A multi-user OFDM digital up-conversion method and demodulation method based on cognitive frequency tuning

Abstract

This invention discloses a multi-user OFDM digital up-conversion and demodulation method based on cognitive frequency tuning, belonging to the field of communication technology. The method includes: based on scanned data within the target operating frequency band of multiple users, sequentially performing spectrum sensing, channel state extraction, idle spectrum identification, resource scheduling, and frequency conversion parameter configuration to obtain a multi-user-specific frequency conversion parameter set; based on the original multi-user data stream, sequentially performing forward error correction coding, adaptive orthogonal amplitude modulation, four-dimensional hyperchaotic layered encryption, training sequence insertion, subcarrier allocation, and orthogonal frequency division multiplexing baseband modulation to obtain multiple independent baseband OFDM time-domain signals; based on the multi-user-specific frequency conversion parameter set, performing reconfigurable digital up-conversion processing, and then sequentially performing signal combining, digital-to-analog conversion, and RF amplification to obtain the RF transmit signal. This invention solves the problems of multi-user signal collision and adjacent channel interference existing in the prior art.

Description

Technical Field

[0001] This invention relates to a multi-user OFDM digital up-conversion method and demodulation method based on cognitive frequency tuning, belonging to the field of communication technology. Background Technology

[0002] With the rapid iteration of technologies such as 6G mobile communication, broadband wireless access, and integrated terrestrial-satellite networks, Orthogonal Frequency Division Multiplexing (OFDM) technology, with its core advantages of strong resistance to multipath fading, high spectrum utilization, and adaptability to multi-user parallel transmission, has become a fundamental physical layer technology for broadband wireless communication systems. Digital up-conversion, as a core component of the OFDM transmitter link, plays a crucial role in the precise transfer of baseband OFDM signals to the radio frequency band. Its performance directly determines the system's transmission capacity, anti-interference level, and multi-user access capability. Global allocation of low-frequency spectrum resources below 6 GHz has been largely completed, and the contradiction between spectrum supply and demand continues to intensify. Extending the operating frequency band to millimeter-wave and terahertz high-frequency bands while achieving dynamic and efficient utilization of spectrum resources has become a core direction for overcoming the capacity bottleneck of communication systems. Frequency conversion technology, which enables the up-and-down conversion of signal frequencies, is a key core technology for wireless communication and radar detection systems. In OFDM communication systems, digital up-conversion transfers the baseband-modulated OFDM signal to the target radio frequency band to adapt to the wireless channel transmission requirements.

[0003] Current mainstream research often employs an architecture that unifies the modulation of multi-user baseband signals, centrally up-converts them to a fixed radio frequency band, and then achieves multi-user multiplexing through subcarrier partitioning. In high-density user scenarios, this architecture is prone to signal collisions among multiple users within the same frequency band, exacerbating adjacent channel interference (ACI) and inter-subcarrier crosstalk, resulting in a significant deterioration in system bit error rate performance. The centralized frequency conversion architecture in the fixed frequency band lacks dynamic awareness and adaptive tuning capabilities for the spectrum environment. It cannot adjust conversion parameters based on real-time spectrum availability, channel quality differences, and user service requirements, leading to a severe waste of scarce spectrum resources and making it difficult to adapt to the dynamic channel characteristics of high-frequency broadband transmission. Furthermore, during multi-user shared channel transmission, there are security risks of information leakage and data interception. Existing architectures struggle to balance spectral efficiency, anti-interference performance, and data security in multi-user transmission. Summary of the Invention

[0004] The purpose of this invention is to provide a demodulation method for multi-user OFDM digital upconversion based on cognitive frequency tuning. By using spectrum sensing and dynamic resource scheduling, each user is allocated a dedicated idle radio frequency subband. Based on reconfigurable digital upconversion, the time domain signals of each baseband OFDM are independently moved to their respective dedicated idle radio frequency subbands. This solves the problems of multi-user signal collision and adjacent channel interference in the prior art and achieves physical isolation of multi-user signals in the frequency domain.

[0005] To solve the above-mentioned technical problems, the present invention is implemented using the following technical solution:

[0006] In a first aspect, the present invention provides a multi-user OFDM digital up-conversion method based on cognitive frequency tuning, executed by a transmitting end, comprising:

[0007] Acquire multiple independent serial binary service data streams to obtain the original data streams from multiple users;

[0008] Based on the scanning data within the target operating frequency band of multiple users, spectrum sensing operation, channel state extraction operation, idle spectrum identification operation, resource scheduling operation and frequency conversion parameter configuration operation are executed sequentially to obtain a set of frequency conversion parameters specific to multiple users.

[0009] Based on the multi-user raw data stream, forward error correction coding, adaptive orthogonal amplitude modulation, four-dimensional hyperchaotic hierarchical encryption, training sequence insertion, subcarrier allocation and orthogonal frequency division multiplexing baseband modulation are executed sequentially to obtain multiple independent baseband OFDM time domain signals.

[0010] Based on the multi-user dedicated frequency conversion parameter set, reconfigurable digital upconversion processing is performed on each baseband OFDM time domain signal to independently move each baseband OFDM time domain signal to a dedicated idle radio frequency sub-band, resulting in multiple frequency domain physically isolated radio frequency sub-band signals.

[0011] Based on the multi-channel frequency-domain isolated radio frequency sub-band signals, signal combining operation, digital-to-analog conversion operation and radio frequency amplification operation are performed sequentially to obtain radio frequency transmission signals, which are then sent into the wireless channel through the transmitting antenna.

[0012] Furthermore, based on the scanning data within the target operating frequency band for multiple users, spectrum sensing, channel state extraction, idle spectrum identification, resource scheduling, and frequency conversion parameter configuration operations are performed sequentially to obtain a set of frequency conversion parameters specific to multiple users, including:

[0013] Periodic energy detection and sampling are performed on the scan data within the operating frequency band of the multi-user target to obtain the raw spectrum sampling data;

[0014] Based on the original spectrum sampling data, the energy distribution and signal-to-noise ratio of each radio frequency sub-band are calculated to form a full-band channel state information dataset.

[0015] Based on the full-band channel state information dataset, spectrum holes are filtered according to a preset transmission signal-to-noise ratio threshold to obtain a set of available idle radio frequency subbands;

[0016] Based on the service bandwidth of each user, the upconversion carrier frequency points of multiple users are optimized and allocated according to the available idle radio frequency subband set, with the goal of maximizing system spectrum utilization and minimizing multi-user adjacent channel interference, and an integer programming optimization model is constructed.

[0017] The integer programming optimization model is expressed as:

[0018] ;

[0019] In the formula, This indicates taking the maximum value. The weighting coefficients representing the system's spectral efficiency. This represents the weighting coefficient for multi-user adjacent channel interference. This represents the total number of users whose spectrum is yet to be allocated in the system. Indicates the total number of available free radio frequency subbands. Indicates the first The users whose spectrum is to be allocated by the system are in the first The decision variables corresponding to each available idle radio frequency subband. Values The time indicates that the execution will be the first The available idle RF subbands are allocated to the first Operations of users whose spectrum is to be allocated in the system. A value of 0 indicates that the first step will not be executed. The available idle RF subbands are allocated to the first Operations of users whose spectrum is to be allocated in the system. Indicates the first Spectrum utilization efficiency of each available idle radio frequency subband Indicates the first The service transmission bandwidth of users whose spectrum is to be allocated in each system; Indicates the first The available idle RF subband and the first The adjacent channel interference intensity between available idle radio frequency subbands, where the first... The available idle RF subband and the first Each available free radio frequency subband is an adjacent available free radio frequency subband. The conditional statement symbol "makes...true" means... This indicates that the logical judgment symbol can be "arbitrarily selected";

[0020] The genetic algorithm is used to solve the integer programming optimization model to match the optimal idle radio frequency subband for each user, and the multi-user spectrum resource scheduling results including carrier center frequency, signal bandwidth and guard interval are obtained.

[0021] Based on the multi-user spectrum resource scheduling results, the interpolation filter coefficients and mixing control words are matched to generate configuration instructions, thereby obtaining a set of multi-user exclusive frequency conversion parameters.

[0022] Further, based on the multi-user raw data stream, forward error correction coding, adaptive orthogonal amplitude modulation, four-dimensional hyperchaotic hierarchical encryption, training sequence insertion, subcarrier allocation, and orthogonal frequency division multiplexing baseband modulation are executed sequentially to obtain multiple independent baseband OFDM time-domain signals, including:

[0023] Based on the original data stream of the multi-user, redundant parity bits are independently added to the bit stream of each user, and forward error correction coding is performed to obtain multiple encoded bit streams with parity bits.

