RONJA (Reasonable Optical Near Joint Access) A Seminar Report Submitted by
RAGHAVENDRA.S.RAO in partial fulfilment for the award of the degree of
BACHELOR OF TECHNOLOGY IN ELECTRONICS AND TELECOMMUNICATION Guided by
Mr. B.B.WATTAMWAR At
MAHARASHTRA INSTITUTE OF TECHNOLOGY AURANGABAD 2013-14
CERTIFICATE This is to certify that, the report “RONJA (Reasonable Optical Near Joint Access)” submitted by Raghavendra.S.Rao is a bonafide work completed under my supervision and guidance in partial fulfilment for award of Bachelor Of Technology (Electronics and Telecommunication) Degree of Maharashtra Institute Of Technology Aurangabad.
Place : Aurangabad Date :
Mr. B.B.Wattamwar
Mrs. V. M. Kulkarni
Guide
Head of the Department
Dr. S. P. Bhosle
Principal Maharashtra Institute Of Technology Aurangabad
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TABLE OF CONTENTS
CHAPTER
I
II
III
IV
V
TITLE
PAGE
ABSTRACT
4
ACKNOWLEDGMENT
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LIST OF ABBREVIATIONS
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INTRODUCTION 1.1 Introduction
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1.2 Necessity and objectives
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1.3 Theme and Organisation
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LITERATURE SURVEY 2.1 Point-to-Point Protocol (PPP)
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2.2 Free Space Vs Radio
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2.3 Optics
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2.4 Signals
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2.5 LED Vs Laser
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SYSTEM DEVELOPMENT 3.1 General Scrutiny
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3.2 Block diagram and its Description
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3.3 Models and their specifications
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CONCLUSION 4.1 Applications and Future Scope
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4.2 Pros & Cons
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REFERENCES
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ABSTRACT RONJA (Reasonable Optical Near Joint Access) – Allows one to make a free space 10Mbps full-duplex Ethernet bridge between two points up to 1.4 km away using visible incoherent light. The transmitter sends a signal with a Light Emitting Diode (LED), the light rays are collimated (paralleled) by a lens. On the other side of the bridge the receiver uses another lens to focus light onto a photo diode. The Twister is the electronics that cleans up the signal, adds a pulse when no data is being communicated, and adds the link integrity pulse back to the Ethernet cable. The pulse is used to keep the Receiver knowing what a signal is over noise. This report covers the basic introduction to RONJA, Scrutiny of its system functioning, advantages of RONJA along with its future improvements and scopes.
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ACKNOWLEDGEMENT I wish to express my deep gratitude and appreciation for the invaluable guidance of our professors throughout the span of preparing this seminar. We are indebted to our college Principal Dr. S. P. Bhosle. I am also thankful to our HOD Mrs. V. M. Kulkarni and my Seminar Guide Mr.B.B.Wattamwar for his precious and elaborate suggestions. Their excellent guidance made me to complete this task successfully within a short duration. The inspiration behind the every aspect of life constructs a way to get success, which I have got from all the professors of the department. No thanks giving would be complete without mentioning my parents and family members, without their constant support and encouragement, this assignment wouldn’t have been successful.
RAGHAVENDRA.S.RAO
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LIST OF ABBREVIATIONS
SONET-Synchronous Optical Networking
ISP-Internet Service Provider
NBF-NetBIOS Frames protocol
DECnet-Digital Equipment Corporation Networks
IPCP-IP Control Protocol
SSl-Secure Sockets Layer
SSH-Secure Shell
L2TP-Layer 2 Tunneling Protocol
IEEE-Institute of Electrical and Electronics Engineers
FCC-Federal Communications Commission
ASCII-American Standard Code for Information Interchange
RX-Receiver
TX-Transmitter
PCB-Printed Circuit board
HDLC-High-Level Data Link Control
ADCCP-Advanced Data Communication Control Procedures
LAN-Local Area Network
LLC-Logical Link Control
MAC-Media Access Control
CSMA/MD-Carrier Sense Multiple Access with Collision Detection
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INTRODUCTION RONJA is a free-space optical communication system which transmits data wirelessly using beams of light. Ronja can be used to create a 10 Mbit/s full duplex Ethernet point-to-point link, having a range of 1.4 km, through an optoelectronic device you can mount on your house and connect your PC, home or office network with other network. The device consists of a receiver and transmitter pipe (optical head) mounted on a sturdy adjustable holder. Two coaxial cables are used to connect the rooftop installation with a protocol translator installed in the house near a computer or switch. The range can be extended to 1.9 km (1.2 mi) by doubling or tripling the transmitter pipe. A complete RONJA system is made up of 2 transceivers: 2 optical transmitters and 2 optical receivers. They are assembled individually or as a combination. The complete system layout is shown in the block diagram above. The range of the basic configuration is 1.4 km (0.9 miles). .
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NECESSITY AND OBJECTIVES The Foundation of any Project lies in its need which defines its existence. In Today’s Era of Wireless Communication, there is an emerging trend which appeals the use of optical energy to transfer information. Moreover, in it, the most efficient, most advantageous and secure systems are preferred. Ronja is amongst those systems which can easily cater to all these needs. The Demands of Full Duplex, high Speed, Energy efficient and point-to-point secure transmission can be efficiently fulfilled by RONJA, thus proving its necessity and Objectives.
