Improved reception of in-body signals by means of a wearable multi-antenna system

High data-rate wireless communication for in-body human implants is mainly performed in the 402-405 MHz Medical Implant Communication System band and the 2.45 GHz Industrial, Scientific and Medical band. The latter band offers larger bandwidth, enabling high-resolution live video transmission. Although in-body signal attenuation is larger, at least 29 dB more power may be transmitted in this band and the antenna efficiency for compact antennas at 2.45 GHz is also up to 10 times higher. Moreover, at the receive side, one can exploit the large surface provided by a garment by deploying multiple compact highly efficient wearable antennas, capturing the signals transmitted by the implant directly at the body surface, yielding stronger signals and reducing interference. In this paper, we implement a reliable 3.5 Mbps wearable textile multi-antenna system suitable for integration into a jacket worn by a patient, and evaluate its potential to improve the In-to-Out Body wireless link reliability by means of spatial receive diversity in a standardized measurement setup. We derive the optimal distribution and the minimum number of on-body antennas required to ensure signal levels that are large enough for real-time wireless endoscopy-capsule applications, at varying positions and orientations of the implant in the human body

Foldable all-textile cavity-backed slot antennas for personal UWB localization

An all-textile multimoded cavity-backed slot antenna has been designed and fabricated for body-worn impulse radio ultra-wideband (IR-UWB) operation in the 3,744-4,742.4 MHz frequency band, thereby covering Channels 2 and 3 of the IEEE 802.15.4a standard. Its light weight, mechanical flexibility, and small footprint of 35 mm x 56 mm facilitate integration into textile for radio communication equipment for first aid responders, personal locator beacons, and equipment for localization and medical monitoring of children or the elderly. The antenna features a stable radiation pattern and reflection coefficient in diverse operating conditions such as in free space, when subject to diverse bending radii and when deployed on the torso or upper right arm of a test person. The high isolation toward the wearer's body originates from the antenna's hemispherical radiation pattern with a -3 dB beamwidth of 120 degrees and a front-to-back ratio higher than 11 dB over the entire band. Moreover, the antenna exhibits a measured maximum gain higher than 6.3 dBi and a radiation efficiency over 75%. In addition, orientation-specific pulse distortion introduced by the antenna element is analyzed by means of the System Fidelity Factor (SFF). The SFF of the communication link between two instances of this antenna is higher than 94% for all directions within the antenna's -3 dB beamwidth. This easily wearable and deployable antenna is suitable to support IR-UWB localization with an accuracy in the order of 5 cm

Impact of Receivers Location on the Accuracy of Capsule Endoscope Localization

[EN] In recent years, localization for capsule endoscopy applications using Ultra-Wideband (UWB) technology has become an attractive field of study due to its potential benefits for patients. Performance analysis of RF-based localization techniques are very limited in literature. Most of the available studies rely on software simulations using digital human models. Nonetheless, no realistic studies based on in-vivo measurements has been reported yet. This paper investigates the performance of RSS-based technique for three-dimensional (3D) localization in the UWB frequency band. Impact of receivers selection as well as of the evaluated path loss model on the localization accuracy is investigated. Results obtained through CST-based simulations and from recently conducted in-vivo measurements are presented and compared.This work was supported by the European Union's H2020:MSCA:ITN program for the "Wireless In-body Environment Communication- WiBEC" project under the grant agreement no. 675353. This work was also funded by the Ministerio de Economia y Competitividad, Spain (TEC2014-60258-C2-1-R), by the European FEDER funds.Barbi, M.; Garcia-Pardo, C.; Cardona Marcet, N.; Andrea Nevárez; Vicente Pons Beltrán; Frasson, M. (2018). Impact of Receivers Location on the Accuracy of Capsule Endoscope Localization. IEEE. 340-344. https://doi.org/10.1109/PIMRC.2018.8580862S34034

Localization for capsule endoscopy at UWB frequencies using an experimental multilayer phantom

