CN113163482A - Time synchronization method between nodes of wireless sensor network - Google Patents
Time synchronization method between nodes of wireless sensor network Download PDFInfo
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- CN113163482A CN113163482A CN202110116378.8A CN202110116378A CN113163482A CN 113163482 A CN113163482 A CN 113163482A CN 202110116378 A CN202110116378 A CN 202110116378A CN 113163482 A CN113163482 A CN 113163482A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
- H04W56/001—Synchronization between nodes
- H04W56/0015—Synchronization between nodes one node acting as a reference for the others
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- H—ELECTRICITY
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- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L43/00—Arrangements for monitoring or testing data switching networks
- H04L43/10—Active monitoring, e.g. heartbeat, ping or trace-route
- H04L43/106—Active monitoring, e.g. heartbeat, ping or trace-route using time related information in packets, e.g. by adding timestamps
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- H—ELECTRICITY
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- H04W—WIRELESS COMMUNICATION NETWORKS
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- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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Abstract
The invention provides a time synchronization method between wireless sensor network nodes, which comprises the following steps that a wireless sensor periodically sends heartbeat packets with time stamps to a father node, obtains the time difference between the local time of a terminal node and the father node, stores the time difference into a circular queue, and obtains the mean value of the time difference between the local time of the terminal node and the father node and the time difference of related nodes; when a vehicle passes through two adjacent sensor nodes in the same lane, the sensor nodes record the triggering time of the geomagnetic sensor and send the triggering time to a father node; the father node calculates the triggered time difference of two adjacent sensor nodes in the same lane, and the time difference is subtracted from the time difference of the related nodes to obtain the time required by the vehicle to pass through the two adjacent sensor nodes in the same lane, so as to calculate the vehicle speed; and the parent node transmits the processing result to the processing center. By the method for synchronizing the time between the nodes of the wireless sensor network, provided by the invention, high-precision time synchronization between the nodes of the related wireless sensors is realized, the workload of the terminal nodes is reduced, and the battery endurance time is prolonged.
Description
Technical Field
The invention relates to a time synchronization method among nodes of a wireless sensor network, in particular to a method for realizing time synchronization among low-power-consumption high-precision terminal nodes, and belongs to the technical field of wireless sensor networks.
Background
An Intelligent Transportation System (ITS-Intelligent Transportation System) integrates computer technology, information transmission processing technology, automatic control technology and other technologies, and a wireless geomagnetic sensor can be widely applied to the Intelligent Transportation fields of traffic data acquisition, traffic guidance assistance and the like. The equipment required for completing traffic data acquisition by adopting the geomagnetic vehicle detection technology comprises a geomagnetic vehicle flow detection unit (wireless sensor node), a geomagnetic vehicle flow transmission repeater, a geomagnetic vehicle flow detection receiving host (also called as a gateway) and a data processing terminal. The geomagnetic traffic flow detection unit and the geomagnetic traffic flow detection receiving host are optional equipment. The geomagnetic traffic flow detection unit is used for detecting the traffic passing information on the road in real time and can directly transmit the traffic passing information to the gateway. When the distance between the collector and the gateway exceeds a certain range, in order to ensure reliable communication between the collector and the gateway, the data can be forwarded between the collector and the gateway through a repeater. Among the collected traffic data, vehicle speed is one of the key data. In order to realize vehicle speed detection, two geomagnetic traffic flow detection units (wireless sensor nodes) are buried under the road surface at the same lane and at an interval of L meters, and the vehicle speed can be obtained by detecting the time difference of the vehicle passing through the two sensors, so that the L value is not large, the national standard requires 3 to 5 meters, and the speed can be approximately constant; in order to meet the national standard requirement that the speed detection precision is not lower than 98% when the vehicle speed is 60-120 Km/H, the time of two sensor nodes on the same lane must be strictly synchronous (less than 2.4 ms). Due to the influences of factors such as limited sensor node resources, limited energy, uncertain network load and the like, many mature Wireless Sensor Network (WSN) time synchronization algorithms, such as synchronization algorithms like DTMS, RBS, TPSN, LTS and the like, are not suitable for geomagnetic vehicle detection wireless sensor networks. Some algorithms are complex in process and require stronger computing power and more resources; some can be completed only by multiple times of interactive communication, the power consumption is large, and the national standard requirement of battery endurance time of at least 5 years cannot be met; due to the influence of uncertainty of various devices, loads and message transmission delay, data transmission delay is unpredictable, and the factors influencing time synchronization uncertainty are more. Even if the initial state can realize strict time synchronization, due to the discreteness among devices, the time between two nodes can be deviated after a period of time, and the time synchronization operation among the nodes of the wireless sensor network needs to be carried out periodically. The method is an important problem for realizing high-precision and low-power consumption time synchronization among wireless sensor nodes with limited resources and energy.
