Comparative evaluation of semi-passive versus fully passive IRS channel estimation

Establish a rigorous performance-and-cost comparison between semi-passive intelligent reflecting surface (IRS) channel estimation—where sensing devices with receive RF chains are integrated into the IRS—and fully passive IRS channel estimation based on cascaded user–IRS–base-station channels, identifying the operating regimes and system conditions under which each approach is preferable.

Background

The paper presents two IRS configurations for channel estimation: semi-passive IRSs equipped with sensors/receive chains enable direct estimation of BS/user-to-IRS channels, while fully passive IRSs rely on estimating cascaded channels at the BS/user via training and reflection patterns.

Although many design methods exist for the passive approach and initial schemes exist for semi-passive designs, a principled comparison in terms of estimation accuracy, overhead, energy consumption, hardware cost, and overall system performance has not been established.

References

It is noted that there has been very limited work on semi-passive IRS channel estimation, and it is still unclear how this approach is compared with the passive IRS channel estimation in terms of performance and cost.

— Intelligent Reflecting Surface Aided Wireless Communications: A Tutorial (2007.02759 - Wu et al., 2020) in Section IV-C (Other Related Work and Future Direction)