View source for RONJA

{{about|Reasonable Optical Near Joint Access|other topics|ronja (disambiguation)}}
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[[File:Ronja beam Prostejov.jpg|thumb|right|Single high-brightness LED with a cheap [[loupe]] lens creates a bright narrow<ref name="rts_di"/> beam that can stream DVD-quality video over neighbourhoods. A few steps aside and the narrow beam becomes invisible.]]
[[File:Twibright Ronja with its user.jpg|thumb|Twibright Ronja with {{convert|130|mm|in|adj=on}} diameter lenses, operating on a {{convert|1205|m|yd|adj=on}} link using visible red light, max. range {{convert|1300|m|yd}}, with HPWT-BD00-E4000 transmit LED. Installed on a rooftop, with its user, in Czech Republic.<ref name="ronja.twibright.com">{{cite web|url=http://ronja.twibright.com/installations.php|title=154 Registered Installations of Ronja|website=ronja.twibright.com|access-date=3 June 2017}}</ref><ref>{{cite web|url=http://images.twibright.com/tns/1208.html|title=[1208] ronja/installations/czech/zdar_n_sazavou|website=images.twibright.com|access-date=3 June 2017}}</ref>]]
[[File:RonjaHolder.jpg|thumb|right|Three bolts preloaded with pink rubber blocks facilitate fine adjustment of the optical head direction with a gear ratio 1:300.<ref name="rts_di"/> The bolt on the right side is a part of a rough adjustment mechanism which allows pointing the optical head in virtually any direction.]]
[[File:RonjaFog.jpg|thumb|right|Artificially enhanced picture of a situation where a Ronja link stops working because of heavy fog]]
'''RONJA''' ('''Reasonable Optical Near Joint Access''') is a [[free-space optical communication]] system developed in the [[Czech Republic]] by Karel Kulhavý of Twibright Labs. Released in 2001. It transmits data [[wireless]]ly using beams of [[light]]. Ronja can be used to create a 10&nbsp;Mbit/s [[full duplex]] [[Ethernet]] [[point-to-point (telecommunications)|point-to-point]] [[telecommunications link|link]]. It has been estimated that 1,000 to 2,000 links have been built worldwide.<ref>{{Cite journal | doi = 10.1177/0162243910368398| title = Free Space Optics in the Czech Wireless Community: Shedding Some Light on the Role of Normativity for User-Initiated Innovations| journal = Science, Technology, & Human Values| volume = 36| issue = 4| pages = 423–450| year = 2010| last1 = Soderberg | first1 = J.| s2cid = 145786449}}</ref>
The basic configuration has a range of {{convert|1.4|km|mi|abbr=on}}. The device consists of a receiver and [[transmitter]] pipe (optical head) mounted on a sturdy adjustable holder. Two [[coaxial cable]]s are used to connect the rooftop installation with a protocol translator installed in the house near a [[computer]] or [[network switch|switch]]. By doubling or tripling the transmitter pipe, the range can be extended to 1.9 km (1.2 mi).
Building instructions, blueprints, and schematics are published under the [[GNU Free Documentation Licence|GNU Free Documentation License]], with development using only [[free software]] tools. The author calls this level of freedom "User Controlled Technology".<ref name="Ronja - BRL-CAD">{{cite web|url=http://brlcad.org/wiki/Ronja|title=Ronja – BRL-CAD|website=brlcad.org|access-date=3 June 2017}}</ref> Ronja is a project of [[Twibright Labs]].
