Novel underwater vehicle communication system and method

Abstract

The invention discloses a novel underwater vehicle communication system and a novel underwater vehicle communication method in the technical field of communication, the novel underwater vehicle communication system comprises a water surface mother ship, an underwater vehicle and a relay R module, the water surface mother ship transmits information to the underwater relay R module through an umbilical cable; the underwater relay R module comprises an electro-optical conversion unit used for converting an electric signal into an optical signal, the underwater relay R module transmits the converted optical signal to the underwater vehicle through a UWOC link, and the underwater vehicle is provided with a photoelectric receiving unit used for converting the optical signal into the electric signal. The power line carrier communication is wired communication, is not influenced by underwater tide, noise, water temperature and the like, and is high in stability.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and particularly to a novel underwater vehicle communication system and method. Background Art

[0002] As the pace of human understanding and development of the ocean gradually accelerates, the need for communication between land and water has become increasingly urgent. In activities such as ocean scientific investigations, ocean environmental monitoring, ocean resource surveys and development, and fishery resource fishing, there is an urgent need for a wireless, reliable, and highly secure two-way information transmission method between underwater terminals such as underwater robots and underwater sensors and the surface mother ship to transmit information such as text, voice, images, and control signals.

[0003] The underwater acoustic channel is one of the most complex channels in the field of wireless communication. This is caused by the scattering and refraction effects generated by the undulating waves on the sea surface, the layered non-uniformity and unevenness of the seabed, and the inhomogeneity of the seawater medium during the propagation of sound waves in the ocean. In addition, the complexity of the shallow water acoustic channel is also reflected in its variation with time and space.

[0004] Power Line Communication (PLC) is a technology that uses existing power lines for signal transmission. The advantage of PLC link signal transmission is that it makes full use of the existing power transmission lines without introducing new communication lines, and the implementation cost is low. Currently, power line communication based on umbilical cables is widely used in underwater communication.

[0005] Underwater Wireless Optical Communication (UWOC) is a new technology that uses light waves as information carriers to transmit information through underwater channels. Compared with underwater acoustic communication, it has the advantages of high communication rate, large capacity, short delay, and good security.

[0006] In view of the current problem of unstable transmission of ocean exploration data, we need to provide a hybrid cooperative communication system that combines underwater power line and underwater wireless optical communication to achieve stable and reliable information transmission between the surface mother ship and the underwater vehicle, so as to solve the above problems. Summary of the Invention

[0007] The purpose of the present invention is to provide a novel underwater vehicle communication system and method to solve the problems raised in the above background art.

[0008] To achieve the above purpose, the present invention provides the following technical solutions:

[0009] A new underwater vehicle communication system, including a surface mother ship, an underwater vehicle, and a relay R module. The surface mother ship transmits information to the underwater relay R module through an umbilical cable. The underwater relay R module includes an electro-optical emission unit for converting an electrical signal into an optical signal. The underwater relay R module transmits the converted optical signal to the underwater vehicle through a UWOC link. The underwater vehicle is provided with a photoelectric receiving unit for converting the optical signal into an electrical signal.

[0010] A further solution: The carrier of the underwater relay R module includes an underwater robot.

[0011] A further solution: The surface mother ship uses a PLC link to transmit signals.

[0012] A further solution: The electro-optical emission unit includes a DBPSK adjustment unit, a band-pass filter, a DC bias unit, and a laser drive unit.

[0013] A further solution: The photoelectric receiving unit includes a filter, a photodetector, an AC / DC component separator, and a DBPSK demodulator.

