A single radio chain multi-user private semantic multiplexing communication system and method based on programmable metasurface

Abstract

The application discloses a single-radio-chain multi-user private semantic multiplexing communication system and method based on a programmable metasurface. The system comprises: a sending end configured to provide a private message of a receiving end and send a public transmission symbol; a programmable metasurface configured to load a random discrete phase configuration in a channel estimation stage and load a discrete phase configuration generated by a joint modulator in a semantic transmission stage; a coordinator configured to enable stage scheduling and synchronization; a channel estimator configured to obtain a cascaded reflection channel estimation value according to the random phase configuration and a pilot observation; a semantic extractor configured to convert the private message into an ordered compressed semantic feature; a joint modulator configured to fuse the multi-user semantic feature and the cascaded reflection channel estimation value, generate the public transmission symbol and the discrete phase configuration; and a plurality of receiving ends configured to recover corresponding private messages from self-received samples. The application is used for realizing concurrent semantic transmission of multi-user private messages when a direct link is unavailable.

Description

Technical Field

[0001] This invention relates to the field of user-private semantic communication, and specifically to a single-RF chain multi-user private semantic multiplexing communication system and method based on a programmable metasurface. Background Technology

[0002] In existing multi-user downlink communication, multi-antenna or multi-RF chain schemes require large-scale RF hardware and are costly. Orthogonal resource schemes (such as time division and frequency division) require sequential or distributed resource services to different users, which can easily increase resource consumption and transmission latency. When the transmitter is configured with only a single RF chain, only one common transmission symbol can be generated each time the channel is used, which greatly limits the degree of freedom for active transmission of multiple users' private data streams in parallel.

[0003] Existing multi-user semantic communication schemes can achieve parallel transmission through methods such as sharing time-frequency resources, semantic feature overlay, or joint coding. However, when the private semantic messages of multiple users are carried by the same public transmission signal, the semantic features of different users will couple with each other in the wireless channel. As the number of users serving simultaneously increases, interference between users and aliasing of received signals intensify. Each receiver, relying solely on its own mixed received signal, finds it difficult to effectively distinguish the target private semantic information from the semantic information of other users, easily leading to lexical recovery errors, sentence structure disruption, or decreased semantic similarity. Especially under single-RF chain conditions, if the multi-user semantic features, the channel states of each user, and the controllable propagation dimension are not jointly designed, parallel transmission, although achievable, still suffers from significant interference and difficulties in private message recovery.

[0004] Existing programmable metasurface-assisted communication schemes typically use programmable metasurfaces for coverage enhancement, beamforming, or interference suppression, with the reflection phase determined individually based on channel conditions. Even with metasurface-assisted parallel transmission, semantic feature processing, common transmitted symbol generation, and metasurface phase configuration are often separated, making it difficult to ensure that the received signals of each user simultaneously match their target private semantic representation. Furthermore, practical programmable metasurfaces only support finite discrete phases, and single-RF chain RF front-ends typically employ finite discrete constellations. Schemes designed based on continuous variables or idealized degrees of freedom are difficult to directly adapt to actual hardware.

[0005] In summary, the existing technology has the following defects and shortcomings:

[0006] (a) Multi-antenna or multi-RF chain solutions have high hardware costs, while orthogonal resource solutions have high resource consumption and high transmission latency;

[0007] (ii) Under single radio frequency chain conditions, existing multi-user semantic communication schemes have multi-user semantic features coupled with each other, making it difficult for the receiver to effectively distinguish and recover each user's private message from the aliased signal.

[0008] (iii) The semantic feature processing, emission symbol generation and metasurface phase configuration of existing programmable metasurface-assisted schemes are separated from each other and have not been jointly optimized.

[0009] (iv) Existing solutions are mostly based on continuous variables or idealized degrees of freedom, which are difficult to adapt to the finite discrete phase constraints of actual programmable metasurfaces and the finite discrete constellation constraints of single radio frequency chains.

[0010] Therefore, there is an urgent need for a technical solution that can, under the conditions that the transmitter has only a single radio frequency chain, there is no available direct link between the transmitter and the receiver, and the transmitted symbols and metasurface phases are both subject to discrete set constraints, jointly process the semantic features of multi-user private messages with the state of each user's cascaded reflection channel, synchronously generate common transmitted symbols and metasurface phase configurations, reduce multi-user coupling and message aliasing in parallel transmission, and enable multiple receivers to recover their respective private messages from the same wireless transmission. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of the prior art and provide a single-RF chain multi-user private semantic multiplexing communication system and method based on a programmable metasurface.

[0012] The present invention achieves the above objectives by adopting the following technical solution: Firstly, the present invention provides a single-RF chain multi-user private semantic multiplexing communication system based on a programmable metasurface, comprising:

[0013] The transmitting end is configured with a single radio frequency chain to provide private messages corresponding to multiple receiving ends, and transmits wireless signals one by one according to the discrete transmit symbol sequence output by the channel state information sensing joint modulator during the multi-user semantic transmission phase.

[0014] The programmable metasurface includes N controllable reflection units, which are used to receive random discrete phase configurations issued by the coordinator during the channel estimation phase, receive the discrete phase configuration sequence output by the channel state information sensing joint modulator during the multi-user semantic transmission phase, and complete phase switching under the timing enable of the coordinator, so that the transmitting end signal reaches multiple receiving ends via the cascaded reflection link between the transmitting end, the programmable metasurface and the receiving end.

[0015] The coordinator is used to perform phase scheduling, phase control, and timing synchronization processing. During the channel estimation phase, it generates or reads random discrete phase configurations from the discrete phase codebook according to the pilot sampling number and sends them to the programmable metasurface. At the same time, it triggers the transmitter to send pilots and notifies the channel estimator to record the current phase configuration. During the multi-user semantic transmission phase, it senses the discrete transmit symbol sequence and discrete phase configuration sequence output by the joint modulator according to the channel state information and enables synchronization between the transmitter and the programmable metasurface.