Disclosure of Invention
The invention aims to provide a time synchronization method among nodes of a wireless sensor network, which can solve the problem of realizing accurate time synchronization among the nodes of the network under the conditions of limited resources, energy, cost and volume.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a time synchronization method between wireless sensor network nodes comprises the following steps:
the method comprises the steps that I, a wireless sensor network terminal node periodically sends heartbeat packets with time stamps to a father node, namely a geomagnetic traffic flow detection receiving host;
II, after receiving the heartbeat packet, the father node passes the formula
TZi0＝(1/N)[(TF1-TZi1)+(TF2-TZi2)+...+(TFn-TXZin)]
Obtaining the time difference T between the local time of the terminal node and the father nodeZi0The mean value of the time difference between the local time of the terminal node Zi and the father node; t isFj-TZijAfter receiving the jth heartbeat packet of the node i, the father node receives the time difference between the terminal node Zi local time and the father node; storing the difference value into a circular queue, and solving the mean value of the time difference between the local time of the terminal node and the time difference of the father node;
calculating the time difference of the relevant node and the time value of the terminal node based on the father node clock according to the average value of the local time of the terminal node and the time difference of the father node;
and taking the father node time as a reference, calculating the terminal node time:
TZi＝TF1+TZi0
correlation terminal node A, B time difference calculation:
TZAB0＝TZA0-TZB0
when the vehicle sequentially passes through two adjacent sensor nodes on the same lane, the sensor nodes record the triggered time of the geomagnetic sensor and pack and send the time to a father node;
v, the father node calculates the triggered time difference of two adjacent sensor nodes in the same lane, and the time difference is subtracted from the relevant node time difference calculated in the step III to obtain the time required by the vehicle to pass through the two adjacent sensor nodes in the same lane, and the vehicle speed is calculated;
the vehicle passes through two adjacent nodes A, B in sequence, and the time difference is calculated as follows:
Δt＝TZAB0-TZAB
TZABa, B time difference is triggered for two node local events;
the vehicle speed calculation formula is as follows:
V＝L/Δt
l is the set distance between two nodes;
and VI, the father node transmits the processing result to the processing center.
Preferably, the passing of the vehicle and the triggering of the geomagnetic sensor in step iv are implemented by comparing a current geomagnetic detection signal with a dynamically formed geomagnetic signal detection threshold, where the geomagnetic signal detection threshold is calculated by:
C0＝(1/N)(C1+C2+...+Cn)+K
c0 is a geomagnetic signal threshold, Cj is a geomagnetic signal value detected at the j-th time, and K is a correction constant.
Preferably, in the step ii, a moving average filtering algorithm is used to obtain a mean value of time differences between the local time of the terminal node and the parent node.
Preferably, the time synchronization between the terminal nodes is completed by the parent node by processing the received heartbeat packet, and the clock synchronization on the terminal nodes is not needed.
The invention has the advantages that: by the method for time synchronization among the nodes of the wireless sensor network, provided by the invention, high-precision time synchronization among the nodes of the related wireless sensors is realized, the calculation requirements of time key related parameters are met, the workload of the terminal nodes is reduced, and the battery endurance time is obviously prolonged.
