A Technique for Massive Spectrum Sharing with Ultra-Dense In-Building Small Cells in 5G Era

This paper presents a technique to share extensively both licensed and unlicensed spectrums with densely deployed small cells (SCs) in 3- dimensional (3D) multistory buildings to achieve high spectral and energy efficiencies for fifth generation (5G) mobile networks. We consider non- orthogonal spectrum sharing with SCs in each building by forming 3D clusters of SCs subject to a minimum distance between co-channel SCs. Therefore, the same spectrum can be reused multiple times per building by sharing with SCs in each 3D cluster. We assume that SCs are enabled with multiband, i.e. dual-band, to exploit licensed shared access (LSA) to share the licensed space-satellite spectrum and licensed assisted access (LAA) to share the 60 GHz unlicensed spectrum with SCs. We derive system- level capacity, spectral efficiency, and energy efficiency metrics for non-orthogonal spectrum sharing with SCs in L>1 buildings over a macrocell coverage of a mobile network. Extensive system level simulation is carried out. It is shown that the proposed non-orthogonal spectrum sharing technique outperforms significantly the technique for orthogonal spectrum sharing for both LSA and LAA and can meet easily the expected spectral efficiency and energy efficiency requirements for 5G mobile networks.