A method and system for adjusting an OTFS-based communication waveform

Abstract

The application relates to the technical field of communication, and particularly discloses a communication waveform adjustment method and system based on OTFS, which comprises the following steps: defining a time-delay Doppler domain signal to be transmitted; establishing a channel response function under satellite communication by using star-ground statistical channel information; determining the signal-to-noise ratio of the terminal time-delay Doppler domain according to the channel response function and the Doppler domain signal; and solving the optimal weighting and optimal rate of the terminal according to the signal-to-noise ratio and a preset signal constraint condition. The application can fully utilize limited frequency spectrum resources and improve the communication rate of a multi-user communication system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of communication technology, in particular to a communication waveform adjustment method and system based on OTFS. BACKGROUND

[0002] With the increasing demand of satellite users for communication service quality, and the problem of bandwidth resource shortage caused by large-scale user access, how to effectively improve the spectral efficiency of satellite communication system under the condition of limited frequency resources has become one of the key problems to be solved at present.

[0003] Orthogonal time frequency space modulation (OTFS, Orthogonal Time Frequency Space) is a new modulation method proposed in recent years. Unlike OFDM, which transmits information in the frequency domain, OTFS transmits information in the time delay-Doppler domain. The advantages of OTFS include but are not limited to being able to adapt to high-speed mobile environments and being able to estimate channels with less overhead. Orthogonal time frequency space modulation OTFS provides a possibility for solving the problem of effectively improving the spectral efficiency of satellite communication system. SUMMARY

[0004] In view of the above problems, the purpose of the present application is to provide a communication waveform adjustment method and system based on OTFS, which can make full use of limited frequency spectrum resources and improve the communication rate of a multi-user communication system.

[0005] The present application provides a communication waveform adjustment method based on OTFS, comprising:

[0006] defining a time delay-Doppler domain signal to be transmitted;

[0007] establishing a channel response function under satellite communication using satellite-ground statistical channel information;

[0008] determining the signal-to-noise ratio of the terminal time delay-Doppler domain according to the channel response function and the Doppler domain signal;

[0009] solving the optimal weighting and optimal rate of the terminal according to the signal-to-noise ratio and a preset signal constraint condition.

[0010] In a possible implementation, the definition of the time delay-Doppler domain signal to be transmitted comprises:

[0011] The time delay-Doppler domain signal to be transmitted is defined according to the following formula:

[0012] ;

[0013] ;

[0014] wherein, For time-delayed Doppler domain signals, For the time-delayed Doppler domain, For delay index, For Doppler indexing, The smallest resolvable unit interval in the Doppler domain. for The time-delayed Doppler domain plane of the dimension, For the number of time-domain subcarriers, The number of samples in the time domain signal. This represents the signal sampling time interval.

[0015] In one possible implementation, establishing the channel response function for satellite communication using satellite-to-ground statistical channel information includes:

[0016] The channel response function is established according to the following formula. :

[0017] ;

[0018] in, For the first between stars and Earth Channel attenuation along the path, For the first The delay of the path, For the first Doppler frequency shift along the path This represents the total number of paths. For path indexing, For Dirichlet functions, For the initial reference delay parameter variable, This refers to the initial reference frequency shift parameter variable.

[0019] In one possible implementation, the establishment of the channel response function for satellite communication using satellite-to-ground statistical channel information further includes:

[0020] The channel response function is transformed to the time-delay Doppler domain, as shown in the following formula:

[0021] ;

[0022] in, For the channel response function, For the first between stars and Earth Channel attenuation along the path, For the first The delay of the path, For the first Doppler frequency shift along the path This represents the number of paths from the satellite to the terminal. For the number of paths index, For the first Transformation matrix of the path channel, The channel dimension is dimension.

[0023] In one possible implementation, the establishment of the channel response function for satellite communication using satellite-to-ground statistical channel information further includes:

[0024] Determined according to the following formula :

[0025] ;

[0026] in, This indicates the conjugate transpose. This represents the number of paths from the satellite to the terminal. for Point Fourier transform matrix, yes 3D identity matrix For the first The terminal's first Path channel conversion matrix, For the first The terminal's first The delay of the path is The circular matrix at time, For the first The terminal's first The frequency shift of the path is The diagonal matrix at time, The integer Doppler frequency shift index number. For fractional Doppler index number, For the terminal's serial number, This is the index for the number of paths.

