CN113179497A - Distributed real-time beacon scheduling method based on time slot in industrial Internet of things - Google Patents
Distributed real-time beacon scheduling method based on time slot in industrial Internet of things Download PDFInfo
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- H04W—WIRELESS COMMUNICATION NETWORKS
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- H04W72/12—Wireless traffic scheduling
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Abstract
The invention provides a time slot-based distributed real-time beacon scheduling method in an industrial Internet of things, which is mainly divided into three parts: (1) calculating candidate transmission scheduling of the node; (2) a reply method of transmission scheduling; (3) a collision decision mechanism for transmission scheduling. The method comprises the steps of firstly calculating candidate transmission scheduling information of a node in a given time slot of a system, setting a weight value of the transmission scheduling, then broadcasting the candidate transmission scheduling information to a group of specific neighbor node sets by the node according to a conflict judgment method of the transmission scheduling, and replying a data packet to the node according to a competition mechanism of the transmission scheduling after the specific neighbor node receives the transmission scheduling information. The invention realizes complete and conflict-free real-time beacon transmission scheduling aiming at the scene that the nodes in the duty ratio network wake up in a time slot.
Description
Technical Field
The invention relates to the field of time slot-based distributed real-time beacon scheduling methods in industrial Internet of things, in particular to a time slot-based distributed real-time beacon scheduling method in industrial Internet of things.
Background
The development of the intelligent manufacturing industry is not independent of the industrial internet of things, which is an important way for realizing industrial 4.0. The deep integration of the Internet of things and the industrial production link can effectively promote the industrial production efficiency. The industrial Internet of things is a comprehensive subject and relates to a plurality of fields, wherein sensor technology is an important foundation for the application of the industrial Internet of things.
In order to enable sensor nodes to operate more durably and effectively and improve the performance of an industrial internet of things, a sensor sleep mechanism has been introduced to reduce the consumption of electric quantity, namely, the sensor nodes work in a duty ratio mode. In a duty cycle network, each node has two operating states, an active state and a sleep state. All functional modules of the sensor in the sleep state are turned off to save energy consumption, and the beacon data packet sent by the neighbor node can be received only when the sensor node is in the active state.
Beacon scheduling is a very important task in a duty cycle network, where each sensor node needs to broadcast a beacon packet locally without collision to all neighboring nodes within a one-hop range, and the beacon transmission scheduling delay is the number of work cycles required for all sensor nodes to broadcast a beacon packet without collision to all neighboring nodes. The Minimum beacon transmission scheduling delay problem (MLBS) is that it attracts a lot of attention to find a conflict-free Minimum beacon delay scheduling scheme. Many researchers have made research contributions to the MLBS problem that sensor nodes are always awake, and all have achieved good results. Because the working mode of the sensor node in the duty ratio network is completely different from that of the traditional network, the MLBS problem in the duty ratio network is more complex and difficult.
Most of the previous researches are developed aiming at a centralized algorithm, and the method cannot be applied to the condition of frequent and dynamic changes of nodes and network topological structures in the industrial Internet of things. Chinese patent publication No. CN101299699A, published as 11/05/2008, discloses a node apparatus and method for beacon scheduling in an ad-hoc network and a data transmission method thereof, which reduce energy consumption of nodes in the ad-hoc network when data communication between the nodes frequently occurs. The beacon transmitting node checks its remaining energy. If the remaining energy is below a predetermined level, the beaconing node informs other nodes of the schedule to change its beacon period. Then, the beacon transmitting node increases the beacon period and transmits the beacon at the increased beacon period. The patent is also not suitable for the condition of frequent and dynamic changes of nodes and network topological structures in the industrial Internet of things.
Disclosure of Invention
The invention provides a time slot-based distributed real-time beacon scheduling method in an industrial Internet of things, which researches the problem of real-time distributed beacon scheduling in a duty ratio network and realizes complete conflict-free beacon transmission scheduling.
