AU2007253450B2

AU2007253450B2 - Method and arrangement for transmission of data with at least two radiation sources

Info

Publication number: AU2007253450B2
Application number: AU2007253450A
Authority: AU
Inventors: Sebastian Randel; Harald Rohde
Original assignee: Osram GmbH
Current assignee: Osram GmbH
Priority date: 2006-05-24
Filing date: 2007-05-14
Publication date: 2010-07-29
Anticipated expiration: 2027-05-14
Also published as: JP2009538071A; CN101449492A; JP4637263B2; AU2007253450A1; KR101414671B1; EP2020102B1; CN101449492B; EP2020102A1; WO2007135014A1; ES2569935T3; DE102006024421B3; KR20090024726A

Description

- 1 Method and arrangement for transmission of data with at least two radiation sources The invention relates to a method and an arrangement for 5 transmission of data with at least two radiation sources. A radiation source whose intensity can be varied rapidly, that is to say with high frequency, can be utilized for transmitting data. This way of transmitting data has the 10 advantage, for example, of being less susceptible to electromagnetic interference. Furthermore, it is possible more easily than in the case of transmission by means of WLAN, for example, to block the signals. This can serve for example to keep the signals in a space. 15 Examples of radiation sources which can be rapidly modulated are light emitting diodes (LEDs) and laser diodes. It is known to perform an on/off keying for transmitting the 20 data, that is to say to switch the radiation source back and forth between an off state and an on state, Furthermore, it is known to operate an LED by means of OFDM (orthogonal frequency division multiplex) for transmission. 25 Against this background, it would be desirable to specify a method and an arrangement for transmission of data with at least two radiation sources by means of which an increased transmission rate can be achieved. 30 In accordance with a first aspect of the present invention there is provided a method for transmission of data with at - 2 least two radiation sources, the radiation sources emit radiation with in each case a definable intensity that is substantially constant on average over time. Furthermore, at least two of the intensities are varied with a respective 5 carrier frequency. At least one portion of the data is transmitted by means of a phase relationship of the carrier frequencies of at least two of the radiation sources among one another. 10 The radiation sources can be e.g. recombination radiation sources such as LEDs, laser diodes, thermal emitters such as incandescent bulbs, or fluorescent tubes. In this case, it is possible for all the radiation sources to be the same type of radiation source, e.g. a group of ten LEDS, but it is also 15 possible for a mixture of different types of radiation sources to be used, e.g. one fluorescent tube and two LEDs. At least two of the radiation sources are operated in such a way that they emit a definable intensity that is substantially 20 constant on average over time, wherein the intensities are varied with a respective carrier frequency. The average over time therefore relates e.g. to at least one period duration of the carrier frequency. 25 A phase relationship of the carrier frequencies of at least two of the radiation sources among one another is used for transmitting at least one portion of the data. By way of example, for a coding of a bit, in the case of a 0 (zero), it is possible to use the same phase angle for two radiation 30 sources, while for a 1 (one) the phases of the radiation sources can be shifted relative to one another, e.g. by 180*.

