What is the Optimal Network Deployment for a Fixed Density of Antennas?

TL;DR

This paper investigates the optimal network deployment strategy for fixed antenna density, balancing BS density and antennas per BS to maximize area spectral efficiency considering practical factors like pilot contamination and LoS/NLoS conditions.

Contribution

It introduces a comprehensive evaluation of the trade-offs between BS density and antennas per BS under fixed antenna density, providing insights into optimal deployment for maximizing spectral efficiency.

Findings

Existence of an optimal BS density for given UE density.

Trade-off between receive power gain and beamforming gain.

Densification improves power gain but is limited by pilot contamination.

Abstract

In this paper, we answer a fundamental question: when the total number of antennas per square kilometer is fixed, what is the optimal network deployment? A denser network with a less number of antennas per base station (BS) or the opposite case. To evaluate network performance, we consider a practical network scenario with a fixed antennas density and multiuser multiple-input-multiple-output (MU-MIMO) operations for single-antenna users. The number of antennas in each BS is calculated by dividing the antenna density by the BS density. With the consideration of several practical network models, i.e., pilot contamination, a limited user equipment (UE) density and probabilistic line-of-sight (LoS)/non-line-of-sight (NLoS) path loss model, we evaluate the area spectral efficiency (ASE) performance. From our simulation results, we conclude that there exists an optimal BS density for a certain UE density to maximize the ASE performance when the antenna density is fixed. The intuition is that (i) by densifying the network with more BSs, we can achieve a receive power gain due to the smaller distance between the typical UE and its serving BS; (ii) by installing more antennas in each BS, we can achieve a beamforming gain for UEs using MU-MIMO, although such beamforming gain is degraded by pilot contamination; (iii) thus, a trade-off exists between the receive power gain and the beamforming gain, if we fix the antenna density in the network.