Roadside unit content code placement system and method capable of sensing vehicle movement

Abstract

The invention discloses a roadside unit content code placement system capable of sensing vehicle movement. The roadside unit content code placement system comprises a cloud server, a macro base station, roadside units, area controllers and vehicle users. The invention also provides a roadside unit content coding placement method, which comprises the following steps that: firstly, the area controller constructs and maintains a probability distribution relationship of the content obtained by the vehicle user from each roadside unit based on the distribution of the residence time of the vehicle passing through the target road section within the range of each roadside unit, and forms a decision support model; generating a content code placement decision of the roadside unit according with the maximum hit rate; the area controller optimizes a repeated cache placement strategy of the adjacent roadside units based on the average vehicle speed in the roadside unit range; and the decision support model performs on-demand network coding on the to-be-cached content, so that a vehicle user downloads content blocks from a roadside unit as many as possible, downloading from a remote base station is reduced, the transmission delay of the content is reduced, the utilization rate of a system cache space is improved, and the service quality of the vehicle user is improved.

Description

Technical Field

[0001] The present invention relates to the field of network communication technology, and in particular to a roadside unit content coding placement system and method capable of sensing vehicle movement. Background Art

[0002] In the coming era of widespread Internet of Vehicles and autonomous driving, road administration departments will provide vehicle users with a series of data content services including high-precision maps, real-time road and traffic data, environmental data, etc. through road side units (RSU). These services will greatly enhance the vehicle's environmental perception capabilities, optimize path planning, improve driving safety and efficiency, and provide key support for the development of intelligent transportation systems and autonomous driving technologies.

[0003] These contents to be served are not only closely related to the geographical location, but also generally have the characteristics of high storage overhead, time sensitivity and frequent updates. Therefore, the content storage architecture based on remote cloud servers may have problems of inefficiency and response delays. In order to solve these problems, a more efficient edge data storage solution is needed. Roadside unit caching technology has been proven to be an effective way to solve the problem of in-vehicle content transmission. By enabling the roadside unit with caching function, in-vehicle users can directly obtain the required content from the local cache of the roadside unit, reducing dependence on remote base stations, thereby achieving low-latency content delivery, reducing the burden on the backhaul network, and significantly improving the service quality of in-vehicle content distribution.

[0004] Existing strategies consider cooperative caching when designing roadside unit caches for two reasons: on the one hand, due to the limited cache capacity of roadside units, it is impossible to pre-store all the content that may be needed in one roadside unit; on the other hand, due to mobility issues, the delivery process may need to cross the coverage of multiple roadside units to complete. However, in order to ensure the quality of service, adjacent roadside units will partially cache the same content blocks repeatedly, wasting cache space. Summary of the invention

[0005] The present invention provides a roadside unit content coding placement system and method capable of perceiving vehicle movement, thereby solving the problem of space waste in placing roadside unit content.

[0006] To achieve the above object, the present invention provides the following technical solution: a roadside unit content coding placement system capable of sensing vehicle movement, comprising a (Remote) Cloud Server (CS), a Macro Site (MS), a Road Side Unit (RSU), an Area Control Unit (AC) and a vehicle user, characterized in that:

[0007] A cloud server storing source files of all content used to serve vehicle users of the roadside unit content coding placement system;

[0008] The macro base station is connected to the cloud server through the Internet. When the vehicle user cannot obtain the required content through the roadside unit, the vehicle user obtains the source content stored on the cloud server through the macro base station;

[0009] A roadside unit is a local server installed on the roadside and communicating with the vehicle onboard unit (OBU) within its communication coverage area; the roadside unit communicates with the macro base station and the regional controller, and the roadside unit is configured with a local data storage medium, including but not limited to a hard disk, a solid-state disk, a disk array, a network attached storage (NAS) or a hybrid storage system thereof, and caches the content to be served from the cloud server under the control of the regional controller to meet the content service needs of vehicle users within the coverage area;

[0010] The vehicle user is the person to be served. The vehicle user communicates with the roadside unit and macro base station within the coverage area through the on-board unit of the vehicle to obtain the required file content.

[0011] The regional controller is a dedicated server connected to the roadside unit, or an application running on a roadside unit that can perform corresponding management functions. It is used to sense the movement information of vehicles in the area, and form content storage decisions for each roadside unit based on the disclosed roadside unit content coding placement method to complete the content caching of the roadside unit.

