Im Bereich der Zugangsnetze werden zukünftig drahtlose Multihop-Erweiterungen des Internets durch mobile Ad-hoc-Netze sowie durch drahtlose vermaschte Netze (sog. Wireless Mesh Networks) Verbreitung finden, da diese Netztechnologien den Datentransfer einfacher und schneller, womöglich auch deutlich kostengünstiger, durchführen können als zellulare Mobilfunknetze.

The thesis work details the design and testing of a wireless electrocardiogram (ECG) system. This system includes a wireless ECG device, as well as software packages to visually display the waveform locally on a computer and remotely on a web page. The remote viewing capability also extends to using an Android phone application. The purpose of the system is to serve as a means for a doctor or physician to check up on a patient away from a hospital setting. This system allows for a patient to be in their home environment while giving health vital information, primarily being the heart’s activity through the ECG, to medical personnel.

Includes bibliographical references (p. 70-74). / Wireless local and metropolitan area network (WLAN/WMAN) technologies, more specifically IEEE 802.11 (or wireless fidelity, WiFi) and IEEE 802.16 (or wireless interoperability for microwave access, WiMAX), are well-suited to enterprise networking since wireless offers the advantages of rapid deployment in places that are difficult to wire. However, these networking standards are relatively young with respect to their traditional mature high-speed low-latency fixed-line networking counterparts. It is more challenging for the network provider to supply the necessary quality of service (QoS) to support the variety of existing multimedia services over wireless technology. Wireless communication is also unreliable in nature, making the provisioning of agreed QoS even more challenging. Considering the advantages and disadvantages, wireless networks prove well-suited to connecting rural areas to the Internet or as a networking solution for areas that are difficult to wire. The focus of this study specifically pertains to IEEE 802.16 and the part it plays in an IEEE vertically integrated wireless Internet (WIN): IEEE 802.16 is a wireless broadband backhaul technology, capable of connecting local area networks (LANs), wireless or fixed-line, to the Internet via a high-speed fixed-line link.

