— The channel capacity of a MIMO telecommunication system depends on different parameters such as the signal-to-noise ratio, the space-time characteristics of the propagation channel, the antenna array geometry and the antenna pattern. However, the propagation channel remains the strongest constraint imposed on designers of new radio air interfaces. Using a MIMO channel model, computer simulations are performed to highlight the relation between the radiation pattern of subspace channels and the physical space-time characteristics of the propagation channel. This provides a better understanding of the subspace channel origins and achievability of degrees of freedom. In addition to the simulation approach, UWB MIMO channel measurements are used. Both simulation and experimental results show that there is not a bijective relation between physical paths and subspace channels. The number of subspace channels is the same but the amplitudes and directions can be different, leading to inaccuracies in the space-time characteristics of the propagation channel. Nevertheless, the results are promising for fast-jointed DoA-DoD channel estimation.