Method and optical wireless device for creating an information storage

Abstract

An optical wireless device for transmitting an optical wireless signal via an optical wireless channel, comprising: an electrical signal source configured to provide a data signal; and an optical signal source configured to convert the data signal into an optical wireless signal and transmit the optical wireless signal. The optical wireless device is configured to: obtain channel information including information associated with non-linear channel distortion of the optical wireless signal, and perform adaptation on the modulation of the optical signal source by changing the operating state of the electrical signal source to adapt the non-linear channel distortion, and / or perform adaptation on the operating point of the optical signal source to adapt the non-linear channel distortion.

Description

Technical Field

[0001] The present invention relates to an optical wireless device, an optical wireless network, a method for creating an information memory for an optical wireless device, and a method for creating an information memory for an optical wireless device. Furthermore, the present invention relates to an adaptive transmitter for optically wireless communication for simulating a modulation signal. Background Art

[0002] Modern optical wireless transceivers use orthogonal frequency division multiplexing (OFDM) to achieve high data rates and ensure high robustness against multipath propagation. Here, OFDM is often combined with adaptive bit loading. When the received signal and thus the carrier-to-noise ratio (CNR) is high, for example because the transmission distance is short, more bits can be encoded per carrier. The product of the symbol rate and the sum of the encoded bits of all carriers corresponds to the data rate. The data rate can be maximized by increasing the symbol rate and / or the CNR. A higher symbol rate requires a higher bandwidth. However, this is also limited by optical emitters such as light-emitting diodes (LEDs); lasers or laser diodes. Due to non-linear distortion, the CNR is again reduced by noise. Typically, the optical emitter (e.g., an LED) is the component with the strongest non-linear distortion. To reduce these distortions and obtain the highest possible peak data rate, the modulation or level control, i.e., the signal amplitude at the transmitter, is reduced. However, this reduces the signal power and thus the range or coverage of the optical wireless data connection.

[0003] Today, in the literature, a modulation that represents a trade-off between data rate and range has been selected. Since the non-linear distortion and the range depend non-linearly on the modulation, there is a modulation in which the range becomes maximum for a defined data rate [a][b][c].

[0004] Other methods include, for example, non-linear pre-distortion or post-distortion of the signal to compensate for non-linearity [d]. However, these methods are complex in terms of sizing and production.

[0005] Higher data transmission rates are required in optical wireless transmission that allows reliable data transmission.

[0006] Therefore, a transmitter for optical wireless communication that can provide high data rates and high ranges would be desirable. Summary of the Invention

[0007] Accordingly, it is an object of the present invention to provide an optical wireless device, an optical wireless network, a method for creating an information memory for the purposes of the present invention, and a corresponding computer program product that allows optical wireless communication at high data rates and high ranges.

[0008] The core idea of the present invention is to achieve, for example, adjusting or compensating or reducing non - linear channel distortion by adjusting the operating point of the optical signal source and / or by changing the operating state of the electrical signal source of the optical wireless device, so as to always obtain the best compromise between data rate and range, and thus these two parameters can always be optimized.

[0009] According to an embodiment, an optical wireless device for transmitting an optical wireless signal via an optical wireless channel includes an electrical signal source configured to provide a data signal. In addition, the optical wireless device includes: an optical signal source configured to convert the data signal into an optical wireless signal and transmit the transmitted optical wireless signal. The optical wireless device is configured to: obtain channel information including information associated with the non - linear channel distortion of the optical wireless channel, and is implemented to perform an adjustment on the modulation of the optical signal source by changing the operating state of the electrical signal source to adjust the non - linear channel distortion, and / or perform an adjustment on the operating point of the optical signal source to adjust the non - linear channel distortion.

[0010] According to an embodiment, the adjustment of the non - linear channel distortion depends on the current transmitter - receiver arrangement or the current channel attenuation.

[0011] According to an embodiment, an optical wireless network includes at least one such optical wireless device and an additional receiver for receiving the optical wireless signal.

[0012] According to an embodiment, a method for creating an information memory for an optical wireless device includes arranging a transmitter and a receiver for transmitting an optical wireless signal via an optical wireless channel to allow adjustment of the modulation of the optical signal source. The method includes repeatedly transmitting the optical wireless signal for different distances between the transmitter and the receiver, such that multiple modulations are used for transmission at each distance, which allows finding an ideal modulation for the current channel attenuation. The method includes determining at least one achievable data rate and / or noise ratio for each of the transmitted signals at the location of the receiver, and determining the modulation to be selected for each of the distances, by using which the data rate or the noise ratio is at a maximum. The method includes compiling the modulations to be selected for different distances. Knowing the modulation settings for obtaining the maximum data rate or the maximum noise ratio at the corresponding channel attenuation, the modulation can be adjusted during operation when a corresponding event occurs, such that the data rate or the noise ratio remains at a maximum.

[0013] According to an embodiment, a method for creating an information memory for an optical wireless device includes arranging a transmitter and a receiver for transmitting an optical wireless signal via an optical wireless channel to allow adjustment of an operating point of an optical signal source. The method includes repeating the transmission of the optical wireless signal for different distances between the transmitter and the receiver such that the transmission is performed using a plurality of operating points at each distance. The method includes determining an achievable data rate and / or noise ratio for each of the transmitted signals at the location of the receiver, and determining an operating point to be selected for each of the distances, by using which the data rate or the noise ratio is at a maximum. Further, the method includes compiling the operating points selected for different distances. Thus, the method for collecting data for adjusting the operating point can be performed in a manner similar to the method for collecting information for modulating the optical signal source.

[0014] Another embodiment relates to a computer program or a data storage medium having stored thereon such a computer program for performing the method described herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The particularly preferred embodiments of the present invention will be discussed below with reference to the accompanying drawings. They show:

[0016] Figure 1a is a schematic block diagram of an optical wireless network having an optical wireless device according to an embodiment;

[0017] Figure 1b is an exemplary schematic diagram of a graph for illustrating modulation of an optical signal source corresponding to an embodiment;

[0018] Figure 2a is a schematic diagram of an exemplary graph for illustrating the described embodiment, in which the achievable data rate is plotted for different distances;

[0019] Figure 2b is an exemplary illustration of different achievable data rates DR / Mbps (thick line) for different transmitter modulations and with respect to the DC component of the received power according to an embodiment;

[0020] Figure 3 is a schematic block diagram of an optical wireless network according to an embodiment, in which the optical wireless device includes a transmitter;

[0021] Figure 4 is a schematic block diagram of a part of a device according to an embodiment, in which the transmitter is modified for Figure 3 is modified;

[0022] Figure 5 is a schematic block diagram of a part of a device according to an embodiment, in which a driver circuit is configured to implement a variable gain adjusted based on a control signal;

[0023] Figure 6 is a schematic block diagram of an optical wireless network according to an embodiment that allows a receiver to provide feedback as compared to an optical wireless network of Figure 3 ;

[0024] Figure 7 is similar to Figure 6 and is a schematic block diagram of an optical wireless network according to an embodiment, wherein a measuring device is configured to determine an alternating component of an amplifier signal;

[0025] Figure 8 is an exemplary comparison of available data rates DR for distances plotted on the abscissa and for different operating points of an optical signal source according to an embodiment;

[0026] Figure 9 is a schematic block diagram of an optical wireless network according to an embodiment, wherein a processor device is implemented on the receiver side to provide a control signal for adjusting a driver circuit;

[0027] Figure 10a is a schematic block diagram of a part of an optical wireless device according to an embodiment;

[0028] Figure 10b is a schematic block diagram of another optical wireless device according to an embodiment, including an adjustment element for receiving a control signal;

[0029] Figure 11 is again Figure 2a some curves;

[0030] Figures 12a to 12c is an exemplary table for illustrating how adjusted values are obtained at an optical wireless device according to an embodiment, wherein the tables are linked to each other by respective characteristics;

[0031] Figure 13 is a schematic flow chart of a known method, wherein the result of channel estimation leads to a corrected bit rate of a data signal;

[0032] Figure 14 is a schematic flow chart of a method according to an embodiment that takes into account changes in channel attenuation;

[0033] Figure 15 is a schematic block diagram of another method according to an embodiment for modifying Figure 14 ;

[0034] Figure 16 is a schematic flow chart of a method according to an embodiment for determining the modulation of an optical signal source to be selected; and

[0035] Figure 17 is a schematic flow chart of a method according to an embodiment for determining the operating point of an optical signal source to be selected. Detailed implementation manners

[0036] Before discussing embodiments of the present invention in more detail based on the accompanying drawings, it should be noted that the same, functionally identical or similar elements, objects and / or structures have the same reference numerals in different drawings, so that the descriptions of these elements illustrated in different embodiments are interchangeable or mutually applicable.

[0037] The embodiments described below are described in the context of multiple details. However, the embodiments can also be implemented without these detailed features. In addition, for clarity, the embodiments are described by using block diagrams instead of detailed descriptions. In addition, the details and / or features of each embodiment can be easily combined with each other as long as they are not explicitly described otherwise.

[0038] Some embodiments herein are discussed in the context of optical wireless communication, in which the term LiFi (Light Fidelity) is also used. According to the embodiments to be described below, this is combined with the generation of quantum keys, that is, cryptographic keys generated by using quantum-based methods. The advantages obtained thereby can also be used in other fields of wireless communication, so that the described embodiments are not limited to optical wireless communication, but can also be used in other fields of wireless communication, such as the field of radio wave communication in the frequency range starting from about 800 MHz, where frequencies and technologies particularly suitable for beamforming are possible, for example, in the frequency band starting from 4 GHz, but also applicable to higher frequencies of at least 40 GHz, such as in the range of about 50 GHz or 60 GHz. Although devices for active direct radio transmission - that is, beamforming - are preferred, mechanical devices such as antenna housings can also be used for beamforming.