[0016] The channel estimator is used to receive multiple sets of random phase configurations provided by the coordinator and pilot observations fed back by each receiver, construct a phase configuration matrix and obtain the cascaded reflection channel estimation vector of each user by solving the pseudo-inverse least squares problem, and send it to the channel state information sensing joint modulator.

[0017] A semantic extractor is used to utilize pre-configured semantic extraction maps. Each user's private messages are converted into an ordered compressed semantic feature sequence and sent to the channel state information-aware joint modulator.

[0018] Channel state information-aware joint modulator, used to utilize pre-configured joint modulation maps By fusing multi-user semantic features with cascaded reflection channel estimates, a common transmitted symbol and the phase state of each reflection unit are determined and output from the finite discrete transmit constellation and the finite discrete phase codebook in each channel use, generating a discrete transmit symbol sequence and a discrete phase configuration sequence.

[0019] Multiple receivers, the k-th receiver is used to receive the wireless signal reflected by the programmable metasurface and collect the received samples, utilizing a pre-configured semantic reconstruction map. The private message corresponding to the receiving end is recovered from the received sample; wherein the direct link between the sending end and each receiving end is blocked or attenuated to the point of being unusable, and the wireless transmission is completed via a cascaded reflection link consisting of the sending end, the programmable metasurface and the receiving end, k=1,2,...,K, where K is the total number of receiving ends.

[0020] Furthermore, the channel estimator is configured as follows:

[0021] Will Constructing a configuration matrix by arranging the group of random discrete phase configurations in columns. The pilot received signals from each receiver are stacked together. , and in accordance with The cascaded reflection channel estimation vector of the k-th receiver is obtained, where express The Moore-Penrose pseudoinverse, where P is the transmit power.

[0022] Furthermore, the semantic extractor is configured as follows:

[0023] The currently pending private message from the k-th receiver is sorted according to message type. Divided into L semantic units that maintain their original order, and using a pre-configured semantic extraction mapping with fixed parameters. Generate an ordered compressed semantic feature sequence:

[0024] ;

[0025] ;

[0026] in, This indicates pre-configured mapping parameters. Indicates the first Compression features of semantic units For feature dimensions;

[0027] The mapping At least the following steps should be completed: semantic unit numeration, sequential information combination, context association, and dimensional compression.

[0028] Furthermore, the channel state information-aware joint modulator is configured as follows:

[0029] The real and imaginary parts of the cascaded reflection channel estimation vectors for all users are expanded according to a fixed user order to construct real-valued channel features. ;

[0030] In the Each semantic location will be all The semantic features of each user at this location are concatenated as follows: Then, it is concatenated with the real-valued channel features to form joint input features. Arrange the joint input features of all L semantic positions as follows: ;

[0031] Using pre-configured and fixed-parameter joint modulation mapping right Process the data and output the constellation rating tensor. and metasurface phase rating tensor ;

[0032] Perform a maximum value decision on the transmitted constellation score tensor within the candidate constellation index set to obtain the discrete constellation index. And directly mapped to public emission symbols. ,in ;

[0033] For each reflection unit, a maximum value decision is performed on the metasurface phase score tensor within the candidate phase index set to obtain a discrete phase index. Mapped to reflection coefficient .

[0034] Furthermore, the discrete emission symbols originate from a finite phase-shift keying constellation. The reflection coefficients of each reflection unit in the discrete phase configuration are selected from the discrete reflection coefficient codebook. Selected from, ,in B is the number of control bits for each reflection unit;

[0035] The discrete transmission symbol sequence Satisfying average transmit power constraints ,in , which represents the total number of channel uses for a transport block.

[0036] Furthermore, the coordinator is configured as follows:

[0037] During the channel estimation phase, the random discrete phase configuration is directly sent to the programmable metasurface in groups, and the same configuration is provided to the channel estimator.

[0038] During the multi-user semantic transmission phase, each symbol or corresponding constellation index in the discrete transmit symbol sequence output by the channel state information sensing joint modulator is sent to the transmit buffer of the transmitter, and each phase index in the discrete phase configuration sequence is sent to the configuration buffer of the programmable metasurface.

[0039] Before the start of the t-th channel use, a switching enable signal is sent to the programmable metasurface, and upon receiving the ready signal returned by the programmable metasurface, the transmitter is triggered to send the corresponding common transmission symbol through the single radio frequency chain. The programmable metasurface maintains the corresponding discrete phase configuration during the effective duration of the common transmission symbol. constant.

[0040] Furthermore, the kth receiver is configured as follows:

[0041] Collect received samples according to channel usage number , corresponding to each semantic unit The next batch of received samples is The real and imaginary parts of each group of complex received samples are expanded in a fixed order to obtain the received features. ;

[0042] Arrange all L groups of received features according to their semantic position. Utilizing pre-configured semantic reconstruction mappings with fixed parameters Obtain the reconstructed private message ,in Pre-configured reconfiguration parameters for the k-th receiver;

[0043] The mapping At least the received feature recovery, semantic location association, and semantic unit decision processing should be completed.

[0044] Furthermore, the coordinator is also configured to: re-trigger the channel estimation phase to update the cascaded reflection channel estimation values ​​of each user when the channel estimation update period arrives, the pilot check error exceeds a preset threshold, or a change in user location is detected.

[0045] Secondly, the present invention provides a single-RF chain multi-user private semantic multiplexing communication method based on a programmable metasurface, applied to the above-mentioned system, comprising the following steps:

[0046] In the channel estimation step, the coordinator triggers the system to enter the channel estimation phase. According to the pilot sampling number, it generates or reads multiple sets of random discrete phase configurations from the discrete phase codebook. The random discrete phase configurations are provided to the programmable metasurface and the channel estimator respectively, and the transmitter is synchronously triggered to send fixed known pilots. Each receiver measures and feeds back the corresponding pilot received signal. The channel estimator obtains the cascaded reflection channel estimate value of each user by solving the pseudo-inverse least squares problem based on the random discrete phase configuration and the pilot received signal.

