Sweep time-delay cross-correlation analog-digital hybrid multiple access method

Abstract

The invention designs an analog-digital hybrid multiple access method based on time scanning-time delay cross-correlation, and belongs to the field of wireless communication. The method comprises the following steps: deeply analyzing a bottom layer principle related to sliding, carrying out band-pass filtering (BPF) processing on a transmitting signal received by a receiving end, and generating a local generation signal by utilizing a multi-frequency signal formed by a limited number of cosine functions; the filtered receiving signal is multiplied by a local generation signal to realize bandwidth compression; the frequency of the multi-frequency signal is of a series of equal-amplitude Dirac comb-shaped structures, and the frequency spectrum interval is slightly smaller than the frequency spectrum interval of the sending signal; and performing low-pass filtering on the multi-frequency signal after bandwidth compression through a low-pass filter, removing distorted interference information, sampling the filtered signal, and obtaining a detection pulse and a sequence after matched filtering in a digital domain through digital-to-analog conversion. According to the scheme, the characteristic of bandwidth compression is reserved, and meanwhile the number of hardware circuits is minimized, so that low-cost and high-precision multi-link CIR estimation in an MISO scene is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wireless communication, in particular to a mixed analog-digital time-sweep-time delay correlation multiple access method. BACKGROUND

[0002] MISO system is an important architecture form of multi-antenna communication, and is widely used in various emerging scenarios such as cellular communication, Internet of vehicles, and unmanned aerial vehicle communication, due to its advantages in signal space diversity, beamforming, and anti-interference capability.

[0003] When the traditional channel estimation method is directly applied to the MISO system, it often faces the challenges of high estimation complexity, large training overhead, and difficulty in balancing sparsity and accuracy. STDCC is a special spectrum compression technology used to reduce the dependence of large bandwidth CIR estimation on ADC sampling rate. In the STDCC technology, the transmitter generates a probe signal composed of a bipolar PN sequence, and the receiver uses the same but slightly lower chip rate PN sequence than the transmitter in the analog domain to perform a sliding correlation operation, generating a time-expanded version of the CIR. Currently, the application and research of STDCC technology mainly focuses on the SISO scenario. However, in many practical applications, the MISO scenario is often involved, such as wireless positioning technology, which usually involves multiple base stations estimating the CIR to determine the location information. One intuitive method is to perform regular STDCC in time sequence to estimate the CIR of each link, which is called time division multiple access, but this method has obvious drawbacks, not only requiring time synchronization, but also significantly increasing the processing time. Another method is to use orthogonal sequences with good autocorrelation properties as the transmission sequence, and directly extend the regular STDCC to the MISO scenario, i.e., using code division multiple access. However, the regular STDCC is implemented in pure analog domain, and if it is directly extended, the number of analog circuits depends on the number of inputs of the MISO system, which not only leads to a significant increase in cost, but also makes the receiver more bulky and cumbersome.

[0004] The prior art disclosed in the publication No. CN108650006A describes a non-orthogonal multiple access method based on large-scale MIMO, which comprises the following steps: Step 1: determining the optimal demodulation sequence, Step 2: determining the received power of the user, Step 3: determining the optimal transmit power of the user, Step 4: determining the data frame structure: different users accessing the same base station synchronously transmit according to the same uplink frame structure, and the time slot length used by the user does not exceed the coherence time of the wireless channel; Step 5: pilot selection method: the user obtains the pilot in the following manner: each user independently selects the pilot used by the user from a given pilot set; Step 6: on the basis of Steps 4 and 5, multiple user terminals transmit signals to the base station with optimal transmit power, and after the base station receives the signals, the channel hardening capability of large-scale MIMO is used to estimate the composite channel of multiple users at the antenna end, and the serial interference cancellation technology is used to finally complete the recovery of all user signals. The overall system is large and cannot realize one-to-many multi-link communication work. SUMMARY

[0005] In view of the deficiencies of the prior art, a time-sweep-time delay cross-correlation analog-digital hybrid multiple access method is provided, which has simple steps and is convenient to use, and splits the STDCC process into two stages of analog domain bandwidth compression and digital domain channel impulse response (CIR) estimation. High-precision CIR estimation is realized and mutual interference between multiple links is avoided.

