Coexistence of radar and communication systems in CBRS bands through downlink power control

Citizen Broadband Radio Service band (3550-3700 GHz) is seen as one of the key frequency bands to enable improvements in the performance of wireless broadband and cellular systems. A careful study of interference caused by a secondary cellular communication system coexisting with an incumbent naval radar is required to establish a pragmatic protection distance, which not only protects the incumbent from harmful interference but also can increase spectrum access opportunity for the coexisting secondary system. In this context, this paper investigates the co-channel and adjacent channel coexistence of a ship-borne naval radar with a wide-area cellular communication system and presents the analysis of interference caused by downlink transmissions of the cellular system on the naval radar for different values of radar protection distance. The results of such analysis suggest that maintaining a protection distance of 30 km from the radar will ensure the required INR protection criterion of -6 dB at the radar receiver with > 0.9 probability, even when the secondary network operates on the same channel as the radar. Novel power control algorithms to assign operating powers to the coexisting cellular devices are also proposed to further reduce the protection distance from radar while still meeting the radar INR protection requirement.