A method for detecting the optimal timing threshold of bit value based on receiving volume segmentation

Abstract

A method for detecting the optimal timing threshold value of a bit value based on receiving volume segmentation, firstly designing the channel and transmission parameters, calculating the hit rate of the coded information molecules and the molecules reaching the receiving end; designing the segmentation of the receiver volume, recalculating the probability distribution function of the number of molecules received by the receiver; then optimizing the detection timing of the receiving end, obtaining the time slot reception probability of the receiving end, and then obtaining the simplest detection threshold; using the above system model and detection threshold, generating a mathematical expression of the bit error rate in molecular communication, using the mathematical expression of the bit error rate to simulate and calculate the bit error rate; finally using the Monte Carlo method to verify the mathematical expression of the bit error rate, realizing the threshold detection of optimizing the detection time under the receiving volume segmentation with high reception success rate, high reliability and low complexity. The present invention effectively improves the reliability of the system.

Description

Technical Field

[0001] The invention belongs to the field of molecular communication, and in particular relates to a method for detecting a bit value optimal timing threshold based on receiving volume segmentation. Background Art

[0002] Molecular communication is a medium- and short-range molecular communication technology that achieves communication between nanomachines through diffusion. Traditional communication technology is limited to electromagnetic signals and cannot achieve mutual communication between nanoscale devices with smaller specifications. However, molecular communication is based on the information transmission of biological signals and is more suitable for nanoscale communication. Information particles are modulated by concentration, time, and type. The simplest of these is concentration modulation (OOK). The specific modulation rules are as follows: In a time slot, the transmitter encodes the molecules of a certain concentration as "1", otherwise, it is encoded as "0"; the receiver compares the received molecular concentration with a pre-set threshold, and decodes it as "1" if it is higher than the threshold, otherwise, it is decoded as "0". In the process of molecular transmission, not all information particles emitted by the transmitter reach the receiver within the time slot under consideration. Some information particles remain in the channel and reach the receiver in the subsequent time slot, which leads to ISI. At the same time, the random movement of the emitting molecules in the communication fluid causes the molecules to reach the receiver in a probabilistic manner, and the detection timing will also affect the system performance. The receiving surface of the receiving end is fixed, which is not conducive to further improving the detection success rate. If ISI is taken into consideration, improper detection timing is selected, and the receiving volume is not optimized, the overall system performance may be reduced. Summary of the invention

[0003] In order to overcome the above technical problems, the present invention proposes a method for optimal timing threshold detection of bit values ​​based on receiving volume segmentation, which reduces the bit error rate of system detection from two aspects. On the one hand, by dividing the volume of the receiving sphere, n smaller receiving receptors are divided on the surface of the receiving end, thereby expanding the receiving surface of the receiving end and improving the detection success rate; on the other hand, the detection time of the receiving end is optimized, and the detection is performed in the interval with the highest probability of molecular hits to maximize the detection success rate; therefore, the reliability of the system can be effectively improved through the above two optimization angles.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] A method for detecting a bit value optimal timing threshold based on receiving volume segmentation, the detection method comprising the following steps:

[0006] Step 1: Design the channel and transmission parameters, build a system model for molecular communication, and calculate the hit rate of the encoded information molecules and the molecules reaching the receiver;

[0007] Step 2: Design the segmentation of the receiver volume and recalculate the probability distribution function of the number of molecules received by the receiver;

[0008] Step 3: Optimize the receiver detection timing to obtain the receiver's time slot reception probability, and then obtain the simplest detection threshold through the equal probability method of zero bit storage;

[0009] Step 4: Use the above system model and detection threshold to generate a mathematical expression for the bit error rate in molecular communication, and use the mathematical expression for the bit error rate to simulate and calculate the bit error rate.

