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RONJA (Reasonable Optical Near Joint Access) is a
free-space optical communication Free-space optical communication (FSO) is an optical communication technology that uses light propagating in free space to wirelessly transmit data for telecommunications or computer networking. "Free space" means air, outer space, vacuum, or ...
system originating in the
Czech Republic The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. The ...
, developed by Karel Kulhavý of Twibright Labs and released in 2001. It transmits data
wireless Wireless communication (or just wireless, when the context allows) is the transfer of information between two or more points without the use of an electrical conductor, optical fiber or other continuous guided medium for the transfer. The most ...
ly using beams of
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...
. Ronja can be used to create a 10 Mbit/s
full duplex A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow ...
Ethernet Ethernet () is a family of wired computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks (WAN). It was commercially introduced in 1980 and first standardized in 198 ...
point-to-point link. It has been estimated that 1000 to 2000 links have been built worldwide. The range of the basic configuration is . The device consists of a receiver and
transmitter In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna (radio), antenna. The transmitter itself generates a radio frequency alternating current, which i ...
pipe (optical head) mounted on a sturdy adjustable holder. Two
coaxial cable Coaxial cable, or coax (pronounced ) is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric ( insulating material); many coaxial cables also have a p ...
s are used to connect the rooftop installation with a protocol translator installed in the house near a
computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...
or
switch In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of ...
. The range can be extended to by . Building instructions, blueprints, and schematics are published under the GNU Free Documentation Licence. Only
free software Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, no ...
tools are used in the development. The author calls this level of freedom "User Controlled Technology". Ronja is a project of Twibright Labs.


Manufacture

The building instructions are written with an inexperienced builder in mind. Basic operations like
drilling Drilling is a cutting process where a drill bit is spun to cut a hole of circular cross-section in solid materials. The drill bit is usually a rotary cutting tool, often multi-point. The bit is pressed against the work-piece and rotated at ra ...
,
soldering Soldering (; ) is a process in which two or more items are joined by melting and putting a filler metal (solder) into the joint, the filler metal having a lower melting point than the adjoining metal. Unlike welding, soldering does not involv ...
etc., are explained. Several techniques – drilling templates, detailed checks after soldering, testing procedures – are employed to minimize errors at critical places and help to speed up work.
Printed circuit board A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in Electrical engineering, electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a L ...
s are downloadable ready for manufacture, with instructions for the fabhouse. People with no previous experience with building electronics have reported on the mailing list that the device ran on the first try. 154 installations worldwide have been registered into a gallery with technical data and pictures.


Range

With the brightest variant of
Lumileds Lumileds is a lighting company that develops, manufactures, and distributes LEDs, light bulbs, and related products for automotive lighting, general lighting, and specialty lighting. Lumileds operates as a private company, having funds affili ...
HPWT-BD00-F4000 LED and 130 mm diameter cheap magnifying glass lenses, the range is 1.4 km. The less bright, but easier to buy E4000 variant of HPWT-BD00 yields 1.3 km. The speed is always 10 Mbit/s full duplex regardless of the distance.


Models

* ''Ronja Tetrapolis'': Range of , red visible light. Connect with
8P8C A modular connector is a type of electrical connector for cords and cables of electronic devices and appliances, such as in computer networking, telecommunication equipment, and audio headsets. Modular connectors were originally developed for ...
connector into a
network card A network interface controller (NIC, also known as a network interface card, network adapter, LAN adapter or physical network interface, and by similar terms) is a computer hardware component that connects a computer to a computer network. Ear ...
or switch. * ''Ronja 10M Metropolis'': Range of , red visible light. Connects to
Attachment Unit Interface The Attachment Unit Interface (AUI) is a physical and logical interface defined in the original IEEE 802.3 standard for 10BASE5 Ethernet and the previous DIX standard. The physical interface consists of a 15-pin D-subminiature connection that ...
. * ''Ronja Inferno'': Range of , invisible infrared light. * ''Ronja Benchpress'': A measurement device for developers for physical measurement of lens/LED combination gain and calculation of range from that * ''Ronja Lopipe'': The original (discontinued) design using red visible light and a RS232 interface for a max 115 kbit/s PPP/SLIP link.


