Downlink Performance of Dense Antenna Deployment: To Distribute or Concentrate?

TL;DR

This paper compares dense antenna deployment strategies in 5G, finding small cell densification generally outperforms massive MIMO in SIR coverage and energy efficiency, with multi-carrier transmission influencing these outcomes.

Contribution

It provides a novel closed-form derivation of SIR coverage probability for different deployment strategies using stochastic geometry.

Findings

Small cell densification outperforms massive MIMO in SIR and EE.

Increasing sub-bands (L) improves SIR but reduces EE.

The results are validated through numerical simulations.

Abstract

Massive multiple-input multiple-output (massive MIMO) and small cell densification are complementary key 5G enablers. Given a fixed number of the entire base-station antennas per unit area, this paper fairly compares (i) to deploy few base stations (BSs) and concentrate many antennas on each of them, i.e. massive MIMO, and (ii) to deploy more BSs equipped with few antennas, i.e. small cell densification. We observe that small cell densification always outperforms for both signal-to-interference ratio (SIR) coverage and energy efficiency (EE), when each BS serves multiple users via L number of sub-bands (multi-carrier transmission). Moreover, we also observe that larger L increases SIR coverage while decreasing EE, thus urging the necessity of optimal 5G network design. These two observations are based on our novel closed-form SIR coverage probability derivation using stochastic geometry, also validated via numerical simulations.