[0024] Based on the multi-path coded bit stream with parity bits, bit interleaving is performed path by path to break up continuous burst errors and obtain a multi-user coded bit sequence.

[0025] The real-time channel signal-to-noise ratio of each user's dedicated radio frequency subband is compared with the preset channel quality threshold to obtain the modulation order matching result for each user.

[0026] Based on the modulation order matching result, the multi-user coded bit sequence is mapped to complex modulation symbols to obtain a multi-user modulation symbol sequence; wherein, for users with channel quality below a preset threshold, BPSK or QPSK low-order modulation is used to map the multi-user coded bit sequence to complex modulation symbols; for users with channel quality above the preset threshold, 16QAM or 64QAM high-order modulation is used to map the multi-user coded bit sequence to complex modulation symbols.

[0027] Perform a four-dimensional hyperchaotic hierarchical encryption operation on the multi-user modulation symbol sequence to obtain the encrypted multi-user modulation symbol sequence;

[0028] The encrypted multi-user modulation symbol sequence is inserted with a predefined training sequence and subcarriers are allocated. Each user's data is mapped to the corresponding subcarrier position to obtain the multi-user frequency domain symbol sequence.

[0029] Perform an N-point inverse fast Fourier transform on the multi-user frequency domain symbol sequence to convert the frequency domain symbols into a discrete time domain sampling sequence, thereby obtaining OFDM discrete time domain symbols, where N is a positive integer;

[0030] Copy the tail sampling points of the OFDM discrete time domain symbol and concatenate them to the head of the OFDM discrete time domain symbol as a cyclic prefix to obtain an OFDM time domain symbol with a cyclic prefix;

[0031] A time-domain windowing operation is performed on the OFDM time-domain symbol with the cyclic prefix to obtain multiple independent baseband OFDM time-domain signals.

[0032] Further, a four-dimensional hyperchaotic hierarchical encryption operation is performed on the multi-user modulation symbol sequence to obtain an encrypted multi-user modulation symbol sequence, including:

[0033] A four-dimensional hyperchaotic Lorenz continuous system is constructed, and the system parameters are set to make the four-dimensional hyperchaotic Lorenz continuous system in a hyperchaotic state, thus obtaining a continuous chaotic system model;

[0034] The four-dimensional hyperchaotic Lorenz continuous system is represented as follows:

[0035] ;

[0036] In the formula, State variable representing the amplitude of the main oscillation rate of change over time Represents the state variables of the orthogonal auxiliary field rate of change over time Represents potential energy or vertical gradient state variables rate of change over time Represents the state variables of the extended dimension of hyperchaos. rate of change over time Indicates control and The linear coupling strength between and Parameters of self-damping attenuation, Indicates only control The vertical decay parameter of the dissipation rate, Indicates control Linear excitation intensity as an excitation parameter to induce chaotic behavior, Indicates control The feedback parameters, which determine the intensity and polarity of the self-feedback, define the hyperchaotic properties.

[0037] The continuous chaotic system model is discretized and iterated using the fourth-order Runge-Kutta method to obtain the continuous equation. Based on the continuous equation, independent initial values ​​are configured for different users to generate four discrete chaotic sequences.

[0038] The iterative solution to the equation is expressed as:

[0039] ;

[0040] In the formula, This represents the estimated slope value at the starting point of the interval. This represents the first slope estimate at the midpoint of the interval. This represents the second slope estimate at the midpoint of the interval. This represents the estimated slope at the endpoint of the interval. Indicates a fixed iteration step size. Denotes the right-hand side function of the first-order differential equation for a four-dimensional hyperchaotic Lorenz continuous system. Indicates the first The current value of the iteration. Indicates the first The current state value of the iteration. Indicates the first The current state value of the iteration

[0041] The continuous chaotic system model was numerically discretized using the fourth-order Runge-Kutta method to obtain the iterative solution equations.

[0042] Based on iteratively solving the equations, each user is configured with a different initial state vector, and four discrete chaotic sequences are generated iteratively.

[0043] Based on the four discrete chaotic sequences, encryption operations are performed on the modulation symbol sequences of different users to obtain multi-user encrypted modulation symbol sequences;

[0044] The four discrete chaotic sequences include a first discrete chaotic sequence X, a second discrete chaotic sequence Y, a third discrete chaotic sequence Z, and a fourth discrete chaotic sequence W;

[0045] Using the first discrete chaotic sequence X, a bit XOR scrambling operation is performed on the modulation symbol sequence of the first part of the users to obtain the encrypted modulation symbol sequence of the first part of the users, represented as:

[0046] ;

[0047] In the formula, This indicates the first part of the user's encrypted modulation symbol sequence. Bit encryption bits, This represents the first part of the user's original plaintext modulation symbol sequence. Bit encryption bits, This represents the binary bitwise XOR operator. This represents the rounding function. Indicates the first The chaotic sample value of the first discrete chaotic sequence corresponding to the bit encryption bits. This represents the preset chaotic quantization bit precision parameter. This represents the modulo operator;

[0048] Using the second discrete chaotic sequence Y to generate a random permutation index P, the modulation symbol sequence D of the second group of users is rearranged to obtain the encrypted modulation symbol sequence of the second group of users, as follows:

[0049] ;

[0050] In the formula, This indicates the second part of the user's encrypted modulation symbol sequence. Bit encryption bits, This represents the function for retrieving the position index. Indicates the first The random permutation index symbol generated from the chaotic sampled values ​​of the second discrete chaotic sequence corresponding to the bit encryption bits.

[0051] By performing a constellation rotation operation on the modulation symbol sequence of the third part of the users using the third discrete chaotic sequence Z, the encrypted modulation symbol sequence of the third part of the users is obtained;

[0052] The constellation rotation angle and the third part of the user encryption modulation symbol are respectively represented as follows:

[0053] ;

[0054] ;

[0055] In the formula, Indicates the rotation angle of the modulation constellation point. This represents the floor function. Indicates the first The chaotic sample value of the third discrete chaotic sequence corresponding to the bit encryption bits. This represents the third part of the user's encrypted modulation symbols. This represents the third part of the user modulation symbol before encryption. Denotes the phase rotation factor in the complex field, where, , This indicates the angle scaling precision parameter. Represents the cosine function. Represents the sine function;

[0056] An amplitude perturbation operation is performed on the modulation symbol sequence of the fourth user group using the fourth discrete chaotic sequence W, resulting in the encrypted modulation symbol sequence of the fourth user group; the encrypted modulation symbol sequence of the fourth user group is represented as:

[0057] ;

[0058] In the formula, This represents the fourth part of the user encryption modulation symbols. This represents the fourth part of the user modulation symbol before encryption. This represents the preset amplitude disturbance intensity coefficient, used to control the impact of chaotic disturbances on the signal amplitude. Indicates the first The chaotic sample value of the fourth discrete chaotic sequence corresponding to the bit encryption bits.

[0059] Further, predefined training sequences are inserted into the encrypted multi-user modulation symbol sequences, and subcarriers are allocated to map each user's data to the corresponding subcarrier position, resulting in a multi-user frequency domain symbol sequence, including:

[0060] In response to the accuracy constraints of the receiver channel estimation, a predefined training sequence is generated as a pilot reference sequence;

[0061] Based on the preset subcarrier mapping position, the pilot reference sequence is inserted into the corresponding position in the encrypted modulation symbol sequence of each user to obtain the multi-user symbol sequence after the pilot is inserted.

[0062] Based on the total number of subcarriers in the OFDM system and their orthogonality constraints, each user is assigned a mutually orthogonal dedicated subcarrier group to generate user subcarrier mapping rules;

[0063] According to the user subcarrier mapping rule, each user symbol sequence after the pilot is inserted is mapped to the corresponding subcarrier position to obtain a multi-user frequency domain symbol sequence.

[0064] Furthermore, based on the multi-user dedicated frequency conversion parameter set, reconfigurable digital up-conversion processing is performed on each baseband OFDM time-domain signal to independently shift each baseband OFDM time-domain signal to a dedicated idle RF sub-band, resulting in multiple frequency-domain physically isolated RF sub-band signals, including:

[0065] Based on the multi-user dedicated frequency conversion parameter set, the digital mixing frequency and the sampling rate conversion parameters of the interpolation filter are independently configured for each baseband OFDM time domain signal, generating the upconversion control parameters for each channel.

[0066] Based on the frequency conversion control parameters of each channel, interpolation filtering and digital mixing operations are sequentially performed on each baseband OFDM time domain signal to independently shift each baseband OFDM time domain signal to its corresponding dedicated idle RF sub-band, thereby obtaining multiple physically isolated RF sub-band signals in the frequency domain.

