阅读说明：本技术 一种基于lfm技术的卫星物联网传输方法和系统 (LFM technology-based satellite Internet of things transmission method and system ) 是由 白宝明 余忠洋 夏家宝 罗进 张景 魏肖 于 2021-09-15 设计创作，主要内容包括：本发明提供一种基于线性调频(LFM)技术的卫星物联网传输方法和系统。该方法包括：发送端将获取的多用户信息分别依次通过编码器和交织器进行处理得到码字；将码字分别进行Walsh直接序列扩频变换处理后进一步进行LFM调制处理得到调制序列,并将调制序列进行叠加处理得到混合调制序列并传输到接收端；接收端对接收到的数据信号进行解啁啾处理得到解啁啾信号,对解啁啾信号进行DFT,对获取的频域数据进行取模值运算、取平方、取最大值以及取对数操作,并进一步获取传输数据符号的解调LLR矩阵；基于获取的解调LLR矩阵与Walsh矩阵进行相关运算得到解扩软信息；并基于解扩软信息得到各用户信息的原始数据比特流。本发明有助于实现卫星物联网的多用户传输。(The invention provides a satellite internet of things transmission method and system based on a Linear Frequency Modulation (LFM) technology. The method comprises the following steps: the sending end respectively processes the acquired multi-user information through the encoder and the interleaver in sequence to obtain a code word; respectively carrying out Walsh direct sequence spread spectrum conversion processing on the code words, further carrying out LFM modulation processing on the code words to obtain modulation sequences, and carrying out superposition processing on the modulation sequences to obtain mixed modulation sequences and transmitting the mixed modulation sequences to a receiving end; the receiving end performs de-chirp processing on the received data signal to obtain a de-chirp signal, performs DFT on the de-chirp signal, performs modulus value operation, squaring, maximum value taking and logarithm taking on the obtained frequency domain data, and further obtains a demodulation LLR matrix of the transmission data symbol; performing correlation operation on the acquired demodulation LLR matrix and the Walsh matrix to obtain despreading soft information; and obtains an original data bit stream of each user information based on the despread soft information. The invention is beneficial to realizing multi-user transmission of the satellite Internet of things.)

1. A satellite Internet of things transmission method based on an LFM technology is characterized by comprising the following steps:

s1 multiuser information { d } to be acquired by sending end₁，d₂，...，d_nRespectively processing the codes by an (N, K) encoder and an interleaver in sequence to obtain a code word { c₁，c₂，...，c_n}；

S2 sender converts code word c₁，c₂，...，c_nRespectively carrying out Walsh direct sequence spread spectrum conversion processing to obtain code words

S3 sender pairs code word separatelyLFM modulation processing is carried out to obtain a spread spectrum factor SF₀The symbol length isModulated sequence s_c1，s_c2，...，s_cnIn which SF is_iRepresents the inner spreading factor of Walsh direct sequence spread spectrum, and modulates the sequence s_c1，s_c2，...，s_cnPerforming superposition processing to obtain a mixed modulation sequence s_c(ii) a And mixing and concoctingSequence s_cTransmitting to a receiving end;

s4 the receiving end receives the data signal r transmitted by the transmitting end_k(l) Where k is 0, 1.. N-1, N denotes a data symbol length, l is 0, 1.. M-1,represents the number of orthogonal chirps;

s5 receiving port pair data signal r_k(l) Performing chirp removing processing to obtain corresponding chirp removing signal r'_k(l)；

S6 receiving end-to-chirp-removal signal r'_k(l) Performing M-point DFT operation to obtain frequency domain data R_k(q), wherein q ═ 0, 1.., M-1;

s7 receiving end-to-frequency domain data R_k(q) performing a modulo operation to obtain

S8 receiving end pairCarrying out square taking, maximum value taking and logarithm taking operations, and further obtaining a demodulation LLR matrix Lambda of the transmission data symbol;

s9, the receiving end carries out correlation operation based on the obtained demodulation LLR matrix lambada and the Walsh matrix to obtain the despreading soft information of each user information;

and S10, the receiving end processes the obtained de-spread soft information through a de-interleaver and a decoder respectively to obtain the original data bit stream of each user information.

