C-V2X mode 4 trade-off communication method and system

Abstract

The invention provides a C-V2X mode 4 trade-off communication method and system, and the method comprises the steps: calculating the maximum resource selection window overlap ratio of a reselected vehicle to other vehicles when a vehicle triggers resource reselection; when the maximum resource selection window overlapping ratio of the reselection vehicle and other vehicles is not greater than an ORAS threshold value for restraining the reselection vehicle to select and execute, executing an SPS method; when the maximum resource selection window overlapping ratio of the reselection vehicle and other vehicles is larger than a threshold value used for restraining the reselection vehicle to select and execute ORAS, executing an ORAS method, setting pk of the reselection vehicle to be 1, judging whether the maximum resource selection window overlapping ratio is larger than the threshold value after each time of data transmission, and preparing for next data transmission or triggering resource reselection of SPS according to a judgment result; according to the embodiment of the invention, semi-persistent resource occupation and data transmission are executed until resource reselection, so that the problem of continuous resource conflict caused by the semi-persistent characteristic of the SPS can be obviously improved on the premise of not obviously increasing the probability of resource conflict, and unnecessary increase of the channel busy rate is avoided when the problem of continuous resources is improved.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication technology, and specifically relates to a C-V2X mode 4 trade-off communication method and system. Background Art

[0002] As an irreplaceable means of transportation, motor vehicles have led to a continuous increase in people's demand for them. However, while the rapid growth in the number of motor vehicles has brought about convenient transportation, it has also brought about serious problems such as traffic accidents, urban congestion and environmental pollution. In order to effectively alleviate these problems, vehicle-to-everything (V2X) technology came into being. As a core component of the Intelligent Traffic System (ITS), this technology has brought unprecedented changes to road traffic by supporting information interaction between vehicles (V2V), vehicles and roads (V2I), vehicles and pedestrians (V2P), and vehicles and networks (V2N).

[0003] At present, there are two main V2X communication technology standard routes in the world: Dedicated Short Range Communication (DSRC) and Cellular Vehicle-to-Everything (C-V2X). Among them, DSRC is led by the Institute of Electrical and Electronics Engineers (IEEE) to formulate standards, with V2V and V2I as the main communication methods. The C-V2X technical standard is led by the 3rd Generation Partnership Project (3GPP), and C-V2X has advantages over DSRC in both technical and commercial aspects.

[0004] In terms of resource allocation methods, depending on whether the cellular base station participates in resource scheduling, the resource allocation method of C-V2X can be divided into Mode 3 (centralized resource allocation method) and Mode 4 (distributed resource allocation method). In Mode 3, resources are uniformly scheduled by cellular base stations, which requires that vehicle communications be within the coverage of cellular base stations. Since vehicles may travel outside the coverage of cellular networks in actual operation, communication between vehicles cannot always rely on cellular base stations, so Mode 4 is particularly important for C-V2X. In Mode 4, vehicles can autonomously select resources, and in order to reduce the probability of resource conflicts, C-V2X introduces a perception-based semi-persistent resource selection (Semi-Persistent Scheduling, SPS) method for services with periodic characteristics and relatively constant data packet sizes.

[0005] The current status of research on SPS at home and abroad can be mainly divided into two directions: performance evaluation of SPS and optimization of SPS to improve its performance. In SPS, when the resource selection window of the reselected vehicle overlaps with the resource selection window of other vehicles, resource conflicts may still occur, and the semi-continuous characteristics of SPS will cause this resource conflict to continue until the reselected vehicle or the vehicle with which it has a resource conflict triggers resource reselection again, that is, the continuous resource problem of SPS is more serious. The RAS method proposed by other scholars will significantly increase the probability of resource conflicts while improving the problem of continuous resource conflicts. Therefore, the present invention optimizes RAS and proposes a trade-off method between SPS and RAS. Summary of the invention

[0006] In order to solve the problems existing in the prior art, the present invention provides a trade-off communication method for C-V2X mode 4, which uses a trade-off method of SPS and RAS to improve the above problems. The trade-off method allows the vehicle to flexibly choose to execute SPS or ORAS according to its resource reselection status. When the vehicle is likely to have a resource conflict, it will choose to execute ORAS to alleviate the continuous resource conflict problem caused by the semi-continuous characteristic of SPS; when the vehicle is unlikely to have a resource conflict, it will choose to execute SPS to avoid unnecessary increase in channel busy rate.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is: a C-V2X mode 4 trade-off communication method, comprising the following steps:

[0008] When a vehicle triggers resource reselection, the maximum resource selection window overlap ratio mr between the reselected vehicle and other vehicles is calculated;

[0009] When the maximum resource selection window overlap ratio mr of the reselected vehicle and other vehicles is not greater than the ORAS threshold r used to constrain the reselected vehicle selection execution th , execute the SPS method;

[0010] When the maximum resource selection window overlap ratio mr of the reselected vehicle and other vehicles is greater than the ORAS threshold r used to constrain the reselected vehicle selection execution th , execute the ORAS method and reselect the vehicle's p k Set to 1 to determine whether mr is greater than r after each data transmission. th , and prepare for the next data transmission or trigger SPS resource reselection based on the judgment result;

[0011] Perform semi-continuous resource occupation and data transmission until resources are reselected.

