Minimizing Decoding Delay IDNC Network Coding Method Based on Vehicular Network Model

Abstract

The present invention discloses a method for minimizing decoding delay in an IDNC network coding based on a vehicle networking model, including: (1) The RSU broadcasts and sends data packets; (2) Obtain the receiving status feedback information of each vehicle node for receiving data packets; (3) Construct a local IDNC graph for each vehicle node according to the receiving status feedback information, and find the main layer of the optimal local IDNC graph; (4) Construct the optimal secondary layer, thereby obtaining the optimal coding clique, and add the nodes involved in the coding clique to the maximum independent set; (5) According to the transmission conflict, delete the vehicle nodes that have been used as sending or receiving nodes in the maximum independent set, update the vehicle nodes, and obtain the updated maximum independent set; (6) Repeat (5) until the vehicle nodes outside the maximum independent set cannot form a local IDNC graph; (7) According to minimizing the decoding delay, obtain the maximum weight coding clique according to the maximum independent set, and transmit the maximum weight coding clique.

Description

Technical Field

[0001] The present invention belongs to the technical fields of Internet of Vehicles and network coding, and relates to a minimum decoding delay IDNC network coding method based on an Internet of Vehicles model. Background Art

[0002] The theory of network coding was formally proposed by R. Ahlswede et al. in 2000 and applied to error-free broadcast channels. In traditional communication, intermediate nodes in the network only play a role in storing and forwarding data packets. According to network coding technology, intermediate nodes can encode and forward data packets. This fundamentally changes the information processing and transmission modes in communication networks, improves the data throughput of network transmission, and plays an important role in optimizing network performance. Among them, IDNC is an opportunistic network coding, which is particularly suitable for application scenarios sensitive to delay.

[0003] The Internet of Vehicles is to connect vehicles, people, roads, control platforms, etc. by using technologies such as 5G networks, artificial intelligence, and big data, so as to improve driving safety and comfort. By utilizing the characteristic that IDNC can reduce network decoding delay, applying IDNC with low encoding and decoding complexity to the communication (V2V) between vehicle nodes can reduce the number of data exchanges in the cooperation of each vehicle terminal to recover data, thereby reducing delay and improving the performance of the Internet of Vehicles.

[0004] Traditional network coding transmits and recovers data for each terminal in the form of base station broadcasting. Due to the particularity of this application scenario of the Internet of Vehicles: on the one hand, a group of vehicle nodes with close geographical locations have received a group of data packets broadcast from a roadside unit (RSU), and only missed some data packets individually. Compared with recovering the lost data packets through the RSU again, the cooperative recovery through short-range transmission between each vehicle node can not only relieve the load of the base station but also complete the recovery of data packets faster and more reliably; on the other hand, different vehicle nodes are interested in different data in the RSU. In traditional V2V communication, vehicle nodes only receive the data packets they want. Summary of the Invention

[0005] Objective: In order to overcome the deficiencies existing in the prior art, the present invention provides a minimum decoding delay IDNC network coding method based on an Internet of Vehicles model.

[0006] In this application, vehicle nodes will receive data packets that they were not originally interested in, which will expand the data packet sets owned by each vehicle node, and these uninteresting data packets will increase the opportunity to form immediately decodable encoded packets next time, thereby lowering the lower limit of decoding delay.

[0007] Technical solution: To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] In the first aspect, a method for minimizing decoding delay IDNC network coding based on a vehicle networking model is provided, including:

[0009] Step (1): The roadside unit RSU broadcasts and sends data packets to all vehicle nodes within its coverage area;

[0010] Step (2): The RSU obtains the reception status feedback information of each vehicle node for receiving the data packets;

[0011] Step (3): The RSU constructs a local IDNC graph for each vehicle node according to the reception status feedback information, and finds the main layer of the optimal local IDNC graph;

[0012] Step (4): The RSU constructs an optimal secondary layer for the optimal local IDNC graph according to the reception status feedback information, thereby obtaining an optimal coding clique, and adds the nodes involved in this coding clique to the maximum independent set;

[0013] Step (5): According to the transmission conflict, delete the vehicle nodes that have already served as sending or receiving nodes in the maximum independent set, update the vehicle nodes, and update the local IDNC graph, the main layer and the secondary layer of the optimal local IDNC graph, and the optimal coding clique, to obtain an updated maximum independent set;

[0014] Step (6): Repeat Step (5) until the vehicle nodes outside the maximum independent set cannot form a local IDNC graph, that is, the node set in its local IDNC graph is an empty set;

[0015] Step (7): According to minimizing the decoding delay, obtain a maximum weight coding clique according to the maximum independent set, and transmit this maximum weight coding clique;

[0016] If the system transmission task is not completed, iterate and run Steps (2) to (7).