[0014] Another object of the present invention is to provide a new underwater vehicle communication method, specifically including the following steps:

[0015] The first step: The surface mother ship transmits a control signal to the relay through an umbilical cable. The signal received by the relay R module is:

[0016]

[0017] Where P S is the average transmission power, x is the signal transmitted by the underwater robot through the PLC link, and n SR represents Gaussian white noise, and h SR is the PLC channel fading factor, and its modulus follows a logarithmic distribution;

[0018] The fading amplitude h SR of the power line PLC follows a log-normal distribution, then the signal-to-noise ratio γ SR follows a log-normal distribution, expressed as:

[0019]

[0020] Where μ u = 2μ SR + ln P R / σ b 2 , σ u = 2σ SR , μ v = 2μSR +ln P R / ((1 + β)σ b 2 ),σ v =2σ SR ;

[0021] Since the log - normal distribution can be approximated as a gamma distribution, the probability density function PDF of the instantaneous signal - to - noise ratio γ SR is further expressed as:

[0022]

[0023] where, is the shading degree parameter in the Gamma - distribution PDF, and are the average power of the shaded area in the Gamma - distribution PDF;

[0024] Step 2: The relay R module then transmits the information to the submersible through the UWOC link. The RF alternating - current signal x is first converted into an optical signal based on the sub - carrier modulation method via a binary phase - shift keying scheme. To ensure that the transmitted optical signal is not distorted in the UWOC link, a direct - current bias B needs to be superimposed on x in the modulation module of the information source, so as to ensure the non - negativity of the modulation signal. Therefore, the transmitted optical signal can be expressed where P s1 represents the transmission power of the optical transmitter, and η represents the electro - optical conversion coefficient. Therefore, the optical signal at R can be expressed as

[0025] Step 3: The relay adopts the decode - and - forward scheme. Therefore, the signal received by the submersible is:

[0026]

[0027] where P R is the average transmission power at D, is the optical signal after relay decoding, n RD represents the AWGN with zero mean and variance N, and I represents the channel gain of the UWOC. Considering the joint influence of UOT fading I a and pointing error I p , it is defined as I = I a I p .

[0028] The channel gain I of the underwater wireless optical UWOC link in this system follows an EGG distribution with pointing error. The PDF and CDF expressions of its instantaneous signal - to - noise ratio γ RD are:

[0029]

[0030]

[0031] is the average signal-to-noise ratio of the UWOC link, E[·] is the expected symbol, r represents the type of detection technology (r = 1 for HD technology; r = 2 for IM / DD technology), ω, λ, a, b, and c are the fading parameters of the EGG distribution, A o and ξ are parameters regarding the pointing error, is the Fox’s H function;

[0032] For the two detection methods of heterodyne detection HD and intensity modulation and direct detection IM / DD, the expression of the unified system average channel capacity is:

[0033]

[0034] where τ = 1 for HD technology and τ = e / (2π) represents IM / DD. According to equations (3), (5), and (6), the average channel capacity of the DF system is:

[0035]

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows: The power line carrier communication of the present invention is a wired communication, which is not affected by underwater tides, noise, water temperature, etc., and has strong stability. Moreover, through the method of cooperative relay, the robustness and flexibility of the entire underwater communication system can be effectively enhanced, the transmission distance and range of signals can be increased. Compared with single underwater acoustic communication, the power line communication based on umbilical cable and the underwater optical wireless cooperative communication system can integrate the advantages of both, and has broad application prospects in land and water communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a cooperative communication system diagram of a novel underwater vehicle communication system;

[0038] Figure 2 is a schematic diagram of the communication structure of a novel underwater vehicle communication system;

[0039] Figure 3 is a comparison diagram of the channel capacity of the cooperative communication system of the present invention with the optical detection method and the impulse noise in the power line;

[0040] Figure 4 is a flowchart of the steps of a novel underwater vehicle communication method. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] In order to make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0042] Please refer to Figures 1-4 , the present invention provides a technical solution:

[0043] A novel underwater vehicle communication system includes a surface mother ship, an underwater vehicle, and a relay R module. The surface mother ship transmits information to the underwater relay R module through an umbilical cable. The underwater relay R module includes an electro-optical emission unit for converting an electrical signal into an optical signal. The underwater relay R module transmits the converted optical signal to the underwater vehicle through a UWOC link. The underwater vehicle is provided with a photoelectric receiving unit for converting the optical signal into an electrical signal.

