Detection method and device of molecular code division multiple access system based on zero-forcing frequency domain equalization

Abstract

The invention discloses a zero-forcing frequency domain equalization-based molecular code division multiple access system detection method and device. The method comprises the following steps of: constructing a molecular code division multiple access system; each nano emitter performs spectrum spreading on data by using a spectrum spreading sequence, and represents a molecular concentration signal of bit information by releasing A-type and B-type molecules; sampling the received molecular concentration signal at the fusion center, and determining a concentration difference observation value of A type molecules and B type molecules; on the basis of the observation value, organizing data in a block transmission mode and inserting a cyclic prefix to eliminate inter-block interference, and forming a time domain observation vector; converting the time domain signal into a frequency domain signal; suppressing inter-symbol, inter-chip and multi-access interference by applying a zero-forcing frequency domain equalization algorithm; performing inverse fast Fourier transform on the equalized signal, converting the equalized signal back to a time domain, and obtaining a judgment variable through de-spreading operation; and comparing the judgment variable with a zero threshold, if the judgment variable is greater than 0, judging as 1, otherwise, judging as-1, and outputting a decoding bit sequence.

Description

Technical Field

[0001] This invention relates to the field of molecular communication technology, and in particular to a detection method and apparatus for a molecular code division multiple access system based on zero-forced frequency domain equalization. Background Technology

[0002] In nanocommunication systems, molecular communication utilizes molecular diffusion or reaction as an information transmission mechanism, offering advantages such as low energy consumption and biocompatibility, and is widely used in scenarios such as medical diagnosis, in vivo drug delivery, and in vivo sensing.

[0003] In diffusion-based molecular communication systems, information molecules are transmitted through Brownian motion in a fluid medium. Due to the slow molecular transmission speed and the strong randomness of the diffusion process, there is significant inter-symbol interference and on-chip interference between received signals. In molecular communication code division multiple access systems with multi-user parallel communication, multiple access interference will also occur. Existing signal detection methods are mostly designed for single-user systems, either detecting information from each user individually or relying on highly complex signal processing algorithms, which are not suitable for nanoscale devices with limited computing power. Summary of the Invention

[0004] Therefore, it is necessary to propose a detection method and device for molecular code division multiple access systems based on zero-forced frequency domain equalization to address the above problems.

[0005] A detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization, the method comprising: A molecular code division multiple access system is constructed, comprising K nano-emitters and a fusion center. The nano-emitters transmit information molecules through a diffusion medium, and the fusion center is used for signal detection. Binary molecular shift keying modulation is employed, and each nano-emitter spreads the data using a spreading sequence with values ​​of {+1,-1}, and releases molecular concentration signals representing bit information by releasing A-type and B-type molecules; At the fusion center, the received molecular concentration signal is sampled to determine the observed concentration difference between type A and type B molecules; Based on the concentration difference observations, the data is organized using a block transmission method, with each data block being M bits in length, corresponding to MN chip observations; and a cyclic prefix is ​​inserted between data blocks to eliminate inter-block interference, and the discrete observations are preprocessed into time-domain observation vectors. The time-domain observation signal is converted into a frequency-domain signal using a fast Fourier transform; The zero-force frequency domain equalization algorithm is applied to equalize the frequency domain signal; The equalized signal is converted back to the time domain by inverse fast Fourier transform, and the decision variable is obtained by despreading. Based on the decision variable, for each bit of each nano-emitter, the decision variable is compared with a zero threshold: if the decision variable is greater than 0, the bit is judged to be 1; otherwise, the bit is judged to be -1, thereby outputting the decoded bit sequence as the detection result.

[0006] Preferably, the binary molecular shift keying modulation is employed, and each nano-emitter uses a spreading sequence with values ​​{+1,-1} to spread the data, specifically including: in molecular code division multiple access, the first... The information to be transmitted by each nano-emitter is represented as follows: ,in Each nano-emitter sends the first Each bit is passed through a length of The spread spectrum sequence is extended, and this sequence can be represented as... ,in ,and When using binary molecular shift keying modulation, each pulse is emitted... The first molecule, type A molecule represents '1', type B molecule represents '-1', and the second molecule... The nano-emitter transmits the first... When the data is bit-sized, its molecular emission signal can be expressed as: in It is a nano-emitter At the moment of molecular pulse emission, the pulses of type A and type B molecules are respectively generated by... and It is represented and defined as: ( ), and when hour, ( ).