--3 Other phase angles are also possible. A further possibility consists in using e.g. the phase angles of more than two radiation sources in order to code in each case a plurality of bits in a clock cycle. Further possibilities arise by using a 5 known method for frequency and/or phase modulation wherein a relationship between the phase angles of two radiation sources is additionally used. Examples of known modulation methods are, inter alia: 10 - phase shift keying, PSK; - differential phase shift keying, DPSK; - frequency division multiplex, FDM; - quadrature amplitude modulation, QAM; - minimum shift keying, MSK; 15 - quadrature phase modulation, QPM. With some of the methods it is already possible to transmit a plurality of bits in a clock cycle. 20 The method according to the invention makes it possible to increase the data rate and/or to improve the transmission quality. Preferably, at least one radiation source is used for emission 25 of visible light. This makes it possible, for example, without an additional light source, to realize an indication of whether data are currently being transmitted, e. g. by virtue of the radiation source always being switched off if no data are currently to be transmitted. 30 - 4 Preferably, the intensities of at least one portion of the radiation sources are defined in such a way that the radiation is suitable for illumination. This affords the advantage that data transmission and illumination, e. g. of a room, can be 5 performed simultaneously by means of the radiation sources. As an alternative or in addition a radiation source can also be used for emission of non-visible light, in particular infrared or ultraviolet radiation. This affords the advantage 10 that it is possible to use a phase relationship between the radiation source for emission of non-visible light and at least one further radiation source for transmission of at least one portion of the data. This results in improved security since e.g. ultraviolet radiation does not penetrate 15 through a glass pane. Since receiving the data also necessitates receiving the ultraviolet radiation, the data can no longer be received behind the glass pane. It is possible for the intensities of at least two of the 20 radiation sources to be different. A definable type of illumination can be obtained as a result. By way of example, when a plurality of LEDs of different colors are used, a definable overall light color can be achieved. 25 In one advantageous configuration of the invention, spectra of the radiation sources substantially do not overlap. This is understood to mean, for example, that in a spectral range emitted by one of the radiation sources, the other radiation sources emit only low intensity, as is the case e.g. with LEDs 30 of different colors. It is expedient to use at least one radiation source whose radiation substantially contains - 5 precisely one wavelength, in particular an LED. This avoids a crosstalk of the signals of the individual radiation sources and thus reduces the susceptibility of the transmission to interference. This results in a higher transmission rate. 5 In one advantageous configuration of the invention, for at least one intensity, the variation extent to which it is varied is small in comparison with the intensity, in particular less than 10% of the intensity, and in a particular 10 configuration less than 1% of the intensity. What is achieved as a result is that the intensity appears largely constant including at a carrier frequency discernable to the eye. Furthermore, it has the advantage that the intensity can thereby be chosen to be close to a maximum possible intensity 15 for the radiation source. In a further advantageous development of the invention, at least one carrier frequency is greater than 100 Hz, in particular equal to 100 kHz. What is thereby achieved is that 20 the intensity of the corresponding radiation source appears to be constant to the human eye. Furthermore, the use of a high carrier frequency has the advantage of enabling a high data rate. 25 In a further advantageous development of the invention, the carrier frequencies are identical. This results in a simplification when receiving the data, since the same frequency can always be sampled. It is therefore possible here to make use of the fact that a plurality of carriers of 30 identical frequency and identical phase angle can be used to transmit data.

