Multi-band CAP digital chaotic encryption method and system in band-limited visible light communication system

Abstract

The invention relates to the technical field of visible light communication (VLC), particularly discloses a multi-band CAP digital chaotic encryption method and system in a band-limited visible light communication system, and designs three encryption modes of chaotic constellation mapping, chaotic index selection and chaotic PWC coding. According to the chaotic constellation mapping, the positions of constellation points in the corresponding original constellation set are adjusted according to the constellation bits, and a new chaotic constellation set is obtained; the chaotic index selection is used for scrambling a corresponding relation between two distinguishable constellation modes and two encrypted chaotic constellation sets; and performing sub-band sequence chaotic encryption on m sub-bands obtained after block creation by chaotic PWC coding, disorganizing the sequence of the m sub-bands, and then performing PWC coding. Three encryption modes are designed, when confidential information is located in the coverage range of the VLC system, useful information in the system can be prevented from being eavesdropped by unauthorized malicious users, and therefore the information transmission safety is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of visible light communication (VLC), and particularly to a multi-band CAP digital chaos encryption method and system in a band-limited visible light communication system. Background Art

[0002] Visible light communication (VLC) using commercial light-emitting diodes (LEDs) has become increasingly attractive in sixth-generation (6G) and Internet of Things (IoT) systems due to its abundant and unregulated spectral resources, no electromagnetic radiation, and high security. However, the communication capacity of an actual VLC system is severely limited by a small modulation bandwidth and severe non-linearity.

[0003] Many techniques have been proposed to expand the available bandwidth of VLC systems. First, analog or digital equalization techniques can be applied to break through the limited bandwidth of LEDs. On the other hand, various spectrally efficient modulation and multiple access techniques can also be considered to improve the achievable data rate of VLC systems, including carrierless amplitude and phase (CAP) modulation, orthogonal frequency division multiplexing (OFDM) with high-order modulation formats. In addition, compared with OFDM, CAP has the advantages of lower implementation cost and lower peak-to-average power ratio (PAPR). To improve the link performance, multi-band CAP (mCAP) has been further proposed, which divides the available signal bandwidth into m sub-bands to improve the tolerance to the low-pass effect of LEDs.

[0004] In recent years, a new index modulation mCAP (mCAP-IM) technique has been proposed to obtain better bit error rate (BER) performance than traditional mCAP. In mCAP-IM, the sub-bands of traditional mCAP are divided into two parts: active sub-bands and inactive sub-bands. The active sub-bands can be modulated by constellation data symbols, while the inactive sub-bands are empty. To further improve the spectral efficiency (SE) of mCAP-IM, mCAP with dual-mode index modulation (mCAP-DM) has been proposed in the literature, where all sub-bands are modulated to transmit data symbols. For an actual mCAP-DM VLC system, the signal-to-noise ratio (SNR) of the high-frequency sub-bands is lower than that of the low-frequency sub-bands. Therefore, all sub-bands are in a state of SNR imbalance, which leads to a decline in the overall BER performance. To solve the SNR imbalance problem, paired coding (PWC) is introduced to improve the overall performance of the system, which requires no overhead and has low computational complexity. Although mCAP-DM VLC has inherent security against eavesdroppers outside its coverage area, they may still be eavesdropped by accidental or unauthorized users when confidential information is within the system coverage area. Therefore, there are still communication security risks in mCAP-DM VLC systems. Summary of the Invention

[0005] The present invention provides a multi-band CAP digital chaos encryption method and system in a band-limited visible light communication system, and the technical problem to be solved is that there are still potential communication security hazards in the mCAP-DM VLC system.