[0039] Therefore, according to embodiments of the present invention, as an alternative or supplement to optical wireless communication, radio wavelengths can be used, especially those particularly suitable for radio relay transmission, such as by using the so-called beamforming technology. This is particularly advantageous for transmitters that cause substantially non-linear distortion or contribute significantly to overall non-linearity, as in the case of optical transmitters, and is also advantageous for other non-linear transmitters, such as non-linear antenna characteristics in radio wave transmitters.

[0040] The following embodiments relate to optical wireless signal transmission or data transmission. Within the embodiments described herein, it is also referred to as LiFi (Light Fidelity). Here, the term LiFi also relates to terms such as IrDA (Infrared Data Association) or OWC (Optical Wireless Communication). This means that the terms optical wireless data transmission and LiFi are synonyms. Here, optical wireless data transmission refers to the transmission of electromagnetic signals through a free transmission medium such as air or different gases or fluids. For this purpose, for example, wavelengths in the ultraviolet (UV) range of at least 53 nm and in the infrared range of up to 1550 nm, for example, can be used, and other wavelengths different from those used for radio standards are also possible. Optical wireless data transmission must also be distinguished from fiber-optic based optical data transmission, for example, achieved through optical waveguides or optical waveguide cables.

[0041] Figure 1a A schematic block diagram of an optical wireless network 100 is shown, which has an optical wireless device 10 according to an embodiment and a receiver 12 or receiver device that implements receiving the signal 14 transmitted by the optical wireless device 10. The optical wireless device 10 can be implemented to transmit an optical wireless signal 14 and can be used as an optical wireless transmitter. Without limitation, the optical wireless device can also be implemented to receive optical wireless signals and, for example, can be an optical wireless transceiver. In addition, the receiver device can be configured to transmit the optical wireless signal back to the optical wireless device 10, that is, to be formed as a transceiver. The channel 16 between the optical wireless device 10 and the receiver 12 can thus be used unidirectionally or bidirectionally. The channel 16 can cause channel-induced distortion of the optical wireless signal 14, that is, can provide channel distortion. The channel distortion can in particular be non-linear and can have different effects, for example, for different frequency ranges or wavelength ranges.

[0042] The optical wireless device 10 includes an electrical signal source 18 configured to provide a data signal 22. In addition, the optical wireless device 10 includes an optical signal source 24 configured to: convert the data signal 22 into an optical wireless signal 14 and emit it. The optical signal source 24 can include an optical transmitter, such as a laser source or a light-emitting diode, with the light-emitting diode being preferred. The operating point of the optical transmitter can correspond to the direct current component of the current consumption of the optical transmitter (optical signal source) 24.

[0043] The electrical signal source 18 and the optical signal source 24 can be directly coupled or can even form an integrated device. However, this does not exclude intermediate processing of the electrical data signal, for example, by using filters, amplifiers, etc.

[0044] The optical wireless device 10 is configured to obtain channel information 26, which includes information associated with the non-linear distortion of the signal 14 in the optical wireless channel 16. Here, the channel information 26 can indicate, for example, information accompanying the distance 28 between the receiver 12 and the optical wireless device 10 or directly indicate such information, where, for example, continuous or discrete range values are possible. Alternatively or additionally, the channel information 26 can also be related to or can indicate the noise ratio, where the noise ratio can be related to the reception quality of the optical wireless signal 14 at the position of the receiver 12. Such information can be obtained or received by the receiver 12, but can also be estimated by the receiver 12 by taking channel reciprocity, where the receiver 12 receives the optical wireless signal, where the same wavelength range as the optical wireless signal 14 can but does not have to be used.

[0045] The optical wireless device 10 is configured to perform an adjustment to the modulation of the optical signal source 24 based on the channel information to at least partially perform an adjustment to the non-linear channel distortion. To this end, the optical wireless device 10 can change the operating state of the electrical signal source 18, for example, by changing the modulation of the digital signal processor (DSP) and / or by adjusting the gain of the driver of the electrical signal source 18. Other devices are also possible. As an alternative or supplement to the adjustment of the operating state of the electrical signal source 18, the optical wireless device can perform an adjustment to the operating point of the optical signal source 24 to adjust the modulation of the optical signal source.

[0046] For example, this adjustment can be performed at least as part of the compensation for the non-linear channel distortion, that is, to cancel the present or specified or current non-linear channel distortion. Non-linear pre-distortion and / or post-distortion can be used, which can improve linearity, which can be considered as compensation. Embodiments relate to selecting the operating state of the transmitter such that the present non-linear distortion no longer interferes, which may also mean, for example, accepting strong distortion at long distances. The adjustment in combination with the embodiments can have the purpose of improving the signal quality / data rate. Except for the case of increased modulation or decreased operating point, this can be considered as reduction.

[0047] Changing the operating state of the electrical signal source 18 and / or adjusting the operating point of the optical signal source 24 can be performed by respective control devices (not shown) that evaluate the channel information 26 and derive the parameters to be adjusted for the electrical signal source 18 or the optical signal source 24. To this end, for example, an information memory can be provided that directly indicates the parameters to be adjusted, or has stored calculation rules, and the parameters to be adjusted according to the calculation rules can be derived by using the channel information 26.

[0048] According to an embodiment, the channel information 26 can be based on a noise ratio, such as a signal-to-noise ratio (SNR) and / or a carrier-to-noise ratio (CNR). The noise ratio can be associated with the optical wireless signal 14 and the channel information 26 can be further based on the signal power of the optical wireless signal at the receiver 12, such as a power spectral density (PSD) or a direct current component of the photocurrent at the anode or cathode of the photodiode of the receiver 12. These values also depend on the distance 28 such that the noise ratio and / or the signal power at the location of the receiver 12 can be inferred based on the distance 28 by at least considering the values adjusted in the optical wireless device 10.

[0049] The optical wireless device 10 can be configured to adjust the modulation of the optical signal source 24 during operation, which means different adjustments of the modulation of the optical signal source at different times, such as when determining a change in the optical wireless channel 16. According to an embodiment, the optical wireless signal 14 is a first optical wireless signal transmitted in a first transmission interval. In a later second transmission interval, a later second optical wireless signal is transmitted by the device 10, such as by using the optical signal source 24. The optical wireless device 10 is configured to, in order to transmit the later optical wireless signal in the later second transmission interval, determine that the channel attenuation has increased compared to the first transmission interval, and is configured to increase the modulation and / or reduce the operating point in order to benefit from a greater signal modulation / signal power or reduce power dissipation, where a greater non-linear distortion is accepted, however this is not important for the data rate / error rate. Alternatively or additionally, the optical wireless device can be configured to, in order to transmit a later signal, determine that the channel attenuation has decreased compared to the first transmission interval, and reduce the modulation and / or increase the operating point in order to reduce non-linear distortion, such as of an electrical signal source. For example, reducing the modulation can be achieved by reducing the power of the electrical signal source 18. Adjusting the operating point will be discussed in detail in connection with the embodiments described herein.

[0050] Improving or deteriorating the channel, i.e., determining a reduced or increased channel attenuation, can be communicated to the optical wireless device 10 explicitly or implicitly, for example, by transmitting the corresponding values of the noise ratio or signal power at the receiver 12. Alternatively or additionally, the optical wireless device 10 can estimate the respective values based on the received optical wireless signal, such as by receiving the signal (optical wireless signal) 32. According to an embodiment, the optical wireless device 10 is configured to estimate the channel attenuation and is configured to estimate the non-linear distortion based on reference information indicating the noise at the receiver 12 of the optical wireless channel 16.

[0051] According to an embodiment, the optical wireless device 10 is configured to estimate the channel attenuation based on the signal power at the receiver 12 and the signal power at the transmitter of the optical wireless channel 16 (i.e., the optical signal source 24).

[0052] According to an embodiment, the optical wireless device 10 includes: an information memory (not shown) and / or a channel estimator (not shown), configured to output information indicating a relationship between a signal transmitted in the optical wireless channel 16 and non-linear distortion.

[0053] According to an embodiment, the channel information 26 is at least partially based on: feedback from the receiver 12 regarding the signal power of the optical wireless signal 14 at the receiver 12, the noise ratio and / or the error rate of the optical wireless signal 14 at the receiver 12. The noise ratio and the error rate are directly related to each other, which is why the relationship with the noise ratio also represents the relationship with the error rate. For the feedback, the information can be stated explicitly, or it can be stated based on other information, such as the index of a look-up table, etc. According to an embodiment, the optical wireless device 10 is configured to transmit the optical wireless signal 14 via the optical wireless channel 16. Optionally, the device 10 can be configured to receive the optical wireless signal 32, which can be received via the optical wireless channel 16, for example starting from the receiver 12 or another device. The optical wireless device 10 can be configured to perform channel estimation on the optical wireless channel 16 based on the optical wireless signal 32 to determine the noise ratio of the optical wireless signal 32.

[0054] Alternatively or additionally, the optical wireless device 10 can be configured to receive the channel information 26 from the receiver 12 of the optical wireless signal 14. The optical wireless device 10 can be configured to adjust the modulation of the optical signal source 24 based on the channel information by increasing the alternating component of the electrical signal (data signal) 22 towards a second alternating component for a subsequent optical wireless signal, such that it indicates a reduced received power and / or a reduced noise ratio at the receiver of the optical wireless signal compared to a previous transmission interval. Thereby, the operating point of the optical signal source 24 is adjusted.

[0055] Alternatively or additionally, the optical wireless device 10 can be configured to adjust the operating state of the driver circuit of the electrical signal source 18 for adjusting the modulation of the optical signal source 24. Such a driver circuit can include an amplifier element, which is configured to amplify the received processor signal or convert it into a current. The optical wireless device 10 can be configured to adjust the gain of the amplifier element to change the operating state of the driver circuit, thereby adjusting the non-linear distortion at the optical signal source. For example, the driver circuit can include an adaptive attenuation member to adjust the gain of the amplifier element. Alternatively or additionally, the active adjustment of the gain factor of the amplifier element can be adjusted by the driver circuit.