[0017] In some embodiments, the RSU constructs a local IDNC graph for each vehicle node according to the reception status feedback information, including:

[0018] Node V i generates a node v i,j,k in its local IDNC graph, indicating that vehicle node V i sends a data packet P j to vehicle node V k ; where i, j, k are the numbers of the sending vehicle node, the receiving vehicle node, and the data packet respectively;

[0019] Determine a certain vehicle node V iCoded connection edges of the local IDNC graph:

[0020] If the j-th vehicle node V j and the m-th vehicle node V m can both receive the data packet P i from the sending vehicle node V k , then the node v i,j,k and the node v i,m,k satisfy the local IDNC coding condition and form a coded connection edge;

[0021] If the vehicle node V j can receive the data packet P i from the sending vehicle node V k , and at the same time another vehicle node V m can receive the data packet P i from the sending vehicle node V l , and the receiving vehicle nodes V j and V m already have the data packets needed by each other, that is, the receiving vehicle node V j has the data packet P l , and the receiving vehicle node V m has the data packet P k , then the node v i,j,k and the node v i,m,l satisfy the local IDNC coding condition and form a coded connection edge;

[0022] According to the IDNC coding condition, if there is a connection edge between the node v i,j,k and the node v i,m,k , then α ijk,iml = 1, otherwise α ijk,iml = 0.

[0023] In some embodiments, according to the transmission conflict, the vehicle nodes that have already been used as sending or receiving nodes in the maximum independent set are deleted, including: determining the transmission conflict condition:

[0024] If the vehicle node V i sends the data packet P k to the vehicle node V j in a certain time slot, then in the same time slot, V j can neither be used as a sending node to send data packets to the vehicle node V m , nor can it be used as a receiving node to receive data packets sent by other vehicle nodes V m .

[0025] In some embodiments, according to the minimization of decoding delay, the maximum weight coding clique is obtained according to the maximum independent set, including:

[0026] Construct the optimization problem P1:

[0027]

[0028] where represents the set of the largest coding cliques in the IDNC graph;

[0029] When only considering the main graph:

[0030]

[0031] When considering the combination of the main graph and the secondary graph:

[0032]

[0033] where E[D] is the average decoding delay; M ω represents the set of receiving nodes whose wants sets are not empty, G represents the set of vehicle terminals that can act as senders simultaneously within time slot t, represents the set of receivers that can immediately decode a coded data packet P i sent by a sending vehicle node V * ; p i,j represents the packet loss rate from the sending vehicle node V i to the receiving vehicle node V j ; K F represents the maximum weight coding clique of the main graph, K S represents the maximum weight coding clique of the secondary graph, N represents the number of source data packets in one frame, F j represents the set of main data packets required by the vehicle node V j ; H j represents the set of data packets owned by the vehicle node V j ;

[0034] The optimization problem P1 is transformed into the optimization problem P2:

[0035]

[0036] The optimization problem P2 is equivalent to the maximum weight coding clique problem P3, where the weight ω i of the node v i,j,k in the main graph of the local IDNC graph belonging to the node V F (v i,j,k ) is expressed as:

[0037] ω F (v i,j,k ) = 1 - p i,j

[0038] where belonging to the node V iNode v in the secondary graph of the local IDNC graph i,j,k Weight ω S (v i,j,k ) is expressed as:

[0039]

[0040] In some embodiments, a method for solving the maximum weight coded clique problem P3 includes:

[0041] Step S1, initialize the maximum weight coded clique K as an empty set, and initialize the maximum weight coded clique K i of each vehicle node V i as an empty set, and initialize the maximum independent set S as the set of all vehicle nodes within the current RSU coverage range;

[0042] Step S2, construct the local IDNC graphs of all vehicle nodes in the maximum independent set S, and calculate the weights ω F (v i,j,k ) of all nodes in the corresponding primary graphs of |S| local IDNC graphs;

[0043] Step S3, find |S| maximum weight coded cliques K i corresponding to the |S| primary graphs;

[0044] Step S4, according to the magnitudes of the primary graph coded clique weights, select the clique K i with the largest coded clique weight from the |S| maximum weight coded cliques K i of the primary graphs, and construct a secondary coded clique for it;

[0045] Step S5, delete the nodes corresponding to the transmitting vehicle nodes and receiving vehicle nodes in the maximum weight coded clique K obtained in step S4 from the maximum independent set S, so as to avoid transmission conflicts;

[0046] Step S6, if the vehicle nodes in the updated maximum independent set S cannot form a local IDNC graph, that is, the node set in its local IDNC graph is an empty set; then output the maximum weight coded clique K; otherwise, go to the iterative steps S2 to S4.

