Cross-domain high and low speed multi-user access method and system based on OTFS system

Abstract

The invention discloses a cross-domain high and low speed multi-user access method and system based on an OTFS system, and relates to the technical field of wireless communication, and the method comprises the steps: an OFDM transmitting end carries out the first preprocessing of information symbols, maps the information symbols to a time delay-Doppler domain, and distributes the information symbols to different users; constructing a time-frequency domain conversion scheme based on the first preprocessing, and converting the multi-user signal from a time delay Doppler domain to a time-frequency domain to obtain a time-frequency domain composite signal; an OFDM receiving end receives the time-frequency domain composite signal, recovers the multi-user signal through time-frequency domain demodulation, and performs primary detection on a time delay Doppler domain signal of a low-speed transmitting end to obtain a low-speed signal detection result; and carrying out secondary detection on the low-speed signal detection result to obtain high-speed and low-speed transmitting end signals, and recovering the high-speed and low-speed transmitting end signals to the time delay Doppler domain. According to the method, multi-user interference can be effectively avoided, so that the spectrum efficiency is improved, and the decoding accuracy of the system is improved according to the processing condition of the received complex signal by the base station in reality.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a high- and low-speed multi-user access method and system based on a cross-domain OTFS system. Background Art

[0002] Orthogonal Time Frequency Space (OTFS) modulation technology has received extensive attention for its excellent performance in high-speed scenarios. In the context of the combination of OTFS and multiple access, some scholars have proposed an OTFS multiple access system that does not require a guard interval, and analyzed that the scheme avoids multi-user interference (MUI) under the premise of ideal pulses, thus proving that the system has higher spectrum efficiency than traditional guard band multiple access schemes. However, the computational complexity of the system is high in practical applications, and in the scenario of multi-user access, the channel model is relatively simple and cannot meet the processing conditions of the complex signals received by the base station in reality.

[0003] In view of this, it is necessary to design a cross-domain high-low-speed multi-user access solution in the OTFS system to solve the above problems. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, in order to solve the above technical problems, the present invention provides the following technical solutions: a high-low speed multi-user access method based on cross-domain in OTFS system, comprising: an OFDM transmitter performs a first preprocessing on information symbols, and maps the information symbols to a delay-Doppler domain and allocates them to different users;

[0006] Based on the first preprocessing, a time-frequency domain conversion scheme is constructed, and the multi-user signal is converted from the delay-Doppler domain to the time-frequency domain to obtain a composite signal in the time-frequency domain;

[0007] The OFDM receiving end receives the time-frequency domain composite signal, and recovers the multi-user signal through time-frequency domain demodulation, performs a detection on the delay Doppler domain signal of the low-speed transmitting end, and obtains a low-speed signal detection result;

[0008] The low-speed signal detection result is subjected to secondary detection to obtain high-speed and low-speed transmitting end signals, and restored to the delay Doppler domain to complete multi-user access.

[0009] As a preferred solution of the high-low speed multi-user access method based on cross-domain OTFS system described in the present invention, wherein: the first preprocessing includes:

[0010] Modulating the information bit stream to generate modulated symbols;

[0011] The modulated symbols are mapped to the delay-Doppler grid, and the delay domain and Doppler domain are further divided into M equal parts and N equal parts. The calculation formula of the distribution method is as follows:

[0012]

[0013] in, is the set of allocation schemes, q is the index value of the user, (k, l) is the coordinate of the delay-Doppler resource block occupied by the user in the subdivided delay-Doppler domain, g1 and g2 are the number of grids occupied by dividing the delay axis and Doppler axis into several parts respectively, To round down q / g1, u and v are the index values ​​after dividing the delay axis and Doppler axis equally, (q) g1 is the smallest non-negative integer equal to the remainder when q is divided by g1.

[0014] As a preferred solution of the high-low speed multi-user access method based on cross-domain OTFS system described in the present invention, wherein: the conversion of multi-user signals from the delay Doppler domain to the time-frequency domain includes:

[0015] receiving an allocated delay-Doppler domain signal, the delay-Doppler domain signal including a specific symbol block for each user;

[0016] The multi-user signal in the delay-Doppler domain is converted into the time-frequency domain signal by using the inverse symplectic finite Fourier transform;

[0017] The time-frequency domain signals of each user after ISFFT conversion are combined to form a time-frequency domain composite signal containing multi-user data;

[0018] The time-frequency domain composite signal is packaged into a transmittable signal format and uploaded.

