Modulation and demodulation method and modem based on time diversity and full carrier symbol index differential chaotic shift keying

Abstract

The present application relates to a kind of modulation and demodulation methods based on time diversity and full carrier index difference chaotic shift keying, the method is suitable for a variety of channels, especially suitable for power line transmission channel, the method is mainly summarized as follows: modulator uses time diversity technology, uses different time to transmit reference information or modulated information multiple times, using index bit to divide the information carrier except reference carrier into two types of carriers activated in turn, and using different modulation signals transmitted in odd and even time to distinguish binary bits.Demodulator obtains reference signal by averaging the signal of different time on reference carrier, and obtains the signal transmitted in odd and even time of each carrier by averaging the signal of odd and even time of information carrier, each information carrier will first distinguish the carrier activated in advance according to the different signal transmitted in odd and even time, so as to recover mapping bit, and then demodulate the corresponding modulation bit on the carrier activated in advance.The present application will improve the anti-noise performance and transmission rate of system.

Description

Technical Field

[0001] The present invention relates to the fields of power line communication technology and wireless communication technology, and in particular to a time diversity and full carrier index differential chaotic shift keying modulation and demodulation method and modem, which is particularly suitable for data transmission over power line channels. Background Art

[0002] Differential Chaotic Shift Keying (DCSK) is an incoherent chaotic digital communication modulation method that uses a chaotic signal as a carrier. It has low implementation complexity. DCSK-based communication schemes are effective against various background and impulse noises in power line channels, making them an excellent alternative for power line communication.

[0003] Power-line communication (PLC) is a key technology for building smart grids. It does not require laying additional communication links, but uses existing low-voltage power lines to transmit information.

[0004] Patent document CN116405360A discloses a high-data-rate carrier-indexed differential chaotic keying modulation and demodulation method and system based on a scrambled matrix. This method, which employs a repetitive circuit and averaging process, can significantly reduce the noise component in the decision variable and improve the system's bit error performance. However, because this patent only selects one carrier from multiple carriers based on the index bit to transmit DCSK modulation symbols, while the remaining carriers do not transmit any information, the system's transmission rate and energy efficiency are extremely low. The present invention utilizes repeated transmission of a reference signal and its transformed signal on each carrier. This method not only uses the index bit to select an active carrier for DCSK modulation symbol transmission, but also utilizes inactive carriers for modulation symbol transmission, significantly improving the system's transmission rate and energy efficiency. Summary of the Invention

[0005] In response to the background noise, impulse noise, and multipath fading present in power line communication channels, the present invention provides a modulation and demodulation method and modem based on time diversity and full-carrier label index differential chaotic shift keying. To resist various noises in the power line channel, the modulator adopts time diversity to transmit reference information or modulation information multiple times at different times, and at the receiving end, the information transmitted in different time slots is combined in an equal-gain manner.

[0006] The technical solutions of the present invention are as follows:

[0007] On the one hand, the present invention provides a differential chaotic shift keying modulation and demodulation method based on time diversity and full-carrier label indexing, which is characterized in that: at the transmitting end: time diversity technology is used to transmit reference information or modulation information multiple times at different times, and the code chip length C of each frame is determined by 2g consecutive moments and the code chip length L of each moment, C = 2g*L; m+1 carriers are used to simultaneously transmit information, where carrier No. 1 is used to transmit reference information s1, and the same code chip group {r1, r2, r3, ..., r1} is repeatedly transmitted at 2g consecutive moments. L The remaining carriers 2 to m+1 are used to transmit modulation information, and carrier index modulation is introduced, including the steps of:

[0008] c. Group the input bit sequence into groups, each containing q bits. The first q1 bits are mapping bit groups, used to select q2 first-activated carriers and m-q2 second-activated carriers from carriers 2 to m+1. The last q-q1 bits are modulation bit groups, which consist of a first modulation bit group and a second modulation bit group.