[0047] Furthermore, step S3, finding |S| maximum weight coded cliques K i corresponding to the |S| primary graphs includes:

[0048] (S31) Select the node with the largest weight from all nodes in the local IDNC coding graph and add this node to the maximum weight coded clique K i ;

[0049] (S32) Exclude the maximum weight coded clique K from the local IDNC coding graphi Select the node with the largest weight among the remaining nodes other than Add this node to the maximum weight coding clique K i ;

[0050] (S33) Delete the nodes in the local IDNC coding graph that do not have coding connection edges with any node in the coding clique K i and update the local IDNC coding graph;

[0051] (S34) If the node set in the main IDNC coding graph corresponding to the updated vehicle node V i is not equal to the empty set, then update the node weights and go to the iteration (S32) to (S33), otherwise, output the maximum weight coding clique K of the main graph i .

[0052] Furthermore, in step S4, according to the size of the main graph coding clique weights, select the clique K with the largest coding clique weight from the maximum weight coding cliques K of |S| main graphs i to construct a secondary coding clique for it, including: i ,

[0053] (S41) Delete the nodes in the original local IDNC coding graph that do not have coding connection edges with any node in the main coding clique K i ;

[0054] (S42) Select the node with the largest weight from all the secondary nodes in the updated local IDNC coding graph Add this node to the maximum weight coding clique K i ;

[0055] (S43) Delete the nodes in the updated local IDNC coding graph that do not have coding connection edges with any node in the coding clique K i and update the local IDNC coding graph;

[0056] (S44) If the node set in the secondary IDNC coding graph corresponding to the updated vehicle node V i is not equal to the empty set, then update the node weights and go to the iteration (S42) to (S43), otherwise, output the maximum weight coding clique K of the double-layer graph i , and update the maximum weight coding clique K = K ∪ K i .

[0057] In a second aspect, the present invention provides a minimized decoding delay IDNC network coding device based on a vehicle networking model, including a processor and a storage medium;

[0058] The storage medium is used to store instructions;

[0059] The processor is configured to operate according to the instructions to execute the steps of the method according to the first aspect.

[0060] In a third aspect, the present invention provides a storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the steps of the method according to the first aspect are implemented.

[0061] Advantageous effects: The minimized decoding delay IDNC network coding method based on the vehicle networking model provided by the present invention has the following advantages: A two-layer IDNC coding graph based on a primary layer and a secondary layer is constructed. According to this graph, considering recovering the data packets in the Lacks\Wants sets of vehicle nodes to increase the probability that the vehicle node successfully decodes the data packets in its Wants set next time, the decoding delay of the network can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 A flowchart of constructing a maximum weight coding clique for the method according to an embodiment of the present invention;

[0063] Figure 2 A system example diagram of an embodiment of the present invention;

[0064] Figure 3 A conventional local IDNC coding graph;

[0065] Figure 4 A local IDNC coding graph constructed by the method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0066] The present invention will be further described below in conjunction with the drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be used to limit the protection scope of the present invention.

[0067] In the description of the present invention, the meaning of several is more than one, the meaning of multiple is more than two, greater than, less than, exceeding, etc. are understood as not including the present number, and above, below, within, etc. are understood as including the present number. If the first and second are described only for the purpose of distinguishing technical features, they should not be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence of the indicated technical features.

[0068] In the description of the present invention, the description with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0069] Traditional network coding transmits and recovers data for each terminal in the form of base station broadcasts. Due to the particularity of the vehicle-to-everything (V2V) application scenario: on the one hand, a group of vehicle nodes with similar geographical locations have received a group of data packets broadcast from a roadside unit (RSU), and only missed some data packets individually. Compared with recovering the lost data packets through the RSU again, the cooperative recovery through short-range transmission between vehicle nodes can not only relieve the load of the base station but also complete the recovery of data packets faster and more reliably; on the other hand, different vehicle nodes are interested in different data in the RSU. In traditional vehicle-to-vehicle (V2V) communication, vehicle nodes only receive the data packets they want. In this solution, vehicle nodes will receive data packets that they are not originally interested in, which will expand the set of data packets owned by each vehicle node, and these uninteresting data packets will increase the chance of forming an immediately decodable coded packet next time, thereby reducing the lower limit of decoding delay.

