Waveform design and receiving method of orthogonal time-frequency code domain

Abstract

The application provides a waveform design and receiving method in orthogonal time-frequency code domain. The method comprises the following steps: allocating orthogonal spread spectrum combination to each waveform in a waveform group by using an orthogonal spread spectrum sequence pool; each waveform carries transmission data in the orthogonal time-frequency code domain according to the allocated orthogonal spread spectrum combination; after receiving each waveform, a receiver estimates the multipath time delay, multipath fading and multipath Doppler experienced by multiple waveforms according to the orthogonal spread spectrum combination of each waveform; the receiver detects the transmission data carried by each waveform by using the estimated multipath time delay, multipath fading and multipath Doppler of each waveform, using the MMSE criterion and the orthogonal spread spectrum combination structure. The method of the application designs unique orthogonal spread spectrum combination for different waveforms in the same waveform group, realizes the orthogonal transmission of multiple waveforms under the same DD domain resource, and provides an alternative scheme for multi-user data transmission under high-speed mobile conditions.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a waveform design and reception method in the orthogonal time-frequency code domain. Background Technology

[0002] In 2017, scholars proposed Orthogonal Time-Frequency Space (OTFS) modulation technology at the Institute of Electrical and Electronics Engineers (IEEE) 2017 Wireless Communication and Network Conference. From a communication principle perspective, OTFS technology can be regarded as a precoded Orthogonal Frequency Division Multiplexing (OFDM) modulation technology.

[0003] OTFS transforms time-frequency (TF) domain data to the delay-Doppler (DD) domain using a symmetric Fourier transform, and considers the system input-output relationship in the DD domain. Note that in high-speed mobile scenarios, the DD domain channel exhibits potential sparsity and stability compared to the time-frequency domain channel; therefore, the likelihood of deep fading in the OTFS system is significantly reduced compared to OFDM modulation. For this reason, OTFS technology has become a viable alternative for reliable transmission in high-speed mobile scenarios.

[0004] Currently, one existing multi-waveform orthogonal transmission scheme for an OTFS system includes considering the input-output relationship of the system in the DD domain. The input-output relationship of the OTFS system indicates a two-dimensional cyclic shift between transmitted and received data. Each waveform utilizes only a portion of the DD domain resources for data transmission, and other data processing methods, such as interleaving, are used to mitigate interference between multiple waveforms.

[0005] The disadvantages of the existing OTFS multi-waveform orthogonal transmission scheme include: the current OTFS multi-waveform scheme makes strong assumptions about the sparsity of the channel, and its performance under actual channel conditions needs to be verified; in addition, each waveform in this type of scheme only utilizes a portion of the DD domain resources, which will result in a waste of DD domain resources when there are few concurrent transmissions. Summary of the Invention

[0006] The embodiments of the present invention provide a waveform design and reception method for orthogonal time-frequency code domains to achieve orthogonal transmission of multiple waveforms using the same DD domain resources.

[0007] To achieve the above objectives, the present invention adopts the following technical solution.

[0008] A waveform design and reception method in the orthogonal time-frequency code domain includes:

[0009] The orthogonal spread spectrum sequence pool is used to assign orthogonal spread spectrum combinations to each waveform in the waveform group;

[0010] Each waveform carries the transmitted data in the orthogonal time-frequency code domain according to the assigned orthogonal spread spectrum combination;

[0011] After receiving each waveform, the receiver estimates the multipath delay, multipath fading, and multipath Doppler experienced by the multiple waveforms based on the orthogonal spread spectrum combination of each waveform.

[0012] The receiver uses the estimated multipath delay, multipath fading, and multipath Doppler of each waveform, and employs the minimum mean square error (MMSE) criterion and orthogonal spread spectrum combination structure to detect the transmitted data carried by each waveform.

[0013] Preferably, the method of assigning orthogonal spreading combinations to each waveform in the waveform group using an orthogonal spreading sequence pool includes:

[0014] Let MΔf be the bandwidth occupied by the waveform group when transmitting data, and NT be the time, where M represents the number of subcarrier intervals Δf and N represents the number of time slots T. Let there be Γ waveforms in the waveform group, and the sequence number of each waveform be γ, where γ = 1, 2, ..., Γ.