Limitations

By definition, clear
visibility The visibility is the measure of the distance at which an object or light can be clearly discerned. In meteorology it depends on the transparency of the surrounding air and as such, it is unchanging no matter the ambient light level or time of ...
between the transmitter and receiver is essential. If the beam is obscured in any way, the link will stop working. Typically, problems may occur during conditions of
snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout ...
or dense
fog Fog is a visible aerosol consisting of tiny water droplets or ice crystals suspended in the air at or near the Earth's surface. Reprint from Fog can be considered a type of low-lying cloud usually resembling stratus, and is heavily influ ...
. One device weighs 15.5 kg and requires 70 hours of building time. It requires an ability to set full duplex manually on the network card or switch to take advantage of full duplex, since it doesn't support
autonegotiation Autonegotiation is a signaling mechanism and procedure used by Ethernet over twisted pair by which two connected devices choose common transmission parameters, such as speed, duplex mode, and flow control. In this process, the connected devices ...
. Must be plugged directly into PC or switch using the integral 1 m Ethernet cable.


Technology

A complete RONJA system is made up of 2
transceivers In radio communication, a transceiver is an electronic device which is a combination of a radio ''trans''mitter and a re''ceiver'', hence the name. It can both transmit and receive radio waves using an antenna, for communication purposes. Thes ...
: 2 optical
transmitters In electronics and telecommunications, a radio transmitter or just transmitter is an electronic device which produces radio waves with an antenna. The transmitter itself generates a radio frequency alternating current, which is applied to the ...
and 2 optical receivers. They are assembled individually or as a combination. The complete system layout is shown in the
block diagram A block diagram is a diagram of a system in which the principal parts or functions are represented by blocks connected by lines that show the relationships of the blocks.
.


Optical receiver – Preamplifier stage

] The usual approach in FSO (Free Space Optics)
preamplifier A preamplifier, also known as a preamp, is an electronic amplifier that converts a weak electrical signal into an output signal strong enough to be noise-tolerant and strong enough for further processing, or for sending to a power amplifier an ...
s is to employ a
transimpedance amplifier In electronics, a transimpedance amplifier (TIA) is a current to voltage converter, almost exclusively implemented with one or more operational amplifiers. The TIA can be used to amplify the current output of Geiger–Müller tubes, photo multipli ...
. A transimpedance amplifier is a very sensitive
broadband In telecommunications, broadband is wide bandwidth data transmission which transports multiple signals at a wide range of frequencies and Internet traffic types, that enables messages to be sent simultaneously, used in fast internet connections. ...
high-speed device featuring a
feedback loop Feedback occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to ''feed back'' into itself. The notion of cause-and-effect has to be handled c ...
. This fact means the layout is plagued with stability problems and special compensation of
PIN diode A pin is a device used for fastening objects or material together. Pin or PIN may also refer to: Computers and technology * Personal identification number (PIN), to access a secured system ** PIN pad, a PIN entry device * PIN, a former Dutch de ...
capacitance Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized are ...
must be performed, therefore this doesn't allow selection of a wide range of cheap PIN photodiodes with varying capacitances. Ronja however uses a feedbackless design where the PIN has a high working
electrical resistance The electrical resistance of an object is a measure of its opposition to the flow of electric current. Its reciprocal quantity is , measuring the ease with which an electric current passes. Electrical resistance shares some conceptual parallels ...
(100
kilohm Ohm (symbol Ω) is a unit of electrical resistance named after Georg Ohm. Ohm or OHM may also refer to: People * Georg Ohm (1789–1854), German physicist and namesake of the term ''ohm'' * Germán Ohm (born 1936), Mexican boxer * Jörg Ohm (bor ...
s) which together with the total input capacitance (roughly 8 pF, 5 pF PIN and 3 pF input
MOSFET The metal–oxide–semiconductor field-effect transistor (MOSFET, MOS-FET, or MOS FET) is a type of field-effect transistor (FET), most commonly fabricated by the controlled oxidation of silicon. It has an insulated gate, the voltage of which d ...
cascode The cascode is a two-stage amplifier that consists of a common-emitter stage feeding into a common-base stage. Compared to a single amplifier stage, this combination may have one or more of the following characteristics: higher input–output ...
) makes the device operate with a
passband A passband is the range of frequencies or wavelengths that can pass through a filter. For example, a radio receiver contains a bandpass filter to select the frequency of the desired radio signal out of all the radio waves picked up by its antenn ...
on a 6 dB/oct slope of low pass formed by PIN working resistance and total input capacitance. The signal is then immediately amplified to remove the danger of contamination by
signal noise In electronics, noise is an unwanted disturbance in an electrical signal. Noise generated by electronic devices varies greatly as it is produced by several different effects. In particular, noise is inherent in physics, and central to the ...
, and then a compensation of the 6 dB/oct slope is done by derivator element on the programming pins of an NE592 video amplifier. A surprisingly flat characteristic is obtained. If the PIN diode is equipped with 3 kΩ working resistor to operate in flat band mode, the range is reduced to about 30% due to
thermal noise A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically. Thermals are created by the uneven heating of Earth's surface from solar radiation, and are an example ...
from the 3 kΩ resistor.