[0006] To solve the above technical problems, the present invention provides a multi-band CAP digital chaos encryption method in a band-limited visible light communication system, including the steps of:

[0007] Dividing the input bits into multiple groups;

[0008] Modulating each group of input bits to obtain a corresponding modulation signal;

[0009] The modulation of each group of input bits specifically includes:

[0010] Dividing the input bits of each group into index bits and constellation bits;

[0011] Performing chaotic constellation mapping on the original constellation sets of the first constellation mode and the second constellation mode according to the constellation bits to obtain a first chaotic constellation set and a second chaotic constellation set;

[0012] Performing chaotic index selection according to the index bits, including determining the indices of the first sub-band set using the first constellation mode and the second sub-band set using the second constellation mode, and performing dual-mode index modulation on each sub-band according to the selection relationship between the index bit value, constellation mode and the first chaotic constellation set, second chaotic constellation set of each sub-band to obtain the modulation signal corresponding to the group of input bits.

[0013] Further, the chaotic constellation mapping is specifically:

[0014] Determining the permutation vectors corresponding to the original constellation sets of the first constellation mode and the second constellation mode according to the constellation bits, and disturbing the positions of the constellation points in the original constellation sets according to their respective permutation vectors to obtain the corresponding first chaotic constellation set and second chaotic constellation set.

[0015] Further, the selection relationship between the index bit value, constellation mode and the first chaotic constellation set, second chaotic constellation set of each sub-band is:

[0016] When the index bit value of the sub-band is the first preset value, the first constellation mode selects the first chaotic constellation set, and the second constellation mode selects the second chaotic constellation set;

[0017] When the index bit value of the sub-band is the second preset value, the first constellation mode selects the second chaotic constellation set, and the second constellation mode selects the first chaotic constellation set.

[0018] Further, the method further includes the steps of:

[0019] Connect multiple groups of modulation signals to obtain an mCAP block;

[0020] Perform chaotic PWC coding on the mCAP block, specifically including:

[0021] Shuffle the order of the m sub-bands of the mCAP block according to a preset rule;

[0022] Perform angular rotation on each of the m sub-bands after the order is shuffled;

[0023] Take the real part and the imaginary part of the rotated sub-band to perform cross pairing to obtain m coding messages;

[0024] Perform upsampling on the m coding messages respectively and then pass them through in-phase and quadrature filters to generate a transmitted signal for transmission.

[0025] Further, the method further includes the steps of:

[0026] Filter the received signal through m pairs of matched filters to obtain m sub-band received signals;

[0027] Perform sub-band frequency domain equalization and chaotic PWC decoding on the m sub-band received signals to obtain an mCAP block;

[0028] Divide the mCAP block into multiple sub-blocks, perform signal detection on each sub-block through a log-likelihood ratio detector, and then perform chaotic constellation demapping and chaotic index selection inverse to the chaotic constellation mapping and the chaotic index selection to recover the corresponding index bits and constellation bits;

[0029] Integrate the recovered index bits and constellation bits to obtain output bits.

[0030] The present invention also provides a multi-band CAP digital chaotic encryption system in a band-limited visible light communication system, which is characterized in that it includes a transmitting end; the transmitting end includes a bit allocator and a modulator;

[0031] The bit allocator is used to evenly divide the input bits into multiple groups;

[0032] The modulator includes a plurality of sub-modulators connected in one-to-one correspondence with the multiple groups of the input bits; each sub-modulator includes a bit divider, a chaotic index selector, a chaotic constellation mapper, and a dual-mode index modulator;

[0033] The bit divider is used to divide the input bits of each group into index bits and constellation bits; the chaotic constellation mapper is used to perform chaotic constellation mapping on the original constellation sets of the first constellation mode and the second constellation mode according to the constellation bits to obtain a first chaotic constellation set and a second chaotic constellation set; the chaotic index selector is used to determine the indexes of the first sub-band set adopting the first constellation mode and the second sub-band set adopting the second constellation mode according to the index bits; the dual-mode index modulator is used to perform dual-mode index modulation on each sub-band according to the selection relationship between the index bit value, constellation mode of each sub-band and the first chaotic constellation set and the second chaotic constellation set to obtain the modulation signal corresponding to the input bits of this group.