[0027] In one possible implementation, determining the signal-to-noise ratio in the Doppler domain of the terminal delay based on the channel response function and the Doppler domain signal includes:

[0028] Satellite awaiting launch to terminal The time-delay Doppler domain signal vectorization formula is as follows:

[0029] ;

[0030] in, For the first The time-delay Doppler domain signal of each terminal, for The time-delayed Doppler domain plane of the dimension, For the first The transmitted signal of each terminal is a vector with dimension , is a vectorized representation.

[0031] In a possible implementation, the determining of the signal-to-noise ratio of the terminal in the delay-Doppler domain according to the channel response function and the Doppler domain signal further includes:

[0032] The received signal of the terminal is obtained according to the following formula:

[0033] ;

[0034] wherein, is a normalized noise in the delay-Doppler domain, is a received signal of the i th terminal, is a transmitted signal of the i th terminal, is a transmission channel matrix of the i th terminal signal, is a weight factor of the terminal, is a number of the terminal. In a possible implementation, the determining of the signal-to-noise ratio of the terminal in the delay-Doppler domain according to the channel response function and the Doppler domain signal further includes: The signal-to-noise ratio is obtained according to the following formula:

[0035]

[0036] ;

[0037] ;

[0038] wherein, is a total number of terminals, is a terminal index, is a target terminal index, denotes a trace function, is a channel strength of the terminal i added with a waveform shaping matrix, is a sum of channel strengths of all terminals except the terminal i added with a waveform shaping matrix, is a noise existing in the transmission of the i th terminal. In a possible implementation, the solving of the optimal weighting and the optimal rate of the terminal according to the signal-to-noise ratio and a preset signal constraint condition includes: The objective function is obtained according to the following formula:

[0039]

[0040] ​​​​​​​​​

[0041] ;

[0042] wherein, is a total shaping matrix, is a total number of terminals, is a terminal index, is a target terminal index, is a weight coefficient of a terminal , and are auxiliary variables, is a trace function, is a channel strength of a terminal to which a waveform shaping matrix is added, is a sum of channel strengths of all terminals except for a terminal to which a waveform shaping matrix is added, denotes a constant, is noise present in transmission of an terminal, is a waveform shaping matrix of an terminal, is a conjugate transpose form of a waveform shaping matrix of an terminal, denotes that a matrix is semi-positive definite denotes a shaping power limit, is a constant real number, is a transmission channel matrix of a signal of an terminal, is a conjugate transpose form of a transmission channel matrix of an terminal.

[0043] The application also provides an OTFS-based communication waveform adjustment system for implementing any of the communication waveform adjustment methods, comprising:

[0044] a signal definition module configured to define a time-delay Doppler domain signal to be transmitted;

[0045] a channel response function establishment module configured to establish a channel response function under satellite communication by using statistical channel information of the satellite;

[0046] a signal-to-noise ratio determination module configured to determine a signal-to-noise ratio of a terminal time-delay Doppler domain according to the channel response function and the Doppler domain signal;

[0047] a solving module configured to solve an optimal weighted sum and an optimal rate of the terminal according to the signal-to-noise ratio and a preset signal constraint condition.

[0048] The OTFS-based communication waveform adjustment method and system provided by the application have good adaptability to large Doppler frequency offset in a high-mobility scenario of satellite-ground communication, can fully utilize limited spectrum resources, and improve the communication rate of a multi-user communication system. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 A flowchart of the OTFS-based communication waveform adjustment method provided by the embodiment of the application is shown in

[0050] Figure 2 A principle diagram of OTFS signal processing provided by the embodiment of the application is shown in

[0051] Figure 3 A communication diagram provided by the embodiment of the application is shown in DETAILED DESCRIPTION

[0052] The embodiments of the application will be further described in detail below with reference to the accompanying drawings and embodiments. The detailed description and drawings of the following embodiments are used to exemplarily illustrate the principles of the application, but cannot be used to limit the scope of the application, that is, the application is not limited to the preferred embodiments described, and the scope of the application is defined by the claims.

[0053] In the description of the application, it should be noted that, unless otherwise specified, the meaning of "a plurality of" is two or more; the terms "first", "second", etc. are only used for description purposes, and cannot be understood as indicating or implying relative importance; the above terms in the application can be understood according to the specific meaning by the person skilled in the art.

[0054] Figure 1 A flowchart of the OTFS-based communication waveform adjustment method provided by the embodiment of the application is shown in Figure 1 A OTFS-based communication waveform adjustment method provided by the application includes:

[0055] Step S1, defining a time delay Doppler domain signal to be transmitted;

[0056] In one possible implementation, a low-orbit satellite is defined, and the orbit height is , and a set of ground terminal users .