2. The LFM technology-based satellite Internet of things transmission method according to claim 1, wherein in step S5, the receiving end pair data signal r_k(l) Performing chirp removing processing to obtain corresponding chirp removing signal r'_k(l) The specifically adopted chirp-removing processing function is as follows:

3. the LFM technology-based satellite internet of things transmission method according to claim 2, wherein in step S6, the M-point DFT operation function specifically adopted is:

4. the LFM technology-based satellite Internet of things transmission method as claimed in claim 3, wherein in step S8, a demodulation LLR matrix Λ of the transmission data symbols is obtained, wherein the demodulation LLR matrix Λ is

In the formula, b_k，lRepresents the data symbol d in the k-th symbol period_kMiddle ith binary bit, Λ (b)_k，l) Representing the data symbol d in the corresponding k-th symbol period_kThe demodulated LLR of the ith binary bit, μ represents the set correction factor,andrespectively representing an index set with the l-th position of 0 and an index set with the l-th position of 1 in binary bit representations corresponding to decimal numbers from 0 to M-1 according to natural mapping.

5. The LFM technology-based satellite internet of things transmission method according to claim 4, wherein in step S9, performing correlation operation based on the obtained demodulation LLR matrix Λ and Walsh matrix to obtain despread soft information of each user information, specifically includes:

performing correlation operation on the acquired demodulation LLR matrix lambda and the address codes of the 1 st row and the 2 nd row.

Where Λ ((k +1) × m) denotes the (k +1) × m elements in the matrix Λ, Λ i (k) denotes despread soft information corresponding to the i-th user information, and W (i, m) denotes the (i, m) elements in the Walsh matrix.

6. A satellite Internet of things transmission system based on an LFM technology is characterized by comprising a sending end and a receiving end; wherein the content of the first and second substances,

the sending end is used for obtaining the multi-user information d₁，d₂，...，d_nRespectively processing the codes by an (N, K) encoder and an interleaver in sequence to obtain a code word { c₁，c₂，...，c_n}; will code word c₁，c₂，...，c_nRespectively carrying out Walsh direct sequence spread spectrum conversion processing to obtain code wordsRespectively to code wordLFM modulation processing is carried out to obtain a spread spectrum factor SF₀The symbol length isModulated sequence s_c1，s_c2，...，s_cnAnd will modulate the sequence s_c1，s_c2，...，s_cnPerforming superposition processing to obtain a mixed modulation sequence s_c(ii) a And mixing the modulated sequences s_cTransmitting to a receiving end;

the receiving end is used for receiving the data signal r transmitted by the transmitting end_k(l) Where k is 0, 1.. N-1, N denotes a data symbol length, l is 0, 1.. M-1,represents the number of orthogonal chirps; for data signal r_k(l) Performing chirp removing processing to obtain corresponding chirp removing signal r'_k(l) (ii) a To chirp-removed signal r'_k(l) Performing M-point DFT operation to obtain frequency domain data R_k(q), wherein q ═ 0, 1.., M-1; for frequency domain data R_k(q) performing a modulo operation to obtainTo pairCarrying out square taking, maximum value taking and logarithm taking operations, and further obtaining a demodulation LLR matrix Lambda of the transmission data symbol; performing correlation operation on the acquired demodulation LLR matrix lambda and a Walsh matrix to obtain despreading soft information of each user information; and respectively processing the obtained de-spread soft information through a de-interleaver and a decoder to obtain the original data bit stream of each user information.

Technical Field

The invention relates to the technical field of intelligent interaction, in particular to a satellite internet of things transmission method and system based on a Linear Frequency Modulation (LFM) technology.

Background

Compared with the ground internet of things communication, the satellite internet of things communication is relatively far away, so that great transmission link loss is brought, and further, the receiving power becomes very small. Spread spectrum modulation techniques such as Direct Sequence Spread Spectrum (DSSS), Chirp Spread Spectrum (CSS), etc. need to be considered further in addition to the use of superior performance coding schemes. Compared with the DSSS technology, the CSS technology has stronger Doppler frequency shift resistance and can effectively resist multipath fading. The Linear Frequency Modulation (LFM) technology is an improved CSS technology, and has been widely applied to transmission systems of the internet of things.

