Signal processing method and system based on time domain cyclic time delay doppler shift

Abstract

The application relates to the technical field of wireless communication, and discloses a signal processing method and system based on time domain cyclic time delay Doppler shift, which comprises the following steps: obtaining a to-be-sent signal vector of a transmitting end antenna; performing time delay Doppler modulation on the to-be-sent signal vector to obtain a first time domain signal vector; performing time domain cyclic time delay Doppler shift on the first time domain signal vector to obtain a second time domain signal vector; adding a cyclic prefix to the second time domain signal vector to obtain a third time domain signal vector; and sending the third time domain signal vector to a double-fading wireless channel. The application provides a complete and ultra-low complexity scheme for obtaining transmitting diversity gain based on a time delay Doppler waveform communication system, which can not only obtain full transmitting diversity gain, but also has lower calculation complexity, saves communication resources, has good robustness, and has a wide application scenario.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, in particular to a signal processing method and system based on time domain cyclic delay Doppler shift. BACKGROUND

[0002] In a delay Doppler (DD) waveform system based on multiple-input multiple-output (MIMO) technology, the diversity gain of the system is a key indicator for the system to provide reliable communication services. The greater the diversity gain, the faster the system bit error rate decreases with the increase of the signal-to-noise ratio, and the better the communication performance. A commonly used method to increase the system diversity gain is to use MIMO technology. Both the transmit antenna diversity gain and the receive antenna diversity gain belong to spatial diversity.

[0003] In a MIMO-based communication system, it is relatively simple and direct to obtain receive antenna diversity, but it is very difficult to obtain transmit antenna diversity gain. How to design a low-complexity and efficient method to extract transmit antenna diversity gain is a problem to be solved in a multiple-input multiple-output delay Doppler waveform wireless communication system. SUMMARY

[0004] To solve the above technical problems, the present application provides a signal processing method and system based on time domain cyclic delay Doppler shift, which increases the equivalent number of channel paths to the original number of transmit antennas by performing different cyclic delays and Doppler shifts on time domain symbols in advance, thereby realizing transmit diversity gain. The present application not only has low computational complexity, but also has good gain effect.

[0005] In a first aspect, the present application provides a signal processing method based on time domain cyclic delay Doppler shift, which comprises:

[0006] obtaining a to-be-sent signal vector of a transmitting end antenna, performing delay Doppler modulation on the to-be-sent signal vector to obtain a first time domain signal vector;

[0007] performing time domain cyclic delay Doppler shift on the first time domain signal vector to obtain a second time domain signal vector, wherein the time domain cyclic delay Doppler shift comprises cyclic delay shift and cyclic Doppler shift;

[0008] adding a cyclic prefix to the second time domain signal vector to obtain a third time domain signal vector, and sending the third time domain signal vector to a double-fading wireless channel.

[0009] Further, the step of performing time domain cyclic delay Doppler shift on the first time domain signal vector to obtain a second time domain signal vector comprises:

[0010] Based on the number of shift steps, cyclic delay shift and cyclic Doppler shift are performed respectively to obtain the cyclic delay shift matrix and the cyclic Doppler shift matrix. The number of shift steps includes the number of delay shift steps and the number of Doppler shift steps.

[0011] Multiplying the cyclic delay shift matrix and the cyclic Doppler shift matrix yields the time-domain cyclic shift matrix;

[0012] Based on the time-domain cyclic shift matrix, the signal vector to be transmitted is subjected to time-domain cyclic delay Doppler shift to obtain a second time-domain signal vector.

[0013] Furthermore, the time-domain cyclic shift matrix is ​​represented by the following formula:

[0014]

[0015] In the formula, Indicates the number of delay shift steps. This represents the Doppler shift step, and N represents the number of quadrature amplitude modulation symbols that make up the vector of the signal to be transmitted. express The cyclic delay shift matrix of the step, express The cyclic Doppler shift matrix of the step, TD-CDDS represents the time-domain cyclic delay Doppler shift;

[0016] The second time-domain signal vector is represented by the following formula:

[0017]

[0018] In the formula, s zz Represents the first time-domain signal vector. Let represent the time-domain cyclic shift matrix, and t represent the t-th transmitting antenna.