[0009] d. First activate the carrier to transmit the pre-modulation bit group at 2g consecutive moments, and use the reference chaotic signal to represent the modulation bit 1 or 0. That is, when the modulation bit transmitted is 1, s is transmitted at 2g consecutive moments. f ={r1,r2,r3,......,r L}, when the transmitted modulation bit is 0, s is transmitted at 2g consecutive moments f ={-r1,-r2,-r3,......,-r L};

[0010] e. The post-activation carrier transmits different chip groups at odd and even times to represent the modulation bit 1 or 0, that is, when the modulation bit transmitted is 1, the odd time transmits s so ={r1,r2,r3,......,r L}, even-numbered time transmission

[0011] s se ={-r1,-r2,-r3,......,-r L}, when the modulation bit is 0, s is transmitted at odd times so ={-r1,-r2,-r3,......,-r L}, transmit s at even times se ={r1,r2,r3,......,r L};

[0012] At the receiving end: a matched filter is used to receive the m+1 carrier and process it in the order of the frames, including the following steps:

[0013] a. In each chip period T c Sampling is not performed, that is, 2gL code chip sampling values ​​are obtained from each carrier branch, and the sampling value of the reference information on carrier No. 1 is stored in vector R 1×2gL In the matrix, the sampling values ​​of the modulation information of carriers 2 to m+1 are stored in the matrix I m×2gL middle;

[0014] b. Perform time gain processing and group averaging on the received signal;

[0015] c. Determine the first activated carrier and the last activated carrier by correlation operation, and restore the mapping bit by combining the number of the first activated carrier;

[0016] d. Determine the modulation bit based on the sign of the correlation result;

[0017] e. Arrange the bits carried by the first activated carrier in carrier number order to form a first modulated bit sequence; arrange the bits carried by the second activated carrier in carrier number order to form a second modulated bit sequence; arrange the first modulated bit sequence and the second modulated bit sequence to obtain a modulated bit sequence; and arrange the mapped bits and the modulated bits to obtain the original bit sequence.

[0018] Furthermore, the step b. performing time gain processing and grouping averaging on the received signal is specifically:

[0019] - vector R 1×2gL The data is divided into a group for every L columns, and 2g groups are obtained for each row. The L sample values ​​are averaged according to the order of each group of data and stored in the vector N. 1×L middle;

[0020] - The matrix I m×2gL The data in the matrix is ​​grouped every L rows, and each row gets 2g groups. The data of the odd group is averaged according to the order of arrangement within the group and the L sample values ​​are stored in the matrix O. m×L In the even group, the data is averaged according to the order of the group and the L sample values ​​are stored in the matrix E. m×L middle;

[0021] Furthermore, the step c. determines the first activated carrier and the last activated carrier by correlation operation, and restores the mapping bit by using a combination method according to the number of the first activated carrier, specifically:

[0022] - vector N 1×L Respectively with the matrix O m×L and matrix E m×L Related and stored in the matrix CO m×1 and matrix CE m×1 middle;

[0023] - The matrix CO m×1 and matrix CE m×1 Add up to get the correlation matrix C m×1 ;

[0024] -Correlation matrix C m×1 The absolute value of the q2 carriers with the largest absolute value is calculated, that is, the carriers are activated first, and the mapping bits are restored using the combination method according to their carrier labels;

[0025] - The remaining m-q2 carriers with smaller absolute values ​​are the later activated carriers.

[0026] Furthermore, the step d. is based on the sign of the correlation result, that is, the correlation matrix C m×1 The symbol determines the modulation bit, specifically:

[0027] The sign of the carrier index row corresponding to the first activated carrier determines the bit transmitted by the first activated carrier. If the sign is positive, it is judged as "1", and if the sign is negative, it is judged as "0";

[0028] The sign of the carrier index row corresponding to the post-activated carrier determines the bit transmitted by the post-activated carrier. If the sign is positive, it is judged as "0", and if the sign is negative, it is judged as "1".

[0029] In another aspect, the present invention further provides a differential chaotic shift keying modem based on time diversity and full carrier indexing, comprising a modulator and a demodulator, wherein the modulator modulates an input signal according to the method described at the transmitting end, and the demodulator demodulates a received signal according to the method described at the receiving end.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1) Through time diversity, that is, using 2g consecutive different time periods to transmit the same chaotic signal, the negative impact of background noise and impulse noise in the power line channel can be effectively improved, and the system's bit error rate performance and data transmission rate can be improved.