[0006] To achieve the above technical purpose, the present application discloses a time-sweep-time delay cross-correlation analog-digital hybrid multiple access method for multiple link CIR estimation in a multiple-input single-output (MISO) receiving end, wherein the transmitting signal received by the receiving end is first compressed in bandwidth in the analog domain, and then CIR estimation is performed in the digital domain after analog-digital conversion. While maintaining bandwidth compression, the number of analog circuits is maximally reduced. Specifically,

[0007] The transmitting signal received by the receiving end is first processed by a band-pass filter (BPF), and a local generated signal is generated by using a plurality of cosine functions. The filtered receiving signal is multiplied by the local generated signal to realize bandwidth compression. The frequencies of the multi-frequency signal are a series of equal-amplitude Dirac comb structures, and the spectral interval is slightly smaller than the spectral interval of the transmitting signal. The bandwidth-compressed multi-frequency signal is low-pass filtered by a low-pass filter to remove distorted interference information, and the filtered signal is sampled, and then a probe pulse and a matched filtered sequence are obtained in the digital domain through digital-analog conversion. To simplify the analysis, first only consider single-input single-output SISO scene under a single link, and then consider the expression of multi-link propagation, and then linearly superimpose the signals of each link to obtain the time-domain inflated committed information rate CIR under MISO.

[0008] For multi-link CIR estimation in the receiving end of the multiple-input single-output MISO scene, the transmitting signal received by the receiving end is first compressed in the analog domain, and then the CIR estimation is performed in the digital domain after analog-to-digital conversion. While maintaining bandwidth compression, the number of analog circuits is minimized. Specifically: The transmitting signal received by the receiving end is first processed by a band-pass filter BPF, and a local generated signal is generated by a multi-frequency signal composed of a limited number of cosine functions; the filtered received signal is multiplied by the local generated signal to realize bandwidth compression; the frequency of the multi-frequency signal is a series of equal-amplitude Dirac comb structures, and the spectral interval is slightly smaller than the spectral interval of the transmitting signal; the bandwidth compressed multi-frequency signal is low-pass filtered by a low-pass filter to remove distorted interference information, and the filtered signal is sampled, and then the detection pulse and the matched filtered sequence are obtained in the digital domain through digital-to-analog conversion; To simplify the analysis, first only consider single-input single-output SISO scene under a single link, and then consider the expression of multi-link propagation, and then linearly superimpose the signals of each link to obtain the time-domain inflated committed information rate CIR under MISO.

[0009] Further, the transmitting signal after band-pass filtering received by the receiving end is expressed as: , In the formula, subscript j represents the jth transmitting end in the MIMO scene, represents the transmitting signal generated at the transmitting end, represents a periodically repeated signal; The local generated signal generated by the multi-frequency signal composed of a limited number of cosine functions is expressed as: , In the formula, represents the number of cosine functions, represents the angular frequency of the jth cosine function, and the chip rate of the local generated signal is slightly smaller than the chip rate of the transmitting signal , , The transmitting signal is multiplied by the local generated signal to realize bandwidth compression by using the formula: The transmitting signal is calculated by using the formula: ​the Fourier transform of , , is the Dirac function, , denotes the m-th transmitted signal, with a chip rate of and a good autocorrelation, denotes the signal amplitude, denotes the period of the transmitted signal ; The Fourier transform of the locally generated signal is calculated using the formula: , , , denotes the number of cosine functions, denotes the angular frequency of the m-th cosine function, and is slightly smaller than ; ; The Fourier transform of the bandwidth-compressed signal is given by: When , a spectrally compressed version of and an interference component are generated; The spectrally compressed version is given by: , and the spectral spacing is changed from to ; The interference information is given by: .