[0007] Preferably, the step of releasing molecular concentration signals representing bit information by releasing type A and type B molecules specifically includes: the first... Nano-emitters At any moment Launch a When a pulse composed of molecules is applied, the fusion center is at... The molecular concentration sampled at time t obeys Fick's second law, given as: ,in, The diffusion coefficient is... For the first Distance between each emitter and the fusion center, molecular concentration It is a time-domain impulse function representing channel state information for a given distance. Molecular concentration at The maximum value is reached at time , and its maximum value is .

[0008] Preferably, the step of sampling the received molecular concentration signal at the fusion center to determine the observed concentration difference between type A and type B molecules specifically includes: in the first... The first bit At each chip sampling time t, among which The observed concentration difference between type A and type B molecules is derived and expressed as follows: in, This indicates a round-down operation. This represents the modulo operation; while and They represent the first The nano-emitter sends the first... Particle counting noise caused by different types of molecules during a single molecular pulse; when the number of molecules in each chip... Or the total number of molecules in each symbol When large enough, and Both can be approximated as Gaussian noise with a mean of zero, and their variances are respectively as well as ,in, To accommodate the volume of the fused central spherical detector, the detection radius is... .

[0009] Preferably, the step of sampling the received molecular concentration signal at the fusion center to determine the observed concentration difference between type A and type B molecules specifically includes: when any nanoemitter is at its peak... After emitting a molecular pulse, the desired molecular concentration at the fusion center will be The fusion center reaches its maximum value at its peak time. The concentration of molecules is sampled at a location, and the observed concentration difference between type A and type B molecules can be expressed as: ,in, , .

[0010] Preferably, the data is organized using a block transfer method based on the concentration difference observations, with each data block being M bits in length and corresponding to MN chip observations. Specifically, this includes: the observations in the current data block that are related to... All observations corresponding to each sampling time point are represented as follows: in, It is a dimension The channel state information matrix is ​​in the form of: , It is a size of The matrix, Includes all influence observation vectors bits, i.e. , It is the observation noise vector .

[0011] Preferably, the step of inserting a cyclic prefix between data blocks to eliminate inter-block interference and preprocessing discrete observations into time-domain observation vectors specifically includes: through... Determine the time-domain observation vector, where, , It is a size of The matrix, by Constructed, that is .

[0012] Preferably, converting the time-domain observation signal into a frequency-domain signal using a Fast Fourier Transform (FFT) specifically includes: transforming the time-domain observation vector using an FFT transform matrix. Convert to frequency domain observation vector in, It is a circular matrix The diagonalized matrix can be represented as: .

[0013] Preferably, the application of the zero-forced frequency domain equalization algorithm to equalize the frequency domain signal specifically includes: through... Obtain the equalized signal ,in, It is a diagonal balanced matrix, which can be represented as , Corresponding to the The equalization coefficient of each subcarrier.

[0014] A detection device for a molecular code division multiple access system based on zero-forced frequency domain equalization, the device comprising: K nano-emitters, each configured to: employ binary molecular shift keying modulation, spread the data using a spreading sequence with values ​​of {+1,-1}, and generate a molecular concentration signal by releasing type A and type B molecules to represent bit information; The fusion center, connected to the nano-emitter via a diffusion medium, is configured as follows: The received molecular concentration signal is sampled to determine the observed concentration difference between type A and type B molecules; Based on the concentration difference observations, the data is organized in a block transmission manner. Each data block is M bits long and corresponds to MN chip observations. A cyclic prefix is ​​inserted between data blocks to eliminate inter-block interference. The discrete observations are preprocessed into time-domain observation vectors. The time-domain observation vector is converted into a frequency-domain signal using a fast Fourier transform; The zero-force frequency domain equalization algorithm is applied to equalize the frequency domain signal; The equalized signal is converted back to the time domain by inverse fast Fourier transform, and the decision variable is obtained by despreading. Based on the decision variable, for each bit of each nano-emitter, the decision variable is compared with a zero threshold: if the decision variable is greater than 0, the bit is judged to be 1; otherwise, the bit is judged to be -1, thereby outputting the decoded bit sequence as the detection result.

