On the Coverage and Capacity of Ultra-Dense Networks with Directional Transmissions

TL;DR

This paper analyzes the coverage and capacity of ultra-dense networks with directional transmissions, revealing how beam pattern adaptation can mitigate interference issues in extremely dense deployments.

Contribution

It provides new analytical expressions and asymptotic analysis for coverage probability and ASE in UDNs considering realistic path loss and beamforming patterns.

Findings

Beam pattern adaptation prevents coverage degradation at high base station densities.

Coverage probability decreases when near-field path loss exponent ≤ 2, unless mitigation strategies are used.

Asymptotic analysis shows potential for unlimited densification with proper beamforming.

Abstract

We investigate the performance of a downlink ultra-dense network (UDN) with directional transmissions via stochastic geometry. Considering the dual-slope path loss model and sectored beamforming pattern, we derive the expressions and asymptotic characteristics of the coverage probability and constrained area spectrum efficiency (ASE). Several special scenarios, namely the physically feasible path loss model and adjustable beam pattern, are also analyzed. Although signal-to-interference-plus-noise ratio collapsing still exists when the path loss exponent in the near-field is no larger than 2, using strategies like beam pattern adaption, can avoid the decrease of the coverage probability and constrained ASE even when the base station density approaches infinity.