CN115623449A - Internet of vehicles relay node switching mechanism applied to two-dimensional and three-dimensional scenes - Google Patents

Abstract

The vehicle networking relay node switching mechanism applied to 2D and 3D scenarios considers the impact of road height difference and environmental obstacles on the V2V communication range, and combines the distribution of nodes within the two-hop range to determine the two Whether the selection method of the relay node is applicable to the current scenario, and complete the node switching strategy. Calculate the two-hop communication range along the road length obtained by the GPSR method and the traversal method; judge whether the GPSR calculation result is less than the maximum value of the traversal result; if it is less than, start the three-dimensional relay method; Dimension relay method. The present invention dynamically estimates the communication range of the current relay node, and studies when to adopt the trigger and exit mechanism of the key three-dimensional area to match the corresponding relay node selection method. It is more helpful to ensure the characteristics of ultra-low latency and high reliability of V2V communication in combination with actual scenarios, thereby improving the efficiency of emergency message dissemination.

Description

Switching Mechanism of IoV Relay Node Applied to 2D and 3D Scenes

technical field

The invention relates to a V2V communication technology in a vehicle ad hoc network, in particular to a vehicle relay node switching mechanism applied to two-dimensional and three-dimensional scenes.

Background technique

As an important part of modern intelligent transportation, the Internet of Vehicles is widely used in intelligent transportation. Among them, emergency message broadcasting, as a security application of the Internet of Vehicles, can provide an efficient and safe driving environment, effectively avoid casualties and reduce economic losses. delay, higher reliability, and higher speed.

Existing relay node selection methods focus on research in two-dimensional scenarios, using a fixed communication range, only considering the message propagation performance of one hop, and selecting the next hop relay node of the source node. The structure of 3D road is complex and has characteristics different from that of 2D road. Obstacles between layers make the communication range of the sending node vary greatly at different layers. With the ups and downs of the terrain, the effective height of the V2V base station antenna will change accordingly, affecting the change of the actual communication range. It is precisely because of this difference in communication range that often affects the connectivity of relay node performance and the probability of hop increase. Therefore, the relay node selection method for 2D scenarios cannot be simply extended and applied to 3D scenarios.

Contents of the invention

The purpose of the present invention is to consider the influence of road elevation differences and environmental obstacles (such as vegetation, rocks, etc.) on the communication range of relay nodes, and the method for selecting relay nodes in two-dimensional scenarios is no longer applicable to current key three-dimensional areas. A handover mechanism for relay nodes in Internet of Vehicles is proposed.

In order to solve the above problems, the present invention adopts the following technical solutions:

The source node sends a request to the destination node;

Each node collects vehicle location (longitude, latitude and altitude) through GPS and sensors, and obtains surrounding environment information through GIS assistance;

The source node obtains the location information of other nodes through the beacon Beacon;

Obtain the height h _Rx of the vehicle antenna from the ground;

Calculate the effective height h _Tx of the source node antenna and the Euclidean distance between vehicles according to the position of the vehicle and the height of the vehicle from the ground;

h _Tx = the ground altitude of the source node - the ground altitude of the mobile node location + the height of the vehicle antenna from the ground;

Calculate the path loss PL(d) between the source node and other nodes using the revised IEEE802.16d model, as shown in (1);

Wherein, d ₀ is a reference distance, γ=a-bh _Tx +c/h _Tx , a, b, and c are parameters, C _f is a coefficient related to the carrier frequency, and C _Rx is a coefficient related to the receiving antenna.

In the 3D road scene, the relay node vehicles of the Internet of Vehicles will fade due to shadows caused by terrain, obstacles, and adjacent large vehicles.

Shadow fading describes the slow-changing characteristics of the median value of the signal level in a medium-scale interval (hundreds of wavelengths). The characteristics of shadow fading can be described by random variables with a log-normal distribution, namely:

PL'(d)=PL(d)+X _σ (2)

X _σ is a random variable with zero-mean Gaussian distribution. The type, density and width of environmental obstacles will affect the value of X _σ .

