1 Efficient Spectrum Management: Challenges and Solutions Tarek M.Salem, Sherine M. Abd El-kader Salah M.Ramadan , M.Zaki Abdel-Mageed Electronics Research Institute, Computers and Systems Dept, Al-Azhar University, Computers and Systems Dept, Cairo, Egypt Cairo, Egypt Abstract: Cognitive Radio (CR) technology has been proposed in recent years as a revolutionary solution towards more efficient utilization of the scarce spectrum resources in an adaptive and intelligent way. By tuning the frequency to the temporarily unused licensed band and adapting operating parameters to environment variations, cognitive radio technology provides future wireless devices with additional bandwidth, reliable broadband communications, and versatility for rapidly growing data applications. To realize the goal of spectrum aware communication, the CR devices need to incorporate the spectrum sensing, decision, sharing, and mobility functionalities. The main challenge in CRAHNS is to integrate these functions in the layers of the protocol stack, so that the CR users can communicate reliably in a distributed manner over multi-hop/multi-spectrum environment without infrastructure support.. In this book chapter, current research challenges of the CRAHNs are presented. First, spectrum management functionalities such as spectrum sensing, spectrum sharing, and spectrum decision, and spectrum mobility are introduced from the viewpoint of a network requiring distributed coordination. Moreover, the influence of these functions on the performance of the upper layer protocols are investigated and open research issues in these areas are also outlined. Finally, the proposed tools, and best simulator to solve research challenges in spectrum management are explained. This gives an insight in choosing the suitable tool, and the suitable simulator that fit for solving