Multiuser MIMO downlink systems with limited feedback and remote sensing of vital signs
Ermanna Conte · Padua Research Archive (University of Padova) · 2010
This PhD thesis collects the main contribution of my research activity, performed during my PhD program. As the title suggests, it is divided into two main parts. The first part collects the research I performed since the beginning of my PhD on Multiuser multiple input multiple output (MIMO) downlink systems with limited feedback; the topic is part of the wide research work on the fourth generation cellular systems. When I begun my research, on January 2007, most of the theoretical analysis had already been illustrated; therefore, my work focused on optimizing system parameters considering the limited resources available in a realistic scenario. The main contributions are on the design of the low rate feedback channel, and sub-optimal, low complexity scheduling algorithms, both in single carrier and in a orthogonal frequency division multiplexing (OFDM) scenario. The second, and most recent part of the thesis deals with remote sensing of vital signs, i.e. respiration and heart rate; I have been addressing this topic since October 2008, in cooperation with Philips Research, Eindhoven (NL), where I have been visiting student. We investigated the ultra wide band technology for remote sensing of vital signs. We propose a generic model for the received signal and described how vital sign modulates the main parameters of the received signal. Furthermore, we focused on detection techniques of respiration and heart beating periods; we derived the ML period estimator of a zero mean signal with unknown shape, and we proposed a novel low complexity approximated ML estimator. The proposed methods have application in many areas where only the periodicity is required and the complexity is an important issue. In particular, we applied the proposed algorithms to the remote heart rate estimation problem; both simulation and experimental results indicate that the proposed method outperforms the state of the art methods in detecting the period of a signal with low signal to noise ratio like the heart beating, even with a short observation of the periodic signal. %Communication and radar ha complementary a Though the two parts of research I performed during my PhD program seem to have little in common, they can be investigated with the same analytical tools, particularly for signal processing and detection techniques.