[0057] The time delay Doppler domain signal to be transmitted is defined according to the following formula:

[0058] ;

[0059] ;

[0060] wherein, For time-delayed Doppler domain signals, For the time-delayed Doppler domain, For delay index, For Doppler indexing, The smallest resolvable unit interval in the Doppler domain. , for The time-delayed Doppler domain plane of the dimension, For the number of time-domain subcarriers, The number of samples in the time domain signal. The signal sampling time interval, The duration of an OTFS data frame. This refers to the signal bandwidth.

[0061] Step S2: Establish the channel response function for satellite communication using satellite-to-ground statistical channel information;

[0062] Satellite-to-ground statistical channel information typically includes channel fading coefficient, multipath delay, and Doppler shift, with typical examples including the TDL model.

[0063] In one possible implementation, the channel response function is established according to the following formula. :

[0064] ;

[0065] in, For the first between stars and Earth Channel attenuation along the path, For the first The delay of the path, For the first Doppler frequency shift along the path For path indexing, For Dirichlet functions, For the initial reference delay parameter variable, This refers to the initial reference frequency shift parameter variable.

[0066] In the actual transmission process, the defined time-delay Doppler domain signal will be... The time-delayed Doppler signal is converted to the time-frequency domain using the inverse Sinthysmometric Fourier transform (ISFFT), and then converted to the time-domain signal using the Heisenberg transform for transmission. After transmission through a channel with time delay and Doppler frequency shift characteristics, at the receiving end, the received time-domain signal is converted to the time-frequency domain using the Wegener transform, and then converted to the time-delayed Doppler domain using the Sinthysmometric Fourier transform (SFFT) to obtain the received time-delayed Doppler signal. The principle of OTFS signal processing is as follows: Figure 2 As shown.

[0067] The channel response function is converted to the delay-Doppler domain, and the formula is as follows:

[0068] ;

[0069] wherein, is a channel response function, is a channel attenuation of a path between a satellite and a terminal, is a delay of the path, is a Doppler shift of the path, is a number of paths from a satellite to a terminal, is a path index, is a transformation matrix of a path channel, indicates that the channel dimension is . In a possible implementation, the channel response function under satellite communication is established by using statistical channel information between a satellite and a terminal, and the method further includes: is determined according to the following formula:

[0070]

[0071] wherein, indicates a conjugate transpose, is a number of paths from a satellite to a terminal,

[0072] is a point Fourier transform matrix, is a dimension unit matrix,

[0073] is a transformation matrix of a path channel of a terminal, is a circulant matrix with a delay of a path of a terminal being , and is a diagonal matrix with a frequency shift of a path of a terminal being , wherein is an integer Doppler shift index number, is a fractional Doppler index number, is a number of terminals, is a path index. ; ; ; ; and

[0074] ;

[0075] ​​​​​​​​​in, For diagonal matrix functions, for of Power of 1 For cyclic matrix functions, The inverse Fourier transform unit. It is the imaginary unit.

[0076] Step S3: Determine the signal-to-noise ratio in the Doppler domain of the terminal delay based on the channel response function and the Doppler domain signal;

[0077] In one possible implementation, the time-delayed Doppler domain signal to be transmitted from the satellite to user q is vectorized, as shown in the following formula:

[0078] ;

[0079] in, For the first The time-delay Doppler domain signal of each terminal, for The time-delayed Doppler domain plane of the dimension, For the first The transmitted signal of each terminal For dimension The vector, It is a vectorized representation.

[0080] Define the time-delay Doppler domain beamforming vector .

[0081] Assuming each beam serves only one ground user, using a one-to-one mode, the actual satellite transmission to the terminal... The time-delayed Doppler domain signal is , .

[0082] The terminal is obtained according to the following formula. Received signal:

[0083] ;

[0084] in, For time-delayed Doppler domain normalized noise, , For the first The received signal of each terminal For the first The transmitted signal of each terminal For the first The transmission channel matrix of each terminal signal. For the terminal Weighting factors This is the terminal's number.

[0085] The signal-to-noise ratio is obtained according to the following formula :

[0086] ;

[0087] wherein, is the total number of terminals, is the terminal index, is the target terminal index, denotes a trace function, is the channel strength of the terminal with the waveform shaping matrix, is the sum of the channel strengths of all terminals except the terminal with the waveform shaping matrix, is the noise existing in the transmission of the terminal .

[0088] Step S4: The optimal weighted sum and optimal rate of the terminal are solved according to the signal-to-noise ratio and a preset signal constraint condition.