[0070] Embodiment 1

[0071] A method for minimizing decoding delay in an IDNC network coding based on a vehicle-to-everything model, comprising:

[0072] Step (1): The roadside unit RSU broadcasts data packets to all vehicle nodes within its coverage area;

[0073] Step (2): The RSU obtains the reception status feedback information of each vehicle node for receiving data packets;

[0074] Step (3): The RSU constructs a local IDNC graph for each vehicle node according to the reception status feedback information, and finds the main layer of the optimal local IDNC graph;

[0075] Step (4): The RSU constructs an optimal secondary layer for the optimal local IDNC graph according to the reception status feedback information, thereby obtaining an optimal coding clique, and adding the nodes involved in the coding clique to the maximum independent set;

[0076] Step (5): According to the transmission conflict, delete the vehicle nodes that have been used as sending or receiving nodes in the maximum independent set, update the vehicle nodes, and update the local IDNC graph, the primary and secondary layers of the optimal local IDNC graph, and the optimal coding clique to obtain the updated maximum independent set;

[0077] Step (6): Repeat Step (5) until the vehicle nodes outside the maximum independent set cannot form a local IDNC graph, that is, the node set in its local IDNC graph is an empty set;

[0078] Step (7): According to the minimization of decoding delay, obtain the maximum weight coding clique according to the maximum independent set and transmit the maximum weight coding clique;

[0079] If the system transmission task is not completed, iterate and run Steps (2) to (7).

[0080] In some embodiments, the RSU constructs a local IDNC graph for each vehicle node according to the received status feedback information, including:

[0081] In the local IDNC graph of node V i generate node v i,j,k , indicating that vehicle node V i sends data packet P j to vehicle node V k ; where i, j, k are the numbers of the sending vehicle node, receiving vehicle node, and data packet respectively;

[0082] Determine the coding connection edges of the local IDNC graph of a certain vehicle node V i :

[0083] If the j-th vehicle node V j and the m-th vehicle node V m can both receive data packet P i from the sending vehicle node V k , then node v i,j,k and node v i,m,k meet the local IDNC coding condition and form a coding connection edge;

[0084] If vehicle node V j can receive data packet P i from the sending vehicle node V k , and at the same time another vehicle node V m can receive data packet P i from the sending vehicle node V l , and the receiving vehicle node V j and the receiving vehicle node V m already have the data packets needed by each other respectively, that is, the receiving vehicle node V jowns data packet P l and the receiving vehicle node V m owns data packet P k then node v i,j,k and node v i,m,l meet the local IDNC coding condition and form a coding connection edge;

[0085] According to the IDNC coding condition, if there is a connection edge between node v i,j,k and node v i,m,k then α ijk,iml = 1, otherwise α ijk,iml = 0.

[0086] In some embodiments, according to the transmission conflict, delete the vehicle nodes that have been used as sending or receiving nodes in the maximum independent set, including: determining the transmission conflict condition:

[0087] If the vehicle node V i sends data packet P k to the vehicle node V j in a certain time slot, then in the same time slot, V j can neither be used as a sending node to send a data packet to the vehicle node V m nor be used as a receiving node to receive data packets sent by other vehicle nodes V m .

[0088] In some embodiments, according to the minimization of decoding delay, obtain the maximum weight coding clique according to the maximum independent set, including:

[0089] Construct the optimization problem P1:

[0090]

[0091] where represents the set of the maximum coding cliques in the IDNC graph;

[0092] When only considering the main graph:

[0093]

[0094] When considering the combination of the main graph and the secondary graph:

[0095]

[0096] where E[D] is the average decoding delay; M ω represents the set of receiving nodes whose wants sets are not empty, G represents the set of vehicle terminals that can simultaneously act as senders in time slot t, represents the set that can immediately decode a coded data packet P i sent by a sending vehicle node V* Set of receiving ends, p i,j Indicates the sending vehicle node V i To the receiving vehicle node V j Packet loss rate, K F Indicates the maximum weight coded clique of the main graph, K S Indicates the maximum weight coded clique of the secondary graph, N represents the number of source data packets in a frame of data, F j Indicates the vehicle node V j Set of main data packets required, H j Indicates the vehicle node V j Set of data packets owned;

[0097] The optimization problem P1 is transformed into the optimization problem P2:

[0098]

[0099]

[0100] The optimization problem P2 is equivalent to the maximum weight coded clique problem P3, where the node v in the main graph of the local IDNC graph belonging to the node V i In the main graph of the local IDNC graph of i,j,k Weight ω F (v i,j,k ) is expressed as:

[0101] ω F (v i,j,k ) = 1 - p i,j

[0102] Where the node v in the secondary graph of the local IDNC graph belonging to the node V i In the secondary graph of the local IDNC graph of i,j,k Weight ω S (v i,j,k ) is expressed as:

[0103]

[0104] In some embodiments, the method for solving the maximum weight coded clique problem P3 includes:

[0105] Step S1, initialize the maximum weight coded clique K as an empty set, and initialize the maximum weight coded clique K of each vehicle node V i As an empty set, initialize the maximum independent set S as the set of all vehicle nodes within the current RSU coverage range; i As an empty set, initialize the maximum independent set S as the set of all vehicle nodes within the current RSU coverage range;