[0010] As a preferred implementation, in step 2, recalculating the probability distribution function of the number of molecules received by the receiver includes the following method:

[0011] Establish a three-dimensional unbounded diffusion channel model without flow;

[0012] Set the initial and boundary conditions of the receiver absorption;

[0013] The hit rate of the molecule reaching the receiver within a preset time is calculated based on the initial conditions and boundary conditions;

[0014] The probability of the molecules being absorbed by the receiver within a preset time is calculated based on the hit rate;

[0015] The number of molecules accepted by the receiver at a specified reaction rate is calculated based on the probability of absorbed molecules;

[0016] The probability distribution function of the number of molecules received by the receiver is calculated based on the number of molecules accepted.

[0017] As a preferred implementation, in step 2, the probability distribution function is specifically:

[0018]

[0019] Among them, r s is the radius of the receiver receptor, n is the number of receivers, erf is the error function, and erfc is the complementary error function.

[0020] As a further preferred implementation, step 3 specifically includes the following steps:

[0021] By quantizing the time interval, the probability of a particle hitting the receiver in the duration T after the particle is released in the (i-1)th time slot is calculated;

[0022] Optimize the duration T to obtain the receiver collision probability at the best time;

[0023] Calculate the number of particles r received by the receiver in the i-th time slot i ;

[0024] Calculate the number of times the receiver successfully receives r i Probability of information molecules;

[0025] Define the signal-to-noise ratio and receiver decoding rules;

[0026] The simplest detection threshold is calculated based on the equal probability of zero bit storage.

[0027] As a preferred implementation, in step 1, the encoded information molecules and the hit rate of the molecules reaching the receiver are calculated using traditional CSK coding.

[0028] As a preferred implementation, in step 4, the simulation is performed using the method of passing 0 to get 1 and passing 1 to get 0.

[0029] The technical concept of the present invention is as follows: the present invention considers a flow-free three-dimensional unbounded diffusion channel model, adopts OOK modulation, increases receiving receptors by dividing the receiving end volume, optimizes the detection time, and studies the performance of the molecular communication network. The present invention proposes a bit value optimal timing threshold detection method based on receiving volume segmentation, and develops low-complexity, high-hit-rate, and low-bit-error-rate communication technology in molecular communication. The receiving probability expression of the receiving end after the volume is divided and the mathematical expression of the bit error rate after the volume and detection time are optimized are obtained, highlighting the influence of the receiving end volume and detection timing optimization on the bit error rate of the molecular communication network.

[0030] The beneficial effects of the present invention are:

[0031] 1. Establish a volume-optimized molecular communication network system model. On this basis, obtain mathematical expressions such as the probability distribution function of the number of molecules received by the receiving end of the molecular communication network under OOK modulation;

[0032] 2. Through the idea of ​​equal probability threshold, the decoding rules are established, and the mathematical expression of the bit error rate of molecular communication is obtained by increasing the receiving receptors at the receiving end and optimizing the interval with the maximum probability of molecular hit during transmission;

[0033] 3. Functional verification is completed through the Monte Carlo method. The results show that under the traditional OOK modulation, the molecular communication network increases the receiving receptors on the receiving end surface through volume segmentation and optimizes the detection timing under the receiving end volume, which significantly improves the threshold detection. In addition, the simulation results show the trend of the bit error rate of the molecular communication network under OOK modulation as the SNR changes. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1The main components and flow chart of the MC system. The system network consists of a transmitter, encoding, channel, receiver preprocessing, decoding, and receiver. The transmitter generates information particles and encoding, and the encoding and decoding process the molecules. The channel follows the random diffusion of Brownian motion. The receiver preprocessing includes: volume segmentation and optimization of detection time. The receiver performs threshold judgment and decoding.

