  This demo paper presents a dApp-based real-time spectrum sharing scenario
where a 5th generation (5G) base station implementing the NR stack adapts its
transmission and reception strategies based on the incumbent priority users in
the Citizen Broadband Radio Service (CBRS) band. The dApp is responsible for
obtaining relevant measurements from the Next Generation Node Base (gNB),
running the spectrum sensing inference, and configuring the gNB with a control
action upon detecting the primary incumbent user transmissions. This approach
is built on dApps, which extend the O-RAN framework to the real-time and user
plane domains. Thus, it avoids the need of dedicated Spectrum Access Systems
(SASs) in the CBRS band. The demonstration setup is based on the open-source 5G
OpenAirInterface (OAI) framework, where we have implemented a dApp interfaced
with a gNB and communicating with a Commercial Off-the-Shelf (COTS) User
Equipment (UE) in an over-the-air wireless environment. When an incumbent user
has active transmission, the dApp will detect and inform the primary user
presence to the gNB. The dApps will also enforce a control policy that adapts
the scheduling and transmission policy of the Radio Access Network (RAN). This
demo provides valuable insights into the potential of using dApp-based spectrum
sensing with O-RAN architecture in next generation cellular networks.