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The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
FIG. 1 is a flow chart of a terminal node of the present invention
FIG. 2 is a flow diagram of a parent node of the present invention
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a time synchronization method among nodes of a wireless sensor network, which can solve the problem of realizing accurate time synchronization among the nodes of the network under the conditions of limited resources, energy, cost and volume. The device for realizing the method comprises a geomagnetic traffic flow detection unit (wireless sensor node), a geomagnetic traffic flow transmission repeater, a geomagnetic traffic flow detection receiving host (also called as a gateway) and a data processing terminal. The geomagnetic traffic flow detection unit and the geomagnetic traffic flow detection receiving host are optional equipment. The geomagnetic traffic flow detection unit is used for detecting the traffic passing information on the road in real time and can directly transmit the traffic passing information to the gateway. When the distance between the collector and the gateway exceeds a certain range, in order to ensure reliable communication between the collector and the gateway, the data can be forwarded between the collector and the gateway through a repeater. The wireless sensor nodes are buried under the road surface through the drill holes in the middle of the lane, and the distance is 5 meters when the double nodes are arranged; the repeater and the receiving host are arranged on a signal lamp pole or an electronic police cross bar; the data processing terminal is placed in the signal cabinet. The wireless sensor node senses the vehicle state through the magnetoresistive sensing (AMR), records corresponding time and sends the vehicle state to a geomagnetic vehicle flow detection receiving host (father node) in a wireless mode; the method comprises the steps that a timestamp heartbeat packet is sent to a father node periodically when no vehicle exists; the father node receives the heartbeat packet to obtain a time value of the terminal node relative to the time reference of the father node; and when vehicles exist, the father node receives the event trigger time value and transmits the calculation processing result and other intelligent traffic parameters to the data processing terminal in a wired or wireless mode.
The method for time synchronization among the nodes of the wireless sensor network comprises the following steps: firstly, a father node processes a received heartbeat packet sent by a terminal node to obtain a time value corresponding to the terminal node by taking a father node clock as a reference and a time difference value between related terminal nodes; and when no external event is triggered, the terminal node dynamically forms a geomagnetic signal detection threshold.
Calculating the time difference between the terminal node and the father node:
TZi0＝(1/N)[(TF1-TZi1)+(TF2-TZi2)+...+(TFn-TXZin)]
obtaining the time difference T between the local time of the terminal node and the father nodeZi0The mean value of the time difference between the local time of the terminal node Zi and the father node; t isFj-TZijAnd after the father node receives the jth heartbeat packet of the node i, the time difference between the local time of the terminal node Zi and the father node is obtained.
And taking the father node time as a reference, calculating the terminal node time:
TZi＝TF1+TZi0
correlation terminal node A, B time difference calculation:
TZAB0＝TZA0-TZB0
the vehicle passes through two adjacent nodes A, B in sequence, and the time difference is calculated as follows:
Δt＝TZAB0-TZAB
TZABa, B time difference is triggered for two node local events;
the vehicle speed calculation formula is as follows:
V＝L/Δt
l is the set distance between two nodes;
geomagnetic signal detection threshold calculation:
C0＝(1/N)(C1+C2+...+Cn)+K
c0 is a geomagnetic signal threshold, Cj is a geomagnetic signal value detected at the j-th time, and K is a correction constant.
The vehicle triggers the state change of the geomagnetic sensor, the terminal node processes the detection value of the geomagnetic sensor according to the signal detection threshold value to obtain the characteristic value of the vehicle and corresponding time, and the processing result is sent to the father node.
And the father node receives the vehicle detection characteristic value record of the relevant terminal node, wherein the record comprises the detection value and the corresponding time. The time difference of the vehicle passing through two adjacent terminal nodes can be obtained through computer processing, and further other concerned parameters such as vehicle speed and the like can be calculated.
In addition to the above embodiments, the present invention may have other embodiments. All technical solutions which adopt equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.
