Accession Number : AD0282944

Title :   INVESTIGATION AND FEASIBILITY STUDY OF GALLAGER CODE

Corporate Author : ROME AIR DEVELOPMENT CENTER GRIFFISS AFB N Y

Report Date : 15 JUN 1962

Pagination or Media Count : 1

Abstract : The Gallager low-density parity-check code was investigated to establish its error-correction capabilities and to evolve economical decoder designs. Computer simulations produced experimental digit error rates for block-lengths ranging from 124 to 1008 and code rates between 1/4 and 2/3. Decoder output error rates were measured for a decision receiver with selected numbers of errors randomly distributed in a code block. Employing an approximate theory, this data was converted into expressions relating probability of error to SNR for coherent, incoherent, and Rayleigh-fading Gaussian channels. A likelihood receiver was simulated by drawing random samples from the distribution of likelihood ratios for coherent and Rayleigh-fading Gaussian channels. Digit error rates down to the region 1/1000 to 1/10,000 were measured as function of SNR. The dependence of error rate on two decoder parameters, the quantization accuracy and the number of iterations per block, was also investigated by computer simulation. (Author)

Descriptors :   *COMPUTER LOGIC, *DIGITAL COMPUTERS, *ERRORS, COMPUTERS, CRYSTAL LATTICES, DESIGN, GROWTH(PHYSIOLOGY), MATHEMATICAL ANALYSIS, MICROSTRUCTURE, NUCLEAR RADIATION SPECTROMETERS, PARITY, TESTS, X RAY DIFFRACTION

Distribution Statement : APPROVED FOR PUBLIC RELEASE