In-Band Full-Duplex Underwater Acoustic Communications

dc.contributorSong, Aijun
dc.contributorGurbuz, Sevgi
dc.contributorHong, Xiaoyan
dc.contributorHu, Fei
dc.contributorXia, Xiang-Gen
dc.contributor.advisorSong, Aijun
dc.contributor.authorGuo, Zheng
dc.contributor.otherUniversity of Alabama Tuscaloosa
dc.descriptionElectronic Thesis or Dissertationen_US
dc.description.abstractIn-band full-duplex (IBFD) communications is a promising technique for increased spectral efficiency. This dissertation investigates IBFD acoustic communications in the underwater environment. Four research thrusts are investigated. Due to the absence of near-field acoustic propagation models, these efforts are supported by extensive field tests in local rivers and lakes. Firstly, the near-field SI characteristics were analyzed at multiple acoustic frequencies. The SI cancellation performance deteriorated with the increased signal carrier frequency. Fast channel fluctuations were identified as the reason for the deterioration. The channel variation ratio (CVR) was proposed to quantify the intensity of channel fluctuations. Experimental and simulated results showed that CVRs were larger at higher acoustic frequencies, and large CVRs led to the deteriorated SI suppression. Secondly, the impact of channel fluctuations on the performance of the least-squares channel estimator was quantified. The channel estimation performance, measured by the channel estimation mean squared error (MSE) and the signal prediction error (SPE), was linked with the CVR by analytic expressions. Both the MSE and SPE had an error floor for time-varying impulse responses. It was confirmed that an optimum estimated channel length, achieving the minimum estimation error, existed for time-varying impulse responses. Next, multiple SI suppression methods, including physical separation, digital SI cancellation, directional transducers, and acoustic baffles, were investigated through field experiments. It was found that a 7-m physical separation provided a maximum SI reduction of 32.6 dB. The achieved digital SI cancellation decreased with the increased physical separation ranges. Marginal SI suppression was observed with directional transducers and acoustic baffles. Lastly, an iterative IBFD receiver was developed for IBFD acoustic communications. A control mechanism was used to regulate the digital SI cancellation. The SI cancellation control mechanism and the receiver performance were evaluated by the experimental measurements. A bit error rate (BER) in the order of $10^{-2}$ was achieved at the range of 80 m for IBFD communications with the 28-kHz carrier frequency in a lake environment. With a lower carrier frequency of 10 kHz, a similar BER was demonstrated at the extended range of 100 m with a smaller receiving array.en_US
dc.publisherUniversity of Alabama Libraries
dc.relation.hasversionborn digital
dc.relation.ispartofThe University of Alabama Electronic Theses and Dissertations
dc.relation.ispartofThe University of Alabama Libraries Digital Collections
dc.rightsAll rights reserved by the author unless otherwise indicated.en_US
dc.subjectChannel estimation
dc.subjectChannel fluctuations
dc.subjectIn-band full-duplex communications
dc.subjectSelf-interference cancellation
dc.subjectUnderwater acoustic communications
dc.titleIn-Band Full-Duplex Underwater Acoustic Communicationsen_US
dc.typetext of Alabama. Department of Educational Leadership, Policy, and Technology Studies engineering University of Alabama
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