Indoor localization of smart hand-held devices is essential for location-based services of pervasive applications. The previous research mainly focuses on exploring wireless signal fingerprints for this purpose, and several shortcomings need to be addressed first before real-world usage, e.g., demanding a large number of access points or labor-intensive site survey. In this paper, through a systematic empirical study, we first gain in-depth understandings of Bluetooth characteristics, i.e., the impact of various factors, such as distance, orientation, and obstacles on the Bluetooth received signal strength indicator (RSSI). Then, by mining from historical data, a novel localization model is built to describe the relationship between the RSSI and the device location. On this basis, we present an energy-efficient indoor localization scheme that leverages user motions to iteratively shrink the search space to locate the target device. An Motion-assisted Device Tracking Algorithm has been prototyped and evaluated in several real-world scenarios. Extensive experiments show that our algorithm is efficient in terms of localization accuracy, searching time and energy consumption.

Energy-Efficient Indoor Localization of Smart Hand-Held Devices Using Bluetooth

This paper analyzes the use of wide-area measurement technologies including satellite-based methods for the command and control of power systems. The methods studied include the global positioning system (GPS) and low earth orbit satellites (LEOS). Satellite technologies have been used in a variety of applications requiring precise timing between geographically diverse locations. The deregulation of the electric power industry is placing increased demands on power transmission system utilization. Because deregulated power systems utilize long-distance high-power exchanges, satellite-based communication systems are useful in control of geographically large interconnected power systems. In this paper, the satellite-based measurements and commands are introduced for wide-area control. With the support of wide-area signals, a multiagent supervisory-level power system stabilizer is proposed here as a potential wide-area control structure. Increased loading of transmission facilities is an impetus for accurate dynamic thermal overhead electrical conductor ratings. The application of satellite-based measurement for improving the dynamic thermal rating of overhead transmission circuits is suggested.

Use of Satellite Technologies for Power System Measurements, Command, and Control

Coordinated control of distributed energy resources (DER) is essential for the operation of islanded microgrids (MGs). Conventionally, such coordination is achieved by drooping the frequency of the reference voltage versus active (or reactive) power. The conventional droop method ensures synchronized operation and even power sharing without any communication link. However, that method produces unwanted frequency fluctuations, which degrade the power quality. In order to improve the power quality of islanded MGs, a novel decentralized control method is proposed in this paper. In this method, the GPS timing technology is utilized to synchronize the DERs to a common reference frame, rotating at a nominal frequency. In addition, an adaptive Q–f droop controller is introduced as a backup to ensure stable operation during GPS signal interruptions. In the context of the common reference frame, even sharing of active ( $i_{d}$ ) and reactive ( $i_{q}$ ) components of the current are achieved based on $v_{d}\,\hbox{-}\,i_{d}$ and $v_{q}\,\hbox{-}\,i_{q}$ droop characteristics. The method has been tested on a laboratory-scale MG. Experimental results demonstrate the efficacy of the proposed method in terms of dynamics, power quality, and robustness with respect to GPS interruptions.

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A GPS-Based Decentralized Control Method for Islanded Microgrids

A multiband microstrip patch antenna with defected ground structure for its applications

Disclosed herein is a system for detecting manipulation of a global time source such as a Global Navigational Satellite System (GNSS) signal and mitigating against such manipulation. A plurality of receivers with geographical diversity receive GNSS signals, and calculate a time signal to be distributed to consuming devices. The receivers also communicate calculated time signals with other receivers. The receivers compare the time signals, and when a difference between the time signals exceeds a predetermined threshold, the receivers indicate that manipulation is likely. Such indication is shared across the network of receivers. The indication is further shared with consuming devices of the time signal from the compromised receiver. A second time signal that is not compromised may be shared with the consuming devices and/or used by the consuming devices. The consuming devices may modify their behavior when in receipt of the indication.

Manipulation resilient time distribution network

The authors present a series of tutorials which consider the Global Positioning System (GPS) and its application in the field of electric power systems. The first tutorial article is intended as an introduction to the GPS-it is not specific to power systems applications-and gives the reader an insight into the operation of GPS and an understanding of the many acronyms used in this area. Subsequent tutorials will cover existing applications of GPS in power systems and the future of GPS.

P. Crossley

Papers

GPS applications in power systems. I. Introduction to GPS