[0012] Preferably, in the system, several roadside units near the road are controlled by a regional controller; and the regional controller is connected to a traffic flow sensing system integrated in the roadside units, so that the regional controller knows or can predict the roadside units that vehicles will pass through in the next few minutes, and understands the distribution of the residence time within each roadside unit, which can be generated by counting past historical information, and the regional controller is also aware of the available space in the roadside unit cache and the content requests issued by passing users. Based on the above information, the regional controller determines the content blocks that should be cached by each roadside unit.

[0013] The present invention also provides a method for placing roadside unit content coding that can perceive vehicle movement, comprising the following steps:

[0014] S1. The regional controller constructs and maintains the probability distribution relationship of vehicle users obtaining content from each roadside unit based on the distribution of the residence time of passing vehicles on the target road section within the range of each roadside unit, forms a decision support model, and generates content coding placement decisions for roadside units that meet the maximum hit rate;

[0015] S2, the regional controller will optimize the repeated cache placement strategy of adjacent roadside units based on the average vehicle speed within the roadside unit range, thereby improving the cache space utilization;

[0016] S3. The decision support model performs on-demand network coding on the cached content. The encoded content blocks are cached in the roadside unit RSU. Vehicle users can download more content blocks from the roadside unit and reduce downloading from remote base stations.

[0017] Preferably, in step S1, the regional controller constructs and maintains a probability distribution relationship of vehicle users acquiring content from each roadside unit based on the distribution of the residence time of vehicles passing through the target road section within the range of each roadside unit:

[0018]

[0019] Among them, φ r (b) represents the probability that the bth content block is downloaded by the vehicle user at the rth roadside unit, X r represents the last content block number received by the vehicle user when staying within the coverage area of ​​the rth roadside unit; T r is the total number of content blocks downloaded by the vehicle user when staying within the coverage area of ​​the rth roadside unit; r (b) and the threshold value τ of the quality service requirement determine B r :

[0020]

[0021] Among them, B r represents the total number of cached content blocks of the rth roadside unit, B r (b)=1 indicates that the rth roadside unit caches the bth content block; based on this information, the regional controller determines the content block that each roadside unit should cache.

[0022] Preferably, in step S2, according to φ r (b) Obtain the preliminary caching plan B of the vehicle at the roadside unit r Although the repeated redundant caching of content blocks in adjacent roadside units can improve the hit rate, the coded blocks after encoding are different and do not need to be cached repeatedly, so the space utilization can be further improved. Then, according to the two situations that occur, including:

[0023] 1) The space occupied by the coding block downloaded by the vehicle at the roadside unit is smaller than the roadside unit cache space. At this time, the roadside unit cache space is not fully utilized and can be allocated to adjacent roadside units with overlapping coverage;

[0024] 2) The space occupied by the code blocks downloaded by the vehicle at the roadside unit is larger than the roadside unit cache space, and it is necessary to borrow the space of adjacent roadside units with overlapping coverage;

[0025] Solve the optimization problem through linear programming, as follows:

[0026] Objective function:

[0027] in, represents the hit rate of the vehicle downloading the content block from the rth roadside unit under the network coding method, and R represents the number of roadside units;

[0028] Constraint 1:

[0029] Constraint 2:

[0030] Constraint 3:

[0031] in, represents the number of duplicate cache content blocks of the rth roadside unit and the r+1th roadside unit, represents the number of non-repetitive cache content blocks of the rth roadside unit, B r represents the total number of cache content blocks of the rth roadside unit;

[0032] Constraint 4:

[0033] Constraint 5:

[0034] in, represents the number of cache content blocks belonging to the rth roadside unit in the cache space between the rth roadside unit and the r+1th roadside unit; represents the average stay time of vehicles within the rth roadside unit;

[0035] Constraint 6:

[0036] Constraint 7:

[0037] Constraint 8:

[0038] Among them, E r The number of content blocks representing the sum of the number of cached content blocks belonging to the rth roadside unit in the non-repeated cache portion of the rth roadside unit and the cache space between the rth roadside unit and the r+1th roadside unit;

[0039] Constraint 9:

[0040] The above formula is the method for calculating the hit rate of the content block;

[0041] Finally, the redundant placement of adjacent roadside units is obtained Where r∈{1,2,…,R-1}; for the second case, Can be negative. When it is a negative number, it means that its space is borrowed to the adjacent roadside unit for use; according to the redundant placement as well as Determine the number of network coding blocks E cached by each roadside unit r .