[0015] The columns of the Discrete Fourier Transform (DFT) matrix are used to form an orthogonal spread spectrum sequence pool. Where q represents the spreading factor, and E is expressed as:

[0016]

[0017] E = [e1 … e] q (2)

[0018] Where vector Let the i-th column of matrix E be the i-th orthogonal spreading sequence;

[0019] In the orthogonal spread spectrum sequence pool E, q orthogonal spread spectrum sequences are selected in sequence to form orthogonal spread spectrum combinations of different waveforms. Each waveform is assigned to two different orthogonal spread spectrum combinations, and the orthogonal spread spectrum combinations assigned to each waveform are orthogonal in the time-frequency code domain.

[0020] Orthogonal spread spectrum combination of the γth waveform Represented as:

[0021]

[0022] Preferably, each waveform carries transmitted data in the orthogonal time-frequency code domain according to the assigned orthogonal spreading combination, including:

[0023] Each waveform utilizes the orthogonal spreading combination S assigned to it. γ Carrying data in the orthogonal time-frequency code domain Using orthogonal spread spectrum combination S γ The sequence used for pilot symbols carries pilot symbols, and is combined using orthogonal spread spectrum S. γ The sequence used for data symbols carries the data symbols, resulting in... d γ The i-th column is represented as:

[0024]

[0025] Where I qb Diag[S] represents the identity matrix with qb rows and qb columns. γ (:,i),S γ (:,i),…,S γ (:,i)] represents S γ (:,i) is a block diagonal matrix with qb rows and b columns of diagonal elements.

[0026] Each waveform is transformed from the time-delay Doppler domain to the time-frequency domain through a two-dimensional DFT transformation for data transmission.

[0027] Preferably, after receiving each waveform, the receiver estimates the multipath delay, multipath fading, and multipath Doppler experienced by the multiple waveforms based on the orthogonal spread spectrum combination of each waveform, including:

[0028] When the receiver receives signals from multiple waveforms, it transforms each waveform from the time-frequency domain to the time-delay Doppler domain through a two-dimensional DFT transform.

[0029] The signal carried by the waveform group received by the receiver in the time length NT and bandwidth MΔf is set as follows.

[0030] The receiver separates the data carried by each waveform according to the orthogonal spread spectrum combination specified in formula (3) and the inverse process of formula (4). The calculation process is shown in formulas (5) and (6):

[0031]

[0032] in The i-th column is obtained by the following operation:

[0033]

[0034] According to the orthogonal spreading combination specified in formula (3), the spreading sequences used to carry pilot symbols for each waveform are completely orthogonal. The pilot data carried by each waveform is extracted and denoted as... Based on the assumption of biorthogonality between transmitted and received waveforms With d γ The relationship between (:,1) is:

[0035]

[0036] In formula (7), Let represent a complex Gaussian noise matrix, where the noise follows a constant with mean 0 and variance σ. 2 The complex Gaussian distribution, Let α be an index matrix, and let α be the index of the index matrix. Column elements are All other elements are 0. Represents the time-delay domain sampling matrix. Represents the channel fading matrix. M0 represents the Doppler domain sampling matrix, M0 represents the number of oversampling points in the receiver delay domain, and M0 > M;

[0037]

[0038]

[0039]

[0040] in and Represents the time delay and Doppler of a certain path, and represents the multipath delay and multipath fading of the estimated waveform, n0=1,…,N,n=1,…,N,m0=1,…,M0,m=1,…,M;

[0041] Represents the time delay sampling matrix The element in row m and column m0;

[0042] This represents the element in the n0th row and nth column of the Doppler domain sampling function;

[0043] This refers to the element in the m0th row and n0th column of the channel fading matrix;

[0044] The sequence number indicating multipath delay.

[0045] The serial number refers to the multipath Doppler signal.

