skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Optical Focusing-Based Adaptive Modulation for Air-to-Underwater Optoacoustic Communication
Nonlinear optoacoustics enable effective communication across the air-water interface. However, the requirement of a high-power laser and the vapor cloud buildup can limit the power efficiency and data rate. Thus, a proper modulation and encoding scheme is necessary. This article tackles this issue by presenting an optical focusing-based adaptive modulation (OFAM) technique that can dynamically control the underwater acoustic source (plasma) and acoustic pressure. Specifically, the article describes two variants of OFAM for a single laser transmitter with stationary focusing (OFAM-1D) and dynamic focusing (OFAM-3D). The data rate of OFAM-1D and OFAM-3D is approximately 6 and 4.4 times higher than peak detection based on-off keying (PDOOK). Furthermore, both techniques are 137% more power efficient than PDOOK. Studying the bit error rate (BER) in the presence of ambient underwater noises for different node positions has indicated that OFAM can achieve low BER even at a 300-m depth for 50- and 60-mJ laser pulse energy. Moreover, machine learning (ML) techniques have been leveraged in the demodulation process for increased robustness. Specifically, the random forest (RF) model could yield up to 94.75% demodulation accuracy. Our results indicate that OFAM can lead to a new paradigm of air to underwater wireless communication.  more » « less
Award ID(s):
1917539
PAR ID:
10530993
Author(s) / Creator(s):
; ; ;
Publisher / Repository:
IEEE
Date Published:
Journal Name:
IEEE Sensors Journal
Volume:
24
Issue:
6
ISSN:
1530-437X
Page Range / eLocation ID:
8596 to 8614
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; (, IEEE)
    Wireless communication from air-to-underwater is quite challenging because of the lack of proper physical signal that propagates well in both air and water medium. Photoacoustic energy transfer mechanism is the most promising method for such cross-medium communication, where a high energy pulsed light is focused on the water surface, causing the generation of an acoustic signal inside the water. Since acoustic signals can travel a long distance inside the water, this method enables an airborne unit to reach nodes at increased underwater depth. Yet the achievable bit rate for this process is very low. When a pulsed laser light with a higher repetition rate is focused inside the water, a vapor cloud is generated around the focus point, which blocks subsequent generation of acoustic signal and consequently limits the achievable bit rate. This paper opts to overcome such a limitation by proposing a novel pulse position modulation technique which can avoid such generation of vapor cloud and increases the bit rate significantly. 
    more » « less
  2. ; (, 52nd Asilomar Conference on Signals, Systems, and Computers)
    Orthogonal frequency division multiplexing (OFDM) is a candidate technique to provide high-speed data transmissions for optical communication systems. For intensity modulation and direct detection (IM/DD) optical communication systems, only real and non-negative valued signals can be transmitted due to the natural properties of the transmitters and receivers. This paper proposes a technique called magnitude-phase optical OFDM (MPO-OFDM) that transmits the magnitude and phase of the conventional complex valued OFDM signal successively, similar to polar-based OFDM. Unlike polar-based OFDM, however, the proposed MPO-OFDM quantizes, encodes, and transmits the phase information using pulse amplitude modulation (PAM) to reduce the interference introduced by the additive noise on the phase. Considering the peak radiation power constraint of optical devices, the magnitude component of the MPO-OFDM signal experiences clipping distortion. In this paper, we optimally adjust the modulation index to control the scale of the magnitude component and achieve the highest signal to noise ratio (SNR). For the same transmitted data rate, the proposed MPO-OFDM can achieve a lower bit error rate than previously proposed techniques. For a similar BER performance, MPO-OFDM can support a higher throughput than the other techniques tested. 
    more » « less
  3. ; (, 2022 Sixth Underwater Communications and Networking Conference (UComms))
    Orthogonal Signal Division Multiplexing (OSDM) has shown great robustness against multipath and Doppler effects in underwater acoustic channels, while however having a low spectral efficiency. In this work, a novel transmission method, named Spatial Modulation-based OSDM (SM-OSDM), is proposed to improve the spectral efficiency while keeping the Bit Error Rate (BER) low, where multiple transducers are utilized at the transmitter side but only one is active in each time slot. The simulation results prove that the SMOSDM offers higher spectral efficiency than Single-Input SingleOutput (SISO)-OSDM and lower BER compared with MultipleInput Multiple-Output (MIMO)-OSDM. 
    more » « less
  4. ; ; ; (, Microelectromechanical systems)
    The present work reports on the novel implementation of a miniaturized receiver for underwater networking merging a Piezoelectric Micromachined Ultrasonic Transducer (PMUT) array and signal conditioning circuitry in a single, packaged device. Tests in both a large water tank and a pool demonstrated that the system can attain large enough Signal-to-Noise Ratio (SNR) for communication at distances beyond two meters. An actual communication test, implementing an Orthogonal Frequency Division Multiplexing (OFDM) scheme, was used to characterize the performance of the link in terms of Bit Error Rate (BER) vs SNR. In comparison to previous work demonstrating high-data rate communication for intra-body links and acoustic duplexing, this implementation allows for significantly larger distances of transmission, while addressing the signal conditioning and submersible packaging needs for underwater conditions, thus enabling PMUT arrays for operating as complete underwater communication receivers. 
    more » « less
  5. ; ; ; (, ACM)
    This paper investigates how an airborne node can eavesdrop on the underwater acoustic communication between submerged nodes. Conventionally, such eavesdropping has been assumed impossible as acoustic signals do not cross the water-air boundary. Here, we demonstrate that underwater acoustic communications signals can be picked up and (under certain conditions) decoded using an airborne mmWave radar due to the minute vibrations induced by the communication signals on the water surface. We implemented and evaluated a proof-of-concept prototype of our method and tested it in controlled (pool) and uncontrolled environments (lake). Our results demonstrate that an airborne device can identify the modulation and bitrate of acoustic transmissions from an uncooperative underwater transmitter (victim), and even decode the transmitted symbols. Unlike conventional over-the-air communications, our results indicate that the secrecy of underwater links varies depending on the modulation type and provide insights into the underlying reasons behind these differences. We also highlight the theoretical limitations of such a threat model, and how these results may have a significant impact on the stealthiness of underwater communications, with particular concern to submarine warfare, underwater operations (e.g., oil & gas, search & rescue, mining), and conservation of endangered species. Finally, our investigation uncovers countermeasures that can be used to improve or restore the stealthiness of underwater acoustic communications against such threats. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email