[0106] Step S2, construct the local IDNC graphs of all vehicle nodes in the maximum independent set S, and calculate the weights ω of all nodes in the main graphs corresponding to |S| local IDNC graphs F (vi,j,k );

[0107] Step S3. Obtain |S| maximum-weight coding cliques K corresponding to |S| main graphs i ;

[0108] Step S4. According to the weights of the main-graph coding cliques, select the clique K with the largest coding-clique weight from the |S| maximum-weight coding cliques K of the |S| main graphs i to construct a secondary coding clique for it; i

[0109] Step S5. In the maximum independent set S, delete the nodes corresponding to the transmitting vehicle nodes and receiving vehicle nodes in the maximum-weight coding clique K obtained in Step S4, so as to avoid transmission conflicts;

[0110] Step S6. If the vehicle nodes in the updated maximum independent set S cannot form a local IDNC graph, that is, the node set in its local IDNC graph is an empty set; then output the maximum-weight coding clique K; otherwise, go to the iterative Steps S2 to S4.

[0111] Furthermore, in the said Step S3, obtaining |S| maximum-weight coding cliques K corresponding to |S| main graphs i includes:

[0112] (S31) Select the node with the largest weight from all the nodes in the local IDNC coding graph Add this node to the maximum-weight coding clique K i ;

[0113] (S32) Select the node with the largest weight from the remaining nodes in the local IDNC coding graph except for the maximum-weight coding clique K i Add this node to the maximum-weight coding clique K ; i

[0114] (S33) Delete the nodes in the local IDNC coding graph that do not have coding connection edges with any node in the coding clique K i and update the local IDNC coding graph;

[0115] (S34) If the node set in the main IDNC coding graph corresponding to the updated vehicle nodes V i is not equal to an empty set, then update the node weights and go to iterate (S32) to (S33), otherwise, output the maximum-weight coding clique K of the main graph i .

[0116] Furthermore, in the said Step S4, according to the weights of the main-graph coding cliques, from the |S| maximum-weight coding cliques K of the |S| main graphs​​i Select the clique K with the largest coded clique weight from i , and construct a secondary coded clique for it, including:

[0117] (S41) Delete the nodes in the original local IDNC coding graph that do not have coded connection edges with any node in the primary coded clique K i ;

[0118] (S42) Select the node with the largest weight from all secondary nodes in the updated local IDNC coding graph Add this node to the maximum weight coded clique K i ;

[0119] (S43) Delete the nodes in the updated local IDNC coding graph that do not have coded connection edges with any node in the coded clique K i , and update the local IDNC coding graph;

[0120] (S44) If the node set in the secondary IDNC coding graph corresponding to the updated vehicle node V i is not equal to the empty set, then update the node weights and go to the iteration (S42) to (S43), otherwise, output the maximum weight coded clique K of the bilayer graph i , and update the maximum weight coded clique K = K ∪ K i .

[0121] In some embodiments, Figure 1 is a flowchart of the minimum decoding delay IDNC network coding method for the vehicle networking model.

[0122] According to the data packet information required by each vehicle node and the IDNC network coding conditions, the specific method is:

[0123] (1) Generate a node v i,j,k , representing that the vehicle node V i sends a data packet P j to the vehicle node V k ;

[0124] (2) For the coded connection edges of the local IDNC graph, if both the vehicle node V j and the vehicle node V m can receive the data packet P i from the sending vehicle node V k , then the node v i,j,k and the node v i,m,k satisfy the local IDNC coding conditions and form a coded connection edge;

[0125] If the vehicle node V j can receive the data packet from the sending vehicle node V iReceive data packet P at k , while another vehicle node V m can receive data packet P from the sending vehicle node V i . And the receiving vehicle node V l and the receiving vehicle node V j respectively already have the data packets required by each other, that is, the receiving vehicle node V m has data packet P j , and the receiving vehicle node V l has data packet P m , then node v k and node v i,j,k satisfy the local IDNC coding condition and form a coding connection edge; i,m,l

[0126] According to the IDNC coding condition, if there is a connection edge between node v i,j,k and node v i,m,k , then α ijk,iml = 1, otherwise α ijk,iml = 0;

[0127] (3) Node weight. In the specific implementation, the node weight is related to the link reliability. The higher the link reliability, the greater the probability that the user receives the coded packet, and the greater the assigned weight. The node weight of the main graph is defined as ω F (v i,j,k ) = 1 - p i,j , and the node weight of the secondary graph is defined as

[0128] (4) Construct the corresponding maximum weight coding clique K according to each local IDNC graph. The process schematic diagram is as Figure 1 shown. The specific method is:

