A multipath-resistant LoRa communication method combining block interleaving and matched filtering

Abstract

This invention discloses a multipath-resistant LoRa communication method combining block interleaving and matched filtering, belonging to the field of Internet of Things (IoT) technology. The steps are as follows: Block interleaving reduces the amplitude of strong multipath signals by dividing the signal into equal blocks and then swapping the order of these blocks, followed by deinterleaving at the receiver; matched filtering increases the signal-to-noise ratio (SNR). Matched filtering is selected based on amplitude criteria, first filtering the preamble symbol, then performing circular correlation operations using the preamble and data symbols. This method effectively resists multipath interference and improves the bit error rate performance of LoRa communication. It is low in complexity, low in power consumption, and simple to implement, making it suitable for multipath-intensive indoor and outdoor communication scenarios and shallow water acoustic communication.

Description

Technical Field

[0001] This invention relates to the field of Internet of Things (IoT) technology, and specifically to a multipath LoRa communication method that combines block interleaving and matched filtering. Background Technology

[0002] LoRa (Long Range) is a long-range wireless transmission technology based on spread spectrum technology, and one of many LPWAN communication technologies. It provides users with a simple, long-range, and low-power wireless communication solution. LoRa uses Frequency Shift Chirp Modulation (FSCM) technology, which effectively resists multipath effects and signal fading, ensuring signal transmission quality in complex environments. Compared to traditional wired communication, LoRa eliminates the need for complex cabling and equipment, reducing installation and maintenance costs. Furthermore, LoRa technology supports a large number of device connections, making it suitable for scenarios requiring numerous device connections, such as the Internet of Things (IoT). Therefore, LoRa technology can be applied in smart cities, smart agriculture, smart healthcare, logistics tracking, and shallow-sea communication.

[0003] Within cities, numerous obstacles obstruct the signal transmission path, causing signals to travel through multiple paths, including refraction and reflection, to reach the receiver. Multipath interference caused by multipath effects is therefore significant. Similarly, in the ocean, signals are absorbed and reflected at the sea surface and seabed before reaching the receiver. Signal fading and multipath interference drastically degrade communication quality. Channel coding, channel equalization, Rake reception, and diversity techniques are common methods for handling multipath problems; however, these methods are power-consuming and complex. Therefore, finding low-power and low-complexity anti-multipath methods has been a long-standing research focus. Summary of the Invention

[0004] The purpose of this invention is to reduce the impact of multipath interference on LoRa wireless communication and to provide a multipath-resistant LoRa communication method that combines block interleaving and matched filtering. This invention utilizes block interleaving technology to decompose strong multipath interference into multiple weak multipath interferences at different locations. Matched filtering using channel information from preamble and data symbols increases the signal-to-noise ratio, thus achieving reliable LoRa communication.

[0005] The objective of this invention can be achieved by adopting the following technical solutions:

[0006] A multipath LoRa communication method combining block interleaving and matched filtering, the multipath LoRa communication method comprising the following steps:

[0007] Symbol modulation: The source generates data symbols, inserts a preamble symbol before the data symbols, and performs LoRa modulation on the data symbols and the preamble symbol to obtain a LoRa modulated signal;

[0008] Specifically, in the above symbol modulation, the source generates a data symbol 'a', inserts eight preamble symbols before the data symbol 'a', and performs LoRa modulation on the data symbol and the preamble symbols to obtain the LoRa modulated signal 'x'. a,n (k), where when n = 1, 2, 3, 4, 5, 6, 7, 8, it represents the preamble symbol, and when n = 9, 10, 11, ..., it represents the data symbol generated by the source;

[0009] Block interleaving: The LoRa modulated signal is divided into average blocks, and the order of the signal blocks of the modulated signal is swapped.

[0010] Specifically, in the above-mentioned block interleaving, the LoRa modulated signal x a,n (k) Perform block interleaving processing, that is, x a,n (k) Divide the signal into 4 equal blocks, keep the order of the first and fourth blocks unchanged, and swap the order of the second and third blocks to obtain signal x'. a,n (k).