[0042] Preferably, in step S3, the network coding method formula is:

[0043] E=(e1,…,e m ) T =C·B=(c i,1 ,…,c i,n )·(b1,…,b n ) T ,i∈[1,m]

[0044] The encoding process is recorded as E = C·B, where E = (e1,…,e m ) T is a set of m (m ≥ n) coding blocks generated after the coding operation. Any coding block e in the set i It is composed of n source content blocks in a selected finite field such as GF(2 8 ) is generated by a linear combination of i,n It is called coding block e i The encoding vector, whose elements are randomly generated from a finite field; B represents the set of source content blocks. After the source file is split, it contains n content blocks b1, b2, …, b n .

[0045] Compared with the prior art, the present invention has the following beneficial effects: the present invention solves the problem of space waste in placing roadside unit content; it is suitable for application scenarios where the roadside unit cache space is limited, and can enable vehicle users to download as many content blocks as possible from the roadside unit, reducing the number of content blocks they directly download from the remote base station, thereby reducing content transmission delays, improving the utilization rate of the limited space of the roadside unit, saving cache space, and at the same time improving the hit rate of the roadside unit cache content in the Internet of Vehicles, thereby improving system work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0047] In the attached picture:

[0048] Figure 1 It is a structural schematic diagram of the Internet of Vehicles edge cache model of the present invention;

[0049] Figure 2 It is a flow chart of the method for placing roadside unit content coding according to the present invention. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0051] Example: Figure 1 As shown, the present invention provides a roadside unit content coding placement system that can perceive vehicle movement, including a (Remote) Cloud Server (CS), a Macro Site (MS), a Road Side Unit (RSU), an Area Control Unit (AC) and a vehicle user, characterized in that:

[0052] A cloud server storing source files of all content used to serve vehicle users of the roadside unit content coding placement system;

[0053] The macro base station is connected to the cloud server through the Internet. When the vehicle user cannot obtain the required content through the roadside unit, the vehicle user obtains the source content stored on the cloud server through the macro base station;

[0054] A roadside unit is a local server installed on the roadside and communicating with the vehicle onboard unit (OBU) within its communication coverage area; the roadside unit communicates with the macro base station and the regional controller, and the roadside unit is configured with a local data storage medium, including but not limited to a hard disk, a solid-state disk, a disk array, a network attached storage (NAS) or a hybrid storage system thereof, and caches the content to be served from the cloud server under the control of the regional controller to meet the content service needs of vehicle users within the coverage area;

[0055] The vehicle user is the person to be served. The vehicle user communicates with the roadside unit and macro base station within the coverage area through the on-board unit of the vehicle to obtain the required file content.

[0056] The regional controller is a dedicated server connected to the roadside unit, or an application running on a roadside unit that can perform corresponding management functions. It is used to sense the movement information of vehicles in the area, and form content storage decisions for each roadside unit based on the disclosed roadside unit content coding placement method to complete the content caching of the roadside unit.

[0057] Specifically, in the system, several roadside units near the road are controlled by a regional controller; and the regional controller is connected to the traffic flow sensing system integrated in the roadside unit, so that the regional controller knows or can predict the roadside units that the vehicle will pass through in the next few minutes, and understands the distribution of the stay time within each roadside unit, which can be generated by counting past historical information, and the regional controller is also aware of the available space in the roadside unit cache and the content requests issued by passing users. Based on the above information, the regional controller determines the content blocks that each roadside unit should cache.

[0058] like Figure 2 As shown, the present invention also provides a method for placing roadside unit content encoding that can perceive vehicle movement, and completes the placement of roadside unit content:

[0059] S1: Reference Figure 1 ,Based on the distribution of the residence time of passing vehicles on the target road section within the range of each roadside unit, the regional controller builds and maintains the probability distribution relationship of vehicle users obtaining content from each roadside unit, forms a decision support model, and generates content coding placement decisions for roadside units that meet the maximum hit rate.

[0060] The regional controller is based on the distribution of the stay time of passing vehicles in each roadside unit on the target road section, which can be generated by statistically analyzing past historical information, and then constructing and maintaining the probability distribution relationship of vehicle users obtaining content from each roadside unit:

[0061]

[0062] Among them, X r Indicates the number of the last content block received by the vehicle user when staying within the coverage area of ​​the rth roadside unit. r is the total number of content blocks downloaded by the vehicle user when staying within the coverage area of ​​the rth roadside unit. r (b) and the threshold value τ of the quality service requirement determine B r :

[0063]

[0064] Among them, B r represents the total number of cached content blocks of the rth roadside unit, B r(b)=1 indicates that the rth roadside unit caches the bth content block.

