Wavelength reuse techniques for bidirectional ultra-wide band (UWB) over fiber (UWBoF) networks are presented. The downstream optical signal from the central station (CS) is reused for upstream data transmission with the original data erased at the base station (BS). Two wavelength reuse schemes for the generation of a clear optical carrier at the BS are theoretically analyzed and experimentally demonstrated. In the first scheme, the wavelength reuse is based on phase-modulation to intensity-modulation (PM-IM) conversion and destructive interferencing using a polarization modulator (PolM) and a fiber Bragg grating (FBG). A theoretical analysis is performed which is verified by an experiment. In the second scheme, the wavelength reuse is based on injection locking of a Fabry–Pérot laser diode (FP-LD) and polarization multiplexing. The UWB injection signal contributes to better BERs of both downstream and upstream services and a lower power penalty cause by the wavelength reuse of the whole system than the baseband signal. A bidirectional point-to-point transmission of over a 25-km single-mode fiber (SMF) using a single wavelength from the CS in each scheme is demonstrated.

No / A novel MIMO/diversity Planar Inverted-F antenna (PI FA) is presented for UWB applications. This antenna assembly is formed by two identical PIFAs, a T-shaped decoupling structure which connects the two PIFAs and a finite ground plane. The compact envelope dimension of this antenna is 50 × 90 × 7.5 mm3. Theoretical and experimental characteristics are illustrated for this antenna that fully covers an operating frequency band of 3.1 – 10.6 GHz for UWB applications, at a reflection coefficient and mutual coupling better than −10 dB and −20 dB respectively. An acceptable agreement is also obtained between computed and measured radiation patterns and gains. These characteristics demonstrate that the proposed antenna is an attractive candidate to provide pattern diversity in enhancing the channel capacity while operating in a rich scattering environment.

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Ultra wideband (UWB) is a promising technology for short range and high-speed wireless communications such as home entertainment, wireless video downloading, wireless LAN, wireless USB and so on. This dissertation studied several important issues in the application of UWB technology and its contributions are summarized as follows. First, a 2-stage optimal UWB pulse shaping filter design procedure is proposed, which not only satisfies the FCC transmission spectral masks but also suppress the multiple access interference (MAI). The major advantages of the proposed joint optimization method are: (1) it has superior MAI suppression capability; (2) it can achieve the best system performance by optimizing transmitting and receiving filters jointly. Second, a pulse shaping optimizer is proposed to achieve the best received signal-to-noise ratio (SNR). Since the objective function of the SNR optimization has multiple maxima, genetic algorithms are adopted in this all-pass filter optimization. Third, a novel analytical method of assessing the narrowband performance degradation due to UWB interferences is proposed. This method models the UWB interferences as a composite signal of white Gaussian noise and jamming tones. Finally, a RAKE receiver simulation model under a realistic UWB channel is proposed and numerical results are presented. Overall, this dissertation investigates several important issues in the application of UWB technology, and provides some insights on the role of UWB technology in the evolving course of wireless communications. / Ph. D.

Ultra-Wideband (UWB) technologies are at the forefront of wireless communications, offering the possibility to provide extremely high data rate wireless solutions. In addition to high data rate applications, UWB technologies also offer an extremely low cost alternative for many low data rate systems. In this thesis, we describe the design of a CMOS pulse generator for impulse based UWB systems. The structure of our pulse generator is based on the topology of a single tap CMOS power amplifier. By increasing the number of taps on a CMOS power amplifier, it is possible to generate sub-nanosecond pulses with a desired shape. A power saving scheme that significantly reduces the power consumed at low data rates is also described. The versatility of our design lies in the ability to support dynamically varying output power levels and center frequencies. Our pulse generator design is extended to a rectified cosine generator, necessary for a multiband approach. The performance of our pulse generators is estimated through simulation with a target technology of TSMC 0.18 µm CMOS at a supply voltage of 1.8 V. The simulation results indicate that our pulse generator produces high fidelity Gaussian monocycle pulses with a pulse width of approximately 160 ps and a peak output power of more than 10 mW. We believe that our design of a CMOS pulse generator for UWB systems is a feasible option for many applications in which power and cost are most important. / Master of Science

In Impulse Radio based Ultra Wide Band (UWB) systems, where sub-nano second pulses are used, synchronization is very challenging because of their short pulse duration and very low duty cycle. Coherent detection of ultra wide-band signals requires complex channel estimation algorithms. In impulse based UWB systems, suboptimal receivers that require no channel estimation are proposed for low data rate applications using non coherent detection of energy. This approach requires integrators that collect energy and detect the incoming stream of bits for detection and synchronization. These techniques yield reasonable performance when compared to coherent detection techniques that require complex hardware and dissipate more energy. Non-coherent detection is a promising technique for low complexity, low cost and low data rate ultra-wideband communication applications like sensor area networks. In the past, several attempts have been made to characterize the performance of the energy collection receivers for synchronization using various metrics that include time of arrival and BER measurements. A comprehensive study of the synchronization problem using Probability of False Alarm is limited. The current thesis attempts to characterize the synchronization problem using Probability of False Alarm and Probability of Detection under various channel models and also discusses the importance of the length of the integration window for energy collection receivers. The current work also focuses on the performance evaluation of synchronization for Impulse based UWB systems using energy capture method and modeling them using the Probability of False Alarm and Probability of Detection under various channel models. In these systems, the integration region of a receiver integrator significantly affects the bit error rate (BER) performance. The effect of the integration window on the performance of the algorithm is also studied. This work also discusses the trade-offs between complexity and precision in using these algorithms for synchronization of Impulse based Direct Sequence Ultra Wideband Systems (DS-UWB). Signal to Noise Ratio vs. Probability of Detection, Probability of False Alarm are plotted for different channel models. / Master of Science

