A cooperative transmission method and system for CR-NOMA vehicle networking

Abstract

The application discloses a CR-NOMA vehicle networking cooperative transmission method and system, and relates to the technical field of vehicle networking. The method comprises the following steps: a first transmission stage main network transmitter broadcasts a main signal, and a vehicle-mounted mobile base station (VMBS) collects energy from the main signal and decodes by using a power splitting technology; a second transmission stage VMBS superimposes a regenerated main signal and two secondary user signals in a NOMA power domain by using the collected energy and broadcasts, a full-duplex relay decodes a target secondary user signal based on non-ideal interference cancellation and forwards the target secondary user signal to an edge user, and a main network receiver performs non-ideal cancellation on relay interference and combines the relay interference with a direct transmission signal. The application combines CR (cognitive radio), NOMA, CDRT and SWIPT technologies, constructs a full-duplex relay non-ideal interference cancellation model, introduces four power threshold ratios to accurately evaluate system performance, and realizes energy self-sufficiency of the VMBS and high-reliability coverage of the edge user.

Description

Technical Field

[0001] This invention relates to the field of network transmission technology, and in particular to a collaborative transmission method and system for CR-NOMA vehicle networking. Background Technology

[0002] With the deep integration of 6G and Intelligent Transportation Systems (ITS), the Internet of Vehicles (IoV) places stringent demands on massive connectivity, ultra-high reliability, and low-latency communication. However, traditional network architectures based primarily on fixed roadside units (RSUs) suffer from coverage blind spots and insufficient flexibility. Vehicle-mounted mobile base stations (VMBSs), as dynamically deployable communication nodes, can effectively address these shortcomings, but they face the dual challenges of limited energy and scarce spectrum resources. Furthermore, users located at the edge of VMBS coverage suffer from significant path loss, making it difficult to guarantee Quality of Service (QoS).

[0003] The integration of cognitive radio (CR) and non-orthogonal multiple access (CR-NOMA) is an effective way to improve spectrum efficiency, while Coordinated Direct and Relay Transmission (CDRT) technology can ensure coverage for edge users by dynamically selecting direct or relay links. Wireless Powered Communication (SWIPT) technology offers a possibility for solving the power supply problem of VMBS.

[0004] However, when integrating the above technologies into VMBS-enabled vehicular networks, a core challenge arises: non-ideal interference cancellation. In practical systems, NOMA's serial interference cancellation (SIC) is difficult to perfect, resulting in residual interference (ipSIC). Simultaneously, while full-duplex (FD) relays improve spectral efficiency, they introduce self-interference (RSI) that is difficult to completely eliminate and cross-layer interference (CI) to the main network. Existing research either relies on the assumption of ideal interference cancellation or only considers a single non-ideal factor, failing to comprehensively characterize the profound impact of non-ideal interference cancellation on the performance of CR-NOMA vehicular network systems integrating CDRT and SWIPT within a unified framework. This leads to discrepancies between theoretical analysis and practical application, making it difficult to accurately guide system design and parameter optimization.

[0005] Therefore, there is an urgent need for a new transmission mechanism and analysis method that can effectively integrate the advantages of CDRT and SWIPT technologies, and accurately evaluate and optimize system performance while fully considering various non-ideal interference elimination factors, so as to achieve energy self-sufficiency of VMBS and high-reliability coverage for edge users. Summary of the Invention

[0006] This invention provides a collaborative transmission method and system for CR-NOMA vehicle networking to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, a cooperative transmission method for CR-NOMA vehicle-to-everything (V2X) networks is provided, applied to a system comprising a main network transmitter, a main network receiver, a vehicle-mounted mobile base station, a full-duplex relay, a secondary network center user, and a secondary network edge user. The method includes:

[0008] First transmission phase:

[0009] S1. The main network transmitter broadcasts the main signal to the main network receiver, the vehicle-mounted mobile base station, and the secondary network center user.

[0010] S2. The vehicle-mounted mobile base station adopts power splitting technology, and according to a preset energy collection ratio coefficient, divides the received main signal into a first branch signal for energy collection and a second branch signal for information decoding; the vehicle-mounted mobile base station collects energy from the first branch signal to support subsequent transmission, and decodes the second branch signal to attempt to recover the main signal;

[0011] Second transmission phase:

[0012] S3. After the vehicle-mounted mobile base station successfully decodes the main signal, it uses the collected energy to superimpose the regenerated main signal, the first user signal, and the second user signal in the power domain according to the non-orthogonal multiple access principle to generate a first composite signal; the power allocation coefficients of the regenerated main signal, the second user signal, and the first user signal decrease sequentially; the vehicle-mounted mobile base station broadcasts the first composite signal to the full-duplex relay and the secondary network center user;

[0013] S4. The full-duplex relay receives the first composite signal and, based on non-ideal interference cancellation technology, sequentially decodes the regenerated main signal and the target secondary user signal, wherein the target secondary user signal is the second user signal; wherein, the non-ideal interference cancellation includes non-ideal suppression of full-duplex self-interference and non-ideal cancellation of interference between non-orthogonal multiple access users.

[0014] S5. The full-duplex relay forwards the decoded target secondary user signal to the secondary network edge user; at the same time, the main network receiver performs non-ideal interference cancellation on the interference signal from the full-duplex relay, and performs maximum ratio combining of the interference-cancelled signal with the main signal received in the first transmission stage to obtain the final received signal.

