Signal detection method based on double pilot frequency block structure

Abstract

The invention discloses a signal detection method based on a double-pilot-block structure, which comprises the following steps: (1) generating a baseband sending signal with the double-pilot-block structure, generating a sending data block and two pilot blocks, and uniformly inserting the double-pilot-block structure into the data block to obtain the double-pilot-block structure; (2) generating a passband sending signal; (3) passing through a single-scale multi-path lagging channel model with a time-varying Doppler scaling factor; (4) representing a received signal passing through a single-scale multi-path lagging channel; and (5) enabling the received signal to pass through a repeated window matched filter. The invention realizes successful detection of the received signal under the influence of the single-scale multipath lagging channel with the time-varying Doppler scaling factor, and greatly increases the length of the detection sequence while maintaining the bandwidth efficiency by taking the dual-pilot frequency structure as a part of the detection sequence, thereby improving the signal detection performance.

Description

Technical Field

[0001] The present invention relates to the field of communication system signal detection in complex scenarios, and in particular to a signal detection method based on a dual pilot block structure. Background Art

[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 technologies have been widely used in communication technologies, such as Orthogonal Frequency Division Multiplex (OFDM) and Orthogonal Chirp Division Multiplex (OCDM).

[0003] In response to the common signal detection methods in complex scenarios such as underwater acoustic communications, the domestic application number 202110982064.6 discloses "a real-time detection and extraction method for underwater acoustic communication signals under low signal-to-noise ratio", improves the spectral subtraction algorithm, performs spectral subtraction and noise reduction on underwater acoustic communication signals, and designs a real-time detection and extraction method for underwater acoustic communication signals under low signal-to-noise ratio. The domestic application number 202310681294.8 discloses a "compression method and device for underwater acoustic communication preamble signal detection model", and uses a lightweight convolutional neural network to design a high-performance, low-computation, and low-parameter underwater acoustic communication preamble signal detection method.

[0004] Although the above methods have explored the signal detection methods in complex scenarios such as underwater acoustic communications to a certain extent, they are still mainly limited to the design using preamble codes. In an environment with limited energy, it is difficult to improve the detection performance by increasing the length of the detection sequence, which limits the detection effect of the signal.

[0005] Currently, the commonly used signal detection method is to use the preamble code to complete the detection. However, considering the more complex communication environment, such as the underwater acoustic communication environment, there are challenges such as long channel tail time and limited energy resources. Improving the detection performance by increasing the preamble code length has limited effect.

[0006] Therefore, technicians in this field are committed to developing a signal detection method that is applicable to complex scenarios and can both increase the detection sequence length and improve the detection performance. Summary of the invention

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

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

[0009] (1) generating a baseband transmission signal having a dual pilot block structure;

[0010] 1a, generate a sending data block;

[0011] 1b, generate two pilot blocks;

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

[0013] (2) generating a passband transmit 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 a single-scale multipath lag channel;

[0016] (5) The received signal is passed through a repeated window matched filter.

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

[0018] The present invention proposes a signal detection method based on a dual pilot block structure and designs a dual pilot block transmission structure which can be applicable to signals using different modulation technologies. 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 the present invention realizes the successful detection of the received signal under the influence of the single-scale multipath lag channel with a time-varying Doppler scaling factor. By considering the dual pilot structure as a part of the detection sequence, the length of the detection sequence is greatly increased while maintaining the bandwidth efficiency, thereby improving the signal detection performance.

[0020] In a preferred embodiment of the present invention, the step 1a generates a data block using a complex alphabet table to generate a data vector, and uses orthogonal amplitude modulation to generate a data block. The data vector d(i) is modulated by a modulation matrix of size N×N. Determined by the modulation technique used by the signal;

[0021] The two pilot blocks in step 1b are defined as and Where p is the pilot vector, L is the length, is an L×L inverse discrete Fresnel transform matrix.

