Optimal pilot power based channel estimation improves the throughput of intelligent reflective surface assisted systems

Intelligent reflecting surfaces (IRS) have emerged as a promising technology of managing the radio signal propagation by relying on a large number of low-cost passive reflecting elements. In this letter, the optimal pilot power allocation required for accurate channel estimation of IRS-assisted communication systems is investigated. In contrast to conventional channel estimators, where pilot signals are usually designed to be constant-enveloped, we reconsider the pilot design to improve the passive beamforming performance thus resulting in an improved achievable rate. At first sight the result of our analysis appears counter-intuitive, suggesting that at a given total power, more power should be allocated to estimate low-gain channels, since the channel phase impairments are more severe than those of highgain channels. Our simulation results show that when the number of IRS elements is 4, the rate improvement of our proposed channel estimation scheme over the conventional counterpart may be as high as 25%