Absorption shift keying molecular communication system and method based on genetic algorithm codebook

Abstract

The invention discloses an absorption shift keying molecular communication system and method based on a genetic algorithm codebook. The system comprises a model construction module, a codebook generation module and a signal demodulation module. The model construction module is used for constructing a molecular communication model under an absorption frequency shift keying architecture, and a sending end adopts an absorption frequency shift keying combined pulse position modulation as a hybrid modulation scheme of the molecular communication model; the codebook generation module is used for establishing a fitness function taking decoding error probability minimization as a target, optimizing a codebook through a genetic algorithm, and dynamically generating a system codebook adaptive to molecular channel characteristics; the signal demodulation module optimizes a molecular communication model based on a system codebook in combination with a two-step detector, and performs signal demodulation at a receiving end by using the optimized molecular communication model. The method is superior to an existing coding scheme, and the reliability of a molecular communication system under the condition that absorption frequency shift keying is combined with pulse position modulation under the constraint of an actual molecular channel is obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of molecular communication technology, specifically relating to an absorption-shift-bonding molecular communication system and method based on a genetic algorithm codebook. Background Technology

[0002] Molecular diffusion communication utilizes biochemical signals as carriers of information, offering unique advantages such as high biocompatibility and low energy consumption. These characteristics make molecular communication technology particularly suitable for specialized communication scenarios, including targeted drug delivery systems and microscale environmental monitoring, and it is a key technology for future nanonetworks. However, the practical deployment of molecular communication faces significant challenges. The main limitation stems from severe inter-symbol interference (ISI), caused by the slow and random diffusion of molecules, leading to the persistent presence of residual molecules from previous transmissions. Furthermore, energy constraints in nanoscale devices further complicate reliable communication.

[0003] To address these issues, researchers have developed innovative modulation schemes. Concentration-shift keying (CPS) encodes information as different concentrations of released molecules, and the receiver identifies the signal by comparing the received concentration to a preset threshold). Pulse position modulation is another popular modulation technique, where the transmitter releases molecular pulses in different time slots, and the receiver recovers the position of the emitted pulses by detecting the maximum concentration of molecules in the time slot.

[0004] Besides modulation techniques, signal detection and demodulation methods at the receiver constitute a crucial component in improving the reliability of molecular communication systems. Traditional fixed-threshold demodulation compares the detected molecular concentration in the current time slot with a predetermined concentration threshold. Furthermore, a novel bio-inspired demodulation algorithm suitable for binary signals has been proposed, which does not require explicit channel state information and exhibits strong biocompatibility. Similarly, probabilistic model-based demodulation algorithms adaptively adjust the molecular concentration threshold, thereby improving the reliability of diffusion-based molecular communication.

[0005] Error control coding introduces redundant bits into the transmitted information and utilizes this redundancy for error correction at the receiver. Existing research has explored classical error control codes such as Hamming codes, low-density parity-check codes, Reed-Solomon codes, and Reed-Muller codes, as well as novel coding schemes specifically tailored for molecular communication. Therefore, developing coding schemes with low redundancy and high error correction capabilities is crucial for advancing molecular communication technology.

[0006] Genetic algorithms, as a heuristic search algorithm in the field of artificial intelligence for solving optimization problems, simulate the natural evolutionary process to optimize solutions. They demonstrate powerful global search capabilities in codebook design for communication systems. This algorithm selects the optimal codebook by optimizing algorithm parameters; specifically, it selects codewords from all possible binary sequences to minimize the bit error rate. This method explores channel coding design approaches to improve coding performance, thus providing new insights into enhancing the effectiveness of coding schemes.

[0007] A recently proposed absorption shift keying (APS) introduces a novel scheme characterized by a system model consisting of two absorbers / receivers, one designated as the harvester node whose surface properties can dynamically switch between an absorption state and a transparent state. The information to be transmitted is divided into two parts: one modulated by the transmitter via conventional signaling, and the other an additional bitstream encoded onto the operational state transitions of the harvester node. By dynamically controlling the operational state of the harvester node, the system not only mitigates inter-node interference but also captures residual molecules from the environment, thereby achieving energy recovery for subsequent transmission. This architecture achieves a dual objective: enhancing communication performance while effectively combining information transmission with energy harvesting.