[0046] Utilizing the sparsity of multipath in the time-delay Doppler domain An estimate was made, and the following results were obtained. Where P << M0 represents the true multipath number, Extract the rows corresponding to the P estimated multipaths to obtain Ω γ yes In the rows corresponding to the P estimated multipaths, the values ​​in equation (7) are reduced by 1. With v γ The part other than that is recorded as Estimate Ω using the MMSE criterion γ This completes the channel estimation, which is expressed by the following formula:

[0047]

[0048] Where η pilot This represents the power ratio of noise to pilot symbols in the data carried by each waveform. P×P This represents an identity matrix with P rows and P columns.

[0049] Preferably, the receiver utilizes the estimated multipath delay, multipath fading, and multipath Doppler of each waveform, and employs the minimum mean square error (MMSE) criterion and orthogonal spread spectrum combination structure to detect the transmitted data carried by each waveform, including:

[0050] The number of system waveforms Γ is known, and the waveform number γ is obtained according to the orthogonal spread spectrum combination designed for each user in formula (3), based on the d in formula (7). γ The cyclic structure of the matrix allows formula (7) to be rewritten as:

[0051]

[0052] It means With d γ Between (:,1), the phase deviation in formula (7) Indicator Matrix Time-delay domain sampling matrix Channel fading matrix Doppler domain sampling matrix Combined channel fading;

[0053] The estimated multipath delay The combined effects of multipath Doppler and multipath fading Substitution In this process, the input-output relationship between the received signal and the transmitted signal was obtained. It is receiving signals The middle pilot symbol portion, received signal The form corresponding to the data symbols in the middle is as follows

[0054] The channel fading is obtained through (7), and the corresponding data symbols and pilot symbols are in the form of...

[0055] The channel fading matrix is ​​placed in a matrix The relationship between received data symbols and transmitted data symbols is obtained as follows:

[0056]

[0057] The left side of formula (10) represents the received signal. Reshape into vector form. This represents the channel fading between the received and transmitted signals. The data term on the right-hand side of the equation represents the fading of the transmitted signal. Reshape into vector form. This represents the Gaussian noise term.

[0058] Data recovery of waveform groups based on orthogonal spread spectrum combination is achieved using MMSE equalization, as expressed by the following formula:

[0059]

[0060] Where η pilot I represents the ratio of noise to the power of data symbols in the data carried by each waveform. bN×bN Describes an identity matrix with bN rows and bN columns. express The transpose and conjugate of , Indicates the received signal The operation of reshaping into a column vector;

[0061] The vector form of the transmitted signal obtained in formula (11) This refers to the transmitted data carried by the γth waveform. The same operation is performed on the other waveforms to complete the detection of the transmitted data carried by all Γ waveforms.

[0062] As can be seen from the technical solutions provided by the embodiments of the present invention above, the embodiments of the present invention provide a waveform design and reception method for orthogonal time-frequency code domain. This method designs a unique orthogonal spread spectrum combination for different waveforms in the same waveform group, realizes multi-waveform orthogonal transmission using the same DD domain resources, and provides an alternative solution for multi-user data transmission under high-speed mobile conditions.

[0063] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and will become apparent from the description or may be learned by practice of the invention. Attached Figure Description

[0064] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0065] Figure 1 A flowchart illustrating a waveform design and reception method for orthogonal time-frequency code domains provided in an embodiment of the present invention;

[0066] Figure 2 This is a schematic diagram illustrating the simultaneous and reliable data transmission of five waveforms in a vehicle-to-everything (V2X) scenario, based on the method of this embodiment of the invention. Detailed Implementation

[0067] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0068] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or couplings. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items.

[0069] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0070] To facilitate understanding of the embodiments of the present invention, the following will provide further explanation and description with reference to the accompanying drawings and several specific embodiments. These embodiments do not constitute a limitation on the embodiments of the present invention.

[0071] This invention provides a waveform design and reception method for orthogonal time-frequency code domains. This method designs unique orthogonal spreading combinations for different waveforms within the same waveform group, achieving orthogonal transmission of multiple waveforms using the same DD domain resources. Specifically, based on the orthogonal spreading combination, each waveform carries orthogonal pilot and data symbols, thus providing the system with universal robustness under different DD domain channel conditions. Furthermore, each waveform occupies the same DD domain resources, achieving full resource utilization even with a low number of concurrent waveforms.

