CN-121396710-B - Multi-user transmitter design method for space-based asynchronous communication

CN121396710BCN 121396710 BCN121396710 BCN 121396710BCN-121396710-B

Abstract

A method for designing multi-user transmitter in space-base asynchronous communication includes constructing space-base uplink asynchronous communication system model, characterizing received signal of base station as superposition of code book coding pulse shaping signal after time delay and channel weighting by each user, decomposing received signal into target signal, multi-symbol asynchronous interference and effective noise, determining signal-to-interference-noise ratio of each user, constructing code book optimization problem of transmitting signal by taking minimum signal-to-noise ratio of all users as target and taking code word power normalization as constraint condition, constructing task space by time delay information by using meta learning algorithm to carry out off-line pre-training to obtain meta model, using current time delay as input at on-line stage to quickly generate adaptive code book by meta model, using said code book to encode transmitting symbol by transmitter to generate transmitting signal. The invention improves the signal-to-interference-and-noise ratio of the multi-user received signal, thereby realizing the reliability of the wide-area asynchronous communication of the unmanned plane.

Inventors

ZHANG XIANCHAO
Ye Shuxiao
YE NENG
DING XUHUI
SHAO YUFENG

Assignees

嘉兴大学

Dates

Publication Date: 20260512
Application Date: 20251224

Claims (10)