[0019] As a preferred solution of the high-low speed multi-user access method based on cross-domain OTFS system described in the present invention, wherein: the conversion into time-frequency domain signals includes:

[0020] The delay Doppler domain signal x[k,l] after the fixed allocation is converted into the time-frequency domain transmission signal through ISFFT. The calculation formula after conversion is as follows:

[0021]

[0022] n=0,1,...,((N / g2)-1),m=0,1...,((M / g1)-1)

[0023]

[0024] Wherein, M and N correspond to the number of grids further allocated in the delay domain and Doppler domain, q is the index value of the user, (k, l) is the coordinate of the delay-Doppler resource block occupied by the user in the subdivided delay-Doppler domain, g1 and g2 are the number of grids occupied by dividing the delay axis and the Doppler axis into several parts respectively, X[m,n] is the time-frequency domain signal after ISFFT processing of the signal, m corresponds to the frequency axis, and n corresponds to the time axis.

[0025] As a preferred solution of the high-low speed multi-user access method across domains in the OTFS system described in the present invention, wherein: the packaging into a transmittable signal format includes:

[0026] The time-frequency domain data of the high-speed transmitter and the low-speed transmitter are processed respectively, and the time-frequency domain signal is converted to the time domain through Heisenberg transform and digital-to-analog conversion. The time-domain transmission signal is amplified by the transmitting antenna. The transmission signal is expressed as follows:

[0027]

[0028] Among them, X[m,n] is the time-frequency domain signal, s(t) is the time domain transmission signal, g tx (t) is the pulse shaping waveform at the transmitting end, M and N correspond to the number of grids further allocated in the delay domain and Doppler domain, T is the subcarrier spacing, and Δf is a symbol duration respectively;

[0029] In the OTFS system, the channel is represented as follows:

[0030]

[0031] Where h(τ,υ) is the channel response in the delay-Doppler domain, τ i is the delay, υ i is Doppler, h i is the channel coefficient;

[0032] When receiving a signal, the received signal in the time-frequency domain is represented as follows:

[0033] r(t)=∫∫h(τ,υ)s(t-τ)e j2πυ(t-τ) dτdυ+w(t)

[0034] Among them, w(t) is the channel Gaussian white noise, and h(τ,υ) is the channel response in the delay Doppler domain.

[0035] As a preferred solution of the high-low speed multi-user access method across domains in the OTFS system described in the present invention, wherein: the one-time detection includes:

[0036] The data of the low-speed transmitter is filtered through the MMSE algorithm to obtain the time-frequency domain data of the low-speed transmitter;

[0037] The channel-related part is matrixed, and the matrix calculation formula of the received signal is as follows:

[0038] r=Hs+w

[0039]

[0040]

[0041] Among them, r is the received vector in the time-frequency domain, H is the equivalent channel matrix of MN×MN, w is the noise vector, and h i is the channel coefficient, Π is the permutation matrix, is a diagonal matrix;

[0042] According to the OTFS input-output relationship, the calculation formula of the TF domain equivalent channel is as follows:

[0043]

[0044] The calculation formula for DD domain equivalent is as follows:

[0045]

[0046] Among them, H eq According to the different equivalent channel representations in the delay-Doppler domain and the time-frequency domain, I n and I m When a rectangular pulse is used, the pulse shaping matrix becomes the unit matrix, F m and F n is the normalized DFT matrix of M and N points, The operation is the Kronecker product, The operation is transpose conjugate;

[0047] Substituting the TF domain equivalent channel expression into the standard MMSE algorithm formula, the time-frequency domain MMSE algorithm for delay-Doppler channel is obtained;

[0048] The time-frequency domain MMSE algorithm measures the detection performance by minimizing the mean square error. The standard MMSE algorithm calculation formula is as follows:

[0049]

[0050] Among them, y is the corresponding received signal, H eq is the equivalent channel, σ 2 is the noise power, () H is the transpose conjugate operation.

[0051] As a preferred solution of the high-low speed multi-user access method based on cross-domain OTFS system described in the present invention, wherein: the step of restoring to the delay Doppler domain includes:

[0052] After the low-speed transmitter completes a detection, the low-speed transmitter data after passing through the time-frequency low-speed channel is obtained;

[0053] Subtract the composite signal data in the time-frequency domain from the low-speed transmitting end data to obtain the high-speed transmitting end data of the receiving end, perform secondary MMSE detection, and fully restore to the entire time-frequency domain;

[0054] A symplectic finite Fourier transform operation is performed on the time-frequency domain signal of the high-speed transmitter to obtain the delay-Doppler domain high-speed user data.