[0019] Furthermore, after transmitting the third time-domain signal vector to the dual-fading wireless channel, the method further includes:

[0020] The fourth time-domain signal vector is obtained from the dual-fading wireless channel by the receiving antenna, and the cyclic prefix in the fourth time-domain signal vector is removed to obtain the fifth time-domain signal vector.

[0021] The fifth time-domain signal vector is demodulated using a time-delay Doppler method to obtain the modulation domain signal vector.

[0022] Furthermore, the fifth time-domain signal vector is represented by the following formula:

[0023]

[0024] where t represents the tth transmit antenna, r represents the rth receive antenna, N r represents the number of receive antennas, s zz represents a first time-domain signal vector, P represents the number of paths of a double-fading wireless channel, i represents the ith path, N represents the number of quadrature amplitude modulation (QAM) symbols constituting a to-be-transmitted signal vector, and respectively represent the equivalent fading coefficient, the equivalent Doppler, and the equivalent time delay between the rth receive antenna and the tth transmit antenna after the ith path is subjected to a cyclic time delay shift of steps and a cyclic Doppler shift of steps, represents a cyclic time delay shift matrix of steps, represents a cyclic Doppler shift matrix of steps, and w r represents a noise vector of the rth receive antenna.

[0025] Further, the time-domain Doppler-like modulation includes quadrature time-frequency-space modulation and affine frequency division multiplexing modulation.

[0026] Further, the size of the cyclic prefix is greater than or equal to the maximum time delay of the double-fading channel.

[0027] In a second aspect, the present application provides a signal processing system based on time-domain cyclic time delay Doppler shift, the system comprising:

[0028] a time delay Doppler modulation module configured to obtain a to-be-transmitted signal vector of a transmit antenna, and to perform time delay Doppler-like modulation on the to-be-transmitted signal vector to obtain a first time-domain signal vector;

[0029] a time delay Doppler shift module configured to perform time-domain cyclic time delay Doppler shift on the first time-domain signal vector to obtain a second time-domain signal vector, the time-domain cyclic time delay Doppler shift including cyclic time delay shift and cyclic Doppler shift;

[0030] a cyclic prefix adding module configured to add a cyclic prefix to the second time-domain signal vector to obtain a third time-domain signal vector, and to transmit the third time-domain signal vector to a double-fading wireless channel.

[0031] Further, the time delay Doppler shift module comprises:

[0032] a first matrix generating module configured to perform cyclic time delay shift and cyclic Doppler shift according to a shift step number to obtain a cyclic time delay shift matrix and a cyclic Doppler shift matrix, the shift step number including a time delay shift step number and a Doppler shift step number;

[0033] a second matrix generating module, configured to multiply the cyclic time delay shift matrix and the cyclic Doppler shift matrix to obtain a time-domain cyclic shift matrix;

[0034] a cyclic shift module, configured to perform time-domain cyclic time delay Doppler shift on the to-be-sent signal vector according to the time-domain cyclic shift matrix to obtain a second time-domain signal vector.

[0035] Further, the system further comprises:

[0036] a cyclic prefix removing module, configured to acquire a fourth time-domain signal vector from the double-fading wireless channel through a receiving-end antenna, remove a cyclic prefix in the fourth time-domain signal vector to obtain a fifth time-domain signal vector;

[0037] a time delay Doppler demodulating module, configured to perform time delay Doppler demodulation on the fifth time-domain signal vector to obtain a modulation-domain signal vector.