[0089] In a possible implementation, the optimization beamforming vector is solved by setting the target function as the maximum weighted sum rate:

[0090] ;

[0091] wherein, is the weight factor of the user .

[0092] Firstly, the Lagrange dual transformation is performed on the target function, and the fraction in the log function is converted:

[0093] ;

[0094] Then, the target function is still in a non-convex form, and the quadratic transformation method is used to introduce an auxiliary variable and process the third term of the target function:

[0095] ;

[0096] ;

[0097] The target function is updated as follows:

[0098] ;

[0099] Finally, three variables and constraints existing in the target function are observed, and by fixing and , and in turn, the optimal solution of the target function is obtained. , derivation, the optimal solution of the process:

[0100] ;

[0101] The objective function is obtained according to the following formula :

[0102] ;

[0103] Wherein, is the total shaping matrix, is the total number of terminals, is the terminal index, is the target terminal index, is the weight coefficient of the terminal , and are auxiliary variables, is the trace function, is the channel strength of the terminal plus the waveform shaping matrix, is the sum of the channel strengths of all terminals except the terminal plus the waveform shaping matrix, denotes a constant, is the noise existing in the transmission of the terminal , is the waveform shaping matrix of the terminal , is the conjugate transpose form of the waveform shaping matrix of the terminal , denotes that the matrix is semi-positive definite denotes the shaping power limit, is a constant real number, is the transmission channel matrix of the signal of the terminal , is the conjugate transpose form of the transmission channel matrix of the terminal .

[0104] By setting the iteration optimization condition and the convergence threshold of the objective function, the optimal weighted sum and the optimal rate of the terminal are solved.

[0105] The application also provides an OTFS-based communication waveform adjustment system for realizing the communication waveform adjustment method, comprising:

[0106] A signal definition module is configured to define a time delay Doppler domain signal to be transmitted.

[0107] A channel response function establishment module is configured to establish a channel response function under satellite communication by using statistical channel information of satellite-ground.

[0108] a signal-to-noise ratio determination module configured to determine a signal-to-noise ratio of the terminal in the delay-Doppler domain according to the channel response function and the Doppler domain signal;

[0109] a solution module configured to solve the optimal weighting and the optimal rate of the terminal according to the signal-to-noise ratio and a preset signal constraint condition.

[0110] The OTFS-based communication waveform adjustment method and system provided by the application consider the downlink transmission performance of a multi-beam satellite in ground communication, take the satellite transmitting end beam forming vector as an optimization variable, solve the optimization problem of maximizing the user weighted sum rate under the constraint of the total satellite transmitting power, realize the purpose of fully utilizing satellite resources and maximizing the system weighted sum rate, and improve the performance of the satellite-ground communication system.

[0111] The above merely illustrates the specific implementation of the application, but the protection scope of the application is not limited to this, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A method for adjusting an OTFS-based communication waveform, characterized in that, Comprising: defining a time-delay Doppler domain signal to be transmitted; establishing a channel response function under satellite communication by using statistical channel information between satellite and ground; determining a signal-to-noise ratio of a terminal in time-delay Doppler domain according to the channel response function and the Doppler domain signal; solving a maximum weighted sum rate of the terminal according to the signal-to-noise ratio and preset signal constraint conditions; the solving of the maximum weighted sum rate of the terminal according to the signal-to-noise ratio and preset signal constraint conditions comprises: The objective function is obtained according to the following equation : wherein is a signal-to-noise ratio, is a total shaping matrix, is a total number of terminals, is a terminal index, is a target terminal index, is a weight coefficient of a terminal , and are auxiliary variables, is a trace function, is a channel strength of a terminal to which a waveform shaping matrix is added, is a sum of channel strengths of all terminals except for a terminal to which a waveform shaping matrix is added, denotes a constant, is a noise present in a transmission of an nth terminal, is a waveform shaping matrix of an nth terminal, is a conjugate transpose form of a waveform shaping matrix of an nth terminal, denotes that a matrix is semi-positive definite denotes a shaping power limit, is a constant real number, is a transmission channel matrix of a signal of an nth terminal, is a conjugate transpose form of a transmission channel matrix of an nth terminal.

2. The communication waveform adjustment method according to claim 1, characterized by, the defining of the time-delay Doppler domain signal to be transmitted comprises: defining a time-delay Doppler domain signal to be transmitted according to the following formula: wherein, is a delay-Doppler domain signal, is a delay-Doppler domain range, is a delay index, is a Doppler index, is a Doppler domain minimum resolution unit interval, is is a delay-Doppler domain plane of dimension, is a number of time domain subcarriers, is a number of time domain signal samples, is a signal sample time interval.

