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WO2013001408A1 - Procédés de codage et de décodage de lumière codée - Google Patents

Procédés de codage et de décodage de lumière codée Download PDF

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Publication number
WO2013001408A1
WO2013001408A1 PCT/IB2012/053073 IB2012053073W WO2013001408A1 WO 2013001408 A1 WO2013001408 A1 WO 2013001408A1 IB 2012053073 W IB2012053073 W IB 2012053073W WO 2013001408 A1 WO2013001408 A1 WO 2013001408A1
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WO
WIPO (PCT)
Prior art keywords
sequence
light
light source
information
symbols
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/IB2012/053073
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English (en)
Inventor
Constant Paul Marie Jozef Baggen
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
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 Koninklijke Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Publication of WO2013001408A1 publication Critical patent/WO2013001408A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • H04B10/114—Indoor or close-range type systems
    • H04B10/116—Visible light communication

Definitions

  • the present invention relates to coded light, specifically in relation to methods for encoding and decoding coded light.
  • the invention also relates to corresponding information encoders and decoders.
  • LEDs light emitting diodes
  • LEDs have become sufficiently bright and inexpensive, to serve as a light source in for example illumination arrangements such as lamps with adjustable color.
  • illumination arrangements such as lamps with adjustable color.
  • An adjustable color lighting system is typically constructed by using a number of primary colors, and in one example, the three primaries red, green and blue are used. The color of the generated light is determined by the LEDs that are used, as well as by the mixing ratios. To generate "white", all three LEDs have to be turned on.
  • the illumination arrangement For further decreasing the energy consumption of the illumination arrangement it is possible to include light sensors and presence detectors, which will detect changes in ambient lighting and approaching persons, respectively. Such additions may in turn lead to a decrease in the time the illumination arrangement is active, as well as an intensity decrease by taking into account the ambient lighting.
  • a hardware component with the illumination arrangement for allowing some sort of communication between the different illumination arrangements, thereby further decreasing the energy consumption.
  • a number of wireless technologies have been developed, including for example RF transmission circuitry supporting IEEE 802.11.
  • RF transmission circuitry supporting IEEE 802.11 a problem with such wireless technologies are that they lead to a great increase of the cost of the illumination arrangement and thus the resulting lighting system.
  • IR infra-red
  • Manchester code is commonly used as a means to modulate coded light.
  • the above is at least partly met by a method for encoding an information sequence to be emitted as coded light by at least one light source, the method comprising the steps of receiving an input string representing the information sequence, dividing the input string into a plurality of pairs of bits, mapping each of the plurality of pairs of bits into one of four symbols based on a predetermined schedule, thereby forming a sequence of channel symbols, and providing the sequence of channel symbols to be emitted by the light source, wherein a pulse width of an active portion of each of the symbols of the sequence of channel symbols are based on a predetermined dimming level of light emitted by the light source.
  • the invention is based on the understanding that it may be possible to, in comparison to a Manchester type coding scheme, drastically increase the bit rate of transmitted information for a given bandwidth of the transmitted signal. This is achieved by upgrading the mapping scheme for each pair of bits by including an additional two waveforms/symbols, resulting in a total of four waveforms/symbols as compared to the only two waveforms/symbols used in Manchester coding.
  • the increased bit rate is provided by synchronizing the transmitter with the receiver and thereby allowing for information to be sampled at all clock transitions.
