6G Wireless Communications in 7–24 GHz Band: Opportunities, Techniques, and Challenges

The sixth generation (6G) wireless communication nowadays is seeking a new spectrum to inherit the pros and discard the cons of sub-6 GHz, millimeter-wave (mmWave), and sub-terahertz (THz) bands. To this end, an upper mid-band with a Frequency Range (FR) spanning from 7 GHz to 24 GHz, also known as FR3, has emerged as a focal point in 6G communications. Thus, as an inevitable prerequisite, a comprehensive investigation encompassing spectrum utilization and channel characteristics is the first step to exploiting potential applications and prospects of using FR3 in the 6G ecosystem. In this paper, we provide FR3 synergies with emerging technologies including non-terrestrial network (NTN), massive multi-input multi-output (mMIMO), reconfigurable intelligent surface (RIS), and integrated sensing and communications (ISAC). Furthermore, leveraging ray-tracing simulations, our investigation unveils the similarity of channel characteristics in FR3 with other FRs. The analysis of RIS-aided communication shows the insight of higher spectral efficiency achieved in FR3 compared to other FRs when using the same RIS size. Finally, challenges and promising directions are discussed for wireless systems in FR3.