Optical transmitter – Nebulus infrared LED driver

The HSDL4220
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
LED A light-emitting diode (LED) is a semiconductor Electronics, device that Light#Light sources, emits light when Electric current, current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy i ...
is originally unsuitable for 10 Mbit/s operation. It has a
bandwidth Bandwidth commonly refers to: * Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range * Bandwidth (computing), the rate of data transfer, bit rate or thr ...
of 9 MHz, where 10 Mbit/s
Manchester Manchester () is a city in Greater Manchester, England. It had a population of 552,000 in 2021. It is bordered by the Cheshire Plain to the south, the Pennines to the north and east, and the neighbouring city of Salford to the west. The t ...
-modulated systems need bandwidth of around 16 MHz. Operation in a usual circuit with current drive would lead to substantial signal corruption and range reduction. Therefore, Twibright Labs developed a special driving technique consisting of driving the LED directly with 15-fold 74AC04 gate output in parallel with RF voltage applied current-unlimited directly to the LED through large capacitors. As the voltage to keep the nominal LED average current (100mA) varies with temperature and component tolerances, an AC-bypassed current sense resistor is put in series with the LED. A feedback loop measures voltage on this resistor and keeps it at a preset level by varying supply voltage of the 74AC04 gates. Therefore, the nominally digital 74AC04 is operating as a structured power
CMOS Complementary metal–oxide–semiconductor (CMOS, pronounced "sea-moss", ) is a type of metal–oxide–semiconductor field-effect transistor (MOSFET) fabrication process that uses complementary and symmetrical pairs of p-type and n-type MOSFE ...
switch completely in analog mode. This way the LED
junction Junction may refer to: Arts and entertainment * ''Junction'' (film), a 2012 American film * Jjunction, a 2002 Indian film * Junction (album), a 1976 album by Andrew Cyrille * Junction (EP), by Basement Jaxx, 2002 * Junction (manga), or ''Hot ...
is flooded and cleared of carriers as quickly as possible, basically by
short circuit A short circuit (sometimes abbreviated to short or s/c) is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance. This results in an excessive current flowing through the circuit ...
discharge. This pushes the speed of the LED to maximum, which makes the output optical signal fast enough so that the range/power ratio is the same as with the faster red HPWT-BD00-F4000 LED. The side effects of this brutal driving technique are: 1) the LED overshoots at the beginning of longer (5 MHz/1 MHz) impulses to about 2x brightness. This was measured to have no adverse effect on range. 2) A blocking
ceramic capacitor A ceramic capacitor is a fixed-value capacitor where the ceramic material acts as the dielectric. It is constructed of two or more alternating layers of ceramic and a metal layer acting as the electrodes. The composition of the ceramic material de ...
bank backing up the 74AC04 switching array is crucial for correct operation, because charging and discharging the LED is done by short circuit. Under dimensioning this bank causes the leading and trailing edges of the optical output to grow longer.