In order to solve the technical problems, the technical scheme of the invention is as follows:
a distributed real-time beacon scheduling method based on time slots in an industrial Internet of things comprises the following steps:
s1: defining a multi-hop duty ratio sensor network G ═ V, E, wherein V represents a set of sensor nodes in the network, E represents a set of edges in the network, an edge exists between two sensor nodes, and only when the two sensor nodes are located in the transmission range of each other, each sensor node randomly and independently selects an active time slot, and only wakes up in the active time slot of each working cycle to receive a beacon data packet sent by a neighbor node;
s2: adding an interference model into the duty ratio sensor network G, and defining a minimum delay beacon scheduling optimization problem of the duty ratio sensor network with an active time slot;
s3: calculating node candidate scheduling information on a work period starting time slot j, and then broadcasting the candidate scheduling information to corresponding neighbor nodes;
s4: the node receiving the candidate scheduling information replies a data packet according to the self state and a conflict judgment mechanism of transmission scheduling;
s5: after step S4, candidate scheduling information of each time slot is obtained, and a conflict-free real-time beacon transmission scheduling scheme is obtained according to the candidate scheduling information of each time slot.
Preferably, in step S1, the sensor node has two states, including an active state and a sleep state, the sensor node receives the beacon packet sent by its neighboring node if and only if it is in the active state, the duty cycle is defined as the ratio of the time in the active state to the time in the whole working cycle, the working cycle is divided into a plurality of time slots with the same size, each sensor node randomly and independently selects one of the time slots as the active time slot, in the active time slot of each working cycle, the sensor node is in the active state, and in the other time slots of each working cycle, the sensor node is in the sleep state.
Preferably, the interference model in step S2, specifically, the protocol interference model:
in the duty ratio sensor network G, a beacon transmission range of any sensor node v is a unit circle with v as a center, an interference radius is r (v) ≧ 1, the interference range is a circle with r (v) as a radius, inr (v) represents a node set colliding with the node v, the node set colliding with the node v is a node which cannot transmit a beacon packet simultaneously with v, and any pair of sensor nodes cannot transmit the beacon packet simultaneously and only when one of the following three conditions is satisfied:
(1) nodes u, v are within beacon transmission range of each other;
(2) there is one node w located within the beacon transmission range of u and within the interference range of v;
(3) there is one node w located within the beacon transmission range of v and within the interference range of u.
Preferably, the minimum delay beacon scheduling optimization problem for a duty cycle sensor network with one active slot is defined as:
defining 1.1 given multi-hop duty cycle industrial sensor network G ═ V, E, time slot based distributed scheduling on network G, denoted by Sch, where
And the following conditions are satisfied:
a. scheduling for any one transmission
Where C is an integer greater than or equal to 0 and x ═ w (w), w (w) denotes the active time slot of node w, where,
represents the transmission schedule sent from node u to node w at time T, | T | represents the duty cycle;
b. scheduling for any two transmissions
And
v ≠ u, if and only if t1 ≠ t2
And
a formalized definition of the problem is obtained according to the above definition:
inputting:
one duty cycle network G ═ V, E;
the active time slot of each sensor node, i.e. w (u),
and (3) outputting:
vertex-based beacon scheduling
Wherein SchminThe following conditions are satisfied:
Schminsatisfies the definition 1.1;
for any one of the schedules Sch', BL (Sch) satisfying definition 1.1min) BL (Sch) ≦ BL (Sch)min) And BL (Sch) represents a beacon transmission schedule Sch, respectivelyminAnd the delay of Sch.
Preferably, in the duty cycle sensor network G, each sensor node maintains the following information:
the unique ID of the node u and the work plan of the node u;
neighbor information of the node u comprises a unique ID and a work plan of the neighbor node v;
the forbidden transmission time slot fts (u) of node u.
Preferably, the step S3 is to calculate the node candidate scheduling information in the work cycle start time slot j, specifically as follows:
candidate transmission schedule cts (u) of node u ← [ u, v, j, weight ], wherein v and j respectively denote a beacon receiving node and a transmission time slot, and weight denotes a weight value of the candidate transmission schedule;
on a given time slot j of a system, firstly judging whether a node u can transmit in the time slot and whether a neighbor node in an active state exists, if so, calculating corresponding candidate transmission scheduling, and setting scheduling weight as the number of the neighbor nodes in the active state; if the condition is not satisfied, it indicates that there is no active node for node u in time slot j or that node u may not transmit in the time slot.
