Cognitive Radio Network (CRN) has emerged as a promising technology to exploit the unused portions of spectrum in an effective manner. The fixed spectrum allocation is used to refer the unused portions of spectrum are called as 'Spectrum holes'. Cognitive radio network detect this type of issue and also it, allowing devices to sense the spectrum for unused portions and use the most suitable ones. Cognitive radio networks are the next generation of the key enabling technology that enables dynamic spectrum access. The spectrum allocation is one of the most important issues in CRNs.