OFDM coexistence wireless communication transceiving method for coping with symbol asynchronous situation

Abstract

The present application belongs to the technical field of wireless communication, and discloses an OFDM coexistence wireless communication transceiving method for coping with symbol non-synchronization. The present application provides an OFDM coexistence wireless communication transceiving method for coping with symbol non-synchronization, including system composition structure, working principle, non-synchronization secondary signal arrival detection, and synchronization error blind estimation method. By using the empty sub-carrier in the main system OFDM signal, CRx can detect whether there is non-synchronization secondary signal component in the received signal, and then estimate the symbol synchronization error by finding the best compensation value to make the signal energy on the empty sub-carrier minimum, and further jointly demodulate the primary and secondary signals. Through the simulation results, the effectiveness of the sub-methods involved in the present application is verified, and it is verified that the present application can greatly improve the bit error rate performance of the OFDM coexistence wireless communication system under the condition of symbol non-synchronization.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, and particularly relates to an OFDM co-current wireless communication transceiver method for dealing with symbol asynchrony. Background Technology

[0002] Symbiotic Radio (SR) is a novel wireless communication technology based on cognitive radio and cooperative environmental backscatter communication, boasting extremely high energy efficiency, high spectral efficiency, and high cost efficiency, making it particularly suitable for Internet of Things (IoT) applications. A SR system consists of a primary system and a secondary system. The primary system typically utilizes active communication devices for data transmission; in the secondary system, the secondary transmitter (STx) is usually a passive device with a simple circuit structure, capable of data acquisition, storage, and backscatter transmission, at a significantly lower cost than active communication devices. Specifically, the STx uses the received radio frequency signal from the primary system as a carrier and modulates its own information onto this signal by changing the antenna's load impedance, transmitting it to the receiver via backscatter. Simultaneously, since the signal reflected by the secondary system contains components of the primary signal, it can serve as a beneficial multipath signal to enhance the transmission of the primary signal in the primary system.

[0003] On the other hand, Orthogonal Frequency Division Multiplexing (OFDM) technology, as a multi-carrier transmission technology, divides an entire spectrum into multiple mutually orthogonal subcarriers, converting high-speed data signals into multiple parallel low-speed sub-data streams for modulation and transmission. Since the signal bandwidth on each sub-channel is less than the channel coherence bandwidth, each sub-channel can be considered a flat fading channel, thereby eliminating inter-symbol interference. OFDM technology has been adopted by various wireless communication standards, including IEEE 802.11a for wireless local area networks, 4G LTE, and 5G NR. Co-existing wireless communication can utilize various widely distributed OFDM systems in the environment as its main system component, which can not only promote the deployment and implementation of large-scale IoT communication but also assist high-speed mobile communication networks in achieving further performance improvements. To achieve correct demodulation of primary and secondary signals at the receiver, the primary system symbols and secondary system symbols need to be synchronized in the time domain. However, perfect symbol synchronization is difficult to achieve in practice. This invention proposes a corresponding transceiver method for such situations.

[0004] Existing technology: Traditional OFDM coexisting wireless communication system

[0005] 1) Technical Description:

[0006] In a traditional OFDM (Orthogonal Frequency Division Multiplexing) coexisting wireless communication system, there are a primary system and a secondary system. The primary system uses multiple orthogonal subcarriers to transmit data simultaneously to improve spectral efficiency and reduce signal interference; the secondary system modulates the signal onto the primary system signal in the environment and backscatters it to the receiver.

[0007] Such systems typically operate in a synchronous communication environment, where clock synchronization and symbol alignment between the primary and secondary signals are crucial for effective communication.

[0008] 2) Technical problems existing in the current technology:

[0009] Symbol asynchrony problem: In dynamic and complex wireless communication environments, traditional OFDM co-current wireless communication systems face the problem of symbol asynchrony. This asynchrony leads to interference between signals, affecting the quality and stability of communication.

[0010] Limitations of a single communication environment: Traditional OFDM system design does not fully consider environments with multiple users and multiple service providers coexisting. For example, in smart city or industrial IoT scenarios, multiple wireless devices and services coexist, requiring more flexible and robust communication solutions.

[0011] Resource allocation problem: In multi-user environments, effectively allocating limited radio resources (such as subcarriers) is a challenge. Traditional OFDM systems cannot effectively handle this resource contention, leading to decreased communication efficiency.