Preferably, the node that receives the candidate scheduling information in step S4 replies the packet according to its own state and a collision determination mechanism of transmission scheduling, specifically:
after receiving the candidate scheduling information broadcasted by the node u, the node v firstly judges whether the node v is in an active state in the time slot of CTS (u), t (u), and ignores the scheduling information if the node v is in a sleep state; if the node is in an active state, after receiving the candidate scheduling information transmitted by all the related neighbor nodes, the node v selects the candidate scheduling with the largest weight value from all the candidate scheduling by adopting a node reply algorithm, replies 'support' information to the sending node to indicate that the scheduling is agreed, and replies 'release' information to the rest of the sending nodes to indicate that the scheduling is rejected.
Preferably, after step S4, if the neighboring nodes all agree to the candidate scheduling, the node establishes the candidate scheduling information as the scheduling in this time slot, and updates the corresponding transmission prohibited time slot, that is, fts (u) ═ fts (u) < tj.
Preferably, when candidate scheduling information of the next time slot is calculated, candidate transmission scheduling is calculated for each node, and the corresponding transmission-prohibited time slot is updated until each node in the network broadcasts its beacon information to each neighbor node.
Preferably, after step S4 in step S5, candidate scheduling information of each time slot is obtained, and a collision-free real-time beacon transmission scheduling scheme is obtained, specifically:
initially, all nodes u capable of sending beacon packets in a Time Slot J are set to a Time Slot Synchronization state, the other nodes are set to a Not Ready state, and each node needs to maintain a variable y for indicating the number of neighbor nodes in an active state in the given Time Slot J of the system;
after a node enters a Time Slot Synchronization state, the 'Synchronization' message is firstly broadcast to synchronize all nodes capable of sending data packets on a Time Slot J, and if the node receives the 'Synchronization' message of all nodes which are in the same Time Slot capable of sending the data packets as the node, the node enters a Ready state;
when a node enters into Ready state, firstly calculating candidate transmission scheduling information CTS on a time slot J according to step S3, broadcasting the CTS to all neighbor nodes, initializing y to the number of neighbor nodes in active state on the time slot J, then the node enters into wait state, and waits for the scheduling reply information sent back by the neighbor nodes;
for each node u, after receiving the 'support' message replied by the neighbor node v, if the node u is in the wait state, the following operations are performed: 1) y ← y-1; 2) if y is 0, determining candidate transmission schedule cts (u) ═ u, v, J, weight ] as formal scheduling on time slot J, node u will enter Scheduled state, indicating that scheduling has been completed on J time slot and updating corresponding prohibited transmission time slot, i.e., fts (u) ═ fts (u) U, and if node u is not in the wait state, ignoring the message;
for each node u, if it receives the "replay" reply message of the neighbor node v, if the node u is in wait state, it directly enters Not Ready state to wait for being scheduled on other time slots.
Compared with the prior art, the technical scheme of the invention has the beneficial effects that:
the novel time slot-based distributed real-time Beacon transmission Scheduling algorithm provided by the invention can effectively solve the MLBSDCO problem (minimum Latency Beacon Scheduling for Duty-Cycled sensor networks with One active time slot) aiming at the scene that the nodes in the Duty ratio network wake up in One time slot, and realizes a correct, complete and conflict-free real-time Beacon transmission Scheduling scheme.
Drawings
FIG. 1 is a schematic flow chart of the method of the present invention.
Fig. 2 is a diagram of an example of a duty cycle sensor network in an embodiment.
Fig. 3 is schematic diagrams of three scenarios in which a collision occurs between any pair of nodes u and v under the protocol interference model in the embodiment, where (a) indicates that the nodes u and v are located within the beacon transmission range of each other, (b) indicates that there is a node w located within the beacon transmission range of u and within the interference range of v, and (c) indicates that there is a node w located within the beacon transmission range of v and within the interference range of u.
Fig. 4 is a schematic diagram of a state change of each node in the embodiment.
