CN112994845A - RTK data transmission method, system and storage medium based on combination of LoRa and LDPC - Google Patents

RTK data transmission method, system and storage medium based on combination of LoRa and LDPC Download PDF

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CN112994845A
CN112994845A CN202110183600.6A CN202110183600A CN112994845A CN 112994845 A CN112994845 A CN 112994845A CN 202110183600 A CN202110183600 A CN 202110183600A CN 112994845 A CN112994845 A CN 112994845A
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ldpc
hamming
lora
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decoding
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CN112994845B (en
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熊连海
陈住生
胡峰
程健
黄巍
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Wuhan Mengxin Technology Co ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0057—Block codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0064—Concatenated codes
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0071—Use of interleaving
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W4/00—Services specially adapted for wireless communication networks; Facilities therefor
    • H04W4/06—Selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS]; Services to user groups; One-way selective calling services

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Abstract

The invention relates to an RTK data transmission method, system and storage medium based on combination of LoRa and LDPC, the method includes performing LDPC encoding on RTK data to obtain LDPC encoded code words; interleaving the LDPC coded code words, and performing Hamming coding on the interleaved LDPC coded code words to obtain Hamming coded code words; transmitting the Hamming code words through an LoRa data link; receiving a Hamming coding code word, and carrying out Hamming decoding on the Hamming coding code word to obtain a Hamming decoding code word; and de-interleaving the Hamming decoding code word, and performing LDPC decoding on the de-interleaved Hamming decoding code word to obtain RTK data. The RTK high-precision positioning method based on the combination of LoRa broadcast communication and LDPC coding and decoding can well reduce errors caused by multipath and Doppler effect influence generated by movement, improve the LoRa transmission distance, and further solve the problem that an RTK high-precision positioning system cannot be used in a remote place without network coverage.

Description

RTK data transmission method, system and storage medium based on combination of LoRa and LDPC
Technical Field
The invention relates to the field of communication, in particular to an RTK data transmission method, system and storage medium based on combination of LoRa and LDPC.
Background
The current high-precision differential positioning system consists of a reference station and a rover station. Both the reference station and the rover station contain data links. The precise coordinates of the reference station require that the receiver of the reference station is known and is responsible for estimating the range error of each satellite and generating a differential correction value for it. The reference station is then responsible for transmitting the differential corrections or raw observations over the appropriate data link to the user receiver at the rover station. And the user receiver can combine the received differential correction value and the own observation data to calculate a positioning result with higher precision level.
Currently, 4G/NB-IOT technology is generally adopted for the data link part, but the 4G/NB-IOT coverage is not available in some remote places. This limits the application of high precision differential positioning.
Disclosure of Invention
The invention aims to solve the technical problem of providing an RTK data transmission method, system and storage medium based on combination of LoRa and LDPC, which can increase data transmission distance, thereby solving the problem that no network coverage exists in remote places and an RTK high-precision positioning system cannot be used.
The technical scheme for solving the technical problems is as follows: an RTK data transmission method based on combination of LoRa and LDPC comprises the following steps,
s1, performing LDPC encoding on the RTK data to obtain an LDPC encoded code word;
s2, interleaving the LDPC coded code words, and carrying out Hamming coding on the interleaved LDPC coded code words to obtain Hamming coded code words;
s3, transmitting the Hamming code words through an LoRa data link;
s4, receiving the Hamming code word, and carrying out Hamming decoding on the Hamming code word to obtain a Hamming decoding code word;
s5, de-interleaving the Hamming decoding code word, and performing LDPC decoding on the de-interleaved Hamming decoding code word to obtain the RTK data.
The invention has the beneficial effects that: the RTK high-precision positioning method based on the combination of the LoRa broadcast communication and the LDPC coding and decoding adopts a mode of combining the relatively advanced LDPC coding and decoding and the Hamming coding and decoding of the LoRa RF, can better solve the problems of errors caused by multipath and Doppler effect influence generated by movement, and improve the LoRa transmission distance, thereby solving the problem that the RTK high-precision positioning system cannot be used in a remote place without network coverage and needing to build a reference station and a server by spending a large amount of time, money and space; compared with a GNSS RTK positioning system only using LoRa, the added LDPC coding ensures that the BER of data transmitted by a data link is reduced under the condition of the same transmission distance.
On the basis of the technical scheme, the invention can be further improved as follows.
