Radar Sensor and Data Communication System Based on OFDM Without Cyclic Prefix

The high data rate and large bandwidth of orthogonal frequency division multiplexing (OFDM) modulations have made the integrated waveform design using OFDM-based signals a popular research topic in recent years. However, OFDM signals are sensitive to the Doppler frequency bias and multipath effects, which are traditionally accommodated by cyclic prefixes (CPs) inserted before each OFDM symbol. Since the CP is the partial copy of the OFDM symbol, it not only loses energy in communication systems but also forms false targets after radar signal processing. To address the shortcomings of conventional OFDM, this article proposes a modified CP-free OFDM joint radar communication system (JRCS). It transmits the OFDM pulse signal to certain targets and/or communication systems and receives echoes in the pulse repetition interval. By removing CP, the radar system can compress the echoes without ghost targets. Through reasonable sampling which should be designed significantly, the communication systems demodulate the OFDM pulse to extract information without intersymbol interference (ISI) in multipath channels. Furthermore, the constraints of the time, frequency, and sampling on the system are analyzed in detail and an illustrating system under an air-to-ground scenario is constructed. Simulation results show that the proposed signal design and processing method has a better performance compared to conventional OFDM signals.