[0012] In summary, traditional OFDM co-current wireless communication systems face challenges in complex environments with symbol asynchrony. These challenges require solutions using more advanced technologies and algorithms to improve the adaptability, efficiency, and stability of communication systems. Summary of the Invention

[0013] To address the problems existing in the prior art, this invention provides an OFDM co-current wireless communication transceiver method for dealing with symbol asynchrony.

[0014] This invention is implemented as follows: an OFDM co-current wireless communication transceiver method for handling symbol asynchrony includes:

[0015] Step 1: In the main system transmission, the total number of OFDM subcarriers is N, including D data subcarriers carrying modulated signals, and the remaining V = N – D subcarriers are empty subcarriers that do not carry signals;

[0016] Step 2, during the transmission of the secondary system, after STx senses the signal sent by PTx, STx can choose to remain unchanged or send the secondary signal by backscattering the main signal.

[0017] Step 3: Based on the received signal, CRx further detects whether there are asynchronous secondary signals included in the received signal.

[0018] Step four: When CRx detects that the asynchronous secondary signal is contained in the received signal, it further estimates the symbol synchronization error and uses the estimation result to jointly demodulate the primary and secondary signals.

[0019] Furthermore, in the main system transmission, the total number of OFDM subcarriers is N, including D data subcarriers carrying modulated signals, and the remaining V = N – D subcarriers are empty subcarriers that do not carry signals.

[0020] Define the p-th main signal block to be sent at PTx as follows:

[0021] s(p)=[s(pD),...,s(pD+D-1)] T ,

[0022] Define the index of the data subcarrier as k1<… <k D and define the matrix First, after the Inverse Discrete Fourier Transform (IDFT), the main signal block in the time domain is... Where F N Let be an N-point Fourier transform matrix; further, after adding a cyclic prefix (CP) before the signal block, PTx sends out the signal; where the length of CP is defined as N. cp The OFDM symbol period is N t =N cp +N.

[0023] Furthermore, during the transmission of the secondary system, after STx senses the signal sent by PTx, STx can choose to remain unchanged or send the secondary signal by backscattering the main signal:

[0024] Without STx sending the secondary signal, the time-domain signal received at CRx after removing CP is:

[0025]

[0026] Where Hd is the cyclic matrix composed of the impulse response hd of the PTx-CRx link channel, Hr is the cyclic matrix composed of the impulse response hr of the PTx-STx-CRx link channel, and u(p) is additive white Gaussian noise (AWGN).

[0027] When STx transmits a secondary signal, the transmitted secondary signal is a BPSK signal, i.e., c(p)∈{-1,+1}, and its period is equal to the period of the primary system OFDM symbol; the synchronization error between the primary system OFDM symbol and the secondary signal is... Furthermore, for the p-th OFDM symbol, the signal transmitted by STx is consider For case 1, This is case 2; in case 1, after removing CP, the time-domain signal received at CRx is...

[0028]

[0029] The primary and secondary signals can be demodulated using traditional methods; in case 2, the time-domain signal received at CRx is

[0030]

[0031] Where diag(a) represents a diagonal matrix with elements of vector a as diagonal elements.

[0032] Furthermore, based on the received signal described above, CRx further detects whether there are asynchronous secondary signals included in the received signal:

[0033] When STx does not transmit a secondary signal or when STx transmits a secondary signal and belongs to case 1, the received signal on the empty subcarrier only contains AWGN; when STx transmits a secondary signal and belongs to case 2, the received signal on the empty subcarrier includes inter-carrier interference (ICI) and AWGN.

[0034] Furthermore, the detection method:

[0035] Therefore, the presence of asynchronous secondary signals in the received signal can be determined by the following energy detection:

[0036]

[0037] Where, σ 2 γ is the AWGN power, and γ is a given threshold.

[0038] After CRx detects the arrival of the asynchronous secondary signal, it minimizes the signal energy on the empty subcarrier by compensating the received signal y(p) in the time domain, thereby estimating the symbol synchronization error; the compensation matrix is ​​defined as Λ(t)=diag([-1 1×t ,1 1×(N-t) The cost function is:

[0039]

[0040] in, It is the index of the empty subcarrier. The symbol synchronization error can be estimated by performing a one-dimensional search on t.