[0015] The embodiments of the present invention have the following beneficial effects: This invention achieves a balance between low complexity and high reliability by introducing binary molecular shift-keying modulation and a block transmission structure, combined with a zero-force frequency domain equalization algorithm. It approximates noise as a Gaussian distribution, simplifying detection and analysis. Through cyclic prefix and frequency domain processing, it effectively suppresses inter-symbol interference, on-chip interference, and multiple access interference, significantly reducing computational complexity and making it suitable for resource-constrained nanoscale devices. Ultimately, it improves the bit error rate performance and anti-interference capability of molecular communication systems, providing an efficient solution for multi-user parallel communication. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be 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.

[0017] in: Figure 1 This is a flowchart illustrating a detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization, as described in an embodiment of the present invention. Figure 2 This is a schematic diagram of a diffusion-type molecular communication system model using code division multiple access in a detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization, as described in an embodiment of the present invention. Detailed Implementation

[0018] 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.

[0019] This invention provides a detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization, such as... Figure 1 , 2 As shown, the method includes: Step 1: Construct a molecular code division multiple access system, including K nano-emitters and a fusion center. The nano-emitters transmit information molecules through a diffusion medium, and the fusion center is used for signal detection. Specifically, the molecular code division multiple access system consists of The system consists of multiple nano-emitters and a spherical transparent receiver located at the fusion center. During information transmission, the nano-emitters release two types of information molecules (Type A and Type B) into a three-dimensional fluid medium. This medium is infinitely spatial, homogeneous, stable, and without flow boundaries. The fusion center can then... Molecular concentration signals are sampled and detected within a spherical detection space.

[0020] In molecular code division multiple access, nano-emitters release... Each molecular pulse is used to transmit one bit of information, and each pulse contains Each molecule. The time interval between two adjacent pulses is called a chip, and its duration is... Second. Definition If the extension factor is , then the symbol duration is When binary molecular shift keying is used, This also corresponds to one bit period. The duration of the bit.

[0021] In a code-division multiple access system, the first... The information to be transmitted by each nano-emitter is represented as follows: ,in To achieve multiple access, each nano-emitter sends the first... Each bit is passed through a length of The spreading sequence is extended, and the spreading sequence can be represented as follows: ,in ,and Since the transmission distances between different nano-emitters and the fusion center vary, a constant can be defined for the entire molecular code division multiple access system to achieve synchronous transmission between different nano-emitters. .

[0022] Furthermore, regardless of the distance between the nano-emitter and the fusion center, it is assumed that the fusion center samples at the desired peak of the molecular concentration pulse. To achieve this, a time delay is set. To adjust the initial emission time of different nano-emitters, so that the molecular pulses emitted by different nano-emitters are aligned at the concentration peak time of the fusion center.

[0023] Step 2: Using binary molecular shift keying modulation, each nano-emitter spreads the data using a spreading sequence with values ​​of {+1,-1}, and releases molecular concentration signals representing bit information by releasing type A and type B molecules; Specifically, when using binary molecular shift keying (BMoSK) modulation, each pulse emission The number of molecules is as follows: type A molecules represent '1', and type B molecules represent '-1'. Therefore, the number of molecules is... The nano-emitter transmits the first... When the data is bit-sized, its molecular emission signal can be expressed as:

[0024] (1)

[0025] in, It is a nano-emitter The moment of molecular pulse emission, u is the bit index, one bit is divided into N chips, q is the chip index, and t is the time scale. The pulses of type A and type B molecules are respectively generated by... and They are defined as follows: ( ), and when hour, ( ).

[0026] Molecules diffuse freely in a stagnant, boundaryless fluid medium, and this medium is homogeneous and stable; nano-emitters At any moment Launch a When a pulse composed of molecules is applied, the fusion center is at... The molecular concentration sampled at time t obeys Fick's second law, given as: (2)

[0027] in, The diffusion coefficient is... For the first Distance between each emitter and the fusion center, molecular concentration It is a time-domain impulse function representing channel state information for a given distance. Molecular concentration at The maximum value is reached at time , and its maximum value is , where e is the natural base.

[0028] To ensure that the maximum desired concentrations from different nanoemitters arrive at the fusion center simultaneously, a uniform sampling time is defined. To satisfy The premise is launch delay Given .