[0035] Figure 2 This is a schematic diagram of the molecular communication transmission model. In this model, it is assumed that the transmitter is small enough to be regarded as a point, the closest distance between the transmitter and the receiving surface is d, the center distance between the transmitter and the receiving center is r0, and the radius of the receiving sphere is r r , the receiver radius is r s , the diffusion coefficient D of the channel remains unchanged;

[0036] Figure 3 The relationship between the bit error rate and signal-to-noise ratio of the molecular communication network is shown when the signal-to-noise ratio SNR takes different values, under the basic zero-bit storage equal probability threshold and the threshold for optimizing the detection time under the segmented receiving volume. Among them, the ISI interference between the signals is considered, the distance between the transmitter and the receiver center is r0 = 1e-7m, and the radius of the sphere at the receiving end is r r =1e-8m, the shortest distance between the transmitting and receiving surfaces is d=r0-r r , receiver receptor radius r s =4e-12m, diffusion coefficient D = 7.94e-10m 2 / s. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0038] Reference Figure 1 to Figure 3 , a method for detecting the optimal timing threshold of a bit value based on receiving volume segmentation, comprising the following steps:

[0039] Step 1: Design the channel and transmission parameters, build the improved molecular communication system model, and use traditional CSK coding to obtain the encoded information molecules and the hit rate of the molecules reaching the receiving end;

[0040] Figure 2 This is a schematic diagram of the molecular communication network system model. The network consists of a transmitter, a Poisson channel, and a receiver. The model assumes that the transmitter is small enough to be regarded as a point, the closest distance between the transmitter and the receiver is d, the center distance between the transmitter and the receiver is r0, and the radius of the receiver's sphere is r. r , the receiver radius is r s, the diffusion coefficient D of the channel remains unchanged.

[0041] A flowless three-dimensional unbounded diffusion channel model is established, assuming that the medium is unconstrained and thus extends to infinity in all directions. The emitters are assumed to be small enough to be considered as points, and diffuse independently and randomly in the channel through Brownian motion;

[0042] Due to the segmented receiving volume, a spherical receiver at the receiving end is used with a smaller radius receptor for reception. If a molecule collides with one of the n receptors deployed on the receiver surface, it will be absorbed by the receiver. But if it collides with the receiver surface without touching the receptor, it will bounce back.

[0043] The absorptivity of a spherical receiver, according to Fick's second law, is as follows:

[0044]

[0045] Where D is the diffusion coefficient, is the Laplace operator, and p(r, t|r0) is the molecular distribution function starting at distance r0 at time t.

[0046] Consider the simple modulation method of OOK. i = 1, the transmitter will N tx Information particles are released into the environment; otherwise, no molecules are released.

[0047] The initial conditions for absorption by the spherical receiver are as follows:

[0048]

[0049]

[0050] Where σ is the impulse function.

[0051] The boundary conditions for the spherical receiver absorption are as follows:

[0052]

[0053] Where r is equal to r r is the radius of the receiver, and w represents the reaction rate of the receiver.

[0054] Using the initial and boundary conditions, the hit rate of a molecule arriving at the receiver at time t can be expressed as:

[0055]

[0056] Among them, f hit (t) is the hit rate of information particles changing with time t, r0 is the starting distance from the transmitter to the receiver, β=(wrr +D) / (Dr r ) is the abstraction coefficient.

[0057] Step 2: Design the segmentation of the receiver volume and obtain the mathematical expressions such as the probability distribution function of the number of molecules received by the receiver;

[0058] First, the absorptivity of a spherical receiver with absorbing receptors is established. The diffusing molecules are absorbed by the receptors only when they collide with the receptors. The other parts of the receiver surface cannot absorb the molecules.

[0059] Therefore, the probability that a molecule is absorbed by the receiver before time t is:

[0060]

[0061] Among them, F hit (t) is the molecular distribution function absorbed by the receiver before time t, erf is the error function, and erfc is the complementary error function.

[0062] Given any reaction rate w, the number of molecules received by the receiving end in steady state is:

[0063]

[0064] β=(wr r +D) / (Dr r )

[0065] By taking into account the diffusion resistance of the receiver volume partition, the probability of absorbing a molecule on the spherical receiver surface at t→∞ is r r / r0, the relationship between the receiver and the receiving body is multiples of.

[0066]

[0067] Among them, r s is the radius of the receiver receptor and n is the number of receiver receptors.

[0068] By comparison, w and β are rewritten as follows:

[0069]

[0070] The reaction rate w depends on the number of receptors n and the radius rs of the receptor.