[0055] Another object of the present invention is to provide a high- and low-speed multi-user access system based on a cross-domain in an OTFS system. To solve the above technical problems, the present invention provides the following technical solutions: A high- and low-speed multi-user access system based on a cross-domain in an OTFS system, comprising: a first preprocessing module, a time-frequency domain conversion module, a low-speed demodulation detection module, and a high-speed detection module;

[0056] The first preprocessing module is used for performing first preprocessing on information symbols at the OFDM transmitting end, and mapping the information symbols to the delay-Doppler domain to allocate them to different users;

[0057] The time-frequency domain conversion module is used to construct a time-frequency domain conversion scheme based on the first preprocessing, and convert the multi-user signal from the delay-Doppler domain to the time-frequency domain to obtain a time-frequency domain composite signal;

[0058] The low-speed demodulation detection module is used for receiving the time-frequency domain composite signal at the OFDM receiving end, restoring the multi-user signal through time-frequency domain demodulation, and performing a detection on the delay Doppler domain signal of the low-speed transmitting end to obtain a low-speed signal detection result;

[0059] The high-speed detection module is used to perform secondary detection on the low-speed signal detection result to obtain high-speed and low-speed transmitting end signals, and restore them to the delay Doppler domain to complete multi-user access.

[0060] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and is characterized in that when the processor executes the computer program, the steps of the cross-domain high-low-speed multi-user access method in the OTFS system are implemented as described above.

[0061] A computer-readable storage medium having a computer program stored thereon, characterized in that when the computer program is executed by a processor, the steps of the cross-domain high- and low-speed multi-user access method in the OTFS system are implemented as described above.

[0062] Beneficial effects of the present invention: A cross-domain high-low-speed multi-user access scheme in an OTFS system designed by the present invention can effectively avoid multi-user interference, thereby improving spectrum efficiency, and improve the decoding accuracy of the system according to the processing conditions of the complex signals received by the base station in reality. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0064] Figure 1 This is a schematic diagram of the structure of a terminal in the first embodiment of the present invention;

[0065] Figure 2 is a flow chart of the transmitting end in the first embodiment of the present invention;

[0066] Figure 3 A schematic diagram of the structure of a computer device in a third embodiment of the present invention;

[0067] Figure 4 This is an ISFFT processing diagram of the high-speed transmitter in the first embodiment of the present invention;

[0068] Figure 5 A data model diagram reserved for the high-speed transmitter TF domain in the first embodiment of the present invention;

[0069] Figure 6 This is a diagram of the TF domain data model of the low-speed transmitting end in the first embodiment of the present invention;

[0070] Figure 7 is a flow chart of a receiving end in the first embodiment of the present invention;

[0071] Figure 8 This is a diagram showing the bit error rate detection results of the high and low speed transmitting ends in the first embodiment of the present invention. DETAILED DESCRIPTION

[0072] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0073] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0074] Example 1

[0075] Reference Figure 1 , which is an embodiment of the present invention, provides a high- and low-speed multi-user access method across domains in an OTFS system.

[0076] Before describing the embodiments of the present application in detail, some related concepts are first explained for the sake of clarity.

[0077] OTFS (Orthogonal Time Frequency Space): OTFS is a new modulation technology based on the time-frequency domain, which can transmit signals in the Delay Doppler (DD) domain. Compared with the traditional OFDM technology, OTFS has stronger resistance to multipath and Doppler frequency shift, and is suitable for multi-user communications in high-speed mobile scenarios.

[0078] Inverse Symplectic Finite Fourier Transform (ISFFT) and Symplectic Finite Fourier Transform (SFFT): ISFFT is a transform method that converts signals from the delay-Doppler domain to the time-frequency domain, and is usually used at the transmitter. In contrast, SFFT is a transform used by the receiver to restore signals from the time-frequency domain to the delay-Doppler domain. These two transforms are the core of cross-domain processing in the OTFS system, and are used to realize the conversion and processing of signals between different domains.

[0079] Delay-Doppler Domain (DD): Delay-Doppler domain is a method to describe the propagation characteristics of signals in different transmission environments by introducing delay and Doppler shift. Delay represents the time delay of the signal, and Doppler shift represents the frequency offset caused by the relative motion of the sending and receiving devices. OTFS technology can better handle signal transmission problems in high-speed mobile environments by mapping and processing signals in the DD domain.

