NR-DCSK signal modulation and demodulation method and system based on RIS assistance

Abstract

The invention discloses an RIS assistance-based NR-DCSK signal modulation and demodulation method and a RIS assistance-based NR-DCSK signal modulation and demodulation system. The modulation method comprises the following steps: generating a discrete chaotic signal sequence and an RIS reflection group; copying the discrete chaotic signal sequence for N times to obtain a first reference signal, and performing index modulation on the first reference signal based on an RIS reflection group to obtain a second reference signal; preprocessing data bits in a symbol period to obtain modulation bits and index bits; modulating the modulation bit by using the first reference signal to generate a first information signal, and performing index modulation on the first information signal based on the RIS reflection group and the index bit to obtain a second information signal; combining the second reference signal and the second information signal to obtain a modulated NR-DCSK signal; and sending the NR-DCSK signal. In the demodulation process, the additional index bit information in the information signal segment can be extracted by carrying out correlation operation on the information signal segment and each reference signal segment and utilizing the excellent self-correlation characteristic of the chaotic signal, so that the spectrum efficiency and the data transmission rate of the NR-DCSK communication system can be remarkably improved, and better system error code performance can be obtained.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication technology, and particularly relates to a RIS-assisted NR-DCSK signal modulation, demodulation method and system. Background Art

[0002] At present, wireless communication systems face problems such as low spectral efficiency, poor anti-interference ability, and insufficient transmission reliability in complex channel environments. The traditional Noise Reduction Differential Chaos Shift Keying (NR-DCSK) technology utilizes the non-linear characteristics of chaotic signals and has the advantages of strong anti-interference ability and high security, and has been widely applied in communication scenarios with low power consumption and low complexity. However, the traditional NR-DCSK system has significant limitations: firstly, its spectral efficiency is relatively low because half of each symbol period is used to transmit the reference signal, resulting in limited energy efficiency and data transmission rate; secondly, in wireless channels with severe multipath fading and noise interference, the performance of the NR-DCSK system will significantly decline, making it difficult to meet the requirements of high-reliability communication.

[0003] In recent years, Reconfigurable Intelligent Surface (RIS) technology, as an emerging wireless communication assistance technology, provides a new solution for improving the spectral efficiency and anti-interference ability of communication systems by intelligently regulating the reflection characteristics of electromagnetic waves. However, existing RIS technologies are mainly applied to signal enhancement and beamforming, and have not been deeply combined with chaotic signal modulation technology, failing to fully exploit their potential in spectral efficiency improvement and signal modulation. Summary of the Invention

[0004] Object of the Invention: The technical problem to be solved by the present invention is to provide a RIS-assisted NR-DCSK signal modulation, demodulation method and system in view of the deficiencies of the prior art.

[0005] To solve the above technical problem, in the first aspect, a RIS-assisted NR-DCSK signal modulation method is disclosed, including the following steps:

[0006] Step S1, generating a discrete chaotic signal sequence and a RIS reflection group;

[0007] Step S2, replicating the discrete chaotic signal sequence N times and recombining it to obtain a first reference signal, and performing index modulation on the first reference signal based on the RIS reflection group to obtain a second reference signal;

[0008] Step S3, preprocess the data bits within one symbol period to obtain modulation bits and index bits;

[0009] Step S4, modulate the preprocessed modulation bits using the first reference signal to generate a first information signal, and perform index modulation on the first information signal based on the RIS reflection groups and the index bits to obtain a second information signal, which now carries the index bits;

[0010] Step S5, combine the second reference signal and the second information signal to obtain the modulated NR-DCSK signal;

[0011] Step S6, transmit the modulated NR-DCSK signal.

[0012] Furthermore, in step S1, denote the generated discrete chaotic signal sequence as r[k], where 0 ≤ k ≤ β - 1, and β represents the length of the discrete chaotic signal sequence within one symbol period; denote the number of generated RIS reflection groups as N, N > 0. Different RIS reflection groups correspond to different time delays when reflecting the discrete chaotic signal sequence, and each time delay corresponds to a first index bit combination. Each combination contains NN bits where NN = log2 N, and there are a total of N groups of first index bit combinations.

