A Theoretical Framework Toward Realizing Spectral and Energy Efficiencies of 6G Mobile Networks

This paper presents a theoretical framework by exploiting the four most interconnected-domain, including, power, time, frequency, and space, with in-building small cells to address expected spectral efficiency and energy efficiency requirements for the future sixth-generation (6G) mobile networks. More specifically, the framework takes advantage of higher degrees of freedom by employing multiband enabled small cells in frequency-domain, non-orthogonal spectrum reuses to small cells per building in spatial-domain, on/off switching of small cells in power-domain, and eICIC techniques due to sharing spectrums with small cells in time-domain. System-level average capacity, spectral efficiency, and energy efficiency metrics are derived, and extensive numerical and simulation results are carried out to demonstrate the impact of each domain on spectral efficiency and energy efficiency performances. Finally, it is shown that the proposed framework can satisfy the expected spectral efficiency and energy efficiency requirements for 6G mobile networks.