WO2022262172A1

WO2022262172A1 - Multi-carrier underwater acoustic anti-interference communication method based on index modulation

Info

Publication number: WO2022262172A1
Application number: PCT/CN2021/127830
Authority: WO
Inventors: 王彪; 张明亮; 朱雨男; 李涵琼; 吴承希; 张友文
Original assignee: 江苏科技大学
Priority date: 2021-06-15
Filing date: 2021-11-01
Publication date: 2022-12-22
Also published as: JP7455428B2; CN113395117A; CN113395117B; JP2023534326A

Abstract

A multi-carrier underwater acoustic anti-interference communication method based on index modulation. Considering solving the problems of a bit error rate of a receiving end of a system being relatively high due to discontinuous frequency band interference in an underwater acoustic communication environment, etc., on the basis that a one-dimensional sub-carrier state index modulation technique is introduced into a traditional underwater acoustic FBMC communication system, a communication frequency band of an FBMC-IM system is divided according to a discontinuous interference frequency range, such that sub-carriers of a part aliasing with discontinuous frequency band interference signals are silent, and subcarriers which are not interfered with are kept in an active state and bear a communication signal, thereby realizing the division of discontinuous communication frequency bands, avoiding the effect of interference, and improving an anti-interference capability. The method is innovative compared with the existing aspect of interference avoidance for underwater acoustic multi-carrier communications.

Description

A multi-carrier underwater acoustic anti-jamming communication method based on index modulation

technical field

The invention relates to the technical field of underwater acoustic communication, in particular to an index modulation-based multi-carrier underwater acoustic anti-jamming communication method.

Background technique

In recent decades, research on underwater acoustic high-speed communication at home and abroad has mainly focused on multi-carrier modulation technology, among which Orthogonal Frequency Division Multi-plexing (OFDM) technology is typical, and its advantage lies in the data The transmission rate is high and the spectrum utilization rate is high, but in order to improve the performance of the system, OFDM needs to add a cyclic prefix to overcome its inter-carrier interference and inter-symbol interference. In order to solve the disadvantages of OFDM out-of-band radiation and out-of-band attenuation, a Filter Bank Multi-Carrier (FBMC) underwater acoustic communication technology is proposed. The biggest advantage is that the system still has Strong resistance to inter-carrier interference and inter-symbol interference. Although compared with OFDM, the performance of FBMC system has been improved, but there is still interference between subcarriers and symbols in FBMC system. In order to solve the problem that useful symbols are interfered by superposition of surrounding symbols, one-dimensional index information is introduced by the idea of transmitting information in the space domain (only the activated part of the antenna is used to transmit information, and the unactivated antenna is used as auxiliary transmission index information), adding The empty carrier allows some sub-carriers to be activated to carry information, and proposes underwater acoustic multi-carrier communication based on one-dimensional index modulation. In addition, narrowband interference (Narrow Band Interference, NBI) is a common type of interference in the underwater acoustic communication environment. It has high energy and occupies part of the bandwidth of the system, destroying the orthogonality between sub-carriers, which will lead to poor communication performance of multi-carrier systems. There are still relatively few studies on these interference avoidance methods in the field of underwater acoustic communication.

Contents of the invention

The invention provides an underwater acoustic multi-carrier anti-interference communication method to solve the problems of discontinuous frequency band interference in the current underwater acoustic communication environment, which leads to a high bit error rate at the receiving end of the communication system.

A multi-carrier underwater acoustic anti-interference communication method based on index modulation, comprising the steps of:

Step 1: Add one-dimensional index information to the traditional underwater acoustic FBMC communication system to obtain the FBMC underwater acoustic communication system based on index modulation;

Step 2: Calculate and simulate the bit error rate of the underwater acoustic FBMC-IM communication system with different numbers of activated subcarriers, and determine the appropriate number of activated subcarriers as an interference-free underwater acoustic FBMC-IM communication system;

Step 3: Considering that there is discontinuous frequency band interference in the underwater acoustic communication environment, adding discontinuous frequency band interference in the interference-free underwater acoustic FBMC-IM system communication environment of the step 2;

Step 4: According to the frequency range of discontinuous interference in the underwater acoustic communication environment, divide the communication frequency band of the FBMC-IM system without interference, so that the subcarriers that overlap with the discontinuous frequency band interference signal are silent, and the subcarriers that are not interfered Keep active and carry communication signals, realize discontinuous communication frequency band division, and obtain underwater acoustic FBMC-IM anti-jamming communication system to realize multi-carrier underwater acoustic anti-jamming communication.

