Considerations on the Licensed Shared Access (LSA) architecture from the incumbent perspective

As the amount of mobile data continues to grow rapidly, finding frequency bands without incumbent usage for mobile network operators (MNOs) in a harmonized manner becomes increasingly challenging. This motivates the search for new methods to increase the efficiency of current spectrum usage by exploring the new possibilities to allow multiple services to share the same frequency band in a controlled manner. This kind of spectrum sharing should be conducted in a way that requires minimum changes to the functionalities and the architecture of the systems involved and especially to the current holders of the spectrum usage rights, thus, the incumbent spectrum users. In this paper, we concentrate on the emerging Licensed Shared Access (LSA) concept which is currently receiving a lot of attention in European regulation and standardization. We discuss different types of incumbents and the critical factors for allowing spectrum sharing with LSA from their perspective. Finally, we propose an architecture for LSA that takes into account these critical factors while guaranteeing certain quality of service (QoS) conditions for all involved systems.