[0012] Furthermore, in the ORAS method, only v t With v i , v t When selecting resources, two different resources are always randomly selected from the candidate resource list. i Only one resource will be selected, namely v t Execute the resource selection step of RAS, v i Executes the resource selection step of SPS. t With v i At most one identical resource will be selected, using event O z Indicates v in ORAS t With v i During resource selection, z identical resources are selected, and the value of z is 0 or 1.

[0013] Further, after triggering the SPS resource reselection, the resource reselection includes the following steps:

[0014] S1: The reselecting vehicle determines the resource perception window and resource selection window according to the reselection time. The vehicle selects a subchannel within the selection window for periodic transmission based on the perception result.

[0015] S2: The reselected vehicle creates an available resource set based on the perception result of the resource occupancy status within the resource perception window;

[0016] S3: A candidate resource set is formed based on the available resource set, where the resources in the candidate resource set are the resources with the lowest received signal strength indication value, and the number of resources in the candidate resource set is equal to 20% of the total number of resources in the resource selection window; the vehicle randomly selects a resource in the candidate resource set for semi-continuous transmission.

[0017] Furthermore, in the SPS method, the vehicle triggers resource reselection conditions including: after each resource selection, the vehicle randomly selects a counter value according to the counter value range corresponding to the resource reservation interval, and the counter value is used as the number of semi-continuous transmissions. Each time the vehicle uses the selected resource to transmit data once, the counter value is reduced by one. When the counter value is 0, it will probabilistically determine whether to reselect. The vehicle maintains the resource with a probability p k Continue to occupy and reserve the resource and reselect the counter value, or k Trigger resource and counter value reselection.

[0018] Furthermore, the duration of the resource perception window is fixed at 1000ms, which is used to determine the idle resources in the selection window. The duration of the resource selection window is set to be the same as the resource reservation interval, and the duration of the resource selection window does not exceed 100ms.

[0019] Furthermore, in S2, the available resource set does not include resources that are occupied according to the direct link control information successfully received in the perception window and resources whose reference signal receiving power value is greater than a given threshold. When creating the available resource set, subframe skipping processing is performed. When the number of resources in the available resource set is less than 20% of the total number of resources in the resource selection window, the RSRP threshold is iteratively increased by 3dB until the number of resources in the available resource set exceeds 20% of the total number of resources in the resource selection window.

[0020] Further, performing resource selection of the RAS includes: selecting and reserving two different sub-channel resources and alternately allocating the two different sub-channel resources, specifically:

[0021] At each resource selection or reselection, the vehicle will randomly select two different resources from the candidate resource list;

[0022] During data transmission, the vehicle will use the odd and even values ​​of the counter value to alternately use the two occupied resources.

[0023] In a second aspect, the present invention provides a trade-off communication system for C-V2X mode 4, including an initialization module, a trade-off strategy module, a performance calculation module, and a semi-persistent transmission module;

[0024] The initialization module is used to initialize the resource allocation related information and perform the initial random resource allocation to the vehicle;

[0025] The trade-off strategy module is used to enable the vehicle to select a resource allocation method;

[0026] The performance calculation module is used to calculate the performance indicators of the system to measure the severity of resource conflicts and continuous resource conflicts;

[0027] The semi-continuous transmission module is used to enable the vehicle to occupy resources and transmit data semi-continuously.

[0028] In a third aspect, the present invention also provides a computer device, comprising a processor and a memory, wherein an executable program is stored in the memory, and when the processor executes the executable program, the trade-off communication method of C-V2X mode 4 described in the present invention can be executed.

[0029] At the same time, a computer-readable storage medium is provided, in which a computer program is stored. When the computer program is executed by a processor, the trade-off communication method of C-V2X mode 4 described in the present invention can be implemented.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] The present invention improves RAS, provides ORAS, and proposes a trade-off method for SPS and RAS based on SPS and ORAS; the trade-off method allows a vehicle to flexibly choose to execute SPS or ORAS according to the status of its resource reselection, and when a resource conflict may occur in the vehicle, that is, when the problem of continuous resource conflict needs to be alleviated, ORAS will be executed, and in the case where two vehicles may have a resource conflict, such as a transmitting vehicle and an interfering vehicle, ORAS only needs to select two resources, while RAS requires both the transmitting vehicle and the interfering vehicle to select two resources, that is, the increase in channel busy rate caused by ORAS is slower than that of RAS; it can be ensured that the problem of continuous resource conflict of SPS is significantly improved without excessively increasing the probability of resource conflict. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the trade-off method.

