Coordinated FMCW and OFDM for Integrated Sensing and Communication

TL;DR

This work presents Co-FMCW-OFDM, a practical ISAC waveform that superimposes FMCW radar signals onto OFDM communications, sharing the same front end and spectrum. It introduces two bistatic sensing algorithms, FCCR and DMD, to extract target delays and Doppler, and a sensing-aided SIC-based channel estimation framework that reconstructs and cancels the FMCW interference in the time domain before OFDM demodulation. A realistic channel model with non-integer delays is handled by leveraging sensing results to estimate a multi-path effective channel and mitigate interference, yielding superior sensing accuracy, channel estimation NMSE, and BER compared with conventional OFDM and OFDM-plus-FMCW schemes. The approach emphasizes practicality, low complexity, and compatibility with existing vehicular hardware, enabling robust ISAC in dynamic environments and high-mobility scenarios.

Abstract

We propose a coordinated FMCW-OFDM (Co-FMCW-OFDM) system that enables integrated sensing and communication (ISAC) by allowing sensing and communication to share the same RF front end, antennas, and spectral resources. In the proposed ISAC system, the FMCW signal is superimposed on the OFDM signal and serves dual purposes: facilitating bistatic sensing and enabling channel estimation at the receiver end. Based on proposed Co-FMCW-OFDM waveform, we propose two efficient sensing algorithms-fast cyclic correlation radar (FCCR) and digital mixing and down-sampling (DMD)- which significantly reduce system complexity while accurately estimating target range and velocity. We consider a realistic channel model where delays can take any value, not just integer multiples of the sampling period. This leads to a significantly larger number of effective paths compared to the actual number of targets, which makes the sensing, channel estimation, and interference cancellation more challenging. Leveraging the sensing results, we develop a sensing-aided effective channel estimation method which effectively reconstructs the channel under arbitrary delay condition based on successive interference cancellation and propose an interference cancellation scheme that removes the FMCW signal before the OFDM demodulation. Simulation results demonstrate that the proposed system achieves superior sensing accuracy, improved channel estimation, and lower bit error rate (BER) compared to conventional OFDM systems with embedded pilots. The proposed scheme demonstrates superior BER performance in comparison to the conventional OFDM-plus-FMCW approach.

Figures (16)

• Figure 1: Coordinated FMCW and OFDM scheme for ISAC
• Figure 2: One symbol of Co-FMCW-OFDM waveform
• Figure 3: An example of original and effective channel profile
• Figure 4: Receiver Algorithm Diagram
• Figure 5: Simulated and theoretic RMSE of time domain channel estimation