Joint Waveform and Receiver Design for CoChannel Hybrid ActivePassive Sensing With Timing Uncertainty We consider a hybrid activepassive radar system that employs a wireless source as a passive illuminator of opportunity (IO) and a cochannel active radar transmitter operating in the same frequency band to seek spectral efficiency. The hybrid system can take advantage of the strengths of passive radar (e.g., energy efficiency, bimultistatic configuration, and spatial diversity) as well as those of active radar (dedicated transmitter, flexible transmit beam steering, waveform optimized for sensing, etc.). To mitigate the mutual interference and locationinduced timing uncertainty between the radar and communication signals, we propose two designs for the joint optimization of the radar waveform and receive filters. The first is a maxmin (MM) criterion that optimizes a worstcase performance metric over a timing uncertainty interval, and the other a weightedsum (WS) criterion that forms a weighted sum of the performance metric at each delay within the delay uncertainty interval. Both design criteria result in nonconvex constrained optimization problems that are solved by sequential convex programming methods. When timing uncertainty vanishes, the two designs become identical and admit a simpler solution. Numerical results are presented to demonstrate the performance of the proposed hybrid schemes in comparison with conventional activeonly and passiveonly radar systems.

Spatial Coexistence of Cooperative Radar and Communication Systems Future generations of cellular systems need to meet stringent requirements for bandwidth and latency. This entitles maximum utilization of the available wireless spectrum. Given that some of the spectrum bands are underutilized, e.g. radar band. In this paper, we study the utilization of the radar spectrum for commercial cellular usage for meeting future generations of cellular systemsu0027 spectral demands. We propose to avoid destructive high power interference from seaborne radar transmitters with high power that can saturate the cellular base station receivers by using a projection based approach. Additionally, in our design, the radar transmitters will be cooperating with cellular system by transmitting useful broadcast communication signal. Towards that, we study the channel between seaborne multiple input multiple output (MIMO) radar system and MIMO cellular systems. The high power radar signal is projected onto the small singular value subspace of the channel, and therefore, reaches the base station with low power. In our design, the small singular values are selected so that the received power at the cellular base stations is within acceptable cellular system power constraints. Simulation results show that the amount of power transmitted from the radar to the base station increases as the threshold increases, which allows the radar to be cooperatively capable of transmitting communication signals to cellular base stations. Moreover, as the threshold increases, the accuracy of localizing the radar target increases.