This work addresses Channel Assignment in a multi-radio multi-channel (MRMC) Wireless Mesh Network (WMN) using both Wi-Fi and Dynamic Spectrum Access (DSA) spectrum bands and standards. This scenario poses new challenges because nodes are spread out geographically so may have differing allowed channels and experience different levels of external interference in different channels. A solution must meet two conflicting requirements simultaneously: 1) avoid or minimise interference within the network and from external interference sources, and 2) maintain connectivity within the network. These two requirements must be met while staying within the link constraints and the radio interface constraints, such as only assigning as many channels to a node as it has radios. This work's original contribution to the field is a unified framework for channel optimisation and assignment in a WMN that uses both DSA and traditional Wi-Fi channels for interconnectivity. This contribution is realised by providing and analysing the performance of near-optimal Channel Assignment (CA) solutions using metaheuristic algorithms for the MRMC WMNs using DSA bands. We have created a simulation framework for evaluating the algorithms. The performance of Simulated Annealing, Genetic Algorithm, Differential Evolution, and Particle Swarm Optimisation algorithms have been analysed and compared for the CA optimisation problem. We introduce a novel algorithm, used alongside the metaheuristic optimisation algorithms, to generate feasible candidate CA solutions. Unlike previous studies, this sensing and CA work takes into account the requirement to use a Geolocation Spectrum Database (GLSD) to get the allowed channels, in addition to using spectrum sensing to identify and estimate the cumulative severity of both internal and external interference sources. External interference may be caused by other secondary users (SUs) in the vicinity or by primary transmitters of the DSA band whose emissions leak into adjacent channels, next-toadjacent, or even into further channels. We use signal-to-interference-plus-noise ratio (SINR) as the optimisation objective. This incorporates any possible source or type of interference and makes our method agnostic to the protocol or technology of the interfering devices while ensuring that the received signal level is high enough for connectivity to be maintained on as many links as possible. To support our assertion that SINR is a reasonable criterion on which to base the optimisation, we have carried out extensive outdoor measurements in both line-of-sight and wooded conditions in the television white space (TVWS) DSA band and the 5 GHz Wi-Fi band. These measurements show that SINR is useful as a performance measure, especially when the interference experienced on a link is high. Our statistical analysis shows that SINR effectively differentiates the performance of different channels and that SINR is well correlated with throughput and is thus a good predictor of end-user experience, despite varying conditions. We also identify and analyse the idle times created by Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) contention-based Medium Access Control (MAC) operations and propose the use of these idle times for spectrum sensing to measure the SINR on possible channels. This means we can perform spectrum sensing with zero spectrum sensing delay experienced by the end user. Unlike previous work, this spectrum sensing is transparent and can be performed without causing any disruption to the normal data transmission of the network. We conduct Markov chain analysis to find the expected length of time of a sensing window. We also derive an efficient minimum variance unbiased estimator of the interference plus noise and show how the SINR can be found using this estimate. Our estimation is more granular, accurate, and appropriate to the problem of Secondary User (SU)-SU coexistence than the binary hypothesis testing methods that are most common in the literature. Furthermore, we construct confidence intervals based on the probability density function derived for the observations. This leads to finding and showing the relationships between the number of sampling windows and sampling time, the interference power, and the achievable confidence interval width. While our results coincide with (and thus are confirmed by) some key previous recommendations, ours are more precise, granular, and accurate and allow for application to a wider range of operating conditions. Finally, we present alterations to the IEEE 802.11k protocol to enable the reporting of spectrum sensing results to the fusion or gateway node and algorithms for distributing the Channel Assignment once computed. We analyse the convergence rate of the proposed procedures and find that high network availability can be maintained despite the temporary loss of connectivity caused by the channel switching procedure. This dissertation consolidates the different activities required to improve the channel parameter settings of a multi-radio multi-channel DSA-WMN. The work facilitates the extension of Internet connectivity to the unconnected or unreliably connected in rural or peri-urban areas in a more cost-effective way, enabling more meaningful and affordable access technologies. It also empowers smaller players to construct better community networks for sharing local content. This technology can have knock-on effects of improved socio-economic conditions for the communities that use it.

Yes / In this research work, a planar crossed exponentially tapered slot antenna with a multi-resonance function is introduced. The presented antenna design is ascertained on a low-cost Rogers 5870 dielectric with a circular schematic. The antenna is designed to support several frequency spectrums of the current and future wireless communications. The configuration of the design contains a pair of crossed exponentially tapered slots intersected by a star-shaped slot in the back layer and a bowtie-shaped radiation stub with a discrete feeding point extended among the stub parts. The crossed exponential slots exhibit a wide impedance, and the star slot generates an extra resonance at the upper frequencies. For S11 ≤ -6, the antenna provides a wide operation band of 1.7 to 5.9 GHz supporting several frequency bands of 3G, 4G, and 5G communication. The fundamental characteristics of the proposed slot radiator are studied, and good performances have been achieved. / European Union’s Horizon 2020 research and innovation programme under grant agreement H2020-MSCA-ITN-2016 SECRET-722424.

