On the Coexistence of Multi-Static Tracking Radars with Cell Free Massive MIMO

In this paper, we evaluate the performance of a coexistence based integrated communications and sensing (ICS) system, combining a cell free massive multiple input multiple output (CF-mMIMO) system with a multi-static sensing radar. The multi-static radar is assumed to consist of multiple sensors, all tracking a single target and connected to a fusion centre (FC). The radar subsystem is further assumed to employ a two level extended Kalman filter (EKF) that performs the tracking at both the individual sensors and at the FC. The communications subsystem is assumed to consist of the uplink of a CF-mMIMO system and its operation is divided into two sub-frames, viz. channel estimation and data transmission. We evaluate the system performance in terms of the achievable rates by the communication subsystem and the mean square error (MSE) tracking performance of the radar subsystem. Via extensive numerical simulations, we show that due to the increased diversity offered by distributed nature of both the subsystems, they are able to coexist without causing significant deterioration in each other's performance.