[0010] Furthermore, the spectrally compressed version and the interference information are separated from the bandwidth-compressed signal: The bandwidth-compressed information is given by: , , denotes the interference component of the m-th link during the sliding process, denotes the time-domain dilated version of the transmitted signal , and are the inverse Fourier transforms of the spectrally compressed version and the interference information , respectively, and The relationship between is given by: , indicates compared with in time domain times expansion, i.e. the bandwidth is compressed times in frequency domain; using a low-pass filter to reduce the interference information, the filtered signal is represented as: , then the filtered signal is sampled at a sampling rate of to obtain the sampled signal: , wherein, denotes a sampling point, denotes a sampling time interval; approximates the oversampling version of .

[0011] Further, to eliminate the adverse effects of distortion on CIR estimation and ensure that the sliding correlation can generate a distortion-free signal , a low-pass filter is used to filter out the interference information part of the distortion , and the spectrum compression version is retained to improve the estimation accuracy of the CIR: The frequency domain response of the low-pass filter is solved as follows: , wherein, u(f) is a step function, is the main energy concentration interval of .

[0012] Further, in the digital domain, the process of obtaining the probe pulse is as follows: , wherein, denotes a complex conjugate, is the matched filtered version of the transmitted sequence input into the matched filter, since the transmitted signal is multiplied by the locally generated signal , the result is the time domain expansion version of , denotes the time domain expansion version of , denotes the sampled signal; The matched filter is represented as: , In the formula, For time-domain dilated version The pulse width, i.e. the duration, is used to obtain the sequence after digital domain matched filtering. for: , In the formula, Evenness implies the complex amplitude of the m-th path in the j-th link. We first considered only the SISO scenario, i.e., a single link, which is represented as: , Then, considering multipath propagation, we have: , Further linear superposition of the signals from each link yields the MISO scenario, where the received signal is a linear superposition of signals from each link, filtered and sampled, and then matched with the digital domain matched-filtered sequence. Perform correlation calculations to solve for the sliding correlation peak. : , Using sliding correlation peaks The transmitted sequences exhibit good autocorrelation and cross-correlation, yielding the following: , After the transmitted signal reaches the receiver through the channel, the received signal is filtered. express: , , The output of the sliding correlation is calculated using the following formula. : , Furthermore, we obtained The result is: , pass In the MISO scenario, the first CIR of link time-domain dilation; Among them, through the attenuation factor and latency Accurately estimate the first in the MISO scenario The CIR of a link time-domain dilation is expressed as: , Multipath delay Represented as: , In the formula, and respectively represent the sampling point of the peak value and the sampling point of the peak value; similarly, the attenuation factor is defined as the ratio of the peak value to the peak value.

[0013] A computer device comprises a processor and a memory, the processor is electrically connected with the memory, the memory is used for storing instructions and data, and the processor is used for executing the time-sweep-time delay cross-correlation analog-digital hybrid multiple access method.

[0014] Beneficial effects: the method splits the STDCC process into two stages of bandwidth compression in the analog domain and channel impulse response estimation in the digital domain. By preserving the characteristics of bandwidth compression while minimizing the number of hardware circuits, low-cost and high-precision multi-link CIR estimation in the MISO scenario is achieved, avoiding mutual interference between multiple links, effectively reducing the number of analog circuits, preserving the characteristics of bandwidth compression while minimizing the number of hardware circuits; the theoretical feasibility of the proposed scheme can be verified through formula derivation and simulation, and the key parameters affecting the performance are analyzed in depth to select the best parameters. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 The mixed multiple access structure schematic diagram involved in the time-sweep-time delay cross-correlation analog-digital hybrid multiple access method of the application; Figure 2 The equivalent system structure schematic diagram of the detection pulse involved in the time-sweep-time delay cross-correlation analog-digital hybrid multiple access method of the application; Figure 3 The bandwidth compression in the analog domain and the CIR estimation in the digital domain in the embodiment of the application; Figure 4 When and , the comparison between the compressed version and the interference information ; Figure 5 When and , the comparison between the spectrum compression version before and after compression and the compressed version ; Figure 6 The comparison between the sliding correlation output and the real CIR in the embodiment of the application; Figure 7 This is a schematic diagram of the dynamic range of the equivalent system of the scan-delay cross-correlation analog-digital hybrid multiple access method in this embodiment of the invention; Figure 8 This is a schematic diagram of the autocorrelation and cross-correlation of the Gold sequence in an embodiment of the present invention; Figure 9 This is a schematic diagram illustrating the influence of the root index of the ZC sequence on autocorrelation in an embodiment of the present invention; Figure 10 This is a schematic diagram of the autocorrelation and cross-correlation of the ZC sequence in an embodiment of the present invention. Detailed Implementation

