Analysis of Integrated Differential Absorption Radar and Subterahertz Satellite Communications Beyond 6G

The integration of sub-Terahertz (sub-THz) communication beyond $\mathbf {100 }\text{ GHz}$ with differential absorption radar (DAR) as part of the evolution toward 5G-sdvanced and 6G nonterrestrial networks (NTNs) and beyond is critical for enabling intrinsic coexistence between these technologies. This study presents the first comprehensive analysis of an integrated sensing and communication (ISAC) system that combines satellite-centric sub-THz communications with DAR. We propose adapting the DAR waveform to be compatible with communication modulation, mathematically proving that this integration does not compromise DAR's sensing capabilities. In addition, we explore two methods to increase communication throughput with minimal impact on sensing performance: increasing the modulation order and increasing the number of symbols per chirp pulse. The results, validated through extensive simulations using published atmospheric models from the International Telecommunication Union (ITU) and the high resolution transmission molecular absorption database, reveal significant system tradeoffs. Our findings demonstrate that data rates can be enhanced up to 500 times without substantial degradation in estimation accuracy. However, excessively high data rates lead to significant estimation errors in the sensing system. This research underscores the potential of sub-THz ISAC systems for advanced satellite communications and remote sensing applications.