Millimeter-Wave Spectrum Utilization Improvement in Multi-Operator Networks: A Framework Using the Equal Likelihood Criterion

In this paper, we present a framework to give a comprehensive review of how to improve the spectrum utilization of millimeter-wave (mmWave) systems using indoor small cells in multi-operator network scenarios. More specifically, the framework concerns with the improvement of the utilization of the 28 GHz mmWave spectrum allocated to an arbitrary number of mobile network operators (MNOs) in a country using numerous spectrum allocation techniques, namely Static and Equal Spectrum Allocation (SESA), Flexible and Unequal Spectrum Allocation (FUSA), and Countrywide Full Spectrum Allocation (CFSA). A number of spectrum utilization improvement mechanisms such as spectrum trading, spectrum sharing, and spectrum reusing are then exploited into SESA, FUSA, and CFSA techniques in four major-interconnected domains, including time, frequency, power, and space. Using the Equal Likelihood Criterion and the properties of left-justified Pascal’s triangle, the average capacity, spectral efficiency (SE), and energy efficiency (EE) performance metrics for each spectrum allocation technique in each domain are derived. Extensive system-level numerical and simulation results and analyses are carried out to evaluate the performance of each technique in each domain for example scenario of a country with four MNOs. Overall, it is shown that, in the power-domain, CFSA outperforms SESA and FUSA (when operating either at the interweave or at the underlay spectrum access technique), whereas, in the time-domain and frequency-domain, SESA and FUSA outperform CFSA, in terms of the average capacity, SE, and EE. Finally, we show that CFSA in the power-domain outperforms SESA and FUSA operating in any domain to achieve the prospective SE and EE requirements for the sixth-generation (6G) mobile networks.