[0011] De-blocking interleaving: The received signal is divided into inverse average blocks, and the order of the signal blocks of the received signal is swapped;

[0012] Specifically, in the above-mentioned deblocking interleaving, the receiving end receives signal r a,n (k), and for r a,n (k) Perform deblocking and interleaving processing on the received signal r a,n (k) Divide the signal into 4 equal blocks, keeping the order of the first and fourth blocks unchanged, and swap the order of the second and third blocks to obtain the de-blocked interleaved signal r'. a,n (k).

[0013] Incoherent demodulation: The de-blocked interleaved signal is multiplied by the conjugate of the base signal, then a discrete Fourier transform is performed, and the absolute value is calculated to obtain the incoherent demodulated output signal.

[0014] Specifically, in the above incoherent demodulation, r' a,n (k) conjugate with the basis signal Multiply the components, perform a discrete Fourier transform, and then calculate the absolute value to obtain the incoherent demodulated output signal y. q .

[0015] Joint demodulation: First, the noncoherent demodulated output signal is judged to separate the preamble symbol and the data symbol; second, the amplitude of the preamble symbol is determined. If the amplitude determination condition is met, the preamble symbol and the data symbol are matched and filtered; if the amplitude determination condition is not met, the value is assigned.

[0016] Specifically, in the aforementioned joint demodulation, y is first determined. q Is it a leading symbol? If y q It is a leading symbol, denoted as y. 2q,n , n∈{1,2,...,8} represents 8 leading symbols; if y q If it is not a leading symbol, then it is a data symbol, denoted as y. 1q Secondly, calculate the average value y of the eight leading symbols. 2q , for y 2q Amplitude judgment is performed, and the judgment condition is "y 2q Does y exist in? 2q The maximum peak value is "α times the peak value", where α∈(0,1). If the amplitude judgment condition is met, matched filtering is used for y. 2q Perform filtering to filter out values ​​less than y. 2q Set the value of the maximum peak value α times to zero, and retain values ​​greater than or equal to y. 2q The value is α times the maximum peak value, and then the filtered y is used. 2q With y 1q Perform circumferential related calculations to obtain R. y2qy1q If the amplitude judgment condition is not met, an assignment process is performed, and y is... 1q The value assigned to y 2q .

[0017] Symbol determination: Find the maximum value of the input data and determine the index value corresponding to the maximum value of the input data as the received LoRa symbol;

[0018] Specifically, in the symbol decision, for the input data R y2qy1q Or y 2q Perform sign-based decision and search for input data. or y 2q The maximum value is used to determine the index value corresponding to the maximum value as the received LoRa symbol.

[0019] Furthermore, the LoRa modulated signal x after symbol modulation a,n (k) is described as:

[0020]

[0021] In the formula, k∈{0,1,2,...,M-1} is the discrete-time domain independent variable, and M=2 SFThe number of possible transmitted symbols is represented by SF, which denotes the spreading factor. Its value is typically SF∈{7,8,9,10,11,12}, and a∈{0,1,2...,M-1}. Symbol modulation enhances the noise immunity, multipath immunity, and Doppler frequency offset immunity of both the preamble and data symbols.

[0022] Furthermore, the block interleaving involves dividing the LoRa modulated signal into four equal signal blocks and swapping the order of the second and third signals. The signal x' after block interleaving processing is... a,n (k) can be described as:

[0023]

[0024] Block interleaving is simple to implement; simply changing the order of signal blocks can improve the LoRa signal's resistance to multipath interference.

[0025] Furthermore, the received signal is the signal r after passing through a multipath channel. a,n (k), receiving signal r a,n (k) can be described as:

[0026]

[0027] In the formula, h0 represents the attenuation coefficient of the direct path signal, h i Let I represent the channel attenuation coefficient of the i-th path interference, p represent the multipath number, and I n,i (k) indicates that the nth LoRa signal is affected by interference from the i-th path. After passing through the multipath channel, the received signal r a,n (k) can be divided into two parts: direct path signal and multipath interference signal set.