[0013] Furthermore, step S2 includes: Denote the first reference signal r′1 = {r[k], r[k - β], …, r[k - N*β + β]}. The first reference signal includes N segments of reference signal segments. Corresponding the N segments of reference signal segments to the N groups of first index bit combinations respectively, generating the second reference signal includes:

[0014] Denote the reflection groups corresponding to the N groups of first index bit combinations as RIS-1, …, RIS-N respectively, and the time delays generated by the reflection of the reflection groups as τ1, …, τ N , respectively reflect the N segments of reference signal segments using the corresponding reflection groups to generate the second reference signal r = {α*r[k - τ1], α*r[k - β - τ2], …, α*r[k - N*β + β - τ N}, where 0 < α < 1, and α is the reflection coefficient generated during the reflection of the reflection group.

[0015] Furthermore, step S3 includes: Split the data bits to obtain modulation bits and index bits. The number of bits of the index bits is N*NN. Split the index bits into N groups, and each group of NN bits forms a second index bit combination, and the second index bit combination is one of the N groups of first index bit combinations.

[0016] Furthermore, step S4 includes: Convert the modulation bits into bipolar bits d through polarity conversion i ;

[0017] Multiply the first reference signal r′1 and the bipolar bit d i and use a delay element to delay each segment of the signal respectively to generate a first information signal r′2 = {d i *r[k - N*β], d i *r[k - N*β - β], …, d i *r[k - 2N*β + β]}, and the first information signal includes N segments of information signal segments;

[0018] Denote the RIS reflection groups corresponding to N groups of second index bit combinations as RIS-i1, …, RIS-iN, and their corresponding time delays as τ i1 , …, τ iN respectively reflect the N segments of information signal segments using the corresponding RIS reflection groups to generate a second information signal r2 = {α*d i *r[k - N*β - τ i1 , α*d i *r[k - N*β - β - τ i2 , …, α*d i *r[k - 2N*β + β - τ iN}.

[0019] In a second aspect, a method for demodulating an RIS-assisted NR-DCSK modulated signal is disclosed, including:

[0020] Receiving an NR-DCSK signal obtained by the RIS-assisted NR-DCSK signal modulation method according to any one of claims 1-5;

[0021] Extracting a second reference signal and a second information signal from the received NR-DCSK signal;

[0022] Calculating N groups of second index bit combinations based on the second reference signal and the second information signal;

[0023] Respectively according to the time delays corresponding to the first index bit combinations and the time delays corresponding to the second index bit combinations, deleting the time delays in the second reference signal and the second information signal to generate a first reference signal and a first information signal;

[0024] Calculating the modulation bits within one symbol period based on the first reference signal and the first information signal.

[0025] Furthermore, calculating N groups of second index bit combinations based on the second reference signal and the second information signal includes:

[0026] Each information signal segment in the second information signal is correlated with N reference signal segments in the second reference signal. N correlation values are obtained for each segment. The maximum correlation value for each segment is obtained through comparison, and the reference signal segment corresponding to the maximum correlation value for each segment is taken. According to the reflection group number and time delay corresponding to the number of the reference signal segment, the corresponding second index bit combination is obtained. The second index bit combination is the index bit information carried by the information signal segment, and a total of N groups of second index bit combinations are obtained. By performing a correlation operation between the information signal segment and each reference signal segment and utilizing the excellent autocorrelation characteristics of the chaotic signal, the additional index bit information in the information signal segment can be extracted.

[0027] Further, based on the first reference signal and the first information signal, calculating the modulation bits within one symbol period includes: obtaining N reference signal segments from the first reference signal and performing an averaging operation on the N reference signal segments; obtaining N information signal segments from the first information signal and performing an averaging operation on the N information signal segments; performing a correlation operation on the averaged reference signal and the averaged information signal to obtain a correlation value R i ; if the correlation value R i is greater than 0, the modulation bit d i is 1, otherwise the modulation bit d i is -1.

[0028] In a third aspect, a RIS-assisted NR-DCSK signal modulation system is disclosed, including a chaotic signal generator, N RIS reflection group controllers, N RIS reflection groups, a polarity converter, a bit splitter, N index selectors, a multiplier, 3 adders, and 2N - 1 delay elements. The chaotic sequence generator is used to generate a discrete chaotic signal sequence r[k], where 0 ≤ k ≤ β - 1, and β represents the length of the discrete chaotic signal sequence within one symbol period;

[0029] The N RIS reflection group controllers are used to control different reflection time delays τ1,..., τ N corresponding to each reflection group, and each reflection time delay corresponds to a group of first index bit combinations;

[0030] The N RIS reflection groups are used to reflect the first reference signal and the first information signal;

[0031] The bit splitter is used to split the index bits into N groups of second index bit combinations. The second index bit combination is determined by the information stream transmitted from the source end and consists of NN data, where NN = log2 N;

