Accession Number : AD0862236

Title :   Modeling and Data Analyses - Short and Medium Range Digital Troposcatter Tests.

Descriptive Note : Final technical rept.,

Corporate Author : SIGNATRON INC LEXINGTON MA

Personal Author(s) : Bello, Phillip A. ; Ehrman, Leonard ; Arnstein, Donald S.

Report Date : OCT 1969

Pagination or Media Count : 308

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. Two such approaches suggested are the use of synthetic simulations and stored channel simulators so that the same channel fading sequence can be used to test competing modems. (Author)

Descriptors :   *DATA PROCESSING), (*RADIO TRANSMISSION, (*DATA TRANSMISSION SYSTEMS, ERRORS), SCATTERING, TROPOSPHERE, DIGITAL SYSTEMS, COMPUTER PROGRAMS, MATHEMATICAL MODELS, MODULATION.

Subject Categories : Radio Communications
      Non-radio Communications

Distribution Statement : APPROVED FOR PUBLIC RELEASE