[0065] The regional controller then predicts the roadside units that the vehicle will pass through and the duration of its stay. Based on this information, the regional controller can determine the content blocks that should be cached at each roadside unit that the vehicle will pass through. To ensure service quality, since adjacent roadside units will cache some content blocks repeatedly, the vehicle will download redundant content blocks within the overlapping coverage of adjacent roadside units, which may lead to a waste of cache space.

[0066] S2: The regional controller will optimize the repeated cache placement strategy of adjacent roadside units based on the average vehicle speed within the roadside unit range to improve the cache space utilization.

[0067] According to φ r (b) The preliminary caching scheme B of the vehicle at the roadside unit can be obtained r Although the hit rate can be improved by redundantly caching content blocks in adjacent roadside units, the encoded blocks are different after encoding and do not need to be cached repeatedly, so the space utilization can be further improved. Then, two situations will occur here:

[0068] 1) The space occupied by the coding block downloaded by the vehicle at the roadside unit is smaller than the roadside unit cache space. At this time, the roadside unit cache space is not fully utilized and can be allocated to adjacent roadside units with overlapping coverage;

[0069] 2) The space occupied by the coding block downloaded by the vehicle at the roadside unit is larger than the roadside unit cache space, and it is necessary to borrow the space of the adjacent roadside unit with overlapping coverage;

[0070] Solve the optimization problem through linear programming, as follows:

[0071] Objective function: Constraint 1 Constraint 2 Constraint 3 Constraint 4 Constraint 5 Constraint 6 Constraint 7 Constraint 8 Constraint 9

[0072] Get the redundant placement of adjacent roadside units Where r∈{1,2,…,R-1}; for the second case, Can be negative. When it is a negative number, it means that its space is borrowed to the adjacent roadside unit for use; according to the redundant placement as well as Determine the number of network coding blocks E cached by each roadside unit r .

[0073] S3: The decision support model performs on-demand network coding on the cached content. The encoded content blocks are cached in the roadside unit. Vehicle users can download more content blocks from the roadside unit instead of from the remote base station.

[0074] If the roadside unit stores the source data packets, the vehicle users must download them in sequence, and the vehicles will download repeatedly within the overlapping range. However, in the network coding method, the roadside unit stores mixed coding blocks of the source data. Then, as long as the vehicle users download the specified number of coding blocks, the source data can be decoded without considering which ones are downloaded.

[0075] A simulation experiment was designed to verify that vehicle users can download more content blocks from roadside units rather than from remote base stations.

[0076] In summary, the method for placing roadside unit content coding that can perceive vehicle movement is aimed at a roadside unit content coding placement system including a cloud server, a macro base station, a roadside unit, a regional controller, and a vehicle user. The above components form a vehicle network edge cache model. Based on the distribution of the residence time of vehicles passing through the target section within the range of each roadside unit, the probability distribution relationship of vehicle users obtaining content from each roadside unit is constructed and maintained to form a decision support model, and a content coding placement decision that meets the maximum hit rate of the roadside unit is generated. The repeated cache placement strategy of adjacent roadside units is optimized based on the average vehicle speed within the roadside unit range to improve the cache space utilization. The content to be cached is network encoded on demand, so that vehicle users can download more content blocks from the roadside unit instead of from the remote base station. The problem of space waste in the placement of roadside unit content is solved. The transmission delay of service content is reduced, and the working efficiency of the vehicle network edge cache model is improved.

[0077] Finally, it should be noted that the above description is only a preferred example of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A roadside unit content coding placement system capable of sensing vehicle movement, comprising a cloud server, a macro base station, a roadside unit, a regional controller, and a vehicle user, characterized in that: A cloud server storing source files of all content used to serve vehicle users of the roadside unit content coding placement system; The macro base station is connected to the cloud server through the Internet. When the vehicle user cannot obtain the required content through the roadside unit, the vehicle user obtains the source content stored on the cloud server through the macro base station; A roadside unit is a local server installed on the roadside and communicating with the vehicle-mounted units within its communication coverage area; The roadside unit communicates with the macro base station and the regional controller, and the roadside unit is equipped with a local data storage medium, which caches the content to be served from the cloud server under the control of the regional controller, thereby meeting the content service needs of vehicle users in the coverage area; The vehicle user is the person to be served. The vehicle user communicates with the roadside unit and macro base station within the coverage area through the on-board unit of the vehicle to obtain the required file content. The regional controller is a dedicated server connected to the roadside unit, or an application running on a roadside unit that can perform corresponding management functions. It is used to sense the movement information of vehicles in the area, and form content storage decisions for each roadside unit based on the disclosed roadside unit content coding placement method to complete the content caching of the roadside unit.

