AMC-ROBO coding interleaving method in power line carrier communication

Abstract

This invention discloses an adaptive ROBO coding interleaving method for power line carrier communication, mainly addressing the problems of single modulation scheme and low spectrum utilization in existing ROBO coding interleaving modes. The implementation scheme is as follows: Sub-frequency bands are divided according to channel conditions, and the modulation scheme of each sub-frequency band is determined; data groups are divided according to the modulation scheme of each sub-frequency band, and the number of subcarriers, bits, and sub-interleavers occupied in each data group is calculated; redundant data is padded to the data after each copy based on the calculated data; the copied data after redundancy padded is cyclically shifted to ensure that the same data can be transmitted on different sub-frequency bands in different copies; sub-interleaving and constellation mapping are performed on the data groups sequentially according to the frequency band in which the data groups are located. This invention improves the data transmission rate, enhances system flexibility and resource utilization, and can be used in power line carrier communication to improve the data transmission performance of the system.

Description

Technical Field

[0001] This invention belongs to the field of mobile communications, and specifically relates to an adaptive coding interleaving method that can be used in power line carrier communication to improve the data transmission performance of the system. Background Technology

[0002] Power line communication (PLC) technology is a communication technology that uses power lines to transmit signals and data. It boasts advantages such as ease of use, long transmission distance, and low construction costs. Currently, PLC technology has achieved near-universal coverage, becoming the dominant communication method in power systems. As a new and effective communication method, PLC communication can meet the ever-increasing demands for business volume and communication capacity in today's information age. Using PLC technology to connect user terminals to the nearest broadband network equipment can effectively solve the "last mile" problem of broadband network access.

[0003] The performance of PLC technology is easily constrained by the actual communication environment. PLC communication channels are characterized by significant time-varying attenuation and diverse interference noise, resulting in substantial interference during transmission. Furthermore, the diverse structures and complex load conditions of power distribution networks make the transmission characteristics of high-speed data signals via power lines extremely complex. Orthogonal Frequency Division Multiplexing (OFDM) technology, with its strong anti-interference, anti-multipath, and anti-attenuation capabilities, effectively overcomes the harsh environment of power line channels and is widely used in power line communication systems. Based on this, existing technologies propose using ROBO coding and interleaving in the frequency domain to improve the system's reliability in frequency-selective channels. ROBO coding and interleaving technology mainly includes three parts: data copying, data packetization, and sub-interleaving. Data copying utilizes diversity gain to copy and transmit data multiple times to ensure correct reception at the receiving end. Data packetization further subdivides the data of each symbol, ensuring that the same data group can be transmitted in different frequency bands after multiple copies. Sub-interleaving involves interleaving data within each data group according to certain rules to improve the system's anti-interference performance.

[0004] Traditional ROBO coding interleaving schemes utilize diversity and interleaving techniques, which improves the stability and reliability of data transmission. However, with the rapid increase in communication demands, improving the system's information transmission rate has become a crucial indicator of communication performance. In traditional schemes, each ROBO coding interleaving mode employs the same quadrature amplitude modulation (QAM) scheme across the entire frequency band. While this ensures effective transmission in frequency-selective fading bands, it also leads to underutilization of high-performance frequency bands, wasting bandwidth resources and reducing the system's transmission rate to some extent.

[0005] Patent document with application number 201811191967.7 discloses "A demodulation method and apparatus for ROBO encoding", which improves the decoding method of ROBO interleaving by storing the first data of each copy in a buffer area, and then merging the second data with the data in the buffer area. This method reduces the system memory and the data processing latency. However, since the method only improves the system at the receiving end, the reliability of the data during channel transmission is still low.

[0006] Patent document with application number 201710764337.3 discloses a method for frequency domain information expansion of data symbols in power line carrier communication. It replaces the original ROBO expansion with multiple frequency domain information diversity expansions, which simplifies the frequency domain processing circuit and improves system reliability. However, this method only changes the mapping rules. The data still uses the same modulation method across the entire frequency band. It does not use different coding and interleaving methods for the data under different channel qualities. Therefore, it lacks full utilization of channel resources, resulting in the failure to effectively improve the data transmission rate and frequency band utilization. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of the prior art by proposing an adaptive coding modulation (AMC-ROBO) interleaving method for power line carrier communication, which can improve the data transmission rate and bandwidth utilization of the power line carrier communication system while ensuring data reliability.