[0067] Furthermore, based on the multi-channel frequency-isolated RF sub-band signals, signal combining, digital-to-analog conversion, and RF amplification operations are sequentially performed to obtain the RF transmitted signal, including:

[0068] The multiple frequency-domain physically isolated radio frequency subband signals are power combined to obtain multiple radio frequency subband signals;

[0069] Multiple radio frequency subband signals are superimposed and merged into a single broadband radio frequency digital signal to obtain a combined radio frequency digital signal.

[0070] The combined radio frequency digital signal is subjected to digital-to-analog conversion processing to obtain an analog radio frequency signal;

[0071] The analog radio frequency signal is sequentially amplified and filtered to obtain the radio frequency transmission signal.

[0072] Secondly, the present invention provides a demodulation method based on cognitive frequency tuning for multi-user OFDM digital up-conversion, executed by a receiving end, comprising:

[0073] It receives radio frequency transmitted signals and sequentially performs radio frequency receiving operations and digital down-conversion operations to obtain a baseband multi-user combined signal;

[0074] Based on the multi-user dedicated frequency conversion parameter set of the transmitting end, perform user separation operation on the baseband multi-user combined signal to extract the independent baseband sub-band signal of each user;

[0075] Synchronization correction, orthogonal frequency division multiplexing demodulation, and channel estimation are sequentially performed on the independent baseband subband signals of each user to obtain the demodulated frequency domain subcarrier data of each user.

[0076] Based on the encryption and modulation parameters corresponding to the multi-user raw data stream at the transmitting end, the frequency domain subcarrier data demodulated by each user is sequentially subjected to modulation demapping, four-dimensional hyperchaotic layered decryption, and forward error correction decoding to obtain the serial binary service data of each user.

[0077] The radio frequency transmission signal is obtained by performing the multi-user OFDM digital up-conversion method based on cognitive frequency tuning as described in the first aspect.

[0078] Further, the system receives the radio frequency (RF) transmitted signal and sequentially performs RF receiving and digital down-conversion operations to obtain a baseband multi-user combined signal, including:

[0079] The system receives the radio frequency transmitted signal and performs low-noise amplification and filtering processes sequentially to obtain an analog received radio frequency signal.

[0080] The analog received radio frequency signal is converted from analog to digital to obtain a digital received signal;

[0081] Based on the preset a priori frequency point of cognitive frequency tuning, digital downconversion and decimation filtering are performed on each user subband in the digital received signal, and the dedicated idle radio frequency subband corresponding to each user is moved to the baseband. The moved baseband OFDM time domain signals are then superimposed into a baseband multi-user combined signal.

[0082] Furthermore, based on the multi-user dedicated frequency conversion parameter set at the transmitting end, a user separation operation is performed on the baseband multi-user combined signal to extract the independent baseband sub-band signal for each user, including:

[0083] Based on the center frequency and signal bandwidth corresponding to the optimal idle radio frequency subband of each user in the multi-user dedicated frequency conversion parameter set of the transmitting end, digital filtering and extraction processing is performed on the baseband multi-user combined signal to separate the independent baseband subband signal of each user.

[0084] Gain adjustment is performed on each baseband sub-band signal to normalize the power of each baseband sub-band signal to a preset level range, thereby extracting the independent baseband sub-band signal for each user.

[0085] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0086] 1. This invention obtains idle radio frequency subbands within the target operating frequency band of multiple users through spectrum sensing, channel state extraction, idle spectrum identification, and resource scheduling operations. It then generates a set of dedicated frequency conversion parameters for each user by combining frequency conversion parameter configuration operations, ensuring that each user occupies only their corresponding dedicated idle radio frequency subband. Furthermore, through reconfigurable digital upconversion processing, the time-domain signals of each baseband OFDM are independently moved to their respective dedicated idle radio frequency subbands, achieving physical isolation of multi-user signals in the frequency domain, avoiding the sharing of the same frequency band by multiple user signals, and eliminating multi-user signal collisions and adjacent channel interference at the source.

[0087] 2. This invention allocates mutually orthogonal dedicated subcarrier groups to each user and, combined with reconfigurable digital upconversion processing, independently shifts the time-domain signals of each baseband OFDM signal to dedicated idle radio frequency subbands, enabling orthogonal isolation of user signals in both the subcarrier and radio frequency domains. Simultaneously, through idle spectrum identification operations, it filters spectrum holes based on a preset transmission signal-to-noise ratio threshold to obtain a set of available idle radio frequency subbands. Then, through resource scheduling operations, it constructs an integer programming optimization model to optimize the allocation with the goal of maximizing system spectrum utilization and minimizing multi-user adjacent channel interference, thereby improving the utilization rate of scarce spectrum resources while eliminating multi-user signal collisions and adjacent channel interference.

[0088] 3. This invention encrypts multi-user modulation symbol sequences through four-dimensional hyperchaotic layered encryption operations. It utilizes four discrete chaotic sequences to perform bit XOR scrambling, random permutation rearrangement, constellation rotation, and amplitude perturbation operations on the modulation symbol sequences of multiple user groups, respectively, to obtain multi-user encrypted modulation symbol sequences. This provides multiple chaotic encryption protections for each user's data during physical layer transmission. Combined with channel coding protection provided by forward error correction coding operations, it ensures the frequency domain physical isolation of multi-user signals to eliminate collisions and adjacent channel interference, while also taking into account the reliability of data transmission and effectively resisting the risks of information leakage and data interception.

[0089] 4. This invention performs user separation operations on the baseband multi-user combined signal based on the multi-user dedicated frequency conversion parameter set of the transmitting end, extracting the independent baseband sub-band signal for each user. Then, it sequentially performs synchronization correction, orthogonal frequency division multiplexing demodulation, and channel estimation operations on each user's independent baseband sub-band signal to obtain the demodulated frequency domain subcarrier data for each user. Next, based on the encryption and modulation parameters corresponding to the original multi-user data stream of the transmitting end, it sequentially performs modulation demapping, four-dimensional hyperchaotic layered decryption, and forward error correction decoding operations on the demodulated frequency domain subcarrier data for each user, restoring the serial binary service data for each user. This allows the receiving end to form a one-to-one inverse processing relationship with the reconfigurable digital up-conversion processing, orthogonal frequency division multiplexing baseband modulation, four-dimensional hyperchaotic layered encryption, and forward error correction coding operations of the transmitting end through user separation, orthogonal frequency division multiplexing demodulation, four-dimensional hyperchaotic layered decryption, and forward error correction decoding operations, respectively. This enables complete reception and secure recovery of multi-user signals under frequency domain physical isolation conditions. Attached Figure Description

[0090] Figure 1 This is a flowchart illustrating a multi-user OFDM digital upconversion method based on cognitive frequency tuning provided in an embodiment of the present invention.

[0091] Figure 2 This is a schematic flowchart of a demodulation method based on cognitive frequency tuning in a multi-user OFDM digital up-conversion method provided in an embodiment of the present invention.

[0092] Figure 3 This is a schematic diagram of the three-dimensional phase trajectory of the four-dimensional hyperchaotic Lorenz continuous system provided in an embodiment of the present invention. Detailed Implementation

[0093] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0094] Example 1

[0095] like Figure 1 As shown, this embodiment introduces a multi-user OFDM digital up-conversion method based on cognitive frequency tuning, executed by the transmitting end, including:

[0096] Step 1: Obtain multiple independent serial binary service data streams to obtain the original data streams for multiple users.

[0097] This embodiment obtains multiple independent serial binary service data streams to get the original data streams of multiple users. This provides multiple independent data inputs for subsequent forward error correction coding, adaptive orthogonal amplitude modulation, and four-dimensional hyperchaotic layered encryption operations. This ensures that each user's service data maintains an independent processing path throughout the entire physical layer transmission link, avoiding mutual coupling of multi-user data in the baseband processing stage.

[0098] Step 2: Based on the scanning data within the target operating frequency band of the multi-user, perform spectrum sensing operation, channel state extraction operation, idle spectrum identification operation, resource scheduling operation, and frequency conversion parameter configuration operation in sequence to obtain a set of frequency conversion parameters specific to the multi-user.

[0099] This embodiment, based on the scanning data within the target operating frequency band of multiple users, sequentially performs spectrum sensing, channel state extraction, idle spectrum identification, resource scheduling, and frequency conversion parameter configuration operations to obtain a set of frequency conversion parameters specific to each user. By real-time sensing and extraction of the energy distribution, signal-to-noise ratio, and interference level of each radio frequency sub-band within the target operating frequency band, spectrum holes are filtered to obtain a set of available idle radio frequency sub-bands, and the optimal idle radio frequency sub-band is matched for each user. This enables subsequent upconversion processing to flexibly move each user's signal to an idle spectrum location, avoiding multiple users sharing the same frequency band.