[0015] S6. The secondary network center user receives the first composite signal, and based on the non-orthogonal multiple access decoding order, uses non-ideal interference cancellation technology to sequentially eliminate the regenerated main signal and the second user signal, and then extracts the first user signal as its own signal; the secondary network edge user receives the full-duplex relay forwarded signal and extracts the second user signal as its own signal.

[0016] Furthermore, the method also includes defining multiple power threshold ratios to classify and evaluate the system transmission performance, wherein the power threshold ratios include:

[0017] The main network power allocation ratio is used to characterize whether the main signal has sufficient decoding power advantage at the receiving end;

[0018] The edge user power advantage ratio is used to characterize whether the second user signal has a sufficient decoding power advantage relative to the first user signal.

[0019] The central user decoding power margin ratio is used to characterize whether the remaining power of the central user of the sub-network is sufficient to support decoding its own signal after eliminating interference signals;

[0020] The relay serial decoding ratio is used to characterize whether the power coordination condition for serial interference cancellation is met between the regenerated main signal and the second user signal at a full-duplex relay.

[0021] Furthermore, in step S4, the feasibility of the full-duplex relay decoding the regenerated main signal and the target secondary user signal is jointly constrained by the main network power allocation ratio, the edge user power advantage ratio, and the relay serial decoding ratio.

[0022] Furthermore, the feasibility of the secondary network center user successfully extracting its own signal is jointly constrained by the main network power allocation ratio, the edge user power advantage ratio, and the center user decoding power margin ratio.

[0023] Further, step S2 includes:

[0024] The power splitter of the vehicle-mounted mobile base station divides the power of the received main signal according to a preset energy harvesting ratio coefficient to obtain a first branch signal with a first power ratio and a second branch signal with a second power ratio, wherein the second power ratio is the complement of the first power ratio.

[0025] The vehicle-mounted mobile base station converts the radio frequency energy of the first branch signal into DC energy and stores it through a rectifier circuit.

[0026] The vehicle-mounted mobile base station performs down-conversion, analog-to-digital conversion, and baseband demodulation on the second branch signal, and performs channel decoding in an attempt to recover the original information carried by the main signal.

[0027] Furthermore, the steps for performing non-ideal interference cancellation in the full-duplex relay include:

[0028] The full-duplex relay, based on prior knowledge of its own transmitted signal and estimation of the self-interference channel, reconstructs an estimated value of the self-interference signal from the received signal containing self-interference, and subtracts the estimated value from the received signal to form a residual self-interference signal.

[0029] The full-duplex relay, in accordance with the non-orthogonal multiple access decoding order from high to low power, first decodes the regenerated main signal and then removes the component of the regenerated main signal from the received signal;

[0030] The full-duplex relay performs a decoding operation again on the remaining signal after eliminating the regenerated primary signal component, in order to recover the target secondary user signal.

[0031] Further, in step S5, the step of the main network receiver performing non-ideal interference cancellation on the interference signal from the full-duplex relay includes:

[0032] The main network receiver reconstructs an estimated value of the interference signal based on prior knowledge of the full-duplex relay interference signal and an estimate of the interference channel, and subtracts the estimated value from the received signal to suppress cross-layer interference generated by the full-duplex relay.

[0033] The present invention also provides a cooperative transmission system for CR-NOMA vehicle networking, the system comprising:

[0034] Main signal broadcast module: Used to control the main network transmitter to broadcast the main signal to the main network receiver, vehicle-mounted mobile base station and secondary network center users during the first transmission phase;

[0035] Vehicle-mounted mobile base station processing module: used to control the vehicle-mounted mobile base station to adopt power splitting technology, divide the received main signal into an energy harvesting part and an information decoding part according to a preset energy harvesting ratio coefficient, obtain energy from the energy harvesting part, and decode the information decoding part;

[0036] Composite signal generation and broadcasting module: After the vehicle-mounted mobile base station successfully decodes the main signal, it controls the vehicle-mounted mobile base station to use the collected energy to superimpose the regenerated main signal, the first user signal and the second user signal in the power domain according to the non-orthogonal multiple access principle to generate a first composite signal, and broadcast it to the full-duplex relay and secondary network center users.

[0037] Relay interference cancellation and decoding module: used to control the full-duplex relay to perform non-ideal interference cancellation on the received first composite signal, and decode the regenerated main signal and the target secondary user signal, wherein the target secondary user signal is the second user signal;

[0038] The final received signal synthesis module is used to control the full-duplex relay to forward the target secondary user signal to the secondary network edge user, and at the same time control the main network receiver to perform non-ideal interference cancellation on the interference signal from the full-duplex relay, and combine it with the main signal received in the first transmission stage to obtain the final received signal through maximum ratio combining.

[0039] The secondary network user signal extraction module is used to control the secondary network center user to extract the first user signal from the first composite signal based on the non-orthogonal multiple access decoding order and non-ideal interference cancellation technology, and to control the secondary network edge user to extract the second user signal from the full-duplex relay forwarded signal.

[0040] Furthermore, the relay interference cancellation and decoding module and the secondary network user signal extraction module further evaluate and determine the feasibility of signal decoding based on multiple preset power threshold ratios; the power threshold ratios include the main network power allocation ratio, the edge user power advantage ratio, the central user decoding power margin ratio, and the relay serial decoding ratio.