[0038] The application provides a signal processing method and system based on time-domain cyclic time delay Doppler shift. The method can increase the number of equivalent branches and improve the diversity order of the system. The application can be applied to all antenna systems based on time delay Doppler and has wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 is a single-input single-output time delay Doppler waveform communication system model schematic diagram;

[0040] Figure 2 is a flowchart of the signal processing method based on time-domain cyclic time delay Doppler shift in the embodiment of the application;

[0041] Figure 3 is a sending-end model schematic diagram of a multiple-input multiple-output time delay Doppler waveform communication system based on TD-CDDS provided by the embodiment of the application;

[0042] Figure 4 is a bit error rate comparison schematic diagram of an AFDM system under different antenna settings in a numerical simulation experiment;

[0043] Figure 5 is a structure schematic diagram of the signal processing system based on time-domain cyclic time delay Doppler shift in the embodiment of the application. DETAILED DESCRIPTION

[0044] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0045] In the field of wireless communication technology, the waveform on the time delay Doppler domain or the transform domain corresponding to the time delay Doppler domain is called a time delay Doppler waveform, and such a waveform has a strong anti-Doppler frequency shift capability and is the most potential candidate waveform for the sixth generation of mobile communication systems. Typical time delay Doppler waveforms include orthogonal time frequency space, affine frequency division multiplexing, etc. In a time delay Doppler waveform communication system, there are single-input single-output systems and multiple-input multiple-output systems, etc. The following will take a single-input single-output time delay Doppler waveform communication system as an example to illustrate this type of communication system.

[0046] Please refer to Figure 1 , where the subscript zz of all variables represents any kind of time delay Doppler waveform, such as orthogonal time frequency space (OTFS), affine frequency division multiplexing (AFDM), etc. It is assumed that x zz is a to-be-sent signal vector composed of N orthogonal amplitude modulation (QAM) symbols in the time delay Doppler modulation domain, and the size of each vector is N x 1. For OTFS, it corresponds to the time delay-Doppler domain, and AFDM corresponds to the discrete affine Fourier transform domain. At the transmitting end of the communication system, the time delay Doppler modulation is performed on x zz , i.e. OTFS corresponds to OTFS modulation, and AFDM corresponds to AFDM modulation, so as to transform to obtain a time domain signal vector s zz , the size of which is N x 1. Then, a cyclic prefix (CP) with a size equal to the maximum time delay of the channel is added to obtain a time domain signal vector with a cyclic prefix , which is then sent to a double-fading wireless channel through the transmitting end antenna; the time domain signal vector received by the receiving end antenna from the double-fading wireless channel is The CP is cut off from the vector to obtain a time domain signal vector d zz , the size of which is N x 1.

[0047] The double-fading wireless channel is modeled on the time delay Doppler domain to obtain:

[0048]

[0049] where P represents the double-fading wireless channel is composed of P paths, h i , τ i and v i represent the fading system, time delay and Doppler of the i-th path, respectively.

[0050] The relationship between the time-domain signal vectors without cyclic prefix at the transmitting end and the receiving end is:

[0051]

[0052] where H represents the equivalent time-domain channel matrix, H i represents the sub-time-domain channel matrix, where,

[0053]

[0054] Π N is a forward circular matrix, which has the function of simulating time delay, and its specific expression is:

[0055]

[0056] Δ N is a one-step frequency shift diagonal matrix, which has the function of simulating Doppler frequency shift, and its specific expression is:

[0057]

[0058] k i and l i represent the normalized Doppler frequency shift and time delay in the digital domain, which correspond to v i and τ i , respectively.

[0059] Finally, the d zz is subjected to time delay Doppler demodulation, so as to obtain the time delay Doppler modulation domain signal vector y zz , each vector in the vector has a size of N × 1, and w is a noise vector.

[0060] After the single-input single-output time delay Doppler waveform communication system is described, the multi-input multi-output system is easy to understand, which refers to a technical system using multiple antennas to transmit and receive signals in the field of wireless communication. Assuming that the multi-input multi-output time delay Doppler waveform communication system has N t transmitting end antennas and N r receiving end antennas, it is denoted as N t × N rIn a MIMO system, the channel between each pair of transmitting antenna and receiving antenna is only different in the fading coefficient of each path, and the number of paths, the time delay of paths and the Doppler of paths are all the same, so the diversity gain order of the system is the product of the number of paths P and the number of receiving antennas, and is irrelevant to the number of transmitting antennas N. t In a MIMO system, the channel between each pair of transmitting antenna and receiving antenna is only different in the fading coefficient of each path, and the number of paths, the time delay of paths and the Doppler of paths are all the same, so the diversity gain order of the system is the product of the number of paths P and the number of receiving antennas, and is irrelevant to the number of transmitting antennas N. r In a MIMO system, the channel between each pair of transmitting antenna and receiving antenna is only different in the fading coefficient of each path, and the number of paths, the time delay of paths and the Doppler of paths are all the same, so the diversity gain order of the system is the product of the number of paths P and the number of receiving antennas, and is irrelevant to the number of transmitting antennas N.

