Frequency-Domain Sensing in Time-Varying Channels

Joint Communications and Sensing (JCAS) in mobile networks are typically based on Orthogonal Frequency Division Multiplexing (OFDM) systems. For time-varying channels, large Doppler frequencies in OFDM JCAS can cause notable intercarrier interference, which has not been considered for sensing. In this letter, we propose a frequency-domain sensing framework for OFDM JCAS systems. We first derive a frequency-domain closed-form expression of the received signals, to characterise the delay and Doppler frequency impact within and across OFDM blocks. We then develop intra-block and inter-block sensing algorithms, based on the expression. The framework is further completed with exemplified pilot design and periodogram sensing algorithm. Simulation results demonstrate the effectiveness of the proposed framework.