Cost–benefit of joint reflection amplitude and phase optimization for IRS elements

Ascertain whether the performance gain achieved by jointly optimizing the reflection amplitude and phase shifts of intelligent reflecting surface elements—where the control variables may be either discrete or continuous—is sufficiently large to justify the increased hardware cost and algorithmic complexity in practical IRS-aided wireless communication systems.

Background

The paper studies beamforming optimization for IRS-aided wireless systems under practical discrete phase-shift constraints, assuming unit reflection amplitude for each IRS element (i.e., amplitude fixed to maximize reflection). While amplitude control is theoretically possible, it is costlier to implement alongside phase control.

In the conclusion, the authors highlight that although optimizing both amplitude and phase could improve performance, solving the joint optimization is more challenging. Critically, they explicitly state that it is unclear whether the additional performance gain would be large enough to justify the increased hardware cost and algorithm complexity, identifying a key open question for practical design trade-offs.