[0061] In order to further improve the reliability of the communication system and increase the diversity gain order, please refer to Figure 2 The first embodiment of the present application provides a signal processing method based on time-domain cyclic delay-Doppler shift, which comprises steps S10-S30:

[0062] In step S10, a to-be-sent signal vector of a transmitting antenna is obtained, and time delay-Doppler modulation is performed on the to-be-sent signal vector to obtain a first time-domain signal vector.

[0063] In step S20, cyclic delay shift and cyclic Doppler shift are performed on the first time-domain signal vector according to a preset step number to obtain a second time-domain signal vector.

[0064] In a time delay-Doppler waveform system based on a multiple-input multiple-output technology, the diversity gain of the system is a key index for the system to provide reliable communication services, and the greater the diversity gain, the faster the system bit error rate decreases with the increase of the signal-to-noise ratio, and the better the communication performance. According to the above introduction, it is very difficult to obtain the diversity gain of the transmitting antenna. In order to further improve the reliability of the communication system and increase the diversity gain order, the present application provides a time-domain cyclic delay-Doppler shift (TD-CDDS) method. The core idea of the present application is to perform time-domain Doppler shift on the time-domain signal in advance at the transmitting antenna and then send it to a double-fading wireless channel, so as to increase the equivalent number of paths between the transmitting end and the receiving end, thereby increasing the diversity gain order of the system. The specific steps are as follows:

[0065] In step S201, cyclic delay shift and cyclic Doppler shift are respectively performed according to a shift step number to obtain a cyclic delay shift matrix and a cyclic Doppler shift matrix, and the shift step number includes a time delay shift step number and a Doppler shift step number.

[0066] In step S202, a time-domain cyclic shift matrix is calculated according to the cyclic delay shift matrix and the cyclic Doppler shift matrix.

[0067] Step S203, according to the time domain cyclic shift matrix, time domain cyclic time delay Doppler shift is carried out to the to-be-sent signal vector, and a second time domain signal vector is obtained.

[0068] In the present application, the time domain cyclic time delay Doppler shift of the to-be-sent signal is realized through a time domain cyclic shift matrix. Please refer to Figure 3 , it is assumed that the time delay Doppler modulation is carried out to the to-be-sent signal vector of the tth (t=2, …, N t ) sending end antenna, and a time domain signal vector s zz is obtained. zz The time domain signal vector s is subjected to step 1 cyclic time delay shift and step 2 cyclic Doppler shift, and is recorded as step TD-CDDS, and a time domain signal vector s is obtained. The expression is as follows:

[0069]

[0070] It can be seen that through step 1 cyclic time delay shift and step 2 cyclic Doppler shift, a cyclic time delay shift matrix and a cyclic Doppler shift matrix are respectively generated. The two matrices are multiplied, and a time delay cyclic shift matrix is obtained. Through the time delay cyclic shift matrix , the time domain cyclic time delay Doppler shift of the to-be-sent signal vector can be realized, so as to obtain the time domain signal vector after the shift.

[0071] Step S30, a cyclic prefix is added to the second time domain signal vector, a third time domain signal vector is obtained, and the third time domain signal vector is sent to a double-fading wireless channel.

