Wireless channel performance with topological antenna diversity

Topological Antenna Diversity is achieved through exploitation of the Orbital Angular Momentum (OAM) of the transmitted electromagnetic wave. Topological diversity has recently been proposed as a great potential of improving the spectral efficiency (capacity) of radio transmissions [1]. OAM accounts for the phase front of the transmitted wave by providing independent phase states, thus, additional modes of propagation (degrees of freedom) resulting in independent simultaneous wireless radio links. OAM transmission has only very recently been applied to radio transmissions at much lower frequencies [1], [2], [3], [4] and, as such, these experiments raise as many questions as answers. For example, what aspects are fundamentally new? How can we best exploit this fascinating technique for realistic wireless systems? What are the benefits of OAM transmissions compared to multiple input-multiple output (MIMO) systems in terms of both simplicity and performance improvement?