A signal detection method based on a dual pilot block structure

Abstract

This invention discloses a signal detection method based on a dual-pilot block structure, comprising: (1) generating a baseband transmission signal with a dual-pilot block structure, generating a transmission data block and two pilot blocks, and uniformly inserting the dual-pilot block structure into the data block to obtain the dual-pilot block structure; (2) generating a passband transmission signal; (3) using a single-scale multipath lag channel model with a time-varying Doppler scaling factor; (4) representing the received signal after passing through the single-scale multipath lag channel; and (5) passing the received signal through a repetitive window matched filter. This invention achieves successful detection of the received signal under the influence of a single-scale multipath lag channel with a time-varying Doppler scaling factor. By treating the dual-pilot structure as part of the detection sequence, the length of the detection sequence is significantly increased while maintaining bandwidth efficiency, thereby improving signal detection performance.

Description

Technical Field

[0001] This invention relates to the field of signal detection in communication systems under complex scenarios, and in particular to a signal detection method based on a dual pilot block structure. Background Technology

[0002] In communication systems, signal detection technology is a prerequisite for successful communication, especially in complex scenarios such as underwater acoustic communication. Recently, various modulation techniques have been widely applied to communication technologies, such as Orthogonal Frequency Division Multiplexing (OFDM) and Orthogonal Chirp Division Multiplexing (OCDM).

[0003] For signal detection methods commonly used in complex scenarios such as underwater acoustic communication, domestic application number 202110982064.6 discloses "A Real-time Detection and Extraction Method for Underwater Acoustic Communication Signals under Low Signal-to-Noise Ratio," which improves the spectral subtraction algorithm and performs spectral subtraction and noise reduction processing on the underwater acoustic communication signal, designing a real-time detection and extraction method for underwater acoustic communication signals under low signal-to-noise ratio. Domestic application number 202310681294.8 discloses "A Compression Method and Device for Underwater Acoustic Communication Preamble Signal Detection Model," which utilizes a lightweight convolutional neural network to design a high-performance, low-computational-load, and low-parameter-load underwater acoustic communication preamble signal detection method.

[0004] While the above methods have explored signal detection methods in complex scenarios such as underwater acoustic communication to some extent, they are still mainly limited to the design using preambles. In environments with limited energy, it is difficult to improve detection performance by increasing the detection sequence length, thus limiting the signal detection effect.

[0005] Currently, the commonly used signal detection method is to use preambles for detection. However, considering more complex communication environments, such as underwater acoustic communication, there are challenges such as long channel tail time and limited energy resources. Increasing the preamble length can only improve the detection performance to a limited extent.

[0006] Therefore, those skilled in the art are dedicated to developing a signal detection method that can both increase the detection sequence length and improve detection performance for complex scenarios. Summary of the Invention

[0007] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is how to increase the detection sequence length.

[0008] To achieve the above objectives, the present invention provides a signal detection method based on a dual-pilot block structure, characterized in that it includes:

[0009] (1) Generate a baseband transmission signal with a dual pilot block structure;

[0010] 1a, Generate and send data blocks;

[0011] 1b, Generate two pilot blocks;

[0012] 1c, The pilot block structure is evenly inserted into the data block to obtain a dual pilot block structure;

[0013] (2) Generate a passband transmission signal;

[0014] (3) Through a single-scale multipath hysteresis channel model with a time-varying Doppler scaling factor;

[0015] (4) Represents the received signal after passing through a single-scale multipath lag channel;

[0016] (5) Pass the received signal through a repetitive window matched filter.

[0017] Existing signal detection methods mainly focus on the design of preambles, without considering the use of more known transmitted information to design corresponding algorithms to improve signal detection performance.

[0018] This invention proposes a signal detection method based on a dual-pilot block structure. A dual-pilot block transmission structure is designed that can be applied to signals using different modulation techniques. The repeated pilots between each data block are regarded as part of the detection sequence, which effectively increases the detection sequence length.

[0019] The detection method designed in this invention achieves successful detection of received signals under the influence of a single-scale multipath hysteresis channel with a time-varying Doppler scaling factor. By treating the dual-pilot structure as part of the detection sequence, the length of the detection sequence is significantly increased while maintaining bandwidth efficiency, thereby improving signal detection performance.

