Cognitive Radio Dynamic Access Techniques |
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| Authors: | I Budiarjo M K Lakshmanan H Nikookar |
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| Affiliation: | (1) International Research Centre for Telecommunications and Radar, Department of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology, Mekelweg 4, 2628CD Delft, The Netherlands |
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| Abstract: | The ever growing demand for wireless services has placed enormous burden on valuable resources such as spectral bandwidth.
This has resulted in a major rethinking in resource allocation policies culminating in an explosion of research activity in
the field of Cognitive Radio (CR) towards optimum resource usage. In this tutorial paper the physical layer design and transmission
techniques for CR in the context of efficient spectrum utilization are discussed. Spectrum sensing as the key element of CR
awareness is described. Orthogonal frequency division multiplexing (OFDM) as a spectrally efficient modulation scheme is discussed
and the rationale for its use in the CR system is explained. Spectrum pooling for efficient use of spectrum is studied and
the role of adaptive OFDM techniques in this method is highlighted. Wavelet basis function as a replacement of Fourier transform
in OFDM is evaluated. MIMO system as an added value to the CR performance is described. Adaptive Waveform and beamforming
as alternative techniques in CR are reviewed.
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| Keywords: | Adaptive bit loading Beamforming Cognitive radio MIMO OFDM Spectrum pooling TDCS WDCS and Wavelet |
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