I. Introduction
In order to support the rising demand for ubiquitous wireless connectivity anywhere in the upcoming Internet-of-Everything (IoE) era, along with the soaring data-hungry applications development, fifth-generation (5G) cellular networks may not be adequately efficient to meet the demands in terms of capacity. This observation leads the researchers to carry out cutting-edge research to explore newer dimensions in upcoming sixth-generation (6G) cellular technology. Intelligent reflecting surface (IRS) is a key enabler of data transmission technology, with a vision to be deployed in 6G cellular communication systems to significantly enhance spectral efficiency. IRS is the advanced version of massive multiple-input multi-output (mMIMO) data transmission system [1], which is the prime transmission technology in 5G cellular networks. IRS is a controllable metasurface comprised of a large number of passive reflecting elements (PREs) that use very little power to control the phase and/or amplitude changes of incident signals to the IRS [2], [3], [4], [5].