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This thesis describes the design of a Virtual Application Networking Infrastructure (VANI) node that can be used to facilitate network architecture experimentation. Cur- rently the VANI nodes provide four classes of physical resources – processing, reconfig- urable hardware, storage and interconnection fabric – but the set of sharable resources can be expanded. Virtualization software allows slices of these resources to be appor- tioned to VANI nodes that can in turn be interconnected to form virtual networks, which can operate according to experimental network and application protocols. This thesis discusses the design decisions that have been made in the development of this system and provides a detailed description of the prototype, including how users interact with the resources and the interfaces provided by the virtualization layers.

This thesis describes the design of a Virtual Application Networking Infrastructure (VANI) node that can be used to facilitate network architecture experimentation. Cur- rently the VANI nodes provide four classes of physical resources – processing, reconfig- urable hardware, storage and interconnection fabric – but the set of sharable resources can be expanded. Virtualization software allows slices of these resources to be appor- tioned to VANI nodes that can in turn be interconnected to form virtual networks, which can operate according to experimental network and application protocols. This thesis discusses the design decisions that have been made in the development of this system and provides a detailed description of the prototype, including how users interact with the resources and the interfaces provided by the virtualization layers.

Wireless networks are growing at a phenomenal rate. This growth is causing an overcrowding of the unlicensed RF spectrum, leading to increased interference between co-located devices. Existing decentralized medium access control (MAC) protocols (e.g. IEEE 802.11a/b/g standards) are poorly designed to handle interference in such dense wireless environments. This is resulting in networks with poor and unpredictable performance, especially for delay-sensitive applications such as voice and video. This dissertation presents a practical conflict-graph (CG) based approach to designing self-organizing enterprise wireless networks (or WLANs) where interference is centrally managed by the network infrastructure. The key idea is to use potential interference information (available in the CG) as an input to algorithms that optimize the parameters of the WLAN.We demonstrate this idea in three ways. First, we design a self-organizing enterprise WLAN and show how the system enhances performance over non-CG based schemes, in a high fidelity network simulator. Second, we build a practical system for conflict graph measurement that can precisely measure interference (for a given network configuration) in dense wireless environments. Finally, we demonstrate the practical benefits of the conflict graph system by using it in an optimization framework that manages associations and traffic for mobile VoIP clients in the enterprise. There are a number of contributions of this dissertation. First, we show the practical application of conflict graphs for infrastructure-based interference management in dense wireless networks. A prototype design exhibits throughput gains of up to 50% over traditional approaches. Second, we develop novel schemes for designing a conflict graph measurement system for enterprise WLANs that can detect interference at microsecond-level timescales and with little network overhead. This allows us to compute the conflict graph up to 400 times faster as compared to the current best practice proposed in the literature. The system does not require any modifications to clients or any specialized hardware for its operation. Although the system is designed for enterprise WLANs, the proposed techniques and corresponding results are applicable to other wireless systems as well (e.g. wireless mesh networks). Third, our work opens up the space for designing novel fine-grained interference-aware protocols/algorithms that exploit the ability to compute the conflict graph at small timescales. We demonstrate an instance of such a system with the design and implementation of an architecture that dynamically manages client associations and traffic in an enterprise WLAN. We show how mobile clients sustain uninterrupted and consistent VoIP call quality in the presence of background interference for the duration of their VoIP sessions.

Despite the fact ultra-wideband (UWB) technology has been around for over 30 years, there is a newfound excitement about its potential for communications. With the advantageous qualities of multipath immunity and low power spectral density, researchers are examining fundamental questions about UWB communication systems. Majorly the whole report gives a complete picture about properties of UWB signal and its advantages and disadvantages, generation of the UWB pulse using various techniques, Modulation scheme, Test bed, applications, UWB regulations. The report mainly concerns with the survey about various techniques and also its comparison of generating UWB pulses using various components. There is a general description on various modulation and demodulation scheme that are relevant to UWB technology and its various applications concerning different fields.   This report clearly explains how UWB is far better than RFID and difference between active and passive RFID and its communication protocol, message format. Clear explanation about advantage of higher operating frequencies and low power spectral density. Properties of UWB pulse gives clear idea why we go for UWB and in near future lot of applications will discover. Generation of UWB is a tedious process and in this report readers can understand the various method of generation its advantages and its drawbacks. Modulation and demodulation scheme gives clear idea about how UWB are modulated and demodulated as well as its probability of error and in which situation which modulation is suitable. By using future testbed concept, smaller size UWB chip will be designed and used in various application efficiently. Application gives clear idea about how to take advantage of various properties.

