Abstract-In vivo wireless medical devices have the potential to play a vital role in future healthcare technologies by improving the quality of human life. In order to fully exploit the capabilities of such devices, it is necessary to characterize and model the in vivo wireless communication channel. This model will have a significant role in improving the communications performance of embedded medical devices in terms of power and spectral efficiency. In this paper, the state of the art in this field is presented to provide a comprehensive understanding of current models, considering various communication methods, operational frequencies, and antenna design. Finally, open research areas are discussed for the future studies.Index Terms-In vivo channel characterization, in/on-body communication, wireless body area networks (WBAN), wireless implantable medical devices.