Non-Cooperative Multi-User Range and Doppler Sensing Using OFDM Signals

The growing demand for efficient and multifunctional use of the radio frequency spectrum has become vital, yielding the integration of communication and sensing within limited resources. Orthogonal frequency division multiplexing (OFDM) stands out due to its high spectral efficiency, flexible signal design, and dominance in communication generations. This study introduces a novel approach for simultaneous range and Doppler velocity estimation for multiple users employing OFDM signals within an identical 800 MHz bandwidth, differentiated by slight carrier frequency offsets at 3.8 GHz and 3.85 GHz, without altering the OFDM waveform structure. Unlike time-division (TDMA) or frequency-division (FDMA) multiple access methods, this approach maximizes spectral and temporal efficiency by leveraging subcarrier orthogonality, independent modulation symbols, and minor frequency offsets to mitigate cross-user interference without additional management. Comprehensive theoretical analysis, simulations, and experimental validations demonstrate that multiple users can perform accurate and concurrent sensing tasks using identical spectral and temporal resources.