Coexistence of Satellite-borne Passive Radiometry and Terrestrial NextG Wireless Networks in the 1400-1427 MHz Restricted L-Band

The rapid growth of wireless technologies has fostered research on spectrum coexistence worldwide. One idea that is gaining attention is using frequency bands solely devoted to passive applications, such as passive remote sensing. One such option is the 27 MHz L-band spectrum from 1.400 GHz to 1.427 GHz. Active wireless transmissions are prohibited in this passive band due to radio regulations aimed at preventing Radio Frequency Interference (RFI) on highly sensitive passive radiometry instruments. The Soil Moisture Active Passive (SMAP) satellite, launched by the National Aeronautics and Space Administration (NASA), is a recent space-based remote sensing mission that passively scans the Earth's electromagnetic emissions in this 27 MHz band to assess soil moisture on a global scale periodically. This paper evaluates using the restricted L-band for active terrestrial wireless communications through two means. First, we investigate an opportunistic temporal use of this passive band within a terrestrial wireless network, such as a cluster of cells, during periods when there is no Line of Sight (LoS) between SMAP and the terrestrial network. Second, leveraging stochastic geometry, we assess the feasibility of using this passive band within a large-scale network in LoS of SMAP while ensuring that the error induced on SMAP's measurements due to RFI is below a given threshold. The methodology established here, although based on SMAP's specifications, is adaptable for utilization with various passive sensing satellites regardless of their orbits or operating frequencies.