CN106507468B - A kind of wireless sensor network time synchronization method and system - Google Patents
A kind of wireless sensor network time synchronization method and system Download PDFInfo
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- CN106507468B CN106507468B CN201710023622.XA CN201710023622A CN106507468B CN 106507468 B CN106507468 B CN 106507468B CN 201710023622 A CN201710023622 A CN 201710023622A CN 106507468 B CN106507468 B CN 106507468B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W84/00—Network topologies
- H04W84/18—Self-organising networks, e.g. ad-hoc networks or sensor networks
Abstract
The present invention discloses a kind of wireless sensor network time synchronization method and system, which comprises building multilayer wireless sensor network model；Obtain the time synchronization information of auxiliary node and father node two-way communication；According to the time synchronization information, the relative time offset of the auxiliary node and the father node and the relative time offset of the child node and the auxiliary node are estimated using maximal possibility estimation function, complete the time synchronization to auxiliary node and child node relative to father node.Corresponding 2 auxiliary nodes of host node of the invention, the robustness of algorithm can be effectively improved by additional auxiliary node, child node in network carries out time synchronization using the synchronizing information for monitoring father node and auxiliary node, interacts small, solves the problems, such as multihop network bad adaptability；The time synchronization that auxiliary node and child node are carried out using maximal possibility estimation function, improves time precision.
Description
Technical field
The present invention relates to wireless communication fields, more particularly to a kind of wireless sensor network time synchronization method and are
System.
Background technique
Wireless sensor network passes through nothing by the miniature multi-function sensor (microsensor node) of a large amount of cooperatings
The ad hoc network system that the mode of line communication is formed.Currently, application of higher wireless sensor network is very extensive, it can be used for ring
Border monitoring, the fields such as medical research.It is widely applied so that wireless sensor network, which is difficult, the specific standard of fixation, greatly
Part is according to current environment, purposes, and scale in time adjusts.This is also just to sensor processing terminal and radio node
Technological challenge is caused, a variety of environment should be adapted to, also to guarantee accuracy, the reliability of own hardware simultaneously.
Each node of wireless sensor network will do it time synchronization when data are transmitted, but each node will receive such as hardware
Service life, the influence of the factors such as Communication Jamming make time synchronization process error occur, to generate extreme influence to detection data.
Wireless sensor node is because from charged pool and capacity has eye, so that Time synchronization technique is in the case where guaranteeing precision, and also
Energy consumption is reduced as far as possible, and there is presently no technologies can meet both the above situation simultaneously.
ROS algorithm energy based on only receiving end synchronous protocol (Only Receive Synchronization, ROS) disappears
Consume extremely low, but synchronization accuracy is not high, and multihop network bad adaptability.
Summary of the invention
The object of the present invention is to provide a kind of wireless sensor network time synchronization method and systems, existing same to overcome
The problem of timing tracking accuracy is low in one step process and multihop network bad adaptability.
To achieve the above object, the present invention provides following schemes:
A kind of wireless sensor network time synchronization method, comprising:
Multilayer wireless sensor network model is constructed, the wireless sensor network includes father node, auxiliary node and son
Node；
It is corrected according to time of the time of terminal server to the father node；The terminal server for institute whether there is or not
The aggregation node of line sensor network nodes；
Obtain the time synchronization information of the auxiliary node and the father node two-way communication, the time synchronization information packet
Include the time synchronization request that the auxiliary node is sent and the time synchronization response message that the father node is sent；
According to the time synchronization information, the auxiliary node and the father node are estimated using maximal possibility estimation function
Relative time offset；
According to the auxiliary node with the relative time offset of the father node and the time of the father node to described auxiliary
The time of node is helped to be corrected；
According to the time synchronization information, the child node and the auxiliary node are estimated using maximal possibility estimation function
Relative time offset；
According to the relative time offset and the child node and the auxiliary node of the auxiliary node and the father node
Relative time offset calculate relative time offset of the child node relative to the father node；
According to the child node relative to the relative time offset of the father node and the time of the father node to described
The time of child node is corrected.