From the modulation process, the LFM technique combines the CSS spreading technique with the Frequency Shift Keying (FSK) modulation technique that carries data symbols, thereby achieving a high order frequency shifted CSS modulation. At present, the coding schemes adopted in the relevant documents about LFM technology are all Hamming (Hamming) codes specified in the physical layer protocol thereof, and few other coding schemes are involved. In the Hamming-LFM scheme, since the Hamming code is a coding scheme based on hard decision decoding, the LFM demodulation method only needs to output a hard decision result, but is not suitable for coding schemes such as Turbo codes, Low Density Parity Check (LDPC) codes and the like based on soft decision decoding. In the prior art, some methods use the quadrature binary peak difference decision method to obtain a so-called "soft" information, which is then sent to the Turbo decoder. However, the performance gain of the non-coherent soft-decision demodulation method is very limited. Some non-coherent Frequency Shift Keying (FSK) systems obtain a non-coherent soft decision demodulation method suitable for a bit interleaving coding modulation iterative system by using a first-order Taylor series expansion and double maximum approximation method of a Bessel function, but the logarithm operand of the non-coherent soft decision demodulation method is very large, and the non-coherent soft decision demodulation method grows exponentially along with the increase of the modulation order, so that the non-coherent soft decision demodulation method cannot be suitable for the application of satellite Internet of things transmission.

Meanwhile, in the transmission of the internet of things on the ground, besides using multiple access technologies such as classical Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA) and Code Division Multiple Access (CDMA), a certain attention and research are paid to a multi-user transmission scheme related to the LFM technology. However, for multi-user transmission of the satellite internet of things, due to the characteristic of limited power, the traditional power allocation strategy and the power domain multiple access technology are no longer applicable. In addition, the satellite internet of things transmits far more than the ground internet of things. This results in a large power loss on the transmission link, so that the receiving power at the receiving end becomes very low, and further, the LFM modulation using a large spreading factor is required in addition to the coding scheme with excellent performance. On the other hand, a multi-user transmission scheme based on LFM modulation with the same large spreading factor is difficult to implement without the aid of power allocation and successive interference cancellation strategies. This is because two or more superimposed LFM signals may have destructive collisions at the same bandwidth and spreading factor.

Therefore, there is an urgent need to provide a multi-user transmission technical scheme capable of adapting to the satellite internet of things based on the LFM technology.

Disclosure of Invention

In view of the above problems, the present invention aims to provide a satellite internet of things transmission method and system based on LFM technology.

The purpose of the invention is realized by adopting the following technical scheme:

in a first aspect, the invention provides a satellite internet of things transmission method based on an LFM technology, which includes:

s1 multiuser information { d } to be acquired by sending end₁,d₂,…,d_nRespectively processing the codes by an (N, K) encoder and an interleaver in sequence to obtain a code word { c₁,c₂,…,c_n}；

S2 sender converts code word c₁,c₂,…,c_nRespectively carrying out Walsh direct sequence spread spectrum conversion processing to obtain code words

S3 sender pairs code word separatelyLFM modulation processing is carried out to obtain a spread spectrum factor SF₀The symbol length isModulated sequence s_c1,s_c2,…,s_cnIn which SF is_iRepresents the inner spreading factor of Walsh direct sequence spread spectrum, and modulates the sequence s_c1,s_c2,…,s_cnPerforming superposition processing to obtain a mixed modulation sequence s_c(ii) a And mixing the modulated sequences s_cTransmitting to a receiving end;

s4 the receiving end receives the data signal r transmitted by the transmitting end_k(l) Where k is 0,1, … N-1, N denotes the data symbol length, l is 0,1, … M-1,represents the number of orthogonal chirps;

s5 receiving port pair data signal r_k(l) Performing chirp removing processing to obtain corresponding chirp removing signal r'_k(l)；