[0056] The amplifier element can be coupled to a resistor circuit for adjusting the gain. The optical wireless device 10 can be configured to adjust the gain at least approximately continuously and / or discretely adjust the resistance. For example, continuous variation can be achieved by using a potentiometer. The resistor circuit can alternatively or additionally include a plurality of switch states, where different resistors for adjusting the gain are coupled to the amplifier element. The optical wireless device 10 can be configured to select and adjust one of the plurality of switching states for changing the control.

[0057] According to an embodiment, the electrical signal source 18 can include: a signal processor, particularly a digital signal processor DSP, configured to provide a processor signal to the driver circuit. The driver circuit can be configured to control its gain according to the processor signal. The signal processor can be configured to adapt the alternating component of the processor signal through a digital-to-analog converter to feed signals of different intensities into the driver circuit.

[0058] In other words, embodiments of the present invention describe an optical wireless transmitter that solves the emitter non-linearity problem through adaptive AC modulation. The AC modulation follows the current channel attenuation caused by geometric channel loss or absorption in the channel. At small distances, the channel loss is very low, such that the received signal is strong. Then, the modulation is reduced, such that the non-linear distortion in the emitter and other transmitter components is reduced. Therefore, a higher CNR can be obtained, and thus a higher peak data rate. If the communication distance is high, and thus the channel attenuation is high, the modulation is increased. A higher transmit power is accompanied by a higher connection range. If the control is properly configured, the data rate for the entire distance also increases. At larger communication distances, it is advantageous for bit loading to have a reduced modulation depth. Due to the higher modulation, the non-linear distortion increases, but due to the lower modulation depth, a particularly high CNR may not be required. Once the noise from non-linear distortion is exceeded by another noise factor (e.g., internal receiver noise), then the increased signal power from the higher signal modulation is greater than the increased noise power. Therefore, the CNR and data rate increase.

[0059] Figure 1bAn exemplary schematic diagram of a graph with a curve G is shown, which curve G exemplarily represents the signal amplitude S of an optical transmitter of an optical signal source such as the optical signal source 24 over a time t. In order to change the average value MW of the DC component that can describe the description of, for example, the operating point adjusted by the provided current, the signal of the alternating component with a range of values ​​H that can be described by the amplitude A can be changed. The operating state of the optical signal source 24 or the range of values ​​H can be changed by changing the value of the average value, which can occur, for example, via the operating point of the optical signal source and / or via the DC component of the electrical signal source 18 fed to the optical signal source. In addition, changing the range of values ​​H can lead to changing the modulation, which can occur, for example, by changing the amplitude of the electrical signal, such as via a variable gain factor. Modulation can here mean a change in amplitude that is different from the adaptive operating point. Both can be summarized by the term operating state.

[0060] Figure 2a Exemplary graphs 341 to 345 are shown for discussing the embodiments described herein. On the abscissa, the unit meter (m) is shown and indicated by the parameter z, for example. Figure 1a The distance 28. On the ordinate the data rate DR is indicated in Mbps obtained in a non-limiting experiment represented by the different curves 341 to 345.

[0061] The dashed curves show the measured values ​​for different AC transmitter modulations. These values ​​correspond to the effective values ​​of the alternating component of the optical transmit power. The solid lines indicate the performance of the adaptive transmitter to obtain the envelope of all curves. Changing the modulation is firstly related to the AC signal part.

[0062] The different curves 341 to 344 differ in relation to the transmitter modulation adjusted in relation to the optical signal source 24. Different modulations represented by the effective value (eff) of the alternating component (AC) of 9.3 dBm, 13.7 dBm, 17.2 dBm or 22.0 dBm will result in different data rates for different distances z. For example, in a direct comparison of curves 341 to 344, it can be seen that low modulation at short distances corresponding to relatively low channel attenuation can result in higher data rates than larger modulations due to the reduction of nonlinear distortion in the transmitter and receiver. For larger distances z, higher modulation provides an advantage, for example, it can be seen that curve 343 is used for a distance of 6 meters, while curve 344 is used for distances exceeding 7 meters.

[0063] Therefore, the variable modulation exemplarily represented by curve 345 according to embodiments described herein enables a continuous high data rate for different distances, for example for different channel attenuations by taking into account non-linear distortions, which is advantageous.

[0064] In other words, Figure 2aShows the data rate of the optical wireless transceiver over the entire range. The transceiver transmits an OFDM signal through adaptive bit loading, thus adapting the data rate to the channel attenuation. Curves for different transmitter modulations are shown. Encodes the effective value of the alternating component of the optical power. The dashed curve corresponds to the configuration, one of which is selected in the conventional method. High transmitter power (strong modulation) is accompanied by a low maximum data rate (due to nonlinear distortion) but a high range. At the same time, a lower transmitter power (lower modulation) is accompanied by a high maximum data rate but a lower range. The adaptive modulation described herein increases the modulation as the communication distance z increases to increase the data rate DR in that distance. If this is achieved, the DR-z curve of the envelope corresponds to the curves of the respective configurations. It can be clearly seen how the range or data rate increases compared to the conventional method.

[0065] Figure 2b Shows for different transmitter modulations the exemplary illustration of the different curves of the achievable data rate DR / Mbps and with respect to the DC component of the received power (ΦRX DC / dBm). In contrast, in Figure 2a DR has been plotted against the communication distance z.

[0066] The different curves 681 to 684 are related to different effective values of the alternating component of the optical transmitter power .

[0067] Figure 3 Shows a schematic block diagram of an optical wireless network 300 according to an embodiment. The optical wireless network includes an optical wireless device 30 according to an embodiment and a receiver 12 shown in detail compared to Figure 1a For example, the receiver 12 may include a receiver 17 implemented to receive an optical wireless signal 14'.

[0068] The device (optical wireless device) 30 may have the same functions as device 10. The device (optical wireless device) 30 may include a transmitter 35, which may include, for example, an electrical signal source 18' and an optical signal source 24. The electrical signal source 18' of the device (optical wireless device) 30 includes, for example, a signal processor (DSP) 36, which is configured to output a processor signal 38 and apply it to a driver circuit 42, possibly having a variable gain factor to obtain a data signal 22. The optical signal source 24 is implemented to receive the data signal 22 and transmit an optical wireless signal 14. After passing through the channel 16, the distorted signal 14' is received by the photodetector 44 of the receiver 12, which may provide a received signal based on it. The received signal 46 may be provided to an amplifier 48 of the receiver 12, which may be configured to provide an amplified signal 52, which may be provided to a signal processor such as DSP 54 to process the information transmitted by the device (optical wireless device) 30.

[0069] In other words, Figure 3 An optical wireless data transmission path including a transmitter (optical wireless device) 30 and a receiver 17 is shown. The system (optical wireless network) 300 is shown in a simplified unidirectional manner, but may actually also be configured in a bidirectional manner. The digital signal processor (DSP) 36 feeds a modulated data signal (processor signal) 38 into the driver circuit 42 of the optical wireless transmitter (optical wireless device) 30. In the system (optical wireless network) 300, the driver is a variable gain component. In an alternative embodiment, alternatively or additionally, the DSP 36 may provide a variable output level through an analog-to-digital converter. It is decisive that the signal (data signal) 22 is fed to the optical wireless transmitter (optical signal source) 24 (e.g., a light-emitting diode or a laser diode) at the output of the driver circuit 42, and its modulation is variably adjustable. The transmitted optical signal is indicated by 14 at the time of transmission, and by 14' when it is incident on the receiver. The photodetector 44 (e.g., a photodiode) detects the signal 14' and converts it into a received signal 46. The signal 46 is amplified by an amplifier 48 (e.g., a transimpedance amplifier). The amplified signal 52 is fed into the DSP 54, where it is demodulated and further processed. In a transceiver for a bidirectional data connection, the transmitter 35 and the receiver 17 form a transceiver. In this case, the DSP may combine the functions of the block showing DSP 36 and the block showing DSP 54.

[0070] Figure 4 A schematic block diagram of a part of the device 40 is shown, particularly its transmitter 35'. For example, in the transmitter 35', the concept of changing the operating state of the electrical signal source to adapt to non-linear channel distortion is illustrated. In Figure 4In an embodiment, to this end, an analog implementation of the variable gain of the amplifier or driver circuit 42 is illustrated. The gain control can be performed continuously or gradually. The driver circuit 42 includes an adaptive or variable attenuation member 56 or an attenuation circuit configured to adjust the gain of the amplifier element. In Figure 4 the variable driver gain is achieved by the variable attenuation member 56 in the driver circuit 42 and can be controlled, for example, via the control signal 58. Thus, the output of the amplifier element 62, i.e., the data signal 22, can be adjusted.

[0071] The control signal 58 can be based on at least one of several possible information sources and can send the corresponding information as an analog signal, such as via signal amplitude, frequency, ON OFF level, etc. Alternatively, the control signal 58 can include a message within a communication protocol that carries the corresponding information for controlling the corresponding element at the device 40 and is decoded or interpreted, for example. The information source can be directly or indirectly, i.e., explicitly or implicitly, related to a measured quantity related to the channel or channel attenuation, such as the distance between the transmitter / receiver, the resulting change in the DC component or AC component of the received signal, etc. Alternatively, the message can implicitly or explicitly indicate what adjustment must be performed at the transmitting device.

[0072] To adjust the modulation of the optical signal source 24, the channel information can be based on the DC component of the optical wireless signal such as signal 14 received by the receiver of the optical wireless channel 16 and can be associated with the adjustment of the attenuation member of the electrical signal source at the transmitter, such as the device 40. Alternatively or additionally, to adjust the modulation of the optical signal source 24, the channel information sent by the control signal 58 can be based on the AC component of the optical wireless signal such as signal 14 received by the receiver of the optical wireless channel 16 and can be associated with the adjustment of the gain factor of the electrical signal source.

[0073] According to an embodiment, the information memory can be provided in the transmitting device, for example, in the form of a look-up table or the like. Different predefined values of the modulation associated with different channel distortion values can be stored in the information memory. The optical wireless device can be configured to obtain the value to be adjusted for the modulation from the information memory by using the channel information 26 and apply the value, for example, for the value of the signal (control signal) 58.