Optionally, the building multilayer wireless sensor network model specifically includes:
Construct the first layer network:
Randomly selecting any wireless sensor network node is father node, and the father node is this wireless sensor network
Host node；
Two nodes randomly selected in the father node communication range are auxiliary node, and the auxiliary node is in the father
The two sides of node；
Choosing the shared node in the father node and the auxiliary node communication range is child node；
One father node, two auxiliary nodes and several child nodes constitute the first layer network；
It constructs the 2nd and arrives N layer network, N >=2:
Choose the auxiliary node of N-1 layer network or father node of any node as n-th layer network in child node；
The auxiliary node that a node in the communication range of the father node of the n-th layer network is n-th layer network is chosen,
The auxiliary node of the n-th layer network and the father node of N-1 layer network are respectively the two of the father node of the n-th layer network
Side；
Choose the shared section in the father node of the n-th layer network and the auxiliary node communication range of the n-th layer network
Point is the child node of n-th layer network；
One father node and an auxiliary node corresponding with one father node and several child node structures
At a small network of single-hop in n-th layer network, the n-th layer network includes the small network of several single-hops.
Optionally, the auxiliary node communication range of the father node for choosing the n-th layer network and the n-th layer network
Interior shared node is that the child node of n-th layer network specifically includes:
For the shared node of the nodal information of the small network of single-hop in multiple same layer networks can be received simultaneously, institute is judged
Whether the priority for stating the father node of the small network of multiple single-hops is identical, obtains the first judging result, described in the priority expression
The father node of multiple small networks of single-hop carries out the sequencing of time synchronization；
If first judging result indicates that the priority of the father node of the small network of the multiple single-hop is different, described total
There is node that the small network of single-hop where the high father node of priority is added；
If first judging result indicates that the priority of the father node of the small network of the multiple single-hop is identical, institute is judged
State shared node receive the information that multiple father nodes with the small network of the single-hop in layer network are sent time it is whether identical, obtain
To the second judging result；
If second judging result indicates that the shared node receives the small network of single-hop in multiple same layer networks
The time for the information that father node is sent is different, then father node institute corresponding to the information most received fastly is added in the shared node
The small network of single-hop.
A kind of Time Synchronization for Wireless Sensor Networks system, comprising:
Model construction module, for constructing multilayer wireless sensor network model, the wireless sensor network includes father
Node, auxiliary node and child node；
First correction module, for being corrected according to the time of terminal server to the time of the father node；It is described
Terminal server is the aggregation node of all wireless sensor network nodes；
Module is obtained, it is described for obtaining the time synchronization information of the auxiliary node and the father node two-way communication
Time synchronization information includes the time synchronization request that the auxiliary node is sent and the time synchronization response that the father node is sent
Information；
First estimation module, for being estimated using maximal possibility estimation function described auxiliary according to the time synchronization information
Help the relative time offset of node Yu the father node；
Second correction module, for being saved according to the relative time offset of the auxiliary node and the father node and the father
The time of point is corrected the time of the auxiliary node；
Second estimation module, for estimating child node using maximal possibility estimation function according to the time synchronization information
With the relative time offset of the auxiliary node；
Computing module, for according to the relative time offset of the auxiliary node and the father node and the child node with
The relative time offset of the auxiliary node calculates relative time offset of the child node relative to the father node；
Third correction module, for according to the child node relative to the father node relative time offset and the father
The time of node is corrected the time of the child node.
Optionally, the model construction module specifically includes:
First layer network struction submodule, for construct the first layer network, described first layer network include a father node,
Two auxiliary nodes and several child nodes, specifically include:
First father node selection unit is father node, the father for randomly selecting any wireless sensor network node
Node is the host node of this wireless sensor network；
First auxiliary node selection unit, for randomly selecting two nodes in the father node communication range as auxiliary
Node, the auxiliary node is in the two sides of the father node；
First child node selection unit, choosing the father node with the shared node in the auxiliary node communication range is
Child node；
2nd constructs submodule to N layer network, and N layer network is arrived for constructing the 2nd, if the n-th layer network includes in N >=2
The dry small network of single-hop, specifically includes:
Second father node selection unit, any node in auxiliary node or child node for choosing N-1 layer network
Father node as n-th layer network；
Second auxiliary node selection unit, one in the communication range of the father node for choosing the n-th layer network
Node is the auxiliary node of n-th layer network, and the auxiliary node of the n-th layer network and the father node of N-1 layer network exist respectively
The two sides of the father node of the n-th layer network；
Second child node selection unit, for choosing the father node of the n-th layer network and the auxiliary of the n-th layer network
Shared node in node communication range is the child node of n-th layer network；
The small network struction unit of single-hop, for constructing the small network of single-hop, the small network of single-hop include a father node with
And an auxiliary node corresponding with one father node and several child nodes are constituted.
