Cross-layer underwater magnetic induction communication current distribution method, device and medium

Abstract

The invention discloses a current distribution method and device for cross-layer underwater magnetic induction communication and a medium, and belongs to the field of digital information transmission, and the method comprises the steps: building a magnetic induction communication system circuit model which comprises a transmitter and a receiver, based on a probability density function of a misalignment factor between a transmitting coil of a transmitter and a receiving coil of a receiver, calculating a probability density function of mutual inductance, and receiving power, transmitting current and transmitting power, and by taking limited channel capacity and limited average power as constraints, according to the probability density function of mutual inductance and the receiving power; calculating an effective capacity expression of magnetic induction communication, establishing a mathematical optimization problem based on the effective capacity expression and constraints, and solving the optimization problem by using a convex optimization theory to obtain a current distribution method of cross-layer underwater magnetic induction communication; the equipment and the medium are used for implementing the method. According to the invention, the hardware cost and the size are reduced, the delay-sensitive service requirements are better met, and the universality and the application value are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of digital information transmission, and particularly relates to a current distribution method, device and medium for cross-layer underwater magnetic induction communication. Background Art

[0002] The electromagnetic wave communication technology has achieved remarkable development, with significant improvements in aspects such as transmission rate, bit error rate, and bandwidth utilization. However, in the underwater environment, the dynamic underwater conditions and harsh propagation environment will seriously hinder the transmission of electromagnetic waves. In such scenarios, the magnetic induction (MI) communication technology based on the mutual inductance effect of coils exhibits advantages such as high penetration efficiency, stable channel state, and small antenna size.

[0003] The basic principle of magnetic induction communication is to induce an electromotive force in the receiving coil through the current change in the transmitting coil, thereby realizing signal transmission. Different from traditional electromagnetic wave communication, magnetic induction communication relies on near-field magnetic field coupling and has advantages such as high penetration, strong channel stability, low power consumption, and small antenna size. These characteristics make it particularly suitable for complex environments and harsh scenarios. In underground wireless sensor networks (WUSN), magnetic induction communication is widely used in agricultural monitoring, underground resource exploration, and earthquake early warning; in the underwater environment, it is used for marine resource investigation, ecological monitoring, and submarine communication; in the industrial field, it is used for equipment monitoring and control in environments such as mines and pipelines.

[0004] Jia Tang and Xi Zhang proposed a statistical quality-of-service (QoS)-driven power and rate adaptation mechanism in their published paper "Quality-of-Service Driven Power and Rate Adaptation for Multichannel Communications over Wireless Links" (J. Tang and X. Zhang, "Quality-of-service driven power and rate adaptation for multichannel communications over wireless links," in IEEE Transactions on Wireless Communications, vol. 6, no. 12, pp. 4349-4360, December 2007, doi: 10.1109 / TWC.2007.06031.) to optimize the performance of multichannel wireless communication systems. The specific steps of this method are as follows: First, a mathematical model of the multichannel communication system is established through theoretical analysis, clarifying the relationship between QoS objectives (such as user rate, delay, false alarm rate, etc.) and channel states. Then, a power and rate adaptation algorithm based on QoS requirements is designed, optimizing power allocation and rate adjustment to meet users' expectations for service quality. In terms of system architecture, a multichannel collaborative optimization strategy is proposed, combining channel switching and resource allocation mechanisms to ensure efficient utilization between channels. There are three deficiencies in this method: First, the model directly determines the value of the average received power. However, in reality, the average received power is affected by the performance of the transceiver and the environment, and what can usually be determined is the average power of the transmitter. Second, it is assumed that the channel condition may be infinitely good. However, in reality, due to various factors, the maximum channel capacity is limited. Third, the model directly performs power allocation without modeling the specific circuit and ignores the power loss in the circuit.

[0005] Jianyu Wang, Wenchi Cheng, and Hailin Zhang proposed an optimal current control scheme for a magnetic induction through-the-earth communication system based on MISO-OFDM in their published paper "Optimal Current Control for MISO-OFDM Based Through-the-Earth Communications with Magnetic Induction" (J. Wang, W. Cheng and H. Zhang, "Optimal Current Control for MISO-OFDM Based Through-the-Earth Communications with Magnetic Induction," 2021 IEEE / CIC International Conference on Communications in China (ICCC), Xiamen, China, 2021, pp. 133-138, doi: 10.1109 / ICCC52777.2021.9580360.). In the implementation process, first, a system model is established and the characteristics of the magnetic induction channel are analyzed, and the frequency-domain channel matrix is constructed by combining OFDM technology; then, with the goal of maximizing the system channel capacity, an optimization problem with constraints is constructed, and the Lagrangian dual decomposition method is used to design the optimal current allocation algorithm, and the optimal current amplitude allocation of each transmitting antenna on each subcarrier is realized through iterative solution; at the same time, the water-filling algorithm is combined to dynamically adjust the subcarrier power, and the power is preferentially allocated to the subcarriers with better channel conditions to improve the spectral efficiency. There are two deficiencies in this method: one is that this method only considers using the channel capacity as the optimization function, but in actual communication, the real-time and effectiveness of communication need to be considered, and it is not appropriate to use the channel capacity as the information transmission rate; the other is that this model ignores the dynamic change of the channel conditions caused by the change of the coil direction. Summary of the Invention

