Adaptive Transmit Beamforming for DoA Estimation in Dynamic and Resource-Constrained DFRC Systems

Dual-function radar communication (DFRC) systems incorporate both radar and communication functions by sharing spectrum, hardware and radio frequency (RF) chains. Future technologies, such as 6G, are envisioned to support multiple communication platforms along with radar sensing, thus leading to competition for the available resources and variability in their allocation. If communication takes precedence over sensing, the RF chains and antennas allocated to sensing are less and potentially changing for every communication frame. Consequently, sensing over the entire field-of-view (FOV) within a frame with varying resources requires real-time adaptive beamforming strategy. Existing sensing techniques such as time-division multiplexing, sequential scan over the FOV and beam redesign using optimization approaches are impractical in such scenarios due to high latency and execution overheads. We propose a resource-aware technique for transmit analog beamformer design to sense the entire FOV within the communication frame. The proposed technique leverages time-sliced beam allocation along with adaptive windowing to result in a balanced cumulative array factor over the FOV thereby ensuring better direction-of-arrival (DoA) estimation reliability. Extensive simulation studies show that the proposed technique has consistent target detection and angle estimation performance in all directions and adapts to varying resource availability with time.