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THEME AND ORGANISATION Ronja has a Theme of Pure Optical Communication in Synergy with Networking, associated with it. It is all concerned about the transmission and reception of data within the boundaries defined by its Design and Structural capabilities obeying all the necessary Protocols. Twilight laboratories, Prague, Czech Republic, is the organization which is associated with RONJA
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LITERTURE SURVEY Point-to-Point Protocol: Point-to-Point Protocol (PPP) is a data link protocol used to establish a direct connection between two nodes. It can provide connection authentication, transmission encryption and compression. PPP is used over many types of physical networks including serial cable, phone line, trunk line, cellular telephone, specialized radio links, and fiber optic links such as SONET. PPP is also used over Internet access connections. Internet service providers (ISPs) have used PPP for customer dial-up access to the Internet, since IP packets cannot be transmitted over a modem line on their own, without some data link protocol. Two derivatives of PPP, Point-toPoint Protocol over Ethernet (PPPoE) and Point-to-Point Protocol over ATM (PPPoA), are used most commonly by Internet Service Providers (ISPs) to establish a Digital Subscriber Line (DSL) Internet service connection with customers. PPP is commonly used as a data link layer protocol for connection over synchronous and asynchronous circuits, where it has largely superseded the older Serial Line Internet Protocol (SLIP) and telephone company mandated standards (such as Link Access Protocol, Balanced (LAPB) in the X.25 protocol suite). The only requirement for PPP is that the circuit provided be duplex. PPP was designed to work with numerous network layer protocols, including Internet Protocol (IP), TRILL, Novell's Internetwork Packet Exchange (IPX), NBF, DECnet and AppleTalk. PPP permits multiple network layer protocols to operate on the same communication link. For every network layer protocol used, a separate network control protocol (NCP) is provided in order to encapsulate and negotiate options for the multiple network layer protocols. It negotiates network-layer information, e.g. network address or compression options, after the connection has been established. For example, Internet Protocol (IP) uses the IP Control Protocol (IPCP), and Internetwork Packet Exchange (IPX) uses the Novell IPX Control Protocol (IPX/SPX). NCPs include fields containing standardized codes to indicate the network layer protocol type that the PPP connection encapsulates. The phases of the Point to Point Protocol according are listed below:
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Link Dead: This phase occurs when the link fails, or one side has been told to disconnect (e.g. a user has finished his or her dialup connection.) Link Establishment Phase: This phase is where Link Control Protocol negotiation is attempted. If successful, control goes either to the authentication phase or the Network-Layer Protocol phase, depending on whether authentication is desired. Authentication Phase: This phase is optional. It allows the sides to authenticate each other before a connection is established. If successful, control goes to the network-layer protocol phase. Network-Layer Protocol Phase: This phase is where each desired protocols' Network Control Protocols are invoked. For example, IPCP is used in establishing IP service over the line. Data transport for all protocols which are successfully started with their network control protocols also occurs in this phase. Closing down of network protocols also occur in this phase.
Link Termination Phase: This phase closes down this connection. This can happen if there is an authentication failure, if there are so many checksum errors that the two parties decide to tear down the link automatically, if the link suddenly fails, or if the user decides to hang up his connection. 11
Many protocols can be used to tunnel data over IP networks. Some of them, like SSL, SSH, or L2TP create virtual network interfaces and give the impression of a direct physical connections between the tunnel endpoints. On a Linux host for example, these interfaces would be called tun0. As there are only two endpoints on a tunnel, the tunnel is a point-to-point connection and PPP is a natural choice as a data link layer protocol between the virtual networks interfaces. PPP can assign IP addresses to these virtual interfaces, and these IP addresses can be used, for example, to route between the networks on both sides of the tunnel.
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Free Space vs. Radio Radio (Such as IEEE 802.11) can also be used to create a network bridge. Free Space Optics have some advantages and disadvantages compared to Radio.
1. Eavesdropping Because of the nature of radio waves, it is harder to contain where the radio waves go, even in directional point to point networks a signal can still be eavesdropped over a large area. For example a typical parabolic antenna has a beam width of 16⁰, at 1.4km one would still be able to receive the signal 194 meters on either side of where it is pointing. The signal can also be listened to behind the intended location. With a free space network you must intercept the light beam, this is much more difficult and can be detected.
2. Interference Radio waves can interfere with each other. This interference is one of the reasons the FCC licenses spectrum. There are blocks of spectrum free to use, but other devices are also using them. As an example if you used the public block in the 2.4GHz range, your signal can get interference from portable phones, wireless access points, microwave ovens, car alarms, and security cameras. This can make your signal less dependable. Free space optic networks are free from these types of interference. 3. Distance Radio waves have improved distance over free space optics. Free space optics is limited to how far it can travel through the atmosphere because of absorption. 4. Fresnel Zones The Fresnel zone of light is very small compared to radio waves. If there is an obstruction in the first Fresnel zone it will produce interference.
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Optics Geometric: The RONJA uses a double convex spherical lens, which is typical found in magnifying glasses. As shown in Figure 2, the RONJA uses the lens to take light from a LED and collimate it, as well as take incoming light into a point. The Transmitter side takes light from a LED and it will collimate it towards the Receiver side. The Receiver will take incoming parallel light and will focus it into a point using a double Convex Lens.
