A dynamic reservation based semi-persistent scheduling method

Abstract

The application discloses a kind of based on dynamic reservation's semi-persistent scheduling method.The method specifically includes the following steps: constructing dynamic car-to-car communication model;Modification side chain control information SCI format, use reservation field to carry reservation resource information;Monitoring channel resource state, calculate channel busy rate;According to channel busy rate, dynamically adjust the timing of transmission reservation information.The application modifies the semi-persistent scheduling scheme based on perception in C-V2X mode 4, so that vehicles carry resource information planned to be used in the future in the process of transmitting messages, and dynamically adjust the timing of transmitting reservation information according to channel busy rate, which can effectively reduce the probability of resource selection conflict between vehicles in high-density environment and improve the data packet delivery rate of car-to-car communication.

Description

Technical Field

[0001] This invention relates to the fields of wireless communication and vehicle networking technologies, specifically to a semi-persistent scheduling method based on dynamic reservation. Background Technology

[0002] With social development and the continuous improvement of people's living standards, the increase in various means of transportation has greatly facilitated people's daily travel; on the other hand, the increasing number of vehicles on the road has also brought greater challenges to travel safety and efficiency.

[0003] The rapid development of vehicle-to-everything (V2X) communication has provided a solution to the aforementioned problems. To achieve high-quality vehicle-to-vehicle communication, 3GPP defined two communication modes in Release 14: Mode 3 and Mode 4. In Mode 3, when the vehicle is within the coverage area of ​​the cellular network, site resources are selected, allocated, and reserved by the eNodeB. In Mode 4, the vehicle can autonomously select and manage its radio resources without any cellular infrastructure support. Since full cellular coverage has not yet been achieved, C-V2X Mode 4 is considered the baseline mode for C-V2X.

[0004] Mode 4 defines a perceptual semi-persistent scheduling (SB-SPS) scheme. In this scheme, vehicles periodically monitor channel resource usage and utilize available resources within a certain timeframe (the perceptual window) before sending a message. To ensure timely information updates between vehicles, vehicles will frequently occupy limited channel resources. Furthermore, vehicles always randomly select from the best-quality resources based on channel monitoring results. Due to limited resources, in high-density environments, vehicles will engage in more intense competition for the few available resources. If selection conflicts occur between different vehicles, message reception may fail at the receiving vehicle due to insufficient signal-to-interference-plus-noise ratio (SINNR).

[0005] Therefore, optimizing the SB-SPS algorithm in Mode 4 is of great significance for reducing resource selection conflicts and improving data transmission reliability. For example, in existing technology, a cooperative V2X wireless resource allocation and scheduling method (202010526918.5) reduces the probability of selection conflicts by utilizing SCI (Self-Cooperation Information) to transmit cooperative information. In this method, vehicles add RC (Reservation Control) and resource reservation information to the SCI and transmit it. Furthermore, when the RC reaches a specific value... nextThe method begins transmitting reserved information at a certain time. However, when a vehicle's RC=1, it compares its selection with the cooperative information of other vehicles. If a selection conflict is detected, a backoff and reselection occurs. When node density is high, resource conflicts occur frequently, thus increasing the likelihood of vehicle backoff and reselection under this method. Furthermore, signal interference between vehicles is severe in high-density environments, increasing the possibility of packet loss. Therefore, the information after backoff and reselection may not be shared with other vehicles due to packet loss, reducing the effectiveness of the cooperative information. Summary of the Invention

[0006] The purpose of this invention is to overcome the deficiencies in the prior art and provide a semi-persistent scheduling method based on dynamic reservation, aiming to reduce resource selection conflicts in Mode 4 communication and improve the reliability of vehicle communication. To achieve this objective, this invention provides a semi-persistent scheduling method based on dynamic reservation, the main steps of which include:

[0007] S1. Construct a dynamic vehicle-to-vehicle communication model;

[0008] S2. Pre-allocate wireless channel resources;

[0009] S3. The vehicle decides in advance whether to reselect channel resources;

[0010] S4. Modify the format of the sidechain control information (SCI) to use reserved fields to carry reserved resource information;

[0011] S5. Monitor channel resource status and calculate channel busy rate;

[0012] S6. Adjust the timing of transmitting reserved information dynamically based on the channel busy rate.