[0041]

[0042] After estimating the symbol synchronization error, the primary and secondary signals can be detected using the ML criterion, which can be expressed as follows:

[0043]

[0044] in, The demodulation result of s(p) This is the demodulation result of c(p).

[0045] The present invention also provides an OFDM coexisting wireless communication system, characterized in that it comprises:

[0046] The main system transmitter (PTx) is equipped with an OFDM transmitter for generating and transmitting OFDM signals containing data subcarriers;

[0047] The secondary system transmitter (STx) is equipped with a sensing module and a BPSK modulator, which is used to sense the primary system signal and transmit the secondary signal as needed;

[0048] The receiver (CRx), equipped with a receiver module, mixer, and digital signal processor (DSP), is used to receive and process signals from the PTx and STx;

[0049] The signal processing module includes algorithms for performing time-domain signal compensation, energy detection, synchronization error estimation, and signal demodulation.

[0050] The main system transmitter (PTx) can dynamically adjust the number and allocation of OFDM subcarriers according to preset parameters to optimize spectrum utilization;

[0051] The secondary system transmitter (STx) has adaptive modulation capability, which can automatically select the optimal transmission strategy based on the status of the primary system and channel conditions;

[0052] The receiver (CRx) has high-sensitivity reception capabilities and can operate stably in complex wireless communication environments.

[0053] The system's signal processing module employs advanced algorithms to accurately estimate and compensate for time deviations in cases of symbol asynchrony;

[0054] The system can effectively separate and demodulate primary and secondary signals in the presence of symbol asynchrony, ensuring the accuracy and stability of data transmission.

[0055] The system features a modular design, making it easy to expand and upgrade, and adaptable to different communication needs and technological evolution.

[0056] The system includes intelligent management software for data acquisition, analysis, and optimization to improve overall system performance and user experience.

[0057] Based on the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solution to be protected by this invention are as follows:

[0058] First, the main content of this invention is to propose an OFDM co-occurrence wireless communication transceiver method to address symbol asynchrony, involving system composition, working principle, asynchronous secondary signal arrival detection, and a blind estimation method for synchronization errors. The basic working principle of the OFDM co-occurrence wireless communication transceiver method to address symbol asynchrony is as follows: PTx uses Orthogonal Frequency Division Multiplexing (OFDM) technology to modulate information and transmits OFDM signals through an active radio frequency link, transmitting main information with CRx. On the other hand, after detecting the main signal from PTx, STx periodically switches its antenna impedance, modulating secondary information onto the incident signal from PTx and backscattering it to CRx, thereby achieving secondary information transmission. Due to the limited signal processing capability of STx, it is difficult to align the secondary system symbols with the main system symbols. In this scenario, the CRx can utilize the empty subcarrier structure in the primary system's OFDM signal to aid in the joint demodulation of primary and secondary signals. First, the CRx determines whether the received signal energy on the empty subcarrier exceeds a specific threshold, thus detecting the presence of asynchronous secondary signal components in the CRx's received signal. If detected, the CRx then performs time-domain compensation on the received signal to find the optimal compensation value that minimizes the signal energy on the empty subcarrier, thereby estimating the symbol synchronization error and assisting in the joint demodulation of primary and secondary signals. The method proposed in this invention can significantly improve the bit error rate performance of primary and secondary signal demodulation in OFDM co-existing wireless communication systems under symbol synchronization conditions.

[0059] Second, this invention proposes an OFDM co-current wireless communication transceiver method to address symbol asynchrony, including system structure, working principle, asynchronous secondary signal arrival detection, and a blind estimation method for synchronization error. First, this invention proposes that, using the empty subcarrier in the OFDM signal of the main system, CRx can detect the presence of asynchronous secondary signal components in the received signal; then, by finding the optimal compensation value to minimize the signal energy on the empty subcarrier, the symbol synchronization error is estimated; finally, the estimated symbol synchronization error is used to jointly demodulate the main and secondary signals. Simulation results verify the effectiveness of the proposed method and demonstrate that this invention can significantly improve the demodulation bit error rate performance of the main and secondary signals in OFDM co-current wireless communication systems under symbol asynchrony. From a practical application perspective, this invention can effectively promote the performance improvement of high-speed mobile communication and high spectral efficiency and high energy efficiency low-speed IoT communication, possessing significant application value and development potential.