[0008] The technical solution to achieve the objective of this invention is as follows: by dividing frequency bands, and according to the QAM coding method under each frequency band, adaptive data packetization and sub-interleaver allocation are performed at the transmitting end; inter-group cyclic shifting is performed according to the number of replications and the number of data packets; and sub-interleaving of data in each group is performed according to certain rules. The steps include the following:

[0009] 1) Determine the amount of data to be sent, the bit rate, and the number of copies based on actual requirements;

[0010] 2) Divide the frequency bands:

[0011] 2a) The receiver sends a probe frame consisting of frame control information and a preamble sequence to the transmitter;

[0012] 2b) After receiving the probe frame, the transmitting end adaptively divides the frequency bands based on the binary division method;

[0013] 3) Determine the modulation scheme for the sub-band:

[0014] 3a) Write the number of sub-bands into the Channel Quality field of the SACK frame in binary form;

[0015] 3b) Based on the number of sub-bands, calculate the average signal-to-noise ratio (SNR) of each sub-band, and compare the average SNR with the set thresholds k1 and k2 to determine its modulation scheme:

[0016] If SNR≤k1, then binary phase shift keying (BPSK) modulation is used;

[0017] If k1 < SNR ≤ k2, then quadrature phase shift keying (QPSK) modulation is used;

[0018] If SNR>k2, then 16-order quadrature amplitude modulation (16QAM) is used for modulation.

[0019] Where k1 is the signal-to-noise ratio threshold boundary between BPSK modulation and QPSK modulation, and k2 is the signal-to-noise ratio threshold boundary between QPSK modulation and 16QAM modulation.

[0020] 3c) Write the QAM modulation scheme of each sub-band into the Reserved field of the SACK frame;

[0021] 4) Divide the data into groups according to the QAM modulation scheme of each frequency band;

[0022] 5) Calculate the number of bits N in each data group based on the QAM modulation scheme of each data group and the number of carriers contained in each data group. Bits_per_group ;

[0023] 6) Based on the number of bits in each data group and the input data length N raw Calculate the number of bits N in the last data group during each copy. Bits_of_last_group If the last data group has fewer bits than the size of a complete data group, it needs to be padded. The total number of bits N after padding is calculated based on the number of bits in each data group and the number of data groups. Bits_per_Copy ;

[0024] 7) According to the cyclic shift parameters specified in the IEEE 1901 protocol, cyclic shift is performed in each copy in units of data groups to further improve the system's ability to resist frequency-selective fading.

[0025] 8) Use the number of carriers contained in the data group of the 16QAM band as the size of the sub-interleaver, and perform sub-interleaving and mapping on the cyclically shifted data in each data group according to the rules of the sub-interleaver in the IEEE 1901 protocol;

[0026] 9) Use the data groups from all frequency bands at each time point to form a symbol, and generate a complete time-frequency resource block based on the number of its data groups:

[0027] If the number of data groups in each symbol equals the number of copies, then a complete time-frequency resource block is generated directly.

[0028] Otherwise, redundant data needs to be padded at the end of the last symbol before a complete time-frequency resource block is generated.

[0029] 10) QAM modulation is performed on the data of the time-frequency resource block according to the divided sub-frequency bands;

[0030] 11) At the receiving end, the frequency domain data after time-frequency conversion is de-QAM modulated and de-ROBO interleaved, and the N copies of data are combined by maximum ratio to obtain the original bit stream.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] First, because the present invention uses multiple modulation methods in the ROBO coding interleaving algorithm, it not only improves the data transmission rate but also improves the resource utilization of the system based on the original algorithm structure.

[0033] Secondly, this invention improves the robustness and reliability of data transmission by performing cyclic shifting and sub-interleaving on the data group, transmitting the same data on different sub-frequency bands, and encoding it with different modulation methods. Attached Figure Description

[0034] Figure 1 This is a flowchart illustrating the overall implementation of the present invention;

[0035] Figure 2 This is a schematic diagram of data grouping in this invention;

[0036] Figure 3 This is a symbol diagram of the ROBO encoding after interleaving in an embodiment of the present invention;

[0037] Figure 4 This is a flowchart of the ROBO output sub-process in this invention;

[0038] Figure 5 The figure shows a comparison of the bit error rate simulation results using the present invention and the existing single QAM modulation method. Detailed Implementation

[0039] The embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] This example is based on the power line communication system in the IEEE 1901 protocol. The system consists of two parts: frame control information and payload. The ROBO coding and interleaving process is performed after the payload data has been scrambled, Turbo interleaved, and channel interleaved. The data after ROBO coding and interleaving will be QAM modulated and IFFT transformed to convert the frequency domain to the time domain. After a series of processing steps, it will be transmitted.

