A method for underwater acoustic high-speed communication using acoustic vortex

Abstract

The present invention provides a method for underwater acoustic communication using acoustic vortex waves, which specifically comprises the following steps: a receiving end performs acoustic vortex phase compensation on signals received on concentric circular arc array elements to obtain acoustic vortex receiving signals under different acoustic vortex modes; a coarse Doppler search is first performed on signals received by different array elements in different acoustic vortex modes, a fine search is performed on signals with clear Doppler offsets, and a Doppler compensation value is calculated; for signals with fuzzy Doppler offsets, the Doppler search results of two adjacent circular arc arrays are judged, and the Doppler compensation value is calculated using the Doppler search results of the two adjacent circular arc arrays; the Doppler compensated signals are subjected to time delay compensation in combination with the array element radius of each circular arc array, and then superimposed to obtain receiving array signals of different acoustic vortex modes; and the receiving array signals are then processed to restore data information transmitted by the acoustic vortex underwater acoustic communication.

Description

Technical Field

[0001] The present invention belongs to the technical field of underwater acoustic communication, and in particular relates to an underwater acoustic high-speed communication method using an acoustic vortex. Background Art

[0002] Currently, the application of vortex waves in the air, which carry orbital angular momentum through light or electromagnetic waves, is relatively mature. However, due to the various disadvantages of other communication methods besides sound waves in the marine environment, such as the large transmission attenuation, strong reflection and scattering of light waves, it is difficult to carry out long-distance communication underwater. Therefore, only acoustic vortex waves can be used for underwater communication. Similar to optical vortices, the phase of sound waves changes by an integer multiple of 2π with each full rotation around the center of the vortex during propagation, resulting in a vortex-like twist. At the same time, the phenomenon of zero sound intensity on the central axis is called an acoustic vortex.

[0003] The use of acoustic vortex waves with vortex characteristics for multiplexing communication has become one of the breakthroughs in current research. Acoustic vortex waves refer to a phenomenon in which the phase of an acoustic wave changes by an integer multiple of 2π every time it rotates around the center of the vortex during propagation, producing a vortex-like twist, and the sound intensity on the central axis is zero. The principle of its generation is to add a rotation phase factor e related to the spatial azimuth angle θ to the normal sound wave. jLθ Normal sound waves are converted into acoustic vortex waves. When L = 0, there is no vortex torsion, equivalent to a plane wave. The larger the value of |L|, the greater the angle of the sound wave torsion. The sign of L indicates the direction of the sound wave torsion. In theory, the value of L can be any integer, with no upper or lower limit. However, in practice, it is still limited by factors such as the number of array elements.

[0004] At the same time, by leveraging the orthogonal properties of different modes of acoustic vortex waves, multiple channels of acoustic vortex waves can be transmitted in parallel within the same bandwidth. In theory, acoustic vortex waves with different eigenvalues ​​will not interfere with each other. This also enables the establishment of a multi-modal acoustic vortex multiplexing system. In theory, a set of filters can be used at the receiving end to perfectly separate and detect acoustic vortexes of different modes. Summary of the Invention

[0005] The present invention proposes a method for underwater acoustic communication using acoustic vortex waves. The present invention utilizes the orthogonality of vortex waves for multiplexing communication. At the same time, when performing Doppler search on the acoustic vortex underwater acoustic communication signal, different Doppler search judgment methods are selected according to different signal qualities, thereby improving the accuracy and speed of the Doppler search.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for underwater acoustic communication using acoustic vortex waves, specifically comprising:

[0008] The receiving end performs acoustic vortex phase compensation on the signals received on the concentric arc array elements to obtain acoustic vortex receiving signals under different acoustic vortex modes;

[0009] For signals received by different acoustic vortex modes and different array elements, a coarse Doppler search is first performed. For signals with clear Doppler offsets, a fine search is performed to calculate the Doppler compensation value. For signals with ambiguous Doppler offsets, the Doppler search results of two adjacent circular arrays are judged and the Doppler compensation value is calculated using the Doppler search results of the two adjacent circular arrays.