[0100] Step 3: Based on the original multi-user data stream, perform forward error correction coding, adaptive orthogonal amplitude modulation, four-dimensional hyperchaotic hierarchical encryption, training sequence insertion, subcarrier allocation, and orthogonal frequency division multiplexing baseband modulation in sequence to obtain multiple independent baseband OFDM time-domain signals.

[0101] This embodiment, based on the multi-user raw data stream, sequentially executes forward error correction coding, adaptive orthogonal amplitude modulation, four-dimensional hyperchaotic hierarchical encryption, training sequence insertion, subcarrier allocation, and orthogonal frequency division multiplexing (OFDM) baseband modulation to obtain multiple independent baseband OFDM time-domain signals. Forward error correction coding provides channel coding protection; adaptive orthogonal amplitude modulation dynamically adapts the modulation order according to channel quality; four-dimensional hyperchaotic hierarchical encryption encrypts physical layer data; training sequence insertion provides reference signals for synchronization correction and channel estimation at the receiver; and subcarrier allocation and OFDM baseband modulation map each user's data to mutually orthogonal dedicated subcarrier groups and convert them into time-domain signals, providing multiple independent baseband signals with coding, encryption, and pilot protection for subsequent reconfigurable digital upconversion processing.

[0102] Step 4: Based on the multi-user dedicated frequency conversion parameter set, perform reconfigurable digital upconversion processing on each baseband OFDM time domain signal to independently move each baseband OFDM time domain signal to a dedicated idle radio frequency subband, thereby obtaining multiple frequency domain physically isolated radio frequency subband signals.

[0103] This embodiment, based on the multi-user dedicated frequency conversion parameter set, performs reconfigurable digital upconversion processing on each baseband OFDM time-domain signal to independently move each baseband OFDM time-domain signal to a dedicated idle radio frequency sub-band, resulting in multiple frequency-domain physically isolated radio frequency sub-band signals. This allows each user signal to be moved to its corresponding dedicated idle radio frequency sub-band according to spectrum sensing and resource scheduling results, forming physical isolation in the frequency domain and eliminating multi-user signal collisions and adjacent channel interference from the root.

[0104] Step 5: Based on the multi-channel frequency-domain isolated radio frequency sub-band signals, perform signal combining operation, digital-to-analog conversion operation and radio frequency amplification operation in sequence to obtain radio frequency transmission signal, and send it into the wireless channel through the transmitting antenna.

[0105] This embodiment, based on the multiple frequency-domain isolated RF sub-band signals, sequentially performs signal combining, digital-to-analog conversion, and RF amplification operations to obtain an RF transmission signal, which is then sent into the wireless channel through a transmitting antenna. This combines multiple frequency-domain physically isolated RF sub-band signals into a single broadband RF digital signal, which is then sent into the wireless channel after digital-to-analog conversion and RF amplification. While maintaining the frequency-domain physical isolation characteristics of each user signal, this embodiment achieves efficient combining and RF transmission of multiple RF sub-band signals.

[0106] Example 2

[0107] Based on the same inventive concept as Embodiment 1, this embodiment describes the implementation steps of a multi-user OFDM digital up-conversion method based on cognitive frequency tuning, executed by the transmitting end, including:

[0108] Step 1: Obtain multiple independent serial binary service data streams to obtain the original data streams for multiple users.

[0109] Step 1.1: Assign each user an independent spectrum resource identifier and encryption key identifier to obtain a user resource allocation scheme.

[0110] Step 1.2: Based on the user resource allocation scheme, generate serial binary bit sequences for the corresponding user communication services one by one, and output multiple non-overlapping bit streams in parallel to obtain multiple independent serial binary service data as the original data stream for multiple users.

[0111] Step 2: Based on the scanning data within the target operating frequency band of the multi-user, perform spectrum sensing operation, channel state extraction operation, idle spectrum identification operation, resource scheduling operation, and frequency conversion parameter configuration operation in sequence to obtain a set of frequency conversion parameters specific to the multi-user.

[0112] Step 2.1: Perform periodic energy detection and sampling on the scanning data within the multi-user target operating frequency band to obtain the raw spectrum sampling data.

[0113] Step 2.2: Based on the original spectrum sampling data, calculate the energy distribution and signal-to-noise ratio of each radio frequency sub-band to form a full-band channel state information dataset.

[0114] Step 2.3: Based on the full-band channel state information dataset, filter spectral holes according to the preset transmission signal-to-noise ratio threshold to obtain a set of available idle radio frequency subbands.

[0115] Step 2.4: Based on the service bandwidth of each user, optimize the allocation of upconversion carrier frequency points for multiple users according to the available idle radio frequency subband set, with the goal of maximizing system spectrum utilization and minimizing adjacent channel interference for multiple users, and construct an integer programming optimization model.

[0116] In this embodiment, the integer programming optimization model is expressed as:

[0117] ;

[0118] In the formula, This indicates taking the maximum value. The weighting coefficients representing the system's spectral efficiency. This represents the weighting coefficient for multi-user adjacent channel interference. This represents the total number of users whose spectrum is yet to be allocated in the system. Indicates the total number of available free radio frequency subbands. Indicates the first The users whose spectrum is to be allocated by the system are in the first The decision variables corresponding to each available idle radio frequency subband. Values The time indicates that the execution will be the first The available idle RF subbands are allocated to the first Operations of users whose spectrum is to be allocated in the system. A value of 0 indicates that the first step will not be executed. The available idle RF subbands are allocated to the first Operations of users whose spectrum is to be allocated in the system. Indicates the first Spectrum utilization efficiency of each available idle radio frequency subband Indicates the first The service transmission bandwidth of users whose spectrum is to be allocated in each system; Indicates the first The available idle RF subband and the first The adjacent channel interference intensity between available idle radio frequency subbands, where the first... The available idle RF subband and the first Each available free radio frequency subband is an adjacent available free radio frequency subband. The conditional statement symbol "makes...true" means... The logical judgment symbol is "arbitrary".

[0119] Step 2.5: Use a genetic algorithm to solve the integer programming optimization model, match the optimal idle radio frequency subband for each user, and obtain the multi-user spectrum resource scheduling results including carrier center frequency, signal bandwidth, and guard interval.

[0120] Step 2.6: Based on the multi-user spectrum resource scheduling results, match the interpolation filter coefficients and the mixing control word to generate configuration instructions, and obtain a set of multi-user exclusive frequency conversion parameters.

[0121] Step 3: Based on the original multi-user data stream, perform forward error correction coding, adaptive orthogonal amplitude modulation, four-dimensional hyperchaotic hierarchical encryption, training sequence insertion, subcarrier allocation, and orthogonal frequency division multiplexing baseband modulation in sequence to obtain multiple independent baseband OFDM time-domain signals.

[0122] Step 3.1: Based on the original data stream of the multi-user users, add redundant parity bits independently to the bit stream of each user, and perform forward error correction coding to obtain a multi-channel encoded bit stream with parity bits.

[0123] Step 3.2: Perform bit interleaving processing on each of the multi-channel encoded bit streams with parity bits, and break up continuous burst errors to obtain a multi-user encoded bit sequence.

[0124] Step 3.3: Compare the real-time channel signal-to-noise ratio of each user's dedicated radio frequency subband with the preset channel quality threshold to obtain the modulation order matching result for each user.

[0125] Step 3.4: Map the multi-user coded bit sequence to complex modulation symbols based on the modulation order matching result to obtain the multi-user modulation symbol sequence.

[0126] Specifically, for users whose channel quality is below a preset threshold, BPSK or QPSK low-order modulation methods are used to map the multi-user coded bit sequence into complex modulation symbols; for users whose channel quality is above a preset threshold, 16QAM or 64QAM high-order modulation methods are used to map the multi-user coded bit sequence into complex modulation symbols.

[0127] Step 3.5: Perform a four-dimensional hyperchaotic hierarchical encryption operation on the multi-user modulation symbol sequence to obtain the encrypted multi-user modulation symbol sequence.

[0128] Step 3.5.1: Construct a four-dimensional hyperchaotic Lorenz continuous system and set the system parameters to make the four-dimensional hyperchaotic Lorenz continuous system be in a hyperchaotic state, thus obtaining a continuous chaotic system model.

