Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics

A NOVEL CONSTRUCTION OF VECTOR COMBINATORIAL (VC) CODE FAMILIES AND DETECTION SCHEME FOR SAC OCDMA SYSTEMS

There has been growing interests in using optical code division multiple access (OCDMA) systems for the next generation high-speed optical fiber networks. The advantage of spectral amplitude coding (SAC-OCDMA) over conventional OCDMA systems is that, when using appropriate detection technique, the multiple access interference (MAI) can totally be canceled. The motivation of this research is to develop new code families to enhance the overall performance of optical OCDMA systems. Four aspects are tackled in this research. Firstly, a comprehensive discussion takes place on all important aspects of existing codes from advantages and disadvantages point of view. Two algorithms are proposed to construct several code families namely Vector Combinatorial (VC). Secondly, a new detection technique based on exclusive-OR (XOR) logic is developed and compared to the reported detection techniques. Thirdly, a software simulation for SAC OCDMA system with the VC families using a commercial optical system, Virtual Photonic Instrument, “VPITM TransmissionMaker 7.1” is conducted. Finally, an extensive investigation to study and characterize the VC-OCDMA in local area network (LAN) is conducted. For the performance analysis, the effects of phase-induced intensity noise (PIIN), shot noise, and thermal noise are considered simultaneously. The performances of the system compared to reported systems were characterized by referring to the signal to noise ratio (SNR), the bit error rate (BER) and the effective power (Psr). Numerical results show that, an acceptable BER of 10−9 was achieved by the VC codes with 120 active users while a much better performance can be achieved when the effective received power Psr > -26 dBm. In particular, the BER can be significantly improved when the VC optimal channel spacing width is carefully selected; best performance occurs at a spacing bandwidth between 0.8 and 1 nm. The simulation results indicate that VC code has a superior performance compared to other reported codes for the same transmission quality. It is also found that for a transmitted power at 0 dBm, the BER specified by eye diagrams patterns are 10-14 and 10-5 for VC and Modified Quadratic Congruence (MQC) codes respectively

