CODING AND ENCRYPTION FOR WAVELENGTH DIVISION MULTIPLEXING VISIBLE LIGHT COMMUNICATIONS

Abstract

The method includes a first encryption step of encrypting each of a plurality of data streams to obtain a respective encrypted data stream, a mapping step of mapping the plurality of encrypted data streams obtained in the first encryption step to a plurality of transmission streams for transmission via the optical transmission units, wherein the transmission streams and optical transmission units are in a one-to-one relationship, and wherein each transmission stream is mapped to by at least two of the plurality of encrypted data streams. The method further includes a second encryption step of encrypting each of the plurality of transmission streams to obtain a respective encrypted transmission stream, and a transmission step of transmitting each of the plurality of encrypted transmission streams obtained in the second encryption step via a respective optical transmission unit.

Claims

1. A method of transmitting multiple data streams via multiple optical transmission units adapted for optical communication using wavelength division multiplexing, the method comprising: a first encryption step of encrypting each of a plurality of data streams to obtain a respective encrypted data stream; and a mapping step of mapping the plurality of encrypted data streams obtained in the first encryption step to a plurality of transmission streams for transmission via the optical transmission units, wherein the transmission streams and optical transmission units are in a one-to-one relationship, and wherein each transmission stream is mapped to by at least two of the plurality of encrypted data streams; a second encryption step of encrypting each of the plurality of transmission streams to obtain a respective encrypted transmission stream; and a transmission step of transmitting each of the plurality of encrypted transmission streams obtained in the second encryption step via a respective optical transmission unit.

2. The method according to claim 1, wherein in the first encryption step the plurality of data streams are encrypted individually, using a distinct encryption scheme for each data stream.

3. The method according to claim 1, wherein in the mapping step each transmission stream is obtained as an interleaved sequence of data portions of at least two of the plurality of encrypted data streams.

4. The method according to claim 1, wherein in the mapping step each of the plurality of encrypted data streams is mapped to each of the plurality of transmission streams.

5. A method of receiving multiple encrypted transmission streams via multiple optical reception units adapted for optical communication using wavelength division multiplexing, the method comprising: a reception step of receiving a plurality of encrypted transmission streams at a plurality of optical reception units, wherein the received encrypted transmission streams and the optical reception units are in a one-to-one relationship; a first decryption step of decrypting each of the plurality of encrypted transmission streams to obtain a respective transmission stream; a mapping step of mapping the plurality of transmission streams obtained in the first decryption step to a plurality of encrypted data streams, wherein each transmission stream is mapped to at least two of the plurality of encrypted data streams; and a second decryption step of decrypting each of the plurality of encrypted data streams to obtain a respective data stream.

6. The method according to claim 5, wherein in the second decryption step the plurality of encrypted data streams are decrypted individually, using a distinct decryption scheme for each encrypted data stream.

7. The method according to claim 5, wherein in the mapping step each encrypted data stream is obtained as an interleaved sequence of data portions of the plurality of transmission streams, such that for each transmission stream at least two of the plurality of encrypted data streams contain a data portion of the respective transmission stream.

8. A transmission device for transmitting multiple data streams via multiple optical transmission units adapted for optical communication using wavelength division multiplexing, the transmission device comprising: a first encryption unit for encrypting each of a plurality of data streams to obtain a respective encrypted data stream; and a mapping unit for mapping the plurality of encrypted data streams obtained by the first encryption unit to a plurality of transmission streams for transmission via the optical transmission units, wherein the transmission streams and optical transmission units are in a one-to-one relationship, and wherein each transmission stream is mapped to by at least two of the plurality of encrypted data streams; a second encryption unit for encrypting each of the plurality of transmission streams to obtain a respective encrypted transmission stream; and a transmission unit for transmitting each of the plurality of encrypted transmission streams obtained by the second encryption unit, wherein the transmission unit comprises the multiple optical transmission units, and each encrypted transmission stream is transmitted via a respective optical transmission unit.