[0047] In the semantic feature extraction step, the semantic extractor acquires private messages corresponding to multiple receivers and utilizes pre-configured semantic extraction mappings. Each of the aforementioned private messages is converted into an ordered compressed semantic feature sequence;

[0048] In the joint modulation step, the channel state information-aware joint modulator acquires the cascaded reflection channel estimates and the ordered compressed semantic feature sequences of each user, and utilizes a pre-configured joint modulation map. Multi-user semantic features are fused with cascaded reflection channel estimates. In each channel use, a common transmitted symbol is determined from a finite discrete transmit constellation, and the phase state of each reflection unit is determined from a finite discrete phase codebook, generating a discrete transmit symbol sequence and a discrete phase configuration sequence.

[0049] In the synchronous transmission step, the coordinator controls the programmable metasurface to switch sequentially according to the phase configuration in the discrete phase configuration sequence based on the discrete transmission symbol sequence and the discrete phase configuration sequence, and triggers the transmitter to transmit the corresponding common transmission symbol in the discrete transmission symbol sequence through a single radio frequency chain after each phase configuration takes effect;

[0050] In the semantic reconstruction step, the k-th receiver receives the wireless signal reflected by the programmable metasurface and collects the received samples, utilizing a pre-configured semantic reconstruction map. Recover the private message corresponding to the receiving end from the received sample;

[0051] In this configuration, the direct links between the transmitter and each receiver are blocked or attenuated to the point of being unusable. Wireless transmission is completed via a cascaded reflection link consisting of the transmitter, the programmable metasurface, and the receiver, where k = 1, 2, ..., K, and K is the total number of receivers.

[0052] Furthermore, in the channel estimation step:

[0053] The coordinator establishes pilot sampling numbers. For each pilot sampling number, a set of random discrete phase configurations is generated or read from the discrete phase codebook. The reflection coefficient of each reflecting unit is derived from the discrete phase codebook. Selected independently and evenly;

[0054] The transmitting end transmits fixed, known pilot signals at each pilot sampling time. ;

[0055] The channel estimator will Constructing a configuration matrix by arranging the group of random discrete phase configurations in columns. The pilot received signals from each receiver are stacked together. ,according to The cascaded reflection channel estimation vector of the k-th receiver is obtained, where, express The Moore-Penrose pseudo-rebel.

[0056] Compared with the prior art, the main technical effects of the present invention using the above technical solution include:

[0057] By explicitly excluding direct links, the semantic features of each user's private message are jointly processed with the estimated values ​​of the cascaded reflection channel from the transmitter to the programmable metasurface to the receiver. During each channel usage, discrete common transmission symbols for the single-RF chain transmitter and discrete phase configurations for the programmable metasurface are synchronously generated. The jointly generated common transmission symbols and discrete phase configurations, after passing through the cascaded reflection channels of different users, form distinct reception characteristics that can be used to reconstruct their respective target private messages. This eliminates the need to configure independent RF chains, independent spatial data streams, or independent time-frequency resources for each receiver, enabling concurrent transmission of multiple private semantic messages and significantly reducing hardware costs and resource overhead.

[0058] In the channel estimation phase, the coordinator directly sends random discrete phase configurations to the programmable metasurface group by group and provides the same configuration to the channel estimator. After each receiver feeds back pilot observations, the channel estimator obtains the estimated value of the cascaded reflection channel based on the pseudo-inverse of the configuration matrix. This estimation result is bound to the user number and input into the joint modulation mapping, so that both the discrete transmitted symbols and discrete phase configurations change together with the current propagation environment and multi-user semantic content, realizing the joint perception and adaptation of channel state and semantic content.

[0059] Semantic extraction mapping transforms private messages into ordered and compressed semantic features, while the receiving end semantic reconstruction mapping utilizes multiple received samples corresponding to the same semantic unit to recover the message. Thus, the limited number of channel uses prioritizes carrying features related to the message meaning, and the contextual association between semantic units can reduce the impact of noise and local symbol errors caused by multi-user coupling on the overall meaning recovery, improving the semantic reliability of transmission.

[0060] During the online operation phase, the joint modulation mapping only outputs discrete symbols from the finite phase shift keying constellation and discrete phase indices from the finite phase codebook, without generating continuous transmission symbols. The generated transmission symbol sequence satisfies the average transmit power constraint, thus enabling direct integration with a single-RF-chain RF front-end and a low-bit programmable metasurface controller. The online phase only performs fixed-parameter mapping calculations and discrete decisions, reducing online computational complexity.

[0061] The coordinator ensures a one-to-one correspondence between the corresponding transmitted symbols and phase configurations through ready feedback and synchronization triggering mechanisms, avoiding transmission errors caused by misalignment of transmitted symbols and phase configurations. It also re-executes channel estimation when the channel changes, ensuring the system's adaptability to dynamic environments. Attached Figure Description

[0062] Figure 1 This is a block diagram of a single-RF chain multi-user private semantic multiplexing communication system based on a programmable metasurface, provided by an embodiment of the present invention. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0064] This invention assumes that the direct links between the transmitter and each receiver are blocked or attenuated to the point of being unusable, and all wireless transmissions are completed via a cascaded reflection link consisting of the transmitter, programmable metasurface, and receiver. During the channel estimation phase, the coordinator generates or reads multiple sets of random phase configurations from the discrete phase codebook according to the pilot sampling number, and directly issues phase control commands to the programmable metasurface, simultaneously triggering the transmitter to send known pilots. The channel estimator obtains the cascaded reflection channel estimate using a pseudo-inverse least squares method based on the phase configuration provided by the coordinator and the pilot observations fed back by each receiver. The semantic extractor uses a pre-configured mapping to convert the private messages of multiple users into ordered compressed semantic features. The channel state information-aware joint modulator uses a pre-configured mapping to fuse the multi-user semantic features with the cascaded reflection channel estimate, selecting a common transmit symbol and the phase state of each reflection unit from the finite phase shift keying constellation and the finite metasurface phase codebook respectively during each channel use, ensuring that the transmit symbol sequence satisfies the average transmit power constraint. The transmitting end sends the discrete common transmission symbols through a single radio frequency chain, and the programmable metasurface synchronization adopts the corresponding discrete phase configuration; each receiving end then uses a pre-configured semantic reconstruction map to recover the corresponding private message from its own received samples. Thus, concurrent transmission of multi-user private semantic information can be achieved without configuring independent radio frequency chains or independent time-frequency resources for different receiving ends.

