Prognostics and health management design for rotary machinery systems—Reviews, methodology and applications

One of the most important design problems for multi-UAV (Unmanned Air Vehicle) systems is the communication which is crucial for cooperation and collaboration between the UAVs. If all UAVs are directly connected to an infrastructure, such as a ground base or a satellite, the communication between UAVs can be realized through the in-frastructure. However, this infrastructure based communication architecture restricts the capabilities of the multi-UAV systems. Ad-hoc networking between UAVs can solve the problems arising from a fully infrastructure based UAV networks. In this paper, Flying Ad-Hoc Networks (FANETs) are surveyed which is an ad hoc network connecting the UAVs. The differences between FANETs, MANETs (Mobile Ad-hoc Networks) and VANETs (Vehicle Ad-Hoc Networks) are clarified first, and then the main FANET design challenges are introduced. Along with the existing FANET protocols, open research issues are also discussed.

Flying Ad-Hoc Networks (FANETs)

The growing commercial interest in indoor location-based services (ILBS) has spurred recent development of many indoor positioning techniques. Due to the absence of global positioning system (GPS) signal, many other signals have been proposed for indoor usage. Among them, Wi-Fi (802.11) emerges as a promising one due to the pervasive deployment of wireless LANs (WLANs). In particular, Wi-Fi fingerprinting has been attracting much attention recently because it does not require line-of-sight measurement of access points (APs) and achieves high applicability in complex indoor environment. This survey overviews recent advances on two major areas of Wi-Fi fingerprint localization: advanced localization techniques and efficient system deployment. Regarding advanced techniques to localize users, we present how to make use of temporal or spatial signal patterns, user collaboration, and motion sensors. Regarding efficient system deployment, we discuss recent advances on reducing offline labor-intensive survey, adapting to fingerprint changes, calibrating heterogeneous devices for signal collection, and achieving energy efficiency for smartphones. We study and compare the approaches through our deployment experiences, and discuss some future directions.

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Wi-Fi Fingerprint-Based Indoor Positioning: Recent Advances and Comparisons

The spatial features of emitted wireless signals are the basis of location distinction and determination for wireless indoor localization. Available in mainstream wireless signal measurements, the Received Signal Strength Indicator (RSSI) has been adopted in vast indoor localization systems. However, it suffers from dramatic performance degradation in complex situations due to multipath fading and temporal dynamics.Break-through techniques resort to finer-grained wireless channel measurement than RSSI. Different from RSSI, the PHY layer power feature, channel response, is able to discriminate multipath characteristics, and thus holds the potential for the convergence of accurate and pervasive indoor localization. Channel State Information (CSI, reflecting channel response in 802.11 a/g/n) has attracted many research efforts and some pioneer works have demonstrated submeter or even centimeter-level accuracy. In this article, we survey this new trend of channel response in localization. The differences between CSI and RSSI are highlighted with respect to network layering, time resolution, frequency resolution, stability, and accessibility. Furthermore, we investigate a large body of recent works and classify them overall into three categories according to how to use CSI. For each category, we emphasize the basic principles and address future directions of research in this new and largely open area.

https://ink.library.smu.edu.sg/cgi/viewcontent.cgi?article=5541&context=sis_research

From RSSI to CSI: Indoor localization via channel response

The spatial features of emitted wireless signals are the basis of location distinction and determination for wireless indoor localization. Available in mainstream wireless signal measurements, the Received Signal Strength Indicator (RSSI) has been adopted in vast indoor localization systems. However, it suffers from dramatic performance degradation in complex situations due to multipath fading and temporal dynamics. Break-through techniques resort to finer-grained wireless channel measurement than RSSI. Different from RSSI, the PHY layer power feature, channel response, is able to discriminate multipath characteristics, and thus holds the potential for the convergence of accurate and pervasive indoor localization. Channel State Information (CSI, reflecting channel response in 802.11 a/g/n) has attracted many research efforts and some pioneer works have demonstrated submeter or even centimeter-level accuracy. In this article, we survey this new trend of channel response in localization. The differences between CSI and RSSI are highlighted with respect to network layering, time resolution, frequency resolution, stability, and accessibility. Furthermore, we investigate a large body of recent works and classify them overall into three categories according to how to use CSI. For each category, we emphasize the basic principles and address future directions of research in this new and largely open area.

From RSSI to CSI: Indoor Localization via Channel Response, A survey on indoor localization using PHY-layer information

Precise time-of-arrival (TOA) estimation is challenging in dense multipath environments because the leading-edge path of a received signal may not be the strongest path. In this paper, we propose a threshold-based coherent TOA estimation scheme for impulse radio-based ultrawideband (UWB) systems. The scheme uses a dedicated ranging sequence with a good cross-correlation property and a search-back process that considers the count of threshold crossings to find the leading edge of the received signal. We derive an approximate closed-form expression for the optimal threshold that restrains the mean absolute error. We show by simulations that high-precision short-distance ranging is achieved without introducing too much latency.

A Novel Threshold-Based Coherent TOA Estimation for IR-UWB Systems

The design of an experimental AGPS-based (Assisted Global Positioning System) elderly tracking system is described. The system includes: a wearable AGPS terminal with HSPA two-way communication capability and designed for 10 days of continuous battery operation, a GPS assistance data server with reference GPS stations, location database and server, application server, and web server and client. Assistance data is retrieved by the wearable AGPS terminal using the SUPL protocol (Secured User Plane Location). This paper describes the design of each component based on key considerations such as accuracy, availability, battery life-time, and user behavior.

/pdf/an-agps-based-elderly-tracking-system-4w0h7q0wuz.pdf

Albert Kai-Sun Wong

Papers

A Novel Threshold-Based Coherent TOA Estimation for IR-UWB Systems

An AGPS-based elderly tracking system

A hybrid numerical/experimental technique for determining the heat dissipated during low cycle fatigue

An effective vorticity-vector potential formulation for the numerical solution of three-dimensional duct flow problems

Determining stress components from the thermoelastic data—A theoretical study