2. The roadside unit content coding placement system capable of sensing vehicle movement according to claim 1, characterized in that: In the system, several roadside units near the road are controlled by a regional controller; and the regional controller is connected to a traffic flow sensing system integrated in the roadside units, and the content blocks that each roadside unit should cache are determined through the regional controller.

3. A method for placing roadside unit content codes that can perceive vehicle movement, characterized in that: The following steps are involved: S1. The regional controller constructs and maintains the probability distribution relationship of vehicle users obtaining content from each roadside unit based on the distribution of the residence time of passing vehicles on the target road section within the range of each roadside unit, forms a decision support model, and generates content coding placement decisions for roadside units that meet the maximum hit rate; S2, the regional controller optimizes the repeated cache placement strategy of adjacent roadside units based on the average vehicle speed within the roadside unit range; S3. The decision support model performs on-demand network coding on the cached content. The encoded content blocks are cached to the roadside unit RSU. The vehicle user downloads the content blocks from the roadside unit, reducing the download from the remote base station.

4. The method for placing roadside unit content codes capable of perceiving vehicle movement according to claim 3, characterized in that: In step S1, the regional controller constructs and maintains the probability distribution relationship of vehicle users obtaining content from each roadside unit based on the distribution of the residence time of vehicles passing through the target road section within the range of each roadside unit: Among them, φ r (b) represents the probability that the bth content block is downloaded by the vehicle user at the rth roadside unit, X r represents the last content block number received by the vehicle user when staying within the coverage area of ​​the rth roadside unit; T r is the total number of content blocks downloaded by the vehicle user when staying within the coverage area of ​​the rth roadside unit; r (b) and the threshold value τ of the quality service requirement determine B r : Among them, B r represents the total number of cached content blocks of the rth roadside unit, B r (b)=1 indicates that the rth roadside unit caches the bth content block; based on this information, the regional controller determines the content block that each roadside unit should cache.

5. The method for placing roadside unit content codes capable of perceiving vehicle movement according to claim 4, characterized in that: In step S2, according to φ r (b) Obtain the preliminary caching plan B of the vehicle at the roadside unit r , in order to further improve the space utilization; solve the optimization problem through linear programming, as follows: Objective function: in, represents the hit rate of the vehicle downloading the content block from the rth roadside unit under the network coding method, and R represents the number of roadside units; Constraint 1: Constraint 2: Constraint 3: in, represents the number of duplicate cache content blocks of the rth roadside unit and the r+1th roadside unit, represents the number of non-repetitive cache content blocks of the rth roadside unit, B r represents the total number of cache content blocks of the rth roadside unit; Constraint 4: Constraint 5: in, represents the number of cache content blocks belonging to the rth roadside unit in the cache space between the rth roadside unit and the r+1th roadside unit; represents the average stay time of vehicles within the rth roadside unit; Constraint 6: Constraint 7: Constraint 8: Among them, E r represents the number of content blocks in the non-repeated cache portion of the r-th roadside unit and the cache space between the r-th roadside unit and the r+1-th roadside unit, which belongs to the r-th roadside unit; Constraint 9: The above formula is the method for calculating the hit rate of the content block; Finally, the redundant placement of adjacent roadside units is obtained Where r∈{1,2,…,R-1}, according to the amount of redundant placement as well as Determine the number of network coding blocks E cached by each roadside unit r .

6. The method for placing roadside unit content codes capable of perceiving vehicle movement according to claim 5, characterized in that: In step S3, the network coding method formula is: E=(e1,…,e m ) T =C·B=(c i,1 ,…,c i,n )·(b1,…,b n ) T ,i∈[1,m] The encoding process is recorded as E = C·B, where E = (e1,…,e m ) T is a set of m (m ≥ n) coding blocks generated after the coding operation. Any coding block e in the set i It is composed of n source content blocks in a selected finite field such as GF(2 8 ) is generated by a linear combination of i,n It is called coding block e i The encoding vector, whose elements are randomly generated from a finite field; B represents the set of source content blocks. After the source file is split, it contains n content blocks b1, b2, …, b n .

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