[0065] Example 1: System Architecture

[0066] Specifically, such as Figure 1 As shown, the single-RF chain multi-user semantic multiplexing communication system based on a programmable metasurface of the present invention comprises the following components:

[0067] Coordinator: The coordinator performs phase scheduling, phase control, and timing synchronization. During the channel estimation phase, the coordinator follows the pilot sampling number... The system generates or reads random phase indexes from the discrete phase codebook, directly issues phase configuration control commands to the programmable metasurface, and synchronously triggers the transmitter to send pilot signals and notifies the channel estimator to record the current phase configuration. During the multi-user semantic transmission phase, the coordinator senses the discrete transmit symbol sequence and discrete phase configuration sequence output by the joint modulator based on the channel state information, and synchronously enables the transmitter and the programmable metasurface so that the corresponding discrete transmit symbols and phase configurations take effect synchronously in the same channel usage.

[0068] Channel estimator: The channel estimator performs pilot observation processing and pseudo-inverse least squares solution processing, and receives information from the coordinator. Based on the random phase configuration and pilot observations fed back from each receiver, a phase configuration matrix is ​​constructed, and the cascaded reflection channel estimation vector for each user is obtained. It is then sent to the channel state information sensing joint modulator.

[0069] Transmitter: The transmitter adopts a single-RF chain structure, responsible for providing signals to the first... The first to the second Each receiver receives a private message and perceives the discrete transmitted symbol sequence output by the joint modulator according to the channel state information. Send wireless signals one by one.

[0070] Semantic extractor: The semantic extractor performs pre-configured semantic feature mapping. The system performs semantic unit partitioning, context association, and feature compression on each user's private messages, outputting the corresponding ordered semantic feature sequence. .

[0071] Channel State Information Aware Joint Modulator: The channel state information aware joint modulator performs a pre-configured joint mapping. The multi-user semantic features are fused with the cascaded reflection channel estimate, and the discrete transmitted symbol sequence is synchronously output through two discrete decision branches. and metasurface discrete phase configuration sequence .

[0072] Programmable metasurfaces: Programmable metasurfaces include Each controllable reflection unit performs phase index addressing and synchronization switching. During the channel estimation phase, the programmable metasurface receives the random discrete phase configuration directly from the coordinator; during the multi-user semantic transmission phase, the programmable metasurface receives the discrete phase configuration output by the channel state information sensing joint modulator and completes the switching under the timing enable of the coordinator, so that the transmitter signal reaches multiple receivers only through the cascaded reflection link.

[0073] Receiver: The receiver includes the first receiver to the second receiver. The first receiver. Each receiver groups and expands its received samples into real and imaginary parts, and then uses a pre-configured semantic reconstruction mapping. Restore the private message corresponding to this receiver.

[0074] Example 2: System Model and Problem Modeling

[0075] The system includes a transmitter using a single radio frequency chain and a transmitter with... A programmable metasurface with a reflective unit and There are one receiver. Direct links between the transmitter and each receiver are blocked or attenuated to the point of being unusable; therefore, the system only considers the transmitter-programmable metasurface-receiver cascaded reflection link. Let the user set and the... The cascaded reflection channel vector for each user is:

[0076] , ;

[0077] in, Indicates that the transmitting end signal passes through the first The first reflecting unit reaches the first... The cascaded reflection channel coefficients formed by each receiver. The cascaded reflection channel remains unchanged within a transport block, and its estimated value is obtained in the channel estimation stage described later.

[0078] Assume each reflection unit consists of Each control bit determines the phase state, supporting a total of [number] discrete phases. The corresponding discrete reflection coefficient codebook is:

[0079] , ;

[0080] The transmitter selects transmission symbols only from a finite phase-shift keying constellation, and does not use continuous-value transmission symbols. Assume the transmission constellation contains... The power of each candidate point and each symbol is Then the set of discrete emission symbols is:

[0081] , ;

[0082] In the When the secondary channel is used, the programmable metasurface employs a phase configuration vector:

[0083] , ;

[0084] No. The receiver is at the first The received signal when using the secondary channel is:

[0085] ;

[0086] in, This represents received noise, and the formula does not include a direct link term, indicating that the same discrete common transmitted symbol... It propagates to each receiver only through the discrete phase configuration of the programmable metasurface and the cascaded reflection channel corresponding to the user.

[0087] Suppose it is sent to the first The complete private message of each receiver is , its origin It consists of several private message blocks arranged in sequence, and in the text implementation, the private message block is a sentence. Among them, the first... A private message block According to the aforementioned method, it is divided into Each semantic unit is processed within a transport block. The received samples are stacked as follows: After that, the Each receiving end invokes a pre-configured semantic reconstruction map. Obtain the One reconstructed private message block :

[0088] ;

[0089] ;

[0090] ;

[0091] After processing all private message blocks in sequence, the reconstruction results are combined into a reconstructed private message in the original order.

[0092] make Indicates the first The semantic recovery quality of each receiver. The goal of the system operation is to maximize the average semantic recovery quality of all receivers while satisfying the constraints of discrete transmit constellation, discrete reflection phase, and average transmit power. The problem is modeled as follows:

[0093] ;

[0094] ;

[0095] ;

[0096] ;

[0097] in, The expected power calculation represents the upper limit of the average transmit power allowed within a transport block. This addresses the randomness of private message values ​​and channel noise. In the implementation of text-based private messages, Sentence-level semantic similarity is used. For the first... The first receiver end The original sentence With reconstructing sentences ,use Generate embedding vectors respectively The corresponding cosine semantic similarity is:

[0098] ;

[0099] The corresponding cosine semantic similarity is used to measure the degree of semantic similarity between individual sentence pairs.

[0100] The first Each receiving end The semantic recovery quality is obtained by averaging the cosine semantic similarities between the original sentences and the reconstructed sentences.