[0016] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0017] This invention discloses a hybrid analog-digital multiple access method based on sweep-delay cross-correlation, which decomposes the sliding correlation process into two steps: the first step is bandwidth compression, denoted as "sliding"; the second step is CIR estimation, denoted as "correlation". The "sliding" step is performed in the analog domain, while the "correlation" step is implemented in the digital domain. From the principle of STDCC, it is desirable that the spectrum of the locally generated signal is a series of Dirac combs with spectral spacing slightly smaller than that of the transmitted signal. To achieve this goal, the proposed method uses a multi-frequency signal composed of a finite number of cosine signals as the locally generated signal, setting specific frequencies so that its spectrum is a series of equal-amplitude Dirac comb structures with spectral spacing slightly smaller than that of the transmitted signal. Bandwidth compression is achieved by multiplying the received signal with the locally generated signal. Subsequently, the resulting signal is low-pass filtered and sampled, and digital correlation is performed in the digital domain to obtain the time-dilated CIR. Then, a further step is performed on the time-dilated CIR. By scaling the data by a factor of 1, the CIR can be estimated.

[0018] like Figure 1 and Figure 2 As shown, the transmitted signal received by the receiver is first processed by a bandpass filter (BPF) and then a locally generated signal is generated using a multi-frequency signal composed of a finite number of cosine functions. Bandwidth compression is achieved by multiplying the filtered received signal with the locally generated signal; The frequency of the multi-frequency signal is a series of equal-amplitude Dirac comb structures, and the spectral spacing is slightly smaller than that of the transmitted signal. The bandwidth-compressed multi-frequency signal is low-pass filtered to remove distorted interference information, and the filtered signal is sampled. Then, the probe pulse and the matched-filtered sequence are obtained in the digital domain through digital-to-analog conversion. To simplify the analysis, we first consider a single link in a single-input single-output (SISO) scenario, then consider the expression of multi-link propagation, and then linearly superimpose the signals of each link to obtain the time-domain inflated committed information rate (CIR) in MISO.

[0019] where we assume that there are transmitters in total, and the signal transmitted by the th transmitter is denoted as: , , where denotes the length of the signal transmitted by the th transmitter, the chip rate of the transmitted sequence is , the orthogonal sequence with good autocorrelation is , denotes the signal amplitude, denotes the period of .

[0020] The locally generated signal is a multi-frequency signal composed of a finite number of cosine functions, denoted as: , where denotes the number of cosine functions, denotes the angular frequency of the th cosine function, and is slightly less than . Since the received signal is a superposition of delayed versions, where , it is not a loss of generality to analyze based on ; multiplying the transmitted signal by the locally generated signal , we can represent it as: , Now we will further analyze the characteristics of from the perspective of the frequency domain, the Fourier transform of is: , the Fourier transform of is: , the Fourier transform of is denoted as: , When ,​ One compressed version of this part is denoted as , whose expression is , Compared with , there is a compression effect of times in the frequency domain, and the amplitude is reduced by half. The remaining part is interpreted as the interference caused by the "sliding" process, denoted as , whose expression is , Figure 3 The schematic diagram of bandwidth compression in the analog domain and CIR estimation in the digital domain in the proposed scheme is given. The first step is "sliding", that is, and convolution generates two parts, where is the compressed version of the spectrum of , and the spectral interval is changed from to , is the interference component generated in the "sliding" process, which will be removed by filtering later.