[0074] Figure 5 A schematic block diagram of a part of the device 50 is shown, where the driver circuit 42'' is configured to provide a variable gain of the driver circuit 42'' based on the control signal 58. To this end, in cooperation with the amplifier element 62, it can vary in the circuit or the variable attenuation member 56', and thus the gain of the driver circuit 42'' can be adjusted to adjust the modulation of the optical signal source 24.

[0075] Here, it can be based onFigure 1a selects based on the channel information 26 in Figure 4 and / or Figure 5 a control signal 58 such that an adjustment of the driver circuit 42' and / or the driver circuit 42'' is performed depending on the channel information to at least partially compensate for non-linear distortion.

[0076] Thus, an implementation of an embodiment corresponding to the present invention described herein may include an implementation in a transmitter. In other words, adaptive modulation may be implemented in an analog manner in the transmitter 35 of the system (optical wireless network) 300. According to an embodiment, adaptive modulation may be implemented fully or partially in a digital manner. In an analog implementation, the driver circuit 42 has a variable gain. For example, the gain control occurs continuously or gradually. For example, by using an adjustable attenuation element ( Figure 4 ) or adjusting an active gain factor ( Figure 5 ) to change the gain. Both implementations are controlled by the control signal 58.

[0077] Figure 4 illustrates the implementation of variable driver gain through a variable attenuation member 56 in the driver, and Figure 5 illustrates the implementation of variable transmitter gain through variable gain by a resistor network (variable attenuation member) 56' in the driver.

[0078] The amplifier element 62 indicates an amplifier that can have variable gain in the context of a variable switch and / or due to variable control. For example, a variable switch with an attenuation circuit (variable attenuation member) 56 can be adjusted. This means that the modulation of the transmitter (optical signal source) 24 can occur by adjusting the control of the driver circuit 42' / 42'', such as by the signal amplitude and / or the effective value of the alternating component of the signal (processor signal) 38 and / or by changing the operating state of the amplifier element, such as adjusting the gain factor.

[0079] The illustrated implementation is a design example in the context of an embodiment of the present invention. Clearly, other corresponding resistors can also be changed and variable amplifiers can be implemented in other known architectures. The amplifier can also operate in an inverting configuration or can be configured differentially. As previously mentioned, the adjustment can be implemented gradually or continuously. For example, different resistors and switches can be used to gradually implement, where the impedance is changed by opening and closing the switches, thus changing the gain. In this case, the switch can be a transistor. Alternatively, one or more transistors can also be connected in parallel to the resistor. The voltage at the control input of the transistor is used to adjust the channel resistance of the transistor to change the gain of the VGA.

[0080] Changing the gain of the system, i.e., changing the process itself, will again cause nonlinear distortion, and the nonlinear distortion itself will cause a decrease in CNR. To solve this problem, there are many configuration options:

[0081] · The time when the data signal (data packet, data frame) is known to be transmitted in the system. For this purpose, the DSP 36 provides, for example, a logic control signal. During signal transmission, the gain cannot be adjusted or the gain does not change or remains at least approximately constant. The gain is adjusted accordingly between data packets / frames.

[0082] · The adjustment is very weak or in small steps / change rates such that the noise of the nonlinear distortion caused by gain adjustment is small relative to other effective noise sources (e.g., receiver noise). To adjust gradually, the step size must be very small, which may be impractical in most systems. For continuous gain adjustment, the change in gain is very slow, i.e., over a large time interval, i.e., over multiple data packets / frames. Within the period of one data packet, the gain can be approximated as constant.

[0083] As mentioned, alternatively or additionally, the modulation of the data signal 22 can be adjusted completely or partially by the DSP 36. During the generation of the OFDM signal, when the attenuation in the optical channel is particularly strong, the DSP can provide higher power for the entire carrier. Thus, when the channel attenuation is particularly weak, the DSP can reduce the power of each carrier. In this case, not only the nonlinear distortion at the optical transmitter, i.e., the optical signal source 24, is amplified, but also the nonlinear distortion at the digital-to-analog converter DAC of the DSP 36 is amplified. The overall noise of the nonlinear distortion adjusted relative to other noise components remains decisive.

[0084] This function should not be confused with the conventional adaptive power loading, as it is sometimes used for OFDM. Here, the power of each carrier on the signal spectrum is varied such that the connected non-ideal transmission function, such as low-pass attenuation, is compensated [e, f], where this distortion is called linear distortion. In contrast, in the present invention, the influence of channel attenuation is compensated for the influence of nonlinear distortion. As Figure 2a shown, the adjustment occurs not only when the signal is very weak but also in the case of a very strong signal, because benefits can be obtained from stronger or weaker modulation, for example, already from a distance of about ~1 meter.

[0085] As an alternative to determining the control signal 58 at the optical wireless device itself, the corresponding information can also be received by a receiver 12' established for this purpose, for example, as Figure 6 shown, which shows in connection with Figure 3Schematic block diagram of an optical wireless network 300' that, compared to the optical wireless network 300, allows feedback from the receivers 12' and 17' to the optical wireless device 30. To this end, the receiver 12' may include a measuring device 64 configured to, for example, receive and - for example, with respect to the received power - evaluate the received signal 46. The measuring device 64 may be configured to detect the DC component of the photocurrent of the received signal 46 and transmit this information or information derived therefrom, such as a quantization value or the same information, to the optical wireless device 30.

[0086] Figure 7 shows a similar Figure 6 optical wireless network 300'', in which the measuring device 64' is configured to detect the AC signal power, i.e., the alternating component of the amplifier signal 52. As an alternative or addition to the result of the measuring device 64, this measurement result may form at least part of the control signal 58 for the optical wireless device 30. While in the optical wireless network 300', the channel information is based on the DC component of the optical wireless signal 14' received by the receiver 12'' of the optical wireless channel 16, and it may be associated, for example, for adjusting the attenuation member of the electrical signal source, Figure 7 a configuration is described in which the channel information is based on the alternating component of the optical wireless signal 14' received by the receiver 12'' of the optical wireless channel 16 and is associated with the adjustment of the gain factor of the electrical signal source. For example, the receiver 12' may be used to adjust the transmitter 35', and the receiver 12'' is used to adjust the transmitter 35''.

[0087] In both cases, a control signal is provided for variable modulation. Some embodiments described herein provide for the use of calculation rules for generating the control signal 58. Alternatively or additionally, during operation, the calculation rules may also be applied to predetermine the control signal 58, such as for storage in an information or data memory. As elucidated by equation (1), the CNR can be formed by the signal power to the noise power The signal power and the noise power may be replaced by the respective effective voltage values. In the following considerations, the voltage will accordingly be considered as the effective value. In the model described herein by way of example, the noise consists of the independent noise amount of the internal receiver noise and the non-linear distortion noise at the transmitter or receiver Compared to depending on the system can generally be neglected until over-driving occurs in the receiver. For example, lower transmitter modulation prevents the occurrence of over-driving, or makes it appear only at larger received levels, such that the dynamic range of the link - for example, the dynamic range of the data link - also increases towards shorter distances. The signal voltage The relationship with the transmitter modulation is approximately linear, but The dependency is highly non - linear. As an example, third - order beat forcing is stated, which increases with the square of the modulation. This explains why the CNR can be increased when reducing the modulation.

[0088] (1)

[0089] According to an embodiment, the optical wireless device is implemented to adapt the modulation of the optical signal source 14 / 24, and can be adapted to obtain, in the order of magnitude of the internal receiver noise, the noise component caused by non - linear distortion in the overall noise at the location of the receiver. In this case, the highest data rate is usually obtained. Here, the order of magnitude means that the value corresponds to at least 1 / 3 and at most 10 times of another value, which means that the noise component of non - linear distortion in the overall noise at the location of the receiver is at least 33% and at most 1000% of the internal receiver noise.

[0090] In other words, according to an embodiment, the control device of the optical wireless device and / or the regulation implemented by the processor (DSP) 36 can be interpreted such that the modulation of the signal of the optical signal source 24 is regulated such that the non - linear distortion noise does not reduce the CNR and thus does not reduce the data rate. In fact, this means should be at the order of magnitude of the receiver noise which can represent, for example, the amount of regulation. At the same time, in some configurations, it is intended to select a modulation that is not too low to prevent too low a signal voltage from also limiting the CNR, in which case the CNR is only formed by and In fact, should have approximately the same amount as the dominant noise source, which means or In this case, increasing the noise power by . Further reduction will reduce the modulation , but to a greater extent than the noise power. The basic goal of variable transmitter modulation is to maximize the CNR at a specific distance with a specific reception level.

[0091] For example, the control signal 58 providing modulation for the transmitter control can be determined as follows:

[0092] · By assuming that the signal at the receiver of the communication partner is similar, the control signal can be generated at one's own receiver.

[0093] ° Figure 6: Measure the DC received power at measurement block 64 either before or after the optical detector 44. In the case of a photodiode, this means measuring the DC component of the photocurrent at the anode or cathode of the photodiode. This signal is amplified and provided to the driver circuit 42.

[0094] ° Figure 7 : Measure the AC signal power at block 64'. After the transimpedance amplifier 48, the signal 52 can be tapped and the AC component (e.g., determine the RMS value) can be determined. This voltage is amplified accordingly and provided to the driver circuit 42.

[0095] · At the receiver 12' / 12'' of the communication partner: A system with bit loading has the function of evaluating the error rate or CNR of the system in order to be able to adjust the bit loading accordingly. By sending a corresponding message in the same or different wavelength range or frequency range, this information and the current bit loading can be passed to the communication partner on the protocol side. Alternatively, on the protocol side, it is also possible to directly pass whether to increase or decrease the modulation.

[0096] · The optical wireless device can have additional optical detectors that also detect signals. This receiver can use large photodetectors. In the case of low bandwidth, the signal can be amplified in a particularly noise-free manner to generate a measured value of the DC component of the signal 14'.

[0097] · The optical wireless device can have a rangefinder, such as a time-of-flight sensor. The channel attenuation can be inferred from this distance.