[0034] Preferably, the chaotic constellation mapping is specifically as follows:

[0035] Determine the permutation vectors corresponding to the original constellation sets of the first constellation mode and the second constellation mode according to the constellation bits, and scramble the positions of the constellation points in the original constellation sets according to their respective permutation vectors to obtain the corresponding first chaotic constellation set and second chaotic constellation set.

[0036] Preferably, the selection relationship between the index bit value, constellation mode of each sub-band and the first chaotic constellation set and the second chaotic constellation set is as follows:

[0037] When the index bit value of the sub-band is the first preset value, the first constellation mode selects the first chaotic constellation set, and the second constellation mode selects the second chaotic constellation set;

[0038] When the index bit value of the sub-band is the second preset value, the first constellation mode selects the second chaotic constellation set, and the second constellation mode selects the first chaotic constellation set.

[0039] Preferably, the system further includes a chaotic PWC encoder and a transmission signal generator;

[0040] The chaotic PWC encoder is used to connect multiple groups of modulation signals to obtain an mCAP block, scramble the order of the m sub-bands of the mCAP block according to a preset rule, perform angular rotation on each sub-band of the scrambled m sub-bands, and take the real part and imaginary part of the rotated sub-band to perform cross pairing to obtain m coding information;

[0041] The transmission signal generator is used to perform upsampling on the m coding information respectively and then pass through in-phase and quadrature filters to generate a transmission signal.

[0042] Preferably, the system further includes a receiving end; the receiving end includes a filtering module, a frequency-domain equalizer, a chaotic PWC decoder, a demodulator and a bit integrator;

[0043] The filtering module is used to filter the received signal through m pairs of matched filters to obtain m sub-band received signals;

[0044] The frequency-domain equalizer is used to perform sub-band frequency-domain equalization on the m sub-band received signals;

[0045] The chaotic PWC decoder is used to perform chaotic PWC decoding on the m sub-band received signals after frequency-domain equalization to obtain m CAP blocks;

[0046] The demodulator includes a block splitter for dividing the m CAP blocks into multiple sub-blocks, and multiple sub-demodulators connected to the multiple sub-blocks one by one; each of the sub-demodulators includes an LLR detector, a chaotic index decoder, and a chaotic constellation demapper;

[0047] The LLR detector is used to perform log-likelihood ratio detection on the sub-blocks to obtain detection signals;

[0048] The chaotic index decoder and the chaotic constellation demapper are used to perform chaotic constellation demapping and chaotic index selection inverse to the chaotic index selector and the chaotic constellation mapper on the detection signals to recover the corresponding index bits and constellation bits;

[0049] The bit integrator is used to integrate the recovered index bits and constellation bits to obtain output bits.

[0050] The multi-band CAP digital chaotic encryption method and system in the band-limited visible light communication system provided by the present invention designs three encryption methods: chaotic constellation mapping, chaotic index selection, and chaotic PWC coding. The chaotic constellation mapping adjusts the positions of constellation points in the corresponding original constellation set according to constellation bits to obtain a new chaotic constellation set; the chaotic index selection scrambles the corresponding relationship between two distinguishable constellation patterns and two encrypted chaotic constellation sets; the chaotic PWC coding performs sub-band sequential chaotic encryption on the m sub-bands obtained after block creation, shuffles the order of the m sub-bands, and then performs PWC coding. The present invention designs three encryption methods, which can prevent the useful information in the system from being eavesdropped by unauthorized malicious users when the confidential information is within the coverage of the VLC system, thereby enhancing the security of information transmission. Description of the Drawings

[0051] Figure 1 is the schematic diagram of signal transmission of the multi-band CAP digital chaotic encryption method and system in the band-limited visible light communication system provided by the embodiment of the present invention;

[0052] Figure 2 is the schematic diagram of signal reception of the multi-band CAP digital chaotic encryption method and system in the band-limited visible light communication system provided by the embodiment of the present invention;

[0053] Figure 3 It is the schematic diagram of chaotic PWC coding provided by the embodiment of the present invention;

[0054] Figure 4 It is the schematic diagram of chaotic PWC decoding provided by the embodiment of the present invention. Specific embodiments