[0033] Figure 2 Comparison of resource conflict probability between the trade-off method and SPS and RAS under different numbers of vehicles.

[0034] Figure 3 The trade-off method is compared with the continuous resource conflict problem of SPS and RAS under different numbers of vehicles.

[0035] Figure 4 Comparison of channel busy rates between the trade-off method and SPS and RAS under different numbers of vehicles.

[0036] Figure 5 This is the impact of resource retention probability on SPS reselection ratio in the trade-off method. DETAILED DESCRIPTION

[0037] The present invention will be described in detail below in conjunction with the accompanying drawings of the specific description.

[0038] Cellular Vehicle-to-Everything (C-V2X) provides innovative solutions to problems such as traffic accidents, urban congestion and environmental pollution by realizing real-time information interaction between vehicles and other traffic participants. Among the autonomous resource selection methods of C-V2X, the perception-based semi-persistent resource selection (Semi-Persistent Scheduling, SPS) method has attracted much attention due to its low probability of resource conflict. The SPS method may still face resource conflict problems in some cases, and its semi-persistent characteristics will further lead to continuous resource conflict problems. The Resource Alternative Selection (RAS) algorithm can be used to alleviate the continuous resource conflict problem, but the RAS method selects and reserves two different resources at a time, which will cause a sharp increase in the probability of resource conflict. Therefore, the present invention proposes a trade-off method between the SPS method and the RAS method, which allows the vehicle to flexibly select a resource allocation method based on its situation during resource reselection.

[0039] Reference Figure 1 The specific implementation steps of the present invention are as follows:

[0040] 1. There is a vehicle triggering resource reselection. When there is a vehicle triggering resource reselection in the system, the reselecting vehicle will perceive the resource selection window time domain range of other vehicles in the resource perception window and calculate mr.

[0041] 2. Select SPS or ORAS according to mr. The reselected vehicle flexibly selects the resource allocation method according to its resource reselection status. If mr≤r th , it can be considered that the probability of resource conflict between the reselected vehicle and other vehicles is small, so the reselected vehicle will choose to execute SPS to avoid executing ORAS when there is no resource conflict, which will cause the channel busy rate to increase unnecessarily. th , it can be considered that the probability of resource conflict between the reselected vehicle and other vehicles is high. If the reselected vehicle chooses to execute SPS at this time, it is likely to cause continuous resource conflict problems. Therefore, in this case, the trade-off method will make the reselected vehicle execute ORAS. k It will be set to 1 and check whether mr is greater than r after each data transmission. th This not only enables the vehicle that chooses to execute ORAS to avoid unnecessary resource reselection, but also ensures that the vehicle triggers SPS resource reselection in time when the probability of resource conflict is small or even no resource conflict occurs.

[0042] 3. Perform semi-continuous resource occupation and data transmission until resources are reselected.

[0043] In the SPS method, the vehicle's occupation of resources is periodic, but when the number of transmissions of the occupied resources reaches the predetermined number of semi-continuous transmissions, resource reselection may occur. The number of semi-continuous transmissions is also called the counter value, and its size depends on the resource reservation interval. After each resource selection, the vehicle will randomly select a counter value based on the counter value range corresponding to the resource reservation interval, and the counter value will be used as the number of semi-continuous transmissions. Each time the vehicle uses the selected resource to transmit data once, the counter value is reduced by one. When the counter value is 0, it will be probabilistically determined whether to reselect. Specifically, the vehicle maintains the resource with a probability p. k Continue to occupy and reserve the resource, and reselect the counter value, p k ∈[0,0.8], or with probability 1-p k Trigger resource and counter value reselection. If resource reselection is triggered, the reselection steps are as follows:

[0044] Step 1: The reselecting vehicle determines the resource perception window and resource selection window respectively according to the reselection time, where the perception window duration is fixed at 1000ms, which is used to determine the idle resources in the selection window, and the duration of the resource selection window (maximum 100ms) is set to be the same as the resource reservation interval. The vehicle can select a subchannel in the selection window for periodic transmission based on the perception results.

[0045] Step 2: The reselected vehicle creates an available resource set based on the perception result of the resource occupancy status in the perception window. The available resource set does not include resources that are occupied according to the direct link control information successfully received in the perception window and resources whose reference signal received power (RSRP) value is greater than a given threshold. Due to the influence of half-duplex communication, when creating an available resource set, it is also necessary to skip subframe processing. If the number of resources in the available resource set is less than 20% of the total number of resources in the resource selection window, the reference signal received power threshold is iteratively increased by 3dB until the number of resources in the available resource set exceeds 20% of the total number of resources in the resource selection window.

