System Design for Ultra-Low-Power UWB-based Indoor Localization
ABSTRACT In this paper, we propose a 3-tier ultra wide-band indoor localization system for autonomously powered sensor network applications. It consists of a large number of cost-effective tags, a number of cheap and low-power hubs and few synchronized base stations. Using the UWB characteristics and the hierarchical scheme, the localization system enables ultra-low-power, autonomous tags and precise positioning. We present how ambiguous solutions (coordinates and transmission time of an unknown node) can be eliminated with the help of the proper geometry of 4 reference nodes. A method for optimizing the number and placement of hubs is proposed. Different positioning algorithms are discussed and compared based on the position accuracy a.f.o range errors. We determine the optimal algorithm for different scenarios. Simulations are conducted to investigate the performance degradation due to timing errors.
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ABSTRACT: This paper presents a fully integrated flexible ultra-low power UWB impulse radio receiver, capable of cm-accurate ranging. Ultra-low-power consumption is achieved by employing the quadrature analog correlating receiver architecture, by exploiting the duty-cycled nature of the system, by operating in the sub-1 GHz band as well as by careful circuit design. Two pulse rates, 39.0625 Mpulses per second (Mpps) and 19.531 Mpps, and a wide range of processing gains (0-18 dB) are supported. Also, the acquisition algorithm and accuracy can be adapted at run time. This flexible implementation allows to dynamically trade power consumption for performance depending on the operating conditions and the application requirements. The receiver prototype was manufactured in 130 nm CMOS and the active circuit area measures 4.52 mm<sup>2</sup>. The IC contains a complete analog front-end, digital backend and implements the algorithms necessary for acquisition, synchronization, data reception and ranging. Consuming 4.2 mW when operating at 39.0625 Mpps, it achieves an energy efficiency of 108 pJ/pulse. A 1.3 Mb/s wireless link over more than 10 m in an office-like environment has been demonstrated under direct line-of-sight (LOS) conditions with a raw packet-error-rate (PER) less than 10% and cm-accurate ranging.IEEE Journal of Solid-State Circuits 02/2010; · 3.06 Impact Factor
Conference Proceeding: A 0.4-1.4V 24MHz fully integrated 33µW, 104ppm/V supply-independent oscillator for RFIDs[show abstract] [hide abstract]
ABSTRACT: In RFID-tags with pulse-based UWB communication, accurate supply-independent low-power oscillators are required. The 24 MHz oscillator presented was realized in a 130 nm CMOS technology. It has an ultra-low supply voltage dependency of 104 ppm/V over a voltage range of 1.4 V to 0.4 V. This was achieved by the use of two nested ultra-low-power voltage regulators and a novel circuit technique based on the attraction of two oscillator frequencies. The mean power consumption is 33 muW over the 1 V voltage span. No external biasing and no trimming or calibration was used.ESSCIRC, 2009. ESSCIRC '09. Proceedings of; 10/2009
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ABSTRACT: We present a 3-tier UWB-based indoor localization system. It consists of a large number of energy-scavenging-based cost-effective transmit-only tags, a small number of battery powered hubs as relay stations and a few base stations. This hierarchical scheme is driven by the energy available at each node. Localization is based on the arrival time of the UWB pulses at reference nodes.We describe how the coordinates and transmit time of a tag are determined and how the ambiguous solution is eliminated with the proper geometry of 4 reference nodes. We formulate where to place the hubs as an optimization problem. The localization performance of the system is investigated as a function of several parameters such as non-ideal hub placement, hub localization error and TOA error.IEEE Transactions on Wireless Communications 07/2009; · 2.42 Impact Factor