Análisis del estado del arte de las técnicas de acceso dinámico al espectro aplicadas en redes inalámbricas de nueva generación

El documento no cuenta con anexos.La contradicción entre la prevista escasez del espectro electromagnético disponible, y la subutilización de los canales de frecuencia asignados, requieren un cambio de paradigma del anacrónico modelo de acceso estático; hacia un modelo de acceso al espectro dinámico, flexible y de alta eficiencia. Con base en lo anterior, en este trabajo de investigación se presenta un estudio y análisis detallado de las diferentes técnicas de Acceso Dinámico al Espectro (DSA, Dymamic Spectrum Access), reconociendo su enorme potencial para mejorar el uso de recursos radio en Redes Inalámbricas de Nueva Generación (NGWN, New Generation Wireless Networks) como 5G, Small Cells, Redes Ultradensas y Redes Heterogéneas. Se ha establecido que mediante el uso de DSA, la necesidad de espectro para el despliegue de miles de millones de dispositivos de Internet de las Cosas (IoT, Internet of Things) pilar de las comunicaciones 5G se puede reducir drásticamente, debido a la posibilidad de reuso o reciclaje de canales de comunicación libres o licenciados, explotándolos bien sea de manera oportunista y/o simultánea.The contradiction between the anticipated scarcity of the available electromagnetic spectrum, and the underutilization of the assigned frequency channels, requires a paradigm shift from the anachronistic static access model; towards a dynamic, flexible, and highly efficient spectrum access model. Based on the above, this research work presents a detailed study and analysis of the different techniques of Dynamic Spectrum Access (DSA, Dynamic Spectrum Access), recognizing their enormous potential to improve the use of radio resources in Wireless Networks of New Generation (NGWN, New Generation Wireless Networks) such as 5G, Small Cells, Ultradense Networks, and Heterogeneous Networks. It has been established that through the use of DSA, the need for spectrum for the deployment of billions of Internet of Things (IoT, Internet of Things) devices pillar of 5G communications can be drastically reduced, due to the possibility of reuse or recycling of free or licensed communication channels, exploiting them either opportunistically and/or simultaneously

Cognitive radio networks : quality of service considerations and enhancements

The explosive growth of wireless and mobile networks, such as the Internet of Things and 5G, has led to a massive number of devices that primarily use wireless channels within a limited range of the radio frequency spectrum (RFS). The use of RFS is heavily regulated, both nationally and internationally, and is divided into licensed and unlicensed bands. While many of the licensed wireless bands are underutilised, useable unlicensed bands are usually overcrowded, making the efficient use of RFS one of the critical challenges faced by future wireless communication technologies. The cognitive radio (CR) concept is proposed as a promising solution for the underutilisation of useful RFS bands. Fundamentally, CR technology is based on determining the unoccupied licensed RFS bands, called spectrum white spaces or holes, and accessing them to achieve better RFS utilisation and transmission propagation. The holes are the frequencies unused by the licensed user, or primary user (PU). Based on spectrum sensing, a CR node, or secondary user (SU), senses the surrounding spectrum periodically to detect any potential PU transmission in the current channel and to identify the available spectrum holes. Under current RFS regulations, SUs may use spectrum holes as long as their transmissions do not interfere with those of the PU. However, effective spectrum sensing can introduce overheads to a CR node operation. Such overheads affect the quality of service (QoS) of the running applications. Reducing the sensing impact on the QoS is one of the key challenges to adopting CR technology, and more studies of QoS issues related to implementing CR features are needed. This thesis aims to address these QoS issues in CR while considered the enhancement of RFS utilisation. This study concentrates on the spectrum sensing function, among other CR functions, because of its major impact on QoS and spectrum utilisation. Several spectrum sensing methods are reviewed to identify potential research gaps in analysing and addressing related QoS implications. It has been found that none of the well-known sensing techniques is suitable for all the diverse QoS requirements and RFS conditions: in fact, higher accuracy sensing methods cause a significant QoS degradation, as illustrated by several simulations in this work. For instance, QoS degradation caused by high-accuracy sensing has not yet been addressed in the IEEE 802.11e QoS mechanism used in the proposed CR standard, IEEE 802.11af (or White-Fi). This study finds that most of the strategies proposed to conduct sensing are based on a fixed sensing method that is not adaptable to the changeable nature of QoS requirements. In contrast, this work confirms the necessity of using various sensing techniques and parameters during a CR node operation for better performance