9. The transmission device according to claim 8, wherein the first encryption unit is configured to encrypt the plurality of data streams individually, using a distinct encryption scheme for each data stream.

10. The transmission device according to claim 8, wherein the mapping unit is configured to generate each transmission stream by sequentially interleaving data portions of at least two of the encrypted data streams.

11. The transmission device according to claim 8, wherein the optical transmission units are optical diodes emitting light at mutually different wavelengths.

12. A reception device for receiving multiple encrypted transmission streams via a plurality of optical reception units adapted for optical communication using wavelength division multiplexing, the reception device comprising: a reception unit comprising the plurality of optical reception units, for receiving a plurality of encrypted transmission streams at the plurality of optical reception units, wherein the encrypted transmission streams and the optical reception units are in a one-to-one relationship; a first decryption unit for decrypting each of the plurality of encrypted transmission streams to obtain a respective transmission stream; a mapping unit for mapping the plurality of transmission streams obtained by the first decryption unit to a plurality of encrypted data streams, wherein each encrypted data stream is mapped to by at least two of the plurality of transmission streams; and a second decryption unit for decrypting each of the plurality of encrypted data streams to obtain a respective data stream.

13. The reception device according to claim 12, wherein the second decryption unit is configured to decrypt the plurality of encrypted data streams individually, using a distinct decryption scheme for each encrypted data stream.

14. The reception device according to claim 12, wherein the mapping unit is configured to generate each encrypted data stream by sequentially interleaving data portions of the transmission streams, such that for each transmission stream at least two of the plurality of encrypted data streams contain a data portion of the respective transmission stream.

15. The reception device according to claim 12, wherein each optical reception unit comprises a photodetector and an optical filters, wherein the optical filters of the multiple optical reception unit have mutually different pass bands.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0029] Embodiments of the disclosure are explained below in an exemplary manner with reference to the accompanying drawings, wherein

[0030] FIG. 1 schematically illustrates an example of a VLC system to which embodiments of the disclosure may be applied,

[0031] FIG. 2A schematically illustrate a conventional mapping scheme,

[0032] FIG. 2B schematically illustrates an example of a mapping scheme that may be employed in embodiments of the disclosure,

[0033] FIG. 3 is a flow chart schematically illustrating an example of a transmission method according to embodiments of the disclosure,

[0034] FIG. 4A and FIG. 4B schematically illustrate examples of transmission devices according to embodiments of the disclosure,

[0035] FIG. 5 is a flow chart schematically illustrating an example of a reception method according to embodiments of the disclosure,

[0036] FIG. 6 schematically illustrates an example of an integrated device for transmission and reception according to embodiments of the disclosure, and

[0037] FIG. 7 schematically illustrates an example of a reception device according to embodiments of the disclosure.

DETAILED DESCRIPTION

[0038] It has been found that WDM can be jointly embedded in a VLC system by using inherent frequency gaps of colored LEDs to enable simultaneous transmission of multiple signals. FIG. 1 schematically illustrates examples of a transmitter (e.g. a VLC transmitter) 100 and a receiver (e.g. a VLC receiver) 200 employing WDM.

[0039] In the transmitter 100, a plurality of data streams are generated. This proceeds e.g. via an Arbitrary Waveform Generator (AWG) 110 outputting a plurality of signals. The plurality of signals may be (individually) amplified by an amplifier 120 comprising an amplification stage for each signal. The plurality of amplified signals may then be input to a bias unit 130 which impresses each signal in accordance with data to be transmitted, thereby generating the plurality of data streams. The data streams may be encoded for optical transmission by an encoder unit (not shown in the figure). The (encoded) data streams may be transmitted via optical transmission units 140A, 140B, 140C. The optical transmission units 140A, 140B, 140C may be LEDs (optical diodes) that emit light at mutually different wavelengths.