[0032] 2) The present invention not only utilizes the selection of carrier numbers to transmit the mapped bits, but also utilizes the carrier number index modulation to select the first activated carrier to transmit the first modulated bits, and also utilizes the last activated carrier to transmit the last modulated bits.

[0033] 3) To distinguish between the first-activated and the last-activated carriers at the receiving end, the present invention transmits different chips at odd and even times on the two types of carriers. This transmits more information bits than existing DCSK systems, improving energy efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1The figure shows the transmission signal frame structure transmitted on the carrier waves that are activated successively;

[0035] Figure 2 The structure of the DCSK modulator based on full-carrier index modulation is shown;

[0036] Figure 3 The structure of the DCSK demodulator based on full-carrier index modulation is shown; DETAILED DESCRIPTION

[0037] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0038] During modulation, the duration of L chips is considered as one transmission moment. To ensure the effectiveness of diversity, the same reference information or modulation information is transmitted at 2g consecutive different moments. The chip length of each frame is C = 2g*L. The modulator uses m+1 carriers to transmit each frame of information simultaneously, and the carriers are numbered from 1 to m+1. Carrier 1 transmits the reference information. Therefore, the signal s1 transmitted by carrier 1 will transmit the chip group {r1, r2, r3, ..., r1} at 2g consecutive moments. L}, and then the code chips are waveform-shaped. The remaining carriers numbered 2 to m+1 will transmit information. In order to transmit more bits and improve the performance of the system, carrier index modulation will be introduced. The detailed process is as follows. In the first step, the input bit sequence will be grouped first, and then the bits of each group will be transmitted within a frame. Each group contains q bits, of which the first q1 bits are mapping bit groups and the last q-q1 bits are modulation bit groups. The modulation bit groups are further divided into two groups, namely the pre-modulation bit group and the post-modulation bit group. In the second step, each group of bit sequences will generate a transmission signal according to the following steps. First, the combination method is used to select q2 pre-activated carriers from the carriers numbered 2 to m+1 according to the mapping bits to transmit the pre-modulation bit group. The remaining m-q2 carriers are called post-activated carriers and will be used to transmit the post-modulation bit group. In order to enable the receiving end to distinguish the q2 pre-activated carriers from the m-q2 post-activated carriers, the pre-activated carriers will use the reference chaotic signal (denoted as r = {r1, r2, r3, ..., r L}) Transmit the pre-modulation bit group. When the transmitted modulation bit is 1, transmit s at 2g consecutive moments. f ={r1,r2,r3,......,r L}, when the transmitted modulation bit is 0, s is transmitted at 2g consecutive moments f ={-r1,-r2,-r3,......,-r LThe carrier is activated later and different chip groups are transmitted at odd and even times. When the modulated bit is 1, the odd time transmits s so ={r1,r2,r3,......,r L}, transmit s at even times se ={-r1,-r2,-r3,......,-r L}, when the modulation bit is 0, s is transmitted at odd times so ={-r1,-r2,-r3,......,-r L}, transmit s at even times se ={r1,r2,r3,......,r L}.

