A Flexible Licensed Spectrum Allocation Technique for Millimeter-Wave Mobile Systems Toward 6G

In this paper, we propose a flexible licensed spectrum allocation (FLSA) technique to liberalize allocating the licensed 28 GHz millimeter-wave (mmWave) spectrum to mobile network operators (MNOs) of a country to achieve countrywide high spectrum utilization. The proposed FLSA technique liberalizes allocating the licensed mmWave spectrum exclusively to an MNO for a certain renewal term in accordance with its number of subscribers with respect to that of other MNOs. The spectrum allocated to an MNO is updated at each renewal term compliant with the change in its number of subscribers over the previous term. We formulate FLSA and find the optimal amount of spectrum for each MNO at each renewal term. We derive average capacity, spectral efficiency (SE), energy efficiency (EE), and cost efficiency (CE) for all MNOs. Extensive numerical and simulation results for an example scenario of a country consisting of four MNOs show that FLSA can improve both average capacity and SE by 25%, whereas EE and CE by 20% countrywide. Moreover, we show that FLSA can achieve both SE and EE requirements for sixth-generation (6G) mobile systems by reusing the spectrum per MNO to small cells of about 18% less number of buildings.