Wireless networks are growing at a phenomenal rate. This growth is causing an overcrowding of the unlicensed RF spectrum, leading to increased interference between co-located devices. Existing decentralized medium access control (MAC) protocols (e.g. IEEE 802.11a/b/g standards) are poorly designed to handle interference in such dense wireless environments. This is resulting in networks with poor and unpredictable performance, especially for delay-sensitive applications such as voice and video. This dissertation presents a practical conflict-graph (CG) based approach to designing self-organizing enterprise wireless networks (or WLANs) where interference is centrally managed by the network infrastructure. The key idea is to use potential interference information (available in the CG) as an input to algorithms that optimize the parameters of the WLAN.We demonstrate this idea in three ways. First, we design a self-organizing enterprise WLAN and show how the system enhances performance over non-CG based schemes, in a high fidelity network simulator. Second, we build a practical system for conflict graph measurement that can precisely measure interference (for a given network configuration) in dense wireless environments. Finally, we demonstrate the practical benefits of the conflict graph system by using it in an optimization framework that manages associations and traffic for mobile VoIP clients in the enterprise. There are a number of contributions of this dissertation. First, we show the practical application of conflict graphs for infrastructure-based interference management in dense wireless networks. A prototype design exhibits throughput gains of up to 50% over traditional approaches. Second, we develop novel schemes for designing a conflict graph measurement system for enterprise WLANs that can detect interference at microsecond-level timescales and with little network overhead. This allows us to compute the conflict graph up to 400 times faster as compared to the current best practice proposed in the literature. The system does not require any modifications to clients or any specialized hardware for its operation. Although the system is designed for enterprise WLANs, the proposed techniques and corresponding results are applicable to other wireless systems as well (e.g. wireless mesh networks). Third, our work opens up the space for designing novel fine-grained interference-aware protocols/algorithms that exploit the ability to compute the conflict graph at small timescales. We demonstrate an instance of such a system with the design and implementation of an architecture that dynamically manages client associations and traffic in an enterprise WLAN. We show how mobile clients sustain uninterrupted and consistent VoIP call quality in the presence of background interference for the duration of their VoIP sessions.

Opportunistic networks are constructed by devices carried by people and vehicles. The devices use short range radio to communicate. Since the network is mobile and often sparse in terms of node contacts, nodes store messages in their buffers, carrying them, and forwarding them upon node encounters. This form of communication leads to a set of challenging issues that we investigate: congestion, transfer ordering, and resilience. Congestion occurs in opportunistic networks when a node's buffers becomes full. To be able to receive new messages, old messages have to be evicted. We show that buffer eviction strategies based on replication statistics perform better than strategies that evict messages based on the content of the message. We show that transfer ordering has a significant impact on the dissemination of messages during time limited contacts. We find that transfer strategies satisfying global requests yield a higher delivery ratio but a longer delay for the most requested data compared to satisfying the neighboring node's requests. Finally, we assess the resilience of opportunistic networks by simulating different types of attacks. Instead of enumerating all possible attack combinations, which would lead to exhaustive evaluations, we introduce a method that use heuristics to approximate the extreme outcomes an attack can have. The method yields a lower and upper bound for the evaluated metric over the different realizations of the attack. We show that some types of attacks are harder to predict the outcome of and other attacks may vary in the impact of the attack due to the properties of the attack, the forwarding protocol, and the mobility pattern. / WISENET

Sensor networks consist of small sensing devices that collaboratively fulfill a sensing task, such as monitoring the soil in an agricultural field or measuring vital signs in a marathon runner. To avoid cumbersome and expensive cabling, nodes in a sensor network are powered by batteries and communicate wirelessly. As a consequence of the latter, a sensor network's communication is affected by its radio environment, i.e., the environment's propagation characteristics and the presence of other radio devices. This thesis addresses three issues related to the impact of the radio environment on sensor networks. Firstly, in order to draw conclusions from experimental results, it is necessary to assess how the environment and the experiment infrastructure affect the results. We design a sensor network testbed, dubbed Sensei-UU, to be easily relocatable. By performing an experiment in different environments, a researcher can asses the environments’ impact on results. We further augment Sensei-UU with support for mobile nodes. The implemented mobility approach adds only little variance to results, and therefore enables repeatable experiments with mobility. The repeatability of experiments increases the confidence in conclusions drawn from them. Secondly, sensor networks may experience poor communication performance due to cross-technology radio interference, especially in office and residential environments. We consider the problem of detecting and classifying the type of interference