# The Impact of Antenna Height Difference on the Performance of Downlink Cellular Networks

## TL;DR

This paper analyzes how antenna height differences impact the performance of dense downlink cellular networks, revealing that increased density can degrade coverage and throughput, with optimal density balancing these effects.

## Contribution

It introduces a model considering practical antenna height differences and derives the relationship between network density, coverage, and throughput, providing guidelines for network densification.

## Key findings

- Coverage probability and throughput decrease with high base station density.
- Critical density for maximizing throughput is inversely proportional to the square of antenna height difference.
- Network densification benefits are limited by antenna height differences.

## Abstract

Capable of significantly reducing cell size and enhancing spatial reuse, network densification is shown to be one of the most dominant approaches to expand network capacity. Due to the scarcity of available spectrum resources, nevertheless, the over-deployment of network infrastructures, e.g., cellular base stations (BSs), would strengthen the inter-cell interference as well, thus in turn deteriorating the system performance. On this account, we investigate the performance of downlink cellular networks in terms of user coverage probability (CP) and network spatial throughput (ST), aiming to shed light on the limitation of network densification. Notably, it is shown that both CP and ST would be degraded and even diminish to be zero when BS density is sufficiently large, provided that practical antenna height difference (AHD) between BSs and users is involved to characterize pathloss. Moreover, the results also reveal that the increase of network ST is at the expense of the degradation of CP. Therefore, to balance the tradeoff between user and network performance, we further study the critical density, under which ST could be maximized under the CP constraint. Through a special case study, it follows that the critical density is inversely proportional to the square of AHD. The results in this work could provide helpful guideline towards the application of network densification in the next-generation wireless networks.