[0041] refer to Figure 1 The implementation steps of this example in a power line carrier communication system are as follows:

[0042] Step 1: Determine the amount of data to be sent, the bitrate, and the number of copies.

[0043] To achieve better communication performance under different channel conditions and communication requirements, it is necessary to set the amount of data to be sent and the bit rate according to the system requirements. There are three options for the amount of data: 72PB, 132PB and 520PB; and two options for the bit rate: 1 / 2 bit rate and 16 / 18 bit rate.

[0044] To overcome the severe frequency selective fading problem in power line communication channels, data needs to be copied multiple times to improve the diversity gain at the receiver. The number of copies is set to either no copy or multiple copies. The more copies, the higher the reliability and redundancy of the system.

[0045] Step 2: Adaptively divide sub-frequency bands and determine the modulation scheme of each sub-frequency band for coding.

[0046] 2.1) The receiver sends a probe frame consisting of frame control information and a preamble sequence to the transmitter. The preamble sequence is a data stream of a specific length known to the receiver and is used for channel estimation.

[0047] 2.2) After receiving the probe frame, the transmitting end adaptively divides the frequency bands based on the binary division method:

[0048] 2.2.1) Divide the entire channel into two sub-bands and perform channel estimation for each sub-band;

[0049] 2.2.2) Compare the channel estimation results of the two sub-bands. If the difference in signal-to-noise ratio between the two sub-bands is greater than the set threshold d, then further subdivide each sub-band into two sub-bands.

[0050] 2.2.3) Repeat step 2.2.2) until the number of sub-bands reaches the upper limit of 8;

[0051] 2.3) Write the number of sub-bands into the Channel Quality field of the SACK frame in binary form;

[0052] 2.4) Set the threshold k1 for dividing BPSK modulation and QPSK modulation, and the threshold k2 for dividing QPSK modulation and 16QAM modulation. Calculate the average signal-to-noise ratio (SNR) of each sub-band based on the number of sub-bands:

[0053]

[0054] Where, N carrier_per_band The number of subcarriers in each subband, snr i The signal-to-noise ratio for each subcarrier;

[0055] 2.5) Compare the average signal-to-noise ratio with the two set thresholds k1 and k2 to determine the modulation scheme:

[0056] If SNR≤k1, then binary phase shift keying (BPSK) modulation is used;

[0057] If k1 < SNR ≤ k2, then quadrature phase shift keying (QPSK) modulation is used;

[0058] If SNR>k2, then 16-order quadrature amplitude modulation (16QAM) is used for modulation.

[0059] 2.6) Write the QAM modulation scheme of each sub-band into the Reserved field of the SACK frame to inform the receiver of the modulation scheme of each sub-band:

[0060] First, expand the 8-bit Reserved field to 16 bits, with each sub-band occupying 2 bits.

[0061] Then, based on the modulation scheme of each sub-band, the 2-bit information is encoded:

[0062] If the sub-band is BPSK modulation, then the 2-bit code is 00;

[0063] If the sub-band is QPSK modulated, then the 2-bit code is 01;

[0064] If the sub-band is 16QAM modulation, then the 2-bit encoding is 11.

[0065] Step 3: Divide the data into groups.

[0066] Data groups are divided according to the QAM modulation scheme of each frequency band to facilitate subsequent cyclic shifting in units of data groups. During cyclic shifting, it is necessary to ensure that the number of bits within each data group is the same. Since different modulation schemes carry different numbers of bits per subcarrier, the number of carriers in each data group also differs under different modulation schemes. Figure 2As shown, the data groups need to be divided according to the QAM modulation method of each frequency band. That is, different numbers of data groups are divided in different QAM frequency bands to ensure that the number of bits in each data group is the same. The specific implementation is as follows:

[0067] Divide each BPSK subband into a data group;

[0068] Each QPSK subband is divided into two data groups;

[0069] Each 16QAM sub-band is divided into four data groups.

[0070] Step 4: Calculate the number of bits occupied by each data group.