[0101] ;

[0102] Semantic recovery quality is used to average all sentences from the same user. The closer The more consistent the semantics of the reconstructed message with the original message, the better. Since this implementation uses a constant-amplitude discrete constellation, any... All meet Therefore, the average transmit power constraint holds true with equality; when the power does not exceed This constraint still applies when dealing with other discrete constellations. Problem modeling is used to constrain... Figure 1 The common operational goal of all the block diagrams is determined by the parameters during online execution. , and It directly performs mapping calculations and discrete decision-making.

[0103] Example 3: Cascaded Reflection Channel Estimation Algorithm Performed by the Channel Estimator

[0104] Channel estimation is performed before multi-user semantic transmission. Since this implementation does not consider direct links, pilot observations only include cascaded reflection links and received noise. After the coordinator triggers channel estimation, the transmitter continuously... Send a fixed known pilot signal at each sampling time. The programmable metasurface employs a set of random discrete phase configurations at each sampling time. :

[0105] ;

[0106] The reflection coefficient of each reflecting unit is from Selected independently and evenly. Each receiver measures the pilot received signal for each configuration and feeds it back to the channel estimator. The received signal and noise are stacked separately as follows:

[0107] , ;

[0108] Will Arrange the random phase configurations column-wise to construct the configuration matrix: ;

[0109] According to the no-direct-link reception model, the pilot observations in the channel estimation phase satisfy: ;

[0110] The channel estimator uses the Moore-Penrose pseudoinverse of the configuration matrix to obtain the first... Concatenated reflection channel estimation vectors for each receiver:

[0111] ;

[0112] in, express The Moore-Penrose pseudo-rebel. To make all Each cascaded reflection channel coefficient is identifiable, and the configuration matrix should have full row rank; during implementation, it can be set as follows: And employs mutually distinct random phase configurations. The channel estimator... Perform the above calculations separately, and... The channel estimation completion signal is sent along with the user ID to the channel state information sensing joint modulator and then returned to the coordinator.

[0113] Example 4: Online Algorithm Execution

[0114] 4.1 Stage scheduling and synchronization control executed by the coordinator

[0115] The coordinator maintains four operational states: initialization, channel estimation, multi-user semantic transmission, and transmission completion. After system startup, the coordinator first triggers the channel estimation phase. In this phase, the coordinator directly sends random discrete phase configurations to the programmable metasurface according to the sampling number and informs the channel estimator of the same configuration. Only after receiving the cascaded reflection channel estimation completion signal does the coordinator allow the semantic extractor and the channel state information-aware joint modulator to process the current multi-user private messages.

[0116] The phase configuration in the multi-user semantic transmission phase is generated by the channel state information-aware joint modulator; the coordinator controls the programmable metasurface to switch to the corresponding phase configuration, and triggers the transmitter to send the corresponding discrete transmission symbols after confirming that the phase configuration is effective, thereby avoiding misalignment between the transmission symbols and the phase configuration.

[0117] 4.2 Mapping performed by the semantic extractor

[0118] The sending end provides the semantic extractor with respectively... The currently pending private message to be transmitted at the receiving end. For the first... At each receiving end, the semantic extractor first divides the currently transmitted private message into categories that maintain their original order according to message type. Each semantic unit is then used to call a semantic extraction mapping with fixed parameters. Generate an ordered compressed semantic feature sequence:

[0119] ;

[0120] in, This indicates pre-configured mapping parameters. Indicates the first Compression features of semantic units. Mapping At a minimum, semantic unit numeration, sequential information combination, contextual association, and dimensionality compression should be completed, but there are no restrictions on specific network names, number of layers, or connection forms. (For lengths less than...) The currently pending private message can be padded with padding units; for messages exceeding a certain length... Private messages can be divided into multiple private message blocks and processed in multiple transport blocks respectively.

[0121] 4.3 Mapping performed by the channel state information-aware joint modulator

[0122] The channel state information-aware joint modulator first expands the real and imaginary parts of the channel estimation vectors of all users concatenated in a fixed user order to form real-valued channel characteristics:

[0123] ;

[0124] In the Each semantic location will be all The semantic features of each user at this location are concatenated and then concatenated with the real-valued channel features to form the joint input features:

[0125] ;

[0126] Let each semantic unit correspond to The total number of channel uses in a transport block is [number]. The channel state information-aware joint modulator arranges the joint input features according to their semantic positions. and call the mapping with fixed parameters. Output the constellation rating tensor once. and metasurface phase rating tensor :

[0127] ;

[0128] in, This represents the pre-configured union mapping parameters, with an index range of... , , , as well as . Indicates the first The semantic position corresponding to the first In the use of the secondary channel, the first Scoring of candidate launch constellation sites; Indicates the first at the same time The first reflector unit adopts the... Scoring of each candidate phase state. Each dimension and physical channel uses the following numbering:

[0129] ;

[0130] Mapping The task should at least complete the fusion of multi-user semantic features and cascaded reflection channel estimates, the correlation calculation between different semantic locations, and the output of two discrete scoring tensors, but is not limited to the type of sequence calculation unit or feedforward calculation unit used internally. The candidate constellation index uses... Candidate phase index adopts Thus, they correspond one-to-one with discrete sets.

[0131] Send symbol branches within the candidate constellation index set Perform the maximum value decision to obtain the discrete constellation index. And directly mapped to power of Phase shift keying symbols:

[0132] ;

[0133] ;

[0134] ;

[0135] The phase configuration branch, for each reflection unit, configures the candidate phase index set within the set. Perform the maximum value decision to obtain the discrete phase index. and corresponding reflection coefficient:

[0136] ;

[0137] ;

[0138] The joint modulator is numbered according to the physical channel. ,Will Or send the corresponding constellation index to the sending end, and The data is sent to the programmable metasurface. Both decisions are made directly within a finite set, without generating continuously emitted symbols or requiring requantization of the continuous solutions during the online phase.

[0139] 4.4 Synchronous transmission processing performed by the transmitter and the programmable metasurface

[0140] The transmitting end writes discrete transmission symbols into the transmission buffer according to the channel usage number; the programmable metasurface writes the same symbols into the transmission buffer according to the channel usage number. Each discrete phase index is written to the configuration cache. Before the secondary channel is used, the programmable metasurface checks whether all phase indices belong to the coordinator's switching enable. Then, each reflection unit is addressed and switched to a specific state.