Detailed Description
The drawings are for illustrative purposes only and are not to be construed as limiting the patent;
for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product;
it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
Example 1
The embodiment provides a time slot-based distributed real-time beacon scheduling method in an industrial internet of things, which includes the following steps, as shown in fig. 1:
s1: defining a multi-hop duty ratio sensor network G ═ V, E, wherein V represents a set of sensor nodes in the network, E represents a set of edges in the network, an edge exists between two sensor nodes, and only when the two sensor nodes are located in the transmission range of each other, each sensor node randomly and independently selects an active time slot, and only wakes up in the active time slot of each working cycle to receive a beacon data packet sent by a neighbor node;
s2: adding an interference model into the duty ratio sensor network G, and defining a minimum delay beacon scheduling optimization problem of the duty ratio sensor network with an active time slot;
s3: calculating node candidate scheduling information on a work period starting time slot j, and then broadcasting the candidate scheduling information to corresponding neighbor nodes;
s4: the node receiving the candidate scheduling information replies a data packet according to the self state and a conflict judgment mechanism of transmission scheduling;
s5: after step S4, candidate scheduling information of each time slot is obtained, and a conflict-free real-time beacon transmission scheduling scheme is obtained according to the candidate scheduling information of each time slot.
All the sensor nodes do not need to negotiate in advance and determine their own activity and sleep time slots by themselves, in step S1, the sensor nodes include an active state and a sleep state, the sensor nodes receive beacon packets sent by their neighboring nodes if and only if they are in the active state, the duty cycle is defined as the ratio of the time of the active state to the time of the whole working cycle, the working cycle is divided into a plurality of time slots of the same size, each sensor node randomly and independently selects one of the time slots as an active time slot, in the active time slot of each working cycle, the sensor node is in the active state, and in the other time slots of each working cycle, the sensor node is in the sleep state. The length of the time slot is set to ensure that the sensor node can complete the sending and receiving of the beacon data packet. If the sensor node needs to send a beacon packet, it can complete the transmission at any time slot as long as the receiver is active and the transmission does not cause a collision. Fig. 2 shows an example of a duty cycle network with 6 nodes, the numbers above the nodes represent the active time slots of the sensor nodes, and a working cycle is divided into 3 time slots, in the duty cycle network, each sensor node wakes up only at a certain time slot of each working cycle, so that the time slot-based real-time beacon distributed scheduling algorithm essentially generates a collision-free beacon transmission plan for all the sensor nodes in the network, and is a vertex-based beacon scheduling task.
In order to obtain a vertex-based beacon scheduling of the network G, the existence of an interference model needs to be considered, and common interference models are divided into a protocol model and a physical model, in this embodiment, the interference model in step S2 is specifically a protocol interference model:
in the duty ratio sensor network G, a beacon transmission range of any sensor node v is a unit circle with v as a center, an interference radius is r (v) ≧ 1, the interference range is a circle with r (v) as a radius, inr (v) represents a node set colliding with the node v, the node set colliding with the node v is a node which cannot transmit a beacon packet simultaneously with v, and any pair of sensor nodes cannot transmit the beacon packet simultaneously and only when one of the following three conditions is satisfied:
(1) nodes u, v are within beacon transmission range of each other;
(2) there is one node w located within the beacon transmission range of u and within the interference range of v;
(3) there is one node w located within the beacon transmission range of v and within the interference range of u.
A possible conflicting relationship between any two nodes is shown in fig. 3. If the nodes u and v meet one of the three conditions, the two nodes are in conflict, namely the beacon data packets cannot be sent at the same time, otherwise, the two nodes are not in conflict, and the beacon data packets can be sent in the same time slot.
The minimum delay beacon scheduling optimization problem for a duty cycle sensor network with one active slot is defined as:
defining 1.1 given multi-hop duty cycle industrial sensor network G ═ V, E, time slot based distributed scheduling on network G, denoted by Sch, where
And the following conditions are satisfied:
a. scheduling for any one transmission
Where C is an integer greater than or equal to 0 and x ═ w (w), w (w) denotes the active time slot of node w, where,
represents the transmission schedule sent from node u to node w at time T, | T | represents the duty cycle;
b. scheduling for any two transmissions
And
v ≠ u, if and only if t1 ≠ t2
And
by definition, a qualified time-slot-based distributed schedule (essentially a vertex-based schedule) is guaranteed firstly that the receiver is active (condition 1 in the definition), and secondly that all transmission schedules in the same time slot are non-conflicting (condition 2 in the definition);
a formalized definition of the problem is obtained according to the above definition:
inputting:
one duty cycle network G ═ V, E;
the active time slot of each sensor node, i.e. w (u),
and (3) outputting:
vertex-based beacon deployment
Wherein SchminThe following conditions are satisfied:
Schminsatisfies the definition 1.1;
for any one of the schedules Sch, BL (Sch) satisfying definition 1.1min) BL (Sch) ≦ BL (Sch)min) And BL (Sch) represents a beacon transmission schedule Sch, respectivelyminAnd the delay of Sch.
