UWB technology provides an excellent means for wireless positioning due to its high resolution capability in the time domain. Its ability to resolve multipath components makes it possible to obtain accurate location estimates without the need for complex estimation algorithms. In this article, theoretical limits for TOA estimation and TOA-based location estimation for UWB systems have been considered. Due to the complexity of the optimal schemes, suboptimal but practical alternatives have been emphasized. Performance limits for hybrid TOA/SS and TDOA/SS schemes have also been considered. Although the fundamental mechanisms for localization, including AOA-, TOA-, TDOA-, and SS-based methods, apply to all radio air interface, some positioning techniques are favored by UWB-based systems using ultrawide bandwidths.

Localization via ultra-wideband radios: a look at positioning aspects for future sensor networks

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Localization via Ultra- Wideband Radios

A new antenna, the planar inverted cone antenna (PICA), provides ultrawideband (UWB) performance with a radiation pattern similar to monopole disk antennas , but is smaller in size. Extensive simulations and experiments demonstrate that the PICA antenna provides more than a 10:1 impedance bandwidth (for VSWR<2) and supports a monopole type omnidirectional pattern over 4:1 bandwidth. A second version of the PICA with two circular holes changes the current flow on the metal disk and extends the high end of the operating frequency range, improving the pattern bandwidth to 7:1.

A new ultrawideband printed monopole antenna: the planar inverted cone antenna (PICA)

Summary Ultra-wideband (UWB) communication techniques have attracted a great interest in both academia and industry in the past few years for applications in short-range wireless mobile systems. This is due to the potential advantages of UWB transmissions such as low power, high rate, immunity to multipath propagation, less complex transceiver hardware, and low interference. However, tremendous R&D efforts are required to face various technical challenges in developing UWB wireless systems, including UWB channel characterization, transceiver design, coexistence and interworking with other narrowband wireless systems, design of the link and network layers to benefit from UWB transmission characteristics. This paper is to provide an overview of UWB communications, summarize the previous research results, and identify further research issues that need to be tackled. The emphasis is placed on the commercial wireless communications. Copyright # 2003 John Wiley & Sons, Ltd.

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Ultra-Wideband Wireless Communications

This paper investigates a ranging method employing ultra wideband (UWB) pulses under the existence of the line of sight (LOS) path in a multipath environment Our method is based on the estimation of time of arrival of the first multipath It averages the received pulses over multiple time frames, performs a correlation operation on the averaged signal, and detects the peak of the correlated signal Our method reduces the ranging accuracy over conventional methods, and its accuracy is close to the Cramer-Rao lower bound (CRLB) on even for a low SNR

An accurate ultra wideband (UWB) ranging for precision asset location

Precision coordinated maneuvering of multiple space vehicles would offer significant performance advantages to both commercial and scientific missions by increasing the versatility and potential capabilities of the formation. Ultra-wideband systems can provide centimeter level accuracy ranging measurements over distances of kilometers, using only milliwatts of power from an omni-directional transceiver no bigger than a pager. Using these precise range measurements between the vehicles, it is possible to resolve the relative geometry of the entire formation. The ultra-wideband (UWB) system presented in this work is not RADAR; it is active ranging over a code divisible multiple access (CDMA) communications channel with no carrier frequency. Each transceiver is given a unique pseudo-random noise code, which is broadcast using pulse position modulation (shifting pulses or monocycles forward or backward in time relative to an constant rate pulse train), in a type of call and return scheme to measure time of flight between vehicles. As a byproduct of CDMA encoding, a UWB navigation system could also provide a megabit per second communications channel to each vehicle, providing further savings of power, weight, and cost. A simple ranging experiment has been designed as a proof of concept. The experiment includes bench top equipment for sending and receiving ultrawideband monocycles and post processing algorithms for determining range. To implement the system, it was necessary to design and develop ultra-wideband antennas to efficiently propagate the monocycle pulses with minimal distortion. These antennas were tested in an anechoic chamber constructed for the ranging experiment and data on their characterization is presented in this paper. This paper presents the experimentally derived ranging accuracies and compares them to theoretically derived ranging accuracies for the UWB based measurement. It also provides a characterization of the distortions encountered in the pulse waveform during transmission and reception from our custom antennas. UWB ranging systems offer a robust solution to relative vehicle navigation in a variety of space mission configurations.

D. Liccardo

Papers

Ultra-wideband for navigation and communications