Sensing-Driven Spatial Reuse in Shared Spectrum: ns-3 Implementation and Evaluation of Radiation Null Steering

Efficient coexistence management is essential for maximising spectrum utilisation in shared 5G New Radio–Unlicensed (NR-U) environments, where heterogeneous radio access technologies compete for the same channel resources. Conventional omnidirectional Listen-Before-Talk (LBT) mitigates persistent interference, yet fails to fully exploit the spatial reuse potential of active antenna arrays in dense deployments. This work introduces a practical null space projected LBT and digital precoder that jointly suppress interference from and toward coexisting nodes while remaining 3GPP- and regulatory-compliant. Implemented in ns-3 and 5G-LENA, system-level simulations demonstrate that the proposed approach enables concurrent transmissions, substantially enhances spatial reuse, and reduces latency compared to legacy LBT schemes.