WO2001006663A2 - Systeme et procede de communication optique non filaire - Google Patents

Systeme et procede de communication optique non filaire Download PDF

Info

Publication number
WO2001006663A2
WO2001006663A2 PCT/US2000/018200 US0018200W WO0106663A2 WO 2001006663 A2 WO2001006663 A2 WO 2001006663A2 US 0018200 W US0018200 W US 0018200W WO 0106663 A2 WO0106663 A2 WO 0106663A2
Authority
WO
WIPO (PCT)
Prior art keywords
signals
signal
temporally
delayed
transmission
Prior art date
Application number
PCT/US2000/018200
Other languages
English (en)
Other versions
WO2001006663A3 (fr
Inventor
Christopher C. Davis
Original Assignee
University Of Maryland
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by University Of Maryland filed Critical University Of Maryland
Priority to US10/018,957 priority Critical patent/US7106971B1/en
Priority to AU15683/01A priority patent/AU1568301A/en
Publication of WO2001006663A2 publication Critical patent/WO2001006663A2/fr
Publication of WO2001006663A3 publication Critical patent/WO2001006663A3/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum

Definitions

  • the present invention relates to optical communication.
  • Optical communication is in increasing demand.
  • digital data is carried in an optical signal.
  • the digital data consists of bits of information (e.g., "Is" and "0s").
  • Such data is transmitted in an optical signal using modulation.
  • modulation which can be used in optical communication are modulation based on amplitude, frequency, phase, polarization, or a combination thereof.
  • Communication between a source node and destination node is conducted through one or more links.
  • a link can include logical and/or physical layers to support data transfer.
  • An optical wireless communication system includes a physical layer with an optical wireless link.
  • An optical wireless link can be any optical link through a turbulent medium such as, the atmosphere.
  • an optical wireless link can include, but is not limited to, an optical line of sight
  • LOS LOS link that uses a transmitter, such as, a laser or light-emitting diode (LED).
  • a transmitter such as, a laser or light-emitting diode (LED).
  • Data is transmitted on the emitted beam using some form of amplitude, frequency, phase, or polarization modulation, or a combination thereof.
  • Optical wireless links are increasingly popular as they can provide relatively low cost, high performance communications over short distances - typically up to a few kilometers at sea level.
  • Other advantages of optical wireless links are: no FCC spectrum allocation is required for their use, they have a high degree of physical security because of the directionality of the transmitted beam, the communication channel infrastructure exists with a low probability of detection, and easy set-up and removal.
  • Optical wireless links have a further advantage in that no communication channel infrastructure such as, optical fibers, needs to be installed.
  • an optical wireless link can be a separate stand alone path between a source node and destination node or it can be combined with any other type of conventional communication link, such as, a fiber link, RF link, or wired link.
  • the optical beam passes from transmitter to receiver along a path through the atmosphere. Since the atmosphere is a turbulent medium the optical wavefronts are distorted in passing from transmitter to receiver. Such fluctuations in received power are unpredictable and can result in the loss of data (that is, "1" bits can be detected as “0" bits). This fluctuation problem is known as fading. Because of the potential for fading, there is some probability that the fluctuating received intensity will fall below a threshold value and lead to unacceptable bit error rates on an optical wireless link.
  • the present invention provides a system and method for optical wireless communication with fading resistance.
  • a delayed diversity approach is used to reduce fading significantly.
  • Data is sent in a set of light signals (also called diverse light signals) which each have a different polarization and/or a different wavelength.
  • the diverse light signals are also temporally different in that they are transmitted in a delayed fashion with respect to one another. In this way, each light signal is carried over a different, uncorrelated "channel" through the atmosphere.
  • original data in each received light signals is temporally adjusted and combined into a single output data signal.
  • each bit in the output data signal is then due to the reception of the combined diverse light signals.
  • a combined output data signal can still be generated at relatively high accuracy from the original data carried in one or more of the other diverse light signals.
  • the other one or more light signals pass through the different respective temporal channels in the atmosphere and therefore are not likely to experience the same fading condition.
  • a method for optical wireless communication includes the steps of receiving a source data signal having data, creating a set of temporally distinguishable transmission signals, and converting the set of temporally distinguishable transmission signals to obtain corresponding a set of temporally distinguishable light signals.
  • Each light signal has a modulation representation of the data from the source data signal.
  • a transmitting step is added to transmit the set of temporally distinguishable light signals in a single output transmission beam through the turbulent medium.
  • the method includes receiving the single output transmission beam after it has passed through a turbulent medium; detecting temporally distinguishable light signals within the received single output transmission beam to obtain corresponding temporally distinguishable data signals; temporally adjusting each temporally distinguishable data signals obtained in the detecting step; and logically evaluating bits in each of said temporally adjusted temporally distinguishable data signals to obtain a single output data signal.
  • a system for optical wireless communication includes means for receiving a source data signal having data; means for creating a set of temporally distinguishable transmission signals; and means for converting the set of temporally distinguishable transmission signals to obtain corresponding a set of temporally distinguishable light signals, each light signal having a modulation representation of the data from the source data signal; whereby, the set of light signals can pass through uncorrelated channels in a turbulent medium.
  • the system can also include a transmitter means for transmitting the set of temporally distinguishable light signals in a single output transmission beam through a turbulent medium.
  • the system can include means for receiving the single output transmission beam after it has passed through a turbulent medium; means for detecting temporally distinguishable light signals within the received single output transmission beam to obtain corresponding temporally distinguishable data signals; means for temporally adjusting each obtained temporally distinguishable data signal obtained; and means for logically evaluating bits in each of said temporally adjusted temporally distinguishable data signals to obtain a single output data signal.
  • Further embodiments include communications systems that utilize amplitude modulation, polarization modulation, frequency modulation, or any combination of these or other modulation techniques.
  • FIG. 1 A is an illustration of the relationship between the environment in which the present invention operates and conventional layers of communications systems.
  • FIG. IB is a diagram of a bi-directional full-duplex optical wireless communication system including an optical wireless link in an example of the present invention.