[0044] A further solution: The carrier of the underwater relay R module includes an underwater robot.

[0045] A further solution: The surface mother ship uses a PLC link to transmit signals.

[0046] A further solution: The electro-optical emission unit includes a DBPSK adjustment unit, a band-pass filter, a DC bias unit, and a laser drive unit.

[0047] A further solution: The photoelectric receiving unit includes a filter, a photodetector, an AC / DC component separator, and a DBPSK demodulator.

[0048] Another object of the present invention is to provide a novel underwater vehicle communication method, which specifically includes the following steps:

[0049] The first step: The surface mother ship transmits a control signal to the relay through an umbilical cable. The signal received by the relay R module is:

[0050]

[0051] where P S is the average transmission power, x is the signal transmitted by the underwater robot through the PLC link, n SR represents Gaussian white noise, h SR is the PLC channel fading factor, and its modulus follows a logarithmic distribution;

[0052] The fading amplitude h SR of the power line PLC follows a log-normal distribution, then the signal-to-noise ratio γ SR follows a log-normal distribution, which is expressed as:

[0053]

[0054] where μ u = 2μ SR + lnP R / σb 2 , σ u = 2σ SR , μ v = 2μ SR + ln P R / ((1 + β)σ b 2 ), σ v = 2σ SR ;

[0055] Since the log-normal distribution can be approximated as a gamma distribution, the probability density function PDF of the instantaneous signal-to-noise ratio γ SR is further expressed as:

[0056]

[0057] where, is the shading degree parameter in the Gamma distribution PDF, and are the average power of the shaded area in the Gamma distribution PDF;

[0058] Step 2: The relay R module then transmits the information to the submersible through the UWOC link. The RF alternating current signal x is first converted into an optical signal based on the subcarrier modulation method via the binary phase shift keying scheme. To ensure that the transmitted optical signal is not distorted in the UWOC link, a DC bias B needs to be superimposed on x in the modulation module of the information source, so as to ensure the non-negativity of the modulation signal. Therefore, the transmitted optical signal can be expressed where P s1 represents the transmission power of the optical transmitter, and η represents the electro-optical conversion coefficient. Therefore, the optical signal at R can be expressed as

[0059] Step 3: The relay adopts the decode-and-forward scheme. Therefore, the signal received by the submersible is:

[0060]

[0061] where P R is the average transmission power at D, is the optical signal after relay decoding, n RD represents AWGN with a mean of zero and a variance of N, and I represents the UWOC channel gain. Considering the combined effects of UOT fading I a and pointing error I p , it is defined as I = I a I p .

[0062] The channel gain I of the underwater wireless optical UWOC link in this system follows an EGG distribution with pointing error, and its instantaneous signal-to-noise ratio γ RD The PDF and CDF expressions of are:

[0063]

[0064]

[0065] is the average signal-to-noise ratio of the UWOC link, E[·] is the expectation symbol, r represents the type of detection technology (r = 1 for HD technology; r = 2 for IM / DD technology), ω, λ, a, b, and c are the fading parameters of the EGG distribution, A o and ξ are parameters regarding the pointing error, is the Fox’s H function;

[0066] For the two detection methods of heterodyne detection HD and intensity modulation and direct detection IM / DD, the expression of the unified system average channel capacity is:

[0067]

[0068] where τ = 1 for HD technology and τ = e / (2π) represents IM / DD. According to Eqs. (3), (5), and (6), the average channel capacity of the DF system is:

[0069]

[0070] As Figure 3 shown, Figure 3 is a comparison diagram of the channel capacity of the cooperative communication system with the optical detection method and the impulse noise in the power line. It can be seen from the figure that when the underwater optical wireless link adopts the heterodyne detection HD technology, the cooperative communication system has better system performance. At the same time, it can be seen that when the impulse noise in the power line PLC channel is small, the cooperative communication system has a larger channel capacity.