Further, in S1, specifically,
s11, converting the check matrix H of the LDPC code into [ IP ] through a Gaussian elimination method, and simultaneously recording column replacement information Rt; wherein I is a unit array of (n-k) x (n-k), P is a check array of (n-k) x k, n is the code group bit number of the LDPC code, k is the information bit number of the LDPC code, and n-k is the check bit number of the LDPC code;
s12, setting the supervision bit as c, and cT＝P*xT(ii) a Wherein x is an information bit in the RTK data, c is a row vector of 1 x (n-k), and x is a row vector of 1 x k;
s13, coding the RTK data according to the parity bit c to obtain an initial coding code word utmpWherein u istmp＝[c|x]，utmpIs a 1 xn row vector;
s14, obtaining the initial coding code word u according to the column permutation information RttmpCorresponding column elements to obtain LDPC coded codeword u, where u [ Rt]＝utmpAnd u is a row vector of 1 × n.
Further, in the S5, the LDPC decoding of the hamming decoded codeword after deinterleaving includes,
s501, setting the iteration number i to be 0, and setting the maximum iterationNumber of times is imax；
S502, calculating a checksum sequence S of the ith iteration according to the check matrix H of the LDPC codei(ii) a According to a checksum sequence siDetermining codeword sequence ziWhether it is correct; if codeword sequence ziIf the result is correct, S511 is executed; if codeword sequence ziIf not, executing S503;
s503, initializing codeword sequence ziBit j in (1) is 0;
s504, calculating a code word sequence ziJ-th bit code word in
Figure BDA0002942143390000036
Metric value of corresponding probability inversion
Figure BDA0002942143390000037
S505, according to the measurement value
Figure BDA0002942143390000039
Generating random bits satisfying Bernoulli probability distribution
Figure BDA0002942143390000038
S506, judging the random bit
Figure BDA0002942143390000032
Whether it is equal to 1; if so, then according to
Figure BDA0002942143390000031
A sequence of codewords ziCode word in
Figure BDA0002942143390000034
Iterative update to codewords
Figure BDA0002942143390000033
Then, S507 is performed, in which,
Figure BDA0002942143390000035
is a second moldPerforming addition operation; if not, directly executing S507;
s507, let j equal to j + 1;
s508, judging whether J is less than or equal to J-1, wherein J is a code word sequence ziThe total number of bits in; if yes, skipping to execute S504; if not, executing S509;
s509, let i ═ i + 1;
s510, judging that i is less than imaxWhether the result is true or not; if yes, skipping to execute S502; if not, executing S511;
s511, stopping LDPC decoding and outputting code word sequence zi。
The beneficial effect of adopting the further scheme is that: the invention adopts a decoding algorithm based on probability inversion, improves the performance of the decoding algorithm and can further increase the data transmission distance.
Further, in the step S502, a checksum sequence S of the ith iteration is calculated according to the check matrix H of the LDPC codeiIs specifically represented by the formula si＝zi*HT(ii) a Wherein z isiIs the codeword sequence of the ith iteration; when i is 0, ziIn particular a hard bit sequence; when i > 0, ziSpecifically, decoding a code word sequence output iteratively;
a checksum sequence s will be calculatediIs given by the formula si＝zi*HTConversion into a checksum sequence siThe matrix of (1) is calculated as an equation, the checksum sequence siThe matrix calculation equation of (a) is specifically,
Figure BDA0002942143390000041
then there is a change in the number of,
Figure BDA0002942143390000042
wherein the content of the first and second substances,
Figure BDA0002942143390000043
is a checksum sequence siM-th checksum element of (1), hmIs the M-th row vector of the check matrix H, M belongs to [0, M-1 ]]，
Figure BDA0002942143390000044
Is the operation of addition of the modulus two,
Figure BDA0002942143390000045
is a sequence of codewords ziH of the j-th bit code wordm,jIs the mth row and jth column element of the check matrix H, J belongs to [0, J-1 ]]M is the total row number of the check matrix H, J is the total column number of the check matrix H, the codeword sequence ziThe total number of bits in (a) is equal to the total column number of the check matrix H.
Further, in the step S502, according to the checksum sequence SiDetermining codeword sequence ziThe specific steps of whether the process is correct or not are,
if M is greater than or equal to 0 and less than or equal to M-1, all
Figure BDA0002942143390000046
Is 0, then the codeword sequence z is determinediIs correct; if the mth checksum element exists for m.ltoreq.M-1 of 0. ltoreq.