[0020] In a preferred embodiment of the present invention, step 1a, generating the data block, uses a complex number table to generate a data vector and uses quadrature amplitude modulation to generate the data block. The data vector d(i) is modulated by a modulation matrix of size N×N. It depends on the modulation technique used in the signal;

[0021] The two pilot blocks mentioned in step 1b are respectively defined as follows: and Where p is the pilot vector and L is the length. It is an L×L inverse discrete Fresnel transformation matrix.

[0022] In another preferred embodiment of the present invention, in step 1c, pilot blocks of length L are inserted before and after the data block. The i-th transmission block of the transmission signal having a dual pilot block structure is composed of the following parts. The length of the entire transmission block is M = 2L + N;

[0023] In step 1c, there are two consecutive pilot blocks between the data blocks, which constitutes a double pilot block, denoted as... The length is 2L, and its nth element is represented as [s rep ] n ;

[0024] In step 1c, the baseband transmission sequence is represented as follows: The nth element of the transmission sequence is denoted as s[n].

[0025] The signal detection method proposed in this invention utilizes the repetition pattern of dual pilot blocks between data blocks, establishes multiple detection windows with fixed intervals, generates multiple correlation peaks using cross-correlation operations, and then realizes signal detection using a repetition window detector.

[0026] In another preferred embodiment of the present invention, the passband transmission signal in step (2) is described as follows: Where f c It is the carrier frequency.

[0027] In another preferred embodiment of the present invention, in step (3), considering the impact of Doppler spread, the transmitted signal is passed through a single-scale multipath lag channel model. In the mobile scenario, considering the change in the relative speed of the transmitting and receiving ends, the Doppler scaling factor is time-varying.

[0028] In another preferred embodiment of the present invention, in step (4), at the receiving end, the OCDM received signal is represented as

[0029]

[0030] Where * denotes the convolution operation, and the passband contains additive white Gaussian noise. The mean is zero and the variance is σ. 2 .

[0031] In another preferred embodiment of the present invention, step (5) of passing the received signal through a repetitive window matched filter includes:

[0032] 5a, Model the detector as a binary hypothesis test;

[0033] 5b, Sample the bandpass received signal;

[0034] 5c, Obtain the discrete form of the local template;

[0035] Perform a cross-correlation operation on 5d to obtain the filter output;

[0036] 5e, using a repeated window matched filter detector to detect multiple peaks;

[0037] 5f, perform a binary hypothesis test on the output of the repetitive window matched filter detector.

[0038] Considering the limited energy bandwidth resources in underwater and other scenarios, excessively long detection sequences reduce the energy available for communication, thus lowering communication accuracy. This invention utilizes a dual-pilot block structure for detection. This structure serves as the training sequence within the information block during communication, used for measuring various channel parameters and is an essential part of communication transmission. Applying this structure to signal detection does not add redundant information.

[0039] At the transmitting end, the spacing of the dual pilot block structure is known. Considering the increasing influence of Doppler variations on the signal in the communication channel, a repeating window detector is designed, which can successfully detect signals using the dual pilot block structure. The repeating window matched filter detector designed in this invention can successfully cover the problem of correlation peak position changes caused by Doppler and other influences, achieving successful signal detection while ensuring bandwidth efficiency. Simultaneously, this design can shorten signal transmission time and improve energy utilization.

[0040] In another preferred embodiment of the invention, in step 5a, the detector is modeled as a binary hypothesis test. This indicates that only noise exists. The model, which assumes the presence of both transmitted signal and noise, can be represented as follows:

[0041]

[0042] In another preferred embodiment of the present invention, in step 5e, the repeated window matched filter detector is designed with a fixed interval of repeated search windows to detect each generated peak value, and the output of the repeated window matched filter detector is expressed as follows:

[0043]

[0044] subset Include Let α represent the floor function. max It is the maximum absolute value of the Doppler scaling factor.