[0060] Third, the technical solution of this invention fills a technical gap in the industry both at home and abroad: In response to the unresolved problem of signal reception performance degradation caused by symbol asynchrony in co-existing wireless communication, this invention proposes a solution based on blind parameter estimation and signal compensation, which can effectively improve the signal reception and demodulation performance under symbol asynchrony.

[0061] Fourth, this invention proposes an OFDM co-current wireless communication transceiver method to address symbol asynchrony, and its main technical advancements and advantages are as follows:

[0062] 1) Multi-scenario adaptability: This method can effectively handle symbol asynchrony between primary and secondary systems and is applicable to various wireless communication scenarios, especially in complex wireless communication environments such as cities and mountainous areas, which can improve communication reliability.

[0063] 2) Improve signal utilization efficiency: By embedding the signal of the secondary system into the empty subcarriers of the primary system, this method improves the utilization efficiency of the signal spectrum. This method is particularly suitable for communication environments with limited spectrum resources.

[0064] 3) Reduce interference and improve accuracy: In the case of symbol asynchrony, the method of the present invention can reduce inter-carrier interference (ICI) through energy detection and time-domain signal compensation, thereby improving the accuracy and reliability of the signal.

[0065] 4) Stability in complex environments: This method can work stably in complex wireless communication environments, and can effectively detect and compensate for time synchronization errors even in the presence of such errors.

[0066] 5) Adaptability and flexibility: Through dynamic energy detection and symbol synchronization error estimation, the method of the present invention can adapt to different communication conditions and environments, providing greater flexibility and adaptability.

[0067] The method of the present invention has achieved significant technical progress in solving the symbol asynchrony problem in the prior art and improving communication efficiency and stability. Attached Figure Description

[0068] Figure 1 This is a flowchart of an OFDM co-current wireless communication transceiver method for dealing with symbol asynchrony provided in an embodiment of the present invention.

[0069] Figure 2 This is a schematic diagram of the system composition provided in an embodiment of the present invention.

[0070] Figure 3 This is a diagram of the primary and secondary signal structure under symbol asynchronous conditions provided in an embodiment of the present invention. Detailed Implementation

[0071] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0072] Example 1: OFDM Co-current Wireless Communication System in Urban Environment

[0073] Scenario: In an urban environment, multiple users communicate using different wireless devices (such as smartphones and laptops). These devices are all equipped with wireless communication modules that support OFDM technology.

[0074] System Configuration:

[0075] Main system transmitter (PTx): Equipped with an OFDM transmitter, capable of dynamically adjusting the number and allocation of data subcarriers according to user needs and network conditions.

[0076] Subsystem transmitter (STx): Equipped with an intelligent sensing module, it can sense the signal status of the main system and send sub-signals at appropriate times.

[0077] Receiver (CRx): Equipped with a high-sensitivity receiver module, it can stably receive signals from PTx and STx in urban environments.

[0078] Implementation plan:

[0079] When users conduct data communication, PTx sends OFDM signals based on the current network conditions.

[0080] After STx senses the signal from PTx, it decides whether to send the signal based on network load and channel conditions.

[0081] The signals received by the CRx are processed by a digital signal processor (DSP), which uses advanced algorithms to compensate for time delays and demodulate the signals.

[0082] Example 2: OFDM co-current wireless communication in a suburban wireless monitoring system

[0083] Scenario setting: In the suburbs, multiple wireless surveillance cameras are deployed, and these cameras transmit data via OFDM technology.

[0084] System Configuration:

[0085] Main system transmitter (PTx): Located in the monitoring center, it is responsible for sending control signals and receiving monitoring data.

[0086] Subsystem transmitter (STx): Located at each surveillance camera, it is able to send surveillance data after detecting the PTx signal.

[0087] Receiver (CRx): Located in the monitoring center, it is used to receive data from surveillance cameras.

[0088] Implementation plan:

[0089] The monitoring center's PTx sends control signals to direct each surveillance camera to collect data.

[0090] After each camera's STx detects the control signal, it begins sending monitoring data.

[0091] After receiving the monitoring data, the CRx in the monitoring center processes it through the DSP to monitor the situation in the suburbs in real time.

