Visible Light Communication

—Indoor localization is very important to enable Internet-of-things (IoT) applications. Visible light communication (VLC)-based indoor localization approaches embrace many advantages, such as utilization of existing ubiquitous lighting infrastructure, high location and orientation accuracy, and no interruption to RF-based devices. However, existing VLC-based localization methods lack a real-time backward channel from the device to landmarks and necessitate computation at the device, which make them unsuitable for real-time tracking of small IoT devices. In this paper, we propose and prototype a retroreflector-based visible light localization system RETRO, that establishes an almost zero-delay backward channel using a retroreflector to reflect light back to its source. RETRO locates passive IoT devices without requiring computation and heavy sensing (e.g. camera) at the devices. Multiple photodiodes (i.e. landmarks) are mounted on any single unmodified light source to sense the retroreflected optical signal (i.e. location signature). We theoretically derive a closed-form expression for the reflected optical power related to the location and orientation of the retroreflector, and validate the theory by experiments. The characterization of received optical power is applied to a received signal strength indicator (RSSI) and trilateration based localization algorithm. Extensive experiments demonstrate centimeter-level location accuracy and single-digit angular error.

VLC is an emerging optical wireless communication technology that can be added as a complementary feature into existing lighting infrastructures for alleviating pressure on the rapidly dwindling radio frequency spectrum. Although LEDs have been traditionally used as transmitters in VLC, the growing urgency for higher data rates in the gigabit class range has deviated focus toward the consideration of LDs as potential sources for VLC due to their unique features of high modulation bandwidth, efficiency, and beam convergence. This article focuses on the principles of LD-based VLC systems, highlighting the operational characteristics and link configurations. The unique features of LDs compared to LEDs are discussed alongside the communication and illumination aspects of different classifications of LD-VLC. The challenges in terms of practical implementation and the potential applications that might arise from this communication technology are also discussed.

Visible Light Communication (VLC) is promising new technology to be applied in the lighting system infrastructure. This communication function should not interfere with the existing lighting system. In order to prevent from this interference, the utilized modulation scheme should have a limited dynamic range to avoid flickering and dimming effect. We propose Pulse Position Modulation (PPM) technique in our VLC system due to its very minimum dynamic range feature. This paper describes the design and analysis of VLC physical layer using PPM scheme to obtain a stable illumination. The design of physical layer consists of analog front end (AFE) circuit and the data processing which is implemented in microcontroller and FPGA. Based on the test results of our VLC system using low cost photo detector, the system is able to provide stable illumination while reaching the maximum data transfer rate of 20 kbps.

As a new generation green lighting source, the light emitting diode (LED) is rapidly replacing traditional incandescent and fluorescent light sources. Apart from providing energy savings, the use of LED lighting technology creates scope for an innovative optical wireless communication technology known as visible light communication (VLC), which takes advantage of the superior modulation capability of LEDs to transmit data through a wireless channel. VLC is capable of concurrently providing communication as well as illumination. For making commercial implementation of VLC feasible, it is necessary to incorporate it with dimming schemes that will provide energy savings, moods, and increase the aesthetic value of the place using this technology. However, general dimming techniques have an adverse effect on communication since they limit the achievable data rate of a VLC link. This drives the necessity of formulating efficient dimming techniques, which will create a balance between the two most basic functions of VLC: illumination and communication. This paper focuses on dimming mechanisms that can be implemented in VLC systems to save energy and provide precise illumination control. The motivation behind this control mechanism, current challenges in practical implementation, driver circuitry, recent progress, and future prospects are also concisely presented.

The design and implementation of medium access control (MAC) layer for network-enabled visible light communication (VLC) system is presented in this paper. The point-to-point link was chosen because of its simple in configuration as well as implementation. Whereas the FPGA Zybo Zynq-7000 is employed for prototyping the hardware of VLC system because of it serve a Linux operating system (OS), i.e. Xillinux. Our MAC layer has been realized in Python programming and running above the Zynq-7000 processor. The designed MAC Layer is adapted from IEEE 802.15.7 standard, specifically for delivering and receiving the MAC frames from the coordinator to the device or vice versa, wrapping the IP packets and unwrapping the MAC Frames with MAC headers and trailers, and performing the error detection in which the cyclic redundant check 16 (CRC-16) was selected. According to the functionality test, our proposed VLC system can perform to send the multimedia contents (video and image) as well as data packet for internet accessing purpose like a wireless fidelity (Wi-Fi) connectivity. Thus, it can be concluded that the implemented MAC layer has met the functionality specifications referred to the IEEE 802.15.7 standard. We also provide the Pseudo-code of designed MAC layer and its Python script (source-code) implementation that can be found in the Appendix section.

