Feasibility of SC-FDMA Re-Encoding for Packetized LTE-V2X microDoppler Sensing

Abstract

LTE vehicle-to-everything (LTE-V2X) sidelink uses a DFT-spread single-carrier frequency-division multiple access (SC-FDMA) waveform on the PC5 interface. This feasibility study examines whether known LTE-V2X sidelink transmissions from an ego vehicle can be used as a signal of opportunity for extracting microDoppler of other vehicles that are not equipped with LTE-V2X. The proposed receiver adapts WiSee symbol normalization from OFDM to SC-FDMA by dividing received resource elements by the locally reconstructed DFT-spread symbols rather than by raw frequency domain data constellation symbols. This work assumes ideal synchronization and cyclic prefix removal and focuses solely on the useful SC-FDMA waveform. DMRS-based channel estimation, resource-pool selection, and multi-user MAC contention are treated as deployment constraints rather than fully implemented PHY/MAC functions. A simple vehicle-pass simulation shows that the resulting slow-time signal can reveal microDoppler signatures from an oncoming vehicle in an adjacent lane, including the near-range vehicle-body double-bounce component identified in our prior V2V GSCM work. An active sub-frame fidelity model is also derived to relate packet generation and the number of useful SC-FDMA symbols per sidelink subframe to the achievable Doppler FFT resolution appropriate for vehicular microDoppler shifts.