Luis Diez

Co-creating the cities of the future

In recent years, the evolution of urban environments, jointly with the progress of the Information and Communication sector, have enabled the rapid adoption of new solutions that contribute to the growth in popularity of Smart Cities. Currently, the majority of the world population lives in cities encouraging different stakeholders within these innovative ecosystems to seek new solutions guaranteeing the sustainability and efficiency of such complex environments. In this work, it is discussed how the experimentation with IoT technologies and other data sources form the cities can be utilized to co-create in the OrganiCity project, where key actors like citizens, researchers and other stakeholders shape smart city services and applications in a collaborative fashion. Furthermore, a novel architecture is proposed that enables this organic growth of the future cities, facilitating the experimentation that tailors the adoption of new technologies and services for a better quality of life, as well as agile and dynamic mechanisms for managing cities. In this work, the different components and enablers of the OrganiCity platform are presented and discussed in detail and include, among others, a portal to manage the experiment life cycle, an Urban Data Observatory to explore data assets, and an annotations component to indicate quality of data, with a particular focus on the city-scale opportunistic data collection service operating as an alternative to traditional communications.

Novel impedance matching materials and strategies for air-coupled piezoelectric transducers

This paper reviews the ideal configuration of air-coupled transducers and compares it with that of actual ones. This reveals the main problems present nowadays in the design and construction of these transducers, consequently, some solutions are proposed: 1. Modification of the selection criteria for the matching layers, with a proposal of a new kind of impedance matching materials and 2. New design strategies to cope with the inevitable non-ideal features present in the design.

Design and integration of a low-complexity dosimeter into the smart city for EMF assessment

Despite the increasing usage of mobile communications, strengthened by the growing penetration of smartphones, end users seem to be concerned about the potential health risks of the electromagnetic fields (EMF) induced by such technologies, according to the latest statistics gathered by the Eurobarometer. The Low EMF Exposure Networks (LEXNET) project aims at designing techniques able to reduce the corresponding exposure, without jeopardizing the quality of experience perceived by the end-users. In order to tackle that goal, a first step must be to accurately estimate such exposure, even in large areas, and with real operating networks. This paper introduces the work that is being carried out to deploy a number of low-complexity dosimeters to characterize the EMF at four different bands. The devices exploit the facilities provided by a wireless sensor network testbed, and are therefore integrated as another IoT (Internet of Things) node. The preliminary measurements that are discussed in the paper assess the validity and feasibility of this novel methodology, which provides clear advantages to other traditional procedures, such as the use of drive tests and/or spectrum analyzers.

EMF-Aware Cell Selection in Heterogeneous Cellular Networks

The growing concern on the exposure of users to the electromagnetic field (EMF) has recently brought new challenges to the mobile research community. In this letter, we propose a novel cell association framework for heterogeneous cellular networks (HetNets), which aims to balance the load amongst heterogeneous cells so as to improve the resource usage and to increase the user satisfaction in terms of both data rate and EMF exposure. We model the cell selection problem as a General Assignment Problem (GAP) and we present two heuristic algorithms, which solve it with limited complexity. Our analysis shows that the proposed solutions lead to notable improvements with respect to legacy association schemes.

Electromagnetic Field Assessment as a Smart City Service: The SmartSantander Use-Case

Despite the increasing presence of wireless communications in everyday life, there exist some voices raising concerns about their adverse effects. One particularly relevant example is the potential impact of the electromagnetic field they induce on the population’s health. Traditionally, very specialized methods and devices (dosimetry) have been used to assess the strength of the E-field, with the main objective of checking whether it respects the corresponding regulations. In this paper, we propose a complete novel approach, which exploits the functionality leveraged by a smart city platform. We deploy a number of measuring probes, integrated as sensing devices, to carry out a characterization embracing large areas, as well as long periods of time. This unique platform has been active for more than one year, generating a vast amount of information. We process such information, and the obtained results validate the whole methodology. In addition, we discuss the variation of the E-field caused by cellular networks, considering additional information, such as usage statistics. Finally, we establish the exposure that can be attributed to the base stations within the scenario under analysis.

A Geometric Programming Solution for the Mutual-Interference Model in HetNets

It is well known that the use of heterogeneous networks and densification strategies will be crucial to handle the wireless cellular traffic increase that is foreseen in the forthcoming years. Hence, the scientific community is putting effort into the proposal and assessment of radio resource management solutions for this type of deployments. For that, an accurate modeling of the underlying resources is mandatory. In this letter, we propose a mutual-interference model, which enables a precise estimation of the signal-to-interference and noise ratio (SINR), compared with the widespread constant-load alternative. This is of utter relevance, since the SINR has a direct influence on the spectral efficiency and, consequently, on the resources to be allocated. We also propose a transformation of the corresponding resource assignment problem, so that it can be solved using geometric programming techniques. The validity of this transformation is assessed by comparing the corresponding solution with the one that would have been obtained exploiting a heuristic approach (simulated annealing).

Complementing radio-planning tools to analyze EMF-aware access selection

In spite of the growing presence of wireless communications, some concerns have recently loomed about the potential risks of the exposure to the electromagnetic fields they induce. In this paper we introduce a methodology that would allow to study the performance of enhanced access selection mechanisms, which include the willingness to reduce such exposure. The proposed framework has been conceived with the main goal of complementing other types of analysis that, despite providing a much more accurate characterization of the physical parameters, do not offer the degree of flexibility that would be required to understand the performance of these novel resource management solutions.

An energy-oriented optimization algorithm for solving the cell assignment problem in 4G-LTE communication networks

This paper presents a novel algorithm for solving the cell assignment problem with special emphasis on energy awareness. The algorithm aims at finding the minimum number of base stations (BSs) that have to be turned on to guarantee the required service to the maximum number of users at lowest cost. The main contribution of the algorithm is the design of an effective solution that ensures an optimal assignment in a subset of base stations N ⊆ N resulting in a drastic reduction of the search space within every subset N, eliminating the exponential growth over the number of users M, i.e. reducing the complexity from O(NM) to O(1). A branch-and-bound approach has been designed to determine the optimal base station assignments. Experiments demonstrate that our solution performs as expected in terms of profit, served clients, and energy savings due to active BSs, at the expense of very reasonable execution time overhead.

A reward-based routing protocol to reduce the EMF exposure over wireless mesh networks

This paper presents Reward Based Routing Protocol (RBRP), a novel routing protocol for wireless mesh networks, that aims at reducing and fairly distributing the Electromagnetic Field (EMF) Exposure caused by wireless transmissions. The basis of this protocol is a reward-based scheme in which intermediate nodes forward packets and receive a reward proportional to the degree of exposure they generate. By means of a simulation campaign over the NS-3 framework, we assess that RBRP clearly outperforms a legacy approach in terms of exposure, while it does not show a worse behaviour, when considering other figures of merit.

Design and Implementation of the Open Connectivity Services Framework

The Open Connectivity Services (OConS) framework is currently being defined within the framework of the SAIL project. Its main objective is to offer adaptive connectivity services to seamlessly address user and service requirements while complying with operator policies and dealing with the heterogeneous and changing network conditions of the future Internet. This paper describes a realization of this framework. It supports flexible integration of both legacy and novel mechanisms and protocols by mapping them to three abstract functional entities: information, decision and execution elements. Organization of these entities is done through an orchestration process to combine and integrate the various mechanisms into a full service for the user. We introduce the OConS protocol used for communication between the presented entities as well as the role played by the orchestration process. We then present the concrete example of a testbed based on this implementation, which shows the feasibility and effectiveness of the proposed approach.