Optionally, the second child node selection unit specifically includes:
First result judgment sub-unit, for the section for the small network of single-hop in multiple same layer networks can be received simultaneously
The shared node of point information, judges whether the priority of the father node of the small network of the multiple single-hop is identical, the priority list
Show that the father node of the small network of the multiple single-hop carries out the sequencing of time synchronization；
First is added subelement, if indicating the father node of the small network of the multiple single-hop for first judging result
Priority is different, then the small network of single-hop where the high father node of priority is added in the shared node；
Second result judgment sub-unit, if first judging result indicates the father node of the small network of the multiple single-hop
Priority is identical, then judges that the shared node receives the letter that the father node of the small network of single-hop in multiple same layer networks is sent
Whether the time of breath is identical；
Second is added subelement, if indicating that the shared node receives multiple same layer nets for second judging result
The time for the information that the father node of the small network of single-hop in network is sent is different, then the letter most received fastly is added in the shared node
The small network of single-hop where the corresponding father node of breath.
The specific embodiment provided according to the present invention, the invention discloses following technical effects:
1, present invention building multilayer wireless sensor network model, corresponding 2 auxiliary nodes of host node, by additional auxiliary
Help node that can effectively improve the robustness of algorithm；Child node in network is synchronous with auxiliary node using father node is monitored
Information carries out time synchronization, interacts small；When father node is damaged or is interfered, node, which is also an option that, to be continued to
Other nodal informations carry out deadline synchronization, solve the problems, such as multihop network bad adaptability.
2, the present invention carries out the time synchronization of auxiliary node and child node using maximal possibility estimation function, improves well
Time precision, in network-wide basis in addition to host node, other father nodes only distribute single auxiliary node, not will cause energy and
The waste of resource, the advantages of inheriting former ROS algorithm low energy consumption.
Detailed description of the invention
It in order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, below will be to institute in embodiment
Attached drawing to be used is needed to be briefly described, it should be apparent that, the accompanying drawings in the following description is only some implementations of the invention
Example, for those of ordinary skill in the art, without any creative labor, can also be according to these attached drawings
Obtain other attached drawings.
Fig. 1 is a kind of flow chart of wireless sensor network time synchronization method embodiment of the present invention；
Fig. 2 is the structure chart of multilayer wireless sensor network model of the present invention；
Fig. 3 is a kind of time synchronization model of wireless sensor network time synchronization method of the present invention；
Fig. 4 is a kind of flow chart of Time Synchronization for Wireless Sensor Networks system embodiment of the present invention.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts every other
Embodiment shall fall within the protection scope of the present invention.
The object of the present invention is to provide a kind of wireless sensor network time synchronization method and systems, existing same to overcome
The problem of timing tracking accuracy is low in one step process and multihop network bad adaptability.
In order to make the foregoing objectives, features and advantages of the present invention clearer and more comprehensible, with reference to the accompanying drawing and specific real
Applying mode, the present invention is described in further detail.
Fig. 1 is a kind of flow chart of wireless sensor network time synchronization method embodiment of the present invention.As shown in Figure 1, one
Kind wireless sensor network time synchronization method, comprising:
Step 101, multilayer wireless sensor network model is constructed, the wireless sensor network includes father node, auxiliary
Node and child node.As shown in Fig. 2, building multilayer wireless sensor network model specifically includes:
Step 1011, the first layer network is constructed:
Choosing any wireless sensor network node is father node, and the father node is the master of this wireless sensor network
Node, only one host node of entire wireless sensor network.Under normal circumstances, preferential selected distance aggregation node distance compared with
Closely, preferable with aggregation node (being equivalent to terminal handler) bidirectional communication environments, the node of ambient stable is host node.Such as
Selection node 1 is father node, and node 1 is the host node of network.