[0040] The receiver 200 may comprise a lens 210, a plurality of optical filters (color filters) 220, a plurality of photodetectors 230, an amplifier 240, a filter (e.g. a low pass filter) 250, and a decoding unit 260. The optical filters 220 may have mutually different pass bands, i.e. each optical filter may allow passage of a distinct wavelength or range of wavelengths, while blocking all other wavelengths. Each optical filter 220 may be arranged in conjunction with a corresponding photodetector 230. After focusing be the lens 210, the received optical signals may be optically filtered by the optical filters 220 and converted into electrical signals at corresponding photodetectors 230. After filtering at the filter 250, decoding may be performed in the decoding unit 260.

[0041] Using the optical communication system of FIG. 3, the data throughput is enhanced by a factor corresponding to the number of data streams (e.g. three in the illustrated example). In order to avoid interference of spatially adjacent channels, and in order to enhance security, Forward Error Correction (FEC) and encryption schemes may be employed. The former aids the target user (receiver) to recover the signal successfully, and the latter prevents eavesdropping by third parties.

[0042] FIG. 2A schematically illustrates a conventional mapping scheme. This scheme corresponds to horizontal mapping, as described e.g. in T. A. Khan et al., Visible Light Communication using Wavelength Division Multiplexing for Smart Spaces, in Proceedings of the .sub.9th Annual IEEE Consumer Communications and Networking Conference (CCNC'12), Jan. 2012. For example, three (7,4)-Bose-Chaudhuri-Hocquenghem (BCH)-Codes 310A, 310B, 310C (data streams) may be independently transmitted via Red (R), Green (G), and Blue (B) channels, using optical transmission units 140A, 140B, 140C. In the figure, the horizontal axis represents time, and the vertical axis indicates wavelength or frequency of emitted light.

[0043] FIG. 2B schematically illustrates an example of a mapping scheme that may be employed in embodiments of the disclosure.

[0044] A plurality of data streams may be individually encoded for optical transmission, e.g. as (7,4)-BCH-Codes. Any suitable encoding scheme may be used at this stage. Further, depending on the data streams that are received as an input, encoding may not be required. Each data stream may be obtained from an individual user of a multi-user WDM-VLC system, or all data streams may be obtained from a single user. Also combinations of these two extremal cases are possible.

[0045] The plurality of (encoded) data streams may be subjected to (first) encryption, e.g. by scrambling of symbols in the (encoded) data streams or by encrypting the (encoded) data streams using an appropriate encryption algorithm. Scrambling is understood to involve interchanging positions of symbols in a respective stream, or introducing phase shifts into a respective stream, e.g. according to a scrambling sequence generated by a generating algorithm. The symbol positions may be changed in a (pseudo-)random manner, and the phase shifts may be pseudo-random phase shifts. The scrambling sequence (scrambling scheme, encryption algorithm, or encryption scheme in general) may be varied with time. Likewise, an encryption key may be varied with time. The data streams may be encrypted individually, i.e. each data stream may be encrypted according to a distinct encryption scheme (e.g. scrambling scheme, or encryption scheme in general). These encryption schemes may be confidential to both internal users (i.e. users providing the data streams) and external users.

[0046] After encryption, the encrypted data streams may be subjected to WDM, i.e. the encrypted data streams may be mapped to a plurality of data streams. For each optical transmission unit, there may be a corresponding transmission stream. That is, the numbers of optical transmission units and transmission streams may be equal, and the optical transmission units and transmission streams may be in a one-to-one relationship. The mapping may proceed according to a predetermined mapping scheme. Successful transmission (decoding) may require that the mapping scheme is known to the receiver side. In the mapping, each transmission stream may be obtained as an interleaved sequence of data portions of encrypted data streams (e.g. of at least two encrypted data streams). To this end, each transmission stream may be (virtually) divided into a plurality of sequential slots (e.g. corresponding to blocks) in the time domain. For each of these slots, a data portion (e.g. block) of one of the plurality of encrypted data streams may be selected for providing the content of the respective slot. Each slot or block may comprise a predetermined number of symbols. Put differently, blocks of the encrypted data streams may be distributed to the transmission streams. To avoid trivial mapping, each transmission stream may be mapped to by at least two encrypted data streams, i.e. each transmission stream may comprise contributions (data portions, e.g. blocks) from at least two different encrypted data streams. To ensure optimal utilization of time-frequency resources, the number of (encrypted) data streams may be equal to the number of transmission streams, and hence the number of (encrypted) data streams may be equal to the number of optical transmission units.