[0092] In both embodiments, the OFDM co-current wireless communication system can effectively provide stable and efficient data transmission in different environments and application scenarios, while also handling symbol asynchrony issues in complex communication environments. For example... Figure 1 As shown, the OFDM co-current wireless communication transceiver method for dealing with symbol asynchrony provided by the present invention includes the following steps:

[0093] S101, In the main system transmission, the total number of OFDM subcarriers is N, including D data subcarriers that carry modulated signals, and the remaining V = N – D subcarriers are empty subcarriers that do not carry signals;

[0094] S102, In the secondary system transmission, after STx senses the signal sent by PTx, STx can choose to remain unchanged or send the secondary signal;

[0095] S103, based on the received signal, CRx further detects whether there is an asynchronous secondary signal included in the received signal.

[0096] like Figure 2 As shown, an OFDM co-current wireless communication transceiver system for dealing with symbol asynchrony consists of a single-antenna user equipment (UE), a base station (BS) with K antennas, and an active amplified smart surface with M reflective elements.

[0097] In the main system transmission provided by this invention, the total number of OFDM subcarriers is N, including D data subcarriers carrying modulated signals, and the remaining V = N – D subcarriers are empty subcarriers that do not carry signals.

[0098] Define the p-th main signal block to be sent at PTx as follows:

[0099] s(p)=[s(pD),...,s(pD+D-1)] T ,

[0100] Define the index of the data subcarrier as k1<… <k D and define the matrix First, after the Inverse Discrete Fourier Transform (IDFT), the main signal block in the time domain is... Where F N Let be an N-point Fourier transform matrix; further, after adding a cyclic prefix (CP) before the signal block, PTx sends out the signal; where the length of CP is defined as N. cp The OFDM symbol period is N t =N cp +N.

[0101] In the secondary system transmission provided by this invention, after STx senses the signal sent by PTx, STx can choose to remain unchanged or send the secondary signal:

[0102] Without STx sending the secondary signal, the time-domain signal received at CRx after removing CP is:

[0103]

[0104] Where Hd is the cyclic matrix composed of the impulse response hd of the PTx-CRx link channel, Hr is the cyclic matrix composed of the impulse response hr of the PTx-STx-CRx link channel, and u(p) is additive white Gaussian noise (AWGN).

[0105] When STx transmits a secondary signal, the transmitted secondary signal is a BPSK signal, i.e., c(p)∈{-1,+1}, and its period is equal to the OFDM symbol period of the main system; for example Figure 3 As shown, the synchronization error between the primary system OFDM symbols and the secondary signals is... Furthermore, for the p-th OFDM symbol, the signal transmitted by STx is consider For case 1, This is case 2; in case 1, after removing CP, the time-domain signal received at CRx is...

[0106]

[0107] The primary and secondary signals can be demodulated using traditional methods; in case 2, the time-domain signal received at CRx is

[0108]

[0109] Where diag(a) represents a diagonal matrix with elements of vector a as diagonal elements.

[0110] Based on the received signal described above, the present invention provides that CRx further detects whether there is an asynchronous secondary signal included in the received signal:

[0111] When STx does not transmit a secondary signal or when STx transmits a secondary signal and belongs to case 1, the received signal on the empty subcarrier only contains AWGN; when STx transmits a secondary signal and belongs to case 2, the received signal on the empty subcarrier includes inter-carrier interference (ICI) and AWGN.

[0112] The detection method provided by this invention:

[0113] Therefore, the presence of asynchronous secondary signals in the received signal can be determined by the following energy detection:

[0114]

[0115] Where, σ 2 γ is the AWGN power, and γ is a given threshold.

[0116] After CRx detects the arrival of the asynchronous secondary signal, it minimizes the signal energy on the empty subcarrier by compensating the received signal y(p) in the time domain, thereby estimating the symbol synchronization error; the compensation matrix is ​​defined as Λ(t)=diag([-1 1×t ,1 1×(N-t) The cost function is:

[0117]

[0118] in, It is the index of the empty subcarrier. The symbol synchronization error can be estimated by performing a one-dimensional search on t.

[0119]

[0120] After estimating the symbol synchronization error, the primary and secondary signals can be detected using the ML criterion, which can be expressed as follows:

[0121]

[0122] in, The demodulation result of s(p) This is the demodulation result of c(p).

