Multi-Tier mmWave Networks: Improving Fairness for Spectrally-Efficient Downlink Scheduling

Millimeter wave (mmWave) communications provide a very promising solution to bandwidth scarcity. However, mmWave signals suffer from high attenuation and are very susceptible to blockage, which makes traditional cellular network architectures unsuitable. Multi-tier mmWave network architectures leverage relay access points (APs) to shorten transmission distances and alleviate blockage, but such architectures pose challenges to the scheduling between each tier. To address this, here we analyze the downlink scheduling problem for a multi-tier mmWave network, and we propose a cross-tier scheduling scheme with polynomial complexity, which ensures every user is served by at least one access point while optimizing sum throughput. Numerical analysis shows that the proposed scheduling has major gains in downlink rate fairness and service coverage, with only a small reduction in spectral efficiency compared to the state-of-art.