AAWSAP DIRD, High-Frequency Gravitational Wave Communications, April 2010

This Defense Intelligence Reference Document, DIA-08-1004-005, is dated 6 April 2010. The Defense Intelligence Agency's Defense Warning Office prepared it under the Advanced Aerospace Weapon System Applications program. It reviews proposed laboratory generators and detectors for high-frequency gravitational waves. It favors a piezoelectric approach for proof-of-concept tests, IR-excited molecules for an operational transmitter and the Li-Baker detector as the receiver. It estimates about 1.9 million bits per second over 7,000 km through the Earth and discusses timing standards and interplanetary navigation uses.

From the source:Release of 2026-09-18 Incident: 4/6/10, Las Vegas, Nevada. Released with redactions. This document is a Defense Intelligence Reference Document (DIRD), a technical reference format used by the Defense Intelligence Agency (DIA) to capture baseline knowledge on a specific topic for later analytic use. DIRDs are best understood as reference and synthesis products rather than as original research. It is one of 38 DIRDs produced under the Advanced Aerospace Weapon System Applications Program (AAWSAP) between 2009 and 2011. Because AAWSAP’s scope permitted a broad range of supporting topics, not every DIRD in the series directly concerns aerospace systems or future threat assessment. The following summary reflects the DIRD’s scope and framing at the time of writing and should not be read as implying current validation of the concepts discussed. This DIRD examines whether high-frequency gravitational waves could serve as a communications medium while avoiding the attenuation that limits radio-frequency systems. The report surveys proposed transmitter and detector concepts, argues that gravitational-wave communications could support secure point-to-point links, timing standards, and interplanetary navigation, and gives particular attention to laboratory generator concepts and the Li-Baker detector as possible building blocks for such a system. The document makes clear, however, that the entire concept depends on capabilities that had not been demonstrated in practice, including laboratory-scale generation and reliable detection of usable high-frequency gravitational-wave signals. It is an exploratory systems-oriented review built around a future communications concept.

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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 TOMA, 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.
f
{ ~/
~ ,___..L,._________,,, cf,0eo-\~
Search space
Without using
freq & time
standards
Search space
Using freq & ~ Frequency search space - c;
time standards
Figure 20. Acquisition Search Space Improvement Accruing from HFGW FTS
An equation for acquisition search space time is presented in Equation (12)
Tacq = Nphase* Nfreq*Ncode*(ta) (12)
where Npha se = number of phase space cases to check for acquisition,
Ntreq = number of frequency cases to check for acquisition,
Ncode = number of code sync possibilities to check and
ta = acquisition test time, per test case.
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 Shih Keying and is the encoding of data bits using
incremental phase modulation. These acronyms are specified in the nomenclature
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