[0129] Each sending vehicle node can help other receiving vehicle nodes recover the local IDNC coding connection graph G corresponding to the data packet. Take the initialized local IDNC coding connection graph G S = G;

[0130] K i represents a certain maximum weight coding clique selected in the local IDNC coding connection graph. Initially represents an empty set;

[0131] Iterative operation: Update the node weight ω*(v i,j,k ) = ω(v i,j,k )·∑α ijk,i′j′k′ ω(v i′,j′,k′ ); Select the maximum weight node Update​ ∪ represents the intersection; delete the local IDNC - coded connection graph G S in K i any node that is not connected to the nodes in, and update the local IDNC - coded connection graph;

[0132] If the updated IDNC - coded connection graph then go to iterative operation, otherwise output the maximum - weight coded clique.

[0133] Figure 2 is an example graph. In this example, there are five vehicle nodes V1, V2, V3, V4, V5, and 5 data packets P1, P2, P3, P4, P5. The importance of each data packet for different vehicle nodes is different. The main task of transmission is to restore the Wants sets of each vehicle node. Among them, the Wants set of V1, W1 = {P3, P5}, and the Wants sets of the remaining vehicles are W2 = {P2}, W3 = {P1}, W4 = {P4}, W5 = {P2} respectively. The Lacks sets of each vehicle are L1 = {P3, P5}, L2 = {P2}, L3 = {P1, P2}, L4 = {P4}, L5 = {P2, P3} respectively. Assume that this information can be accurately fed back to the RSU through the feedback channel.

[0134] According to the traditional IDNC coding method, only the Wants sets of each vehicle node are considered for restoration, without considering the received Lacks\Wants part. The corresponding local IDNC - coded connection graph is as Figure 3 shown. The nodes within the solid - line box can form a maximum - weight coded clique. The coding method during the entire restoration stage is as follows:

[0135] First time - slot: Vehicle V1 sends a coded data packet Vehicles V2, V4, V5 can all recover the data packets required in their respective Wants sets through network decoding. At this time, the Wants sets of vehicles V2, V4, V5 are empty sets, and the Wants sets of V1 and V3 remain unchanged, still being W1 = {P2, P5} and W3 = {P1};

[0136] Second time - slot: Vehicle V2 sends a coded data packet Vehicles V1, V3 can all recover the data packets required in their respective Wants sets through network decoding. At this time, the Wants sets of all vehicle nodes except vehicle V1 are empty sets, and the Wants set of vehicle V1 is updated to W1 = {P5};

[0137] Third time - slot: Vehicle V2 sends data packet P5, and vehicle V1 obtains its own data packet P5;

[0138] Next, the IDNC coding method described in this patent will be elaborated. The corresponding local IDNC - coded connection graph is asFigure 4 As shown, the nodes of the solid lines represent the nodes of the main layer of the local IDNC coding connection graph, and the nodes of the dashed lines represent the nodes of the secondary layer of the local IDNC coding connection graph. The nodes within the solid-line box can form the main clique of the maximum-weight coding clique, and the nodes within the dashed-line box can form the secondary clique of the maximum-weight coding clique. The coding method during the entire recovery phase is as follows:

[0139] First time slot: Vehicle V4 sends a coded data packet Both vehicles V1 and V2 can recover the data packets required within their respective Wants sets through network decoding. Vehicle V3 can recover the data packets within its Lacks\Wants set. At this time, the Wants set and Lacks set of vehicle V2 are updated to empty sets, and the Wants sets and Lacks sets of the remaining vehicle nodes are updated as follows: W1 = L1 = {P5}, W3 = {P1}, L3 = {P1, P2}, W4 = L4 = {P4}, W5 = {P2}, L5 = {P2, P3};

[0140] Second time slot: Vehicle V2 sends a coded data packet Vehicles V1, V3, V4, and V5 can all recover the data packets required within their respective Wants sets through network decoding. At this time, the Wants sets of all vehicle nodes are empty sets;

[0141] Therefore, according to the double-layer IDNC coding method based on the main layer and the secondary layer, only two time slots are required to complete the recovery of the data packets, and fewer time slots can be used to complete the data packet transmission.

[0142] The present invention provides a minimum decoding delay IDNC network coding method based on a vehicle-to-everything (V2X) model, constructs a double-layer IDNC coding graph based on the main layer and the secondary layer. According to this graph, considering the recovery of the data packets within the Lacks\Wants sets of vehicle nodes to increase the probability that the vehicle nodes can successfully decode the data packets within their Wants sets next time, the decoding delay of the network can be reduced.

