Showing papers on "Word error rate published in 1969"

Interaction of information in word recognition.

Abstract: Quantitative predictions are made from a model for word recognition. The model has as its central feature a set of \"logogens\": devices which accept information relevant to a particular word response irrespective of the source of this information. When more than a threshold amount of information has accumulated in any logogen, that particular response becomes available for responding. The model is tested against data available on the effect of word frequency on recognition, the effect of limiting the number of response alternatives, the interaction of stimulus and context, and the interaction of successive presentations of stimuli. The implications of the underlying model are largely upheld. Other possible models for word recognition are discussed as are the implications of the Logogen Model for theories of memory.

Error rate considerations for coherent phase-shift keyed systems with co-channel interference

Abstract: In this paper we present a theoretical analysis of the performance of an m-phase coherent phase-shift keyed system in the presence of random gaussian noise and interference. An explicit expression is given for the probability of error of the phase angle of the received signal; we show that this probability of error can be expressed as a converging power series. We show that the coefficients of this series are expressible in terms of well-known and well-tabulated functions, and we give methods of evaluating the character error rates of the systems. We also show that this error rate is minimum when all the interference power is concentrated in a single interferer, and that it attains its maximum [P m ] max when the total interference power is equally distributed amongst the K interferers. The limiting case when K goes to infinity is considered. The cases of K = 1, and m = 2, 4, 8, and 16 are treated in some detail, and the results are given graphically. The usefulness of the results presented in this paper is that the designer can have at his disposal very simple expressions with which to evaluate the performance of any given Coherent Phase-Shift Keyed system when the received signal is corrupted by both interference and random gaussian noise.

A Simple Approximation of Data System Error Rate

Abstract: A simple error rate approximation is derived, and bounds on the accuracy are found. The results are applied to the question of how accurately the system error rate may be determined by using nonrandom data.

Rate optimization for digital frequency modulation

Abstract: The data rate of a multilevel digital FM system is optimized subject to fixed RF bandwidth, signal-to-noise ratio, and output error rate. The possibility of optimizing such a system was first considered by J. R. Pierce at Bell Telephone Laboratories. He made the observation that it is possible to send many levels slowly or fewer levels rapidly for an FM wave of fixed RF bandwidth and error rate, and that there must be a choice of signaling rate and number of levels that optimize the data rate. The rigorous treatment of this problem is the subject of this paper. The mathematical model we analyze uses frequency-shift keying at the transmitter and ideal discrimination detection with an integrate-and-dump circuit as the post-detection filter. Our results are exhibited graphically showing the various dependencies among the pertinent system parameters.

Data recovery in a photo-digital storage system

Abstract: A data-recovery feature has been developed for recovering electron-beam recorded information which is microscopic in dimension and has been partially obliterated by flaws in a photographic-film recording medium. This feature provides (1) backup procedures that exploit redundancies in the recording format for the synchronization and identification of data, (2) coding for error detection and correction of 5 independent characters in5 0 data character lines, (3) variation of machine parameters that affect reading performance, and (4) statistically optimized schedules for applying a variety of recovery techniques. Error rate is reduced from one error line in about 100 lines to less than one error line in 2.7 × 106 lines.

Multiple comparisons in psychological experiments

Abstract: A simple relation between error rates using multiple t-tests and Scheffe's multiple-comparison procedure is pointed out. Errors in the development of some new multiple-comparison procedures are indicated. An experimental error rate approach using a flexible error rate is advocated.

Modeling and Data Analyses - Short and Medium Range Digital Troposcatter Tests. Volume I.

Abstract: : The report concerns the modeling of troposcatter channels and modems together with data reduction efforts connected with a series of tests conducted at the RADC troposcatter test bed between September 1967 and March 1968 Two high speed digital data techniques were tested in addition to data transmission over the conventional FDM/FM system Limited channel measurements were taken concurrently with data transmission by utilizing the received signals Mathematical models were developed for the modem receivers which accounted for all critical determinants of system behavior Such factors as AGC, non-linearity of detectors, non-ideal combining, inter-symbol interference, and others were included The complex Gaussian scatter channel model was used in conjunction with experimentally determined median envelope frequency correlation functions to form a mathematical channel model With the aid of the mathematical models, theoretical predictions of error rate and error rate scatter were made It was found that the observed error rate scatter occupancy was consistent with that predicted theoretically for 20-minute measurement time per error rate sample As a result of the knowledge gained on this program, it is concluded that new approaches must be made to the comparative evaluation of modems which alleviate the error rate scatter problem (Author)