  • FIG. IC is a diagram of an optical wireless communication system including two uni-directional optical wireless links in an example of the present invention.
  • FIG. 2 is an illustration of a communications system according to the present invention.
  • FIGs. 3A and 3B are illustrations of a communications system according to the present invention that utilizes polarization division.
  • FIGs. 4A and 4B are illustrations of a communications system according to the present invention that utilizes frequency division.
  • FIGs. 5 A and 5B are illustrations of a communications system according to the present invention that utilizes both frequency and polarization division.
  • FIG. 6 is an illustration of a routine for optical communication through a turbulent medium.
  • FIGs. 7A-7P are diagrams related to theoretical discussion and/or test results according to example implementations of the present invention.
  • FIG. 7A is a diagram plotting the fraction of the time that a fade of a given depth will occur for various levels of intensity variance according to one example fading model.
  • FIG. 7B is a plot of BER as a function of threshold setting.
  • FIGs. 7C, 7D, 7E, and 7F show calculations of BER for different levels of intensity variance, and for different settings of the threshold setting for detection of a "one".
  • FIG. 7G shows experimental data from experiments carried out on the
  • FIGs.7H-7N show additional data recorded at the University of Maryland test range.
  • FIGs. 70 and 7P show aperture averaging calculations for the following optical link conditions: a 1.3 ⁇ m laser and a 1km range.
  • FIG. 7O shows aperture averaging for three different degrees of "weak” turbulence.
  • FIG. 7P shows aperture averaging for three different degrees of "strong” turbulence.
  • a " delay ed-diversity" communication technique is provided that reduces fading. This technique takes advantage of the changes in the characteristics of the atmospheric path between the transmitter and the receiver.
  • a set of delayed diversity signals are generated and used to carry information from an original data signal over an optical wireless link. By introducing a delay during a multiple data stream transmission, the probability of simultaneous errors in the streams is markedly reduced.
  • the delayed diversity scheme introduces a latency into communication over an optical wireless link, data arrives continuously at the receiver. This latency is generally of no consequence for data transfer and can be managed to be short enough so as to be unnoticeable during voice communication.
  • the set of diverse lights signals can be made diverse, that is, distinguishable from one another based on a polarization and/or wavelength.
  • polarization and wavelength diversity can be used separately or combined in various ways: one or more wavelengths, each with up to two orthogonal polarization states (e.g., s and p polarization) can be used.
  • Two orthogonal polarization states can be used to provide clock recovery by transmitting, for example, all the "ones" in a bit stream vertically polarized and all the "zeros" horizontally polarized.
  • Various error-correcting codes can be incorporated into two or more channels (polarization plus wavelength diversity) to provide improvements in performance.
  • a full duplex system incorporating polarization diversity is implemented.
  • a receiver/transmitter (also called a transceiver) module sends one polarization and receives the same polarization, an orthogonal polarization, or both.
  • Different wavelengths for example UV, visible, near- infrared, and middle-infrared can be used to overcome atmospheric attenuation caused by scatting (aerosols, fog, rain, etc) and abso ⁇ tion (pollutants).
  • different infra-red wavelengths in common infrared windows such as 1.3 micron and 1.5 micron windows are used.
  • a data stream (represented as a string of "ones” and “zeros" in an on-off-keyed (OOK) optical beam) is transmitted in orthogonal polarization states, separate wavelengths, or both, but with an appropriate time delay between two channels.
  • the received data streams are interleaved (that is synchronized and combined) after reintroduction of the same delay into the opposite channel.
  • a significant reduction in fractional fade time results. Since atmosphere turbulence has a power spectrum roughly below 1 kHz, with predominant frequencies in the tens of Hz range, over times of 10 milliseconds (ms) or longer the turbulence effects along the path of an optical beam are uncorrelated.
  • the present invention relates to optical wireless communication.
  • the present invention is described with respect to one example environment of optical wireless communication provided in a computer networking environment.
  • FIG. 1A is a diagram of an optical wireless communication system 100 that includes an optical wireless link 110 in an example networking environment of the present invention. Communication including data transfer is carried out between two nodes 120, 130. Each node 120, 130 includes a number of layers 1 to N, where N is an integer equal to or greater than 1. The layers are used to support to functionality required to carry out different services and protocols.
  • layer 1 is the physical layer.
  • Layer 1 includes the hardware in the present invention, including, a transmitter and/or receiver as described further below.
  • the other higher layers 2 through N can include, but are not limited to, layers supporting packet-switched communication such as, any one or more of a network interface layer, Internet layer, Transport layer, and an Application layer.
  • a suite of protocols such as, Transmission Control Protocol/ Internet protocol (TCP/IP) as used in the Internet can be included. Communication according to other standards and protocols can be used, including but not limited to, Ethernet, Asynchronous Transfer Mode(ATM),
  • FIGs. IB and IC illustrate architectures of hardware in layer 1 according to embodiments of the present invention.
  • FIG. IB is a diagram of a bi-directional full-duplex optical wireless communication system having a first transceiver 140 at node 120 and a second transceiver 150 at node 130. Each transceiver 140, 150 is coupled to optical wireless link 110.
  • Transceiver 140 can include one or more transmitters and one or more receivers for sending and receiving a set of delayed diversity light signals.
  • Optical wireless link 110 is any portion of an optical communications link that passes light signals through a turbulent medium.
  • transceiver 140 can be integrated on a single optical- electronic monolithic device to form a compact device.
  • transceiver 150 can be integrated on a single optical-electronic monolithic device to form a compact device.
  • FIG. 1 C is a diagram of an optical wireless communication system where optical wireless link 110 includes two uni-directional optical wireless links 110a,
  • a transmitter 160 transmits a first set of delayed diversity light signals over optical wireless link 110a to a receiver 170.
  • a transmitter 180 transmits a first set of delayed diversity light signals over optical wireless link 110b to a receiver 190.
  • the present invention improves fade resistance and decreases bit error rate for data transfer over optical wireless link 110.
  • the present invention represents a hardware solution for improving bit error rate. Any other conventional technique for further improving bit error rate can also be used in nodes 120 and 130, in combination with the present invention.
  • any coding technique such as, those involving Reed-Solomon codes, Turbo codes, Viterbi codes, or concatenated codes can be used.
  • these examples are illustrative and not intended to necessarily limit the present invention.
