Modified Block Coordinate Descent Method for Intelligent Reflecting Surface-Aided Space-Time Line Coded Systems

Abstract

The intelligent reflecting surface (IRS) technology can be combined with the space-time line code (STLC) to reduce the channel estimation overhead for adjusting the IRS phase shifts. However, the computational complexity to design the phase shift values of IRS elements can increase prohibitively with the increment of IRS elements. To reduce the design complexity for the IRS-aided STLC system, we propose a modified block coordinate descent (MBCD) algorithm that can simply design the phase shift values of the IRS. The proposed MBCD algorithm can dramatically reduce the computational complexity with no compromise of performance compared to the various existing methods, such as a semidefinite relaxation method, an alternating direction method of multipliers, an analytic constant modulus algorithm, and a complex unit-modulus constraint relaxation method.