Licensed Shared Access - State-of-the-Art and current Challenges

In the context of a wireless communication infrastructure, the Licensed Shared Access (LSA) concept is currently being developed by CEPT regulation and ETSI standardization bodies, with the aim of enabling cellular operators to have access to further spectral resources on a licensed shared basis. Even though spectrum owners, also known as Incumbents, will cooperate with cellular operators in the framework of a Sharing Agreement that is typically set-up for a long-term basis, the LSA concept will in addition, under specific conditions, give Incumbents the opportunity to reclaim spectrum on a per-need basis. Obviously, this new concept for managing spectrum introduces a number of novel challenges, such as vacate in a coordinated manner the LSA bands in case of a corresponding request being triggered by Incumbents, coordinate the LSA spectrum when it is used in proximity to neighbouring countries and/or regulation domains, establish protection zones in which maximum interference levels are guaranteed to Incumbents, etc. This paper gives an overview on the LSA state-of-the-art and elaborates the key challenges to be addressed in the future design of LSA systems.