== Manufacture ==
The building instructions are written with an inexperienced builder in mind. Basic operations like [[drilling]], [[soldering]] etc., are explained.<ref>{{cite web|url=http://ronja.twibright.com/fundamentals.php|title=Fundamentals of manufacturing operations|website=ronja.twibright.com|access-date=3 June 2017}}</ref> Several techniques – drilling templates,<ref>{{cite web|url=http://ronja.twibright.com/drawings/|title=All Ronja Drawings|website=ronja.twibright.com|access-date=3 June 2017}}</ref> detailed checks after soldering,<ref name="Building Ronja 10M Receiver">{{cite web|url=http://ronja.twibright.com/receiver/building.php|title=Building Ronja 10M Receiver|website=ronja.twibright.com|access-date=3 June 2017}}</ref><ref>{{cite web|url=http://ronja.twibright.com/transmitter/building.php|title=Building Ronja 10M Metropolis Transmitter|website=ronja.twibright.com|access-date=3 June 2017}}</ref><ref>{{cite web|url=http://ronja.twibright.com/twister2/building.php|title=Building Ronja Twister2 PCB|website=ronja.twibright.com|access-date=3 June 2017}}</ref><ref>{{cite web|url=http://ronja.twibright.com/nebulus/building.php|title=Building Ronja Nebulus|website=ronja.twibright.com|access-date=3 June 2017}}</ref> testing procedures<ref>{{cite web|url=http://ronja.twibright.com/tetrapolis/testing.php|title=Testing Ronja Tetrapolis|website=ronja.twibright.com|access-date=3 June 2017}}</ref><ref>{{cite web|url=http://ronja.twibright.com/metropolis/testing.php|title=Testing Ronja 10M Metropolis|website=ronja.twibright.com|access-date=3 June 2017}}</ref><ref>{{cite web|url=http://ronja.twibright.com/inferno/testing.php|title=Testing Ronja Inferno|website=ronja.twibright.com|access-date=3 June 2017}}</ref> – are employed to minimize errors at critical places and help to speed up work. [[Printed circuit board]]s are downloadable ready for manufacture, with instructions for the fabhouse.<ref>{{cite web|url=http://ronja.twibright.com/twister2/pcb.php|title=Twister2 PCB|website=ronja.twibright.com|access-date=3 June 2017}}</ref><ref>{{cite web|url=http://ronja.twibright.com/transmitter/pcb.php|title=Ronja: Ordering TX PCB's|website=ronja.twibright.com|access-date=3 June 2017}}</ref> 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.<ref name="ronja.twibright.com"/>
== Range ==
With the brightest variant of [[Lumileds]] HPWT-BD00-F4000 LED and 130&nbsp;mm diameter cheap magnifying glass lenses, the range is {{cvt|1.4|km|mi}}.<ref name="Ronja - BRL-CAD"/><ref name="docplayer.cz">{{cite web|url=http://docplayer.cz/9741937-Evropsky-polytechnicky-institut-s-r-o-1-soukroma-vysoka-skola-na-morave-kunovice-pocitacove-site.html|title=Evropský polytechnický institut, s.r.o. 1. soukromá vysoká škola na Moravě Kunovice POČÍTAČOVÉ SÍTĚ – PDF|website=docplayer.cz|access-date=3 June 2017}}</ref> The dimmer but more affordable E4000 variant of HPWT-BD00 yields {{convert|1.3|km|mi}}.<ref>{{cite web|url=http://ronja.twibright.com/metropolis/dist.php|title=Ronja 10M Metropolis, Tetrapolis, Inferno, Rexlator distance issues|website=ronja.twibright.com|access-date=3 June 2017}}</ref> The speed is always 10&nbsp;Mbit/s full duplex regardless of the distance.
== Models ==
* ''Ronja Tetrapolis'': Range of {{convert|1.4|km|mi|abbr=on}}, red visible light. Connect with [[8P8C]] connector into a [[network card]] or switch.
* ''Ronja 10M Metropolis'': Range of {{convert|1.4|km|mi|abbr=on}}, red visible light. Connects to [[Attachment Unit Interface]].
* ''Ronja Inferno'': Range of {{convert|1.25|km|mi|abbr=on}}, 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&nbsp;kbit/s PPP/SLIP link.<ref>{{cite web|url=https://linas.org/mirrors/atrey.karlin.mff.cuni.cz/2002.01.03/~clock/twibright/ronja/|title=Twibright Labs : Ronja|website=linas.org|access-date=3 June 2017}}</ref>
== Limitations ==
By definition, clear [[visibility]] 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]] or dense [[fog]].<ref>{{cite journal|title=Download Limit Exceeded|citeseerx = 10.1.1.963.9463}}</ref><ref>{{cite web|url=http://cimsec.org/naval-application-tech-lifi/27242|title=Naval Applications for LiFi: The Transmitting Tool|date=10 August 2016|website=cimsec.org|access-date=3 June 2017}}</ref> One device weighs {{cvt|15.5|kg}}<ref name="rts_di"/> and requires 70 hours of building time.<ref>{{cite web|url=http://ronja.twibright.com/faq/cost.php|title=How much does Ronja cost?|website=ronja.twibright.com|access-date=3 June 2017}}</ref> It requires an ability to set full duplex manually on the network card or switch to take advantage of full duplex,<ref>{{cite web|url=http://ronja.twibright.com/tetrapolis/modules.php|title=Ronja Tetrapolis: Requirements (Modules, Material, Tools, Software)|website=ronja.twibright.com|access-date=3 June 2017}}</ref> since it doesn't support [[autonegotiation]].<ref name=rts_di>{{cite web|url=http://ronja.twibright.com/tetrapolis/spec.php|title=Ronja Tetrapolis Specification|website=ronja.twibright.com|access-date=3 June 2017}}</ref> Must be plugged directly into PC or switch using the integral {{convert|1|metre}} Ethernet cable.<ref name=rts_di />
== Technology ==
[[File:RONJA System Overview.jpg|thumb|Block diagram of a full duplex RONJA system.]]
