The future of Wireless Communication Technology is going to be basically based on Cognitive Radio (CR) or Intelligent Radio (IR). At present the Spectrum allocation governed by the government agencies or the service providers who are in need of more spectrums, to manage the increasing frequency demands from the end users as the technological improvement increases exponentially. Efficient utilization of this scared Electromagnetic Radio Spectrum is the basis for the Cognitive Radio (CR). Spectrum Sensing being the fundamental issue of the Cognitive Radio i.e., detecting the underutilized spectrum of Primary User (PU) or Licensed User that can be efficiently utilized by the Secondary User (SU) or Unlicensed User. The spectrum is a scared natural resource, so it becomes essential to detect the unused spectrum of the PU to utilize it by other Users. The unused spectrums that are identified idle can be efficiently managed by spectrum management techniques. The managed spectrum should be mobilized for efficient utilization by the SUs. The spectrum mobilized can be shared properly by the SUs for proper usage which all governed by the physical layer operations of the Cognitive Radio. In this review paper, the fundamental issues of physical layer functions i.e., Spectrum Sensing, Spectrum Sharing, Spectrum Management and the NeXt generation Cognitive Radio functions have been analyzed cheap mlb jerseys from china and as a future work the higher layer issues of Cognitive Radio are considered to be the Link Layer, Network layer operations.