[EN] Localization inside the human body using ultrawideband (UWB) wireless technology is gaining importance in several medical applications such as capsule endoscopy. Performance analysis of RF based localization techniques are mainly conducted through simulations using numerical human models or through experimental measurements using homogeneous phantoms. One of the most common implemented RF localization approaches uses the received signal strength (RSS). However, to the best of our knowledge, no experimental measurements employing multilayer phantoms are currently available in literature. This paper investigates the performance of RSS-based technique for two-dimensional (2D) localization by employing a two-layer experimental phantom-based setup. Preliminary results on the estimation of the in-body antenna coordinates show that RSS-based method can achieve a location accuracy on average of 0.5-1 cm within a certain range of distances between in-body and on-body antenna.This work was supported by the European Union’s H2020:MSCA:ITN program for the ”Wireless In-body Environment Communication- WiBEC” project under the grant agreement no. 675353. This work was also funded by the Programa de Ayudas de Investigación y Desarrollo (PAID-01-16) from Universitat Politècnica de València and by the Ministerio de Economía y Competitividad, Spain (TEC2014-60258-C2-1-R), by the European FEDER funds.Barbi, M.; Pérez Simbor, S.; García Pardo, C.; Andreu Estellés, C.; Cardona Marcet, N. (2018). Localization for capsule endoscopy at UWB frequencies using an experimental multilayer phantom. Institute of Electrical and Electronics Engineers (IEEE). https://doi.org/10.1109/WCNCW.2018.8369015

Experimental Assessment of Time Reversal for In-Body to In-Body UWB Communications

