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This Defense Intelligence Reference Document was prepared by the Defense Intelligence Agency under its Advanced Aerospace Weapon System Applications (AAWSA) program, is dated 6 April 2010 and is part of a series of advanced technology reports produced in FY 2009. It reviews proposed laboratory generators and detectors of high-frequency gravitational waves for communications. It favors an infrared-excited molecules transmitter and the Li-Baker detector, estimating about 1.9 million bits per second over 7,000 km through the Earth. It also discusses timing standards and interplanetary navigation uses.
UNCLASSIFIED//5O9 OFFICIO I Yli'F 'iUlb¥ 3.3.2 Search Space Improvement Accruing From HFGW FTS The following points are relevant with respect to the universal use of HFGW FTS among all remote terminals (including for instance cell phone handsets and their associated cellular towers): • During signal acquisition the receiving terminal must perform a search of the search space of frequency, phase, and code to acquire the transmitting terminal signal. • If there is less noise in these parameters the search space is reduced, speeding acquisition. • Ultra-fast acquisition allows more efficient TDMA, or Time Domain Multiple Access style operations, such as transmit on demand, that use bandwidth more efficiently. The smaller resultant search space is depicted graphically in Figure 20. Figure 20. Acquisition Search Space Improvement Accruing from HFGW FTS Search space Without using freq & time standards An equation for acquisition search space time is presented in Equation (12) Tacq = Nphase*Nfreq*Ncode*(ta) where Nphase = number of phase space cases to check for acquisition, Nfreq = number of frequency cases to check for acquisition, Ncode = number of code sync possibilities to check and ta = acquisition test time, per test case. (12) In a typical example, if 30 MHz chipping is used with a 5 μsec error, there will be 150 code sync possibilities to check. If a case where a frequency error of 1 Hz is used within the acquisition window would cause a missed acquisition, and the worst case frequency error is 150 Hz, then the number of frequencies that must be checked is also 150. Finally, we must check each possible phase possibility, say 16 different options for 16- PSK. PSK stands for Phase Shift Keying and is the encoding of data bits using incremental phase modulation. These acronyms are specified in the nomenclature 28 UNCLASSIFIED/ /f81il 8ffl@Itltt ""!!! one I
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Report, from the dia collection. The PDF is mirrored here; the original link is above. 57 pages are in the text index: search them above, or from the library's search.