RF Transceiver system design for IoT in wide area networks

Abstract. Wireless communication has grown rapidly in the last two decades. New applications and advancement in technology is boosting the demand. Internet of things (IoT) is nowadays topic of discussion for everyone related to the wireless communication industry. IoT is a system of interconnected devices which can be people, animals, things or machines each with a unique identifier and the ability to transfer data over a network without any interaction with humans or computers. The aim of this thesis is system design of RF transceiver for IoT devices operating in wide area networks. Several service providers are struggling to capture the IoT market. In this thesis detailed system design of third generation partnership project (3GPP) newly specified user equipment category M1 also known as long term evolution machine (LTE-M) is presented. LTE-M can operate in both full duplex and half duplex and it uses the same signal structure as the current operational standard long term evolution (LTE). The designed transceiver is able to operate in half duplex and meet the performance requirement (95 % throughput) specified by 3GPP. Radio frequency transceivers have various architectures and each architecture has its own pros and cons associated with it. This transceiver is designed to be integrated in a wearable device. Constraints like small size and low power restrictions led to the choice of direct conversion architecture for the design. Simulations were performed in ADS to verify the theoretical results

Nonlinear effects in lte downlink signals and application of a compensation technique at the receiver side

This article proposes a nonlinear compensation technique for long-term evolution downlink signals based on the memoryless solid-state power amplifier model, which provides a simple and effective linearization technique at the receiver side, allowing a reduction in the error vector magnitude measured characteristics. The error vector magnitude per subcarrier is analyzed for different appropriate resource blocks allocations in the long-term evolution signal to examine the distortion due to the nonlinear effects produced by a power amplifier in the experimental setup.CICYT TEC2008-06259/TECCICE P07-TIC-0264

Sensores passivos alimentados por transmissão de energia sem fios para aplicações de Internet das coisas

Nowadays, the Wireless Sensor Networks (WSNs) depend on the battery duration of the sensors and there is a renewed interest in creating a passive sensor network scheme in the area of Internet of Things (IoT) and space oriented WSN systems. The challenges for the future of radio communications have a twofold evolution, one being the low power consumption and, another, the adaptability and intelligent use of the available resources. Specially designed radios should be used to reduce power consumption, and adapt to the environment in a smart and e cient way. This thesis will focus on the development of passive sensors based on low power communication (backscatter) with Wireless Power Transfer (WPT) capabilities used in IoT applications. In that sense, several high order modulations for the communication will be explored and proposed in order to increase the data rate. Moreover, the sensors need to be small and cost e ective in order to be embedded in other technologies or devices. Consequently, the RF front-end of the sensors will be designed and implemented in Monolithic Microwave Integrated Circuit (MMIC).Atualmente, as redes de sensores sem fios dependem da duração da bateria e,deste modo, existe um interesse renovado em criar um esquema de rede de sensores passivos na área de internet das coisas e sistemas de redes de sensores sem fios relacionados com o espaço. Os desafios do futuro das comunicações de rádio têm uma dupla evolução, sendo um o baixo consumo de energia e, outro, a adaptação e o uso inteligente dos recursos disponíveis. Rádios diferentes dos convencionais devem ser usados para reduzir o consumo de energia e devem adaptar-se ao ambiente de forma inteligente e eficiente, de modo a que este use a menor quantidade de energia possível para estabelecer a comunicação. Esta tese incide sobre o desenvolvimento de sensores passivos baseados em comunicação de baixo consumo energético (backscatter) com recurso a transmissão de energia sem fios de modo a que possam ser usados em diferentes aplicações inseridas na internet das coisas. Nesse sentido, várias modulações de alta ordem para a comunicação backscatter serão exploradas e propostas com o objectivo de aumentar a taxa de transmissão de dados. Além disso, os sensores precisam de ser reduzidos em tamanho e económicos de modo a serem incorporados em outras tecnologias ou dispositivos. Consequentemente, o front-end de rádio frequência dos sensores será projetado e implementado em circuito integrado de microondas monolítico.Programa Doutoral em Engenharia Eletrotécnic