[0046] Step 3: A candidate resource set is formed based on the available resource set. The resources in the candidate resource set are the part of resources with the lowest received signal strength indication (RSSI) value, and the number of resources in the set is equal to 20% of the total number of resources in the resource selection window. The vehicle randomly selects a resource in the candidate resource set for semi-continuous transmission.

[0047] The RAS method includes two core stages: selecting and reserving two different sub-channel resources and allocating the two resources alternately. Unlike the SPS method, the RAS method causes the vehicle to randomly select two different resources from the candidate resource list each time a resource is selected or reselected. Then, during the data transmission process, the vehicle will use the odd or even value of the counter to alternately use the two occupied resources. In this way, RAS can almost avoid all continuous resource conflicts caused by the semi-continuous nature of SPS.

[0048] Analyze the SPS method and RAS method, and launch the vehicle v t With interference vehicle v i To solve the continuous resource conflict problem, we can consider launching vehicle v t With interference vehicle v i The resource selection windows completely overlap.

[0049] In the SPS method, the launching vehicle v t With interference vehicle v i The resource conflict of S will cause continuous resource conflict due to its semi-persistent nature. Therefore, in the analysis process, event S x Indicates the launch vehicle v in SPS t With interference vehicle v i When selecting resources, x identical resources are selected, and the value of x is 0 or 1. When x = 1, it means that the launch vehicle v t With interference vehicle v i A resource conflict has occurred. Use event C s Represents the launching vehicle v in the SPS method t With interference vehicle v i Resource conflicts occurred in two consecutive data transmissions, that is, the transmitting vehicle v t With interference vehicle v i A continuous resource conflict has occurred. Use event N s Represents the launching vehicle v in the SPS method t With interference vehicle v i There is no resource conflict in this data transmission, but there was a resource conflict in the last data transmission, that is, the transmitting vehicle v t With interference vehicle v i A resource conflict occurred, but no continuous resource conflict issues were raised.

[0050] Due to the semi-persistent nature of the SPS method, the launching vehicle v t With interference vehicle v i Before triggering resource reselection, a resource will always be kept for data transmission. Therefore, P(C s |S0)=0,P(N s |S0)=0,P(Cs |S1)=1,P(N s |S1) = 0. Where P(A|B) is the conditional probability, which means the probability of event A occurring under the condition that event B occurs.

[0051] When the resource selection window is completely overlapped, launch the vehicle v t With interference vehicle v i The candidate resource lists of will also completely overlap. Therefore, P(S0)=1-1 / R LC , P(S1)=1 / R LC , R LC is the number of resources in the candidate resource set. Since S0 and S1 are complete event groups, according to the total probability formula, in the SPS method, the launching vehicle v t With interference vehicle v i The probability of consecutive resource conflicts is:

[0052]

[0053] Launch vehicle v t With interference vehicle v i The probability that a resource conflict occurs but does not cause a continuous resource conflict problem is:

[0054]

[0055] In the RAS method, the process of vehicles occupying resources for data transmission is relatively complicated. t With interference vehicle v i When selecting resources, two different resources need to be selected and reserved. t The two selected resources are i There are three possible situations for the two selected resources, namely, both resources are different, there is one identical resource, or both resources are identical. You can use event R y Indicates the launch vehicle v in RAS t With interference vehicle v i When selecting resources, y identical resources are selected, and the values ​​of y are 0, 1, and 2. Use event C r Indicates the launch vehicle v in RAS t With interference vehicle v i A continuous resource conflict occurs, using event N r Indicates the launch vehicle v in RAS t With interference vehicle v i A resource conflict occurred, but no continuous resource conflict issues were raised.

[0056] When the resources selected by the two vehicles are different, there will be no resource conflict, and there will be no continuous resource conflict problem. r |R0)=0,P(N r |R0)=0; In the case that the resources selected by the two vehicles are the same, resource conflict may occur, but the RAS method makes the transmitting vehicle v t With interference vehicle v i By using the two selected resources alternately, the continuous resource conflict problem can be effectively solved. r |R1)=0,P(N r |R1)=1 / 4; When the resources selected by the two vehicles are the same, if the launching vehicle v t With interference vehicle v i If the same resource is selected when the counter value is odd, or the same resource is selected when the counter value is even, a resource conflict will occur, and it will cause continuous resource conflict problems. r |R2)=1 / 2,P(N r |R2)=0.