[0072] The method of this invention can be used in scenarios where multiple high-speed mobile users transmit data simultaneously. Each user uses a different orthogonal time-frequency code domain waveform; the receiving end sequentially performs channel estimation and data detection for each of the multiple orthogonal time-frequency code domain waveforms. In this embodiment, the bandwidth occupied by the waveform group for data transmission is set to MΔf, and the time is set to NT, where M represents the number of subcarrier intervals Δf, and N represents the number of time slots T. Furthermore, it is assumed that there are Γ waveforms in the waveform group, each with an index γ, where γ = 1, 2, ..., Γ.

[0073] The processing flow of a waveform design and reception method in the orthogonal time-frequency code domain provided by this invention is as follows: Figure 1 As shown, the processing steps include the following:

[0074] Step S1: Assign an orthogonal spreading combination to each waveform in the waveform group using the orthogonal spreading sequence pool;

[0075] Step S2: The waveform carries the transmitted data in the orthogonal time-frequency code domain according to the assigned orthogonal spreading combination;

[0076] Step S3: The receiver estimates the channel fading experienced by multiple waveforms;

[0077] Step S4: The receiver detects the data carried by multiple waveforms.

[0078] Specifically, step S1 above includes: assigning orthogonal spread spectrum combinations to the waveforms in the waveform group, including:

[0079] The columns of the DFT (Discrete Fourier Transform) matrix are used to form an orthogonal spread spectrum sequence pool. Where q represents the spreading factor, which is the length of the spreading sequence. Specifically, E is represented as:

[0080]

[0081] In addition, E can also be represented as:

[0082] E = [e1 … e] q (2)

[0083] Where vector Let represent the i-th column of matrix E, also known as the i-th orthogonal spreading sequence. Subsequently, q orthogonal spreading sequences are selected sequentially from the orthogonal spreading sequence pool E to form orthogonal spreading combinations of different waveforms. Here, the sequences in the orthogonal spreading combination are functionally divided into two categories: those used for pilot symbols and those used for data symbols.

[0084] In this embodiment, each waveform is assigned to two different orthogonal spread spectrum combinations, and the orthogonal spread spectrum combinations assigned to each waveform are orthogonal in the time-frequency code domain.

[0085] And the orthogonal spread spectrum combination of the γth waveform Represented as:

[0086]

[0087] Specifically, step S2 includes: each waveform is configured according to the orthogonal spread spectrum combination, carrying pilot symbols according to the sequence used for pilot symbols, and carrying data symbols according to the sequence used for data symbols.

[0088] Each waveform is based on the assigned orthogonal spread spectrum combination A γ Carrying data in the orthogonal time-frequency code domain get During the specific carrying process, d γ The i-th column is represented as:

[0089]

[0090] Where I qb Diag[S] represents the identity matrix with qb rows and qb columns. γ (:,i),S γ (:,i),…,S γ [:,i] indicates that S is used as the base. γ(:,i) is a block diagonal matrix with qb rows and b columns of diagonal elements.

[0091] Subsequently, each waveform is transformed from the time-delay Doppler domain to the time-frequency domain through a two-dimensional DFT transform for data transmission. Correspondingly, when the receiver receives signals from multiple waveforms, it transforms each waveform from the time-frequency domain to the time-delay Doppler domain through a two-dimensional DFT transform.

[0092] Specifically, step S3 includes: after receiving each waveform, the receiver first estimates the multipath delay of each waveform, and then uses the minimum mean square error (MMSE) criterion and orthogonal spread spectrum combination structure to estimate the combined effects of multipath fading and multipath Doppler on each waveform.

[0093] The received waveform group is set to carry the signal over the MΔf bandwidth for a time length of NT.