Figure BDA0002942143390000047
If not 0, the codeword sequence z is determinediIs not correct.
Further, in said S504, a codeword sequence z is calculatediJ-th bit code word in
Figure BDA0002942143390000048
Metric value of corresponding probability inversion
Figure BDA0002942143390000049
The formula (2) is specifically shown in the specification,
Figure BDA00029421433900000410
wherein y is zi|i＝0。
Further, in the step S505, according to the metric value
Figure BDA00029421433900000411
Generating random bits satisfying Bernoulli probability distribution
Figure BDA00029421433900000412
The formula of (a) is as follows,
Figure BDA00029421433900000413
wherein the content of the first and second substances,
Figure BDA00029421433900000414
is the bit flip probability.
Further, in the S1, specifically performing binary LDPC encoding on the RTK data; in S5, the hamming decoding codeword after de-interleaving is specifically subjected to binary LDPC decoding.
Based on the RTK data transmission method based on the combination of LoRa and LDPC, the invention also provides an RTK data transmission system based on the combination of LoRa and LDPC.
An RTK data transmission system based on combination of LoRa and LDPC comprises a reference station and a rover station; a reference station GNSS receiver, an LDPC encoder, an interleaver and a reference station LoRa RF which are connected in sequence are arranged in the reference station; a rover GNSS receiver, an LDPC decoder, a deinterleaver and a rover LoRa RF which are connected in sequence are arranged in the rover; the reference station LoRa RF is communicatively coupled with the rover station LoRa RF;
the reference station GNSS receiver is used for receiving RTK data of a satellite;
the LDPC encoder is used for performing LDPC encoding on the RTK data to obtain an LDPC encoded code word;
the interleaver is configured to interleave the LDPC encoded codeword;
the reference station LoRa RF is used for carrying out Hamming coding on the LDPC coded code words after interleaving to obtain Hamming coded code words, and the Hamming coded code words are transmitted through a LoRa data link;
the rover station LoRa RF is used for receiving the Hamming code words transmitted from the reference station LoRa RF and carrying out Hamming decoding on the Hamming code words to obtain Hamming decoding code words;
the de-interleaver is used for de-interleaving the Hamming decoding code word;
the LDPC decoder is used for performing LDPC decoding on the Hamming decoding code word after de-interleaving to obtain the RTK data;
the rover GNSS receiver is used for receiving the RTK data decoded by the LDPC decoder.
The invention has the beneficial effects that: the RTK high-precision positioning method based on the combination of LoRa broadcast communication and LDPC coding and decoding adopts a mode of combining more advanced LDPC coding and decoding and Hamming coding and decoding carried by LoRa RF, can well reduce the Doppler effect influence generated by errors and motion caused by multipath, and improve the LoRa transmission distance, thereby solving the problem that no network coverage exists in remote places and an RTK high-precision positioning system can not be used, and needing not to spend a large amount of time, money and space to build a reference station and a server; compared with a GNSS RTK positioning system only using LoRa, the added LDPC coding ensures that the BER of data transmitted by a data link is reduced under the condition of the same transmission distance.
Based on the RTK data transmission method based on the combination of LoRa and LDPC, the invention also provides a computer storage medium.
A computer storage medium comprising at least one instruction which, when executed, implements the steps of the method for RTK data transmission based on the combination of LoRa and LDPC as described above.
Drawings
FIG. 1 is a flowchart of an RTK data transmission method based on the combination of LoRa and LDPC;
FIG. 2 is a block diagram of two-level encoding;
FIG. 3 is a decoding flow diagram based on probability flipping;
fig. 4 is a block diagram of an RTK data transmission system based on combination of LoRa and LDPC.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
As shown in fig. 1, an RTK data transmission method based on the combination of LoRa and LDPC includes the following steps,
s1, performing LDPC encoding on the RTK data to obtain an LDPC encoded code word;
s2, interleaving the LDPC coded code words, and carrying out Hamming coding on the interleaved LDPC coded code words to obtain Hamming coded code words;
s3, transmitting the Hamming code words through an LoRa data link;
s4, receiving the Hamming code word, and carrying out Hamming decoding on the Hamming code word to obtain a Hamming decoding code word;
s5, de-interleaving the Hamming decoding code word, and performing LDPC decoding on the de-interleaved Hamming decoding code word to obtain the RTK data.