[0055] The following specifically clarifies the implementation manner of the present invention in conjunction with the drawings. The given embodiments are only for illustrative purposes and should not be construed as a limitation of the present invention. The included drawings are only for reference and illustration and do not constitute a limitation on the protection scope of the patent of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0056] The multi-band CAP digital chaotic encryption method in the band-limited visible light communication system provided by the embodiment of the present invention, as Figure 1 shown in the schematic diagram, the method includes the steps:

[0057] S1. Evenly divide the input bits into multiple groups;

[0058] S2. Modulate each group of input bits to obtain the corresponding modulation signal;

[0059] S3. Connect the multiple groups of modulation signals to obtain an mCAP block;

[0060] S4. Perform chaotic PWC coding on the mCAP block;

[0061] S5. Upsample each of the m coded messages and then pass them through in-phase and quadrature filters to generate a transmitted signal for transmission.

[0062] In step S1 of this embodiment, it is assumed that the input bits are divided into G groups, and b bits in each group are used to generate an mCAP sub-block with a length of N.

[0063] Step S2 of this embodiment specifically includes the steps:

[0064] S21. Divide the input bits of each group into index bits and constellation bits;

[0065] S22. Perform chaotic constellation mapping on the original constellation sets of the first constellation mode and the second constellation mode according to the constellation bits to obtain a first chaotic constellation set and a second chaotic constellation set;

[0066] S23. Perform chaotic index selection according to the index bits, including determining the indexes of the first sub-band set adopting the first constellation mode and the second sub-band set adopting the second constellation mode, and performing dual-mode index modulation on each sub-band according to the selection relationship between the index bit value, constellation mode and the first chaotic constellation set, second chaotic constellation set of each sub-band to obtain the modulation signal corresponding to the input bits of this group.

[0067] In step S21 of this embodiment, the b bits of each group are further divided into index bits b i and constellation bits b c , that is, b = b i + b c . Specifically, the b i bits are the indexes for selecting k sub-bands from N sub-bands through a chaotic index selector, adopting the first constellation mode (constellation mode 1) or the second constellation mode (constellation mode 2), while the remaining N - k sub-bands adopt another constellation mode (constellation mode 2 or constellation mode 1). And the b c bits generate corresponding constellation symbols through a chaotic constellation mapper to perform DM.

[0068] In step S22 of this embodiment, the two original constellation sets corresponding to constellation mode 1 with constellation order M1 and constellation mode 2 with constellation order M2 are respectively expressed as:

[0069]

[0070] In the formula, [·] T represents the transpose operation, represents the M1 constellations in X1, represents the M2 constellations in X2. Since X1 and X2 are two distinguishable constellation sets, so it satisfies

[0071] The chaotic constellation mapping is specifically:

[0072] Determine the permutation vectors corresponding to the original constellation sets of the first constellation mode and the second constellation mode according to the constellation bits, and scramble the positions of the constellation points in the original constellation sets according to their respective permutation vectors to obtain the corresponding first chaotic constellation set and second chaotic constellation set.

[0073] For the two distinguishable constellation sets X1 and X2 in the mCAP-DM system, the chaotic constellation mapping process is performed on each constellation set. For the g-th sub-block, the permutation vectors corresponding to the constellation sets X1 and X2 can be respectively expressed as:

[0074]

[0075] The first chaotic constellation set and the second chaotic constellation set of the current constellation sets X1 and X2 obtained after performing the chaotic constellation mapping are respectively expressed as follows:

[0076]

[0077] where src{·,·} represents a scrambling function for scrambling constellation sets X1 and X2 according to the respective permutation vectors and the permutation vectors contain the new positions of the constellation points in the corresponding constellation sets.

