  While spectrum at millimeter wave (mmWave) frequencies is less scarce than at
traditional frequencies below 6 GHz, still it is not unlimited, in particular
if we consider the requirements from other services using the same band and the
need to license mmWave bands to multiple mobile operators. Therefore, an
efficient spectrum access scheme is critical to harvest the maximum benefit
from emerging mmWave technologies. In this paper, motivated by previous results
where spectrum pooling was proved to be more feasible at high mmWave
frequencies, we study the performance of a hybrid spectrum scheme where
exclusive access is used at frequencies in the 20/30 GHz range while spectrum
pooling/unlicensed spectrum is used at frequencies around 70 GHz. Our
preliminary results show that hybrid spectrum access is a promising approach
for mmWave networks, and motivate further studies to achieve a more complete
understanding of both technical and non technical implications.
