etic field on the surface [63]. In terms of information transmission, the uniqueness theorem is a rather tight bottleneck. Even if we have six possible quantities for encoding information, only two of them are able to carry independent information. In other words, it states that polarization increases the Number of Degrees of Freedom available by a factor of up to 2. In the following the Number of Degrees of Freedom associated with polarization will be called PNDF. The uniqueness theorem is a consequence of some subtle relations present in Maxwell's equations in free space: the divergence equations impose a dependence between the components of the electric field and the components of the magnetic field SO that one of the three components of E and of H vectors is related to the other two, while the curl equations impose a dependence between E and H. The uniqueness theorem states also that the maximum amount of information can be collected on a surface surrounding the source, and collecting data on multiple surfaces or in volumes does not offer improvements. However, in practical cases the observation domain So does not surround the entire source, and it is often quite small. In this case the estimation of the degrees of freedom of the field is not easy. Loosely speaking, when we consider the full functional dependence of the communication process at the DPL, the Hilbert- Schmidt decomposition is applied to the full electric and magnetic vector fields (e(r, t), h(r, t)) observed on the surface S. The number of singular values above the uncertainty level is the Space-Time-Polarization Number of Degrees of Freedom of the Field (STPNDF). In the case of a small observation domain (e.g., using antennas whose size does not exceed a couple of wavelengths), the STPNDF is small and the singular values of the radiation operator tend to decrease more slowly than for large antennas. In this case it is possible to get a couple of "extra" degrees of freedom since we have a couple of singular values above the noise which we would