[0071] 4.1) Set the number of bits carried by each subcarrier according to different modulation schemes (BPSC):

[0072] If the sub-band is BPSK modulated, then BPSC is 1;

[0073] If the sub-band is QPSK modulated, then BPSC is 2;

[0074] If the sub-band is 16QAM modulation, then BPSC is 4.

[0075] 4.2) Calculate the number of bits N contained in each data group. Bits_per_group :

[0076] N Bits_per_group =N Carrier_per_group ×BPSC

[0077] Where, N Carrier_per_group The number of subcarriers contained in each data group.

[0078] Step 6: Calculate the number of bits to copy the last data group each time, and pad the last data group.

[0079] 6.1) Based on the number of bits N in the bit stream generated after channel interleaving raw and the number of bits N in each data group Bits_per_Group Calculate the number N of complete data sets contained in each copy. Group_per_Copy :

[0080] N Group_per_Copy =[N raw / N Bits_per_Group ]

[0081] Where [] represents the floor function;

[0082] 6.2) Based on the number N of complete data sets in each copy... Group_per_Copy and the number of bits N in each data groupBits_per_Group Calculate the number of remaining bits N in the last data group. Bits_of_last_group :

[0083] N Bits_of_last_group =N raw -N Bits_per_Group ×N Group_per_Copy

[0084] If N Bits_of_last_Group If the value is not 0, it means that the last data group in each copy is not filled with bits, so the last data group needs to be filled to ensure that multiple complete data groups are formed in each copy.

[0085] 6.3) Calculate the number of bits N required for padding. pad :

[0086] N pad =N Bits_per_Group -N Bits_of_last_group ;

[0087] 6.4) Fill the last data group with the required number of bits:

[0088] When the number of copies is N, it means that after multiple copies, N original bitstream sequences are generated. The last data group of these N sequences needs to be padded with bits. The rules for padding redundant data are as follows:

[0089] Transform the first bit of the original bit stream to the Nth bit. pad Bitwise copy to the end of the first group of sequences;

[0090] The Nth bit of the original bitstream pad +1 to the 2×Nth position pad The bits are copied to the end of the second sequence.

[0091] Continue in this manner to fill in the last data.

[0092] Step 7: Calculate the number of bits copied each time after padding.

[0093] After data filling is complete, multiple complete data groups with equal bit counts are generated in each copy. Therefore, the number of bits contained in each copy can be determined based on the carrier number and corresponding sub-frequency band in each data group. Specifically, it is based on the bit count N of the last data group in each copy, as calculated above. Bits_of_last_Group The value is determined:

[0094] If N Bits_of_last_Group = 0 means that multiple complete data groups have already been formed before each copy, and no further padding is needed. In this case, the number of bits per copy is: N Bits_per_Copy =NBits_per_Group ×N Group_per_Copy ;

[0095] If N Bits_of_last_Group If the value is not equal to 0, it means that the last data group was incomplete before padding. Therefore, the last data group of the copy needs to be padded. After padding, the total number of bits for the entire copy is calculated as follows:

[0096] N Bits_per_Copy =N Bits_per_Group ×(N Group_per_copy +1).

[0097] Step 8: Perform a circular shift on the data set.

[0098] The copied data is cyclically shifted in units of data groups. After shifting, the same data group can be effectively prevented from remaining on the same subcarrier after copying, thus making full use of the system's diversity characteristics and enhancing the payload's resistance to channel fading. The implementation steps include the following:

[0099] 8.1) Calculate the number of bits in each symbol:

[0100] To calculate the cyclic shift parameters, we first need to calculate the number of bits in each symbol. That is, in the time-frequency resource block, the number of bits on all subcarriers over a symbol's time length is taken as the number of bits in one symbol, and the number of bits N in each symbol is calculated. Bits_per_Symbol :

[0101] N Bits_per_Symbol =N Carrier ×BPSC

[0102] Where, N Carrier This refers to the number of subcarriers available in the system.