[0028] Furthermore, the deblocking and interleaving process involves dividing the received signal into four equal signal blocks and swapping the order of the second and third signal blocks. The signal r' after the deblocking and interleaving process is... a,n (k) can be described as:

[0029]

[0030] After block interleaving and deblock interleaving, the direct path signal remains unchanged. The deblock interleaved signal can be represented as:

[0031]

[0032] Among them, I' n,i (k) is the interference signal I n,i(k) The signal after deblocking and interleaving. Since the deblocking and interleaving process can change the order between multipath interference signal blocks, multiple multipath interference terms with smaller amplitudes are formed in the demodulation domain, thereby suppressing multipath interference signals.

[0033] Furthermore, the incoherent demodulation is the demodulation of the block-interleaved signal r' a,n (k) Multiply by the conjugate of the basis signal, then perform a discrete Fourier transform, take the absolute value, and then perform incoherent demodulation on the resulting signal y. q It can be described as:

[0034]

[0035] In the formula Let represent the conjugate of the basis signal, DFT represent the Discrete Fourier Transform, and q∈{0,1,2,...,M-1} be the independent variables in the demodulation domain. The signal r' after demultiplexing is used... a,n (k) Multiply by the conjugate of the base signal The purpose of obtaining a single-frequency signal is to despread it; the purpose of performing a discrete Fourier transform is to convert the discrete-time signal into a demodulation domain signal, thereby realizing the conversion of the detection of the single-frequency signal to the demodulation domain.

[0036] Furthermore, in the joint demodulation, if the amplitude decision condition is met, the preamble symbol and data symbol undergo matched filtering. First, for y... 2q Perform filtering, then y 1q With y 2q Perform circumferential related calculations, and finally make a sign determination.

[0037] For y 2q The formula for calculating filtering is:

[0038]

[0039] y 1q With y 2q The expression for performing circumference-related operations is:

[0040]

[0041] In the formula, d∈{0,1,2,...,M-1} is the independent variable of the demodulation domain.

[0042] The expression for symbolic decision is:

[0043]

[0044] If the amplitude decision condition is met, it indicates that strong multipath interference still exists after block interleaving and deblock interleaving processing. The symbol decision is easily affected by noise, which can lead to symbol misjudgment. In this case, using matched filtering can greatly increase the signal-to-noise ratio of the signal, thereby ensuring the accuracy of symbol decision.

[0045] Furthermore, if the amplitude decision condition is not met during the joint demodulation, an assignment process is performed. First, y is... 1q The value assigned to y 2q Then for y 2q Perform a sign decision; the expression for the sign decision is:

[0046]

[0047] If the amplitude decision condition is not met, it indicates that there is no strong multipath interference after block interleaving and deblock interleaving, and the signal has strong noise immunity. In this case, the sign decision can be made after the value assignment process. This method can greatly reduce the computational complexity of the demodulation process.

[0048] The present invention has the following advantages and effects compared with the prior art:

[0049] (1) The present invention adopts a LoRa communication method combining block interleaving and matched filtering. Block interleaving and deblock interleaving can reduce multipath interference, and matched filtering can increase the effective signal-to-noise ratio of the signal, thereby ensuring the reliability of communication and improving the bit error rate performance of the communication system.

[0050] (2) The present invention adopts the method of block interleaving and deblock interleaving. After the LoRa modulation signal is processed by block interleaving, the order of the signal blocks of the LoRa modulation signal can be changed. After passing through the multipath channel, multipath interference signal is introduced. After deblock interleaving, not only can the order of the signal blocks of the LoRa modulation signal be restored, but the order of the signal blocks of the multipath interference signal can also be changed, thereby decomposing strong multipath interference into multiple weak multipath interferences at different positions, effectively improving the bit error rate performance of LoRa communication.