[0008] However, key challenges remain optimizing demodulation schemes and developing efficient channel coding methods suitable for this dual-functional architecture. Existing schemes lack solutions for optimizing the trade-off between energy harvesting efficiency and communication reliability. Addressing these limitations is crucial to unlocking the full potential of absorption shift keying in practical molecular communication systems. Summary of the Invention

[0009] This invention aims to address the shortcomings of existing technologies and provides the following solutions:

[0010] An absorption-shift-bonding molecular communication system based on a genetic algorithm codebook includes: a model building module, a codebook generation module, and a signal demodulation module;

[0011] The model building module is used to build a molecular communication model under the absorption frequency shift keying architecture. The transmitting end adopts absorption frequency shift keying combined with pulse position modulation as the hybrid modulation scheme of the molecular communication model.

[0012] The codebook generation module is used to establish a fitness function with the goal of minimizing the decoding error probability, and to optimize the codebook through a genetic algorithm to dynamically generate a system codebook that adapts to the characteristics of the molecular channel.

[0013] The signal demodulation module optimizes the molecular communication model based on the system codebook and a two-step detector, and uses the optimized molecular communication model to demodulate the signal at the receiving end.

[0014] Preferably, in the model building module, the molecular communication model includes a source emitter T. x spherical absorber and spherical absorber Unbounded three-dimensional fluid medium;

[0015] The spherical absorber The spherical absorber is an information decoding receiver. A state node whose state is variable.

[0016] Preferably, in the model building module, the absorption frequency shift keying combined with pulse position modulation includes:

[0017] At the source transmitter T x to the spherical absorber In the active link, the source transmitter T x Information is encoded into the time slot position of molecular pulses by pulse position modulation, and molecules are released only in predefined time slots within each symbol duration to reduce intermolecular interference;

[0018] In the spherical absorption receiver to the spherical absorber In a passive link, the spherical absorber The absorption states of the surface are dynamically switched, and additional information bits are mapped to the state transitions, while the remaining molecules are captured for energy recovery.

[0019] Preferably, the workflow of the codebook generation module is as follows:

[0020] Each molecular individual is represented as a unit of length 2. k The vector, where each of the molecular individuals represents a candidate codebook, the candidate codebook will be selected from 2 n The selection is made from the entire set of possible n-bit sequences, using an algorithm to select the position containing 2. k A codebook of binary sequences, and composed of binary sequences {C} s |s = 1, 2, ..., 2 k}express;

[0021] Establish the fitness function with the objective of minimizing the decoding error probability:

[0022]

[0023] P s，f =P(C s |C f )

[0024] s = 1, 2, ..., 2 kf = 1, 2, ..., 2 k

[0025] in, Let P represent the fitness function, k represent the number of information bits, and P represent the information bit number. s,f C represents the probability of a codeword error. s Represents the transmitted binary sequence, C f Represents the detected binary sequence;

[0026] The genetic algorithm is used to optimize the candidate codebook, and the system codebook adapted to the molecular channel characteristics is dynamically generated.

[0027] Preferably, in the signal demodulation module, the two-step detector includes:

[0028] First, the pulse position modulation signal of the active link is recovered using a simplified maximum likelihood detector. The decision rule is as follows:

[0029]

[0030] in, Indicate the decision-making rules, S represents the pulse position modulation signal generated from the active link in the u-th sequence. R y represents the set of all possible active link signals. u (i) indicates that the spherical receiver detects the received signal of the u-th sequence at time i. Let M represent the pulse position modulation signal released by the u-th sequence at time i, and M represent the number of time slots;

[0031] Then, the threshold of the passive link is calculated based on the decoded pulse position modulation signal:

[0032]

[0033] Where ω represents the threshold of the passive link, E a Y represents the number of emitted molecules. ISI Y represents the statistical average of inter-symbol interference. IEI The statistical average value of the interference within the symbol is represented by h[1], which represents the spherical absorber. The probability of a time slot arriving when closed. Indicates a spherical absorber The probability of a time slot arriving when it is enabled.

[0034] This invention also provides an absorption-shift bonded molecular communication method based on a genetic algorithm codebook. The method, applied to the aforementioned system, includes the following steps:

[0035] A molecular communication model based on absorption frequency shift keying architecture is constructed, and the transmitting end adopts absorption frequency shift keying combined with pulse position modulation as a hybrid modulation scheme for the molecular communication model.

[0036] A fitness function is established with the goal of minimizing the decoding error probability, and a system codebook that adapts to the molecular channel characteristics is dynamically generated by optimizing the codebook through a genetic algorithm.

