Distributed or networked systems become rapidly intractable as their size augments. This is due to the combinatorial explosion taking place in the state space, but also in the trajectory space. The latter is reinforce...
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ISBN:
(纸本)0780395670
Distributed or networked systems become rapidly intractable as their size augments. This is due to the combinatorial explosion taking place in the state space, but also in the trajectory space. The latter is reinforced by the amount of concurrency in the system (the fact that several non related events can occur simultaneously). We describe a triple strategy to extend standard monitoring approaches to such systems. We first use a true concurrency semantics to represent trajectories of the system. We then describe a very compact data structure to handle sets of trajectories, that we call the trellis of the system. This notion generalizes to distributed systems the standard notion of trellis of an automaton, where one dimension is time, and the other dimension encodes possible states at each time. Finally, we show that trellises have nice factorization properties, that allow the design of distributed monitoring approaches. In other words, a problem like state estimation for example, can be solved by parts, component per component, provided interactions between components are properly handled. We illustrate the approach on a distributed diagnosis problem.
This paper proposes a new structure of single parity check (SPC) product codes, which are inherently embedded with an interleaver. The complexity of decoding of the new SPC product codes is the same as the one of the ...
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ISBN:
(纸本)0780386051
This paper proposes a new structure of single parity check (SPC) product codes, which are inherently embedded with an interleaver. The complexity of decoding of the new SPC product codes is the same as the one of the existing single parity check product codes by use of message passing algorithm. Simulation results and bound analysis demonstrate a significant BER performance improvement compared to the existing single parity check product codes for high code rate at medium SNRs.
Like turbo codes, repeat-accumulate codes have remarkably good performance when r greater than or equal to 3, where r is the number of repetition times. In this letter, we present space-time codes with full antenna di...
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Like turbo codes, repeat-accumulate codes have remarkably good performance when r greater than or equal to 3, where r is the number of repetition times. In this letter, we present space-time codes with full antenna diversity using "weighted" nonbinary repeat-accumulate codes. Compared with the space-time turbo codes in Liu et al. and So et al., the main advantage of this new scheme is to construct space-time codes with full diversity for any m less than or equal to r and any length of frame without searching for interleavers, where m is the number of transmit antennas. These space-time codes have rate m/r and so, have full rate when m = r. Furthermore, they have an efficient decoding based on the message passing algorithm.
Bayesian networks compute marginal distributions through the "messagepassing" algorithm-a series of local calculations involving neighboring cliques of variables in a clique tree. In this work, these messag...
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Bayesian networks compute marginal distributions through the "messagepassing" algorithm-a series of local calculations involving neighboring cliques of variables in a clique tree. In this work, these messagepassing computations are extended to the case of degenerate Gaussian potentials which are multivariate Gaussian densities that can have two different kinds of degeneracies corresponding to projections with zero variance and projections with infinite variance. The basic operations of the message passing algorithm, such as representing conditional distributions, extending potentials, and conditioning on observations, create or operate on potentials with various kinds of degeneracies thereby demonstrating the need for such methodology. Computer implementation of this scheme follows easily from the details within and some computational aspects are discussed. We also demonstrate an application of our methodology to automatic musical accompaniment.
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