[0013] Furthermore, in step S1, a dynamic vehicle-to-vehicle communication scenario is established, as detailed below:

[0014] N vehicles are traveling on a two-way four-lane highway segment with a total length of L and a lane width of W. The vehicle set is n = {1, 2, ..., N}. The vehicle positions follow a Poisson distribution based on the lane spacing. Assume the highway segment extends laterally from left to right, with the origin at the leftmost point of the first lane furthest from the second lane, the lane distribution direction as the x-axis, and the rightward extension direction of the lanes as the y-axis. Then the positions of the n vehicles are represented as (x... n ,y n ), where x n This indicates the vehicle's position on the x-axis, x n ∈[0,4*W],y n This indicates the vehicle's position on the y-axis. n∈[0,L]; Vehicles in lanes one and two travel in the same direction, while vehicles in lanes three and four travel in the opposite direction to those in lanes one and two. All vehicles travel at a constant speed of v.

[0015] Further, in step S2, according to the semi-persistent scheduling method based on dynamic reservation as described in claim 1, the operating frequency band for vehicle communication is 5.9 GHz, the available wireless channel bandwidth is 10 Hz, and it is divided into resource blocks (RBs) in the time-frequency domain. In the time domain, each RB has a width of 1 ms, which is the length of one subframe; in the frequency domain, each RB has a width of 180 kHz, corresponding to 12 15 kHz subcarriers, and the number of RBs in the same subframe is 50. Then, 25 RBs form a subchannel, and each subframe contains two channel resources. Considering a 100 ms selection window, each vehicle has 200 selectable channel resources during the selection window.

[0016] Furthermore, in step S3, after the vehicle selects the channel resource to be used for this round of transmission, it reserves the probability P before using the resource to transmit a message for the first time. keep Decide whether it is necessary to reselect the channel resources to be used in the next round of transmission;

[0017] Furthermore, in step S3, the vehicle generates a random number t before the first transmission and sets the reselection flag Flag. resel Configure the settings. Here, t follows a uniform distribution and ranges between [0,1]. If t rand >P keep Then the vehicle selects a new resource for the next round of transmission, i.e., Flag. resel =1; otherwise, Flag resel =0 indicates that the next round of vehicle transmission will use the resources currently in use.

[0018] Furthermore, in step S4, the sidechain control information (SCI) is 32 bits long and is divided into the following fields: message priority (3 bits); resource reservation interval (4 bits); frequency domain position of reserved resource (X bits); time difference (4 bits); modulation and coding strategy (5 bits); retransmission flag (1 bit); and reservation field (15-X bits).

[0019] Furthermore, in step S4, X is calculated as follows:

[0020]

[0021] Where, N Subch This represents the number of channel resources contained in a subframe. In this method, N is preset. SubchThe value is 2, so X = 2 is calculated. Therefore, there are 13 bits of available space remaining in the reserved field, which will be used to carry the time-frequency information of the resources used in the next round of transmission.

[0022] Further, in step S4, the transmitted data packet size is 190 bytes. According to the baseline assumptions in Annex a.2 of 3GPP TR 36.885, i.e., with a sidelink bandwidth of 10MHz, containing 50 RBs, QPSK modulation, and a coding rate of 0.5, when the TB Size Index (ITBS) is 7, the number of RBs required to transmit a 300-byte BSM message is 20. Adding the two RBs occupied by the SCI, a total of 22 RBs are used per transmission, which can be completed using one resource. Therefore, this method takes 2 bits from the SCI reserved field to indicate the frequency domain information of the reserved resources. When the vehicle's message transmission frequency is 100ms, since the vehicle can only send messages a maximum of 15 times using the same resource, meaning the next transmission subframe is at most 1500ms away from the current subframe, the reserved resource information is represented in binary form, and the required number of bits is calculated. Therefore, the remaining 11 bits in the reserved field are used to represent the subframe information where the reserved resource is located.

