With the rapid development of wireless networking technology and the great growth of the service demand, accurate location estimation of a mobile station (MS) in an indoor wireless system has gained considerable attention. Since most wireless communication systems used for indoor position location may suffer from dense NLOS propagation error, which leads to a severe degradation of position accuracy. In this thesis, we propose a hybrid TOA/RSSI wireless positioning technique for indoor UWB systems to gain favorable position accuracy, by using the fine resolution of UWB signals, geometrical feature of cell layout, the path loss model and the received signal strength, based on the time of arrival (TOA) range measurements. The algorithm induces the objective function from the geometrical relationships of the base stations (BSs) and TOA range circles, and utilizes the received signal strength and pre-estimated path loss model, which should be well approximating the propagation conditions, to discriminate between LOS or NLOS range measurements and define the weight factors used to describe how credible TOA range measurements are and take effect on the objective function during the location calculating process. Simulation results show that the positioning accuracy of the hybrid TOA/RSSI method is much higher than that of other positioning methods under different distributed NLOS errors.

No description available.

No description available.

The direct sequence ultra-wideband (DS-UWB) system has the characteristics of low transmission power constraints and wide transmitted bandwidth. The wide bandwidth will introduce fine timing resolution and severe inter-symbol interference (ISI), which will is cause larger delay spread. Therefore, the traditional acquisition methods are no longer suitable here. A modified acquisition method and a coarse channel estimation algorithm are proposed in this thesis. Three different strategies with composition of acquisition and channel estimation are compared. Based on three strategies, the tasks of coarse acquisition and channel estimation can be achieved with limited length of acquisition sequence. From simulation results, the parallel strategy is robust enough to operate under the UWB channel in severe ISI conditions and the time duration for completing the tasks of coarse acquisition and channel estimation meets the specification of IEEE 802.15.3a.

Since the Federal Communication Commission released the unlicensed 3.1-10.6 GHz frequency band for commercial use in early 2002, the ultra wideband (UWB) has developed from an emerging technology into a mainstream research area. The UWB technology, which utilizes wide spectrum, opens a new era of possibility for practical applications in radar sensing, one of which is the human vital sign monitoring. The aim of this thesis is to study and research the possibility of a new generation humanrespiration monitoring sensor using UWB radar technology and to develop a new prototype of UWB radar sensor for system-on-chip solutions in CMOS technology. In this thesis, a lowpower Gaussian impulse UWB mono-static radar transceiver architecture is presented. The UWB Gaussian pulse transmitter and receiver are implemented and fabricated using 90nm CMOS technology. Since the energy of low order Gaussian pulse is mostly condensed at lower frequency, in order to transmit the pulse in a very efficient way, higher order Gaussian derivative pulses are desired as the baseband signal. This motivates the advancement of the design into UWB high-order pulse transmitter. Both the Gaussian impulse UWB transmitter and Gaussian higher-order impulse UWB transmitter take the low-power and high-speed advantage of digital circuit to generate different waveforms. The measurement results are analyzed and discussed. This thesis also presents a low-power UWB mono-static radar transceiver architecture exploiting the full benefit of UWB bandwidth in radar sensing applications. The transceiver includes a full UWB band transmitter, an UWB receiver front-end, and an on-chip diplexer. The non-coherent UWB transmitter generates pulse modulated baseband signals at different carrier frequencies within the designated 3-10 GHz band using a digitally controlled pulse generator. The test shows the proposed radar transceiver can detect the human respiration pattern within 50 cm distance. The applications of this UWB radar sensing solution in commercialized standard CMOS technology include constant breathing pattern monitoring for gated radiation therapy, realtime monitoring of patients, and any other breathing monitoring. The research paves the way to wireless technology integration with health care and bio-sensor network.