[0010] The Doppler-compensated signal is combined with the array element radius of each circular array, delay compensated and then superimposed to obtain receiving array signals of different acoustic vortex modes; the receiving array signals are then processed to restore the acoustic vortex underwater acoustic communication transmission data information.

[0011] Furthermore, the specific process of performing a detailed search for a signal with a clear Doppler shift and calculating a Doppler compensation value according to the present invention is as follows:

[0012] When the maximum value of the Doppler coarse search correlation peak is greater than or equal to the detection threshold, the signal quality is considered good; the Doppler fine search frequency upper limit Δf is calculated based on the Doppler compensation value corresponding to the maximum value. L and the lower limit Δf H , perform a Doppler fine search; obtain the Doppler compensation value corresponding to the maximum value of the Doppler fine search correlation peak.

[0013] Furthermore, the specific process of the present invention for determining the Doppler search results of two adjacent circular arrays for a signal with ambiguous Doppler shift and calculating the Doppler compensation value using the Doppler search results of the two adjacent circular arrays is as follows:

[0014] When the Doppler coarse search correlation peak is less than the detection threshold, the signal quality is considered to be poor; the correlation peaks of the same acoustic vortex mode of two adjacent circular arrays are compared with the detection threshold. When both are greater than the detection threshold, the upper limit Δf of the Doppler fine search frequency is calculated based on the Doppler coarse search results of the two adjacent circular arrays. L and the lower limit Δf H , perform a Doppler fine search;

[0015] When the maximum value of the Doppler fine search correlation peak is greater than or equal to the set threshold, it is used as the Doppler compensation value;

[0016] When the maximum value of the Doppler fine search correlation peak is less than the set threshold, the average value of the Doppler compensation values ​​of the two adjacent circular arrays is recorded as the Doppler compensation value of the current circular array.

[0017] Furthermore, the present invention calculates the upper limit Δf of the Doppler fine search frequency based on the Doppler coarse search results of two adjacent circular arc arrays. L and the lower limit Δf H for:

[0018]

[0019]

[0020] in, and is the Doppler coarse search result of two adjacent circular arrays, and Δf2 is the search step size.

[0021] Furthermore, the receiving array of the receiving end of the present invention is composed of a quarter arc array composed of M concentric circles, and the number of array elements in each arc array is the same as N.

[0022] Furthermore, the process of generating the transmission signal at the transmitting end of the present invention is as follows:

[0023] Assume that the number of elements of the transmitting circular array at the signal transmitting end is N, calculate the total number of acoustic vortex modes that can be transmitted simultaneously H, and generate H OFDM transmission signals s h (t);

[0024] Combining OFDM signals of different modes and the initial phase of the transmitting circular array, an acoustic vortex underwater acoustic high-speed communication signal is generated on the transmitting circular array.

[0025] Furthermore, the present invention is used to generate H OFDM transmission signals s h (t) FTS signal s FTS (t) Using broadband segment sequence generation.

[0026] Furthermore, the present invention is used to generate H OFDM transmission signals s h (t) TTS signal s TTS (t) is generated using a pseudo-random sequence.

[0027] Furthermore, the present invention transmits the acoustic vortex mode L on the nth array element on the circular array. h The initial phase for:

[0028]

[0029] Furthermore, the present invention generates an acoustic vortex underwater acoustic high-speed communication signal on a transmitting circular array as follows:

[0030] According to the OFDM signal h (t) and initial phase Generate the acoustic vortex mode L on the nth array element on the transmitting circular arrayh The signal Sig h (t,n), and then superimpose the signals of all modes on the n-th array element on the transmitting circular array to generate the acoustic vortex underwater acoustic high-speed communication signal Sig of the n-th array element on the transmitting circular array send (t,n).

[0031] Beneficial effects

[0032] (1) When performing Doppler search on acoustic vortex underwater acoustic communication signals, the present invention selects different Doppler search judgment methods according to different signal qualities, thereby improving the accuracy and speed of Doppler search.