[0032] The N index selectors are used to select the RIS reflection groups corresponding to the N groups of second index bit combinations;

[0033] The polarity converter is used to convert the modulated bits into bipolar bits;

[0034] The multiplier is used to multiply the first reference signal by the bipolar bits to generate a first information signal;

[0035] The first group of N - 1 delay elements are used to delay the N - 1 reference signal segments by β, …, (N - 1)*β respectively; the second group of N delay elements are used to delay the N information signal segments in the first information signal by N*β respectively to carry the index bit information;

[0036] The first adder is used to recombine each delayed reference signal segment into a second reference signal; the second adder is used to recombine each delayed information signal segment into a second information signal; the third adder is used to recombine the second reference signal and the second information signal into an NR - DCSK signal and then transmit it.

[0037] In a fourth aspect, a RIS - assisted NR - DCSK signal demodulation system is disclosed, including a reference signal averager, an information signal averager, a register, and a DSP chip. The register is used to receive the NR - DCSK signal obtained from a RIS - assisted NR - DCSK signal modulation system according to claim 9, and extract N reference signal segments and N information signal segments from the received NR - DCSK signal;

[0038] The reference signal averager is used to average the N reference signal segments after extraction and removal of the delay; the information signal averager is used to average the N information signal segments after extraction and removal of the delay;

[0039] The DSP chip is used to perform segment - by - segment correlation between the N reference signals and each information signal segment, obtaining N correlation values for each segment, comparing to obtain the maximum value of each value, and restoring the index bits according to the reflection group number and delay corresponding to the number of the reference signal segment; performing correlation on the averaged reference signal and information signal, and comparing and judging the correlation values to restore the modulated bits.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] Through the index modulation and demodulation method of the RIS-assisted NR-DCSK communication system proposed by the present invention, the transmitter makes full use of the index information of the RIS reflection group, significantly improving the spectral efficiency, and enhancing the reliability of the system through the reflection of the RIS on the NR-DCSK signal; the receiver, through a rigorous demodulation process, utilizes the correlation between the reference signal and the information signal and the correspondence between the RIS reflection group index and the index bit, effectively extracts and demodulates the index bit and the modulation bit at the transmitter, and accurately restores the original information under the interference of the wireless channel. This method combines the excellent characteristics of the chaotic signal sequence with the RIS reflection technology, further improving the transmission efficiency and reliability of the communication system, and providing an innovative solution for efficient and reliable wireless communication. Description of the Drawings

[0042] The following further specifically describes the present invention in conjunction with the drawings and specific embodiments, and the above and / or other advantages of the present invention will become clearer.

[0043] Figure 1 It is a schematic flowchart of a RIS-assisted NR-DCSK signal modulation method provided by an embodiment of the present application.

[0044] Figure 2 It is a schematic flowchart of a RIS-assisted NR-DCSK signal demodulation method provided by an embodiment of the present application.

[0045] Figure 3 It is a schematic structural diagram of a RIS-assisted NR-DCSK signal modulation system provided by an embodiment of the present application;

[0046] Figure 4 It is a schematic structural diagram of a RIS-assisted NR-DCSK signal demodulation system for demodulating index bits provided by an embodiment of the present application;

[0047] Figure 5 It is a schematic structural diagram of a RIS-assisted NR-DCSK signal demodulation system for demodulating modulation bits provided by an embodiment of the present application; Detailed Embodiments

[0048] The following will describe the embodiments of the present invention in conjunction with the drawings.

[0049] The present invention proposes a method and system for modulating and demodulating NR-DCSK signals assisted by RIS. By introducing the index modulation technology of the RIS reflection group, the non-linear characteristics of chaotic signals are combined with the dynamic tunability of RIS, significantly improving the spectral efficiency, anti-interference ability and transmission reliability of the system. Specifically, the present invention uses the RIS reflection group as index information to perform index modulation on NR-DCSK signals, achieving an improvement in spectral efficiency without increasing additional bandwidth. At the same time, the reflection of RIS on NR-DCSK signals enhances the transmission quality and anti-multipath interference ability of the signals. The present invention provides an efficient and reliable communication solution for the field of wireless communication, having important theoretical significance and practical application value.

[0050] The first embodiment of this application discloses a method for modulating NR-DCSK signals assisted by RIS, as Figure 1 shown, including the following steps:

[0051] Step S1, generating a discrete chaotic signal sequence and an RIS reflection group;

[0052] Denote the generated discrete chaotic signal sequence as r[k], where 0 ≤ k ≤ β - 1, and β represents the length of the discrete chaotic signal sequence within one symbol period; denote the number of generated RIS reflection groups as N, where N > 0; different RIS reflection groups generate different time delays when reflecting the discrete chaotic signal, corresponding to determined first index bit combinations, each combination containing the number of bits NN as log2 N, and there are a total of N groups of determined first index bit combinations. The corresponding relationships among the reflection group, time delay and first index bit combination are shown in Table 1 and Table 2.