[0006] To overcome the above-mentioned drawbacks of the prior art, the object of the present invention is to provide a current allocation method, device and medium for cross-layer underwater magnetic induction communication. By establishing an actual magnetic induction communication circuit model, using the mutual inductance of coils to transmit information, through the parameters of the circuit model, signal models and power models related to communication are obtained. Through the probability density function of the mutual inductance between two coils, the randomness of the directions of the transmitting and receiving coils is simulated. A statistical quality of service framework is introduced into the magnetic induction communication circuit to ensure limited communication delay and queue length, effectively improving the performance of the link layer, and thereby establishing an effective capacity model for magnetic induction communication; taking the effective capacity of the communication system as the optimization objective, and taking the limited average power of the transmitter and the limited channel capacity as constraints, a mathematical optimization model is established, and the KKT conditions are used to obtain the closed-form solution of the optimal current allocation method; taking the current as the optimization variable, which is closer to the actual circuit than the power variable, and adjusting the current allocation strategy from the circuit level; when the requirement for the quality of service of communication is high, more current is allocated when the channel is bad to ensure that the queue length of the receiver will not overflow at this time, reducing the probability of congestion, so as to improve the information transmission rate under limited delay and improve the effectiveness and reliability of the communication system.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows: A current allocation method for cross-layer underwater magnetic induction communication, where the magnetic induction communication is a stationary and ergodic random service process, including the following steps: Step 1, establish a circuit model of the magnetic induction communication system, including a transmitter with a transmitting coil and a receiver with a receiving coil; Step 2, calculate the probability density function of the mutual inductance based on the probability density function of the mutual inductance misalignment factor between the transmitting coil and the receiving coil; Step 3, based on the circuit model established in Step 1, calculate the received power and the transmitted power ; Step 4, according to the probability density function of the mutual inductance obtained in Step 2 and the received power calculated in Step 3, calculate the effective capacity expression of the magnetic induction communication system with the quality of service index ; Step 5, based on the transmitted current and the transmitted power obtained in Step 3, add actual constraints; Step 6, based on the effective capacity expression obtained in Step 4 and the actual constraints added in Step 5, establish a mathematical optimization problem, and use convex optimization theory to solve the optimization problem to obtain a current allocation method for underwater magnetic induction communication with quality of service guarantee.

[0008] In Step 1, the transmitter includes a current source connected in series , a transmitting coil , a resonant capacitor , an equivalent internal resistance ; Among them, the current source The current value is , Transmitting coil The inductance value is , resonant capacitor The capacitance value is , equivalent internal resistance The resistance value is ; The receiver includes a receiving coil connected in series , a resonant capacitor , an equivalent internal resistance , a load resistor ; The receiving coil The inductance value is , resonant capacitor The capacitance value is , equivalent internal resistance The resistance value is , load resistance The resistance value is ; The transmitting coil Coil radius Larger than the receiving coil Coil radius 10 times more, receiving coil Considered as being placed in the transmitting coil In the uniform magnetic field generated, magnetic induction communication is regarded as a random service process, which is stable and ergodic.

[0009] The operating frequency of the magnetic induction communication system is recorded as ; Transmitter current source The current and terminal voltage are recorded as , ; The transmitter and receiver communicate through mutual inductance coupling and load resistance The voltage at both ends is used as the receiving signal; the transmitting coil Inductance value With receiving coil Inductance value Satisfy the resonance condition: , ; Transmitting coil With receiving coil The mutual inductance between 。