[0037] Based on the system codebook, the molecular communication model is optimized by combining a two-step detector, and the optimized molecular communication model is used for signal demodulation at the receiving end.

[0038] Preferably, the molecular communication model includes a source emitter T x spherical absorber and spherical absorber Unbounded three-dimensional fluid medium;

[0039] The spherical absorber The spherical absorber is an information decoding receiver. A state node whose state is variable.

[0040] Preferably, the absorption frequency shift keying combined with pulse position modulation includes:

[0041] At the source transmitter T x to the spherical absorber In the active link, the source transmitter T x Information is encoded into the time slot position of molecular pulses by pulse position modulation, and molecules are released only in predefined time slots within each symbol duration to reduce intermolecular interference;

[0042] In the spherical absorption receiver to the spherical absorber In a passive link, the spherical absorber The absorption states of the surface are dynamically switched, and additional information bits are mapped to the state transitions, while the remaining molecules are captured for energy recovery.

[0043] Preferably, the method for obtaining the system codebook includes:

[0044] Each molecular individual is represented as a unit of length 2. k The vector, where each of the molecular individuals represents a candidate codebook, the candidate codebook will be selected from 2 n The selection is made from the entire set of possible n-bit sequences, using an algorithm to select the position containing 2. k A codebook of binary sequences, and composed of binary sequences {C} s |s = 1, 2, ..., 2 k}express;

[0045] Establish the fitness function with the objective of minimizing the decoding error probability:

[0046]

[0047] P s，f =P(C s |C f )

[0048] s = 1, 2, ..., 2 k f = 1, 2, ..., 2 k

[0049] in, Let P represent the fitness function, k represent the number of information bits, and P represent the information bit number. s,f C represents the probability of a codeword error. s Represents the transmitted binary sequence, C f Represents the detected binary sequence;

[0050] The genetic algorithm is used to optimize the candidate codebook, and the system codebook adapted to the molecular channel characteristics is dynamically generated.

[0051] Preferably, the two-step detector includes:

[0052] First, the pulse position modulation signal of the active link is recovered using a simplified maximum likelihood detector. The decision rule is as follows:

[0053]

[0054] in, Indicate the decision-making rules, S represents the pulse position modulation signal generated from the active link in the u-th sequence. R y represents the set of all possible active link signals. u (i) indicates that the spherical receiver detects the received signal of the u-th sequence at time i. Let M represent the pulse position modulation signal released by the u-th sequence at time i, and M represent the number of time slots;

[0055] Then, the threshold of the passive link is calculated based on the decoded pulse position modulation signal:

[0056]

[0057] Where ω represents the threshold of the passive link, E a Y represents the number of emitted molecules. ISI Y represents the statistical average of inter-symbol interference. IEIThe statistical average value of the interference within the symbol is represented by h[1], which represents the spherical absorber. The probability of a time slot arriving when closed. Indicates a spherical absorber The probability of a time slot arriving when it is enabled.

[0058] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0059] In this invention, a molecular communication system scheme based on absorption frequency shift keying combined with pulse position modulation is proposed. The codebook optimized by a genetic algorithm dynamically adapts to the channel conditions of the codewords, and experiments verify a reduction in the system's bit error rate. Simulation experiments show that this invention outperforms existing coding schemes, significantly improving the reliability of the molecular communication system under actual molecular channel constraints. Furthermore, the codebook design is compatible with both joint detectors and two-step detectors, providing a suitable balance between performance and complexity. A probability transition matrix is ​​constructed for the diffusion molecular communication model, providing a mathematical foundation and theoretical derivation for the decoding error probability under the genetic algorithm, and the correctness of the derivation is verified for the current system model. Attached Figure Description

[0060] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0061] Figure 1 This is a schematic diagram of the system structure according to an embodiment of the present invention;

[0062] Figure 2 This is a molecular communication model diagram according to an embodiment of the present invention;

[0063] Figure 3 This is a diagram of the genetic algorithm structure according to an embodiment of the present invention;

[0064] Figure 4 This is a schematic diagram of a representative genetic operation in an embodiment of the present invention;

[0065] Figure 5 The diagram shows the system performance of this invention under different encoding methods. Detailed Implementation

[0066] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0067] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0068] Example 1

[0069] In this embodiment, as Figure 1 As shown, an absorption-shift-bonding molecular communication system based on a genetic algorithm codebook includes: a model building module, a codebook generation module, and a signal demodulation module.

