A roadside unit content coding placement system and method capable of sensing vehicle movement

Abstract

The present invention discloses a roadside unit content coding placement system that can perceive vehicle movement, including a cloud server, a macro base station, a roadside unit, a regional controller, and a vehicle user. The present invention also provides a roadside unit content coding placement method. First, the regional controller constructs and maintains a probability distribution relationship for vehicle users to obtain content from each roadside unit based on the distribution of the residence time of vehicles passing through a target road section within the scope of each roadside unit, forms a decision support model, and generates a content coding placement decision for the roadside unit that meets the maximum hit rate. The regional controller optimizes the repeated cache placement strategy of adjacent roadside units based on the average vehicle speed within the scope of the roadside unit. The decision support model performs on-demand network coding on the cached content, so that the vehicle user downloads as many content blocks as possible from the roadside unit and reduces downloading from remote base stations, thereby reducing content transmission delay, improving system cache space utilization, and improving vehicle user service quality.

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 (RSUs). These services will greatly enhance the vehicle's environmental perception capabilities, optimize route 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 with 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 caching function of the roadside unit, the in-vehicle user can directly obtain the required content from the local cache of the roadside unit, reducing the 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: first, due to the limited cache capacity of roadside units, it is impossible to pre-store all the content that may be needed in a single roadside unit; second, due to mobility issues, delivery may need to cross the coverage area of ​​multiple roadside units. However, to ensure quality of service, adjacent roadside units will partially cache the same content blocks, 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 roadside unit content placement.

[0006] To achieve the above objectives, the present invention provides the following technical solutions: a vehicle-movement-aware roadside unit content coding placement system, comprising a (remote) cloud server (CS), a macro site (MS), a roadside unit (RSU), an area control unit (AC), and a vehicle user;

[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 can obtain the source content stored on the cloud server through the macro base station.

[0009] A roadside unit (RSU) is a local server installed on the roadside that communicates with onboard units (OBUs) of vehicles within its coverage area. RSUs communicate with macro base stations and regional controllers and are equipped with local data storage media, including but not limited to hard disks, solid-state drives, disk arrays, network attached storage (NAS), or hybrid storage systems. Under the control of the regional controller, RSUs cache content to be served from cloud servers 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 the 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 by 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. 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 for 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 dwell 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 the roadside unit 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 cached content is coded on demand through the decision support model. The coded 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 T represents the last content block number received by the vehicle user when staying within the coverage 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 :

[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 has cached 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 redundant caching of content blocks in adjacent roadside units can improve the hit rate, the encoded blocks are different after encoding and do not need to be cached repeatedly, which can further improve space utilization. Then, according to the two situations that occur, including:

[0023] 1) The space occupied by the code blocks downloaded by the vehicle at the roadside unit is smaller than the roadside unit cache space. In this case, 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 a vehicle downloading a 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, Indicates the number of duplicate cache content blocks of the rth roadside unit and the r+1th roadside unit, represents the number of non-repeated cache content blocks of the r-th roadside unit, B r represents the total number of cached content blocks of the rth roadside unit;

[0032] Constraint 4:

[0033] Constraint 5:

[0034] in, Indicates 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 content blocks;

[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 When it is a negative number, it means that its space is borrowed to the adjacent roadside unit; 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 It 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 linear combination on it; C is called the encoding matrix, and the vector c i，n It is called the 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 existing technology, the beneficial effects of the present invention are as follows: the present invention solves the problem of space waste in placing roadside unit content; it is suitable for application scenarios where the cache space of the roadside unit 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 download directly from the remote base station, thereby reducing the transmission delay of the content, 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 cache content of the roadside unit in the vehicle network, thereby improving the 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 figure:

[0048] Figure 1 It is a structural 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 content coding of roadside units according to the present invention. DETAILED DESCRIPTION

[0050] The preferred embodiments of the present invention are described below with reference to 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 base station (MS), a roadside unit (RSU), an area controller (AC), and a vehicle user;

[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 can obtain the source content stored on the cloud server through the macro base station.

[0054] A roadside unit (RSU) is a local server installed on the roadside that communicates with onboard units (OBUs) of vehicles within its coverage area. RSUs communicate with macro base stations and regional controllers and are equipped with local data storage media, including but not limited to hard disks, solid-state drives, disk arrays, network attached storage (NAS), or hybrid storage systems. Under the control of the regional controller, RSUs cache content to be served from cloud servers 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 a 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 by 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. 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, thereby completing the placement of roadside unit content:

[0059] S1: Reference Figure 1 ,Based on the distribution of the residence time of vehicles passing through the target ,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 encoding 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 vehicles passing through the target road section within the range of each roadside unit. It 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 last content block number received by the vehicle user when staying within the coverage 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 has cached 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, adjacent roadside units will cache some content blocks repeatedly. Vehicles in adjacent roadside units will download redundant content blocks within their overlapping coverage areas, 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 cache space utilization.