[0041] Furthermore, the vehicle-mounted mobile base station processing module includes:

[0042] Power splitter: used to dynamically divide the received signal power into a first branch signal for energy harvesting and a second branch signal for information decoding according to a preset energy harvesting ratio coefficient;

[0043] Energy harvesting and storage unit: used to convert the radio frequency energy of the first branch signal into DC energy and store it;

[0044] Information decoding unit: used to demodulate and decode the second branch signal to recover the main signal.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] 1. This invention, for the first time, organically integrates CDRT and SWIPT technologies within the CR-NOMA vehicle-to-everything (V2X) framework enabled by VMBS, proposing a complete CS cooperative transmission mechanism. This mechanism enables VMBS to both harvest energy from the main network signal for self-sustainability and provide reliable coverage for edge users through relay cooperation, achieving efficient coordination between the energy domain and the cooperative domain.

[0047] 2. This invention constructs a comprehensive non-ideal interference cancellation model, which simultaneously considers residual self-interference (RSI), cross-layer interference (CI), and non-ideal SIC (ipSIC) of NOMA in FD relays, making the system model and analysis results closer to the complex communication environment of actual vehicle-to-everything (V2X) networks.

[0048] 3. This invention creatively introduces and defines four key power threshold ratios, transforming the performance analysis under complex non-ideal interference elimination into a discussion of power allocation coefficient inequalities. This not only derives precise closed-form expressions for outage probability and throughput but also clearly reveals the system's operating state and performance bottlenecks under different power configurations and channel conditions, providing clear theoretical guidance for system optimization design. Simulation results show that, compared to traditional solutions, this invention can significantly reduce edge user outage probability and improve system throughput under specific conditions.

[0049] 4. Through simulation verification, this invention clarifies the constraints under which the proposed mechanism demonstrates its performance advantages. For example, when the relay's SIC capability reaches a certain threshold, the cooperative gain of this invention will dominate. This points the way for the research and development of interference cancellation technology and the optimization of system parameters in practical deployments. Attached Figure Description

[0050] Figure 1 This is a flowchart illustrating a collaborative transmission method for CR-NOMA vehicle networking according to an embodiment of the present invention.

[0051] Figure 2 This is a functional block diagram of a collaborative transmission system for CR-NOMA vehicle networking provided in an embodiment of the present invention;

[0052] Figure 3 This is a simulation curve of the main network receiver (PR) interruption probability as a function of transmit power ρ in one embodiment of the present invention;

[0053] Figure 4 This is a simulation curve of the interruption probability of the secondary network center user (SU1) as a function of the transmit power ρ in one embodiment of the present invention;

[0054] Figure 5 This is a simulation curve showing the change in the outage probability of the secondary network edge user (SU2) as a function of the transmit power ρ in one embodiment of the present invention.

[0055] Figure 6 This is a simulation curve showing the impact of the energy harvesting ratio coefficient on the interruption probability of the sub-network center user (SU1) and the sub-network edge user (SU2) in one embodiment of the present invention.

[0056] Figure 7 This is a simulation curve showing the effect of the energy harvesting ratio coefficient on the interruption probability of the main network receiver (PR) in one embodiment of the present invention.

[0057] Figure 8 This is a simulation curve of the network throughput as a function of transmit power ρ in one embodiment of the present invention;

[0058] Figure 9In one embodiment of the present invention, the system throughput varies with the self-interference cancellation capability parameter of the full-duplex relay. The changing simulation curve. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0060] This application provides a cooperative transmission method for CR-NOMA vehicle-to-everything (V2X) communication. The implementing entity of this method can be any node device or its control unit in the V2X communication system, including but not limited to a main network transmitter, a main network receiver, a vehicle-mounted mobile base station (VMBS), a full-duplex relay (R), a secondary network center user (SU1), and a secondary network edge user (SU2). Each node device is equipped with corresponding radio frequency transceiver modules, signal processing modules, energy management modules, and control modules to implement the communication process described in this invention.

[0061] The simulation and analysis process of the CR-NOMA vehicle-to-everything (V2X) cooperative transmission system presents relevant data graphs. MATLAB is used to perform numerical simulations of the obtained theoretical results, and the Monte Carlo method is used for simulation verification. The number of simulations is [number missing]. Without loss of generality, The parameters of the Gauss-Chebyshev quadrature formula are: .

[0062] Depend on Figure 3 Therefore, this experiment compares and analyzes the CR-NOMA vehicle-to-everything (V2X) cooperative transmission method proposed in this invention with the classic NOMA method. Furthermore, it can be observed that, regardless of the model, as... As the value increases, the probability of PR being interrupted decreases. It is worth noting that in... In the case of PR signal power allocation coefficient The larger the value, the lower the PR interruption probability at the same transmit power. At this point, the PR signal power allocation coefficient is... satisfy However, when ,and First, it can be seen that the interruption probability is significantly higher in this case than in the previous case, but it still satisfies the condition that... The conclusion that the PR interruption probability decreases with increasing transmit power still holds true. Because of the presence of full-duplex relay interference in the method proposed in this invention, the PR interruption probability in the proposed system can never reach the required interruption probability; the magnitude of this difference depends on the PR's SIC capability against interference signals.