[0072] After the cyclic prefix is added to the time domain signal vector obtained through the TD-CDDS, it can be sent to the double-fading wireless channel. The receiving end antenna can obtain the time domain signal vector from the channel and remove the cyclic prefix according to the operation of the original system, and the time domain signal vector after the removal of the cyclic prefix is obtained, that is, formula (6) is substituted into formula (2), and the following formula is obtained:

[0073]

[0074] In the formula, s represents the TD-CDDS matrix, that is, the time delay cyclic shift matrix, s represents the component of the time domain signal vector received by the rth receiving end antenna and coming from the tth sending end antenna, wherein t=2, …, N ​

[0075]

[0076]

[0077]

[0078] is the fading coefficient of the ithpath between the rthreceive antenna and the tthtransmit antenna, and denote the equivalent fading coefficient, the equivalent Doppler and the equivalent delay of the ithpath between the rthreceive antenna and the tthtransmit antenna after step cyclic Doppler shift and step cyclic delay shift, respectively, is an exponential constant.

[0079] It can be seen from equation (7) that the step TD-CDDS on the time-domain signal vector in equation (5) is equivalent to that the P paths of the channel are simultaneously subjected to step cyclic delay shift and step cyclic Doppler shift, while the exponential constant attached to the equivalent fading coefficient does not change the amplitude of the original fading coefficient .

[0080] Since the symbol received by a receive antenna is the superposition of the symbols from all transmit antennas, the time-domain signal vector received by the rthreceive antenna can be expressed as:

[0081]

[0082] where w r is the noise vector of the rthreceive antenna.

[0083] Let PATH = {(k1, l1),..., (k P , l P )} be the set of time-domain Doppler parameter pairs of the original channel paths, then denotes the set of equivalent time-domain Doppler parameter pairs after step TD-CDDS on the tthtransmit antenna.

[0084]

[0085] Equation (8) is equivalent to that there are paths with different delays or different Dopplers, where |. | denotes the cardinality of the set, i.e., the number of elements, thus N t x N r is the diversity order of the system.

[0086] When the cardinality |PATH [ALL] | = N [ALL] P, the sets t PATH have no common elements, N t × N r diversity order of the system is N t PN r , that is, the diversity order obtained by using the TD-CDDS method provided by the application is N t times larger than the diversity order of the system before TD-CDDS, that is, full transmit diversity gain is obtained. Since the reflectors of the channel are sparse, the condition |PATH [ALL] | = N t P can be met in practical applications by adjusting the TD-CDDS step number of each antenna in advance through experience, so as to obtain full transmit diversity gain.

[0087] It can be seen that the technical solution provided by the application does not need to make any changes to the receiving end. The TD-CDDS matrix derived according to formula (7) is a sparse permutation matrix, that is, there is only one non-zero value in each row and each column, which is only related to the TD-CDDS step number and is irrelevant to the rapidly changing channel. Therefore, the TD-CDDS matrix only needs to be calculated once at the sending end with extremely low computational complexity and can be used all the time, which is simple to operate. Compared with the classical Alamouti transmit diversity method which needs at least two information symbol vectors time to achieve, TD-CDDS is completed within one information symbol vector time, and there is no limit to the number of transmit antennas, which is particularly suitable for high-mobility scenarios such as vehicle networks, unmanned aerial vehicle clusters, and space-air-ground integrated wireless communication systems with high reliability and low transmission delay.

[0088] The following verifies the performance of the above-mentioned signal processing method based on time-domain cyclic time delay Doppler shift in the AFDM system through numerical simulation, taking bit error rate (BER) as the evaluation standard for channel estimation accuracy. The number of paths between each pair of transmit and receive antennas is 2, the time-domain Doppler parameter pair of the two paths is [-1, 0] and [1, 0], the AFDM subcarrier spacing is Δf AFDN = 4 kHz, the number of subcarriers is N AFDN = 10, and the carrier frequency f cThe maximum mobile speed corresponding to 4 GHz fc is 1080 km per hour, and other main simulation parameters are shown in Table 1, wherein the maximum likelihood detector is the most commonly used optimal detector. The ratio of the time domain received data signal power to the noise power is denoted as SNR (signal-to-noise ratio).

