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Traditionally, electrical brain-computer interfaces (BCIs) have required the assembly of two separate components: electrodes for interfacing with tissue and electronics for signal acquisition and stimulation. Furthermore, these electronics required cabled connections to workstations for data processing and control. Efforts to overcome these limitations have made significant progress in the last decade. Now, there are in vivo validated monolithic electrophysiological BCI devices, exemplified by the Neuropixels, that integrate the two components onto a single platform. At the same time, a new generation of fully wireless BCI devices that reside entirely under the skin has been developed. Despite these advancements, the current state-of-the-art BCIs have yet to overcome both challenges simultaneously. Multi-channel, high-bandwidth monolithic BCIs still require percutaneous wired connections, whereas wireless BCIs rely on the assembly of discrete components that result in bulky form factors. The next generation of BCIs calls for a new paradigm that integrates electrodes and electronics into a miniaturized form factor while supporting a fully wireless operation. This thesis contributes to the collaborative effort that presents such a paradigm through the development of a wireless, battery-free micro-electrocorticography (μECoG) device that monolithically integrates electrodes, signal processing, data telemetry, and powering onto a single complementary metal-oxide-semiconductor (CMOS) substrate. The device contains 65,536 recording and 16,384 stimulation channels, from which a programmable subset of up to 1024 channels can berecorded at a given time. Implemented in a mechanically flexible, 50-μm-thick form factor with a total volume of only 7.2 mm³, the device is implanted entirely in the subdural space and conforms to the contour of the cortical tissue surface. A custom "relay station" provides wireless powering and bi-directional communication to the implant from outside the body. The system was validated through a series of proof-of-concept in vivo recordings from different cortical regions of a pig and non-human primates, reliably decoding brain signals at high spatiotemporal resolution. By using a unique, fully integrated architecture, the BCI developed in this work achieves orders-of-magnitude improvements in volumetric efficiency and channel count over existing approaches, setting a milestone for the next generation of BCI devices.

Dans cette thèse, on vise deux types d'applications de l’antenne à résonateur diélectrique (DRA): 1) La réalisation d’un élément rayonnant pour un réseau phasé embarqué sur un véhicule terrestre ou un avion. Cet élément de base requiert une couverture en élévation supérieure à celle des éléments imprimés pour permettre une poursuite typique comprise entre ±70°. La couverture dans un cône large est assurée avec une bonne pureté de polarisation circulaire en alimentant l’antenne à travers deux ouvertures à fente en H orthogonales parfaitement découplées en bande X. 2) La deuxième structure est destinée à la diversité d’antennes dans le contexte des réseaux corporels embarqués ou Body Area Network (BAN). L’antenne à diversité combine une antenne fente en boucle avec un DRA ce qui permet dans un espace compact de réaliser des diagrammes de type “broadside” et “endfire” respectivement. Les alimentations considérées sont de 2 types; Soit purement planaire (microruban et coplanaire) soit mixte en combinant une alimentation coaxiale et une alimentation coplanaire. Caractéristiques principales des antennes à résonateur diélectrique (DRA): Pour répondre aux attentes des utilisateurs en termes de débit, les systèmes de communication sans fils se tournent vers des fréquences de plus en plus élevées. La conséquence de cette montée en fréquence est notamment l’augmentation des pertes au niveau des éléments conducteurs et donc une diminution de l’efficacité globale des systèmes de communication. Dans ces circonstances, les DRA offre de meilleurs résultats par rapport à d'autres familles d'antennes à base d’éléments métalliques. De plus, les DRA offrent des pertes diélectriques négligeables, elles sont peu sensibles aux variations de température et s’intègrent facilement sur des technologies de fabrication planaires / Technologies such as direct broad cast satellite system (DBSS), Geosynchronous Earth Orbit (GEO) and Low Earth Orbit (LEO) satellite communications , global positioning system (GPS), high accuracy airborne navigation system and a large variety of radar systems demand for high level of antenna performance. Similar is the requirement for upcoming land based wireless systems such as cellular and indoor communication systems that is needed some more specific and additional features added to the antenna to compensate for the deficiencies encountered in system's performance. Though metallic antennas are capable enough to fulfil all the operational requirements, however at very high frequencies and under hostile temperature conditions they are constrained to face certain limitations. To avoid these constraints the performance of Dielectric Resonator Antennas (DRAs) is evaluated and their new applications are proposed. In the thesis, two types of antenna applications are sought :-First is for tracking and satellite applications that needs a larger aperture coverage in elevation plane. This coverage is realized with a good CP purity by proposing two ports dual linearly polarized DRA working at X-band. The DRA is excited by two orthogonal H-shaped aperture slots yielding two orthogonal polarizations in the broadside direction. A common impedance bandwidth of 5.9% and input port isolation of -35 dB are obtained. The broadside radiation patterns are found to be highly symmetric and stable with cross polarization levels -15dB or better over the entire matching frequency band. The maximum measured gain is found to be 2.5dBi at 8.4 GHz.- The 2nd type of antenna is a dual pattern diversity antenna to be used in the Body Area Network (BAN) context. This antenna combines a slot loop and DRA yielding broadside and end-fire radiation patterns respectively. Based upon the feeding techniques, the DG antenna is further divided into two categories one with planar feeds and the other with non-planar feeds (slot loop excited by planar CPW but DRA excited by vertical monopole) .Both types are successfully designed and measured upon body when configured into different propagation scenarios. The non-planar feeds antenna allows wider common impedance bandwidths than the planar feeds (4.95% vs 1.5%).In both cases, a maximum value of DG=9.5dB was achieved when diversity performance tests were carried out in rich fading environments. This value is close to the one (10 dB) theoretically reached in a pure Rayleigh environment and was obtained with efficiencies of 70% and 85% for the slot loop and the DRA respectively. Therefore, we conclude that these antennas could be used on the shoulders or the chest of professional clothes (firemen, policemen, soldier) where full planar integration is not a key issue but where the communication must be efficient in harsh environments and for various gestures, positions and scenarios