[0078] In step S23 of this embodiment, the chaotic index selection process is performed for two distinguishable constellation patterns within each sub-block. When DM without chaotic index selection is performed, each constellation pattern corresponds to a fixed constellation set. However, for DM encrypted based on chaotic index selection, according to the binary scrambling vector, for two distinguishable constellation patterns, namely constellation pattern 1 and constellation pattern 2, and two encrypted constellation sets and the corresponding relationship between them is scrambled. The corresponding relationship between the two distinguishable constellation patterns 1 and 2 and the two encrypted constellation sets and in the g-th sub-block is shown in Table 1. We can see that when the index bit value of the sub-band is equal to 0, the two encrypted constellation sets corresponding to constellation pattern 1 and constellation pattern 2 are and respectively. However, when the index bit value of the sub-band is equal to 1, the corresponding relationship between constellation pattern 1 and constellation pattern 2 is reversed, that is, the two encrypted constellation sets corresponding to constellation pattern 1 and constellation pattern 2 become and

[0079] Table 1 Corresponding relationship of chaotic index selection in sub-block

[0080]

[0081] Step S4 of this embodiment specifically includes the steps of:

[0082] S41. Shuffle the order of the m sub-bands of the mCAP block according to a preset rule;

[0083] S42. Perform angular rotation on each of the m sub-bands with the shuffled order;

[0084] S43. Take the real part and the imaginary part of the rotated sub-band to perform cross pairing to obtain m coded information.

[0085] For chaotic PWC coding, after the block is created, sub-band sequential chaotic encryption is performed on the m sub-bands obtained. The order of the m sub-bands is scrambled, and the m sub-bands in the newly generated sub-band order are independently rotated by an angle, and the real and imaginary parts of each sub-band are taken to perform cross pairing, thus completing the chaotic PWC coding process. For chaotic PWC decoding, first, the cross pairing of the real and imaginary parts of each sub-band is undone, and then angle rotation and sub-band sequential chaotic decryption are performed to obtain the correct order of the m sub-bands for signal demodulation.

[0086] Figure 3 FIG. is an example diagram of chaotic PWC coding, which takes two sub-bands x SB1 and x SB1 as inputs to illustrate the coding process of chaotic PWC coding, and finally obtains the coded sub-bands x SB1,PWC and x SB2,PWC . Figure 4 FIG. is an example diagram of chaotic PWC decoding, which takes two coded sub-band inputs y SB1,PWC and y SB2,PWC as examples to illustrate the decoding process of chaotic PWC decoding, and finally obtains the decoded sub-bands y SB1 and y SB2 .

[0087] The three-dimensional chaotic digital encryption scheme needs to have the keys of chaotic constellation scrambling, chaotic pattern scrambling, and chaotic PWC coding simultaneously to obtain an accurate transmitted signal, thereby enhancing the security of signal transmission.

[0088] Steps S1 to S5 are the processes at the signal transmitter. At the signal receiver, the signal reception, demodulation, etc. are basically carried out in a process reverse to that of the transmitter to obtain the output bits. More specifically, as Figure 2 shown, the encryption method further includes the steps of:

[0089] Filtering the received signal through m pairs of matched filters to obtain m sub-band received signals;

[0090] Performing sub-band frequency domain equalization and chaotic PWC decoding on the m sub-band received signals to obtain m CAP blocks;

[0091] Dividing the m CAP blocks into multiple sub-blocks, and for each sub-block, performing signal detection through a log-likelihood ratio detector and then performing chaotic constellation demapping and chaotic index selection reverse to chaotic constellation mapping and chaotic index selection to recover the corresponding index bits and constellation bits;

[0092] Integrating the recovered index bits and constellation bits to obtain the output bits.

[0093] It should be understood that various forms of the processes shown above can be used, with steps reordered, added, or deleted. For example, the steps described in the present invention can be executed in parallel, sequentially, or in different orders, as long as the desired results of the technical solution of the present invention can be achieved. This embodiment does not limit this here.

[0094] Corresponding to the multi-band CAP digital chaos encryption method in the above-mentioned band-limited visible light communication system, an embodiment of the present invention further provides a multi-band CAP digital chaos encryption system in a band-limited visible light communication system, as Figure 1 and Figure 2 shown. The system includes a transmitting end and a receiving end. The transmitting end includes a bit allocator, a modulator, a chaotic PWC encoder, and a transmitted signal generator.

