Abstract

In this paper, we analyze and optimize the energy efficiency of downlink cellular networks. With the aid of tools from stochastic geometry, we introduce a new closed-form analytical expression of the potential spectral efficiency (bit/sec/m2). In the interference-limited regime for data transmission, unlike currently available mathematical frameworks, the proposed analytical formulation depends on the transmit power and deployment density of the base stations. This is obtained by generalizing the definition of coverage probability and by accounting for the sensitivity of the receiver not only during the decoding of information data, but during the cell association phase as well. Based on the new formulation of the potential spectral efficiency, the energy efficiency (bit/Joule) is given in a tractable closed-form formula. An optimization problem is formulated and is comprehensively studied. It is mathematically proved, in particular, that the energy efficiency is a unimodal and strictly pseudo-concave function in the transmit power, given the density of the base stations, and in the density of the base stations, given the transmit power. Under these assumptions, therefore, a unique transmit power and density of the base stations exist, which maximize the energy efficiency. Numerical results are illustrated in order to confirm the obtained findings and to prove the usefulness of the proposed framework for optimizing the network planning and deployment of cellular networks from the energy efficiency standpoint.

Highlights

  • The Energy Efficiency (EE) is regarded as a key performance metric towards the optimization of operational cellular networks, and the network planning and deploymentManuscript received August 2, 2017; revised November 19, 2017; accepted January 9, 2018

  • We have introduced a new closedform analytical expression of the potential spectral efficiency of cellular networks

  • Unlike currently available analytical frameworks, we have shown that the proposed approach allows us to account for the tight interplay between transmit power and density of the base stations in cellular networks

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Summary

INTRODUCTION

The Energy Efficiency (EE) is regarded as a key performance metric towards the optimization of operational cellular networks, and the network planning and deployment. It is worth nothing that the conclusion that the PSE is independent of Ptx is valid regardless of the specific path-loss model being used2 It depends, on the other hand, on the assumptions of interference-limited operating regime and of having BSs that emit the same Ptx. It depends, on the other hand, on the assumptions of interference-limited operating regime and of having BSs that emit the same Ptx Based on these observations, we conclude that a new analytical formulation of the PSE that explicitly depends on the transmit power and density of the BSs, and that is tractable enough for system-level EE optimization is needed. This approach, in addition, has the inconvenience of formulating the optimization problem for an operating regime where cellular networks are unlikely to operate in practice

State-of-the-Art on System-Level EE Optimization
Research Contribution and Novelty
SYSTEM MODEL
Cellular Network Modeling
Load Modeling
Cell Association Criterion
Power Consumption Modeling
A NEW ANALYTICAL FORMULATION OF THE PSE
Analytical Formulation of the PSE
Closed-Form Expressions of PSE and Pgrid
SYSTEM-LEVEL EE OPTIMIZATION
Preliminaries
Optimal Transmit Power Given the Density of the BSs
Optimal Density Given the Transmit Power of the BSs
On the Dependency of Optimal Transmit Power and Density of the BSs
Joint Optimization of Transmit Power and Density of the BSs
10 LM-1 LM-2
CONCLUSION
Full Text
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