"Our modern society is increasingly relying on the collection, processing, and sharing of digital information. There are two fundamental trends: (1) Enabled by the rapid developments in sensor, wireless, and networking technologies, communication and networking are becoming more and more pervasive and ad hoc. (2) Driven by the explosive growth of hardware and software capabilities, computation power is becoming a public utility and information is often stored in centralized servers which facilitate ubiquitous access and sharing. Many emerging platforms and systems hinge on both dimensions, such as E-healthcare and Smart Grid. However, the majority information handled by these critical systems is usually sensitive and of high value, while various security breaches could compromise the social welfare of these systems. Thus there is an urgent need to develop security and privacy mechanisms to protect the authenticity, integrity and confidentiality of the collected data, and to control the disclosure of private information. In achieving that, two unique challenges arise: (1) There lacks centralized trusted parties in pervasive networking; (2) The remote data servers tend not to be trusted by system users in handling their data. They make existing security solutions developed for traditional networked information systems unsuitable. To this end, in this dissertation we propose a series of user-centric security and privacy mechanisms that resolve these challenging issues in untrusted network and computing environments, spanning wireless body area networks (WBAN), mobile social networks (MSN), and cloud computing. The main contributions of this dissertation are fourfold. First, we propose a secure ad hoc trust initialization protocol for WBAN, without relying on any pre-established security context among nodes, while defending against a powerful wireless attacker that may or may not compromise sensor nodes. The protocol is highly usable for a human user. Second, we present novel schemes for sharing sensitive information among distributed mobile hosts in MSN which preserves user privacy, where the users neither need to fully trust each other nor rely on any central trusted party. Third, to realize owner-controlled sharing of sensitive data stored on untrusted servers, we put forward a data access control framework using Multi-Authority Attribute-Based Encryption (ABE), that supports scalable fine-grained access and on-demand user revocation, and is free of key-escrow. Finally, we propose mechanisms for authorized keyword search over encrypted data on untrusted servers, with efficient multi-dimensional range, subset and equality query capabilities, and with enhanced search privacy. The common characteristic of our contributions is they minimize the extent of trust that users must place in the corresponding network or computing environments, in a way that is user-centric, i.e., favoring individual owners/users."

The Finite Difference Time Domain (FDTD) Method has been a powerful tool in numerical simulation of electromagnetic (EM) problems for decades. In recent years, it has also been applied to biomedical research to investigate the interaction between EM waves and biological tissues. In Wireless Body Area Networks (WBANs) studies, to better understand the localization problem within the body, an accurate source/receiver model must be investigated. However, the traditional source models in FDTD involve effective volume and may cause error in near field arbitrary direction. This thesis reviews the basic mathematical and numerical foundation of the Finite Difference Time Domain method and the material properties needed when modeling a human body in FDTD. Then Coincident Phase Centers (CPCs) point sources models have been introduced which provide nearly the same accuracy at the distances as small as 3 unit cells from the phase center. Simultaneously, this model outperforms the usual sources in the near field when an arbitrary direction of the electric or magnetic dipole moment is required.

