Ultra-Dense Networks for 5G and Beyond

1Fundamental Limits of Ultra‐dense Networks

Marios Kountouris and Van Minh Nguyen

Mathematical and Algorithmic Sciences Lab, Paris Research Center, Huawei Technologies Co. Ltd., France

1.1 Introduction

Mobile traffic has significantly increased over the last decade, mainly due to the stunning expansion of smart wireless devices and bandwidth‐demanding applications. This trend is forecast to be maintained, especially with the deployment of fifth generation (5G) and beyond networks and machine‐type communications. A major part of the mobile throughput growth during the past few years has been enabled by the so‐called network densification, i.e. adding more base stations (BSs) and access points and exploiting spatial reuse of the spectrum. Emerging 5G cellular network deployments are envisaged to be heterogeneous and dense, primarily through the provisioning of small cells such as picocells and femtocells. Ultra‐dense networks (UDNs) will remain among the most promising solutions to boost capacity and to enhance coverage with low‐cost and power‐efficient infrastructure in 5G networks. The underlying foundation of this expectation is the presumed linear capacity scaling with the number of small cells deployed in the network. In other words, doubling the number of BSs doubles the capacity the network supports in a given area and this can be done indefinitely. Nevertheless, in this context, several important questions arise: how close are we to fundamental limits of network densification? ...