Abstract:  In this paper, a cooperative multiple-input multiple-output (MIMO) radar and communication systems is studied, where the two systems work cooperatively on the basis of coexistence. The knowledge of communication system is shared with the radar system, so that the communication signals can be accurately decoded at radar receivers.Then target returns contributed from both the radar transmitters and communication transmitters are employed to complete the radar task. The cooperative systems can be equivalent to a hybrid active-passive MIMO radar network, which helps to improve the radar performance. With the information shared by the radar system, the communication system can estimate the parameters of the radar target. Thus, the communication signals bounced off from the target are exploited to complete the communication task on the basis of the traditional communication, which helps to improve the communication performance.The target detection probability and mutual information are derived for the radar-communication systems, respectively. It is shown that there is a performance gain due to the cooperation between the radar and communication systems. Furthermore, the power resource assignment of the cooperative MIMO radar and communication systems with limited power is discussed, and the optimal power allocation is presented numerically.