[0022] In another preferred embodiment of the present invention, in step 1c, a pilot block of length L is inserted before and after the data block, and the i-th transmission block of the transmission signal with 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 data blocks, which are double pilot blocks, expressed as The length is 2L, and its nth element is represented by [s rep ] n ;

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

[0025] The signal detection method proposed by the present invention utilizes the repetitive mode of dual pilot blocks between data blocks, establishes multiple detection windows with fixed intervals, generates multiple correlation peaks by cross-correlation operation, and then realizes signal detection by using a repetitive window detector.

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

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

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

[0029]

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

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

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

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

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

[0035] 5d, perform cross-correlation operation to obtain the filter output;

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

[0037] 5f, binary hypothesis testing on the output of the repeated window matched filter detector.

[0038] Considering that energy and bandwidth resources are limited in underwater scenes, if the length of the detection sequence is too long, the energy used for communication will be reduced, and the communication accuracy will be reduced. The dual pilot block structure used in the present invention is used for detection. This structure is a training sequence in the information block in communication, which is used to measure various parameters of the channel and is an indispensable part of communication transmission. Using this structure for signal detection will not add additional redundant information.

[0039] At the transmitting end, the interval of the dual pilot block structure is known. Considering the phenomenon that the influence of Doppler changes on the signal in the communication channel gradually increases, a repeated window detector is designed, and the dual pilot block structure can be successfully used for signal detection. The repeated window matched filter detector designed by the present invention can successfully cover the problem of correlation peak position changes caused by the influence of Doppler, etc., and achieve successful signal detection while ensuring bandwidth efficiency. At the same time, the design can shorten the signal transmission time and improve energy utilization.

[0040] In another preferred embodiment of the present invention, in step 5a, the detector is modeled as a binary hypothesis test. indicates that only noise exists. Indicates that there are transmitted signals and noise, and the models of these two assumptions can be expressed as

[0041]

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

[0043]

[0044] Among them, the subset Include represents the ceiling function, α max 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, which is expressed as:

[0046]

[0047] where Γ RMMF is the discrimination threshold, given by r RWMF [n] in The case is determined based on statistical information and a false alarm probability.

[0048] Most existing signal detection methods use preamble codes for signal detection. Considering that there are many types of interference and long duration in complex scenes such as underwater, if the detection sequence is contaminated by noise, the signal cannot be detected. The existing methods have weak anti-interference capabilities.

[0049] The signal detector based on the dual pilot block structure used in the present invention has a detection sequence evenly distributed throughout the entire transmitted signal, and is not easily affected by noise interference generated when a certain section of the signal is received, and has a strong anti-interference ability. For the dual pilot block structure, a repeated window is used to simultaneously search for multiple peaks, and the phenomenon of partial peak loss caused by noise interference can be detected through the repeated window, thereby increasing the probability of successful signal detection. The signal detection method based on the dual pilot block structure designed by the present invention can cope with the phenomenon of preamble code detection failure caused by noise interference, and achieve successful detection of signals under continuous noise interference.

[0050] Technical Effects

[0051] (1) The present invention achieves successful detection of signals in complex scenarios such as underwater. By considering 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 repeated window matched filter detector in the present invention can successfully cover the problem of correlation peak position changes caused by the influence of Doppler, etc., while ensuring bandwidth efficiency and achieving 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 phenomenon of preamble code detection failure caused by noise interference and achieve successful signal detection under continuous noise interference.

[0054] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a specific implementation process of a signal detection method based on a dual pilot block structure according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0056] The following describes several preferred embodiments of the present invention with reference to the drawings in the specification, so that the technical content is clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0057] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0058] The present invention provides a signal detection method based on a dual pilot block structure. Considering the current situation of limited resources in complex scenes such as underwater, the signal detection range is no longer limited to the preamble code, thereby improving the anti-interference performance of the system. The dual pilot block structure designed by the present invention for signal detection regards the repeated pilot between each data block as part of the detection sequence, thereby increasing the number of detectable samples. The present invention uses a repetitive window detector to realize the detection of signals based on a dual pilot block structure. In the design process of the repetitive window, the influence of underwater characteristics such as Doppler on the received signal is considered to improve the detection effect. The dual pilot block structure used in the present invention can assist in the measurement of various parameter information of the underwater channel and reduce redundant information in the subsequent signal demodulation process. The signal detection method proposed by the present invention is suitable for various common signal modulation technologies at present and has universality.