[0070] The model building module is used to build a molecular communication model under the absorption frequency shift keying architecture. The transmitting end adopts a hybrid modulation scheme of absorption frequency shift keying combined with pulse position modulation as the molecular communication model.

[0071] In the model building module, molecular communication models, such as Figure 2 As shown, it contains the source emitter T x spherical absorber and spherical absorber Unbounded three-dimensional fluid medium; spherical absorber For information decoding receivers, spherical absorbers A state node whose state is variable.

[0072] In this embodiment, the two receivers share the same radius r, from T x arrive and The Euclidean distances between the centers are denoted as d1 and d2, respectively. To simplify the analysis, T is... x It is positioned at the origin of the coordinate system. In this model, Used as the primary information decoding receiver, while It is a variable state node that can switch between absorbing and non-absorbing states. When in the off state (non-absorbing state), When the system loses its ability to absorb information molecules, it degenerates into having only a single absorber / receptor. Basic configuration. T x The emitted molecules propagate within the medium via Brownian motion, controlled by a constant diffusion coefficient D.

[0073] For basic scenarios ( (In the off state), the molecules released at t0 = 0 are reactivated at time t > 0. The probability of absorption hitting p(t, d1) is given by the following formula:

[0074]

[0075] Where erfc(·) denotes the complementary error function; therefore, T x The molecules released at t=0 arrive at the nth time slot. The probability is:

[0076] h[η]=p(T s ,d1)-p((η-1)T s ,d1),η=1,2,…

[0077] Among them, T s Indicates the duration of the symbol.

[0078] when When activated (in the on state), its absorption capacity alters the spatial distribution of molecules. Specifically, it reaches... The molecules on the surface are instantly captured, thus disrupting... Statistical analysis of the number of molecules arriving. Under these conditions... Corrected hit probability at the location Approximately:

[0079]

[0080] Where, d ij express The center and The distance between the nearest points, ζ represents the calculation parameter; the corresponding time slot arrival probability becomes:

[0081]

[0082] Absorption frequency shift keying combined with pulse position modulation includes: at the source transmitter T x To spherical absorber In the active link, the source transmitter T x Information is encoded into the time slot positions of molecular pulses through pulse position modulation, and molecules are released only in predefined time slots within each symbol duration to mitigate intermolecular interference. This is achieved using a spherical absorber receiver. To spherical absorber In a passive link, a spherical absorber / receiver The absorption states of the surface are dynamically switched, and additional information bits are mapped to the state transitions, while the remaining molecules are captured for energy recovery.

[0083] In this embodiment, in the proposed molecular communication system scheme combining absorption frequency shift keying and pulse position modulation, it is assumed that whenever m information bits are transmitted via pulse position modulation in the active link, additional bits are transmitted through state transitions in the passive link. That is, when M=2 m m+1 information bits are transmitted within each time slot. For clarity, the u-th transmitted symbol is defined as... in, This represents the pulse position modulation signal generated from the active link, while This represents the state-coded signal from the passive link. Specifically, It is a vector of length M, and at the same time, instruct The absorption state.

[0084] The codebook generation module is used to establish a fitness function with the goal of minimizing the decoding error probability, and to optimize the codebook through a genetic algorithm to dynamically generate a system codebook that adapts to the characteristics of the molecular channel.

[0085] Workflow in the codebook generation module:

[0086] Each molecular individual is represented as a unit of length 2. k The vector, where each molecule represents a candidate codebook, will be generated from 2... n Choose from the entire set of n possible n-bit sequences (n represents the code length), and select the position containing 2 bits using the algorithm. k A codebook of binary sequences, and composed of binary sequences {C} s |s = 1, 2, ..., 2 k The codebook design plays a crucial role in enhancing the performance of molecular communication systems, especially for molecular communication system architectures based on absorption frequency shift keying (IFSB) combined with pulse position modulation (PPM). This is achieved by optimizing the codeword structure and state mapping rules to improve reliability. In IFSB-PPM molecular communication systems, the codebook not only designs codewords for PPM modulation in the active link but also dynamically coordinates state coding in the passive link to mitigate inter-symbol interference (ISI).

[0087] Mapping the e-th group of information bits to codewords in the codebook The transmitted pulse position signal is represented as:

[0088]

[0089] The passive link signals transmitted as a sequence are represented as:

[0090]

[0091] The probability of incorrect decision between any two sets of codewords can be represented by a probability transition matrix:

[0092]

[0093] The basis of channel coding design depends on the codeword error decision probability P. s，f =P(C s |C f ), where C s Represents the transmitted binary sequence, C f Let represent the binary sequence to be detected, and s = 1, 2, ..., 2 k f = 1, 2, ..., 2 k The goal of codebook design is to minimize the decoding error probability. A fitness function is established with the goal of minimizing the decoding error probability.