Further, in the FBMC underwater acoustic communication system in step 1, the transmitting end of the system needs to perform bit splitting processing on the transmitted information, which is divided into constellation modulation bits and index modulation bits; the data information bits input to the transmitting end are defined as A bits, and one FBMC The number of all subcarriers in the block is M, and the information at the sending end is divided into G groups after shunting processing, and the number of bits contained in each group is P bits; similarly, all subcarriers M are divided into g subcarrier blocks, M subcarrier blocks The carrier is divided into G sub-carrier blocks, and the number of carriers in each sub-carrier block is Q, so that the P-bit information of each group is correspondingly mapped to a sub-carrier block with a length of Q; P-bit information in each group = divided into P ₁ Bits and P ₂ bits are two parts, P ₁ bit is an index modulation bit, which is used to control the position of the activated subcarrier; P ₂ bit is a constellation modulation bit, which is mapped to the activated k subcarriers.

Furthermore, all the subcarriers of the FBMC-IM system are divided into 128 subcarrier groups, and 4, 3, 2, and 1 subcarriers are selected from each group of 4 subcarriers to activate, so that the activated subcarriers are in an active state, and no The activated sub-carriers are in a silent state, and according to different positions of the activated sub-carriers, index signals are used for corresponding mapping to complete index modulation.

Further, in step 2, the bit error rate of the underwater acoustic FBMC-IM communication system is calculated and simulated with different numbers of activated subcarriers, and the simulation parameters are set as follows:

Set the baseband bandwidth to 6400Hz, the number of subcarriers to 512, the baseband sampling frequency to 12800Hz, the number of FBMC symbols to 20, the communication frequency range to 12.8k Hz to 19.2k Hz, and the range of signal-to-noise ratio to 0dB to 30dB.

Further, in step 3, adding discontinuous frequency band interference in the underwater acoustic communication environment is as follows: preset the communication interference frequency band range, randomly generate a random variable X within the communication frequency band range, and X obeys the mathematical expectation of μ, variance The normal distribution random number of σ ² is denoted as N(μ,σ ² ); use the filter function to design a bandpass filter, calculate and set the parameters, let the normal distribution random number N(μ,σ ² ) pass through the band Pass filter, so that this section of random numbers falling within the preset communication interference frequency band passes through the filter; Convolve this section of random numbers after band-pass filtering with the transmission signal modulated by the filter bank to obtain A continuous frequency band interference; non-continuous frequency band interference has at least two or more interference frequency band segments to be discontinuous, therefore, another continuous frequency band interference is set in another frequency band range within the communication frequency band range, and so on , and then these frequency band interferences are superimposed to obtain artificially set non-continuous frequency band interference.

Further, in step 3, it is assumed that there is a discontinuous frequency band interference composed of two narrow-band interference segments in the underwater acoustic communication environment, and the interference frequency ranges are set to 14.3kHz-14.8kHz and 16.8kHz-17.8kHz.

Further, in step 4, the specific process of communication is as follows: firstly, the communication signal is added to an empty carrier through index modulation to obtain an index-modulated communication signal, and then the index-modulated communication signal is equally spaced according to the non-continuous frequency band interference measured by environmental perception. The frequency band is divided so that the subcarriers of the aliased interference signal frequency band are all silent, no communication signals are transmitted, and the subcarriers without aliasing are active. After multi-carrier modulation by the filter, they reach the receiving end through the underwater acoustic channel , after filter multi-carrier demodulation, the frequency band is divided according to environmental perception, and the communication signal to be demodulated is obtained by index modulation, and then the FBMC-IM communication signal index demodulation and decoding are performed to restore the original communication signal.

Beneficial effects of the present invention:

The research on FBMC underwater acoustic anti-interference communication technology based on index modulation in the present invention solves the problem that the discontinuous frequency band interference in the underwater acoustic communication environment leads to a high bit error rate at the receiving end of the system. According to the frequency range of discontinuous interference, FBMC- The communication frequency band of the IM system is divided so that the subcarriers that overlap with the discontinuous frequency band interference signal are silent, and the undisturbed subcarriers remain active and carry communication signals, realizing discontinuous communication frequency band division and avoiding interference. influences. Compared with the existing underwater acoustic anti-jamming communication technology, the present invention has certain advantages.

Description of drawings

Fig. 1 is a flowchart of an underwater acoustic multi-carrier anti-jamming communication method according to the present invention.