Transceiver – Ronja Twister

Ronja Twister is an electronic interface for free space optical datalink based on counter and shift register chips. It is a part of the Ronja design. It is effectively an optical Ethernet transceiver without the optical drive part. The original design has been superseded with Twister2 but the logic circuit remained the same.


Open source hardware approach

Soderberg, studying Ronja sociologically, writes: "Arguably, the first project that vindicated the methods and licensing schemes of free software development, applied those practices to open hardware development, and pulled off a state-of-the-art technology without any backing from universities or firms, was the Ronja project." The whole
toolchain In software, a toolchain is a set of programming tools that is used to perform a complex software development task or to create a software product, which is typically another computer program or a set of related programs. In general, the tools form ...
is built strictly upon free tools and the
source files In computing, source code, or simply code, is any collection of code, with or without comments, written using a human-readable programming language, usually as plain text. The source code of a program is specially designed to facilitate the w ...
are provided, free, under the
GPL The GNU General Public License (GNU GPL or simply GPL) is a series of widely used free software licenses that guarantee end users the four freedoms to run, study, share, and modify the software. The license was the first copyleft for general u ...
. This allows anyone to enter the development, start manufacture or invest into the technology without entry costs. Such costs normally can include
software licence A software license is a legal instrument (usually by way of contract law, with or without printed material) governing the use or redistribution of software. Under United States copyright law, all software is copyright protected, in both source c ...
costs, time investment into resolution of compatibility issues between proprietary applications, or costs of
intellectual property Intellectual property (IP) is a category of property that includes intangible creations of the human intellect. There are many types of intellectual property, and some countries recognize more than others. The best-known types are patents, cop ...
licence negotiations. The decision to conceive the project this way was inspired by observed organizational efficiency of
Free Software Free software or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software is a matter of liberty, no ...
. On Christmas 2001, Ronja became the world's first 10 Mbit/s Free Space Optics device with free sources. Examples of tools used in development: *
gEDA The term gEDA refers to two things: # A set of software applications (CAD tools) used for electronic design released under the GPL. As such, gEDA is an ECAD (electronic CAD) or EDA (electronic design automation) application suite. gEDA i ...
gschem (
Schematic capture Schematic capture or schematic entry is a step in the design cycle of electronic design automation (EDA) at which the electronic diagram, or electronic schematic of the designed electronic circuit is created by a designer. This is done interactiv ...
) *
QCAD QCAD is a computer-aided design (CAD) software application for 2D design and drafting. It is available for Linux, Apple macOS, Unix and Microsoft Windows. The QCAD GUI is based on the Qt framework. QCAD is partly released under the GNU General ...
*
BRL-CAD BRL-CAD is a constructive solid geometry (CSG) solid modeling computer-aided design (CAD) system. It includes an interactive geometry editor, ray tracing support for graphics rendering and geometric analysis, computer network distributed frameb ...
* The PCB program *
Sodipodi Sodipodi was an open-source software, open-source vector graphics editor, discontinued in 2004. It is the predecessor to Inkscape. Development Sodipodi started as a Fork (software development), fork of Gill, a vector-graphics program written by ...
for
Vector graphics Vector graphics is a form of computer graphics in which visual images are created directly from geometric shapes defined on a Cartesian plane, such as points, lines, curves and polygons. The associated mechanisms may include vector display a ...


See also

*
Wireless community network Wireless community networks (WCNs) or wireless community projects or simply community networks, are non-centralized, self-managed and collaborative networks organized in a grassroots fashion by communities, NGO's and cooperatives in order to provi ...
*
Visible light communication In telecommunications, visible light communication (VLC) is the use of visible light (light with a frequency of 400–800  THz/wavelength of 780–375  nm) as a transmission medium. VLC is a subset of optical wireless communications tec ...
*
List of device bandwidths This is a list of interface bit rates, is a measure of information transfer rates, or digital bandwidth capacity, at which digital interfaces in a computer or network can communicate over various kinds of buses and channels. The distinction can ...