[0098] · In a two-way optical wireless device, the control signal can be generated in the DSP 54 by digital data processing of the signal 52. By determining harmonic distortion, intermodulation products, or other information about the nonlinear distortion extracted from the signal or test signal, the transmitter modulation of the opposite-end device can be determined. In this way, the channel attenuation and channel distortion can be calculated by correlating the channel distortion with the system-specific transmit power. Obviously, the described DSP functions can also be implemented similarly in the receiver.

[0099] The context between the measured quantity in the receiver and the change in the gain in the transmitter can be linear or nonlinear, where the nonlinear adjustment allows a larger dynamic adjustment range.

[0100] Figure 6 An optical wireless transceiver with variable driver gain is shown, where the gain is adjusted by a control signal from the receiver, which is exemplarily generated by measuring the DC component of the photocurrent.

[0101] Figure 7An optical wireless transceiver with variable driver gain is shown, where the gain is adjusted by a control signal from the receiver, which is generated from the signal of the driver circuit 42 after the amplifier 48.

[0102] As an alternative or in addition to changing the operating state of the electrical signal source, such as by adjusting the signal amplitude in the signal processor 66 and / or by adjusting the gain in the driver circuit 42 for the adjustment of non-linear channel distortion, the adjustment of the operating point of the optical signal source 24 can also occur.

[0103] Figure 8 An exemplary comparison of the achievable data rate DR with respect to the distance z plotted on the abscissa is shown. Here, the curves 661, 662, and 663 show different operating currents ILED DC of the optical signal source 24. Here, it can be seen that at smaller distances, for example up to one meter, higher currents are accompanied by higher data rates, but once the distance exceeds one meter, this effect reaches a certain saturation as the curves 662 and 663 approach each other and almost overlap at distances exceeding 1.5 meters. On the other hand, at larger distances, for example exceeding 5 meters, higher data rates can be obtained using higher operating currents (curve 663) as well as lower operating currents (curve 661) than using an average operating current (curve 662).

[0104] In other words, Figure 8 The cross-distance data rates for different LED operating points are shown.

[0105] As an operating point, for example, the applied time-averaged operating current or working current can be adjusted. As an alternative or in addition to creating an information memory with different values for modulation, an information memory can be created for the operating point or the same information memory with different predefined values associated with different channel distortion values. Such an optical wireless device can be configured to obtain and apply the value to be adjusted for the operating point from the information memory using channel information.

[0106] The optical wireless device implemented to adjust the operating point of the optical signal source 24 can be configured to increase the operating point in the case where non-linear distortion dominates or has a relevant share in the overall noise and at the same time the high noise ratio of the optical wireless signal at the receiver of the optical wireless signal and at the same time the high data rate in the optical wireless signal. Refer to Figure 8, this is the case for relatively short distances, e.g., less than one meter. Alternatively or additionally, such a device can be implemented to reduce the operating point in cases where the non-linear distortion hardly contributes significantly to the overall noise and the signal power of the optical wireless signal at the receiver is weak. Such a process can significantly reduce the power consumption of the transmitter. Depending on the transceiver arrangement, an increase of up to 10%, 30% or even more than 50% can be achieved. For example, when the data rate is reduced by less than 5% due to adapting the operating point through non-linear distortion, the non-linear distortion component is irrelevant.

[0107] As discussed in the context of adapting the modulation, such a determination can be made by obtaining the corresponding information from the receiver or by making a corresponding determination at the location of the transmitter, i.e., the optical wireless device.

[0108] In other words, as an alternative or complement to adapting the transmitter modulation, the transmitter can benefit from variable operating point adjustment of the optical transmitter (i.e., with and without variable transmitter modulation). The transmitter operating point has an impact on the efficiency, bandwidth, and linearity of the transmitter. The relevant or decisive aspect of OFDM data transmission is that linearity has a significant impact on the maximum data rate, but once the receiver noise dominates, the impact is smaller. In this range, the operating point only affects the data rate through the dependencies of bandwidth and efficiency. This impact is generally much weaker. Figure 8 Measurements in [ ] show these contexts in the cross-distance data rate curves for different LED operating point currents at a corresponding equal transmitter modulation.

[0109] As in the case of variable transmitter modulation, an adaptive transmitter can utilize this behavior. If the CNR (and data rate) is high, this will generally be limited by non-linear distortion. In that case, the operating point is increased, e.g., to reduce the distortion. Thus, a higher maximum data rate is obtained. If the received signal is weak due to a long communication distance, the operating point will be reduced. However, this will not reduce Figure 8 the data rate at the three operating points at z = 3m in [ ]. However, in this example, this will reduce the current consumption by approximately 25%. Since the transmitter is a significant consumer in the transceiver, on the one hand, the power consumption of the entire system is reduced, and on the other hand, the thermal load is reduced, thus extending the service life.

[0110] Similar to variable transmitter modulation, the control signal for such adjustment can be generated in the receiver of its own transceiver or in the DSP of the communication partner. The operating point can be adjusted directly by the amplifier or driver circuit 42, or can be impressed via, for example, a bias tee or AC coupling. Then, the operating point is changed accordingly by the adaptation component. In a discrete amplifier that is at least part of the driver circuit 42, this can occur by adjusting the common-mode voltage with a control voltage (control signal) 58. According to an embodiment, in the bias tee, the control voltage or control signal 58 can also be applied directly. In AC coupling, the DC component can be adjusted, for example, via the voltage division ratio of a voltage divider by configuring at least one of the impedances in a controllable manner. Digital programming of the amplifier or driver circuit 42 with variable output level is also possible.

[0111] Figure 9 A schematic block diagram of an optical wireless network 300''' is shown, where a processor device (DSP) 54 is implemented on the receiver side to provide a control signal 58 for adjusting the driver circuit 42. Alternatively or additionally, the signal (control signal) 58 can also be used to adjust the operating point of the optical signal source 24. Contrary to the description in the Figure 6 and Figure 7 context, this means that the control signal 58 can also be provided by the processor device (DSP) 54. Different from the illustration in Figure 9 , the control signal 58 can also be provided directly to a processor device (DSP) 36 that implements the corresponding instructions or derives the control requirements to be generated therefrom.

[0112] Furthermore, Figure 9 An information memory 72 is shown, as an alternative or addition to the control signal 58, where instructions for controlling the driver circuit 42 and / or the optical signal source 24 can be stored. This information can be used, for example, to interpret the control signal 58, such as when the signal processor (DSP) 36 receives the control signal.

[0113] The information memory 72 can include different predefined values for the operating point and / or modulation that are associated with different values of channel distortion and are stored. The optical wireless device can be configured to obtain and apply values for the operating point to be adjusted from the information memory 72 by using channel information such as the control signal 58.

[0114] In other words, Figure 9 A schematic block diagram of an optical wireless network 300''' is shown, where the control signal 58 is generated by a block (DSP) 54 of the receiver chain of the optical wireless signal 14. Alternatively, the control signal can also be generated based on reception at the transceiver, i.e., in the opposite direction and / or for other signals such as reference signals or pilot signals.

[0115] Figure 10a FIG. 1 shows a schematic block diagram of a portion of an optical wireless device 110 according to an embodiment. The optical wireless device 110 is exemplarily implemented to adapt the modulation of an optical signal source by changing the operating state of an electrical signal source, and exemplarily receives a control signal 58, for example, as described in the context of Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 10a or Figure 10b . The optical wireless device 10 may include an adjustment element 74, which may be used as an alternative or supplement to the variable attenuation members 56 or 56' in Figure 4 or Figure 5 . Thus, the control of the driver circuit 42 can be derived from the control signal 58. In other words, Figure 10a FIG. 2 shows a schematic block diagram of an optical wireless device for adapting the gain of a driver circuit 42 to affect the modulation of an optical signal source.

[0116] Figure 10b FIG. 3 shows a schematic block diagram of another optical wireless device 110' according to an embodiment, including an adjustment element 76 for receiving a control signal 58. The optical wireless device 110 may use the control signal 78 obtained therefrom to control the optical signal source 24 and / or the electrical signal source, i.e., the signal processor (DSP) 36 and / or the driver circuit 42.

[0117] In other words, Figure 10b FIG. 4 shows a schematic block diagram of an optical wireless device for adapting the operating point of an optical signal source 24. The transmitter can be adjusted via the DC component (signal 78a) of the amplifier or driver circuit 42 and / or via a control signal of the transmitter, i.e., the optical signal source 24 itself - control signal 78b. The signals 78a and 78b may be the same or the same in terms of amplitude, frequency, etc., but may also be different from each other.

[0118] The behavior of the adjustment element 74 and / or 76 may be linear or non - linear, but preferably non - linear. Optionally, the adjustment element 74 and / or 76 may be coupled to an information memory 72. Here, it can be defined which gain or characteristic in the electrical signal source or the optical signal source is adjusted with what control signal 58 or with what amplitude, frequency, or other characteristic. In other words, some characteristics of the embodiments described herein can also be described as:

[0119] - Control signal 58:

[0120] - Having a known dependence on channel attenuation and thus can be used to infer channel attenuation,

[0121] - For example, it is derived from a receiver (DC / AC component, before or after the receiver amplifier; or from the receiver DSP as PSD (Power Spectral Density); or as a data packet from the opposite transceiver), or from distance measurement (e.g., beacon, etc.)

[0122] - Adjusting element 74 (e.g., variable attenuation member 56 or 56'):

[0123] - Define how the change of the control signal 58 causes the change of the gain;

[0124] - The transmission function is non - linear because it attempts to maximize the CNR by changing the modification and allows the dynamic adjustment range to be as large as possible

[0125] - Behavior:

[0126] - A look - up table can be stored, which defines which gain is adjusted for which control signal.

[0127] - Alternatively, the gain can be optimized iteratively: if the control signal changes by a predetermined value, increase the gain; if the CNR / data rate in the DSP drops, perform the opposite adjustment; repeat the process until no further improvement can be obtained.