1. A method for designing a multi-user transmitter for space-based asynchronous communication, comprising: Constructing a space-based uplink asynchronous communication system model, characterizing a base station received signal as a codebook coding pulse forming signal superposition of each user after time delay and channel weighting, decomposing the received signal into a target signal, multi-symbol asynchronous interference and effective noise through maximum ratio combination, and calculating the energy of the decomposed signal to determine the signal-to-interference-and-noise ratio of each user; The method comprises the steps of optimizing and solving a codebook, namely constructing a codebook optimizing problem of a transmitting signal by taking the minimum signal-to-interference-and-noise ratio in all users as a target and taking codeword power normalization as a constraint condition, constructing a task space by using time delay information by adopting a meta-learning algorithm, performing offline pre-training to obtain a meta-model, and quickly generating an adaptive codebook by using the current time delay as input in an online stage through the meta-model, wherein the codebook is used for encoding a transmitting symbol by a transmitter to generate the transmitting signal.
2. The method for designing a multi-user transmitter for space-based asynchronous communication according to claim 1, wherein, The system modeling and performance analysis steps include: S101, constructing a space-based uplink asynchronous receiving signal model of a base station and N user terminals, and representing the receiving signals of the base station as codebook coding pulse forming signal superposition of each user through transmission delay and channel coefficient weighting; step S102, maximum ratio combining is carried out on the received signals, and the received signals to be detected are decomposed into target signals and multi-symbol asynchronous interference and effective noise caused by time delay difference; Step S103, calculating target signal energy based on the channel coefficient statistical characteristics and the number of transmitted symbols; Step S104, calculating interference energy by the product operation of channel conjugation, codeword element conjugation and a transmission symbol based on the sampling offset of the pulse shaping function; Step S105, calculating effective noise energy based on the noise power and the second order statistic of the channel; And step S106, determining the signal-to-interference-and-noise ratio of the users according to the target signal energy, the interference energy and the effective noise energy of each user.
3. The method for designing a multi-user transmitter for space-based asynchronous communication according to claim 2, wherein, In step S101, the base station received signal is characterized as: ; Wherein, the Is the first Individual user is at the first A received signal of each sampling point; 、 Base station and the first First, second Channel coefficients between individual users; is the first The individual users transmit signals at the moment Is used for the sampling value of (a), Is the sampling period; the total number of the user terminals in the system; is the first The signals of the individual users take values at asynchronous sampling moments; 、 Base station and the first First, second Signal propagation delay between individual users; is the first Individual user is at the first Additive white gaussian noise at each sampling point; ; for the number of symbol blocks, Is the codeword length.
4. A method for designing a multi-user transmitter for space-based asynchronous communication according to claim 3, In step S102, after performing maximum ratio combining on the received signals, the received signals to be detected are expressed as: ; Wherein, the Is the first Individual user number Detection signals of the symbol blocks; is the first Individual user code word number The conjugate transpose of the individual chips, Represents a conjugate transpose; ; ; is the first Individual user number A received signal of each sampling point; 、 respectively the first First, second The individual users transmit signals at the moment Is used for the sampling value of (a), 。
5. The method for designing a multi-user transmitter for space-based asynchronous communication according to claim 4, wherein, In step S103, the calculated first The target signal energy of each user is: ; Wherein, the For the desired operator, the target signal vector , Is the square of the L2 norm, Is the fourth moment of the channel.
6. The method for designing a multi-user transmitter for space-based asynchronous communication according to claim 4, wherein, In step S104, the calculated first Inter-user interference energy experienced by individual users: ; Wherein, the , Representing integer index Absolute value of (2); Is the maximum intersymbol interference span; 、 is the first Index of the chips in the code words of the individual users; 、 is the first Index of the chips in the code words of the individual users; is a pulse shaping function.
7. The method for designing a multi-user transmitter for space-based asynchronous communication according to claim 4, wherein, In step S105, the calculated first The effective noise energy suffered by the individual users is: ; Wherein the noise signal vector , Is the first Individual user is at the first Additive white gaussian noise at each sampling point; Representing the variance of additive gaussian white noise; Is the square of the L2 norm.
8. A method for designing a multi-user transmitter for space-based asynchronous communication according to any one of claims 3 to 7, In the codebook optimization solving step, the constructed codebook optimization problem is as follows: ; Wherein, the Is the first The code words of the symbol streams of the individual users, In the form of a codebook, the code means, ; First, the Signal-to-interference-and-noise ratio of individual users The method comprises the following steps: ; In the formula, In order for the energy of the target signal to be sufficient, As a result of the vector of the target signal, As the energy of the interference between the users, Is the first Individual user pair number Interference vectors for individual users; is noise term energy; is the first Effective noise vectors for individual users; in order for the operator to be desirable, Is the square of the L2 norm.
9. The method for designing a multi-user transmitter for space-based asynchronous communication according to claim 8, wherein, In the codebook optimization solving step, a meta-learning depth deterministic strategy gradient algorithm is adopted, and an offline pre-training is carried out by constructing a task space by using a delay vector, wherein the process comprises the following steps: 1) Randomly generating a large number of user time delay configuration construction task spaces within a preset time delay range, and uniformly extracting a batch of task samples; 2) Collecting a small amount of channel data for each task to form a support set for rapid adaptation and independent channel data to form a query set for verification; 3) Copying the meta model into a task-specific fast model through internal circulation, generating a candidate codebook based on a support set, evaluating the minimum signal-to-interference-and-noise ratio, and iteratively updating fast model parameters; 4) The performance is evaluated on the query set of all tasks through the outer loop, the meta-loss is calculated, and the meta-model is updated, so that the meta-model obtains the universal capability of quickly adapting to the new time delay configuration.
10. The method for designing a multi-user transmitter for space-based asynchronous communication according to claim 8, wherein, In the codebook optimization solving step, the current time delay is taken as input in an online stage, and an adaptive codebook is rapidly generated through gradient updating, and the process comprises the following steps: 1) The system continuously monitors the transmission time delay from each user to the base station, and immediately triggers the rapid adaptation when a new time delay configuration time is detected; 2) The adaptation process adopts an offline pre-trained meta-model as an initial parameter, carries out iterative optimization based on the current time delay environment and channel data acquired in real time, generates a candidate codebook each time of iteration, evaluates the minimum user signal-to-interference-and-noise ratio of the candidate codebook, and reversely fine-adjusts the meta-model parameter so as to gradually adapt to a new scene; 3) And taking the codebook which is generated after iterative optimization and maximizes the minimum signal-to-interference-and-noise ratio in all users as an adaptive codebook under the current time delay configuration, wherein the codebook is used for encoding a transmitting symbol by a transmitter to generate a transmitting signal.