After host node 1 determines, data information is sent out to determine the communication range of host node.Each node in range
It is sent out the node statistics information with itself unique ID after receiving packet, has second within the scope of host node to choose
More connection number destination nodes.It can also be received while each node sends mutually message within the scope of host node from other nodes
Statistical information, ignore if the node outside host node communication range receives statistical information.Nodes records in range are simultaneously
It counts and quantity information is fed back into host node after all ID quantity received, can be received after being sent out data such as node 2
The statistical information of node 3 and node 4, and node 3 would only receive the statistical information of node 2.Subsequent host node is according to receiving
The fed back statistics information of range interior nodes, the second multi-connection number destination node 2 of confirmation are used as auxiliary node.Choose father node 1 with
Shared node 3 and 4 in 2 communication range of auxiliary node is child node.So far the single-hop networks building for completing a small range, that is, save
The small synchronous network of point 1-4 composition.
Because of the spatiality of wireless sensor network, node 1 is only capable of the part of nodes of synchronization master side with node 2,
So centainly having the node of one with 2 near symmetrical of node, such as node 5, the node 17 and node 18 of 1 other side of host node can
Another single-hop networks are formed with node 1 and node 5, the same level as node 2 is supplemented.
In conclusion 1, two auxiliary node 2 and 5 of a father node and child node 3,4,17 and 18 constitute first layer net
Network.
Step 1012, N layer network is arrived in building the 2nd, N >=2:
Any node in the auxiliary node 2 and 5 or child node 3,4,17 and 18 of the first layer network is chosen as the 2nd layer of net
One father node of network；By taking node 2 as an example, node 2 is a father node of the second layer network at this time.
Choose the auxiliary section that a node in the communication range of the father node of first layer network is the second layer network
Point, the auxiliary node of second layer network and the father node of the first layer network are respectively in the father node of second layer network
Two sides.The auxiliary node that node 12 is node 2 is such as chosen, node 12 and node 1 are respectively in the two sides of node 2.
It chooses shared in the father node of second layer network and the auxiliary node communication range of second layer network
Node is the child node of the second layer network.Such as choosing the node 10,11,13 in 12 communication range of node 2 and node is child node,
Then node 2,12,10,11,13 constitutes a small network of single-hop of the second layer network.According to the above method, node 3,8,6,7 and 9
The small network of single-hop is constituted, node 4,15,14 and 16 constitutes a small network of single-hop.
The auxiliary node and child node of subsequent double layer network continue to form oneself three to external radiation respectively as host node
Layer network.Finally all nodes of network-wide basis is made to have the father node of oneself, completes the topology constructing of the whole network.
For the shared node of the nodal information of the small network of single-hop in multiple same layer networks can be received simultaneously, institute is judged
Whether the priority for stating the father node of the small network of multiple single-hops is identical, obtains the first judging result, described in the priority expression
The father node of multiple small networks of single-hop carries out the sequencing of time synchronization, and the priority with the auxiliary node of layer network is higher than son
The priority of node.
If first judging result indicates that the priority of the father node of the small network of the multiple single-hop is different, described total
There is node that the small network of single-hop where the high father node of priority is added.Assuming that node 13 is in respectively where node 2 and node 4
In two double layer networks, i.e. node 13 can be respectively received node 2 and node 12, the these two pair of node 4 and node 15 it is two-way
Synchronizing information.But the rank of node 2 is higher than node 4, and node 2 is wanted as auxiliary node and host node direct communication, time precision
Higher than the precision of the node 4 only synchronized by passively receiving, therefore node 13 is divided into the single-hop networks where node 2.
Node 13 abandons the message from node 4 and node 15 received.
If first judging result indicates that the priority of the father node of the small network of the multiple single-hop is identical, institute is judged
State shared node receive the information that multiple father nodes with the small network of the single-hop in layer network are sent time it is whether identical, obtain
To the second judging result；
If second judging result indicates that the shared node receives the small network of single-hop in multiple same layer networks
The time for the information that father node is sent is different, then father node institute corresponding to the information most received fastly is added in the shared node
The small network of single-hop.I.e. if single child node can receive the nodal information of the single-hop networks of two same layer ranks simultaneously,
Then select the single-hop networks of that most fast received a pair of of node as synchronizing network.Closely then transmission speed is fast for euclidean distance between node pair, but
Not absolutely, such as encountering strong interference or communicating unstable rule may make to synchronize to be unable to complete, and most fast receive then means letter
Number propagation time it is short, be interfered small.Therefore child node preferentially selects the shortest father node institute of fastest transmission i.e. transmission time
In network as oneself single-hop networks.