Fig. 2 is a block diagram of a sending end of an underwater acoustic FBMC communication system based on index modulation according to the present invention.

FIG. 3 is an index modulation subcarrier mapping table in an embodiment of the present invention.

Fig. 4 is a simulation comparison diagram of the bit error rate of the underwater acoustic FBMC-IM in the embodiment of the present invention.

FIG. 5 is a schematic diagram of a system communication frequency band under discontinuous frequency band interference in an embodiment of the present invention.

Fig. 6 is a process diagram of underwater acoustic FBMC-IM anti-interference processing according to an embodiment of the present invention.

Fig. 7 is a comparison chart of the bit error rate of the underwater acoustic FBMC-IM anti-jamming communication system in the embodiment of the present invention.

detailed description

The technical solution of the present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Fig. 2, the index modulation in the present invention is evolved from the idea of transmitting information in the space domain, and only some activated antennas are used to transmit information, and the unactivated antennas are used as auxiliary transmission index information. According to this idea, the underwater acoustic FBMC communication system based on index modulation can be obtained by introducing the one-dimensional subcarrier state information index modulation into the underwater acoustic FBMC communication system model. The specific steps are shown in Figure 1.

Step 1: In the underwater acoustic FBMC-IM communication system model, the transmitting end first performs bit splitting processing on the information to be transmitted, and divides it into constellation modulation bits and index modulation bits. Assuming that the data information bits input to the sending end are A bits, and the number of all subcarriers in one FBMC block is M, the information at the sending end is divided into G groups after shunting processing, and the number of bits contained in each group is P bits; the same Divide all subcarriers M into g subcarrier blocks, M subcarriers are divided into G subcarrier blocks, and the number of carriers in each subcarrier block is Q, so that each group of P bit information can be mapped to a length of Q. on the subcarrier block. The P bit information in each group can be divided into two parts: P ₁ bit and P ₂ bit. P ₁ bit is the index modulation bit, which is used to control the position of the activated subcarrier; P ₂ bit is the constellation modulation bit, which is mapped to Among the activated k subcarriers.

If the length of the subcarrier block is Q=4, and the number of active subcarriers in the subcarrier block is K=2, only 2 subcarriers are in the active state for each transmission, and the remaining subcarriers are in the silent state. Then the activated subcarriers and the corresponding activated subcarrier position lookup table can be shown in the index modulation subcarrier mapping table in Figure 3. In the table, E represents the activated real carrier in the subcarrier block, and 0 represents the silent empty space in the subcarrier block. carrier.

After obtaining the FBMC-IM received data symbols at the receiving end, these FBMC-IM data symbols are grouped. According to the index information, select the corresponding mapping method such as the table lookup method or the combined number method, that is, according to the activated subcarriers and the corresponding activated subcarrier position index information carried, they can be detected, and the index position decoding and constellation symbols can be realized. decoding.

Step 2: Calculate and simulate the bit error rate of the underwater acoustic FBMC-IM communication system with different numbers of activated subcarriers. The simulation parameters are set as follows:

As shown in FIG. 4 , it is a simulation comparison diagram of the bit error rate of the underwater acoustic FBMC-IM of the present invention, and all subcarriers of the FBMC-IM system are divided into 128 subcarrier groups (blocks). Select 4, 3, 2, and 1 subcarriers from each group of 4 subcarriers to activate, so that the activated subcarriers are in an active state, and the inactive subcarriers are in a silent state. According to the different positions of the activated subcarriers, use the index signal Perform corresponding mapping to complete index modulation. It can be clearly seen from the simulation results that the index-modulated FBMC-IM system has a better bit error rate performance because a large number of empty subcarriers are added to the system. At the same time, for each subcarrier group (block), as the signal-to-noise ratio increases, the number of activated subcarriers decreases and the number of inactive subcarriers increases, the lower the bit error rate, the better the performance.

