Diseños de capa cruzada para redes inalámbricas de área corporal energéticamente eficientes: una revisión

RESUMEN: El diseño de capa cruzada se considera una poderosa alternativa para dar solución a las complejidades introducidas por las comunicaciones inalámbricas en redes de área corporal (WBAN), donde el modelo clásico de comunicaciones no ha exhibido un desempeño adecuado. Respecto al problema puntual de consumo de energía, hemos preparado la presente revisión de las publicaciones más relevantes que tratan la eficiencia energética para WBAN usando diseño de capa cruzada. En este artículo se proporciona una revisión exhaustiva de los avances en aproximaciones, protocolos y optimizaciones de capa cruzada cuyo objetivo es incrementar el tiempo de vida de las redes WBAN mediante el ahorro de energía. Luego, se discute los aspectos relevantes y deficiencias de las técnicas de capa cruzada energéticamente eficientes. Además, se introducen aspectos de investigación abiertos y retos en el diseño de capa cruzada para WBAN. En esta revisión proponemos una taxonomía de las aproximaciones de capa cruzada, de modo que las técnicas revisadas se ajustan en categorías de acuerdo a los protocolos involucrados en el diseño. Una clasificación novedosa se incluye para hacer claridad en los conceptos teóricos involucrados en cada esquema de capa cruzada y para luego agrupar aproximaciones similares evidenciando las diferencias con otras técnicas entre sí. Nuestras conclusiones consideran los aspectos de movilidad y modelamiento del canal en escenarios de WBAN como las direcciones para futura investigación en WBAN y en aplicaciones de telemedicina.ABSTRACT: Cross-layer design is considered a powerful alternative to solve the complexities of wireless communication in wireless body area networks (WBAN), where the classical communication model has been shown to be inaccurate. Regarding the energy consumption problem, we have prepared a current survey of the most relevant scientific publications on energy-efficient cross-layer design for WBAN. In this paper, we provide a comprehensive review of the advances in cross-layer approaches, protocols and optimizations aimed at increasing the network lifetime by saving energy in WBANs. Subsequently, we discuss the relevant aspects and shortcomings of these energy-efficient cross-layer techniques and point out the open research issues and challenges in WBAN cross-layer design. In this survey, we propose a taxonomy for cross-layer approaches to fit them into categories based on the protocols involved in the cross-layer scheme. A novel classification is included to clarify the theoretical concepts behind each cross-layer scheme; and to group similar approaches by establishing their differences from the other strategies reviewed. Our conclusion considers the aspects of mobility and channel modeling in WBAN scenarios as the directions of future cross-layer research for WBAN and telemedicine applications

A comprehensive review of wireless body area network

Recent development and advancement of information and communication technologies facilitate people in different dimensions of life. Most importantly, in the healthcare industry, this has become more and more involved with the information and communication technology-based services. One of the most important services is monitoring of remote patients, that enables the healthcare providers to observe, diagnose and prescribe the patients without being physically present. The advantage of miniaturization of sensor technologies gives the flexibility of installing in, on or off the body of patients, which is capable of forwarding physiological data wirelessly to remote servers. Such technology is named as Wireless Body Area Network (WBAN). In this paper, WBAN architecture, communication technologies for WBAN, challenges and different aspects of WBAN are illustrated. This paper also describes the architectural limitations of existing WBAN communication frameworks. blueFurthermore, implementation requirements are presented based on IEEE 802.15.6 standard. Finally, as a source of motivation towards future development of research incorporating Software Defined Networking (SDN), Energy Harvesting (EH) and Blockchain technology into WBAN are also provided

Reducing linearity requirements for in-body communication in the medical implant communication service band

Mestrado em Engenharia Eletrónica e TelecomunicaçõesSem resumo disponíve

Experimental Characterisation of Body-Centric Radio Channels Using Wireless Sensors

