of the computations realized when comparing to original definitions. Also, two parallel approaches (intrinsic parallelism and data parallelism) for the computation of the distributions are proposed, implemented and assessed by using a parallel DSP-based system. Finally, a further simplification by truncating the simplified expressions is proposed; this truncation is restricted by the error in spectral estimations. Results are applied to the development of a real-time spectrum analyzer for Doppler blood flow instrumentation.

An approximation for reconfigurable Fuzzy Takagi-Sugeno networked control

The paper propose a control strategy from the definition of a Takagi-Sugeno approach, considering computer network reconfiguration. The focus is on computer networks and how control techniques are modified using Fuzzy Takagi-Sugeno control. Control reconfiguration is presented as an available approach for fault coverage in order to keep system performance. Reconfiguration is pursued as a response of time delay modification rather than fault appearance, although this is the basis for control reconfiguration. The focus is on reconfigurable control law due to the presence of local faults and its resulting time delays.

Reconfigurable Fuzzy Takagi Sugeno Networked Control using Cooperative Agents and Local Fault Diagnosis

Nowadays dynamic behaviour performed by a computer network system shows the posibility to be addressed from the perspective of a control system. This paper discusses the use of Fuzzy Takagi Sugeno real time control and local fault diagnosis with hardware-in-the-loop (HIL) magnetic levitator (maglev) using xPC Target. Here xPC Target is used as operating environment for real time processing and to connect a computer network system. In that respect, this paper proposes a control reconfiguration approach based upon a cooperative agent strategy and local fault diagnosis using Takagi-Sugeno technique. Several stages are studied, how local fault diagnosis produce a warning value, how computer network is reconfigured, as well as how control techniques are modified using Fuzzy Takagi-Sugeno Control.

Computadora de Vuelo Triplex de Diseño y Manufactura Mexicana para el Microsatélite Satex

Este trabajo describe la arquitectura disenada y fabricada para la computadora de vuelo (CV) del microsatelite experimental Satex (MES) la cual utiliza un sistema triplex de procesadores que se basa en una tarjeta de procesamiento principal y dos refacciones completas de respaldo. La CV esta compuesta por seis circuitos impresos, cada uno con componentes de montaje superficial ensamblados en ambas caras de los tabloides para reducir el numero de tarjetas y por tanto su peso. La mayor parte de los componentes utilizados son de calificacion militar, solo los procesadores son de tipo industrial con rango de temperatura extendida por lo cual se le agregan protecciones electronicas contra radiacion. Se ofrecen las caracteristicas globales de la computadora, sus procesos de validacion y resultados de confiabilidad operativa obtenidos con la norma militar MIL-HDBK217f.

Red Reconfigurable Mediante el Modelo de Control Predictivo para Tres Bandas Transportadoras como Caso de Estudio

In this work a co-design strategy to a reconfigurable distributed environment using real time scheduling strategies is presented. The proposal is applied to the study of a three band conveyor belt and a control system is added to the design using the predictive control model. The bounding of the response time and the change of scenario based on finite state machines, allow that the time response be pseudo dynamic and known. It is concluded that the reconfiguration+modelling+design strategy fulfils the expectations of maintaining certain level of performance although uncertainties are present due to time delays.

The impact of delay in dominating set and neighbor elimination based broadcasting in ad hoc networks

In a broadcasting task, a source sends a message to all the nodes of a network. There exist methods for flooding a network intelligently and for scheduling node activities. Dominating sets and neighbor elimination based broadcasting is currently the most efficient broadcasting scheme in terms of the number of retransmitted messages to complete a broadcast. It provides basis for defining other broadcasting protocols by changing the definition of the delay (timeout) function used to decide how long a dominating node should wait before making a retransmission. In this article, we propose thirteen such variants. They are all reliable, meaning that all the nodes connected to a source will receive the message, assuming an ideal MAC layer. Eight of them are hexagonal based; four are distance-based, giving priority to the neighbors that are further or nearer from the retransmitting node; and one is using a random timeout. Beyond these variants, we propose three different ways to update the timeout values during a broadcasting process. Our experimental data shows that the updating process of the timeout values has no significant impact compared to the selected timeout function. From the thirteen variants we deliberately proposed some worst-case timeout functions to see its impact in the broadcasting process. We confirm by our experimental data that indeed the selected timeout function has an impact in the broadcasting process. Although our experimental data shows that the new further distance-based scheme outperforms almost all schemes in terms of number of messages to complete a broadcast, it also shows that a random function (the way IEEE 802.11 works) is a very good choice.