[0010] Step 2 specifically includes the following steps: When the transmitting coil and the receiving coil are parallel and aligned with each other, the mutual inductance between the transmitting coil and the receiving coil is denoted as , and the mutual inductance when parallel and aligned with each other is calculated using Stokes' theorem: (1) where is the magnetic permeability, is the number of turns of the transmitting coil, is the number of turns of the receiving coil, is the radius of the transmitting coil, is the radius of the receiving coil, is the distance between the centers of the two coils; Derive the probability density function (PDF) of the mutual inductance of the actual configuration consisting of a single coil and a collinear coil array according to the Stochastic Misalignment Model. Among them, the directions of the transmitting coil and the receiving coil in the Stochastic Misalignment Model are uniformly distributed. Then, through the probability density function (PDF) of the mutual inductance, determine the expected attenuation caused by misalignment and define the misalignment factor , the misalignment factor , the mutual inductance and the mutual inductance when the two coils are parallel and aligned with each other: (2) In an underwater magnetic induction communication system, the probability density function of the mutual inductance misalignment factor between two coils is expressed as: (3) Finally, use the probability density function of the mutual inductance misalignment factor to calculate the probability density function of the mutual inductance 。

[0011] Step 3 specifically includes the following steps: Represent the symbol to be transmitted as , , where ; after digital-to-analog conversion (DAC), the current of the transmitter when transmitting the th symbol is: ​​​​​ (4) Among them, is the emission current, is the operating frequency; Then, according to Kirchhoff's voltage law, the relationship between the emission voltage when the transmitter transmits the th symbol, the emission current and the received current is expressed as: (5) (6) Among them, is the resistance value of the equivalent resistance of the transmitter, is the resistance value of the equivalent resistance of the receiver, is the mutual inductance between the transmitting coil and the receiving coil ; Based on Equations (5) and (6), the received current and the received voltage when transmitting the th symbol are derived as follows: (7) (8) Among them, represents independent and identically distributed (i.i.d.) Gaussian white noise in the communication system, with zero mean and variance ; After performing analog-to-digital conversion (ADC) on the received voltage , the baseband signal obtained is: (9) Among them, represents independent and identically distributed (i.i.d.) Gaussian white noise in the communication system, with zero mean and variance ; Then, based on the baseband signal , the received current and the received power are obtained: (10) (11) Among them, is the normalized equivalent resistance on the load resistance of the receiver; According to Kirchhoff's voltage law, the emission voltage and the emission power are obtained: (12) (13) Among them, is the normalized equivalent resistance of the receiving end at the transmitting end.

[0012] Step 4 specifically includes the following steps: For the said random service process, the queue length exceeds the threshold The probability decreases exponentially with the increase of the threshold and is expressed as: (14) Among them, is the quality of service index, which reflects the probability decay rate of the queue length exceeding the threshold ; Based on the effective bandwidth theory, the definition of effective capacity is given dually: Under the QoS requirements that satisfy specific statistical delay constraints, the maximum constant arrival rate that a given service process can support, and its expression is: (15) Among them, represents the expected value of the signal-to-noise ratio (SNR) of the receiving end; thus, in the OSI seven-layer model, the data link layer controls the achievable rate of the physical layer cross-layer through the quality of service index Let the sequence represent the discrete, stationary, and ergodic random service process of the magnetic induction communication system, and represents the sum of the first terms. Let the Gartner-Elli limit of exist and be convex and differentiable, then the effective capacity is defined as: (16) When the sequence is an uncorrelated sequence, the above formula is simplified to: (17) For the said magnetic induction communication system, the signal-to-noise ratio at the receiver load resistance is expressed as: (18) Among them, is the power of the load resistance, is the noise power, is the transmitting current, is the transmitting coil and the receiving coil the mutual inductance between them, , is the resistance value of the load resistor, is the resistance value of the receiver equivalent resistor, is the transmitting coil and the receiving coil the mutual inductance between them; Assume that both the transmitter and the receiver have appropriate encoding and decoding schemes so that the magnetic induction communication system can reach the channel capacity. Then the achievable rate is expressed as , then the effective capacity is expressed as: (19) where, , is the transmitting coil and the receiving coil the mutual inductance between them the probability density function of.

[0013] The actual constraints added in step 5 are specifically: Add a peak current constraint to the transmitting current: (20) where, is the transmitting current, is the peak current allowed by the transmitter, is the maximum achievable rate, is the transmitting coil and the receiving coil the mutual inductance between them, , is the resistance value of the load resistor, is the resistance value of the receiver equivalent resistor, is the transmitting coil and the receiving coil the mutual inductance between them; And add an average power constraint to the transmitting power: (21) where, is the average power constraint value.