[0053] Table 1 Index mapping table corresponding to a reflection group-index bit combination with NN = 2

[0054] RIS reflection group number Delay identifier <![CDATA[Index bit combination (NN = log24 = 2)]]> RIS-1 <![CDATA[τ1]]> [0，0] RIS-2 <![CDATA[τ2]]> [0，1] RIS-3 <![CDATA[τ3]]> [1，0] RIS-4 <![CDATA[τ4]]> [1，1]

[0055] Table 2 Index mapping table corresponding to a reflection group-index bit combination with NN = 4

[0056] RIS reflection group number Delay identifier <![CDATA[Index bit combination (NN = log216 = 4)]]> RIS-1 <![CDATA[τ1]]> [0，0，0，0] RIS-2 <![CDATA[τ2]]> [0，0，0，1] RIS-3 <![CDATA[τ3]]> [0，0，1，0] RIS-4 <![CDATA[τ4]]> [0，0，1，1] RIS-5 <![CDATA[τ5]]> [0，1，0，0] RIS-6 <![CDATA[τ6]]> [0，1，0，1] RIS-7 <![CDATA[τ7]]> [0，1，1，0] RIS-8 <![CDATA[τ8]]> [0，1，1，1] RIS-9 <![CDATA[τ9]]> [1，0，0，0] RIS-10 <![CDATA[τ 10 > [1，0，0，1] RIS-11 <![CDATA[τ 11 > [1，0，1，0] RIS-12 <![CDATA[τ 12 > [1，0，1，1] RIS-13 <![CDATA[τ 13 > [1，1，0，0] RIS-14 <![CDATA[τ 14 > [1，1，0，1] RIS-15 <![CDATA[τ 15 > [1，1，1，0] RIS-16 <![CDATA[τ 16 > [1，1，1，1]

[0057] Step S2, replicating the discrete chaotic signal sequence N times and recombining them to obtain a first reference signal, and performing index modulation on the first reference signal based on the RIS reflection group to obtain a second reference signal; specifically as follows:

[0058] The NR-DCSK symbol sequence r[k] is copied N times, delayed differently, and recombined to obtain the first reference signal r′1 = {r[k], r[k - β],..., r[k - N*β + β]}, with a length of N*β. Each small reference signal segment has a length of β, and there are N segments in total. The reference signal segments correspond to the determined first index bit combination as reference information;

[0059] Denote the reflection groups corresponding to the N groups of first index bit combinations as RIS-1,..., RIS-N, and the time delays generated by the reflection groups as τ1,..., τ N , as shown in Table 3 and Table 4. Reflect the N reference signal segments through the corresponding reflection groups respectively to generate the second reference signal r1 = {α*r[k - τ1], α*r[k - β - τ2],..., α*r[k - N*β + β - τ N}, where 0 < α < 1, and α is the reflection coefficient generated during the reflection of the reflection group.

[0060] Table 3 A reference signal segment number - reflection group number - reflection time delay - index mapping table corresponding to the index bit combination when NN = 2

[0061] Reference signal segment Reflection group number Sorted delay <![CDATA[Index bit combination (NN = log24 = 2)]]> 1 RIS-1 <![CDATA[τ1]]> [0，0] 2 RIS-2 <![CDATA[τ2]]> [0，1] 3 RiS-3 <![CDATA[τ3]]> [1，0] 4 RIS-4 <![CDATA[τ4]]> [1，1]

[0062] Table 4 A reference signal segment number - reflection group number - reflection time delay - index mapping table corresponding to the index bit combination when NN = 4