PhDWireless sensors and their applications have become increasingly attractive for industry, building automation and energy control, paving the way for new applications of sensor networks which go well beyond traditional sensor applications. In recent years, there has been a rapid growth in the number of wireless devices operating in close proximity to the human body. Wearable sensor nodes are growing popular not only in our normal living lifestyle, but also within healthcare and military applications, where different radio units operating in/on/off body communicate pervasively. Expectations go beyond the research visions, towards deployment in real-world applications that would empower business processes and future business cases. Although theoretical and simulation models give initial results of the antenna behaviour and the radio channel performance of wireless body area network (WBAN) devices, empirical data from different set of measurements still form an essential part of the radio propagation models. Usually, measurements are performed in laboratory facilities which are equipped with bulky and expensive RF instrumentation within calibrated and controllable environments; thus, the acquired data has the highest possible reliability. However, there are still measurement uncertainties due to cables and connections and significant variations when designs are deployed and measured in real scenarios, such as hospitals wards, commercial buildings or even the battle field. Consequently, more flexible and less expensive measurement tools are required. In this sense, wireless sensor nodes offer not only easiness to deploy or flexibility, but also adaptability to different environments. In this thesis, custom-built wireless sensor nodes are used to characterise different on-body radio channels operating in the IEEE 802.15.4 communication standard at the 2.45 GHz ISM band. Measurement results are also compared with those from the conventional technique using a Vector Network Analyser. The wireless sensor nodes not only diminished the effect of semi-rigid or flexible coaxial cables (scattering or radiation) used with the Vector Network Analyser (VNA), but also provided a more realistic response of the radio link channel. The performance of the wireless sensors is presented over each of the 16 different channels present at the 2.45 GHz band. Additionally, custom-built wireless sensors are used to characterise and model the performance of different on-body radio links in dynamic environments, such as jogging, rowing, and cycling. The use of wireless sensors proves to be less obstructive and more flexible than traditional measurements using coaxial cables, VNA or signal generators. The statistical analysis of different WBAN channels highlighted important radio propagation features which can be used as sport classifiers models and motion detection. Moreover, specific on-body radio propagation channels are further explored, with the aim to recognize physiological features such as motion pattern, breathing activity and heartbeat. The time domain sample data is transformed to the frequency domain using a non-parametric FFT defined by the Welch’s periodogram. The Appendix-Section D explores other digital signal processing techniques which include spectrograms (STFT) and wavelet transforms (WT). Although a simple analysis is presented, strong DSP techniques proved to be good for signal de-noising and multi-resolution analysis. Finally, preliminary results are presented for indoor tracking using the RSS recorded by multiple wireless sensor nodes deployed in an indoor scenario. In contrast to outdoor environments, indoor scenarios are subject to a high level of multipath signals which are dependent on the indoor clutter. The presented algorithm is based on path loss analysis combined with spatial knowledge of each wireless sensor

Smart Devices and Systems for Wearable Applications

Wearable technologies need a smooth and unobtrusive integration of electronics and smart materials into textiles. The integration of sensors, actuators and computing technologies able to sense, react and adapt to external stimuli, is the expression of a new generation of wearable devices. The vision of wearable computing describes a system made by embedded, low power and wireless electronics coupled with smart and reliable sensors - as an integrated part of textile structure or directly in contact with the human body. Therefore, such system must maintain its sensing capabilities under the demand of normal clothing or textile substrate, which can impose severe mechanical deformation to the underlying garment/substrate. The objective of this thesis is to introduce a novel technological contribution for the next generation of wearable devices adopting a multidisciplinary approach in which knowledge of circuit design with Ultra-Wide Band and Bluetooth Low Energy technology, realization of smart piezoresistive / piezocapacitive and electro-active material, electro-mechanical characterization, design of read-out circuits and system integration find a fundamental and necessary synergy. The context and the results presented in this thesis follow an “applications driven” method in terms of wearable technology. A proof of concept has been designed and developed for each addressed issue. The solutions proposed are aimed to demonstrate the integration of a touch/pressure sensor into a fabric for space debris detection (CApture DEorbiting Target project), the effectiveness of the Ultra-Wide Band technology as an ultra-low power data transmission option compared with well known Bluetooth (IR-UWB data transmission project) and to solve issues concerning human proximity estimation (IR-UWB Face-to-Face Interaction and Proximity Sensor), wearable actuator for medical applications (EAPtics project) and aerospace physiology countermeasure (Gravity Loading Countermeasure Skinsuit project)