[0047] In general, for N encrypted data streams and N transmission streams, an m-th block of an n-th transmission stream corresponds to an m-th block of an encrypted data stream the number of which is given by a function F(n,m) which implements the mapping scheme. Said function may be known to the receiver side. The mapping scheme may be varied with time. Further, the mapping scheme may be said to present another layer of security (i.e. encryption).

[0048] A particular mapping scheme that may be employed in embodiments of the disclosure is diagonal mapping. However, the present disclosure is not to be understood to be limited to diagonal mapping. In diagonal mapping, each of the plurality of encrypted data streams may be mapped to each of the plurality of transmission streams in the mapping step. Since each encrypted data stream is mapped to each transmission stream, each transmission stream comprises contributions (data portions, e.g. blocks) of each encrypted data stream. Thus, each transmission stream may be obtained as an interleaved sequence of data portions of each of the plurality of encrypted data streams.

[0049] In more detail, in diagonal mapping a first block of a first transmission stream may correspond to a first block of a first encrypted data stream, a second block of the first transmission stream may correspond to a second block of a second encrypted data stream, and so forth. Further, a second block of the second transmission stream may correspond to a second block of the first encrypted data stream, a third block of the second transmission stream may correspond to a third block of the second encrypted data stream, and so forth. In other words, if diagonal mapping is employed, each transmission stream may be mapped to by each encrypted data stream in a cyclical manner. In general, for N encrypted data streams and N transmission streams, an m-th block of an n-th transmission stream corresponds to an m-th block of an (((n+m+1) mod N) +1)-th encrypted data stream.

[0050] When employing diagonal mapping, each data stream will be transmitted by each optical transmission unit, i.e. there are a plurality (three in the example of FIG. 2B) of independent channel realizations.

[0051] While mapping according to the present disclosure has been explained with reference to encrypted data streams and transmission streams, it is understood that the above description generalizes to any kind of input streams and any kind of output streams.

[0052] Subsequent to mapping, each transmission stream may be subjected to (second) encryption. Unless indicated otherwise, encryption at this stage may proceed as described above for encryption of the (encoded) data streams. The encryptions scheme (e.g. scrambling sequence or encryption key) may be varied with time. The transmission streams may be encrypted individually, i.e. transmission stream may be encrypted according to a distinct encryption scheme (e.g. scrambling sequence). The encryption schemes may be confidential to external users, but may be known to internal users (i.e. users providing the data streams).

[0053] As indicated above, it is the purpose of the first encryption to protect each individual user in the multi-user WDM-VLC system from eavesdropping, i.e. from eavesdropping by other internal users, and also from eavesdropping by third parties (external eavesdropping). Thus, (first) encryption information (encryption scheme, e.g. scrambling scheme or a key for encryption/decryption) may not be shared among the internal users of the multi-user WDM-VLC system. Further, it is the purpose of the second encryption to protect the internal users against external eavesdropping. Accordingly, (second) encryption information (encryption scheme, e.g. scrambling scheme or a key for encryption/decryption) may be shared among the internal users of the multi-user WDM-VLC system.

[0054] FIG. 3 is a flow chart schematically illustrating an example of a transmission method according to embodiments of the disclosure.

[0055] At step S501, which is a first encryption step, the plurality of data streams may be encrypted, as described with reference to FIG. 2B above. Encrypting the plurality of data streams may involve scrambling (symbols of) each of the plurality of data streams or encrypting each of the plurality of data streams using a suitable encryption algorithm. Each data stream may be encrypted using a unique (i.e. data stream specific) encryption scheme (e.g. scrambling scheme, or key). As an outcome of this step, a plurality of encrypted data streams are obtained.