3. The communication waveform adjustment method according to claim 1, characterized by, the establishing of the channel response function under satellite communication by using statistical channel information between satellite and ground comprises: The channel response function is established according to the following equation : wherein, is the channel attenuation of the i-th path between satellite and ground, is the delay of the i-th path, is the Doppler shift of the i-th path, is the total number of paths, is the path index, is the Dirac delta function, is the start reference delay parameter variable, is the start reference frequency shift parameter variable.​​​ 4. The communication waveform adjustment method according to claim 3, characterized by, the establishing of the channel response function under satellite communication by using statistical channel information between satellite and ground further comprises: converting the channel response function to time-delay Doppler domain, and the formula is as follows: wherein, a channel response function, is a channel attenuation for the th path, is a delay for the th path, is a Doppler shift for the th path, is a number of paths from the satellite to the terminal, is an index for the number of paths, is a transformation matrix for the th path channel, denotes a channel dimension of dimensions.

5. The communication waveform adjustment method according to claim 4, characterized by, the establishing of the channel response function under satellite communication by using statistical channel information between satellite and ground further comprises: The following formula is used to determine : in, This indicates the conjugate transpose. This represents the number of paths from the satellite to the terminal. for Point Fourier transform matrix, yes 3D identity matrix For the first The terminal's first Path channel conversion matrix, For the first The terminal's first The delay of the path is The circular matrix at time, For the first The frequency shift of the i-th path of each terminal is The diagonal matrix at time, The integer Doppler frequency shift index number. For fractional Doppler index number, For the terminal's serial number, This is the index for the number of paths.

6. The communication waveform adjustment method of claim 1, wherein the determining of the signal-to-noise ratio of the terminal in time-delay Doppler domain according to the channel response function and the Doppler domain signal comprises: Satellite to be launched to terminal of the time delay Doppler domain signal vectorization, as follows: wherein, is the time delay-Doppler domain signal of the th terminal, is the time delay-Doppler domain plane of dimension is the transmit signal of the th terminal, is a vector of dimension is the vectorized representation.​​ 7. The communication waveform adjustment method according to claim 6, characterized by, the determining of the signal-to-noise ratio of the terminal in time-delay Doppler domain according to the channel response function and the Doppler domain signal further comprises: The received signal of the terminal is obtained according to the following equation: ​ wherein is the normalized noise in the delay-Doppler domain, is the received signal of the th terminal, is the transmit signal of the th terminal, is the transmission channel matrix of the th terminal signal, is the weight factor of the terminal , and is the number of terminals.

8. The communication waveform adjustment method according to claim 7, characterized by, the determining of the signal-to-noise ratio of the terminal in time-delay Doppler domain according to the channel response function and the Doppler domain signal further comprises: The signal-to-noise ratio is obtained according to the following formula : wherein, is the total number of terminals, is the terminal index, is the target terminal index, denotes the trace function, is the channel strength of the terminal with the waveform shaping matrix, is the sum of the channel strengths of all terminals except the terminal with the waveform shaping matrix, is the noise present in the transmission of the terminal 9.A system for adjusting OTFS-based communication waveforms, configured to implement the method for adjusting communication waveforms according to any one of claims 1-8. Comprising: a signal defining module, configured to define a time-delay Doppler domain signal to be transmitted; a channel response function establishing module, configured to establish a channel response function under satellite communication by using statistical channel information between satellite and ground; a signal-to-noise ratio determining module, configured to determine a signal-to-noise ratio of a terminal in time-delay Doppler domain according to the channel response function and the Doppler domain signal; a solving module, configured to solve a maximum weighted sum rate of the terminal according to the signal-to-noise ratio and preset signal constraint conditions; the solving module is further configured to: The objective function is obtained according to the following equation : In the formula, For signal-to-noise ratio, For the total integer matrix, The total number of terminals, For terminal indexing, Index for the target terminal. For the terminal The weighting coefficients, and As an auxiliary variable, For trace function, To add a waveform shaping matrix to the terminal Channel strength, In addition to the terminal, a waveform shaping matrix is ​​added. The channel strength of all other terminals, Represents a constant. For the first The noise present in the transmission of the terminal is the noise of the first terminal. Waveform shaping matrix for each terminal, For the first The conjugate transpose of the waveform shaping matrix for each terminal. Represents a matrix as positive semidefinite Indicates shaping power limit. For constant real numbers, For the first The transmission channel matrix of each terminal signal. For the first The conjugate transpose of the transmission channel matrix of each terminal.

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