Design of interstellar digital communication links: Some insights from communication engineering

Messerschmitt, David G.; Morrison, Ian S.

doi:10.1016/j.actaastro.2011.10.005

Cited by 11 publications

(26 citation statements)

References 17 publications

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“…The IP suggests an immediate answer to the second question because it establishes that the energy Figure 2: The cumulative distribution function F PG (p) of processing gain PG for a CR signal H = X/ X , a Gaussian CR X, and any r. It is plotted on a log-log plot (10 log 10 p vs log 10 F P (p)) for K = 10 n and n ∈ [1,8].…”

Section: Radio-frequency Interferencementioning

confidence: 98%

Interstellar communication: The case for spread spectrum

Messerschmitt

2012

Acta Astronautica

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Spread spectrum, widely employed in modern digital wireless terrestrial radio systems, chooses a signal with a noise-like character and much higher bandwidth than necessary. This paper advocates spread spectrum modulation for interstellar communication, motivated by robust immunity to radio-frequency interference (RFI) of technological origin in the vicinity of the receiver while preserving full detection sensitivity in the presence of natural sources of noise. Receiver design for noise immunity alone provides no basis for choosing a signal with any specific character, therefore failing to reduce ambiguity. By adding RFI to noise immunity as a design objective, the conjunction of choice of signal (by the transmitter) together with optimum detection for noise immunity (in the receiver) leads through simple probabilistic argument to the conclusion that the signal should possess the statistical properties of a burst of white noise, and also have a large time-bandwidth product. Thus spread spectrum also provides an implicit coordination between transmitter and receiver by reducing the ambiguity as to the signal character. This strategy requires the receiver to guess the specific noise-like signal, and it is contended that this is feasible if an appropriate pseudorandom signal is generated algorithmically. For example, conceptually simple algorithms like the binary expansion of common irrational numbers like π are shown to be suitable. Due to its deliberately wider bandwidth, spread spectrum is more susceptible to dispersion and distortion in propagation through the interstellar medium, desirably reducing ambiguity in parameters like bandwidth and carrier frequency. This suggests a promising new direction in interstellar communication using spread spectrum modulation techniques.

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Section: Radio-frequency Interferencementioning

confidence: 98%

Interstellar communication: The case for spread spectrum

Messerschmitt

2012

Acta Astronautica

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“…Fridman (2011) concluded that broadband emission employing frequency-shift keying (FSK) would be preferred by energy-conscious civilizations seeking to transmit informationbearing signals using similar capabilities to our own. Messerschmitt (2012); Messerschmitt & Morrison (2012) similarly arrived at the idea that broadband communication might be preferable by considering robustness to radio frequency interference (RFI), and further deduced that this emission may have time-bandwidth extents influenced by the properties of the interstellar medium (ISM). In other words, the coherence of a modulated information-bearing signal would be limited in time or bandwidth extent by the combined effects of the relative motion of the source and receiver and the inhomogenous plasma occupying the intervening space.…”

Section: Artificial Radio Emissionmentioning

confidence: 99%

Searching for Extraterrestrial Intelligence with the Square Kilometre Array

Siemion¹,

Benford²,

Jin³

et al. 2015

Proceedings of Advancing Astrophysics With the Square Kilometre Array — PoS(AASKA14)

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The vast collecting area of the Square Kilometre Array (SKA), harnessed by sensitive receivers, flexible digital electronics and increased computational capacity, could permit the most sensitive and exhaustive search for technologically-produced radio emission from advanced extraterrestrial intelligence (SETI) ever performed. For example, SKA1-MID will be capable of detecting a source roughly analogous to terrestrial high-power radars (e.g. air route surveillance or ballistic missile warning radars, EIRP † ∼ 10 17 erg sec −1 ) at 10 pc in less than 15 minutes, and with a modest four beam SETI observing system could, in one minute, search every star in the primary beam out to ∼100 pc for radio emission comparable to that emitted by the Arecibo Planetary Radar (EIRP ∼ 2 x 10 20 erg sec −1 ) ‡ . The flexibility of the signal detection systems used for SETI searches with the SKA will allow new algorithms to be employed that will provide sensitivity to a much wider variety of signal types than previously searched for.Here we discuss the astrobiological and astrophysical motivations for radio SETI and describe how the technical capabilities of the SKA will explore the radio SETI parameter space. We detail several conceivable SETI experimental programs on all components of SKA1, including commensal, primary-user, targeted and survey programs and project the enhancements to them possible with SKA2. We also discuss target selection criteria for these programs, and in the case of commensal observing, how the varied use cases of other primary observers can be used to full advantage for SETI.Advancing Astrophysics with the Square Kilometre Array

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“…2) Civilizations: Initial discovery of a signal from a civilization and establishment of two-way communication lacks coordination, and this presents a difficult challenge [6]. Discovery of the signal absent any prior knowledge of its structure or parameterization is crucial.…”

Section: Requirementsmentioning

confidence: 99%

“…5) Codebook design: The design challenge can be stated as finding a codebook consisting of a set of N cod codewords as in (6). This choice is subject to a constraint on the average energy (assuming codewords are equally likely)…”

Section: A Primer On Channel Codingmentioning

confidence: 99%

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Design for minimum energy in interstellar communication

Messerschmitt

2015

Acta Astronautica

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Microwave digital communication at interstellar distances applies to starship and extraterrestrial civilization (SETI and METI) communication. Large distances demand large transmitted power and/or large antennas, while the propagation is transparent over a wide bandwidth. Recognizing a fundamental tradeoff, reduced energy delivered to the receiver at the expense of wide bandwidth (the opposite of terrestrial objectives) is advantageous. Wide bandwidth also results in simpler design and implementation, allowing circumvention of dispersion and scattering arising in the interstellar medium and motion effects and obviating any related processing. The minimum energy delivered to the receiver per bit of information is determined by cosmic microwave background alone. By mapping a single bit onto a carrier burst, the Morse code invented for the telegraph in 1836 comes closer to this minimum energy than approaches used in modern terrestrial radio. Rather than the terrestrial approach of adding phases and amplitudes to increases information capacity while minimizing bandwidth, adding multiple timefrequency locations for carrier bursts increases capacity while minimizing energy per information bit. The resulting location code is extremely simple and yet can approach the minimum energy as bandwidth is expanded. It is consistent with easy discovery, since carrier bursts are energetic and straightforward modifications to post-detection pattern recognition can identify burst patterns. The interstellar coherence hole captures the time and frequency coherence constraints, and observations of the environment by transmitter and receiver constrain the burst parameters and limit the search scope.

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Design of interstellar digital communication links: Some insights from communication engineering

Cited by 11 publications

References 17 publications

Interstellar communication: The case for spread spectrum

Interstellar communication: The case for spread spectrum

Searching for Extraterrestrial Intelligence with the Square Kilometre Array

Design for minimum energy in interstellar communication

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