a sensor network is exposed to. We find that different sources of interference each leave a characteristic "fingerprint" on individual, corrupt 802.15.4 packets. We design and implement the SoNIC system that enables sensor nodes to classify interference using these fingerprints. SoNIC supports accurate classification in both a controlled and an uncontrolled environment. Finally, we consider transmission errors in an outdoor sensor network. In such an environment, errors occur despite the absence of interference if the signal-to-noise ratio at a receiver is too low. We study the characteristics of corrupt packets collected from an outdoor sensor network deployment. We find that content transformation in corrupt packets follows a specific pattern, and that most corrupt packets contain only few errors. We propose that the pattern may be useful for applications that can operate on inexact data, because it reduces the uncertainty associated with a corrupt packet. / WISENET

In the past two decades, wireless communication systems have grown with an unprecedented speed from radio paging and cellular telephony to multimedia platforms offering voice and video streaming . One undesired outcome of this expansion is a heavy utilization of the available frequency spectrum. Particular pressure comes from new multimedia applications, which require larger operational bandwidth for their implementations. Conventional coding, modulation and multiplexing techniques are unable to overcome the problem associated with the limited frequency spectrum, and therefore modern wireless systems are improved through the utilization of the space/angle domain. In order to improve capacity and reliability with the space/angular domain, wireless systems require the use of multiple element antennas (MEA) accompanied by appropriate signal processing algorithms. Typically multiple antennas are used to steer the beams of the line of sight (LOS) signal toward desired users and nulls in the direction of undesired users. However, in the case of indoor environments, the presence of reflections, scattering and refraction caused by the environment, it is better to make use of non-line of sight (NLOS) signal propagation. As these types of MEA antenna systems are a relatively new concept in wireless communications, their potential needs be tested experimentally in real world conditions. To achieve this goal, prototype systems capable to implement various modulation, coding and transmission schemes for MEA are required. This thesis investigates the benefits of MEA systems by building and testing such systems in indoor environments. The project area spans across many disciplines including wireless communications, antennas, embedded systems and RF hardware design, and therefore the thesis begins with essential background information. This concerns some fundamental concepts of a wireless communication channel and its information capacity. These are accompanied by ample considerations of signal propagation and adverse effects of reflection, scattering and diffraction. Also included are the signal modulation and coding. Following this background information, the main topic concerning diversity and multiple-input multiple output system that involves the use of multiple element antennas is introduced. This background material sets the reasons for investigating of two types wireless communication systems that include multiple element antennas: antenna diversity and MIMO. Following the literature review, the thesis reports on investigations that realize the thesis aims. The first part of the undertaken investigations concerns an indoor 2×2 MEA diversity system in which MEAs accompany conventional transceivers. In the experiments, Bluetooth transceivers aimed for a short range operation at 2.45 GHz are used, which are both connected to a 2-element antenna array. The connection is made via a switched beamforming network which involves 4-port hybrid circuits. Two ports of these hybrids are used for connecting antennas, while the one of the remaining two is connected to the Tx or Rx transceiver. By switching between these two input ports of the hybrid, two different radiation patterns can be formed, at both Tx and Rx. One Bluetooth transceiver is stationary while the other is made mobile by employing a purpose built mechanical sub-system covering the precise movement within a circle of 3 m. Both the movement and collection of the data as well as the display of the obtained results are accomplished with the in-house developed software run on a micro-controller and computer. Experimentally, it is shown that the proper Tx and Rx mode for a given position, improves the received signal strength. This leads to improved signal to noise ratio (SNR) and thus the quality of signal transmission. The implementation of this concept only requires a signal quality indicator, and simple feedback between the receiver and the transmitter. In the selected transceivers, "RSSI" was the quality indicator used, and is present in many modern wireless transceivers. Also, any signal quality indicator can be used. Although the experiments were performed with respect to the transmit/receive pattern diversity, they can also be easily extended to other forms of antenna diversity such as polarization or field diversity. The undertaken investigations are original in terms of the full proof of benefits of pattern diversity for indoor wireless systems. The second part of the undertaken investigations focuses on the design, development and testing of a full indoor multiple element antenna system. This demonstrator system includes two main modules: the baseband processor (based on a field programmable gate array) and the RF front end. The FPGA signal processing module is designed around the Altera Stratix II S260 chip, which is commercially available. Suitable hardware design is required to accomplish MIMO signal transmission. The RF front end module performing direct conversion between baseband and 2.45 GHz or 5 GHz radio frequency bands