A complete RONJA system is made up of 2 [[transceivers]]: 2 optical [[transmitters]] and 2 optical [[Optical receiver|receivers]]. They are assembled individually or as a combination. The complete system layout is shown in the [[block diagram]].
=== Optical receiver – Preamplifier stage ===
[[File:RONJA-installations-world.png|thumb|Map showing the distribution of the 153 registered installations of RONJA as of 1 October 2007. Based on data found at the [http://ronja.twibright.com/installations.php official RONJA website]]]
The usual approach in FSO (Free Space Optics) [[preamplifier]]s is to employ a [[transimpedance amplifier]]. A transimpedance amplifier is a very sensitive [[broadband]] high-speed device featuring a [[feedback loop]]. This fact means the layout is plagued with stability problems and special compensation of [[PIN diode]] [[capacitance]] 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<ref name="Building Ronja 10M Receiver"/> where the PIN has a high working [[electrical resistance]] (100 [[Ohm|kilohm]]s)<ref name="Building Ronja 10M Receiver"/> which together with the total input capacitance (roughly 8 pF, 5 pF PIN and 3 pF<ref>{{cite web|url=http://www.nxp.com/documents/data_sheet/BF908-R_N.pdf|title=NXP Semiconductors: BF 908 Datasheet, page 2, table row "input capacitance at gate 1"|website=nxp.com|access-date=3 June 2017}}</ref> input [[MOSFET]] [[cascode]]) makes the device operate with a [[passband]] on a 6&nbsp;dB/oct slope of low pass formed by PIN working resistance and total input capacitance.<ref>[https://web.archive.org/web/20170809130013/http://electric2.ee.psu.ac.th/~ton/FSO_Ronja_TENCON2006_Final2.pdf 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) (full text), pag 2 upper left, mention about "unwanted lossy integrator".]</ref><ref name="How does Ronja work">{{cite web|url=http://ronja.twibright.com/technotes/how_rx.php|title=How does Ronja work?|website=ronja.twibright.com|access-date=3 June 2017}}</ref> The signal is then immediately amplified to remove the danger of contamination by [[signal noise]], and then a compensation of the 6&nbsp;dB/oct slope is done by derivator element on the programming pins<ref>{{cite web|url=http://www.nxp.com/documents/data_sheet/NE592.pdf|title=Philips Semiconductors RF Communications Products: NE592 Product specification, page 1 lines 6–7 of the 1st paragraph and page 8, heading "FILTER NETWORKS".|website=nxp.com|access-date=3 June 2017}}</ref> of an NE592 video amplifier.<ref>[https://web.archive.org/web/20170809130013/http://electric2.ee.psu.ac.th/~ton/FSO_Ronja_TENCON2006_Final2.pdf 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) (full text)]</ref><ref name="How does Ronja work"/> 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]] from the 3 kΩ resistor.
=== Optical transmitter – Nebulus infrared LED driver ===
The HSDL4220 [[infrared]] [[light-emitting diode|LED]] is originally unsuitable for 10&nbsp;Mbit/s operation. It has a [[Bandwidth (signal processing)|bandwidth]] of 9&nbsp;MHz,<ref>{{cite web|url=http://www.mouser.com/ds/2/239/LiteOn_HSDL_4220_4230-195195.pdf|title=HSDL-4220 Datasheet|website=mouser.com|access-date=3 June 2017}}</ref> where 10&nbsp;Mbit/s [[Manchester encoding|Manchester]]-modulated systems need bandwidth of around 16&nbsp;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.<ref>{{cite web|url=http://ronja.twibright.com/schematics/nebulus_00.pdf|title=Ronja Nebulus (infrared transmitter) schematic|website=twibright.com|access-date=3 June 2017}}</ref> 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<ref>{{cite web|url=http://ecee.colorado.edu/~mathys/ecen1400/pdf/references/74AC04.pdf|title=Fairchild: 74AC04 Datasheet|website=colorado.edu|access-date=3 June 2017}}</ref> 74AC04 is operating as a structured power [[CMOS]] switch completely in analog mode.