S6 receiving end-to-chirp-removal signal r'_k(l) Performing M-point DFT operation to obtain frequency domain data R_k(q), wherein q is 0,1, …, M-1;

s7 receiving end-to-frequency domain data R_k(q) performing a modulo operation to obtain

S8 receiving end pairCarrying out square taking, maximum value taking and logarithm taking operations, and further obtaining a demodulation LLR matrix Lambda of the transmission data symbol;

s9, the receiving end carries out correlation operation based on the obtained demodulation LLR matrix lambada and the Walsh matrix to obtain the despreading soft information of each user information;

and S10, the receiving end processes the obtained de-spread soft information through a de-interleaver and a decoder respectively to obtain the original data bit stream of each user information.

In one embodiment, in step S5, the receiving end pair data signal r_k(l) Performing chirp removing processing to obtain corresponding chirp removing signal r'_k(l) The specifically adopted chirp-removing processing function is as follows:

in one embodiment, in step S6, the M-point DFT operation function specifically adopted is:

in one embodiment, in step S8, a demodulation LLR matrix Λ of the transmission data symbols is obtained, where the demodulation LLR matrix is

In the formula, b_k,Represents the data symbol d in the k-th symbol period_kMiddle ith binary bit, Λ (b)_k,) Representing the data symbol d in the corresponding k-th symbol period_kThe demodulated LLR of the ith binary bit, μ represents the set correction factor,andrespectively representing an index set with the l-th position of 0 and an index set with the l-th position of 1 in binary bit representations corresponding to decimal numbers of 0-M-1 according to natural mapping.

In one embodiment, in step S9, performing a correlation operation based on the obtained demodulation LLR matrix Λ and the Walsh matrix to obtain despread soft information of each user information includes:

and performing correlation operation on the acquired demodulation LLR matrix lambda and the address codes of the 1 st row and the 2 nd row … nth row in the Walsh matrix respectively to obtain despread soft information of each user information, wherein the adopted correlation operation function is as follows:

wherein, Λ_i((k +1) × m) ∈ Λ, Λ ((k +1) × m) denotes the (k +1) × m elements in the matrix Λ, Λ_i(k) Represents despread soft information corresponding to the ith user information, and W (i, m) represents an element of (i, m) in the Walsh matrix.

In a second aspect, the invention provides a satellite internet of things transmission system based on an LFM technology, which comprises a sending end and a receiving end; wherein the content of the first and second substances,

the sending end is used for obtaining the multi-user information d₁,d₂,…,d_nRespectively processing the codes by an (N, K) encoder and an interleaver in sequence to obtain a code word { c₁,c₂,…,c_n}; will code word c₁,c₂,…,c_nRespectively carrying out Walsh direct sequence spread spectrum conversion processing to obtain code wordsRespectively to code wordLFM modulation processing is carried out to obtain a spread spectrum factor SF₀The symbol length isModulated sequence s_c1,s_c2,…,s_cnAnd will modulate the sequence s_c1,s_c2,…,s_cnPerforming superposition processing to obtain a mixed modulation sequence s_c(ii) a And mixing the modulated sequences s_cTransmitting to a receiving end;

the receiving end is used for receiving the data signal r transmitted by the transmitting end_k(l) Where k is 0,1, … N-1, N denotes a data symbol length, l is 0,1, … M-1,represents the number of orthogonal chirps; for data signal r_k(l) Performing de-chirp processing to obtain corresponding de-chirp signal r'_k(l) (ii) a To chirp-removed signal r'_k(l) Performing M-point DFT operation to obtain frequency domain data R_k(q), wherein q is 0,1, …, M-1; for frequency domain data R_k(q) performing a modulo operation to obtainTo pairCarrying out square taking, maximum value taking and logarithm taking operations, and further obtaining a demodulation LLR matrix Lambda of the transmission data symbol; performing correlation operation on the acquired demodulation LLR matrix lambda and a Walsh matrix to obtain despreading soft information of each user information; and respectively processing the obtained de-spread soft information through a de-interleaver and a decoder to obtain the original data bit stream of each user information.