[0094] Based on the orthogonal spread spectrum combination specified in formula (3) and the inverse process of formula (4), the data carried by each waveform can be separated. The physical processes are shown in equations (5) and (6):

[0095]

[0096] in The i-th column is obtained by the following operation:

[0097]

[0098] Furthermore, according to the orthogonal spread spectrum combination specified in formula (3), the spread spectrum sequences used to carry pilot symbols for each waveform are completely orthogonal. Therefore, the pilot data carried by each waveform can be extracted and denoted as... Based on the assumption of biorthogonality between transmitted and received waveforms, it can be found that The first column and d γ The relationship between (:,1) is:

[0099]

[0100]

[0101] In formula (7), Let represent a complex Gaussian noise matrix, where the noise follows a constant with mean 0 and variance σ. 2 The complex Gaussian distribution. Let α be an index matrix, and let α be the index of the index matrix. Column elements are All other elements are 0. Represents the time-delay domain sampling matrix. Represents the channel fading matrix. Let M0 represent the Doppler domain sampling matrix, and M0 represent the number of oversampling points in the receiver delay domain, where M0 > M.

[0102]

[0103]

[0104]

[0105] in and Let n0 = 1, ..., N, m0 = 1, ..., M0, m = 1, ..., M;

[0106] Represents the time delay sampling matrix The element in row m and column m0;

[0107] This represents the element in the n0th row and nth column of the Doppler domain sampling function;

[0108] This refers to the element in the m0th row and n0th column of the channel fading matrix;

[0109] The sequence number indicating multipath delay.

[0110] The serial number refers to the multipath Doppler signal.

[0111] Utilizing the sparsity of multipath in the time-delay Doppler domain An estimate was made, and the following results were obtained. Where P << M0 represents the true multipath number, Extract the rows corresponding to the P estimated multipaths to obtain Remove from equation (7) With v γ The part other than that is recorded as Estimate Ω using the MMSE criterion γ This completes the channel estimation, which is expressed by the following formula:

[0112]

[0113] Where η pilot This represents the power ratio of noise to pilot symbols in the data carried by each waveform. P×PThis represents an identity matrix with P rows and P columns.

[0114] Specifically, step S4 includes: the receiver uses the estimated multipath delay, multipath fading and multipath Doppler of each waveform, and uses the MMSE criterion and orthogonal spread spectrum combination structure to complete the detection of the data carried by different waveforms.

[0115] Next, the estimated multipath delay is used... The estimated combined effects of multipath Doppler and multipath fading (that is, to) The data is recovered by estimating the rows corresponding to the P estimated multipaths. Note that the number of system waveforms Γ is known, and the sequence number γ of the waveform can be obtained from the orthogonal spread spectrum combination designed for each user in formula (3). Therefore, only d in formula (7) is needed. γ It is unknown. Based on the fact that formula (7) contains d γ The cyclic structure of the matrix can be used to rewrite formula (7) as follows:

[0116]

[0117] Here, It means With d γ Between (:,1), (7) is biased. Indicator Matrix Time-delay domain sampling matrix Channel fading matrix Doppler domain sampling matrix Joint channel fading. The estimated multipath delay... The combined effects of multipath Doppler and multipath fading (that is, to) Substitute the estimated rows corresponding to the P estimated multipaths into the equation. In this process, the input-output relationship between the received and transmitted signals was obtained. Note that... Only receive signals The middle pilot symbol portion. For the received signal. Regarding the data symbols in the text, their corresponding form is as follows: The channel fading can also be obtained through (7) (according to formula (1), only all of (7) need to be converted). Replace with (That's all). The form corresponding to the data symbols and pilot symbols is as follows: The channel fading matrix is ​​placed in a matrix Thus, we obtain the following relationship between received data symbols and transmitted data symbols:

[0118]

[0119] The left side of the equation here represents the signal to be received. Reshape into vector form. This represents the channel fading between the received and transmitted signals. The data term on the right-hand side of the equation represents the fading of the transmitted signal. Reshape into vector form. This represents the Gaussian noise term.

[0120] Therefore, based on the preceding steps, this embodiment of the invention proposes to utilize MMSE equalization to achieve data recovery of waveform groups based on orthogonal spread spectrum combination. The specific formula is expressed as follows:

[0121]

[0122] Where η pilot This represents the ratio of noise to the power of the data symbols carried by each waveform. bN×bN This represents an identity matrix with bN rows and bN columns. express The transpose and conjugate of . Indicates the received signal The operation of reshaping into a column vector.