Step 3: Add discontinuous frequency band interference in the underwater acoustic communication environment, and its settings are as follows:

Assuming that a communication interference frequency range is predetermined, a random variable X is randomly generated within the communication frequency range, and X obeys a normal distribution random number with mathematical expectation μ and variance σ ² , denoted as N(μ,σ ² ). Then use the filter function to design a bandpass filter, calculate and set parameters, determine the order of the filter, and set the frequency range of the bandpass filter according to the frequency range of discontinuous frequency band interference in the actual underwater acoustic environment

Wherein, W _n is the frequency range of discontinuous interference frequency bands, and n is the number of discontinuous interference frequency bands, (for example, under the situation as shown in Figure 5, setting filter order is 1000, two bandpass filter parameters Set as W ₁ =[0.2725 0.2850] and W ₂ =[0.6600 0.7225]). Then let the upper normal distribution random number pass through the band-pass filter, so that the segment of random number falling within the preset communication interference frequency band passes through the filter. Then, the band-pass filtered random number is convolved with the transmission signal modulated by the filter bank, so that a continuous frequency band interference is simply obtained. Discontinuous frequency band interference can only be said to be discontinuous if there are at least two or more than two interference frequency band segments. In the same way, another continuous frequency band interference is set in another frequency band range within the communication frequency band range. By analogy, and then superimposing these frequency band interferences, the artificially assumed non-continuous frequency band interference can be obtained.

As shown in Figure 5, it is a schematic diagram of the system communication frequency band under the discontinuous frequency band interference of the present invention. Here, discontinuous frequency band interference is added in the uninterrupted underwater acoustic FBMC-IM system communication environment. It is composed of two narrow-band interference segments. The frequency ranges are set to 14.3kHz to 14.8kHz and 16.8kHz to 17.8kHz.

Step 4: From step 3, divide the communication frequency band of the system according to the discontinuous interference frequency range in the underwater acoustic communication environment:

As shown in Figure 6, it is a schematic diagram of underwater acoustic FBMC-IM anti-interference processing of the present invention. First, the communication signal is added to the empty carrier through index modulation to obtain an index-modulated communication signal, and then the index is modulated according to the discontinuous frequency band interference measured by environmental perception. The communication signal is divided into equal-spaced frequency bands, so that the subcarriers of the aliased interference signal frequency band are all silent, no communication signals are transmitted, and the subcarriers without aliasing are in an active state to obtain ③, and then filter multi-carrier modulation Finally, it reaches the receiving end through the underwater acoustic channel, and obtains ④ through multi-carrier demodulation of the filter, divides the frequency band according to the environmental perception, and obtains the communication signal to be demodulated by index modulation ⑤, and then performs index demodulation and decoding of the FBMC-IM communication signal Recover the original communication signal to get ⑥.

Finally, simulate the underwater acoustic FBMC-IM anti-interference communication system in the embodiment of the present invention, calculate and analyze the bit error rate:

As shown in Figure 7, it is a comparison chart of the bit error rate of the underwater acoustic FBMC-IM anti-interference communication system of the present invention. The communication frequency range of the known underwater acoustic FBMC-IM communication system is 12.8k Hz to 19.2k Hz, and the discontinuous interference frequency The interference frequency ranges from 14.3kHz to 14.8kHz and 16.8kHz to 17.8kHz. Anti-interference processing is performed on the underwater acoustic FBMC-IM communication system under discontinuous frequency band interference to realize discontinuous communication frequency band division. The simulation results can be seen in the figure. With the increase of the signal-to-noise ratio, the underwater acoustic FBMC-IM anti-jamming system under the condition of discontinuous frequency band interference, the bit error rate is significantly lower than that of the unprocessed FBMC-IM after silent processing of the subcarriers of the discontinuous interfered frequency band system, and the error rate gap between the processed anti-jamming system and the system is small under the condition of no interference. It shows that the interference processing scheme effectively solves the aliasing problem of communication signals and interference signals, significantly reduces the bit error rate at the receiving end, and greatly improves the anti-interference ability of the system.

The above descriptions are only preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments, but all equivalent modifications or changes made by those of ordinary skill in the art according to the disclosure of the present invention should be included within the scope of protection described in the claims.

Claims

A multi-carrier underwater acoustic anti-interference communication method based on index modulation, characterized in that: comprising the following steps:

Step 1: Add one-dimensional index information to the traditional underwater acoustic FBMC communication system to obtain the FBMC underwater acoustic communication system based on index modulation;

Step 2: Calculate and simulate the bit error rate of the underwater acoustic FBMC-IM communication system with different numbers of activated subcarriers, and determine the appropriate number of activated subcarriers as an interference-free underwater acoustic FBMC-IM communication system;

Step 3: Considering that there is discontinuous frequency band interference in the underwater acoustic communication environment, adding discontinuous frequency band interference in the interference-free underwater acoustic FBMC-IM system communication environment of the step 2;