[0080] Time-Frequency Domain (TF): The time-frequency domain is a field used to describe the changes of signals in two dimensions: time and frequency. In wireless communications, the frequency and time changes of signals are key factors in analyzing channel characteristics. Through the analysis of the time-frequency domain, the dynamic changes of the spectrum distribution of the signal over time can be more intuitively represented. OTFS (Orthogonal Time-Frequency-Space) modulation technology converts the signal from the delay-Doppler domain to the time-frequency domain for transmission in the wireless channel. Through processing in the TF domain, frequency-selective fading and time-selective fading can be effectively anti-interference processed to ensure the stability and robustness of the signal in complex propagation environments.

[0081] Interleaved allocation scheme: Interleaved allocation scheme is a mechanism for allocating delay and Doppler resource blocks to different users. By dividing the delay axis and Doppler axis into several equal parts and allocating them to different users, it ensures that each user can effectively utilize the resources in the delay-Doppler domain. The allocation strategy of this scheme takes into account the interference between users and the rational use of spectrum resources.

[0082] MMSE (Minimum Mean Square Error) algorithm: The MMSE algorithm is a signal detection algorithm based on minimizing mean square error, mainly used for receiving end signal processing. The algorithm processes the received multi-user signal in the time-frequency domain, filters interference and restores the signal to the delay-Doppler domain. MMSE can optimize the decoding process, reduce the bit error rate, and improve the accuracy of signal detection. It is especially suitable for high-speed and low-speed mixed multi-user scenarios.

[0083] Equivalent channel matrix: In the OTFS system, the equivalent channel matrix is ​​a mathematical model that describes the relationship between the input signal and the output signal. In a multi-user environment, signal transmission will be affected by multipath effects and Doppler frequency shift. The equivalent channel matrix expresses these effects through matrixization, helping the system to demodulate and recover signals more accurately.

[0084] First, the high-speed and low-speed multi-user access method based on the cross-domain OTFS system provided by the present application can be applied to Figure 1 In the terminal shown. Figure 1 As shown, the terminal may include one or two ( Figure 1 Only one is shown in the figure) processor and memory for storing data, wherein the processor may include but is not limited to a processing system such as a microprocessor MCU or a programmable logic device FPGA. The above terminal may also include a transmission device and an input and output device for communication functions. It can be understood by ordinary technicians in this field that Figure 1 The structure shown is only for illustration and does not limit the structure of the above terminal. Figure 1More or fewer components as shown, or with Figure 1 Different configurations shown.

[0085] The memory can be used to store computer programs, such as the computer program corresponding to the high-low speed multi-user access method across domains in the OTFS system in this embodiment. The processor executes various functional applications and data processing by running the computer program stored in the memory, that is, implementing the above method. The memory may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage systems, flash memory, or other non-volatile solid-state memory. In some instances, the memory may further include a memory remotely arranged relative to the processor, and these remote memories may be connected to the terminal via a network. Examples of the above-mentioned network include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0086] The transmission device is used to receive or send data via a network. The above-mentioned network includes a wireless network provided by a communication provider of the terminal. In one example, the transmission device includes a network adapter (Network Interface Controller, referred to as NIC), which can be connected to other network devices through a base station so as to communicate with the Internet. In one example, the transmission device can be a radio frequency (Radio Frequency, referred to as RF) module, which is used to communicate with the Internet wirelessly.

[0087] like Figure 2-Figure 7 As shown, the embodiment of the present invention provides a high-low speed multi-user access method based on cross-domain in OTFS system, and the method is applied to Figure 1 The terminal in is used as an example to illustrate, including the following steps:

[0088] S1: The OFDM transmitter performs a first preprocessing, through which information symbols are mapped to a delay-Doppler domain and allocated to different users;

[0089] Furthermore, the first preprocessing includes,

[0090] The information bit stream is modulated to generate modulated symbols; it should be noted that the modulation method used in the present invention includes but is not limited to QAM modulation;

[0091] The modulated symbols are mapped to the delay-Doppler grid, and the delay domain and Doppler domain are further subdivided into M equal parts and N equal parts, where the delay-Doppler resource block occupied by the user is a combination of equal parts along the delay domain and Doppler. The calculation formula of the allocation method is as follows:

[0092]

[0093] Wherein, q represents the index value of the user, i.e., the qth user, (k, l) represents the coordinates of the delay-Doppler resource block occupied by the user in the subdivided delay-Doppler domain, g1 and g2 represent the number of grids occupied by dividing the delay axis and the Doppler axis into several parts respectively, Indicates that q / g1 is rounded down. Assuming that the total number of users is Q, then Q = g1g2. u and v represent the index values ​​after the delay axis and the Doppler axis are evenly divided. The index value u satisfies The index value v satisfies (q) g1 Represents the smallest nonnegative integer equal to the remainder when q is divided by g1.

