Millimeter wave and UWB propagation for high throughput indoor communications

Millimeter-wave systems at 60 GHz and ultra-wideband (UWB) systems in the microwave range of 3-10 GHz have been received with great interest for their high data rate wireless communications. In design, test and optimization of future wireless systems, channel models featuring the relevant characteristics of radiowave propagation are required. Furthermore, detailed understanding of the propagation channel and its interaction with system, creates insights into possible solutions. In this work, both theoretical (ray-tracing) and statistical models of the 60 GHz and UWB channels are studied. Propagation characteristics of the 60 GHz and UWB indoor channels are also compared for providing useful information on design of radio systems. More specifically, based on real-time channel sounder measurements performed in the 60 GHz band, propagation mechanisms including person blocking effect are concluded. Ray-based models in LOS and NLOS indoor corridors are proposed. Multipath power distributions in the 60 GHz band are studied first time. Moreover, propagation interdependencies of path loss, shadowing, number of paths, Rice K-factor and cross polarization discrimination (XPD) with channel delay spread are established. In the UWB propagation channel, frequency- and bandwidth- dependencies are investigated. Multipath and clustering propagation characteristics are analyzed. A new cluster model is proposed and compared with the classical Saleh-Valenzuela model for gaining more understanding of channel general properties. Finally, the performance and capacities of the 60 GHz UWB and MIMO (multiple-in and multiple-out) systems are analyzed for providing reliable parameters for system design and useful information for standardization groups

Modelling and characterisation of antennas and propagation for body-centric wireless communication

PhDBody-Centric Wireless Communication (BCWC) is a central point in the development of fourth generation mobile communications. The continuous miniaturisation of sensors, in addition to the advancement in wearable electronics, embedded software, digital signal processing and biomedical technologies, have led to a new concept of usercentric networks, where devices can be carried in the user’s pockets, attached to the user’s body or even implanted. Body-centric wireless networks take their place within the personal area networks, body area networks and body sensor networks which are all emerging technologies that have a broad range of applications such as healthcare and personal entertainment. The major difference between BCWC and conventional wireless systems is the radio channel over which the communication takes place. The human body is a hostile environment from radio propagation perspective and it is therefore important to understand and characterise the effect of the human body on the antenna elements, the radio channel parameters and hence the system performance. This is presented and highlighted in the thesis through a combination of experimental and electromagnetic numerical investigations, with a particular emphasis to the numerical analysis based on the finite-difference time-domain technique. The presented research work encapsulates the characteristics of the narrowband (2.4 GHz) and ultra wide-band (3-10 GHz) on-body radio channels with respect to different digital phantoms, body postures, and antenna types hence highlighting the effect of subject-specific modelling, static and dynamic environments and antenna performance on the overall body-centric network. The investigations covered extend further to include in-body communications where the radio channel for telemetry with medical implants is also analysed by considering the effect of different digital phantoms on the radio channel characteristics. The study supports the significance of developing powerful and reliable numerical modelling to be used in conjunction with measurement campaigns for a comprehensive understanding of the radio channel in body-centric wireless communication. It also emphasises the importance of considering subject-specific electromagnetic modelling to provide a reliable prediction of the network performance

Coexistence Mechanism for Colocated HDR/LDR WPANs Air Interfaces

This paper addresses the issues of interference management among Low Data Rate (LDR) and High Data Rate (HDR) WPAN air interfaces that are located in close-proximity (up to 10 cm) and eventually on the same multimode device. After showing the noticeable performance degradation in terms of Bit Error Rate (BER) and goodput due to the out-of-band interference of an HDR air interface over an LDR air interface, the paper presents a novel coexistence mechanism, named Alternating Wireless Activity (AWA), which is shown to greatly improve the performance in terms of goodput of the most interference vulnerable air interface (i.e., the LDR air interface). The main difference of the proposed mechanism with respect to other collaborative mechanisms based on time-scheduling is that it synchronizes the transmission of the LDR and HDR WPANs at the superframe level instead of packet level. Advantages and limitations of this choice are presented in the paper. Furthermore the functionalities of the AWA mechanism are positioned in a common protocol layer over the Medium Access Control (MAC) sublayers of the HDR and LDR devices and it can be used with any standard whose MAC is based on a superframe structure

Analysis of wideband phased array beamforming at millimeter wave frequencies

Abstract. Industries are undergoing an information and communication technology-driven transformation as the world becomes increasingly digitally and globally linked. 5G technology provides a common basis for providing the multiple vertical sectors with a more cost-effective, open, and wide ecosystem solutions. Due to the generally large attainable bandwidths, high frequency technologies have emerged as a promising solution for future wireless communications and attracted great interest in the literature. The millimeter wave (mmWave), i.e., the frequency range 30–300 GHz, would enable the exploitation of tens of gigahertz transmission bands, resulting in a massive channel capacities of even over one Tbps. However, one of the most challenging issues in high-frequency communication connections is the significant channel losses that require highly directional antennas and, in most cases, line-of-sight link between the transmitter and receiver. In this thesis, we study the beamforming design for wideband systems with different bandwidths. The simulation results show that with a larger bandwidth, the power loss increases with the beamforming angle. The loss of power behavior due to beam squinting effect is quite similar over different distances