[0023] Furthermore, in step S5, the vehicle needs to sense the channel resource status before selecting resources. First, the vehicle detects the channel resource status, eliminates unavailable resources, and then randomly selects resources needed for subsequent transmission from the resources with the best quality (accounting for 20% of the total resources). Simultaneously, the vehicle also calculates the current channel load based on the channel's RSSI. Specifically, assuming the selection time is t, within the time interval [t-100ms, t], the vehicle monitors the channel and calculates the channel busy rate (CBR). The CBR is calculated as follows:

[0024]

[0025] Subch busy This indicates the number of subchannels in which the vehicle detected RSSI exceeding a preset threshold within the past 100ms. total This indicates the total number of sub-channels in the past 100ms.

[0026] Further, in step S6, after the vehicle selects a resource, it randomly determines the number of consecutive transmissions using that resource, denoted as RC, with a value range of [RC1, RC2]. Then, the vehicle periodically transmits the Basic Safety Message (BSM) over a period of time. The value of RC decrements by 1 with each transmission. When the value of RC reaches zero, the vehicle uses the previously set reselection flag (Flag). reselA decision is made as to whether to perform a reselection. Furthermore, the vehicle determines the RC value when it begins transmitting reserved information based on the CBR calculation results. Specifically, RC is defined as the remaining number of times the reserved information is transmitted on the selected resource at the start of transmission. annc And preset two CBR thresholds, namely CBR low and CBR high Based on the measured range of CBR, RC annc The setup method is as follows:

[0027] (1) CBR>CBR low At this point, the channel load is high, the number of available resources begins to decrease, and the probability of resource conflicts increases. With a fixed message transmission frequency, an increase in the number of vehicles also means increased transmission interference between vehicles, and a higher possibility of packet loss. Therefore, to ensure that reserved information can be effectively transmitted to other vehicles on the road, the time for starting the transmission of reserved resource information needs to be advanced accordingly. Therefore, RC... annc The values ​​of are represented as follows:

[0028]

[0029] Among them, CBR high and CBR low These are the preset channel busy rate thresholds. This indicates rounding down the value of variable A.

[0030] (2)CBR <CBR low At this time, the channel load is low and there are plenty of available resources, so there is no need to transmit reserved information multiple times. annc =5;

[0031] Furthermore, in step S5, during the perception process, the vehicle needs to exclude channel resources with reference signal received power exceeding a threshold. In addition, since the SCI includes resources that other vehicles will need to use for future transmissions, when a vehicle receives a signal from another vehicle, it needs to decode the SCI in the other vehicle's message to obtain reserved resource information. Then, the corresponding resources are excluded from the vehicle's candidate resource list, forming a new candidate resource list, and available resources are randomly selected from this new list.

[0032] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0033] (1) The present invention discloses a semi-persistent scheduling method based on dynamic reservation, which uses SCI to transmit reserved resource information and can provide more reference for the vehicle resource selection process.