Photonic Vector Processing Techniques for Radiofrequency Signals

[EN] The processing of radiofrequency signals using photonics means is a discipline that appeared almost at the same time as the laser and the optical fibre. Photonics offers the capability of managing broadband radiofrequency (RF) signals thanks to its low transmission attenuation, a variety of linear and non-linear phenomena and, recently, the potential to implement integrated photonic subsystems. These features open the door for the implementation of multiple functionalities including optical transportation, up and down frequency conversion, optical RF filtering, signal multiplexing, de-multiplexing, routing and switching, optical sampling, tone generation, delay control, beamforming and photonic generation of digital modulations, and even a combination of several of these functionalities. This thesis is focused on the application of vector processing in the optical domain to radiofrequency signals in two fields of application: optical beamforming, and photonic vector modulation and demodulation of digital quadrature amplitude modulations. The photonic vector control enables to adjust the amplitude and phase of the radiofrequency signals in the optical domain, which is the fundamental processing that is required in different applications such as beamforming networks for direct radiating array (DRA) antennas and multilevel quadrature modulation. The work described in this thesis include different techniques for implementing a photonic version of beamforming networks for direct radiating arrays (DRA) known as optical beamforming networks (OBFN), with the objectives of providing a precise control in terrestrial applications of broadband signals at very high frequencies above 40 GHz in communication antennas, optimizing the size and mass when compared with the electrical counterparts in space application, and presenting new photonic-based OBFN functionalities. Thus, two families of OBFNs are studied: fibre-based true time delay architectures and integrated networks. The first allow the control of broadband signals using dispersive optical fibres with wavelength division multiplexing techniques and advanced functionalities such as direction of arrival estimation in receiving architectures. In the second, passive OBFNs based on monolithically-integrated Optical Butler Matrices are studied, including an ultra-compact solution using optical heterodyne techniques in silicon-on-insulator (SOI) material, and an alternative implementing a homodyne counterpart in germanium doped silica material. In this thesis, the application of photonic vector processing to the generation of quadrature digital modulations has also been investigated. Multilevel modulations are based on encoding digital information in discrete states of phase and amplitude of an electrical signal to enhance spectral efficiency, as for instance, in quadrature modulation. The signal process required for generating and demodulating this kind of signals involves vector processing (phase and amplitude control) and frequency conversion. Unlike the common electronic or digital implementation, in this thesis, different photonic based signal processing techniques are studied to produce digital modulation (photonic vector modulation, PVM) and demodulation (PVdM). These techniques are of particular interest in the case of broadband signals where the data rate required to be managed is in the order of gigabit per second, for applications like wireless backhauling of metro optical networks (known as fibre-to-the-air). The techniques described use optical dispersion in optical fibres, wavelength division multiplexing and photonic up/down conversion. Additionally, an optical heterodyne solution implemented monolithically in a photonic integrated circuit (PIC) is also described.[ES] El procesamiento de señales de radiofrecuencia (RF) utilizando medios fotónicos es una disciplina que apareció casi al mismo tiempo que el láser y la fibra óptica. La fotónica ofrece la capacidad de manipular señales de radiofrecuencia de banda ancha, una baja atenuación, procesados basados en una amplia variedad de fenómenos lineales y no lineales y, recientemente, el potencial para implementar subsistemas fotónicos integrados. Estas características ofrecen un gran potencial para la implementación de múltiples funcionalidades incluyendo transporte óptico, conversión de frecuencia, filtrado óptico de RF, multiplexación y demultiplexación de señales, encaminamiento y conmutación, muestreo óptico, generación de tonos, líneas de retardo, conformación de haz en agrupaciones de antenas o generación fotónica de modulaciones digitales, e incluso una combinación de varias de estas funcionalidades. Esta tesis se centra en la aplicación del procesamiento vectorial en el dominio óptico de señales de radiofrecuencia en dos campos de aplicación: la conformación óptica de haces y la modulación y demodulación vectorial fotónica de señales digitales en cuadratura. El control fotónico vectorial permite manipular la amplitud y fase de las señales de radiofrecuencia en el dominio óptico, que es el procesamiento fundamental que se requiere en diferentes aplicaciones tales como las redes de conformación de haces para agrupaciones de antenas y en la modulación en cuadratura. El trabajo descrito en esta tesis incluye diferentes técnicas para implementar una versión fotónica de las redes de conformación de haces de en agrupaciones de antenas, conocidas como redes ópticas de conformación de haces (OBFN). Se estudian dos familias de redes: arquitecturas de retardo en fibra óptica y arquitecturas integradas. Las primeras permiten el control de señales de banda ancha utilizando fibras ópticas dispersivas con técnicas de multiplexado por división de longitud de onda y funcionalidades avanzadas tales como la estimación del ángulo de llegada de la señal en la antena receptora. En la segunda, se estudian redes de conformación pasivas basadas en Matrices de Butler ópticas integradas, incluyendo una solución ultra-compacta utilizando técnicas ópticas heterodinas en silicio sobre aislante (SOI), y una alternativa homodina en sílice dopado con germanio. En esta tesis, también se han investigado técnicas de procesado vectorial fotónico para la generación de modulaciones digitales en cuadratura. Las modulaciones multinivel codifican la información digital en estados discretos de fase y amplitud de una señal eléctrica para aumentar su eficiencia espectral, como por ejemplo la modulación en cuadratura. El procesado necesario para generar y demodular este tipo de señales implica el procesamiento vectorial (control de amplitud y fase) y la conversión de frecuencia. A diferencia de la implementación electrónica o digital convencional, en esta tesis se estudian diferentes técnicas de procesado fotónico tanto para la generación de modulaciones digitales (modulación vectorial fotónica, PVM) como para su demodulación (PVdM). Esto es de particular interés en el caso de señales de banda ancha, donde la velocidad de datos requerida es del orden de gigabits por segundo, para aplicaciones como backhaul inalámbrico de redes ópticas metropolitanas (conocida como fibra hasta el aire). Las técnicas descritas se basan en explotar la dispersión cromática de la fibra óptica, la multiplexación por división de longitud de onda y la conversión en frecuencia. Además, se presenta una solución heterodina implementada monolíticamente en un circuito integrado fotónico (PIC).[CA] El processament de senyals de radiofreqüència (RF) utilitzant mitjans fotònics és una disciplina que va aparèixer gairebé al mateix temps que el làser i la fibra òptica. La fotònica ofereix la capacitat de manipular senyals de radiofreqüència de banda ampla, una baixa atenuació, processats basats en una àmplia varietat de fenòmens lineals i no lineals i, recentment, el potencial per implementar subsistemes fotònics integrats. Aquestes característiques ofereixen un gran potencial per a la implementació de múltiples funcionalitats incloent transport òptic, conversió de freqüència, filtrat òptic de RF, multiplexació i demultiplexació de senyals, encaminament i commutació, mostreig òptic, generació de tons, línies de retard, conformació de feix en agrupacions d'antenes i la generació fotònica de modulacions digitals, i fins i tot una combinació de diverses d'aquestes funcionalitats. Aquesta tesi es centra en l'aplicació del processament vectorial en el domini òptic de senyals de radiofreqüència en dos camps d'aplicació: la conformació òptica de feixos i la modulació i demodulació vectorial fotònica de senyals digitals en quadratura. El control fotònic vectorial permet manipular l'amplitud i la fase dels senyals de radiofreqüència en el domini òptic, que és el processament fonamental que es requereix en diferents aplicacions com ara les xarxes de conformació de feixos per agrupacions d'antenes i en modulació multinivell. El treball descrit en aquesta tesi inclou diferents tècniques per implementar una versió fotònica de les xarxes de conformació de feixos en agrupacions d'antenes, conegudes com a xarxes òptiques de conformació de feixos (OBFN), amb els objectius de proporcionar un control precís en aplicacions terrestres de senyals de banda ampla a freqüències molt altes per sobre de 40 GHz en antenes de comunicacions, optimitzant la mida i el pes quan es compara amb els homòlegs elèctrics en aplicacions espacials, i la presentació de noves funcionalitats fotòniques per agrupacions d'antenes. Per tant, s'estudien dues famílies de OBFNs: arquitectures de retard en fibra òptica i arquitectures integrades. Les primeres permeten el control de senyals de banda ampla utilitzant fibres òptiques dispersives amb tècniques de multiplexació per divisió en longitud d'ona i funcionalitats avançades com ara l'estimació de l'angle d'arribada del senyal a l'antena receptora. A la segona, s'estudien xarxes de conformació passives basades en Matrius de Butler òptiques en fotònica integrada, incloent una solució ultra-compacta utilitzant tècniques òptiques heterodinas en silici sobre aïllant (SOI), i una alternativa homodina en sílice dopat amb germani. D'altra banda, també s'ha investigat en aquesta tesi tècniques de processament vectorial fotònic per a la generació de modulacions digitals en quadratura. Les modulacions multinivell codifiquen la informació digital en estats discrets de fase i amplitud d'un senyal elèctric per augmentar la seva eficiència espectral, com ara la modulació en quadratura. El processat necessari per generar i desmodular aquest tipus de senyals implica el processament vectorial (control d'amplitud i fase) i la conversió de freqüència. A diferència de la implementació electrònica o digital convencional, en aquesta tesi s'estudien diferents tècniques de processament fotònic tant per a la generació de modulacions digitals (modulació vectorial fotònica, PVM) com per la seva demodulació (PVdM). Això és de particular interès en el cas de senyals de banda ampla, on la velocitat de dades requerida és de l'ordre de gigabits per segon, per a aplicacions com backhaul sense fils de xarxes òptiques metropolitanes (coneguda com fibra fins l'aire). Les tècniques descrites es basen en explotar la dispersió cromàtica de la fibra òptica, la multiplexació per divisió en longitud d'ona i la conversió en freqüència. A més, es presePiqueras Ruipérez, MÁ. (2016). Photonic Vector Processing Techniques for Radiofrequency Signals [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/63264TESI