Millimetre-Wave Fibre-Wireless Technologies for 5G Mobile Fronthaul

The unprecedented growth in mobile data traffic, driven primarily by bandwidth rich applications and high definition video is accelerating the development of fifth generation (5G) mobile network. As mobile access network evolves towards centralisation, mobile fronthaul (MFH) architecture becomes essential in providing high capacity, ubiquitous and yet affordable services to subscribers. In order to meet the demand for high data rates in the access, Millimetre-wave (mmWave) has been highlighted as an essential technology in the development of 5G-new radio (5G-NR). In the present MFH architecture which is typically based on common public radio interface (CPRI) protocol, baseband signals are digitised before fibre transmission, featuring high overhead data and stringent synchronisation requirements. A direct application of mmWave 5G-NR to CPRI digital MFH, where signal bandwidth is expected to be up to 1GHz will be challenging, due to the increased complexity of the digitising interface and huge overhead data that will be required for such bandwidth. Alternatively, radio over fibre (RoF) technique can be employed in the transportation of mmWave wireless signals via the MFH link, thereby avoiding the expensive digitisation interface and excessive overhead associated with its implementation. Additionally, mmWave carrier can be realised with the aid of photonic components employed in the RoF link, further reducing the system complexity. However, noise and nonlinearities inherent to analog transmission presents implementation challenges, limiting the system dynamic range. Therefore, it is important to investigate the effects of these impairments in RoF based MFH architecture. This thesis presents extensive research on the impact of noise and nonlinearities on 5G candidate waveforms, in mmWave 5G fibre wireless MFH. Besides orthogonal frequency division multiplexing (OFDM), another radio access technology (RAT) that has received significant attention is filter bank multicarrier (FBMC), particularly due to its high spectral containment and excellent performance in asynchronous transmission. Hence, FBMC waveform is adopted in this work to study the impact of noise and nonlinearities on the mmWave fibre-wireless MFH architecture. Since OFDM is widely deployed and it has been adopted for 5G-NR, the performance of OFDM and FBMC based 5G mmWave RAT in fibre wireless MFH architecture is compared for several implementations and transmission scenarios. To this extent, an end to end transmission testbed is designed and implemented using industry standard VPI Transmission Maker® to investigate five mmWave upconversion techniques. Simulation results show that the impact of noise is higher in FBMC when the signal to-noise (SNR) is low, however, FBMC exhibits better performance compared to OFDM as the SNR improved. More importantly, an evaluation of the contribution of each noise component to the overall system SNR is carried out. It is observed in the investigation that noise contribution from the optical carriers employed in the heterodyne upconversion of intermediate frequency (IF) signals to mmWave frequency dominate the system noise. An adaptive modulation technique is employed to optimise the system throughput based on the received SNR. The throughput of FBMC based system reduced significantly compared to OFDM, due to laser phase noise and chromatic dispersion (CD). Additionally, it is shown that by employing frequency domain averaging technique to enhance the channel estimation (CE), the throughput of FBMC is significantly increased and consequently, a comparable performance is obtained for both waveforms. Furthermore, several coexistence scenarios for multi service transmission are studied, considering OFDM and FBMC based RATs to evaluate the impact inter band interference (IBI), due to power amplifier (PA) nonlinearity on the system performance. The low out of band (OOB) emission in FBMC plays an important role in minimising IBI to adjacent services. Therefore, FBMC requires less guardband in coexistence with multiple services in 5G fibre-wireless MFH. Conversely, OFDM introduced significant OOB to adjacent services requiring large guardband in multi-service coexistence transmission scenario. Finally, a novel transmission scheme is proposed and investigated to simultaneously generate multiple mmWave signals using laser heterodyning mmWave upconversion technique. With appropriate IF and optical frequency plan, several mmWave signals can be realised. Simulation results demonstrate successful simultaneous realisation of 28GHz, 38GHz, and 60GHz mmWave signals