uses the commercially available MAX2829 chip. The interface between FPGA and RF front end is a set of analogue to digital (ADC) and digital to analogue (DAC) converters that operate on signals between the FPGA and the RF transmitter/receiver modules. They are capable of handling 12/14 bit signals at up to 125 MSmp/sec. The data rate chosen in these investigations is 3.125 Mbps. In addition to the MAX2829 IC chip, amplifiers, switches and antennas are included in the RF module. The development of this wireless communication system has been accomplished through a number of design, development and testing stages. Most of the research effort concerned FPGA based signal processing because this part of the system is where the information processing takes place. For the MIMO system, the transmitted signal has to be modulated and coded, with efficient utilization of the multiple element antennas in both these processes. The prerequisite to signal demodulation is signal synchronization. In turn, the decoding requires the knowledge of characteristics of the channels that are formed between transmitting and receiving antennas. For an efficient FPGA hardware design, all the numerical operations must occur in fixed point arithmetic. To accomplish all of these functions, suitable baseband signal processing algorithms were developed as part of the thesis work. First, they were written in MATLAB and then transferred to C++ which is closer to the FPGA implementation. Having confirmed their validity, they were hardware deployed. In the investigated MIMO demonstrator, QPSK modulation and the Alamouti coding scheme were selected for modulating and coding of the transmitted signal. The implementation of the hardware baseband module was validated using a purpose developed channel emulator. This emulator was capable of implementing the channel properties from actual measurements and from theoretical models. The applied theoretical models concern the single and double bounce scattering models, as well as a full EM model and include full EM interactions within array antennas formed by wire dipoles. These models produce random characteristics of the complex channel matrix which describes the channel properties for narrow or wideband case. With this channel emulator, investigations were performed with respect to channel estimation. The training and semi-blind channel estimation methods were tested using the developed emulator. To schedule signal transmission as well as to obtain suitable insight into individual processes, two extra modules were developed as part of the thesis project. These are the scheduler and visualisation modules. The scheduling hardware controls data packets for at the transmitter, and oversees the packets being decoded at the receiver module. For the visualization module, specialized hardware buffers and analysis modules are created for data storage. The signals resulting from the encoding and decoding processes are stored in these buffers, synchronized to each other, which allows for synchronous visualization of the signals. The data from these buffers is streamed to a PC via a 100 Mbit Ethernet connection and a soft-core processor (running uClinux) in the baseband board. Using a web browser on the PC, a graphical interface using scalable vector graphics (SVG) is used for interaction with the embedded web server to display and control what the hardware is sending and receiving. Due to latency, only a quasi-real time display on PC is possible, as 10 ms of time domain data takes 60 ms to display. The FPGA hardware performs real-time continuous data transmission and decoding, and the latency is only in the visualization system. Using the developed baseband system it was shown that the proposed semi-blind channel estimation was advantageous over the classical training approach when the channel properties change during packets transmissions. The developed channel emulator, semi-blind channel estimation algorithm and the visualisation software are the original contributions of this thesis. Having established the proper functioning of the FPGA baseband processor, the remaining investigations concerned the development of the RF transceiver module. This task was accomplished using guidelines offered by the MAX chip manufacturer. The challenge concerned its manufacturing in 4-layer board format. This part of the project required the outsourcing of the PCB manufacturing and component assembly to obtain successful production of the RF front-end board. The RF tests undertaken as part of the project verified the operation of this RF hardware. With the successful development of individual baseband and RF modules, the last part of project concerned the integration of them. Because most of the benefits of the 2×2 MIMO system were demonstrated via the use of a channel emulator, this part of the thesis consisted of the results of a number of experiments. Considerable effort was spent for the full integration of the RF and baseband modules to make them ready for real-time operation. Some of the undertaken tasks were new, as they were not required for experiments using only the baseband system and channel emulator. One of the new challenges concerned proper symbol synchronization. Two novel algorithms were proposed and verified. One of these were based on a simple comparison between "I" and "Q" components of the received signal and the other one involving a correlation of the signal to a known training sequence. The last experiment involved the experimental measurements of signals transmitted over air using the testbed. As the number of interfaces was limited only one transmitting and one receiving antenna was connected to the 2×2 baseband system. However, the Alamouti scheme is able to function when only one of the two antenna is connected, and therefore real-time performance in an indoor environment was successfully tested. The presented designs, algorithms and visualisation form a strong platform for other researchers to continue and expand the work done in this project.