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Signals Information in a computer is stored as a set of hi/lo values or binary. For example, an ASCII ’a’ is represented as 01100001. This can be communicated as two sets of different voltages, or like in the RONJA blink on and blink off. There are many ways to encode the information to make it more resistant to noise or to make sure that timings are synchronized. The next subsections go over some of the encodings used in Ethernet 10BASE-T and 100BASE-TX. The RONJA currently supports 10BASE-T.
NRZ Encoding NRZ (Non-Return to Zero) is a simple encoding, hi for 1 and lo for 0, each bit delimited by time (See Figure 6). In NRZ, clock timing is important and is often used internally when everything is operating off the same clock. Imagine a long stream of 1’s there would not be any indication of how to set your clock between bits. If this information is sent to another system that has a slightly different clock, it could easily become out of sync.
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Manchester Encoding An Ethernet 10Base-T network sends its data in a Manchester encoding. A property of the Manchester encoding is that it needs twice the bandwidth of the data com-pared to NRZ, thus a response capable of 10 MHz is needed (1 Hz/bit). Our LED and photo diode are capable of handling these response times.
Encoding a Data Byte: Encoding is the process of adding the correct transitions to the message signal in relation to the data that is to be sent over the communication system. The first step is to establish the data rate that is going to be used. Once this is fixed, then the mid-bit time can be determined as ½ of the data rate period. In our example we are going to use a data rate of 4 kHz. This provides a bit period of 1/f = 1/4000 = 0.00025s or 250 μs. Dividing by two gives us the midbit time (which we will label “T”) of 125 μs. Now let's look at how we use this to encode a data byte of 0xC5 (11000101b). The easiest method to do this is to use a timer set to expire or interrupt at the T interval. We also need to set up a method to track which ½ bit period we are currently sending. Once we do this, we can easily encode the data and output the message signal.
1. Begin with the output signal high. 2. Check if all bits have been sent, If yes, then go to step 7 3. Check the next logical bit to be coded 4. If the bit equals “1”, then call ManchesterOne(T) 5. Else call ManchesterZero(T) 16
6. Return to step 2 7. Set output signal high and return
Implementation of ManchesterOne(T) 1. Set the output signal low 2. Wait for mid-bit time (T) 3. Set the output signal high 4. Wait for mid-bit time (T) 5. Return
Implementation of ManchesterZero(T) 6. Set the output signal high 7. Wait for mid-bit time (T) 8. Set the output signal low 9. Wait for mid-bit time (T) 10. Return
These easy routines will provide an output at the microcontroller pin that exactly encodes the data into a Manchester message signal at the desired data rate. The accuracy of the data rate and duty cycle depends on the accuracy of the clock source and the method used to create the wait times.
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Manchester Decoding Decoding is where most people attempting to work with Manchester have questions. There are several ways to approach this and each has unique benefits. This section will describe how to implement two different methods. To start we will look at the steps that are needed for either methodology. 1. The data rate clock must be either known or discovered (we will assume a known value) 2. We must synchronize to the clock (distinguish a bit edge from a mid-bit transition) 3. Process the incoming stream and recover the data using the previous two steps. 4. Buffer or store this data for further processing. This provides the basic outline for how we will perform Manchester decoding. All that remains is to implement this in software. As mentioned, we have two different options for consideration. One is based on timing while the other utilizes sampling.
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Timing Based Manchester Decode In this approach we will capture the time between each transition coming from the demodulation circuit. The Input Capture function on a micro-controller is very useful for this because it will generate an interrupt, precise time measurements, and allow decision processing based on the elapsed counter value. 1. Set up timer to interrupt on every edge (may require changing edge trigger in the ISR) 2. ISR routine should flag the edge occurred and store count value 3. Start timer, capture first edge and discard this. 4. Capture next edge and check if stored count value equal 2T (T = ½ data rate) 5. Repeat step 4 until count value = 2T (This is now synchronized with the data clock) 6. Read current logic level of the incoming pin and save as current bit value (1 or 0) 7. Capture next edge a. Compare stored count value with T b. If value = T i. Capture next edge and make sure this value also = T (else error) ii. Next bit = current bit iii. Return next bit c. Else if value = 2T i. Next bit = opposite of current bit ii. Return next bit d. Else i. Return error 8. Store next bit in buffer 9. If desired number of bits are decoded; exit to continue further processing 10. Else set current bit to next bit and loop to step 7
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MLT-3(multi-level transmit) MLT-3 is a encoding used in Ethernet 100BASE-TX. It changes from its current state to the next every time there is a high. It has 3 states: typically positive, zero, and negative. A reason to use this encoding is to reduce the frequency by four (one cycle: hi-med-lo-med) compared to something like Manchester. This makes it easy to be transferred in copper cable. It reduces the frequency traveling through copper cable for the 100BASE-TX to 31.25 MHz. This is of no help in reducing the frequency when you have only two states on and off. Creating a third state with the LED alone (such as half intensity), would reduce the range.
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BiPhase BiPhase adds a level of complexity to the coding process but in return includes a way to transfer the bit frame data clock that can be used in the decoding to increase accuracy. BiPhase coding says that there will be a state transition in the message signal at the end of every bit frame. In addition, a logical “1” will have an additional transition at the mid-bit.