Mobile and Wireless Communications

Mobile and Wireless Communications have been one of the major revolutions of the late twentieth century. We are witnessing a very fast growth in these technologies where mobile and wireless communications have become so ubiquitous in our society and indispensable for our daily lives. The relentless demand for higher data rates with better quality of services to comply with state-of-the art applications has revolutionized the wireless communication field and led to the emergence of new technologies such as Bluetooth, WiFi, Wimax, Ultra wideband, OFDMA. Moreover, the market tendency confirms that this revolution is not ready to stop in the foreseen future. Mobile and wireless communications applications cover diverse areas including entertainment, industrialist, biomedical, medicine, safety and security, and others, which definitely are improving our daily life. Wireless communication network is a multidisciplinary field addressing different aspects raging from theoretical analysis, system architecture design, and hardware and software implementations. While different new applications are requiring higher data rates and better quality of service and prolonging the mobile battery life, new development and advanced research studies and systems and circuits designs are necessary to keep pace with the market requirements. This book covers the most advanced research and development topics in mobile and wireless communication networks. It is divided into two parts with a total of thirty-four stand-alone chapters covering various areas of wireless communications of special topics including: physical layer and network layer, access methods and scheduling, techniques and technologies, antenna and amplifier design, integrated circuit design, applications and systems. These chapters present advanced novel and cutting-edge results and development related to wireless communication offering the readers the opportunity to enrich their knowledge in specific topics as well as to explore the whole field of rapidly emerging mobile and wireless networks. We hope that this book will be useful for students, researchers and practitioners in their research studies