The invention adopts LoRa as the basic transmission technology of the data link, solve the difficult problem that there is not 4G/NB-IOT to cover in the remote place, the invention adopts LDPC to encode and decode and LoRa broadcast communication to combine the way, further improve anti multipath and Doppler frequency offset ability of LoRa, reduce BER.
LoRa is a low-power consumption low-cost wireless physical layer standard, erects with low costsly, and transmission distance is far away, has realized low-power consumption and long-range unity. The high precision differential positioning system has great advantages in using the LoRa as the data link technology. Currently, the LoRa physical layer uses hamming coding, and only one hamming coding method can be selected from four hamming coding methods (5,4), (6,4), (7,4) and (8,4), where n-k is the check bit number and k is the information bit number in (n, k) hamming coding. The (5,4) and (6,4) hamming codes have no error correction capability, so in order to ensure the decoding performance, it is better to select a coding and decoding mode with error correction capability, such as the (7,4) hamming code, but the performance of the (7,4) hamming code is not ideal, which results in high BER and affects the transmission distance.
The low density check code (LDPC code) is a block code with forward error correction function, has good performance, and the check matrix H only contains a small amount of non-zero elements, and just the sparsity of the check matrix ensures that the decoding complexity and the minimum code distance only show linear increase along with the code length. The invention selects a regular check matrix, and considers that the long code performance of the LDPC code is good, so when selecting the LDPC (n, k), a check matrix H with larger n and k is preferentially selected, for example, a check matrix H with k being 2048 and n being 4096 is considered.
Specifically, the present invention adopts a two-stage encoding and decoding composed of an LDPC encoding and decoding and a hamming encoding and decoding in series, as shown in fig. 2; for the encoding end, the RTK data is firstly subjected to LDPC (4096,2048) encoding and interleaving before entering the LoRa RF, and then the interleaved codeword data enters the LoRa RF and is subjected to Hamming (5,4) encoding again; for a decoding end, the data of an air interface is decoded by Hamming (5,4) of a receiving end LoRa RF, the decoded data is output to be deinterleaved and decoded by LDPC (4096,2048), and finally the original RTK data is output.
In this particular embodiment:
in the S1, specifically performing binary LDPC encoding on the RTK data; in S5, the hamming decoding codeword after de-interleaving is specifically subjected to binary LDPC decoding.
In this particular embodiment:
specifically, the step S1 is,
s11, converting the check matrix H of the LDPC code into [ IP ] through a Gaussian elimination method, and simultaneously recording column replacement information Rt; wherein I is a unit array of (n-k) x (n-k), P is a check array of (n-k) x k, n is the code group bit number of the LDPC code, k is the information bit number of the LDPC code, and n-k is the check bit number of the LDPC code;
s12, setting the supervision bit as c, and cT＝P*xT(ii) a Wherein x is an information bit in the RTK data, c is a row vector of 1 x (n-k), and x is a row vector of 1 x k;
s13, coding the RTK data according to the parity bit c to obtain an initial coding code word utmp(ii) a Wherein u istmp＝[c|x]，utmpIs a 1 xn row vector;
s14, obtaining the initial coding code word u according to the column permutation information RttmpCorresponding column elements to obtain LDPC coded codeword u, where u [ Rt]＝utmpAnd u is a row vector of 1 × n.