[0063] Reference signal segment Reflection group number Sorted delay <![CDATA[Index bit combination (NN = log216 = 4)]]> 1 RIS-1 <![CDATA[τ1]]> [0，0，0，0] 2 RIS-2 <![CDATA[τ2]]> [0，0，0，1] 3 RIS-3 <![CDATA[τ3]]> [0，0，1，0] 4 RIS-4 <![CDATA[τ4]]> [0，0，1，1] 5 RIS-5 <![CDATA[τ5]]> [0，1，0，0] 6 RIS-6 <![CDATA[τ6]]> [0，1，0，1] 7 RIS-7 <![CDATA[τ7]]> [0，1，1，0] 8 RIS-8 <![CDATA[τ8]]> [0，1，1，1] 9 RIS-9 <![CDATA[τ9]]> [1，0，0，0] 10 RIS-10 <![CDATA[τ 10 > [1，0，0，1] 11 RIS-11 <![CDATA[τ 11 > [1，0，1，0] 12 RIS-12 <![CDATA[τ 12 > [1，0，1，1] 13 RIS-13 <![CDATA[τ 13 > [1，1，0，0] 14 RIS-14 <![CDATA[τ 14 > [1，1，0，1] 15 RIS-15 <![CDATA[τ 15 > [1，1，1，0] 16 RIS-16 <![CDATA[τ 16 > [1，1，1，1]

[0064] Step S3, preprocess the data bits within one symbol period to obtain the modulation bits and the index bits;

[0065] The data bits are segmented to obtain the modulation bits and the index bits. The number of bits of the index bits is N*NN. The index bits are split into N groups, and each group of NN bits forms a second index bit combination. The N groups of second index bit combinations are denoted as b1,..., b N , where b N = {b N1 , b N2 ,..., b NN}, and the second index bit combination is one of the N groups of first index bit combinations; in the specific implementation process, the data bits within one symbol period can be segmented according to a preset rule. For example, the first N*NN bits are the index bits, and the remaining bits behind are the modulation bits, or the front are the modulation bits, and the last N*NN bits are the index bits. This embodiment does not make specific limitations on the segmentation method.

[0066] Step S4: Modulate the modulation bits using the first reference signal to generate a first information signal, and perform index modulation on the first information signal based on the RIS reflection group and the index bits to obtain a second information signal, which carries the index bits at this time. Specifically, it includes the following steps:

[0067] Convert the modulation bits into bipolar bits d through polarity conversion i ;

[0068] Multiply the first reference signal r′1 and the bipolar bit d i and use a delay element to delay each segment of the signal respectively to generate a first information signal r′2 = {d i *r[k - N*β], d i *r[k - N*β - β], …, d i *r[k - 2N*β + β]}; The length of the first information signal r′2 is N*β, and the length of each small segment of the information signal segment is β, with a total of N segments.

[0069] Denote the reflection groups corresponding to N groups of second index bit combinations as RIS-i1, …, RIS-iN, and the time delays generated by them are τ i1 , …, τ iN , respectively reflect the N segments of information signal segments using the corresponding reflection groups to generate a second information signal r2 = {α*d i *r[k - N*β - τ i1 , α*d i *r[k - N*β - β - τ i2 , …, α*d i *r[k - 2N*β - τ iN}.

[0070] Step S5: Combine the second reference signal r1 and the second information signal r2 to obtain the modulated NR-DCSK signal x[k], with a length λ = 2*N*β.

[0071] Step S6: Transmit the modulated NR-DCSK signal x[k].

[0072] The second embodiment of the present application discloses a RIS-assisted NR-DCSK signal demodulation method, as Figure 2 shown, including:

[0073] Step R1: Receive the NR-DCSK signal y[k] obtained according to the above-mentioned RIS-assisted NR-DCSK signal modulation method;

[0074] Step R2: Extract the second reference signal and the second information signal from the received NR-DCSK signal y[k]. Specifically, assuming that the synchronization operation has been completed, the first N segments are extracted from the received NR-DCSK signal y[k] as the reference signal segments (the second reference signal), and the last N segments are used as the information signal segments (the second information signal). Each small segment has a length of β, and the entire signal has a total of 2N segments with a total length of 2 * N * β. The N reference signal segments extracted are y1[k], y1[k - β], …, y1[k - N * β + β], and the N information signal segments extracted are y2[k], y2[k - β], …, y2[k - N * β + β].

[0075] Step R3: Based on the second reference signal and the second information signal, calculate N groups of second index bit combinations, including:

[0076] Perform a correlation calculation between each information signal segment in the second information signal and the N reference signal segments in the second reference signal. Each segment obtains N correlation values. Specifically, perform a correlation calculation between the first information signal segment extracted from the second information signal and the N reference signal segments in the second reference signal to obtain the first group of N correlation values R1 = {R 11 , R 12 , …, R 1N}. Perform a correlation operation between the second to the Nth information signal segments and the N reference signal segments respectively to obtain the second to the Nth groups of N correlation values R2, …, R N ;

[0077] Compare R1, R2, …, R N , obtain the maximum correlation value for each segment, select the reference signal segment corresponding to the maximum correlation value for each segment, and obtain the corresponding second index bit combination according to the reflection group number and delay corresponding to the number of the reference signal segment. The second index bit combination is the index bit information carried by the information signal segment, and a total of N groups of second index bit combinations are obtained.