[0103] 8.2) Calculate the number N of data groups in each symbol based on the number of bits in each symbol and the number of bits in each data group. Group_per_Symbol :

[0104]

[0105] 8.3) Calculate the number N of data groups in the last symbol during the first copy, based on the number of data groups in each symbol and the number of data groups in each copy. Group_last_Symbol :

[0106] N Group_last_Symbol =N Group_per_Copy %N Group_per_Symbol ,

[0107] Where N Group_per_SymbolThe number of data sets contained in each symbol, % is the modulo operation; if N Group_last_Symbol If N = 0, then the number of data sets in the last symbol is equal to the number of data sets in each symbol, i.e., N Group_last_Symbol =N Group_per_Symbol ;

[0108] 8.5) Calculate the cyclic shift parameters:

[0109] The cyclic shift parameter determines the shift length when each bit stream sequence is cyclically shifted in units of data groups. The calculation method of the cyclic shift parameter GSN is different for different number of copies. The cyclic shift parameter for different number of copies is determined by the number of data groups in each symbol and the number of data groups in the last symbol.

[0110] The specific calculation process for the cyclic shift parameter GSN is as follows:

[0111] If the number of copies N = 1, then the cyclic shift parameter GSN(0) for the first copy is 0;

[0112] If the number of copies N = 2, then the cyclic shift parameter GSN(0) for the first copy is 0, and the second copy is determined in the following two cases:

[0113] If N Group_last_Symbol Not equal to N Group_per_Symbol Then GSN(1) = 0;

[0114] If N Group_last_Symbol equals N Group_per_Symbol Then GSN(1) = 1;

[0115] If the number of copies N is any number other than 1 and 2, and less than N... Group_per_Symbol If the result is any other integer, then the circular shift parameter GSN(0) for the first copy is 0, and the circular shift parameter for subsequent copies is calculated according to the following rules:

[0116] If N Group_last_Symbol =N Group_per_Symbol , then GSN(i)=i, i=1, 2,...,N-1;

[0117] If N Group_last_Symbol ≠N Group-per_Symbol In this case, if N Group_last_Symbol ≠1, and N Group_per_Symbol / N Group_last_Symbol =a, then the N copies are divided into N / a groups, where a is an integer. The circular shift parameter of the first group is 0, the circular shift parameter of the second group is 1, the circular shift parameter of the third group is 2, and so on.

[0118] In other cases, no circular shift is performed;

[0119] 8.6) The data group is cyclically shifted according to the generated cyclic shift parameters. When the system copy count is 4 and the channel is divided into 7 sub-frequency bands, a time-frequency resource block is generated after the cyclic shift, such as... Figure 3 As shown.

[0120] Step 9: Set the capacity of the sub-interleaver and assign a sub-interleaver to each data group.

[0121] To randomize the bit stream during data transmission, the cyclically shifted bit stream needs to be interleaved.

[0122] The capacity of the sub-interleaver, i.e., the number of sub-interleavers in each data set, is calculated as follows:

[0123] 9.1) Set the number of carriers contained in each sub-interleaver to be equal, and set the capacity of each sub-interleaver to the number of carriers in the data group of the highest modulation order frequency band, that is, the number of carriers in each data group of the 16QAM band;

[0124] 9.2) Based on the different number of carriers in different frequency band data groups and the different number of sub-interleavers in different frequency band data groups, sub-interleavers are allocated according to the modulation scheme of different frequency bands, i.e.:

[0125] In the BPSK band, four sub-interleavers are assigned to each data group;

[0126] In the QPSK band, two sub-interleavers are allocated to each data group;

[0127] In the 16QAM band, a sub-interleaver is assigned to each data group;

[0128] The implementation process of steps 8 and 9 above is as follows: Figure 4 As shown.

[0129] Step 10: Perform sub-interleaving and QAM modulation on the data set.

[0130] 10.1) Data is sub-interleaved within each data group according to the rules of the sub-interleaver in the IEEE 1901 protocol. Specifically, data is shifted within sub-interleavers of different frequency bands according to the index table in the protocol. This is implemented by using different minimum interleaving units based on the modulation scheme.

[0131] In BPSK modulation, shifting is performed in units of 1 bit.

[0132] In QPSK modulation, shifting is performed in 2-bit units.

[0133] In 16QAM modulation, shifting is performed in 4-bit units.

[0134] 10.2) Modulate the data group with QAM according to the sub-band in which the data group is located.

[0135] The above outlines the main steps of the adaptive ROBO coding interleaving scheme at the transmitting end. At the receiving end, after de-ROBO coding interleaving of the received data, the received N sets of data need to be combined using the maximum ratio based on channel conditions.

[0136] Step 11, merge the largest ratios.