[0094] Specifically, the delay-Doppler resource blocks occupied by the users are allocated after being subdivided along the delay axis and the Doppler axis, ensuring that the resource blocks of each user do not overlap, thus forming an effective multi-user resource allocation strategy.

[0095] S2: constructing a time-frequency domain conversion scheme based on the first preprocessing to convert the multi-user signal from the delay-Doppler domain to the time-frequency domain;

[0096] Further, converting the multi-user signal from the delay-Doppler domain to the time-frequency domain includes,

[0097] receiving an allocated delay-Doppler domain signal, the delay-Doppler domain signal including a specific symbol block for each user;

[0098] The inverse symplectic finite Fourier transform is used to convert the multi-user signal in the delay-Doppler domain into a signal in the time-frequency domain; the allocated signal x[k,l] is converted into a transmitted signal X[m,n] in the time-frequency domain through ISFFT. The calculation formula after conversion is as follows:

[0099]

[0100] n=0,1,...,((N / g2)-1),m=0,1...,((M / g1)-1)

[0101]

[0102] Where M and N correspond to the number of grids further allocated in the delay domain and Doppler domain, q is the index value of the user, (k, l) is the coordinate of the delay Doppler resource block occupied by the user in the subdivided delay Doppler domain, and g 1 and g 2 The number of grids occupied by dividing the delay axis and the Doppler axis into several parts respectively, X[m,n] is the time-frequency domain signal after the signal ISFFT processing, m corresponds to the frequency axis, and n corresponds to the time axis.

[0103] The time-frequency domain signals of each user after ISFFT conversion are combined to form a composite signal containing multi-user data;

[0104] Packing the combined time-frequency domain signals into a transmittable signal format and preparing them for transmission on the physical layer;

[0105] The time-frequency domain data of the high-speed transmitter and the low-speed transmitter are processed respectively. The time-frequency domain signal X[m,n] is converted to the time domain through Heisenberg transform and digital-to-analog conversion, and the time domain transmission signal s(t) is obtained by amplifying the transmitting antenna. The high-speed transmitter is expressed as follows:

[0106]

[0107] Among them, X[m,n] is the time-frequency domain signal, s(t) is the time domain transmission signal, g tx (t) is the pulse shaping waveform at the transmitting end, M and N correspond to the number of grids further allocated in the delay domain and Doppler domain, T is the subcarrier spacing, and Δf is a symbol duration respectively;

[0108] In the OTFS system, the channel is represented as follows:

[0109]

[0110] Where h(τ,υ) is the channel response in the delay-Doppler domain, τ i is the delay, υ i is Doppler, h i is the channel coefficient;

[0111] When receiving a signal, the representation in the time-frequency domain is as follows:

[0112] r(t)=∫∫h(τ,υ)s(t-τ)e j2πυ(t-τ) dτdυ+w(t)

[0113] Among them, w(t) is the channel Gaussian white noise, and h(τ,υ) is the channel response in the delay Doppler domain.

[0114] Furthermore, in a multi-user communication system, after the uplink transmission process is processed by inverse symplectic finite Fourier transform, the signal of each user is mapped to a specific resource block in the delay-Doppler domain; when these resource blocks are converted to the time-frequency domain, they will form a distribution feature with the same modulus value in the entire time-frequency plane; based on this feature, for each individual user, only those resource blocks that can completely reconstruct the original time-frequency domain signal need to be selected during its transmission;

[0115] Furthermore, given the inherent mathematical properties of ISFFT, under the same channel conditions, after multiple users have completed their ISFFT operations, different, non-overlapping time-frequency domain resource blocks can be carefully selected and allocated to each user, thereby ensuring that the data of all users can be evenly distributed within the complete time-frequency domain. This selection and allocation mechanism enables the transmitter to effectively manage the data mapping relationship between the delay-Doppler domain and the time-frequency domain, thereby achieving an efficient and reliable multi-user transmission solution.

[0116] S3: The OFDM receiving end receives the composite signal in the time-frequency domain and recovers the multi-user data through time-frequency domain demodulation, performs a detection on the delay-Doppler domain signal of the low-speed transmitting end, and obtains the delay-Doppler domain signal of the low-speed transmitting end;

[0117] Furthermore, a test includes,

[0118] Through the MMSE algorithm, the data of the low-speed transmitter is preferentially screened out to obtain the time-frequency domain data of the low-speed transmitter;

[0119] In order to facilitate subsequent use, the channel-related part is matrixed, and the matrix calculation formula of the received signal is as follows:

[0120] r=Hs+w

[0121]

[0122] Among them, r is the received vector in the time-frequency domain, H is the equivalent channel matrix of MN×MN, w is the noise vector, and h i is the channel coefficient, Π is the permutation matrix, is a diagonal matrix.

