Underwater sound adaptive transmission method based on affine domain two-dimensional index modulation

Abstract

The invention discloses an underwater acoustic adaptive transmission method based on affine domain two-dimensional index modulation, and belongs to the technical field of communication. The method comprises the following steps of: 1, designing a transmitting link of an underwater acoustic self-adaptive transmission system based on affine domain two-dimensional index modulation; and step 2, an underwater acoustic adaptive transmission system receiving link design scheme based on affine domain two-dimensional index modulation. According to the invention, on the basis of the channel information of the feedback link on the sending link, the appropriate carrier index and parameter index are combined together, and adaptive transmission is carried out on the indexed imitated radio frequency division multiplexing signal by activating a part of subcarriers and distributing pre-chirp parameters on the activated subcarriers. And at a receiving end, based on the estimated channel state information, carrying out joint detection on a received signal through a maximum likelihood criterion. The method provided by the invention improves the spectrum efficiency and the transmission robustness of underwater acoustic communication, is very suitable for an underwater acoustic self-adaptive transmission system based on a feedback link, and fully embodies the superior performance of the underwater acoustic self-adaptive transmission system.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and relates to adaptation, index modulation (Index Modulation), feedback link, and affine frequency division multiplexing (Affine Frequency Division Multiplexing) technology. Background Art

[0002] With the continuous development and utilization of marine resources and the continued advancement of marine informatization, underwater acoustic communication, as the most feasible and widely used means of information transmission in the marine environment, plays a vital role in multiple fields, including ocean exploration, intelligent equipment coordination, underwater monitoring, and military communications. However, due to the inherent physical characteristics of underwater channels, such as slow propagation speed, limited bandwidth, significant multipath effects, and severe Doppler spread, underwater acoustic communication systems face severe challenges in terms of transmission rate, spectral efficiency, and system robustness, becoming a key bottleneck restricting the efficient transmission of marine information. Especially in the context of increasingly scarce underwater acoustic communication channel resources and the exponential growth of communication data volume, it is urgent to seek new modulation schemes and resource utilization strategies to improve the overall performance of underwater communication systems. Indexed modulation (IM) technology has attracted widespread attention in recent years as an effective means of improving spectral efficiency. This technology uses the activation state of communication resources (such as subcarriers and antennas) to carry additional information, thereby expanding information carrying methods and increasing system capacity without increasing bandwidth or power consumption. On the other hand, AFDM (Advanced Frequency Division Multiplexing) technology, as a new multi-carrier modulation scheme, uses multiple linear frequency modulation signals generated by the inverse discrete affine Fourier transform (IDAFT) to carry information, and can adapt to different transmission environments by adjusting the two chirp parameters of the discrete affine Fourier transform (DAFT). Therefore, this patent proposes for the first time an underwater acoustic adaptive transmission method based on affine domain dual-dimensional index modulation, introduces the dual-dimensional index modulation mechanism into the AFDM framework, fully taps the information carrying potential of the resource dimension in the affine domain, and realizes efficient underwater acoustic communication based on the time-frequency joint index. At the same time, by designing a feedback link to achieve parameter adaptive adjustment, the system can dynamically adjust the transmission parameters according to the underwater acoustic channel state, thereby improving the spectrum efficiency and transmission robustness of the underwater acoustic communication system, fully demonstrating its superior performance. Summary of the Invention

[0003] The purpose of the present invention is to design an underwater acoustic adaptive transmission method based on affine domain two-dimensional index modulation to improve the spectrum efficiency and robust communication performance of the underwater acoustic communication system.