[0014] Step 6 specifically includes the following steps: Let , then the objective function is expressed as: (22) where, is the transmitting current, is the quality of service index, , is the resistance value of the load resistor, is the resistance value of the receiver equivalent resistor, For the mutual inductance between the transmitting coil and the receiving coil is the mutual inductance is the probability density function of the mutual inductance ; Rewrite the objective function to minimize the rewritten objective function, and obtain the optimization problem: (23) where is the maximum achievable rate, is the resistance value of the normalized equivalent resistance of the receiving end at the transmitting end, is the operating frequency; Use the KKT conditions to derive the solution of this optimization problem, that is, the optimal current control method is: (24) where , , , the Lagrange multiplier is obtained by numerical solution; Under the optimal current control method, the effective capacity is expressed as: (25) where the square of the current and the square of the current in Equation (25) are expressed as: (26) In particular, when , the optimal current control method of the magnetic induction communication system converges to: (27) where ; The corresponding effective capacity is: (28) When , , , and the magnetic induction communication system is not affected by the peak rate limit, and the channel outage probability is zero; the optimal current control method converges to: (29) The corresponding effective capacity is: (30).

[0015] A current distribution device for cross-layer underwater magnetic induction communication, comprising: Memory: used to store a computer program for implementing a current distribution method for cross - layer underwater magnetic induction communication; Processor: used to implement a current distribution method for cross - layer underwater magnetic induction communication when executing the computer program.

[0016] A computer - readable storage medium stores a computer program, and when the computer program is executed by a processor, it implements the steps of a current distribution method for cross - layer underwater magnetic induction communication.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: First, the present invention establishes a magnetic induction communication system at the circuit level, optimizes the problem with current as the decision variable, directly models the transmit power, receive power, transmit symbol, and receive symbol from circuit parameters, reduces the hardware cost and volume, and at the same time makes the present invention closer to the actual situation of physical - layer transmission.

[0018] Second, since the present invention introduces a statistical quality - of - service framework, it no longer takes the general channel capacity as the optimization goal, but takes the effective capacity as the optimization goal, and uses the quality - of - service index to measure the probability of queue overflow or delay overflow, and can measure the system performance from the data - link layer, better meeting the requirements of delay - sensitive services.

[0019] Third, since the present invention obtains the convergence expression of the optimal current distribution strategy in extreme cases from a complex optimal current distribution strategy, the current control is simpler, easier to control, can achieve the optimal control effect, and has stronger universality and application value.

[0020] In summary, the present invention provides a more reliable quality - of - service guarantee for the magnetic induction communication link. Under the condition of meeting certain quality - of - service requirements, through the effective bandwidth theory for modeling, it can obtain the optimal current distribution method across layers, greatly improving the effectiveness and reliability of the magnetic induction communication system. Brief Description of the Drawings

[0021] Figure 1 It is a flowchart of the present invention.

[0022] Figure 2(a) is the circuit diagram of the transmitting loop of the present invention; Figure 2(b) is the circuit diagram of the receiving loop of the present invention.

[0023] Figure 3(a) is a schematic diagram of the application scenario of the present invention; Figure 3(b) is a schematic diagram of the statistical QoS framework from the transmitting coil to the sensor link.

[0024] Figure 4 It is a comparison diagram of the current control strategies of WFWR and WF in the simulation experiment of the present invention.

[0025] Figure 5 This is a comparison chart of normalized effective capacities of different current adaptive distribution schemes in the simulation experiment of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0027] Reference Figure 1 , the implementation steps of the current distribution method for cross-layer underwater magnetic induction communication described in the present invention are further described in detail.

[0028] Step 1, as shown in FIG3(a), a circuit model of a magnetic induction communication system is established, including a transmitter with a transmitting coil arranged on a ship and a receiver with a receiving coil arranged in an underwater sensor; As shown in Figure 2(a), the transmitter consists of a current source connected in series , a transmitting coil , a resonant capacitor , an equivalent internal resistance ; As shown in Figure 2(b), the receiver includes a receiving coil connected in series , a resonant capacitor , an equivalent internal resistance , a load resistor , where the current source The current value is , Transmitting coil The inductance value is , resonant capacitor The capacitance value is , equivalent internal resistance The resistance value is ; Receiving coil The inductance value is , resonant capacitor The capacitance value is , equivalent internal resistance The resistance value is , load resistance The resistance value is ; Transmitting coil Coil radius Larger than the receiving coil Coil radius 10 times more, receiving coil Considered as being placed in the transmitting coil In the uniform magnetic field generated, magnetic induction communication is regarded as a random service process, which is stable and ergodic.

