Weighted Sum-Rate Comparisons in IRS-Aided STLC Systems Considering Signaling Overhead

In this study, an intelligent reflecting surface (IRS)-aided space-time line coded system is considered. The IRS phase shift methods maximizing the instantaneous signal-to-noise ratio (SNR) can achieve near-optimal IRS beamforming performance but require high signaling overhead to obtain every instantaneous channel state information. The IRS phase shift methods maximizing average SNR can reduce signaling overhead while the IRS beamforming gain is degraded. Considering the signaling overheads and IRS beamforming gain, the weighted sum-rate is modeled to compare the instantaneous and average SNR maximization methods. Simulation results show that as the line-of-sight path weakens, the instantaneous SNR maximization methods outperform the average SNR maximization methods. On the other hand, as the number of IRS elements and/or uplink weight increases, the average SNR maximization methods can outperform the instantaneous SNR maximization methods.