The distributed real-time beacon scheduling problem in the duty ratio network is that each node locally calculates a collision-free beacon sending plan according to the information of the node and the neighbor. To compute this beacon schedule, each node needs to maintain the following information:
the unique ID of the node u and the work plan of the node u;
neighbor information of the node u comprises a unique ID and a work plan of the neighbor node v;
the forbidden transmission time slot fts (u) of node u.
In step S3, the calculation of the node candidate scheduling information in the work cycle start time slot j includes the following specific steps:
candidate transmission schedule cts (u) of node u ← [ u, v, j, weight ], wherein v and j respectively denote a beacon receiving node and a transmission time slot, and weight denotes a weight value of the candidate transmission schedule;
on a given time slot j of a system, firstly judging whether a node u can transmit in the time slot and whether a neighbor node in an active state exists, if so, calculating corresponding candidate transmission scheduling, and setting scheduling weight as the number of the neighbor nodes in the active state; if the condition is not satisfied, it indicates that there is no active node for node u in time slot j or that node u may not transmit in the time slot.
In step S4, the node that receives the candidate scheduling information replies the data packet according to its own state and the collision determination mechanism of transmission scheduling, which specifically includes:
after receiving the candidate scheduling information broadcasted by the node u, the node v firstly judges whether the node v is in an active state in the time slot of CTS (u), t (u), and ignores the scheduling information if the node v is in a sleep state; if the node is in an active state, after receiving the candidate scheduling information transmitted by all the related neighbor nodes, the node v selects the candidate scheduling with the largest weight value from all the candidate scheduling by adopting a node reply algorithm, replies 'support' information to the sending node to indicate that the scheduling is agreed, and replies 'release' information to the rest of the sending nodes to indicate that the scheduling is rejected.
After step S4, if the neighboring nodes agree with the candidate scheduling, the node establishes the candidate scheduling information as the scheduling in the time slot, and updates the corresponding transmission prohibited time slot, that is, fts (u) ═ fts (u) < u > j.
And calculating the candidate scheduling information of the next time slot, calculating the candidate transmission scheduling for each node, and updating the corresponding transmission prohibition time slot until each node in the network broadcasts the beacon information to each neighbor node.
After step S4 in step S5, candidate scheduling information of each time slot is obtained, and a conflict-free real-time beacon transmission scheduling scheme is obtained, as shown in fig. 4, specifically:
initially, all nodes u capable of sending beacon packets in a Time Slot J are set to a Time Slot Synchronization state, the other nodes are set to a Not Ready state, and each node needs to maintain a variable y for indicating the number of neighbor nodes in an active state in the given Time Slot J of the system;
after a node enters a Time Slot Synchronization state, the 'Synchronization' message is firstly broadcast to synchronize all nodes capable of sending data packets on a Time Slot J, and if the node receives the 'Synchronization' message of all nodes which are in the same Time Slot capable of sending the data packets as the node, the node enters a Ready state;
when a node enters into Ready state, firstly calculating candidate transmission scheduling information CTS on a time slot J according to step S3, broadcasting the CTS to all neighbor nodes, initializing y to the number of neighbor nodes in active state on the time slot J, then the node enters into wait state, and waits for the scheduling reply information sent back by the neighbor nodes;
for each node u, after receiving the 'support' message replied by the neighbor node v, if the node u is in the wait state, the following operations are performed: 1) y ← y-1; 2) if y is 0, determining candidate transmission schedule cts (u) ═ u, v, J, weight ] as formal scheduling on time slot J, node u will enter Scheduled state, indicating that scheduling has been completed on J time slot and updating corresponding prohibited transmission time slot, i.e., fts (u) ═ fts (u) U, and if node u is not in the wait state, ignoring the message;
for each node u, if it receives the "replay" reply message of the neighbor node v, if the node u is in wait state, it directly enters Not Ready state to wait for being scheduled on other time slots.