System design and performance analysis of wireless body area networks

One key solution to provide affordable and proactive healthcare facilities to overcome the fast world population growth and a shortage of medical professionals is through health monitoring systems capable of early disease detection and real-time data transmission leading to considerable improvements in the quality of human life. Wireless body area networks (WBANs) are proposed as promising approaches to providing better mobility and flexibility experience than traditional wired medical systems by using low-power, miniaturised sensors inside, around, or off the human body and are employed to monitor physiological signals. However, the design of reliable and energy efficient in-body communication systems is still a major research challenge since implant devices are characterised by strict requirements on size, energy consumption and safety. Moreover, there is still no agreement regarding QoS support in WBANs. The first part of this work concentrates on the design and performance evaluation of WBAN communication systems involving the ‘in-body to in-body’ and ‘in-body to on-body’ scenarios. The essential step is to derive the statistical WBAN path loss (PL) models, which characterise the signal propagation energy loss transmitting via intra-body region. Moreover, from the point of view of human body safety evaluation, the obtained specific absorption rate (SAR) values are compared with the latest Institute of Electrical and Electronics Engineers (IEEE) 802.15.6 Task Group technical standard and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) safety guidelines. Link budget analysis is then presented using a range of energy-efficient modulation schemes, and the results are given including the transmission distance, data rate and transmitting power in individual sections. On the other hand, major quality of service (QoS) support challenges in WBANs are discussed and investigated. To achieve higher lifetime and lower network energy consumption, different data routing protocol methods, including incremental relaying and the two-relay based routing technique are taken into account. A set of key QoS metrics for linear mathematical models is given along with the related subjective functions. The incremental relaying routing protocol promises significant enhancements in in-body WBAN network lifetime by minimising the overall communication distance while the two-relay based routing method achieves better performance in terms of emergency data transmission and high traffic condition, QoS-aware WBANs design. Moreover, to handle real-time high data transmission applications such as capsule endoscope image transmission, a flexible QoS-aware wireless body area sensor networks (WBASNs) model is proposed and evaluated that can bring novel solutions for a realistic multi-user hospital environment regarding information packet collision probability, manageable numbers of sensor nodes and a wide range of data rates

Ultra wideband gigabit powerline communication

PhDPowerline Communication (PLC) has long been established for low data rate applications by the electric supply companies. Since 1991, the European CENELEC standard EN 50065 has ruled the use of 3 - 148.5KHz frequency range for narrow band PLC applications. Sim- ilar standard has been established by the IEEE in the US, where a frequency range of 50 - 450KHz is available. The fast growth of Internet since the 1990s accelerated the demands for digital communication services. Furthermore, with the develop- ment of in-home networking, there is a need to establish high speed data links between multiple household devices. This makes PLC sys- tems march rapidly into the high frequency range above 1MHz. Exist- ing broadband PLC system in the 1.6 - 30MHz frequency range only provides data rates smaller than 200Mbps. With the growing demand of multimedia services such as High De nition (HD) video streaming, much faster transmission speed up to Gigabits per second is required and this can be achieved by increasing the operating frequencies. Ultra Wideband (UWB) transmission in free space provides extremely broad bandwidth for short-range, high data rate applications. If UWB signals could be transmitted over the powerline channels in the high frequency range above 30MHz, data rates up to gigabits per second could be achieved. In this thesis, the possibility of implementing ultra wideband trans- mission over the low voltage indoor powerline is investigated. The starting point is to understand the signal propagation characteristics over powerline cables, in the UWB frequency range. Experimental re- sults indicate that the signal degrades at an acceptable rate over the mains cable in a scaled down UWB frequency band (50MHz - 1GHz), which provides a potential operation band for UWB over PLC ap- plications. Key component for the PLC system, a broadband Radio Frequency (RF) coupler is designed and developed, to introduce UWB signals to the transmission channel. With the channel properties and coupling unit, extensive experimental investigations are carried out to analyse the powerline network environment, including channel loss, noise and radiated emission. Furthermore, theoretical channel capac- ity and link budget are derived from measured parameters. It is shown that the indoor powerline is a suitable media for data transmission in the high frequency range from 50 to 550MHz in the home environment. Finally, system level performance is analysed by modelling the Phys- ical Layer (PHY) data transmission. The Multiband-OFDM UWB proposal for IEEE 802.15.3a standard is used to predict the transmis- sion performance under di erent propagation paths and data rates. The research work conducted in this project has proven that UWB over PLC is highly feasible for future in-home applications. With the global promotion of smart grid applications, UWB over PLC will play an important role in providing high speed data transmission over the power networks

Statistical characterization of UWB channels for wireless personal area networks applications

Ultra Wide Band es una tecnología introducida recientemente para comunicaciones. Las restricciones en la máxima potencia radiada impuestas por la FCC hace que UWB sea una tecnología apta para redes de área personal (WPAN). El diseño e implementación de sistemas UWB para redes de área personal precisa de un buen conocimiento de las caracter´ýsticas de propagación del canal. Para algunas aplicaciones, la distancia entre las antenas puede ser muy pequeña y esto lleva a tener que analizar un serio problema, concretamente, las condiciones de propagación de campo lejano de las antenas pueden no cumplirse. Varios efectos como pérdidas extras o distorsiones para distancias muy cortas pueden producirse y tienen que ser analizados. El objetivo principal de esta tesis es analizar los efectos de campo cercano para sistemas UWB investigando principalmente dos parámetros: pérdidas del enlace y distorsión. El análisis de dichos efectos se ha llevado a cabo analíticamente y mediante simulaciones para luego ser comparado con las medidas realizadas. Las pérdidas en el enlace, distorsiones y otros parámetros importantes del canal han sido extraídos y analizados