[0071]

[0072] Therefore, the probability that the receiver successfully receives the particle within t seconds after releasing it is:

[0073]

[0074] Among them, r s is the radius of the receiver receptor, n is the number of receivers, erf is the error function, and erfc is the complementary error function.

[0075] Step 3: Optimize the detection timing of the receiving end to obtain the time slot reception probability of the receiving end, and then obtain the simplest detection threshold through the equal probability method of zero bit storage, so as to realize the threshold estimation in the bit error rate analysis in step 4;

[0076] By quantizing the time interval, the probability of a particle hitting the receiver during the duration T after the particle is released in the (i-1)th time slot is:

[0077]

[0078]

[0079] Where T is the duration of the molecule, i represents the molecule time slot, r0 is the distance from the transmitter to the center of the receiver, and r r is the receiver radius, and α is the duration influence coefficient.

[0080] By optimizing the duration T, the probability of receiver collision at the best time is obtained as:

[0081]

[0082] Among them, w1 is the optimization start time weight, w2 is the optimization end time weight, t M It is the corresponding moment when the number of molecules at the receiving end reaches the maximum.

[0083]

[0084] Where d = r0-r r It is the shortest distance from the transmitter to the receiving surface.

[0085] Due to the nature of diffusion channels, all emitted molecules are not necessarily received within a certain duration, so the previously emitted molecules will interfere with the later emitted molecules, resulting in ISI.

[0086] The average number of particles received in the kth time slot is Where N tx is the number of molecules transmitted in a single time. According to the transmission characteristics of molecules in the channel, the number of particles received by the receiving end in the i-th time slot is r i Follows Poisson distribution:

[0087]

[0088]

[0089] Among them, s i is the molecule transmitted in the current time slot, C0 is the average number of particles received in the 0th time slot, L represents the channel length, n0 is the channel noise, Represents ISI noise.

[0090] make

[0091] Finally, the receiver successfully receives r i The probability of information molecules follows the following Poisson distribution:

[0092]

[0093] Define the signal-to-noise ratio for bit error analysis in step 4:

[0094]

[0095] First, the decoding rule at the receiver: If the receiver r i <tao is judged as 0, otherwise, it is judged as 1.

[0096] Among them, r i is the number of received molecules, and tao is the detection threshold.

[0097] According to the principle that the number of received molecules is the same regardless of whether 1 or 0 is sent under equal probability, the detection threshold is calculated

[0098] P(r i =tao|s i =0) = P(r i =tao|s i =1)

[0099]

[0100] Step 4: Based on the established system model, channel parameters and thresholds, the mathematical expression of the bit error rate in molecular communication is obtained by using the idea of ​​transmitting 0 and getting 1 and transmitting 1 and getting 0 to conduct simulation experiments;

[0101] According to the threshold value derived above and the probability distribution function of the corresponding channel parameters and the number of molecules received by the receiver, a processing model is established at the receiving end through OOK modulation and threshold decoding rules. The volume segmentation of the receiving end and the determination of the best detection time are used to greatly improve the probability of successful reception at the receiving end, thereby obtaining a more reasonable threshold value. Finally, according to the error code rule, the general bit error rate mathematical expression of molecular communication is obtained. The specific process is as follows:

[0102] According to the two bit error conditions of sending 0 and receiving 1 and sending 1 and receiving 0, the receiver end that obeys Poisson's law derived above successfully receives r iThe probability distribution of the numerator gives the bit error rate that obeys the Q function distribution.

[0103] The molecular communication model assumes that the transmission of 0 and 1 is equally likely, so the final bit error rate is:

[0104] P e (s i , tao)=1 / 2[Q(λ-R0, tao)+1-Q(λ, tao)]

