Showing papers on "Word error rate published in 1970"

On optimum recognition error and reject tradeoff

Abstract: The performance of a pattern recognition system is characterized by its error and reject tradeoff. This paper describes an optimum rejection rule and presents a general relation between the error and reject probabilities and some simple properties of the tradeoff in the optimum recognition system. The error rate can be directly evaluated from the reject function. Some practical implications of the results are discussed. Examples in normal distributions and uniform distributions are given.

Error detection and correction system

Abstract: This relates to an error detection and correction system for use in the receive terminal of a restricted disparity ternary code communication system. A word disparity counter and sequence detector detects sequences of consecutive ternary code groups which should contain predetermined disparity characteristics. A differential counter computes the expected disparity characteristics of such sequences. The detected and expected disparity characteristics are compared and any differences therebetween adjusts the counter to compensate for the difference. An error rate detector also responds to the difference to provide an error signal when a predetermined number of the differences occur in a given time interval. The error signal indicates an out-of-synchronism condition and is employed to regain synchronism.

Recognition memory as influenced by differential attention to semantic and acoustic properties of words

Abstract: Lists of 264 words were studied by 75 Ss. The Ss were divided into three groups instructed to remember either meaning or sound or both meaning and sound of the study words. During recognition, S was required to indicate which word of each test pair had been presented earlier. The incorrect alternative for each test pair was a homophone, synonym, or a word unrelated to the correct choice. Recognition increased as instructional emphasis on remembering word meaning increased. Overall recognition was best when the incorrect choice was unrelated to the study word, and worst when the incorrect choice was a synonym of the study word. The high performance levels obtained under some conditions suggest that word features other than semantic and plume tic information are important for word recognition.

Data error detector for determining the error rate prior to equalization

Abstract: A transversal filter or equalizer will reduce to zero, errors that result from amplitude or phase distortion in the transmission facility where such distortion is within the equalization range of the transversal filter. The equalized output is used as a reference and is connected to one input of a comparator. The unequalized data signal is connected to another input of the comparator and the comparator produces an error signal at its output whenever an error occurs. The error signal actuates an indicator such as an impulse counter thereby giving bit-by-bit error indications.

Word recognition by means of orthogonal functions

Abstract: This paper describes experiments in which word recognition is based on comparing the projections of input words on an orthogonal basis with those of a stored library of words. An initial orthogonal basis is determined from the generalized spectrum of short time segments selected from a vocabulary of ten words. The initial basis is optimized by minimizing the complementary error energy. By projecting a spoken word onto the optimum orthogonal basis, a sequence of numbers is generated to represent the word. By correlating the absolute values of the sequence with those of a stored library of words, the spoken word is identified. The percent of correct recognition varies from 71.6 to 96.6 percent for two speakers. Techniques are developed to improve the recognition scores and to reduce the lengthy computer processing time and large storage requirement. First a master template is made for each word by averaging six templates for the particular word. For one speaker the percent of correct recognition increases to 100 percent when incoming words are compared against the master templates. For a second speaker, the recognition rates improve significantly and vary between 93 and 98 percent when the master templates are used. To further improve the recognition process, the feasibility of grouping words into several classes is demonstrated. The classifications are based on the locations of formant regions and the time durations of each spoken word.

Coherency for the Binary Symmetric Channel

Abstract: For the purpose of communication system planning, predictions of system performance based upon models of an ideal coherent channel are extensively used. Previous work has demonstrated the deleterious effects of radio frequency (RF) phase error on channel performance by machine computation of an integral derived by statistically averaging over the phase error. The required receiver performance in estimating the RF phase for detecting binary coherent signals is further examined. Upper and lower bounds are generated which measure the inaccuracy of the familiar performance formula derived from the idealized coherent channel model. The bounds are obtained analytically without resorting to machine computation. The Tikhonov probability distribution for the RF reference phase error is used. The principal result is the relation \sigma_{\varpi}^{2} \leq (kE/N_{0})^{-1} where \sigma_{\varpi}^{2} is the variance in the error of the derived carrier phase, E/N_{0} is the energy (per uncoded symbol) to noise density ratio required by the ideal coherent channel, and k is a factor relating to the tolerable degradation in error rate as given by the bounds. If k is on the order of 3 the symbol error rate no more than doubles; in general a k of 10 will suffice for no degradation in error rate.

Estimation of Bit Probability of Error Using Sync Word Error Rate Data

Abstract: Assuming bit errors are independently distributed with a constant probability of error p e , it is shown that a simple estimator is highly efficient for estimation of p e . The estimator is based on a simple function of the number of sync words containing no bit errors. The estimator is shown to be maximum likelihood, minimum chi-square, and modified minimum chi-square when the quality index reported is simply the percent of frames containing zero errors. An approximate confidence interval for p e is obtained, and a determination of the number of sync words to observe in order to obtain an approximate confidence interval of fixed length is indicated. The method of scoring which can be used to obtain a more efficient estimator of p e is described.

Theory and design of coherent digital systems which track Doppler frequency

Abstract: A unified theory from which the design of a large class of coherent digital communication systems can be optimally carried out is presented. In the design of digital communication systems, the error rate is the criterion which is invariably emphasized. In many digital systems, however, there is relative motion between transmitter and receiver which must be estimated by making use of Doppler frequency information. A new analysis of a general class of coherent digital systems is herein developed, in which the tradeoffs that exist between Doppler measurement capability and bit demodulation error rate are quantitatively presented. The theoretically unrecoverable power loss which exists when employing frequency division multiplexing subcarriers as compared to time division multiplexing is described. The results point out that there is significant parametric dependence of the optimal choice of system parameters on the carrier loop signal-to-noise ratio and the data rate.

Error rate minimization for improved phase- locked loop damping characteristics

Abstract: Phase locked loop damping characteristics optimization based on input rms error rate minimization and transient error integral square value limitation

Hardware Evaluations of Simple Radio Positioning System Based on Direct Sequence Spread Spectrum

Abstract: This paper proposes a simple positioning scheme without huge computational cost. The proposed scheme employs a three-element loop array for the transmitter. A Direct-Sequence Spread Spectrum (DS/SS) sequence is transmitted at a frequency of Low Frequency (LF) band. We evaluate location determination error rate by using a computer simulator and theoretical analysis. The theoretical analysis agrees with the simulation result. The difference is at most 1.3 dB at error rate of 10−5. Computer simulation result shows that the proposed technique can identify the region of 2 by 3 meters at the region determination error rate of 10−2. In order to show the hardware complexity requirement for implementing the proposed receiver, the impact of bit width for ADC (Analog-to-Digital Converter), and digital signal processing block to the error rate performance is evaluated by computer simulation. Computer simulation shows that the proposed scheme can be constructed by 2-bit ADC and 5-bit integrate and dump filter.

An Evaluation of Experimental How-Malfunctioned Codes

Abstract: In three learning-recall studies, the existing coding procedure by which Air Force maintenance technicians record and describe equipment malfunctions was compared to four experimental codes. The four three-symbol experimental codes included all numeric symbols, all alphabetical symbols, alphanumeric symbols, and a mnemonic code that had a high association value with the corresponding descriptor statements. Performance using the five experimental conditions was evaluated in three separate studies: first, under short-term recall, second, under paired-associate learning, and third, under long-term recall. All experiments demonstrated superior performance with the mnemonic code condition. The mnemonic codes produced approximately one-half the average error rate for short-term recall, were twice as easily learned, and achieved nearly half the error rate for long-term recall when compared to the existing coding technique.