[0095] The bit allocator is used to evenly divide the input bits into multiple groups;

[0096] The modulator includes a plurality of sub-modulators connected in one-to-one correspondence with multiple groups of input bits; each sub-modulator includes a bit divider, a chaotic index selector, a chaotic constellation mapper, and a dual-mode index modulator;

[0097] The bit divider is used to divide the input bits of each group into index bits and constellation bits; the chaotic constellation mapper is used to perform chaotic constellation mapping on the original constellation sets of the first constellation mode and the second constellation mode according to the constellation bits to obtain a first chaotic constellation set and a second chaotic constellation set; the chaotic index selector is used to determine the indexes of the first sub-band set using the first constellation mode and the second sub-band set using the second constellation mode according to the index bits; the dual-mode index modulator is used to perform dual-mode index modulation on each sub-band according to the selection relationship between the index bit values of each sub-band, the constellation mode, and the first chaotic constellation set and the second chaotic constellation set to obtain the modulation signal corresponding to the group of input bits;

[0098] The chaotic PWC encoder is used to connect multiple groups of modulation signals to obtain an mCAP block, shuffle the order of the m sub-bands of the mCAP block according to a preset rule, perform angle rotation on each of the shuffled m sub-bands, and take the real part and the imaginary part of the rotated sub-bands to perform cross pairing to obtain m encoded messages;

[0099] The transmitted signal generator is used to perform upsampling on each of the m encoded messages and then pass them through in-phase and quadrature filters to generate a transmitted signal.

[0100] The receiving end includes a filtering module, a frequency domain equalizer, a chaotic PWC decoder, a demodulator, and a bit integrator. The filtering module is used to filter the received signal through m pairs of matched filters to obtain m sub-band received signals;

[0101] The frequency-domain equalizer is used to perform sub-band frequency-domain equalization on the m sub-band received signals;

[0102] The chaotic PWC decoder is used to perform chaotic PWC decoding on the m sub-band received signals after frequency-domain equalization to obtain mCAP blocks;

[0103] The demodulator includes a block splitter that divides the mCAP blocks into multiple sub-blocks, and multiple sub-demodulators connected one-to-one with the multiple sub-blocks; each sub-demodulator includes an LLR detector, a chaotic index decoder, and a chaotic constellation demapper;

[0104] The LLR detector is used to perform log-likelihood ratio detection on the sub-blocks to obtain detection signals;

[0105] The chaotic index decoder and the chaotic constellation demapper are used to perform chaotic constellation demapping and chaotic index selection inverse to the chaotic index selector and the chaotic constellation mapper on the detection signals to recover the corresponding index bits and constellation bits;

[0106] The bit integrator is used to integrate the recovered index bits and constellation bits to obtain output bits.

[0107] The embodiments described in the present invention can be implemented in a computing system including backend components (e.g., as a data server), or a computing system including middleware components (e.g., an application server), or a computing system including frontend components (e.g., a user computer having a graphical user interface or a web browser through which the user can interact with the implementation manners of the systems and technologies described herein), or a computing system including any combination of such backend components, middleware components, or frontend components. The components of the system can be interconnected with each other through digital data communication in any form or medium (e.g., a communication network). Examples of communication networks include: local area network (LAN), wide area network (WAN), blockchain network, and the Internet.