A technique for wall compensation in the ultra-wideband (UWB) through-wall imaging radar is presented. The UWB system can be utilize in high precision measurements, but due to phase distortion and amplitude attenuation caused by the wall the precision is limited, the target is displaced, and the image is defocused.  In order to mitigate the wall effects, two methods are applied in this project. First, the unknown wall transfer function is estimated using real data measurements to design the inverse filter. Secondly, FIR Wiener filter is designed to improve the received m-sequence. After all, each method is tested using three parameters, the signal to noise ratio (SNR), the signal to clutter ratio (SCR), and the relative position error (RPE).  The inverse filter can eliminate the wall effects very well; it could correct not only the position of the target but also the image defocus. The new method can give improve the image quality and that can extend the use of UWB radar in many applications.

Ultra-wideband (UWB) communications has emerged as a promising technology for high data rate wireless personal area networks (WPANs). Several proposals for UWB-based WPANs have been made. One widely popular proposal is based on multi-channel OFDM. This proposal was recently standardized by European Computer Manufacturers Association (ECMA). In this dissertation, we address several important aspects that impact the performance of OFDM-based UWB systems. First, we propose an interference management distributed reservation protocol (IMDRP) for these communications. IM-DRP aims at reducing interference between uncooperative beacon groups that operate simultaneously over the same area. We then integrate IM-DRP into the design of a rate adaptation strategy that exploits the multi-rate capability of OFDM-based UWB systems. Besides maintaining a target packet error rate, our proposed strategy attempts to reduce the required reservation time over a link, hence allowing more links to be concurrently activated. Second, we propose a novel overhearing-aware joint routing and rate selection (ORRS) scheme. For a given source-destination pair, ORRS aims at selecting a path and its transmission rates that achieve the minimum channel reservation time, leading to low blocking rate for prospective reservations and high network throughput. At the same time, ORRS takes advantage of packet overhearing, a typical characteristic of broadcast communications. Finally, we propose a novel resource utilization mechanism (RUM) for improving the throughput in multi-rate UWB-based WPANs. RUM exploits opportunistic-relaying and time-spreading techniques to improve link reliability and increase the transmission rate, and hence network throughput. Simulation results indicate that our proposed protocols and schemes achieve significant throughput improvement compared with other protocols.

In February 2002, the FCC (2002 a, b) issued a ruling that ultra-wideband (UWB) could be used for data communications as well as for radar and safety applications. UWB system is constrained to have a maximum power transmission of -41 dBm and a bandwidth ranging from 3.1-10.6 GHz. UWB co-exists and does not interfere with the existing narrowband or wideband communication systems in the same spectrum. However, due to its low power in the same bandwidth, UWB is affected by the so-called narrowband (NB) interference. This thesis presents a method to estimate and detect narrowband signals in radio impulse receiver with the intention to eliminate the NB interference. <p>Narrowband bandwidth is very small compared to the bandwidth of UWB therefore the interference can be considered as a single tone. To detect such a tone using conventional techniques is not feasible at least up to this time for UWB as current technology can not support such high data rates. Alternatives way to track down the narrowband signal include using a power spectral density estimation technique called spectrogram. For all cases, the spectrogram at specific frequency range where the narrowband active statistically be larger than its overall average power. Here, a threshold detector is built which reports detection at the frequency range where the narrowband is located if the spectrogram exceeds a threshold value. <p>Upon completing of successful NB detection, the NB signal in the UWB system will be estimated in digital form and cancelled in analog form. The pipelined LMS algorithm is used to estimate the NB signal; the algorithm is implemented using a built-in IP core from the Altera DSP library which can be simulated in either Matlab platform or in FPGA boards. The design correctness has been validated by means of Monte-Carlo simulation and hardware implementation using standard UWB IEEE standard channel models, Time Hopping-Pulse Position Modulation and the rake receiver technique.

In February 2002, the FCC (2002 a, b) issued a ruling that ultra-wideband (UWB) could be used for data communications as well as for radar and safety applications. UWB system is constrained to have a maximum power transmission of -41 dBm and a bandwidth ranging from 3.1-10.6 GHz. UWB co-exists and does not interfere with the existing narrowband or wideband communication systems in the same spectrum. However, due to its low power in the same bandwidth, UWB is affected by the so-called narrowband (NB) interference. This thesis presents a method to estimate and detect narrowband signals in radio impulse receiver with the intention to eliminate the NB interference. <p>Narrowband bandwidth is very small compared to the bandwidth of UWB therefore the interference can be considered as a single tone. To detect such a tone using conventional techniques is not feasible at least up to this time for UWB as current technology can not support such high data rates. Alternatives way to track down the narrowband signal include using a power spectral density estimation technique called spectrogram. For all cases, the spectrogram at specific frequency range where the narrowband active statistically be larger than its overall average power. Here, a threshold detector is built which reports detection at the frequency range where the narrowband is located if the spectrogram exceeds a threshold value. <p>Upon completing of successful NB detection, the NB signal in the UWB system will be estimated in digital form and cancelled in analog form. The pipelined LMS algorithm is used to estimate the NB signal; the algorithm is implemented using a built-in IP core from the Altera DSP library which can be simulated in either Matlab platform or in FPGA boards. The design correctness has been validated by means of Monte-Carlo simulation and hardware implementation using standard UWB IEEE standard channel models, Time Hopping-Pulse Position Modulation and the rake receiver technique.