[0029] The operating frequency of the magnetic induction communication system is recorded as ; Transmitter current source The current and terminal voltage are respectively denoted as , ; The transmitter and the receiver communicate through mutual inductance coupling, and the voltage across the load resistor is used as the received signal; The inductance value of the transmitting coil and the inductance value of the receiving coil satisfy the resonance condition: , ; The mutual inductance between the transmitting coil and the receiving coil is denoted as .

[0030] Step 2, Calculate the probability density function of the mutual inductance based on the probability density function of the mutual inductance misalignment factor between the transmitting coil and the receiving coil; When the transmitting coil and the receiving coil are parallel and aligned with each other, the mutual inductance between the transmitting coil and the receiving coil is denoted as , and use Stokes' theorem to calculate the mutual inductance when parallel and aligned with each other: (1) where is the magnetic permeability, is the number of turns of the transmitting coil, is the number of turns of the receiving coil, is the radius of the transmitting coil, is the radius of the receiving coil, is the distance between the centers of the two coils; Derive the probability density function (PDF) of the mutual inductance of an actual configuration consisting of a single coil and a collinear coil array according to the Stochastic Misalignment Model (G. Dumphart and A.Wittneben, "Stochastic misalignment model for magneto-inductive SISO and MIMO links," 2016 IEEE 27th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), Valencia, Spain, 2016, pp. 1-6, doi:10.1109 / PIMRC.2016.7794767.). In the Stochastic Misalignment Model, the orientations of the transmitting and receiving coils are uniformly distributed. Then, determine the expected attenuation caused by misalignment through the PDF of the mutual inductance and define the misalignment factor , the misalignment factor , the mutual inductance and the mutual inductance when the two coils are parallel and aligned with each other: (2) In an underwater magnetic induction communication system, the radius of the transmitting coil is much larger than the radius of the receiving coil. Then, the receiving coil is placed in the uniform magnetic field generated by the transmitting coil, and the probability density function of the mutual inductance misalignment factor between the two coils is expressed as: (3) Finally, use the probability density function of the mutual inductance misalignment factor to calculate the probability density function of the mutual inductance .

[0031] Step 3: Based on the circuit model established in Step 1, calculate the received power and the transmitted power ; Represent the symbol to be transmitted as , , where ; after digital-to-analog conversion (DAC), since the source signal is a sine wave, the current of the transmitter when transmitting the th symbol is: (4) Among them, is the emission current, is the operating frequency; Then, according to Kirchhoff's voltage law, the relationship between the emission voltage when the transmitter transmits the th symbol, the emission current and the received current is expressed as: (5) (6) Among them, is the resistance value of the equivalent resistance of the transmitter, is the resistance value of the equivalent resistance of the receiver, is the mutual inductance between the transmitting coil and the receiving coil ; Based on Equations (5) and (6), the received current and the received voltage when transmitting the th symbol are derived as follows: (7) (8) Among them, represents independent and identically distributed (i.i.d.) Gaussian white noise in the communication system, with zero mean and variance ; after the received voltage is subjected to analog-to-digital conversion (ADC), the baseband signal obtained is: (9) Among them, represents independent and identically distributed (i.i.d.) Gaussian white noise in the communication system, with zero mean and variance ; then, based on the baseband signal the received current and the received power are obtained: (10) (11) Among them, is the normalized equivalent resistance on the load resistance of the receiver; It should be noted that due to the mutual inductance between the transmitting and receiving circuits, the transmitted power is not only determined by the parameters of the transmitting circuit, but also the influence of the receiver due to mutual inductance The equivalent resistance generated on the transmitter; according to Kirchhoff's voltage law, the transmitting voltage is obtained and transmit power : (12) (13) in, is the normalized equivalent resistance of the receiving end at the transmitting end.

[0032] Step 4: Calculate the service quality index according to the probability density function of the mutual inductance obtained in step 2 and the received power calculated in step 3 The effective capacity of the magnetic induction communication system expression; For the random service process, the queue length Exceeding the threshold The probability of increases and decreases at an exponential rate, expressed as: (14) in, is the service quality index, which reflects the queue length exceeding the threshold The probability decay rate can be used to measure data link layer indicators such as queue or delay overflow probability; Based on the effective bandwidth theory, the definition of effective capacity is given dually: the maximum constant arrival rate that a given service process can support under the QoS requirements that meet specific statistical delay constraints. Its expression is: (15) in, Indicates the expected value of the signal-to-noise ratio (SNR) at the receiving end; as shown in Figure 3 (b), in the OSI seven-layer model, the data link layer uses the service quality index Control the achievable rate of the physical layer across layers; set the sequence represents the discrete, stationary and ergodic random service process of the magnetic induction communication system, and express forward The sum of the terms, let The Gartner-Elli limit exists and is convex and differentiable, then the effective capacity Defined as: (16) when sequence When is an uncorrelated sequence, the above formula is simplified to: (17) For the magnetic induction communication system, the signal-to-noise ratio at the receiver load resistance is expressed as: (18) where, is the power of the load resistance, is the noise power, is the transmission current, is the transmitting coil and the receiving coil is the mutual inductance between them, , is the resistance value of the load resistance, is the resistance value of the receiver equivalent resistance, is the transmitting coil and the receiving coil is the mutual inductance between them; Assume that both the transmitter and the receiver have appropriate encoding and decoding schemes so that the magnetic induction communication system can reach the channel capacity. Then the achievable rate is expressed as , and the effective capacity is expressed as: (19) where, , is the transmitting coil and the receiving coil is the mutual inductance between them and the probability density function of