[0143] Embodiment 2

[0144] Second, this embodiment provides a minimum decoding delay IDNC network coding device based on a vehicle-to-everything (V2X) model, including a processor and a storage medium;

[0145] The storage medium is used to store instructions;

[0146] The processor is used to operate according to the instructions to execute the steps of the method according to Embodiment 1.

[0147] Embodiment 3

[0148] In a third aspect, the present embodiment provides a storage medium having a computer program stored thereon, and when the computer program is executed by a processor, the steps of the method described in Embodiment 1 are implemented.

[0149] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0150] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram can be implemented by computer program instructions, and the combination of the flows and / or blocks in the flowchart and / or block diagram can also be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the specified functions in Figure 1 one or more of the flows Figure 1 or blocks.

[0151] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device that implements the specified functions in Figure 1 one or more of the flows Figure 1 or blocks.

[0152] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the specified functions in Figure 1 one or more of the flows Figure 1 or blocks.

[0153] The above description is only a preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A minimized decoding delay IDNC network coding method based on a vehicle networking model, characterized in that Including: Step (1): The roadside unit RSU broadcasts and sends data packets to all vehicle nodes within its coverage area; Step (2): The RSU obtains the reception status feedback information of each vehicle node for receiving the data packets; Step (3): The RSU constructs a local IDNC graph for each vehicle node according to the reception status feedback information, and finds the main layer of the optimal local IDNC graph; Step (4): The RSU constructs an optimal secondary layer for the optimal local IDNC graph according to the reception status feedback information, thereby obtaining an optimal coding clique, and adding the nodes involved in the coding clique to the maximum independent set; Step (5): According to the transmission conflict, delete the vehicle nodes that have been used as sending or receiving nodes in the maximum independent set, update the vehicle nodes, and update the local IDNC graph, the main layer and the secondary layer of the optimal local IDNC graph, and the optimal coding clique to obtain an updated maximum independent set; Step (6): Repeat Step (5) until the vehicle nodes outside the maximum independent set cannot form a local IDNC graph, that is, the node set in its local IDNC graph is an empty set; Step (7): According to the minimization of the decoding delay, the maximum weight coding clique can be obtained according to the maximum independent set, and the maximum weight coding clique is transmitted; If the system transmission task is not completed, iterate and run Steps (2) to (7); Among them, according to the minimization of the decoding delay, the maximum weight coding clique can be obtained according to the maximum independent set, including: Construct the optimization problem P1: Among them represents the set of the largest coding cliques in the IDNC graph; When only considering the main graph: When considering the combination of the main graph and the secondary graph: where \(e[D(K)]\) is the average decoding delay; \(M\) ω denotes the set of receiving nodes for which the wants set is not empty, \(G\) denotes the set of vehicle terminals that can act as transmitters simultaneously within time slot \(t\), denotes the set of receivers that can immediately decode an encoded data packet \(P\) i transmitted by a transmitting vehicle node \(V\) * , \(p\) i,j denotes the packet loss rate from transmitting vehicle node \(V\) i to receiving vehicle node \(V\) j , \(K\) F denotes the maximum - weight coding clique of the primary graph, \(K\) S denotes the maximum - weight coding clique of the secondary graph, \(N\) denotes the number of source data packets in one frame, \(F\) j denotes the set of primary data packets required by vehicle node \(V\) j , \(H\) j denotes the set of data packets owned by vehicle node \(V\) j ; The optimization problem P1 is transformed into the optimization problem P2: The optimization problem P2 is equivalent to the maximum - weight coded clique problem P3, where the node v that belongs to the main graph in the local IDNC graph of node V i in the main graph i,j,k The weight ω F (v i,j,k ) is expressed as: ω F (v i,j,k ) = 1 - p i,j Among them, those belonging to node V i Node v in the secondary graph of the local IDNC graph of i,j,k Weight ω S (v i,j,k ) is expressed as:

2. The minimized decoding delay IDNC network coding method based on the vehicle networking model according to claim 1, wherein The RSU constructs a local IDNC graph for each vehicle node according to the reception status feedback information, including: Node V i Generate node v in the local IDNC graph i,j,k , represents the vehicle node V i To vehicle node V j Send data packet P k ; Where i, j, k are the numbers of the sending vehicle node, receiving vehicle node, and data packet respectively; Determine the encoding connection edges of the local IDNC graph of a vehicle node V i : If the j-th vehicle node V j and the m-th vehicle node V m can both receive the data packet P i from the sending vehicle node V k , then the node v i,j,k and the node v i,m,k satisfy the local IDNC coding condition and form a coding connection edge; If vehicle node V j is able to receive data packet P i from sending vehicle node V k , and at the same time another vehicle node V m is able to receive data packet P i from sending vehicle node V l , and the receiving vehicle node V j and the receiving vehicle node V m respectively already have the data packets required by the other party, that is, the receiving vehicle node V j has data packet P l , and the receiving vehicle node V m has data packet P k , then node v i,j,k and node v i,m,l meet the local IDNC coding conditions and form a coding connection edge; According to the IDNC coding condition, if there is a connection edge between node v i,j,k and node v i,m,k , then α ijk,iml = 1, otherwise α ijk,iml = 0.