[0094]

[0095] in, The fitness function is represented by k, which represents the number of information bits. A system codebook that adapts to the characteristics of the molecular channel is dynamically generated by optimizing the candidate codebook through a genetic algorithm.

[0096] In this embodiment, the codebook generation module calculates P s，f This is a necessary task. The calculation method varies depending on the detection method used in the signal conditioning module. Taking ideal maximum likelihood detection as an example, the ideal maximum likelihood detector will incorrectly detect codewords in the following situations:

[0097]

[0098] Among them, Λ u (i|C s ) indicates sending the binary sequence C s The Poisson distribution parameter Λ is given. u (i|c f ) represents the binary sequence C f The Poisson distribution parameters are given below, where m represents the number of bits before active link coding. Consider the number of transmitted molecules E. a The Poisson distribution parameter Λ is very large. u (i) In the case where Y is not large enough, here we assume that Y u (i) can be approximated by a Gaussian distribution, i.e. The parameters are now calculated as follows:

[0099]

[0100] α j =E a H[l+i-j+1](1-H[l+i-j+1])

[0101] l ISI =min(l,ML)

[0102] l = M(u-1)

[0103]

[0104] in, This represents the mean. α represents variance. j Indicates the calculation parameter, l ISI Let represent the length of the intersymbol interference (ISI), L represent the length of the previously transmitted sequence, l represent the start point of the time slot in the sequence, and H[j] represent the average probability of arrival. Let Also considering a Gaussian distribution, μ z (i) represents the mean. Z represents the variance. Therefore, Z can be written as...

[0105]

[0106] In summary, Q(·) represents the Gaussian Q-function, and the transmitted codeword C is... s Error detection is C f The probability is:

[0107]

[0108] The signal demodulation module is based on the system codebook, combines a two-step detector to optimize the molecular communication model, and uses the optimized molecular communication model to perform signal demodulation at the receiving end.

[0109] In this embodiment, binary concentration-shift keying (BPS) is a mature technique in molecular communication. The transmitter releases molecules at the beginning of the symbol duration to transmit a bit "1", but does not release molecules for a bit "0". At the receiver, if the number of molecules absorbed at the end of the symbol duration exceeds a predetermined threshold, a bit "1" is detected; otherwise, a bit "0" is detected. Currently, two detection schemes have been proposed for molecular communication systems combining absorption frequency-shift keying (BPS) with pulse position modulation (PPM): a joint detector and a two-step detector. The joint detector employs a joint decoding strategy, maximizing system reliability by jointly optimizing the likelihood functions of the active and passive links. A representative joint detector method is the ideal maximum likelihood detector, whose decision rule is:

[0110]

[0111] in, Let Y represent the signal transmitted in the u-th sequence, S represent the set of all possible signals, and Y represent the signal transmitted in the u-th sequence. u(i) indicates that the spherical receiver detects the received signal of the u-th sequence at time i. The two-step detector is a step-by-step signal processing scheme. In the signal demodulation module of this embodiment, the two-step detector includes:

[0112] First, a simplified maximum likelihood detector is used to recover the pulse position modulation signal of the active link. The decision rule is as follows:

[0113]

[0114] in, Indicate the decision-making rules, S represents the pulse position modulation signal generated from the active link in the u-th sequence. R Represents the set of all possible active link signals. Let M represent the pulse position modulation signal released by the u-th sequence at time i, and M represent the number of time slots;

[0115] Then, the threshold of the passive link is calculated based on the decoded pulse position modulation signal:

[0116]

[0117] Where ω represents the threshold of the passive link, E a Y represents the number of emitted molecules. ISI Y represents the statistical average of inter-symbol interference. IEI The statistical average value of the interference within the symbol is represented by h[1], which represents the spherical absorber. The probability of a time slot arriving when closed. Indicates a spherical absorber The arrival probability of the time slot at startup. The signal Y received during the duration. u (i) If the number of observed molecules is less than the threshold ω, the passive link state is decoded as "1" (absorption); otherwise, it is "0". This rule can be simplified to:

[0118]

[0119] Example 2

[0120] In this embodiment, an absorption-shift bonded molecular communication method based on a genetic algorithm codebook includes the following steps:

[0121] S1. Construct a molecular communication model under the absorption frequency shift keying architecture. The transmitting end adopts a hybrid modulation scheme of absorption frequency shift keying combined with pulse position modulation as the molecular communication model.