[0033] Step 5: Based on the transmission current and the transmission power obtained in Step 3, add actual constraints; Due to the hardware limitations of the transmitter, add a peak current constraint to the transmission current: (20) where, is the transmission current, is the peak current allowed by the transmitter, is the maximum achievable rate, is the transmitting coil and the receiving coil is the mutual inductance between them, , is the resistance value of the load resistance, is the resistance value of the receiver equivalent resistance, is the transmitting coil and the receiving coil is the mutual inductance between them; And add an average power constraint to the transmission power: (21) where, is the average power constraint value.

[0034] Step 6: Based on the effective capacity expression obtained in Step 4 and the actual constraints added in Step 5, establish a mathematical optimization problem, solve the optimization problem using convex optimization theory, and obtain a current allocation method for underwater magnetic induction communication with quality of service guarantee; For convenience, let , then the objective function is expressed as: (22) where is the transmitted current, is the quality of service index, , is the resistance value of the load resistor, is the resistance value of the equivalent resistor at the receiver, is the transmitting coil and the receiving coil the mutual inductance between them, is the mutual inductance the probability density function of; Since is a monotonically decreasing function of, the objective function is rewritten to minimize the rewritten objective function, and the optimization problem is obtained: (23) where is the maximum achievable rate, is the resistance value of the normalized equivalent resistor at the receiver with respect to the transmitter, is the operating frequency; In this way, the optimization problem becomes to minimize the rewritten objective function. Since this is a convex optimization problem, the solution of this optimization problem is derived using the KKT conditions, that is, the optimal current control method is: (24) where , , , the Lagrange multiplier is obtained by numerical solution; Under the optimal current control method, the effective capacity is expressed as: (25) where the square of the current and the square of the current in Equation (25) are expressed as: (26) In particular, when When the magnetic induction communication system can tolerate arbitrarily large queuing delays, the optimal current control method converges to: (27) where ; The corresponding effective capacity is: (28) When the magnetic induction communication system cannot tolerate any non-zero delay; in this case, , and the magnetic induction communication system is not affected by the peak rate limit, and the channel outage probability is zero; the optimal current control method converges to: (29) The corresponding effective capacity is: (30).

[0035] A current distribution device for cross-layer underwater magnetic induction communication, comprising: A memory: for storing a computer program for implementing a current distribution method for cross-layer underwater magnetic induction communication; A processor: for implementing a current distribution method for cross-layer underwater magnetic induction communication when executing the computer program.

[0036] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of a current distribution method for cross-layer underwater magnetic induction communication are implemented.

[0037] Simulation experiment Figure 4 shows a comparison of the current control strategies of WFWR and WF in the case where arbitrarily long delays can be tolerated ( ). Set the following parameters: operating frequency , transmission distance , coil resistance , load resistance , coil radius , , number of turns of the coil , maximum normalized achievable rate , average transmit power , noise power .

[0038] Compared with the WF strategy, it can be observed that imposing a current rate constraint introduces a current rate constraint threshold. When When exceeding the peak rate constraint threshold, the current will be reduced to reduce energy consumption while maintaining a constant achievable rate. By comparing the truncation thresholds of the two strategies, it can be clearly seen that the truncation threshold of WFWR shifts to the left, indicating that WFWR uses power more efficiently by reserving energy for use when the current is lower. This results in a reduction in the outage probability of approximately , thus improving the stability of information transmission.

[0039] Figure 5 shows the comparison of the effective capacities of different current adaptive allocation schemes. When , the optimal current adaptive control strategy converges to the water-filling strategy. When , it converges to the channel inversion current control strategy. When the statistical QoS requirements become more stringent, the normalized effective capacities of all current control schemes will decrease. However, the current adaptive control scheme of the present invention always achieves the highest effective capacity.