Step 102, it is corrected according to time of the time of terminal server to the father node；The terminal server
For the aggregation node of all wireless sensor network nodes.
Step 103, the time synchronization information of the auxiliary node and the father node two-way communication is obtained, the time is same
Step information includes the time synchronization request that the auxiliary node is sent and the time synchronization response message that the father node is sent.
Step 104, according to the time synchronization information, the auxiliary node and institute are estimated using maximal possibility estimation function
State the relative time offset of father node.
Step 105, according to the time of the relative time offset and the father node of the auxiliary node and the father node
The time of the auxiliary node is corrected.
Step 106, according to the time synchronization information, using maximal possibility estimation function estimate the child node with it is described
The relative time offset of auxiliary node.
Step 107, according to the relative time offset of the auxiliary node and the father node and the child node with it is described
The relative time offset of auxiliary node calculates relative time offset of the child node relative to the father node.
Step 108, according to the child node relative to the father node relative time offset and the father node when
Between the time of the child node is corrected.
Fig. 4 is a kind of time synchronization model of wireless sensor network time synchronization method of the present invention.As shown in figure 4, section
Point P is host node (father node, 2 node 1 of corresponding diagram), and node A is auxiliary node (2 node 2 of corresponding diagram), and node B is child node
(2 node 3 of corresponding diagram).Node P and A carries out two-way communication, and node B obtains the communication information packet of P and A by monitoring.
(1) for P-A node,WithIndicate that node A sends the time point of information and A receives P return information
Time point,WithThe time point of information is received for node P and the time point of information is sent to A.Point A existsMoment to
Node P send one group of data, node P inThis data packet of reception, and parsed the time tag in data packetWith posterior nodal point P hardware layer by after data processing inMoment retransmits back node A, takes respectively in data packet at this time
BandTime identifier.Final node A existsThe data packet that reception is passed back to node P, and solve
First three time tag in data packet is analysed.
WhereinFor the i-th wheel synchronous two-way communication time point, d is fixed delay,
For the relative clock offset between node A and P, XiFor the transmission random delay of A to P, YiFor the transmission random delay of P to A, Xi,
Yi,D is unknown quantity, remaining parameter is known.
Firstly, XiWith YiIndependently submitting to the exponential distribution that mean value is a, (pertinent literature is proved random delay can be with independently
Exponential distribution indicate).Then:
Because of Xi>=0, Yi>=0, soAccording to
Formula (3) and formula (4) available likelihood function based on maximal possibility estimation:
Wherein,With d andThe respectively abscissa and ordinate of reference axis is established and is sat
System is marked, then straight lineWithIntersection point are as follows:
The abscissa of straight-line intersection W is d
Maximum value, i.e. the value range of d For i
Own in memory space after secondary transmissionMinimum value,For in memory space after i transmission
It is allMaximum value.According to maximal possibility estimation function property, as long as
Minimum, then maximal possibility estimation functionMaximum is taken, so obtaining the maximal possibility estimation of d:
It can obtain simultaneously:
The time of node A is then added into relative clock offsetThe time synchronization of counterpart node P can be completed:TAFor the time after synchronizing.