[0033] (2) The present invention utilizes the orthogonal characteristics of different modal acoustic vortex waves to carry out underwater high-speed acoustic vortex communication, and utilizes multi-modal acoustic vortex wave multiplexing technology to improve the communication capacity while ensuring the communication performance.

[0034] (3) The present invention utilizes an acoustic vortex combined array as a receiving array for underwater high-speed acoustic vortex communication. While ensuring that the array size and area remain unchanged, the communication distance is increased, the array gain is improved, and the communication performance is further improved.

[0035] (4) To reduce the impact of Doppler on the system, a pseudo-random sequence is used to generate a TTS signal for measuring Doppler. This signal has a high frequency domain resolution and can accurately measure the Doppler frequency deviation of the system.

[0036] (5) To ensure the system's ability to resist multipath, a broadband short sequence is used to generate the FTS signal for measuring multipath. This signal has high time domain resolution and can measure the multipath structure of the channel with high precision, while also measuring the frequency selective fading of the channel.

[0037] (6) The present invention performs accurate multipath compensation on the Doppler-compensated signal, reduces the bit error rate, and improves communication performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a flow chart of the acoustic vortex underwater acoustic communication transmitter;

[0039] Figure 2 Schematic diagram of OFDM signal structure;

[0040] Figure 3 This is a schematic diagram of the acoustic vortex underwater acoustic communication receiving array;

[0041] Figure 4 This is a flow chart of the acoustic vortex underwater acoustic communication receiving end;

[0042] Figure 5 Flowchart for Doppler search. DETAILED DESCRIPTION

[0043] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other unless there is a conflict.

[0044] In order to illustrate the technical solution of the present invention, specific embodiments are provided below.

[0045] The present invention provides a method for underwater acoustic communication using acoustic vortex waves, including communication steps between a signal transmitter and a signal receiver, as follows:

[0046] The steps of the transmitter of the underwater high-speed communication system of the acoustic vortex are as follows:

[0047] (1) Using the number of transmitting circular array elements and the element radius, determine the total number of acoustic vortex modes and the maximum communication distance. The specific process of this step is:

[0048] (1.1) Using the number of transmitting circular array elements N, calculate the total number of acoustic vortex modes H that can be emitted simultaneously.

[0049]

[0050] in, Indicates rounding down.

[0051] (1.2) Combined with the number of transmitting circular array elements N, element radius R, sound speed c and sampling rate f s , calculate the maximum distance D of acoustic vortex underwater acoustic communication max .

[0052]

[0053] (2) Use the broadband short sequence, pseudo-random sequence, and data information to generate the FTS signal for measuring multipath, the TTS signal for measuring Doppler, and the data signal, respectively. These three signals are superimposed to form the OFDM signal. The specific process of this step is as follows:

[0054] (2.1) Using a short sequence with wide bandwidth {A i}, each value A in the sequence i The carrier frequency f corresponding to the i-th sub-pulse i , the sub-pulse width is T, the number of sub-pulses is N, and the generated FTS signal s for measuring multipath FTS (t).

[0055]

[0056]

[0057] Where rect(t) is the rectangle function.

[0058] (2.2) Using pseudo-random sequence {B j}, through spread spectrum coding, generate the TTS signal s for measuring Doppler TTS (t).

[0059]

[0060] (2.3) The data Mess to be transmitted is grouped according to the total number H of acoustic vortex modes emitted to obtain H groups of data information.

[0061]

[0062] Where h=1,2,…,H

[0063] (2.4) Scramble, interleave and channel code the hth group of data information Mess(h) to generate data signal s Code (t,h).

[0064] (2.5) The FTS signal s of the measured multipath FTS (t), TTS signal s for measuring Doppler TTS (t) and data signal s Code (t,h) superposition, generating H OFDM transmission signals s h (t).

[0065] s h (t) = s FTS (t)+s TTS (t)+s Code (t,h)

[0066] (3) Combine the OFDM signals of different modes and the initial phase of the transmitting circular array to generate the signal on the transmitting array element. The specific process of this step is:

[0067] (3.1) According to the total number of acoustic vortex modes, determine the acoustic vortex mode L corresponding to each OFDM signal h .

