Doppler Characterization in Ultra Wideband BAN Channels During Breathing

[EN] Monitoring the physical parameters from devices inside the body, using ultra wideband (UWB) technology, enables the development of high bandwidth demanding applications in real time. The relative movement of the nodes deployed in the body, due to breathing, can give rise to a frequency shifting effect, increasing the fading level in the propagation channel during transmissions. In this article, therefore, we present a study of the frequency effects on the propagation channel derived from the relative movement between two nodes of a wireless body area network (WBAN), at least one of them placed inside the human body, caused by breathing. The study is performed on the basis of the Doppler spectrum characterization in terms of the shape fitting and frequency spread parameter derivation. Continuous wave (CW) signals have been used to cover the UWB range at four selected frequencies: 3.1, 4.8, 6, and 8.5 GHz, and a liquid phantom has been employed for emulating the dielectric properties of the high water content tissues at the considered UWB frequencies.This work was supported in part by the Ministerio de Economia y Competitividad (MINECO), Spain, under Grant TEC2016-78028-C3-2-P, in part by the European Union's H2020-MSCA-ITN Program by the "mmWave Communications in the Built Environments-WaveComBE" Project, under Grant 766231, and in part by the European FEDER funds.García-Serna, RG.; Garcia-Pardo, C.; Molina-García-Pardo, JM.; Juan Llacer, L.; Cardona Marcet, N. (2020). Doppler Characterization in Ultra Wideband BAN Channels During Breathing. IEEE Transactions on Antennas and Propagation. 68(2):1066-1073. https://doi.org/10.1109/TAP.2019.2951849S1066107368

Development and Experimental Analysis of Wireless High Accuracy Ultra-Wideband Localization Systems for Indoor Medical Applications

This dissertation addresses several interesting and relevant problems in the field of wireless technologies applied to medical applications and specifically problems related to ultra-wideband high accuracy localization for use in the operating room. This research is cross disciplinary in nature and fundamentally builds upon microwave engineering, software engineering, systems engineering, and biomedical engineering. A good portion of this work has been published in peer reviewed microwave engineering and biomedical engineering conferences and journals. Wireless technologies in medicine are discussed with focus on ultra-wideband positioning in orthopedic surgical navigation. Characterization of the operating room as a medium for ultra-wideband signal transmission helps define system design requirements. A discussion of the first generation positioning system provides a context for understanding the overall system architecture of the second generation ultra-wideband positioning system outlined in this dissertation. A system-level simulation framework provides a method for rapid prototyping of ultra-wideband positioning systems which takes into account all facets of the system (analog, digital, channel, experimental setup). This provides a robust framework for optimizing overall system design in realistic propagation environments. A practical approach is taken to outline the development of the second generation ultra-wideband positioning system which includes an integrated tag design and real-time dynamic tracking of multiple tags. The tag and receiver designs are outlined as well as receiver-side digital signal processing, system-level design support for multi-tag tracking, and potential error sources observed in dynamic experiments including phase center error, clock jitter and drift, and geometric position dilution of precision. An experimental analysis of the multi-tag positioning system provides insight into overall system performance including the main sources of error. A five base station experiment shows the potential of redundant base stations in improving overall dynamic accuracy. Finally, the system performance in low signal-to-noise ratio and non-line-of-sight environments is analyzed by focusing on receiver-side digitally-implemented ranging algorithms including leading-edge detection and peak detection. These technologies are aimed at use in next-generation medical systems with many applications including surgical navigation, wireless telemetry, medical asset tracking, and in vivo wireless sensors