[0039] The demodulation method corresponding to the receiving end is as follows. The m+1 carriers will be received using matched filters and processed in sequence according to the order of the frames. The sampled values ​​of the reference information transmitted on carrier 1 will be stored in vector R 1×2gL The remaining carrier samples numbered 2 to m+1 will be stored in the matrix I m×2gL In order to obtain time gain, R 1×2gL The data in the table are grouped into 2g groups every L columns, and then the L sample values ​​are averaged according to the order of each group of data to obtain the vector N. 1×L . Will I m×2gL The data is grouped into L groups per row, and 2g groups are obtained per row. The data of the odd group are averaged according to the order of arrangement within the group and stored in O m×L In the even group, the data is averaged according to the order of the group, and the L sample values ​​are stored in E m×L In. 1×L Respectively with O m×L and E m×L Related and stored separately in CO m×1 and CE m×1 In. CO m×1 and CE m×1 Adding them together will give C m×1 . m×1 The q2 carriers with the largest absolute value are activated first, and the mapping bits are restored using the combination method according to their carrier numbers. The remaining m-q2 carriers with smaller absolute values ​​are activated later. m×1The symbols of the carriers activated first and second determine the information bits transmitted. The symbol of the carrier label row corresponding to the first carrier activated first determines the bit transmitted by the first carrier activated first. If the symbol is positive, it is judged as "1", and if the symbol is negative, it is judged as "0". The symbol of the carrier label row corresponding to the second carrier activated later determines the bit transmitted by the second carrier activated later. If the symbol is positive, it is judged as "0", and if the symbol is negative, it is judged as "1". Arranging the bits carried by the first carrier activated first in the order of carrier labels will obtain the first modulated bit sequence, and arranging the bits carried by the second carrier activated later in the order of carrier labels will obtain the second modulated bit sequence. Arranging the first and second modulated bits will obtain the modulated bit sequence. Arranging the mapped bits and the modulated bits will obtain the bit sequence of each frame.

[0040] Example:

[0041] Figure 2 The figure shows the structure of the DCSK modulator based on time diversity and full carrier index modulation for power line channels. The bit sequence transmitted by the system includes a carrier index modulation mapping bit sequence and a DCSK modulation bit sequence in each frame. The bit sequence of each frame is expressed as The bit sequence Mapping bit stream to carrier label, bit sequence and The total number of carriers is m+1, and the carrier frequencies corresponding to them are f1 to f1, respectively. m+1 , where the reference information is transmitted using a carrier with a carrier frequency of f1. From the m carriers, q2 carriers are selected as the first activated carriers and m-q2 carriers are selected as the second activated carriers. and After being mapped into DCSK modulation information symbols by the polarity converter, that is, the modulation bit "0" or "1" will be mapped into the DCSK modulation information symbol "1" or "-1" respectively.

[0042] The specific modulation process of the modulator is as follows: the chaotic signal generator R generates a chaotic signal of length L The time diversity device T uses 2g time moments to generate four frame structures with a length of 2gL chips. Figure 1 As shown, first activate the carrier to use all transmission at 2g time or To distinguish "0" and "1". The post-activated carrier is transmitted at odd and even times respectively. or To distinguish "0" and "1". The reference carrier branch will select the frame with frame structure Z1 for transmission. The frames transmitted by the remaining m carriers will be determined by the mapping bits and modulation bits, as detailed below. The bit sequence to be transmitted in each frame is si First, it is divided into 3 groups. The first q1 bits are mapping bits, the middle q2 bits are first modulation bits, and the last m-q2 bits are second modulation bits. The q1 mapping bits are indexed by the modulator to select q2 carriers from the carriers numbered 2 to m as the first activated carriers and record the carrier numbers in ascending order as N1 = {i1, i2, ..., i q2}where i1 represents the smallest number of the first activated carrier, i q2 Indicates that the largest number of carriers is activated first, and i1 to i q2 Belongs to [2,...,m+1]. The remaining m-q2 carriers are activated later and the carrier numbers are marked in ascending order as N2={j1,j2,...,j m-q2}, where j1 represents the smallest index among the later activated carriers, j m-q2 Represents the largest number among the activated carriers and j1 to j m-q2 Belongs to [2,...,m+1]. The corresponding index modulator will generate a control signal for the output frequency of the oscillator corresponding to the carrier numbered 2 to m, so that the frequency is f t,1 to f t,q2 The activated carriers correspond to the carrier numbers i1, i2, ..., i q2 , frequency f s,1 to f s,m-q2 The inactive carriers are numbered in the order of j1, j2, ..., j m-q2 The information modulation signal s(t) is generated by superimposing the m+1 signals.