[0034] (2) The present invention discloses a semi-persistent scheduling method based on dynamic reservation, which monitors the channel busy rate (CBR) and dynamically adjusts the transmission timing of the reservation information according to the monitoring results. This can reduce the uncertainty and suddenness of the resource selection process in mode 4, thereby improving the quality of resource selection and the reliability of communication between vehicles. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a vehicle-to-vehicle communication scenario in an embodiment of the present invention;

[0036] Figure 2 This is a flowchart of a semi-persistent scheduling method based on dynamic reservation disclosed in an embodiment of the present invention;

[0037] Figure 3 A schematic diagram illustrating the probability of selection conflict under different vehicle densities;

[0038] Figure 4 A schematic diagram showing the data packet reception rate under different vehicle densities;

[0039] Figure 5 To select a graph showing the relationship between collision probability and the communication distance between the sender and receiver;

[0040] Figure 6 This is a graph showing the relationship between data packet delivery rate and the communication distance between the sender and receiver. Detailed Implementation

[0041] 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 embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0042] Example 1:

[0043] like Figure 2 The illustration shows a vehicle-to-everything (V2X) power control method based on surrounding node density prediction disclosed in this embodiment. In the perception-based semi-persistent scheduling process, an LSTM network is added as an auxiliary to collect surrounding density data, predict and control the transmit power. Specific steps include:

[0044] S1, Establish as follows Figure 1 The diagram shows a vehicle-to-vehicle communication scenario. The steps for establishing this scenario are as follows:

[0045] N vehicles are traveling on a two-way four-lane highway segment with a total length of L and a lane width of W. The vehicle set is n = {1, 2, ..., N}, and the vehicle positions follow a Poisson distribution based on the lane spacing. Assume the highway segment extends laterally from left to right. The origin is defined by the leftmost point of the first lane (farthest from the second lane), the direction of lane distribution is the x-axis, and the direction of lane extension to the right is the y-axis. The positions of the n vehicles are represented as (x...). n ,y n ), where x n This indicates the vehicle's position on the x-axis, x n ∈[0,4*W],y n This indicates the vehicle's position on the y-axis. n ∈[0,L]. Vehicles in lanes one and two travel in the same direction, while vehicles in lanes three and four travel in the opposite direction to those in lanes one and two. All vehicles travel at a constant speed of v; each vehicle is equipped with an LSTM prediction network module.

[0046] S2. Pre-allocate wireless channel resources. The specific process is as follows:

[0047] The vehicle communication operates at a frequency of 5.9 GHz, with an available wireless channel bandwidth of 10 Hz, divided into resource blocks (RBs) in the time and frequency domains. In the time domain, each RB is 1 ms wide, constituting one subframe; in the frequency domain, each RB is 180 kHz wide, corresponding to 12 15 kHz subcarriers, with 50 RBs within the same subframe. Then, 25 RBs form a subchannel, and each subframe contains two channel resources. Considering a 100 ms selection window, each vehicle has 200 selectable channel resources during the selection window.

[0048] S3. The vehicle decides in advance whether to reselect channel resources.

[0049] After the vehicle selects the channel resource to be used in this round of transmission, it reserves the probability P before using the resource to transmit a message for the first time. keep Decide whether it is necessary to reselect the channel resources to be used in the next round of transmission;

[0050] Specifically, the vehicle generates a random number t before the first transmission and sets a reselection flag Flag. resel Configure the settings. Here, t follows a uniform distribution and ranges between [0,1]. If t>P keep Then the vehicle selects a new resource for the next round of transmission, i.e., Flag. resel =1; otherwise, Flag resel =0 indicates that the next round of vehicle transmission will use the resources currently in use.

[0051] S4. Modify the format of the sidechain control information (SCI) to use reserved fields to carry reserved resource information.

[0052] Specifically, the sidechain control information (SCI) is 32 bits long and is divided into the following fields: message priority (3 bits); resource reservation interval (4 bits); frequency domain position of the reserved resource (X bits); time difference (4 bits); modulation and coding strategy (5 bits); retransmission flag (1 bit); and reservation field (15-X bits). The calculation method for X is as follows:

[0053]

[0054] Where, N Subch This represents the number of channel resources contained in a subframe. In this method, N is preset. Subch The value is 2, so X = 2 is calculated. Therefore, there are 13 bits of available space remaining in the reserved field, which will be used to carry the time-frequency information of the resources used in the next round of transmission.

