Coprime-Based Frame-Level Sensing OFDM Waveform for 5G NR Integrated Radar Sensing and Communication via Downlink Sensing

In fifth-generation (5G) new radio (NR) integrated sensing and communication (ISAC) systems, the overhead of sensing time resources in waveform design is a key metric. Traditional uniform pulse sensing waveforms, which require fixed time slot positions, incur large sensing overhead and may not be feasible within the context of existing 5G NR standards for low-latency scenarios. To address this issue, two novel frame-level sensing waveform designs based on double coprime sampling are proposed via downlink sensing. Specifically, two types of novel orthogonal frequency-division multiplexing (OFDM) structure pulse sensing waveforms based on coprime sampling are first proposed to accommodate the specific 5G NR frame structure. Then, a low-complexity frequency-domain radar signal processing method is proposed for sensing target detection and velocity estimation based on the constructed equivalent virtual fast-slow-time domain signal. Moreover, the theoretical sensing performance of the proposed waveforms and the computational complexity of the sensing method are thoroughly analyzed. Compared with the conventional uniform OFDM-based waveform design, the proposed coprime-based frame-level OFDM sensing waveforms utilize significantly fewer time slots, resulting in reduced sensing overhead with slight sensing performance loss. Numerical examples are presented to illustrate that the proposed waveforms can offer robust sensing performance with reduced sensing overhead and have a computational complexity a little higher than that of conventional fast Fourier transform algorithms.