[0089] System parameters Values Carrier frequency 4 GHz Subcarrier spacing 4 kHz Number of symbols (number of subcarriers) 10 Maximum Doppler shift 4 kHz Maximum moving speed 1,080 kmph Number of multipaths 2 Digital modulation scheme BPSK Detector Maximum likelihood detector

[0090] Table 1 System parameter setting

[0091] Attached Figure 4 The bit error rate of the AFDM system under different antenna settings is shown. For convenience of observation, auxiliary lines of diversity gain orders ρ = 2, ρ = 4 and ρ = 8 are provided. In a single-input single-output AFDM communication system, the diversity gain order is the multipath number 2; in a 2 × 1 AFDM communication system, the diversity gain order is 4, that is, the number of transmitting antennas 2 multiplied by the multipath number 2; in a 2 × 2 AFDM communication system, the diversity gain order is 8, that is, the number of transmitting antennas 2 multiplied by the multipath number 2 multiplied by the number of receiving antennas 2. That is, the TD-CDDS method provided by the application can significantly improve the transmit diversity gain, and has a lower bit error rate than the traditional method.

[0092] The signal processing method based on time domain cyclic time delay Doppler shift provided by the embodiment increases the equivalent branch number of the double-fading wireless channel to the original number of transmitting antennas, because the diversity order of the system using the time delay Doppler waveform is equal to the multipath number in the channel, so increasing the equivalent branch number by the method provided by the application can improve the diversity order of the system, that is, the transmit diversity gain is obtained. Moreover, only the time domain cyclic time delay Doppler shift needs to be added between the time delay Doppler modulation and the cyclic prefix addition at the transmitting end, and the receiving end is consistent with the original system operation and does not need additional changes. Therefore, the application can not only realize full transmit diversity gain, but also has low computational complexity and good gain effect, and can be used in all time delay Doppler-based communication systems, and has a very wide prospect in engineering.

[0093] Please refer to Figure 5 Based on the same inventive concept, the signal processing system based on time domain cyclic time delay Doppler shift provided by the second embodiment of the application comprises:

[0094] The time delay Doppler modulation module 10 is configured to obtain a to-be-sent signal vector of a transmitting antenna, perform time delay Doppler modulation on the to-be-sent signal vector, and obtain a first time domain signal vector.

[0095] a time delay Doppler shift module 20, configured to perform time domain cyclic time delay Doppler shift on the first time domain signal vector to obtain a second time domain signal vector, wherein the time domain cyclic time delay Doppler shift comprises cyclic time delay shift and cyclic Doppler shift;

[0096] a cyclic prefix adding module 30, configured to add a cyclic prefix to the second time domain signal vector to obtain a third time domain signal vector, and send the third time domain signal vector to the double-fading wireless channel.

[0097] The time delay Doppler shift module 10 comprises:

[0098] a first matrix generating module 101, configured to perform cyclic time delay shift and cyclic Doppler shift according to a shift step number to obtain a cyclic time delay shift matrix and a cyclic Doppler shift matrix, wherein the shift step number comprises a time delay shift step number and a Doppler shift step number;

[0099] a second matrix generating module 102, configured to multiply the cyclic time delay shift matrix and the cyclic Doppler shift matrix to obtain a time domain cyclic shift matrix;

[0100] a cyclic shift module 103, configured to perform time domain cyclic time delay Doppler shift on the to-be-sent signal vector according to the time domain cyclic shift matrix to obtain a second time domain signal vector.

[0101] Further, the system further comprises:

[0102] a cyclic prefix removing module 40, configured to obtain a fourth time domain signal vector from the double-fading wireless channel through a receiving end antenna, and remove a cyclic prefix in the fourth time domain signal vector to obtain a fifth time domain signal vector;

[0103] a time delay Doppler demodulation module 50, configured to perform time delay Doppler demodulation on the fifth time domain signal vector to obtain a modulation domain signal vector.

[0104] The technical features and technical effects of the signal processing system based on time domain cyclic time delay Doppler shift are the same as those of the method, and will not be repeated here.