[0051] (3) If strong multipath interference still exists after block interleaving and deblock interleaving, it indicates that the multipath interference suppression method using block interleaving and deblock interleaving has failed. At this time, the present invention uses matched filtering and utilizes the channel information of the preamble symbol to perform circumferential correlation operation between the preamble symbol and the data symbol, thereby increasing the effective signal-to-noise ratio of the signal, ensuring the communication quality under strong multipath interference, and improving the bit error rate performance of LoRa communication.

[0052] (4) The block interleaving and matched filtering adopted in this invention has the advantages of low complexity, low power consumption and simple implementation, and is suitable for multipath dense indoor and outdoor communication scenarios and shallow sea acoustic communication and other fields. Attached Figure Description

[0053] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0054] Figure 1 This is a flowchart of a multipath LoRa communication method combining block interleaving and matched filtering in one embodiment;

[0055] Figure 2 This is a schematic diagram of the LoRa signal interference model in the embodiment;

[0056] Figure 3 This is a schematic diagram of the data symbol demodulation domain signal using the classical method in Example 1;

[0057] Figure 4 This is a schematic diagram of the demodulation domain signal of the preamble symbol in Example 1;

[0058] Figure 5 This is a schematic diagram of the demodulated domain signal of the data symbols after block interleaving and deblock interleaving in Example 1;

[0059] Figure 6 This is a schematic diagram of the channel impulse response of the shallow sea channel in Example 2;

[0060] Figure 7 This is a schematic diagram of the data symbol demodulation domain signal using the classical method in Example 2;

[0061] Figure 8 This is a schematic diagram of the data symbol demodulation domain signal in Example 2, which uses block interleaving and deblock interleaving but does not use matched filtering;

[0062] Figure 9 This is a schematic diagram of the demodulation domain signal of the preamble symbol in Example 2;

[0063] Figure 10 This is a schematic diagram of the demodulated domain signal after preamble symbol filtering in Example 2;

[0064] Figure 11 This is a schematic diagram of the data symbol demodulation domain signal in Example 2, which employs block interleaving and deblock interleaving and uses matched filtering. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. 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.

[0066] Example 1

[0067] This embodiment discloses a multipath-resistant LoRa communication method combining block interleaving and matched filtering. First, the source generates a data symbol 'a', which is then LoRa modulated to obtain a LoRa modulated signal 'x'. a,n (k), when n = 1, 2, ..., 8, it indicates that a preamble symbol is being transmitted, which is the LoRa symbol when a value of 0; when n = 9, 10, 11, ..., it indicates that a data symbol is being transmitted. The calculation formula is as follows:

[0068]

[0069] In the formula, k∈{0,1,2,...,M-1} is the discrete-time domain independent variable, and M=2 SF SF represents the spreading factor, which is the number of symbols that can be transmitted. Its value is generally SF∈{7,8,9,10,11,12}, and a∈{0,1,2,...,M-1}. In this embodiment, the spreading factor SF is set to 9, and the transmitted data symbol a is 256. The LoRa modulated signal is then segmented and interleaved, i.e., the LoRa signal x... a,n (k) Divide the signal into 4 blocks of equal length, keeping the order of the first and fourth blocks unchanged, and swap the order of the second and third blocks to obtain x'. a,n (k), the calculation formula is as follows:

[0070]

[0071] The signal x' processed by block interleaving a,n (k) After passing through a multipath channel, the signal reaches the receiver. The signal received at the receiver can be modeled as follows:

[0072]

[0073] Where h0 represents the attenuation coefficient of the direct path signal, h i Let I represent the channel attenuation coefficient of the i-th path interference, p represent the multipath number, and I n,i (k) indicates that the nth LoRa signal is affected by an interference signal from the i-th path. A schematic diagram of the LoRa interference signal model is shown below. Figure 2 As shown, its expression is:

[0074]

[0075]

[0076] In the formula u i Let be the delay of the i-th multipath signal. In this embodiment, the parameters of the multipath channel are set as follows: the number of multipaths p is 3; the channel attenuation coefficients h0 = h1 = h2 = h3 = 1; and the multipath delays u1 = 64, u2 = 96, u3 = 125.