[0137] At the receiving end, the QAM demodulated data is deinterleaved according to the interleaving principle, and then the data copied multiple times is combined by maximum ratio to increase the diversity gain of the system. The specific implementation is as follows:

[0138] 11.1) Data Cleaning:

[0139] Data cleaning is to remove outliers from the received data. For N identical data in N copies, first determine the sign of the received data points, and then remove outliers from each group of data based on the sign of the data.

[0140] 11.2) Merging of maximum ratios:

[0141] In the frequency domain, the data after removing outliers is combined by maximum ratio based on the channel conditions. That is, firstly, the weight of the sub-channel power corresponding to each data point in each group of sub-channels is calculated, and then the corresponding data is combined by weighting according to the weight.

[0142] This completes the AMC-ROBO encoding interleaving in power line carrier communication.

[0143] The numbers used in the above steps are only for the purpose of clearly describing the present invention, and their order is not limited.

[0144] The effects of this invention can be further illustrated by the following simulation results:

[0145] I. Simulation conditions:

[0146] Channel environment: Frequency-selective fading channel with a multipath number of 4;

[0147] Data volume: 520PB;

[0148] Number of copies: 4

[0149] Pilot insertion method: Insert one pilot signal for every four valid data points.

[0150] II. Simulation Content

[0151] The entire frequency band was divided into four sub-bands, and the modulation scheme of each sub-band was adaptively set to two combinations: QPSK, BPSK, QPSK, QPSK and QPSK, BPSK, BPSK, QPSK, according to the channel conditions. The bit error rate performance was simulated in an OFDM power line carrier communication system using the adaptive ROBO interleaving method of this invention and the traditional ROBO method, respectively. The results are shown in Figure 5.

[0152] from Figure 5 As can be seen, compared with the traditional single modulation method, the bit error rate of this invention is lower than that of the full-band QPSK modulation scheme, thus improving the reliability of data transmission. Furthermore, since the number of transmitted symbols is less than that of the full-band BPSK modulation scheme during simulation, the resource utilization of the system is improved.

[0153] The above results demonstrate that the present invention can achieve a flexible trade-off between transmission reliability and bandwidth utilization in practical applications, thereby maximizing system performance.

[0154] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An adaptive coding interleaving method in power line carrier communication, characterized in that, It includes the following: 1) Determine the amount of data to be sent, the code rate, and the number of copies according to actual requirements; 2) Divide the sub - frequency bands: 2a) The receiving end sends a detection frame composed of frame control information and a preamble sequence to the sending end; 2b) After receiving the detection frame, the sending end adaptively divides the sub - frequency bands based on the dichotomy method; 3) Determine the modulation method of the sub - frequency bands: 3a) Write the number of sub - frequency bands in binary form into the Channel Quality field of the SACK frame; 3b) According to the number of sub - frequency bands, calculate the average signal - to - noise ratio SNR of each sub - frequency band, and compare the average signal - to - noise ratio with two set thresholds k1 and k2 to determine its modulation method: If SNR≤k1, then use Binary Phase - Shift Keying (BPSK) modulation; If k1 < SNR≤k2, then use Quadrature Phase - Shift Keying (QPSK) modulation; If SNR>k2, then use 16 - Quadrature Amplitude Modulation (16QAM) modulation; Where k1 is the signal - to - noise ratio threshold boundary between BPSK modulation and QPSK modulation, and k2 is the signal - to - noise ratio threshold boundary between QPSK modulation and 16QAM modulation 3c) Write the modulation method of each sub - frequency band into the Reserved field of the SACK frame; 4) Divide the data groups according to the modulation method of each frequency band; 5) Calculate the number of bits N in each data group based on the modulation scheme of each data group and the number of carriers contained in each data group. Bits_per_group ; 6) Based on the number of bits in each data group and the input data length N raw Calculate the number of bits N in the last data group during each copy. Bits_of_last_group If the last data group has fewer bits than the size of a complete data group, it needs to be padded. The total number of bits N after padding is calculated based on the number of bits in each data group and the number of data groups. Bits_per_Copy ; The number of bits of the last data group in each copy is calculated as follows: 8a) Based on the number of bits N in the bit stream generated after channel interleaving raw and the number of bits N in each data group Bits_per_Group Calculate the number N of complete data sets contained in each copy. Group_per_Copy : N Group_per_Copy =[N raw / N Bits_per_Croup ]; Where [] is the floor operation; 8b) Based on the number N complete data sets in each copy Group_per_Copy and the number of bits N in each data group Bits_per_Group Calculate the number of remaining bits N in the last data group. Bits_of_last_group : N Bits_of_last_group =N raw -N Bits_per_Group ×N Group_per_Copy ; The total number of bits N for each copy is calculated based on the number of bits contained in each data group and the number of data groups. Bits_per_Copy The formula is as follows: 7) According to the cyclic shift parameters specified in the IEEE 1901 protocol, perform cyclic shift within each copy in units of data groups to further improve the system's ability to resist frequency - selective fading; 8) Use the number of carriers contained in the data group of the 16QAM frequency band as the size of the sub - interleaver, and perform sub - interleaving and mapping on the data after cyclic shift within each data group according to the rules of the sub - interleaver in the IEEE 1901 protocol; 9) Form a symbol with the data groups at all frequency bands at each moment, and generate a complete time - frequency resource block according to the number of its data groups: If the number of data groups in each symbol is equal to the number of copies, directly generate a complete time - frequency resource block, Otherwise, redundant data needs to be filled at the end of the last symbol, and then a complete time - frequency resource block is generated; 10) Modulate the data of the time - frequency resource block according to the divided sub - frequency bands; 11) At the receiving end, demodulate and perform de - ROBO interleaving on the frequency - domain data after time - frequency transformation, and perform maximum ratio combining on the data of N copies to obtain the original bit stream.