[0021] Figure 4 When and , and spectrum, it can be seen that the energy of is mainly concentrated in the main lobe interval , therefore, the defined low-pass filter is used to filter out the distortion part and keep . Figure 5 When and , the comparison of before compression and after compression can be seen that is the compressed version of the spectrum of . and have the same envelope, and the amplitude of is half of . In addition, compared with , the bandwidth is compressed by 100 times, that is, the sliding factor .

[0022] Let and be the inverse Fourier transforms of and , Decomposed into two parts: , In the formula, Interpreted as the first during the sliding process Interference components of the link, yes The time-domain dilated version. and The relationship between them is represented as follows: , Compared to There is one in the time domain A multiplier of expansion, that is The bandwidth is compressed in the frequency domain. times, This represents the noisy, broadband distortion signal generated by the "sliding" process, achieved by applying a low-pass filter. To reduce The interference; the filtered signal is represented as: , Then to by The sampling rate is used to obtain the sampled signal: , In the formula, Indicates the sampling point. Indicates the sampling time interval. Approximate oversampling version .

[0023] In the number domain, let and The relevant operations are represented in the form of convolution as follows: , In the formula, Indicates complex conjugation. Known as a probe pulse, It is a sending sequence The matched-filtered version, due to the transmitted signal Multiply by the locally generated signal What we get is the time-domain dilated version. , It should be The time-domain dilated version of , therefore let the matched filter be: , In the formula, For time-domain dilated version the pulse width (duration) of the pulse, further, the sequence matched filtered in digital domain is: , wherein, ; further expressed as: , Figure 3 The second step "correlation" in the above equation is the generation process of . Firstly, the "sliding" generated is filtered and sampled, then the correlation operation is performed in digital domain and to obtain .

[0024] When the transmitted signal passes through the channel to the receiving end, the filtered signal at the receiving end is: , wherein, ; after sampling , the correlation operation is performed with the sequence in digital domain, expressed as: ), further, the result of is: , , It can be seen that can be regarded as the CIR of the first link time domain expansion in the SISO scenario.

[0025] The above is a simplified analysis, only considering the SISO scenario, i.e. a single link, and then extended to the MISO scenario. In the MISO scenario, the received signal is a linear superposition of signals from each link, and after filtering and sampling, the correlation operation is performed with , expressed as , whose expression is: , wherein, is called sliding correlation peak, due to the good autocorrelation and cross-correlation of the transmitted sequence, we get: , When the signal passes through the channel to the receiving end, the filtered signal at the receiving end is: , wherein, , after sampling , the correlation operation is performed with , expressed as: , In the formula, The output is referred to as sliding-dependent. Associative. and It can be further obtained The result is: , In the MISO scenario, the first CIR of link time-domain dilation.

[0026] Finally, to accurately estimate the CIR, i.e., the attenuation factor... and latency The concept of a reference peak will be introduced, defined as a digital domain sequence. The autocorrelation is expressed as: , Multipath delay It can be represented as: , In the formula, and They represent peak sampling points and The sampling point of the peak value. Similarly, the attenuation factor. Defined as Peak and The ratio of peak values. Figure 6 Give when At that time, the sliding correlation output of the proposed hybrid analog-digital multiple access design scheme Comparison with a real CIR. Clearly, the proposed multiple access system can accurately distinguish each link and identify each path.