[0129] Figure 3 This is a schematic diagram of the three-dimensional phase trajectory of a four-dimensional hyperchaotic Lorenz continuous system provided in an embodiment of the present invention. In this embodiment, the four-dimensional hyperchaotic Lorenz continuous system is represented as follows:

[0130] ;

[0131] In the formula, State variable representing the amplitude of the main oscillation rate of change over time Represents the state variables of the orthogonal auxiliary field rate of change over time Represents potential energy or vertical gradient state variables rate of change over time Represents the state variables of the extended dimension of hyperchaos. rate of change over time Indicates control and The linear coupling strength between and Parameters of self-damping attenuation, Indicates only control The vertical decay parameter of the dissipation rate, Indicates control Linear excitation intensity as an excitation parameter to induce chaotic behavior, Indicates control The strength and polarity of the self-feedback determine the feedback parameters of the hyperchaotic properties.

[0132] Step 3.5.2: The continuous chaotic system model is discretized and iterated using the fourth-order Runge-Kutta method to obtain the continuous equation. Based on the continuous equation, independent initial values ​​are configured for different users to generate four discrete chaotic sequences.

[0133] In this embodiment, the iterative solution of the equation is expressed as:

[0134] ;

[0135] In the formula, This represents the estimated slope value at the starting point of the interval. This represents the first slope estimate at the midpoint of the interval. This represents the second slope estimate at the midpoint of the interval. This represents the estimated slope at the endpoint of the interval. Indicates a fixed iteration step size. Denotes the right-hand side function of the first-order differential equation for a four-dimensional hyperchaotic Lorenz continuous system. Indicates the first The current value of the iteration. Indicates the first The current state value of the iteration. Indicates the first The current state value of the iteration.

[0136] Step 3.5.3: The continuous chaotic system model is numerically discretized using the fourth-order Runge-Kutta method to obtain the iterative solution equations.

[0137] Step 3.5.4: Based on iteratively solving the equations, configure different initial state vectors for each user, and iteratively generate four discrete chaotic sequences.

[0138] Step 3.5.5: Based on the four discrete chaotic sequences, perform encryption operations on the modulation symbol sequences of different users respectively to obtain multi-user encrypted modulation symbol sequences.

[0139] In this embodiment, the four discrete chaotic sequences include a first discrete chaotic sequence X, a second discrete chaotic sequence Y, a third discrete chaotic sequence Z, and a fourth discrete chaotic sequence W.

[0140] The four discrete chaotic sequences include a first discrete chaotic sequence X, a second discrete chaotic sequence Y, a third discrete chaotic sequence Z, and a fourth discrete chaotic sequence W;

[0141] Using the first discrete chaotic sequence X, a bit XOR scrambling operation is performed on the modulation symbol sequence of the first part of the users to obtain the encrypted modulation symbol sequence of the first part of the users, represented as:

[0142] ;

[0143] In the formula, This indicates the first part of the user's encrypted modulation symbol sequence. Bit encryption bits, This represents the first part of the user's original plaintext modulation symbol sequence. Bit encryption bits, This represents the binary bitwise XOR operator. This represents the rounding function. Indicates the first The chaotic sample value of the first discrete chaotic sequence corresponding to the bit encryption bits. This represents the preset chaotic quantization bit precision parameter. This represents the modulo operator.

[0144] Using the second discrete chaotic sequence Y to generate a random permutation index P, the modulation symbol sequence D of the second group of users is rearranged to obtain the encrypted modulation symbol sequence of the second group of users, as follows:

[0145] ;

[0146] In the formula, This indicates the second part of the user's encrypted modulation symbol sequence. Bit encryption bits, This represents the function for retrieving the position index. Indicates the first The random permutation index symbol generated from the chaotic sampled values ​​of the second discrete chaotic sequence corresponding to the bit encryption bits.

[0147] By performing a constellation rotation operation on the modulation symbol sequence of the third part of the user using the third discrete chaotic sequence Z, the encrypted modulation symbol sequence of the third part of the user is obtained.

[0148] In this embodiment, the constellation rotation angle and the third part of the user encryption modulation symbol are respectively represented as:

[0149] ;

[0150] ;

[0151] In the formula, Indicates the rotation angle of the modulation constellation point. This represents the floor function. Indicates the first The chaotic sample value of the third discrete chaotic sequence corresponding to the bit encryption bits. This represents the third part of the user's encrypted modulation symbols. This represents the third part of the user modulation symbol before encryption. Denotes the phase rotation factor in the complex field, where, , This indicates the angle scaling precision parameter. Represents the cosine function. This represents the sine function.

[0152] An amplitude perturbation operation is performed on the modulation symbol sequence of the fourth user group using the fourth discrete chaotic sequence W, resulting in the encrypted modulation symbol sequence of the fourth user group; the encrypted modulation symbol sequence of the fourth user group is represented as:

[0153] ;

[0154] In the formula, This represents the fourth part of the user encryption modulation symbols. This represents the fourth part of the user modulation symbol before encryption. This represents the preset amplitude disturbance intensity coefficient, used to control the impact of chaotic disturbances on the signal amplitude. Indicates the first The chaotic sample value of the fourth discrete chaotic sequence corresponding to the bit encryption bits.

[0155] Step 3.6: Insert predefined training sequences into the encrypted multi-user modulation symbol sequence and perform subcarrier allocation to map each user's data to the corresponding subcarrier position to obtain the multi-user frequency domain symbol sequence.

[0156] Step 3.6.1: In response to the accuracy constraints of the receiver channel estimation, generate a predefined training sequence as a pilot reference sequence.

[0157] Step 3.6.2: Based on the preset subcarrier mapping position, insert the pilot reference sequence into the corresponding position in the encrypted modulation symbol sequence of each user to obtain the multi-user symbol sequence after inserting the pilot.

[0158] Step 3.6.3: Based on the total number of subcarriers in the OFDM system and their orthogonality constraints, assign each user a dedicated group of mutually orthogonal subcarriers to generate user subcarrier mapping rules.

[0159] Step 3.6.4: According to the user subcarrier mapping rule, map each user symbol sequence after inserting the pilot to the corresponding subcarrier position to obtain a multi-user frequency domain symbol sequence.

[0160] Step 3.7: Perform an N-point inverse fast Fourier transform based on the multi-user frequency domain symbol sequence to convert the frequency domain symbols into a discrete time domain sampling sequence, thereby obtaining OFDM discrete time domain symbols.

[0161] Where N is a positive integer.

[0162] Step 3.8: Copy the tail sampling points of the OFDM discrete time domain symbol and concatenate them to the head of the OFDM discrete time domain symbol as a cyclic prefix to obtain an OFDM time domain symbol with a cyclic prefix.

[0163] Step 3.9: Perform a time-domain windowing operation on the OFDM time-domain symbol with the cyclic prefix to obtain multiple independent baseband OFDM time-domain signals.

[0164] Step 4: Based on the multi-user dedicated frequency conversion parameter set, perform reconfigurable digital upconversion processing on each baseband OFDM time domain signal to independently move each baseband OFDM time domain signal to a dedicated idle radio frequency sub-band, thereby obtaining multiple frequency domain physically isolated radio frequency sub-band signals.

[0165] Step 4.1: Based on the multi-user dedicated frequency conversion parameter set, independently configure the digital mixing frequency and the sampling rate conversion parameters of the interpolation filter for each baseband OFDM time domain signal, and generate the upconversion control parameters for each channel.

[0166] Step 4.2: According to the frequency conversion control parameters of each channel, perform interpolation filtering and digital mixing operations sequentially on each baseband OFDM time domain signal to independently move each baseband OFDM time domain signal to its corresponding dedicated idle radio frequency sub-band, thereby obtaining multiple radio frequency sub-band signals that are physically isolated in the frequency domain.

[0167] Step 5: Based on the multi-channel frequency-domain isolated RF sub-band signals, perform signal combining operation, digital-to-analog conversion operation and RF amplification operation in sequence to obtain RF transmission signal, and send it into the wireless channel through the transmission antenna.

[0168] Step 5.1: Perform power combining processing on the multiple frequency-domain physically isolated radio frequency subband signals to obtain multiple radio frequency subband signals.

[0169] Step 5.2: Superimpose and merge the multiple RF subband signals into one broadband RF digital signal to obtain the combined RF digital signal.

[0170] Step 5.3: Perform digital-to-analog conversion on the combined radio frequency digital signal to obtain an analog radio frequency signal.

[0171] Step 5.4: Perform power amplification and filtering on the analog radio frequency signal in sequence to obtain the radio frequency transmission signal.