[0029] Step 3: At the fusion center, sample the received molecular concentration signal to determine the observed concentration difference between type A and type B molecules; Specifically, the fusion center can distinguish between type A and type B molecules; when there are When the nano-emitters send signals to the fusion center according to equation (1), at the first... The first bit At each chip sampling time (where The observed concentration difference between type A and type B molecules can be derived and expressed as: (3)

[0030] in, This indicates a round-down operation. This represents the modulo operation; while and They represent the first The nano-emitter sends the first... Particle counting noise caused by different types of molecules during a molecular pulse.

[0031] When the number of molecules in each chip Or the total number of molecules in each symbol When large enough, and Both can be approximated as Gaussian noise with a mean of zero, and their variances are respectively as well as ,in, To accommodate the volume of the fused central spherical detector, the detection radius is... Therefore, these counting noises follow the following normal distribution: , .

[0032] According to equation (2) Characteristics, when a certain nano-emitter is at time After emitting a molecular pulse, the desired molecular concentration at the fusion center will be It reaches its maximum value at that time. Therefore, in order to detect from The first nano-emitter Each bit, the fusion center at time Molecular concentrations are sampled at various points, and correspondingly, the observed concentration difference between type A and type B molecules at these sampling times can be expressed as:

[0033] (4)

[0034] According to the pulse function As can be seen from the characteristics, inter-symbol interference (ISI) and on-chip interference decay rapidly over time. Therefore, it is assumed that the maximum duration of ISI / on-chip interference is... In this case, the chip in equation (4) It can be rewritten in the following form:

[0035] (5)

[0036] In equation (5), and Having the same statistical properties, similarly, and It also has the same statistical properties.

[0037] Therefore, equation (5) can be expressed in an equivalent form as: (6)

[0038] make Then equation (6) can be rewritten in a more manageable form: (7)

[0039] in, This term can be well approximated as noise following a Gaussian distribution, with the distribution being: ,in .

[0040] Step 4: Based on the concentration difference observations, organize the data using a block transfer method. Each data block is M bits long and corresponds to MN chip observations. Insert a cyclic prefix between data blocks to eliminate inter-block interference and preprocess the discrete observations into a time-domain observation vector. Specifically, after the received signal is sampled and represented, the fusion center begins to process the signal based on a length of... Bit-by-bit detection is performed on the observed vector. For ease of detection, it is assumed that data is transmitted in blocks, each block being of length [missing information]. . No. The data block transmitted by a nano-emitter can be represented as: In this case, for a given transmitted data block, its spread spectrum signal will be distributed in... On each observation, the range is from arrive .

[0041] (8)

[0042] When considering inter-block interference The front of the middle Each observation should be added from the previous data block. The interference consists of bits. This interference can be represented as... This proves that the current data block contains... All observations corresponding to each sampling time point are represented as follows:

[0043] (9)

[0044] in, It is a dimension The matrix is ​​of the form: (10)

[0045] The left block matrix (10) is a block of size 10. The matrix, whose beginning is filled with... One zero. In equation (9), ,here This represents the Kronecker product. Therefore, It is a size of The matrix. Includes all influence observation vectors bits, i.e. Furthermore, due to this Each observation has experienced a complete length of [length missing]. On-chip interference, observation noise vector It can be approximated as having a mean of zero and a covariance matrix of... The Gaussian distribution.

[0046] To eliminate inter-block interference and introduce cyclic characteristics into the channel state information matrix for frequency domain detection, a cyclic prefix is ​​inserted between two adjacent data blocks as a guard interval. The length of the cyclic prefix should be greater than the length of the on-chip interference. To completely cancel inter-block interference, its length can be set to the last block length after spread spectrum. Values.

[0047] After the spread spectrum operation is completed The end Each chip is copied and placed at the beginning of the data block. Subsequently, the nano-emitter sends a sequence containing... cyclic prefix chips and A complete data block of a normal data chip. After receiving it, the fusion center will... One chip observation is discarded, and the rest are retained. Several observations are used for signal processing. Due to the insertion of the aforementioned cyclic prefix, the channel state information matrix... Converted to a size of Circular matrix Its diagonal element is , denoted as:

[0048] (11)

[0049] Therefore, the observation equation (9) can now be written in the following form: (12)

[0050] in, It is a size of The matrix, by Constructed, that is .