  • FIG.2 is an illustration of a communications system 201 according to the present invention.
  • Data to be transmitted by communications system 201 is represented as source data 210.
  • Source data 210 can be digital data representative of any desired information.
  • Source data 210 is a return-to-zero signal according to an embodiment of the present invention, though other types of data signals can be used without departing from the scope of the present invention.
  • Source data 210 is processed by a delay duplicator 220 within communications system 201.
  • Delay duplicator 220 receives as an input the source data 210, and produces an output that includes a set of transmission signals. At least one of the set of transmission signals corresponds to the source data itself, while at least another of the set of transmission signals corresponds to the source data delayed a first time, t,.
  • the set of transmission signals includes at least two transmission signals that can be temporally distinguished from one another. In other words, one of the transmission signals corresponds a delayed version of the other transmission signal in a system that includes two transmission signals. More than two transmission signals can be used, as will be discussed more fully below.
  • the delay t into one of the transmission signals, the communications system 201 will ultimately transmit the same signal twice, at two different times.
  • the temporal separation between the two transmissions will thus be equal to t,. While a turbulent medium may introduce an error into an optical communication, such a medium is always in flux and so the likelihood of errors at two different times is not generally correlated. Thus, i ⁇ P(T) is the likelihood of an error at any given time T, then the likelihood of error for the same piece of data in two temporally displaced data signals will approach P(T) 2 , as long as the two signals are displaced by a sufficient amount of time. So, for example, if the error rate of a particular optical communications channel is a relatively unacceptable 10 "4 , the use of a duplicated signal with an appropriate delay can reduce this error rate to the more acceptable level of 10 "8 .
  • the delay t, introduced by the delay duplicator is at least approximately 1 millisecond according to the present invention.
  • the delay t is between approximately 1 millisecond and approximately 10 milliseconds. More preferably, the present inventor has discovered that the delay t, should be between approximately 5 and approximately 10 milliseconds.
  • the delay duplicator 220 produces an output that includes a set of temporally distinguishable transmission signals.
  • the set of temporally distinguishable transmission signals are converted into optical signals by a converter 230.
  • Such conversion is accomplished through modulation of one or more light sources with the transmission signals resulting in a set of light signals corresponding to the temporally distinguishable transmission signals.
  • modulation can include amplitude, frequency, phase, or polarization modulation, or a combination of these.
  • one or more division techniques can be used such as two light sources with different frequencies, polarizations, etc.
  • a light source can include a laser or LED beam.
  • a 1.3 micron ( ⁇ ) or a 1.55 ⁇ laser can be used as a light source.
  • the laser can be a pig-tailed laser diode.
  • the laser output can be boosted with an erbium doped fiber amplifier (EDFA) and can be collimated to prevent spreading as would be apparent to one skilled in the relevant art.
  • EDFA erbium doped fiber amplifier
  • the laser can be fiber coupled.
  • Other light sources or modulation techniques could be used with departing from the scope of the present invention. For example, different wavelengths such as UV, visible, near-infrared, and middle-infrared can be used to overcome atmospheric attenuation caused by scattering (from aerosols, fog, rain, etc.) as well as by abso ⁇ tion (from, for example, pollutants).
  • the converter 230 receives the set of temporally distinguishable transmission signals as inputs and produces a set of light signals as outputs.
  • Transmitter 240 transmits the light signals received from converter 230.
  • Such transmission includes the combination of the light signals from converter 230 into a single light beam. Such combination can be accomplished, for example, through the use of a polarizing beam splitter or a dichroic mirror, or a combination of the two, as will be described more fully below.
  • the light signals are received by a receiver 250.
  • the receiver separates the light beam back into separate light signals. Such separation can also be accomplished, for example, through the use of a polarizing beam splitter, a dichroic mirror, or a combination of the two, as will be described more fully below.
  • Detectors 260 convert each light signal back into a received data signal in a manner that would be apparent to one skilled in the relevant art given this disclosure.
  • the detectors 260 thus can include one detector for each light signal to be detected.
  • the output of detectors 260 is a set of received data signals that correspond to the set of temporally distinguishable transmission signals produced by delay duplicator 220.
  • the received data signals would be identical to the transmission signals.
  • errors may be introduced as a result of fading.
  • the probability that a single bit was lost in both transmission signals is much less likely than the loss of any bit within one of the transmission signals.
  • the error rate can be significantly reduced.
  • Such a single output signal is generated by synchronizer 270. Synchronizer 270 receives received data signals from detectors 260.
  • Synchronizer 270 introduces the necessary delays to the received data signals so that they are temporally aligned with one another. For example, if the set of temporally distinguishable transmission signals generated by delay duplicator 220 includes two signals, a first transmission signal without a delay and a second transmission signal with a 3 millisecond delay, then synchronizer 270 introduces a 3 millisecond into the received data signal that corresponds to the first transmission signal. Thus, in this example, both of the received data signals should correspond to the original source data signal with a 3 millisecond delay. Once the appropriate delay or delays have been introduced, the received data signals are combined to produce a single output data signal.
  • the synchronizer can use logic, for example an OR gate, to combine the signals.
  • the communications system 201 of FIG. 2 has been described in terms of the use of a set of temporally distinguishable transmission signals including a delayed and a non-delayed data signal, more that two such transmission signals could be used.
  • the set of transmission signals could include a non-delayed transmission signals and three additional transmission signals delayed at times t réelle t 2 , and t 3 , respectively.
  • Such delay times could be 1, 2, and 3 milliseconds, respectively.
  • Other delay times could be used without departing from the scope of the present invention.
  • the times could be 3, 6, and 9 milliseconds; 1, 5, and 10 milliseconds, or any other appropriate delay times.
  • examples have now been given which include 2 and 4 temporally distinguishable transmission signals, any number of temporally distinguishable delay signals could be used without departing from the scope of the present invention.