[0108] The computer program for implementing the method and system of the present invention can be written in any combination of one or more programming languages and stored in a computer-readable storage medium. These computer programs can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing devices, such that when the computer programs are executed by the processor, the functions / operations specified in the flowchart and / or block diagram are implemented. The computer programs can be executed entirely on the machine, partially on the machine, as an independent software package partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0109] A computer-readable storage medium can be a tangible medium that can contain or store a computer program for use by or in connection with an instruction execution system, apparatus, or device. The computer-readable storage medium can include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. Alternatively, the computer-readable storage medium can be a machine-readable signal medium. More specific examples of the machine-readable storage medium would include electrical connections based on one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a compact disc read-only memory (CD ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0110] In summary, the multi-band CAP digital chaos encryption method and system in the band-limited visible light communication system provided by the embodiments of the present invention design three encryption methods: chaotic constellation mapping, chaotic index selection, and chaotic PWC coding. Chaotic constellation mapping adjusts the positions of constellation points in the corresponding original constellation set according to constellation bits to obtain a new chaotic constellation set; chaotic index selection scrambles the correspondence between two distinguishable constellation patterns and two encrypted chaotic constellation sets; chaotic PWC coding performs sub-band sequential chaos encryption on the m sub-bands obtained after block creation, shuffles the order of the m sub-bands, and then performs PWC coding. The present invention designs three encryption methods, which can prevent the useful information in the system from being eavesdropped by unauthorized malicious users when the confidential information is within the coverage of the VLC system, thereby enhancing the security of information transmission.

[0111] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent substitution methods and are all included in the protection scope of the present invention.

Claims

1. A multi-band CAP digital chaos encryption method in a band-limited visible light communication system, characterized in that, Including the steps: Evenly divide the input bits into multiple groups; Modulate each group of input bits to obtain corresponding modulation signals; Modulating each group of input bits specifically includes: Divide the input bits of each group into index bits and constellation bits; Perform chaotic constellation mapping on the original constellation sets of the first constellation mode and the second constellation mode according to the constellation bits to obtain a first chaotic constellation set and a second chaotic constellation set; Perform chaotic index selection according to the index bits, including determining the indexes of the first subband set using the first constellation mode and the second subband set using the second constellation mode, and performing dual-mode index modulation on each subband according to the index bit value, constellation mode, and the selection relationship between the first chaotic constellation set and the second chaotic constellation set of each subband to obtain the modulation signal corresponding to this group of input bits.

2. The multi-band CAP digital chaos encryption method in the band-limited visible light communication system according to claim 1, wherein The chaotic constellation mapping is specifically: Determine the permutation vectors corresponding to the original constellation sets of the first constellation mode and the second constellation mode according to the constellation bits, and scramble the positions of the constellation points in the original constellation sets according to their respective permutation vectors to obtain the corresponding first chaotic constellation set and second chaotic constellation set.

3. The multi-band CAP digital chaos encryption method in the band-limited visible light communication system according to claim 2, characterized in that, The selection relationship between the index bit value, constellation mode, and the first chaotic constellation set and the second chaotic constellation set of each subband is: When the index bit value of the subband is the first preset value, the first constellation mode selects the first chaotic constellation set, and the second constellation mode selects the second chaotic constellation set; When the index bit value of the subband is the second preset value, the first constellation mode selects the second chaotic constellation set, and the second constellation mode selects the first chaotic constellation set.

4. The multi-band CAP digital chaotic encryption method in the band-limited visible light communication system according to claim 3, characterized in that, This method further includes the steps: Connect multiple groups of modulation signals to obtain an mCAP block; Perform chaotic PWC coding on the mCAP block, specifically including: Shuffle the order of the m subbands of the mCAP block according to a preset rule; Perform angular rotation on each of the m subbands after the order is shuffled; Take the real part and imaginary part of the rotated subbands to perform cross pairing to obtain m encoded messages; After upsampling the m encoded messages respectively and then passing them through in-phase and quadrature filters, generate a transmitted signal for transmission.

5. The multi-band CAP digital chaotic encryption method in the band-limited visible light communication system according to claim 4, characterized in that, This method further includes the steps: Filter the received signal through m pairs of matched filters to obtain m subband received signals; Perform subband frequency domain equalization and chaotic PWC decoding on the m subband received signals to obtain an mCAP block; Divide the mCAP block into multiple sub-blocks, perform signal detection on each sub-block through a log-likelihood ratio detector, and then perform chaotic constellation demapping and chaotic index selection inverse to the chaotic constellation mapping and the chaotic index selection to recover the corresponding index bits and constellation bits; Integrate the recovered index bits and constellation bits to obtain output bits.