[0123] It can be observed that the vector form of the transmitted signal obtained in formula (11) This refers to the transmitted data carried by the γth waveform. By performing the same operation on the other waveforms, the transmitted data carried by all Γ waveforms can be detected.

[0124] like Figure 2 As shown, the method provided in this embodiment of the invention can achieve simultaneous and reliable data transmission of five waveforms in a vehicle-to-everything (V2X) scenario (maximum Doppler frequency of 700Hz). Specifically, compared with OFDM technology, when q=10, the bit error rate is 10^- ... -2 In this embodiment of the invention, the orthogonal time-frequency code domain waveform can bring a bit error rate gain of 12dB. Therefore, this embodiment of the invention provides an alternative solution for reliable multi-user transmission under high-speed mobile conditions.

[0125] In summary, the embodiments of the present invention design unique orthogonal spread spectrum combinations for different waveforms within the same waveform group, realizing orthogonal transmission of multiple waveforms using the same DD domain resources. Specifically, based on the orthogonal spread spectrum combination, each waveform carries orthogonal pilot symbols and data symbols, thus giving the system universal robustness to different DD domain channel conditions; furthermore, each waveform occupies the same DD domain resources, maintaining full resource utilization even with a low number of concurrent waveforms.

[0126] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of one embodiment, and the modules or processes shown in the drawings are not necessarily essential for implementing the present invention.

[0127] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of the present invention.

[0128] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for apparatus or system embodiments, since they are basically similar to method embodiments, the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments. The apparatus and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0129] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A waveform design and reception method in the orthogonal time-frequency code domain, characterized in that, include: The orthogonal spread spectrum sequence pool is used to assign orthogonal spread spectrum combinations to each waveform in the waveform group; Each waveform carries the transmitted data in the orthogonal time-frequency code domain according to the assigned orthogonal spread spectrum combination; After receiving each waveform, the receiver estimates the multipath delay, multipath fading, and multipath Doppler experienced by the multiple waveforms based on the orthogonal spread spectrum combination of each waveform. The receiver uses the estimated multipath delay, multipath fading, and multipath Doppler of each waveform, and employs the minimum mean square error (MMSE) criterion and orthogonal spread spectrum combination structure to detect the transmitted data carried by each waveform.

2. The method according to claim 1, characterized in that, The method of assigning orthogonal spreading combinations to each waveform in a waveform group using an orthogonal spreading sequence pool includes: The bandwidth occupied by the waveform group when transmitting data is set to... The time is ,in Indicates subcarrier spacing The number, Indicates time slot The number of waveforms, assuming there are a total of There are 10 waveforms, and the sequence number of each waveform is 1. , ; The columns of the Discrete Fourier Transform (DFT) matrix are used to form an orthogonal spread spectrum sequence pool. ,in Indicates the spreading factor. Represented as: (1) (2) Where vector Representation matrix The Column, for the first A number of orthogonal spread spectrum sequences; In the orthogonal spread spectrum sequence pool Select in sequence A number of orthogonal spreading sequences are used to form orthogonal spreading combinations of different waveforms. Each waveform is assigned to two different orthogonal spreading combinations, and the orthogonal spreading combinations assigned to each waveform are orthogonal in the time-frequency code domain. No. Orthogonal spread spectrum combination of waveforms Represented as: (3)。 3. The method according to claim 2, characterized in that, The various waveforms, according to their assigned orthogonal spreading combinations, carry transmitted data in the orthogonal time-frequency code domain, including: Each waveform utilizes the orthogonal spread spectrum combination assigned to it. Carrying data in the orthogonal time-frequency code domain Using orthogonal spread spectrum combination The sequence used for pilot symbols carries pilot symbols and is combined using orthogonal spread spectrum. The sequence used for data symbols carries the data symbols, resulting in... , The The column is represented as: (4) in express OK The identity matrix of columns, Indicates diagonal elements OK A block diagonal matrix; Each waveform is transformed from the time-delay Doppler domain to the time-frequency domain through a two-dimensional DFT transformation for data transmission.