[0123] According to the OTFS input-output relationship, the calculation formula of the TF domain equivalent channel is as follows:

[0124]

[0125] The calculation formula for DD domain equivalent is as follows:

[0126]

[0127] Among them, H eq According to the different equivalent channel representations in the delay-Doppler domain and the time-frequency domain, I n and I m When a rectangular pulse is used, the pulse shaping matrix becomes the unit matrix, F m and F n is the normalized DFT matrix of M and N points, The operation is the Kronecker product, The operation is transpose conjugate.

[0128] Substituting the TF domain equivalent channel expression into the standard MMSE algorithm formula, the time-frequency domain MMSE algorithm for delay-Doppler channel is obtained;

[0129] The time-frequency domain MMSE algorithm measures the detection performance by minimizing the mean square error. The standard MMSE algorithm calculation formula is as follows:

[0130]

[0131] Among them, y is the corresponding received signal, H eq is the equivalent channel, σ 2 is the noise power, () H is the transpose conjugate operation.

[0132] Specifically, at the receiving end, a composite signal in the time-frequency domain of the high-speed and low-speed transmitters that occupies the entire time-frequency domain can be obtained. In order to distinguish the high-speed and low-speed transmitters and restore the high-speed transmitter data to the DD domain, the present invention adopts the MMSE algorithm. The core of the detection algorithm has two points. The first core is to preferentially filter out the low-speed transmitter signal data from the mixed signal. The second core is to use the characteristics of the symplectic finite Fourier transform under the condition of staggered distribution to restore the high-speed transmitter data to the DD domain. The time-frequency domain data needs to be completely restored to the entire time-frequency domain, and the related interference will greatly affect the recovery accuracy, thereby affecting the bit error rate. Therefore, the MMSE detection algorithm that is convenient for placing the detection algorithm in the time-frequency domain for processing is selected, thereby improving the system bit error rate.

[0133] S4: Perform secondary detection on the low-speed signal detection result to obtain high-speed and low-speed transmitting end signals, and restore them to the delay Doppler domain.

[0134] Further, the steps of restoring to the delay-Doppler domain include:

[0135] After the low-speed transmitter has correctly detected the data, the low-speed transmitter data after passing through the time-frequency low-speed channel is obtained;

[0136] The time-frequency domain composite signal is subtracted from the data to obtain the high-speed transmitting end data of the receiving end, and a secondary MMSE detection is performed to fully restore the entire time-frequency domain;

[0137] Perform symplectic finite Fourier transform operation on the time-frequency domain signal of the high-speed transmitter to obtain DD domain high-speed user data.

[0138] Furthermore, the characteristics of the symplectic finite Fourier transform also roughly divide the demodulation process into two steps, including,

[0139] The signal received from the base station contains data of multiple users. In the demodulation process of the time-frequency domain, each part of the time-frequency domain resource block contains the complete data information of different users, and the part containing user data is completely restored to the entire time-frequency domain;

[0140] The recovered signal is processed by symplectic finite Fourier transform operation to recover the delay Doppler signal of the user.

[0141] Example 2

[0142] As an embodiment of the present invention, a high-low speed multi-user access system based on cross-domain in OTFS system is provided, comprising: a first pre-processing module, a time-frequency domain conversion module, a low-speed demodulation detection module and a high-speed detection module;

[0143] The first preprocessing module is used for performing first preprocessing at the OFDM transmitting end, and mapping information symbols to the delay-Doppler domain and allocating them to different users through the first preprocessing;

[0144] The time-frequency domain conversion module is used to construct a time-frequency domain conversion scheme based on the first preprocessing to convert the multi-user signal from the delay-Doppler domain to the time-frequency domain;

[0145] The low-speed demodulation detection module is used for receiving the composite signal in the time-frequency domain at the OFDM receiving end and recovering the multi-user data through time-frequency domain demodulation, and performing a detection on the delay Doppler domain signal of the low-speed transmitting end to obtain the low-speed signal detection result;

[0146] The high-speed detection module is used to perform secondary detection on the low-speed signal detection result to obtain high-speed and low-speed transmitting end signals and restore them to the delay Doppler domain.

