Integrated sensing and communications in 6G non-terrestrial networks.

Integrated Sensing and Communication (ISAC) is considered an important enabling technology for future 6G systems, as it allows communication and sensing functionalities to share the same waveform, spectrum, and hardware resources. Its integration with Non-Terrestrial Networks (NTNs) is particularly relevant because satellites and aerial platforms can provide wide-area connectivity while also supporting sensing functions. This thesis investigates an ISAC system based on a 5G New Radio waveform in a bistatic sensing configuration, with a 5G base station acting as the sensing transmitter, a spatially separated user equipment acting as the sensing receiver, and two moving UAV targets. The processing chain includes 5G NR waveform generation, DM-RS-based channel estimation, background suppression, range and angular processing, two-dimensional CFAR detection, DBSCAN clustering, and multi-target tracking. The study evaluates the effect of channel bandwidth, subcarrier spacing, DM-RS pilot configuration, and transmit power on both communication and sensing performance. Communication performance is assessed through Block Error Ratio (BLER) and throughput, while sensing performance is evaluated using Probability of Detection, range resolution, and target-velocity estimation. The results show that increasing bandwidth improves throughput and range resolution and generally enhances target detection. Larger subcarrier spacing increases the maximum unambiguous Doppler and velocity range, while increasing transmit power improves both communication reliability and sensing performance, although the Probability of Detection improves more gradually than BLER. Overall, the results highlight the need to jointly consider communication and sensing requirements when configuring future ISAC systems for NTN scenarios.