[0122] The molecular communication model includes a source-emitter T x spherical absorber and spherical absorber Unbounded three-dimensional fluid medium; spherical absorber For information decoding receivers, spherical absorbers A state node whose state is variable.

[0123] Absorption frequency shift keying combined with pulse position modulation includes: at the source transmitter T x To spherical absorber In the active link, the source transmitter T x Information is encoded into the time slot positions of molecular pulses through pulse position modulation, and molecules are released only in predefined time slots within each symbol duration to mitigate intermolecular interference; this is achieved using a spherical absorber receiver. To spherical absorber In a passive link, a spherical absorber / receiver The absorption states of the surface are dynamically switched, and additional information bits are mapped to the state transitions, while the remaining molecules are captured for energy recovery.

[0124] S2. Establish a fitness function with the goal of minimizing the decoding error probability, and optimize the codebook through a genetic algorithm to dynamically generate a system codebook that adapts to the characteristics of the molecular channel.

[0125] Methods for obtaining the system codebook include: representing individual molecules as units of length 2. k The vector, where each molecule represents a candidate codebook, will be generated from 2... n The selection is made from the entire set of possible n-bit sequences, using an algorithm to select the position containing 2. k A codebook of binary sequences, and composed of binary sequences {C} s |s = 1, 2, ..., 2 k} indicates that a fitness function is established with the goal of minimizing the decoding error probability:

[0126]

[0127] P s，f =P(C s |C f )

[0128] s = 1, 2, ..., 2 k f = 1, 2, ..., 2 k

[0129] in, Let P represent the fitness function, k represent the number of information bits, and P represent the information bit number. s,f C represents the probability of a codeword error. s Represents the transmitted binary sequence, C fThe binary sequence to be detected is represented; a system codebook adapted to the molecular channel characteristics is dynamically generated by optimizing the candidate codebook through a genetic algorithm.

[0130] S3. Based on the system codebook, the molecular communication model is optimized by combining a two-step detector, and the optimized molecular communication model is used to demodulate the signal at the receiving end.

[0131] The two-step detector consists of: first, recovering the pulse position modulation signal of the active link using a simplified maximum likelihood detector, with the decision rule being:

[0132]

[0133] in, Indicate the decision-making rules, S represents the pulse position modulation signal generated from the active link in the u-th sequence. R y represents the set of all possible active link signals. u (i) indicates that the spherical receiver detects the received signal of the u-th sequence at time i. Let M represent the pulse position modulation signal released by the u-th sequence at time i, and M represent the number of time slots; then, the threshold of the passive link is calculated based on the decoded pulse position modulation signal:

[0134]

[0135] Where ω represents the threshold of the passive link, E a Y represents the number of emitted molecules. ISI Y represents the statistical average of inter-symbol interference. IEI The statistical average value of the interference within the symbol is represented by h[1], which represents the spherical absorber. The probability of a time slot arriving when closed. Indicates a spherical absorber The probability of a time slot arriving when it is enabled.

[0136] Example 3

[0137] like Figure 3 The diagram illustrates an encoding structure with a code length of 8 bits and an information bit length of 4 bits. The transmitter needs to send a message sequence e (4 bits in this example). The codebook contains 2... k The encoder maps sequence e to codeword C using 16 codewords (in this example). s C s It is a codeword in the codebook with a length of n. Subsequently, the codeword is segmented using a parity index: even-numbered index bits are sent to... The middle is used for state transitions, while the odd index bits are based on The current state is assigned to a predefined time slot via pulse position modulation. After channel transmission, an n-bit codeword is received and mapped to one of the codewords in the selected codebook.

[0138] Codebook design plays a crucial role in enhancing the performance of molecular communication systems, particularly for molecular communication system architectures based on absorption frequency shift keying (IFSB) combined with pulse position modulation (PPM). Optimizing codeword structure and state mapping rules improves reliability. In IFSB-PPM molecular communication systems, the codebook not only designs codewords for PPM modulation in the active link but also dynamically coordinates state coding in the passive link to mitigate inter-symbol interference (ISI).

[0139] Figure 4 This is a representative genetic operation where the chosen codeword is represented by an 8-bit code and a 3-bit information bit encoding. In the crossover operation, gene segments from the first and second generation parents undergo single-point crossover to produce new offspring. The mutation operation introduces random perturbations. Furthermore, elitist strategies preserve the best-fit individuals by directly transferring them to the next generation without participating in crossover or mutation.