Take the minimum allowable path loss D of the uplink and downlink transmission lines of two nodes in general scenarios as the benchmark;

Determine whether the total loss PL'(d) between the source node and an arbitrary node is less than the D value, so as to obtain the candidate relay node within the communication range of the source node;

Find the next hop relay node of the source node according to the greedy algorithm GPSR, and record its length _R1 from the path of the source node;

Repeat the greedy algorithm to find the second-hop relay node of the source node, and record the length _R2 of the road from it to the first-hop relay node;

Calculate the total length W _GPSR of the two-hop road for message propagation under the GPSR algorithm;

W _GPSR = Length _R1 + Length _R2 (3)

Calculate the road length from other candidate nodes to the source node within the communication range of the source node;

Traverse the candidate nodes of the source node, assuming they are the first-hop relay nodes of the source node, and find the second-hop candidate nodes in their communication range. Use the longest node along the road among the second-hop candidate nodes as the second-hop relay, and calculate the road length from it to the first-hop relay node;

Calculate the total length of the two-hop road of the traversal method {W ₂ ,W ₃ ,W _i, ...,Wn};

The maximum value of the traversal results is used as the total length of the two-hop road in the dynamic three-dimensional relay method;

W _{dynamic three-dimensional relay} =MAX{W ₂ ,W ₃ ,W _i ,...,Wn} (4)

Judging whether W _GPSR is smaller than W _{dynamic 3D relay} , if the judgment condition is met, the region triggers the relay node selection mechanism for switching from 2D to 3D, and switches from the first relay node entering the area to the relay in the 3D road scene If the node selection method is not satisfied, continue to use the previous two-dimensional road scene relay node selection method. If the relay node selection method in the 2D road scene has been switched from 2D to 3D before, but it is found that the Nth relay node does not meet the switching threshold condition, the Nth node exits the 3D road relay node selection method, Select the appropriate relay node selection method for the two-dimensional road scene, and the switching algorithm is completed.

The present invention is applied to the switching judgment of relay node selection methods for two-dimensional roads and three-dimensional roads. The method can effectively judge the key characteristics of roads that need to be selected by relay nodes in three-dimensional scenes, and provides switching thresholds and switching mechanisms, which can be used according to specific scenarios. Determine a more reasonable relay node selection method.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings that are required in the description of the embodiments or the prior art.

FIG. 1 is a flow chart of triggering or exiting a relay node switching mechanism of the Internet of Vehicles applied to two-dimensional and three-dimensional scenarios provided by an embodiment of the present invention;

Fig. 2 is the specific flowchart of step S200 in Fig. 1;

3 is a schematic diagram of the two-hop selection of the GPSR method and the two-hop selection of the three-dimensional dynamic relay method in the relay node switching mechanism of the Internet of Vehicles applied to the two-dimensional and three-dimensional scenes provided by the example of the present invention.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

The present invention provides a detailed description of the switching threshold and mechanism of the relay node of the Internet of Vehicles applied to two-dimensional and three-dimensional scenes in conjunction with Fig. 1, including the following steps:

S100, the source node and other vehicles on the road in the direction of message propagation obtain their own three-dimensional position coordinates by means of GPS, including longitude, latitude and altitude; obtain the target environmental obstacle parameters by means of GIS;

S200. Find all candidate nodes within the actual communication range of the source node according to the three-dimensional position information and obstacle parameters acquired in S100;

S300. Obtain the sum of the respective two-hop communication distances of the greedy algorithm GPSR and the three-dimensional traversal method;

S400. Using the two-hop result of the GPSR method as a switching threshold, and defining the maximum value of the result obtained by the three-dimensional traversal method as the total length of the two-hop road in the dynamic three-dimensional relay method. Comparing the results of the two, if the two-hop distance of the dynamic three-dimensional relay method is greater than the current threshold, the switching mechanism of the relay node is triggered.

S500. The first relay node that satisfies the threshold judgment condition starts the three-dimensional road relay node selection method, and if the judgment condition is not satisfied, there is no need to switch or exit the three-dimensional road relay node selection method. If the relay node selection method in the 2D road scene has been switched from 2D to 3D before, but it is found that the Nth relay node does not meet the switching conditions, the Nth node will exit the 3D road relay node selection method, and select A suitable two-dimensional road scene relay node selection method, the switching mechanism is completed.

