Large-scale MIMO textile technology for enhanced terminals

Abstract

The increasing demand for higher data rates imposed by the next generation of wireless communication networks has postulated Multiple-Input Multiple-Output (MIMO) systems as one of the main technological solutions. While the development of a large number of antennas is relatively feasible at the base station (BS) side due to the available space, it is not so viable at the end user side. Therefore, the user end can be considered as a clear bottle–neck of the communication since in MIMO systems the throughput gains are limited by the minimum number of antennas existing at the transmitter or the receiver. With the aim of overcoming this limitation, in this Thesis textile multi–antenna based terminals are presented. Specifically, the textile solution based on large–scale MIMO technology explored in this work allows to provide the energy and spectral efficiency benefits offered by MIMO technology directly to the end user (e.g. exploiting their own garments or accessories) without compromising the size, weight and, ultimately the portability of the user equipment (UE). Motivated with the aforementioned target, the main results provided by this Thesis can be classified in three. First, the design, fabrication and experimental characterization of different textile antenna arrays is performed. Concretely, one design is developed to be integrated at the backside of a jacket operating at 3.5 GHz, while the other design is developed to be conformed in a helmet operating at 4.9 GHz. Additionally, due to the fact that the textile solution is developed to work in the very close proximity of the human body, offering information regarding the human exposure to electromagnetic fields (EMF) seems to be relevant. Thus, an study to quantify the specific absorption rate (SAR) is also performed. It should be noted that these designs can be applied to emergency scenarios, where first responders can improve their communication capabilities with the deployment of a large number of antennas in their garments. Second, carrying out the experimental characterization of the performance in terms of achievable rates for a textile multi–antenna terminal in order to show the real advantages of deploying a large number of antennas at the user end. With that objective, a measurement campaign that allows to model the wireless channel in relevant Outdoor-to-Indoor (O2I) propagation environments was performed in Valpara´ıso (Chile). Finally, the third part of this Thesis pretends to evaluate the role that textile multi– antenna terminals might play as a part of future public safety network solutions. To this end, a two–hop link network proposal based on advanced long–term evolution (LTE) standard is also proposed. Among other things, the device technology and the network elements required to implement such a network concept, as well as, a possible design principle based on the reliable connectivity principle required by emergency communications, are presented.