The invention has the beneficial effects that: in the satellite Internet of things transmission method provided by the invention, an improved soft-decision noncoherent demodulation method based on DFT is provided, and the demodulation method has lower realization complexity and excellent demodulation performance. Meanwhile, the method and the device can be suitable for satellite Internet of things transmission under an extremely low signal-to-noise ratio, and can meet the multi-user transmission requirement of the satellite Internet of things.

Drawings

The invention is further illustrated by means of the attached drawings, but the embodiments in the drawings do not constitute any limitation to the invention, and further drawings may be obtained by those skilled in the art without inventive effort, based on the following drawings.

Fig. 1 is a schematic flow chart of a method for transmitting a satellite internet of things based on an LFM technology according to an embodiment of the present invention;

fig. 2 is a schematic diagram of a processing flow of a sending end according to an embodiment of the present invention;

fig. 3 is a schematic diagram of a processing flow of a receiving end according to an embodiment of the present invention;

FIG. 4 is a flow chart of a soft-decision non-coherent demodulation method according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of error performance according to an embodiment of the present invention;

fig. 6 is a frame structure diagram of a satellite internet of things transmission system based on an LFM technology according to an embodiment of the present invention

Detailed Description

The invention is further described in connection with the following application scenarios.

Referring to fig. 1, an embodiment of the present invention provides a method for transmitting a satellite internet of things based on an LFM technology, where the method includes the following steps:

s1 multiuser information { d } to be acquired by sending end₁,d₂,…,d_nRespectively processing the codes by an (N, K) encoder and an interleaver in sequence to obtain a code word { c₁,c₂,…,c_n}; wherein d is_iIndicating the ith user information, c_iA code word corresponding to the ith user information;

s2 sender converts code word c₁,c₂,…,c_nRespectively carrying out Walsh direct sequence spread spectrum conversion processing to obtain code words

S3 sendingEnd-to-end code wordLFM modulation processing is carried out to obtain a spread spectrum factor SF₀The symbol length isModulated sequence s_c1,s_c2,…,s_cnAnd will modulate the sequence s_c1,s_c2,…,s_cnPerforming superposition processing to obtain a mixed modulation sequence s_c(ii) a And mixing the modulated sequences s_cTransmitting to a receiving end; wherein SF_iRepresenting inner spreading factors corresponding to Walsh codes;

s4 the receiving end receives the data signal r transmitted by the transmitting end_k(l) Where k is 0,1, … N-1, N denotes the data symbol length, l is 0,1, … M-1,represents the number of orthogonal chirps;

s5 receiving port pair data signal r_k(l) Performing chirp removing processing to obtain corresponding chirp removing signal r'_k(l)；

The specifically adopted chirp-removing processing function is as follows:

s6 receiving end-to-chirp-removal signal r'_k(l) Performing M-point DFT operation to obtain frequency domain data R_k(q), wherein q is 0,1, …, M-1;

the M-point DFT operation function is specifically adopted as follows:

s7 receiving end-to-frequency domain data R_k(q) performing a modulo operation to obtain

S8 receiving end pairCarrying out square taking, maximum value taking and logarithm taking operations, and further obtaining a demodulation LLR matrix Lambda of the transmission data symbol;

wherein the demodulation LLR matrix

In the formula, b_k,Represents the data symbol d in the k-th symbol period_kMiddle ith binary bit, Λ (b)_k,l) Representing the data symbol d in the corresponding k-th symbol period_kThe demodulated LLR of the ith binary bit, μ represents the set correction factor,andrespectively representing an index set with the l position of 0 and an index set with the l position of 1 in binary bit representations corresponding to decimal numbers from 0 to M-1 according to natural mapping;

s9, the receiving end carries out correlation operation based on the obtained demodulation LLR matrix lambada and the Walsh matrix to obtain the despreading soft information of each user information;

performing correlation operation on the obtained demodulation LLR matrix Lambda and the address codes of the 1 st row and the 2 nd row … nth row in the Walsh matrix respectively to obtain despreading soft information of each user information, wherein the adopted correlation operation function is as follows:

wherein, Λ_i((k +1) × m) ∈ Λ, Λ ((k +1) × m) represents the matrix ΛThe (k +1) × m elements, Λ_i(k) Represents despread soft information corresponding to the ith user information, W (i, m) represents an element of (i, m) in the Walsh matrix;

s10 receiving end processes the obtained de-spread soft information through de-interleaver and decoder respectively to obtain original data bit stream { d'₁,d′₂,…,d′_n}。

