OFDM Radar Onboard Moving Platform for GMTI

Typical scenarios for Integrated Sensing and Communication (ISAC) involve networks of moving nodes, such as UAVs, aircraft, or vehicles, that transmit waveforms enabling both inter-node communication and radar-based surveillance. In this context, Orthogonal Frequency-Division Multiplexing (OFDM) waveforms offer a unified solution for supporting wireless communication alongside ground moving target indication (GMTI), i.e., the detection of targets moving on or above the surface across wide monitored areas, a key capability for autonomous navigation, standoff sensing, and situational awareness. Platform motion causes Doppler spreading of clutter echoes from stationary objects, complicating the detection of slow-moving targets. Effective clutter mitigation requires the use of multiple receiving channels and space-time processing (STAP) to exploit spatial and Doppler diversity and suppress clutter while preserving target echoes. However, while classical radar systems exploit trains of coherent pulses and constant-envelope waveforms to apply mature STAP techniques, the use of OFDM complicates this approach: its time-varying, information-bearing structure breaks the assumptions underlying conventional STAP methods. The scenario further complicates under bistatic configurations or when operating with low-gain antennas and limited onboard processing, conditions typical of low-cost platforms. This chapter investigates the joint effects of platform motion and waveform variability on radar GMTI performance, proposing tailored strategies for OFDM-based ISAC systems. The analysis is supported by theoretical insights, simulations, and experimental data collected in vehicular scenarios.