Estudio, diseño e implementación de la capa física para comunicaciones remotas utilizando tecnologías NVS

In the last years, IoT communications networks have improved significantly, both in terms of coverage and in terms of efficiency and performance. Although these improvements are very relevant, they do not cover the entire world territory. Very isolated areas of the world, such as the poles or mountainous areas that are difficult to access, do not have this type of data coverage, as the terrain characteristics limit the access of IoT devices in these environments. Currently, existing solutions are focused on satellite communications that, although they allow communication in these scenarios, have a very high economic cost.

On the other hand, a possible solution would be the use of HF communications. Thanks to this type of communication, speeds of up to 100 kbps can be achieved, according to standards and previous research. One of the applications of HF communications is communication through the ionosphere. This type of link provides ideal characteristics for long distance communications.

In the last four years, the research group on Internet technologies (GRITS) at the La Salle School of Engineering (Ramon Llull University), has focused on ionospheric communications and, especially, on NVIS technology (Near Vertical Incidence Skywave). In particular, it has focused on communications with the Juan Carlos I Antarctic Base. This type of HF communication offers ideal characteristics for long-range remote communications, with a radius of up to 350 km and without the need for direct vision between the different transceivers.

The purpose of this thesis is to define the best NVIS technology communications scenario for an IoT coverage network in remote environments. One of the main goals is to decrease the power consumption of remote devices. This will provide long range communication and maximize battery life for these types of devices, a major factor for IoT communications. In addition, the proposed solution attempts to mitigate the economic over-cost that would be involved in using satellites as a means of communication, by adapting the development of the technology to low-cost devices.

As a main improvement factor, this thesis focuses on the definition of a physical layer adapted to the NVIS communication environment. In order to optimize this link, the main characteristics of a multipath wireless environment, the Doppler Shift, Doppler and Delay Spread, are studied, allowing the definition of the most adapted frame times for this channel. Furthermore, the characteristics of QAM, PSK and FSK modulations (from order 2 to 32) in very low power transmissions (from 0.5 W to 25 W) and in a multipath environment are compared. This analysis will allow to define the best communication frame, establishing the physical layer for NVIS communications in remote environments.

Finally, and in order to demonstrate the viability of the technology developed in an industrial environment, a process of knowledge transfer from the academic world to the business world is defined and implemented. The different markets where this type of communications could be integrated are studied, and a value proposal for the remote communications market is defined, all with the aim of reaching a conclusion on both the economic viability and the need for the technology for a non-military use scenario.