Visible Light Communication (VLC) is an emerging field in Optical Wireless Communication (OWC) which utilizes the superior modulation bandwidth of Light Emitting Diodes (LEDs) to transmit data. In modern day communication systems, the most popular frequency band is Radio Frequency (RF) mainly due to little interference and good coverage. However, the rapidly dwindling RF spectrum along with increasing wireless network traffic has substantiated the need for greater bandwidth and spectral relief. By combining illumination and communication, VLC provides ubiquitous communication while addressing the shortfalls and limitations of RF communication. This paper provides a comprehensive survey on VLC with an emphasis on challenges faced in indoor applications over the period 1979-2014. VLC is compared with infrared (IR) and RF systems and the necessity for using this beneficial technology in communication systems is justified. The advantages of LEDs compared to traditional lighting technologies are discussed and comparison is done between different types of LEDs currently available. Modulation schemes and dimming techniques for indoor VLC are discussed in detail. Methods needed to improve VLC system performance such as filtering, equalization, compensation, and beamforming are also presented. The recent progress made by various research groups in this field is discussed along with the possible applications of this technology. Finally, the limitations of VLC as well as the probable future directions are presented.

Teknologi komunikasi data berbasis nirkabel saat ini marak digunakan. Penerapannya pun mulai bermacam-macam, dari WiMax sampai penggunaan Wi-Gig (Wireless Gigabyte). Teknologi berlomba-lomba untuk mencari pengganti teknologi Wi-Fi yang saat ini bukanlah teknologi komunikasi data tercepat. Dengan memanfaatkan penggunaan LED (light emitting diode) di manapun untuk saat ini, secara teoritis lampu LED bisa digunakan sebagai media transmisi dengan kecepatan tinggi. Visible Light Communication adalah sistem komunikasi yang menggunakan cahaya tampak sebagai media transmisi. Dalam jurnal ini, dikembangkan sistem VLC untuk mengirimkan data dari GPS (Global Positioning System) menuju perangkat mobile dengan menggunakan blok transmitter dengan LED sebagai pengirim dan diterima oleh detektor cahaya (photodiode) sebagai penerima informasi yang dikirim oleh LED. Hasil pengukurannnya mencakup nilai parameter-parameter komunikasi data dan jarak yang lebih menjangkau antara transmitter dengan receiver adalah 75 cm dengan kecepatan maksimum 250 mbps. Dengan begitu dapat disimpulkan bahwa Li-Fi dapat mengirim data yang lebih besar untuk sistem GPS yang sangat penting dalam manajemen untuk implementasi kebutuhan navigasi di jalan raya. Kata Kunci : Light Fidelity, Visible Light Communication, Navigasi GPS; Manajemen Proyek, 1. PENDAHULUAN Saat ini teknologi nirkabel sudah ada di mana-mana dan kemampuan mentransmisikan data sudah melampaui 7000 terra byte setiap harinya. Sehingga komunikasi nirkabel sudah menjadi kebutuhan yang sangat penting dalam peradaban manusia seperti halnya air dan listrik. Hal tersebut sudah menjadi salah satu faktor penting untuk kemajuan dan perkembangan sains dan ilmu pengetahuan, hukum, dan bisnis. Perlu adanya teknologi untuk mendukung semua mobilitas tersebut secara efisien dengan harga yang terjangkau. Dengan adanya demand (permintaan) kebutuhan tersebut, teknologi Light Fidelity (Li-Fi) kini sedang dikembangkan untuk keperluan transmisi broadband dengan cepat dan tidak memakan banyak biaya. Li-Fi menggunakan media cahaya (visible light) sebagai media transmisi. Selain bandwidth-nya yang lebih lebar, Li-Fi mempunyai keuntungan dari sisi kesehatan. Selama ini, gelombang komunikasi radio tinggi mempunyai kekurangan pada range frequency yang dapat membahayakan manusia jika terpapar pada frekuensi yang tinggi pada saat di dekat BTS dalam waktu yang cukup lama. Meskipun gelombang radiasi tersebut tidak benar-benar menghasilkan mutasi DNA yang signifikan pada satu individu, namun hal tersebut menjadi salah satu hal yang patut dikhawatirkan. Selain itu, Li-Fi pun dapat digunakan pada tempat-tempat yang tidak memungkinkan untuk menggunakan frekuensi radio tinggi seperti di tempat pengaturan trafik pesawat di bandara atau di rumah sakit. Oleh karena itu, teknologi Li-Fi dapat dikembangkan dalam teknologi GPS yang saat ini sedang menjadi trend di dunia. Yang mana penggunaan GPS hampir meliputi di seluruh bagian sektor ekonomi, hukum, dan sosial. Dengan adanya kecepatan yang melebihi kecepatan yang sudah ada, semua sektor pun akan lebih terkoneksi antara satu sama lain kurang dari beberapa detik saja. Hal ini tentu membantu perkembangan ekonomi dan industri pada suatu Negara, serta dapat membantu mensejahterakan warga negaranya. Dalam jurnal ini membahas implementasi perencanaan penggunaan gelombang cahaya tampak yang dapat mentransmisikan data dengan menggunakan jumlah LED yang cukup banyak dan berukuran kecil, serta pengukuran dan analisis dari baut per second untuk mengetahui jumlah kali per detik sinyal dalam perubahan data komunikasi. Bitrate untuk mengetahui kualitas output yang dihasilkan, dan lebar pita (bandwidth) untuk mengetahui perhitungan konsumsi data yang tersedia ketika sedang berkomunikasi.