[0027] The dynamic range of the sliding correlation describes the sliding correlation peak. The relationship between the main lobe and side lobes is a key indicator in CIR estimation, used to assess interference between multiple links and self-interference caused by the sliding process. However, the scan-time-delay cross-correlation analog-digital hybrid multiple access method splits the conventional STDCC into two parts, requiring a redefinition of the dynamic range of the system constituted by the proposed scan-time-delay cross-correlation analog-digital hybrid multiple access method, such as... Figure 7 As shown, The ratio of the main lobe peak value to the side lobe peak value. Furthermore, to characterize the overall dynamic range of the scan-delay cross-correlation analog-digital hybrid multiple access method of the present invention, the concept of average dynamic range will be introduced, defined as the average of the dynamic ranges of all links, expressed as: , wherein denotes the maximum amplitude of the main lobe, denotes the maximum amplitude of the side lobe. denotes the inverse Fourier transform of The expression of , The time resolution is inversely proportional to the bandwidth of the transmitted signal For the proposed design of hybrid analog-digital multiple access system, the time resolution is defined as: , The minimum delay that the proposed system can distinguish two multipath signals is given.

[0028] The proposed design of hybrid analog-digital multiple access system has an upper limit for the maximum resolvable multipath delay, i.e. the maximum time delay that can accurately identify the multipath in the channel, denoted as: , If the maximum delay spread of the channel exceeds , the residual paths in one probe period will interfere with the subsequent measurement. The STDCC-based CIR estimation expects the average dynamic range to be as large as possible, so that the estimated CIR is closer to the true value; the time resolution is as small as possible, so that more accurate multipath information can be obtained, and the maximum resolvable multipath delay is as large as possible, so as to avoid the interference of the residual paths in one probe period on the measurement of the next period. Among them, the bandwidth of the transmitted signal has an impact, but for the time resolution , it is expected that the bandwidth of the transmitted signal is as large as possible, and for the maximum resolvable multipath delay , it is expected that the bandwidth of the transmitted signal is as small as possible, and the two are mutually restrictive. By increasing the sequence length to improve the maximum resolvable multipath delay , the demand for the bandwidth of the transmitted signal is reduced, but the increase of the sequence length will bring an increase in the calculation time. Therefore, for the practical application of the proposed design of hybrid analog-digital multiple access system, the three key system parameters of the average dynamic range , the time resolution and the maximum resolvable multipath delay need to be considered comprehensively, so that the impulse response of the wireless channel in the MISO scenario can be more accurately estimated.

[0029] The transmission sequence of the multiple access design for STDCC not only needs to have good orthogonality to distinguish different links, but also needs to have good autocorrelation characteristics so that the CIR can be accurately estimated in the correlation operation in the digital domain. Based on this, the autocorrelation and cross-correlation of Gold sequences and ZC sequences are analyzed to prove that they can be used as the transmission sequence of the proposed method.

[0030] Gold sequences are a kind of pseudo-random sequences with excellent autocorrelation and cross-correlation characteristics, which are widely used in modern communication systems. Gold sequences are combined sequences generated by combining two m-sequences through a specific combination method. The emergence of Gold sequences solves the problem of mutual interference that may exist in traditional m-sequences in a multi-user environment. The generation method of Gold sequences is based on the following two steps: selecting two m-sequences with the same period but different feedback polynomials; combining the two m-sequences through an XOR operation.

[0031] Different initial states or feedback polynomials of m-sequences can generate different Gold sequences. In addition, Gold sequences have the following properties: (1) Good cross-correlation, Gold sequences have very small cross-correlation in a multi-user environment, which means that the interference between different users is minimal.

[0032] (2) Gold sequences have very good autocorrelation, and their autocorrelation function is close to the Dirac function.

[0033] (3) Simple generation method, the generation method of Gold sequences is based on the XOR operation of two m-sequences, which has lower complexity compared to other sequence generation methods.

[0034] As shown in Figure 8 , four groups of Gold sequences are selected, and the autocorrelation characteristics of each group of Gold sequences and the cross-correlation characteristics with other groups are compared. It can be seen that Gold sequences have excellent autocorrelation and cross-correlation characteristics, and their generation method is simple, which can be used as the transmission sequence of the proposed method.

