Abstract: The coexistence of radar and communication has received a lot of attention from the research community in the recent years due to a considerable number of wireless systems that share the same spectral band, e.g.,  LTE, 5G, WiFi and S-band radars. In a plain coexistence scenario, each system tries to mitigate the interference from the other one. In a co-operative scenario, there is some exchange of information between the two systems, for example, channel state or interference awareness. In this talk, waveform optimization methods for target detection and parameter estimation are presented in a co-operative scenario. Mutual Information, and channel and interference awareness are exploited in optimization. Generalized multicarrier waveform model is employed in the radar system. Additional constraints on the waveform properties are imposed. In target parameter estimation, the objective function maximizes the Fischer Information (or minimizes CRB). Simulation examples of optimizing waveforms for target detection and parameter are provided. Time allowing, precoder-decoder design approach employing interference alignment is presented for co-existing radar and communication system.