Claims

1. A current distribution method for cross-layer underwater magnetic induction communication, where the magnetic induction communication is a stationary and ergodic random service process, characterized in that, It includes the following steps: Step 1: Establish a circuit model of the magnetic induction communication system, including a transmitter with a transmitting coil and a receiver with a receiving coil; Step 2: Calculate the probability density function of mutual inductance based on the probability density function of the mutual inductance misalignment factor between the transmitting coil and the receiving coil; Step 3, based on the circuit model established in Step 1, calculate the received power and the transmitted power ; Step 4: Calculate the effective capacity of the magnetic induction communication system with the quality of service index according to the probability density function of mutual inductance obtained in Step 2 and the received power calculated in Step 3 expression; Step 5: Add actual constraints based on the transmitted current and the transmitted power obtained in Step 3; Step 6: Based on the effective capacity expression obtained in Step 4 and the actual constraints added in Step 5, establish a mathematical optimization problem, solve the optimization problem using convex optimization theory, and obtain a current allocation method for underwater magnetic induction communication with quality of service guarantee.

2. The current distribution method according to claim 1, characterized in that, In Step 1, the transmitter includes a current source connected in series , a transmitting coil , a resonant capacitor , an equivalent internal resistance resistor ; Among them, the current source has a current value of , the transmitting coil has an inductance value of , the resonant capacitor has a capacitance value of , the equivalent internal resistance resistor has a resistance value of ; The receiver includes a receiving coil connected in series , a resonant capacitor , an equivalent internal resistance , a load resistor ; Among them, the receiving coil has an inductance value of , the resonant capacitor has a capacitance value of , the equivalent internal resistance resistor has a resistance value of , the load resistor has a resistance value of ; The transmitting coil Coil radius Larger than the receiving coil Coil radius 10 times more, receiving coil Considered as being placed in the transmitting coil In the uniform magnetic field generated, magnetic induction communication is regarded as a random service process, which is stable and ergodic.

3. The current distribution method according to claim 1, wherein In step 1, the operating frequency of the magnetic induction communication system is denoted as ; the current and terminal voltage of the transmitter current source are respectively denoted as , ; The transmitter and the receiver communicate through mutual inductance coupling, and the voltage across the load resistor is used as the received signal; the inductance value of the transmitting coil and the inductance value of the receiving coil meet the resonance condition: , ; the mutual inductance between the transmitting coil and the receiving coil is denoted as .

4. The current distribution method according to claim 1, wherein Step 2 specifically includes the following steps: When the transmitting coil and the receiving coil are parallel and aligned with each other, the mutual inductance between the transmitting coil and the receiving coil is denoted as , and the mutual inductance when they are parallel and aligned with each other is calculated using Stokes' theorem: (1) Among them, is the magnetic permeability, is the number of turns of the transmitting coil, is the number of turns of the receiving coil, is the radius of the transmitting coil, is the radius of the receiving coil, is the distance between the centers of the two coils; Derive the probability density function (PDF) of mutual inductance for an actual configuration consisting of a single coil and a collinear coil array according to the Stochastic Misalignment Model, where the directions of the transmitting and receiving coils in the Stochastic Misalignment Model are uniformly distributed. Then, determine the expected attenuation caused by misalignment through the PDF of mutual inductance, and define the misalignment factor , the misalignment factor , mutual inductance , and the mutual inductance when the two coils are parallel and aligned with each other The relationship between them is as follows: (2) In the underwater magnetic induction communication system, the probability density function of the mutual inductance misalignment factor between two coils is expressed as: (3) Finally, the probability density function of the mutual inductance misalignment factor is used to calculate the probability density function of the mutual inductance . .

5. The current distribution method according to claim 1, characterized in that, Step 3 specifically includes the following steps: The symbol to be transmitted is represented as , , where ; after digital-to-analog conversion (DAC), the current of the transmitter when transmitting the th symbol is: (4) Among them, is the emission current, is the operating frequency; Then, according to Kirchhoff's voltage law, the relationship between the transmission voltage when the transmitter transmits the th symbol, the transmission current and the received current is expressed as: (5) (6) Among them, is the resistance value of the transmitter equivalent resistance, is the resistance value of the receiver equivalent resistance, is the transmitting coil and the receiving coil is the mutual inductance between them; Derivation based on Equation (5) and Equation (6) gives the received current and the received voltage when transmitting the th symbol as follows: (7) (8) wherein, represents independent and identically distributed (i.i.d.) Gaussian white noise in a communication system, having zero mean and variance ; after performing analog-to-digital conversion (ADC) on the received voltage , the baseband signal obtained is: (9) Among them, represents the independent and identically distributed (i.i.d.) Gaussian white noise in the communication system, with zero mean and variance ; then according to the baseband signal the received current and the received power are obtained as follows: (10) (11) Among them, is the normalized equivalent resistance on the load resistance of the receiver; According to Kirchhoff's voltage law, the emission voltage and the emission power are obtained as follows: (12) (13) Among them, is the normalized equivalent resistance of the receiving end at the transmitting end.