[0172] Example 3

[0173] Based on the same inventive concept as other embodiments, this embodiment introduces a demodulation method based on a cognitive frequency tuning multi-user OFDM digital up-conversion method, such as... Figure 2 As shown, this is executed by the receiving end and includes:

[0174] Step 1: Receive the radio frequency transmission signal and sequentially perform radio frequency reception and digital down-conversion operations to obtain the baseband multi-user combined signal.

[0175] In this embodiment, the radio frequency (RF) transmission signal is received, and the RF reception operation and digital down-conversion operation are performed sequentially to obtain the baseband multi-user combined signal. Through the digital down-conversion operation adapted to the reconfigurable digital up-conversion processing of the transmitting end, the received broadband RF signal is shifted to the baseband, providing the baseband multi-user combined signal containing complete multi-user information for subsequent user separation operations, thus achieving a smooth connection between RF reception and baseband processing.

[0176] Step 2: Based on the multi-user dedicated frequency conversion parameter set of the transmitting end, perform user separation operation on the baseband multi-user combined signal to extract the independent baseband sub-band signal of each user.

[0177] In this embodiment, based on the multi-user dedicated frequency conversion parameter set of the transmitting end, a user separation operation is performed on the baseband multi-user combined signal to extract the independent baseband sub-band signal of each user. This allows the receiving end to accurately separate the baseband sub-band signal of each user in the digital domain based on the multi-user dedicated frequency conversion parameter set generated by the transmitting end's spectrum sensing and resource scheduling results. This forms a one-to-one inverse processing relationship with the reconfigurable digital up-conversion processing of the transmitting end, ensuring that the multi-user signal can be received without crosstalk under the condition of physical isolation in the frequency domain.

[0178] Step 3: Perform synchronization correction, orthogonal frequency division multiplexing demodulation, and channel estimation operations sequentially on the independent baseband subband signals of each user to obtain the demodulated frequency domain subcarrier data of each user.

[0179] In this embodiment, synchronization correction, orthogonal frequency division multiplexing demodulation, and channel estimation operations are sequentially performed on the independent baseband subband signals of each user to obtain the demodulated frequency domain subcarrier data of each user. The synchronization correction operation determines the starting position of the OFDM symbol of each user to eliminate timing deviation. The orthogonal frequency division multiplexing demodulation operation converts the time domain signal into frequency domain subcarrier data. The channel estimation operation provides channel state information for subsequent demapping processing, which corresponds to the training sequence insertion operation and orthogonal frequency division multiplexing baseband modulation operation at the transmitting end, thus recovering the modulated frequency domain subcarrier data of each user.

[0180] Step 4: Based on the encryption and modulation parameters corresponding to the original multi-user data streams from the transmitting end, perform modulation demapping, four-dimensional hyperchaotic layered decryption, and forward error correction decoding operations sequentially on the demodulated frequency domain subcarrier data of each user to obtain the serial binary service data of each user.

[0181] In this embodiment, based on the encryption and modulation parameters corresponding to the original multi-user data streams from the transmitting end, modulation demapping, four-dimensional hyperchaotic layered decryption, and forward error correction decoding are sequentially performed on the demodulated frequency domain subcarrier data of each user to obtain the serial binary service data of each user. This enables the receiving end to form a one-to-one inverse processing relationship with the adaptive orthogonal amplitude modulation, four-dimensional hyperchaotic layered encryption, and forward error correction coding operations of the transmitting end through modulation demapping, four-dimensional hyperchaotic layered decryption, and forward error correction decoding operations, respectively. This ensures reliable decryption of physical layer encrypted data and effective correction of transmission errors while restoring the serial binary service data of each user.

[0182] In this embodiment, the radio frequency transmission signal is obtained by performing the multi-user OFDM digital up-conversion method based on cognitive frequency tuning as described in Embodiment 1 or 2.

[0183] Example 4

[0184] Based on the same inventive concept as other embodiments, this embodiment describes the implementation steps of a demodulation method based on a cognitive frequency tuning multi-user OFDM digital up-conversion method, executed by the receiving end, including:

[0185] Step 1: Receive the radio frequency transmission signal and sequentially perform radio frequency reception and digital down-conversion operations to obtain the baseband multi-user combined signal.

[0186] Step 1.1: Receive the radio frequency transmitted signal and perform low-noise amplification and filtering processes in sequence to obtain the analog received radio frequency signal.

[0187] Step 1.2: Perform analog-to-digital conversion on the analog received radio frequency signal to obtain a digital received signal.

[0188] Step 1.3: Based on the preset a priori frequency point of cognitive frequency tuning, perform digital downconversion and decimation filtering on each user subband in the digital received signal, move the dedicated idle radio frequency subband corresponding to each user to the baseband, and superimpose the moved baseband OFDM time domain signals into a baseband multi-user combined signal.

[0189] Step 2: Based on the multi-user dedicated frequency conversion parameter set of the transmitting end, perform user separation operation on the baseband multi-user combined signal to extract the independent baseband sub-band signal of each user.

[0190] Step 2.1: Based on the center frequency and signal bandwidth corresponding to the optimal idle radio frequency subband of each user in the multi-user dedicated frequency conversion parameter set of the transmitting end, perform digital filtering and decimation processing on the baseband multi-user combined signal to separate the independent baseband subband signal of each user.

[0191] Step 2.2: Adjust the gain of each baseband sub-band signal to normalize the power of each baseband sub-band signal to a preset level range, and extract the independent baseband sub-band signal for each user.

[0192] Step 3: Perform synchronization correction, orthogonal frequency division multiplexing demodulation, and channel estimation operations sequentially on the independent baseband subband signals of each user to obtain the demodulated frequency domain subcarrier data of each user.

[0193] Step 4: Based on the encryption and modulation parameters corresponding to the original multi-user data streams from the transmitting end, perform modulation demapping, four-dimensional hyperchaotic layered decryption, and forward error correction decoding operations sequentially on the demodulated frequency domain subcarrier data of each user to obtain the serial binary service data of each user.

[0194] In this embodiment, the radio frequency transmission signal is obtained by performing the multi-user OFDM digital up-conversion method based on cognitive frequency tuning as described in Embodiment 1 or 2.

[0195] In summary, this invention obtains idle radio frequency subbands within the target operating frequency band of multiple users through spectrum sensing, channel state extraction, idle spectrum identification, and resource scheduling operations. Combined with frequency conversion parameter configuration operations, it generates a set of dedicated frequency conversion parameters for each user, ensuring that each user occupies only their corresponding dedicated idle radio frequency subband. Furthermore, through reconfigurable digital upconversion processing, the time-domain signals of each baseband OFDM are independently moved to their respective dedicated idle radio frequency subbands, achieving physical isolation of multi-user signals in the frequency domain. This avoids multiple user signals sharing the same frequency band and eliminates multi-user signal collisions and adjacent channel interference at the source.

[0196] This invention allocates each user with a dedicated group of mutually orthogonal subcarriers and, combined with reconfigurable digital upconversion processing, independently moves each baseband OFDM time-domain signal to a dedicated idle radio frequency subband, achieving orthogonal isolation of user signals in both the subcarrier and radio frequency domains. Simultaneously, through idle spectrum identification, it filters spectrum holes based on a preset transmission signal-to-noise ratio threshold to obtain a set of available idle radio frequency subbands. Furthermore, through resource scheduling, it constructs an integer programming optimization model to optimize allocation, aiming to maximize system spectrum utilization and minimize multi-user adjacent channel interference. This improves the utilization of scarce spectrum resources while eliminating multi-user signal collisions and adjacent channel interference.

[0197] This invention encrypts multi-user modulation symbol sequences through a four-dimensional hyperchaotic layered encryption operation. It utilizes four discrete chaotic sequences to perform bit XOR scrambling, random permutation rearrangement, constellation rotation, and amplitude perturbation operations on the modulation symbol sequences of multiple user groups, resulting in a multi-user encrypted modulation symbol sequence. This provides multiple layers of chaotic encryption protection for user data during physical layer transmission. Combined with channel coding protection provided by forward error correction coding, it ensures frequency domain physical isolation of multi-user signals to eliminate collisions and adjacent channel interference, while also considering the reliability of data transmission and effectively resisting the risks of information leakage and data interception.