  • the communications system 201 of FIG. 2 reduces error in an optically transmitted signal by taking advantage of the non-correlation of error probability over a communications channel at two points in time separated by at least about 1 millisecond. While such a system with its associated method, discussed below, serves to reduce errors, other conventional error reduction techniques can also be used within such a system and method without departing from the scope of the present invention. For example, the use of packet-switching in a duplex link as well as coding techniques can also be used with the present invention to further reduce error, as would be apparent to one skilled in the relevant art given this description.
  • FIGs. 3 A and 3B illustrate details of a communications system similar to that described in connection with FIG.2, and which uses polarization modulation together with polarizing beam splitters in order to implement the present invention.
  • FIG. 3 A specifically illustrates the transmission side 301 of the communications system of FIGs. 3A and 3B.
  • source data is duplicated into two identical source data signals 311, 312.
  • one of the two source data signals is subject to a delay 320.
  • the delay 320 can be greater than approximately 1 millisecond, between approximately 1 millisecond and approximately 10 milliseconds, and preferably, can be between approximately 5 and approximately 10 milliseconds.
  • the delay output 313 is simply a delayed version of source data signal 311. In this way, signals 312 and 313 constitute temporally distinguishable transmission signals.
  • transmission signal 313 is converted into a horizontally polarized optical signal 314.
  • Laser 1 330 can be the type discussed above in connection with the communications system 201 of FIG. 2 and can include the additional components necessary to effectuate the conversion described, as would be apparent to one skilled in the relevant art. Modulation can be accomplished, for example, with amplitude modulation, though other types of modulation can be used without departing from the scope of the present invention.
  • transmission signal 312 is converted into a vertically polarized optical signal 315.
  • Signals 314 and 315 are polarized orthogonal to one another.
  • signals 314 and 315 are polarization divided and amplitude modulated light signals representative of transmission signals 313 and 312, respectively.
  • Polarization beam splitter 350 serves to combine signals 314 and 315 into a single transmission beam 316.
  • Polarization beam splitter 350 is of the type known to those skilled in the relevant art.
  • Polarization beam splitter 350 allows one of the two polarized optical signals, for example signal 315, to pass through while an orthogonally polarized signal 314 is reflected off an internal surface and caused to be co-incident with the first signal 315.
  • the output is a single transmission beam 316 that includes both optical signals 314 and 315.
  • FIG. 3B illustrates of the receiver side 302 of the communications system of FIGs. 3 A and 3B.
  • the input to the receiver side is reception beam 317.
  • Reception beam 317 corresponds to transmission beam 316 after having passed through the a turbulent medium and so may differ from transmission beam 316 at least to the extent that fading has occurred.
  • Reception beam 317 is input into a polarization beam splitter 355 similar to polarization beam splitter 350 used at the transmitter side 301.
  • the polarization beam splitter 355 separates the reception beam 317 back into separate optical signals 318, 319 based on the polarization of those signals.
  • Optical signals 318 and 319 are converted back into electrical signals by detectors 1 and 2, 360 and 365, respectively.
  • Delay 370 is introduced to received data signal 361 in order to produce a delayed received data signal 363.
  • Delay 370 is substantially the same as delay 320, so that received data signal 363 is aligned with received data signal 362. Since delay 370 is introduced into to what was the vertically polarized optical signal 318, and since delay 320 was introduced to source data signal 311 prior to conversion to optical signal 314 with horizontal polarization, received data signal
  • FIGs. 4A and 4B illustrate details of a communications system similar to that described in connection with FIG. 2, and which uses wavelength division together with dichroic mirrors in order to implement the present invention.
  • the structure of FIGs. 4A and 4B generally corresponds to that of FIGs. 3 A and 3B except for the details of wavelength division and beam combination and separation. Thus, like elements have been similarly numbered and will not be explained in detail again.
  • FIG. 4 A specifically illustrates the transmission side 401 of the communications system of FIGs. 4A and 4B.
  • the delay output 313 is simply a delayed version of source data signal 311. In this way, signals 312 and 313 constitute temporally distinguishable transmission signals.
  • transmission signal 313 is converted into an optical signal 414 with a wavelength of 1.55 ⁇ .
  • modulation merely involves the turning on and off of laser 1 430, i.e., amplitude modulation. While amplitude modulation is described in connection with the structure of FIGs. 4 A and 4B, other types of modulation could be used without departing from the scope of the present invention.
  • Laser 1 430 can be the type discussed above in connection with the communications system 201 of FIG. 2 and having a wavelength of 1.55 ⁇ .
  • laser 1 430 can include the additional components necessary to effectuate the conversion described, as would be apparent to one skilled in the relevant art.
  • transmission signal 312 is converted into an optical signal 414 with a wavelength of 1.3 ⁇ .
  • signals 414 and 415 are modulated light signals having the frequencies indicated and representative of transmission signals 313 and 312, respectively.
  • Dichroic mirror 450 serves to combine signals 414 and 415 into a single transmission beam 416.
  • Dichroic mirror 450 is of the type known to those skilled in the relevant art. Dichroic mirror 450 allows one of the two optical signals having a first wavelenth, for example signal 415, to pass through while the other signal having a second wavelength, for example signal 414 is reflected off an internal surface and caused to be co-incident with the first signal 415.
  • the output is a single transmission beam 416 that includes both optical signals 414 and 415.
  • FIG.4B illustrates of the receiver side 402 of the communications system of FIGs. 4A and 4B.
  • the input to the receiver side is reception beam 417.
  • Reception beam 417 corresponds to transmission beam 416 after having passed through the a turbulent medium and so may differ from transmission beam 416 at least to the extent that fading has occurred.
  • Reception beam 417 is input into a dichroic mirror 455 similar to dichroic mirror 450 used at the transmitter side 401.
  • the dichroic mirror 455 separates the reception beam 417 back into separate optical signals 418, 419 based on the frequency of those signals.
  • Optical signals 418 and 419 are converted back into electrical signals by detectors 1 and 2, 460 and 465, respectively.
  • signals 461 and 462 represent received data signals.
  • Delay 370 is introduced to received data signal 461 in order to produce a delayed received data signal 463. As discussed above in connection with FIGs.
  • delay 370 is substantially the same as delay 320, so that received data signal 463 is aligned with received data signal 462. Since delay 370 is introduced into to what was optical signal 418, and since delay 320 was introduced to source data signal 311 prior to conversion to optical signal 414, received data signal 462 and delayed received data signal 463 should correspond to received versions of transmission data signals 311 and 312, respectively. Thus, by OR-ing signals 463 and 462 together at logic gate 380, an output data signal 390 can be produced in substantially the same manner as that discussed above in connection with the structure of FIGs. 3A and 3B.
