Two-Stage Precoding Design in Rician Channel for HAP Massive MIMO Systems

In this paper, we propose a new two-stage precoding design for the high altitude platform (HAP) massive MultipleInput Multiple-Output (MIMO) systems. The outer precoding design is based on the lower bound of the signal-to-leakage-plusnoise-ratio (SLNR) and then the SLNR-based design problem is reduced to a trace quotient problem (TQP) in Rician channel. An iterative algorithm is proposed to achieve the optimal results for the TQP. Numerical results illustrate that the proposed method has better sum rate performance for the HAP Massive MIMO systems and lower computational complexity compared to the existing outer precoding design for the Rician channel.