Notes


References

* * page 56
Unstrung: Da Doo Ron RONJA

Ronja talk at WSFII London 2005
(archive.org)
Hack a Day: Ronja

Building a Ronja-lightlink: A User Testimonial
(web.archive.org)
The 3D modeling software BRL-CAD, originally developed by the US Army since 1979, showcases Ronja as a project which uses BRL-CAD

Phanumas Khumsat, Noppadol Wattanapisit, Karel Kulhavey, "Low-Cost Laser-Based Wireless Optical Transceiver for 10-Mbps Ethernet Link", Proceedings of IEEE Region 10 Conference (TENCON), Hong Kong, China (2006), which publishes the Ronja design with minor modifications, publishes the Ronja receiver and transmitter schematics virtually unchanged, and features a photograph of a Ronja Twister built on the official Ronja PCB.

Phanumas Khumsat, Noppadol Wattanapisit, Karel Kulhavey, "Optical Front-Ends for Low-Cost Laser-Based 10-Mbps Free-Space Optical Transceiver" (full text), Proceeding of IEEE Asia Pacific Conference on Circuits and Systems 2006, 1911–1914 (2006), which publishes the Ronja design with minor modifications, publishes the Ronja receiver and transmitter schematics virtually unchanged, and features a photograph of the official Ronja optical heads and holders.


* ttp://hdl.handle.net/2077/24450 Johan Söderberg: Free software to open hardware: Critical theory on the frontiers of hacking Doctoral Dissertation, University of Gothenburg, , Sweden, 2011.
David Němec: Cableless optical transmission (in Czech), Master diploma thesis, Institute of Telecommunications, Faculty of Electrical Engineering and Communication, Brno, Czech Republic, 2012.

Santi Phasuk (สันติ ผาสุข): Design and Implementation of a Data Transceiver via Visible Light Beam (in Thai with English abstract), Master Thesis, Kasetsart University, Bangkok, Thailand, 2011.

B. Bakala: Realization of Optical Link, Bachelor project, Department of Telecommunication Engineering, Czech Technical University, Prague, Czech Republic, 2011.

Jan Matyáš: FPGA-Based Ronja Twister (full text), Bachelor's Thesis, Department of Computer Systems, Faculty of Information Technology, Brno University of Technology, Czech Republic, 2011.

Bc. Lukáš Chobot: Wireless data transfer via optical modules (in Czech), Diploma Thesis, Faculty of Applied Computer Science, Tomas Bata University, Zlín, Czech Republic, 2011.

Bc. Filip Němec: Optical Cableless Transmittion (in Czech), Master's Thesis, Department of Telecommunications, Faculty of Electrical Engineering and Communication, Brno University of Technology, Czech Republic, 2010.

T. Szabo: Design and realization of wireless optical connection RONJA (mentioned in annual report), Master thesis, Department of Telecommunications, Faculty of Electrical Engineering and Information, Slovak University Of Technology in Bratislava, Slovakia, 2007.

Bc. Ľubomír Adámek: Wireless Data Transmission (in Czech), Diploma Thesis, Faculty of Applied Computer Science, Tomas Bata University, Zlín, Czech Republic, 2006.

Libor Štěpán: Wireless Optical Link for LAN Ethernet (in Czech), Bachelor Thesis, Faculty of Applied Computer Science, Tomas Bata University, Zlín, Czech Republic, 2006.

M. A. Chancey: Short Range Underwater Optical Communication Links (full text), Master Thesis, North Carolina State University, USA, 2005.


External links

* {{official, http://ronja.twibright.com
RONJA Adaptation for Underwater

British council project – Promotion of ronja in community networks in UK 2004
Free software projects Open hardware electronic devices Physical layer protocols