[0141] Once the programmable metasurface returns a ready signal, the coordinator triggers the transmitter to send a defined discrete symbol via a single radio frequency chain. The programmable metasurface remains active during the effective duration of the symbol. Unchanged. Multiple receivers simultaneously acquire the received signal, due to the cascading reflection channels of each user. Unlike other methods, the discrete transmit symbols and discrete phase configurations are jointly generated by the joint modulator based on multi-user semantic features and cascaded reflection channel estimates, thereby enabling each receiver to form reception features for reconstructing its own target private message.

[0142] 4.5 Mapping performed by the receiving end

[0143] No. Each receiver collects the received signal according to the channel usage number. Since each semantic unit corresponds to... The secondary channel is used, and the receiver will communicate with the primary channel. The received sample groups corresponding to each semantic unit are:

[0144] ;

[0145] The receiving end expands the real and imaginary parts of each group of complex received samples in a fixed order to obtain the received characteristics:

[0146] ;

[0147] All After arranging the received features according to their semantic positions, the first... Each receiving end calls a semantic reconstruction mapping with fixed parameters. Receive the corresponding private message:

[0148] ;

[0149] in, Indicates the first Reconstruction parameters pre-configured at each receiver. Mapping At a minimum, the system should complete received feature recovery, semantic location association, and semantic unit decision-making. For text messages, candidate lemma scores can be output and combined sequentially to form a reconstructed sentence; for other data types, the corresponding reconstructed semantic units can be output. Each receiver only uses its own received signal and its corresponding mapping, without needing to obtain other users' private messages or received samples.

[0150] Example 5: Complete Online Execution Sequence

[0151] step Coordinator initializes user IDs and discrete transmission constellations. Discrete Phase Codebook .

[0152] step The coordinator triggers the channel estimation phase by generating or retrieving samples according to the sampling number. A set of random discrete phase configurations is directly sent to the programmable metasurface in groups, and the transmitter is synchronously triggered to send fixed known pilots; the channel estimator records the phase configurations and the pilot observations fed back by each receiver, and constructs the configuration matrix and the pilot observation model.

[0153] step The channel estimator obtains respectively It sends the information to the channel state information sensing joint modulator and feeds back a completion signal to the coordinator.

[0154] step The sending end will Each private message to be transmitted is input into the semantic extractor; the semantic extractor performs separate operations on each message. Output .

[0155] step The channel state information-aware joint modulator constructs real-valued channel features and joint input features, and inputs the complete joint input sequence. Output the constellation score tensor and the metasurface phase score tensor.

[0156] step The channel state information-aware joint modulator performs discrete maximum value decision and generates... and The data is then written to the sender buffer and the programmable metasurface configuration buffer, respectively.

[0157] step The coordinator triggers the use of each channel sequentially; the programmable metasurface completes its operation first under the coordinator's switching enable. The system loads and returns a ready signal, after which the transmitter then sends a signal via a single radio frequency chain. .

[0158] step Each receiving end simultaneously collects received samples and constructs semantic unit-level received features.

[0159] step : No. Each receiving end executes Restore your own private messages It then sends a transmission completion status message back to the coordinator.

[0160] step If the channel estimation update cycle is reached, the pilot check error exceeds the threshold, or the user's location changes, the coordinator returns to step [step number]. Re-estimate the cascaded reflection channel; otherwise, return to step [step]. Continue transmitting the next set of multi-user private messages.

[0161] The following is a specific application example to help understand the implementation of the present invention.

[0162] Instance parameter settings:

[0163] Consider a scenario where a transmitter (e.g., a base station) simultaneously transmits private text messages to K=2 receivers (e.g., two user equipment units). The transmitter is configured with a single RF chain, and a programmable metasurface is deployed between the transmitter and receivers. Direct links between the transmitter and each receiver are disabled by buildings. The programmable metasurface contains N=64 reflective elements, and the phase state of each element is determined by B=3 control bits. Discrete phase codebook is The sending end uses a QPSK constellation, i.e. The transmit power P=1. Each semantic unit corresponds to Secondary channel usage: One transport block contains L=32 semantic units, and the total number of channel usages is T=128.

[0164] Channel estimation stage:

[0165] Coordinator establishes pilot sampling number ,make For each pilot sampling number, the coordinator independently and uniformly generates a phase configuration for 64 reflection units from the 8-PSK discrete phase codebook. The coordinator distributes the phase configurations to the programmable metasurface group by group and synchronously triggers the transmitter to send fixed known pilots. The two receivers measure the pilot received signals and feed them back to the channel estimator. The channel estimator constructs a 64×128 configuration matrix A and uses the cascaded reflection channel estimation vector formula to obtain the cascaded reflection channel estimation vectors for both users. .

[0166] Semantic feature extraction stage:

[0167] The sending end inputs two private text messages, one for each of the two users, into the semantic extractor. The semantic extractor performs lexical segmentation on each message, preserving the original word order, and uses a pre-trained Transformer encoder to generate an ordered compressed semantic feature sequence with 32 semantic positions. , .

[0168] Joint modulation stage:

[0169] The channel state information-aware joint modulator concatenates the channel estimation vectors of the two users. Expanding the real and imaginary parts, constructing real-valued channel features. (2 users × 64 reflection units × 2). At each semantic location, the semantic features of the two users are concatenated. Then concatenated with channel features to form Arrange the joint input features of all semantic locations as follows: .

[0170] Using pre-trained joint modulation mapping (Based on the Transformer architecture) Process V and output the constellation score tensor. and metasurface phase rating tensor .

[0171] For each channel use at each semantic location, at each of the four QPSK candidate constellation points. Perform the maximum value decision to obtain the corresponding QPSK symbol; for each reflection unit, perform the following checks on the eight candidate phase states: Perform the maximum value decision to obtain the corresponding phase index.