Development of an integrated silicon photonic transceiver for access networks

Debido a la imparable aparición de dispositivos móviles multifunción junto con aplicaciones que requieren cada vez más un mayor ancho de banda en cualquier momento y en cualquier lugar, las futuras redes de acceso deberán ser capaces de proporcionar servicios tanto inalámbricos como cableados. Es por ello que una solución a seguir es el uso de sistemas de comunicaciones ópticas como medio de transporte de señales inalámbricas en enlaces de radio sobre fibra. Con ello, se converge a un dominio óptico reduciendo y aliviando el cuello de botella entre los estándares de acceso inalámbrico y cableado. En esta tesis, como parte de los objetivos establecidos en el proyecto europeo HELIOS en el que está enmarcada, se han investigado y desarrollado los bloques funcionales básicos necesarios para realizar un transceptor fotónico integrado trabajando en el rango de longitudes de onda milimétricas, y haciendo uso de los formatos de modulación más robustos y que mejor se adaptan al ámbito de aplicación considerado. El trabajo que se presenta en esta tesis se puede dividir básicamente en tres partes. La primera de ellas ofrece una descripción general de los beneficios del uso de la fotónica en silicio para el desarrollo de enlaces inalámbricos a velocidades de Gbps, así como el estado del arte de los transceptores desarrollados por los grupos de investigación más activos y punteros para satisfacer las necesidades de mercado, cada vez más exigentes. La segunda parte se centra en el estudio y desarrollo del transmisor integrado de onda milimétrica. Primero realizamos una breve introducción teórica tanto del funcionamiento de los dispositivos que forman parte del transmisor, como a los formatos de modulación existentes, centrando la atención en la modulación por desplazamiento de fase (PSK) que es la que se va a utilizar en el desarrollo de los dispositivos implicados, y más concretamente en la modulación (diferencial) de fase en cuadratura ((D)QPSK). También se presentan los bloques básicos que integran nuestro transmisor y se fijan las especificaciones que deben cumplir dichos bloques para conseguir una transmisión libre de errores. El transmisor está compuesto por un filtro/demultiplexor encargado de separar dos portadoras ópticas separadas una frecuencia de 60 GHz. Una de estas portadoras es modulada al pasar por un modulador DQPSK basado en una estructura de dos MachZehnders (MZs) anidados, para ser nuevamente combinada con la otra portadora óptica que se ha mantenido intacta. Una vez combinadas, éstas son fotodetectadas para ser transmitidas inalámbricamente. En la tercera parte de esta tesis, se investiga el uso de un esquema de diversidad en polarización junto a un receptor DQPSK integrado para la demodulación de la señal recibida. El esquema de diversidad en polarización está formado básicamente por dos bloques: un separador de polarización con el objetivo de separar la luz a la entrada del chip en sus dos componentes ortogonales; y un rotador de polarización. En lo que se refiere al receptor DQPSK propiamente dicho, se ha investigado y optimizado cada uno de los bloques funcionales que lo componen. Éstos son básicamente un divisor de potencia termo-ópticamente sintonizable basado en un interferómetro MZ, en serie con un interferómetro MZ que introduce un retardo de duración de un bit en uno de sus brazos, para obtener una correcta demodulación diferencial. El siguiente bloque que forma parte de nuestro receptor DQPSK es un 2x4 acoplador de interferencia multimodal actuando como un híbrido de 90 grados, cuyas salidas van a parar a dos fotodetectores balanceados de germanio. Las contribuciones principales de esta tesis han sido: ¿ Demostración de un filtro/demultiplexor con tres grados de sintonización con una relación de extinción superior a 25dB. ¿ Demostración de un rotador con una longitud de tan sólo 25µm y CMOS compatible. ¿ Demostración de un modulador DPSK a una velocidad máxima de 20 Gbit/s. ¿ Demostración de un demodulador DQPSK a una velocidad máxima de 20 Gbit/s.Due to the relentless emergence of multifunction mobile devices with applications that require increasingly greater bandwidth at anytime and anywhere, future access networks must be capable of providing both wireless and wired services. The use of optical communications systems as transport medium of wireless signals over fiber radio links is a steady solution to be taken into account. This will make possible a convergence to an optical domain reducing and alleviating the bottleneck between wireless access standards and current wired access. In this thesis, as part of the objectives of the European project HELIOS in which it is framed, we have investigated and developed the basic functional blocks needed to achieve an integrated photonic transceiver working in the range of millimetre wavelengths, and using robust modulation formats that best fit the scope considered. The work presented in this thesis can be basically divided into three parts. The first one provides an overview of the benefits of using silicon photonics for the development of wireless links at rates of Gbps, and the state of the art of the transceivers reported by the most important research groups in order to meet the increasingly demanding needs¿ market. The second part focuses on the study and development of millimetre-wave integrated transmitter. First we provide a brief theoretical introduction of the operation principles of the devices involved in the transmitter such as a modulation formats, focusing on the phase shift keying (PSK) which is the one that will be used, particularly the (differential) quadrature phase shift keying ((D) QPSK). We also present the building blocks involved in our transmitter and we set the specifications that must be met by these devices in order to achieve an error-free transmission. The transmitter includes a filter/demultiplexer which must separate two optical carriers 60 GHz separated. One of these optical carriers is modulated by passing through a DQPSK Mach-Zehnder-based modulator (MZM) by arranging two MZMs in a nested configuration. Using a combiner, the modulated optical signal and the un-modulated carrier are combined and photodetected to be transmitted wirelessly. In the third part of this thesis, we investigate the use of a polarization diversity scheme with an integrated DQPSK receiver for demodulating of the wireless signal. The polarization diversity scheme basically consists of two blocks: a polarization splitter in order to separate the random polarization state of the incoming light into its two orthogonal components, and a polarization rotator. Regarding the DQPSK receiver itself, all the functional blocks that comprise it have been investigated and optimized. It basically includes a thermo-optically tunable MZ interferometer power splitter, in series with a MZ interferometer that introduces, in one of its arms, a delay of one bit length in order to obtain a correct differential demodulation. The next building block of our DQPSK receiver is a 2x4 multimode interference coupler acting as a 90 degree hybrid, whose outputs are connected to two balanced germanium photodetectors. The main contributions of this thesis are: ¿ Demonstration of a filter/demultiplexer with three degrees of tuning and an extinction ratio greater than 25dB. ¿ Demonstration of a polarization rotator with a length of only 25¿m and CMOS compatible. ¿ Demonstration of a DPSK modulator at a maximum rate of 20 Gbit/s. ¿ Demonstration of a DQPSK demodulator to a maximum rate of 20 Gbit/s.Aamer, M. (2013). Development of an integrated silicon photonic transceiver for access networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/31649TESI