[0056] Optionally, prior to step S501, an encoding step of encoding each of a plurality of data streams for optical transmission may be provided (not shown in FIG. 3).

[0057] At step S502, which is a mapping step, the encrypted data streams obtained at step S501 may be mapped to a plurality of transmission streams, as described with reference to FIG. 2B above.

[0058] The number of transmission streams may be equal to the number of optical transmission units and to the number of encrypted data streams. Each transmission stream may be mapped to by at least two encrypted data streams. If diagonal mapping is employed, each transmission stream may be mapped to by each encrypted data stream, in a cyclical manner. As an outcome of this step, a plurality of transmission streams are obtained.

[0059] At step S503, which is a second encryption step, each of the plurality of transmission streams may be encrypted, as described with reference to FIG. 2B above. Encrypting the plurality of transmission streams may involve scrambling (symbols of) each of the plurality of transmission streams or encrypting each of the plurality of transmissions streams using a suitable encryption algorithm. Each transmission stream may be encrypted using a unique (i.e. transmission stream specific) encryption scheme (e.g. scrambling scheme, or key). As an outcome of this step, a plurality of encrypted transmission streams are obtained.

[0060] At step S504, which is a transmission step, each of the plurality of encrypted transmission streams obtained at step S503 may be transmitted via a corresponding optical transmission unit. Each transmission stream may be transmitted as a corresponding optical signal. The optical transmission units may be colored LEDs (optical diodes) that emit light at mutually different wavelengths, such as red, green and blue LEDs, for example. Thus, each transmissions stream may be transmitted as a corresponding optical signal of a specific wavelength.

[0061] FIG. 4A and FIG. 4B schematically illustrate examples of transmission devices 400 according to embodiments of the disclosure. FIG. 4A relates to a multi-user case in which each user provides a data stream and FIG. 4B relates to a single-user case in which a single user provides a plurality of data streams, in order to profit from increased bandwidth for transmission.

[0062] A plurality of data streams e.g. provided by a plurality of individual users may be input to the transmission device 400 of FIG. 4A. The transmission device 400 may comprise a plurality of encoding units (e.g. FEC encoders) 410A, 410B, 410C, a first encryption unit 420, a mapping unit 430, a second encryption unit 440, and a plurality of optical transmission units 140A, 140B, 140C. The first encryption unit 420 may comprise a plurality of first encryption sub-units 420A, 420B, 420C, e.g. one first encryption sub-unit for each data stream. The second encryption unit 440 may comprise a plurality of second encryption sub-units 440A, 440B, 440C, e.g. one second encryption sub-unit for each transmission stream.

[0063] Each of the encoding units 410A, 410B, 410C may be configured to encode a corresponding data stream for optical transmission, e.g. using FEC encoding. The first encryption unit 420 may be configured to encrypt each of the plurality of data streams, as described above with reference to step S501. For example, each of the first encryption sub-units 420A, 420B, 420C of the first encryption unit 420 may be configured to encrypt a corresponding one of the plurality of data streams, e.g. by scrambling the corresponding data stream. The mapping unit 430 may be configured to perform the mapping described with reference to step S502. The second encryption unit 440 may be configured to encrypt each of the plurality of transmission streams, as described above with reference to step S503. For example, each of the second encryption sub-units 440A, 440B, 440C of the second encryption unit 440 may be configured to encrypt a corresponding one of the plurality of transmission streams, e.g. by scrambling the corresponding transmission stream. Each of the plurality of optical transmission units 140A, 140B, 140C may be configured to transmit a corresponding one of the plurality of encrypted transmission streams. Each optical transmission unit 140A, 140B, 140C may be a colored LED (optical diode). The colored LEDs may emit light at mutually different wavelengths, i.e. each colored LED may emit light at a distinct wavelength. The plurality of optical transmission units 140A, 140B, 140C may be comprised by a transmission unit of the transmitter device 400 (not shown in the figure).