Because the LDPC decoding at the receiving end can only adopt a hard decision mode, the common hard decision decoding is bit flip decoding, soft information is not needed in decoding, and the calculation is simple. However, the existing bit flipping decoding algorithm has poor performance; therefore, the invention optimizes the existing decoding algorithm of bit flipping and adopts the decoding algorithm based on probability flipping; the decoding process based on probability inversion (i.e. the specific step of LDPC decoding on the deinterleaved hamming decoding codeword in S5) is specifically shown in fig. 3:
s501, setting the iteration number i to 0, and setting the maximum iteration number imax。
S502, calculating a checksum sequence S of the ith iteration according to the check matrix H of the LDPC codei(ii) a According to a checksum sequence siDetermining codeword sequence ziWhether it is correct; if codeword sequence ziIf the result is correct, S511 is executed; if codeword sequence ziIf not, executing S503;
specifically, a checksum sequence s of the ith iteration is calculated according to a check matrix H of the LDPC codeiIs specifically represented by the formula si＝zi*HT(ii) a Wherein z isiIs the codeword sequence of the ith iteration; when i is 0, ziIn particular a hard bit sequence; when i > 0, ziSpecifically, decoding a code word sequence output iteratively;
a checksum sequence s will be calculatediIs given by the formula si＝zi*HTConversion into a checksum sequence siThe matrix of (1) is calculated as an equation, the checksum sequence siThe matrix calculation equation of (a) is specifically,
Figure BDA0002942143390000091
a variation of the above matrix calculation equation would be,
Figure BDA0002942143390000092
wherein the content of the first and second substances,
Figure BDA0002942143390000093
is a checksum sequence siM-th checksum element of (1), hmIs the M-th row vector of the check matrix H, M belongs to [0, M-1 ]]，
Figure BDA0002942143390000094
Is the operation of addition of the modulus two,
Figure BDA0002942143390000095
is a sequence of codewords ziH of the j-th bit code wordm,jIs the mth row and jth column element of the check matrix H, J belongs to [0, J-1 ]]M is the total row number of the check matrix H, J is the total column number of the check matrix H, the codeword sequence ziThe total number of bits in the check matrix H is equal to the total column number of the check matrix H;
further, according to the checksum sequence siDetermining codeword sequence ziThe specific steps of whether the process is correct or not are,
if M is greater than or equal to 0 and less than or equal to M-1, all
Figure BDA0002942143390000096
Is 0, illustrating the check equation si＝zi*HTIf 0 is true, the codeword sequence z is determinediIs correct; if the mth checksum element exists for m.ltoreq.M-1 of 0. ltoreq.
Figure BDA0002942143390000097
If not 0, the codeword sequence z is determinediIs not correct.
S503, initializing codeword sequence ziBit j in (1) is 0.
S504, calculating a code word sequence ziJ-th bit code word in
Figure BDA0002942143390000098
Metric value of corresponding probability inversion
Figure BDA0002942143390000099
In particular, a sequence of code words z is calculatediJ-th bit code word in
Figure BDA00029421433900000910
Metric value of corresponding probability inversion
Figure BDA00029421433900000911
The formula (2) is specifically shown in the specification,
Figure BDA00029421433900000912
wherein y is zi|i＝0。
S505, according to the measurement value
Figure BDA00029421433900000913
Generating random bits satisfying Bernoulli probability distribution
Figure BDA00029421433900000914
In particular, based on the metric values
Figure BDA00029421433900000915
Generating random bits satisfying Bernoulli probability distribution
Figure BDA00029421433900000916
The formula of (a) is as follows,
Figure BDA0002942143390000101
wherein the content of the first and second substances,
Figure BDA0002942143390000102
is the bit flipping probability;
further, according to the simulation result, when the check matrixThe column weight of H is 4 and,
Figure BDA0002942143390000103
Figure BDA0002942143390000104
probability of bit flipping
Figure BDA0002942143390000105
Respectively 0, 0.001, 0.1, 0.2, 0.4, 0.8.
S506, judging the random bit
Figure BDA0002942143390000106
Whether it is equal to 1; if so, then according to
Figure BDA0002942143390000107
A sequence of codewords ziCode word in
Figure BDA0002942143390000108
Iterative update to codewords
Figure BDA0002942143390000109
Then, S507 is performed, in which,
Figure BDA00029421433900001010
performing modulo two addition operation; if not, directly executing S507.
S507, let j equal j + 1.
S508, judging whether J is less than or equal to J-1, wherein J is a code word sequence ziThe total number of bits in; if yes, skipping to execute S504; if not, S509 is executed.
S509 denotes i ═ i + 1.
S510, judging that i is less than imaxWhether the result is true or not; if yes, skipping to execute S502; if not, S511 is executed.
S511, stopping LDPC decoding and outputting code word sequence zi。
The invention adopts a decoding algorithm based on probability inversion, improves the performance of the decoding algorithm and can further increase the data transmission distance.
In the invention, the LDPC coded code words are interleaved by using an interleaver, and the interleaver writes in according to columns and reads out according to rows to realize the interleaving function; when the check matrix H is a 2048 × 4096 sparse matrix H2048,4096The interleaver rows and columns are 64 and 64, respectively.
