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      Time-delay estimation in dispersed spectrum cognitive radio systems

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      Author
      Kocak, F.
      Celebi, H.
      Gezici, S.
      Qaraqe, K. A.
      Arslan, H.
      Poor, H. V.
      Date
      2010
      Source Title
      Eurasip Journal on Advances in Signal Processing
      Print ISSN
      1687-6172
      Publisher
      SpringerOpen
      Volume
      2010
      Pages
      1 - 10
      Language
      English
      Type
      Article
      Item Usage Stats
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      Abstract
      Time-delay estimation is studied for cognitive radio systems, which facilitate opportunistic use of spectral resources. A two-step approach is proposed to obtain accurate time-delay estimates of signals that occupy multiple dispersed bands simultaneously, with significantly lower computational complexity than the optimal maximum likelihood (ML) estimator. In the first step of the proposed approach, an ML estimator is used for each band of the signal in order to estimate the unknown parameters of the signal occupying that band. Then, in the second step, the estimates from the first step are combined in various ways in order to obtain the final time-delay estimate. The combining techniques that are used in the second step are called optimal combining, signal-to-noise ratio (SNR) combining, selection combining, and equal combining. It is shown that the performance of the optimal combining technique gets very close to the Cramer-Rao lower bound at high SNRs. These combining techniques provide various mechanisms for diversity combining for time-delay estimation and extend the concept of diversity in communications systems to the time-delay estimation problem in cognitive radio systems. Simulation results are presented to evaluate the performance of the proposed estimators and to verify the theoretical analysis.
      Keywords
      Cognitive radio
      Combining techniques
      Communications systems
      Cramer Rao lower bound
      Diversity combining
      Maximum likelihood estimator
      ML estimators
      Optimal combining
      Selection combining
      Signal to noise
      Simulation result
      Time delay estimation
      Two-step approach
      Unknown parameters
      Cognitive systems
      Computational complexity
      Cramer-Rao bounds
      Estimation
      Frequency shift keying
      Maximum likelihood estimation
      Optimization
      Radio
      Radio systems
      Signal to noise ratio
      Time delay
      Permalink
      http://hdl.handle.net/11693/22113
      Published Version (Please cite this version)
      http://dx.doi.org/10.1155/2010/675959
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      • Department of Electrical and Electronics Engineering 3339

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