Capacitive communication using human body as a electrical channel has attracted much attention in the area of personal area networks (PANs) since its introduction by Zimmerman in 1995. The reason being that the personal information and communication appliances are becoming an integral part of our daily lives. The advancement in technology is also helping a great deal in making them interesting,useful and very much affordable. If we interconnect these body-based devices with capacitive communication approach in a manner appropriate to the power, size, cost and functionality, it lessens the burden of supporting a communication channel by existing wired and wireless technologies. More than that, using body as physical communication channel for a PAN device compared to traditional radio transmission seems to have a lot of inherent advantages in terms of power and security etc. But still a lot of feasibility and reliability issues have to be addressed before it is ready for prime time. This promising technology is recently sub-classified into body area networks (BAN) and is currently under discussion in the IEEE 802.15.6 Task Group for addressing the technical requirements to unleash its full potential for BANs. This could play a part in Ericsson's envision of  50 billion connections by 2020. This thesis work is part of the main project to investigate the models, interface and derive requirements on the analog-front-end (AFE) required for the system. Also to suggest a first order model of the AFE that suits this communication system.In this thesis work the human body is modeled along with interfaces and transceiver to reflect the true condition of the system functioning. Various requirements like sensitivity, dynamic range, noise figure and signal-to-noise ratio (SNR) requirements are derived based on the system model. An AFE model based on discrete components is simulated, which was later used for proof of concept. Also a first order AFE model is developed based on the requirements derived. The AFE model is simulated under the assumed interference and noise conditions. The first order requirements for the submodules of the AFE are also derived. Future work and challenges are discussed.

M. Tech. Information Networks / This dissertation reports on a prototype implementation of an architecture that seamlessly integrates Wireless Body Area Networks with Web services for ubiquitous healthcare service provisioning. The prototype ubiquitous monitoring system proactively collects body physiological signals of remote patients to recommend diagnostic services. The technologies that are based upon Wireless Body Area Networks and Web services can provide ubiquitous accessibility to variety of services by allowing distributed healthcare resources to be massively reused. This contributes to improving quality of healthcare services and shields individuals from physically moving to locations where healthcare services are provided, except in a critical situation. In addition, the technology can reduce costs of healthcare services by allowing individuals to remotely access services to support their healthcare. Especially our system is designed for ubiquitous monitoring of elderly and patients in recovery (or rehabilitation). The Wireless Body Area Networks - Web services architecture is at crossroad of embedded engineering of hardware, software and networking protocols. Testing of the prototype was carried out on enthusiastic volunteers and it has shown to be an efficient, reliable and support state-of-art service provisioning of ubiquitous healthcare monitoring in health sector.

Personal computing devices are becoming more and more popular. These devices are able to collaborate with each other using wireless communication technologies, and then support many applications. Some interesting examples of these are healthcare, context-aware computing, and sports training. In any such applications, security is of vital importance. Firstly, sensitive personal data is always collected in these applications, thus confidentiality is usually required. Secondly, authenticity and integrity of data or instructions are always critical; incorrect data or instructions are not only useless, but also harmful in some cases. This thesis analyses the security requirements of personal networks, and develops a number of multi-channel security protocols. With the help of out-of-band channels, especially no-spoofing and no-blocking out-of-band channels, these protocols can bootstrap security in personal networks. In particular, three kinds of security protocols have been studied: protocols that use human-controlled channels, protocols that use visible light communications, and protocols that use intra-body communications. Interesting trade-offs have been discovered among communication, computation and security, resulting from different channel implementations and protocols.

