Underlay Radar-Massive MIMO Spectrum Sharing: Modeling Fundamentals and Performance Analysis
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In this work, we investigate underlay radar-massive MIMO cellular coexistence in LoS/near-LoS channels, where both systems are capable of 3D beamforming. The base station (BS) locations are modeled using a homogeneous Poisson point process (PPP), and a single radar is located at the center of a circular exclusion zone (EZ) within which the BSs are prohibited from operating. We derive a tight upper bound on the average interference power at the radar due to the massive MIMO downlink. This is based on a novel construction in which each Poisson Voronoi (PV) cell is bounded by its circumcircle in order to bound the effect of the random cell shapes on average interference. However, this model is intractable for characterizing the interference distribution, due to the correlation between the shapes/sizes of adjacent PV cells. Hence, we propose a tractable nominal interference model where each PV cell is modeled as a circular disk with area equal to the average area of the typical cell. We quantify the gap in the average interference power between these two models, and show that the upper bound is tight for realistic deployment parameters. Under the nominal interference model, we derive the equal interference contour in closed-form, and characterize the interference distribution using the dominant interferer approximation. Finally, we use tractable expressions for the interference distribution to characterize important radar performance metrics such as the spatial probability of false alarm/detection in a quasi-static target tracking scenario. We validate the accuracy of our analytical approximations using numerical results, which reveal useful trends in the average interference as a function of the deployment parameters, and provide useful system design insights in the form of radar receiver operating characteristic (ROC) curves for current and future radar-cellular spectrum sharing scenarios.
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