This paper presents sequence estimation for the frequency selective Rayleigh fading channel. Maximum likelihood estimation using the Viterbi algorithm (***-VA) and sequential sequence estimation (SSE) are developed. B...
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This paper presents sequence estimation for the frequency selective Rayleigh fading channel. Maximum likelihood estimation using the Viterbi algorithm (***-VA) and sequential sequence estimation (SSE) are developed. Both MLSE-VA and SSE consist of a set of Kalman filters which estimate the fading channel as time evolves. Computer simulations for two different channel models show that the error performance of the two approaches is essentially the same. SSE however has considerably less computational complexity than MLSE-VA. To improve the error performance, diversity is combined with both MLSE-VA and SSE. The simulations show that diversity results in a signal to noise ratio gain of greater than 10 dB.
An analogue of a neural network, the number of layers and the number of cells in which may be changed during its retraining is suggested in the paper. The main instrument for constructing such a network is extraction ...
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An analogue of a neural network, the number of layers and the number of cells in which may be changed during its retraining is suggested in the paper. The main instrument for constructing such a network is extraction of maximal common properties of pairs of objects in the training set and of that ones used for retraining. The degree of coincidence of a recognized object with the one presented in the training set may be calculated using their maximal common properties. computational complexities of such a network construction, recognition process and the network retraining are proved. A brief description of a similar network proposed by the author earlier for complex structured objects described using predicate calculus is presented. The analysis of comparison of computational complexity of a complex structured object recognition with various methods of their description is given.
We prove that the optimal lumping quotient of a finite Markov chain can be constructed in O(m 1g n) time, where n is the number of states and in is the number of transitions. Our proof relies on the use of splay trees...
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We prove that the optimal lumping quotient of a finite Markov chain can be constructed in O(m 1g n) time, where n is the number of states and in is the number of transitions. Our proof relies on the use of splay trees (designed by Sleator and Tarjan [J. ACM 32 (3) (1985) 652-686]) to sort transition weights. (C) 2003 Elsevier B.V. All rights reserved.
The maximum common subgraph problem is known to be NP-hard, although it has often been applied to various areas. In the field of molecular biology, we can reduce the problem space by analyzing the structures of chemic...
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The maximum common subgraph problem is known to be NP-hard, although it has often been applied to various areas. In the field of molecular biology, we can reduce the problem space by analyzing the structures of chemical compounds. In doing so, we have found that the tree-width of chemical compounds are bounded by a constant, and that the possible spanning trees of any compound is polynomially bounded. We present a polynomial time algorithm for finding the maximum common connected induced subgraph of a degree-bounded partial k-tree and a connected graph, the number of whose possible spanning trees is polynomial. (C) 2004 Elsevier B.V. All rights reserved.
DNA graphs are the vertex induced subgraphs of De Bruijn graphs over a four letter alphabet. In this paper, we prove the NP-hardness of various recognition problems for subgraphs of De Bruijn graphs;in particular, the...
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DNA graphs are the vertex induced subgraphs of De Bruijn graphs over a four letter alphabet. In this paper, we prove the NP-hardness of various recognition problems for subgraphs of De Bruijn graphs;in particular, the recognition of DNA graphs is shown to be NP-hard. As a consequence, two open questions from a recent paper by Blazewicz et al. (Discrete Appl. Math. 98, (1999) 1) are answered in the negative. (C) 2002 Elsevier Science B.V. All rights reserved.
Accurate on-line tracking of the instantaneous phasor in power-disturbance waveforms is a key element for power-quality monitoring, power-system metering, relaying, control and fault diagnosis in electric power system...
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Accurate on-line tracking of the instantaneous phasor in power-disturbance waveforms is a key element for power-quality monitoring, power-system metering, relaying, control and fault diagnosis in electric power systems. The performance of the measurement techniques in common use or newly developed is briefly reviewed by using three criteria, namely measurement accuracy, dynamic response and real-time capability. Further, a novel complex filter and the associated recursive algorithm for phasor computation are presented, which can achieve both high measurement accuracy in various service conditions and low computational complexity. The proposed method can suppress well signal components other than that selected and is not sensitive to frequency deviation. Its effectiveness and superiority over the Fourier algorithm and the continuous wavelet transform are also ascertained using both simulated and practical power-disturbance waveforms.
The standard definition of tissue P systems includes a special alphabet whose elements are assumed to appear in the initial configuration of the system in an arbitrarily large number of copies. These objects reside in...
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The standard definition of tissue P systems includes a special alphabet whose elements are assumed to appear in the initial configuration of the system in an arbitrarily large number of copies. These objects reside in a distinguished place of the system, called the environment. Such potentially infinite supply of objects seems an unfair tool when designing efficient solutions to computationally hard problems in the framework of membrane computing, by performing a spacetime trade-off. This paper deals with computational aspects of tissue P systems with cell division where there is no environment having the property mentioned above. Specifically, we prove that the polynomial complexity classes associated with tissue P systems with cell division and with or without environment are actually identical. As a consequence, we conclude that it is not necessary to have infinitely many copies of some objects in the initial configuration in order to solve NPcomplete problems in an efficient way.
We prove upper bounds on deterministic communication complexity in terms of log of the rank and simple versions of the corruption bound. Our bounds are a simplified version of the results of Gavinsky and Lovett [8], u...
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We prove upper bounds on deterministic communication complexity in terms of log of the rank and simple versions of the corruption bound. Our bounds are a simplified version of the results of Gavinsky and Lovett [8], using the same set of tools. We also give an elementary proof for the upper bound on communication complexity in terms of rank proved by Lovett [18]. (C) 2018 Elsevier B.V. All rights reserved.
Lightweight description logics are knowledge representation formalisms characterised by the low complexity of their standard reasoning tasks. They have been successfully employed for constructing large ontologies that...
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Lightweight description logics are knowledge representation formalisms characterised by the low complexity of their standard reasoning tasks. They have been successfully employed for constructing large ontologies that model domain knowledge in several different practical applications. In order to maintain these ontologies, it is often necessary to detect the axioms that cause a given consequence. This task is commonly known as axiom pinpointing. In this paper, we provide a thorough analysis of the complexity of several decision, counting, and enumeration problems associated to axiom pinpointing in lightweight description logics. (C) 2017 Elsevier B.V. All rights reserved.
This paper studies sky-wave time-difference-of-arrival (TDOA) localisation in passive-radar systems, and the focus is on two-dimensional localisation on the earth surface. Signals are reflected by the ionosphere layer...
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This paper studies sky-wave time-difference-of-arrival (TDOA) localisation in passive-radar systems, and the focus is on two-dimensional localisation on the earth surface. Signals are reflected by the ionosphere layer before arriving at sensors, making the localisation problem very complicated. Parametric methods are found to be inefficient in this case;therefore, grid-based methods are studied. However, conventional grid-based methods are not guaranteed to find the nearest grid point (NGP) of target, even when the grid map is dense and the measurements are noise-free. Hence, this paper derives the sufficient condition for NGP selection in noiseless environments. Based on it, an ellipsoid-norm method (ENM) is proposed to promise optimal results with noise-free measurements, which consists of a test phase and a search phase. If a given grid map passes the offline test phase, the search phase produces a close-form estimate at a low computational complexity. The impact of noise on ENM is also theoretically analysed. Additionally, ENM is extended to handle cases with inaccurately known ionosphere layer heights. Numerical results show that for different sensor networks, the test phase is feasible by adjusting grid densities;and ENM is superior to the current state-of-the-art in terms of estimation accuracy and computational complexity.
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