[0147] For the specific definition of the high- and low-speed multi-user access system across domains in the OTFS system, please refer to the definition of the high- and low-speed multi-user access method across domains in the OTFS system above, which will not be repeated here. Each module in the above-mentioned high- and low-speed multi-user access system across domains in the OTFS system can be implemented in whole or in part by software, hardware and a combination thereof. The above-mentioned modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory in the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0148] Example 3

[0149] Reference Figure 3 , which is the third embodiment of the present invention. Based on the first two embodiments, the embodiment of the present invention provides a computer device, which may be a server, and its internal structure diagram may be as shown in FIG. Figure 3As shown. The computer device includes a processor, a memory and a network interface connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium.

[0150] The database of the computer device is used to store action detection data. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, the steps in any of the above-mentioned sparse tensor operation acceleration method embodiments are implemented.

[0151] Those skilled in the art will understand that Figure 3 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0152] In one embodiment, an embodiment of the present invention provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps in any of the above-mentioned sparse tensor operation acceleration method embodiments are implemented.

[0153] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory or optical memory, etc. Volatile memory may include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM).

[0154] Example 4

[0155] Reference Figure 8, which is an embodiment of the present invention, provides a high-low speed multi-user access method based on cross-domain in OTFS system. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through simulation experiments.

[0156] Figure 8 The embodiment of the present invention describes the bit error rate statistical curves of the high and low speed transmitting ends when the data symbol signal-to-noise ratio ranges from 0 to 25 dB.

[0157] Basic parameter settings: OTFS delay-Doppler domain grid size is M=32, N=32, carrier frequency f c is 4GHz, the subcarrier spacing Δf is 15KHz, and the maximum channel delay is l max is 3, the maximum Doppler value k max is 3, using 4QAM symbols.

[0158] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A high-speed and low-speed multi-user access method based on cross-domain in OTFS system, characterized in that: include: The OFDM transmitter performs a first preprocessing on the information symbols, and maps the information symbols to a delay-Doppler domain and allocates them to different users; Based on the first preprocessing, a time-frequency domain conversion scheme is constructed, and the multi-user signal is converted from the delay-Doppler domain to the time-frequency domain to obtain a composite signal in the time-frequency domain; The OFDM receiving end receives the time-frequency domain composite signal, and recovers the multi-user signal through time-frequency domain demodulation, performs a detection on the delay Doppler domain signal of the low-speed transmitting end, and obtains a low-speed signal detection result; The low-speed signal detection result is subjected to secondary detection to obtain high-speed and low-speed transmitting end signals, and restored to the delay Doppler domain to complete multi-user access.

2. The cross-domain high-low speed multi-user access method based on the OTFS system according to claim 1, characterized in that: The first preprocessing comprises: Modulating the information bit stream to generate modulated symbols; The modulated symbols are mapped to the delay-Doppler grid, and the delay domain and Doppler domain are further divided into M equal parts and N equal parts. The calculation formula of the distribution method is as follows: in, is the set of allocation schemes, q is the index value of the user, (k, l) is the coordinate of the delay-Doppler resource block occupied by the user in the subdivided delay-Doppler domain, g1 and g2 are the number of grids occupied by dividing the delay axis and Doppler axis into several parts respectively, To round down q / g1, u and v are the index values ​​after dividing the delay axis and Doppler axis equally, (q) g1 is the smallest non-negative integer equal to the remainder when q is divided by g1.

3. The cross-domain high-low speed multi-user access method based on the OTFS system according to claim 2, characterized in that: The step of obtaining the composite signal in the time-frequency domain comprises: receiving an allocated delay-Doppler domain signal, the delay-Doppler domain signal including a specific symbol block for each user; The multi-user signal in the delay-Doppler domain is converted into the time-frequency domain signal by using the inverse symplectic finite Fourier transform; The time-frequency domain signals of each user after ISFFT conversion are combined to form a time-frequency domain composite signal containing multi-user data; The time-frequency domain composite signal is packaged into a transmittable signal format and uploaded.

4. The cross-domain high-low speed multi-user access method based on the OTFS system according to claim 3, characterized in that: The conversion into time-frequency domain signals comprises: The delay Doppler domain signal x[k,l] after the fixed allocation is converted into the time-frequency domain transmission signal through ISFFT. The calculation formula after conversion is as follows: n=0,1,...,((N / g2)-1),m=0,1...,((M / g1)-1) Wherein, M and N correspond to the number of grids further allocated in the delay domain and Doppler domain, q is the index value of the user, (k, l) is the coordinate of the delay-Doppler resource block occupied by the user in the subdivided delay-Doppler domain, g1 and g2 are the number of grids occupied by dividing the delay axis and the Doppler axis into several parts respectively, X[m,n] is the time-frequency domain signal after ISFFT processing of the signal, m corresponds to the frequency axis, and n corresponds to the time axis.