Abstract The value of wearable market is booming, especially in the healthcare application segment. This segment is driven by an increasing need for regular monitoring and early diagnosis of patients with growing prevalence of chronic diseases. Wireless communications worn in the close proximity of the body, the variety of applications, and their requirements set design considerations and challenges. In addition to the technical requirements, coexistence with adjacent wireless body area networks (WBANs) and other wireless systems need to be taken into account. A WBAN system needs to be highly reliable, low power, fast, and interference-immune. This thesis studies the performance of two different PHY layer implementations in interfered fading channels. The systems are the frequency modulated ultra wideband (FM-UWB), defined in the IEEE 802.15.6 standard, and narrowband SmartBAN physical layer. The performance of the systems was analyzed by using software simulators developed in Matlab. The author developed the SmartBAN simulator for the ETSI Technical Committee (TC) SmartBAN to study the performance of the new SmartBAN system. This is the first physical layer performance study of the SmartBAN system. In addition, the open literature does not offer similar results on the FM-UWB as presented in this thesis. Based on the results, it can be concluded that the FM-UWB is performing well in situations where high reliability and high interference tolerance is needed. In addition, the simplicity of the FM-UWB transceiver makes it more suitable than the direct sequence UWB (DS-UWB) for applications with data rates of hundreds of kbps. SmartBAN has the best performance in cases where more relaxed requirements for reliability and interference tolerance can be applied. Nevertheless, it became obvious that both systems need proper coexistence and interference mitigation mechanisms to ensure reliability in all scenarios. / Tiivistelmä Puettavien laitteiden markkina-arvo on voimakkaassa kasvussa erityisesti terveydenhuollon sovellusalueella. Tämän sovellusalueen kiihdyttimenä toimii yhä suurempi tarve potilaiden kunnon jatkuvalle tarkkailulle sekä kroonisille taudeille alttiimpien potilaiden varhaiselle diagnosoinnille. Langattoman kehoverkon (WBAN) suunnittelun suurimpia haasteita ovat langaton tiedonsiirto kehon läheisyydessä, erilaiset sovellustyypit sekä niiden vaatimukset. Teknisten vaatimusten lisäksi on myös huomioitava rinnakkaiset kehoverkot sekä muut langattomat järjestelmät. Kehoverkkojärjestelmän on oltava todella luotettava, matalatehoinen, nopea ja häiriösietoinen. Väitöskirjassa tutkitaan kahta kehoverkon fyysisen kerroksen toteutusta häipyvissä ja häirityissä kanavissa. Nämä toteutukset ovat IEEE 802.15.6 -standardissa määritelty taajuusmoduloitu ultralaajakaista (FM-UWB) sekä kapeakaistainen SmartBAN. Järjestelmien suorituskykyä analysoitiin Matlab-ohjelmistosimulaattoreiden avulla. Työssä kehitettiin SmartBAN-simulaattori ETSI Technical Committee (TC) SmartBAN -työryhmälle järjestelmän suorityskykytutkimukseen. Tässä työssä esitetään SmartBAN-järjestelmän fyysisen kerroksen suorituskykytulokset, jotka ovat ensimmäiset laatuaan. Lisäksi kirjallisuudesta ei löydy vastaavia tuloksia FM-UWB:n osalta, kuten tässä työssä on esitetty. Tuloksien pohjalta voidaan päätellä, että FM-UWB suoriutuu hyvin tilanteissa, joissa vaaditaan suurta luotettavuutta sekä suurta häiriönsietokykyä. Lisäksi yksinkertainen lähetin-vastaanotinrakenne tekee siitä kiinnostavamman vaihtoehdon kuin suorahajotettu UWB (DS-UWB) sovelluksille, jotka vaativat satojen kbps:n tiedonsiirtonopeutta. SmartBAN toimii hyvin tilanteissa, joissa näistä vaatimuksista voidaan hieman joustaa. Kuitenkin on selvää, että molemmat järjestelmät tarvitsevat sopivan rinnakkais- ja häiriönvaimennustekniikan taatakseen luotettavuuden kaikissa tapauksissa.

This paper presents a scheduling algorithm for point to point wireless power transfer system (WPTS) to sensor nodes of wireless body area networks (WBAN). Since the sensors of wireless body area networks are continuously monitoring and sending data to remote central unit, power crisis for these sensor nodes degrades the data transfer of patient monitoring system. Although energy harvesting from ambient sources using electromagnetic induction enhances the longevity of sensor performance, continuous operation in the primary side decreases the overall efficiency. With such paradigm in sight, a framework is proposed for increasing the primary battery longevity and reducing the transmission loss, inductive power is transmitted from primary to secondary unit using medium access control (MAC) protocols for underlying the centralized scheduling opportunity in a collision free scheme for channel access of rare yet critical emergency situation. In a preliminary study, the proposed scheduling for charging sensor nodes in a wireless body area network (WBAN) is evaluated in a case consideration.