[0059] The present invention can adjust the repetition window length as needed, and can realize different detection time length signal detection through setting to meet the needs of different communication scenarios. For the proposed detection method, the detection time length is increased, the detectable data samples are increased, and the detection performance is improved.

[0060] The present invention mainly considers the signal detection method in complex environment communication scenarios. The structure has more obvious advantages in underwater acoustic communication scenarios, which is a representative application scenario. Detection can also be achieved in other communication environments with advantages.

[0061] like Figure 1 As shown, a specific implementation process of a signal detection method based on a dual pilot block structure provided by the present invention is as follows:

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

[0063] 1a, generate the sending data block.

[0064] The data vector is usually generated using a complex alphabet, and modulated using methods such as orthogonal amplitude modulation, expressed 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 technology used by the signal, when using orthogonal frequency division multiplexing, represents the inverse discrete Fourier transform matrix, When orthogonal chirp multiplexing is used and N is an even number, represents the inverse discrete Fresnel transform matrix,

[0065] 1b, generate two pilot blocks.

[0066] The pilot vector is defined as p = [a, 0, ..., 0] T , allocating a fixed energy P. The two pilot blocks of length L are defined as and in is an L×L inverse discrete Fresnel transform matrix. The dual pilot block structure consists of two orthogonal chirp multiplexed subcarriers, which can also be regarded as chirp signals.

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

[0068] The pilot blocks of length L are inserted before and after the data block. The i-th transmission block of the transmission 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 the data blocks, which are called dual pilot blocks and are expressed as The length is 2L, and its nth element is represented by [s rep ] n The baseband transmission sequence is expressed as The nth element of the sent sequence is represented as s[n].

[0069] (2) Step 2: Generate a passband transmit signal

[0070] The above baseband signal is applied to generate a continuous signal using a pulse shaper, which is expressed as

[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 where f c is the carrier frequency.

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

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

[0075]

[0076] where τ p and A p are the propagation delay and time-varying amplitude of the pth path respectively. When considering block processing of the received signal, the amplitude A within the unified transmission block is p 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: represents the received signal after a single-scale multipath lag channel.

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

[0079]

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

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

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

[0083] Model the detector as a binary hypothesis test, indicates that only noise exists. Indicates that there are transmitted signals and noise, and the models of these two assumptions can be expressed as

[0084]

[0085] 5b, the bandpass received signal is sampled.

[0086] For the bandpass received signal, use the sampling frequency T of the transmitter s Sampling is performed, which is represented by

[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 signal also uses T s The sampling frequency is expressed as

[0090]

[0091] 5d, perform cross-correlation operation to obtain the filter output.

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

[0093]

[0094] The value range of the normalized matched filter output is between 0 and 1, and the normalized matched filter output obtained after the cross-correlation operation between the signal of the dual pilot block structure and the local template contains K+1 peaks.

[0095] 5e, multiple peaks are detected using a repeated window matched filter detector.

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

[0097]

[0098] Among them, the subset Include represents the ceiling function, α max is the maximum absolute value of the Doppler scaling factor. i The Doppler scaling factor and the maximum channel delay spread As the signal transmission time increases, the stretching and compression effect of the Doppler scaling factor on the received signal increases accordingly. The number of elements contained in becomes larger gradually. 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, binary hypothesis testing on the output of the repeated window matched filter detector.

