Impact of LOS/NLOS Propagation and Path Loss in Ultra-Dense Cellular Networks

TL;DR

This paper analyzes how LOS and NLOS propagation affect coverage and network performance in ultra-dense cellular networks, revealing that LOS can both improve and hinder coverage depending on the path loss model and association strategy.

Contribution

It introduces a stochastic geometry model incorporating LOS and NLOS components, providing new insights into their impact on coverage probability in UDNs.

Findings

LOS improves coverage with nearest BS association under singular path loss.

Dual slope path loss shows LOS benefits with nearest BS but not with strongest BS association.

Derived tight bounds and expressions for coverage probability considering LOS/NLOS effects.

Abstract

Most prior work on performance analysis of ultra-dense cellular networks (UDNs) has considered standard power-law path loss models and non-line-of-sight (NLOS) propagation modeled by Rayleigh fading. The effect of line-of-sight (LOS) on coverage and throughput and its implication on network densification are still not fully understood. In this paper, we investigate the performance of UDNs when the signal propagation includes both LOS and NLOS components. Using a stochastic geometry based cellular network model, we derive expressions for the coverage probability, as well as tight approximations and upper bounds for both closest and strongest base station (BS) association. Our results show that under standard singular path loss model, LOS propagation increases the coverage, especially with nearest BS association. On the contrary, using dual slope path loss, LOS propagation is beneficial with closest BS association and detrimental for strongest BS association.