Software Radio (SWR) is an enabling technology for Cognitive Radio (CR) systems which promises to (de) modulate any signal, at any frequency. SWR signal, therefore, is composed of different standard's signals and this combination leads to high temporal fluctuations and thus SWR signal inherits high Peak to Average Power Ratio (PAPR). Non-linear analogue components (amplifiers, converters etc.) cause distortions for high PAPR signals which result in system performance degradation. Usually PAPR problem is addressed in time domain while this paper presents frequency domain interpretation of PAPR which is more appropriate in CR dynamic spectrum access context. A new PAPR formulation is presented which depends only upon spectral values of the signal thus associates spectrum with PAPR. As a result this vision assists in spectrum access for CR systems by providing PAPR metric information related to any available bandwidth. Consequently, bandwidth allocation in a spectrum access scenario under PAPR constraint is simplified.
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