The rapid growth of L-band Mobile-Satellite Service (MSS) direct-to-device (D2D) deployments poses potential spectrum coexistence challenges for Global Positioning System (GPS). However, empirical measurements and aggregate-interference modeling studies quantifying the impact of such interference on GPS receivers remain limited. This study assesses the impact of out-of-band emissions (OOBE) from MSS D2D uplinks on GPS L1 receivers. OOBE samples were collected from a D2D transmitter, combined with a GPS L1 baseband signal, and processed via a software-defined GPS receiver to assess performance. Preliminary results, based on two performance metrics, suggest that aggregate-interference scenarios modeled with a homogeneous Poisson point process cause negligible degradation in GPS receiver performance.