[0128] - As an alternative or supplement: The adjusting element 76 for changing the operating point current is controlled by the same control signal 58, but contrary to the adjusting element 74, it adjusts the operating point of the optical transmitter. Figure 10b The control signal 58 can be the same as that in Figure 10a For example, when the adjusting elements 74 and 76 derive different actions from a signal (or two separate signals that may be applicable to the adjusting elements 74 or 76). On the one hand, adjusting the modulation in the DSP and / or amplifier element, and adjusting the operating point of the transmitter in the DSP and / or through the element 76 can occur together, or they can also occur independently of each other.

[0129] The function in the adjusting element 74 and / or 76 can be linear or preferably non - linear, as shown in Figure 10a and Figure 10b as shown.

[0130] Figure 11 Again shows Figure 2a curves 341, 342, 343 and 344 of

[0131] Figure 12a , Figure 12b and Figure 12c respectively show exemplary tables, where the tables of Figures 12a to 12c are related to each other by their respective characteristics. Therefore, Figure 12a and Figure 12bThe table shows the corresponding distance between the wireless transmitter and the corresponding receiver, where Figure 12a The table shows in each row Figure 2a and Figure 11 Different modulations. Figure 12b In the table, measured variables associated with the respective distances are shown, as well as control variables amplified from the measured variables, which can be used, for example, as control signal 58 or as a basis for the same. Figure 12c It is shown by way of example which modulation of the electrical signal source can be related to Figure 12b The corresponding measured quantity of the table is associated with, where the values ​​here are, for example, Figure 12a This means that it can be quantized from different modulations of the table. Figure 12b Infer what the measurement quantity is for different distances (in Figure 12a ), the corresponding data rate can be maximized.

[0132] In other words, Figure 12a The table is in Figure 2a or Figure 11 The exemplary control and the one shown therein (according to Figure 2a Exemplary measurement results of the values ​​of the data rate DR in Mbps are exemplarily shown in the context of the data rate for which the envelope is generated. At each distance between the transmitter and the receiver, different modulations of the optical transmitter have been adjusted. A column of maximum values ​​can be considered as the modulation associated with the channel attenuation selected for the corresponding distance. As can be seen from the highlighted numbers, the 9.3 dBm modulation at a distance of 0.15 meters is the same as the highest data rate at a distance of 0.4 meters. At a distance of 1 meter, the 13.7 dBm modulation provides the best results, while the 17.2 dBm modulation at distances of 2 meters, 4 meters and 6 meters provides the best data rate results. The modulation of 22 dBm is effective at higher distances of 8 meters and 10 meters.

[0133] Figure 12b The expression Figure 2a or Figure 11 Example control of and data rates and values ​​of measured quantities shown therein - such as from Figure 12a Different measured variables can be converted into control variables, whose step widths can be adapted to the hardware of the transmitter and / or receiver and are described in the row "Control variable amplified from measured variable" and can form the basis for control signal 58, for example. The resulting functional connection between measured variable and control variable and between control variable and modulation and / or operating point is, for example, nonlinear.

[0134] Figure 12c The expression Figure 2a or Figure 11 The exemplary control and data rates shown therein and fromFigure 12a and Figure 12b associated results of the table. Indications such as Figure 12b the value of the control quantity can be associated with Figure 2a and / or Figure 11 the modulation of Figure 12a the table, where the control signal 58 is, for example, a voltage level. Alternatively or additionally, the indicated value can be sent as a quantity to be applied within an encoding or bit pattern to a device, thereby changing its state.

[0135] Figure 12a 、 Figure 12b and Figure 12c the teachings of also apply to changing the operating state of an electrical data source to adapt the modulation of an optical signal source and to adapt the operating point of the optical signal source.

[0136] Figure 2a 、 Figure 11 and Figures 12a to 12c the representation shows:

[0137] - measuring the cross-distance DR or CNR of different transmitter modulations,

[0138] - determining the maximum value of all curves for each distance,

[0139] - providing the context between the control quantity of the control signal 58 and the distance.

[0140] - adjusting the modulation or operating point according to the control quantity of the control signal 58

[0141] For example, the control signal can be used as a control for Figure 4 and / or Figure 5 the variable attenuation members 56, 56' of Figure 10a and / or as a basis for adjusting the adjusting element 74 of

[0142] In a similar manner, the control current can be determined from the corresponding maximum value of the data rate of Figure 8 , for example, by determining the distance between the transmitter and the receiver and adjusting the control current according to the corresponding channel attenuation.

[0143] Figure 13 shows a schematic flow chart of a known method 1400, where when the carrier-to-noise ratio changes, the result of the channel estimation 1420 results in a modified bit rate and bit loading of the data signal (step 1410). This change is implemented in step 1430 and results in transmission 1440 before performing an updated check in a further iterative run. Here, t encodes the current time period or current clock, and t + 1 encodes the next time period or clock.

[0144] Figure 14A schematic flow chart of method 1500 according to an embodiment is shown. For example, in one iterative run, the carrier-to-noise ratio is changed, e.g., by changing the channel attenuation or modulation (step 1510). This is accompanied by the data rate at time t and the first error rate 1. Accordingly, a second error rate 2 greater than error rate 1 exists at t at the same data rate. Channel estimation 1520 may provide the CNR and affect the corrected data rate for time interval p + 1. Method 1500 may include a determination: whether control signal 58 has changed between the previous run t and the current run t + 1. If this is not the case, a signal may be sent in step 1540, which, in addition to determination 1535, may perform the conventional method 1400. However, if control signal 58 has changed (path "yes" in determination 1535), it may be determined in determination 1545 whether the channel attenuation has increased. If the result is "yes", the transmitter modulation may be increased in step 1550 and / or the operating point of the optical signal source may be decreased. If determination 1545 provides the result "no", the transmitter modulation may be decreased in step 1560 and / or the operating point of the optical signal source may be increased.

[0145] In other words, Figure 14 A schematic flow chart of a method according to an embodiment is shown, where it is checked whether a control signal indicating the channel attenuation (indicated by control signal 58) has changed between two transmission intervals t; t + 1. If so, it is evaluated whether the channel attenuation has increased, i.e., whether it has decreased. If the attenuation has increased, the transmitter modulation may be increased and / or the operating point may be decreased, i.e., for example, a lower operating point current. Otherwise, the transmitter modulation may be decreased and / or the operating point may be increased. The method may be performed such that, for example, DSP 36 may effect an adaptation of signal transmission depending on the obtained results, such as by adapting the digital signal processing. This may occur, for example, by changing the modulation at the analog-to-digital converter of the DSP itself as described and / or the DSP may adjust the operating point of the transmitter.

[0146] Figure 15 A schematic block diagram of another method 1600 according to an embodiment is shown. Steps 1510, 1520, and 1530 may be implemented in an order corresponding to method 1500. On the other hand, directly at the start of a new iterative loop, a determination 1635 corresponding to determination 1525 may be made in parallel with these steps, whether control signal 58 has changed between the previous time interval t and the current time interval t + 1. If this is the case, it may be checked whether the channel attenuation discussed in determination 1645 has increased. Similar to method 1500, steps 1550 and 1560 may be implemented depending on the response of determination 1645 and may proceed to step 1670, which causes transmission at an adapted transmitter gain.

[0147] Here, the transmitter modulation and / or the operating point are also adapted due to the change control of the control signal 58.

[0148] In other words, Figure 15 A schematic flow chart of a method according to an embodiment is shown, in which it is also checked whether the control signal indicating the channel attenuation (indicated by the control signal 58) has changed between two transmission intervals t; t+1. If so, it is evaluated whether the channel attenuation has increased, i.e., whether it has decreased. If the attenuation has increased, the transmitter modulation can be increased and / or the operating point can be decreased, i.e., for example, the operating point current can be decreased, otherwise the transmitter modulation can be decreased and / or the operating point can be increased. This method can be independent of the bit loading of the DSP. This can be achieved, for example, by controlling the gain and / or the transmitter operating point.

[0149] The embodiments described herein also describe the following optical wireless device, configured to adapt an optical wireless signal, perform adaptation of the modulation of an optical signal source, and / or perform adaptation of the operating point of an optical signal source to change the non-linear distortion generated by the optical wireless device.

[0150] According to an embodiment, in order to adapt the modulation, the amplitude and / or the effective value of the alternating component of the data signal can be adapted, such as by a signal processor and / or a driver circuit or an amplifier circuit.

[0151] According to an embodiment, an optical wireless device for adapting the operating point of an optical signal source can be configured to adapt the DC component of the data signal and / or be configured to adapt the current consumption of the optical transmitter. For example, by using and adjusting a bias tee, a current source, and / or by changing the DC component of the data signal 22, the operating point current can be dipped or the operating point current can be made to dip. Here, the driver can perform the change. According to an embodiment, the driver circuit 42 can be implemented for such adaptation.

[0152] According to an embodiment, an optical wireless device implemented to adapt the modulation of an optical signal source can be configured to increase the signal-to-noise ratio of a later optical wireless signal transmitted via an optical wireless channel at the location of an optical wireless signal receiver in a subsequent transmission interval by adapting the modulation. By reducing non-linear distortion or increasing the signal power, the reception quality can be improved.

[0153] According to an embodiment, an electrical data source can be configured to increase the data rate of a later wireless optical signal based on the increased signal-to-noise ratio. This means that while expecting the receiver to improve the reception quality, the bit loading can be adapted accordingly by modulation in the DSP.

[0154] According to an embodiment, an optical wireless device is implemented to adapt the modulation of an optical signal source and is configured to transmit an optical wireless signal based on a first power value of an electrical signal. The optical wireless device may be configured to adapt the modulation of the optical signal source based on channel information by reducing an alternating component of the electrical signal of a later optical wireless signal toward a second alternating component such that it indicates an increased received power and a reduced noise ratio at a receiver of the optical signal relative to a previous transmission interval. The optical wireless device may additionally be configured such that it adapts the modulation of the optical signal source based on channel information by increasing the alternating component of the electrical signal of a later optical wireless signal toward the second alternating component, the channel information indicating a reduced received power and a reduced noise ratio at a receiver of the optical wireless signal relative to a previous transmission interval. For example, this is indicated in step 1550 and the alternating component is reduced in step 1560.

