A Convex Optimization-Based Three-Slot Framework for OFDM Integrated Sensing and Communication with Interference Cancellation

Integrated Sensing and Communication (ISAC) has emerged as a key enabling technology for future sixth-generation (6G) wireless networks by enabling sensing and communication functionalities to share spectrum, hardware resources, and signal processing infrastructure. However, practical ISAC systems are affected by self-interference, mutual interference between sensing and communication signals, and environmental clutter, which jointly degrade communication reliability and sensing performance. To address these challenges, this paper proposes a novel three-slot interference mitigation framework for downlink ISAC systems. Unlike conventional ISAC approaches that perform joint sensing and communication within a single transmission stage, the proposed framework separates directional sensing, parameter acquisition, and interference-aware joint transmission into three coordinated slots, enabling transmit-side pre-cancellation of sensing-induced mutual interference using estimated interference parameters. Furthermore, joint convex optimization-based beamforming is employed to mitigate self-interference through sidelobe minimization and suppress environmental clutter through spatial null steering while maintaining the desired sensing and communication links. Simulation results demonstrate beam steering, parameter recovery, communication performance after interference cancellation, and target range, velocity, and angle estimation using Range-Doppler and Multiple Signal Classification (MUSIC) processing. The proposed framework presents an interference-aware ISAC architecture that combines a three-slot transmission protocol for mitigating sensing-induced mutual interference with joint beamforming for suppressing self-interference and environmental clutter while supporting simultaneous sensing and communication.