[0105] in,

[0106] Figure 3 The relationship between the bit error rate and signal-to-noise ratio (SNR) of the molecular communication network is shown when the signal-to-noise ratio (SNR) takes different values, under the basic zero-bit storage equal probability threshold and the threshold of optimizing the detection time under segmented receiving volume. Under the two different threshold detection methods, the bit error rate decreases with the increase of the signal-to-noise ratio and gradually tends to 0 when the signal-to-noise ratio (SNR) is snr=10, snr=15, snr=20, snr=25, and snr=30. Among them, the bit error rate after optimizing the detection time under segmented receiving volume is lower, because the traditional threshold detection only receives on the surface of the entire sphere and makes a receiving judgment for the complete duration T. Now the receiving sphere is divided into n receiver receptors, which increases the receiving surface and only makes a judgment when the receiving probability reaches the maximum, increasing the probability of successful molecular reception and improving the transmission reliability, so the bit error rate is lower. Under the same signal-to-noise ratio (SNR), it can be seen that the bit error rate performance of the threshold detection with optimized detection time under segmented receiving volume is better than that of the ordinary threshold detection.

[0107] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for detecting the optimal timing threshold of a bit value based on receiving volume segmentation, characterized in that: The method comprises the following steps: Step 1: Design the channel and transmission parameters, build a system model for molecular communication, and calculate the hit rate of the encoded information molecules and the molecules reaching the receiver; Step 2: Design the segmentation of the receiver volume and recalculate the probability distribution function of the number of molecules received by the receiver; Step 3: Optimize the receiver detection timing to obtain the receiver's time slot reception probability, and then obtain the simplest detection threshold through the equal probability method of zero bit storage; Step 4: Generate a mathematical expression for the bit error rate in molecular communication using the above system model and detection threshold, and use the mathematical expression for the bit error rate to simulate and calculate the bit error rate; In step 1, the boundary conditions absorbed by the spherical receiver are as follows: Where r is equal to r r is the radius of the receiver, w represents the reaction rate of the receiver; Using the initial and boundary conditions, the hit rate of a molecule arriving at the receiver at time t can be expressed as: Among them, f hit (t) is the hit rate of information particles changing with time t, r0 is the starting distance from the transmitter to the receiver, β=(wr r +D) / (Dr r ) is the abstraction coefficient; In step 2, the probability distribution function of the number of molecules received by the receiver is recalculated, including the following method: Establish a three-dimensional unbounded diffusion channel model without flow; Set the initial and boundary conditions of the receiver absorption; The hit rate of the molecule reaching the receiver within a preset time is calculated based on the initial conditions and boundary conditions; The probability of the molecules being absorbed by the receiver within a preset time is calculated based on the hit rate; where the probability of a molecule being absorbed by the receiver before time t is: Among them, F hit (t) is the molecular distribution function absorbed by the receiver before time t, erf is the error function, and erfc is the complementary error function; The number of molecules accepted by the receiver at a specified reaction rate is calculated based on the probability of absorbed molecules; Calculating a probability distribution function of the number of molecules received by the receiver based on the number of molecules received; The probability distribution function is specifically: Among them, r s is the radius of the receiver, n is the number of receivers, erf is the error function, erfc is the complementary error function, r r is the radius of the sphere at the receiving end, r0 is the distance from the transmitting end to the center of the receiving end, D is the diffusion coefficient of the channel, and t is the time; The step 3 specifically includes the following steps: By quantizing the time interval, the probability of a particle hitting the receiver in the duration T after the particle is released in the (i-1)th time slot is calculated; Optimize the duration T to obtain the receiver collision probability at the best time; Calculate the number of particles r received by the receiver in the i-th time slot i ; Calculate the number of times the receiver successfully receives r i Probability of information molecules; Define the signal-to-noise ratio and receiver decoding rules; According to the equal probability method of zero bit storage, the simplest detection threshold is calculated P(r i =tao|s i =0)=P(r i =tao|s i =1) 2. The method for detecting the optimal timing threshold of a bit value based on receiving volume segmentation according to claim 1, characterized in that: In step 1, the encoded information molecules and the hit rate of the molecules reaching the receiver are calculated using traditional CSK coding.

3. The method for detecting the optimal timing threshold of a bit value based on receiving volume segmentation according to claim 1, characterized in that: In step 4, the simulation is performed using the method of passing 0 to get 1 and passing 1 to get 0.

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