[0004] The technical solution of the present invention:

[0005] An underwater acoustic adaptive transmission method based on affine domain two-dimensional index modulation includes the following steps:

[0006] Step 1: Design of the transmitting link of the underwater acoustic adaptive transmission system based on affine domain dual-dimensional index modulation;

[0007] Step 2: Design of receiving link of underwater acoustic adaptive transmission system based on affine domain dual-dimensional index modulation;

[0008] The specific steps in step 1 are as follows:

[0009] Step 1.1: Extract channel information parameters based on the signal of the feedback link;

[0010] Step 1.2: Group the subcarriers and the information bits to be sent. The information bits of each group are mapped into three parts: the first part (B1) is the subcarrier index bit used to indicate the subcarrier to be activated; the second part (B2) is the parameter index bit used to indicate the pre-chirp parameter c2 assigned to each activated subcarrier; and the third part (B3) is the modulation bit used to indicate the traditional modulation symbol mapped through MPSK / MQAM.

[0011] Step 1.3: After mapping the modulation symbols onto the activated subcarriers, the affine Fourier domain data is formed, and then the DAFT matrix A is constructed based on the estimated channel information parameters.

[0012] Step 1.4: Use IDAFT matrix A -1 Transforming the affine Fourier domain data, adding a cyclic prefix to the transformed data to form AFDM-IM data, and transmitting the organized AFDM-IM data on the corresponding transducer according to a conventional scheme;

[0013] The specific steps in step 2 are summarized as follows:

[0014] Step 2.1: Receive according to the traditional scheme;

[0015] Step 2.2: Remove the cyclic prefix of the received data and transform it using the DAFT matrix A.

[0016] Step 2.3: Use the corresponding pilot prior information to perform channel estimation;

[0017] Step 2.4: Perform joint detection and demodulation on the received data based on the estimated channel state information.

[0018] Furthermore, in step 1.1, the signal of the feedback link is

[0019]

[0020] Where α is the channel attenuation, b(θ) is the receiving direction vector, and a(θ) is the sending direction vector. is white noise, ν is Doppler broadening, τ is delay, Representing channel information in feedback link based systems.

[0021] Furthermore, in step 1.2, the candidate values ​​of the pre-chirp parameter c2 are from a predefined set S, and the B2 bit of each sub-block is used to select a pre-chirp parameter arrangement pattern from the set S, that is, to determine the combination of c2 values ​​used for the activated subcarriers in the sub-block, wherein the parameter index bit Predefined collections

[0022] Furthermore, in step 1.3, the modulation symbols are mapped to the activated subcarriers to form affine Fourier domain data, and then the DAFT matrix A is constructed based on the estimated channel information parameters.

[0023]

[0024] Where F is the discrete Fourier transform matrix, Λ c Defined as

[0025]

[0026] Furthermore, in step 1.4, the IDAFT matrix A is used -1 Transform data in the affine Fourier domain

[0027]

[0028] A cyclic prefix is ​​added to the transformed data to form a chirp periodic sequence, forming the complete AFDM-IM data. This adaptive system based on a feedback link is also suitable for multi-element applications. The organized AFDM-IM data is then transmitted to the corresponding transducer using a conventional method.

[0029] Furthermore, in step 2.1, the received signal of the data transmission link is

[0030]

[0031] Where P is the number of paths, d p is the normalized delay, ν p is the Doppler shift, ω r is complex white Gaussian noise.

[0032] Furthermore, in step 2.2, the Chirp cyclic prefix of the received data is removed and the DAFT matrix A is used to transform it.

[0033] y=H eff x+ω (7)

[0034] Among them, H eff is the effective channel matrix.

[0035] Furthermore, in step 2.3, the corresponding pilot prior information is used to perform channel estimation. For a system based on a feedback link, the feedback signal is the estimated channel information, that is,

[0036]

[0037] Among them, l2(·) represents a likelihood function, which is used to estimate the channel parameters, y E represents the part of y related to channel estimation, θ=[h0,…h P-1 ,d0,…d P-1 ,ν0,…ν P-1 ], x pilot is the first symbol in the frame, It is h i,E The first column, h i is the complex gain, α p is the normalized Doppler shift, according to d p ,α p ,h i The estimated effective channel matrix can be derived.

[0038] Furthermore, in step 2.4, the maximum likelihood can be used to perform joint detection on the received data. The maximum likelihood criterion detection is:

[0039]

[0040] in, Indicates the detected subcarrier index, represents the detected modulation symbol, Represents the pre-chirp parameter arrangement patterns of all detected groups.