[0045] In another preferred embodiment of the present invention, in step 5f, a threshold discrimination method is used to perform a binary hypothesis test on the output of the repeated window matched filter detector, expressed as follows:

[0046]

[0047] Where Γ RMMF It is the discrimination threshold, determined by r RWMF [n] in The statistical information under the circumstances and a false alarm probability are determined.

[0048] Most existing signal detection methods use preambles for signal detection. However, considering the variety and duration of interference in complex scenarios such as underwater environments, if the detection sequence is contaminated by noise, the signal cannot be detected. Existing methods have weak anti-interference capabilities.

[0049] The signal detector based on a dual-pilot block structure used in this invention has a detection sequence evenly distributed throughout the transmitted signal, making it less susceptible to noise interference during signal reception and thus exhibiting strong anti-interference capabilities. For the dual-pilot block structure, a repeating window is used to simultaneously search for multiple peaks. Even when noise interference causes some peaks to be missing, the repeating window can detect the remaining peaks, thereby increasing the probability of successful signal detection. The signal detection method based on the dual-pilot block structure designed in this invention can cope with preamble detection failures caused by noise interference, achieving successful signal detection even under continuous noise interference.

[0050] Technical effect

[0051] (1) This invention achieves successful detection of signals in complex scenarios such as underwater. By treating the dual pilot structure as part of the detection sequence, the length of the detection sequence is greatly increased while maintaining bandwidth efficiency, thereby improving signal detection performance.

[0052] (2) The repetitive window matched filter detector in this invention can successfully cover the problem of correlation peak position changes caused by Doppler and other influences. While ensuring bandwidth efficiency, it can achieve successful signal detection. At the same time, it can shorten the signal transmission time and improve energy utilization.

[0053] (3) The present invention can cope with the failure of preamble detection caused by noise interference and achieve successful signal detection under continuous noise interference.

[0054] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0055] Figure 1 This is a specific implementation flow of a signal detection method based on a dual pilot block structure, which is a preferred embodiment of the present invention. Detailed Implementation

[0056] The following description, with reference to the accompanying drawings, illustrates several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0057] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0058] This invention provides a signal detection method based on a dual-pilot block structure. Considering the limited resources in complex underwater environments, the signal detection range is no longer limited to the preamble, thus improving the system's anti-interference performance. The dual-pilot block structure designed in this invention treats the repeated pilots between each data block as part of the detection sequence, increasing the number of detectable samples. This invention utilizes a repeating window detector to achieve signal detection based on the dual-pilot block structure. The design of the repeating window considers the impact of underwater features such as Doppler on the received signal, improving the detection effect. The dual-pilot block structure used in this invention can assist in the measurement of various underwater channel parameters during subsequent signal demodulation, reducing redundant information. The signal detection method proposed in this invention is compatible with various common signal modulation techniques and has versatility.

[0059] This invention allows for adjustment of the repeat window length as needed, enabling signal detection with varying durations to meet the demands of different communication scenarios. For the proposed detection method, increasing the detection duration increases the number of detectable data samples and improves detection performance.

[0060] This invention mainly considers a signal detection method in complex communication environments. This structure has more obvious advantages in underwater acoustic communication scenarios. As a representative application scenario, it can also achieve detection in other communication environments and has advantages.

[0061] like Figure 1 The following is a detailed implementation flow of a signal detection method based on a dual-pilot block structure provided by the present invention, with the following steps:

[0062] (1) Step 1: Generate a baseband transmission signal with a dual pilot block structure.

[0063] 1a, Generate the data block to be sent.

[0064] Data vectors are typically generated using a complex number table and modulated using methods such as quadrature amplitude modulation, denoted as d(i) = [d(iN), d(iN+1), ..., d(iN+N-1)].T The data vector d(i) is modulated by a modulation matrix of size N×N to generate a data block. The modulation matrix Depending on the modulation technique used for the signal, when using orthogonal frequency division multiplexing... Represents the inverse discrete Fourier transform matrix. When using orthogonal chirping multiplexing with N being an even number Denotes the inverse discrete Fresnel transformation matrix.

[0065] 1b, generate two pilot blocks.