[0064] The transmission device 400 illustrated in FIG. 4B is identical to the transmission device 400 illustrated in FIG. 4A, with the exception that it may additionally comprise a signal processing unit 405 for converting a single data stream provided by a user to a plurality of data streams, in accordance with a number of optical transmission units 140A, 140B, 140C of the transmission device 400. Notably, for N data streams, the data rate of the single data stream is an N-fold of the data rate of each of the plurality of data streams. Thus, the transmission device 400 in FIG. 4A may be said to support multi-user communications, while the transmission device of FIG. 4B may be said to support single-user communication with an enhanced bandwidth.

[0065] FIG. 5 is a flow chart schematically illustrating an example of a reception method according to embodiments of the disclosure. Notably, method steps of the reception method may correspond to the inverse of respective method steps of the transmission method described above with reference to FIG. 3.

[0066] At step S505, which is a reception step, a plurality of encrypted transmissions streams (corresponding to the encrypted transmission streams transmitted at step S504 in FIG. 3) may be received. Receiving may be performed by a plurality of optical reception units that may be in a one-to-one relationship with the plurality of encrypted transmission streams. The optical reception units may be sensitive to light at mutually different wavelengths, corresponding to the mutually different wavelengths of emission of the optical transmission units. Each optical reception unit may comprise an optical filter (color filter) that permits passage of a specific wavelength or wavelength band only, and a photodetector arranged behind the optical filter with respect to a received optical signal. Each optical filter may correspond to a respective one of the plurality of optical transmission units (e.g. colored LEDs). That is, light emitted by a given optical transmission unit may have a wavelength that lies in the passband of a corresponding optical filter, and lies in the rejection bands of the remaining optical filters. As an outcome of this step, a plurality of encrypted transmission streams are obtained.

[0067] At step S506, which is a first decryption step, each of the plurality of encrypted transmission streams may be decrypted. Decryption may be performed in accordance with a first decryption scheme, which may be the inverse of an encryption scheme of the second encryption step S503 described above. That is, the first decryption step may be the inverse of the second encryption step S503 described above. Decrypting each of the plurality of encrypted transmission streams may involve (un-)scrambling each of the plurality of encrypted transmission streams, e.g. by interchanging positions of symbols in each encrypted transmissions stream or by introducing appropriate phase shifts into each encrypted transmission stream. The changes of positions of symbols may be chosen to reverse any changes of positions of the symbols in the second encryption step S503 described above. Likewise., the phase shifts may be chosen to compensate for any phase shifts introduced in scrambling the plurality of transmission streams in the second encryption step S503 described above. Decrypting each of the plurality of encrypted transmission streams may also involve decrypting the respective encrypted transmission stream using an appropriate decryption algorithm. Each encrypted transmission stream may be decrypted individually. As an outcome of this step, a plurality of transmission streams are obtained.

[0068] At step S507, which is an (un-)rnapping step, the plurality of transmission streams obtained in step S506 may be mapped to a plurality of encrypted data streams. Each transmission stream may be mapped to at least two of the plurality of encrypted data streams. At this step, each encrypted data stream may be obtained as an interleaved sequence of data portions (e.g. blocks) of the plurality of transmission streams. This step may be the inverse of the mapping step S502 described above. For further details on mapping, reference is made to the above description with reference to FIG. 2B. As an outcome of this step, a plurality of encrypted data streams are obtained.