[0123] This invention proposes an OFDM co-current wireless communication transceiver method to address symbol asynchrony, including system structure, working principle, asynchronous secondary signal arrival detection, and a blind estimation method for synchronization error. Utilizing the empty subcarrier in the primary system's OFDM signal, CRx can detect the presence of asynchronous secondary signal components in the received signal. Then, by finding the optimal compensation value to minimize the signal energy on the empty subcarrier, the symbol synchronization error is estimated, and further, the primary and secondary signals are jointly demodulated. Simulation results verify the effectiveness of the sub-methods involved in this invention and demonstrate that this invention can significantly improve the bit error rate performance of OFDM co-current wireless communication systems under symbol asynchrony. From a practical application perspective, this invention can effectively promote the performance improvement of high-speed mobile communication and high-spectral-efficiency, high-energy-efficiency low-speed IoT communication, possessing significant application value and development potential.

[0124] It should be noted that embodiments of the present invention can be implemented in hardware, software, or a combination of both. The hardware portion can be implemented using dedicated logic; the software portion can be stored in memory and executed by a suitable instruction execution system, such as a microprocessor or dedicated-design hardware. Those skilled in the art will understand that the above-described devices and methods can be implemented using computer-executable instructions and / or included in processor control code, for example, such code provided on a carrier medium such as a disk, CD, or DVD-ROM, a programmable memory such as read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented by hardware circuitry such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field-programmable gate arrays, programmable logic devices, etc., or by software executed by various types of processors, or by a combination of the above-described hardware circuitry and software, such as firmware.

[0125] The beneficial effects of the present invention will be verified through simulation below. The simulation parameters are set as follows: the OFDM subcarrier allocation scheme is configured according to IEEE 802.11a, N=64, D=52, V=12. The direct link between PTx and CRx is blocked, the channel between PTx and STx is a multipath channel, and the channel between STx and CRx is a single-path channel.

[0126] The effectiveness of the asynchronous secondary signal arrival detection algorithm proposed in this invention is demonstrated; furthermore, the detection performance improves with increasing received signal-to-noise ratio (SNR). The symbol synchronization error estimation method proposed in this invention can make the probability of correct estimation approach 1 when the received SNR is greater than 4 dB. The reference baseline curves include STx without transmitting a secondary signal, STx transmitting a secondary signal and belonging to case 1, and STx transmitting a secondary signal and belonging to case 2 (without using the method proposed in this invention). First, the performance of STx without transmitting a signal and STx transmitting a signal and belonging to case 1 represents the upper bound of the main signal bit error rate performance under the current parameter settings. In case 2, the method proposed in this invention can completely restore the main signal bit error rate to normal performance (i.e., the upper bound of performance); on the other hand, compared with the condition without using the method proposed in this invention, the method proposed in this invention can greatly improve the secondary signal bit error rate performance.

[0127] This invention proposes an OFDM co-current wireless communication transceiver method to address symbol asynchrony, including system structure, working principle, asynchronous secondary signal arrival detection, and a blind estimation method for synchronization error. Utilizing the empty subcarrier in the primary system's OFDM signal, CRx can detect the presence of asynchronous secondary signal components in the received signal. Then, by finding the optimal compensation value to minimize the signal energy on the empty subcarrier, the symbol synchronization error is estimated, and further, the primary and secondary signals are jointly demodulated. Simulation results verify the effectiveness of the sub-methods involved in this invention and demonstrate that this invention can significantly improve the bit error rate performance of OFDM co-current wireless communication systems under symbol asynchrony. From a practical application perspective, this invention can effectively promote the performance improvement of high-speed mobile communication and high-spectral-efficiency, high-energy-efficiency low-speed IoT communication, possessing significant application value and development potential.