6. The current distribution method according to claim 1, wherein Step 4 specifically includes the following steps: For the random service process, the probability that the queue length exceeds a threshold decreases exponentially as the threshold increases, expressed as: (14) Among them, is the quality of service index, which reflects the probability decay rate of the queue length exceeding the threshold ; Based on the effective bandwidth theory, the definition of effective capacity is given dually: Under the QoS requirements that satisfy specific statistical delay constraints, the maximum constant arrival rate that a given service process can support, and its expression is: (15) Among them, represents the expected value of the signal-to-noise ratio (SNR) at the receiving end; thus, in the OSI seven-layer model, the data link layer controls the achievable rate of the physical layer cross-layer through the quality of service index Let the sequence represent the discrete, stationary, and ergodic random service process of the magnetic induction communication system, and represents the sum of the first terms. Let the Gartner-Elli limit of exist and be convex and differentiable, then the effective capacity (16) When the sequence is an irrelevant sequence, the above formula simplifies to: (17) For the magnetic induction communication system, the signal-to-noise ratio at the receiver load resistance is expressed as: (18) Among them, is the power of the load resistor, is the noise power, is the transmitting current, is the transmitting coil and the receiving coil is the mutual inductance between them, , is the resistance value of the load resistor, is the resistance value of the equivalent resistor of the receiver, is the transmitting coil and the receiving coil is the mutual inductance between them; Assume that both the transmitter and the receiver have appropriate encoding and decoding schemes such that the magnetic induction communication system can achieve the channel capacity. Then the achievable rate is expressed as , and the effective capacity is expressed as: (19) Among them, , is the transmitting coil and the receiving coil is the mutual inductance between the probability density function of.

7. The current distribution method according to claim 1, wherein The actual constraints added in Step 5 are specifically: Add a peak current constraint for the transmitted current: (20) Wherein, is the emission current, is the peak current allowed by the transmitter, is the maximum achievable rate, is the transmitting coil and the receiving coil is the mutual inductance between them, , is the resistance value of the load resistor, is the resistance value of the equivalent resistor of the receiver, is the transmitting coil and the receiving coil is the mutual inductance between them; And add an average power constraint for the transmitted power: (21) Among them, is the average power constraint value.

8. The current distribution method according to claim 1, wherein Step 6 specifically includes the following steps: Let , then the objective function is expressed as: (22) Among them, is the emission current, is the quality of service index, , is the resistance value of the load resistor, is the resistance value of the receiver equivalent resistor, is the transmitting coil and the receiving coil is the mutual inductance between them, is the mutual inductance is the probability density function; Rewrite the objective function, with the goal of minimizing the rewritten objective function, to obtain an optimization problem: (23) wherein, is the maximum achievable rate, is the resistance value of the normalized equivalent resistance of the receiving end at the transmitting end, is the operating frequency; Use the KKT conditions to derive the solution of this optimization problem, that is, the optimal current control method is: (24) Among them, , , , the Lagrange multiplier is obtained by a numerical solution method; Under the optimal current control method, the effective capacity is expressed as: (25) Among them, the square of the current in formula (25) and the square of the current are expressed as: (26) Specifically, when the optimal current control method for the magnetic induction communication system converges to: (27) Among them, ; The corresponding effective capacity is: (28) When , , , and the magnetic induction communication system is not affected by the peak rate limitation, and the channel outage probability is zero; the optimal current control method converges to: (29) The corresponding effective capacity is: (30)。 9. A current distribution device for cross-layer underwater magnetic induction communication, characterized in that, It includes: A memory: used to store a computer program for implementing a current allocation method for cross-layer underwater magnetic induction communication as described in any one of claims 1 to 8; A processor: used to implement a current allocation method for cross-layer underwater magnetic induction communication as described in any one of claims 1 to 8 when executing the computer program.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, and when the computer program is executed by the processor, it implements the steps of a current allocation method for cross-layer underwater magnetic induction communication as described in any one of claims 1 to 8.

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