Recent years have witnessed a growing demand for broadband wireless communication services such as on-the-go web-browsing, high speed data transfer and streaming of high definition multimedia. In response to this growth, there has been a rapid progress in research and development of technologies supporting high-speed wireless networks offering flexibility and scalability to heterogeneous consumer requirements. A fundamental challenge to the reliable operation of a wireless communication link is the wireless channel which is influenced by time-variant noise, interference, multipath and scarcity of the available frequency spectrum. Due to the wireless nature of the signal transmission and the manner in which energy is distributed or collected, an antenna has a profound influence on an efficient operation of wireless link. Because nowadays an antenna is required to work with many wireless standards, it poses one of the most difficult design and development technological problems. In the past, many antenna designs were concentrated on conventional outdoor applications such as satellite communications, terrestrial point to point communications and cellular base stations. In these applications, the primary design goal was the antenna electrical performance. In case of indoor applications, the designer has to pay attention not only to the electrical performance but also to mechanical, environmental and aesthetic features of antenna. In this thesis, the investigations into design and development of antenna for indoor wireless communication systems that are either currently widespread or quickly entering the consumer market are carried out. First, a single band circularly polarized Radial Line Slot Array antenna covering 2.4GHz ISM frequency spectrum of IEEE 802.11b/g protocol is proposed. Then, an access point antenna for IEEE 802.11a/b/g WLAN applications operating in a dual frequency band covering 2.4GHz and 5.2GHz frequency spectra is described. It consists of a RLSA antenna and a patch antenna combined in one body. During the design stage, in addition to characteristics such as return loss, radiation pattern and polarization, attention is paid to mechanical rigidity, light weight and low visual impact of these radiating structures. A low manufacturing cost is also part of the design strategy. This is important because of competitive commercial market of WLAN applications which is sensitive to the development cost. In theoretical investigations, a Field Matching Method is utilized to achieve a first order approximation to the coaxial-to-waveguide transition forming the feeding element of the RLSA antenna. Next, the full EM analysis (HFSS™) based on Field Element Method is applied to simulate the single and dual band antennas. Both types of access point antennas are manufactured and tested. Experimental results are compared with simulation results. The next part of this thesis presents the investigations into antenna diversity techniques for a wireless communication link in an indoor environment. The design of the automated experimental testbed is presented. This testing facility is used to measure the signal strength levels of a communication link between a mobile wireless device and an access point when they are equipped with multiple element antennas (MEAs). Special attention is given to the benefits of using MEA in a rich scattering environment that is accompanied the experiment. Full design details including electrical and mechanical features are provided. For a given feeding configuration, the testbed allows for measuring the received signal strength when the receiving module is moved over a circular area in an indoor environment. First set of experiments concerns the MEA system that utilizes two single-port transceivers each equipped with either 180º or 90º 3dB hybrid. By using alternatively one of the two input ports of the hybrids to feed a pair of monopole antennas several different transmission or reception modes of the 2x2 MEA communication link are investigated. The next set of experiments focuses on the performances of an indoor wireless system which uses either linearly or circularly polarized antennas at the two sides of the communication link. The overall diversity results indicate that by marginally increasing an overall system complexity (by using simple hybrid circuits and antennas), traditional transceiver systems equipped with MEA can provide significant improvements in the quality of indoor wireless link. The final part of this thesis presents the investigations into the design of planar monopole antennas that offer good return loss and omni-directional radiation pattern characteristics over an Ultra Wide frequency Band (UWB) spanning from 3.1GHz to 10.6GHz. Two types of planar monopole antennas are investigated. First, the ring type square with semi-circular base monopole antenna placed vertically above a finite ground plane is introduced followed by its design, manufacturing and testing. The second UWB antenna which is proposed in this thesis is a printed square with semi-circular base monopole antenna. This antenna is positioned in the same plane as ground and thus offers direct integration with a front-end circuitry of wireless transceiver. Several variations of this type of antenna featuring different outlines are designed, manufactured and tested. The obtained experimental results show a good agreement with the simulation results, as accomplished with the full EM analysis and simulation software HFSS™.