[0057] In the RAS approach, the launching vehicle v t With interference vehicle v i The probability that two resources selected from the candidate resource list are different is:

[0058]

[0059] in, It represents the number of combinations of taking B elements from A different elements, launching vehicle v t With interference vehicle v i The probability that the two selected resources have the same value is:

[0060]

[0061] Launch vehicle v t With interference vehicle v i The probability that both selected resources are the same is:

[0062]

[0063] It can be found that R0, R1, and R2 are complete event groups. Therefore, according to the total probability formula, in RAS, the launching vehicle v t With interference vehicle v i The probability of consecutive resource conflicts is:

[0064]

[0065] Launch vehicle vt With interference vehicle v i The probability that a resource conflict occurs but does not cause a continuous resource conflict problem is:

[0066]

[0067] Due to R LC is equal to 20% of the total number of resources in the resource selection window. Therefore, by comparison, it can be found that in RAS, the launch vehicle v t With interference vehicle v i By alternating the use of the two selected resources, the continuous resource conflict problem caused by the semi-continuous characteristic of SPS can be significantly improved.

[0068] From the above analysis, we can see that the RAS method can improve the problem of continuous resource conflicts, but when the transmitting vehicle v t With interference vehicle v i When two resources randomly selected from the candidate resource list are the same, continuous resource conflict may still occur. t With interference vehicle v i In the ORAS method, the launch vehicle v t When selecting resources, two different resources will always be randomly selected from the candidate resource list, and the interference vehicle v i Only one resource will be selected, the launch vehicle v t Execute the resource selection step of RAS, interfere with vehicle v i Execute the resource selection step of SPS. Thus, the launch vehicle v t With interference vehicle v i At most one identical resource will be selected. You can use event O z Indicates the launch vehicle v in ORAS t With interference vehicle v i When selecting resources, z identical resources are selected, and the value of z is 0 or 1. Using event C o Indicates the launch vehicle v in ORAS t With interference vehicle v i A continuous resource conflict occurs, using event N o Indicates the launch vehicle v in ORAS t With interference vehicle v i A resource conflict occurred, but no continuous resource conflict issues were raised.

[0069] In ORAS, in any case, the launching vehicle v t With interference vehicle vi There will be no continuous resource conflict, so P(C o |O0)=0,P(C o |O1)=0; in the launch vehicle v t With interference vehicle v i The selected resource exists in the same situation, although the launch vehicle v t With interference vehicle v i There will be resource conflicts, but after launching the vehicle v t Alternating the selected resources can effectively avoid the continuous resource conflict problem caused by the semi-continuous nature of SPS, so P(N o |O0)=0,P(N o |O1)=1 / 2.

[0070] In this case, the launching vehicle v t The probability of selecting a resource in a completely overlapping list of candidate resources is the same as:

[0071]

[0072] Therefore, it can be seen that in ORAS, the launching vehicle v t v i The probability of consecutive resource conflicts is:

[0073]

[0074] Launch vehicle v t The probability of a resource conflict occurring but not causing a continuous resource conflict problem is:

[0075]

[0076] By comparison, we can find that compared with RAS, ORAS performs better in improving the problem of continuous resource conflicts.

[0077] A notable feature of RAS is that it requires vehicles to select and alternately use two different resources, which will cause a sharp increase in the channel busy rate. The increase in the channel busy rate will inevitably lead to an increase in the probability of resource conflicts in the system as a whole. Both SPS and RAS have advantages and disadvantages. Although SPS has a more serious problem of continuous resource conflicts than RAS, its probability of resource conflicts is relatively low. Although RAS can significantly improve the problem of continuous resource conflicts, it will also lead to a rapid increase in the probability of resource conflicts. In the RAS method, it can be found that when the transmitting vehicle v t With interference vehicle v i When the selected resources are completely different, there will be no resource conflict, which means that launching a vehicle v t With interference vehicle v iThere is no possibility of continuous resource conflict, and the two vehicles occupy the most resources at this time. In this case, if the launching vehicle v t With interference vehicle v i The SPS method is adopted, which not only does not cause continuous resource conflict problems, but also prevents RAS from unnecessarily increasing the channel busy rate.

[0078] The present invention proposes a trade-off method between SPS and RAS. In the trade-off method, when a resource conflict may occur between vehicles, that is, when the problem of continuous resource conflict needs to be alleviated, ORAS will be executed. ORAS is adopted here not only because ORAS has better performance in the problem of continuous resource conflict than RAS, but also in the case where two vehicles may have a resource conflict, such as when the transmitting vehicle v t With interference vehicle v i , ORAS only needs v t Select two resources, RAS requires launching vehicle v t With interference vehicle v i Both resources must be selected, that is, the increase in channel busy rate caused by ORAS is slower than that of RAS. It should be noted that if there are only two vehicles that may have resource conflicts, ORAS will always let the vehicle with the resource selection window at the back choose two resources; if there are more than two vehicles that may have resource conflicts, ORAS will let the vehicle with the resource selection window at the front perform the SPS resource selection step, and the rest of the vehicles will perform the RAS resource selection step.