Investigation of the impact of fibre impairments and SOA-based devices on 2D-WH/TS OCDMA codes

In seeking efficient last-mile solutions for high-capacity, optical code division multiple access (OCDMA) emerges as a promising alternative high-speed optical network that can securely support a multitude of simultaneous users without requiring extensive equipment. This multiplexing technique has recently been the subject of comprehensive research, highlighting its potential for facilitating high-bandwidth multi-access networking. When contrasted with techniques such as wavelength division multiplexing (WDM) and optical time division multiplexing (OTDM), OCDMA offers a more effective and equitable split of available fibre bandwidth among the users. This thesis presents my research focused on the incoherent OCDMA under the influence of optical fibre impairments that uses picosecond multiwavelength pulses to form two-dimensional wavelength hopping time-spreading (2D-WH/TS) incoherent OCDMA codes. In particular, self-phase modulation, temperature induced fibre dispersion, chromatic dispersion, as well as the impact of semiconductor optical amplifier SOA devices deployment on 2D-WH/TS OCDMA code integrity were investigated. These aspects were investigated using a 17-km long bidirectional fibre link between Strathclyde and Glasgow University. In particular, I investigated the impact of temporal skewing among OCDMA code carriers and the importance of selecting small range of wavelengths as code carriers where wide range manifest high dependency on wavelength. This wavelength dependency is exploited furthermore to measure the induced temperature dispersion coefficient accurately and economically. I have conducted experiments to characterise the impact of SOA-device on 2D OCDMA code carries which is evaluated under different bias conditions. This evaluation addressed the potential challenges and ramifications of the gain recovery time of SOA and its wavelength dependency with respect to gain ratio and self-phase modulation (SPM). The OCDMA code was built using multiplexers and delay lines to create a 2D OCDMA code to allow studying the impact of deploying a SOA under different conditions on each wavelength. The concept described above is then extended to the investigation of the SOA’s impact on a 2D-WH/TS OCDMA prime code under high bias current/gain conditions. The overall performance of two different 2D-WH/TS OCDMA systems deploying the SOA was also calculated. I have also investigated the possibility of manipulating chirp in 2D-WH/TS incoherent OCDMA to counteract the self-phase modulation-induced red shift by using single mode fibre and lithium crystals. I have investigated the performance of the picosecond code based optical signal when subjected to temperature variations similar to that experience by most buried fibre systems. I have proposed and demonstrated a novel technique, which I examined analytically and experimentally, that utilises a SOA at the transmitter to create a new code with a new wavelength hopping and spreading time sequences to achieve a unique physical improved secure incoherent OCDMA communication method. A novel fully automated tuneable compensation testbed is also proposed of an autonomous dispersion management in a WH/TS incoherent OCDMA system. The system proposed manipulates the chirp of OCDMA code carriers to limit chromatic dispersion detrimental effect on transmission systems.In seeking efficient last-mile solutions for high-capacity, optical code division multiple access (OCDMA) emerges as a promising alternative high-speed optical network that can securely support a multitude of simultaneous users without requiring extensive equipment. This multiplexing technique has recently been the subject of comprehensive research, highlighting its potential for facilitating high-bandwidth multi-access networking. When contrasted with techniques such as wavelength division multiplexing (WDM) and optical time division multiplexing (OTDM), OCDMA offers a more effective and equitable split of available fibre bandwidth among the users. This thesis presents my research focused on the incoherent OCDMA under the influence of optical fibre impairments that uses picosecond multiwavelength pulses to form two-dimensional wavelength hopping time-spreading (2D-WH/TS) incoherent OCDMA codes. In particular, self-phase modulation, temperature induced fibre dispersion, chromatic dispersion, as well as the impact of semiconductor optical amplifier SOA devices deployment on 2D-WH/TS OCDMA code integrity were investigated. These aspects were investigated using a 17-km long bidirectional fibre link between Strathclyde and Glasgow University. In particular, I investigated the impact of temporal skewing among OCDMA code carriers and the importance of selecting small range of wavelengths as code carriers where wide range manifest high dependency on wavelength. This wavelength dependency is exploited furthermore to measure the induced temperature dispersion coefficient accurately and economically. I have conducted experiments to characterise the impact of SOA-device on 2D OCDMA code carries which is evaluated under different bias conditions. This evaluation addressed the potential challenges and ramifications of the gain recovery time of SOA and its wavelength dependency with respect to gain ratio and self-phase modulation (SPM). The OCDMA code was built using multiplexers and delay lines to create a 2D OCDMA code to allow studying the impact of deploying a SOA under different conditions on each wavelength. The concept described above is then extended to the investigation of the SOA’s impact on a 2D-WH/TS OCDMA prime code under high bias current/gain conditions. The overall performance of two different 2D-WH/TS OCDMA systems deploying the SOA was also calculated. I have also investigated the possibility of manipulating chirp in 2D-WH/TS incoherent OCDMA to counteract the self-phase modulation-induced red shift by using single mode fibre and lithium crystals. I have investigated the performance of the picosecond code based optical signal when subjected to temperature variations similar to that experience by most buried fibre systems. I have proposed and demonstrated a novel technique, which I examined analytically and experimentally, that utilises a SOA at the transmitter to create a new code with a new wavelength hopping and spreading time sequences to achieve a unique physical improved secure incoherent OCDMA communication method. A novel fully automated tuneable compensation testbed is also proposed of an autonomous dispersion management in a WH/TS incoherent OCDMA system. The system proposed manipulates the chirp of OCDMA code carriers to limit chromatic dispersion detrimental effect on transmission systems