[0051] Step 5: Convert the time-domain observation signal into a frequency-domain signal using a fast Fourier transform; Specifically, to achieve frequency domain signal detection, the received signal needs to be converted to the frequency domain for processing. At the fusion center, the received time-domain discrete signal in equation (12) is... Through a The point-wise Fast Fourier Transform (FFT) converts a signal into the frequency domain. The FFT transform matrix is ​​defined as follows:

[0052] (13)

[0053] Among them, matrix The elements ( ) is defined as ,matrix It is a unitary matrix that satisfies ,in This represents the conjugate transpose operation, while It is called the inverse fast Fourier transform matrix.

[0054] The time-domain signal is transformed by the FFT transform matrix. Converting to the frequency domain signal yields its frequency domain representation. : (14)

[0055] matrix It is a circular matrix The diagonalized matrix can be represented as: (15)

[0056] Furthermore, the spread spectrum data block in the frequency domain is represented as ,in (16)

[0057] Indicates by the first Spread vectors transmitted by nano-emitters The One chip. The noise vector in the frequency domain is expressed as: , of which The component represents the first... The noise on each subcarrier is defined as:

[0058] (17)

[0059] Since the FFT / IFFT transformation is a unitary transformation, after the FFT transformation, It has zero mean and variance. .

[0060] Step 6: Apply the zero-force frequency domain equalization algorithm to perform equalization processing on the frequency domain signal; Specifically, to mitigate the effects of inter-symbol interference and on-chip interference, based on the fundamental principles of linear frequency domain equalization, the equalized signal... It can be represented as: (18)

[0061] in, It is a diagonal balanced matrix, which can be represented as ,in Corresponding to the The equalization coefficient of each subcarrier.

[0062] Zero-forced frequency domain equalization is based on channel state information in the frequency domain. For the target The channel of each nanometer transmitter is inverted to eliminate on-chip interference. The equalization matrix for zero-force frequency domain equalization is then used. It can be calculated using the following formula:

[0063] (19)

[0064] Overall equilibrium matrix It can be represented as: (20)

[0065] in, This represents a diagonal matrix.

[0066] Step 7: Perform an inverse fast Fourier transform on the equalized signal to convert it back to the time domain, and obtain the decision variable through despreading. Specifically, the equilibrium matrix Multiply Obtain the equalized signal After performing the balancing operation, the IFFT matrix is... Multiply by the equilibrium result This converts the signal from the frequency domain back to the time domain. Then, by multiplying by... Complete the despreading to obtain the result used for detecting the first... Emits from a nano-emitter The decision variable has 10 bits. Therefore, we can obtain:

[0067] (twenty one)

[0068] in

[0069] When using zero-forcing frequency domain equalization, the equalization matrix of the zero-forcing frequency domain equalization is... Substituting into (21), at this point, after inverse fast Fourier transform and despreading, the first... Nano-emitters The decision variable block can be represented as: (twenty two)

[0070] According to equation (22), it can be easily seen that if zero-forced frequency domain equalization is used, and different nano-emitters are assigned orthogonal spreading codes, and the transmission distance from each nano-emitter to the fusion center is the same, then we have Furthermore, we can obtain: (twenty three)

[0071] It used This relationship. Therefore, on-chip interference and multiple access interference are completely eliminated.

[0072] Step 8: Based on the decision variable, for each bit of each nano-emitter, compare the decision variable with the zero threshold: if the decision variable is greater than 0, then the bit is judged to be 1; otherwise, the bit is judged to be -1, thereby outputting the decoded bit sequence as the detection result.

[0073] Specifically, during the judgment process, the first The first nano-emitter The decision variable corresponding to each bit is denoted as . It is dimensional vector The first in Each element. Based on this decision variable. It can restore the first The first nano-emitter 1 bit, as shown below:

[0074] (twenty four)

[0075] in , .

[0076] This invention proposes a molecular code division multiple access system based on binary molecular shift keying modulation (BSK) for establishing uplinks between multiple NTs and FCs in diffuse molecular communication. The invention uses values ​​of [value missing]. The spread spectrum sequence enables parallel multiple access communication of multiple nanometer transmitters. By using a pair of isomers (type A and type B) with the same diffusion coefficient as information carriers, representing "+1" and "-1" respectively, this design can approximate the counting noise at the receiver as Gaussian additive noise with constant variance under time-invariant channel conditions, thereby simplifying detection modeling and analysis.