[0035] ZC sequences are a kind of complex exponential sequences with good orthogonality and constant modulus characteristics, which are widely used in wireless communication, radar signal processing, spread spectrum communication and other fields. Its mathematical definition is as follows: , where is the length of the sequence, usually a prime number to avoid repetition. is the root index, which determines the characteristics of the sequence. ZC sequences have the following properties: (1) Constant mode property: The mode length of the ZC sequence is always equal to 1, which means that it does not introduce amplitude changes, making it suitable for signal modulation in wireless communication.

[0036] (2) Good autocorrelation characteristics: The autocorrelation function of the ZC sequence is approximately zero when shifted at non-zero values.

[0037] (3) Good cross-correlation: The cross-correlation between two ZC sequences with different root indices is very low, which makes different ZC sequences possible to distinguish multiple users or multiple signals.

[0038] Because the properties of the ZC sequence depend on the root index To achieve high accuracy in multi-link CIR estimation, i.e., to ensure the autocorrelation function of the transmitted sequence approximates the Dirac pulse, the best-correlation ZC sequences among the generated ZC sequences are selected as the transmitted sequences for the proposed method. For example, Figure 9 The impact of the root index of the ZC sequence on autocorrelation is shown. It can be seen that the choice of root index... At the specified value, the ZC sequence exhibits good autocorrelation. However, when other values ​​are chosen, the ZC sequence displays large sidelobes, indicating poor autocorrelation. These sidelobes negatively impact the accuracy of CIR estimation. Therefore, when selecting the transmission sequence for the proposed multiple access system, the root index should be chosen. The ZC sequences constructed should avoid selecting those with poor autocorrelation. Figure 10 (a), (b), (c), and (d) in the text give... At that time, by The autocorrelation and cross-correlation characteristics of the constructed ZC sequence are shown in (a) r=1, (b) r=511, (c) r=512, and (d) r=1022. It can be seen that the autocorrelation of the ZC sequence is close to that of the Dirac pulse, and the cross-correlation interference is very low. Therefore, the ZC sequence is another option for the transmission sequence of the multiple access design system proposed in this invention.

Claims

1. A hybrid analog-digital multiple access method with scan-time-delay cross-correlation, characterized in that, This method is used for multi-link CIR estimation in multi-input single-output (MISO) scenarios at the receiver. The transmitted signal received at the receiver is first bandwidth compressed in the analog domain, then converted from analog to digital and CIR estimated in the digital domain. This minimizes the number of analog circuits while maintaining bandwidth compression. Specifically: The received transmitted signal is first processed by a bandpass filter (BPF) to generate a locally generated signal using a multi-frequency signal composed of a finite number of cosine functions. The filtered received signal is multiplied by the locally generated signal to achieve bandwidth compression. The frequencies of the multi-frequency signal are a series of equal-amplitude Dirac comb structures, and the spectral spacing is slightly smaller than that of the transmitted signal. The bandwidth-compressed multi-frequency signal is then low-pass filtered to remove distorted interference information. The filtered signal is then sampled, and finally, a digital-to-analog converter is used to obtain the probe pulse and the matched-filtered sequence in the digital domain. To simplify the analysis, we first consider only a single link in the single-input single-output (SISO) scenario, then consider the expression of multi-link propagation, and finally linearly superimpose the signals of each link to obtain the committed information rate (CIR) of time-domain dilation under MISO.