IR-UWB is a wireless system, which sends information data with pulses that have rapid rising and falling time and very short duration of nanosecond or less. However, due to varying communication channel conditions, amplitude of the received signal is not at a constant level. Therefore, automatic signal strength adjustment is required to equalize the impact of variations of the channel conditions. In this thesis, two approaches based on automatic gain control technique are proposed. The first design is a feed-forward automatic gain control system working at baseband. The second design is a feedback automatic gain control system operating at radio or microwave frequency. The corresponding simulation and implementation results are provided to validate the designs. The proposed designs present signal strength controls for impulse-based transceiver systems which are not often addressed in the literature. It is found that the first design does not work well in reality due to the fact that it essentially operates in the baseband and has no impact on the strong or weak signals right after the receiver antenna. The second design functions quite well and presents a dynamic range of 179mV to 1.062V. As a result, it is the choice of this thesis work.

Our study investigates the performance of the WUSB standards and compares it to the Wimedia Standard. To the best of our knowledge, no technical contributions exist in the open literature at present simulating WUSB and its performance. The study showed that WUSB can achieve better throughput when bursting is enabled at the maximum burst size and it provides more accurate timing control of device activity than using the standard facilities of the WiMedia MAC. Our study also addresses protocol extensions and improvement to the original WUSB standard to support better Quality of Service (QoS). First improvement enables a di erent reservation mechanism along with contention based access to support higher priority security and medical system monitoring applications. Second improvement enables the host device to use an adaptive packet loss technique to change the packet size dynamically during the data transmission to achieve packet loss less than 10%. Third improvement enables redundancy in the cluster by adding a backup host to prevent mobility failures and changes. This backup host is chosen by a prede ned cost weighting function.

Ultra-wideband (UWB) wireless communication is a topic of intense research. It has the potential for superior performance over comparable narrowband wireless systems. UWB wireless systems transmit pulses that have energy concentrated mainly from 3.1 GHz to 10.6 GHz. These pulses are transmitted at very low energy levels so as not to interfere with many existing wireless systems that operate in the same band. UWB communication systems can benefit significantly from beamforming networks where the received signal strength depends on angle of arrival. This thesis focuses on the characterization of a digital beamformer in a real wireless channel. The beamformer is evaluated using various methods to judge its performance impact on a real UWB communication system. An analog UWB beamformer in hardware is derived by taking advantage of a simple microwave circuit realization. The analog UWB beamformer is studied and its feasibility is evaluated.

Ultra-wideband (UWB) wireless communication is a topic of intense research. It has the potential for superior performance over comparable narrowband wireless systems. UWB wireless systems transmit pulses that have energy concentrated mainly from 3.1 GHz to 10.6 GHz. These pulses are transmitted at very low energy levels so as not to interfere with many existing wireless systems that operate in the same band. UWB communication systems can benefit significantly from beamforming networks where the received signal strength depends on angle of arrival. This thesis focuses on the characterization of a digital beamformer in a real wireless channel. The beamformer is evaluated using various methods to judge its performance impact on a real UWB communication system. An analog UWB beamformer in hardware is derived by taking advantage of a simple microwave circuit realization. The analog UWB beamformer is studied and its feasibility is evaluated.

Our study investigates the performance of the WUSB standards and compares it to the Wimedia Standard. To the best of our knowledge, no technical contributions exist in the open literature at present simulating WUSB and its performance. The study showed that WUSB can achieve better throughput when bursting is enabled at the maximum burst size and it provides more accurate timing control of device activity than using the standard facilities of the WiMedia MAC. Our study also addresses protocol extensions and improvement to the original WUSB standard to support better Quality of Service (QoS). First improvement enables a di erent reservation mechanism along with contention based access to support higher priority security and medical system monitoring applications. Second improvement enables the host device to use an adaptive packet loss technique to change the packet size dynamically during the data transmission to achieve packet loss less than 10%. Third improvement enables redundancy in the cluster by adding a backup host to prevent mobility failures and changes. This backup host is chosen by a prede ned cost weighting function.