[EN] The standard of in-body communications is limited to the use of narrowband systems. These systems are far from the high data rate connections achieved by other wireless telecommunication services today in force. The UWB frequency band has been proposed as a possible candidate for future in-body networks. However, the attenuation of body tissues at gigahertz frequencies could be a serious drawback. Experimental measurements for channel modeling are not easy to carry out, while the use of humans is practically forbidden. Sophisticated simulation tools could provide inaccurate results since they are not able to reproduce all the in-body channel conditions. Chemical solutions known as phantoms could provide a fair approximation of body tissues¿ behavior. In this work, the Time Reversal technique is assessed to increase the channel performance of in-body communications. For this task, a large volume of experimental measurements is performed at the low part of UWB spectrum (3.1-5.1 GHz) by using a highly accurate phantom-based measurement setup. This experimental setup emulates an in-body to in-body scenario, where all the nodes are implanted inside the body. Moreover, the in-body channel characteristics such as the path loss, the correlation in transmission and reception, and the reciprocity of the channel are assessed and discussed.This work was supported by the Programa de Ayudas de Investigacion y Desarrollo (PAID-01-16) from Universitat Politecnica de Valencia and by the Ministerio de Economia y Competitividad, Spain (TEC2014-60258-C2-1-R), by the European FEDER funds.Andreu-Estellés, C.; Garcia-Pardo, C.; Castelló-Palacios, S.; Cardona Marcet, N. (2018). Experimental Assessment of Time Reversal for In-Body to In-Body UWB Communications. Wireless Communications and Mobile Computing (Online). (8927107):1-12. https://doi.org/10.1155/2018/8927107S1128927107Fireman, Z. (2003). Diagnosing small bowel Crohn’s disease with wireless capsule endoscopy. Gut, 52(3), 390-392. doi:10.1136/gut.52.3.390Burri, H., & Senouf, D. (2009). Remote monitoring and follow-up of pacemakers and implantable cardioverter defibrillators. Europace, 11(6), 701-709. doi:10.1093/europace/eup110Scanlon, W. G., Burns, B., & Evans, N. E. (2000). Radiowave propagation from a tissue-implanted source at 418 MHz and 916.5 MHz. IEEE Transactions on Biomedical Engineering, 47(4), 527-534. doi:10.1109/10.828152Chavez-Santiago, R., Garcia-Pardo, C., Fornes-Leal, A., Valles-Lluch, A., Vermeeren, G., Joseph, W., … Cardona, N. (2015). Experimental Path Loss Models for In-Body Communications within 2.36-2.5 GHz. IEEE Journal of Biomedical and Health Informatics, 1-1. doi:10.1109/jbhi.2015.2418757Khaleghi, A., Chávez-Santiago, R., & Balasingham, I. (2010). Ultra-wideband pulse-based data communications for medical implants. IET Communications, 4(15), 1889. doi:10.1049/iet-com.2009.0692Khaleghi, A., Chávez-Santiago, R., & Balasingham, I. (2011). Ultra-wideband statistical propagation channel model for implant sensors in the human chest. IET Microwaves, Antennas & Propagation, 5(15), 1805. doi:10.1049/iet-map.2010.0537Kurup, D., Scarpello, M., Vermeeren, G., Joseph, W., Dhaenens, K., Axisa, F., … Vanfleteren, J. (2011). In-body path loss models for implants in heterogeneous human tissues using implantable slot dipole conformal flexible antennas. EURASIP Journal on Wireless Communications and Networking, 2011(1). doi:10.1186/1687-1499-2011-51Floor, P. A., Chavez-Santiago, R., Brovoll, S., Aardal, O., Bergsland, J., Grymyr, O.-J. H. N., … Balasingham, I. (2015). In-Body to On-Body Ultrawideband Propagation Model Derived From Measurements in Living Animals. IEEE Journal of Biomedical and Health Informatics, 19(3), 938-948. doi:10.1109/jbhi.2015.2417805Shimizu, Y., Anzai, D., Chavez-Santiago, R., Floor, P. A., Balasingham, I., & Wang, J. (2017). Performance Evaluation of an Ultra-Wideband Transmit Diversity in a Living Animal Experiment. IEEE Transactions on Microwave Theory and Techniques, 65(7), 2596-2606. doi:10.1109/tmtt.2017.2669039Anzai, D., Katsu, K., Chavez-Santiago, R., Wang, Q., Plettemeier, D., Wang, J., & Balasingham, I. (2014). Experimental Evaluation of Implant UWB-IR Transmission With Living Animal for Body Area Networks. IEEE Transactions on Microwave Theory and Techniques, 62(1), 183-192. doi:10.1109/tmtt.2013.2291542Chou, C.-K., Chen, G.-W., Guy, A. W., & Luk, K. H. (1984). Formulas for preparing phantom muscle tissue at various radiofrequencies. Bioelectromagnetics, 5(4), 435-441. doi:10.1002/bem.2250050408Cheung, A. Y., & Koopman, D. W. (1976). Experimental Development of Simulated Biomaterials for Dosimetry Studies of Hazardous Microwave Radiation (Short Papers). IEEE Transactions on Microwave Theory and Techniques, 24(10), 669-673. doi:10.1109/tmtt.1976.1128936YAMAMOTO, H., ZHOU, J., & KOBAYASHI, T. (2008). Ultra Wideband Electromagnetic Phantoms for Antennas and Propagation Studies. IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, E91-A(11), 3173-3182. doi:10.1093/ietfec/e91-a.11.3173Lazebnik, M., Madsen, E. L., Frank, G. R., & Hagness, S. C. (2005). Tissue-mimicking phantom materials for narrowband and ultrawideband microwave applications. Physics in Medicine and Biology, 50(18), 4245-4258. doi:10.1088/0031-9155/50/18/001Yilmaz, T., Foster, R., & Hao, Y. (2014). Broadband Tissue Mimicking Phantoms and a Patch Resonator for Evaluating Noninvasive Monitoring of Blood Glucose Levels. IEEE Transactions on Antennas and Propagation, 62(6), 3064-3075. doi:10.1109/tap.2014.2313139Gezici, S., Zhi Tian, Giannakis, G. B., Kobayashi, H., Molisch, A. F., Poor, H. V., & Sahinoglu, Z. (2005). Localization via ultra-wideband radios: a look at positioning aspects for future sensor networks. IEEE Signal Processing Magazine, 22(4), 70-84. doi:10.1109/msp.2005.1458289Marinova, M., Thielens, A., Tanghe, E., Vallozzi, L., Vermeeren, G., Joseph, W., … Martens, L. (2015). Diversity Performance of Off-Body MB-OFDM UWB-MIMO. IEEE Transactions on Antennas and Propagation, 63(7), 3187-3197. doi:10.1109/tap.2015.2422353SHI, J., ANZAI, D., & WANG, J. (2012). Channel Modeling and Performance Analysis of Diversity Reception for Implant UWB Wireless Link. IEICE Transactions on Communications, E95.B(10), 3197-3205. doi:10.1587/transcom.e95.b.3197Pajusco, P., & Pagani, P. (2009). On the Use of Uniform Circular Arrays for Characterizing UWB Time Reversal. IEEE Transactions on Antennas and Propagation, 57(1), 102-109. doi:10.1109/tap.2008.2009715Chavez-Santiago, R., Sayrafian-Pour, K., Khaleghi, A., Takizawa, K., Wang, J., Balasingham, I., & Li, H.-B. (2013). Propagation models for IEEE 802.15.6 standardization of implant communication in body area networks. IEEE Communications Magazine, 51(8), 80-87. doi:10.1109/mcom.2013.6576343Andreu, C., Castello-Palacios, S., Garcia-Pardo, C., Fornes-Leal, A., Valles-Lluch, A., & Cardona, N. (2016). Spatial In-Body Channel Characterization Using an Accurate UWB Phantom. IEEE Transactions on Microwave Theory and Techniques, 64(11), 3995-4002. doi:10.1109/tmtt.2016.2609409Pahlavan, K., & Levesque, A. H. (2005). Wireless Information Networks. doi:10.1002/0471738646Qiu, R. C., Zhou, C., Guo, N., & Zhang, J. Q. (2006). Time Reversal With MISO for Ultrawideband Communications: Experimental Results. 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Mathematical modeling of ultra wideband in vivo radio channel