[0068]

[0069] (3.2) According to the number of array elements N of the transmitting circular array, calculate the acoustic vortex mode L on the nth array element on the transmitting circular array. h The initial phase

[0070]

[0071] (3.3) According to the OFDM signal sh (t) and initial phase Generate the acoustic vortex mode L on the nth array element on the transmitting circular array h The signal Sig h (t,n).

[0072]

[0073] (3.4) The signals of all modes on the nth array element on the transmitting circular array are superimposed to generate the acoustic vortex underwater acoustic high-speed communication signal Sig of the nth array element on the transmitting circular array send (t,n), and transmitted synchronously.

[0074]

[0075] Assume that the acoustic vortex receiving array is composed of a 1 / 4 arc array composed of M concentric circles, and the number of array elements in each circle is N. The maximum radius of the arc array is R2, the minimum radius is R1, and the radius of the mth concentric arc array is R m .

[0076]

[0077] The receiving end steps of the underwater high-speed communication system of the acoustic vortex are as follows:

[0078] (1) Perform acoustic vortex phase compensation on the signals of N array elements on the concentric circle array to obtain the acoustic vortex receiving signals under different acoustic vortex modes. The specific process is as follows:

[0079] (1.1) According to the acoustic vortex mode L h And the number of circular array elements N, calculate the phase difference of the nth array element on the mth concentric circular array compared to the array element number n=0 in the same circular array

[0080]

[0081] (1.2) The signal Sig on the N array elements on the mth concentric arc array recv (t,m,n) are phase compensated and then superimposed to obtain the acoustic vortex mode L h The acoustic vortex receiving signal Sig(t,m,h).

[0082]

[0083] (2) Perform Doppler search on signals received by different acoustic vortex modes and different array elements.

[0084] Specifically: perform a Doppler coarse search on the signal. If the Doppler coarse search result is greater than or equal to the threshold, perform a Doppler fine search, and the frequency corresponding to the maximum value of the correlation peak of the Doppler fine search is used as the final Doppler compensation value. If the Doppler coarse search result is less than the threshold, determine whether the Doppler coarse search results of the two adjacent concentric circular arc arrays meet the threshold; if the Doppler coarse searches of the two adjacent concentric circular arc arrays are not both greater than the threshold, it is considered that there is a silent vortex mode signal on the current concentric circular arc array; otherwise, the Doppler search results of the two adjacent circular arc arrays are used as the search upper and lower limits, and a Doppler fine search is performed. If the Doppler fine search result is greater than or equal to the threshold, the current value can be used as the final Doppler compensation value; otherwise, the average value of the Doppler search results of the two adjacent circular arc arrays is used as the Doppler compensation value of the current circular arc array. The specific process of this step is:

[0085] (2.1) For the hth acoustic vortex mode and the mth concentric arc array acoustic vortex receiving signal Sig(t,m,h), according to the step size Δf1, within the Doppler frequency deviation allowable range, -Δf max ,Δf max ], the signal is resampled to obtain G groups of compensated signals, which are combined with the locally generated TTS signal s TTS (t) Perform cyclic correlation to obtain the Doppler coarse search correlation peak Value m,h (Δf g ), and calculate the Doppler threshold η c .

[0086]

[0087] Δf g =-Δf max +(g-1)×Δf1

[0088] Among them, δ c is the coarse search threshold coefficient; g=1,2,…,G.

[0089] (2.2) Determine the search correlation peak Value of the hth acoustic vortex mode and the mth concentric arc array m,h (Δf g ) exceeds the Doppler threshold η c .

[0090] When max(Value m,h (Δf g )) is greater than or equal to the detection threshold η c When the current circular array roughly searches for a signal, the Doppler compensation value Δf corresponding to the maximum value g Recorded as Execute step (2.3); otherwise, determine the acoustic vortex mode L of the two adjacent arc arrays hCorrelation Peak Value m-1,h (Δf g ) and Value m+1,h (Δf g ) and the detection threshold η c When Value m-1,h (Δf g ) and Value m+1,h (Δf g ) are greater than or equal to the detection threshold η c , execute (2.4); otherwise, it is considered that the silent vortex mode L on the mth concentric arc array h signal.