[0055] In this embodiment, the transmitted data packet size is 190 bytes. According to the baseline assumptions in Annex a.2 of 3GPP TR 36.885, i.e., with a sidelink bandwidth of 10MHz, containing 50 RBs, QPSK modulation, and a coding rate of 0.5, when the TB Size Index (ITBS) is 7, the number of RBs required to transmit a 300-byte BSM message is 20. Adding the two RBs occupied by the SCI, a total of 22 RBs are used per transmission, which can be completed using one resource. Therefore, this method takes 2 bits from the SCI reserved field to indicate the frequency domain information of the reserved resources. When the vehicle's message transmission frequency is 100ms, since the vehicle can only send messages a maximum of 15 times using the same resource, meaning the next transmission subframe is at most 1500ms away from the current subframe, the reserved resource information is represented in binary form, and the required number of bits is calculated. Therefore, the remaining 11 bits in the reserved field are used to represent the subframe information where the reserved resource is located.

[0056] S5. Monitor channel resource status and calculate channel busy rate.

[0057] Before selecting resources, the vehicle needs to sense the channel resource status. First, the vehicle detects the channel resource status, eliminates unavailable resources, and then randomly selects resources needed for subsequent transmission from the resources with the best quality (accounting for 20% of the total resources). Simultaneously, the vehicle also calculates the current channel load based on the channel's RSSI. Specifically, assuming the selection time is t, within the time interval [t-100ms, t], the vehicle monitors the channel and calculates the channel busy rate (CBR). The CBR is calculated as follows:

[0058]

[0059] Subch busy This indicates the number of subchannels in which the vehicle detected RSSI exceeding a preset threshold within the past 100ms. total This indicates the total number of sub-channels in the past 100ms.

[0060] S6. Adjust the timing of transmitting reserved information dynamically based on the channel busy rate.

[0061] Specifically, after selecting a resource, the vehicle randomly determines the number of consecutive transmissions using that resource, denoted as RC, with a value range of [RC1, RC2]. Then, the vehicle periodically transmits the Basic Safety Message (BSM) over a period of time. The value of RC decrements by 1 with each transmission. When the value of RC reaches zero, the vehicle uses the previously set reselection flag. resel A decision is made as to whether to perform a reselection. Furthermore, the vehicle determines the RC value when it begins transmitting reserved information based on the CBR calculation results. Specifically, RC is defined as the remaining number of times the reserved information is transmitted on the selected resource at the start of transmission. annc And preset two CBR thresholds, namely CBR low and CBR high Based on the measured range of CBR, RC annc The setup method is as follows:

[0062] (1) CBR>CBR low At this point, the channel load is high, the number of available resources begins to decrease, and the probability of resource conflicts increases. With a fixed message transmission frequency, an increase in the number of vehicles also means increased transmission interference between vehicles, and a higher possibility of packet loss. Therefore, to ensure that reserved information can be effectively transmitted to other vehicles on the road, the time for starting the transmission of reserved resource information needs to be advanced accordingly. Therefore, RC... annc The values ​​of are represented as follows:

[0063]

[0064] Among them, CBR high and CBR lowThese are the preset channel busy rate thresholds. This indicates rounding down the value of variable A.

[0065] (2)CBR <CBR low At this time, the channel load is low and there are plenty of available resources, so there is no need to transmit reserved information multiple times. annc =5;

[0066] As mentioned earlier, during the perception process, vehicles need to exclude channel resources with reference signal received power exceeding a threshold. Furthermore, since the proposed scheme modifies the SCI (Signal Channel Information Framework) to include resources needed for future transmissions by other vehicles, when a vehicle receives a signal from another vehicle, it needs to decode the SCI in the other vehicle's message to obtain reserved resource information. Then, the corresponding resources are excluded from the vehicle's candidate resource list, forming a new candidate resource list, from which available resources are randomly selected.