  • the transitions at the period boundaries do not carry information, they exist only to place the signal in the correct state to allow the mid-bit transition.
  • the four different waveforms/symbols each have a form that is based on a predetermined/desired dimming level of light that is to be emitted by the light source.
  • each pair of bits are mapped into one of four symbols based on a predetermined schedule; however the form of the waveform corresponding to a specific symbol is based on a dimming level of light to be emitted by the light source.
  • PWM pulse width modulation
  • the predetermined mapping schedule is preferably achieved by configuring each of the four symbols such that each comprises four binary symbol elements.
  • the mapping is implemented as 11— > -1,1,1,-1; 00— > 1,-1,-1,1; 01— > -1,-1,1,1; and 10— > 1,1,-1,-1.
  • the mapping as well as the encoding of the information sequence will be discussed in detailed below in the detailed description of the invention. Accordingly and in relation to an exemplifying embodiment, if each waveform has a fixed duration (symbol time), the time each ⁇ ' is "active" (duty cycle) is dependent on the desired diming level of light emitted by the light source.
  • a method for decoding an information sequence from a signal received from a light detector comprising the steps of receiving a sequence of channel symbols, calculating a first inner product between the sequence of channel symbols and a first matched filter, calculating a second inner product between the sequence of channel symbols and a second matched filter, the second matched filter being different from the first matched filter, and determining a pair of bits representing the portion of the information sequence based on the first and the second inner product.
  • the disclosed decoding method preferably matches the transmission of the information sequence being encoded using the above discussed encoding method and emitted by the light source.
  • two separate inner products are calculated using two different matched filters, and the results of these calculations are used for determining a corresponding symbol, preferably comprising a pair of bits forming part of a binary string.
  • the information sequence preferably comprises four binary symbol elements, so do the first and the second matched filters. More specifically, the first matched filter is preferably configured to have an essential a sinusoidal form and the second matched filter is preferably configured to have an essential cosinusoidal form.
  • the encoding method may be implemented in an information encoder preferably comprising a control unit configured to receive an input string representing the information sequence, divide the input string into a plurality of pairs of bits, map each of the plurality of pairs of bits into one of four symbols based on a predetermined schedule, thereby forming a sequence of channel symbols, and provide the sequence of channel symbols to be emitted by the light source, wherein a pulse width of an active portion of each of the symbols of the sequence of channel symbols are based on a predetermined dimming level of light emitted by the light source.
  • the decoding method may be implemented in an information decoder preferably comprising a receiver for receiving a sequence of channel symbols, a control unit configured to calculate a first inner product between the sequence of channel symbols and a first matched filter, calculate a second inner product between the sequence of channel symbols and a second matched filter, the second matched filter being different from the first matched filter, and determine a pair of bits representing the portion of the information sequence based on the first and the second inner product.
  • the information encoder and/or decoder may be provided as a separate unit, but may also be incorporated in with a light source of the lighting system or included in a socket of a light source.
  • the light source is preferably selected from a group comprising light emitting diodes (LEDs), organic light emitting diodes (OLEDs), polymeric light emitting diodes (PLEDs), inorganic LEDs, cold cathode fluorescent lamps (CCFLs), hot cathode fluorescent lamps (HCFLs), plasma lamps.
  • LEDs light emitting diodes
  • OLEDs organic light emitting diodes
  • PLEDs polymeric light emitting diodes
  • CCFLs cold cathode fluorescent lamps
  • HCFLs hot cathode fluorescent lamps
  • Fig. 1 illustrates a lighting system according to an embodiment