[0079] Since the overlap of resource selection windows between the reselecting vehicle and other vehicles is one of the main causes of resource conflicts, in the trade-off method, after the vehicle triggers resource reselection, it is necessary to determine whether mr is greater than r th , to decide whether to execute ORAS. mr refers to the maximum resource selection window overlap ratio between the reselected vehicle and other vehicles. th Used to constrain the reselection vehicle selection to perform ORAS, r th ∈[0,1], that is, r th The larger the value is, the more likely the reselecting vehicle is to choose to execute ORAS after resource reselection. Regarding how the reselecting vehicle obtains the resource selection window time domain range of other vehicles, the parameters related to vehicle-triggered resource reselection can be integrated into the through link control information.

[0080] If mr≤r th , it can be considered that the probability of resource conflict between the reselected vehicle and other vehicles is small, so the reselected vehicle will choose to execute SPS to avoid executing ORAS when there is no resource conflict, which will cause the channel busy rate to increase unnecessarily.

[0081] If mr>r th, it can be considered that the probability of resource conflict between the reselected vehicle and other vehicles is high. If the reselected vehicle chooses to execute SPS at this time, it is very likely to cause continuous resource conflict problems. Therefore, in this case, the trade-off method will make the reselected vehicle execute ORAS. k will be set to 1 and will be required to determine whether mr is greater than r after each data transmission. th This not only enables the vehicle that chooses to execute ORAS to avoid unnecessary resource reselection, but also ensures that the vehicle triggers SPS resource reselection in time when the probability of resource conflict is small or even no resource conflict occurs.

[0082] Based on the technical concept of the present invention, a C-V2X mode 4 trade-off communication method system is provided, including an initialization module, a trade-off strategy module, a performance calculation module and a semi-continuous transmission module.

[0083] The initialization module is used to initialize the resource allocation related information and perform the initial random resource allocation to the vehicle;

[0084] The trade-off strategy module is used to enable the vehicle to flexibly select resource allocation methods and is used when the vehicle reselects resources;

[0085] The performance calculation module is used to calculate the performance indicators of the system to measure the severity of resource conflicts and continuous resource conflicts;

[0086] The semi-continuous transmission module is used to enable the vehicle to occupy resources and transmit data semi-continuously.

[0087] The effect of the present invention can be further illustrated by the following simulation example. Simulation conditions: In the simulation of the present invention, the computer system is Windows 11 and the simulation environment is MATLAB 2018b.

[0088] Simulation content and results: Figure 2 The comparison of resource conflict probabilities between the trade-off method, SPS and RAS under different numbers of vehicles is described. It can be observed that as the number of vehicles increases, the probability of resource conflict of each resource selection method shows an upward trend, because the increase in the number of vehicles will inevitably lead to a decrease in the number of idle resources and an increase in the channel busy rate. In addition, the increase in the number of vehicles will also lead to an increase in the number of vehicles triggering resource reselection within a certain period of time, which will cause the incidence of resource selection window overlap to increase, thereby increasing the possibility of resource conflicts. Since RAS requires vehicles to select and reserve two different resources, its channel busy rate will definitely be the highest under the same number of vehicles, which also leads to the resource conflict probability of RAS always being greater than SPS and the trade-off method. In the trade-off method, since there will be vehicles executing ORAS, its resource conflict probability will be slightly higher than SPS. However, at p k= 0, the resource conflict probability of the trade-off method will always be lower than that of SPS. This is because p k = 0, the vehicles in the SPS will frequently trigger resource reselection, which will affect the resource pool perception results of the reselected vehicles. In the trade-off method, when the vehicle chooses to execute ORAS, its p k will be set to 1. In addition, it can be found in the trade-off method that r th The smaller the r, the smaller the probability of resource conflict. This is because the smaller the r th More vehicles that may have resource conflicts can be made to choose to execute ORAS, and then the trade-off method will k Set it to 1 and let these vehicles trigger SPS resource reselection when the probability of resource conflict is small or even impossible.

