Resumen de Análisis y desarrollo de mejoras para la reducción a la exposición a campos electromagnéticos en redes heterogéneas
- español
Junto con los retos técnicos, la adopción de las tecnologías de la información y comunicación (TIC) como base que soporte el desarrollo de otros servicios, también requiere tomar en consideración retos de ámbito social. En este sentido, el necesario incremento en el número de elementos de acceso para dar soporte a la creciente demanda de tráfico, ha despertado recientemente cierta preocupación respecto a la exposición a los campos electromagnéticos (CEM) inducidos por las redes de comunicaciones. Como respuesta a esta preocupación, esta Tesis analiza y propone técnicas de red que permitan analizar y reducir dicha exposición sin tener un impacto negativo en la calidad de los servicios. En primer lugar, se propone una herramienta de medida capaz de evaluar la exposición de la población en su conjunto y de manera continuada.
Desde una perspectiva de gestión de red, en este trabajo se analiza y se proponen mejoras para técnicas de selección de acceso y gestión de recursos, ya que son las técnicas que modulan el uso de los recursos radio-eléctricos, por lo que tienen un gran impacto en la exposición a los CEM. Por otro lado, también se aborda el estudio de nuevas topologías de red que pueden ser relevantes para la exposición a los CEM. En concreto, se propone incluir la exposición electromagnética como métrica de encaminamiento en redes multi-salto, donde los usuarios están muy próximos a los dispositivos que forman la red. Finalmente, teniendo en cuenta que la mayoría del tráfico existente pertenece a contenido audio-visual, se proponen mejoras en servicios tradicionales de video, que permitan reducir la exposición a los CEM sin perjudicar la calidad de los mismos.
- español
Information and communication technologies are being widely adopted, as an enabler for new and legacy services, in nearly all realms, both technological and non-technological. This trend is leading to new technical requirements, which are hardly fulfilled by a single technology. In addition, the communication capacity of wireless networks is increasing, to fulfill the requirements of new communication services. In this respect, future wireless network scenarios are believed to embrace multiple technologies and a remarkably higher density of access elements, to cope with the ever increasing capacity demand. Altogether, future scenarios will be characterized by heterogeneous and dense networks, which will be operated in a coordinated manner to optimize the potential communication capacity in an efficient way.
Taking into account the pervasive presence of communication technologies, its deployment and adoption need not only to face technical challenges, but also societal ones. In this sense, along with well known topics such as power saving, in the last years there has been a growing concern regarding the electro-magnetic fields (EMF) exposure induced by wireless communications. In some cases, this concern is hindering the deployment and adoption of new technologies.
In order to ensure the acceptance of new and more dense communications technologies, it seems that EMF exposure should be considered from different angles. On the one hand, measuring tools able to monitor the exposure levels induced by communications technologies should be designed and implemented. Furthermore, new networking solutions and techniques would also need to consider the EMF, including it as another performance indicator.
This dissertation first tackles the design and development of a sensing tool able to continuously monitor the EMF population exposure over large areas. The tools is designed and developed leveraging a smart-city testbed, and it is actually integrated as another urban service, thus easing its adoption. The deployment of the corresponding sensing devices has been carried out considering the scenario characteristics. Furthermore, a number of factors have been identified to improve the accuracy of the values provided by the tool, as well as the integration of extrapolation techniques. Based on such characterization, a complete methodology, providing meaningful EMF population exposure metrics, is proposed, implemented, and validated.
In addition, the dissertation proposes a simulation framework that fosters the systematic assessment of network solutions over large scenarios, paying special attention to the temporal evolution of the scenario. This aspect is particularly relevant to analyze the impact that different solutions may have over the services run by users. In addition, the assessment of EMF exposure requires simulation models able to consider the utilization of physical radio resources in a realistic way. In this sense, two advanced simulation models are proposed, considering both downlink and uplink communications. Differently to other approaches, the proposed models account for the effect that access selection has over the radio resource efficiency, as a consequence of mutual interference between network elements and terminals. In turn, the simulation models are implemented as optimization problems that are casted so that they can be solved using well known methods. The comparison of these models with legacy approaches shows a relevant difference, which is stronger in dense and heterogeneous scenarios.
Afterwards, and exploiting the aforementioned models, different access selection strategies have been analyzed, in terms of EMF exposure, over large and heterogeneous scenarios. In general, it can be concluded that higher network densities lead to lower exposure, as a consequence of sorter distances between users' devices and network elements. Furthermore, the analysis evinces that tighter cooperation between access elements can also reduce the population exposure.
Besides access selection evaluation, where a user decides the technology to use, this dissertation also tackles the multi-connectivity paradigm, where multiple technologies can be seamlessly used. In this sense, we propose a novel radio resource scheduler able to cover the more relevant requirements of multi-connectivity scenarios. The evaluation carried out yields that the proposed solution ensures system stability regardless of the type of traffic and load regimes. Furthermore, the mathematical framework in which it is based, allows the addition of decision constraints while preserving stability guarantee. This feature is of utter importance, since it enables considering real system constraints, inherent to multi-connectivity scenarios.
Access selection and resource management are likely to be two of the most relevant aspects as far as EMF exposure is concerned, since they rule how the radio resources are used. Nevertheless, other aspects need also to be considered, taking into account the potential importance they will have in envisioned future scenarios. In this regard, multi-hop wireless communications are believed to play a more relevant role either as dedicated connectivity service or as a means to extend the coverage of other systems. Furthermore, it is also important to study how the exposure can be considered from te service perspective. In this sense, this Thesis proposes a novel routing framework to embed the EMF exposure into the design and performance assessment of routing decision procedures for multi-hop networks. In general, the results show that including the EMF exposure as a routing metric yields a fairer exposure distribution without jeopardizing the quality of service.
The dissertation contributions conclude with the proposal of modifications of the legacy protocol stack used for video content delivery service. By using adaptive data protection and transport protocol selection, the proposed solution reduces the number of retransmissions without decreasing the service quality experienced by end users.