(2) synchronous with A-P node for child node B.There are a father node P in a single-hop networks, one auxiliary
Help node A and many child nodes, only with child node B for, node B existsWithAt the time of listen to respectively node A and
The communication information of node P.It is similar with node A and node P bi-directional synchronization:
It can be obtained by formula (8), formula (9) and formula (10):
Wherein, d is fixed delay,For the relative clock offset between node B and P,Between node A and B
Relative clock offset, XB,iFor the transmission random delay of A to B, YB,iFor the transmission random delay of P to B, XB,i, YB,i,For
Unknown quantity, d are to be obtained according to formula (6) estimation (i-1)-th (a upper synchronizing cycle for current period) synchronizing cycle, and be carried
In the packet of auxiliary node A i-th, by Node-B receiver to.Similarly,For (i-1)-th time (current period it is upper together
Step period) it is obtained according to formula (7) estimation synchronizing cycle.Remaining parameter is known.XB,iWith YB,iIndependently submitting to mean value is a's
Exponential distribution, then:
Because of XB,i>=0, YB,i>=0, so
According to formula (12) and the available likelihood function based on maximal possibility estimation of formula (13):
Wherein,
WhenWhen being minimized, maximal possibility estimation letter
Number be maximized, wherein d andIt is obtained by formula (6) and formula (7) estimation, is known quantity, onlyFor unknown quantity.
Therefore, whenIt is maximized,When, likelihood function takes
Maximum value.Known by formula (10)The time of node B is then added into relative clock offset?
Complete the time synchronization of opposite father node P:
TBFor the time after Node B sync.
Fig. 4 is a kind of flow chart of Time Synchronization for Wireless Sensor Networks system embodiment of the present invention.As shown in figure 4, one
Kind Time Synchronization for Wireless Sensor Networks system, comprising:
Model construction module 201, for constructing multilayer wireless sensor network model, the wireless sensor network includes
Father node, auxiliary node and child node.The model construction module specifically includes:
First layer network struction submodule 2011, for constructing the first layer network, described first layer network includes a father
Node, two auxiliary nodes and several child nodes, specifically include:
First father node selection unit is father node, the father for randomly selecting any wireless sensor network node
Node is the host node of this wireless sensor network；
First auxiliary node selection unit, for randomly selecting two nodes in the father node communication range as auxiliary
Node, the auxiliary node is in the two sides of the father node；
First child node selection unit, choosing the father node with the shared node in the auxiliary node communication range is
Child node；
2nd constructs submodule 2012 to N layer network, and N layer network, the n-th layer network packet are arrived for constructing the 2nd in N >=2
The small network of several single-hops is included, is specifically included:
Second father node selection unit, any node in auxiliary node or child node for choosing N-1 layer network
Father node as n-th layer network；
Second auxiliary node selection unit, one in the communication range of the father node for choosing the n-th layer network
Node is the auxiliary node of n-th layer network, and the auxiliary node of the n-th layer network and the father node of N-1 layer network exist respectively
The two sides of the father node of the n-th layer network；
Second child node selection unit, for choosing the father node of the n-th layer network and the auxiliary of the n-th layer network
Shared node in node communication range is the child node of n-th layer network.The second child node selection unit specifically includes:
First result judgment sub-unit, for the section for the small network of single-hop in multiple same layer networks can be received simultaneously
The shared node of point information, judges whether the priority of the father node of the small network of the multiple single-hop is identical, the priority list
Show that the father node of the small network of the multiple single-hop carries out the sequencing of time synchronization；
First is added subelement, if indicating the father node of the small network of the multiple single-hop for first judging result
Priority is different, then the small network of single-hop where the high father node of priority is added in the shared node；
Second result judgment sub-unit, if first judging result indicates the father node of the small network of the multiple single-hop
Priority is identical, then judges that the shared node receives the letter that the father node of the small network of single-hop in multiple same layer networks is sent
Whether the time of breath is identical；
Second is added subelement, if indicating that the shared node receives multiple same layer nets for second judging result
The time for the information that the father node of the small network of single-hop in network is sent is different, then the letter most received fastly is added in the shared node
The small network of single-hop where the corresponding father node of breath.
The small network struction unit of single-hop, for constructing the small network of single-hop, the small network of single-hop include a father node with
And an auxiliary node corresponding with one father node and several child nodes are constituted.
First correction module 202, for being corrected according to the time of terminal server to the time of the father node；Institute
State the aggregation node that terminal server is all wireless sensor network nodes.
Module 203 is obtained, for obtaining the time synchronization information of the auxiliary node and the father node two-way communication, institute
Stating time synchronization information includes that the time synchronization request that the auxiliary node is sent and the time synchronization that the father node is sent are rung
Answer information.
First estimation module 204, for according to the time synchronization information, estimated using maximal possibility estimation function described in
The relative time offset of auxiliary node and the father node.
