  Integrated sensing and communications (ISAC) will be deployed into cellular
communication systems possibly already with 5G-A and surely in 6G. This paper
discusses ISAC use cases, key technology building blocks for system design with
solutions and open research questions. Furthermore, we introduce our
proof-of-concept (PoC) based on commercially available 5G communications
hardware at mm-Wave frequencies, with sensing-specific algorithmic extensions.
This new ISAC PoC can perform jointly high data-rate communications and OFDM
radar sensing in the same frequency band. Initial pedestrian detection results
are shown, indicating the practicability of ISAC in future cellular networks.
The results also indicate our achievable sensing range and provide hints to the
achievable range estimation accuracy, based on the stability of the PoC system
communications hardware.