[0198] This invention performs user separation operations on the baseband multi-user combined signal based on the multi-user dedicated frequency conversion parameter set of the transmitting end, extracting the independent baseband sub-band signal for each user. Then, it sequentially performs synchronization correction, orthogonal frequency division multiplexing demodulation, and channel estimation operations on each user's independent baseband sub-band signal to obtain the demodulated frequency domain subcarrier data for each user. Next, based on the encryption and modulation parameters corresponding to the original multi-user data stream of the transmitting end, it sequentially performs modulation demapping, four-dimensional hyperchaotic layered decryption, and forward error correction decoding operations on the demodulated frequency domain subcarrier data for each user, restoring the serial binary service data for each user. This allows the receiving end to form a one-to-one inverse processing relationship with the reconfigurable digital up-conversion processing, orthogonal frequency division multiplexing baseband modulation, four-dimensional hyperchaotic layered encryption, and forward error correction coding operations of the transmitting end through user separation, orthogonal frequency division multiplexing demodulation, four-dimensional hyperchaotic layered decryption, and forward error correction decoding operations, respectively. This enables complete reception and secure recovery of multi-user signals under frequency domain physical isolation conditions.

[0199] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0200] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0201] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0202] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0203] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A multi-user OFDM digital up-conversion method based on cognitive frequency tuning, characterized in that, Executed by the sender, including: Acquire multiple independent serial binary service data streams to obtain the original data streams from multiple users; Based on the scanning data within the target operating frequency band of multiple users, spectrum sensing operation, channel state extraction operation, idle spectrum identification operation, resource scheduling operation and frequency conversion parameter configuration operation are executed sequentially to obtain a set of frequency conversion parameters specific to multiple users. Based on the multi-user raw data stream, forward error correction coding, adaptive orthogonal amplitude modulation, four-dimensional hyperchaotic hierarchical encryption, training sequence insertion, subcarrier allocation and orthogonal frequency division multiplexing baseband modulation are executed sequentially to obtain multiple independent baseband OFDM time domain signals. Based on the multi-user dedicated frequency conversion parameter set, reconfigurable digital upconversion processing is performed on each baseband OFDM time domain signal to independently move each baseband OFDM time domain signal to a dedicated idle radio frequency sub-band, resulting in multiple frequency domain physically isolated radio frequency sub-band signals. Based on the multi-channel frequency-domain isolated radio frequency sub-band signals, signal combining operation, digital-to-analog conversion operation and radio frequency amplification operation are performed sequentially to obtain radio frequency transmission signals, which are then sent into the wireless channel through the transmitting antenna.

2. The multi-user OFDM digital up-conversion method based on cognitive frequency tuning according to claim 1, characterized in that, Based on the scanned data within the target operating frequency band for multiple users, the following operations are executed sequentially: spectrum sensing, channel state extraction, idle spectrum identification, resource scheduling, and frequency conversion parameter configuration, resulting in a set of frequency conversion parameters specific to each user, including: Periodic energy detection and sampling are performed on the scan data within the operating frequency band of the multi-user target to obtain the raw spectrum sampling data; Based on the original spectrum sampling data, the energy distribution and signal-to-noise ratio of each radio frequency sub-band are calculated to form a full-band channel state information dataset. Based on the full-band channel state information dataset, spectrum holes are filtered according to a preset transmission signal-to-noise ratio threshold to obtain a set of available idle radio frequency subbands; Based on the service bandwidth of each user, the upconversion carrier frequency points of multiple users are optimized and allocated according to the available idle radio frequency subband set, with the goal of maximizing system spectrum utilization and minimizing multi-user adjacent channel interference, and an integer programming optimization model is constructed. The integer programming optimization model is expressed as: ； In the formula, This indicates taking the maximum value. The weighting coefficients representing the system's spectral efficiency. This represents the weighting coefficient for multi-user adjacent channel interference. This indicates the total number of users whose spectrum is yet to be allocated in the system. Indicates the total number of available free radio frequency subbands. Indicates the first The users whose spectrum is to be allocated by the system are in the first The decision variables corresponding to each available idle radio frequency subband. Values The time indicates that the execution will be the first The available idle RF subbands are allocated to the first Operations of users whose spectrum is to be allocated in the system. A value of 0 indicates that the first step will not be executed. The available idle RF subbands are allocated to the first Operations of users whose spectrum is to be allocated in the system. Indicates the first Spectrum utilization efficiency of each available idle radio frequency subband Indicates the first The service transmission bandwidth of users whose spectrum is to be allocated in each system; Indicates the first The available idle RF subband and the first The adjacent channel interference intensity between available idle radio frequency subbands, where the first... The available idle RF subband and the first Each available free radio frequency subband is an adjacent available free radio frequency subband. The conditional statement symbol "makes...true" means... This indicates that the logical judgment symbol can be "arbitrarily selected"; The genetic algorithm is used to solve the integer programming optimization model to match the optimal idle radio frequency subband for each user, and the multi-user spectrum resource scheduling results including carrier center frequency, signal bandwidth and guard interval are obtained. Based on the multi-user spectrum resource scheduling results, the interpolation filter coefficients and mixing control words are matched to generate configuration instructions, thereby obtaining a set of multi-user exclusive frequency conversion parameters.

3. The multi-user OFDM digital up-conversion method based on cognitive frequency tuning according to claim 1, characterized in that, Based on the multi-user raw data stream, forward error correction coding, adaptive orthogonal amplitude modulation, four-dimensional hyperchaotic hierarchical encryption, training sequence insertion, subcarrier allocation, and orthogonal frequency division multiplexing baseband modulation are executed sequentially to obtain multiple independent baseband OFDM time-domain signals, including: Based on the original data stream of the multi-user, redundant parity bits are independently added to the bit stream of each user, and forward error correction coding is performed to obtain multiple encoded bit streams with parity bits. Based on the multi-path coded bit stream with parity bits, bit interleaving is performed path by path to break up continuous burst errors and obtain a multi-user coded bit sequence. The real-time channel signal-to-noise ratio of each user's dedicated radio frequency subband is compared with the preset channel quality threshold to obtain the modulation order matching result for each user. Based on the modulation order matching result, the multi-user coded bit sequence is mapped to complex modulation symbols to obtain a multi-user modulation symbol sequence; wherein, for users with channel quality below a preset threshold, BPSK or QPSK low-order modulation is used to map the multi-user coded bit sequence to complex modulation symbols; for users with channel quality above the preset threshold, 16QAM or 64QAM high-order modulation is used to map the multi-user coded bit sequence to complex modulation symbols. Perform a four-dimensional hyperchaotic hierarchical encryption operation on the multi-user modulation symbol sequence to obtain the encrypted multi-user modulation symbol sequence; The encrypted multi-user modulation symbol sequence is inserted with a predefined training sequence and subcarriers are allocated. Each user's data is mapped to the corresponding subcarrier position to obtain the multi-user frequency domain symbol sequence. Perform an N-point inverse fast Fourier transform on the multi-user frequency domain symbol sequence to convert the frequency domain symbols into a discrete time domain sampling sequence, thereby obtaining OFDM discrete time domain symbols, where N is a positive integer; Copy the tail sampling points of the OFDM discrete time domain symbol and concatenate them to the head of the OFDM discrete time domain symbol as a cyclic prefix to obtain an OFDM time domain symbol with a cyclic prefix; A time-domain windowing operation is performed on the OFDM time-domain symbol with the cyclic prefix to obtain multiple independent baseband OFDM time-domain signals.