[0155] The embodiments described herein provide an optical wireless device as follows, which is implemented to adapt the modulation of an optical signal source and is configured to obtain channel information, such as CNR, as a control signal 58, the control signal including dependencies on channel attenuation and non-linear distortion of the optical wireless channel.

[0156] The optical wireless device described herein may be configured such that an electrical signal source is configured to adapt the data rate of a data signal by bit loading based on the noise ratio of an optical signal transmitted and / or received in a previous transmission interval, as discussed, for example, in Figure 14 and Figure 15 the context of.

[0157] Furthermore, the embodiments described herein provide an optical wireless device formed as a transceiver and configured to transmit and receive optical wireless signals.

[0158] According to an embodiment, the optical wireless device may be configured to partially or fully perform adaptation of the modulation of the optical signal source outside of a transmission interval in which an optical wireless signal is transmitted, for example to prevent non-linearity caused thereby. Alternatively or additionally, the device may be configured to partially or fully perform adaptation of an operating point of the optical signal source outside of a transmission interval in which an optical wireless signal is transmitted, also for preventing non-linearity.

[0159] According to an embodiment, an optical wireless device may be configured to gradually adapt the modulation of an optical signal source, where the step width is adapted to the optical wireless channel such that non-linear distortion occurring due to variations in the optical wireless channel can be neglected. This also allows for adjustment during transmission, even though applying several small steps results in higher time requirements. Alternatively or additionally, the operating point of the optical signal source may be gradually adapted, and the step size may be adapted to the optical wireless channel such that non-linear distortion occurring due to variations in the optical wireless channel can be neglected. For this purpose, the step size may be chosen such that, for example, the noise resulting from non-linear distortion increases the noise at the receiver output by less than 20%, 15%, or 10%, which means that this noise component is significantly smaller than the inherent receiver noise.

[0160] According to an embodiment, the optical wireless device is configured to transmit the optical wireless signal as an amplitude-modulated signal or a multi-carrier modulated signal such as an orthogonal frequency division multiplexing (OFDM) signal.

[0161] According to an embodiment, the optical wireless device is configured to obtain channel information as an instruction to adapt the modulation or adjust the operating point and to implement the instruction. For this purpose, for example, control signal 58 may be used.

[0162] The embodiments described herein further describe an optical wireless network having an optical wireless device according to one of the embodiments described herein and a receiver for receiving an optical wireless signal. The receiver may optionally be configured to output a corresponding feedback for estimating the channel.

[0163] Figure 16 A schematic flow chart of a method 1700 according to an embodiment is shown. Step 1710 includes arranging a transmitter and a receiver for transmitting an optical wireless signal via an optical wireless channel. Step 1720 includes repeatedly transmitting the optical wireless signal for different distances between the transmitter and the receiver such that transmission is performed using multiple modulations at each distance. Referring to Figure 12a 、 Figure 12b and Figure 12c 's tables, several modulations may be tested for different distances, see Figure 12a 's table.

[0164] Step 1730 includes determining, for each of the transmitted signals at the location of the receiver, at least one obtainable data rate and / or noise ratio, see, for example, Figure 12b 's measured quantities and / or Figure 12a 's data rates.

[0165] Step 1740 includes determining the modulation to be selected for each distance, by using which the data rate or the noise ratio is at a maximum, see Figure 12c 's table content.

[0166] Step 1750 includes: compiling the modulations selected for different distances, which can be stored, for example, in the information memory 72.

[0167] Figure 17 FIG. shows a schematic flow chart of a method 1800 according to an embodiment. Compared with the method 1700, it can be used to determine the adjustment of the operating point of an optical signal source. In step 1810, a transmitter and a receiver for transmitting an optical wireless signal via an optical wireless channel are arranged. In step 1820, the optical wireless signal is repeatedly transmitted for different distances between the transmitter and the receiver, so that transmission can be performed using multiple operating points at each distance.

[0168] Step 1830 includes: determining at least one achievable data rate and / or noise ratio for each of the transmitted signals at the position of the receiver.

[0169] In step 1840, the operating point selected for each distance is determined, by using which the data rate or the noise ratio is at a maximum.

[0170] In step 1850, the operating points selected for different distances are compiled.

[0171] According to an embodiment, a change in control can be performed to adjust the operating state of an electrical signal source and to adjust the operating point of an optical signal source, where only one of these two concepts is possible, depending on the later adjustment options in the optical wireless device.

[0172] The embodiment has the following positive side effect, and also prevents or reduces over-driving at the receiver, similar to the automatic gain control (AGC) at the receiver. Since the alternating component of the transmitted signal decreases at low channel attenuation, over-driving is not caused so quickly. If the DC component of the optical signal causes saturation of the receiver, the present invention described herein does not show any improvement.

[0173] The adjustment range can be several dB or can exceed 10 dB, as Figure 2a shown. The specific useful range depends on the maximum modulation depth of the OFDM signal and the specific technical implementation of the adjustment.

[0174] Here, the embodiment is not limited to OFDM signals, but also relates to other types of signal modulations where non-linear distortion may have a negative impact, such as in amplitude modulation.

[0175] Although some aspects have been described in the context of apparatuses, it is clear that these aspects also represent a description of corresponding methods, such that a block or device of an apparatus also corresponds to a corresponding method step or a feature of a method step. Similarly, aspects described in the context of method steps also represent a description of corresponding blocks or details or features of a corresponding apparatus. Some or all of the method steps may be performed by (or using) a hardware apparatus, such as a microprocessor, a programmable computer, or an electronic circuit. In some embodiments, some or several of the most important method steps may be performed by such an apparatus.

[0176] Depending on certain implementation requirements, embodiments of the invention may be implemented in hardware or software. The implementation may be carried out using a digital storage medium, such as a floppy disk, a DVD, a Blu-ray disc, a CD, a ROM, a PROM, an EPROM, an EEPROM, or a flash memory, a hard disk drive, or another magnetic or optical memory having electronically readable control signals stored thereon, which cooperate with or are capable of cooperating with a programmable computer system, so as to perform the corresponding method. Thus, the digital storage medium may be computer-readable. Some embodiments according to the invention include a data carrier comprising electronically readable control signals capable of cooperating with a programmable computer system so as to perform one of the methods described herein.

[0177] In general, embodiments of the invention may be implemented as a computer program product having program code that is operable to perform one of the methods when the computer program product is run on a computer. For example, the program code may be stored on a machine-readable carrier.

[0178] Other embodiments include a computer program for performing one of the methods described herein, wherein the computer program is stored on a machine-readable carrier.

[0179] In other words, an embodiment of the method according to the invention is thus a computer program comprising program code that is operable to perform one of the methods described herein when the computer program is run on a computer. Thus, another embodiment of the method according to the invention is a data carrier (or a digital storage medium or a computer-readable medium) on which a computer program for performing one of the methods described herein is recorded. The data carrier, the digital storage medium, or the computer-readable medium is generally tangible or non-volatile.

[0180] Thus, another embodiment of the method according to the invention is a data stream or a signal sequence representing a computer program for performing one of the methods described herein. The data stream or the signal sequence may be configured, for example, to be sent via a data communication connection, such as via the Internet.

[0181] Another embodiment includes a processing device, such as a computer or a programmable logic device, configured to or adapted to perform one of the methods described herein.

[0182] Another embodiment includes a computer having installed thereon a computer program for performing one of the methods described herein.

[0183] In some embodiments, a programmable logic device (e.g., a field programmable gate array, FPGA) can be used to perform some or all of the functions of the methods described herein. In some embodiments, a field programmable gate array can cooperate with a microprocessor to perform one of the methods described herein. Generally, these methods are preferably performed by any hardware device. This can be general-purpose hardware, such as a computer processor (CPU), or hardware specific to the method, such as an ASIC.

[0184] The above embodiments are only used to illustrate the principles of the present invention. It should be understood that modifications and variations of the arrangements and details described herein will be apparent to other technicians in the art. Therefore, the intention of the present invention is only limited by the scope of the appended claims and not by the specific details presented by the description and interpretation of the embodiments herein.

[0185] References

[0186] [a] Elgala, H.; Mesleh, R.; Haas, H.: A study of LED nonlinearity effects on optical wireless transmission using OFDM. In: Proceedings of the 2009 IFIP International Conference on Wireless and Optical Communications Networks, IEEE, 2009, pp. 1 - 5.

[0187] [b] Huang, Xingxing; Wang, Zhixin; Shi, Jianyang; Wang, Yiguang; Chi, Nan: 1.6 Gbit / s phosphorescent white LED based VLC transmission using a cascaded pre - equalization circuit and a differential outputs PIN receiver. In: Opt. Express 23 (2015), August, Nr. 17, S. 22034–22042. http: / / dx.doi.org / 10.1364 / OE.23.022034.

[0188] [c]Chun, H.; Rajbhandari, S.; Tsonev, D.; Faulkner, G.; Haas, H.; O’Brien, D.: Visible light communication using laser diode based remote phosphor technique. In: 2015 IEEE International Conference on Communications Workshops (ICCW), IEEE, 2015, pp. 1392–1397. http: / / dx.doi.org / 10.1109 / ICCW.2015.7247373.

[0189] [d]Ying, K.; Yu, Z.; Baxley, R. J.; Qian, H.; Chang, G.; Zhou, G. T.: Nonlinear distortion mitigation in visible light communications. In: IEEE Wireless Communications 22 (2015), no. 2, pp. 36–45.

[0190] [e]Khalid, A. M.; Cossu, G.; Corsini, R.; Choudhury, P.; Ciaramella, E.: 1-Gb / s Transmission Over a Phosphorescent White LED by Using Rate-Adaptive Discrete Multitone Modulation. In: IEEE Photonics Journal 4 (2012), no. 5, pp. 1465–1473.

[0191] [f]Hong, Y.; Wu, T.; Chean, L.: On the Performance of Adaptive MIMO-OFDM Indoor Visible Light Communications. In: IEEE Photonics Technology Letters 28 (2016), no. 8, pp. 907–910. http: / / dx.doi.org / 10.1109 / LPT.2016.2517192.