[0077] The receiving end receives the signal r a,n (k) performs synchronization, and then the received signal r a,n (k) Perform deblocking and interleaving processing, that is, the received signal r a,n (k) Divide the signal into 4 equal blocks, keep the order of the first and fourth blocks unchanged, and swap the order of the second and third blocks to obtain the de-blocked interleaved signal r'. a,n (k), the formula for solving the block interleaving is:

[0078]

[0079] Since the direct path signal remains unchanged after block interleaving and deblock interleaving, the signal after deblock interleaving can be represented as:

[0080]

[0081] Among them, I' n,i (k) is the interference signal I n,i (k) The signal after deblocking and interleaving is calculated using the following formula:

[0082]

[0083] Then use r' a,n (k) conjugate with the basis signal Multiply them, then perform a discrete Fourier transform and find their absolute value to obtain y. q y q The calculation formula is:

[0084]

[0085] In the formula, DFT represents Discrete Fourier Transform, q∈{0,1,2,...,M-1} is the independent variable in the demodulation domain, and Λ(q) is the multipath interference term, expressed as:

[0086]

[0087] For y q Make a judgment if yq It is a leading symbol, denoted as y. 2q,n Otherwise, record it as y. 1q After identifying all 8 leading symbols y... 2q,n Then, take 8 leading symbols y. 2q,n mean y 2q , Figure 4 For y 2q A schematic diagram of the demodulated domain signal of the preamble symbol, for y 2q Amplitude judgment is performed, and the judgment condition is "y 2q The question asks whether a value equal to α times the maximum peak value exists. In this embodiment, the amplitude decision parameter α is set to 0.65. Figure 4 After the middle preamble symbol signal undergoes block interleaving and deblock interleaving processing, there is no peak value that satisfies the amplitude decision condition. Therefore, y is first... 1q The value assigned to y 2q Then, for the input signal y 2q Perform a sign decision, that is, find y 2q The maximum value is used to determine the index value corresponding to the maximum value as the received LoRa symbol. The formula for symbol determination is as follows:

[0088]

[0089] Figure 3 This is a schematic diagram of the data symbol demodulation domain signal using the classical method. The classical method refers to the LoRa modulated signal not undergoing block interleaving and deblock interleaving processing; the receiver directly demodulates it upon receipt. Figure 5 This is a schematic diagram of the demodulated domain signal of the data symbols after block interleaving and deblock interleaving. (Comparison) Figure 3 and Figure 5 , Figure 3 The data symbols in the data do not use block interleaving and deblock interleaving processing. Compared with the direct path signal, the peak value of the multipath signal is larger. When making symbol decisions, the multipath signal interferes with the direct path signal very seriously, which is not conducive to symbol decision and is very easy to cause symbol misjudgment. Figure 5 The method employs block interleaving and deblock interleaving. By using block interleaving and deblock interleaving, strong multipath interference peaks can be decomposed into multiple multipath interferences with smaller peak values ​​at different locations, thereby reducing the interference of multipath to the main path and ensuring the accuracy of symbol decision.