[0091] (2.3) On the hth acoustic vortex mode and the mth concentric arc array, according to Calculated Doppler search frequency upper limit Δf L and the lower limit Δf H .

[0092]

[0093]

[0094] For the hth acoustic vortex mode and the mth concentric arc array acoustic vortex receiving signal Sig(t,m,h), according to the step size Δf2, the Doppler search upper limit Δf L and the lower limit Δf H Perform a Doppler search between the hth acoustic vortex mode and the mth concentric arc array to obtain the Doppler search correlation peak Value m,h (Δf g ). m,h (Δf g )The maximum value corresponds to the Doppler compensation value Δf g Recorded as Go to step (2.5).

[0095] (2.4) On the hth acoustic vortex mode and the mth concentric arc array, according to the Doppler rough search results of the two adjacent arc arrays, and Calculated Doppler search frequency upper limit Δf L and the lower limit Δf H .

[0096]

[0097]

[0098] For the hth acoustic vortex mode and the mth concentric arc array acoustic vortex receiving signal Sig(t,m,h), according to the step size Δf2, the Doppler search upper limit Δf L and the lower limit Δf H A Doppler search is performed between the hth acoustic vortex mode and the mth concentric arc array to obtain the maximum value of the Doppler search correlation. m,h (Δf g ), and calculate the detection threshold η x .

[0099]

[0100] Δf g =Δf L +(g-1)×Δf2

[0101] Among them, δ x To fine-tune the threshold coefficient.

[0102] Determine max(Value m,h (Δf g )) Whether it exceeds the Doppler threshold η x When max(Value m,h (Δf g )) is greater than or equal to the detection threshold η x When the Doppler compensation value Δf corresponding to the maximum value is g Record as Otherwise, the average value of the Doppler frequency offsets of the two adjacent circular arrays is recorded as the Doppler frequency offset of the current circular array. Continue with step (2.5).

[0103]

[0104] (2.5) According to the Doppler compensation value Doppler compensation is performed on the acoustic vortex receiving signal Sig(t,m,h) of the hth acoustic vortex mode and the mth concentric arc array to obtain the Doppler compensated signal Sig Dop (t,m,h).

[0105] (3) For the hth acoustic vortex mode, the Doppler-compensated signal Sig on all concentric arc arrays Dop (t,m,h), combined with the radius R of each circular array m , and then perform superposition after time delay compensation to obtain the receiving array signal Sig of the hth acoustic vortex mode Delay (t,h).

[0106]

[0107] Where d is the radius difference of each concentric arc array.

[0108]

[0109] (4) The receiving array signal Sig of the hth acoustic vortex mode Delay (t,h), after filtering, the start and end time of the FTS signal are determined by searching the carrier frequency of the FTS signal of the multipath measurement, and the FTS signal is extracted. The extracted FTS signal is correlated with the local FTS signal to obtain the multipath information. Then, combined with the multipath information, the receiving array signal Sig of the hth acoustic vortex mode is received by the Rake receiver. Delay (t,h) performs multipath compensation to obtain the multipath compensated signal Sig Chan (t,h).

[0110] (5) The signal Sig after multipath compensation for the hth acoustic vortex mode Chan (t,h), perform decoding, deinterleaving and de-interference operations to obtain data information Mess(h), combine them, and restore the acoustic vortex underwater acoustic communication transmission data information Mess.

[0111] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for underwater acoustic communication using acoustic vortex waves, characterized in that: Specifically: The receiving end performs acoustic vortex phase compensation on the signals received on the concentric arc array elements to obtain acoustic vortex receiving signals under different acoustic vortex modes; For signals received by different acoustic vortex modes and different array elements, a coarse Doppler search is first performed. For signals with clear Doppler offsets, a fine search is performed to calculate the Doppler compensation value. For signals with ambiguous Doppler offsets, the Doppler search results of two adjacent circular arrays are judged and the Doppler compensation value is calculated using the Doppler search results of the two adjacent circular arrays. The Doppler-compensated signal is combined with the array element radius of each circular array, delay compensated and then superimposed to obtain receiving array signals of different acoustic vortex modes; the receiving array signals are then processed to restore the acoustic vortex underwater acoustic communication transmission data information.