Claims

1. An optical wireless device for transmitting an optical wireless signal via an optical wireless channel, comprising: an electrical signal source configured to provide a data signal; and an optical signal source configured to convert the data signal into the optical wireless signal and transmit the optical wireless signal; wherein the optical wireless device is configured to: obtain channel information, the channel information including information associated with non - linear channel distortion of the optical wireless signal in the optical wireless channel, and, change an operating state of the electrical signal source by changing at least one of a modulation of a signal processor and a gain factor of a driver in the electrical signal source, thereby performing an adjustment of the modulation of the optical signal source based on the channel information to adjust the non - linear channel distortion, and / or perform an adjustment of an operating point by adjusting a current of the optical signal source to adjust the non - linear channel distortion.

2. The optical wireless device according to claim 1, wherein the adjustment of the non - linear channel distortion depends on a current transmitter - receiver arrangement or a current channel attenuation.

3. The optical wireless device according to claim 1, wherein the channel information is based on a noise ratio of the optical wireless signal and on a signal power of the optical wireless signal at a receiver.

4. The optical wireless device according to claim 3, wherein the noise ratio describes a signal - to - noise ratio SNR or a carrier - to - noise ratio CNR.

5. The optical wireless device according to claim 1, wherein the optical wireless signal is a first optical wireless signal transmitted in a first transmission interval, wherein the optical wireless device is configured to: for transmitting a second optical wireless signal in a later second transmission interval, determine that the channel attenuation has increased compared to the first transmission interval, and, increase the modulation and / or decrease the operating point; and / or wherein the optical wireless device is configured to: for transmitting a second optical wireless signal in a later second transmission interval, determine that the channel attenuation has decreased compared to the first transmission interval, and, decrease the modulation and / or increase the operating point.

6. The optical wireless device according to claim 5, configured to estimate the channel attenuation and configured to estimate the non - linear channel distortion based on reference information indicating noise at a receiver of the optical wireless channel.

7. The optical wireless device according to claim 6, configured to estimate a channel estimate based on a signal power at the receiver and a signal power at a transmitter of the optical wireless channel.

8. The optical wireless device according to claim 6, comprising an information memory and / or a channel estimator configured to output information indicating a link between a signal transmitted in the optical wireless channel and the non - linear channel distortion.

9. The optical wireless device according to claim 1, wherein the channel information is at least partially based on feedback from a receiver of the optical wireless signal regarding: a signal power of the optical wireless signal at the receiver, and a noise ratio of the optical wireless signal at the receiver.

10. The optical wireless device according to claim 1, configured to transmit the optical wireless signal as a first optical wireless signal via the optical wireless channel and implemented to receive a second optical wireless signal via the optical wireless channel, and configured to perform channel estimation on the optical wireless channel based on the second optical wireless signal to determine the noise ratio of the second optical wireless signal.

11. The optical wireless device according to claim 1, configured to receive the channel information from a receiver of the optical wireless signal.

12. The optical wireless device according to claim 1, configured to adapt the optical wireless signal to perform the adaptation on the modulation of the optical signal source and / or on the operating point of the optical signal source to change the non-linear channel distortion generated by the optical wireless device.

13. The optical wireless device according to claim 1, configured to adapt the modulation to adapt the amplitude and / or the effective value of the alternating component of the data signal.

14. The optical wireless device according to claim 1, configured to adapt the operating point to adapt the DC component of the data signal.

15. The optical wireless device according to claim 1, implemented to perform the adaptation on the modulation of the optical signal source, and configured to increase the noise ratio of a later optical wireless signal at a position of a receiver of the optical wireless signal by adapting the modulation, the later optical wireless signal being transmitted via the optical wireless channel in a subsequent transmission interval.

16. The optical wireless device according to claim 15, wherein the electrical signal source is configured to increase the data rate for the later optical wireless signal based on the increased noise ratio.

17. The optical wireless device according to claim 1, implemented to perform the adaptation on the modulation of the optical signal source, and configured to transmit the optical wireless signal based on a first power value of the electrical signal, wherein the optical wireless device is configured to adapt the modulation of the optical signal source based on channel information by reducing the alternating component of the electrical signal to a second alternating component for a later optical wireless signal, such that it indicates increased received power and reduced noise ratio at the receiver of the optical wireless signal compared to a previous transmission interval; and / or wherein the optical wireless device is configured to adapt the modulation of the optical signal source based on channel information by increasing the alternating component of the electrical signal to a second alternating component for a later optical wireless signal, such that it indicates reduced received power and reduced noise ratio at the receiver of the optical wireless signal compared to a previous transmission interval.

18. The optical wireless device according to claim 1, implemented to perform the adaptation on the modulation of the optical signal source, wherein the optical wireless device is configured to adapt the operating state of a driver circuit of the electrical signal source to adapt the modulation of the optical signal source.

19. The optical wireless device according to claim 18, wherein the driver circuit includes an amplifier element configured to amplify a processor signal or convert the processor signal into a current, and wherein the optical wireless device is configured to adjust the gain of the amplifier element to adjust the operating state of the driver circuit to adjust the non-linear channel distortion at the optical signal source.

20. The optical wireless device according to claim 19, wherein the driver circuit includes an adaptive attenuation member to adjust the gain of the amplifier element and / or the driver circuit is configured to actively adjust the gain factor of the amplifier element.

21. The optical wireless device according to claim 19, wherein the amplifier element is coupled to a resistor circuit that adjusts the gain, and wherein the optical wireless device is configured to continuously and / or in a discrete resistive manner adjust the gain.

22. The optical wireless device according to claim 21, wherein the resistor circuit includes a plurality of switch states in which different resistors for adjusting the gain are coupled to the amplifier element, and wherein the optical wireless device is configured to select and adjust one of the plurality of switch states for gain control.

23. The optical wireless device according to claim 18, wherein the electrical signal source includes a signal processor configured to provide a processor signal to the driver circuit, wherein the driver circuit is configured to amplify the processor signal, and wherein the signal processor is configured to adjust the alternating component of the processor signal to adjust the operating state of the driver circuit.

24. The optical wireless device according to claim 1, implemented to perform the adjustment of the modulation of the optical signal source and configured to obtain the channel information as a control signal, the control signal indicating the dependence on the channel attenuation and the non-linear channel distortion of the optical wireless channel.

25. The optical wireless device according to claim 1, implemented to perform the adjustment of the modulation of the optical signal source, wherein the channel information is based on the DC component of the optical wireless signal received by the receiver of the optical wireless channel and is associated with the adjustment of the attenuation member of the electrical signal source.

26. The optical wireless device according to claim 1, implemented to perform the adjustment of the modulation of the optical signal source, wherein the channel information is based on the alternating component of the optical wireless signal received by the receiver of the optical wireless channel and is associated with the adjustment of the gain factor of the electrical signal source.

27. The optical wireless device according to claim 1, the optical wireless device being implemented to perform the adjustment of the modulation of the optical signal source and including an information memory in which different predefined values for the modulation associated with different values of the channel distortion are stored, and the optical wireless device being configured to obtain and apply an adjustable value for the modulation from the information memory by using the channel information; and / or The optical wireless device is implemented to perform the adjustment on the operating point of the optical signal source and includes an information memory, in which different predefined values for the operating point associated with different values of the channel distortion are stored, and the optical wireless device is configured to obtain and apply an adjustable value for the operating point from the information memory by using the channel information.

28. The optical wireless device according to claim 1, which is implemented to perform the adjustment on the modulation of the optical signal source, wherein the optical wireless device is configured to obtain, by means of the adjustment, the noise component of the non-linear channel distortion in the overall noise at the position of the receiver in the order of magnitude of the internal receiver noise.

29. The optical wireless device according to claim 1, wherein the optical signal source includes an optical transmitter, in particular a light-emitting diode, and the operating point corresponds to the DC component of the current consumption of the optical transmitter.

30. The optical wireless device according to claim 1, which is implemented to adjust the operating point, wherein the optical wireless device is configured to increase the operating point when the component of the non-linear channel distortion in the overall noise is dominant or more important and the optical wireless signal has a high noise ratio at its receiver and the optical wireless signal has a high data rate.

31. The optical wireless device according to claim 1, which is implemented to adjust the operating point, wherein the optical wireless device is configured to decrease the operating point when the component of the non-linear channel distortion in the overall noise is not dominant or less important and the optical wireless signal has a low noise ratio at its receiver and the optical wireless signal has a high data rate.

32. The optical wireless device according to claim 1, wherein the electrical signal source is configured to adjust the data rate of the data signal based on the noise ratio of the transmitted and / or received optical signals in the previous transmission interval.

33. The optical wireless device according to claim 1, which is formed as a transceiver and is configured to receive an optical wireless signal.

34. The optical wireless device according to claim 1, which is configured to: perform the adjustment on the modulation of the optical signal source partially or completely outside the transmission interval of the transmitted optical wireless signal; and / or perform the adjustment on the operating point of the optical signal source partially or completely outside the transmission interval of the transmitted optical wireless signal.

35. The optical wireless device according to claim 1, which is configured to: perform the adjustment on the modulation of the optical signal source gradually, wherein the step size is suitable for the optical wireless channel such that the non-linear channel distortion occurring due to the adjustment of the modulation of the optical signal source in the optical wireless channel can be neglected; and / or perform the adjustment on the operating point of the optical signal source gradually, wherein the step size is suitable for the optical wireless channel such that the non-linear channel distortion occurring due to the adjustment of the modulation of the optical signal source in the optical wireless channel can be neglected.

36. The optical wireless device according to claim 1, configured to transmit the optical wireless signal as an amplitude-modulated signal or as an orthogonal frequency division multiplexing (OFDM) signal.

37. The optical wireless device according to claim 1, configured to obtain the channel information as an instruction for adapting the modulation or adjusting the operating point and to implement the instruction.

38. An optical wireless network having the optical wireless device according to claim 1 and a receiver for receiving the optical wireless signal.

Images