This paper proposes a novel mathematical model for an in vivo radio channel at ultra-wideband frequencies (3.1–10.6 GHz), which can be used as a reference model for in vivo channel response without performing intensive experiments or simulations. The statistics of error prediction between experimental and proposed model is RMSE = 5.29, which show the high accuracy of the proposed model. Also, the proposed model was applied to the blind data, and the statistics of error prediction is RMSE = 7.76, which also shows a reasonable accuracy of the model. This model will save the time and cost on simulations and experiments, and will help in designing an accurate link budget calculation for a future enhanced system for ultra-wideband body-centric wireless systems

Bounds on RF cooperative localization for video capsule endoscopy

Wireless video capsule endoscopy has been in use for over a decade and it uses radio frequency (RF) signals to transmit approximately fifty five thousands clear pictures of inside the GI tract to the body-mounted sensor array. However, physician has no clue on the exact location of the capsule inside the GI tract to associate it with the pictures showing abnormalities such as bleeding or tumors. It is desirable to use the same RF signal for localization of the VCE as it passes through the human GI tract. In this thesis, we address the accuracy limits of RF localization techniques for VCE localization applications. We present an assessment of the accuracy of cooperative localization of VCE using radio frequency (RF) signals with particular emphasis on localization inside the small intestine. We derive the Cramer-Rao Lower Bound (CRLB) for cooperative location estimators using the received signal strength(RSS) or the time of arrival (TOA) of the RF signal. Our derivations are based on a three-dimension human body model, an existing model for RSS propagation from implant organs to body surface and a TOA ranging error model for the effects of non-homogenity of the human body on TOA of the RF signals. Using models for RSS and TOA errors, we first calculate the 3D CRLB bounds for cooperative localization of the VCE in three major digestive organs in the path of GI tract: the stomach, the small intestine and the large intestine. Then we analyze the performance of localization techniques on a typical path inside the small intestine. Our analysis includes the effects of number of external sensors, the external sensor array topology, number of VCE in cooperation and the random variations in transmit power from the capsule