2. The method for underwater acoustic communication using acoustic vortex waves according to claim 1, characterized in that: The specific process of performing a fine search for a signal with a clear Doppler shift and calculating the Doppler compensation value is as follows: When the maximum value of the Doppler coarse search correlation peak is greater than or equal to the detection threshold, the signal quality is considered good; the Doppler fine search frequency upper limit Δf is calculated based on the Doppler compensation value corresponding to the maximum value. L and the lower limit Δf H , perform a Doppler fine search; obtain the Doppler compensation value corresponding to the maximum value of the Doppler fine search correlation peak.

3. The method for underwater acoustic communication using acoustic vortex waves according to claim 1 or 2, characterized in that: The specific process of determining the Doppler search results of two adjacent circular arrays for a signal with ambiguous Doppler shift and calculating the Doppler compensation value using the Doppler search results of the two adjacent circular arrays is as follows: When the Doppler coarse search correlation peak is less than the detection threshold, the signal quality is considered to be poor; the correlation peaks of the same acoustic vortex mode of two adjacent circular arrays are compared with the detection threshold. When both are greater than the detection threshold, the upper limit Δf of the Doppler fine search frequency is calculated based on the Doppler coarse search results of the two adjacent circular arrays. L and the lower limit Δf H , perform a Doppler fine search; When the maximum value of the Doppler fine search correlation peak is greater than or equal to the set threshold, it is used as the Doppler compensation value; When the maximum value of the Doppler fine search correlation peak is less than the set threshold, the average value of the Doppler compensation values ​​of the two adjacent circular arrays is recorded as the Doppler compensation value of the current circular array.

4. The method for underwater acoustic communication using acoustic vortex waves according to claim 3, characterized in that: The upper limit Δf of the Doppler fine search frequency is calculated based on the Doppler coarse search results of two adjacent circular arrays. L and the lower limit Δf H for: in, and is the Doppler coarse search result of two adjacent circular arrays, and Δf2 is the search step size.

5. The method for underwater acoustic communication using acoustic vortex waves according to claim 1, characterized in that: The receiving array at the receiving end is composed of a 1 / 4 arc array composed of M concentric circles, and the number of array elements in each arc array is the same as N.

6. The method for underwater acoustic communication using acoustic vortex waves according to claim 1, characterized in that: The process of generating the transmission signal at the transmitter is as follows: Assume that the number of elements of the transmitting circular array at the signal transmitting end is N, calculate the total number of acoustic vortex modes that can be transmitted simultaneously H, and generate H OFDM transmission signals s h (t); Combining OFDM signals of different modes and the initial phase of the transmitting circular array, an acoustic vortex underwater acoustic high-speed communication signal is generated on the transmitting circular array.

7. The method for underwater acoustic communication using acoustic vortex waves according to claim 6, characterized in that: Used to generate H OFDM transmission signals s h (t) FTS signal s FTS (t) Using broadband segment sequence generation.

8. The method for underwater acoustic communication using acoustic vortex waves according to claim 6, characterized in that: Used to generate H OFDM transmission signals s h (t) TTS signal s TTS (t) is generated using a pseudo-random sequence.

9. The method for underwater acoustic communication using acoustic vortex waves according to claim 6, characterized in that: The acoustic vortex mode L on the nth element of the transmitting circular array h The initial phase for:

10. The method for underwater acoustic communication using acoustic vortex waves according to claim 9, characterized in that: The acoustic vortex underwater acoustic high-speed communication signal generated on the transmitting circular array is: According to the OFDM signal h (t) and initial phase Generate the acoustic vortex mode L on the nth array element on the transmitting circular array h The signal Sig h (t,n), and then superimpose the signals of all modes on the n-th array element on the transmitting circular array to generate the acoustic vortex underwater acoustic high-speed communication signal Sig of the n-th array element on the transmitting circular array send (t,n).

Images