3. The minimized decoding delay IDNC network coding method based on the vehicle networking model according to claim 1, wherein According to the transmission conflict, delete the vehicle nodes that have been used as sending or receiving nodes in the maximum independent set, including: determining the transmission conflict condition: If vehicle node V i sends data packet P k to vehicle node V j in a certain time slot, then in the same time slot, V j can neither be a sending node to send a data packet to vehicle node V m , nor be a receiving node to receive data packets sent by other vehicle nodes V m .

4. The minimized decoding delay IDNC network coding method based on the vehicle networking model according to claim 1, wherein The method for solving the maximum weight coding clique problem P3 includes: Step S1: Initialize the maximum weight encoded clique K as an empty set, and initialize each vehicle node V i 's maximum weight encoded clique K i as an empty set, and initialize the maximum independent set S as the set of all vehicle nodes within the current RSU coverage range; Step S2: Construct the local IDNC graphs for all vehicle nodes in the maximum independent set S, and calculate the weights ω of all nodes in the main graphs corresponding to the |S| local IDNC graphs F (v i,j,k ); Step S3, find out |S| maximum weight coding cliques K corresponding to |S| main graphs i ; Step S4. According to the magnitudes of the weights of the main graph encoding cliques, select the clique \(K\) with the largest weight from the \(|S|\) main graphs' maximum-weight encoding cliques \(K\) i to select the clique \(K\) with the largest encoding clique weight i and construct a secondary encoding clique for it. Step S5: Delete the nodes corresponding to the transmitting vehicle nodes and the receiving vehicle nodes in the maximum weight coding clique K obtained in Step S4 in the maximum independent set S, so as to avoid transmission conflicts; Step S6: If the vehicle nodes in the updated maximum independent set S cannot form a local IDNC graph, that is, the node set in its local IDNC graph is an empty set; then output the maximum weight coding clique K; otherwise, go to the iterative Steps S2 to S4.

5. The minimized decoding delay IDNC network coding method based on the vehicle networking model according to claim 4, wherein In the step S3, |S| maximum weight coding cliques K corresponding to |S| main graphs are obtained i including: (S31) Select the node with the largest weight from all nodes in the local IDNC coding graph Add this node to the maximum weight coding clique K i ; (S32) Remove the node with the maximum weight from the remaining nodes in the local IDNC coding graph except for the maximum-weight coding clique K i Select the node with the largest weight among the remaining nodes Add this node to the maximum-weight coding clique K i ; (S33) Delete the nodes in the local IDNC coding graph that do not have coding connection edges with any node in the coding clique K i and update the local IDNC coding graph; (S34) If the node set in the main IDNC coding graph corresponding to the updated vehicle node V i is not equal to the empty set, update the node weights and go to iterations (S32) to (S33); otherwise, output the maximum weight clique K of the main graph i .

6. The minimized decoding delay IDNC network coding method based on the vehicle networking model according to claim 4, wherein In step S4, according to the magnitude of the weights of the main graph encoding cliques, select the clique \(K\) with the largest encoding clique weight from the \(|S|\) largest weight encoding cliques \(K\) of the main graphs i in which to select the clique \(K\) with the largest encoding clique weight i , and construct a secondary encoding clique for it, including: (S41) Delete the nodes in the original IDNC coding graph that do not have coding connection edges with any of the nodes in the main coding clique K i among which there are no coding connection edges with any node; (S42) Select the node with the largest weight from all the secondary nodes in the updated local IDNC coding graph Add this node to the maximum weight coding clique K i ; (S43) Delete the nodes in the updated local IDNC coding graph that do not have coding connection edges with any node in the coding clique K i and update the local IDNC coding graph; (S44) If the node set in the secondary IDNC coding graph corresponding to the updated vehicle node V i is not equal to the empty set, update the node weight and go to iteration (S42) to (S43). Otherwise, output the maximum weight coding clique K of the double-layer graph i , and update the maximum weight coding clique K = K ∪ K i .

7. A minimized decoding delay IDNC network coding device based on a vehicle networking model, characterized in that, Including a processor and a storage medium; The storage medium is used to store instructions; The processor is used to operate according to the instructions to execute the steps of the method according to any one of claims 1 to 6.

8. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, the steps of the method according to any one of claims 1 to 6 are implemented.

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