On Thursday, May 25, 2023, at 11 a.m., Tomás González's doctoral thesis will be read, entitled Uplink physical layer for NVIS remote sensor networks in hostile channels [original title in Spanish: Capa física de enlace ascendente para redes de sensores remotos NVIS en canales hostiles]. The thesis is directed by Dr. Juan Lluís Pijoan. The doctoral student is part of the 'Communications' research line within the Smart Society research group.
The objective of the thesis is to study and improve the physical layer of an NVIS system to use this technology in an ecosystem of remote sensors over hostile channels. The thesis has been developed in the course of the SHETLAND-NET project that had as objective to deploy a network of NVIS sensors for the archipelago of the South Shetland Islands. It was intended to install a low cost and consumption platform, capable of transmitting signals through ionospheric propagation, with the aim of connecting two Antarctic islands in order to transfer sensor data.
A study of the current bibliography and supported by previous studies of the topics has been carried out:
- HF channel probing with different robustness improvement techniques.
- Modulations used in HF and in the new communication standards, outside the HF bandwidth.
- Common antennas in these systems and miniaturization improvements.
With these three points, we want to improve the capabilities of the NVIS technology, doing a channel survey with two propagation modes with the aim of using the polarization diversity technique and thus improving its robustness.
On the other hand, based on this channel study, the SC-FDE modulation is designed, which is presented as the OFDM alternative to the upstream layers, considerably reducing the effects of PAPR generated by the subcarrier subdivision, and is capable of maintaining the advantages of OFDM.
Finally, the proposed improvement is the miniaturization of the antennas used in these systems, proposing a 15-meter horizontal dipole antenna that is buried underground, to reduce the current pollution generated by these antennas, putting in context that They are antennas with sizes of at least 15 meters long.
All these tests have been developed experimentally between the Barcelona and Cambrils radio link available to the School of Engineering La Salle (ETSELS), which are approximately 100 meters away. As final proof, part of these studies have been able to be tested in the 2021-2022 Antarctic Research Campaign.
The court will be made up of Dr. Francesc Tarrés, as President; Dr. Rosa Maria Asina, as Secretary; and Dr. José Antonio Morán, as Vocal.