[0090] Example 2

[0091] This embodiment further discloses a multipath-resistant LoRa communication method combining block interleaving and matched filtering. First, the source generates a data symbol 'a', inserts eight preamble symbols before 'a', and after LoRa modulation, obtains the signal 'x'. a,n(k), when n = 1, 2, ..., 8, it indicates that a preamble symbol is being transmitted; when n = 9, 10, 11, ..., it indicates that a data symbol is being transmitted. a,n The expression for (k) is:

[0092]

[0093] In the formula, k∈{0,1,2,...,M-1} is the discrete-time domain independent variable, and M=2 SF This represents the possible number of symbols to be transmitted. In this embodiment, the spreading factor SF is set to 9, and the number of transmitted data symbols is 256. a,n (k) The signal after the block interleaving operation is x' a,n (k). In this embodiment, a shallow sea channel is used, and the experimental parameters are: transmitter depth S d Set to 10 meters; receiver depth R d Set to 10 meters; horizontal distance R between receiver and transmitter r The channel is set to 100 meters; the system bandwidth B is set to 6 kHz. A schematic diagram of the channel impulse response in shallow water is shown below. Figure 6 Based on the channel impulse response in the figure, it can be observed that shallow sea channels exhibit multipath characteristics. If the first path is considered a direct path, then x' a,n (k) After passing through a shallow sea channel with a multipath number of 8, the signal received at the receiver can be described as follows:

[0094]

[0095] The received signal is synchronized, and then desegmented and interleaved to obtain r'. a,n (k), r' a,n The formula for calculating (k) is:

[0096]

[0097] Use r' a,n (k) and Multiply them, and then take the absolute value of their discrete Fourier transform to obtain y. q y q The expression is as follows:

[0098]

[0099] In the formula, q∈{0,1,2...,M-1} is the independent variable of the demodulation domain, and Λ(q) is the multipath interference term.

[0100] For y q The determination yields 8 leading symbols y. 2q,n n = 1, 2, ..., 8 and one data symbol y1q For 8 preambles y 2q,n Find the mean to get y 2q , leading symbol y 2q A schematic diagram of the demodulated domain signal is shown below. Figure 9 As shown. In this embodiment, the amplitude decision parameter α is set to 0.8. For y 2q Perform amplitude judgment, from Figure 9 From this, we can obtain y 2q The decision condition that the second largest peak value is greater than or equal to α times the largest peak value is met, therefore matched filtering is used. First, for the preamble y... 2q Perform filtering, and convert y 2q Values ​​with a midpoint peak value less than 0.8 times the maximum peak value are set to zero, with the leading sign y. 2q A schematic diagram of the filtered demodulated domain signal is shown below. Figure 10 As shown; then, using y 1q With y 2q Perform circumferential related operations; finally, determine the sign of the results of the circumferential related operations.

[0101] For y 2q The formula for calculating filtering is:

[0102]

[0103] y 1q With y 2q The expression for performing circumference-related operations is:

[0104]

[0105] In the formula, d∈{0,1,2,...,M-1} is the independent variable of the demodulation domain.

[0106] The expression for symbolic decision is:

[0107]

[0108] Figure 7 This is a schematic diagram of the data symbol demodulation domain signal using the classical method. Figure 8 This is a schematic diagram of the demodulated domain signal of data symbols using block interleaving and deblock interleaving but without matched filtering. Figure 11 This is a schematic diagram of the data symbol demodulation domain signal using block interleaving and deblock interleaving with matched filtering. (Comparison) Figure 7 , Figure 8 and Figure 11 , Figure 7 The classical method cannot solve the interference caused by multipath propagation. In symbol decision, the interference caused by multipath propagation seriously affects the accuracy of symbol decision. Figure 8Block interleaving and deblock interleaving failed to reduce interference peaks at strong multipath locations because these methods cannot effectively handle time delay u. i Smaller but more powerful multipath interference is detrimental to symbol decision; Figure 11 After block processing and deblock processing, a matched filtering method is used. Although this method fails to reduce the peak value of multipath interference, it effectively increases the peak value of the direct path signal, and the accuracy of symbol decision is guaranteed.