[0041] Advantages and beneficial effects of the present invention:

[0042] ① The present invention is based on an underwater acoustic adaptive transmission method using affine domain two-dimensional index modulation, which has the characteristics of high spectral efficiency by combining carrier indexing and parameter indexing. ② The present invention adjusts the transmitter parameters based on the channel information extracted from the feedback link signal to adapt to the underwater acoustic channel environment, and has the characteristics of simple method and high transmission reliability. ③ The present invention adopts AFDM, which has the characteristics of full diversity effect and resistance to dual-selection fading channels, and is very suitable for the requirements of underwater acoustic systems based on feedback links for high spectral efficiency and robust transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic diagram of the design of the present invention;

[0044] Figure 2 Schematic diagram of the design scheme for the transmitting link of the underwater acoustic adaptive transmission system based on affine domain dual-dimensional index modulation;

[0045] Figure 3 Schematic diagram of the receiving link design scheme for the underwater acoustic adaptive transmission system based on affine domain two-dimensional index modulation. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further illustrated by the following embodiments.

[0047] The present invention provides an underwater acoustic adaptive transmission method based on affine domain dual-dimensional index modulation, the scheme of which is as follows Figure 1 The specific steps are as follows:

[0048] Step 1: Design of the transmitting link of the underwater acoustic adaptive transmission system based on affine domain dual-dimensional index modulation;

[0049] Step 2: Design of receiving link of underwater acoustic adaptive transmission system based on affine domain two-dimensional index modulation.

[0050] In the first step, the designed underwater acoustic transmission method adopts dual-dimensional index modulation technology and adaptive communication optimization theory, and uses affine Fourier transform with different parameters to process affine Fourier domain information. It has very high ability to resist underwater acoustic time-varying channel fading and high spectrum efficiency. Its schematic diagram is shown as follows: Figure 2 As shown in the figure, at the transmitter end of an underwater acoustic adaptive transmission system based on affine domain dual-dimensional index modulation: first, channel information parameters are extracted based on the feedback link signal; second, subcarriers and information bits to be transmitted are grouped, some subcarriers are activated through an index selector and pre-chirp parameters are assigned, modulation symbols are mapped to the activated subcarriers to generate affine Fourier domain data, and a DAFT matrix is ​​constructed based on the extracted parameters; then, the affine Fourier domain data is transformed using the IDAFT matrix, and a cyclic prefix is ​​added to the transformed data to form AFDM-IM data; finally, the AFDM-IM data is transmitted according to the traditional scheme.

[0051] In the second step, the present invention adopts AFDM and dual-dimensional index modulation and adaptive technology, which not only improves the spectrum efficiency of the system, but also achieves full diversity in the time-varying underwater acoustic channel. The schematic diagram is shown in FIG. Figure 3As shown in the figure, at the data receiving end of the AFDM-based underwater acoustic adaptive transmission system: first, data is received according to the traditional scheme; second, the DAFT matrix A is used to transform the data without the cyclic prefix, and the corresponding pilot prior information can be used to estimate the channel; then, based on the estimated channel information, the traditional maximum likelihood detection algorithm is used to jointly detect the received data; finally, the detected data is demodulated and demapped.

[0052] Example 1:

[0053] An adaptive underwater acoustic transmission method based on affine domain two-dimensional index modulation improves the spectrum efficiency and robustness of underwater acoustic communication by using feedback link signals and two-dimensional index modulation adaptive technology. The steps and details of each step are as follows:

[0054] Step 1: Design of the transmitting link of the underwater acoustic adaptive transmission system based on affine domain dual-dimensional index modulation;

[0055] Step 2: Design of receiving link of underwater acoustic adaptive transmission system based on affine domain two-dimensional index modulation.

