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A polynomial phase model for estimation of underwater acoustic channels using superimposed pilots
LuleƄ University of Technology, Department of Computer Science, Electrical and Space Engineering.
2019 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In underwater acoustic communications the time variation in the channel is a huge chal-

lenge. The estimation of the impulse response at the receiver is crucial for the decoding

of the signal to become accurate. One way is to transmit a superimposed pilot sequence

along the unknown message, and by the knowledge of the sequence have the possibility

to continuously track the variation in the channel over time.

This thesis investigates if it is possible by the aid of superimposed pilot sequences to

separate the taps in the channel impulse response and using a parametric method to

describe the taps as polynomial phase signals.

The method used for separation of the taps was a moving least squares estimator.

Thereafter each tap was optimised to a polynomial phase signal (PPS) using a weighted

non-linear least squares estimator. The non-linear parameters of the model was then

determined with the Levenberg-Marquardt method. The performance of the method was

evaluated both for simulated data as well as for data from eld tests. The performance

was determined by calculating the mean squared error (MSE) of the model over dierent

frame lengths, signal to noise ratio (SNR), weights for the superimposed pilots, rapidness

of time variation and impulse response lengths.

The method was not sensitive to the properties of the channel. Even though the model

had high performance, the complexity of the computations generated long compilation

times. Hence, the method needs further work before a real time implementation could

be possible.

Place, publisher, year, edition, pages
2019.
National Category
Signal Processing
Identifiers
URN: urn:nbn:se:ltu:diva-74460OAI: oai:DiVA.org:ltu-74460DiVA, id: diva2:1324011
External cooperation
FOI
Educational program
Engineering Physics and Electrical Engineering, master's level
Supervisors
Examiners
Available from: 2019-06-25 Created: 2019-06-13 Last updated: 2019-06-25Bibliographically approved

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CiteExportLink to record
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Citation style
  • apa
  • ieee
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  • de-DE
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Output format
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