[0077] This invention transmits data in blocks and avoids inter-block interference by using a cyclic prefix. It shifts the signal detection process from traditional time-domain processing to frequency-domain processing, realizing frequency-domain processing of the signal. This reduces the computational complexity of the system, improves detection efficiency and anti-interference capability, and thus achieves a balance between low complexity and high reliability in molecular communication systems.

[0078] This invention proposes a low-complexity frequency domain equalization algorithm—zero-forced frequency domain equalization. This method can effectively suppress inter-chip interference in molecular code division multiple access systems with low computational complexity, thereby achieving efficient and reliable multi-user signal detection in a nanometer communication environment.

[0079] This invention also provides a detection device for a molecular code division multiple access system based on zero-forced frequency domain equalization, the device comprising: K nano-emitters, each configured to: employ binary molecular shift keying modulation, spread the data using a spreading sequence with values ​​of {+1,-1}, and generate a molecular concentration signal by releasing type A and type B molecules to represent bit information; The fusion center, connected to the nano-emitter via a diffusion medium, is configured as follows: The received molecular concentration signal is sampled to determine the observed concentration difference between type A and type B molecules; Based on the concentration difference observations, the data is organized in a block transmission manner. Each data block is M bits long and corresponds to MN chip observations. A cyclic prefix is ​​inserted between data blocks to eliminate inter-block interference. The discrete observations are preprocessed into time-domain observation vectors. The time-domain observation vector is converted into a frequency-domain signal using a fast Fourier transform; The zero-force frequency domain equalization algorithm is applied to equalize the frequency domain signal; The equalized signal is converted back to the time domain by inverse fast Fourier transform, and the decision variable is obtained by despreading. Based on the decision variable, for each bit of each nano-emitter, the decision variable is compared with a zero threshold: if the decision variable is greater than 0, the bit is judged to be 1; otherwise, the bit is judged to be -1, thereby outputting the decoded bit sequence as the detection result.

[0080] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0081] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization, characterized in that, The method includes: A molecular code division multiple access system is constructed, comprising K nano-emitters and a fusion center. The nano-emitters transmit information molecules through a diffusion medium, and the fusion center is used for signal detection. Binary molecular shift keying modulation is employed, and each nano-emitter spreads the data using a spreading sequence with values ​​of {+1,-1}, and releases molecular concentration signals representing bit information by releasing A-type and B-type molecules; At the fusion center, the received molecular concentration signal is sampled to determine the observed concentration difference between type A and type B molecules; Based on the concentration difference observations, the data is organized using a block transmission method, with each data block being M bits in length, corresponding to MN chip observations; and a cyclic prefix is ​​inserted between data blocks to eliminate inter-block interference, and the discrete observations are preprocessed into time-domain observation vectors. The time-domain observation signal is converted into a frequency-domain signal using a fast Fourier transform; The zero-force frequency domain equalization algorithm is applied to equalize the frequency domain signal; The equalized signal is converted back to the time domain by inverse fast Fourier transform, and the decision variable is obtained by despreading. Based on the decision variable, for each bit of each nano-emitter, the decision variable is compared with a zero threshold: if the decision variable is greater than 0, the bit is judged to be 1; otherwise, the bit is judged to be -1, thereby outputting the decoded bit sequence as the detection result.

2. The detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization according to claim 1, characterized in that, The method employs binary molecular shift keying modulation, where each nano-emitter spreads the data using a spreading sequence with values ​​{+1, -1}. Specifically, in molecular code division multiple access, the first... The information to be transmitted by each nano-emitter is represented as follows: ,in Each nano-emitter sends the first Each bit is passed through a length of The spread spectrum sequence is extended, and this sequence can be represented as... ,in ,and When using binary molecular shift keying modulation, each pulse is emitted... The first molecule, type A molecule represents '1', type B molecule represents '-1', and the second molecule... The nano-emitter transmits the first... When the data is bit-sized, its molecular emission signal can be expressed as: in It is a nano-emitter At the moment of molecular pulse emission, the pulses of type A and type B molecules are respectively generated by... and It is represented and defined as: ( ), and when hour, ( ).