[0100] The threshold discrimination method is used to perform a binary hypothesis test on the output of the repeated window matched filter detector, which is expressed as

[0101]

[0102] where Γ RMMF is the discrimination threshold, given by r RWMF [n] in The receiver collects a sufficient number of noise samples to generate r RWMF [n] in Based on this histogram and the predefined false alarm probability, determine Γ RMMF The value of can realize effective detection of the signal with dual pilot block structure.

[0103] The preferred specific embodiments of the present invention are described in detail above. It should be understood that ordinary technicians in the field can make many modifications and changes based on the concept of the present invention without creative work. Therefore, all technical solutions that can be obtained by technicians in the technical field based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A signal detection method based on a dual pilot block structure, characterized in that: include: (1) generating a baseband transmission signal having a dual pilot block structure; 1a, generate a sending data block; 1b, generate two pilot blocks; 1c, inserting the dual pilot block structure evenly into the data block to obtain the dual pilot block structure; (2) generating a passband transmit signal; (3) Through a single-scale multipath hysteresis channel model with a time-varying Doppler scaling factor; (4) represents the received signal after a single-scale multipath lag channel; (5) The received signal is passed through a repeated window matched filter.

2. The signal detection method based on the dual pilot block structure as claimed in claim 1, characterized in that: Step 1a generates a data block for transmission using a complex alphabet table to generate a data vector, and uses quadrature amplitude modulation to generate a data block. The data vector d(i) is modulated by a modulation matrix of size N×N. Determined by the modulation technique used by the signal; The two pilot blocks in step 1b are defined as and Where p is the pilot vector, L is the length, is an L×L inverse discrete Fresnel transform matrix.

3. The signal detection method based on the dual pilot block structure as claimed in claim 1, characterized in that: In step 1c, a pilot block of length L is inserted before and after the data block. The i-th transmission block of the transmission signal with a dual pilot block structure is composed of the following parts: The length of the entire transmission block is M = 2L + N; In step 1c, there are two consecutive pilot blocks between data blocks, which are double pilot blocks, expressed as The length is 2L, and its nth element is represented by [s rep ] n ; In step 1c, the baseband transmission sequence is expressed as The nth element of the transmitted sequence is represented as s[n].

4. The signal detection method based on the dual pilot block structure as claimed in claim 1, characterized in that: The passband transmission signal in step (2) is described as where f c is the carrier frequency.

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

6. The signal detection method based on the dual pilot block structure as claimed in claim 1, characterized in that: In step (4), at the receiving end, the OCDM received signal is expressed as Where * represents the convolution operation, and the passband is additive white Gaussian noise. The mean is zero and the variance is σ 2 .

7. The signal detection method based on the dual pilot block structure as claimed in claim 1, characterized in that: The step (5) of passing the received signal through a repeated window matched filter comprises: 5a, modeling the detector as a binary hypothesis test; 5b, sampling the bandpass received signal; 5c, obtain the discrete form of the local template; 5d, perform cross-correlation operation to obtain the filter output; 5e, multiple peaks are detected using a repeated window matched filter detector; 5f, binary hypothesis testing on the output of the repeated window matched filter detector.

8. The signal detection method based on the dual pilot block structure as claimed in claim 7, characterized in that: In step 5a, the detector is modeled as a binary hypothesis test, indicates that only noise exists. Indicates that there are transmitted signals and noise, and the model is expressed as 9. The signal detection method based on the dual pilot block structure as claimed in claim 7, characterized in that: In step 5e, in the repeated window matched filter detector, a repeated search window with a fixed interval is designed to detect each generated peak. The output of the repeated window matched filter detector is expressed as Among them, the subset Include represents the ceiling function, α max is the maximum absolute value of the Doppler scaling factor.

10. The signal detection method based on the dual pilot block structure as claimed in claim 7, characterized in that: 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, which is expressed as where Γ RMMF is the discrimination threshold, given by r RWMF [n] in The case is determined based on statistical information and a false alarm probability.

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