  Increasing data traffic demands over wireless spectrum have necessitated
spectrum sharing and coexistence between heterogeneous systems such as radar
and cellular communications systems. In this context, we specifically
investigate the co-channel coexistence between an air traffic control (ATC)
radar and a wide area cellular communication (comms) system. We present a
comprehensive characterization and analysis of interference caused by the comms
system on the ATC radar with respect to multiple parameters such as radar
range, protection radius around the radar, and radar antenna elevation angle.
The analysis suggests that maintaining a protection radius of 50 km around the
radar will ensure the required INR protection criterion of -10 dB at the radar
receiver with ~0.9 probability, even when the radar beam is in the same horizon
as the comms BS. Detailed evaluations of the radar target detection performance
provide a framework to choose appropriate protection radii around the radar to
meet specific performance requirements.