This way the LED [[semiconductor junction|junction]] is flooded and cleared of [[charge carrier|carriers]] as quickly as possible, basically by [[short 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&nbsp;MHz/1&nbsp;MHz) impulses to about 2x brightness. This was measured to have no adverse effect on range. 2) A blocking [[ceramic capacitor]] 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.<ref>{{cite web|url=http://ronja.twibright.com/twister/|title=Ronja Twister|website=ronja.twibright.com|access-date=3 June 2017}}</ref>
The original design has been superseded with Twister2 but the logic circuit remained the same.<ref>{{cite web|url=http://ronja.twibright.com/twister2/|title=Ronja Twister2|website=ronja.twibright.com|access-date=3 June 2017}}</ref>
== 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."<ref>{{cite journal|url=https://policyreview.info/articles/analysis/how-open-hardware-drives-digital-fabrication-tools-such-3d-printer|title=How open hardware drives digital fabrication tools such as the 3D printer|journal=Internet Policy Review|date=18 June 2013 |volume=2 |issue=2 |access-date=3 June 2017 |last1=Söderberg |first1=Johan |doi=10.14763/2013.2.138 |hdl=10419/213966 |hdl-access=free }}</ref>
The whole [[toolchain]] is built strictly upon free tools<ref>{{cite web|url=http://ronja.twibright.com/sw.php|title=Software used for Ronja development|website=ronja.twibright.com|access-date=3 June 2017}}</ref> and the [[source code|source files]] are provided, free, under the [[GNU General Public License|GPL]].<ref>{{cite web|url=http://ronja.twibright.com/schematics/|title=All Schematics|website=ronja.twibright.com|access-date=3 June 2017}}</ref> This allows anyone to enter the development, start manufacture or invest into the technology without [[barriers to entry|entry costs]]. Such costs normally can include [[software licence]] costs, time investment into resolution of compatibility issues between proprietary applications, or costs of [[intellectual property]] licence negotiations. The decision to conceive the project this way was inspired by observed organizational efficiency of [[Free Software]].
On Christmas 2001, Ronja became the world's first 10&nbsp;Mbit/s Free Space Optics device with free sources.<ref>{{cite web|url=https://hardware.slashdot.org/story/01/12/22/1432211/build-your-own-10mbitsec-optical-data-link|title=Build Your Own 10Mbit/sec Optical Data Link – Slashdot|website=hardware.slashdot.org|date=22 December 2001 |access-date=3 June 2017}}</ref>
Examples of tools used in development:
* [[gEDA]] gschem ([[Schematic capture]])<ref>{{citation|url=http://geda.seul.org|title=Schematic capture}}</ref>
* [[QCAD]]
* [[BRL-CAD]]
* The PCB program<ref>{{citation|title=PCB|url=http://pcb.geda-project.org/index.html|publisher=gEDA Project}}</ref>
* [[Sodipodi]] for [[Vector graphics]]
== See also ==
*[[Wireless community network]]
*[[Visible light communication]]
*[[List of device bandwidths]]
== Notes ==
{{reflist}}
== References ==
{{refbegin}}
*{{citation|url=http://www.oreillynet.com/etel/blog/2007/02/ronja_at_10_mbps_the_next_stag.html|publisher=[[O'Reilly Media|O'Reilly Emerging Telephony]]|title=Ronja at 10 Mbit/s, the next stage in wireless mesh networking?|date=February 19, 2007|author=Andy Oram}}
*{{citation|url=https://books.google.com/books?id=2rGVgt7b1dQC&q=twibright+ronja&pg=PA56|publisher=[[Edward Elgar Publishing]]|title=Bridging the Global Digital Divide|date=January 1, 2003|author=Jeffrey James|isbn=9781843767169}} page 56
* [https://web.archive.org/web/20061128002104/http://www.unstrung.com/document.asp?doc_id=18416 Unstrung: Da Doo Ron RONJA]
* [https://archive.org/details/Ronja_WSFII_London Ronja talk at WSFII London 2005] (archive.org)
* [http://www.hackaday.com/2005/06/13/ronja-optical-data-link/ Hack a Day: Ronja]
* [https://web.archive.org/web/20120110171006/http://hansmi.ch/articles/ronja Building a Ronja-lightlink: A User Testimonial] (web.archive.org)
* [http://brlcad.org/wiki/Ronja The 3D modeling software BRL-CAD, originally developed by the US Army since 1979, showcases Ronja as a project which uses BRL-CAD]
* [https://web.archive.org/web/20170809130013/http://electric2.ee.psu.ac.th/~ton/FSO_Ronja_TENCON2006_Final2.pdf 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.]