[0128] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for OFDM co-current wireless communication transceiver to address symbol asynchrony, characterized in that, Includes the following steps: Step 1: In the main system transmission, the total number of OFDM subcarriers is N, including D data subcarriers carrying modulated signals, and the remaining V = N – D subcarriers are empty subcarriers that do not carry signals. Step 2, during the secondary system transmission, after the secondary system transmitter STx senses the signal sent by the main system transmitter PTx, STx chooses to either remain unchanged or send the secondary signal. Step 3: Based on the received signal, the receiver CRx further detects whether there are asynchronous secondary signals included in the received signal; In the main system transmission, the total number of OFDM subcarriers is N, including D data subcarriers carrying modulated signals, and the remaining V = N – D subcarriers are empty subcarriers that do not carry signals. Define the p-th main signal block to be sent at PTx as follows: ， Define the index of the data subcarrier as and define the matrix First, after the Inverse Discrete Fourier Transform (IDFT), the main signal block in the time domain is... ,in Let be an N-point Fourier transform matrix; after adding a cyclic prefix (CP) before the signal block, PTx will send the signal; where the length of CP is defined as... OFDM symbol period is ; Based on the received signal, CRx further detects whether there are asynchronous secondary signals contained in the received signal: When STx does not transmit the secondary signal or when STx transmits the secondary signal and falls under case 1, the received signal on the empty subcarrier only contains AWGN; when STx transmits the secondary signal and falls under case 2, the received signal on the empty subcarrier includes inter-carrier interference (ICI) and AWGN; the synchronization error between the master system OFDM symbol and the secondary signal is... ;consider For case 1, Case 2; The detection method described: The presence of asynchronous secondary signals in the received signal is determined by the following energy detection: ， in, For AWGN power, Given a threshold; After CRx detects the arrival of the asynchronous secondary signal, it minimizes the signal energy on the empty subcarrier by compensating the received signal y(p) in the time domain, thus estimating the symbol synchronization error; the compensation matrix is ​​defined as follows. The cost function is ； in, It is the index of the empty subcarrier. The symbol synchronization error can be estimated by performing a one-dimensional search on t. After estimating the symbol synchronization error, the primary and secondary signals can be detected using the ML criterion, which can be expressed as follows: ， in, for The demodulation results, for The demodulation results, is the secondary signal transmitted by STx; Hd is the cyclic matrix composed of the impulse response hd of the PTx-CRx link channel, and Hr is the cyclic matrix composed of the impulse response hr of the PTx-STx-CRx link channel.

2. The OFDM co-current wireless communication transceiver method for handling symbol asynchrony as described in claim 1, characterized in that, In the secondary system transmission, after STx senses the signal sent by PTx, STx can choose to remain unchanged or send the secondary signal: Without STx sending the secondary signal, the time-domain signal received at CRx after removing CP is: ， Where u(p) is additive white Gaussian noise (AWGN); When STx transmits a secondary signal, the transmitted secondary signal is a BPSK signal, that is... Its period is equal to the OFDM symbol period of the main system; therefore, for the p-th OFDM symbol, the secondary signal transmitted by STx is In case 1, after removing CP, the time-domain signal received at CRx is: ， The primary and secondary signals can be demodulated using traditional methods; in case 2, the time-domain signal received at CRx is ， Where diag(a) represents a diagonal matrix with elements of vector a as diagonal elements. , .

3. An OFDM co-current wireless communication transceiver system for implementing the OFDM co-current wireless communication transceiver method for handling symbol asynchrony as described in claim 1, characterized in that, The system consists of a user with a single antenna, a base station with K antennas, and an active amplified smart surface with M reflective elements.

4. The OFDM coexisting wireless communication transceiver system as described in claim 3, characterized in that, Also includes: The main system transmitter is equipped with an OFDM transmitter for generating and transmitting OFDM signals containing data subcarriers; The secondary system transmitter is equipped with a sensing module and a BPSK modulator, which is used to sense the main system signal and send the secondary signal as needed. The receiver, equipped with a receiver module, mixer and digital signal processor (DSP), is used to receive and process signals from PTx and STx; The signal processing module includes algorithms for performing time-domain signal compensation, energy detection, synchronization error estimation, and signal demodulation.

5. The OFDM coexisting wireless communication transceiver system as described in claim 4, characterized in that, The main system transmitter can dynamically adjust the number and allocation of OFDM subcarriers according to preset parameters to optimize spectrum utilization; The secondary system transmitter has adaptive modulation capability, which can automatically select the best transmission strategy according to the status of the main system and channel conditions; The receiver is able to operate stably in complex wireless communication environments.

6. The OFDM coexisting wireless communication transceiver system as described in claim 5, characterized in that, The system features a modular design, making it easy to expand and upgrade, and adaptable to different communication needs and technological evolution. The system includes intelligent management software for data acquisition, analysis, and optimization to improve overall system performance and user experience.

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