[0056] In the first step, since the underwater acoustic communication system adopts AFDM communication technology, the present invention uses MPSK / MQAM digital modulation technology, a bandwidth of 8 kHz, N = 256 subcarriers, a multi-element feedback link, and an adaptive system data transmission link based on the feedback link. Taking an ordinary single element as an example, the data transmission link will perform the following processing:

[0057] Step 1.1: The signal of the feedback link is

[0058]

[0059] Where α is the channel attenuation, b(θ) is the receiving direction vector, and a(θ) is the sending direction vector. is white noise, v is Doppler broadening, τ is delay, Representing channel information in feedback link based systems.

[0060] Step 1.2: Divide N subcarriers into G groups, each group has n = N / G subcarriers. Assuming that there are M information bits to be transmitted, first divide the M information bits into G groups, each group contains B = M / G information bits. The B information bits of each subblock are further divided into three parts, where the subcarrier index bit Parameter index bit Modulation bit B3 = Klog2(M).

[0061] For the βth sub-block, the subcarrier index can be expressed as I β =[i β,1 ,…iβ,K ], the constellation mapping can be expressed as S β =[s β (1),…,s β (K)], the parameter index case can be expressed as Among them, c 2,K ∈S (i) , Each S (i) It is a vector of length K, which represents the c2 parameter arrangement pattern of K activated subcarriers in the subblock.

[0062] Step 1.3: Map the modulation symbols to the activated subcarriers to form affine Fourier domain data, and then construct the DAFT matrix A based on the estimated channel information parameters.

[0063]

[0064] Where F is the discrete Fourier transform matrix, Λ c Defined as

[0065]

[0066] Step 1.4: Use IDAFT matrix A -1 Transform data in the affine Fourier domain

[0067]

[0068] A Chirp Periodic Prefix (CPP) is added to the transformed data to form complete AFDM-IM data, and the organized AFDM data is sent as a signal on the corresponding transducer according to a traditional solution.

[0069] In the second step, the maximum likelihood detection algorithm is used to perform joint detection on the transmitted data, and the following processing is performed on the data receiving link:

[0070] Step 2.1: The receiving signal of the data transmission link is

[0071]

[0072] Where P is the number of paths, d p is the normalized delay, ν p is the Doppler shift, ω r is complex white Gaussian noise.

[0073] Step 2.2: Remove the Chirp cyclic prefix of the received data and transform it using the DAFT matrix A, that is,

[0074] y=H eff x+ω (7)

[0075] Among them, H eff is the effective channel matrix.

[0076] Step 2.3: Use the corresponding pilot prior information to perform channel estimation. For a system based on a feedback link, the feedback signal is the estimated channel information, i.e.

[0077]

[0078] Among them, l2(·) represents a likelihood function, which is used to estimate the channel parameters, y E represents the part of y related to channel estimation, θ=[h0,…h P-1 ,d0,…d P-1 ,ν0,…ν P-1 ], x pilot is the first symbol in the frame, It is h i,E The first column, h i is the complex gain, α p is the normalized Doppler shift. p ,α p ,h i The estimated effective channel matrix can be derived.

[0079] Step 2.4: Perform joint detection on the received data based on the estimated effective channel matrix, where the maximum likelihood criterion is used for detection:

[0080]

[0081] in, Indicates the detected subcarrier index, represents the detected modulation symbol, Represents the pre-chirp parameter arrangement patterns of all detected groups.

Claims

1. A method for underwater acoustic adaptive transmission based on affine domain two-dimensional index modulation, comprising the following steps: Step 1: Design of the transmitting link of the underwater acoustic adaptive transmission system based on affine domain dual-dimensional index modulation; Step 2: Design of receiving link of underwater acoustic adaptive transmission system based on affine domain dual-dimensional index modulation; Step 1 includes the following steps: Step 1.1: Extract channel information parameters based on the signal of the feedback link; Step 1.2: Group the subcarriers and the information bits to be transmitted. The information bits of each group are mapped into three parts: the first part (B1) is the subcarrier index bit used to indicate the subcarrier to be activated; the second part (B2) is the parameter index bit used to indicate the pre-chirp parameter c2 assigned to each activated subcarrier; and the third part (B3) is the modulation bit used to indicate the traditional modulation symbol mapped through MPSK / MQAM. Step 1.3: After mapping the modulation symbols onto the activated subcarriers, the affine Fourier domain data is formed, and then the DAFT matrix A is constructed based on the estimated channel information parameters. Step 1.4: Use IDAFT matrix A -1 Transforming the affine Fourier domain data, adding a cyclic prefix to the transformed data to form AFDM-IM data, and transmitting the organized AFDM-IM data on the corresponding transducer according to a conventional scheme; Step 2 includes the following steps: Step 2.1: Receive according to the traditional scheme; Step 2.2: Remove the cyclic prefix of the received data and transform it using the DAFT matrix A. Step 2.3: Use the corresponding pilot prior information to perform channel estimation; Step 2.4: Perform joint detection and demodulation on the received data based on the estimated channel state information.

