4 research outputs found

    A Comparative Study of Sparse Associative Memories

    Full text link
    We study various models of associative memories with sparse information, i.e. a pattern to be stored is a random string of 00s and 11s with about log⁥N\log N 11s, only. We compare different synaptic weights, architectures and retrieval mechanisms to shed light on the influence of the various parameters on the storage capacity.Comment: 28 pages, 2 figure

    Statistical mechanics of neural networks: The Hopfield model and the Kac-Hopfield model

    Get PDF
    We survey the statistical mechanics approach to the analysis of neural networks of the Hopfield type. We consider both models on complete graphs (mean-field), random graphs (dilute model), and on regular lattices (Kac-model). We try to explain the main ideas and techniques, as well as the results obtained by them, without however going into too much technical detail. We also give a short history of the main developments in the mathematical analysis of these models over the last 20 years

    MĂ©todos de asignaciĂłn dinĂĄmica de intervalos de tiempo para redes de comunicaciones tĂĄcticas militares

    Get PDF
    Las redes de comunicaciones tĂĄcticas militares tienen como objetivo el intercambio de informaciĂłn entre un gran nĂșmero de unidades tĂĄcticas dispersas en un ĂĄrea, cada una de las cuales tiene un terminal para la transmisiĂłn de datos, optimizando las funciones militares operativas conjuntas. Link-16 es actualmente el estĂĄndar mĂĄs avanzado de este tipo de redes de la OTAN. En esta red, a cada participante se le asigna un grupo de intervalos de tiempo (time slots) para transmitir sus mensajes. Existen tres modos de acceso a esos time slots: dedicado, por contienda y por reasignaciĂłn de time slots (Time Slot Reallocation). En el modo Time Slot Reallocation (TSR) se asigna un mismo conjunto de time slots a varios participantes en la red para la transmisiĂłn de sus mensajes, pero se van distribuyendo dinĂĄmicamente de forma automĂĄtica a cada unidad de acuerdo a sus requisitos de transmisiĂłn en cada periodo de reasignaciĂłn. El algoritmo de asignaciĂłn de time slots reside en cada terminal, que puede calcular quĂ© time slots debe usar en el siguiente periodo de reasignaciĂłn de slots. Cuando la suma de las demandas de bloques de slots de todos los terminales participantes en la red es menor que el nĂșmero de bloques de slots disponible en el conjunto TSR, a cada terminal se le asigna un nĂșmero de bloques de slots igual al demandado, y no existe ningĂșn conflicto. Pero si es mayor, a cada terminal se le asigna un nĂșmero de bloques de slots proporcional al nĂșmero demandado, con lo que se va creando una cola de mensajes sin poder transmitirse en cada terminal, ya que no todos los mensajes podrĂĄn transmitirse en el siguiente periodo de reasignaciĂłn y tendrĂĄn que esperar a los siguientes periodos. El problema del algoritmo de reasignaciĂłn actual es que permite conflictos en la asignaciĂłn de bloques de slots. AdemĂĄs, intenta asignar el mĂĄximo nĂșmero de bloques de slots a las unidades con una mayor prioridad segĂșn un orden, con lo que, a las unidades de menor prioridad les asigna un nĂșmero bastante menor de bloques de slots. Esto quiere decir que la cola mĂĄxima de mensajes que no pueden ser transmitidos para algunos terminales es mucho mayor que para otros terminales. En esta Tesis se estudia la mejora del algoritmo TSR (Time Slot Reallocation) de reasignaciĂłn dinĂĄmica de time slots para una red Link-16, en las dos situaciones posibles: que la suma de las demandas de bloques de slots de todos los terminales participantes en la red sea mayor que el nĂșmero de bloques de slots disponible, o que sea menor. En el primer caso, se propone la utilizaciĂłn de diversas tĂ©cnicas de OptimizaciĂłn Combinatoria. Con ello, se pretende eliminar los casos de conflicto en la asignaciĂłn y minimizar el valor medio de la cola mĂĄxima de mensajes no transmitidos en cada terminal participante, es decir, que las colas de mensajes no transmitidos en todos los participantes en una red se mantengan lo mĂĄs pequeñas posibles en todos los periodos de reasignaciĂłn. En el segundo caso, se propone la utilizaciĂłn de TĂ©cnicas Predictivas y TeorĂ­a de Juegos para asignar los bloques de slots que quedan sin asignar. Con ello se pretende minimizar el tiempo de transmisiĂłn de los mensajes para cada terminal participante en la red, desde que se demandan los slots hasta que se transmiten, ya que, al asignarle mĂĄs bloques de slots, puede transmitir antes en el siguiente periodo de reasignaciĂłn. _____________________________________________The tactical military data communications networks have the purpose of the exchanging of tactical information among different military units, each one of these has a terminal for data communication, optimizing the joint operational military functions. Link-16 is at the moment the most advanced standard of these NATO networks. In this network, each terminal is assigned a pool of time slots to transmit their messages. There are three access modes to these time slots: dedicated access, contention access and Time Slot Reallocation access. In Time Slot Reallocation (TSR) access mode, participants in the networks are assigned the same pool of time slots for the transmission of the messages, and these time slots are dynamically distributed to each transmitter according to its transmission requirements for each reallocation period. An algorithm within the terminals redistributes the pool of time slots in real time to meet these needs for the next reallocation period. If the sum of all time slots blocks requested by all terminals in the network is less than the total number of time slots blocks available for TSR, each terminal is assigned the number of requested time slots blocks, and there is no conflict. But, if it exceeds the total number of time slots blocks available for TSR, each terminal is assigned a number of time slots blocks in proportion to the terminalÂŽs request. So, a queue of messages that has not been transmitted is created in each terminal, because not all messages can be transmitted in the next reallocation period and will have to be transmitted in other periods. The problem in the current assignment algorithm is that there are conflicts in the time slots blocks assignments. Moreover, it tries to assign as many of the time slots blocks as required to satisfy their requests to the terminals with a greater priority according to a priority order, so the terminals with a less priority are assigned a few time slots blocks. That is, the maximum queue of messages that can not be transmitted increase for some terminals. In this Thesis, improved Time Slot Reallocation (TSR) algorithms of dynamic time slots assignment in Link-16 networks are studied for the two possible situations: the sum of all time slots blocks requested by all terminals in the network exceeds the total number of time slots blocks available for TSR, or it is less than the total number of time slots blocks available for TSR. In the first case, the use of different Combinatorial Optimization Techniques is proposed. These new algorithms are focused on avoiding the conflicts in the time slots assignments and minimizing the maximum queue average of messages that can not be transmitted in each participant terminal, that is, the queues of messages that can not be transmitted in all participant terminals in the network keep the smallest as possible for all reallocation periods. In the second case, the use of Predictive Techniques and Game Theory is proposed for the assignment of the slots blocks that not have been assigned. With these methods, the objective is to minimize the time for messages transmission, from the time slots blocks are requested to the messages are transmitted, since when terminals are assigned more time slots blocks, they can transmit before in the next reallocation period
    corecore