[0063] Figure 4 The interruption probability of SU1 was simulated. .along with As the value increases, the interrupt probability of SU1 decreases. The interrupt probability analysis of SU1 mainly requires analyzing... and There are two scenarios. As shown in the diagram, when... When unchanged, it satisfies Under these conditions, SU1 has a lower interrupt probability. This simulation also considered the following factors in addition to the above: and The effect of the size relationship between them on the SU1 interruption probability: maintain As can be seen from the magnified view, when At the same power, the interruption probability of SU1 is slightly greater than that of SU1. The interrupt probability of SU1. However, this difference is not significant. A relatively large value is needed, so generally speaking, the change in the interruption probability is very small. Therefore, we can conclude that... and The relationship has little impact on the interruption of SU1.

[0064] Figure 5 The interruption probability of SU2 was simulated. Considered , The interruption probability under different relations is considered, while also taking into account the different values ​​of R. That is, the probability of U2 being interrupted when R has different SIC capabilities in response to loopback interference. As can be seen from the figure, satisfying... The interruption probability of U2 at the same transmit power is lower than that that of U2 when the following conditions are met. The probability of interruption at that time; when The smaller the value, assuming other parameters remain the same, the lower the interrupt probability of SU2, indicating that a smaller loopback interference has a smaller impact on the interrupt probability. Therefore, based on the above discussion, we can conclude that effectively improving... The size can be reduced, and the impact of loopback interference can be minimized, resulting in a better interruption probability. However, it is important to note that... or The size should not be changed arbitrarily; it is subject to certain limitations and must be guaranteed. and Otherwise, SU2 will not work, meaning the interruption probability of SU2 is 1.

[0065] Figure 6 and Figure 7 The energy harvesting ratio coefficient was discussed separately. The impact on the interruption probabilities of PR, SU1, and SU2. .in, Figure 6 Discussion Impact on the interruption probability of SU1 and SU2 When the value is close to 0, it indicates that most of the energy received by the vehicle-mounted mobile base station is used for decoding, resulting in insufficient transmission power and a high probability of outage. With the increase of energy, the power used for transmission in the energy absorbed by the vehicle-mounted mobile base station increases, ensuring both successful SBS decoding and transmission. As can be seen from the graph, the probability of interruption has decreased. As the voltage continues to increase, most of the energy absorbed by the vehicle-mounted mobile base station is used to transmit signals, which may result in insufficient power for its own decoding, thus increasing the probability of interruption. The difference is more pronounced when the value is close to 1. The vehicle-mounted mobile base station will be unable to decode the signal, resulting in a system interruption. Figure 8 The same applies to discussions about PR.

[0066] Figure 8 The throughput of this network was simulated and analyzed. The simulation used six different sets of... Theoretical analysis shows that in this subnetwork, the interruption probabilities of SU1 and SU2 are both affected by... There are constraints on the size between at least two of them, so the experiment considered four cases. As shown in the figure, when... The value of satisfies or At that time, due to The value of is no longer restricted, so it can be... Taking a larger value results in a larger throughput for the entire subnetwork; when The value of satisfies or As can be observed from the graph, when the transmission power is low, the throughput is higher than in other cases, but as the transmission power gradually increases, the throughput tends to stabilize and remain low; when... The value of satisfies or At this point, the throughput of this network is in the middle range compared to the previous two scenarios.

[0067] Figure 9 The impact of SIC capability at point R on system throughput was discussed, and a comparison was made with the throughput under the traditional NOMA transmission method. .Depend on Figure 9It can be seen that the system throughput of the proposed system decreases as the SIC capability at point R weakens. This means that the interference caused by point R to other nodes increases, hence the throughput decreases. Since traditional overlay cooperative CR-NOMA-ITS networks do not consider relay interference, as... The increase in does not affect the system throughput. Comparing the throughput of the two systems, it can be seen that under the parameter settings of this invention, The throughput curves of the two systems intersect near -20dB. As the size decreases, the throughput of the system proposed in this invention begins to increase. At that time, the throughput of this system was significantly lower than that of the latter, so it can be concluded that the system proposed in this invention is more dependent on the SIC capability of each node.

[0068] System Model and Basic Assumptions:

[0069] Reference Figure 1 The diagram shown illustrates a vehicle-to-everything (V2X) system model based on cognitive radio-nonorthogonal multiple access (CR-NOMA) according to an embodiment of the present invention. The system comprises a primary network and a secondary network.

[0070] The main network consists of a main network transmitter (PT) and a main network receiver (PR). The PT is typically a fixed infrastructure (such as a traffic signal tower) with a fixed power. Broadcast Authorization Main Signal PR (Portable Receiver) systems are deployed at key traffic nodes (such as highway toll booths) to receive and decode main signals.

[0071] The secondary network consists of a vehicle-mounted mobile base station (VMBS), a full-duplex relay (R), a secondary network center user (SU1), and a secondary network edge user (SU2). The VMBS, acting as the transmitter (ST) of the secondary network, has limited energy and must utilize Swippt (Switch-In-Power) technology to harvest energy from the radio frequency signals broadcast by the PT (Platform Targeting Station) to support its operation. SU1 is located in the central coverage area of ​​the VMBS, where channel conditions are relatively good; SU2 is located in the edge coverage area of ​​the VMBS, where channel conditions are relatively poor. Based on Coordinated Direct Transmission and Relay Transmission (CDRT) technology, SU1 communicates with the VMBS via a direct link, while SU2 requires cooperative forwarding via the full-duplex relay R. This embodiment assumes that only the relay R operating in FD mode is equipped with dual antennas (one for receiving and one for transmitting), while the remaining nodes are equipped with single antennas and operate in half-duplex (HD) mode.

