On the Use of Composite Indicators for Mobile Communications Network Management in Smart Sustainable Cities  
[PERSON]  
1 Computer Science Department, Universitat de Valencia, Avinguda de la Universitat s/n, 46100 Burjassot, Spain; [EMAIL_ADDRESS] (J.S. ); [EMAIL_ADDRESS] (S.R. )1 Computer Science Department, Universitat de Valencia, Avinguda de la Universitat s/n, 46100 Burjassot, Spain; jpaquin. gas emissions and contribute within the whole ICTs framework to keep the carbon emission levels in vertical sectors as in 2015, as supported by the Global e-Sustainability Initiative (GeSI) ([[http://gesi.org/](http://gesi.org/)]([http://gesi.org/](http://gesi.org/))). The aim is to reduce the increasing effect of global connectivity and Internet usage on the global energy consumption. One of the largest challenges will be met in densely populated areas, since the capacity of mobile communications networks will be easily reached. United Nations predictions establish that, by 2050, 70% of the world's population will be concentrated in densely populated urban areas. In fact, half of humanity (3.5 billion people) lives in cities today and five-billion people are projected to live in cities by 2030. SDGs define several lines of action regarding this scenario. In particular, Goal 11 \"sustainable cities and communities\" has been proposed in order to tackle this problem, and it is within this Goal, where the smart city paradigm, which is intertwined with beyond 5G communication technologies, becomes of paramount importance. ICTs are then the key in order to ensure a minimum quality of life for citizenship, allowing for the development of affordable and sustainable infrastructures and services. Smart cities require a dense deployment of sensing nodes or access points in order to gather the massive amount of data that are needed to perform the different applications based on the Internet of Things (IoT). Ultra-dense networks are foreseen from the point of view of mobile communications networks [6]. Ultra-dense networks, which can be seen as a densification of heterogeneous networks, are key in 5G cellular network technology [7]. Heterogeneous networks stood as the natural evolution of homogeneous macrocell-based networks, and they have been traditionally defined as the deployment of small cells (femtocells, picocells, relays, or remote radio heads) in the same geographical area as regular macrocells [8]. Unlike macrocell base stations, small base stations are not regularly spaced; instead, they are scattered over the macrocell network. Traditional metrics for measuring and comparing the performance of different designs and technologies in homogeneous networks are the coverage probability and spectral efficiency. However, the particular features of ultra-dense networks support the use of metrics, such as user rate distribution or area spectral efficiency [8]. When evaluating the performance of a given technological solution for mobile communications networks, the main focus is in how capacity achieving this is. However, fairness is a fundamental concept from the point of view of the operation and management of the networks [9], which addresses from the allocation and supply of resources to users [10], to the balance between different communication layers. Hence, fairness is an important input for obtaining a sustainable usage of ultra-dense networks in densely populated areas. Recent 5G standards and beyond 5G research items introduce softwarization, programmability, and virtualization at different layers of the network in order to enable the optimization of global performance, efficiency, automation, and security. Thanks to this new enablers, there is a huge flexibility potential, which paves the way for a cognitive management of mobile communications networks, including the aspects of self-optimization and self-reconfiguration, which are fundamental in ultra-dense networks.