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JournalISSN: 0748-612X

AT&T Bell Laboratories technical journal 

Institute of Electrical and Electronics Engineers
About: AT&T Bell Laboratories technical journal is an academic journal. The journal publishes majorly in the area(s): Unix & Unix filesystem. It has an ISSN identifier of 0748-612X. Over the lifetime, 101 publications have been published receiving 3359 citations.

Papers published on a yearly basis

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Journal ArticleDOI
TL;DR: The optimal trade-offs among the parameters K, N, and μ and the intruder's uncertainty H (H is the "conditional entropy" of the data given the μ intercepted channel bits) were found and a system exists with H ≈ K − l.
Abstract: Consider the following situation. K data bits are to be encoded into N> K bits and transmitted over a noiseless channel. An intruder can observe a subset of his choice of size μ < N. The encoder is to be designed to maximize the intruder's uncertainty about the data given his μ intercepted channel bits, subject to the condition that the intended receiver can recover the K data bits perfectly from the N channel bits. The optimal trade-offs among the parameters K, N, and μ and the intruder's uncertainty H (H is the "conditional entropy" of the data given the μ intercepted channel bits) were found. In particular, it was shown that for μ = N − K, a system exists with H ≈ K − l. Thus, for example, when N = 2K and μ = K, it is possible to encode the K data bits into 2K channel bits, so that by looking at any K channel bits, the intruder obtains no more than one bit of the data.

507 citations

Journal ArticleDOI
TL;DR: These measurements are needed in refining the requirements for portable-radio communication systems that can accommodate low-power radiotelephone sets and large-scale distributions of the small-scale signal medians are approximately log normal.
Abstract: The signal levels around and within eight suburban houses were measured at 800 MHz. These measurements are needed in refining the requirements for portable-radio communication systems that can accommodate low-power radiotelephone sets. The measurements were made from an instrumentation van having an erectable 27-foot-high antenna. Large-scale distributions of the small-scale signal medians are approximately log normal. The decrease in median signal level with distance ranges from d−3 to d−6.2 for the eight houses. Signal decreases as d−4.5 for the overall data set. At 1000 feet, regressions to signal levels range from 12.5 to 37.1 dB below free-space propagation levels for locations outside and locations inside on first and second floors. In basements, regression levels at 1000 feet range from 29 to 48.2 dB below free space. For the overall data set, regression signal levels at 1000 feet are 27.7 dB below free space. For all the basements, this value is 39.6 dB. Other signal statistics are given in this paper.

233 citations

Journal ArticleDOI
J. M. Akinpelu1
TL;DR: The analysis of comparably engineered hierarchical networks shows that these networks do not exhibit a drop in carried load under overloads (in the absence of switching system dynamics), and it is shown that using trunk reservation for first-routed traffic allows the formulation of a control strategy that provides a high level of network carried load during overloads.
Abstract: We report the results of a study of the performance of engineered nonhierarchical and hierarchical routing networks under overloads. This study was motivated by results obtained from mathematical models for small, symmetric, uniformly loaded, nonhierarchical networks with transparent switching systems, showing the existence of network instabilities. We extend the mathematical models to more general nonhierarchical networks, and show with analysis and an extant simulation model that such instabilities are also found in nonsymmetric, nonhierarchical networks. We then use our models to consider whether engineered nonhierarchical networks exhibit such unstable behavior. No instabilities are found in the engineered nonhierarchical networks considered here. However, the nonhierarchical networks consistently demonstrate a drop in carried load between 10- and 15-percent overloads. Our analysis of comparably engineered hierarchical networks shows that these networks do not exhibit a drop in carried load under overloads (in the absence of switching system dynamics). Finally, we show that using trunk reservation for first-routed traffic allows the formulation of a control strategy that provides a high level of network carried load during overloads.

187 citations

Journal ArticleDOI
Biing-Hwang Juang1
TL;DR: A unified theoretical view of the Dynamic Time Warping (DTW) and the Hidden Markov Model (HMM) techniques for speech recognition problems is given and offers insights into the effectiveness of the probabilistic models in speech recognition applications.
Abstract: This paper gives a unified theoretical view of the Dynamic Time Warping (DTW) and the Hidden Markov Model (HMM) techniques for speech recognition problems. The application of hidden Markov models in speech recognition is discussed. We show that the conventional dynamic time-warping algorithm with Linear Predictive (LP) signal modeling and distortion measurements can be formulated in a strictly statistical framework. It is further shown that the DTW/LP method is implicitly associated with a specific class of Markov models and is equivalent to the probability maximization procedures for Gaussian autoregressive multivariate probabilistic functions of the underlying Markov model. This unified view offers insights into the effectiveness of the probabilistic models in speech recognition applications.

165 citations

Journal ArticleDOI
Ward Whitt1
TL;DR: This paper investigates ways to use open models to approximate closed models with specified expected equilibrium populations, especially effective for approximately solving large closed models, where “large” may mean many nodes or many jobs.
Abstract: This paper investigates the relationship between open and closed models for networks of queues. In open models, jobs enter the network from outside, receive service at one or more service centers, and then depart. In closed models, jobs neither enter nor leave the network; instead, a fixed number of jobs circulate within the network. Open models are analytically more tractable, but closed models often seem more realistic. Hence, this paper investigates ways to use open models to approximate closed models. One approach is to use open models with specified expected equilibrium populations. This fixed-population-mean method is especially effective for approximately solving large closed models, where “large” may mean many nodes or many jobs. The success of these approximations is partly explained by limit theorems: Under appropriate conditions, the fixed-population-mean method is asymptotically correct. In some cases the open-model methods also yield bounds for the performance measures in the closed models.

161 citations

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Performance
Metrics
No. of papers from the Journal in previous years
YearPapers
19851
1984100