In the above embodiments, the DFT-based improved soft-decision non-coherent demodulation method (soft-output non-coherent demodulator) has low implementation complexity and excellent demodulation performance. Meanwhile, the method can be suitable for satellite internet of things multi-user transmission scenes under extremely low signal to noise ratio. According to the orthogonality of Walsh codes in a CDMA protocol, the scheme of combining the Walsh codes with the same spreading factor LFM modulation can realize multi-user transmission of the satellite Internet of things.

In an exemplary embodiment, the downlink link is based on a downlink link of satellite internet of things communication, and the transmission bandwidth is B. Without loss of generality, this embodiment takes the example of transmitting three user information simultaneously, and the given BER is 10^-5The time target signal-to-noise ratio is smaller than or equal to minus 26dB, and an exemplary satellite internet of things transmission method based on the LFM technology is provided.

Wherein the use of M_w4 th order Walsh matrix and LFM modulation with spreading factor 13. Wherein, the address code corresponding to the 1 st row in the Walsh matrix is allocated to the 1 st user information; the address code corresponding to the 2 nd line is allocated to the 2 nd user information; the address code corresponding to the 3 rd line is allocated to the 3 rd user information. Referring to fig. 2 and fig. 3, data processing diagrams of a transmitting end (e.g., a low earth orbit satellite) and a receiving end (e.g., a ground station or a user terminal) of the multi-user transmission link system model based on the Walsh-LFM technology are respectively shown. The transmission scheme comprises the following specific steps:

at a sending end: user information 1, user information 2, and user information 3 (i.e., d)₁、d₂And d₃) Respectively passing through the same (N, K) encoder and interleaver to obtain a code word c₁、c₂And c₃。

The code word c₁、c₂And c₃Obtaining code words after Walsh direct sequence spread spectrum conversionAnd

these code words are fed to the outer spreading factor SF, respectively₀Obtaining three symbol lengths in an LFM modulator of 13Modulation sequence s of_c1、s_c2And s_c3And will modulate the sequence s_c1、s_c2And s_c3Are added together to obtain a mixed modulated sequence s_c。

At the receiving end: receiving a data signal r taking into account noise interference during transmission_k(l) Can be expressed as:

where k is 0,1, …, N-1, l is 0,1, …, M-1, N is the length of the transmitted data symbol,is a quadrature chirp number, d_k,iData symbols transmitted in the k symbol period for the ith user information, n_k(l) Is a mean of 0 and a variance ofComplex gaussian random variables.

For received signal r_k(l) Obtaining corresponding chirp-removing signal r by chirp-removing operation_k′(l)：

Wherein the content of the first and second substances,

then the chirp-removing signal r is processed_k' (l) obtaining the demodulation log-likelihood ratios (LLRs) by the modified soft-decision non-coherent demodulation method (soft-output non-coherent demodulator) as shown in fig. 4, wherein the corresponding processing steps are as follows:

to chirp-removed signal r'_k(l) Obtaining R by DFT operation of M points_k(q)：

Wherein q is 0,1, …, M-1,

to R_k(q) is obtained by a modulo value operation

By pairsPerforms a squaring operation, a maximum value selecting operation and a logarithmic operation to obtain a transmission data symbol d_kFirst bit b_k,lDemodulate LLR of (i)

Wherein, b_k,lFor the l binary bit in the k symbol period, mu denotes a correction factor,andrespectively representing an index set with the l-th position of 0 and an index set with the l-th position of 1 in binary bit representations corresponding to decimal numbers from 0 to M-1 according to natural mapping.