  • FIGs. 3A, 3B, 4A, and 4B illustrate embodiments that include a single delay signal and a single type of modulation
  • the present invention is not so limited. Multiple delayed signals and multiple types of modulation can be used without departing from the scope of the present invention.
  • FIG. 5 A illustrates a transmitter side 501 of a communications system including a plurality of delayed signals and division schemes
  • FIG. 5B illustrates a receiver side 502 of the same communications system.
  • data source 210 is duplicated into four data source signals, three of which are subject to delays of times thyroid t 2 , and t 3 at delay elements 531, 532, and 533, respectively.
  • four temporally distinguishable transmission signals can be combined into a singe transmission beam through the use of lasers 1 520, 2 522, 3 353, and 4 524, two polarizing beams splitters 540, 541, and a single dichroic mirror 555, in the manner illustrated.
  • transmitter 501 illustrates one way of combining multiple wavelengths and polarizations, other combinations would not depart from the scope of the present invention, as would be apparent to one skilled in the relevant art given this disclosure.
  • the receiver 502 of FIG. 5B illustrates a slightly different arrangement in order to show that various arrangements are possible.
  • Receiver 502 of FIG. 5B uses polarizing beam splitter 555, dichroic mirrors 560 and 565, and detectors 1 571, 2 572, 3 573, and 4574 to separate the received beam and convert it into received data signals in the manner as shown.
  • appropriate delays t 4 , t 5 , and t ⁇ are introduced at delay elements 581, 582, and 583, respectively. Since the output of detector 1 571, corresponds to the original data signal subject to the longest transmission delay (note that detector 1 corresponds to the horizontally polarized 1.55 ⁇ optical signal originally subject to delay t 3 ) no delay is necessary.
  • the delay elements 581, 582, and 583 must be chosen such that the total delay associated to each received data signals is substantially equal to delay t 3 .
  • t was 1 millisecond
  • t 2 was 2 milliseconds
  • t 3 was 3 milliseconds
  • t 4 should be 2 milliseconds since the horizontally polarized 1.3 ⁇ optical signal corresponds to the source data signal subject to a 1 millisecond delay.
  • t 5 should be 1 millisecond since the vertically polarized 1.55 ⁇ optical signal corresponds to the source data signal subject to a 2 millisecond delay.
  • t 6 should be 3 milliseconds since the vertically polarized 1.3 ⁇ optical signal corresponds to the source data signal that was not subject to delay.
  • FIG. 6 is an illustration of a process flow diagram of a routine for optical communication through a turbulent medium 600 according to the present invention.
  • a source data signal is input.
  • a source data signal can be a digital signal representative of any desired information.
  • a data rate of the source data signal is limited only by the switching speed of the various components used to implement routine 600, as would be apparent to one skilled in the relevant art.
  • a set of temporally distinguishable transmission signals is created. Such a set is created by creating at least one duplicate of the input source data signal and then adding an appropriate delay to one of the data signals within the set.
  • the set of temporally distinguishable data signals can include a non-delayed signal and at least one additional signal distinguishable from the non-delayed signals through the addition of an appropriate delay.
  • Such an appropriate delay can be at least approximately 1 millisecond according to the present invention.
  • the delay is between approximately 1 millisecond and approximately 10 milliseconds. More preferably, the delay should be between approximately 5 and approximately 10 milliseconds.
  • the set of temporally distinguishable transmission signals created in step 620 can include multiple delayed transmission signals with varying delay times.
  • step 630 the set of temporally distinguishable transmission signals are converted to light signals.
  • This step 630 can be performed through modulation of one or more light sources with the transmission signals from step
  • Such modulation can include amplitude, frequency, phase, or polarization modulation, or a combination of these.
  • a light source can include a laser or LED beam.
  • a 1.3 micron ( ⁇ ) or a 1.55 ⁇ laser can be used as a light source.
  • the laser can be a pig-tailed laser diode.
  • the laser output can be boosted with an erbium doped fiber amplifier (EDF A) and can be collimated to prevent spreading as would be apparent to one skilled in the relevant art.
  • the laser can be fiber coupled.
  • Other light sources or modulation techniques could be used with departing from the scope of the present invention.
  • different wavelengths, polarizations, etc. can be used during step 630 in order to accomplish wavelength division, polarization division, etc.
  • Step 640 the light signals produced in step 640 are transmitted.
  • Step 640 can include combining the light signals into a single transmission beam through the use of one or more polarizing beam splitters, dicrhoic mirrors, and the like. Beam steering can also be performed during the transmission step 640 in order to maintain contact with a receiver, as would be apparent to one skilled in the relevant art.
  • a next step 650 the light signals transmitted in step 640 are received.
  • the receiving step 640 can include separating a received beam into various component received light signals through the used of one or more polarizing beam splitters, dichroic mirrors, and the like.
  • a next step 660 the received light signals are detected to obtain corresponding received data signals.
  • detection thus includes conversion of the light signal into an electrical signal with any additional steps necessary to produce a received data signal generally corresponding to one of the set of temporally distinguishable transmission signals created in step 620, above, as would be apparent to one skilled in the relevant art given this disclosure.
  • the received data signals are temporally adjusted and combined to produce a single output data signal.
  • temporal adjustment involves introducing appropriate delays into to the received data signals so as to temporally align the received data signals.
  • Such temporal alignment can involve quartz controlled resynchronization with precise use of clock frequencies as would be apparent to one skilled in the art.
  • headers can be placed within the data signals as appropriate to aid in resynchronization.
  • the received data signals are combined to produce a single output data signal. This combination can be accomplished through the use of a logic gate.
  • the temporally aligned received data signals can be input to an OR-gate so as to produce a single output data signal.
  • Other combination techniques could be used without departing from the scope of the present invention.
  • One application of the present invention is in optical wireless communications for short-range, high data rate links as found in a local area network (LAN) or other type of network.
  • the present invention can be used in packet-switched networks to achieve higher data transmission.
  • the present invention can be used as a link in any type of public or proprietary network.
  • the present invention can be a bridge between networks.
  • the present invention can be used to bridge gaps in ground-based networks as well as ground-to-satellite -22-
  • the present invention can be used to provide links between different sites on different office buildings. This is especially helpful where it is impractical to install fiber optic cable or other types of links due to cost, regulation or physical impediments.