[0072] Channel Model: This embodiment considers the non-line-of-sight (NLoS) transmission scenario common in urban vehicle-to-everything (V2X) environments, and all communication links are assumed to follow independent Rayleigh fading. For nodes... To the node The link, its channel fading coefficient It follows a complex Gaussian distribution with a mean of zero, i.e. Its channel gain Obtain the parameter as The exponential distribution. The receivers are all subjected to signals with a mean of zero and a variance of... The effect of additive white Gaussian noise (AWGN), i.e. .

[0073] Interference Model: This invention specifically models non-ideal interference cancellation in real-world communication environments, including two categories:

[0074] Residual interference: Residual self-interference (RSI) generated by full-duplex relay R after non-ideal self-interference suppression (SIS), and cross-layer interference (CI) generated by R on PR after non-ideal elimination. These residual interferences are modeled as complex Gaussian random variables with zero mean and variance related to the node's SIC capability, denoted as . ,in , Representative node SIC capability at the location.

[0075] Residual interference within non-orthogonal multiple access domains: Residual inter-user interference (RI) that was not completely eliminated due to non-ideal interference cancellation (ipSIC). This interference will be reflected in subsequent performance analysis by affecting the receiver signal-to-interference-plus-noise ratio (SINR).

[0076] Detailed transmission mechanism process:

[0077] This invention proposes a cooperative energy harvesting transfer mechanism integrating CDRT and SWIPT, referred to as the CS cooperative transfer mechanism. This mechanism divides the entire transfer process into two phases, each with a duration of [missing information]. The time slot.

[0078] First transmission time slot:

[0079] Step S1: Main signal broadcast

[0080] The main network transmitter (PT) operates at a fixed power during a predefined first transmission time slot. Construct and broadcast the main signal The target nodes for the broadcast include the primary network receiver PR, the vehicle-mounted mobile base station VMBS, and the secondary network center user SU1.

[0081] PR received signal is ,in Let be the channel fading coefficient of the PT to PR link. The noise at PR is additive white Gaussian noise;

[0082] SU1 receives the signal as follows ,in The channel fading coefficient of the PT to SU1 link is given. It is additive white Gaussian noise at SU1.

[0083] Step S2: VMBS Energy Harvesting and Information Decoding

[0084] The main signal received by VMBS is ,in The channel fading coefficient for the PT to VMBS link is given. This is additive white Gaussian noise at the VMBS. Due to energy constraints, the VMBS uses power splitting (PS) technology to process this signal.

[0085] Specifically, the power shunt built into VMBS operates according to a preset energy harvesting ratio. The received signal power is divided. The power splitter divides the main signal into a first branch signal and a second branch signal. The power proportion of the first branch signal is equal to... Used as the energy harvesting section; the power proportion of the second branch signal is It is used as part of the information decoding process.

[0086] The VMBS rectifier circuit converts the radio frequency energy of the first branch signal into DC energy, which is then stored in the onboard energy storage device. The collected energy... It can be represented as ,in For energy conversion efficiency, This is the energy harvesting ratio coefficient.

[0087] Simultaneously, the VMBS performs down-conversion, analog-to-digital conversion, and baseband demodulation on the second branch signal to obtain a baseband digital signal. It then performs channel decoding on this signal, attempting to recover the original information bitstream carried by the main signal. If decoding is successful (i.e., SINR is greater than or equal to a preset threshold), the VMBS acquires spectrum access rights and operates as a cognitive relay and secondary transmitter in the second time slot; if decoding fails, the VMBS remains silent in the second time slot.

[0088] Second transmission time slot:

[0089] Step S3: VMBS generates and broadcasts the first composite signal.

[0090] If and only if VMBS successfully decodes the main signal in the first time slot Then, the following operations are performed: First, VMBS generates a regenerated master signal with the same content as the original master signal but with adjustable power. Secondly, VMBS acquires the communication data to be sent to the secondary network center user SU1 and the secondary network edge user SU2, respectively, and generates the first user signal through independent channel coding and modulation mapping. Second user signal Then, VMBS regenerates the main signal according to the Non-Orthogonal Multiple Access (NOMA) principle. First user signal Second user signal Assign the first power allocation coefficient respectively Second power allocation coefficient and the third power distribution coefficient To ensure primary network priority and provide compensation for edge users, the power allocation coefficients satisfy... and Next, VMBS performs power scaling on each signal according to the allocation coefficients and then linearly adds them to generate the first composite signal. .in, The transmit power of VMBS in the second time slot is derived from the DC energy collected in the first time slot. Finally, within a predefined second transmission time slot, the VMBS transmits the first composite signal in radio frequency form via the transmit antenna. At the same time, it broadcasts to full-duplex relay R and secondary network center user SU1.

[0091] Step S4: Non-ideal interference cancellation and decoding of full-duplex relays

[0092] The full-duplex repeater R simultaneously receives the first composite signal from the VMBS. And the self-interference signal generated by its own transmitting antenna. The actual received signal of R can be expressed as ,in For relay transmission power, To relay the current transmitted signal, For self-interference channel coefficients, It is additive white Gaussian noise at point R.

[0093] Based on prior knowledge of its transmitted signal and real-time estimation of the self-interference channel, R reconstructs an estimate of the self-interference signal and subtracts this estimate from the received signal to perform interference cancellation. Due to channel estimation errors and non-ideal hardware characteristics, residual self-interference (RSI) still exists after interference cancellation. This residual self-interference is modeled as... ,in is the self-interference cancellation capability coefficient of relay R.

