Faranak Nekoogar

Interference mitigation in transmitted-reference ultra-wideband (UWB) receivers

Transmitted-reference (TR) ultra-wideband transceivers have recently become increasingly popular for their simplicity, capability to reduce the stringent UWB timing requirements, and robust performance in multipath channels. However, the performance of TR receivers is considerably limited by the severity of noise-on-noise component introduced by various types of channel noise such as additive white Gaussian noise (AWGN) or narrowband interference (NBI) on the transmitted signal. It is expected that such receivers will perform poorly at low signal-to-noise ratio links, or in the presence of strong narrowband interferers. In this paper we propose a novel technique that maximizes the extraction of information from reference pulses for UWB-TR receivers. The scheme efficiently processes the incoming signal to suppress different types of interference prior to signal detection. The method described introduces a feedback loop mechanism to enhance the signal-to-noise ratio of reference pulses in a conventional TR receiver. The performance of a conventional TR receiver and a feedback loop TR receiver in the presence of AWGN and strong narrowband interference is investigated by analysis and computer simulations. Our studies show that the reference enhancing feedback loop mechanism greatly improves the robustness of the link performance of TR receivers in the presence of non-UWB interference with modest increase in complexity.

Self organization of wireless sensor networks using ultra-wideband radios

Ultra-wideband (UWB) technology has proven to be useful in short range, high data rate, robust, and low power communications. These features can make UWB systems ideal candidates for reliable data communications between nodes of a wireless sensor network (WSN). However, the low powered UWB pulses can be significantly degraded by channel noise, inter-node interference, and intentional jamming. In This work we present a novel interference suppression technique for UWB based WSN that promises self-organization in terms of power conservation, scalability, and channel estimation for the entire distributed network.

Matching Random Tree Models of Spatio-Temporal Patterns to Tables or Graphs

The problem of matching random tree models of multi-component patterns to tables or graphs containing components extracted from diverse data sources is considered. We focus on bi-level trees whose branches emanate from one root node and terminate on different leaf nodes. Node and branch attributes are treated as random variables. Tree nodes represent pattern components of specified types that occur in tables or graphs to be searched. For each item in the table or graph with a type match to the tree root, there is a set of components from the table or graph that are candidate leaves for optimal matches to the tree model. We adopt a view of optimal matches to random tree models as minimum cost assignments of candidate leaves to tree branches. Model-based formulas are derived for computing costs associated with assignments of specific candidate leaf components from tables or graphs to specific tree branches. We specify an ontology suitable for dynamic geo-spatial query problems in which (1) tree nodes represent physical objects or events on the ground (buildings, roads, communication transmissions...), and (2) branch attributes characterize, with uncertainty, distance or time separations between components, and angles between links connecting components. Our approach is used to search very large images for specific types of buildings in probabilistically constrained spatial arrangements, with the goal of ranking model matches for efficient inspection by human analysts.

A Lumped Circuit for Wideband Impedance Matching of a Non-Resonant, Short Dipole or Monopole Antenna

A new technique is proposed for wideband impedance matching of short dipole- or monopole-like antennas in the VHF-UHF bands. Instead of constructing the network topology for every particular antenna, we propose a simple network of one fixed topology. This network is an inductive L-section cascaded with a high-pass T-section. The network includes five discrete components-three inductors and two capacitors. Although the approach is not general, the paper proves that matching with the present network is close to the theoretical limit impedance matching confirmed by Bode-Fano theory. The matching performance also approaches the performance of the Carlins equalizer for short dipoles and monopoles. The dipoles and monopoles may have different shape and different matching bandwidths. By using the matching circuit of fixed topology we avoid greater difficulties related to the practical realization of the Carlins equalizer. The key point is to minimize the antennas matching network complexity (and loss) so that the circuit can be designed and constructed in a straightforward manner.

Passive RFID for IOT using UWB/UHF hybrid signaling

Advanced passive RFID tags integrated with a suite of sensors can play a significant role in the Internet of Things (IOT) ecosystem for longer range sensor applications. Although readers equipped with IPv6 communications capability allow the transfer of data from passive tags to the IOT world, reliable remote powering of such tag/sensor units still is a limiting factor in harsh propagation environments. In this paper we present a hybrid UWB/UHF signaling for reliable long-range tag-reader communications in challenging environments such as reflective, absorptive, and cluttered channels.