  • Fig. 2 illustrates a light source according to an embodiment
  • Fig. 3 illustrates an information decoder according to an embodiment
  • Fig. 4 - 6 illustrates exemplary Quadrature Manchester Encoding waveforms according to the invention at differently set duty cycles
  • Figs. 7a - 7d illustrate pulse trains for source symbols and channel symbols on the transmitter side according to currently preferred embodiments of the invention
  • Figs. 8a - 8d illustrate pulse trains for portion of the sequence of channel symbols and exemplary matched filters for the calculating inner products for the portion of the sequence of channel symbols.
  • a lighting system 1 comprises at least one light source, schematically denoted by the reference numeral 2.
  • the at least one light source 2 may be a luminaire and/or be part of a lighting control system, thus the lighting system 1 may be denoted as a coded lighting system.
  • a luminaire may comprise at least one light source 2.
  • the term "light source” means a device that is used for providing light in a space, for purpose of illuminating objects in the space.
  • a space is in this context typically an apartment room or an office room, a gym hall, a room in a public place or a part of an outdoor environment, such as a part of a street.
  • Each light source 2 is capable of emitting coded light, as schematically illustrated by the arrow 6.
  • the emitted light thus comprises a modulated part associated with coded light comprising information sequences.
  • the emitted light may also comprise an un-modulated part associated with an illumination contribution.
  • Each light source 2 may be associated with a number of lighting settings, inter alia pertaining to the illumination contribution of the light source, such as color, color temperature and intensity of the emitted light. In general terms the
  • illumination contribution of the light source may be defined as a time-averaged output of the light emitted by the light source 2.
  • the light source 2 will be further described with reference to Fig. 2.
  • the at least one light source 2 emits information sequences via the visible light 6. Before the information sequences are emitted via the visible light 6, it is mapped to a sequence of channels symbols to form a modulated signal. This modulated signal may then act as a control signal to drive the at least one light source. The control signal may thereby determine the pulse train which switches the at least one light source 2 between emitting light (in an "ON"-state) and not emitting light (in an "OFF"-state).
  • the lighting system 1 further comprises an apparatus, termed an information decoder 4.
  • the information decoder 4 is arranged to decode an information sequence from coded light emitted by the at least one light source 2.
  • the information decoder 4 will be further described with reference to Fig. 3.
  • the lighting system 1 may further comprise other devices 10 arranged to control and/or provide information to the at least one light source 2.
  • Fig. 2 schematically illustrates, in terms of a number of functional blocks, a light source 2.
  • the light source 2 comprises an emitter 14 for emitting coded light.
  • the emitter 14 may comprise one or more LEDs, but it could as very well comprise one or more FL or HID sources, etc.
  • the coding schemes may utilize multiple light sources.
  • a 3-level coding scheme may have two LEDs using the mappings (OFF, OFF) for the level "-A", (ON, OFF) for the level "0", and (ON, ON) for the level "+A”. How the levels are determined is disclosed below.
  • the emitter is controlled by a light driver 18.
  • the light driver 18 may comprise or be part of a processing unit 16 such as a central processing unit (CPU).
  • the light driver 18 comprises a receiver 20 and a transmitter 24.
  • the receiver 20 may be arranged to receive settings, control information, code parameters and the like.
  • the receiver 20 may be a receiver configured to receive coded light.
  • the receiver 20 may comprise an infrared interface for receiving infrared light.
  • the receiver 20 may be a radio receiver for receiving wirelessly transmitted information.
  • the receiver 20 may comprise a connector for receiving information transmitted by wire.
  • the wire may be a powerline cable.
  • the wire may be a computer cable.
  • Information pertaining to settings, control information, code parameters and the like may be stored in the memory 22.
