Joint Power Allocation and Relay Beam-forming in Orbital Angular Momentum Amplify-and-Forward Relay Networks

Orbital Angular Momentum (OAM) is a promising technology that can effectively improve the spectral efficiency of wireless communications. However, it is important for OAM to keep the antenna alignment of transmitter and receiver. The alignment requirements greatly increases the difficulty of the practical application of OAM, especially when there is a barrier or a large turning angle between uniform circular arrays (UCAs). In this letter, we studied the application of amplify-and-forward (AF) relay in multiple-input multiple-output (MIMO) OAM system to solve the problem caused by the existence of UCAs corners. In this work, our goal is to achieve the maximum achievable rate by jointly optimizing the source power allocation matrix and the relay pre-coding matrix, constrained by the power of the source and the relay. The problem is expressed as a convex problem by mathematical operations, and then based on the Lagrange dual method, we solved it by proposing an iterative algorithm. Numerical simulations show the superiority of the algorithm.