[0078] Step R4: Delete the delays in the second reference signal and the second information signal respectively according to the delays corresponding to the first index bit combination and the second index bit combination to generate the first reference signal and the first information signal;

[0079] The first index bit combination is known at the receiving end, and the delay of each segment in the reference signal segment is set in sequence.

[0080] Align each reference signal segment and information signal segment according to the corresponding N delays to ensure that each reference signal segment and information signal segment are respectively matched in time, that is, there is no delay effect;

[0081] Step R5: Calculate the modulation bits within one symbol period based on the first reference signal and the first information signal, including:

[0082] Obtain N segments of reference signal segments from the first reference signal, and perform an averaging operation on the N segments of reference signal segments y ′ 1[k] to obtain the averaged reference signal Obtain N segments of information signal segments from the first information signal, and perform an averaging operation on the N segments of information signal segments y′2[k] to obtain the averaged information signal Perform a correlation operation on the averaged reference signal and the averaged information signal to obtain a correlation value R i ; if the correlation value R i is greater than 0, the modulation bit d i is 1, if the correlation value R i is less than or equal to 0, the modulation bit d i is -1.

[0083] Convert the modulation bit d i into the original modulation bit through polarity conversion, and splice the original modulation bit and N groups of second index bit combinations according to a preset rule to demodulate the data bits transmitted by the source end.

[0084] The third embodiment of the present application discloses a RIS-assisted NR-DCSK signal modulation system, as Figure 3 shown, including a chaotic signal generator, N RIS reflection group controllers, N RIS reflection groups, a polarity converter, a bit splitter, N index selectors, a multiplier, 3 adders, and 2N - 1 delay elements, where: the chaotic sequence generator is used to generate a discrete chaotic signal sequence r[k], 0 ≤ k ≤ β - 1, and β represents the length of the discrete chaotic signal sequence within one symbol period;

[0085] The N RIS reflection group controllers are used to control different reflection time delays τ1,..., τ N corresponding to each reflection group, and each reflection group corresponds to a group of first index bit combinations;

[0086] The N RIS reflection groups are used to reflect the first reference signal and the first information signal;

[0087] The bit splitter is used to split the index bits into N groups of second index bit combinations, and the second index bit combinations are determined by the data bits transmitted by the source end and consist of NN bits, where NN = log2N;

[0088] The N index selectors are used to select the reflection groups corresponding to the N groups of second index bit combinations;

[0089] Specifically, the first index selector is used to perform index mapping on the first group of second index bit combinations to obtain the corresponding reflection group, and the second to the Nth index selectors are used to perform index mapping on the remaining groups of second index bit combinations. After reflection through the corresponding reflection groups, the corresponding delays τ i2 , …, τ iN ;

[0090] The polarity converter is used to convert the modulation bit into a bipolar bit d i ;

[0091] The multiplier is used to multiply the first reference signal r′1 by the bipolar bit to generate the first information signal r′2;

[0092] The first group of N - 1 delay elements is used to delay N - 1 segments of the reference signal segments in the first reference signal by β, …, (N - 1)*β respectively, so that they carry reference information; the second group of N delay elements is used to delay N segments of the information signal segments in the first information signal by N*β respectively, so that they carry index bit information;

[0093] The first adder is used to recombine each reflected reference signal segment into the second reference signal r1; the second adder is used to recombine each reflected information signal segment into the second information signal r2; the third adder is used to recombine the second reference signal r1 and the second information signal r2 into the NR - DCSK signal x[k] and then send it out.

[0094] The fourth embodiment of this application discloses a RIS - assisted NR - DCSK signal demodulation system, as shown in Figure 4 and Figure 5 shown, including a reference signal averager, an information signal averager, a register and a DSP chip, where: the register is used to receive the NR - DCSK signal obtained by the above - mentioned RIS - assisted NR - DCSK signal modulation system, and extract N segments of reference signal segments and N segments of information signal segments from the received NR - DCSK signal;

[0095] The reference signal averager is used to average the N segments of reference signal segments extracted and after removing the delay to obtain the averaged reference signal The information signal averager is used to average the N segments of information signal segments extracted and after removing the delay to obtain the averaged information signal

[0096] The DSP chip is used to perform segment - by - segment correlation on the N segments of reference signals and each segment of information signal (such as the correlators 1, 2, ……, N in Figure 4 ), and obtain N correlation values for each segment, and compare to obtain the maximum value (such as Figure 4The absolute value maximum detectors 1, 2, ……, N) in it restore the index bits according to the position of the maximum value (such as Figure 4 the index selector in it); perform correlation on the averaged reference signal and information signal (such as Figure 5 the correlator in it), compare and judge the correlation value to restore the modulation bits (such as Figure 5 the threshold decision in it).

