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WIDEBAND DIGITAL MODULATION AND DETECTION TECHNIQUES FOR TROPOSCATTER.
Quarterly rept. no. 2, 1 Oct-31 Dec 66,
COMMUNICATION SYSTEMS INC PARAMUS N J
Pagination or Media Count:
The objective is to identify and breadboard the modulation technique offering best performance for transmission of high digital data rates over tactical troposcatter paths of 50 to 150 miles at 5 ghz. The study is concerned with higher order modulation coding, in-band diversity and other techniques that may bring about an optimal match to the medium. During this quarter the work was redirected to emphasize operation at data rates of 1.15 and 0.576 megabits per second mbps rather than 2.3 mbps. Carrier-to-noise ratios and error probabilities calculated for the existing modulation method show that thermal noise as well as multipath limit performance for path lengths of 100 to 150 miles. This, along with considerations of equipment simplicity and reliability, ease of synchronization, etc, resulted in the choice of a four-frequency, four-phase modulation pattern with in-band diversity for 0.576 and 1.15 mbps operation 12 and 24 channels. A similar modulation pattern without in-band diversity was chosen for 2.3 mbps operation 48 channels. Preliminary calculations indicate that these modulation patterns will result in approximately 10 db signal-to-thermal noise advantage over the existing dual diversity system at error rates of 0.00001 for 0.576 and 1.15 mpbs operation, and approximately 4 db improvement for 2.3 mbps operation. Author
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