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Modulation Modulation refers to the act of adding the message signal to some form of carrier. The carrier, by definition, is a higher frequency signal whose phase, frequency, amplitude, or some combination thereof, is varied proportionally to the message. This change can be detected and recovered (demodulated) at the other end of the communication channel. There are a number of ways this can be done but for simplicity we will only look at Amplitude Modulation (AM), On-Off Keying (a variation on AM), and Frequency Modulation (FM). Modulation is typically carried out in hardware.
Amplitude Modulation In amplitude modulation, the amplitude of the carrier is changed to follow the message signal. In this case we can see a “ripple” on the carrier, its envelope contains the message. This can be demodulated using an extremely simple envelope detector that captures this ripple as a low frequency response.
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On-Off Keying This form of modulation takes the amplitude modulation as described above to the extreme. In this instance, we have only two states: Carrier and No Carrier. This approach lends itself nicely to the transmission of digital data because the carrier can be simply switched “on” or “off” depending on the state of the data being sent. The demodulated output is either high or low depending on the presence of the carrier.
Frequency Modulation Frequency modulation is more complicated but provides the benefit of constant output power independent of the message being sent. With this approach, the frequency of the carrier is not constant but varies in relation to the message. This requires a much more complicated demodulation circuit typically implemented using a Phase Lock Loop (PLL).
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LED vs LASER
A common response to those introduced to the RONJA is that a LASER should be used instead of a LED. This section will try to compare a LASER vs LED.
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Response Time
The LASER has an advantage of shorter response times than the LED. The LASER diode is stimulated to emit instead of spontaneous like the LED. LASER diodes with less than 1ns (1Ghz) response times are available. It is hard to find diodes with less than 20ns (50Mhz) response times. The LED response time works fine for the RONJA(10Mhz), if we wanted to make a faster link, this is where the LASER could have an advantage.
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Monochromatic
A LASER tends to emit a beam more monochromatic (<5nm FWHM, compared to > 24nm FWHM), it makes it easier to add filters to the optics to only allow the light from the LASER wavelength reducing ambient noise, and possibility of photo diode saturation from outside sources. There are also disadvantages, because of the narrow wavelengths emitted by the laser there could be conditions where that wavelength is absorbed, such as certain ice crystals in the air that absorb certain narrow bands of wavelength. With the LED you are emitting a much broader set of wavelengths. If some of it gets absorbed, you still have the rest to fall back on.
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Scintillation
Scintillation can be far worse for a LASER than the LED because the LASER is more coherent than the LED. As the beam travels through the air, it will hit packets of air of different temperature which have a different index of refraction causing constructive and destructive interference which can ruin your signal. This effect can be especially bad depending on the terrain it travels over. Asphalt, ponds, fountains, all create temperature differences that will contribute to scintillation. 25
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Safety
LASERs can be dangerous. Devices sold to the market place that contain lasers must go through the FDA. Even low powered lasers should have extra safety precautions such as auto shutoff if there is a beam break. For lasers rated higher than IIIa/3R protective eye goggles are needed when working with them. Even light reflected after it has hit a object can be enough to damage the eye depending on the power and wavelength of the LASER.
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SYSTEM DEVELOPMENT General Scrutiny One Ronja device is a single long-distance optical transceiver that is capable of running against the same or compatible device on the other side of the link. The topology is point-topoint. Building a Ronja is rather lenghty job (this will hopefully change in future) that however pays off in a reliable and performant device that is capable of delivering steady connectivity with little maintenance and can be run freely without a need of authorities' approval. Also a possibility of interference and eavesdropping is negligible. Dropouts are infrequent and determined solely by weather and are thus foreseeable.
He who wants to enjoy the adrenaline sport of driving primitive retail parts into flawless cooperation to provide the uncurbed full duplex connectivity experience must withstand these nuisances:
Ronja is somewhat labor expensive. Things have been made much easier by putting the most complicated electronics on a PCB. The cost of parts is negligible in comparison with the labor, for example the components for the whole Ronja 10M Metropolis cost just 1500CZK. Further reduction in labor demands is planned by putting RX and TX on PCB too.
The user must possess certain basic manual skills as soldering, drilling, painting, and technical drawing/schematic reading. But people without any previous experience with soldering have built a piece that worked on the first try! 27
The user must not cut the corners during the building But there are also certain conveniences:
The parts are chosen to be of the widest availability possible and equivalents are provided where applicable
Innovative approach is used to speed up the work and make it convenient. Sector codes are present to make the population easy. Drilling is simplified by drilling templates - just print and no measurement is necessary in the workshop!
The device is based on the KISS rule (Keep It Simple, Stupid) which makes the device plug-and-play immediately after the building provided the user hasn't botched anything.
The design is rugged and over dimensioned to withstand variations in the components. As a consequence, the resulting device is rock solid in steady performance and provides outstanding electromagnetic interference immunity and electromagnetic compatibility. Withstands -20°C as well as direct sunlight and heat with obvious margin. During a lightning storm, lightning strike in proximity usually doesn't generate even a single lost bit.
In case of device failure (direct lightning strike), the measuring points can be inspected and bad components replaced without a need to throw the whole device out.