[0172] Synchronous transmission phase:

[0173] The joint modulator writes 128 QPSK symbols into the transmitter buffer and the corresponding 128 sets (64 symbols per set) of phase indices into the programmable metasurface configuration buffer. The coordinator triggers channel use sequentially: before each channel use begins, the programmable metasurface loads the corresponding phase configuration and feeds back a ready signal; the coordinator then triggers the transmitter to send the corresponding QPSK symbols via a single radio chain. Both users simultaneously receive the radio signal reflected by the programmable metasurface.

[0174] Semantic reconstruction stage:

[0175] Each user divides the 128 received samples into 32 groups of four, with each group corresponding to a semantic unit. The real and imaginary parts of each group of complex received samples are expanded into 8-dimensional real-valued received features. After arranging the 32 groups of received features according to their semantic positions, each user calls a pre-trained semantic reconstruction map. and (Based on the Transformer decoder structure), each private text message is reconstructed.

[0176] Due to the cascaded reflection channels of the two users and The two users have different characteristics, and the joint modulator generates common transmission symbols and metasurface phase configurations based on the semantic features of the two users and the cascaded reflection channel estimates. Therefore, the same transmission generates different received signal features at the two users. Each receiver reconstructs its own target private message accordingly, thereby realizing multi-user private semantic concurrent transmission under a single radio frequency chain.

[0177] The coordinator re-triggers the channel estimation step to update the cascaded reflection channel estimates for each user when one of the following occurs:

[0178] The channel estimation update period has arrived. The system can preset a time period. Every Time-initiated channel reassessment is triggered once.

[0179] The pilot verification error exceeds a preset threshold. The system can periodically insert verification pilots during data transmission. If the channel change calculated based on the verification pilot exceeds a preset threshold, channel re-estimation is triggered.

[0180] A change in user location has been detected. The system can detect changes in user location through location information or changes in received signal strength. When the change exceeds a preset threshold, channel re-estimation is triggered.

[0181] The aforementioned channel update mechanism ensures the system's adaptability to dynamic wireless environments and guarantees that the channel state information-aware joint modulator always performs joint modulation based on accurate cascaded reflection channel estimates.

[0182] The above description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technologies or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A single-RF chain multi-user private semantic multiplexing communication system based on a programmable metasurface, characterized in that, include: The transmitting end is configured with a single radio frequency chain to provide private messages corresponding to multiple receiving ends, and transmits wireless signals one by one according to the discrete transmit symbol sequence output by the channel state information sensing joint modulator during the multi-user semantic transmission phase. The programmable metasurface includes N controllable reflection units, which are used to receive random discrete phase configurations issued by the coordinator during the channel estimation phase, receive the discrete phase configuration sequence output by the channel state information sensing joint modulator during the multi-user semantic transmission phase, and complete phase switching under the timing enable of the coordinator, so that the transmitting end signal reaches multiple receiving ends via the cascaded reflection link between the transmitting end, the programmable metasurface and the receiving end. The coordinator is used to perform phase scheduling, phase control, and timing synchronization. During the channel estimation phase, a random discrete phase configuration is generated or read from the discrete phase codebook according to the pilot sampling number and sent to the programmable metasurface. At the same time, the transmitter is triggered to send pilots and notify the channel estimator to record the current phase configuration. During the multi-user semantic transmission phase, the transmitter and the programmable metasurface are synchronously enabled according to the channel state information to sense the discrete transmit symbol sequence and discrete phase configuration sequence output by the joint modulator. The channel estimator is used to receive multiple sets of random phase configurations provided by the coordinator and pilot observations fed back by each receiver, construct a phase configuration matrix and obtain the cascaded reflection channel estimation vector of each user by solving the pseudo-inverse least squares problem, and send it to the channel state information sensing joint modulator. A semantic extractor is used to utilize pre-configured semantic extraction maps. Each user's private messages are converted into an ordered compressed semantic feature sequence and sent to the channel state information-aware joint modulator. Channel state information-aware joint modulator, used to utilize pre-configured joint modulation maps By fusing multi-user semantic features with cascaded reflection channel estimates, a common transmitted symbol and the phase state of each reflection unit are determined and output from the finite discrete transmit constellation and the finite discrete phase codebook in each channel use, generating a discrete transmit symbol sequence and a discrete phase configuration sequence. Multiple receivers, the k-th receiver is used to receive the wireless signal reflected by the programmable metasurface and collect the received samples, utilizing a pre-configured semantic reconstruction map. The private message corresponding to the receiving end is recovered from the received sample; wherein the direct link between the sending end and each receiving end is blocked or attenuated to the point of being unusable, and the wireless transmission is completed via a cascaded reflection link consisting of the sending end, the programmable metasurface and the receiving end, k=1,2,...,K, where K is the total number of receiving ends.

2. The single-RF chain multi-user private semantic multiplexing communication system based on a programmable metasurface according to claim 1, characterized in that, The channel estimator is configured as follows: Will Constructing a configuration matrix by arranging the group of random discrete phase configurations in columns. The pilot received signals from each receiver are stacked together. , and in accordance with The cascaded reflection channel estimation vector of the k-th receiver is obtained, where express The Moore-Penrose pseudoinverse, where P is the transmit power.

3. The single-RF chain multi-user private semantic multiplexing communication system based on a programmable metasurface according to claim 1, characterized in that, The semantic extractor is configured as follows: The currently pending private messages from the k-th receiving end are sorted according to message type. Divided into L semantic units that maintain their original order, and using a pre-configured semantic extraction mapping with fixed parameters. Generate an ordered compressed semantic feature sequence: ； ； in, This indicates pre-configured mapping parameters. Indicates the first Compression features of semantic units For feature dimensions; The mapping At least the following steps should be completed: semantic unit numeration, sequential information combination, context association, and dimensional compression.