6. The multi-band CAP digital chaotic encryption system in the band-limited visible light communication system is characterized in that, Including a transmitter; the transmitter includes a bit allocator and a modulator; The bit allocator is used to evenly divide the input bits into multiple groups; The modulator includes multiple sub-modulators connected in one-to-one correspondence with multiple groups of the input bits; each sub-modulator includes a bit divider, a chaotic index selector, a chaotic constellation mapper, and a dual-mode index modulator; The bit divider is used to divide the input bits of each group into index bits and constellation bits; the chaotic constellation mapper is used to perform chaotic constellation mapping on the original constellation sets of the first constellation pattern and the second constellation pattern according to the constellation bits to obtain a first chaotic constellation set and a second chaotic constellation set; the chaotic index selector is used to determine the indexes of the first subband set using the first constellation pattern and the second subband set using the second constellation pattern according to the index bits; the dual-mode index modulator is used to perform dual-mode index modulation on each subband according to the selection relationship between the index bit value, constellation pattern of each subband and the first chaotic constellation set, second chaotic constellation set to obtain the modulation signal corresponding to the input bits of this group.

7. The multi-band CAP digital chaos encryption system in the band-limited visible light communication system according to claim 6, characterized in that, The specific chaotic constellation mapping is as follows: Determine the permutation vectors corresponding to the original constellation sets of the first constellation pattern and the second constellation pattern respectively according to the constellation bits, and scramble the positions of the constellation points in the original constellation sets according to their respective permutation vectors to obtain the corresponding first chaotic constellation set and second chaotic constellation set.

8. The multi-band CAP digital chaotic encryption system in the band-limited visible light communication system according to claim 7, characterized in that, The selection relationship between the index bit value, constellation pattern of each subband and the first chaotic constellation set, second chaotic constellation set is as follows: When the index bit value of the subband is the first preset value, the first constellation pattern selects the first chaotic constellation set, and the second constellation pattern selects the second chaotic constellation set; When the index bit value of the subband is the second preset value, the first constellation pattern selects the second chaotic constellation set, and the second constellation pattern selects the first chaotic constellation set.

9. The multi-band CAP digital chaos encryption system in the band-limited visible light communication system according to claim 8, characterized in that: This system further includes a chaotic PWC encoder and a transmitted signal generator; The chaotic PWC encoder is used to connect multiple groups of modulation signals to obtain an mCAP block, scramble the order of the m subbands of the mCAP block according to a preset rule, perform angle rotation on each subband of the scrambled m subbands, and take the real part and imaginary part of the rotated subbands to perform cross pairing to obtain m coded information; The transmitted signal generator is used to perform upsampling on the m coded information respectively and then pass through in-phase and quadrature filters to generate a transmitted signal.

10. The multi-band CAP digital chaotic encryption system in the band-limited visible light communication system according to claim 9, characterized in that: This system further includes a receiving end; the receiving end includes a filtering module, a frequency domain equalizer, a chaotic PWC decoder, a demodulator and a bit integrator; The filtering module is used to filter the received signal through m pairs of matched filters to obtain m subband received signals; The frequency domain equalizer is used to perform subband frequency domain equalization on the m subband received signals; The chaotic PWC decoder is used to perform chaotic PWC decoding on the m subband received signals after frequency domain equalization to obtain an mCAP block; The demodulator includes a block splitter that divides the mCAP block into multiple subblocks, and multiple sub-demodulators connected to the multiple subblocks one by one; each sub-demodulator includes an LLR detector, a chaotic index decoder, and a chaotic constellation demapper; The LLR detector is used to perform log-likelihood ratio detection on the subblock to obtain a detection signal; The chaotic index decoder and the chaotic constellation demapper are used to perform chaotic constellation demapping and chaotic index selection on the detected signal, which are inverse to the chaotic index selector and the chaotic constellation mapper, to recover the corresponding index bits and constellation bits; The bit integrator is used to integrate the recovered index bits and constellation bits to obtain the output bits.

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