[0094] Subsequently, R performs non-ideal interference cancellation (ipSIC) on the interference-cancelled signal. Its decoding order follows the NOMA power allocation principle (higher power signals have higher priority):

[0095] (1) R first regenerates the main signal The target signal is treated as interference, and other signals and RSI are decoded. If successful, the main signal component is reconstructed from the decoded bits and eliminated from the received signal. Due to the non-ideal SiC, residual interference exists in this elimination process.

[0096] (2) R then decodes the remaining signal after eliminating the regenerated main signal component, and attempts to recover the target secondary user signal, i.e., the second user signal. .

[0097] Can R be successfully decoded? and This depends on a combination of constraints related to power allocation and interference cancellation capabilities. This invention defines a key parameter—the Relay Serial Decoding Ratio (RSDR), denoted as... This ratio is used to quantify the constraint. It is related to the power allocation factor and the SIC capability of the relay. The relay can only complete serial decoding when the RSDR meets the preset conditions.

[0098] Step S5: Relay forwarding and main network receiver signal merging

[0099] The full-duplex repeater R successfully decoded the target secondary user signal. Then, it is re-encoded and modulated, and then... The signal is forwarded to the secondary network edge user SU2. Simultaneously, the primary network receiver PR receives the cross-layer interference signal from relay R in the second time slot. Since PR has pre-acquired the interference signal characteristics and channel state information (CSI) of R, it can perform non-ideal interference cancellation on this interference signal. That is, PR reconstructs an estimate of the interference signal and subtracts it from the received signal to suppress most of the interference; this residual cross-layer interference is modeled as... ,in This represents the interference cancellation capability coefficient of the PR. Subsequently, the PR performs maximum ratio combining (MRC) on the interference-suppressed signal and the main signal received through the direct transmission link in the first time slot to obtain a high-quality received signal for final decoding.

[0100] Step S6: Sub-network user signal extraction

[0101] Sub-network center user SU1: SU1 receives the first composite signal from VMBS in the second time slot. Based on the preset power allocation coefficients, SU1 determines its decoding order as follows: prioritize decoding the regenerated main signal with the highest power. Secondly, decode the second user signal. Finally, decode its own signal. SU1 performs sequential interference cancellation, decoding and canceling interference in turn. and After removing the components, the first user signal is recovered from the remaining signal by demodulation. .

[0102] Sub-network edge user SU2: SU2 receives the forwarded signal from full-duplex relay R in the second time slot. This signal contains only the target signal for SU2. The SU2 does not require interference cancellation; it can recover the second user signal by directly performing demodulation and channel decoding. As its own signal.

[0103] Core performance analysis methods:

[0104] To accurately evaluate and optimize the performance of the aforementioned CS transmission mechanism, this invention introduces four innovative power threshold ratios, which divide the system state under complex non-ideal interference elimination into several modes with clear physical meaning.

[0105] (1) Main grid power allocation ratio Defined as ,in The target SINR threshold of the main signal, and , The target transmission rate of the primary signal. This ratio characterizes whether the power of the primary signal is sufficient to counteract interference from secondary network signals. When the actual signal-to-noise ratio meets... When the signal is strong enough, it indicates that the main signal has a decoding power advantage; otherwise, the decoding of the main signal will be limited by interference from the secondary network in the same channel.

[0106] (2) Edge user power advantage ratio Defined as ,in The target SINR threshold for the second user signal, and , This is the target transmission rate for the second user signal. This ratio is the admission condition for the NOMA mechanism to take effect. Only when the actual signal-to-noise ratio meets this condition... Only when the signal of SU2 is in a certain condition can it be effectively separated from the signal of SU1 in the power domain; otherwise, the NOMA mechanism fails, and the decoding of SU1 will be subject to uncontrollable strong interference.

[0107] (3) Decoding power margin ratio of central users Defined as ,in Let be the target SINR threshold for the first user signal, and , The target transmission rate for the first user signal is denoted by . This ratio indicates whether SU1 has sufficient power margin to decode its own signal after successfully eliminating interference signals.

[0108] (4) Relay serial decoding ratio Defined as a composite function related to the SIC capability, RSI variance, and power allocation coefficient at the repeater. This ratio characterizes whether the power configuration of the primary signal and the second user signal at the full-duplex repeater R satisfies the coordination condition for serial interference cancellation.

[0109] Based on the four power threshold ratios mentioned above, the system's outage probability (OP) and throughput performance indicators can be divided into multiple piecewise functions for precise analysis. For example, the outage probability of SU1 can be determined according to... , and The conditions for meeting the requirements are divided into several working modes, such as "ideal SIC of the main signal and equalization of the secondary network" and "ipSIC of the main signal and compensation of the secondary network". The interruption probability expression is different in each mode, thus accurately revealing the performance bottleneck under different conditions.

[0110] Simulation verification and effect analysis:

[0111] Monte Carlo simulations were performed to verify the performance advantages of the proposed CS mechanism and the correctness of the theoretical analysis. The simulation parameters were set as follows: noise variance... Target rate bps / Hz, bps / Hz, bps / Hz, Gauss-Chebyshev tradeoff parameter Energy conversion efficiency .

