Capacity Analysis of Multi-Pair Orbital Angular Momentum Interference Networks

In this paper, we investigate a multi-pair orbital angular momentum (OAM) interference network adopting mode- division multiplexing (MDM) at each transmitter, where multiple transmitter-receiver pairs exploit the same multiple OAM modes. Even though many previous studies on the OAM-MDM exist in literature, they only focused on a single transmitter-receiver pair and did not consider the inter-pair interference. In practice, wireless fronthaul and backhaul links reuse the same frequency band and they may interfere with each other. We first mathematically characterize the Laguerre-Gaussian (LG) beam-based OAM wireless channel and then analyze the channel capacity of the multi-pair OAM interference channel. It is worth noting that this is the first theoretical result in literature. Through extensive computer simulations, we validate the channel capacity of the multi-pair OAM-MDM interference channel by considering the interference among different OAM beams according to various system parameters such as the number of OAM modes, the distance between the transmitter and receiver, the distance between adjacent transmit antennas, the waist of the OAM beams, etc.