5. The cross-domain high-low speed multi-user access method based on the OTFS system according to claim 4, characterized in that: The packaging into a transmittable signal format includes: The time-frequency domain data of the high-speed transmitter and the low-speed transmitter are processed respectively, and the time-frequency domain signal is converted to the time domain through Heisenberg transform and digital-to-analog conversion. The time-domain transmission signal is amplified by the transmitting antenna. The transmission signal is expressed as follows: Among them, X[m,n] is the time-frequency domain signal, s(t) is the time domain transmission signal, g tx (t) is the pulse shaping waveform at the transmitting end, M and N correspond to the number of grids further allocated in the delay domain and Doppler domain, T is the subcarrier spacing, and Δf is a symbol duration respectively; In the OTFS system, the channel is represented as follows: Where h(τ,υ) is the channel response in the delay-Doppler domain, τ i is the delay, υ i is Doppler, h i is the channel coefficient; When receiving a signal, the received signal in the time-frequency domain is represented as follows: r(t)=∫∫h(τ,υ)s(t-τ)e j2πυ(t-τ) dτdυ+w(t) Among them, w(t) is the channel Gaussian white noise, and h(τ,υ) is the channel response in the delay Doppler domain.

6. The cross-domain high-low speed multi-user access method based on the OTFS system according to claim 5, characterized in that: The one-time detection includes, The data of the low-speed transmitter is filtered through the MMSE algorithm to obtain the time-frequency domain data of the low-speed transmitter; The channel-related part is matrixed, and the matrix calculation formula of the received signal is as follows: r=Hs+w Among them, r is the received vector in the time-frequency domain, H is the equivalent channel matrix of MN×MN, w is the noise vector, and h i is the channel coefficient, Π is the permutation matrix, is a diagonal matrix; According to the OTFS input-output relationship, the calculation formula of the TF domain equivalent channel is as follows: The calculation formula for DD domain equivalent is as follows: Among them, H eq According to the different equivalent channel representations in the delay-Doppler domain and the time-frequency domain, I n and I m When a rectangular pulse is used, the pulse shaping matrix becomes the unit matrix, F m and F n is the normalized DFT matrix of M and N points, The operation is the Kronecker product, The operation is transpose conjugate; Substituting the TF domain equivalent channel expression into the standard MMSE algorithm formula, the time-frequency domain MMSE algorithm for delay-Doppler channel is obtained; The time-frequency domain MMSE algorithm measures the detection performance by minimizing the mean square error. The standard MMSE algorithm calculation formula is as follows: Among them, y is the corresponding received signal, H eq is the equivalent channel, σ 2 is the noise power, () H is the transpose conjugate operation.

7. The cross-domain high-low speed multi-user access method based on the OTFS system according to claim 6, characterized in that: The step of restoring to the delay-Doppler domain includes: After the low-speed transmitter completes a detection, the low-speed transmitter data after passing through the time-frequency low-speed channel is obtained; Subtract the composite signal data in the time-frequency domain from the low-speed transmitting end data to obtain the high-speed transmitting end data of the receiving end, perform secondary MMSE detection, and fully restore to the entire time-frequency domain; A symplectic finite Fourier transform operation is performed on the time-frequency domain signal of the high-speed transmitter to obtain the delay-Doppler domain high-speed user data.

8. A system using the high- and low-speed multi-user access method based on cross-domain in OTFS system as claimed in any one of claims 1 to 7, characterized in that: include: A first preprocessing module, a time-frequency domain conversion module, a low-speed demodulation detection module, and a high-speed detection module; The first preprocessing module is used for performing first preprocessing on information symbols at the OFDM transmitting end, and mapping the information symbols to the delay-Doppler domain to allocate them to different users; The time-frequency domain conversion module is used to construct a time-frequency domain conversion scheme based on the first preprocessing, and convert the multi-user signal from the delay-Doppler domain to the time-frequency domain to obtain a time-frequency domain composite signal; The low-speed demodulation detection module is used for receiving the time-frequency domain composite signal at the OFDM receiving end, restoring the multi-user signal through time-frequency domain demodulation, and performing a detection on the delay Doppler domain signal of the low-speed transmitting end to obtain a low-speed signal detection result; The high-speed detection module is used to perform secondary detection on the low-speed signal detection result to obtain high-speed and low-speed transmitting end signals, and restore them to the delay Doppler domain to complete multi-user access.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the high- and low-speed multi-user access method across domains in an OTFS system according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the high-speed and low-speed multi-user access method across domains in an OTFS system according to any one of claims 1 to 7 are implemented.

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