The same or similar reference numerals correspond to the same or similar parts;
the terms describing positional relationships in the drawings are for illustrative purposes only and are not to be construed as limiting the patent;
it should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A distributed real-time beacon scheduling method based on time slots in an industrial Internet of things is characterized by comprising the following steps:
s1: defining a multi-hop duty ratio sensor network G ═ V, E, wherein V represents a set of sensor nodes in the network, E represents a set of edges in the network, an edge exists between two sensor nodes, and only when the two sensor nodes are located in the transmission range of each other, each sensor node randomly and independently selects an active time slot, and only wakes up in the active time slot of each working cycle to receive a beacon data packet sent by a neighbor node;
s2: adding an interference model into the duty ratio sensor network G, and defining a minimum delay beacon scheduling optimization problem of the duty ratio sensor network with an active time slot;
s3: calculating node candidate scheduling information on a work period starting time slot j, and then broadcasting the candidate scheduling information to corresponding neighbor nodes;
s4: the node receiving the candidate scheduling information replies a data packet according to the self state and a conflict judgment mechanism of transmission scheduling;
s5: after step S4, candidate scheduling information of each time slot is obtained, and a conflict-free real-time beacon transmission scheduling scheme is obtained according to the candidate scheduling information of each time slot.
2. The method as claimed in claim 1, wherein the sensor node in step S1 includes an active state and a sleep state, the sensor node receives the beacon packet sent by its neighboring node if and only if it is in the active state, the duty cycle is defined as a ratio of the active state time to the whole duty cycle time, the duty cycle is divided into a plurality of time slots with the same size, each sensor node randomly and independently selects one of the time slots as an active time slot, the sensor node is in the active state in the active time slot of each duty cycle, and the sensor node is in the sleep state in the other time slots of each duty cycle.
3. The time slot-based distributed real-time beacon scheduling method in the industrial internet of things according to claim 2, wherein the interference model in step S2 is specifically a protocol interference model:
in the duty ratio sensor network G, a beacon transmission range of any sensor node v is a unit circle with v as a center, an interference radius is r (v) ≧ 1, the interference range is a circle with r (v) as a radius, inr (v) represents a node set colliding with the node v, the node set colliding with the node v is a node which cannot transmit a beacon packet simultaneously with v, and any pair of sensor nodes cannot transmit the beacon packet simultaneously and only when one of the following three conditions is satisfied:
(1) nodes u, v are within beacon transmission range of each other;
(2) there is one node w located within the beacon transmission range of u and within the interference range of v;
(3) there is one node w located within the beacon transmission range of v and within the interference range of u.
4. The method for time-slot-based distributed real-time beacon scheduling in the industrial internet of things as claimed in claim 3, wherein the minimum delay beacon scheduling optimization problem of the duty cycle sensor network with one active time slot is defined as:
defining 1.1 given multi-hop duty ratio industrial sensor network G ═ V, E, time slot-based distributed scheduling on network G, usingSch represents, wherein
And the following conditions are satisfied:
a. scheduling for any one transmission
Where C is an integer greater than or equal to 0 and x ═ w (w), w (w) denotes the active time slot of node w, where,
represents the transmission schedule sent from node u to node w at time T, | T | represents the duty cycle;
b. scheduling for any two transmissions
And
v ≠ u, if and only if t1 ≠ t2
And
a formalized definition of the problem is obtained according to the above definition:
inputting:
one duty cycle network G ═ V, E;
the active time slot of each sensor node, i.e. w (u),
and (3) outputting:
vertex-based beacon scheduling
Wherein SchminThe following conditions are satisfied:
Schminsatisfies the definition 1.1;
for any one of the schedules Sch', BL (Sch) satisfying definition 1.1min) BL (Sch ') is less than or equal to BL (Sch'), wherein BL (Sch)min) And BL (Sch') represents a beacon transmission schedule Sch, respectivelyminAnd delay of Sch'.