  • optical wireless links as in the present invention can provide physically secure, covert, low probability of detection communications.
  • Optical wireless links as in the present invention can further be used to carry outside television broadcasts, such as, sporting events. No infra-structure cables need to be laid. The power requirement of a compact optical link are low and battery-powered operation is feasible.
  • the inventor has demonstrated that delayed diversity significantly reduces fading on a 1 km test range using a 633 nm laser transmitter working at eye-safe intensity levels.
  • Fading can be understood further as follows. If the average optical power reaching the reaching the receiver is , P and the minimum received power for adequate link performance is P, , then for scintillations that cause the instantaneous received power P to be below P t , a fade results.
  • the fraction of observation time during which the link is in a "fade" condition depends on the strength of the turbulence, as reflected in the statistics of turbulence induced fluctuation of P, P t .
  • the fractional fade time can be computed for certain models of the turbulence, as is shown in an attached Appendix. It can be seen that the fractional fade time increases as the "link margin" P - P t decreases, as the strength of the
  • n The constant C— that appears in Eq. (4) is called the refractive index structure n constant, it is measured in units of m "2/3 and is the most common parameter used to describe the strength of atmospheric turbulence. Its value near the ground typically varies from 10 "16 to 10- 13 m- 23 .
  • the C% (r) parameter will be a constant along the path.
  • ⁇ j may be larger than 25.
  • Eq.(22) can be used to predict the likelihood of received signal level falling below a specified value.
  • Eq.(22) can be used to predict the likelihood of received signal level falling below a specified value.
  • this can be characterized as a. fade.
  • NEP noise equivalent power
  • the NEP is usually defined as the optical input power that provides a signal equal to the noise. This will depend on bandwidth, which itself varies for a given bit rate depending on the precise modulation scheme used. For example, a return-to-zero (RZ) format requires double the bandwidth of a non-return-to-zero format (NRZ). The bandwidth requirement can also increase if error correction is inco ⁇ orated into the data system.
  • FIG. 7A shows some calculations from Eq. (25). The figure shows the fraction of the time that a fade of a given depth will occur for various levels of intensity variance. However, even though the fading characteristics on the link can be calculated in this way, this does not directly predict what will happen to the BER.
  • the received detector signal corresponding to a "one" has a steady value (I), and normalized received signal is 1.
  • the BER can be calculated by assuming that errors result from received noise, which is assumed to be Gaussian distributed about zero. For a detector whose noise is Gaussian distributed about zero with a variance (i 2 N ) the probability that the noise is below a set level i, is
  • the minimum BER results in this case for a decision level setting corresponding to x 2: the decision level lies halfway between the signal levels corresponding to a "one" and a "zero".
  • the BER is a function of S/N is shown for this case in Fig. (7B).
  • the S / N ratio must be 141, or 21.5dB, which requires an input optical signal 11.89 times higher than the noise equivalent power (NEP).
  • the NEP is usually defined as the optical input power that provides a signal equal to the noise. This will depend on bandwidth, which itself varies for a given bit rate depending on the precise modulation scheme used.
  • a return-to-zero (RZ) format requires double the bandwidth of a non-return-to-zero format (NRZ).
  • the bandwidth requirement can also increase if error correction is inco ⁇ orated into the data stream.
  • minimum BER is obtained by setting the detection threshold for a "one" half way between 0 and the received signal level when a "one” is actually received. In this case noise makes equal contributions to errors where "ones" are detected as “zeros” and vice versa. If the threshold level is raised above a normalized value of j , then the probability of
  • Figs. (7C) to (7F) show calculations of BER for different levels of intensity variance, and for different settings of the threshold setting for detection of a "one". It is clear that delayed diversity can significantly improve the performance of the link, especially as the turbulence gets stronger. Changing the threshold detection value from the y value can provide a significant improvement in bit-error-rate performance, provided the link has adequate power margin. This is likely to be an adjustment that would, ideally, be made dynamically with a "smart" system that can spot the change in error performance.
  • FIG. 7G shows experimental data from experiments carried out on the
  • a low frequency modulated bit stream was produced with a chopping wheel.
  • Two orthogonally polarized beams were transmitted downrange and detected independently with a receiver system inco ⁇ orating two photodiodes and a polarizing beam splitter.
  • the receiver had an aperture of 30mm.
  • the laser beam was expanded at the transmitter to approximately 30mm diameter, and was allowed to diverge as it propagated downrange.
  • the beam diameter at the receiver was on the order of 2m, which eliminated any need for beam steering or tracking.
  • the centroid of the received beam wandered about, either because of temperature variations, or because of some mechanical instability of the transmitter.
  • FIGs. 7H-7N show additional data recorded at the University of Maryland test range. These data show both C a n variations during the course of the day on various occasions, time varying background light levels, intensity histograms, and the consistent reduction in fading that can be achieved with the delayed diversity approach. Aperture Averaging
  • a receiver In the practical operation of a line-of-sight communication link, a receiver will collect part of the wavefront that has been transmitted down range through the turbulent atmosphere. If the receiver has a small collection area then the variance of the intensity that it will see is determined by the range length L, and the turbulence level as discussed above. An assessment must be made for a given range / wavelength / C 2 coast scenario whether the turbulence is weak or strong, and then the expected intensity variance calculated. Or, this may be carried out in reverse: the intensity variance is measured, and then the performance of the link can be assessed. If the area of the receiver is increased, then the intensity variance decreases.
  • D is the diameter of the receiver aperture
  • K(p) arccos( /£>) - (pi D)[ ⁇ - (p 2 ID 2 )]' 2 . (35)
  • G (D) represents the intensity variation seen with the actual receiver relative to a point receiver.
  • D the intensity variation seen with the actual receiver relative to a point receiver.
  • a receiver whose diameter satisfies D « * ⁇ L will behave as a point receiver.
  • FIGs. (70) and (7P) show aperture averaging calculations for the following optical link conditions: a 1.3 ⁇ m laser and a 1km range.
  • Fig. (70) shows aperture averaging for three different degrees of "weak” turbulence, specified by the effective C 2 hinder calculated from Eq. (9).
  • Fig. (7P) shows aperture averaging for three different degrees of "strong" turbulence.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Radio Transmission System (AREA)
  • Optical Communication System (AREA)

