62,432 research outputs found
A Survey of Positioning Systems Using Visible LED Lights
© 2018 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.As Global Positioning System (GPS) cannot provide satisfying performance in indoor environments, indoor positioning technology, which utilizes indoor wireless signals instead of GPS signals, has grown rapidly in recent years. Meanwhile, visible light communication (VLC) using light devices such as light emitting diodes (LEDs) has been deemed to be a promising candidate in the heterogeneous wireless networks that may collaborate with radio frequencies (RF) wireless networks. In particular, light-fidelity has a great potential for deployment in future indoor environments because of its high throughput and security advantages. This paper provides a comprehensive study of a novel positioning technology based on visible white LED lights, which has attracted much attention from both academia and industry. The essential characteristics and principles of this system are deeply discussed, and relevant positioning algorithms and designs are classified and elaborated. This paper undertakes a thorough investigation into current LED-based indoor positioning systems and compares their performance through many aspects, such as test environment, accuracy, and cost. It presents indoor hybrid positioning systems among VLC and other systems (e.g., inertial sensors and RF systems). We also review and classify outdoor VLC positioning applications for the first time. Finally, this paper surveys major advances as well as open issues, challenges, and future research directions in VLC positioning systems.Peer reviewe
Daylighting Performance of Solar Control Films for Hospital Buildings in a Mediterranean Climate
One of the main retrofitting strategies in warm climates is the reduction of the effects
of solar radiation. Cooling loads, and in turn, cooling consumption, can be reduced through the
implementation of reflective materials such as solar control films. However, these devices may
also negatively affect daylight illuminance conditions and the electric consumption of artificial
lighting systems. In a hospital building, it is crucial to meet daylighting requirements as well as
indoor illuminance levels and visibility from the inside, as these have a significant impact on health
outcomes. The aim of this paper is to evaluate the influence on natural illuminance conditions
of a solar control film installed on the windows of a public hospital building in a Mediterranean
climate. To this end, a hospital room, with and without solar film, was monitored for a whole year.
A descriptive statistical analysis was conducted on the use of artificial lighting, illuminance levels and
rolling shutter aperture levels, as well as an analysis of natural illuminance and electric consumption
of the artificial lighting system. The addition of a solar control film to the external surface of the
window, in combination with the user-controlled rolling shutter aperture levels, has reduced the
electric consumption of the artificial lighting system by 12.2%. Likewise, the solar control film has
increased the percentage of annual hours with natural illuminance levels by 100–300 lux
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