Downlink and Uplink Cell Association with Traditional Macrocells and Millimeter Wave Small Cells

TL;DR

This paper develops an analytical model for cell association in hybrid networks with sub-6 GHz macrocells and mmWave small cells, analyzing uplink and downlink strategies and the impact of biasing on performance.

Contribution

It introduces a comprehensive analytical framework for mixed macrocell and mmWave small cell networks, including decoupled association strategies and biasing effects.

Findings

Decoupled uplink and downlink association improves coverage.

High biasing values are beneficial for mmWave small cells.

Analytical results closely match simulation data.

Abstract

Millimeter wave (mmWave) links will offer high capacity but are poor at penetrating into or diffracting around solid objects. Thus, we consider a hybrid cellular network with traditional sub 6 GHz macrocells coexisting with denser mmWave small cells, where a mobile user can connect to either opportunistically. We develop a general analytical model to characterize and derive the uplink and downlink cell association in view of the SINR and rate coverage probabilities in such a mixed deployment. We offer extensive validation of these analytical results (which rely on several simplifying assumptions) with simulation results. Using the analytical results, different decoupled uplink and downlink cell association strategies are investigated and their superiority is shown compared to the traditional coupled approach. Finally, small cell biasing in mmWave is studied, and we show that unprecedented biasing values are desirable due to the wide bandwidth.