Filtering and smoothing methods are used to produce an accurate estimate of the state of a time-varying system based on multiple observational inputs (data). Interest in these methods has exploded in recent years, with numerous applications emerging in fields such as navigation, aerospace engineering, telecommunications, and medicine. This compact, informal introduction for graduate students and advanced undergraduates presents the current state-of-the-art filtering and smoothing methods in a unified Bayesian framework. Readers learn what non-linear Kalman filters and particle filters are, how they are related, and their relative advantages and disadvantages. They also discover how state-of-the-art Bayesian parameter estimation methods can be combined with state-of-the-art filtering and smoothing algorithms. The book’s practical and algorithmic approach assumes only modest mathematical prerequisites. Examples include MATLAB computations, and the numerous end-of-chapter exercises include computational assignments. MATLAB/GNU Octave source code is available for download at www.cambridge.org/sarkka, promoting hands-on work with the methods.

贝叶斯滤波与平滑 (Bayesian filtering and smoothing)

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Digital Video And Hdtv Algorithms And Interfaces

Orthogonal frequency division multiplexing (OFDM) is a modulation technique which is now used in most new and emerging broadband wired and wireless communication systems because it is an effective solution to intersymbol interference caused by a dispersive channel. Very recently a number of researchers have shown that OFDM is also a promising technology for optical communications. This paper gives a tutorial overview of OFDM highlighting the aspects that are likely to be important in optical applications. To achieve good performance in optical systems OFDM must be adapted in various ways. The constraints imposed by single mode optical fiber, multimode optical fiber and optical wireless are discussed and the new forms of optical OFDM which have been developed are outlined. The main drawbacks of OFDM are its high peak to average power ratio and its sensitivity to phase noise and frequency offset. The impairments that these cause are described and their implications for optical systems discussed.

OFDM for Optical Communications

Future lightweight, flexible, and wearable electronics will employ visible-light-communication schemes to interact within indoor environments. Organic photodiodes are particularly well suited for such technologies as they enable chemically tailored optoelectronic performance and fabrication by printing techniques on thin and flexible substrates. However, previous methods have failed to address versatile functionality regarding wavelength selectivity without increasing fabrication complexity. This work introduces a general solution for printing wavelength-selective bulk-heterojunction photodetectors through engineering of the ink formulation. Nonfullerene acceptors are incorporated in a transparent polymer donor matrix to narrow and tune the response in the visible range without optical filters or light-management techniques. This approach effectively decouples the optical response from the viscoelastic ink properties, simplifying process development. A thorough morphological and spectroscopic investigation finds excellent charge-carrier dynamics enabling state-of-the-art responsivities >102 mA W-1 and cutoff frequencies >1.5 MHz. Finally, the color selectivity and high performance are demonstrated in a filterless visible-light-communication system capable of demultiplexing intermixed optical signals.

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Color-Selective Printed Organic Photodiodes for Filterless Multichannel Visible Light Communication

Self-assembly offers a unique resource for the preparation of discrete structures at the nano- and microscale, which are either not accessible by other fabrication techniques or require highly expensive and technologically demanding processes. The possibility of obtaining spontaneous organization of separated components, whether they are molecules, polymers, nano- or micro-objects, into a larger functional unit, enables the development of ready-to-use plug and play devices and components at lower costs. Expanding the applicability of self-assembly approaches at the nanoscale to non-conventional substrates would open up new avenues towards multifunctional platforms customized for specific applications. Recently, the combination of the amazing morphological and optical features of self-assembled patterns with the intrinsic properties of optical fibers to conduct light to a remote location has demonstrated the potentiality to open up new intriguing scenarios featuring unprecedented functionalities and performances. The integration of advanced materials and structures at the nanoscale with optical fiber substrates is the idea behind the so-called lab-on-fiber technology, which is an emerging technology at the forefront of nanophotonics and nanotechnology research. Self-assembly processes can have a key role in implementing cost-effective solutions suitable for the mass production of technologically advanced platforms based on optical fibers towards their real market exploitation. Novel lab-on-fiber optrodes would arise from the sustainable integration of functional materials at the nano- and microscale onto optical fiber substrates. Such devices are able to be easily integrated in hypodermic needles and catheters for in vivo theranostics and point-of-care diagnostics, opening up new frontiers in multidisciplinary technological development to be exploited in life science applications. This work is conceived to provide an overview of the latest strategies, based on self-assembly processes, which have been implemented for the realization of lab-on-fiber optrodes with particular emphasis on the perspectives and challenges that lie ahead. We discuss the main fabrication techniques and strategies aimed at developing new multifunctional optical fiber nanoprobes and their application in real scenarios. Finally, we highlight some of the other self-assembly processes that have not yet been applied to optical fiber sensors, but have the potentiality to be exploited in the fabrication of future lab-on-fiber devices.