[0140] During initialization, population diversity is crucial for subsequent search efficiency and can be achieved through uniform distribution or heuristic strategies to ensure broad coverage of the solution space. Subsequently, a fitness function quantifies the quality of each individual in the system. In the selection phase, an elitist strategy is prioritized: high-fitness individuals are directly retained for the next generation, while the remaining parents are selected through a roulette wheel selection process to balance evolutionary speed and diversity. Crossbreeding generates offspring by exchanging chromosome segments between parental individuals, exploring new solution spaces while preserving beneficial genes, thus simulating gene recombination. Mutation introduces random changes to chromosomes with low probability, preventing getting trapped in local optima and improving global search capability. The algorithm terminates when the maximum iteration count is reached or when the fitness change rate falls below a threshold, outputting an optimized codebook.

[0141] Figure 5 The impact of different codebook design methods on performance was further compared. Using an uncoded molecular communication system with absorption frequency shift keying combined with pulse position modulation as a benchmark, the bit error rate (BER) performance of various channel coding schemes for this system was compared. Experimental results show that the channel coding scheme significantly improves the BER performance compared to the uncoded scheme. Specifically, the ideal maximum likelihood detector scheme under the genetic algorithm achieves the most significant improvement, reducing the BER by approximately two orders of magnitude. Furthermore, Reed-Muller (RM(8,4)) coding exhibits consistent performance, verifying the general optimization capability of channel coding in molecular communication systems.

[0142] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A molecular communication system based on a genetic algorithm codebook, characterized in that, include: Model building module, codebook generation module, and signal demodulation module; The model building module is used to build a molecular communication model under the absorption frequency shift keying architecture. The transmitting end adopts absorption frequency shift keying combined with pulse position modulation as the hybrid modulation scheme of the molecular communication model. The codebook generation module is used to establish a fitness function with the goal of minimizing the decoding error probability, and to optimize the codebook through a genetic algorithm to dynamically generate a system codebook that adapts to the characteristics of the molecular channel. The signal demodulation module optimizes the molecular communication model based on the system codebook and a two-step detector, and uses the optimized molecular communication model to demodulate the signal at the receiving end.

2. The absorption-shift-bonding molecular communication system based on genetic algorithm codebook according to claim 1, characterized in that, In the model building module, the molecular communication model includes a source-emitter T. x spherical absorber and spherical absorber Unbounded three-dimensional fluid medium; The spherical absorber The spherical absorber is an information decoding receiver. A state node whose state is variable.

3. The absorption-shift-bonding molecular communication system based on genetic algorithm codebook according to claim 2, characterized in that, In the model building module, the absorption frequency shift keying combined with pulse position modulation includes: At the source transmitter T x to the spherical absorber In the active link, the source transmitter T x Information is encoded into the time slot position of molecular pulses by pulse position modulation, and molecules are released only in predefined time slots within each symbol duration to reduce intermolecular interference; In the spherical absorption receiver to the spherical absorber In a passive link, the spherical absorber The absorption states of the surface are dynamically switched, and additional information bits are mapped to the state transitions, while the remaining molecules are captured for energy recovery.

4. The absorption-shift-bonding molecular communication system based on genetic algorithm codebook according to claim 1, characterized in that, The workflow of the codebook generation module: Each molecular individual is represented as a unit of length 2. k The vector, where each of the molecular individuals represents a candidate codebook, the candidate codebook will be selected from 2 n The selection is made from the entire set of possible n-bit sequences, using an algorithm to select the position containing 2. k A codebook of binary sequences, and composed of binary sequences {C} s |s = 1, 2, ..., 2 k }express; Establish the fitness function with the objective of minimizing the decoding error probability: P s，f =P(C s |C f ) s=1,2,...,2 k ,f=1,2,...,2 k in, Let P represent the fitness function, k represent the number of information bits, and P represent the information bit number. s,f C represents the probability of a codeword error. s Represents the transmitted binary sequence, C f Represents the detected binary sequence; The genetic algorithm is used to optimize the candidate codebook, and the system codebook adapted to the molecular channel characteristics is dynamically generated.