[0071] The above is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application should not easily think of changes or substitutions, and all should be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

1. A new underwater vehicle communication system, comprising a surface mother ship, an underwater vehicle, and a relay R module, characterized in that: The surface mother ship transmits information to the underwater relay R module through an umbilical cable. The underwater relay R module includes an electro-optic conversion unit for converting an electrical signal into an optical signal. The underwater relay R module transmits the converted optical signal to the underwater vehicle through a UWOC link. The underwater vehicle is provided with a photoelectric receiving unit for converting the optical signal into an electrical signal.

2. The novel underwater vehicle communication system according to claim 1, wherein: The carrier of the underwater relay R module includes an underwater robot.

3. A novel underwater vehicle communication system according to claim 1, characterized in that: The surface mother ship uses a PLC link to transmit signals.

4. A novel underwater vehicle communication system according to claim 1, characterized in that: The electro-optic transmitting unit includes a DBPSK adjustment unit, a band-pass filter, a DC bias unit, and a laser driving unit.

5. A novel underwater vehicle communication system and method according to claim 4, characterized in that: The photoelectric receiving unit includes a filter, a photodetector, an AC / DC component separator, and a DBPSK demodulator.

6. A novel underwater vehicle communication method, according to any one of claims 1-5 of a novel underwater vehicle communication system, characterized in that: It includes the following steps: The first step: The surface mother ship transmits a control signal to the relay through an umbilical cable. The signal received by the relay R module is: where P S is the average transmission power, x is the signal transmitted by the underwater robot through the PLC link, and n SR represents Gaussian white noise, and h SR is the PLC channel fading factor, and the modulus thereof follows a logarithmic distribution; The fading amplitude h of the power line PLC SR obeys the log-normal distribution, then the signal-to-noise ratio γ SR obeys the log-normal distribution, which is expressed as: where, μ u = 2μ SR + lnP R / σ b 2 , σ u = 2σ SR , μ v = 2μ SR + lnP R / ((1 + β)σ b 2 ), σ v = 2σ SR ; Since the log-normal distribution can be approximated as a gamma distribution, the probability density function PDF of the instantaneous signal-to-noise ratio γ SR is further expressed as: Among them, is the shadow degree parameter in the Gamma distribution PDF, and is the average power of the shadow area in the Gamma distribution PDF; Step 2: The relay R module then transmits the information to the submersible via the UWOC link. The RF alternating current signal x is first converted into an optical signal based on the subcarrier modulation method via the binary phase shift keying scheme. To ensure that the transmitted optical signal is not distorted in the UWOC link, a DC bias B needs to be superimposed on x in the modulation module of the information source to ensure the non-negativity of the modulation signal. Therefore, the transmitted optical signal can be expressed as where P s1 represents the transmission power of the optical transmitter, and η represents the electro-optical conversion coefficient. Therefore, the optical signal at R can be expressed as The third step: The relay adopts a decode-and-forward scheme. Therefore, the signal received by the underwater vehicle is: Where P R is the average transmit power at D, is the optical signal after relay decoding, n RD represents AWGN with zero mean and variance N, I represents the channel gain of UWOC, considering the joint influence of UOT fading I a and pointing error I p is defined as I = I a I p ; The channel gain I of the underwater wireless optical UWOC link in this system follows the EGG distribution with pointing error, and its instantaneous signal-to-noise ratio γ RD The PDF and CDF expressions are as follows: is the average signal-to-noise ratio of the UWOC link, E[·] is the expected symbol, r represents the type of detection technique (r = 1 for HD technique; r = 2 for IM / DD technique), ω, λ, a, b, and c are the fading parameters of the EGG distribution, A o and ξ are parameters regarding the pointing error, is the Fox’s H function; For the two detection methods of heterodyne detection HD and intensity modulation and direct detection IM / DD, the expression of the unified system average channel capacity is: Among them, τ = 1 is the HD technology, and τ = e / (2π) represents IM / DD. According to equations (3), (5), and (6), the average channel capacity of the DF system is obtained as:

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