Coding for Turbulent Channels. Volume II: Simulator of a 3-Mbps Tropo-Scatter Digital Communication System.
Final technical rept.,
GENERAL ELECTRIC CO SYRACUSE NY HEAVY MILITARY ELECTRONIC SYSTEMS
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A 3-Mbps, 4-frequency, 2-phase, differentially-keyed, adaptive-bias, decision-controlled modem operating over a tropo-scatter path of 175 miles at a frequency of 850 MHz with 10-MHz bandwidth and 28-foot diameter antennas was simulated in this program. The simulation system was operated to produce a set of tape recordings of error performance useful in the design and evaluation of error correcting coding techniques for troposcatter digital data communication. The message used in the simulation runs was a pseudorandom sequence originating from a 16-bit shift register with feedback appropriate for generating a maximal length sequence. Recordings were made of the received sequence, the error sequence, two signal quality parameters, and the system clock square wave. The recording density was chosen so that a 2400-Hz clock frequency is obtained at a playback speed of 60 ips. A total of 1.968,000 bits was transmitted in each simulation run, and signal-to-noise ratios were made for error probabilities generally in the range 0.1 to 0.001. The performance of the system, as indicated by a curve of probability of error versus signal-to-noise ratio, agreed quite closely with published results and permitted a quantitative comparison with results obtained elsewhere with a simulated pilot-tone system. The effects of decision-direction, adaptive-bias, and differential-keying may be predicted from the results. Author
- Non-Radio Communications