[0097] In a specific implementation, the present application provides a computer storage medium and a corresponding data processing unit. Among them, the computer storage medium can store a computer program, and when the computer program is executed by the data processing unit, it can run the content of the invention of a RIS-assisted NR-DCSK signal modulation and demodulation method provided by the present invention and some or all of the steps in each embodiment. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM), etc.

[0098] Those skilled in the art can clearly understand that the technical solutions in the embodiments of the present invention can be implemented by means of a computer program and its corresponding general hardware platform. Based on such an understanding, the essence of the technical solutions in the embodiments of the present invention, or the part that contributes to the prior art, can be embodied in the form of a computer program, that is, a software product. The computer program software product can be stored in a storage medium, including several instructions for causing a device (which can be a personal computer, a server, a single-chip microcomputer, a MUU, or a network device, etc.) including a data processing unit to execute the methods described in each embodiment or some parts of the embodiments of the present invention.

[0099] The present invention provides a RIS-assisted NR-DCSK signal modulation and demodulation method and system. There are many methods and ways to specifically implement this technical solution. The above is only the preferred implementation manner of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention. Each component not clearly defined in this embodiment can be implemented by the prior art.

Claims

1. A RIS-assisted NR-DCSK signal modulation method, characterized in that: The following steps are involved: Step S1, generating a discrete chaotic signal sequence and a RIS reflection group; Step S2, replicating the discrete chaotic signal sequence N times and then recombining them to obtain a first reference signal, and index modulating the first reference signal based on the RIS reflection group to obtain a second reference signal; Step S3, preprocessing the data bits within a symbol period to obtain modulation bits and index bits; Step S4, modulating the modulation bit using the first reference signal to generate a first information signal, and index-modulating the first information signal based on the RIS reflection group and the index bit to obtain a second information signal; Step S5, combining the second reference signal and the second information signal to obtain a modulated NR-DCSK signal; Step S6, sending the modulated NR-DCSK signal.

2. The RIS-assisted NR-DCSK signal modulation method according to claim 1, characterized in that: In step S1, the generated discrete chaotic signal sequence is recorded as r[k], 0≤k≤β-1, β represents the length of the discrete chaotic signal sequence within a symbol period; the number of generated RIS reflection groups is recorded as N, N>0, different RIS reflection groups correspond to different time delays when reflecting the discrete chaotic signal sequence, each time delay corresponds to a first index bit combination, each combination contains a bit number NN of log2N, and there are N groups of first index bit combinations in total.

3. The RIS-assisted NR-DCSK signal modulation method according to claim 2, characterized in that: Step S2 includes: recording a first reference signal r′1={r[k], r[k-β], …, r[kN*β+β]}, wherein the first reference signal includes N reference signal segments, and the N reference signal segments are respectively corresponded to N groups of first index bit combinations, and generating a second reference signal includes: recording the reflection groups corresponding to the N groups of first index bit combinations as RIS-1, RIS-2, …, RIS-N, and the generated delays are τ1, …, τ N , respectively, the N reference signal segments are reflected by the corresponding reflection groups to generate the second reference signal r1 = {α*r[k-τ1], α*r[k-β-τ2], …, α*r[kN*β+β-τ N ]}, 0<α<1, α is the reflection coefficient generated when the reflection group reflects.

4. The RIS-assisted NR-DCSK signal modulation method according to claim 3, characterized in that: Step S3 includes: dividing the data bits to obtain modulation bits and index bits, the number of index bits is N*NN, splitting the index bits into N groups, each group of NN bits constitutes a second index bit combination, and the second index bit combination is one of the N groups of first index bit combinations.

5. The RIS-assisted NR-DCSK signal modulation method according to claim 4, characterized in that: Step S4 includes: converting the modulated bit into a bipolar bit d by polarity conversion. i ; The first reference signal r′1 and the bipolar bit d i Multiply them, and use the delay device to delay each of the signal segments to generate the first information signal r′2={d i *r[kN*β],d i *r[kN*β-β],…,d i *r[k-2N*β+β]}, the first information signal includes N information signal segments; the reflection group corresponding to the N groups of second index bit combinations is RIS-1 i ,…,RIS-N i , and the resulting delays are τ i1 ,…,τ iN , respectively, the N information signal segments are reflected by the corresponding reflection groups to generate the second information signal r2 = {α*d i *r[kN*β-τ i1 ],α*d i *r[kN*β-β-τ i2 ],…,α*d i *r[k-2N*β+β-τ iN ]}.