Kata Kunci : Light Fidelity, Visible Light Communication, Navigasi GPS; Manajemen Proyek,

The new vehicle execution has been persistently improved and the examination results identifying with the wellbeing of vehicle driving have additionally been consistently announced and illustrated, it is attempting to discover an equalization point between the advancement of vehicle speed limit and the assurance of driver's security. Li-Fi is a VLC, visible light communication innovation that manages move of information through enlightenment by removing fibre from optics by sending information through a LED light that fluctuates in the force quicker than a human eye can pursue. In this undertaking we attempt to build up a framework to give the before mishap data to the vehicle control unit with the goal that it empowers the vehicle to anticipate the occurrence of mishap. Vehicle to vehicle correspondence is the best arrangement that has been utilized so as to decrease vehicles' mishaps. The proposed utilization of Li-Fi innovation in this task involves the light emitting diode (LED) bulbs as methods for network by sending information through light range as an optical remote vehicle for signal engendering. Truth be told, the use of LED dispenses with the need of complex remote systems and conventions.

5G networks have to offer extremely high capacity for novel streaming applications. One of the most promising approaches is to embed large numbers of co-operating small cells into the macro-cell coverage area. Alternatively, optical wireless based technologies can be adopted as an alternative physical layer offering higher data rates. Visible light communications (VLC) is an emerging technology for future high capacity communication links (it has been accepted to 5GPP) in the visible range of the electromagnetic spectrum (~370–780 nm) utilizing light-emitting diodes (LEDs) simultaneously provide data transmission and room illumination. A major challenge in VLC is the LED modulation bandwidths, which are limited to a few MHz. However, myriad gigabit speed transmission links have already been demonstrated. Non line-of-sight (NLOS) optical wireless is resistant to blocking by people and obstacles and is capable of adapting its’ throughput according to the current channel state information. Concurrently, organic polymer LEDs (PLEDs) have become the focus of enormous attention for solid-state lighting applications due to their advantages over conventional white LEDs such as ultra-low costs, low heating temperature, mechanical flexibility and large photoactive areas when produced with wet processing methods. This paper discusses development of such VLC links with a view to implementing ubiquitous broadcasting networks featuring advanced modulation formats such as orthogonal frequency division multiplexing (OFDM) or carrier-less amplitude and phase modulation (CAP) in conjunction with equalization techniques. Finally, this paper will also summarize the results of the European project ICT COST IC1101 OPTICWISE (Optical Wireless Communications - An Emerging Technology) dealing VLC and OLEDs towards 5G networks.