2. The underwater acoustic adaptive transmission method based on affine domain dual-dimensional index modulation according to claim 1 is characterized in that: In step 1.1, the signal of the feedback link is Where α is the channel attenuation, b(θ) is the receiving direction vector, and a(θ) is the sending direction vector. is white noise, ν is Doppler broadening, τ is delay, Representing channel information in feedback link based systems.

3. The underwater acoustic adaptive transmission method based on affine domain two-dimensional index modulation according to claim 1 is characterized in that: In step 1.2, the candidate values ​​of the pre-chirp parameter c2 come from a predefined set S. The B2 bit of each sub-block is used to select a pre-chirp parameter arrangement pattern from the set S, that is, to determine the combination of c2 values ​​used for the activated subcarriers in the sub-block. The parameter index bit Predefined collections 4. The underwater acoustic adaptive transmission method based on affine domain dual-dimensional index modulation according to claim 1, characterized in that: In step 1.3, the modulation symbols are mapped to the activated subcarriers to form affine Fourier domain data, and then the DAFT matrix A is constructed based on the estimated channel information parameters. Where F is the discrete Fourier transform matrix, Λ c Defined as 5. The underwater acoustic adaptive transmission method based on affine domain two-dimensional index modulation according to claim 1 is characterized in that: In step 1.4, the IDAFT matrix A is used -1 Transform data in the affine Fourier domain A Chirp period prefix is ​​added to the transformed data to form complete AFDM-IM data, and the organized AFDM-IM data is sent as a signal on the corresponding transducer according to a traditional solution.

6. The underwater acoustic adaptive transmission method based on affine domain two-dimensional index modulation according to claim 1, characterized in that: In step 2.1, the receiving signal of the data transmission link is Where P is the number of paths, d p is the normalized delay, ν p is the Doppler shift, ω r is complex white Gaussian noise.

7. The underwater acoustic adaptive transmission method based on affine domain dual-dimensional index modulation according to claim 1, characterized in that: In step 2.2, the Chirp cyclic prefix of the received data is removed and the DAFT matrix A is used to transform it. y=H eff x+ω (7) Among them, H eff is the effective channel matrix.

8. The underwater acoustic adaptive transmission method based on affine domain dual-dimensional index modulation according to claim 1, characterized in that: In step 2.3, the corresponding pilot prior information is used to perform channel estimation. For the system based on the feedback link, the feedback signal is the estimated channel information, that is, Among them, l2(·) represents a likelihood function, which is used to estimate the channel parameters, y E represents the part of y related to channel estimation, θ=[h0,…h P-1 ,d0,…d P-1 ,ν0,…ν P-1 ], x pilot is the first symbol in the frame, It is h i,E The first column, h i is the complex gain, α p is the normalized Doppler shift, according to d p ,α p ,h i The estimated effective channel matrix can be derived.

9. The underwater acoustic adaptive transmission method based on affine domain dual-dimensional index modulation according to claim 1, characterized in that: In step 2.4, the received data is jointly detected based on the estimated effective channel matrix, where the maximum likelihood criterion is used for detection: in, Indicates the detected subcarrier index, represents the detected modulation symbol, Represents the pre-chirp parameter arrangement patterns of all detected groups.

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