[0067] The specific simulation parameters for this embodiment are shown in Table 1.

[0068] Table 4-1 Simulation Parameter Settings

[0069]

[0070]

[0071] In the above embodiments, Figure 3 , Figure 4 , Figure 5 , Figure 6 The figures show a comparison of the results of this invention, the SPS method specified by 3GPP, and the E-ERRA method based on periodically reserved resource information in Mode 4 communication. The main process of the E-ERRA algorithm is as follows: (1) Establish a candidate resource list; (2) Start broadcasting reserved resource information when the RC value is 5. If the reserved resource is found to be unavailable, other resources are immediately selected from the candidate resource list; (3) Rebroadcast new reserved resource information in subsequent transmissions.

[0072] Figure 3This diagram illustrates the selection conflict probability (SCR) under different vehicle densities in this embodiment of the invention. It can be seen that the SPS algorithm shows a slight difference in selection conflict probability compared to the other two algorithms even at low node densities. With further increases in node density, the SCR of the SPS algorithm increases significantly. While the SCRs of the DRB-SPS and E-ERRA schemes also increase to some extent, both schemes effectively control the generation of selection conflicts by sharing resource information. Furthermore, starting from a vehicle density of 125 vehicles / km, the SCR increase of the E-ERRA algorithm gradually becomes larger. This is because E-ERRA only performs fewer reservation broadcasts, and in high-density environments, the vehicle's reservation message may not be received by other vehicles due to packet loss, resulting in lost reservation information. Additionally, channel changes are more drastic in high-density environments, and the frequency of E-ERRA algorithm adjusting reservation resources also increases accordingly. This can cause previously broadcast reservation information to mislead other vehicles, further reducing the effectiveness of resource reservation. The DRB-SPS algorithm adjusts the timing of the broadcast reservation information in real time according to the channel load. In high-density environments, it ensures that the reservation information can be received by other vehicles through more transmissions, thereby effectively reducing the probability of selection conflicts between different vehicles.

[0073] Figure 4 This diagram illustrates the Packet Reception Rate (PRR) under different vehicle densities in this embodiment of the invention. It can be seen that the PRR of all three schemes decreases with increasing vehicle density. The DRB-SPS and E-ERRA schemes reduce the probability of collisions in high-density environments by exchanging reservation information, thus improving the PRR. Furthermore, thanks to a more efficient resource reservation method, DRB-SPS achieves a higher packet reception rate compared to the E-ERRA scheme.

[0074] Figure 5 This is a graph showing the relationship between the Selective Collision Probability (SCR) and the communication distance between the sender and receiver in this embodiment of the invention. It can be seen that the SCR between node pairs increases with the increase in communication distance. The reserved information exchanged by the E-ERRA and DRB-SPS algorithms enhances the reliability of vehicle resource selection, thus significantly reducing the SCR compared to the SPS algorithm. The graph also shows that the SCR of the E-ERRA algorithm increases significantly at longer distances, which is attributed to the frequent changes in reserved information by the E-ERRA algorithm in high-density environments. As the communication distance increases, the signal strength gradually weakens, which also increases the possibility of the E-ERRA algorithm losing reserved information to some extent. Therefore, its SCR increases faster at longer distances, reaching 8.7% at 300m. In contrast, the DRB-SPS algorithm increases the probability of reserved messages being received through multiple transmissions, achieving only 5.3% at 300m, effectively controlling the SCR.

[0075] Figure 6 This is a graph showing the relationship between Packet Delivery Rate (PDR) and the communication distance between the sender and receiver in this embodiment of the invention. It can be seen that the PDR of all three schemes decreases significantly with increasing communication distance. The E-ERRA and DRB-SPS algorithms achieve higher PDRs by suppressing SCR. Furthermore, it can be observed that the DRB-SPS algorithm achieves a higher PDR than the E-ERRA algorithm even at longer distances. At 300m, the DRB-SPS algorithm still achieves approximately 90% PDR, representing an improvement of about 3.2% compared to the E-ERRA algorithm.