[0089] Figure 3 The comparison of the average order of magnitude of continuous resource conflicts between the trade-off method and SPS and RAS under different numbers of vehicles is described. The average order of magnitude of continuous resource conflicts is used to evaluate the severity of continuous resource conflicts among vehicles in the system. It can be observed that with the increase in the number of vehicles, the average order of magnitude of continuous resource conflicts of each resource selection method shows an upward trend. Because as the number of vehicles in the system increases, the probability of resource conflicts will inevitably increase, which will lead to more serious problems of continuous resource conflicts. Since RAS can alternately use two different resources, the trade-off method enables vehicles that may have resource conflicts to choose to execute ORAS. Therefore, the average order of magnitude of continuous resource conflicts between the trade-off method and RAS is much smaller than that of SPS. In the trade-off method, since the reselected vehicle cannot guarantee that it will execute the appropriate resource selection method every time it reselects resources, for example, when mr≤r th , the reselected vehicle has resource conflicts with other vehicles, but at this time the reselected vehicle will choose to execute SPS, so the average magnitude of continuous resource conflicts in the trade-off method will be slightly higher than that of RAS. In SPS, it can be found that p k = 0.4, the average magnitude of continuous resource conflicts will gradually exceed p as the number of vehicles increases. k = 0. This is because compared to p k =0, p k = 0.4 allows vehicles to use the same resource for more transmissions. When the number of vehicles is small, the probability of resource conflict is low, p k =0.4 can make vehicles occupy non-conflicting resources for more transmission times; and as the number of vehicles increases, the probability of resource conflict will gradually increase, p k = 0.4 will cause vehicles to occupy conflicting resources for more transmission times. At the same time, this is also the trade-off method in p k= 0.4, the average magnitude of continuous resource conflicts is higher than p k = 0. It is not difficult to find that no matter p k =0.4, still p k =0, as r th As r decreases, the average magnitude of continuous resource conflicts in the trade-off method will also decrease, because r th The reduction of will make it easier for vehicles with overlapping resource selection windows to choose to execute ORAS.

[0090] Comprehensive comparison Figure 2 and Figure 3 , it can be found that the trade-off method can always effectively balance the probability of resource conflict and the average magnitude of continuous resource conflict. This is because the trade-off method allows vehicles to flexibly choose to execute SPS or ORAS according to their conditions when reselecting resources, thereby avoiding unnecessary increase in channel busy rate when improving continuous resource problems. In addition, it can be found that in r th = 0.3, the comprehensive performance of the trade-off method is optimal, because th When it is smaller, vehicles with overlapping resource selection windows will be more inclined to choose to execute ORAS, which will cause vehicles that are less likely to have resource conflicts to choose to execute SPS, and more vehicles that may have resource conflicts to choose to execute ORAS. Then, the p of these vehicles that choose to execute ORAS k It will be set to 1 and can always trigger SPS resource reselection when the probability of resource conflict is small or even impossible.

[0091] Figure 4 The comparison of the channel busy rate of the trade-off method with SPS and RAS under different numbers of vehicles is described. It can be found that as the number of vehicles increases, the channel busy rate will continue to increase. This is because the increasing number of vehicles will cause the number of idle resources in the resource pool to continue to decrease. Since RAS requires each vehicle in the system to select two different resources, its channel busy rate is the highest. The trade-off method allows vehicles to flexibly choose the resource selection method to be executed when reselecting resources, and after the vehicle chooses to execute ORAS, it will p k Setting it to 1 and triggering SPS resource reselection in time can effectively avoid the additional increase of channel busy rate. In addition, in the trade-off method, it can be observed that as r th As r increases, the channel busy rate will gradually decrease. This is because the larger the r th Always allow vehicles that trigger resource reselect to be more easily selected to perform SPS.

[0092] Figure 5 Describes the resource retention probability p kThe impact on the SPS reselection ratio. The SPS reselection ratio refers to the ratio of the number of times a vehicle chooses to execute SPS to the total number of resource reselections when it triggers resource reselection. It can be seen from the figure that as the number of vehicles increases, the SPS reselection ratio will continue to decrease. This is because the increase in the number of vehicles will lead to an increase in the incidence of resource selection window overlap, so the trade-off method will make those vehicles that trigger resource reselection more inclined to choose to execute ORAS. It can also be found that p k = 0 when the SPS reselection ratio is always greater than p k = 0.4 when the SPS reselection ratio, because p k = 0, the vehicle triggers resource reselection faster than p k =0.4 and more frequently.

[0093] Optionally, the present invention may also provide a computer device, including a processor and a memory, the memory being used to store a computer executable program, the processor reading part or all of the computer executable program from the memory and executing it, and when the processor executes part or all of the computer executable program, the trade-off communication method of C-V2X mode 4 described in the present invention can be implemented.

[0094] The computer device may be a laptop computer, a desktop computer or a workstation.

[0095] The processor may be a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), an application specific integrated circuit (ASIC), or an off-the-shelf field programmable gate array (FPGA).

[0096] At the same time, a computer-readable storage medium is provided, in which a computer program is stored. When the computer program is executed by a processor, the trade-off communication method of C-V2X mode 4 described in the present invention can be implemented.

[0097] The memory of the present invention may be an internal storage unit of a laptop computer, a desktop computer or a workstation, such as a memory or a hard disk; or an external storage unit, such as a mobile hard disk or a flash memory card.

[0098] Computer-readable storage media may include computer storage media and communication media. Computer storage media include volatile and non-volatile, removable and non-removable media implemented by any method or technology for storing information such as computer-readable instructions, data structures, program modules or other data. Computer-readable storage media may include: read-only memory (ROM), random access memory (RAM), solid-state drive (SSD) or optical disk, etc. Among them, random access memory may include resistance random access memory (ReRAM) and dynamic random access memory (DRAM).