  • the light driver 18 may receive information via the receiver 20 pertaining to an information sequence to be transmitted by means of coded light by the light source 2.
  • the light driver 18 may change the encoding of the coded light such that the coded light emitted by the emitter 14 comprises (an encoded version of) the information sequence.
  • the light driver 18 may be arranged to perform a number of functionalities.
  • the transmitter 24 is arranged to provide the light source 2 with the control signal and thereby drive the light source 2.
  • the light source 2 does not comprise a light driver.
  • the light driver 18 may then be part of the lighting system 1.
  • the information decoder 4 may be arranged to detect and receive light, such as coded light, comprising information sequences emitted by the at least one light source 2 as well as the light emitted by light sources outside the lighting system 1 (not shown). From the detected and received light the receiver 4 is arranged to determine information sequences transmitted by the at least one light sources 2.
  • a functional block diagram for an information decoder 4 according to an embodiment of the present invention is given in Fig. 3.
  • the information decoder 4 further comprises a processing unit 26 arranged to determine, from the signal, a plurality of bit pairs each forming part of the decoded information sequence. This is further explained in relation to Figs. 6a-d.
  • the information decoder 4 may further comprise a memory 28 and a transmitter 30.
  • the memory 28 may store instructions pertaining to the functionalities to estimate an information sequence.
  • the transmitter 30 may be utilized in order to communicate information to the at least one light source 2 in the lighting system 1.
  • each pair of bits from of the source sequence u, of length 2n are encoded into one of four QME symbols, each symbol, i, comprising a sequence of four binary symbol elements z 4i+j , where j ranges from 0 to 3.
  • the sequence of QME symbols makes an output symbol string y of length An.
  • each binary pair [ «2i «2i+i] is mapped onto QME symbol [z 4 i, ⁇ 41+1 , z 4 i +2 , z 4 i +3 ] as follows:
  • each QME symbol corresponds to one of the four basic waveforms shown in Fig.4 for modulating the visible light 6.
  • the light intensity atft corresponding to symbol z ; is such that the average light level a at a detector placed at an arbitrary but fixed distance from the transmitter is constant dc and the average variation of a is zero.
  • the duty cycle for the waveforms are shown to be 50%.
  • Figs.7a-d gives an example of an application of the proposed mapping.
  • a waveform representation for the source sequence u is illustrated in Fig.7b where each source bit has a time duration of T seconds.
  • the amplitude of the waveform is confined to the interval from -1 to +1, but in general it may be from -A to +A if amplitude modulation with amplitude A is used.
  • a waveform representation for the channel sequence z is illustrated in Fig.7d.
  • An inner product is then calculated between each of the groups of the sequence of channel symbols, e.g. z a , Zb, and two matched filters (shown in Figs.
  • the identification of the bit pair corresponding to a given group is determined by analyzing which inner product (i.e. the "inside-outside” inner product or the "left-right” inner product) that has got the largest absolute value as well as the sign of the inner product having the largest absolute value.
  • the "left-right" inner product for z a i.e. z a2
  • the sign is positive, i.e. +.
  • Zb also the "left-right" inner product, i.e. Zb 2 is identified to have the largest absolute value, i.e.
  • matched filters disclosed in Figs. 8a - d are designed to work independently of any duty cycle selected by the transmitter 24, e.g. the duty cycles as illustrated in Figs. 4 - 6. Additionally, the matched filters are also robust to amplitude modulation of the transmitted signal.
  • the communication of information sequences from the transmitter 24 to the receive 34 may be made robust at the same time as it is the mapping scheme allows for both pulse width and amplitude modulation of the signals for the purpose of allowing the visible light 6 to be dimmable.
  • amplitude modulation of the signals are used for dimming levels between e.g. 10% and 100% of the maximal light emission levels and pulse width modulation is used for dimming levels below 10%>.