Second correction module 205, for according to the relative time offset of the auxiliary node and the father node with it is described
The time of father node is corrected the time of the auxiliary node.
Second estimation module 206, for estimating son section using maximal possibility estimation function according to the time synchronization information
The relative time offset of point and the auxiliary node.
Computing module 207, for the relative time offset and the sub- section according to the auxiliary node and the father node
The relative time offset of point and the auxiliary node calculates relative time offset of the child node relative to the father node.
Third correction module 208, for according to the child node relative to the relative time offset of the father node and institute
The time for stating father node is corrected the time of the child node.
Each embodiment in this specification is described in a progressive manner, the highlights of each of the examples are with other
The difference of embodiment, the same or similar parts in each embodiment may refer to each other.For system disclosed in embodiment
For, since it is corresponded to the methods disclosed in the examples, so being described relatively simple, related place is said referring to method part
It is bright.
Used herein a specific example illustrates the principle and implementation of the invention, and above embodiments are said
It is bright to be merely used to help understand method and its core concept of the invention；At the same time, for those skilled in the art, foundation
Thought of the invention, there will be changes in the specific implementation manner and application range.In conclusion the content of the present specification is not
It is interpreted as limitation of the present invention.
Claims (6)
1. a kind of wireless sensor network time synchronization method characterized by comprising
Multilayer wireless sensor network model is constructed, the wireless sensor network includes father node, auxiliary node and child node；
It is corrected according to time of the time of terminal server to the father node；The terminal server is all wireless biographies
The aggregation node of sensor network node；
The time synchronization information of the auxiliary node and the father node two-way communication is obtained, the time synchronization information includes institute
The time synchronization response message that the time synchronization request and the father node for stating auxiliary node transmission are sent；
According to the time synchronization information, the phase of the auxiliary node with the father node is estimated using maximal possibility estimation function
To time migration；
The auxiliary is saved according to the time of the relative time offset and the father node of the auxiliary node and the father node
The time of point is corrected；
According to the time synchronization information, the phase of the child node with the auxiliary node is estimated using maximal possibility estimation function
To time migration；
According to the auxiliary node and the relative time offset of the father node and the phase of the child node and the auxiliary node
Relative time offset of the child node described in time calculations of offset relative to the father node；
According to the child node relative to the relative time offset of the father node and the time of the father node to the sub- section
The time of point is corrected.
2. the method as described in claim 1, which is characterized in that the building multilayer wireless sensor network model specifically wraps
It includes:
Construct the first layer network:
Randomly selecting any wireless sensor network node is father node, and the father node is the master of this wireless sensor network
Node；
Two nodes randomly selected in the father node communication range are auxiliary node, and the auxiliary node is in the father node
Two sides；
Choosing the shared node in the father node and the auxiliary node communication range is child node；
One father node, two auxiliary nodes and several child nodes constitute the first layer network；
It constructs the 2nd and arrives N layer network, N >=2:
Choose the auxiliary node of N-1 layer network or father node of any node as n-th layer network in child node；
The auxiliary node that a node in the communication range of the father node of the n-th layer network is n-th layer network is chosen, it is described
The auxiliary node of n-th layer network and the father node of N-1 layer network are respectively in the two sides of the father node of the n-th layer network；
The shared node chosen in the father node of the n-th layer network and the auxiliary node communication range of the n-th layer network is
The child node of n-th layer network；
One father node and an auxiliary node corresponding with one father node and several child nodes constitute N
A small network of single-hop in layer network, the n-th layer network include the small network of several single-hops.
3. method according to claim 2, which is characterized in that the father node and the N for choosing the n-th layer network
Shared node in the auxiliary node communication range of layer network is that the child node of n-th layer network specifically includes:
For the shared node of the nodal information of the small network of single-hop in multiple same layer networks can be received simultaneously, judge described more
It is a whether identical with the priority of the father node of the small network of the single-hop in layer network, obtain the first judging result, the priority
Indicate that the father node of the small network of single-hop in the multiple same layer network carries out the sequencing of time synchronization；
If first judging result indicates that the priority of the father node of the small network of single-hop in the multiple same layer network is different,
Then the small network of single-hop where the high father node of priority is added in the shared node；
If first judging result indicates the multiple identical with the priority of father node of the small network of the single-hop in layer network,
Then judge that the shared node receives time of information that the father node of the small network of single-hop in multiple same layer networks is sent and is
It is no identical, obtain the second judging result；
If second judging result indicates that the shared node receives father's section of the small network of single-hop in multiple same layer networks
The time for the information that point is sent is different, then the shared node is added where father node corresponding to the information most received fastly
The small network of single-hop.