UWB radio channel and diversity characterization for wireless implanted devices

Las redes de área corporal permiten la interconexión de nodos independientes situados dentro o fuera de la superficie corporal o, incluso, alejados de dicha superficie. En cuanto a las comunicaciones intracorporales, el establecimiento de un enlace robusto con una cápsula endoscópica o con un marcapasos, son ejemplos de los avances tecnológicos conseguidos en las últimas décadas. A pesar de estos desarrollos en asistencia sanitaria, los estándares actuales para este tipo de comunicaciones no permiten conexiones inalámbricas de alta velocidad de transmisión, las cuales son comunes en los servicios actuales de telecomunicaciones. Los sistemas UWB han surgido como potencial candidato para las futuras redes de comunicaciones inalámbricas intracorporales. No obstante, el principal obstáculo de la tecnología UWB para aplicaciones intracorporales es la alta atenuación que sufren las señales transmitidas al atravesar los distintos tejidos corporales, que aumenta drásticamente con el aumento de la frecuencia. Por tanto, es importante una caracterización precisa del canal UWB intracorporal a la hora de validar dicha banda como la adecuada para este propósito.Esta tesis se centra en el análisis de la tecnología UWB para posibilitar comunicaciones intracorporales inalámbricas desde un punto de vista experimental. Para conseguir este objetivo, se ha empleado un novedoso sistema de medidas experimental basado en fantomas en diversos escenarios de propagación intracorporal. De esta forma, se pueden comprobar las pérdidas de propagación en el medio así como la diversidad del canal de una forma fiable. Con el fin de validar los valores obtenidos en el laboratorio, se han comparado y analizado con los obtenidos en un experimento in vivo. Por otro lado, se han diseñado y fabricado nuevas antenas UWB candidatas para comunicaciones intracorporales, empleando técnicas existentes y nuevas de miniaturización y optimización. Finalmente, se han usado técnicas basadas en diversidad para mejorar el rendimiento del canal de propagación en dos escenarios intracorporales diferentes.Wireless Body Area Networks allow the interconnection between independent nodes located either inside or over the body skin or further. Regarding in-body communications, establishing a proper link with a capsule endoscope or with a pacemaker are examples of technological advances achieved in the last decades. In spite of these healthcare developments, current standards for these kind of communications do not allow high data rate wireless connections, which are common in the current telecommunication services. UWB systems have emerged as a potential solution for future wireless in-body communications. Nevertheless, the main drawback of UWB for in-body applications is the high attenuation of human body tissues which increases dramatically with the increment of frequency. Hence, an accurate UWB in-body channel characterization is relevant in order validate UWB frequency band as the best candidate for future networks of implantable nodes. This thesis is devoted to test UWB technology for in-body communications from an experimental point of view. To achieve this goal, a novel spatial phantom-based measurement setup is used in several in-body propagation scenarios. Thus, the losses in the propagation medium and the channel diversity are checked in a reliable way. In order to check the values obtained in laboratory, they are compared and discussed with those obtained in an in vivo experiment. On the other hand, new UWB antenna candidates for inbody communications are designed and manufactured by using typical and new miniaturization and antenna optimization techniques for this purpose. Finally, diversity-based techniques are used to improve the performance of the propagation channel in two different in-body scenarios.Les xarxes d'àrea corporal permeten la interconnexió de nodes independents situats, o bé dins, o bé sobre la pell, o inclús allunyats del propi cos. Pel que fa a les comunicacions intracorporals, l'establiment d'un bon enllaç amb una càpsula endoscòpica o amb un marcapassos, són exemples dels avanços tecnològics aconseguits les darreres dècades. A pesar d'aquests desenvolupaments en assistència sanitària, els estàndards actuals per a aquests tipus de comunicacions no permeten connexions sense fil d'alta velocitat de transmissió, que són habituals als serveis actuals de telecomunicacions. Els sistemes UWB han sorgit com una solució potencial per a les futures comunicacions sense fill intracorporals. No obstant, el principal obstacle de la tecnologia UWB per a les aplicacions intracorporals és l'alta atenuació dels teixits del cos humà, que augmenta dràsticament amb l'increment de freqüència. Per tant, és important una caracterització acurada del canal UWB intracorporal a l'hora de validar la banda de freqüència UWB com a la millor candidata per a les futures xarxes de nodes implantats.Aquesta tesi se centra en l'anàlisi de la tecnologia UWB per a comunicacions intracorporals des d'un punt de vista experimental. Per a aconseguir aquest objectiu s'ha emprat un sistema novedós de mesures experimentals, basat en fantomes, en diversos escenaris de propagació intracorporal. D'aquesta manera es poden comprovar les pèrdues de propagació en el medi i la diversitat del canal d'una forma fiable. Per tal d'avaluar els valors obtinguts al laboratori, s'han comparat i analitzat amb aquells obtinguts en un experiment in vivo. Per altra banda, s'han dissenyat i fabricat noves antenes UWB candidates per a comunicacions intracorporals emprant tècniques típiques i noves de miniaturització i optimització d'antenes per a aquest propòsit. Finalment s'han usat tècniques basades en diversitat per a millorar el rendiment del canal de propagació en dos escenaris intracorporals diferents.Andreu Estellés, C. (2018). UWB radio channel and diversity characterization for wireless implanted devices [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/111836TESI