- 6 The arrangement for transmission of data has at least two radiation sources for emission of radiation with in each case a definable intensity that is substantially constant on average over time, which are configured in such a way that at 5 least two of the intensities are varied with a respective carrier frequency and at least one portion of the data is transmitted by means of a phase relationship of the carrier frequencies of at least two of the radiation sources among one another. 10 Further details and advantages of the invention are explained in more detail on the basis of exemplary embodiments illustrated in the drawing, in which: 15 figure 1 shows a room with a group of three LEDs as illumination and data source figure 2 shows a schematic construction of a receiving unit 20 figure 3 schematically shows the phase profile of three color components The exemplary room illustrated in figure 1 is illuminated by a lamp A. The lamp A contains 30 LEDs. Of these 10 LEDs are red 25 LEDs, 10 are green LEDs and 10 are blue LEDs. The room furthermore contains a table with a computer C situated thereon. A heating regulator H for regulating a room heating is situated on a wall of the room R. 30 Both the computer C and the heating regulator H have a receiving device with which they can receive data transmitted by the lamp A. An exemplary, schematically represented construction of the receiving unit is depicted in figure 2. The receiving unit has three photodiodes with narrowband optical filters F. The filters F are configured such that the 5 respective photodiode P receives only the signal from a respective group of LEDs of the lamp A. One of the photodiodes P therefore receives the red, one the green and one the blue light component. The outputs of the photodiodes P are connected to an electronic evaluation circuit W, which 10 provides for clock recovery and, by means of a phase comparator, determines the data from the phase angle of the LED signals with respect to one another. In a first exemplary embodiment, bits of the data to be 15 transmitted are intended to be coded at the transmitter end in the following manner: if all three color components, that is to say the red, green and blue light, have the same phase angle, then this corresponds to the bit sequence "00", that is to say two successive zeros. If the red and blue color 20 components are in phase and the green color component is in antiphase, that is to say if the green color component has a phase angle offset by 1800, then this corresponds to the bit sequence "01". If the red and green color components are in phase and the blue color component is in antiphase, this 25 corresponds to the bit sequence "10". If the blue and green color components are in phase and the red color component is in antiphase, this corresponds to the bit sequence "11". In a second exemplary embodiment, it is additionally possible 30 to use a plurality of phase angles for a color component. Thus, by way of example, the carrier frequencies of the color -8 components can have in each case two components offset by 450 in terms of the phase angle. These offset components can be used in each case independently of one another. As a result, the coding procedure used for the first exemplary embodiment 5 can be used doubly in the same time. It is thereby possible to obtain double the transmission rate. Figure 3 shows an exemplary profile of the intensities R, G, B of the color components of the lamp A, that is to say of its 10 LEDs. It is assumed here that all 10 LEDs in each case have the corresponding intensity profile since the signal strength is the highest by this means. However, it is also possible for just a portion of the LEDs to be operated in this way, while the remaining portion of the LEDs has a constant intensity. 15 This last can be useful e.g. when the LEDs of a color component are distributed over a large distance, which, as a result of propagation distance differences, would lead to an obscuration of the phase angle and thereby to greater susceptibility to interference. 20 Figure 3 shows a green intensity profile G, a red intensity profile R and a blue intensity profile B. The carrier frequency used here corresponds to 100 kHz, corresponding to a period duration of 10 ps in accordance with figure 3. The 25 light amplitude can be a measure of the light intensity, on the one hand, or alternatively involve a drive voltage for the LEDs L of the lamp A. The on average constant intensities of the LEDs in accordance 30 with figure 3 would lead to an orange light hue at the lamp A. On account of the very high carrier frequency, the -9 fluctuations of the intensities R, G, B are not visible to the human eye and the LEDs L and thus the lamp A emit an apparently constant brightness. Besides the carrier frequency of 100 kHz used here, other carrier frequencies can also be 5 chosen, for example 20 MHz or 10 kHz. The three carrier frequencies illustrated for the color components have sudden phase changes. The phase angle of the color components with respect to one another serves for coding 10 bits as described in the first exemplary embodiment. Within the first 10 ps, all three color components are identical in phase. During the second 10 ps, the red color component is in antiphase, during the third 10 ps all three color components are identical in phase again, and during the fourth 10 ps the 15 green color component is in antiphase. The bits transmitted by means of the phase angles are indicated as numerals in the lower part of figure 3. Thus, the bit sequence "00110001" is transmitted by means of the 20 exemplary intensity profile given in figure 3. The data transmitted in this way by the lamp A and thus the LEDs L can be received by the computer C, for example. By way of example, data from the Internet that are requested by the 25 computer C can be involved in this case. Furthermore, the heating regulator H can also receive data from the lamp A. By way of example, data which serve for controlling the heating systems in the room R are of interest to the heating regulator H. Said data can be communicated to the heating regulator H 30 for example externally via mobile telephone or by a central control system.