[0066] The pilot vector is defined as p = [a, 0, ..., 0]. T A fixed energy P is allocated. Two pilot blocks of length L are defined as follows: and in It is an L×L inverse discrete Fresnel transform matrix. This dual-pilot block structure consists of two orthogonally chirped multiplexed subcarriers, which can also be regarded as chirp signals.

[0067] 1c, The pilot block structure is evenly inserted into the data block to obtain a dual pilot block structure.

[0068] By inserting pilot blocks of length L before and after the data block, the i-th transmission block of the transmitted signal with a dual-pilot block structure can be composed of the following three parts. The length of the entire transmission block is M = 2L + N. There are two consecutive pilot blocks between data blocks, called a double pilot block, denoted as... The length is 2L, and its nth element is represented as [s rep ] n The baseband transmission sequence is represented as follows: The nth element of the transmitted sequence is denoted as s[n].

[0069] (2) Step 2: Generate passband transmission signal

[0070] The aforementioned baseband signal is used to generate a continuous signal using a pulse shaper, denoted as follows:

[0071]

[0072] Where ρ(t) represents the pulse shaper, and the sampling period is set to T. s ≈1 / B, where B is the transmission signal bandwidth. The corresponding passband transmission signal is described as follows: Where f c It is the carrier frequency.

[0073] (3) Step 3: Use a single-scale multipath lag channel model with a time-varying Doppler scaling factor.

[0074] Considering the impact of Doppler spread, the transmitted signal is passed through a single-scale multipath lag channel model. In a mobile scenario, considering the change in the relative velocity between the transmitter and receiver, the Doppler scaling factor becomes time-varying. The single-scale multipath lag channel model can be expressed as follows:

[0075]

[0076] Where τ p and A p These are the propagation delay and time-varying amplitude of the p-th path, respectively. When considering block processing of the received signal, the amplitude A within the unified transmission block is... p It can be considered constant. There are P paths in total, and the time-varying Doppler scaling factor α(t) causes the signal waveform to expand or compress.

[0077] (4) Step 4: This represents the received signal after passing through a single-scale multipath lag channel.

[0078] At the receiving end, the OCDM received signal is represented as:

[0079]

[0080] Where * denotes the convolution operation, and the passband contains additive white Gaussian noise. The mean is zero and the variance is σ. 2 .

[0081] (5) Step 5: Pass the received signal through a repetitive window matched filter.

[0082] 5a, model the detector as a binary hypothesis test.

[0083] Model the detector as a binary hypothesis test. This indicates that only noise exists. The model, which assumes the presence of both transmitted signal and noise, can be represented as follows:

[0084]

[0085] 5b, Sample the bandpass received signal.

[0086] For bandpass received signals, use the sampling frequency T at the transmitting end. s Sampling is performed, represented as

[0087]

[0088] 5c, obtain the discrete form of the local template.

[0089] The local template is a dual-pilot block in the middle of the data block, and its discrete signals also use T. s Sampling is performed at the sampling frequency, denoted as...

[0090]

[0091] Perform a cross-correlation operation on 5d to obtain the filter output.

[0092] The discrete received signal is cross-correlated with a local template to generate a correlation peak, and the output of its normalized matched filter is...

[0093]

[0094] The normalized matched filter output has a value range between 0 and 1. The normalized matched filter output obtained by cross-correlation between the signal with the dual pilot block structure and the local template contains K+1 peaks.

[0095] 5e, using a repeating window matched filter detector to detect multiple peaks.

[0096] In a repetitive window matched filter detector, a repetitive search window with a fixed interval is designed to detect each generated peak. The output of the repetitive window matched filter detector is expressed as follows:

[0097]

[0098] subset Include Let α represent the floor function. max It is the maximum absolute value of the Doppler scaling factor. In the above formula, p... i With Doppler scaling factor and maximum channel delay spread Regarding this, as the signal transmission time increases, the effect of the Doppler scaling factor on the stretching and compression of the received signal increases accordingly, and the subset... The number of elements contained gradually increases. In the above formula, M(i-1) is the time interval between each correlation peak when the strongest path in the channel does not change significantly.

[0099] 5f, perform a binary hypothesis test on the output of the repetitive window matched filter detector.