[0112] Figure 3 This demonstrates the outage probability of the main network receiver (PR) as a function of normalized transmit power. The variation curve of PR. Simulation results show that the interruption probability curve of PR is... The segmented characteristics exhibited by the boundary perfectly match the theoretical analysis. When the condition is satisfied... Under certain conditions, the interruption probability is significantly reduced, and the performance bottleneck mainly comes from the residual interference (CI) of the relay.

[0113] Figure 4 and Figure 5 The outage probabilities of sub-network center user SU1 and edge user SU2 are shown separately. Simulation results verify that... , and The constraint effect of the equal critical ratio on user performance. Especially for SU2, the SIC capability of the relay is relatively strong ( When the conditions are met, the slope of its interruption probability curve under high signal-to-noise ratio is larger, reflecting the diversity gain brought by the CDRT mechanism.

[0114] Figure 6 and Figure 7 Reveals the energy harvesting ratio coefficient Impact on system performance. The simulation curves show a "decline followed by an increase" trend, indicating the existence of an optimal energy harvesting ratio that achieves the best balance between the VMBS's own decoding success rate and subsequent forwarding power, thereby minimizing the interruption probability for each user.

[0115] Figure 9 The total system throughput of the proposed CS mechanism was compared with that of the traditional mechanism. Simulation results show that there is a key relay SIC capability threshold. When the relay's SIC capability exceeds this threshold, the cooperative gain of the CS mechanism begins to appear, and its total throughput significantly surpasses that of the traditional mechanism. This finding provides clear guidance for practical deployment: in dynamic vehicular network scenarios, it is essential to prioritize or enhance the interference cancellation capabilities of relay nodes and master receivers to fully leverage the performance advantages of the cooperative transmission mechanism proposed in this invention.

[0116] System Implementation Example:

[0117] Reference Figure 2 The diagram shown is a functional block diagram of a cooperative transmission system for CR-NOMA vehicle networking provided in an embodiment of the present invention. The system 100 includes:

[0118] The main signal broadcast module 101 is used to control the main network transmitter to broadcast the main signal during the first transmission phase;

[0119] The vehicle-mounted mobile base station processing module 102 is used to control the VMBS to perform power splitting, energy harvesting and information decoding.

[0120] The composite signal generation and broadcasting module 103 is used to control the generation and broadcast of the first composite signal superimposed by NOMA after the VMBS successfully decodes the main signal;

[0121] The relay interference cancellation and decoding module 104 is used to control the full-duplex relay R to perform non-ideal interference cancellation and decode the target signal;

[0122] The final received signal synthesis module 105 is used to control the full-duplex relay forwarding signal and control the main network receiver to perform interference cancellation and maximum ratio combining.

[0123] The subnetwork user signal direction extraction module 106 is used to control each user in the subnetwork to extract its own signal according to the NOMA decoding order.

[0124] The specific functions of each module correspond one-to-one with the steps in the aforementioned method embodiments, and will not be repeated here.

[0125] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A cooperative transmission method for CR-NOMA vehicle-to-everything (V2X) networks, applied to a system comprising a main network transmitter, a main network receiver, a vehicle-mounted mobile base station, a full-duplex relay, a secondary network center user, and a secondary network edge user, characterized in that, The method includes: First transmission phase: S1. The main network transmitter broadcasts the main signal to the main network receiver, the vehicle-mounted mobile base station, and the secondary network center user. S2. The vehicle-mounted mobile base station adopts power splitting technology, and according to a preset energy collection ratio coefficient, divides the received main signal into a first branch signal for energy collection and a second branch signal for information decoding; the vehicle-mounted mobile base station collects energy from the first branch signal to support subsequent transmission, and decodes the second branch signal to attempt to recover the main signal; Second transmission phase: S3. After the vehicle-mounted mobile base station successfully decodes the main signal, it uses the collected energy to superimpose the regenerated main signal, the first user signal, and the second user signal in the power domain according to the non-orthogonal multiple access principle to generate a first composite signal; the power allocation coefficients of the regenerated main signal, the second user signal, and the first user signal decrease sequentially; the vehicle-mounted mobile base station broadcasts the first composite signal to the full-duplex relay and the secondary network center user; S4. The full-duplex relay receives the first composite signal and, based on non-ideal interference cancellation technology, sequentially decodes the regenerated main signal and the target secondary user signal, wherein the target secondary user signal is the second user signal; wherein, the non-ideal interference cancellation includes non-ideal suppression of full-duplex self-interference and non-ideal cancellation of interference between non-orthogonal multiple access users. S5. The full-duplex relay forwards the decoded target secondary user signal to the secondary network edge user; at the same time, the main network receiver performs non-ideal interference cancellation on the interference signal from the full-duplex relay, and performs maximum ratio combining of the interference-cancelled signal with the main signal received in the first transmission stage to obtain the final received signal. S6. The secondary network center user receives the first composite signal, and based on the non-orthogonal multiple access decoding order, uses non-ideal interference cancellation technology to sequentially eliminate the regenerated main signal and the second user signal, and then extracts the first user signal as its own signal; the secondary network edge user receives the full-duplex relay forwarded signal and extracts the second user signal as its own signal.

2. The cooperative transmission method for CR-NOMA vehicle networking according to claim 1, characterized in that, The method further includes defining multiple power threshold ratios to classify and evaluate the system transmission performance, wherein the power threshold ratios include: The main network power allocation ratio is used to characterize whether the main signal has sufficient decoding power advantage at the receiving end; The edge user power advantage ratio is used to characterize whether the second user signal has a sufficient decoding power advantage relative to the first user signal. The central user decoding power margin ratio is used to characterize whether the remaining power of the central user of the sub-network is sufficient to support decoding its own signal after eliminating interference signals; The relay serial decoding ratio is used to characterize whether the power coordination condition for serial interference cancellation is met between the regenerated main signal and the second user signal at a full-duplex relay.