-- 10 It is possible that the mechanical separation of the light sources from one another, that is to say e.g. the use of two LEDs arranged alongside one another, leads to an influencing of propagation distance differences with respect to the 5 receiver. If e.g. a carrier frequency of 1 MHz is used, this corresponds to a wavelength of approximately 300m. If two light sources are fitted remotely from one another, e.g. at a distance of 100m from one another in a sports hall, then a significant and unpredictable phase shift can result. 10 A phase shift by 180' between color components at the transmitter end can therefore lead to a fixed, but unpredictable phase shift at the receiver, under certain circumstances even to in-phase coincidence. Therefore, it is 15 expedient to perform at the receiver firstly a synchronization that makes it possible, by means of a suitable preamble prefixed by the transmitter, for the receiver to determine the phase shift between the components that is brought about by the geometry. The actual reception of the data can then be 20 begun. An alternative to synchronization consists in using, instead of the absolute phase angle of the color components with respect to one another, a change in the phase angles for the 25 coding of bits. By this means, the absolute phase angle of the color components becomes unimportant at the receiver. However, changes in the phase angle arrive unchanged at the receiver. If the lamp A is switched off, transmission of data is no 30 longer readily possible. In order nevertheless to enable a transmission, it is possible, instead of totally turning off - 11 the lamp A, for example, merely to reduce its intensity to an extent such that it emits in daylight, for example, light no longer perceptible to a human eye. It thus appears switched off, while a data transmission is still possible. In this 5 case, a reduced intensity leads to a lower signal-to-noise ratio. This in turn leads e.g. to a lower data transmission rate. A third exemplary embodiment of the method according to the 10 invention arises by virtue of the fact that a further, ultraviolet LED is used in addition to the three color components of the lamp A used in the previous exemplary embodiments. Besides the walls of the room, the radiation of the ultraviolet LED is also unable to penetrate through the 15 windows of the room and therefore cannot be received outside the room provided that there are no doors or other openings. In the third exemplary embodiment, the relative phase angles of the now four color components are used to code a bit 20 sequence comprising three bits in one step. Since the ultraviolet color component cannot be received outside the room, a decoding of the transmission outside the room cannot take place even if the signals of the other three color components can be received. By this means, increased security 25 against interception is achieved, while illumination of the room with the lamp A and data transmission are simultaneously made possible.

Claims

1. A method for transmission of data with at least two radiation sources, wherein: 5 - the radiation sources emit radiation with in each case a definable intensity that is substantially constant on average over time; - at least two of the intensities are varied with a respective carrier frequency; 10 - at least one portion of the data is transmitted by means of a phase relationship of the carrier frequencies of at least two of the radiation sources among one another.

2. The method as claimed in claim 1, wherein at least one of 15 the radiation sources is used for emission of visible light.

3. The method as claimed in claim 1 or 2, wherein at least one of the radiation sources is used for emission of non visible light, in particular infrared or ultraviolet 20 radiation.

4. The method as claimed in any one of the preceding claims, wherein the intensities of at least one portion of the radiation sources are defined in such a way that the radiation 25 is suitable for illumination.

5. The method as claimed in any one of the preceding claims, wherein the intensities of at least two of the radiation sources are different. 30

6. The method as claimed in any one of the preceding claims, - 13 wherein the spectra of the radiation sources substantially do not overlap.

7. The method as claimed in any one of the preceding claims, 5 wherein at least one radiation source is used, whose radiation substantially contains precisely one wavelength, in particular an LED.

8. The method as claimed in any one of the preceding claims, 10 wherein for at least one intensity, the variation extent to which it is varied is less than 10% of the intensity.

9. The method as claimed in any one of the preceding claims, wherein at least one carrier frequency is greater than 100 Hz, 15 in particular equal to 100 kHz.

10. The method as claimed in any one of the preceding claims, wherein the carrier frequencies are identical. 20

11. An arrangement for transmission of data with at least two radiation sources for emission of radiation with in each case a definable intensity that is substantially constant on average over time, which are configured in such a way that at least two of the intensities are varied with a respective 25 carrier frequency and at least one portion of the data is transmitted by means of a phase relationship of the carrier frequencies of at least two of the radiation sources among one another. 30

12. The arrangement as claimed in claim 11, wherein at least one of the radiation sources is a visible or non-visible light - 14 radiation source.

13. The arrangement as claimed in claim 11 or 12, wherein the spectra of the radiation sources substantially do not overlap. 5

14. The arrangement as claimed in claim 11, 12 or 13, wherein at least one of the radiation sources is an LED.

15. The arrangement as claimed in any one of claims 11 to 14, 10 wherein the carrier frequencies of the radiation sources are identical.

16. An arrangement for transmission of data substantially as hereinbefore described with reference to the accompanying 15 drawing. OSRAM GMBH WATERMARK PATENT & TRADE MARK ATTORNEYS 20 P31178AUOO