4. The multi-user OFDM digital up-conversion method based on cognitive frequency tuning according to claim 3, characterized in that, Perform a four-dimensional hyperchaotic hierarchical encryption operation on the multi-user modulation symbol sequence to obtain an encrypted multi-user modulation symbol sequence, including: A four-dimensional hyperchaotic Lorenz continuous system is constructed, and the system parameters are set to make the four-dimensional hyperchaotic Lorenz continuous system in a hyperchaotic state, thus obtaining a continuous chaotic system model; The four-dimensional hyperchaotic Lorenz continuous system is represented as follows: ； In the formula, State variable representing the amplitude of the main oscillation rate of change over time Represents the state variables of the orthogonal auxiliary field rate of change over time Represents potential energy or vertical gradient state variables rate of change over time Represents the state variables of the extended dimension of hyperchaos. rate of change over time Indicates control and The linear coupling strength between and Parameters of self-damping attenuation, Indicates only control The vertical decay parameter of the dissipation rate, Indicates control Linear excitation intensity as an excitation parameter to induce chaotic behavior, Indicates control The feedback parameters, which determine the intensity and polarity of the self-feedback, define the hyperchaotic properties. The continuous chaotic system model is discretized and iterated using the fourth-order Runge-Kutta method to obtain the continuous equation. Based on the continuous equation, independent initial values ​​are configured for different users to generate four discrete chaotic sequences. The iterative solution to the equation is expressed as: ； In the formula, This represents the estimated slope value at the starting point of the interval. This represents the first slope estimate at the midpoint of the interval. This represents the second slope estimate at the midpoint of the interval. This represents the estimated slope at the endpoint of the interval. Indicates a fixed iteration step size. Denotes the right-hand side function of the first-order differential equation for a four-dimensional hyperchaotic Lorenz continuous system. Indicates the first The current value of the iteration. Indicates the first The current state value of the iteration. Indicates the first The current state value of the iteration The continuous chaotic system model was numerically discretized using the fourth-order Runge-Kutta method to obtain the iterative solution equations. Based on iteratively solving the equations, each user is configured with a different initial state vector, and four discrete chaotic sequences are generated iteratively. Based on the four discrete chaotic sequences, encryption operations are performed on the modulation symbol sequences of different users to obtain multi-user encrypted modulation symbol sequences; The four discrete chaotic sequences include a first discrete chaotic sequence X, a second discrete chaotic sequence Y, a third discrete chaotic sequence Z, and a fourth discrete chaotic sequence W; Using the first discrete chaotic sequence X, a bit XOR scrambling operation is performed on the modulation symbol sequence of the first part of the users to obtain the encrypted modulation symbol sequence of the first part of the users, represented as: ； In the formula, This indicates the first part of the user's encrypted modulation symbol sequence. Bit encryption bits, This represents the first part of the user's original plaintext modulation symbol sequence. Bit encryption bits, This represents the binary bitwise XOR operator. This represents the rounding function. Indicates the first The chaotic sample value of the first discrete chaotic sequence corresponding to the bit encryption bits. This represents the preset chaotic quantization bit precision parameter. This represents the modulo operator; Using the second discrete chaotic sequence Y to generate a random permutation index P, the modulation symbol sequence D of the second group of users is rearranged to obtain the encrypted modulation symbol sequence of the second group of users, as follows: ； In the formula, This indicates the second part of the user's encrypted modulation symbol sequence. Bit encryption bits, This represents the function for retrieving the position index. Indicates the first The random permutation index symbol generated from the chaotic sample values ​​of the second discrete chaotic sequence corresponding to the bit encryption bits; By performing a constellation rotation operation on the modulation symbol sequence of the third part of the users using the third discrete chaotic sequence Z, the encrypted modulation symbol sequence of the third part of the users is obtained; The constellation rotation angle and the third part of the user encryption modulation symbol are respectively represented as follows: ； ； In the formula, Indicates the rotation angle of the modulation constellation point. This represents the floor function. Indicates the first The chaotic sample value of the third discrete chaotic sequence corresponding to the bit encryption bits. This represents the third part of the user's encrypted modulation symbols. This represents the third part of the user modulation symbol before encryption. Denotes the phase rotation factor in the complex field, where, , This indicates the angle scaling precision parameter. Represents the cosine function. Represents the sine function; An amplitude perturbation operation is performed on the modulation symbol sequence of the fourth user group using the fourth discrete chaotic sequence W, resulting in the encrypted modulation symbol sequence of the fourth user group; the encrypted modulation symbol sequence of the fourth user group is represented as: ； In the formula, This represents the fourth part of the user encryption modulation symbols. This represents the fourth part of the user modulation symbol before encryption. This represents the preset amplitude disturbance intensity coefficient, used to control the impact of chaotic disturbances on the signal amplitude. Indicates the first The chaotic sample value of the fourth discrete chaotic sequence corresponding to the bit encryption bits.

5. The multi-user OFDM digital up-conversion method based on cognitive frequency tuning according to claim 1, characterized in that, The encrypted multi-user modulation symbol sequence is inserted with a predefined training sequence and subcarriers are allocated to map each user's data to the corresponding subcarrier position, resulting in a multi-user frequency domain symbol sequence, including: In response to the accuracy constraints of the receiver channel estimation, a predefined training sequence is generated as a pilot reference sequence; Based on the preset subcarrier mapping position, the pilot reference sequence is inserted into the corresponding position in the encrypted modulation symbol sequence of each user to obtain the multi-user symbol sequence after the pilot is inserted. Based on the total number of subcarriers in the OFDM system and their orthogonality constraints, each user is assigned a mutually orthogonal dedicated subcarrier group to generate user subcarrier mapping rules; According to the user subcarrier mapping rule, each user symbol sequence after the pilot is inserted is mapped to the corresponding subcarrier position to obtain a multi-user frequency domain symbol sequence.

6. The multi-user OFDM digital up-conversion method based on cognitive frequency tuning according to claim 1, characterized in that, Based on the aforementioned multi-user dedicated frequency conversion parameter set, reconfigurable digital up-conversion processing is performed on each baseband OFDM time-domain signal to independently shift each baseband OFDM time-domain signal to a dedicated idle RF sub-band, resulting in multiple frequency-domain physically isolated RF sub-band signals, including: Based on the multi-user dedicated frequency conversion parameter set, the digital mixing frequency and the sampling rate conversion parameters of the interpolation filter are independently configured for each baseband OFDM time domain signal, generating the upconversion control parameters for each channel. Based on the frequency conversion control parameters of each channel, interpolation filtering and digital mixing operations are sequentially performed on each baseband OFDM time domain signal to independently shift each baseband OFDM time domain signal to its corresponding dedicated idle RF sub-band, thereby obtaining multiple physically isolated RF sub-band signals in the frequency domain.

7. The multi-user OFDM digital up-conversion method based on cognitive frequency tuning according to claim 1, characterized in that, Based on the multi-channel frequency-domain isolated RF sub-band signals, signal combining, digital-to-analog conversion, and RF amplification operations are sequentially performed to obtain the RF transmit signal, including: The multiple frequency-domain physically isolated radio frequency subband signals are power combined to obtain multiple radio frequency subband signals; Multiple radio frequency subband signals are superimposed and merged into a single broadband radio frequency digital signal to obtain a combined radio frequency digital signal. The combined radio frequency digital signal is subjected to digital-to-analog conversion processing to obtain an analog radio frequency signal; The analog radio frequency signal is sequentially amplified and filtered to obtain the radio frequency transmission signal.

8. A demodulation method for a multi-user OFDM digital up-conversion method based on cognitive frequency tuning, characterized in that, Executed by the receiving end, including: It receives radio frequency transmitted signals and sequentially performs radio frequency receiving operations and digital down-conversion operations to obtain a baseband multi-user combined signal; Based on the multi-user dedicated frequency conversion parameter set of the transmitting end, perform user separation operation on the baseband multi-user combined signal to extract the independent baseband sub-band signal of each user; Synchronization correction, orthogonal frequency division multiplexing demodulation, and channel estimation are sequentially performed on the independent baseband subband signals of each user to obtain the demodulated frequency domain subcarrier data of each user. Based on the encryption and modulation parameters corresponding to the multi-user raw data stream at the transmitting end, the frequency domain subcarrier data demodulated by each user is sequentially subjected to modulation demapping, four-dimensional hyperchaotic layered decryption, and forward error correction decoding to obtain the serial binary service data of each user. The radio frequency transmission signal is obtained by performing the multi-user OFDM digital upconversion method based on cognitive frequency tuning as described in any one of claims 1 to 7.

9. The demodulation method of the multi-user OFDM digital up-conversion method based on cognitive frequency tuning according to claim 8, characterized in that, It receives radio frequency (RF) transmitted signals and sequentially performs RF receive operations and digital down-conversion operations to obtain a baseband multi-user combined signal, including: The system receives the radio frequency transmitted signal and performs low-noise amplification and filtering processes sequentially to obtain an analog received radio frequency signal. The analog received radio frequency signal is converted from analog to digital to obtain a digital received signal; Based on the preset a priori frequency point of cognitive frequency tuning, digital downconversion and decimation filtering are performed on each user subband in the digital received signal, and the dedicated idle radio frequency subband corresponding to each user is moved to the baseband. The moved baseband OFDM time domain signals are then superimposed into a baseband multi-user combined signal.

10. The demodulation method of the multi-user OFDM digital up-conversion method based on cognitive frequency tuning according to claim 9, characterized in that, Based on the multi-user dedicated frequency conversion parameter set at the transmitting end, a user separation operation is performed on the baseband multi-user combined signal to extract the independent baseband sub-band signal for each user, including: Based on the center frequency and signal bandwidth corresponding to the optimal idle radio frequency subband of each user in the multi-user dedicated frequency conversion parameter set of the transmitting end, digital filtering and extraction processing is performed on the baseband multi-user combined signal to separate the independent baseband subband signal of each user. Gain adjustment is performed on each baseband sub-band signal to normalize the power of each baseband sub-band signal to a preset level range, thereby extracting the independent baseband sub-band signal for each user.

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