* [https://www.researchgate.net/profile/Phanumas_Khumsat/publication/224693686_Optical_Front-Ends_for_Low-Cost_Laser-Based_10-Mbps_Free-Space_Optical_Transceiver/links/53fdac840cf22f21c2f82347/Optical-Front-Ends-for-Low-Cost-Laser-Based-10-Mbps-Free-Space-Optical-Transceiver.pdf 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.]
* [http://docplayer.cz/9741937-Evropsky-polytechnicky-institut-s-r-o-1-soukroma-vysoka-skola-na-morave-kunovice-pocitacove-site.html  I. Rukovanský, M. Horváth, L. Solárik, P. Cícha: Computer Networks (in Czech), a university lecture textbook, European Polytechnic Institute – a Private University, 2015, pages 66–67]
* [http://hdl.handle.net/2077/24450 Johan Söderberg: Free software to open hardware: Critical theory on the frontiers of hacking], Doctoral Dissertation, University of Gothenburg, {{ISBN|9789197544276}}, Sweden, 2011.
* [https://dspace.vutbr.cz/xmlui/bitstream/handle/11012/8456/Diplomova_prace_bezkabelovy_opticky_prenos_zadani.pdf?sequence=1&isAllowed=y David Němec: Cableless optical transmission (in Czech), Master diploma thesis, Institute of Telecommunications, Faculty of Electrical Engineering and Communication, Brno, Czech Republic, 2012.] {{Webarchive|url=https://web.archive.org/web/20181103180130/https://dspace.vutbr.cz/xmlui/bitstream/handle/11012/8456/Diplomova_prace_bezkabelovy_opticky_prenos_zadani.pdf?sequence=1&isAllowed=y |date=2018-11-03 }}
* [http://doi.nrct.go.th/doi2/ListDoi/Download/90263/4a3faeca0c76500f4b975eddd036335a?Resolve_DOI=10.14457/KU.the.2011.385 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. ]
* [http://ieeexplore.ieee.org/xpl/abstractReferences.jsp?tp=&arnumber=6415059&url=http://ieeexplore.ieee.org/iel5/6407297/6415022/06415059.pdf?arnumber=6415059 B. Bakala: Realization of Optical Link, Bachelor project, Department of Telecommunication Engineering, Czech Technical University, Prague, Czech Republic, 2011.]{{dead link|date=September 2024|bot=medic}}{{cbignore|bot=medic}}
* [https://dspace.vutbr.cz/xmlui/bitstream/handle/11012/55682/12512.pdf?sequence=2&isAllowed=y 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. ]{{Dead link|date=April 2024 |bot=InternetArchiveBot |fix-attempted=yes }}
* [http://digilib.k.utb.cz/bitstream/handle/10563/17383/chobot_2011_dp.pdf?sequence=1&isAllowed=y 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. ]
* [https://dspace.vutbr.cz/bitstream/handle/11012/4618/Diplomova_prace_opticky_bezkabelovy_prenos.pdf?sequence=1 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. ]
* [http://www.fei.stuba.sk/docs/2007/annual_report/14_KTL07.pdf 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.]
* [http://digilib.k.utb.cz/bitstream/handle/10563/2010/ad%c3%a1mek_2006_dp.pdf?sequence=1&isAllowed=y Bc. Ľubomír Adámek: Wireless Data Transmission (in Czech), Diploma Thesis, Faculty of Applied Computer Science, Tomas Bata University, Zlín, Czech Republic, 2006. ]
* [http://digilib.k.utb.cz/bitstream/handle/10563/2174/%C5%A1t%C4%9Bp%C3%A1n_2006_bp.pdf?sequence=1&isAllowed=y Libor Štěpán: Wireless Optical Link for LAN Ethernet (in Czech), Bachelor Thesis, Faculty of Applied Computer Science, Tomas Bata University, Zlín, Czech Republic, 2006. ]
* [https://repository.lib.ncsu.edu/bitstream/handle/1840.16/570/etd.pdf?sequence=1&isAllowed=y M. A. Chancey: Short Range Underwater Optical Communication Links (full text), Master Thesis, North Carolina State University, USA, 2005.]
{{refend}}
== External links ==
{{commons category}}
* {{official|http://ronja.twibright.com}}
* [https://web.archive.org/web/20140416191936/http://www.ece.ncsu.edu/seniordesign/projects_new.php?id=463 RONJA Adaptation for Underwater]
* [https://web.archive.org/web/20070509055342/http://charon.hkfree.org/ronja/ British council project – Promotion of ronja in community networks in UK 2004]
[[Category:Free software projects]]
[[Category:Open hardware electronic devices]]
[[Category:Physical layer protocols]]