Low-Complexity Phase Shift Design for IRS-Aided SU-MIMO Wireless Systems

In this paper, we propose a cost-efficient phase shift design algorithm for a single-user multiple-input multiple-output wireless system assisted by the intelligent reflecting surface. From the baseline algorithm, two-step hardware-aware algorithm-level optimization techniques are newly introduced to reduce the required number of multiply-accumulate (MAC) operations. For the first step, the low-cost iterative-free matrix is constructed to replace the complicated inversion matrix by exploiting spatial correlatedness among the reflecting elements. Then, the previously designed matrix is approximated by exploiting the diagonally-dominant characteristic of the matrix, further optimizing the computational complexity of the algorithm. Experimental results show that the fully-optimized algorithm with the proposed two-step optimization techniques reduces 98.6% of total cost compared to the baseline algorithm while achieving comparable algorithm-level performance.