[0043] like Figure 3 The structure of the DCSK demodulator based on time diversity and full carrier index modulation for power line channels is as follows: the receiver divides the received signal g(t) into m+1 equal-power paths, and then uses the transmitter-side indexes f1 to f m+1 The carrier frequency is mixed with the signal after power division, and then matched filtering is performed. c The sampling is not performed, so that 2gL code chip sampling values ​​are obtained from each carrier branch. And the 2gL sampling values ​​of the reference chaotic signal corresponding to the carrier frequency f1 are stored in the matrix R 1×2gL The carrier frequency is f2 to f m+1 The sampling values ​​corresponding to each carrier are stored in the matrix I m×2gL middle.

[0044] To obtain time gain, R 1×2gL The data in the matrix are grouped into 2g groups every L columns, and then the L sample values ​​are averaged according to the order of each group of data to obtain the matrix N 1×L . Will Im×2gL The data is grouped into L groups per row, and 2g groups are obtained per row. The L sample values ​​of the odd-numbered groups are averaged according to the order of arrangement within the group and stored in the matrix O m×L In the even group, the data is averaged according to the order of the group and the L sample values ​​are stored in the matrix E. m×L In the example, the matrix N 1×L Respectively with O m×L and E m×L Correlation and store the correlation values ​​in CO m×1 and CE m×1 In. The matrix CO m×1 and CE m×1 Adding together will give us the matrix C m×1 . m×1 The q2 carriers with the largest absolute value are activated first, and the q1 mapping bits are restored according to their carrier indexes using the index demodulator based on the combination method. The remaining m-q2 carriers with smaller absolute values ​​are activated later. m×1 Under the control of the mapping bits, the symbols of the carriers activated first and second determine the information bits transmitted. The symbol of the carrier index row corresponding to the first-activated carrier determines the bit transmitted by the first-activated carrier. If the symbol is positive, it is judged as "1", and if the symbol is negative, it is judged as "0". The symbol of the carrier index row corresponding to the second-activated carrier determines the bit transmitted by the second-activated carrier. If the symbol is positive, it is judged as "0", and if the symbol is negative, it is judged as "1". Arranging the bits carried by the first-activated carrier in carrier index order yields the first modulated bit sequence, and arranging the bits carried by the second-activated carrier in carrier index order yields the second modulated bit sequence. Arranging the first and second modulated bits yields the modulated bit sequence. Arranging the mapping bits and the modulation bits yields the bit sequence of each frame.

[0045] The test shows that the present invention adopts time diversity technology to enhance the anti-interference ability of the signal by transmitting the same information multiple times at different time points. This is especially important in noisy environments such as power line channels. The use of carrier number classification modulation and the introduction of carrier label index modulation not only increase the amount of information transmission, but also improve the overall performance of the system. This method allows the modulator to transmit additional information through different carriers, thereby more effectively utilizing the available frequency band resources. A complex encoding and decoding strategy is designed, including bit grouping, separation of mapping bits and modulation bits, and complex processing procedures at the receiving end to ensure accurate transmission and efficient decoding of information. Therefore, the present invention fully considers the characteristics of the power line channel and improves the efficiency and stability of information transmission.