Wherein, in step S100 of this example, the target environmental obstacle can be vegetation, rocks or mountains, etc., and the specific attenuation rate caused by vegetation depends on the type, density and wide range of density of vegetation;

Referring to FIG. 2 , in step S200 of this example, the source node can obtain the three-dimensional position coordinates of other vehicles through the Beacon, and calculate their relative height difference, Euclidean distance. The height of the receiving antenna is the height of the vehicle antenna from the ground, and the height of the transmitting antenna is the relative height difference between the two nodes plus the height of the vehicle from the ground antenna. The path loss of the two vehicles is calculated according to the IEEE802.16d wireless communication model, plus the GIS The obstacle attenuation factor loss is the final total value loss. According to the parameters of the base station wireless equipment selected by the project, the performance of the antenna feeder and other indicators, the maximum allowable path loss of the uplink and downlink lines is calculated. Generally, the allowable path loss of the uplink and downlink transmission lines is taken as the benchmark, and the final path between the two nodes is judged. Whether the loss is less than the benchmark to obtain the next hop relay candidate set node of the source node;

In step S300 of this example, among the candidate nodes of the source node, the node with the farthest message propagation along the road length is selected as the relay node of the first hop according to the greedy algorithm, and the second hop is also selected within the communication range of the first hop For the node along the farthest length of the road, calculate the road length from the second hop node to the source node, and use this as the result of two hops in the GPSR method; traverse the candidate set nodes of the source node, and calculate their road lengths from the source node respectively, and set They act as the sender, find the second-hop candidate nodes within their communication range, select the node with the longest road along the second-hop candidate node as the second-hop relay, calculate the length of the road between them and the sender, and calculate the three-dimensional traversal The total length of the two-hop road {W ₂ ,W ₃ ,W _i ,...,Wn} obtained by the method.

Further, the GPSR and the three-dimensional traversal method of the present invention will be described with reference to FIG. 3 . For example, in Figure 3, S1 is the source node, S2, S3, and S4 are its next-hop candidate nodes, S4 is the farthest along the road length, S5, S6 are candidate nodes within its communication range, and S4, S5 , S6, S7 are all within the communication range of S3;

In step S400 of this example, the result of the two jumps of the GPSR method is compared with the maximum value of the two jumps of the three-dimensional traversal method. The impact on the communication range, the relay node selection method in the two-dimensional scene is not necessarily optimal, the two distances of the dynamic three-dimensional relay method are greater than the two-hop distance of the GPSR method as the threshold condition for triggering the switch of the relay node selection method;

In step S500 of this example, it is determined whether to start the relay node switching mechanism according to the judgment result of step S400. If the judgment condition of step S400 is met, the switching mechanism is started by the first node that meets the condition, and a new three-dimensional road is selected. Relay node selection scheme. If not, there is no need to start the switching mechanism or the node exits the current 3D road relay node selection method. Therefore, a reasonable and effective switching mechanism can be provided for matching different relay node selection methods with different road characteristics.

The above is only a preferred embodiment of the present invention, and does not therefore limit the patent scope of the present invention. Under the inventive concept of the present invention, the equivalent structural transformation made by using the description of the present invention and the contents of the accompanying drawings, or direct/indirect use All other relevant technical fields are included in the patent protection scope of the present invention.

Claims (5)