5. The absorption-shift-bonding molecular communication system based on genetic algorithm codebook according to claim 3, characterized in that, In the signal demodulation module, the two-step detector includes: First, the pulse position modulation signal of the active link is recovered using a simplified maximum likelihood detector. The decision rule is as follows: in, Indicate the decision-making rules, S represents the pulse position modulation signal generated from the active link in the u-th sequence. R y represents the set of all possible active link signals. u (i) indicates that the spherical receiver detects the received signal of the u-th sequence at time i. Let M represent the pulse position modulation signal released by the u-th sequence at time i, and M represent the number of time slots; Then, the threshold of the passive link is calculated based on the decoded pulse position modulation signal: Where ω represents the threshold of the passive link, E a Y represents the number of emitted molecules. ISI Y represents the statistical average of inter-symbol interference. IEI The statistical average value of the interference within the symbol is represented by h[1], which represents the spherical absorber. The probability of a time slot arriving when closed. Indicates a spherical absorber The probability of a time slot arriving when it is enabled.

6. A method for absorption-shift-bonding molecular communication based on a genetic algorithm codebook, wherein the method is applied to the system described in any one of claims 1-5, characterized in that, Includes the following steps: A molecular communication model based on absorption frequency shift keying architecture is constructed, and the transmitting end adopts absorption frequency shift keying combined with pulse position modulation as a hybrid modulation scheme for the molecular communication model. A fitness function is established with the goal of minimizing the decoding error probability, and a system codebook that adapts to the molecular channel characteristics is dynamically generated by optimizing the codebook through a genetic algorithm. Based on the system codebook, the molecular communication model is optimized by combining a two-step detector, and the optimized molecular communication model is used for signal demodulation at the receiving end.

7. The absorption-shift-bonding molecular communication method based on genetic algorithm codebook according to claim 6, characterized in that, The molecular communication model includes a source-emitter T x spherical absorber and spherical absorber Unbounded three-dimensional fluid medium; The spherical absorber The spherical absorber is an information decoding receiver. A state node whose state is variable.

8. The absorption-shift-bonding molecular communication method based on genetic algorithm codebook according to claim 7, characterized in that, The absorption frequency shift keying combined with pulse position modulation includes: At the source transmitter T x to the spherical absorber In the active link, the source transmitter T x Information is encoded into the time slot position of molecular pulses by pulse position modulation, and molecules are released only in predefined time slots within each symbol duration to reduce intermolecular interference; In the spherical absorption receiver to the spherical absorber In a passive link, the spherical absorber The absorption states of the surface are dynamically switched, and additional information bits are mapped to the state transitions, while the remaining molecules are captured for energy recovery.

9. The absorption-shift-bonding molecular communication method based on genetic algorithm codebook according to claim 6, characterized in that, The methods for obtaining the system codebook include: Each molecular individual is represented as a unit of length 2. k The vector, where each of the molecular individuals represents a candidate codebook, the candidate codebook will be selected from 2 n The selection is made from the entire set of possible n-bit sequences, using an algorithm to select the position containing 2. k A codebook of binary sequences, and composed of binary sequences {C} s |s = 1, 2, ..., 2 k }express; Establish the fitness function with the objective of minimizing the decoding error probability: P s，f =P(C s |C f ) s=1,2,...,2 k ,f=1,2,...,2 k in, Let P represent the fitness function, k represent the number of information bits, and P represent the information bit number. s,f C represents the probability of a codeword error. s Represents the transmitted binary sequence, C f Represents the detected binary sequence; The genetic algorithm is used to optimize the candidate codebook, and the system codebook adapted to the molecular channel characteristics is dynamically generated.

10. The absorption-shift-bonding molecular communication method based on genetic algorithm codebook according to claim 8, characterized in that, The two-step detector includes: First, the pulse position modulation signal of the active link is recovered using a simplified maximum likelihood detector. The decision rule is as follows: in, Indicate the decision-making rules, S represents the pulse position modulation signal generated from the active link in the u-th sequence. R y represents the set of all possible active link signals. u (i) indicates that the spherical receiver detects the received signal of the u-th sequence at time i. Let M represent the pulse position modulation signal released by the u-th sequence at time i, and M represent the number of time slots; Then, the threshold of the passive link is calculated based on the decoded pulse position modulation signal: Where ω represents the threshold of the passive link, E a Y represents the number of emitted molecules. ISI Y represents the statistical average of inter-symbol interference. IEI The statistical average value of the interference within the symbol is represented by h[1], which represents the spherical absorber. The probability of a time slot arriving when closed. Indicates a spherical absorber The probability of a time slot arriving when it is enabled.

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