In the invention, a de-interleaver is used for de-interleaving the Hamming decoding code word, and the de-interleaver at a receiving end is written in according to rows and read out according to columns, thereby realizing the de-interleaving function; when the check matrix H is a 2048 × 4096 sparse matrix H2048,4096The deinterleaver rows and columns are 64 and 64, respectively.
The broadcasting side LoRa RF realizes the function of data transmission, and since LDPC encoding is performed before data enters LoRa RF, cr (code rate) of LoRa RF is set to 1, that is, (5,4) hamming encoding is adopted. The receiving end LoRa RF implements the data receiving function, and cr (code rate) of LoRa RF is set to 1, that is, default (5,4) hamming decoding is adopted.
The RTK high-precision positioning method based on the combination of the LoRa broadcast communication and the LDPC coding and decoding adopts a mode of combining the relatively advanced LDPC coding and decoding and the Hamming coding and decoding of the LoRa RF, can well reduce the errors caused by multipath and the Doppler effect influence generated by movement, and improve the LoRa transmission distance, thereby solving the problem that the RTK high-precision positioning system cannot be used in a remote place without network coverage and needing to build a reference station and a server by spending a large amount of time, money and space; compared with a GNSS RTK positioning system only using LoRa, the added LDPC coding ensures that the BER of data transmitted by a data link is reduced under the condition of the same transmission distance.
The existing high-precision differential positioning system consists of a reference station and a rover station. Both the reference station and the rover station contain data links. The precise coordinates of the reference station require that the receiver of the reference station is known and is responsible for estimating the range error of each satellite and generating a differential correction value for it. The reference station is then responsible for transmitting the differential corrections or raw observations over the appropriate data link to the user receiver at the rover station. And the user receiver can combine the received differential correction value and the own observation data to calculate a positioning result with higher precision level. But since the current data link part usually adopts 4G/NB-IOT technology, there are some remote places without 4G/NB-IOT coverage. This limits the application of high precision differential positioning. Therefore, based on the RTK data transmission method based on the combination of LoRa and LDPC, the invention further provides an RTK data transmission system based on the combination of LoRa and LDPC.
As shown in fig. 4, an RTK data transmission system based on combination of LoRa and LDPC includes a reference station and a rover station; a reference station GNSS receiver, an LDPC encoder, an interleaver and a reference station LoRa RF which are connected in sequence are arranged in the reference station; a rover GNSS receiver, an LDPC decoder, a deinterleaver and a rover LoRa RF which are connected in sequence are arranged in the rover; the reference station LoRa RF is communicatively coupled with the rover station LoRa RF;
the reference station GNSS receiver is used for receiving RTK data of a satellite;
the LDPC encoder is used for performing LDPC encoding on the RTK data to obtain an LDPC encoded code word;
the interleaver is configured to interleave the LDPC encoded codeword;
the reference station LoRa RF is used for carrying out Hamming coding on the LDPC coded code words after interleaving to obtain Hamming coded code words, and the Hamming coded code words are transmitted through a LoRa data link;
the rover station LoRa RF is used for receiving the Hamming code words transmitted from the reference station LoRa RF and carrying out Hamming decoding on the Hamming code words to obtain Hamming decoding code words;
the de-interleaver is used for de-interleaving the Hamming decoding code word;
the LDPC decoder is used for performing LDPC decoding on the Hamming decoding code word after de-interleaving to obtain the RTK data;
the rover GNSS receiver is used for receiving the RTK data decoded by the LDPC decoder.
The RTK high-precision positioning method based on the combination of the LoRa broadcast communication and the LDPC coding and decoding adopts a mode of combining the relatively advanced LDPC coding and decoding and the Hamming coding and decoding of the LoRa RF, can well reduce the errors caused by multipath and the Doppler effect influence generated by movement, and improve the LoRa transmission distance, thereby solving the problem that the RTK high-precision positioning system cannot be used in a remote place without network coverage, realizing centimeter-level positioning after the GNSS RTK positioning system is subjected to differential correction, and needing not to spend a large amount of time, money and space to build a reference station and a server; compared with a GNSS RTK positioning system only using LoRa, the added LDPC coding ensures that the BER of data transmitted by a data link is reduced under the condition of the same transmission distance.