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Block Diagram and its Description:
Following is the detailed description of the diagram: Optical Transmitter - Infrared LED driver: The heart of the Optical transmitter is the HSDL4220 infrared LED exclusively suitable for the 10Mb/s operation in this Transmitter. The HSDL-4200 series of emitters are the first in a sequence of emitters that are aimed at high power, low forward voltage, and high speed. These emitters utilize the Transparent Substrate, double heterojunction, Aluminum Gallium Arsenide (TS AlGaAs) LED technology. These devices are optimized for speed and efficiency at emission wavelengths of 875 nm. This material produces high radiant efficiency over a wide range of currents up to 500 mA peak current. The HSDL-4200 series of emitters are available in a choice of viewing angles, the HSDL-4230 at 17° and the HSDL-4220 at 30°. It has a bandwidth of 9 MHz, where 10 Mbit/s Manchester-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 a special driving technique consisting of driving the LED directly with 15-fold 74AC04 gate output in parallel without any current limitation is implemented. As the voltage to keep the nominal LED average current (100mA) varies with temperature and other component characteristic, an ACbypassed 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 29
gates. Therefore the 74AC04 is operating as a structured power CMOS switch completely in analog mode.
This way the LED junction is flooded and cleared of 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 MHz/1 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.
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Optical Receiver - Preamplifier stage: The usual approach in FSO (Free Space Optics) preamplifiers is to employ a transimpedance amplifier. A transimpedance amplifier is a very sensitive broadband high-speed device featuring a feedback loop. Following is the brief scrutiny of a transimpedance amplifier:
The transimpedance amplifier as shown above presents a low impedance to the photodiode and isolates it from the output voltage of the operational amplifier. In its simplest form a transimpedance amplifier has just a large valued feedback resistor, Rf. The gain of the amplifer is set by this resistor and because the amplifier is in an inverting configuration, has a value of -Rf. There are several different configurations of transimpedance amplifiers, each suited to a particular application. The one factor they all have in common is the requirement to convert the low-level current of a sensor to a voltage. The gain, bandwidth, as well as current and voltage offsets change with different types of sensors, requiring different configurations of transimpedance amplifiers. This transimpedance amplifier inside a ronja system also makes use of a PIN diode. A PIN diode is a diode with a wide, undoped intrinsic semiconductor region between a p-type semiconductor and an n-type semiconductor region. The p-type and n-type regions are typically heavily doped because they are used for ohmic contacts. A PIN diode operates under what is known as high-level injection. In other words, the intrinsic "i" region is flooded with charge carriers from the "p" and "n" regions. 31
Its function can be likened to filling up a water bucket with a hole on the side. Once the water reaches the hole's level it will begin to pour out. Similarly, the diode will conduct current once the flooded electrons and holes reach an equilibrium point, where the number of electrons is equal to the number of holes in the intrinsic region. When the diode is forward biased, the injected carrier concentration is typically several orders of magnitude higher than the intrinsic level carrier concentration. Due to this high level injection, which in turn is due to the depletion process, the electric field extends deeply (almost the entire length) into the region. This electric field helps in speeding up of the transport of charge carriers from P to N region, which results in faster operation of the diode, making it a suitable device for high frequency operations. Ronja however uses a feedback-less design where the PIN has a high working electrical resistance (100 kilohms) which together with the total input capacitance (roughly 7 pF, 5 pF PIN and 2 pF input MOSFET cascade) makes the device operate with a passband 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, and then a compensation of the 6 dB/oct slope is done by derivator element on the programming pins of an NE592 video amplifier. The NE592 video amplifier is a monolithic, two-stage, differential output, and wideband video amplifier. It offers fixed gains of 100 and 400 without external components and adjustable gains from 400 to 0 with one external resistor. The input stage is designed so that with the addition of a few external reactive elements between the gain select terminals, the circuit can function as a high-pass, low-pass, or band-pass filter.
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This feature makes the circuit ideal for use as a video or pulse amplifier in communications, magnetic memories, display, video recorder systems, and floppy disk head amplifiers. It is available in an 8-pin version with fixed gain of 400 without external components and adjustable gain from 400 to 0 with one external resistor. Due to this implementation, a surprisingly flat characteristic is obtained in the receiver section of the RONJA. 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.
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Transceiver - Ronja Twister: An optical transceiver module configured for long wave optical transmission is disclosed. Significantly, the transceiver module utilizes components formerly used only for shortwave optical transmission, thereby reducing new component production and device complexity. In one embodiment, the transceiver module includes a transmitter optical subassembly including a laser capable of producing an optical signal. A consolidated laser driver/post amplifier including a first bias current source provides a bias current to the laser for producing the optical signal. A means for amplifying the bias current provided to the laser by the first bias current source is also included as a separate component from the laser driver/post amplifier. The means for amplifying in one embodiment is a field-effect transistor that is operably connected to the laser driver/post amplifier and configured to provide an additional bias current to the laser diode such that sufficient lasing operation of the laser is realized.