Self-assembly on optical fibers: a powerful nanofabrication tool for next generation “lab-on-fiber” optrodes

https://iopscience.iop.org/article/10.1088/2515-7647/aaf74a/pdf

Indoor visible light communications, networking, and applications

The desire to obtain accurate location-based services has increased with the use of mobile devices. In this study, a visible light based indoor localization method that works with both diffusing and nondiffusing lamps is proposed. The received power from the light emitting diodes (LEDs) is used as sensor input, and an extended Kalman filter (EKF) is used for state estimation. The algorithm relies on knowledge of the expected power distribution in the room. The proposed method is robust to low SNR, nonuniform power distributions, and intermittent measurements. The results show that a tracking error around 1 centimeter can be achieved.

Visible Light Positioning with Diffusing Lamps Using an Extended Kalman Filter

Indoor target tracking has garnered interest as communication systems and mobile device capabilities advance. Visible light communication (VLC) is an alternative to RF methods that uses light emitting diodes. In this paper, probabilistic filtering algorithms (particle and extended Kalman filters) are used for indoor tracking. The performance of the filters is compared with an another positioning method: trilateration. Probabilistic filtering methods are shown to be more reliable than trilateration for indoor tracking when non-line-of-sight components are significant. The probabilistic filtering algorithms require a light intensity map that is collected as a fingerprint map prior to tracking. The effect of unpredictable shadowing as the conditions change is examined in a scenario where one of the lamps has been shadowed. Our algorithm tracks the user equipment with less error than trilateration. The results also show that the tracking accuracy for our algorithms is on the order of the grid resolution of the fingerprint map for high signal-to-noise ratio environments.

Effects of unknown shadowing and non-line-of-sight on indoor tracking using visible light

Optical wireless communications (OWC) and the internet of things (IoT) are two recent paradigms that are expected to be ubiquitous in the near future. In this paper, we introduce an early concept of how OWC can play a critical role in IoT applications in the context of real-time location-based services. OWC systems such as visible light communications (VLC) use light-emitting diodes (LED), already present in most user electronics as data transmission nodes. Studies on indoor OWC positioning generally assume that the location of the nodes, the LEDs that are connected to the backbone communications network, is provided to the user equipment (UE). In this paper, we consider a scenario where no a priori knowledge of the LED and UE locations is available, and the UE uses a single photodetector to measure the received optical intensity. We use these measurements to extract the distance between the UE and LEDs, and form geometric relations to find their locations. Once the LED locations have been found, we can track the UE using an extended Kalman filter. The joint source LED localization and UE tracking process is enhanced by using measurements that are collected by other members of the OWC-IoT network. Results show that the root mean square error of the LED localization can be decreased to 10 centimeters, and this leads to a user tracking accuracy better than 20 centimeters using the proposed method.

Localization in Optical Wireless Sensor Networks for IoT Applications

Visible-light communication (VLC) is an optical wireless communication technique that uses light emitting diodes (LEDs) or other optical sources to transmit information to a user equipment (UE) device. An optically-based location determination approach, such as using VLC infrastructure, can meet a desire for location-based services where use of VLC can provide a solution to an indoor localization or navigation problem. A fingerprinting approach can include use of an optical received signal strength (RSS) or other information (e.g., an image of a scene) to generate a spatial fingerprint map of an area. A later-received RSS on the UE device and the prior-generated fingerprint map representative of RSS can be received, and a fingerprint map and RSS observations can be provided as inputs to a Bayesian filter, such as an Extended Kalman Filter (EKF) or a Particle Filter, to provide an estimated position for the UE device.

Zafer Vatansever

Papers

Indoor visible light communications, networking, and applications

Visible Light Positioning with Diffusing Lamps Using an Extended Kalman Filter

Effects of unknown shadowing and non-line-of-sight on indoor tracking using visible light

Localization in Optical Wireless Sensor Networks for IoT Applications

Position localization using visible light communication