Step 4: According to the frequency range of discontinuous interference in the underwater acoustic communication environment, divide the communication frequency band of the FBMC-IM system without interference, so that the subcarriers that overlap with the discontinuous frequency band interference signal are silent, and the subcarriers that are not interfered Keep active and carry communication signals, realize discontinuous communication frequency band division, and obtain underwater acoustic FBMC-IM anti-jamming communication system to realize multi-carrier underwater acoustic anti-jamming communication.
A kind of multi-carrier underwater acoustic anti-jamming communication method based on index modulation according to claim 1, it is characterized in that: in the FBMC underwater acoustic communication system of step 1, the system transmitter needs to carry out bit splitting processing to the information of transmission, split It is the constellation modulation bit and the index modulation bit; define the data information bit input to the sending end as A bit, the number of all subcarriers in one FBMC block is M, and the information at the sending end is divided into G groups after shunting processing, and each group contains The number of bits is P bits; similarly, all subcarriers M are divided into g subcarrier blocks, M subcarriers are divided into G subcarrier blocks, and the number of carriers in each subcarrier block is Q, so that the P bit information of each group corresponds to Mapped to a subcarrier block with a length of Q; P bit information in each group = divided into two parts, P 1 bit and P 2 bit, and P 1 bit is an index modulation bit, which is used to control the position of the activated subcarrier; P 2 bits are constellation modulation bits, and are mapped to activated k subcarriers.
A kind of multi-carrier underwater acoustic anti-jamming communication method based on index modulation according to claim 2, it is characterized in that: all subcarriers of FBMC-IM system are divided into 128 subcarrier groups, select respectively from every group of 4 subcarriers 4, 3, 2, and 1 subcarriers are activated, so that the activated subcarriers are in the active state, and the inactive subcarriers are in the silent state. According to the different positions of the activated subcarriers, the corresponding mapping is performed using the index signal to complete the index modulation.
A kind of multi-carrier underwater acoustic anti-jamming communication method based on index modulation according to claim 1, it is characterized in that: in step 2, under the situation of different activated subcarrier numbers, the bit error rate of underwater acoustic FBMC-IM communication system is calculated and Simulation, the simulation parameters are set as follows:

Set the baseband bandwidth to 6400Hz, the number of subcarriers to 512, the baseband sampling frequency to 12800Hz, the number of FBMC symbols to 20, the communication frequency range to 12.8k Hz to 19.2k Hz, and the range of signal-to-noise ratio to 0dB to 30dB.
A multi-carrier underwater acoustic anti-jamming communication method based on index modulation according to claim 1, characterized in that: in step 3, adding discontinuous frequency band interference in the underwater acoustic communication environment is specifically as follows: preset communication interference frequency band range, the random variable X is randomly generated within the communication frequency band, and X obeys the normal distribution random number with mathematical expectation μ and variance σ 2 , denoted as N(μ,σ 2 ); use the filter function to design a bandpass Filter, calculate and set parameters, let the normal distribution random number N(μ, σ 2 ) pass through the band-pass filter, so that this segment of random number falling within the preset communication interference frequency band passes through the filter; A segment of band-pass filtered random numbers is convolved with the transmission signal modulated by the filter bank to obtain a segment of continuous frequency band interference; non-continuous frequency band interference has at least two or more than two interference band segments to be discontinuous, Therefore, another continuous frequency band interference is set in another frequency band within the communication frequency band, and so on, and then these frequency band interferences are superimposed to obtain artificially set non-continuous frequency band interference.
A multi-carrier underwater acoustic anti-jamming communication method based on index modulation according to claim 1, characterized in that: in step 3, it is set that there is a non-continuous channel consisting of two narrowband interference segments in the underwater acoustic communication environment Band interference, the interference frequency range is set to 14.3kHz-14.8kHz and 16.8kHz-17.8kHz.
A kind of multi-carrier underwater acoustic anti-interference communication method based on index modulation according to claim 1, characterized in that: in step 4, the specific process of communication is as follows: first, the communication signal is added to the empty carrier through index modulation to obtain the index modulation The communication signal, and then according to the discontinuous frequency band interference measured by the environmental perception, divide the frequency band of the index modulation communication signal into equal intervals, so that the subcarriers in the frequency band part of the aliased interference signal are all silent, no communication signal is transmitted, and there is no aliasing part The sub-carriers of the subcarriers are in an active state, and then the filter multi-carrier modulation is performed, and then the underwater acoustic channel reaches the receiving end, after the filter multi-carrier demodulation, the frequency band is divided according to the environmental perception, and the communication signal to be demodulated is obtained by index modulation, and then Perform index demodulation and decoding of the FBMC-IM communication signal to restore the original communication signal.