Description

Multi-user transmitter design method for space-based asynchronous communication Technical Field The invention relates to the technical field of wireless communication, in particular to a method for designing a multi-user transmitter for space-based asynchronous communication. Background The unmanned aerial vehicle autonomous inspection technology is widely applied to the fields of electric power, security protection, agriculture and the like, and depends on the coverage capability of a communication system to a wide geographic area. However, the propagation speed of electromagnetic signals in the air is fixed, and the transmission distance between the ground equipment and the unmanned plane is different. The signals sent by different devices at the same time can reach the unmanned aerial vehicle at different times, so that the problem of serious time delay inconsistency of multi-user communication is caused. Although there is also a certain distance difference between users in the terrestrial fixed communication system, it can control the influence of the time delay difference on the system performance by means such as cyclic prefix. However, in the unmanned aerial vehicle communication scene, the communication distance is further enlarged, and the transmission distance difference between the user and the unmanned aerial vehicle can reach more than a plurality of kilometers, so that the difference magnitude of signal propagation delay is obviously increased, and the cyclic prefix length preset by an air interface system is often exceeded. This extremely amplified spatial position asymmetry severely destroys the synchronization assumption of multi-user communications, which can cause the user transmit signal to be misplaced at the receiving end, severely affecting system performance. In particular, the transmission delays of different users are different, which results in that the optimal utilization points of the users are no longer coincident. When the signal sampling point is not at the optimal sampling point, the sampled signal will face complex inter-symbol interference. This causes inter-user interference, which is changed from one symbol interference in the synchronization hypothesis to multiple symbol crosstalk. This complex asynchronous superposition effect will severely degrade the signal detection performance. However, most existing multi-user transmitters, such as sparse spreading code based transmitters, walsh code based transmitters, and the like, are designed based on ideal synchronous transmission assumptions, and fail to consider asynchronous interference characteristics caused by inconsistent delays in an actual unmanned aerial vehicle inspection environment. Therefore, the transmitter design is required to be performed in a real wide-area asynchronous communication scene, so that the actual requirements of the unmanned aerial vehicle communication system are matched. Disclosure of Invention In view of the analysis, the invention aims to disclose a multi-user transmitter design method for space-based asynchronous communication, which changes the mapping mode of digital signals and physical resources by changing the embedded multi-user codebook structure of the transmitter and improves the signal-to-interference-and-noise ratio of multi-user received signals, thereby realizing the reliability of wide-area asynchronous communication of an unmanned plane. The invention discloses a method for designing a multi-user transmitter for space-based asynchronous communication, which comprises the following steps: Constructing a space-based uplink asynchronous communication system model, characterizing a base station received signal as a codebook coding pulse forming signal superposition of each user after time delay and channel weighting, decomposing the received signal into a target signal, multi-symbol asynchronous interference and effective noise through maximum ratio combination, and calculating the energy of the decomposed signal to determine the signal-to-interference-and-noise ratio of each user; The method comprises the steps of optimizing and solving a codebook, namely constructing a codebook optimizing problem of a transmitting signal by taking the minimum signal-to-interference-and-noise ratio in all users as a target and taking codeword power normalization as a constraint condition, constructing a task space by using time delay information by adopting a meta-learning algorithm, performing offline pre-training to obtain a meta-model, and quickly generating an adaptive codebook by using the current time delay as input in an online stage through the meta-model, wherein the codebook is used for encoding a transmitting symbol by a transmitter to generate the transmitting signal. Further, the system modeling and performance analysis step includes: S101, constructing a space-based uplink asynchronous receiving signal model of a base station and N user terminals, and representing the receiving sig