FR3-DUALIS: A Full-Duplex Dual-Band ISAC Prototype for Upper-FR3 with 360-MHz-Per-Channel OFDM

Integrated sensing and communication (ISAC) has emerged as a key enabling technology for 6G networks. Existing implementations encounter significant trade-offs: single-band full-duplex systems require complex self-interference cancellation, time-division approaches compromise continuous sensing, and multi-waveform systems lack hardware reuse, resulting in limited integration. Time-domain–sampled wideband and multiband prototypes, which could simultaneously improve communication throughput and real-time velocity estimation, have not yet been systematically investigated, even though they offer a promising path toward practical ISAC deployments. This work presents a wideband dual-band full-duplex ISAC prototype operating in the upper FR3 band with a 360 MHz bandwidth. Operating at 24.25 GHz (bistatic communication) and 25.175 GHz (monostatic sensing), each with a transmit channel and a receive channel, the system achieves complete interference elimination through 925 MHz frequency separation. Experimental validation demonstrates zero bit-error rate (BER = 0) for QPSK-OFDM communication, matching communication-only baseline performance, while same-frequency operation for dual functions suffers severe degradation (BER = 0.05), confirming that frequency-domain resource partitioning eliminates cross-function interference without complex digital cancellation. Unified OFDM baseband processing enables architectural sharing with independent waveform optimization, providing 2.49 dB peak-to-sidelobe ratio (PSLR) and 4.43 dB integrated-sidelobe-level ratio (ISLR) improvement using Zadoff-Chu sequences for sensing. These improvements, which are from indoor measurements with a human target moving within 0.5 m to 2 m away from the monostatic sensing antennas, enhance the target discrimination that is critical for resolving human motions. Comprehensive analysis of hardware and signal parameters establishes design guidelines: the number of subcarriers should be larger than 8192 to ensure stable ranging, and 360 MHz maximum bandwidth determined through systematic underflow characterization. Real-time implementation achieves continuous velocity tracking providing 10 velocity estimation results per second (10 Hz refresh rate) with 0.2 m/s resolution, using 1000 symbols per frame for velocity estimation of the target. Results establish frequency-separated dual-band architectures as practical solutions for spectrum-abundant deployments.