[0109] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A multipath-resistant LoRa communication method combining block interleaving and matched filtering, characterized in that, The anti-multipath LoRa communication method includes the following steps: Symbol modulation: The source generates data symbols, inserts a preamble symbol before the data symbols, and performs LoRa modulation on the data symbols and the preamble symbol to obtain a LoRa modulated signal; Block interleaving: The LoRa modulated signal is divided into average blocks, and the order of the signal blocks of the modulated signal is swapped. De-blocking interleaving: The received signal is divided into inverse average blocks, and the order of the signal blocks of the received signal is swapped; Incoherent demodulation: The de-blocked interleaved signal is multiplied by the conjugate of the base signal, then a discrete Fourier transform is performed, and the absolute value is calculated to obtain the incoherent demodulated output signal. Joint demodulation: First, the noncoherent demodulated output signal is judged to separate the preamble symbol and the data symbol; second, the amplitude of the preamble symbol is determined. If the amplitude determination condition is met, the preamble symbol and the data symbol are matched and filtered; if the amplitude determination condition is not met, the value is assigned. Symbol determination: Find the maximum value of the input data and determine the index value corresponding to the maximum value of the input data as the received LoRa symbol.

2. The anti-multipath LoRa communication method based on joint block interleaving and matched filtering according to claim 1, characterized in that, In the symbol modulation, the source generates a data symbol 'a', inserts eight preamble symbols before the data symbol 'a', and performs LoRa modulation on the data symbol and the preamble symbols to obtain the LoRa modulated signal 'x'. a,n (k), where when n = 1, 2, 3, 4, 5, 6, 7, 8, it represents the preamble symbol, and when n = 9, 10, 11, ..., it represents the data symbol generated by the source.

3. The anti-multipath LoRa communication method based on joint block interleaving and matched filtering according to claim 2, characterized in that, In the block interleaving, the LoRa modulated signal x a,n (k) Perform block interleaving processing, that is, x a,n (k) Divide the signal into 4 equal blocks, keep the order of the first and fourth blocks unchanged, and swap the order of the second and third blocks to obtain signal x'. a,n (k).

4. The anti-multipath LoRa communication method based on joint block interleaving and matched filtering according to claim 3, characterized in that, During the deblocking and interleaving process, the receiving end receives signal r. a,n (k), and for r a,n (k) Perform deblocking and interleaving processing on the received signal r a,n (k) Divide the signal into 4 equal blocks, keeping the order of the first and fourth blocks unchanged, and swap the order of the second and third blocks to obtain the de-blocked interleaved signal r'. a,n (k).

5. The anti-multipath LoRa communication method based on joint block interleaving and matched filtering according to claim 4, characterized in that, In the incoherent demodulation, r' a,n (k) conjugate with the basis signal Multiply the components, perform a discrete Fourier transform, and then calculate the absolute value to obtain the incoherent demodulated output signal y. q .

6. The anti-multipath LoRa communication method based on joint block interleaving and matched filtering according to claim 5, characterized in that, In the joint demodulation, y is first determined q Is it a leading symbol? If y q It is a leading symbol, denoted as y. 2q,n , n∈{1,2,...,8} represents 8 leading symbols; if y q If it is not a leading symbol, then it is a data symbol, denoted as y. 1q Secondly, calculate the average value y of the eight leading symbols. 2q , for y 2q Amplitude judgment is performed, and the judgment condition is "y 2q Does there exist a peak value α times the maximum peak value in y? Where α ∈ (0,1), if the amplitude judgment condition is met, matched filtering is used for y. 2q Perform filtering to filter out values ​​less than y. 2q Set the value of the maximum peak value α times to zero, and retain values ​​greater than or equal to y. 2q The value is α times the maximum peak value, and then the filtered y is used. 2q With y 1q Perform circumferential related calculations to obtain If the amplitude judgment condition is not met, an assignment process is performed, and y is set... 1q The value assigned to y 2q .

7. The anti-multipath LoRa communication method based on joint block interleaving and matched filtering according to claim 6, characterized in that, In the symbol decision, the input data Or y 2q Perform sign determination and search for the input data R. y2qy1q or y 2q The maximum value is used to determine the index value corresponding to the maximum value as the received LoRa symbol.

Images