1. A vehicle networking relay node switching mechanism applied to two-dimensional and three-dimensional scenes, characterized in that it comprises the following processes: 1) Obtain the current three-dimensional position information of the vehicle through the vehicle-mounted GPS, including longitude, latitude and altitude; obtain the surrounding environment obstacle parameters by the GIS that comes with the vehicle; 2) Calculate the next-hop available candidate nodes in the source node communication area according to the vehicle coordinates and obstacle parameters; 3) Calculate the farthest communicable position of the next hop of the available candidate node of the source node, and obtain the two-hop communication distance of the GPSR method and the three-dimensional traversal method, wherein the farthest communicable position and communication distance are defined along the road length; 4) Define the maximum value of the results obtained by the three-dimensional traversal method as the total length of the two-hop road of the dynamic three-dimensional relay method, and the two-hop distance calculated by GPSR is smaller than the two-hop distance of the dynamic three-dimensional relay method as the threshold for switching relay nodes in the Internet of Vehicles condition; 5) According to judging whether the current node satisfies the threshold condition, it is decided whether to start the three-dimensional road relay node selection method. 2. A kind of vehicle networking relay node switching mechanism applied to two-dimensional and three-dimensional scenes according to claim 1, characterized in that, step 2) considers high-level differences and obstacles so that the communication ranges of different nodes are relatively large There is a big difference, the communication range of V2V vehicles is no longer fixed, and the specific process of obtaining the next-hop available candidate nodes in the communication area of the source node is as follows: The source node uses Beacon to obtain the location information of other vehicles; The height of the vehicle antenna from the ground is h _Rx , h _Tx = the ground altitude of the source node - the ground altitude of the location of the mobile node + the height of the vehicle antenna from the ground; Calculate the path loss PL(d) between the source node and other nodes using the revised IEEE802.16d model, as shown in (1);

Shadow fading describes the slow-changing characteristics of the median value of the signal level in a medium-scale interval (hundreds of wavelengths). The characteristics of shadow fading can be described by random variables with a log-normal distribution, namely: PL'(d)=PL(d)+X _σ (2) X _σ is a random variable with zero mean Gaussian distribution; Take the minimum allowable path loss D of the uplink and downlink transmission lines of two nodes in general scenarios as the benchmark; Determine whether the total loss PL'(d) between the source node and an arbitrary node is less than the D value, so as to obtain the candidate relay nodes within the communication range of the source node. 3. A kind of vehicle networking relay node switching mechanism that is applied to two-dimensional and three-dimensional scenes according to claim 1, it is characterized in that, in step 3), obtain the specific two-hop communication distance of GPSR method and three-dimensional traversal method The process is as follows: Find the next hop relay node of the source node according to the greedy algorithm GPSR, and record its length _R1 from the path of the source node; Repeat the greedy algorithm to find the second-hop relay node of the source node, and record the length _R2 of the road from it to the first-hop relay node; Calculate the total length W _GPSR of the two-hop road for message propagation under the GPSR algorithm; W _GPSR = Length _R1 + Length _R2 (3) Calculate the road length from other candidate nodes to the source node within the communication range of the source node; Traverse the candidate nodes of the source node, assuming they are the first hop relay nodes of the source node, find the second hop candidate nodes in their communication range, and take the longest node along the road among the second hop candidate nodes as the second hop Relay, calculate the road length from it to the first hop relay node; Calculate the total length of the two-hop road {W ₂ ,W ₃ ,W _i ,...,Wn} obtained by the three-dimensional traversal method. 4. A kind of vehicle networking relay node switching mechanism applied to two-dimensional and three-dimensional scenes according to claim 1, characterized in that, in step 4), according to the two-hop distance set obtained by step 3) three-dimensional traversal method, Select a maximum value from it, and use this maximum value as the total length of the two-hop road of the dynamic three-dimensional relay method, namely: W _{dynamic three-dimensional relay} =MAX{W ₂ ,W ₃ ,W _i ,...,Wn} (4) The two-hop result of the GPSR method is used as the switching threshold, and the two-hop distance obtained by the GPSR method is smaller than the two-hop distance obtained by the dynamic 3D relay method, which is used as the threshold condition for relay node switching between 2D and 3D scenes. 5. A kind of vehicle networking relay node switching mechanism applied to two-dimensional and three-dimensional scenes according to claim 1, characterized in that, in step 5), relay node switching between two-dimensional scenes and three-dimensional scenes is provided mechanism. When a relay node satisfies the threshold condition in step 4), and the two-hop distance obtained by the GPSR method is smaller than the two-hop distance obtained by the dynamic three-dimensional relay method, the first relay node entering the area is switched to the middle relay node in the three-dimensional road scene. Relay node selection method, if not satisfied, continue to use the previous two-dimensional road scene relay node selection. If the relay node selection method in the 2D road scene has been switched from 2D to 3D before, but it is found that the Nth relay node does not meet the switching threshold condition, the Nth node will exit the 3D road relay node selection method, Select the appropriate relay node selection method for the two-dimensional road scene, and the switching mechanism is completed.

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