Ultra Low Power IEEE 802.15.4/ZIGBEE Compliant Transceiver

Low power wireless communications is the most demanding request among all wireless users. A battery life that can survive for years without being replaced, makes it realistic to implement many applications where the battery is unreachable (e.g. concrete walls) or expensive to change (e.g underground applications). IEEE 802.15.4/ZIGBEE standard is published to cover low power low cost applications, where the battery life can last for years, because of the 1% duty cycle of operation. A fully integrated 2.4GHz IEEE802.15.4 Compliant transceiver suitable for low power, low cost ZIGBEE applications is implemented. Direct conversion architecture is used in both Receiver and Transmitter, to achieve the minimum possible power and area. The chip is fabricated in a standard 0.18um CMOS technology. In the transmit mode, the transmitter chain (Modulator to PA) consumes 25mW, while in the receive mode, the iv receiver chain (LNA to Demodulator) consumes 5mW. The Integer-N Frequency Synthesizer consumes 8.5mW. Other Low power circuits are reported; A 13.56 Passive RFID tag and a low power ADC suitable for Built-In-Testing applications

Wideband CMOS Data Converters for Linear and Efficient mmWave Transmitters

With continuously increasing demands for wireless connectivity, higher\ua0carrier frequencies and wider bandwidths are explored. To overcome a limited transmit power at these higher carrier frequencies, multiple\ua0input multiple output (MIMO) systems, with a large number of transmitters\ua0and antennas, are used to direct the transmitted power towards\ua0the user. With a large transmitter count, each individual transmitter\ua0needs to be small and allow for tight integration with digital circuits. In\ua0addition, modern communication standards require linear transmitters,\ua0making linearity an important factor in the transmitter design.In this thesis, radio frequency digital-to-analog converter (RF-DAC)-based transmitters are explored. They shift the transition from digital\ua0to analog closer to the antennas, performing both digital-to-analog\ua0conversion and up-conversion in a single block. To reduce the need for\ua0computationally costly digital predistortion (DPD), a linear and wellbehaved\ua0RF-DAC transfer characteristic is desirable. The combination\ua0of non-overlapping local oscillator (LO) signals and an expanding segmented\ua0non-linear RF-DAC scaling is evaluated as a way to linearize\ua0the transmitter. This linearization concept has been studied both for\ua0the linearization of the RF-DAC itself and for the joint linearization of\ua0the cascaded RF-DAC-based modulator and power amplifier (PA) combination.\ua0To adapt the linearization, observation receivers are needed.\ua0In these, high-speed analog-to-digital converters (ADCs) have a central\ua0role. A high-speed ADC has been designed and evaluated to understand\ua0how concepts used to increase the sample rate affect the dynamic performance