[0076] This invention utilizes modified sidechain control information and dynamically transmits vehicle resource reservation information based on real-time channel status, thereby reducing the uncertainty and suddenness of vehicle resource selection, effectively reducing the probability of mode 4 resource selection conflicts, and improving the reliability of vehicle communication in high-density environments.

[0077] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A semi-persistent scheduling method based on dynamic reservation, characterized in that, Includes the following steps: S1. Construct a dynamic vehicle-to-vehicle communication model; S2. Pre-allocate wireless channel resources; S3. The vehicle decides in advance whether to reselect channel resources; S4. Modify the format of the sidechain control information (SCI) to use reserved fields to carry reserved resource information; S5. Monitor channel resource status and calculate channel busy rate; S6. Based on the channel busy rate, dynamically adjust the timing of transmitting reserved information; after the vehicle selects a resource, randomly determine the number of consecutive transmissions using that resource, denoted as... The range of values ​​is [ , ];in, for The lower limit of the value is preset to 5; for The maximum value for this is set to 15 by default. Then, the vehicle periodically transmits Basic Safety Messages (BSM) over the next period of time; Each time a message is transmitted, The value is -1, when When the value returns to zero, it is determined according to the previous reselection flag. The decision is made on whether to perform a reselection; and the vehicle determines when to begin transmitting reserved information based on the CBR's calculations. The size; specifically, the remaining number of times on the selected resource when the reserved information begins to be transmitted. And preset two CBR thresholds, respectively and Based on the measured range of CBR, The setup method is as follows: (1) If CBR At this point, the channel load is high, the number of available resources begins to decrease, and the probability of resource conflicts increases. With a fixed message transmission frequency, an increase in the number of vehicles also means increased transmission interference between vehicles, and a higher possibility of packet loss. Therefore, to ensure that reserved information can be effectively transmitted to other vehicles on the road, the time for starting the transmission of reserved resource information needs to be advanced accordingly. The values ​​of are represented as follows: in, and These are the preset channel busy rate thresholds; ⌊ A ⌋ indicates the variable Round the value down to the nearest integer. (2) If CBR < At this time, the channel load is low and there are plenty of available resources, so there is no need to transmit reserved information multiple times. =5.

2. The semi-persistent scheduling method based on dynamic reservation according to claim 1, characterized in that, In step S1, a dynamic vehicle-to-vehicle communication model is established, as follows: The vehicle was traveling on a two-way four-lane highway section, the total length of which was... Each lane is 100 km wide The vehicle collection is ={1, 2, …, The average number of vehicles per kilometer on the road follows a Poisson distribution. Assume the road segment extends laterally from left to right, with the origin at the leftmost point of the first lane furthest from the second lane, and the direction of lane distribution as... The axis, the lane extends to the right in the following direction. axis; Then the first The position of the vehicle is represented as ,in Indicates the first The car is The position of the axis ∈[0, 4* ], Indicates the first The car is The position of the axis ∈[0, On a two-way four-lane highway section, vehicles in the first and second lanes travel in the same direction, while vehicles in the third and fourth lanes travel in the opposite direction to those in the first and second lanes. All vehicles travel at a constant speed of [speed value missing]. .

3. The semi-persistent scheduling method based on dynamic reservation according to claim 1, characterized in that, In step S2, the operating frequency band for vehicle communication is 5.9GHz, the available wireless channel bandwidth is 10Hz, and it is divided into resource blocks (RB) in the time-frequency domain. In the time domain, each resource block (RB) has a width of 1ms, which is the length of one subframe; in the frequency domain, each resource block (RB) has a width of 180kHz, corresponding to 12 15kHz subcarriers, and the number of resource blocks (RBs) in the same subframe is 50. Then, 25 resource blocks (RBs) form a sub-channel, and each subframe contains two channel resources; considering a 100ms selection window, each vehicle has 200 selectable channel resources during the selection window.

