Advanced communication scenarios demand the development of new systemswhere antenna theory channel propagation and communication models are seen from a common perspective as a way to understand and optimize the system as a whole. In this context a comprehensive multiantenna formulation for multipleinput multipleoutput systems is presented with a special emphasis on the connection of the electromagnetic and communication principles. Starting from the capacity for amultiantenna system the book reviews radiation propagation and communicationmechanisms paying particular attention to the vectorial directional and timefrequency characteristics of the wireless communication equation for low and highscattering environments.