[0105] In summary, the signal processing method and system based on time domain cyclic time delay Doppler shift proposed in the embodiments of the present application, the method obtains a to-be-sent signal vector of a transmitting end antenna, performs time delay Doppler modulation on the to-be-sent signal vector to obtain a first time domain signal vector, performs time domain cyclic time delay Doppler shift on the first time domain signal vector to obtain a second time domain signal vector, the time domain cyclic time delay Doppler shift includes cyclic time delay shift and cyclic Doppler shift, adds a cyclic prefix to the second time domain signal vector to obtain a third time domain signal vector, and sends the third time domain signal vector to a double-fading wireless channel. The present application proposes a complete and ultra-low complexity scheme for obtaining transmit diversity gain for a communication system based on time delay Doppler waveform, which not only can obtain full transmit diversity gain, but also has lower calculation complexity, saves communication resources, and can be used in all time delay Doppler waveform communication systems, including most 6G candidate waveforms, has good robustness and wide application scenarios.

[0106] Each of the embodiments in the specification is described in a progressive manner, and the same or similar parts of each embodiment can be referred to each other, and each embodiment mainly explains the difference from other embodiments. Especially, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the related parts can be referred to the part of the method embodiment. It should be noted that, the technical features of the above embodiments can be combined arbitrarily, in order to make the description simple, not all possible combinations of the technical features of the above embodiments are described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0107] The above-described embodiments only express several preferred embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be noted that, for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and replacements can be made, and these improvements and replacements should be considered as the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the protection scope of the claims.

Claims

1. A signal processing method based on time-domain cyclic time-delay Doppler shift, characterized in that, The method comprises the following steps: obtaining a to-be-sent signal vector of a sending-end antenna, performing time-delay Doppler modulation on the to-be-sent signal vector to obtain a first time-domain signal vector; performing time-domain cyclic time-delay Doppler shifting on the first time-domain signal vector to obtain a second time-domain signal vector, wherein the time-domain cyclic time-delay Doppler shifting comprises cyclic time-delay shifting and cyclic Doppler shifting; adding a cyclic prefix to the second time-domain signal vector to obtain a third time-domain signal vector, and sending the third time-domain signal vector to a double-fading wireless channel; wherein the step of performing time-domain cyclic time-delay Doppler shifting on the first time-domain signal vector to obtain a second time-domain signal vector comprises: respectively performing cyclic time-delay shifting and cyclic Doppler shifting according to a shifting step number to obtain a cyclic time-delay shifting matrix and a cyclic Doppler shifting matrix, wherein the shifting step number comprises a time-delay shifting step number and a Doppler shifting step number; the shifting step number is determined based on a preset condition, and an expression of the preset condition is: In the formula, represents the union set of the time-domain Doppler parameter pair set of the original channel multipath and the equivalent time-domain Doppler parameter pair set after the cyclic time delay shift and the cyclic Doppler shift of the transmitting end antenna, |. | represents the cardinality of the set, represents the number of transmitting end antennas, and P represents the number of multipaths of the double-fading wireless channel. multiplying the cyclic time-delay shifting matrix and the cyclic Doppler shifting matrix to obtain a time-domain cyclic shifting matrix; performing time-domain cyclic time-delay Doppler shifting on the to-be-sent signal vector according to the time-domain cyclic shifting matrix to obtain a second time-domain signal vector.

2. The time-domain cyclic time-delay Doppler shift based signal processing method according to claim 1, wherein, The time-domain cyclic shifting matrix is expressed by the following formula: In the formula, denotes the time delay shift step number, denotes the Doppler shift step number, N denotes the number of quadrature amplitude modulation symbols constituting a signal vector to be transmitted, denotes a cyclic time delay shift matrix of the step, denotes a cyclic Doppler shift matrix of the step, and TD-CDDS denotes a time domain cyclic time delay Doppler shift. The second time-domain signal vector is expressed by the following formula: wherein denotes a first time-domain signal vector, denotes a time-domain circulant shift matrix, t denotes the tthtransmitting antenna.

3. The time-domain cyclic time-delay Doppler shift based signal processing method according to claim 2, wherein, after the step of sending the third time-domain signal vector to the double-fading wireless channel, the method further comprises the following steps: obtaining a fourth time-domain signal vector from the double-fading wireless channel through a receiving-end antenna, and removing the cyclic prefix in the fourth time-domain signal vector to obtain a fifth time-domain signal vector; performing time-delay Doppler demodulation on the fifth time-domain signal vector to obtain a modulation-domain signal vector.