Before correlation with Walsh codes, a matrix is introduced

The matrix Λ including the demodulated LLR of equation (5) is subjected to correlation with the address codes of the 1 st, 2 nd and 3 rd rows in the Walsh matrix to obtain despread soft information of each user information, that is, despread soft information of each user information

Wherein, Λ_i(k) Denotes soft despread information of the ith user, Λ ((k +1) × m) denotes (k +1) × m elements in Λ, and W (i, m) denotes (i, m) elements in the Walsh matrix.

The obtained de-spread soft information is respectively sent to a de-interleaver and a decoder, so that the original data bit stream of each user information can be recovered.

See, among other things, fig. 5, which shows the error performance of the transmission scheme. From the simulation results, it is understood that BER is 4 × 10^-5The actual signal-to-noise ratios corresponding to user info 1, user info 2, and user info 3 are about-27.7 dB, -27.8dB, and-27.75 dB, respectively, i.e., 1.7dB, 1.8dB, and 1.75dB below the target signal-to-noise ratio (i.e., -26dB), respectively. The method can be suitable for satellite Internet of things transmission under extremely low signal to noise ratio.

In a second aspect, referring to fig. 6, the invention provides a satellite internet of things transmission system based on an LFM technology, which includes a sending end and a receiving end; wherein the content of the first and second substances,

the sending end is used for obtaining the multi-user information d₁,d₂,…,d_nRespectively processing the codes by an (N, K) encoder and an interleaver in sequence to obtain a code word { c₁,c₂,…,c_n}; will code word c₁,c₂,…,c_nRespectively carrying out Walsh direct sequence spread spectrum conversion processing to obtain code wordsRespectively to code wordLFM modulation processing is carried out to obtain a spread spectrum factor SF₀The symbol length isModulated sequence s_c1,s_c2,…,s_cnAnd will modulate the sequence s_c1,s_c2,…,s_cnPerforming superposition processing to obtain a mixed modulation sequence s_c(ii) a And mixing the modulated sequences s_cTransmitting to a receiving end;

the receiving end is used for receiving the data signal r transmitted by the transmitting end_k(l) Where k is 0,1, … N-1, N denotes a data symbol length, l is 0,1, … M-1,represents the number of orthogonal chirps; for data signal r_k(l) Performing chirp removing processing to obtain corresponding chirp removing signal r'_k(l) (ii) a To chirp-removed signal r'_k(l) Performing M-point DFT operation to obtain frequency domain data R_k(q), wherein q is 0,1, …, M-1; for frequency domain data R_k(q) performing a modulo operation to obtainTo pairPerforming operations of squaring, maximum value taking and logarithm taking,further obtaining a demodulation LLR matrix lambda of the transmission data symbol; performing correlation operation on the acquired demodulation LLR matrix lambda and a Walsh matrix to obtain despreading soft information of each user information; and respectively processing the obtained de-spread soft information through a de-interleaver and a decoder to obtain the original data bit stream of each user information.

In one scenario, the transmitting end includes a low earth orbit satellite; the receiving end comprises a ground station or a user terminal.

It should be noted that the transmitting end is further configured to implement method steps corresponding to any one of the embodiments corresponding to steps S1-S3 in the LFM technology-based satellite internet of things transmission method, and the receiving end is further configured to implement method steps corresponding to any one of the embodiments corresponding to steps S4-S10 in the LFM technology-based satellite internet of things transmission method, which is not described herein repeatedly.

From the above description of embodiments, it is clear for a person skilled in the art that the embodiments described herein can be implemented in hardware, software, firmware, middleware, code or any appropriate combination thereof. For a hardware implementation, a processor may be implemented in one or more of the following units: an Application Specific Integrated Circuit (ASIC), a Digital Signal Processor (DSP), a Digital Signal Processing Device (DSPD), a Programmable Logic Device (PLD), a Field Programmable Gate Array (FPGA), a processor, a controller, a microcontroller, a microprocessor, other electronic units designed to perform the functions described herein, or a combination thereof. For a software implementation, some or all of the procedures of an embodiment may be performed by a computer program instructing associated hardware. In practice, the program may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a computer. Computer-readable media can include, but is not limited to, RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be analyzed by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.