Low Power Decoding Circuits for Ultra Portable Devices

A wide spread of existing and emerging battery driven wireless devices do not necessarily demand high data rates. Rather, ultra low power, portability and low cost are the most desired characteristics. Examples of such applications are wireless sensor networks (WSN), body area networks (BAN), and a variety of medical implants and health-care aids. Being small, cheap and low power for the individual transceiver nodes, let those to be used in abundance in remote places, where access for maintenance or recharging the battery is limited. In such scenarios, the lifetime of the battery, in most cases, determines the lifetime of the individual nodes. Therefore, energy consumption has to be so low that the nodes remain operational for an extended period of time, even up to a few years. It is known that using error correcting codes (ECC) in a wireless link can potentially help to reduce the transmit power considerably. However, the power consumption of the coding-decoding hardware itself is critical in an ultra low power transceiver node. Power and silicon area overhead of coding-decoding circuitry needs to be kept at a minimum in the total energy and cost budget of the transceiver node. In this thesis, low power approaches in decoding circuits in the framework of the mentioned applications and use cases are investigated. The presented work is based on the 65nm CMOS technology and is structured in four parts as follows: In the first part, goals and objectives, background theory and fundamentals of the presented work is introduced. Also, the ECC block in coordination with its surrounding environment, a low power receiver chain, is presented. Designing and implementing an ultra low power and low cost wireless transceiver node introduces challenges that requires special considerations at various levels of abstraction. Similarly, a competitive solution often occurs after a conclusive design space exploration. The proposed decoder circuits in the following parts are designed to be embedded in the low power receiver chain, that is introduced in the first part. Second part, explores analog decoding method and its capabilities to be embedded in a compact and low power transceiver node. Analog decod- ing method has been theoretically introduced over a decade ago that followed with early proof of concept circuits that promised it to be a feasible low power solution. Still, with the increased popularity of low power sensor networks, it has not been clear how an analog decoding approach performs in terms of power, silicon area, data rate and integrity of calculations in recent technologies and for low data rates. Ultra low power budget, small size requirement and more relaxed demands on data rates suggests a decoding circuit with limited complexity. Therefore, the four-state (7,5) codes are considered for hardware implementation. Simulations to chose the critical design factors are presented. Consequently, to evaluate critical specifications of the decoding circuit, three versions of analog decoding circuit with different transistor dimensions fabricated. The measurements results reveal different trade-off possibilities as well as the potentials and limitations of the analog decoding approach for the target applications. Measurements seem to be crucial, since the available computer-aided design (CAD) tools provide limited assistance and precision, given the amount of calculations and parameters that has to be included in the simulations. The largest analog decoding core (AD1) takes 0.104mm2 on silicon and the other two (AD2 and AD3) take 0.035mm2 and 0.015mm2, respectively. Consequently, coding gain in trade-off with silicon area and throughput is presented. The analog decoders operate with 0.8V supply. The achieved coding gain is 2.3 dB at bit error rates (BER)=0.001 and 10 pico-Joules per bit (pJ/b) energy efficiency is reached at 2 Mbps. Third part of this thesis, proposes an alternative low power digital decoding approach for the same codes. The desired compact and low power goal has been pursued by designing an equivalent digital decoding circuit that is fabricated in 65nm CMOS technology and operates in low voltage (near-threshold) region. The architecture of the design is optimized in system and circuit levels to propose a competitive digital alternative. Similarly, critical specifications of the decoder in terms of power, area, data rate (speed) and integrity are reported according to the measurements. The digital implementation with 0.11mm2 area, consumes minimum energy at 0.32V supply which gives 9 pJ/b energy efficiency at 125 kb/s and 2.9 dB coding gain at BER=0.001. The forth and last part, compares the proposed design alternatives based on the fabricated chips and the results attained from the measurements to conclude the most suitable solution for the considered target applications. Advantages and disadvantages of both approaches are discussed. Possible extensions of this work is introduced as future work