Abstract

La présente invention concerne un système et un procédé de communication optique non filaire peu susceptible de fading. Une logique de diversité à retard permet en l'occurrence de diminuer de façon importante les phénomènes de fading. Les données sont envoyées en un jeu de signaux lumineux (également appelés signaux lumineux en diversité) différant l'un de l'autre par la polarisation et/ou la longueur d'ondes. Ces signaux lumineux en diversité diffèrent également temporellement dans la mesure où ils sont émis en décalage temporel l'un par rapport à l'autre. Il en résulte que chaque signal lumineux se propage dans l'atmosphère via deux canaux sans corrélation. Au niveau d'un récepteur, les données de chaque signal lumineux reçu sont temporellement recalées puis combinées en un unique signal numérique de sortie. Une combinaison des signaux lumineux en diversité reçus permet alors une bonne précision pour chaque bit dans le signal numérique de sortie. Ainsi, même en cas de fading affectant l'un des signaux lumineux en diversité dans l'un des canaux, il reste possible de produire un signal numérique de sortie combiné à un niveau de précision relativement élevé à partir des données d'origine transportées par l'un au moins des signaux lumineux en diversité.
PCT/US2000/018200 1999-06-30 2000-06-30 Systeme et procede de communication optique non filaire WO2001006663A2 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US10/018,957 US7106971B1 (en) 1999-06-30 2000-06-30 System and method for optical wireless communication
AU15683/01A AU1568301A (en) 1999-06-30 2000-06-30 System and method for optical wireless communication

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US14158799P 1999-06-30 1999-06-30
US60/141,587 1999-06-30

Publications (2)

Publication Number Publication Date
WO2001006663A2 true WO2001006663A2 (fr) 2001-01-25
WO2001006663A3 WO2001006663A3 (fr) 2001-08-09

Family

ID=22496332

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2000/018200 WO2001006663A2 (fr) 1999-06-30 2000-06-30 Systeme et procede de communication optique non filaire

Country Status (2)

Country Link
AU (1) AU1568301A (fr)
WO (1) WO2001006663A2 (fr)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1231732A1 (fr) * 2001-02-03 2002-08-14 Alcatel Méthode pour la transmission de signaux optiques en espace libre
EP1411652A2 (fr) * 2002-10-14 2004-04-21 Deutsches Zentrum für Luft- und Raumfahrt e.V. Méthode de réduction de l'évanouissment apparaissant lors d'une communication optique en espace libre
EP1475905A2 (fr) * 2003-05-08 2004-11-10 Deutsches Zentrum für Luft- und Raumfahrt e.V. Procédé de transmission optique de signeaux numériques
WO2005002102A1 (fr) * 2003-06-13 2005-01-06 The Regents Of The University Of California Procede de correction d'erreur sans voie de retour resistant a l'evanouissement destine a des systemes de transmission optique dans l'espace
EP2083522A1 (fr) 2008-01-23 2009-07-29 Deutsches Zentrum für Luft- und Raumfahrt e.V. Procédé destiné à la transmission d'espace vide optique atmosphérique de signaux numériques et récepteurs pour le procédé
US7574137B1 (en) * 2006-05-05 2009-08-11 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Multi-wavelength time-coincident optical communications system and methods thereof
US9264136B2 (en) 2002-02-22 2016-02-16 Mikko Kalervo Vaananen Broadband wireless communication system and method
CN114465665A (zh) * 2022-01-24 2022-05-10 桂林电子科技大学 一种强湍流信道下基于最大比合并的光束成形方法

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4809257A (en) * 1985-04-02 1989-02-28 International Business Machines Corporation Hierarchical distributed infrared communication system
US5515438A (en) * 1993-11-24 1996-05-07 International Business Machines Corporation Quantum key distribution using non-orthogonal macroscopic signals
US5557443A (en) * 1993-12-09 1996-09-17 Matsushita Electric Industrial Co., Ltd. Optical communication method and optical remote controller
US5675648A (en) * 1992-12-24 1997-10-07 British Telecommunications Public Limited Company System and method for key distribution using quantum cryptography
US5737366A (en) * 1995-12-29 1998-04-07 Lucent Technologies Inc. Method and apparatus for receiving line encoded bursts of information
US5757912A (en) * 1993-09-09 1998-05-26 British Telecommunications Public Limited Company System and method for quantum cryptography
US5793509A (en) * 1994-07-07 1998-08-11 Gpt Limited Telecommunications network

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4809257A (en) * 1985-04-02 1989-02-28 International Business Machines Corporation Hierarchical distributed infrared communication system
US5675648A (en) * 1992-12-24 1997-10-07 British Telecommunications Public Limited Company System and method for key distribution using quantum cryptography
US5757912A (en) * 1993-09-09 1998-05-26 British Telecommunications Public Limited Company System and method for quantum cryptography
US5515438A (en) * 1993-11-24 1996-05-07 International Business Machines Corporation Quantum key distribution using non-orthogonal macroscopic signals
US5557443A (en) * 1993-12-09 1996-09-17 Matsushita Electric Industrial Co., Ltd. Optical communication method and optical remote controller
US5793509A (en) * 1994-07-07 1998-08-11 Gpt Limited Telecommunications network
US5737366A (en) * 1995-12-29 1998-04-07 Lucent Technologies Inc. Method and apparatus for receiving line encoded bursts of information