2. The analog-digital hybrid multiple access method with scan-delay cross-correlation according to claim 1, characterized in that, The transmitted signal, after being received and bandpass filtered, is represented as follows: ， In the formula, the subscript j represents the j-th transmitter in the MIMO scenario. This indicates the transmission signal generated at the transmitting end. Indicates a periodically repeating signal; The locally generated signal generated by a multi-frequency signal composed of a finite number of cosine functions is represented as: ， In the formula, This indicates the number of cosine functions. Indicates the first The angular frequency of a cosine function, and the chip rate of the locally generated signal. Slightly less than the chip rate of the transmitted signal , Using the formula: , will send signal Multiply by the locally generated signal Achieve bandwidth compression; Using the formula: Calculate the transmitted signal Fourier transform , In the formula, For the Dirac function, , Indicates the first Each transmitter has a transmission length of m, and the chip rate of the transmitted signal is... Orthogonal sequences with good autocorrelation Indicates signal amplitude. Indicates the transmission signal The cycle; Using the formula: Calculate the locally generated signal Fourier transform of , In the formula, This indicates the number of cosine functions. Indicates the first The angular frequency of a cosine function, and Slightly smaller ; Bandwidth compressed signal The Fourier transform of it is expressed as: ,when At that time, generate Spectrum compression version and interfering components ; Spectrum compression version The expression is: Spectral spacing is It became ; Interference information The expression is: 。 3. The analog-digital hybrid multiple access method with scan-delay cross-correlation as described in claim 2, characterized in that, Separate the spectrally compressed version and interference information from the bandwidth-compressed signal: Information after bandwidth compression Represented as: , In the formula, Indicates the first step during the sliding process Interference components of the link, Indicates the transmission signal The time-domain dilated version, and These are the spectrum compression versions. and interference information Inverse Fourier transform, and The relationship between them is represented as follows: ， show Compared to In the time domain A multiplier of expansion, that is The bandwidth is compressed in the frequency domain. times; Using a low-pass filter reduce The interference information, the filtered signal is represented as: ， Then the filtered signal by The sampling rate is used to obtain the sampled signal: ， In the formula, Indicates the sampling point. Indicates the sampling time interval; Approximate oversampling version .

4. The analog-digital hybrid multiple access method with scan-delay cross-correlation according to claim 3, characterized in that, To eliminate the adverse effects of distortion on CIR estimation and ensure that sliding correlation can generate distortion-free signals Using a low-pass filter Filter out distorted interference information Preserve the spectrum compression version To improve the accuracy of CIR estimation: low-pass filter The process of solving the frequency domain response is as follows: ， Where u(f) is the step function, yes Most of the energy is concentrated in the region.

5. The analog-digital hybrid multiple access method with scan-delay cross-correlation according to claim 4, characterized in that, In the digital domain, the probe pulse is obtained. The process is as follows: ， In the formula, Indicates complex conjugation. It is the transmission sequence of the input matched filter. The matched-filtered version, due to the transmitted signal Multiply by the locally generated signal What we get is the time-domain dilated version. , express The time-domain dilated version, This represents the sampled signal; The matched filter is represented as: ， In the formula, For time-domain dilated version The pulse width, i.e. the duration, is used to obtain the sequence after digital domain matched filtering. for: ， In the formula, Evenness implies the complex amplitude of the m-th path in the j-th link. We first considered only the SISO scenario, i.e., a single link, which is represented as: ， Then, considering multipath propagation, we have: ， Further linear superposition of the signals from each link yields the MISO scenario, where the received signal is a linear superposition of signals from each link, filtered and sampled, and then matched with the digital domain matched-filtered sequence. Perform correlation calculations to solve for the sliding correlation peak. : ， Using sliding correlation peaks The transmitted sequences exhibit good autocorrelation and cross-correlation, yielding the following: ， After the transmitted signal reaches the receiver through the channel, the received signal is filtered. express: ， ， The output of the sliding correlation is calculated using the following formula. : ， Furthermore, we obtained The result is: ， pass In the MISO scenario, the first CIR of link time-domain dilation; Among them, through the attenuation factor and latency Accurately estimate the first in the MISO scenario The CIR of a link time-domain dilation is expressed as: ， Multipath delay Represented as: ， In the formula, and They represent peak sampling points and The sampling point of the peak; similarly, the attenuation factor. Defined as Peak and The ratio of peak values.

6. A computer device, characterized in that, It includes a processor and a memory, the processor being electrically connected to the memory, the memory being used to store instructions and data, and the processor being used to execute the analog-digital hybrid multiple access method according to any one of claims 1-5.

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