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Physical Layer: In the seven-layer Open Systems Interconnection model (OSI) of computer networking, the physical layer or layer 1 is the first (lowest) layer. The implementation of this layer is often termed PHY. The physical layer consists of the basic networking hardware transmission technologies of a network. It is a fundamental layer underlying the logical data structures of the higher level functions in a network. Due to the plethora of available hardware technologies with widely varying characteristics, this is perhaps the most complex layer in the OSI architecture. The physical layer defines the means of transmitting raw bits rather than logical data packets over a physical link connecting network nodes. The bit stream may be grouped into code words or symbols and converted to a physical signal that is transmitted over a hardware transmission medium. The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium.
The major functions and services performed by the physical layer are:
Bit-by-bit or symbol-by-symbol delivery
Providing a standardized interface to physical transmission media, including
Mechanical specification of electrical connectors and cables, for example maximum cable length
Electrical specification of transmission line signal level and impedance
Radio interface, including electromagnetic spectrum frequency allocation and specification of signal strength, analog bandwidth, etc. 35
Specifications for IR over optical fiber or a wireless IR communication link
Modulation
Line coding
Bit synchronization in synchronous serial communication
Start-stop signaling and flow control in asynchronous serial communication
Circuit switching
Multiplexing
Establishment and termination of circuit switched connections
Carrier sense and collision detection utilized by some level 2 multiple access protocols
Equalization filtering, training sequences, pulse shaping and other signal processing of physical signals
Forward error correction for example bitwise convolutional coding
Bit-interleaving and other channel coding
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Data link layer: The data link layer is the protocol layer that transfers data between adjacent network nodes in wide area network or between nodes on the same local area network segment. The data link layer provides the functional and procedural means to transfer data between network entities and might provide the means to detect and possibly correct errors that may occur in the layer. Examples of data link protocols are Ethernet for local area networks (multi-node), the Pointto-Point Protocol (PPP), HDLC and ADCCP for point-to-point (dual-node) connections. The data link layer is concerned with local delivery of frames between devices on the same LAN. Data-link frames, as these protocol data units are called, do not cross the boundaries of a local network. Inter-network routing and global addressing are higher layer functions, allowing data-link protocols to focus on local delivery, addressing, and media arbitration. In this way, the data link layer is analogous to a neighborhood traffic copy; it endeavors to arbitrate between parties contending for access to a medium, without concern for their ultimate destination. When devices attempt to use a medium simultaneously, frame collisions occur. Data-link protocols specify how devices detect and recover from such collisions, and may provide mechanisms to reduce or prevent them. Delivery of frames by layer 2 devices is effected through the use of unambiguous hardware addresses. A frame's header contains source and destination addresses that indicate which device originated the frame and which device is expected to receive and process it. In contrast to the hierarchical and routable addresses of the network layer, layer-2 addresses are flat, meaning that no part of the address can be used to identify the logical or physical group to which the address belongs. The data link thus provides data transfer across the physical link. That transfer can be reliable or unreliable; many data-link protocols do not have acknowledgments of successful frame reception and acceptance, and some data-link protocols might not even have any form of checksum to check for transmission errors. In those cases, higher-level protocols must provide flow control, error checking, and acknowledgments and retransmission. In some networks, such as IEEE 802 local area networks, the data link layer is described in more detail with media access control (MAC) and logical link control (LLC) sub layers; this means that the IEEE 802.2 LLC protocol can be used with all of the IEEE 802 MAC layers, such as Ethernet, token ring, IEEE 802.11, etc., as well as with some non-802 MAC layers such as FDDI. Other data-link-layer protocols, such as HDLC, are specified to include both sub layers, although some other protocols, such as Cisco HDLC, use HDLC's low-level framing as a MAC layer in combination with a different LLC layer. In the ITU-T G.hn 37
standard, which provides a way to create a high-speed (up to 1 Gigabit/s) local area network using existing home wiring (power lines, phone lines and coaxial cables), the data link layer is divided into three sub-layers (application protocol convergence, logical link control and medium access control). Within the semantics of the OSI network architecture, the data-link-layer protocols respond to service requests from the network layer and they perform their function by issuing service requests to the physical layer.
Data link layer services:
Encapsulation of network layer data packets into frames
Frame synchronization
Logical link control (LLC) sublayer.
Error control (automatic repeat request, ARQ), in addition to ARQ provided by some transport-layer protocols, to forward error correction (FEC) techniques provided on the physical layer, and to error-detection and packet canceling provided at all layers, including the network layer. Data-link-layer error control (i.e. retransmission of erroneous packets) is provided in wireless networks and V.42 telephone network modems, but not in LAN protocols such as Ethernet, since bit errors are so uncommon in short wires. In that case, only error detection and canceling of erroneous packets are provided.
Flow control, in addition to the one provided on the transport layer. Data-link-layer error control is not used in LAN protocols such as Ethernet, but in modems and wireless networks.
Media access control (MAC) sub layer.
Multiple access protocols for channel-access control, for example CSMA/CD protocols for collision detection and re-transmission in Ethernet bus networks and hub networks, or the CSMA/CA protocol for collision avoidance in wireless networks.
Physical addressing (MAC addressing)
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MODELS
Ronja Tetrapolis: Range of 1.4 km (0.87 mi), red visible light. Connect with 8P8C connector into a network card or switch.
Ronja 10M Metropolis: Range of 1.4 km (0.87 mi), red visible light. Connects to Attachment Unit Interface.
