Body area network | EPFL Graph Search

A body area network (BAN), also referred to as a wireless body area network (WBAN) or a body sensor network (BSN) or a medical body area network (MBAN), is a wireless network of wearable computing devices. BAN devices may be embedded inside the body as implants or pills, may be surface-mounted on the body in a fixed position, or may be accompanied devices which humans can carry in different positions, such as in clothes pockets, by hand, or in various bags. While there is a trend toward the miniaturization of devices, in particular body area networks which consist of several miniaturized body sensor units (BSUs) together with a single body central unit (BCU), larger decimeter (tab and pad) sized smart devices still play an important role in terms of acting as a data hub or data gateway and providing a user interface to view and manage BAN applications, in-situ. The development of WBAN technology started around 1995 around the idea of using wireless personal area

Ultra Low-Power Frequency Synthesizers for Duty Cycled IoT radios

Raghavasimhan Thirunarayanan

Internet of Things (IoT), which is one of the main talking points in the electronics industry today, consists of a number of highly miniaturized sensors and actuators which sense the physical environment around us and communicate that information to a central information hub for further processing. This agglomeration of miniaturized sensors helps the system to be deployed in previously impossible arenas such as healthcare (Body Area Networks - BAN), industrial automation, real-time monitoring environmental parameters and so on; thereby greatly improving the quality of life. Since the IoT devices are usually untethered, their energy sources are limited (typically battery powered or energy scavenging) and hence have to consume very low power. Today's IoT systems employ radios that use communication protocols like Bluetooth Smart; which means that they communicate at data rates of a few hundred kb/s to a few Mb/s while consuming around a few mW of power. Even though the power dissipation of these radios have been decreasing steadily over the years, they seem to have reached a lower limit in the recent times. Hence, there is a need to explore other avenues to further reduce this dissipation so as to further improve the energy autonomy of the IoT node. Duty cycling has emerged as a promising alternative in this sense since it involves radios transmitting very short bursts of data at high rates and being asleep the rest of the time. In addition, high data rates proffer the added advantage of reducing network congestion which has become a major problem in IoT owing to the increase in the number of sensor nodes as well as the volume of data they send. But, as the average power (energy) dissipated decreases due to duty cycling, the energy overhead associated with the start-up phase of the radio becomes comparable with the former. Therefore, in order to take full advantage of duty cycling, the radio should be capable of being turned ON/OFF almost instantaneously. Furthermore, the radio of the future should also be able to support easy frequency hopping to improve the system efficiency from an interference point of view. In other words, in addition to high data rate capability, the next generation radios must also be highly agile and have a low energy overhead. All these factors viz. data rate, agility and overhead are mainly dependent on the radio's frequency synthesizer and therefore emphasis needs to be laid on developing new synthesizer architectures which are also amenable to technology scaling. This thesis deals with the evolution of one such all-digital frequency synthesizer; with each step dealing with one of the aforementioned issues. In order to reduce the energy overhead of the synthesizer, FBAR resonators (which are a class of MEMS resonators) are used as the frequency reference instead of a traditional quartz crystal. The FBAR resonators aid the design of fast-startup oscillators as opposed to the long latency associated with the start-up of the crystal oscillator. In addition, the frequency stability of the FBAR lends itself to open-loop architecture which can support very high data rates. Another advantage of the open-loop architecture is the frequency agility which aids easy channel switching for multi-hop architectures, as demonstrated in this thesis.

EPFL2016

Deeply implanted medical device based on a novel ultrasonic telemetry technology

Michela Peisino

Medical devices have gone a long way since their beginning. In the last decades, the trend has been towards Implanted Medical Devices (IMDs). The technology evolution has provided the necessary tools for longer-term, less invasive devices. Several devices for sensing and actuation are commercially available and ease therapy management, while preserving the patient’s life quality. An ideal implant would integrate both sensing and actuating possibilities in a feedback loop, thus achieving optimum therapy. To reach this goal, several challenges remain, in particular concerning power supply and miniaturization. Solving these issues would open new possibilities and allow applications which are not possible yet: better diagnosis could be achieved wherever a continuous, long-term monitoring of physiological parameters in real life conditions is required. For instance, smaller and deeper implanted devices would allow deploying several IMDs in the body, achieving a Body Sensor Network (BSN). Beside therapy, implants could be used for diagnosis in populations at risk. Furthermore, minimal invasive implants would greatly improve medical research, by allowing closer observation, thus helping to understand physiological mechanisms. This thesis describes the author’s contribution to the development of a novel IMD concept, proposed within the European FP7 project ULTRAsponder. The author focused on the integration aspects in the design and manufacturing process of the novel implantable device platform: definition of the technical specifications, assessment of appropriate commercial components, geometrical placement of the Printed Circuit Boards (PCBs) inside the casing, choice of a suitable housing material, and assessment of its effect on the energy transmission. The target is a generic BSN node, which can be implanted wherever needed on a long-term basis and which can operate autonomously. Key features of the proposed system include remote powering of the implanted device and communication with an external Control Unit (CU) by backscattering modulation. For both energy and data transfer, an ultrasonic carrier is used instead of Electromagnetic (EM) waves because it is compatible with Magnetic Resonance Imaging (MRI) and does not interfere with EM emitters like mobile phones and electronic equipment. It also proved to be more efficient than the use of Radio Frequency (RF) waves or magnetic induction to reach deep implants and when using small transducers. The user requirements and the technical constraints towards an optimal implant were evaluated and the characteristics of the proposed system were defined. Appropriate commercial components and emerging technologies were identified, which allowed the development of the device. The originality of this work lies in the integration of different technologies, components and scientific approaches into a novel, promising IMD. In particular, the challenge of achieving an ultrasonic link through a standard medical grade titanium casing is addressed. Titanium casings are the golden standard for biocompatible device housing, but they have a strong influence on ultrasonic energy transfer. Successful integration of ultrasonic transmission and titanium casing ensures the ability of the proposed device to be industrially exploited and commercialized. A demonstrator implant and an external CU have been manufactured, focusing on energy transfer, signal treatment, and backscattering. A commercial, rather large housing was used, in order to demonstrate the industrial viability of the device. In vitro tests validated the energy transfer and the communication between the CU and the Transponder (TR), as well as the user interface. Assessment in real conditions is achieved by in vivo tests on pigs. Functionality was proved, however at a much smaller distance than intended. Future work includes optimization of the ultrasonic transfer, integration of the sensing circuitry, and miniaturization of the resulting device.

EPFL2013

A 2.4-GHz low power polar transmitter for wireless body area network applications

Christian Enz, Vladimir Kopta, Franz Xaver Pengg

A 2.4 GHz low power polar transmitter is proposed in this paper. A dynamic biasing circuit, controlled by a digital envelope signal, is used as a direct digital-to-RF envelope converter. It effectively linearizes the input-output characteristic of the overdriven cascode class-C power amplifier used as the output stage, by dynamically adjusting the bias voltage of the cascode transistor. An equivalent baseband model of the transmitter is presented and used to optimize system parameters and give initial assessment of the achievable performance in terms of efficiency and linearity. Based on these simulations, parameters for transistor-level implementation of the bias circuit are derived. The transmitter is designed in a 65 nm CMOS technology. The post layout simulations indicate that the transmitter successfully meets the requirements of the IEEE 802.15.6 standard for wireless body area networks. The simulated amplifier consumes 4.75 mA from a 1.2 V supply while delivering 1.45 dBm of output power with a peak efficiency of 24 %. The entire transmitter, including the PLL, consumes 7.5 mA.

Springer Verlag2014