5. The time slot-based distributed real-time beacon scheduling method in the industrial internet of things according to claim 4, wherein in the duty cycle sensor network G, each sensor node maintains the following information:
the unique ID of the node u and the work plan of the node u;
neighbor information of the node u comprises a unique ID and a work plan of the neighbor node v;
the forbidden transmission time slot fts (u) of node u.
6. The time slot-based distributed real-time beacon scheduling method in the industrial internet of things according to claim 5, wherein the step S3 of calculating the node candidate scheduling information at the work cycle start time slot j specifically includes the following steps:
candidate transmission schedule cts (u) of node u ← [ u, v, j, weight ], wherein v and j respectively denote a beacon receiving node and a transmission time slot, and weight denotes a weight value of the candidate transmission schedule;
on a given time slot j of a system, firstly judging whether a node u can transmit in the time slot and whether a neighbor node in an active state exists, if so, calculating corresponding candidate transmission scheduling, and setting scheduling weight as the number of the neighbor nodes in the active state; if the condition is not satisfied, it indicates that there is no active node for node u in time slot j or that node u may not transmit in the time slot.
7. The time slot-based distributed real-time beacon scheduling method in the industrial internet of things as claimed in claim 6, wherein the node that receives the candidate scheduling information in step S4 replies with a data packet according to its own state and a collision determination mechanism of transmission scheduling, specifically:
after receiving the candidate scheduling information broadcasted by the node u, the node v firstly judges whether the node v is in an active state in the time slot of CTS (u), t (u), and ignores the scheduling information if the node v is in a sleep state; if the node is in an active state, after receiving the candidate scheduling information transmitted by all the related neighbor nodes, the node v selects the candidate scheduling with the largest weight value from all the candidate scheduling by adopting a node reply algorithm, replies 'support' information to the sending node to indicate that the scheduling is agreed, and replies 'release' information to the rest of the sending nodes to indicate that the scheduling is rejected.
8. The method according to claim 7, wherein after step S4, if the neighboring nodes agree with the candidate scheduling, the node establishes the candidate scheduling information as the scheduling in the time slot, and updates fts (u) ═ fts (u) < u >) which is a transmission-prohibited time slot.
9. The method as claimed in claim 8, wherein the candidate scheduling information of the next time slot is calculated, the candidate transmission scheduling is calculated for each node, and the corresponding transmission-prohibited time slot is updated until each node in the network broadcasts its beacon information to each neighbor node.
10. The time slot-based distributed real-time beacon scheduling method in the industrial internet of things according to claim 9, wherein in the step S5, each node repeats the steps S3 to S4 to obtain a collision-free real-time beacon transmission scheduling scheme, which specifically comprises:
initially, all nodes u capable of sending beacon packets in a Time Slot J are set to a Time Slot Synchronization state, the other nodes are set to a Not Ready state, and each node needs to maintain a variable y for indicating the number of neighbor nodes in an active state in the given Time Slot J of the system;
after a node enters a Time Slot Synchronization state, the 'Synchronization' message is firstly broadcast to synchronize all nodes capable of sending data packets on a Time Slot J, and if the node receives 'Synch' messages of all nodes which are positioned on the same Time Slot capable of sending the data packets as the node, the node enters a Ready state;
when a node enters into Ready state, firstly calculating candidate transmission scheduling information CTS on a time slot J according to step S3, broadcasting the CTS to all neighbor nodes, initializing y to the number of neighbor nodes in active state on the time slot J, then the node enters into wait state, and waits for the scheduling reply information sent back by the neighbor nodes;
for each node u, after receiving the 'support' message replied by the neighbor node v, if the node u is in the wait state, the following operations are performed: 1) t ← y-1; 2) if t is 0, determining candidate transmission schedule cts (u) ═ u, v, J, weight ] as formal scheduling on time slot J, node u will enter into Sch state, indicating that scheduling has been completed on J time slot and updating corresponding prohibited transmission time slot, i.e. fts (u) ═ fts (u) · J, and if node u is not in wait state, ignoring the message;
for each node u, if it receives the "replay" reply message of the neighbor node v, if the node u is in wait state, it directly enters into NotReady state to wait for being scheduled on other time slots.
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