Uplink Communication Signals-Assisted Parameter Estimation of Coherent Sensing Signals for OFDM-Based ISAC Networks

In integrated sensing and communication (ISAC) scenarios, co-frequency interference often induces strong correlation or complete coherence among received signals, leading to degraded resolution for sensing signals. To address this issue, we propose an uplink communication signal-assisted parameter estimation method of coherent sensing signals for ISAC systems based on orthogonal frequency division multiplexing-based (OFDM-based). First, the steering matrix of uplink communication signals from user equipments (UEs) is aligned with that of the sensing signals. Subsequently, the covariance matrix of sensing signals is summed with the covariance matrix of uplink communication signals to construct a new composite covariance matrix, thereby altering the noise subspace distribution in the original sensing covariance matrix. Building upon this modification, subspace-based parameter estimation methods are employed to extract target parameters (e.g., angle, range, and velocity), effectively enhancing the ISAC system's resolving capability for coherent sensing signals. Finally, simulations are conducted for both angle-of-arrival (AoA) estimation and range-Doppler estimation of coherent targets to validate the proposed method. The simulation results demonstrate that, with identical bandwidth conditions, the proposed method significantly improves the distinguishability of the ISAC system in coherent signals and further enhances the performance of the ISAC system in the estimation of target parameters. This work contributes to algorithmic advancement and system design for OFDM-based ISAC implementations.