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

[0068] 1) The space occupied by the code blocks downloaded by the vehicle at the roadside unit is smaller than the roadside unit cache space. In this case, 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 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;

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

[0071] Objective function:

[0072] Constraint 1

[0073] Constraint 2

[0074] Constraint 3

[0075] Constraint 4

[0076] Constraint 5

[0077] Constraint 6

[0078] Constraint 7

[0079] Constraint 8

[0080] Constraint 9

[0081] Get the redundant placement of adjacent roadside units Where r∈{1, 2, ..., R-1}; for the second case, Can be negative, when When it is a negative number, it means that its space is borrowed to the adjacent roadside unit; according to the redundant placement as well as Determine the number of network coding blocks E cached by each roadside unit r .

[0082] 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.

[0083] If the roadside unit stores the source data packets, the vehicle user must download them sequentially, and the vehicle will download them 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 user downloads the specified number of coding blocks, the source data can be decoded, regardless of which ones are downloaded.

[0084] A simulation experiment was designed to verify that vehicle users can download more content blocks from roadside units rather than from remote base stations.

[0085] In summary, the method for placing roadside unit content encoding that can perceive vehicle movement is targeted at a roadside unit content encoding placement system that includes a cloud server, a macro base station, a roadside unit, a regional controller, and vehicle users. The aforementioned components form a vehicle network edge cache model. Based on the distribution of the residence time of vehicles passing through the target road section within the scope of each roadside unit, a probability distribution relationship of vehicle users obtaining content from each roadside unit is constructed and maintained, forming a decision support model, and generating a content encoding placement decision for the roadside unit that meets the maximum hit rate. The repeated cache placement strategy of adjacent roadside units is optimized based on the average vehicle speed within the roadside unit range to improve cache space utilization. The content to be cached is network-coded on demand, allowing vehicle users to download more content blocks from the roadside unit rather than from a remote base station. This solves the problem of space waste in the placement of roadside unit content. It reduces the transmission delay of service content and improves the working efficiency of the vehicle network edge cache model.

[0086] Finally, it should be noted that the above description is merely a preferred embodiment 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 will be able to modify the technical solutions described in the aforementioned embodiments or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for placing content encoding on roadside units (RUs) that can perceive vehicle movement, applied to a RU content encoding placement system. The system includes a cloud server, a macro base station, a RU, a regional controller, and vehicle users. The RUs communicate with the macro base station and the regional controller and, under the control of the regional controller, cache content to be served from the cloud server, thereby meeting the content service needs of vehicle users within the coverage area. The method is characterized by: The method comprises the following steps: 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 dwell 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 the roadside unit that meet the maximum hit rate; S2, the regional controller optimizes the duplicate cache placement strategy of adjacent roadside units based on the average vehicle speed within the roadside unit range; S3: Perform on-demand network coding on the cached content through the decision support model. The encoded content blocks are cached in the roadside unit (RSU). Vehicle users download the content blocks from the RSU, reducing the need to download from remote base stations. 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: ； in, Indicates that the bth content block is in The probability that a roadside unit is downloaded by a vehicle user, Indicates that the vehicle user is in The last content block number received while staying within the coverage area of ​​a roadside unit; For the vehicle user The total number of content blocks downloaded while staying within the coverage area of ​​a roadside unit; and thresholds for quality of service requirements Sure : ； ； in, represents the total number of cached content blocks of the rth roadside unit, Indicates that the rth roadside unit has cached the bth content block. Based on the distribution of vehicle users' residence time within each roadside unit, the probability of each roadside unit being downloaded by vehicle users, and the threshold of quality of service requirements, the regional controller determines the content block that each roadside unit should cache. In step S2, according to Get the preliminary caching plan for vehicles at roadside units To further improve space utilization, we solve the optimization problem through linear programming, as follows: Objective function: ; in, represents the hit rate of a vehicle downloading a 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, Indicates the number of duplicate cache content blocks of the rth roadside unit and the r+1th roadside unit, represents the number of non-repeated cache content blocks of the r-th roadside unit, represents the total number of cached content blocks of the rth roadside unit; Constraint 4: ; Constraint 5: ; in, Indicates 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: ; in, 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; Constraint 9: ; The above formula is the method for calculating the hit rate of content blocks; Finally, the redundant placement of adjacent roadside units is obtained 、 ,in , according to the amount of redundant placement 、 as well as Determines the number of network code blocks cached per roadside unit .

2. The method for placing roadside unit content codes that can perceive vehicle movement according to claim 1, characterized in that: In step S3, the network coding method formula is: ； The encoding process is recorded as ,in is the set of m coding blocks generated after the coding operation, , any code block in the set is generated by linear combination of n source content blocks over a selected finite field; C is called the encoding matrix, and the vector Coded Block 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 .

Images