4. The semi-persistent scheduling method based on dynamic reservation according to claim 1, characterized in that, In step S3, after the vehicle selects the channel resource to be used in this round of transmission, it reserves the probability before using the resource to transmit a message for the first time. Decide whether it is necessary to reselect the channel resources to be used in the next round of transmission; retention probability It is a preset value.

5. A semi-persistent scheduling method based on dynamic reservation according to claim 4, characterized in that, In step S3, the vehicle generates a random number before the first transmission. and the reselection flag Configure settings; in It follows a uniform distribution and ranges between [0, 1]. like If so, the vehicle will select a new resource for the next round of transmission, that is... =1; otherwise, =0 indicates that the next round of vehicle transmission will use the resources currently in use.

6. A semi-persistent scheduling method based on dynamic reservation according to claim 1, characterized in that, In step S4, the total length of the sidechain control information (SCI) is 32 bits, which is divided into the following fields: Message priority, length 3 bits; The resource reservation interval is 4 bits in length. The frequency domain location length of the reserved resource is X bits. This indicates the length of the field used to indicate the frequency domain location of reserved resources; Time difference, 4 bits in length; The modulation and coding strategy has a length of 5 bits. Retransmission flag, 1 bit in length; Reserved field, length 15-X bits; This indicates the length of the field used to indicate the frequency domain location of the reserved resource, with a default value of 2. Therefore, there are 13 bits of available space remaining in the reserved field, which will be used to carry the time-frequency information of the resource used in the next round of transmission.

7. A semi-persistent scheduling method based on dynamic reservation according to claim 6, characterized in that, In step S4, the size of the transmitted data packet is 190 bytes; According to the baseline assumptions in Annex a.2 of 3GPP TR 36.885, that is, with a sidelink bandwidth of 10MHz, including 50 resource blocks (RBs), QPSK modulation, and a coding rate of 0.5, when the index of TB size (ITBS) is 7, the number of resource blocks (RBs) required to transmit a 300-byte BSM message is 20. Adding the two resource blocks (RBs) occupied by the SCI, a total of 22 resource blocks (RBs) are used for each transmission, which can be completed using one resource block. Therefore, 2 bits are taken from the SCI reserved field to indicate the frequency domain information of the reserved resources, and the remaining 11 bits of space in the reserved field are used to indicate the subframe information where the reserved resources are located.

8. A semi-persistent scheduling method based on dynamic reservation according to claim 1, characterized in that, In step S5, the vehicle needs to sense the channel resource status before selecting resources, as follows: First, the vehicle detects the channel resource status, eliminates unavailable resources, and monitors the Received Signal Strength Indicator (RSSI) of each resource. Available resources are sorted in ascending order of RSSI, and resources required for subsequent transmission are randomly selected from the top 20% of resources with the lowest RSSI values. Simultaneously, the vehicle also calculates the current channel load based on the channel's RSSI. Specifically, let the selection time be... ,exist[ -100ms, Within a certain timeframe, the vehicle monitors the channel and calculates the channel busy rate (CBR); the CBR is calculated as follows: in, This indicates the number of sub-channels where the vehicle detected RSSI exceeding a preset threshold within the past 100ms. This indicates the total number of sub-channels in the past 100ms.

9. A semi-persistent scheduling method based on dynamic reservation according to claim 8, characterized in that, In step S5, during the perception period, the vehicle needs to exclude channel resources with reference signal received power higher than the threshold. In addition, since the SCI includes resources that other vehicles will need to use for future transmission, when a vehicle receives a signal from another vehicle, it needs to decode the SCI in the other vehicle's message to obtain the reserved resource information, and then exclude the corresponding resources from the vehicle's candidate resource list to form a candidate resource list, and randomly select available resources from this new candidate resource list.

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