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1231732A1 (fr) * 2001-02-03 2002-08-14 Alcatel Méthode pour la transmission de signaux optiques en espace libre
US10530476B2 (en) 2002-02-22 2020-01-07 Mikko Kalervo Vaananen Broadband wireless communication system and method
US9264136B2 (en) 2002-02-22 2016-02-16 Mikko Kalervo Vaananen Broadband wireless communication system and method
DE10247882B4 (de) * 2002-10-14 2005-03-10 Deutsch Zentr Luft & Raumfahrt Verfahren zum Verringern von bei optischer Freiraum-Kommunikation auftretenden Fading
EP1411652A2 (fr) * 2002-10-14 2004-04-21 Deutsches Zentrum für Luft- und Raumfahrt e.V. Méthode de réduction de l'évanouissment apparaissant lors d'une communication optique en espace libre
EP1411652A3 (fr) * 2002-10-14 2004-09-29 Deutsches Zentrum für Luft- und Raumfahrt e.V. Méthode de réduction de l'évanouissment apparaissant lors d'une communication optique en espace libre
DE10320814A1 (de) * 2003-05-08 2004-12-09 Deutsches Zentrum für Luft- und Raumfahrt e.V. Verfahren zur optischen Übertragung von digitalen Signalen
EP1475905A3 (fr) * 2003-05-08 2005-05-04 Deutsches Zentrum für Luft- und Raumfahrt e.V. Procédé de transmission optique de signeaux numériques
EP1475905A2 (fr) * 2003-05-08 2004-11-10 Deutsches Zentrum für Luft- und Raumfahrt e.V. Procédé de transmission optique de signeaux numériques
US7277644B2 (en) 2003-06-13 2007-10-02 The Regents Of The University Of California Fade-resistant forward error correction method for free-space optical communications systems
WO2005002102A1 (fr) * 2003-06-13 2005-01-06 The Regents Of The University Of California Procede de correction d'erreur sans voie de retour resistant a l'evanouissement destine a des systemes de transmission optique dans l'espace
US7574137B1 (en) * 2006-05-05 2009-08-11 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Multi-wavelength time-coincident optical communications system and methods thereof
EP2083522A1 (fr) 2008-01-23 2009-07-29 Deutsches Zentrum für Luft- und Raumfahrt e.V. Procédé destiné à la transmission d'espace vide optique atmosphérique de signaux numériques et récepteurs pour le procédé
DE102008005791B3 (de) * 2008-01-23 2009-11-19 Deutsches Zentrum für Luft- und Raumfahrt e.V. Verfahren zur atmosphärischen optischen Freiraumübertragung von digitalen Signalen und Empfänger für das Verfahren
CN114465665A (zh) * 2022-01-24 2022-05-10 桂林电子科技大学 一种强湍流信道下基于最大比合并的光束成形方法
CN114465665B (zh) * 2022-01-24 2024-04-02 桂林电子科技大学 一种强湍流信道下基于最大比合并的光束成形方法

Also Published As

Publication number Publication date
WO2001006663A3 (fr) 2001-08-09
AU1568301A (en) 2001-02-05

Similar Documents

Publication Publication Date Title
US7106971B1 (en) System and method for optical wireless communication
Davis et al. Effect of atmospheric turbulence on bit-error rate in an on-off-keyed optical wireless system
JP3014244B2 (ja) 光通信における偏光依存性の歪を補償する装置
Kedar et al. Urban optical wireless communication networks: the main challenges and possible solutions
Kaur et al. Comparative analysis of inter satellite optical wireless channel for NRZ and RZ modulation formats for different levels of input power
US20130071105A1 (en) High Speed Multi-Mode Fiber Transmissions via Orthogonal Wavefronts
CN112436934B (zh) 一种自调焦优化耦合的空间混沌激光保密通信系统及方法
WO2001006663A2 (fr) Systeme et procede de communication optique non filaire
Arikawa et al. Mitigation of fading caused by atmospheric turbulence with FMF coupling and maximum ratio combining used in 320-m free-space optical transmission of
Magidi et al. Review on wavelength division multiplexing free space optics
Alshaer et al. Hybrid MPPM-BB84 quantum key distribution over FSO channel considering atmospheric turbulence and pointing errors
Khan et al. FSO communication: benefits, challenges and its analysis in DWDM communication system
US6970651B1 (en) High-sensitivity tracking in free-space optical communication systems
Sharma et al. Literature survey and issue on free space optical communication system
JP2013543709A (ja) クロマトテンポラルエンコーディングを用いた波長分割多重伝送システムおよび方法
Trisno et al. Delayed diversity for fade resistance in optical wireless communications through turbulent media
Chaudhary et al. Next generation free space optics system in wireless communication technology
WO2002032020A1 (fr) Systeme hybride de communication sans fil combinant des canaux optiques et des canaux non optiques
Ruslan et al. Terrestrial free space optic propagation analysis considering Malaysia weather condition
AU2020103328A4 (en) PAVC- Improvement Techniques of Free Space Optical Link: PERFORMANCE ANALYSIS AND IMPROVEMENT TECHNIQUES OF FREE SPACE OPTICAL LINK IN VARIOUS ATMOSPHERIC CONDITIONS
Kaushal et al. Improvement of ground to satellite FSO link performance using transmit diversity in weak atmospheric turbulence
Roy et al. Performance analysis of multiple TX/RX free space optical system under atmospheric disturbances
Fayadh et al. Establishment network by using FSO link based on MD code for hybrid SCM-SAC-OCDMA wireless system
Bibi et al. A comprehensive survey of free-space optical communication–modulation schemes, advantages, challenges and mitigations
Yasser et al. M-ary ASK Modulation in FSO system with SIMO over log-normal atmospheric turbulence with pointing errors

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A2

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BY BZ CA CH CN CR CU CZ DE DK DM DZ EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT TZ UA UG US UZ VN YU ZA ZW

AL Designated countries for regional patents

Kind code of ref document: A2

Designated state(s): GH GM KE LS MW MZ SD SL SZ TZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN GW ML MR NE SN TD TG

121 Ep: the epo has been informed by wipo that ep was designated in this application
DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
AK Designated states

Kind code of ref document: A3

Designated state(s): AE AG AL AM AT AU AZ BA BB BG BR BY BZ CA CH CN CR CU CZ DE DK DM DZ EE ES FI GB GD GE GH GM HR HU ID IL IN IS JP KE KG KP KR KZ LC LK LR LS LT LU LV MA MD MG MK MN MW MX MZ NO NZ PL PT RO RU SD SE SG SI SK SL TJ TM TR TT TZ UA UG US UZ VN YU ZA ZW

AL Designated countries for regional patents

Kind code of ref document: A3

Designated state(s): GH GM KE LS MW MZ SD SL SZ TZ UG ZW AM AZ BY KG KZ MD RU TJ TM AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE BF BJ CF CG CI CM GA GN GW ML MR NE SN TD TG

WWE Wipo information: entry into national phase

Ref document number: 10018957

Country of ref document: US

REG Reference to national code

Ref country code: DE

Ref legal event code: 8642

122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase in:

Ref country code: JP