Network Deployment for Maximal Energy Efficiency in Uplink with Zero-Forcing

TL;DR

This paper develops an optimization framework for uplink cellular networks with multi-antenna base stations, zero-forcing detection, and imperfect channel knowledge, to maximize energy efficiency through joint parameter tuning.

Contribution

It introduces a new lower bound on spectral efficiency and derives closed-form expressions for optimizing pilot reuse, antennas, and users, revealing the advantages of zero-forcing over maximum ratio combining.

Findings

Massive MIMO configurations are optimal for energy efficiency.

Zero-forcing outperforms maximum ratio combining in EE.

Optimized parameters lead to denser network deployments.

Abstract

This work aims to design a cellular network for maximal energy efficiency (EE). In particular, we consider the uplink with multi-antenna base stations and assume that zero- forcing (ZF) combining is used for data detection with imperfect channel state information. Using stochastic geometry and a new lower bound on the average per-user spectral efficiency of the network, we optimize the pilot reuse factor, number of antennas and users per base station. Closed-form expressions are computed from which valuable insights into the interplay between the optimization variables, hardware characteristics, and propagation environment are obtained. Numerical results are used to validate the analysis and make comparisons with a network using maximum ratio (MR) combining. The results show that a Massive MIMO setup arises as the EE-optimal network configuration. In addition, ZF provides higher EE than MR while allowing a smaller pilot reuse factor and a more dense network deployment.