4. a kind of Time Synchronization for Wireless Sensor Networks system, which is characterized in that the system comprises:
Model construction module, for constructing multilayer wireless sensor network model, the wireless sensor network include father node,
Auxiliary node and child node；
First correction module, for being corrected according to the time of terminal server to the time of the father node；The terminal
Server is the aggregation node of all wireless sensor network nodes；
Module is obtained, for obtaining the time synchronization information of the auxiliary node and the father node two-way communication, the time
Synchronizing information includes the time synchronization request that the auxiliary node is sent and the time synchronization response message that the father node is sent；
First estimation module, for estimating that the auxiliary is saved using maximal possibility estimation function according to the time synchronization information
The relative time offset of point and the father node；
Second correction module, for the relative time offset and the father node according to the auxiliary node and the father node
Time is corrected the time of the auxiliary node；
Second estimation module, for estimating child node and institute using maximal possibility estimation function according to the time synchronization information
State the relative time offset of auxiliary node；
Computing module, for according to the relative time offset of the auxiliary node and the father node and the child node with it is described
The relative time offset of auxiliary node calculates relative time offset of the child node relative to the father node；
Third correction module, for the relative time offset and the father node according to the child node relative to the father node
Time the time of the child node is corrected.
5. system as claimed in claim 4, which is characterized in that the model construction module specifically includes:
First layer network struction submodule, for constructing the first layer network, described first layer network includes a father node, two
Auxiliary node and several child nodes, specifically include:
First father node selection unit is father node, the father node for randomly selecting any wireless sensor network node
For the host node of this wireless sensor network；
First auxiliary node selection unit, for randomly selecting two nodes in the father node communication range as auxiliary section
Point, the auxiliary node is in the two sides of the father node；
First child node selection unit chooses the shared node in the father node and the auxiliary node communication range as son section
Point；
2nd constructs submodule to N layer network, and N layer network is arrived for constructing the 2nd in N >=2, and n-th layer network includes that several single-hops are small
Network specifically includes:
Second father node selection unit, any node conduct in auxiliary node or child node for choosing N-1 layer network
The father node of n-th layer network；
Second auxiliary node selection unit, a node in the communication range of the father node for choosing the n-th layer network
For the auxiliary node of n-th layer network, the auxiliary node of the n-th layer network and the father node of N-1 layer network are respectively described
The two sides of the father node of n-th layer network；
Second child node selection unit, for choosing the father node of the n-th layer network and the auxiliary node of the n-th layer network
Shared node in communication range is the child node of n-th layer network；
The small network struction unit of single-hop, for constructing the small network of single-hop, the small network of single-hop include a father node and and
One corresponding auxiliary node of father node and several child nodes are constituted.
6. system as claimed in claim 5, which is characterized in that the second child node selection unit specifically includes:
First result judgment sub-unit, for believing for the node that can receive the small network of single-hop in multiple same layer networks simultaneously
Breath shared node, judge it is the multiple whether identical with the priority of the father node of the small network of the single-hop in layer network, it is described
Priority indicates that the father node of the small network of single-hop in the multiple same layer network carries out the sequencing of time synchronization；
First is added subelement, if indicating father's section of the small network of single-hop in the multiple same layer network for the first judging result
The priority of point is different, then the small network of single-hop where the high father node of priority is added in the shared node；
Second result judgment sub-unit, if first judging result indicates the small network of single-hop in the multiple same layer network
The priority of father node is identical, then judges that the shared node receives the father node of the small network of single-hop in multiple same layer networks
Whether the time of the information of transmission is identical；
Second is added subelement, if indicating that the shared node receives the list in multiple same layer networks for the second judging result
The time for jumping the information of the father node transmission of small network is different, then the shared node is added corresponding to the information most received fastly
Father node where the small network of single-hop.
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