Ronja Inferno: Range of 1.25 km (0.78 mi), invisible infrared light.
Ronja Bench-press: A measurement device for developers for physical measurement of lens/LED combination gain and calculation of range from that
Ronja Tetrapolis: Ronja Tetrapolis is a device for optical communication with 10Mbps full duplex speed over 1.4km. The device terminates an optical path. To operate a complete link, two devices are necessary. Ronja Benchpress: This is a Ronja model that is not a communication device, but a bench for measuring lens properties. You insert a combination of LED and lens into the bench and measure exact transmitter gain of the lens+LED combination in decibels. You can then use this value to calculate precise range of the device. This is handy for evaluating new types of LEDs, new types of lenses or if you have doubts if your lens is of adequate quality for the device (for example due to greenish haze). Ronja 10M Metropolis: This is another variant of Ronja similar to Ronja Tetropolis, but varying in its technical specifications. Ronja Inferno: Ronja Inferno is a device for optical communication with 10Mbps full duplex speed over 1.25 km using infrared light. The device terminates an optical path. To operate a complete link, two devices are necessary
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Technical specifications: Ronja Inferno: Gross data rate Transmission mode
Nominal range
10 Mbps
Full duplex (half duplex also supported)
1.25 km with 130mm RX loupe lenses and 90mm TX loupe lenses. The switch or cad has to have well implemented PLL.
Minimum
1/4 of nominal range. Further manual reduction possible by change of two passive
operating distance
components in receiver.
Connects with RJ45 jack into IEEE 802.3 UTP interface. Must be plugged directly into data terminal equipment (DTE, PC or a switch) using the integral 1m cable. Auto negotiation not supported, not transparent for auto negotiation signals.
The preamble is chopped off more than specified by IEEE 802.3 which could cause a problem when Ronja is connected into a cascade of pure hubs. However
Data interface
hubs almost don't exist today anymore so it is not a problem.
Doesn't comply to IEEE 802.3 regarding not transmitting when link integrity is not yet established. This violates page 303 14.2 g) - but IEEE 802.3 compliant devices must work with it. Complying to it would make Ronja Tetrapolis more complicated
335mA @12VDC (4.02W) from wall cube, 2W from external heating power supply (switchable off).
Typical Maximum
Power consumption
Idle
225mA 285mA
Full data load (both directions) 275mA 335mA Operating wavelength Optical output
Infrared, 875nm wavelength, 37nm spectral width
30mW
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Ronja Tetrapolis: Gross data rate Transmission mode
10 Mbps
Full duplex (half duplex also supported)
Nominal range
1.4km with 130mm lenses. The switch or cad has to have well implemented PLL.
Minimum
1/4 of nominal range. Further manual reduction possible by change of two passive
operating distance components in receiver.
Connects with RJ45 jack into IEEE 802.3 UTP interface. Must be plugged directly into data terminal equipment (DTE, PC or a switch) using the integral 1m cable. Auto negotiation not supported, not transparent for auto negotiation signals.
The preamble is chopped off more than specified by IEEE 802.3 which could cause a problem when Ronja is connected into a cascade of pure hubs. However hubs
Data interface
almost don't exist today anymore so it is not a problem.
Doesn't comply with IEEE 802.3 regarding not transmitting when link integrity is not yet established. This violates page 303 14.2 g) - but IEEE 802.3 compliant devices must work with it. Complying to it would make Ronja Tetrapolis more complicated
285mA @12VDC (3.42W) from wall cube, 2W from external heating power supply (switchable off).
Typical Maximum
Power consumption
Idle
185mA 245mA
Full data load (both directions) 225mA 285mA Operating wavelength Optical output Divergence cone half angle Estimated Optical EIRP
visible, 625nm, 100nm spectral width (618nm perceived wavelength, red-orange)
17.2mW
1.9mrad (130mm aperture transmitter lens)
20kW (130mm aperture transmitter lens, HPWT-BD00-F4000)
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Operating temperature
-30...+70degC (outdoor part - optical heads, RX, TX), 0...+55degC (indoor part - Twister2)
Operating
Up to 100% (condensing) with lens heating on (outdoor part), up to 95% with lens heating
humidity
off (and indoor electronics).
Weight
15.5kg (one side of a link, on a welded parallel console)
Required visibility 4km at maximum range.
Optical modulation
Indicators LEDs
Aiming system
BPSK (as on AUI aka Manchester) plus 1MHz asynchronous 50% duty cycle square wave between packets. The transmitter appears to shine permanently and steadily no matter if data pass or not. Power, Receive Packet, Transmit Packet Visual, retro reflector for transmitter and DC voltage signal strength monitor port for receiver.
Possible mount places:
Is drilling
Place
Mechanical Installation Constraints
necessary?
Railing, round or rectangular
No
Wall
Yes
Corner of wall
Yes
Chimney
No
Horizontal or tilted surface of masonry or masonry covered with tin, foil etc. Ceiling
Yes Yes
Max. 1m from RJ45 connector is a grounded metal box with dimensions 180x123x62 mm.
