Enhanced Sensing in 6G NTN: Imaging With LEO Satellite and UAV Communication Network

The integration of sensing and communication functions is regarded as an important trend for sixth-generation (6G) nonterrestrial networks (NTNs). One promising application is high-precision imaging based on NTNs. However, the current image resolution based on the satellite signal is unsatisfactory. Additionally, time and carrier phase offsets will accumulate during long-term observations. In this article, we fully consider the NTN infrastructure and design an integrated imaging and communication system based on the cooperation of a low-Earth-orbit (LEO) satellite and an uncrewed aerial vehicle (UAV). This system utilizes the motion of both the LEO satellite and the UAV for imaging performance improvement. First, we present a general system model with communication and imaging functionality. Then, we exploit UAV mobility for resolution improvement, analyzing the theoretical image resolution associated with platform movements, and present an optimization with its closed-form solution. Based on this framework, we further consider the offsets for imaging in practical systems and present a tracking-correction method for offset compensation. Finally, we propose using reference signals in the communication protocol to suppress ambiguity in the image and evaluate the impact of sensing-communication resource allocation on system performance. The prototype system implementation and simulation results demonstrate the effectiveness of our designs, achieving at least a 54% improvement in resolution and an 11.7 dB improvement in the signal-to-noise ratio (SNR).