Ultrawideband Technology for Medical In-Body Sensor Networks: An Overview of the Human Body as a Propagation Medium, Phantoms, and Approaches for Propagation Analysis

[EN] An in-body sensor network is that in which at least one of the sensors is located inside the human body. Such wireless in-body sensors are used mainly in medical applications, collecting and monitoring important parameters for health and disease treatment. IEEE Standard 802.15.6-2012 for wireless body area networks (WBANs) considers in-body communications in the Medical Implant Communications Service (MICS) band. Nevertheless, high-data-rate communications are not feasible at the MICS band because of its narrow occupied bandwidth. In this framework, ultrawideband (UWB) systems have emerged as a potential solution for in-body highdata-rate communications because of their miniaturization capabilities and low power consumption.This work was supported by the Programa de Ayudas de Investigación y Desarrollo (PAID-01-16) at the Universitat Politècnica de València, Spain; by the Ministerio de Economía y Competitividad, Spain (TEC2014-60258-C2-1-R); and by the European FEDER funds. It was also funded by the European Union’s H2020:MSCA:ITN program for the Wireless In-Body Environ-ment Communication–WiBEC project under grant 675353.Garcia-Pardo, C.; Andreu-Estellés, C.; Fornés Leal, A.; Castelló-Palacios, S.; Pérez-Simbor, S.; Barbi, M.; Vallés Lluch, A.... (2018). Ultrawideband Technology for Medical In-Body Sensor Networks: An Overview of the Human Body as a Propagation Medium, Phantoms, and Approaches for Propagation Analysis. IEEE Antennas and Propagation Magazine. 60(3):19-33. https://doi.org/10.1109/MAP.2018.2818458S193360

UWB Path Loss Models for Ingestible Devices

[EN] Currently, some medical devices such as the Wireless Capsule Endoscopy (WCE) are used for data transmission from inside to outside the body. Nevertheless, for certain applications such as WCE, the data rates offered by current medical frequency bands can result insufficient. Ultra Wideband (UWB) frequency band has become an interesting solution for this. However, to date, there is not a formal channel path loss model for the UWB frequency band in the gastrointestinal (GI) scenario due to the huge differences between the proposed studies. There are three main methodologies to characterize the propagation channel, software simulations and experimental measurements either in phantom or in in vivo animals. Previous works do not compare all the methodologies or present some disagreements with the literature. In this paper, a dedicated study of the path loss using the three methodologies aforementioned (simulations, phantoms and in vivo measurements) and a comparison with previous researches in the literature is performed. Moreover, numerical values for a path loss model which agrees with the three methodologies and the literature are proposed. This paper aims at being the starting point for a formal path loss model in the UWB frequency band for WBANs in the GI scenarioThis work was supported in part by the European Union's H2020-MSCA-ITN Program for the "Wireless In-body Environment Communication" Project under Grant 675353, in part by the Programa de Ayudas de Investigacion y Desarrollo (PAID-01-16) from Universitat Politecnica de Valencia, and in part by the Ministerio de Economia y Competitividad, Spain under Grant TEC2014-60258-C2-1-R through the European FEDER Funds.Pérez-Simbor, S.; Andreu-Estellés, C.; Garcia-Pardo, C.; Frasson, M.; Cardona Marcet, N. (2019). UWB Path Loss Models for Ingestible Devices. IEEE Transactions on Antennas and Propagation. 67(8):5025-5034. https://doi.org/10.1109/TAP.2019.2891717S5025503467