Next generation RFID using ultra-wideband signaling

Radio frequency identification (RFID) is a powerful technology for asset monitoring and tracking and has a vast potential to reduce operating costs for many applications. While conventional narrowband RFID systems have successfully been used in several applications, the challenges posed by their signal characteristics has prevented their widespread use in some operational scenarios requiring data security and privacy, long lifetime, and operations in cluttered environments. Even though the state-of-the-art research in narrowband RFID systems has overcome some of these challenges, the use of ultra-wideband (UWB) signaling for tag-reader communications could be another option to address the unresolved problems. In this paper we present a summary of such challenges and explain how UWB technology can provide a viable solution for each of them. More detailed discussions on this topic are available in [1]. This paper is organized as follows. We start with an overview of the key challenges of narrowband signaling in tag-reader communications, then we briefly go over the concept of UWB signaling and discuss the distinct advantages of using UWB for tag-reader communications in various RFID challenges. We conclude the paper with a summary of discussions.

Basics of Radio Frequency Identification (RFID) Systems

With the recent advances in wireless communications, Radio frequency Identification (RFID) technology is becoming more of a reality in terms of their widespread use in various applications. Although RFID provides a general capability for tagging and tracking of objects, and has been in use for decades, no RFID system fits all applications. Therefore, it’s important to start this introductory chapter with an overview of the technology in general terms and continue in the later chapters with more detailed discussions on various techniques that can make RFIDs more adaptable to some specialized applications that face challenges with conventional RFID techniques.

Design Considerations for Secure Wireless Sensor Communication Systems in Harsh Electromagnetic Environments of Nuclear Reactor Facilities

Abstract Wireless sensors can potentially play a significant role in safety, efficiency, and reliability of the instrumentation and control process in current and next generation nuclear power reactors. While conventional narrowband wireless sensors have shown a certain level of success in some nuclear power plants (NPPs), the radio frequency (RF) propagation challenges posed by the heavy metallic and cluttered environment of NPPs has prevented their widespread use in such operations. These challenges include RF wave propagation in harsh (reflective, absorptive, cluttered) environments, data security issues, and RF interference to and from other devices in the vicinity of a nuclear reactor core. In this paper, first we address how ultrawideband (UWB) RF technology can complement the narrowband (i.e., WiFi) solutions that have been used in some NPPs by providing an alternative solution in addressing the signal propagation issues in such electromagnetically harsh environments. Second, we discuss and present the UWB software simulation results on multipath harsh environments, and then address the data security issues. In the final sections of the paper, we present the experimental results of using UWB signaling in a representative harsh environment conducted at the Massachusetts Institute of Technology research reactor site. We plan to develop the UWB communications hardware based on the results of this paper and report on its performance in the field with emphasis on the security aspects of the system in a subsequent paper.

A battery-free RFID sensor tag with fiber-optic tamper detection

We present an ISO18000-6C (EPC Generation 2) compatible battery-free RFID tag designed for a hazardous material monitoring application. This tag is a wirelessly powered sensor device that incorporates a general purpose microprocessor to enable the development of specialized sensor applications. It is housed in a ruggedized enclosure that incorporates a dual-polarized 6 dBi antenna for the 902–928 MHz UHF RFID band. It integrates two custom UHF RFID analog front end ASICs with a general purpose TI MSP430 microcontroller and a fiber-optic tamper detection loop. The tag has a power-up threshold of +3 dBm due to the power requirements of the fiber-optic tamper detection loop. It has a measured operating range of over 5.5 m with a +36 dBm EIRP EPC Generation 2 reader.

Location-based tracking using long-range passive RFID and ultrawideband communications

Reliable positioning capability is a crucial need for first responders in emergency and disaster situations. Lack of a dependable positioning system can result in disruptions in the situational awareness between the local responders in the field and the emergency command and control centers. Indoor localization and navigation poses many challenges for search and rescue teams (i.e. firefighters) such as inability to determine their exact location and communicate with the incident commander outside the building. Although RF navigation and tracking systems have many advantages over other technologies, the harsh indoor RF environment demands new ways of developing and using RF sensor and communication systems. A new approach, proposed recently [1-4], employs passive RFID for geo-location and tracking of a first responder. However, because conventional passive RFID tags have limited communications ranges, a very large number of these tags will be required to fully cover a large multi-storied building without any dead spots. Another technical challenge for conventional RF communications is the transmission of data from the mobile RFID platform (the tag reader) to the outside command and control node, as the buildings walls impose challenges such as attenuation and multipath. In this paper, we introduce a mobile platform architecture that makes optimal use of long-range passive tags, and takes advantage of the frequency diversity of Ultra-wideband (UWB) communication systems for a reliable, robust and yet low-cost infrastructure.