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

Abstract

La présente invention concerne un procédé de codage d'une séquence d'informations devant être émise sous forme de lumière codée par au moins une source de lumière, le procédé comprenant les étapes consistant à recevoir une chaîne d'entrées représentant la séquence d'informations, diviser la chaîne d'entrées en une pluralité de paires de bits, mapper chaque paire de la pluralité de paires de bits sur l'un des quatre symboles sur la base d'un ordonnancement prédéfini, ce qui permet de former une séquence de symboles de canal; et générer la séquence de symboles de canal devant être émise par la source lumineuse, une largeur d'impulsion d'une portion active de chacun des symboles de la séquence de symboles de canal étant basée sur une gradation prédéfinie de l'intensité lumineuse émise par la source lumineuse. La présente invention présente des avantages liés à un débit binaire accru des informations transmises.
PCT/IB2012/053073 2011-06-29 2012-06-19 Procédés de codage et de décodage de lumière codée Ceased WO2013001408A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP11171845 2011-06-29
EP11171845.8 2011-06-29

Publications (1)

Publication Number Publication Date
WO2013001408A1 true WO2013001408A1 (fr) 2013-01-03

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015199538A1 (fr) * 2014-06-27 2015-12-30 Eldolab Holding B.V. Procédé pour attaquer une source de lumière, système d'attaque pour attaquer une source de lumière, et luminaire comprenant ladite source de lumière et ledit système d'attaque
WO2016034033A1 (fr) * 2014-09-05 2016-03-10 深圳光启智能光子技术有限公司 Procédés de codage et de décodage de signal optique, et dispositif
CN105471512A (zh) * 2014-09-05 2016-04-06 深圳光启智能光子技术有限公司 一种光子接收端及其解码方法
CN105471511A (zh) * 2014-09-05 2016-04-06 深圳光启智能光子技术有限公司 一种提高光信号传输可靠性的编解码方法、装置及系统
US9473248B2 (en) 2012-04-13 2016-10-18 Koninklijke Philips N.V. Method and device for visible light communication
WO2018120745A1 (fr) * 2016-12-29 2018-07-05 深圳光启智能光子技术有限公司 Procédé de codage, dispositifs d'envoi et de réception de signal, et procédé, devant être utilisés dans une communication optique
CN109104242A (zh) * 2017-06-21 2018-12-28 沃尔沃汽车公司 用于授权用户的方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070092264A1 (en) * 2005-09-30 2007-04-26 Nec Corporation Visible light control apparatus, visible light control circuit, visible light communication apparatus, and visible light control method
WO2009010916A2 (fr) * 2007-07-16 2009-01-22 Koninklijke Philips Electronics N.V. Commande d'une source lumineuse
US20090208221A1 (en) * 2006-10-23 2009-08-20 Hiroyuki Sasai Optical space transmission system using visible light and infrared light

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070092264A1 (en) * 2005-09-30 2007-04-26 Nec Corporation Visible light control apparatus, visible light control circuit, visible light communication apparatus, and visible light control method
US20090208221A1 (en) * 2006-10-23 2009-08-20 Hiroyuki Sasai Optical space transmission system using visible light and infrared light
WO2009010916A2 (fr) * 2007-07-16 2009-01-22 Koninklijke Philips Electronics N.V. Commande d'une source lumineuse

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9473248B2 (en) 2012-04-13 2016-10-18 Koninklijke Philips N.V. Method and device for visible light communication
WO2015199538A1 (fr) * 2014-06-27 2015-12-30 Eldolab Holding B.V. Procédé pour attaquer une source de lumière, système d'attaque pour attaquer une source de lumière, et luminaire comprenant ladite source de lumière et ledit système d'attaque
US9979477B2 (en) 2014-06-27 2018-05-22 Eldolab Holding B.V. Method for driving a light source, a driver system to drive a light source and a luminaire comprising said light source and driver system
WO2016034033A1 (fr) * 2014-09-05 2016-03-10 深圳光启智能光子技术有限公司 Procédés de codage et de décodage de signal optique, et dispositif
CN105471512A (zh) * 2014-09-05 2016-04-06 深圳光启智能光子技术有限公司 一种光子接收端及其解码方法
CN105471511A (zh) * 2014-09-05 2016-04-06 深圳光启智能光子技术有限公司 一种提高光信号传输可靠性的编解码方法、装置及系统
CN105471512B (zh) * 2014-09-05 2018-08-14 深圳光启智能光子技术有限公司 一种光子接收端及其解码方法
CN105471511B (zh) * 2014-09-05 2018-08-31 深圳光启智能光子技术有限公司 一种提高光信号传输可靠性的编解码方法、装置及系统
US10075238B2 (en) 2014-09-05 2018-09-11 Kuang-Chi Intelligent Photonic Technology Ltd. Methods and devices for optical signal encoding and decoding
WO2018120745A1 (fr) * 2016-12-29 2018-07-05 深圳光启智能光子技术有限公司 Procédé de codage, dispositifs d'envoi et de réception de signal, et procédé, devant être utilisés dans une communication optique
CN109104242A (zh) * 2017-06-21 2018-12-28 沃尔沃汽车公司 用于授权用户的方法

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