4. The time-domain cyclic time-delay Doppler shift based signal processing method according to claim 3, wherein, The fifth time-domain signal vector is expressed by the following formula: where t denotes the tth transmit antenna, r denotes the rth receive antenna, denotes the number of receive antennas, denotes the first time-domain signal vector, P denotes the number of paths of the double-fading wireless channel, i denotes the ith path, and N denotes the number of quadrature amplitude modulation (QAM) symbols constituting the transmitted signal vector, and denote the equivalent fading coefficient, the equivalent Doppler, and the equivalent delay, respectively, of the ith path between the rth receive antenna and the tth transmit antenna after the ith cyclic Doppler shift and the ith cyclic delay shift, denotes the ith cyclic delay shift matrix, denotes the ith cyclic delay shift matrix, denotes the ith cyclic delay shift matrix, denotes the ith cyclic delay shift matrix, denotes the ith cyclic delay shift matrix, denotes the ith cyclic delay shift matrix, denotes the noise vector of the rth receive antenna.​ 5. The time-domain cyclic time-delay Doppler shift based signal processing method of claim 1, wherein, The time-delay Doppler modulation comprises orthogonal time-frequency-space modulation and affine frequency division multiplexing modulation.

6. The time-domain cyclic time-delay Doppler shift based signal processing method of claim 1, wherein, The length of the cyclic prefix is greater than or equal to the maximum time delay of the double-fading wireless channel.

7. A signal processing system based on time domain cyclic time delay Doppler shifting, characterized by, The method comprises the following steps: a time-delay Doppler modulation module, configured to obtain a to-be-sent signal vector of a sending-end antenna, and perform time-delay Doppler modulation on the to-be-sent signal vector to obtain a first time-domain signal vector; a time-delay Doppler shifting module, configured to perform time-domain cyclic time-delay Doppler shifting on the first time-domain signal vector to obtain a second time-domain signal vector, wherein the time-domain cyclic time-delay Doppler shifting comprises cyclic time-delay shifting and cyclic Doppler shifting; a cyclic prefix adding module, configured to add a cyclic prefix to the second time-domain signal vector to obtain a third time-domain signal vector, and send the third time-domain signal vector to a double-fading wireless channel; the time-delay Doppler shifting module comprises: a first matrix generating module, configured to respectively perform cyclic time-delay shifting and cyclic Doppler shifting according to a shifting step number to obtain a cyclic time-delay shifting matrix and a cyclic Doppler shifting matrix, wherein the shifting step number comprises a time-delay shifting step number and a Doppler shifting step number; the shifting step number is determined based on a preset condition, and an expression of the preset condition is: In the formula, represents the union set of the time-domain Doppler parameter pair set of the original channel multipath and the equivalent time-domain Doppler parameter pair set after the cyclic time delay shift and the cyclic Doppler shift of the transmitting end antenna, |. | represents the cardinality of the set, represents the number of transmitting end antennas, and P represents the number of multipaths of the double-fading wireless channel. a second matrix generating module, configured to multiply the cyclic time delay shift matrix and the cyclic Doppler shift matrix to obtain a time-domain cyclic shift matrix; a cyclic shift module, configured to perform time-domain cyclic time delay Doppler shift on the to-be-sent signal vector according to the time-domain cyclic shift matrix to obtain a second time-domain signal vector.

8. The time-domain cyclic time-delay Doppler shift based signal processing system of claim 7, wherein, The system further comprises: a cyclic prefix removing module, configured to acquire a fourth time-domain signal vector from the double-fading wireless channel through a receiving-end antenna, and remove a cyclic prefix in the fourth time-domain signal vector to obtain a fifth time-domain signal vector; a time delay Doppler demodulating module, configured to perform time delay Doppler demodulation on the fifth time-domain signal vector to obtain a modulation-domain signal vector.

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