[0069] At step S508, which is a second decryption step, each of the plurality of encrypted data streams may be decrypted. Decryption may be performed in accordance with a second decryption scheme, which may be the inverse of an encryption scheme of the first encryption step S501 described above. That is, the second decryption step may be the inverse of the first encryption step S501 described above. Decrypting each of the plurality of encrypted data streams may involve (un-)scrambling each of the plurality of encrypted data streams, e.g. by interchanging positions of symbols in each encrypted data stream or by introducing appropriate phase shifts into each encrypted data stream. The changes of positions of symbols may be chosen to reverse any changes of positions of the symbols in the second encryption step S503 described above. Likewise, the phase shifts may be chosen to compensate for any phase shifts introduced in scrambling the plurality of data streams in the first encryption step S501 described above. Decrypting each of the plurality of encrypted data streams may also involve decrypting the respective encrypted transmission stream using an appropriate decryption algorithm. Each encrypted data stream may be decrypted individually. As an outcome of this step, a plurality of data streams are obtained.

[0070] The method may further comprise a decoding step (not shown in FIG. 5) at which each of the plurality of data streams obtained in step S508 may be decoded to a respective decoded data stream.

[0071] The method may yet further comprise an outputting step (not shown in FIG. 5) at which each decoded data stream or each data stream is output.

[0072] Next, a reception device according to embodiments of the disclosure will be described with reference to FIG. 6, which schematically illustrates an example of an integrated device 600 for transmission and reception. Notably, components of the integrated device 600 relating the reception as described in the next paragraph may be provided as parts of a stand-alone reception device.

[0073] Such reception device may comprise a reception unit, a first decryption unit 450, a mapping unit (un-mapping unit) 460, and a second decryption unit 470. The reception unit may comprise a plurality of optical reception units 230, as described above with reference to FIG. 1 and FIG. 5. The reception unit may be configured to perform the processing of step S505 described above. The first description unit 450 may be configure to perform the processing of step S506 described above. The first decryption unit 450 may comprise a plurality of first decryption sub-units (not shown in the figure), their number being equal to the number of encrypted transmission streams, each being configured to decrypt a corresponding one of the plurality of encrypted transmission streams. The mapping unit 460 may be configured to perform the processing of step S507 described above. The second decryption unit 470 may be configure to perform the processing of step S508 described above. The second decryption unit 470 may comprise a plurality of second decryption sub-units (not shown in the figure), their number being equal to the number of encrypted data streams, each being configured to decrypt a corresponding one of the plurality of encrypted data streams.

[0074] The integrated device 600 may further comprise components of the transmission devices described with reference to FIG. 4A or FIG. 4B, such as the first encryption unit 420, the mapping unit 430, the second encryption unit 440, and the transmission unit.

[0075] FIG. 7 schematically illustrates an example of a reception device (centralized reception device) 700 according to embodiments of the disclosure. The reception device 700 may comprise the components relating to reception described with reference to FIG. 6. The reception device may further comprise the components relating to transmission described with reference to FIG. 4A, FIG. 4B, or FIG. 6. The reception device 700 may further comprise connection ports for connecting to one or more user device 800A, 800B, 800C, e.g. via cable. Such cable-connections may employ the USB standard, for example. Each of the user devices 800 may receive an output data stream from the reception device 700. In case that the reception device No is provided also with transmission capability, each of the user devices 800 may provide an input data stream to the reception device 700 for subsequent transmission via WDM-VLC.

[0076] It should be understood that while the above description is made in terms of VLC, the present disclosure id not limited to communication using visible light, and relates in general to optical communication. Optical communication may proceed e.g. via infrared or ultraviolet light, in addition to visible light.

[0077] It should be noted that the apparatus features described above correspond to respective method features that may however not be explicitly described, for reasons of conciseness, and vice versa. The disclosure of the present document is considered to extend also to such method features and apparatus features, respectively.

[0078] It should further be noted that the description and drawings merely illustrate the principles of the proposed apparatus. Those skilled in the art will be able to implement various arrangements that, although not explicitly described or shown herein, embody the principles of the disclosure and are included within its spirit and scope. Furthermore, all examples and embodiment outlined in the present document are principally intended expressly to be only for explanatory purposes to help the reader in understanding the principles of the proposed apparatus. Furthermore, all statements herein providing principles, aspects, and embodiments of the disclosure, as well as specific examples thereof, are intended to encompass equivalents thereof.