6. A RIS-assisted NR-DCSK signal demodulation method, characterized in that: include: Receiving an NR-DCSK signal obtained by the RIS-assisted NR-DCSK signal modulation method according to any one of claims 1 to 5; extracting a second reference signal and a second information signal from the NR-DCSK signal; Calculate N groups of second index bit combinations based on the second reference signal and the second information signal; Deleting the delays in the second reference signal and the second information signal according to the delays corresponding to the first index bit combination and the delays corresponding to the second index bit combination, respectively, to generate the first reference signal and the first information signal; A modulated bit within one symbol period is calculated based on the first reference signal and the first information signal.

7. The RIS-assisted NR-DCSK signal demodulation method according to claim 6, characterized in that: Based on the second reference signal and the second information signal, calculating N groups of second index bit combinations includes: performing correlation calculations on each information signal segment in the second information signal and N reference signal segments in the second reference signal, obtaining N correlation values ​​for each segment, comparing to obtain the maximum correlation value of each segment, taking the reference signal segment corresponding to the maximum correlation value of each segment, and obtaining the corresponding second index bit combination according to the RIS reflection group corresponding to the number of the reference signal segment.

8. The RIS-assisted NR-DCSK signal demodulation method according to claim 7, characterized in that: Based on the first reference signal and the first information signal, calculating the modulated bits within a symbol period includes: obtaining N reference signal segments from the first reference signal, and averaging the N reference signal segments; obtaining N information signal segments from the first information signal, and averaging the N information signal segments; correlating the averaged reference signal with the averaged information signal to obtain a correlation value R i ; If the correlation value R i is greater than 0, then the modulation bit d i is 1, otherwise the modulation bit d i is -1.

9. A RIS-assisted NR-DCSK signal modulation system, characterized in that: It includes a chaotic signal generator, N RIS reflection group controllers, N RIS reflection groups, a polarity converter, a bit splitter, N index selectors, a multiplier, 3 adders, and 2N-1 delays. The chaotic sequence generator is used to generate a discrete chaotic signal sequence r[k], 0≤k≤β-1, β represents the length of the discrete chaotic signal sequence within a symbol period; The N RIS reflection group controllers are used to control the different reflection delays τ1,…,τ corresponding to each reflection group N , each reflection delay corresponds to a set of first index bit combinations; The N RIS reflection groups are used to reflect the first reference signal and the first information signal; The bit splitter is used to split the index bit into N groups of second index bit combinations, where the second index bit combination is determined by the information stream transmitted by the source end and consists of NN data, where NN=log2N; The N index selectors are used to select RIS reflection groups corresponding to N groups of second index bit combinations; The polarity converter is used to convert the modulated bit into a bipolar bit; The multiplier is used to multiply the first reference signal and the bipolar bit to generate a first information signal; The first group of N-1 delayers is used to delay N-1 reference signal segments by β,…,(N-1)*β respectively; the second group of N delayers is used to delay N information signal segments in the first information signal by N*β respectively so that they carry index bit information; The first adder is used to reorganize each delayed reference signal segment into a second reference signal; the second adder is used to reorganize each delayed information signal segment into a second information signal; the third adder is used to reorganize the second reference signal and the second information signal into an NR-DCSK signal and then send it.

10. A RIS-assisted NR-DCSK signal demodulation system, characterized in that: It comprises a reference signal averager, an information signal averager, a register and a DSP chip, wherein the register is used to receive the NR-DCSK signal obtained by the RIS-assisted NR-DCSK signal modulation system according to claim 9, and extract N reference signal segments and N information signal segments from the received NR-DCSK signal respectively; The reference signal averager is used to average the N reference signal segments after the time delay is extracted and removed; the information signal averager is used to average the N information signal segments after the time delay is extracted and removed; The DSP chip is used to correlate N reference signals with each information signal segment by segment, obtain N correlation values ​​for each segment, and compare to obtain the maximum value of each value, and restore the index bit according to the reference signal segment corresponding to the maximum value and the reflection group number; correlate the averaged reference signal and information signal, compare the correlation values ​​to determine and restore the modulation bit.

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