Claims

1. A trade-off communication method for C-V2X Mode 4, characterized in that: The following steps are involved: When a vehicle triggers resource reselection, the maximum resource selection window overlap ratio mr between the reselected vehicle and other vehicles is calculated; When the maximum resource selection window overlap ratio mr of the reselected vehicle and other vehicles is not greater than the ORAS threshold r used to constrain the reselected vehicle selection execution th , execute the SPS method; When the maximum resource selection window overlap ratio mr of the reselected vehicle and other vehicles is greater than the ORAS threshold r used to constrain the reselected vehicle selection execution th , execute the ORAS method and reselect the vehicle's p k Set to 1 to determine whether mr is greater than r after each data transmission. th , and prepare for the next data transmission or trigger SPS resource reselection based on the judgment result; Perform semi-continuous resource occupation and data transmission until resources are reselected.

2. A C-V2X Mode 4 trade-off communication method according to claim 1, characterized in that: In the ORAS method, only v t With v i , v t When selecting resources, two different resources are always randomly selected from the candidate resource list. i Only one resource will be selected, namely v t Execute the resource selection step of RAS, v i Execute the resource selection step of SPS; t With v i At most one identical resource will be selected, using event O z Indicates v in ORAS t With v i During resource selection, z identical resources are selected, and the value of z is 0 or 1.

3. The C-V2X Mode 4 trade-off communication method according to claim 1, characterized in that: After triggering SPS resource reselection, resource reselection includes the following steps: S1: The reselecting vehicle determines the resource perception window and resource selection window according to the reselection time. The vehicle selects a subchannel within the selection window for periodic transmission based on the perception result. S2: The reselected vehicle creates an available resource set based on the perception result of the resource occupancy status within the resource perception window; S3: A candidate resource set is formed based on the available resource set, where the resources in the candidate resource set are the resources with the lowest received signal strength indication value, and the number of resources in the candidate resource set is equal to 20% of the total number of resources in the resource selection window; the vehicle randomly selects a resource in the candidate resource set for semi-continuous transmission.

4. A C-V2X Mode 4 trade-off communication method according to claim 3, characterized in that: In the SPS method, the vehicle triggers resource reselection conditions include: after each resource selection, the vehicle randomly selects a counter value according to the counter value range corresponding to the resource reservation interval. The counter value is used as the number of semi-continuous transmissions. Each time the vehicle uses the selected resource to transmit data once, the counter value decreases by one. When the counter value is 0, it will probabilistically determine whether to reselect. The vehicle maintains the resource with probability p k Continue to occupy and reserve the resource and reselect the counter value, or k Trigger resource and counter value reselection.

5. The C-V2X Mode 4 trade-off communication method according to claim 3, characterized in that: The duration of the resource perception window is fixed at 1000ms, which is used to determine the idle resources in the selection window. The duration of the resource selection window is set to be the same as the resource reservation interval, and the duration of the resource selection window does not exceed 100ms.

6. A C-V2X Mode 4 trade-off communication method according to claim 3, characterized in that: In S2, the available resource set does not include resources that are occupied according to the direct link control information successfully received in the perception window and resources whose reference signal received power value is greater than a given threshold. When creating the available resource set, skip subframe processing is performed. When the number of resources in the available resource set is less than 20% of the total number of resources in the resource selection window, the RSRP threshold is iteratively increased by 3dB until the number of resources in the available resource set exceeds 20% of the total number of resources in the resource selection window.

7. A C-V2X Mode 4 trade-off communication method according to claim 2, characterized in that: The resource selection for performing RAS includes: selecting and reserving two different sub-channel resources and alternately allocating two different sub-channel resources, specifically: At each resource selection or reselection, the vehicle will randomly select two different resources from the candidate resource list; During data transmission, the vehicle will use the odd and even values ​​of the counter value to alternately use the two occupied resources.

8. A C-V2X Mode 4 trade-off communication system, characterized in that: It includes an initialization module, a trade-off strategy module, a performance calculation module and a semi-continuous transmission module; The initialization module is used to initialize the resource allocation related information and perform the initial random resource allocation to the vehicle; The trade-off strategy module is used to enable the vehicle to select a resource allocation method; The performance calculation module is used to calculate the performance indicators of the system to measure the severity of resource conflicts and continuous resource conflicts; The semi-continuous transmission module is used to enable the vehicle to occupy resources and transmit data semi-continuously.

9. A computer device, characterized in that: It includes a processor and a memory, wherein an executable program is stored in the memory, and when the processor executes the executable program, the trade-off communication method of C-V2X mode 4 described in the present invention can be executed.

10. A computer-readable storage medium, characterized in that: A computer program is stored in a computer-readable storage medium, and when the computer program is executed by a processor, the trade-off communication method of C-V2X mode 4 described in the present invention can be implemented.

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