Sharing and dynamic accesses of spectrum and heterogeneous radio access networks have been an important area of research on next generation mobile networks. They require innovations between regulatory policy and technology. The research team of the Dynamic Spectrum Access Laboratory (DSA Lab), Graduate Institute of Communications Engineering and Department of Electrical Engineering, National Taiwan University, has three research objectives: 
　O1) to help ICT industry grasp technology, system and service developments of shared spectra and RAN accesses;
　O2) to provide scientific and technological support and recommendations to both wireless and mobile service operators and regulatory policy-makers; and 
　O3) to develop foresights about spectrum and RAN sharing technologies and operation model developments.

To achieve these objectives via proof-of-concept (POC) demonstrations and to develop an experiment environment for research, together with other research institutes the research team has designed and implemented the Virtually Shared Spectrum Access (ViSSA) platform. ViSSA 2.0 has seven innovatively designed and integrated parts: i) an observatory for periodic spectrum sensing; ii) a monitoring (Figure 2) and management center of spectrum accesses with a spectrum database; iii) an emulator of incumbent spectrum accesses; iv) LTE small cells of multiple networks of secondary accesses; v) feature-based sensing of incumbent signals; vi) License Assisted Access operation management for fair access with WiFi networks; vii) a simplified spectrum access system of a three-tiered spectrum sharing framework; and viii) intra- and inter- Lab networking. The research team has achieved successful experiments and POC demonstrations of spectrum and RAN sharing over ViSSA 2.0.

Figure 2: Monitoring and management display