3. The cooperative transmission method for CR-NOMA vehicle networking according to claim 1, characterized in that, In step S4, the feasibility of the full-duplex relay decoding the regenerated main signal and the target secondary user signal is jointly constrained by the main network power allocation ratio, the edge user power advantage ratio, and the relay serial decoding ratio.

4. The cooperative transmission method for CR-NOMA vehicle networking according to claim 1, characterized in that, In step S6, the feasibility of the secondary network center user successfully extracting its own signal is jointly constrained by the main network power allocation ratio, the edge user power advantage ratio, and the center user decoding power margin ratio.

5. The cooperative transmission method for CR-NOMA vehicle networking according to claim 1, characterized in that, Step S2 includes: The power splitter of the vehicle-mounted mobile base station divides the power of the received main signal according to a preset energy harvesting ratio coefficient to obtain a first branch signal with a first power ratio and a second branch signal with a second power ratio, wherein the second power ratio is the complement of the first power ratio. The vehicle-mounted mobile base station converts the radio frequency energy of the first branch signal into DC energy and stores it through a rectifier circuit. The vehicle-mounted mobile base station performs down-conversion, analog-to-digital conversion, and baseband demodulation on the second branch signal, and performs channel decoding in an attempt to recover the original information carried by the main signal.

6. The cooperative transmission method for CR-NOMA vehicle networking according to claim 1, characterized in that, In step S4, the step of performing non-ideal interference cancellation on the full-duplex relay includes: The full-duplex relay, based on prior knowledge of its own transmitted signal and estimation of the self-interference channel, reconstructs an estimated value of the self-interference signal from the received signal containing self-interference, and subtracts the estimated value from the received signal to form a residual self-interference signal. The full-duplex relay, in accordance with the non-orthogonal multiple access decoding order from high to low power, first decodes the regenerated main signal and then removes the component of the regenerated main signal from the received signal; The full-duplex relay performs a decoding operation again on the remaining signal after eliminating the regenerated primary signal component, in order to recover the target secondary user signal.

7. The cooperative transmission method for CR-NOMA vehicle networking according to claim 1, characterized in that, In step S5, the step of the main network receiver performing non-ideal interference cancellation on the cross-layer interference signal from the full-duplex relay includes: The main network receiver reconstructs an estimated value of the interference signal based on prior knowledge of the full-duplex relay interference signal and an estimate of the interference channel, and subtracts the estimated value from the received signal to suppress cross-layer interference generated by the full-duplex relay.

8. A collaborative transmission system for CR-NOMA vehicle networking, characterized in that, The system for implementing the method of any one of claims 1 to 7 comprises: The main signal broadcast module is used to control the main network transmitter to broadcast the main signal to the main network receiver, vehicle-mounted mobile base station and secondary network center users during the first transmission phase; The vehicle-mounted mobile base station processing module is used to control the vehicle-mounted mobile base station to adopt power splitting technology, and according to a preset energy collection ratio coefficient, divide the received main signal into an energy collection part and an information decoding part, obtain energy from the energy collection part, and decode the information decoding part. The composite signal generation and broadcasting module is used to control the vehicle-mounted mobile base station to use the collected energy to superimpose the regenerated main signal, the first user signal and the second user signal in the power domain according to the non-orthogonal multiple access principle after the vehicle-mounted mobile base station successfully decodes the main signal, generate the first composite signal, and broadcast it to the full-duplex relay and secondary network center users. The relay interference cancellation and decoding module is used to control the full-duplex relay to perform non-ideal interference cancellation on the received first composite signal, and to decode the regenerated main signal and the target secondary user signal, wherein the target secondary user signal is the second user signal; The final received signal synthesis module is used to control the full-duplex relay to forward the target secondary user signal to the secondary network edge user, and at the same time control the main network receiver to perform non-ideal interference cancellation on the cross-layer interference signal from the full-duplex relay, and combine it with the main signal received in the first transmission stage to obtain the final received signal through maximum ratio combining. The secondary network user signal extraction module is used to control the secondary network center user to extract the first user signal from the first composite signal based on the non-orthogonal multiple access decoding order and non-ideal interference cancellation technology, and to control the secondary network edge user to extract the second user signal from the full-duplex relay forwarded signal.

9. A collaborative transmission system for CR-NOMA vehicle networking according to claim 8, characterized in that, The relay interference cancellation and decoding module and the secondary network user signal extraction module further evaluate and determine the feasibility of signal decoding based on multiple preset power threshold ratios; the power threshold ratios include the main network power allocation ratio, the edge user power advantage ratio, the central user decoding power margin ratio, and the relay serial decoding ratio.

10. A collaborative transmission system for CR-NOMA vehicle networking according to claim 8, characterized in that, The vehicle-mounted mobile base station processing module includes: A power splitter is used to dynamically divide the received signal power into a first branch signal for energy harvesting and a second branch signal for information decoding according to a preset energy harvesting ratio coefficient. An energy harvesting and storage unit is used to convert the radio frequency energy of the first branch signal into DC energy and store it. The information decoding unit is used to demodulate and decode the second branch signal to recover the main signal.

Images