Will the Area Spectral Efficiency Monotonically Grow as Small Cells Go Dense?

TL;DR

This paper analyzes how the area spectral efficiency (ASE) in small cell networks is affected by increasing cell density, considering both LoS and NLoS transmissions, revealing that ASE may decrease beyond a certain density threshold.

Contribution

The study introduces a detailed path loss model with LoS/NLoS differentiation into stochastic geometry analysis, providing new insights into ASE behavior in ultra-dense small cell networks.

Findings

ASE growth slows down or decreases beyond a certain small cell density

LoS/NLoS differentiation significantly impacts coverage and ASE analysis

Practical small cell deployment strategies should consider the non-monotonic ASE behavior

Abstract

In this paper, we introduce a sophisticated path loss model into the stochastic geometry analysis incorporating both line-of-sight (LoS) and non-line-of-sight (NLoS) transmissions to study their performance impact in small cell networks (SCNs). Analytical results are obtained on the coverage probability and the area spectral efficiency (ASE) assuming both a general path loss model and a special case of path loss model recommended by the 3rd Generation Partnership Project (3GPP) standards. The performance impact of LoS and NLoS transmissions in SCNs in terms of the coverage probability and the ASE is shown to be significant both quantitatively and qualitatively, compared with previous work that does not differentiate LoS and NLoS transmissions. Particularly, our analysis demonstrates that when the density of small cells is larger than a threshold, the network coverage probability will decrease as small cells become denser, which in turn makes the ASE suffer from a slow growth or even a notable decrease. For practical regime of small cell density, the performance results derived from our analysis are distinctively different from previous results, and shed new insights on the design and deployment of future dense/ultra-dense SCNs.