6G-REFERENCE · 6G haRdware Enablers For cEll fRee cohEreNt Communications & sEnsing

In urban areas, 6G will need to rely on a sustainable solution to cope with the ever-increasing traffic demands and population densification, while providing disruptive capabilities like the materialization of the internet of sense. The solution envisioned by 6G-REFERENCE consist of ultra-dense cell-free deployments for joint coherent communications and sensing at cm-waves, which balance the benefits of sub-6GHz (e.g. reduced pathloss) and mm-wave (e.g. wide bandwidth) ranges. These systems face five fundamental challenges: (i) the need of accurate synchronization among distributed radio units; (ii) fronthaul data distribution; (iii) integration of sensing capabilities; (iv) low complexity/cost/consumption radios; and (v) coexistence with other services. 6G-REFERENCE will develop integrated circuit and antenna component solutions addressing all of them. It will design frequency/time synchronization circuits and a new continuous synchronization framework based on full-duplex. Indeed, full-duplex enabling solutions will be developed targeting such scheme as well as efficient fronthaul data distribution among cascaded radio units, and for enabling integrated monostatic radar sensing. Besides these, on the sensing domain, 6G-REFERENCE will explore environmental sensors integrated in the antenna estates, reuse the synchronization framework for accurate localization, and develop new array solutions like frequency modulation providing spatial superesolution at a contained cost and power consumption. The latter will be also targeted by time modulated arrays providing efficient single-RF chain multibeam operation as well as reconfigurable intelligent surfaces extending the capabilities of small FMA/TMA arrays. Finally, dynamic IF and antenna filtering will be developed to enable efficient spectrum coexistence schemes. The ultimate goal of 6G-REFERENCE is to develop hardware enablers that could end up constituting a reference design of future 6G distributed radios.