NOMA-Oriented Spectrum Sensing for Joint HAP and HEO Nonterrestrial Uplink Communications

Non-Terrestrial Networks (NTNs), as one core infrastructure of the sixth-generation (6G) communication technology, integrate heterogeneous nodes, such as High Earth Orbit (HEO) satellites, to achieve three-dimensional ubiquitous connectivity. However, NTNs face with spectrum scarcity, imposing stringent demands on spectral efficiency and interference management. To address these challenges, we propose a NOMA-oriented spectrum sensing technique for uplink scenarios, where High-Altitude Platforms (HAPs) serve as dynamic aerial nodes for opportunistic transmission within HEO coverage. Specifically, we derive multi-user sensing thresholds to optimize detection accuracy and suppress false alarms. Numerical simulations demonstrate the technique achieves a 33.5% throughput gain over benchmarks at 10 dB and maintains satisfactory performance across PUs’ varying elevation angles and transmission willingness.