The method of LoRa broadcast communication is adopted, namely LoRa RF on the reference station side is used as a broadcast end of the GNSS RTK positioning system, all LoRa RF on the mobile station side is used as a receiving end of the GNSS RTK positioning system, the broadcast end is only responsible for transmitting, and the receiving end is only responsible for receiving. The basic configuration of the LoRa RF at the broadcasting end and the receiving end is the same, and the basic configuration includes frequency points, bandwidth, spreading factor, code rate, length of a preamble, and the like.
Based on the RTK data transmission method based on the combination of LoRa and LDPC, the invention also provides a computer storage medium.
A computer storage medium comprising at least one instruction which, when executed, implements the steps of the method for RTK data transmission based on the combination of LoRa and LDPC as described above.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (10)

1. An RTK data transmission method based on combination of LoRa and LDPC is characterized in that: comprises the following steps of (a) carrying out,
s1, performing LDPC encoding on the RTK data to obtain an LDPC encoded code word;
s2, interleaving the LDPC coded code words, and carrying out Hamming coding on the interleaved LDPC coded code words to obtain Hamming coded code words;
s3, transmitting the Hamming code words through an LoRa data link;
s4, receiving the Hamming code word, and carrying out Hamming decoding on the Hamming code word to obtain a Hamming decoding code word;
s5, de-interleaving the Hamming decoding code word, and performing LDPC decoding on the de-interleaved Hamming decoding code word to obtain the RTK data.
2. The RTK data transmission method based on combination of LoRa and LDPC according to claim 1, wherein: specifically, the step S1 is,
s11, converting the check matrix H of the LDPC code into [ I | P ] by a Gaussian elimination method, and simultaneously recording column replacement information Rt, wherein I is a unit matrix of (n-k) x (n-k), P is a check matrix of (n-k) xk, n is the code block bit number of the LDPC code, k is the information bit number of the LDPC code, and n-k is the check bit number of the LDPC code;
s12, setting the supervision bit as c, and cT＝P*xT(ii) a Wherein x is an information bit in the RTK data, c is a row vector of 1 x (n-k), and x is a row vector of 1 x k;
s13, coding the RTK data according to the parity bit c to obtain an initial coding code word utmpWherein u istmp＝[c|x]，utmpIs a 1 xn row vector;
s14, obtaining the initial coding code word u according to the column permutation information RttmpCorresponding column elements to obtain LDPC coded codeword u, where u [ Rt]＝utmpAnd u is a row vector of 1 × n.
3. The RTK data transmission method based on combination of LoRa and LDPC as claimed in claim 1 or 2, wherein: in S5, the LDPC decoding of the deinterleaved hamming-decoded codeword includes,
s501, setting the iteration number i to 0, and setting the maximum iteration number imax；
S502, calculating the ith according to the check matrix H of the LDPC codeSub-iterative checksum sequence si(ii) a According to a checksum sequence siDetermining codeword sequence ziWhether it is correct; if codeword sequence ziIf the result is correct, S511 is executed; if codeword sequence ziIf not, executing S503;
s503, initializing codeword sequence ziBit j in (1) is 0;
s504, calculating a code word sequence ziJ-th bit code word in
Figure FDA0002942143380000021
Metric value of corresponding probability inversion
Figure FDA0002942143380000022
S505, according to the measurement value
Figure FDA0002942143380000023
Generating random bits satisfying Bernoulli probability distribution
Figure FDA0002942143380000024
S506, judging the random bit
Figure FDA0002942143380000025
Whether it is equal to 1; if so, then according to
Figure FDA0002942143380000026
A sequence of codewords ziCode word in
Figure FDA0002942143380000027
Iterative update to codewords
Figure FDA0002942143380000028
Then, S507 is performed, in which,
Figure FDA0002942143380000029
adding for the second moldCalculating; if not, directly executing S507;
s507, let j equal to j + 1;
s508, judging whether J is less than or equal to J-1, wherein J is a code word sequence ziThe total number of bits in; if not, skipping to execute S504; if not, executing S509;
s509, let i ═ i + 1;
s510, judging that i is less than imaxWhether the result is true or not; if yes, skipping to execute S502; if not, executing S511;
s511, stopping LDPC decoding and outputting code word sequence zi。
4. The method for transmitting RTK data based on the combination of LoRa and LDPC as claimed in claim 3, wherein: in the step S502, a checksum sequence S of the ith iteration is calculated according to the check matrix H of the LDPC codeiIs specifically represented by the formula si＝zi*HT(ii) a Wherein z isiIs the codeword sequence of the ith iteration; when i is 0, ziIn particular a hard bit sequence; when i > 0, ziSpecifically, decoding a code word sequence output iteratively;
a checksum sequence s will be calculatediIs given by the formula si＝zi*HTConversion into a checksum sequence siThe matrix of (1) is calculated as an equation, the checksum sequence siThe matrix calculation equation of (a) is specifically,
Figure FDA0002942143380000031
then there is a change in the number of,
Figure FDA0002942143380000032
wherein the content of the first and second substances,
Figure FDA0002942143380000033
is a checksum sequence siM-th checksum element of (1), hmIs the m-th row vector of the check matrix H, and m belongs to[0,M-1]，
Figure FDA0002942143380000034
Is the operation of addition of the modulus two,
Figure FDA0002942143380000035
is a sequence of codewords ziH of the j-th bit code wordm,jIs the mth row and jth column element of the check matrix H, J belongs to [0, J-1 ]]M is the total row number of the check matrix H, J is the total column number of the check matrix H, the codeword sequence ziThe total number of bits in (a) is equal to the total column number of the check matrix H.