[0100] A threshold discrimination method is used to perform a binary hypothesis test on the output of the repetitive window matched filter detector, expressed as follows:

[0101]

[0102] Where Γ RMMF It is the discrimination threshold, determined by r RWMF [n] in The statistical information under the given conditions and a false alarm probability determine the outcome. The receiver collects a sufficient number of noise samples to generate r. RWMF [n] in The histogram under the given conditions, and based on this histogram and the predefined false alarm probability, determine Γ. RMMF The numerical value enables effective detection of signals for dual-pilot block structures.

[0103] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A signal detection method based on a dual-pilot block structure, characterized in that, include: (1) Generate a baseband transmission signal with a dual pilot block structure; 1a, Generate and send data blocks; 1b, Generate two pilot blocks; 1c, The dual pilot block structure is evenly inserted into the data block to obtain the dual pilot block structure; (2) Generate a passband transmission signal; (3) Through a single-scale multipath lag channel model with a time-varying Doppler scaling factor; (4) Represents the received signal after passing through a single-scale multipath lag channel; (5) Passing the received signal through a repetitive window matched filter, including: 5a, Model the detector as a binary hypothesis test; 5b, Sample the bandpass received signal; 5c, Obtain the discrete form of the local template; Perform a cross-correlation operation on 5d to obtain the filter output; 5e, Detecting multiple peaks using a repetitive window matched filter detector: In the repetitive window matched filter detector, a repetitive search window with a fixed interval is designed to detect each generated peak. The output of the repetitive window matched filter detector is expressed as... in, Represents the output sequence The The value, the first A subset of repeated search windows Include 1) , Used to refer to a subset The index of the element in the middle. This represents the floor function. It is the maximum absolute value of the Doppler scaling factor. The output sequence of the normalized matched filter, Representative sequence The first in One value; 5f, perform a binary hypothesis test on the output of the repetitive window matched filter detector.

2. The signal detection method based on a dual-pilot block structure as described in claim 1, characterized in that, Step 1a describes generating the transmitted data block by using a complex number table to generate a data vector and using quadrature amplitude modulation to generate the data block. , where data vector After a size of modulation matrix modulation, modulation matrix It depends on the modulation technique used in the signal; The two pilot blocks mentioned in step 1b are respectively defined as follows: and ,in For pilot vectors, For length, It is The inverse discrete Fresnel transformation matrix.

3. The signal detection method based on a dual-pilot block structure as described in claim 1, characterized in that, In step 1c, insert a length of [length] before and after the data block. The pilot block, the first of the transmitted signals with a dual pilot block structure A transmission block consists of the following parts The length of the entire transmission block is ; In step 1c, there are two consecutive pilot blocks between the data blocks, which constitutes a double pilot block, denoted as... , length is , its first Each element is represented as ; In step 1c, the baseband transmission sequence Represented as , where the first of the sending sequences Each element is represented as .

4. The signal detection method based on a dual-pilot block structure as described in claim 1, characterized in that, The passband transmission signal described in step (2) is as follows: ,in It is the carrier frequency.

5. The signal detection method based on a dual-pilot block structure as described in claim 1, characterized in that, In step (3), considering the impact of Doppler spread, the transmitted signal is passed through a single-scale multipath lag channel model. In the mobile scenario, considering the change in the relative speed of the transmitting and receiving ends, the Doppler scaling factor is time-varying.

6. The signal detection method based on a dual-pilot block structure as described in claim 1, characterized in that, In step (4), at the receiving end, the OCDM received signal is represented as follows: ， in This represents a convolution operation, with additive white Gaussian noise in the passband. The mean is zero and the variance is .

7. The signal detection method based on a dual-pilot block structure as described in claim 1, characterized in that, In step 5a, the detector is modeled as a binary hypothesis test. This indicates that only noise exists. This indicates the presence of transmitted signals and noise; the model is represented as follows.

8. The signal detection method based on a dual-pilot block structure as described in claim 1, characterized in that, In step 5f, a threshold discrimination method is used to perform a binary hypothesis test on the output of the repetitive window matched filter detector, expressed as follows: in It is the discrimination threshold, determined by exist The statistical information under the circumstances and a false alarm probability are determined.

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