Ultra Wideband Impulse Radio for Wireless Sensing and Identification

by Baghaei Nejad, Majid, PhD

Abstract (Summary)
Ubiquitous computing and Internet-of-Things (IoT) implies an untapped opportunity in the realm of information and communication technology, in which a large number of micro-devices with communication and/or computing capabilities, provides connectivity for anything, by anyone at anytime and anywhere. Especially, these devices can be equipped with sensors and actuators that interact with our living environment. Barcode, smart contactless card, Radio Frequency Identification (RFID) systems, wireless sensor network (WSN), and smart mobile phones are some examples which can be utilized in ubiquitous computing. RFIDs and WSN have been recognized as the two promising enablers for realization of ubiquitous computing. They have some great features such as low-cost and small- size implementation, non-line of sight operation, sensing possibilities, data storing ability, and positioning. However, there are several challenges which need to be addressed, such as limited life time for battery powered device, maintenance cost, longer operation range, higher data rate, and operation in dense multipath and multiuser environment. Ultra-Wideband Impulse Radio (UWB-IR) with its huge advantages has been recognized as a great solution for future WSN and RFID. UWB-IR technique has the possibility of achieving Gb/s data rate, hundreds of meter operation range, pJ energy per bit, centimeter accuracy of positioning, and low cost implementation. In this work utilization of UWB-IR in WSN and RFID is investigated. A wireless sensor network based on UWB-IR is proposed focusing on low-cost and low-power implementation. Our contribution is to imply two different architectures in base station and sensor nodes to satisfy power, complexity and cost constraints. For sensor nodes, an autonomous UWB-IR detection is proposed, which detects the UWB signal autonomously and no restrict synchronization is required. It reduces the circuit complexity significantly. The performance in term of bit-error-rate is compared with two other common detection techniques. It is shown that the new detection is more robustness to timing jitter and clock skew, which consequently reduces the clock and synchronization requirements considerably. A novel wireless sensing and identification system, based on remote-powered tag with asymmetric wireless link, is proposed. Our innovative contribution is to deploy two different UWB and UHF communication techniques in uplink and downlink respectively. In the proposed system, tags capture the required power supply from different environmental sources (e.g. electromagnetic wave transmitted by a reader) and transmit data through an ultra-low power impulse UWB link. A new communication protocol is devised based on slotted-aloha anti-collision algorithm. By introducing several improvements including of pipelined communication, adaptive frame size, and skipping idle slots, the system throughput of more than 2000 tags/s is achieved. To prove the system concept a single chip integrated tag is implemented in UMC 0.18?m CMOS process. The measurement results show the minimum sensitivity of -18.5 dB (14.1 ?W) and adaptive data rate up to 10 Mb/s. It corresponds to 13.9 meters operation range, considering 4W EIRP, a matched antenna to the tag with 0dB gain, and free space path loss. This is a great improvement in operation range and data rate, compared with conventional passive RFID, which data rate is limited to a few hundreds of Kb/s. System integration in a Liquid-Crystal-polymer (LCP) substrate is investigated. The integration of a tunable UWB-IR transmitter and a power scavenging unit are studied. Our contribution includes embedding and modeling the RF components and antenna in substrate and co-optimizing the chip and package with on-chip versus off-chip passives trade-offs. Simulation results verify the potential of system-on-package solution for UWB integration. The effect of antenna miniaturization in a UWB system is studied. Our focus is to scale down a UWB antenna and optimize the performance through the chip-antenna co-design. A tunable impulse- UWB transmitter is designed in two cases - a conventional 50? design and a co-design methodology. The simulation results show that the standard 50? design technique can not reach the best condition in all cases, when a real antenna is placed into the system. The performance can be improved significantly when doing codesign. The antennas and UWB transmitter performances are evaluated in a given UWB systems. It is shown that the operation distance at a target performance is reduced with antenna scaling factor and it can be compensated by antenna-transceiver co-design. The result proves the importance of antenna-transceiver codesign, which needs to be addressed in the earliest phases of the design flow.
Bibliographical Information:


School:Kungliga Tekniska högskolan

School Location:Sweden

Source Type:Doctoral Dissertation

Keywords:Ubiquitous computing; Impulse Radio; Ultra wideband; RFID; Wireless sensor; WSN; Antenna; System-on-Package


Date of Publication:01/01/2008

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