Claims (4)
1. A method for time synchronization among wireless sensor network nodes is characterized by comprising the following steps:
the method comprises the steps that I, a wireless sensor network terminal node periodically sends heartbeat packets with time stamps to a father node, namely a geomagnetic traffic flow detection receiving host;
II, after receiving the heartbeat packet, the father node passes the formula
TZi0＝(1/N)[(TF1-TZi1)+(TF2-TZi2)+...+(TFn-TXZin)]
Obtaining the time difference T between the local time of the terminal node and the father nodeZi0The mean value of the time difference between the local time of the terminal node Zi and the father node; t isFj-TZijAfter receiving the jth heartbeat packet of the node i, the father node receives the time difference between the terminal node Zi local time and the father node; storing the difference value into a circular queue, and solving the mean value of the time difference between the local time of the terminal node and the time difference of the father node;
calculating the time difference of the relevant node and the time value of the terminal node based on the father node clock according to the average value of the local time of the terminal node and the time difference of the father node;
and taking the father node time as a reference, calculating the terminal node time:
TZi＝TF1+TZi0
correlation terminal node A, B time difference calculation:
TZAB0＝TZA0-TZB0
when the vehicle sequentially passes through two adjacent sensor nodes on the same lane, the sensor nodes record the triggered time of the geomagnetic sensor and pack and send the time to a father node;
v, the father node calculates the triggered time difference of two adjacent sensor nodes in the same lane, and the time difference is subtracted from the relevant node time difference calculated in the step III to obtain the time required by the vehicle to pass through the two adjacent sensor nodes in the same lane, and the vehicle speed is calculated;
the vehicle passes through two adjacent nodes A, B in sequence, and the time difference is calculated as follows:
Δt＝TZAB0-TZAB
TZABa, B time difference is triggered for two node local events;
the vehicle speed calculation formula is as follows:
V＝L/Δt
l is the set distance between two nodes;
and VI, the father node transmits the processing result to the processing center.
2. The method for time synchronization between wireless sensor network nodes according to claim 1, wherein the passing of the vehicle and triggering of the geomagnetic sensor in step iv is implemented by comparing a current geomagnetic detection signal with a dynamically formed geomagnetic signal detection threshold, and the geomagnetic signal detection threshold is calculated by:
C0＝(1/N)(C1+C2+...+Cn)+K
c0 is a geomagnetic signal threshold, Cj is a geomagnetic signal value detected at the j-th time, and K is a correction constant.
3. The method of claim 1, wherein in step ii, a moving average filtering algorithm is used to obtain a mean value of the time difference between the local time of the terminal node and the time difference between the parent node and the parent node.
4. The method of claim 1, wherein the time synchronization between the end nodes is performed by the parent node by processing the received heartbeat packet without performing clock synchronization on the end nodes.
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Citations (3)
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| CN104301988A (en) * | 2014-08-17 | 2015-01-21 | 宿迁学院 | Sensor-network-based geomagnetic induction vehicle clock synchronization technology |
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| US20190261439A1 (en) * | 2016-11-10 | 2019-08-22 | Sony Corporation | Wireless apparatus, wireless apparatus processing method, and program |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2854458A1 (en) * | 2013-09-30 | 2015-04-01 | Honeywell International Inc. | Wireless sensor time synchronization |
| CN104301988A (en) * | 2014-08-17 | 2015-01-21 | 宿迁学院 | Sensor-network-based geomagnetic induction vehicle clock synchronization technology |
| US20190261439A1 (en) * | 2016-11-10 | 2019-08-22 | Sony Corporation | Wireless apparatus, wireless apparatus processing method, and program |
Non-Patent Citations (3)
| Title |
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| AZZEDINE BOUKERCHE ET AL: ""Secure time synchronization protocols for wireless sensor networks"", 《IEEE WIRELESS COMMUNICATIONS 》 * |
| NASON TACKETT ET AL: "" An Implementation of Time Synchronization in Low-Power Wireless Sensor Networks"", 《2011 IEEE 43RD SOUTHEASTERN SYMPOSIUM ON SYSTEM THEORY》 * |
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