Enhanced Shannon Capacity with Orbital Angular Momentum Dimension

Abstract

As the typical physical resource of the electro-magnetic wave, the Orbital Angular Momentum (OAM) provides the wireless transmission system with new dimension. The traditiona~ Shannon capacity just concerns the contribution from the electric field strength, which can not show the new dimension of the OAM. Therefore, the enhanced Shannon capacity with the OAM dimension is proposed in this paper. Specifically, the enhanced Shannon capacity originates from two parts. In the first part, the OAM mode can raise the number of independent parallel channels, which transmit electric field strength signals with the same time and frequency. In the second part, since the physical dimension of OAM is independent of the electric field strength, the OAM can vary over time and carry the information independently, which further increases the capacity. Moreover, the power reuse (i.e., the signal power can contribute to the Signal to Noise Ratio (SNR) at the dedicated dimension) realizes the second part of the above enhanced Shannon capacity, which solves the problem of the marginal effect of the traditional Shannon capacity. Particularly, the enhanced Shannon capacity highlights the potential of OAM transmission.