3. The detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization according to claim 2, characterized in that, The molecular concentration signal, which represents bit information by releasing type A and type B molecules, specifically includes: the first Nano-emitters At any moment Launch a When a pulse composed of molecules is applied, the fusion center is at... The molecular concentration sampled at time t obeys Fick's second law, given as: ,in, The diffusion coefficient is... For the first Distance between each emitter and the fusion center, molecular concentration It is a time-domain impulse function representing channel state information for a given distance. Molecular concentration at The maximum value is reached at time , and its maximum value is .

4. The detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization according to claim 3, characterized in that, At the fusion center, the received molecular concentration signal is sampled to determine the observed concentration difference between type A and type B molecules. Specifically, this includes: [The sentence is incomplete and requires further context to be fully translated.] The first bit At each chip sampling time t, among which The observed concentration difference between type A and type B molecules is derived and expressed as follows: in, This indicates a round-down operation. This represents the modulo operation; while and They represent the first The nano-emitter sends the first... Particle counting noise caused by different types of molecules during a single molecular pulse; when the number of molecules in each chip... Or the total number of molecules in each symbol When large enough, and Both can be approximated as Gaussian noise with a mean of zero, and their variances are respectively as well as ,in, To accommodate the volume of the fused central spherical detector, the detection radius is... .

5. The detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization according to claim 3, characterized in that, At the fusion center, the received molecular concentration signal is sampled to determine the observed concentration difference between type A and type B molecules. Specifically, this includes: when any nanoemitter reaches its peak value... After emitting a molecular pulse, the desired molecular concentration at the fusion center will be The fusion center reaches its maximum value at its peak time. The concentration of molecules is sampled at a location, and the observed concentration difference between type A and type B molecules can be expressed as: ,in, , .

6. The detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization according to claim 4 or 5, characterized in that, The data, based on the concentration difference observations, is organized using a block transfer method. Each data block is M bits long and corresponds to MN chip observations. Specifically, it includes: the observations in the current data block that are related to... All observations corresponding to each sampling time point are represented as follows: in, It is a dimension The channel state information matrix is ​​in the form of: , It is a size of The matrix, Includes all influence observation vectors bits, i.e. , It is the observation noise vector .

7. The detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization according to claim 6, characterized in that, The step of inserting a cyclic prefix between data blocks to eliminate inter-block interference and preprocessing discrete observations into time-domain observation vectors specifically includes: through... Determine the time-domain observation vector, where, , It is a size of The matrix, by Constructed, that is .

8. The detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization according to claim 7, characterized in that, The step of converting the time-domain observation signal into a frequency-domain signal using a Fast Fourier Transform (FFT) specifically includes: transforming the time-domain observation vector using an FFT transform matrix. Convert to frequency domain observation vector in, It is a circular matrix The diagonalized matrix can be represented as: .

9. The detection method for a molecular code division multiple access system based on zero-forced frequency domain equalization according to claim 8, characterized in that, The application of the zero-forced frequency domain equalization algorithm to equalize the frequency domain signal specifically includes: through Obtain the equalized signal ,in, It is a diagonal balanced matrix, which can be represented as , Corresponding to the The equalization coefficient of each subcarrier.

10. A detection device for a molecular code division multiple access system based on zero-forced frequency domain equalization, characterized in that, The device includes: K nano-emitters, each configured to: employ binary molecular shift keying modulation, spread the data using a spreading sequence with values ​​of {+1,-1}, and generate a molecular concentration signal by releasing type A and type B molecules to represent bit information; The fusion center, connected to the nano-emitter via a diffusion medium, is configured as follows: The received molecular concentration signal is sampled to determine the observed concentration difference between type A and type B molecules; Based on the concentration difference observations, the data is organized in a block transmission manner. Each data block is M bits long and corresponds to MN chip observations. A cyclic prefix is ​​inserted between data blocks to eliminate inter-block interference. The discrete observations are preprocessed into time-domain observation vectors. The time-domain observation vector is converted into a frequency-domain signal using a fast Fourier transform; The zero-force frequency domain equalization algorithm is applied to equalize the frequency domain signal; The equalized signal is converted back to the time domain by inverse fast Fourier transform, and the decision variable is obtained by despreading. Based on the decision variable, for each bit of each nano-emitter, the decision variable is compared with a zero threshold: if the decision variable is greater than 0, the bit is judged to be 1; otherwise, the bit is judged to be -1, thereby outputting the decoded bit sequence as the detection result.

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