Prolonging the battery lifetime of sensors has been one of the most important issues in wireless sensor networks (WSNs). With the development of Wireless Power Transfer (WPT) technology, sensors can be recharged and possibly have infinite lifetime. One common approach to achieving this is having a wireless charging vehicle (WCV) move in the system coverage area and charge sensors nearby when it stops. The duration that the WCV stays at each charging location, the amount of traffic that each sensor carries, and the transmission power of individual sensors are closely related, and their joint optimization affects not only the data transmissions in the WSN but also energy consumption of the system. This problem is formulated as a mixed integer and nonconvex optimization problem. Different from existing work that either solves similar problems using genetic algorithms or considers charging sensors based on clusters, we consider the optimum charging time for each sensor, and solve the joint communication and charging problem optimally. Numerical results demonstrate that our solution can significantly reduce the average power consumption of the system, compared to the cluster-based charging solution. / Thesis / Master of Applied Science (MASc) / In a wireless sensor network (WSN), sensor nodes monitor the physical environment and forward the collected data to a data sink for further processing. Sensors are battery powered and, therefore, prolonging the lifetime of their batteries is critically important. In a rechargeable WSN (RWSN), prolonging the battery lifetime of sensors is achieved through reducing communication energy and recharging the batteries periodically. Reducing the communication energy consumption is done through choosing the best forwarding sensors (i.e., routing) for data collected by each sensor and deciding the transmission power of each sensor (i.e., power allocation). Recharging the batteries is achieved through harvesting energy from external sources. In this thesis, we consider a RWSN that uses wireless power transfer as the energy harvesting technology and jointly optimizes charging and communications in order to minimize the power consumption of the RWSN.

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Rapid developments in microelectronics technology have allowed for phenomenal achievements in biomedical engineering. In the past few decades, an enormous amount of researches were done in the field of medical implantable microelectronic systems. The prevalence of research in this particular field have led to the design of novel systems for in-vivo applications, for example, using microelectronic systems to replace catheterization in clinical studies of urinary incontinence. In this thesis research, we study two types of wireless modules towards our goal of wireless systems for in-vivo applications. The first system, a 2.4 GHz wireless pressure sensor system, is designed as a pressure sensing module to operate as a part of a pill imaging device published in [32]. This pressure module samples pressure data and passes them to the pill imaging capsule via a serial-port-interface (SPI). The 2.4 GHz wireless pressure system has an overall system dimension of 75.0 x 20.5 x 17.5 mm3 with a current consumption of 5 mA when operating from a 3 V supply. The pressure sensitivity of this system is observed as 1.14 cmH20/LSB (least significant bit). The second system, 125kHz RFID (radio-frequency identification) dual sensor system, is designed to explore the possibility of powering the device and transmitting data using the RFID technology. The 125kHz RFID dual sensor system has an overall system dimension of 30.0 x 15.0 x 15.0 mm3 with a current consumption of 1.5 mA while operating at 3 V. The pressure sensitivity of this system is observed as 2.93 cmH20/LSB and the temperature sensitivity is observed as 0.069 °C/LSB. And, the detections of rapid pressure changes in both systems are successful. The work performed in this thesis research has provided a cost-effective method of designing medical implantable systems using off-the-shelf components as compared to full-custom designs. In this research, it is also observed that power consumption is a major issue in medical implantable systems. Finally, the possibility of transmitting data and powering such systems using RFID technology has been verified. / Thesis / Master of Applied Science (MASc)

The Wake Forest University Physiology/Pharmacology (WFU Phys./Pharm.) electrophysiology research labs currently carry out memory research by recording neural signals from laboratory animals tethered to nearby signal conditioning and recording equipment. A wireless neural signal recording system is desirable because it removes the cumbersome wires from the animal, allowing it to roam more freely. The result is an animal that is more able to behave as it would in its natural habitat, thus opening the possibility of testing procedures that are not possible with wired recording systems. Sampling rates obtained by conventional RF wireless systems tend to be very low (800Hz) since the bandwidth of these RF wireless systems is low. This is because interfacing methods (RS-232) needed to develop RF systems are slow (57.6Kbps). Another shortcoming of RF systems is the high power consumption. This thesis presents development of embedded wireless system to replace wired systems. RF wireless system is developed to replace wired electrophysiology system. An infrared wireless system development is discussed to achieve higher sampling rates unachievable by RF wireless system. Infrared operate at data rates 4Mbps and high sampling rates can be achieved. For this thesis, Infrared system is interfaced to microcontroller using ISA interface. ISA bus is chosen as it operates (at rate of 8Mbytes/sec) faster than RS-232 and easy to program compared to other buses such as PCI. Also, Infrared systems consume low power than RF systems. Power consumption is an important consideration as application in hand is battery powered. / Master of Science