Radio over multimode fiber using VCSELS

Master'sMASTER OF ENGINEERIN

Design and implementation of frequency synthesizers for 3-10 ghz mulitband ofdm uwb communication

The allocation of frequency spectrum by the FCC for Ultra Wideband (UWB) communications in the 3.1-10.6 GHz has paved the path for very high data rate Gb/s wireless communications. Frequency synthesis in these communication systems involves great challenges such as high frequency and wideband operation in addition to stringent requirements on frequency hopping time and coexistence with other wireless standards. This research proposes frequency generation schemes for such radio systems and their integrated implementations in silicon based technologies. Special emphasis is placed on efficient frequency planning and other system level considerations for building compact and practical systems for carrier frequency generation in an integrated UWB radio. This work proposes a frequency band plan for multiband OFDM based UWB radios in the 3.1-10.6 GHz range. Based on this frequency plan, two 11-band frequency synthesizers are designed, implemented and tested making them one of the first frequency synthesizers for UWB covering 78% of the licensed spectrum. The circuits are implemented in 0.25µm SiGe BiCMOS and the architectures are based on a single VCO at a fixed frequency followed by an array of dividers, multiplexers and single sideband (SSB) mixers to generate the 11 required bands in quadrature with fast hopping in much less than 9.5 ns. One of the synthesizers is integrated and tested as part of a 3-10 GHz packaged receiver. It draws 80 mA current from a 2.5 V supply and occupies an area of 2.25 mm2. Finally, an architecture for a UWB synthesizer is proposed that is based on a single multiband quadrature VCO, a programmable integer divider with 50% duty cycle and a single sideband mixer. A frequency band plan is proposed that greatly relaxes the tuning range requirement of the multiband VCO and leads to a very digitally intensive architecture for wideband frequency synthesis suitable for implementation in deep submicron CMOS processes. A design in 130nm CMOS occupies less than 1 mm2 while consuming 90 mW. This architecture provides an efficient solution in terms of area and power consumption with very low complexity

Architectures and Novel Functionalities for Optical Access OFDM Networks "Arquitecturas y Nuevas Funcionalidades para Redes OFDM de Acceso Óptico"