Claims

1. A method for modulation and demodulation based on time diversity and full carrier index differential chaotic shift keying, characterized in that: At the transmitter: time diversity technology is used to transmit the reference information or modulation information multiple times at different times. The chip length C of each frame is determined by 2g consecutive moments and the chip length L of each moment, C = 2g*L; m+1 carriers are used to transmit information simultaneously, where carrier No. 1 is used to transmit the reference information s1, and the same chip group {r1, r2, r3, ..., r1} is repeatedly transmitted at 2g consecutive moments. L The remaining carriers 2 to m+1 are used to transmit modulation information, and carrier index modulation is introduced, including the steps of: a. Group the input bit sequence into groups, each group containing q bits. The first q1 bits are the mapping bit group, which is used to select q2 first-activated carriers and m-q2 second-activated carriers from carriers 2 to m+1. The last q-q1 bits are the modulation bit group, which consists of the first modulation bit group and the second modulation bit group. b. First activate the carrier to transmit the pre-modulation bit group at 2g consecutive moments, and use the reference chaotic signal to represent the modulation bit 1 or 0. That is, when the modulation bit is 1, s is transmitted at 2g consecutive moments. f ={r1,r2,r3,......,r L }, when the transmitted modulation bit is 0, s is transmitted at 2g consecutive moments f ={-r1,-r2,-r3,......,-r L }; c. The post-activation carrier transmits different chip groups at odd and even times to represent the modulation bit 1 or 0, that is, when the modulation bit transmitted is 1, the odd time transmits s so ={r1,r2,r3,......,r L }, transmit s at even times se ={-r1,-r2,-r3,......,-r L }, when the modulation bit is 0, odd-numbered time transmits s so ={-r1,-r2,-r3,......,-r L }, transmit s at even times se ={r1,r2,r3,......,r L }; At the receiving end: a matched filter is used to receive the m+1 carrier and process it in the order of the frames, including the following steps: a. In each chip period T c Sampling is not performed, that is, 2gL code chip sampling values ​​are obtained from each carrier branch, and the sampling value of the reference information on carrier No. 1 is stored in vector R 1×2gL In the matrix, the sampling values ​​of the modulation information of carriers 2 to m+1 are stored in the matrix I m×2gL middle; b. Perform time gain processing and group averaging on the received signal; c. Determine the first activated carrier and the last activated carrier by correlation operation, and restore the mapping bit by combining the number of the first activated carrier; d. Determine the modulation bit based on the sign of the correlation result; e. Arrange the bits carried by the first activated carrier in carrier number order to form a first modulated bit sequence; arrange the bits carried by the second activated carrier in carrier number order to form a second modulated bit sequence; arrange the first modulated bit sequence and the second modulated bit sequence to obtain a modulated bit sequence; and arrange the mapped bits and the modulated bits to obtain the original bit sequence.

2. The method for modulation and demodulation based on time diversity and full carrier label index differential chaotic shift keying according to claim 1, characterized in that: The step b. performing time gain processing and grouping averaging on the received signal is specifically: - vector R 1×2gL The data is grouped every L columns, and each column gets 2g groups. The L sample values ​​are averaged according to the order of each group of data and stored in vector N. 1×L middle; - The matrix I m×2gL The data in the matrix is ​​grouped every L rows, and each row gets 2g groups. The data of the odd group is averaged according to the order of arrangement within the group and the L sample values ​​are stored in the matrix O. m×L In the even group, the data is averaged according to the order of the group and the L sample values ​​are stored in the matrix E. m×L middle.

3. The method for modulation and demodulation based on time diversity and full carrier label index differential chaotic shift keying according to claim 2, characterized in that: The step c. determines the first activated carrier and the last activated carrier by correlation operation, and restores the mapping bit by using a combination method according to the number of the first activated carrier, specifically: - vector N 1×L Respectively with the matrix O m×L and matrix E m×L Related and stored in the matrix CO m×1 and matrix CE m×1 middle; - The matrix CO m×1 and matrix CE m×1 Add up to get the correlation matrix C m×1 ; -Correlation matrix C m×1 The absolute value of the q2 carriers with the largest absolute value is calculated, that is, the carriers are activated first, and the mapping bits are restored using the combination method according to their carrier labels; - The remaining m-q2 carriers with smaller absolute values ​​are the later activated carriers.

4. The method for modulation and demodulation based on time diversity and full carrier label index differential chaotic shift keying according to claim 1, characterized in that: The step d. is based on the sign of the correlation result, that is, the correlation matrix C m×1 The symbol determines the modulation bit, specifically: The sign of the carrier index row corresponding to the first activated carrier determines the bit transmitted by the first activated carrier. If the sign is positive, it is judged as "1", and if the sign is negative, it is judged as "0"; The sign of the carrier index row corresponding to the post-activated carrier determines the bit transmitted by the post-activated carrier. If the sign is positive, it is judged as "0", and if the sign is negative, it is judged as "1".

5. A differential chaotic shift keying modem based on time diversity and full carrier indexing, comprising a modulator and a demodulator, characterized in that: The modulator modulates the input signal according to the method described in the transmitting end of claim 1 or 2.

6. A differential chaotic shift keying modem based on time diversity and full carrier indexing, comprising a modulator and a demodulator, characterized in that: The demodulator demodulates the received signal according to the method described in any one of claims 1-4.

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