| Abstract |
In this survey paper, we investigate some of the challenges to be addressed before a practical real-time secondary market for spectrum can be developed. We present different methods of flexible spectrum allocation such as coordinated usage of resources, integration solutions and secondary access of spectrum. More specifically two methods of secondary access approaches are real-time and non real-time secondary access. However, the main focus of this work is on real-time secondary spectrum utilization which can follow negotiated or opportunistic access strategy. While different solutions for increasing spectrum utilization and efficiency are under investigation, many aspects of spectrum sharing technologies are still open questions. After an extensive literature survey, the major challenges and open questions of the real-time secondary usage of spectrum are addressed here. A number of the proposed solutions are discussed and the open research problems are highlighted. We also provide some insights on potentially important design considerations and requirements when developing successful spectrum management schemes to realize real-time secondary spectrum usage. |