5. The RTK data transmission method based on the combination of LoRa and LDPC according to claim 4, characterized in that: in the S502, according to the checksum sequence SiDetermining codeword sequence ziThe specific steps of whether the process is correct or not are,
if M is greater than or equal to 0 and less than or equal to M-1, all
Figure FDA0002942143380000036
Is 0, then the codeword sequence z is determinediIs correct; if the mth checksum element exists for m.ltoreq.M-1 of 0. ltoreq.
Figure FDA0002942143380000037
If not 0, the codeword sequence z is determinediIs not correct.
6. The RTK data transmission method based on the combination of LoRa and LDPC according to claim 4, characterized in that: in said S504, a codeword sequence z is calculatediJ-th bit code word in
Figure FDA0002942143380000038
Metric value of corresponding probability inversion
Figure FDA0002942143380000039
The formula (2) is specifically shown in the specification,
Figure FDA00029421433800000310
wherein y is zi|i＝0。
7. The RTK data transmission method based on the combination of LoRa and LDPC according to claim 4, characterized in that: in the S505, according to the metric value
Figure FDA00029421433800000311
Generating random bits satisfying Bernoulli probability distribution
Figure FDA00029421433800000312
The formula of (a) is as follows,
Figure FDA00029421433800000313
wherein the content of the first and second substances,
Figure FDA00029421433800000314
is the bit flip probability.
8. The RTK data transmission method based on combination of LoRa and LDPC according to any one of claims 1-2 and 4-7, wherein: in the S1, specifically performing binary LDPC encoding on the RTK data; in S5, the hamming decoding codeword after de-interleaving is specifically subjected to binary LDPC decoding.
9. An RTK data transmission system based on combination of LoRa and LDPC is characterized in that: comprises a reference station and a rover station; a reference station GNSS receiver, an LDPC encoder, an interleaver and a reference station LoRa RF which are connected in sequence are arranged in the reference station; a rover GNSS receiver, an LDPC decoder, a deinterleaver and a rover LoRa RF which are connected in sequence are arranged in the rover; the reference station LoRa RF is communicatively coupled with the rover station LoRa RF;
the reference station GNSS receiver is used for receiving RTK data of a satellite;
the LDPC encoder is used for performing LDPC encoding on the RTK data to obtain an LDPC encoded code word;
the interleaver is configured to interleave the LDPC encoded codeword;
the reference station LoRa RF is used for carrying out Hamming coding on the LDPC coded code words after interleaving to obtain Hamming coded code words, and the Hamming coded code words are transmitted through a LoRa data link;
the rover station LoRa RF is used for receiving the Hamming code words transmitted from the reference station LoRa RF and carrying out Hamming decoding on the Hamming code words to obtain Hamming decoding code words;
the de-interleaver is used for de-interleaving the Hamming decoding code word;
the LDPC decoder is used for performing LDPC decoding on the Hamming decoding code word after de-interleaving to obtain the RTK data;
the rover GNSS receiver is used for receiving the RTK data decoded by the LDPC decoder.
10. A computer storage medium, characterized in that: at least one instruction is included which when executed implements the steps of the LoRa and LDPC combination based RTK data transmission method of any one of claims 1 to 8.
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