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Intelligent reflecting surface enhanced wideband MIMO-OFDM communications From practical model to reflection optimization

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Document pages: 13 pages

Abstract: Intelligent reflecting surface (IRS) is envisioned as a revolutionarytechnology for future wireless communication systems since it can intelligentlychange radio environment and integrate it into wireless communicationoptimization. However, most existing works adopted an ideal IRS reflectionmodel, which is impractical and can cause significant performance degradationin realistic wideband systems. To address this issue, we first study the dualphase- and amplitude-squint effect of reflected signals and present asimplified practical IRS reflection model for wideband signals. Then, an IRSenhanced wideband multiuser multi-input single-output orthogonal frequencydivision multiplexing (MU-MISO-OFDM) system is investigated. We aim to jointlydesign the transmit beamformer and IRS reflection for the case of using bothcontinuous and discrete phase shifters to maximize the average sum-rate overall subcarriers. By exploiting the relationship between sum-rate maximizationand mean square error (MSE) minimization, the original problem is equivalentlytransformed into a multi-block variable problem, which can be efficientlysolved by the block coordinate descent (BCD) method. Complexity and convergencefor both cases are analyzed or illustrated. Simulation results demonstrate thatthe proposed algorithm can offer significant average sum-rate enhancementcompared to that achieved using the ideal IRS reflection model, which confirmsthe importance of the use of the practical model for the design of widebandsystems.

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