2. The method according to claim 1, characterized in that, The preamble sequence in step 2a) is a data stream with a specific length known to the receiving end and is used for channel estimation.

3. The method according to claim 1, characterized in that, After receiving the detection frame as described in step 2b), the sending end adaptively divides the sub - frequency bands based on the dichotomy method, and the implementation includes the following: 3b1) Divide the entire channel into two sub - frequency bands and perform channel estimation on each sub - frequency band; 3b2) Compare the channel estimation results of the two sub - frequency bands. If the difference in the signal - to - noise ratio between the two sub - frequency bands is greater than the set threshold, continue to divide each sub - frequency band into two sub - frequency bands; 3b3) Repeat step 3b2) until the number of sub - frequency bands reaches the upper limit of 8.

4. The method according to claim 1, characterized in that, In step 3b), the average SNR of each sub-band is calculated using the following formula: Where, N Carrier_per_band The number of subcarriers in each subband, snr i The signal-to-noise ratio for each subcarrier.

5. The method according to claim 1, characterized in that, In step 3c), the modulation scheme of each sub-band is written into the Reserved field of the SACK frame. This involves first expanding the 8-bit Reserved field to 16 bits, with each sub-band occupying 2 bits, and then encoding the 2-bit information according to the modulation scheme of each sub-band. If the sub-band is BPSK modulation, then the 2-bit code is 00; If the sub-band is QPSK modulated, then the 2-bit code is 01. If the sub-band is 16QAM modulation, then the 2-bit encoding is 11.

6. The method according to claim 1, characterized in that, Step 4) involves dividing the data into groups based on the modulation scheme of each frequency band. This means dividing different numbers of data groups within different frequency bands. Divide each BPSK subband into a data group; Each QPSK subband is divided into two data groups; Each 16QAM sub-band is divided into four data groups.

7. The method according to claim 1, characterized in that, Step 5) Calculate the number of bits N contained in each data group. Bits_per_group The formula is as follows: N Bits_per_group =N Carrier_per_group ×BPSC; Where, N Carrier_per_group The number of subcarriers contained in each data group. BPSC represents the number of bits carried by each subcarrier under different modulation schemes, and its value is set according to different modulation schemes: If the sub-band is BPSK modulated, then BPSC is 1; If the sub-band is QPSK modulated, then BPSC is 2; If the sub-band is 16QAM modulation, then BPSC is 4.

8. The method according to claim 1, characterized in that, In step 8), the copied data is sub-interleaved within each data group according to the rules of the sub-interleaver in the IEEE 1901 protocol. This involves shifting the data within the sub-interleaver in different frequency bands according to the index table in the protocol. In the BPSK band, each data group contains four sub-interleavers, and each sub-interleaver shifts data in units of one bit. In the QPSK band, each data group contains two sub-interleavers, and each sub-interleaver shifts data in units of two bits. In the 16QAM band, each data group contains a sub-interleaver that shifts data in units of four bits.

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