Integrated approach for antenna reduction and enhanced channel estimation in massive MIMO systems using semi-passive intelligent reflecting surfaces

Abstract

Although massive multiple-input multiple-output (MIMO) systems offer substantial gains in spectral and energy efficiency, they require a large number of expensive active antennas at base station (BS). Intelligent reflecting surface (IRS), comprising semi-passive elements, present a potential solution to reduce deployment costs. This paper investigates the integration of IRS semi-passive elements to achieve a substantial reduction in the number of BS antennas while enhancing channel estimation techniques in massive MIMO systems. The main goal is to find the optimal number of IRS elements to reduce BS antennas cost-effectively, offering guidance to network designers. In addition, we propose a novel channel estimation approach tailored for IRS-integrated systems. Through rigorous analysis, we derive a closed-form formula that clarifies the relationship between the number of BS antennas and the number of IRS elements required for optimal reduction. Furthermore, we present a comparative evaluation of our proposed channel estimation technique against state-of-the-art methods, demonstrating its novelty, advantages, and performance characteristics. According to our findings, integrating approximately 30 IRS elements achieves a decrease of nearly 50% in the number of BS antennas. The suggested channel estimate method exhibits superior performance in IRS-integrated systems, offering valuable insights for practical implementation.