Can We Benefit from Reconfigurable Intelligent Surfaces in Upper Mid-Band 6G Networks? A Critical Look for Promising Use Cases

The upper mid-band frequencies (i.e., 7-24,GHz) are regarded as the golden bands for the sixth-generation (6G) wireless communication systems, combining good coverage, much new spectrum, and many antennas in compact form factors. The first 6G networks will most likely use this band. There is much prior work on channel modeling, coexistence, and possible implementation scenarios in these bands. On the other hand, the use of reconfigurable intelligent surfaces (RISs) has not yet been examined in these bands, even if this transformative technology has generally garnered considerable attention in recent years for its ability to enhance spectral efficiency, coverage, and reliability of wireless channels. There are significant frequency-specific challenges related to RIS deployment, use cases, number of required elements, channel estimation, and control. These are previously unaddressed for the upper mid-band. In this paper, we aim to bridge this gap by exploring various use cases, including RIS-assisted fixed wireless access (FWA), enhanced capacity in mobile communications, and increased reliability at the cell edge. We identify the conditions under which RIS can provide major benefits and optimal strategies for deploying RIS to enhance the performance of 6G upper mid-band communication systems.