Over‐the‐Air Beam‐Sweeping ISAC in the 5G‐NR FR1 Band: From Single‐Receiver Detection to Multi‐Receiver Angle Estimation

Existing integrated sensing and communication (ISAC) prototypes mostly operate at millimetre‐wave or THz frequencies, leaving the sub‐6 GHz band less explored. The limited available bandwidth at these frequencies constrains key sensing parameters, such as range resolution, yet this band dominates commercial 5G deployments, making sub‐6 GHz ISAC relevant to existing infrastructure. This letter investigates beam‐sweeping ISAC in the 5G new radio (NR) frequency range 1 (FR1) at 2.4 GHz with 10 MHz bandwidth, where the coarse range resolution ( m) precludes delay‐based sensing. A received signal model is formulated for a bistatic configuration with a directional multi‐active/multi‐passive (MAMP) antenna array at the transmitter, and an SNR‐maximisation‐based scheme is used for target detection. A multi‐receiver beam‐sweeping scheme is then evaluated, where spatially distributed receive antennas are combined with directional transmission for angle‐domain sensing with narrowband signals. The two schemes are validated through over‐the‐air experiments in a single‐input single‐output (SISO) and a single‐input multiple‐output (SIMO) setup, respectively, achieving 19.06 dB sensing and 16.52 dB communication SNR gains with angle accuracy. The results show that angle‐domain beam‐sweeping is a viable sensing strategy for narrowband sub‐6 GHz 5G NR systems.