En los últimos años ha habido un gran aumento en el despliegue de redes de acceso ópticas de fibra hasta el hogar (FTTH, del inglés fibre-to-the home). FTTH es una solución flexible, una tecnología de acceso de futuro que permite proporcionar tasas de datos del orden de Gbit/s por ususario. Diversos estudios indican que FTTH se convertirá en la diferencia clave entre los operadores más importantes. Además, FTTH es la única tecnolotgía capaz de crear nuevas fuentes de ingresos de aplicaciones de alta velocidad, como por ejemple entretenimiento de alta definición (vído y juegos de alta definición...) Dede el punto de vista del operador, una de las vientajas importantes que proporciona FTTH es que permite una mayor eficiencia operativa en coparción con otras tecnologías de acceso, principalmente por la reducción de costes de mantenimiento y de operación. Además, FTTH reduce los requisitos de los equipos de las centrales. Esta tesis doctoral tiene como ojetivo extender estas ventajas más allá del concepto FTTH mediante la integración de la red óptica de distribución desplegada dentro del hogar así como el enlace radio final de corto o medio alcance inalámbrico. Esto proporciona una arquitctura de red FFTH integrada de extremo a extremo. De este modo, los beneficios de la reducción de costes operativos y mayor eficiencia se extienden hasta el usuario final de la red. En esta tesis doctoral, se propone una arqutectura de acceso integrada óptica-radio basada en la multiplexación por división ortogonal de fecuencia (OFDM, del inglés orthogonal frequency división multiplexing) para proporcionar diferentes servicios al usuario como Internet, teléfono/voz, televisión de lata definición, conexión inalámbrica y seguridad en el hogar. Las señales OFDM se utilizan en muchos estándares inalámbricos como las señales de banda ultraancha (UWB, del inglés ultra-wide band), WiMAX, LTE, WLAN, DVB-T o DAB. Estos formatos aprovechan las características intrínsecas de la modulación OFDM como su mayor inmunidad ante desvanecimiento multi-camino. Esta tesis incluye la propuesta y la demostración experimental de la transmisión simultánea y bi-direccional de señales OFDM multi-estándar en radio-sobre-fibra proporcionando servicios triple-play basados en OFDM como UWB para televisión de alta definición, WiMAX para datos de Internet, y LTE para el servicio telefónico.Morant Perez, M. (2012). Architectures and Novel Functionalities for Optical Access OFDM Networks "Arquitecturas y Nuevas Funcionalidades para Redes OFDM de Acceso Óptico" [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/15076Palanci

Miniaturized antenna and transponder based wireless sensors for internet of things in healthcare

Future medical and healthcare systems will be largely improved by the wide-spreading of internet of things (IoTs). One of the crucial challenges of IoTs for healthcare is at the wireless sensors. Miniaturization of sensor node profile, minimizing power consumption as well as lowering down design/production cost of antenna, RF circuits and sensor modules have become the key issues for realizing more exciting applications in medical and healthcare fields that never seemed to be possible before. In this dissertation work, we first focus on electrically small antenna (ESA) design and fabrication for medical telemetry. A comprehensive analysis of the radiation properties of a novel electrically small folded ellipsoidal ESA is presented, showing its ability to self-resonate and impedance match without external components. It will benefit various size-restricted applications especially with wireless medical implants. The second focus is on healthcare sensors using ESA as the sensing agent, which saves the power and cost by eliminating the need of extra sensing modules. Specifically, miniaturized helix ESAs are integrated with drug reservoirs to function as wireless transponder sensors for real-time drug dosage monitoring. We also introduce a system level innovation of a passive wireless harmonic transponder/harmonic sniffer/frequency hopped interrogator based sensing system. The μL- liquid level resolution and absolute-accuracy passive sensing is demonstrated in the presence of strong direct coupling, background scatters, distance variance as well as near-filed human body movement interference. Furthermore, we investigate how modern ubiquitous wireless sensor networks could take advantage of sensitive nanostructure materials for enhanced performance. Here we propose a new paradigm of chemically-gated mixed modulation on a single homogeneous graphene device in which the chemical exposure directly modulates an electrical carrier signal. To make the device ubiquitously reusable, a method of precisely tuning the charge neutrality point (Vcnp) is introduced by electrochemical calibration with gate voltage pulse sequence. Such chemically gated graphene modulator can be potentially used in a harmonic transponder as a passive ubiquitous sensor node for chemical and bio sensing applications. Overall the research work presented in the dissertation will help enable cost and power-efficient wireless sensor networks in future healthcare IoTs.Electrical and Computer Engineerin