4. The single-RF chain multi-user private semantic multiplexing communication system based on a programmable metasurface according to claim 1, characterized in that, The channel state information-aware joint modulator is configured as follows: The real and imaginary parts of the cascaded reflection channel estimation vectors for all users are expanded according to a fixed user order to construct real-valued channel features. ; In the Each semantic location will be all The semantic features of each user at this location are concatenated as follows: Then, it is concatenated with the real-valued channel features to form joint input features. Arrange the joint input features of all L semantic positions as follows: ; Using pre-configured and fixed-parameter joint modulation mapping right Process the data and output the constellation rating tensor. and metasurface phase rating tensor ; Perform a maximum value decision on the transmitted constellation score tensor within the candidate constellation index set to obtain the discrete constellation index. And directly mapped to public emission symbols. ,in ; For each reflection unit, a maximum value decision is performed on the metasurface phase score tensor within the candidate phase index set to obtain a discrete phase index. Mapped to reflection coefficient .

5. The single-RF chain multi-user private semantic multiplexing communication system based on a programmable metasurface according to claim 1, characterized in that, The discrete emission symbols are from a finite phase-shift keying constellation. The reflection coefficients of each reflection unit in the discrete phase configuration are selected from the discrete reflection coefficient codebook. Selected from, ,in B is the number of control bits for each reflection unit; The discrete transmission symbol sequence Satisfying the average transmit power constraint ,in , which represents the total number of channel uses for a transport block.

6. The single-RF chain multi-user private semantic multiplexing communication system based on a programmable metasurface according to claim 1, characterized in that, The coordinator is configured as follows: During the channel estimation phase, the random discrete phase configuration is directly sent to the programmable metasurface in groups, and the same configuration is provided to the channel estimator. During the multi-user semantic transmission phase, each symbol or corresponding constellation index in the discrete transmit symbol sequence output by the channel state information sensing joint modulator is sent to the transmit buffer of the transmitter, and each phase index in the discrete phase configuration sequence is sent to the configuration buffer of the programmable metasurface. Before the start of the t-th channel use, a switching enable signal is sent to the programmable metasurface, and upon receiving the ready signal returned by the programmable metasurface, the transmitter is triggered to send the corresponding common transmission symbol through the single radio frequency chain. The programmable metasurface maintains the corresponding discrete phase configuration during the effective duration of the common transmission symbol. constant.

7. The single-RF chain multi-user private semantic multiplexing communication system based on a programmable metasurface according to claim 1, characterized in that, The kth receiver is configured as follows: Collect received samples according to channel usage number , corresponding to each semantic unit The next batch of received samples is The real and imaginary parts of each group of complex received samples are expanded in a fixed order to obtain the received features. ; Arrange all L groups of received features according to their semantic position. Utilizing pre-configured semantic reconstruction mappings with fixed parameters Obtain the reconstructed private message ,in Pre-configured reconfiguration parameters for the k-th receiver; The mapping At least the received feature recovery, semantic location association, and semantic unit decision processing should be completed.

8. The single-RF chain multi-user private semantic multiplexing communication system based on a programmable metasurface according to any one of claims 1-7, characterized in that, The coordinator is also configured to re-trigger the channel estimation phase to update the cascaded reflection channel estimates for each user when the channel estimation update period arrives, the pilot check error exceeds a preset threshold, or a change in user location is detected.

9. A single-RF chain multi-user private semantic multiplexing communication method based on a programmable metasurface, applied to the single-RF chain multi-user private semantic multiplexing communication system based on a programmable metasurface as described in any one of claims 1-8, characterized in that, Includes the following steps: In the channel estimation step, the coordinator triggers the system to enter the channel estimation phase. According to the pilot sampling number, it generates or reads multiple sets of random discrete phase configurations from the discrete phase codebook. The random discrete phase configurations are provided to the programmable metasurface and the channel estimator respectively, and the transmitter is synchronously triggered to send fixed known pilots. Each receiver measures and feeds back the corresponding pilot received signal. The channel estimator obtains the cascaded reflection channel estimate value of each user by solving the pseudo-inverse least squares problem based on the random discrete phase configuration and the pilot received signal. In the semantic feature extraction step, the semantic extractor acquires private messages corresponding to multiple receivers and utilizes pre-configured semantic extraction mappings. Each of the aforementioned private messages is converted into an ordered compressed semantic feature sequence; In the joint modulation step, the channel state information-aware joint modulator acquires the cascaded reflection channel estimates and the ordered compressed semantic feature sequences of each user, and utilizes a pre-configured joint modulation map. The multi-user semantic features are fused with the cascaded reflection channel estimate. In each channel use, a common transmission symbol is decided and output from the finite discrete transmission constellation, and the phase state of each reflection unit is decided and output from the finite discrete phase codebook, generating a discrete transmission symbol sequence and a discrete phase configuration sequence. In the synchronous transmission step, the coordinator controls the programmable metasurface to switch sequentially according to the phase configuration in the discrete phase configuration sequence based on the discrete transmission symbol sequence and the discrete phase configuration sequence, and triggers the transmitter to transmit the corresponding common transmission symbol in the discrete transmission symbol sequence through a single radio frequency chain after each phase configuration takes effect; In the semantic reconstruction step, the k-th receiver receives the wireless signal reflected by the programmable metasurface and collects the received samples, utilizing a pre-configured semantic reconstruction map. Recover the private message corresponding to the receiving end from the received sample; In this configuration, the direct links between the transmitter and each receiver are blocked or attenuated to the point of being unusable. Wireless transmission is completed via a cascaded reflection link consisting of the transmitter, the programmable metasurface, and the receiver, where k = 1, 2, ..., K, and K is the total number of receivers.

10. The single-RF chain multi-user private semantic multiplexing communication method based on a programmable metasurface according to claim 9, characterized in that, In the channel estimation step: The coordinator establishes pilot sampling numbers. For each pilot sampling number, a set of random discrete phase configurations is generated or read from the discrete phase codebook. The reflection coefficient of each reflecting unit is derived from the discrete phase codebook. Selected independently and evenly; The transmitting end transmits fixed, known pilot signals at each pilot sampling time. ; The channel estimator will Constructing a configuration matrix by arranging the group of random discrete phase configurations in columns. The pilot received signals from each receiver are stacked together. ,according to The cascaded reflection channel estimation vector of the k-th receiver is obtained, where, express The Moore-Penrose pseudo-rebel.

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