4. The method according to claim 3, characterized in that, After receiving each waveform, the receiver estimates the multipath delay, multipath fading, and multipath Doppler effect experienced by the multiple waveforms based on the orthogonal spread spectrum combination of the waveforms, including: When the receiver receives signals from multiple waveforms, it transforms each waveform from the time-frequency domain to the time-delay Doppler domain through a two-dimensional DFT transform. Set the waveform group received by the receiver in Duration The signal carried on the bandwidth is ; The receiver separates the data carried by each waveform according to the orthogonal spread spectrum combination specified in formula (3) and the inverse process of formula (4). The calculation process is shown in formulas (5) and (6): (5) in The The column is obtained by the following operation: (6) According to the orthogonal spreading combination specified in formula (3), the spreading sequences used to carry pilot symbols for each waveform are completely orthogonal. The pilot data carried by each waveform is extracted and denoted as... Based on the assumption of biorthogonality between transmitted and received waveforms and The relationship is: (7) In formula (7), Let represent a complex Gaussian noise matrix, where the noise follows a constant with mean 0 and variance . The complex Gaussian distribution, Let represent an index matrix, its ... Line number Column elements are All other elements are 0. , Represents the time-delay domain sampling matrix. Represents the channel fading matrix. Represents the Doppler domain sampling matrix. This represents the number of oversampling points in the receiver's time delay domain. ; in and This represents the time delay and Doppler effect of a certain path. Multipath delay, multipath fading ; Represents the time delay sampling matrix No. Okay, number Column elements; Represents the Doppler domain sampling function ; The channel fading matrix is ​​the first Okay, number Column elements; The sequence number indicating multipath delay. ; The serial number refers to the multipath Doppler signal. ; Utilizing the sparsity of multipath in the time-delay Doppler domain An estimate was made, and the following results were obtained. ,in Representing the true multipath number, Zhongyu Extract the rows corresponding to the estimated multipaths to obtain , Zhongyu For each row corresponding to the estimated multipath, excluding the row in equation (7) and The part other than that is recorded as Estimate using MMSE criterion This completes the channel estimation, which is expressed by the following formula: (8) in This represents the power ratio of noise to pilot symbols in the data carried by each waveform. express OK A unit matrix of columns.

5. The method according to claim 4, characterized in that, The receiver utilizes the estimated multipath delay, multipath fading, and multipath Doppler of each waveform, and employs the minimum mean square error (MMSE) criterion and orthogonal spread spectrum combination structure to detect the transmitted data carried by each waveform, including: System waveform count The known waveform number Based on the orthogonal spread spectrum combination designed for each user in formula (3), and based on formula (7) containing... The cyclic structure of the matrix allows us to rewrite formula (7) as follows: (9) It means and Between, in formula (7) phase bias Indicator matrix Time-delay domain sampling matrix Channel fading matrix Doppler domain sampling matrix Combined channel fading; The estimated multipath delay The combined effects of multipath Doppler and multipath fading Substitution In this process, the input-output relationship between the received signal and the transmitted signal was obtained. It is receiving signals The middle pilot symbol portion, received signal The form corresponding to the data symbols in the middle is as follows The channel fading is obtained through (7), and the corresponding data symbols and pilot symbols are in the form of The channel fading matrix is ​​placed in a matrix The relationship between received data symbols and transmitted data symbols is obtained as follows: (10) The left side of formula (10) represents the received signal. Reshape into vector form. This represents the channel fading between the received and transmitted signals. The data term on the right-hand side of the equation represents the fading of the transmitted signal. Reshape into vector form. Represents the Gaussian noise term; Data recovery of waveform groups based on orthogonal spread spectrum combination is achieved using MMSE equalization, as expressed by the following formula: (11) in This represents the ratio of noise to the power of the data symbols carried by each waveform. express OK The unit matrix of columns, express The transpose and conjugate of , Indicates the received signal The operation of reshaping into a column vector; The vector form of the transmitted signal obtained in formula (11) That is, the first The transmitted data carried by each waveform is processed by performing the same operation on other waveforms to complete all the tasks. Detection of transmitted data carried by each waveform.

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