Cable distance between RJ45 connector and optical head mounting points is max. 100m
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Ronja Benchpress: Operating ambient temperature
0…+55°C
Usage environment
Indoor
Operating humidity
0-95% noncondensing
Ronja 10M Metropolis: Gross data rate Transmission mode
Nominal range
Minimum operating distance
10 Mbps
Full duplex only
1.4km with HPWT-BD00-F4000 and 130mm lenses. The switch or cad has to have well implemented PLL.
1/4 of nominal range. Further manual reduction possible by change of two passive components in receiver.
IEEE 802.3 Attachment Unit Interface (AUI). Connector male DB-15 with screws instead of AUI mechanical latch. AUI cable not supported - integrated cable length 1m. The preamble is Data interface
chopped off more than specified by IEEE 802.3 which could cause a problem when Ronja is connected into a cascade of pure hubs. However hubs almost don't exist today anymore so it is not a problem.
Power consumption Operating wavelength Optical output Divergence cone half angle Estimated Optical EIRP
300mA @12VDC (3.6W) from AUI, 2W from external heating power supply (switchable off)
visible, 625nm, 100nm spectral width (618nm perceived wavelength, red-orange)
17.2mW
1.9mrad (130mm aperture transmitter lens)
20kW (130mm aperture transmitter lens, HPWT-BD00-F4000)
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Operating temperature Operating humidity Weight Required visibility
-30…+70°C (outdoor part - optical heads, RX, TX), 0…+55°C (indoor part - AUI interface)
Up to 100% (condensing) with lens heating on, up to 95% with lens heating off.
15.5kg (one side of a link, on a welded parallel console)
4km for uninterrupted operation at full range.
Optical
BPSK (as on AUI) plus 1MHz asynchronous 50% duty cycle square wave between packets.
modulation
The transmitter appears to shine permanently and steadily no matter if data pass or not.
Indicators LEDs Power, Receive Packet, Transmit Packet
CONCLUSION The Twibright Ronja datalink thus, can network neighbouring houses with cross-street ethernet access, solve the last mile problem for ISP’s, or provide a link layer for fast neighbourhood mesh networks. 45
APPLICATIONS AND FUTURE SCOPES 1. Mount Considerations The distances involved requires that the mounts be very stable. If the wind causes an angle change, the end point will be displaced s = d tan θ, where d is the distance between points and θ is the angle change caused by the vibration. An end point displacement of 20cm when d = 1.4km is only an angle change of θ = 0.008◦. If mounted on tall buildings, the swaying of the building can also be a problem as the current design does not compensate for that. At large distances, aiming is difficult. The original RONJA design has a mechanism to make fine adjustments. Improvements to the RONJA design might be a finder scope and auto aiming mounts.
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Fresnel Lenses
Fresnel lenses give you large apertures and shorter focal lengths, while still being light weight. It may be possible to use a large Fresnel lens to get a better signal from the transmitter, or to make the optical tube shorter (smaller focal length). When shortening the focal length extra ambient light may get to the photo diode and that would need to be considered in the design.
3
Shorter and Longer Distances
There may be instances were one needs to create a shorter or longer network bridge. The use of smaller lenses at short distance maybe also be beneficial at times. If a link of smaller than 90m is needed a few of the electronics (a capacitor and resistor) need to be changed in the receiver. To get a longer signal you can also use two or more transmitters pointed to one receiver.
4
Faster Data Transfer
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Our LED has a max response of 20ns (50 MHz). So we would run into a problem if we wanted to increase the speed to 100Mbits/s by transmitting in a similar manner with the LED. There are a few solutions. We could use a LASER which has much faster response rates than LEDs and read in the MLT-3 and transmit NRZ at max frequency of 62.5 MHz, with the receiver converting NRZ back to MLT-3. We can also communicate in parallel instead of serial, we would require several transmitters and receivers. For example if we had three transmitters/receivers then each transmitter could handle a maximum frequency of 21Mhz. Using multiple transmitters/receivers brings up several issues: noise from other transmitters, 4B5B would not guarantee a hi-lo transition for each detector, mounting space issues. One thing is certain making a 100Mbit/s network would be easy.
PROS AND CONS Pros:
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1) The parts were chosen to be of the widest availability possible and equivalents are provided where applicable. 2) Innovative approach is used to speed up the work and make it convenient. Sector codes are present to make the population easy. Drilling is simplified by drilling templates - just print and no measurement is necessary in the workshop! 3) Withstands -20°C as well as direct sunlight and heat with obvious margin. During a lightning storm, lightning strike in proximity usually doesn't generate even a single lost bit. 4) In case of device failure (direct lightning strike), the measuring points can be inspected and bad components replaced without a need to throw the whole device out.
Cons: 1) Ronja is somewhat labor expensive. Things have been made much easier by putting the most complicated electronics on a PCB. The cost of parts is negligible in comparison with the labor, for example the components for the whole Ronja 10M Metropolis cost just 1500CZK. Further reduction in labor demands is planned by putting RX and TX on PCB too. 2) The user must possess certain basic manual skills as soldering, drilling, painting, and technical drawing/schematic reading. But people without any previous experience with soldering have built a piece that worked on the first try! 3) The user must not cut the corners during the building.
REFERENCES
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Twibright Labs. Ronja. .
Kenneth Krane. Modern Physics Second Edition. John Wiley & Sons, Inc.
www.wikipedia.org
Twibright Labs. Making Ronja on short tracks. .
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