CN104780602A - Clock self-synchronizing method in wireless communication network - Google Patents
Clock self-synchronizing method in wireless communication network Download PDFInfo
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- CN104780602A CN104780602A CN201510210356.2A CN201510210356A CN104780602A CN 104780602 A CN104780602 A CN 104780602A CN 201510210356 A CN201510210356 A CN 201510210356A CN 104780602 A CN104780602 A CN 104780602A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
- H04W56/001—Synchronization between nodes
- H04W56/002—Mutual synchronization
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W56/00—Synchronisation arrangements
- H04W56/0035—Synchronisation arrangements detecting errors in frequency or phase
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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
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- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Synchronisation In Digital Transmission Systems (AREA)
- Mobile Radio Communication Systems (AREA)
Abstract
The invention discloses a clock self-synchronizing method in a wireless communication network, and provides a distributed clock frequency calibration method for nodes. The method includes the steps that each node sends a synchronizing sequence to a port at the frequency of the node, when a node in the network obtains the synchronizing sequence of the adjacent node through detection and analysis, and frequency difference between the node and the sending node can be estimated according to the correlation of the synchronizing sequence; if the frequency difference is smaller than a preset range, clock frequency adjustment is not conducted, otherwise, delta is adjusted upwards or downwards, and after a period of time, the clock frequencies of the whole network can be stabilized within a certain frequency difference range. According to the method, on the premise that the wireless communication network is not externally connected with a clock source, synchronizing of a network clock can be maintained through self-synchronizing of clocks among the nodes in the wireless communication network, and interconnection and interworking of the network are guaranteed.
Description
Technical field
The present invention relates to a kind of clock self-synchronization method in cordless communication network, be applied to the network system that wireless communication field needs to carry out clock synchronous, particularly wireless self-organization network system.
Background technology
Cordless communication network can be divided into synchronizing network and asynchronous network according to the mode difference of node visit channel, and synchronizing network, relative to asynchronous network, has that the availability of frequency spectrum is high, an advantage such as the large and high real-time of power system capacity, is therefore widely used.
Clock synchronous is the important foundation of sychronous wireless communication network, is one of core technology of the functions such as wireless signal correctly receives, time division multiple access access, power control, synchronising frequency hopping.In cordless communication network, each node has independently hardware clock, hardware clock carries out timing by crystal oscillator sum counter, due to reasons such as manufacture craft, external environment, hardware aging, there are differences between the frequency of the crystal oscillator of each node hardware clock, the Frequency Synchronization therefore completed between nodal clock is the important leverage of time synchronized between network node.
In prior art, a class relies on external clock reference to complete the time synchronized between wireless communication network node.The satellite time service system such as GPS, the Big Dipper is such as utilized to carry out the time synchronized of cordless communication network, integrated corresponding timing signal receiving system in node, each node disjoint in cordless communication network carry out synchronous with the time of satellite time service system, to complete the time synchronized of whole net.
Utilize IEEE1588 (Digital reference service accurate clock synchronous protocol) time service to carry out the time synchronized of cordless communication network, need, at the external stable clock source of network, to complete the time synchronized of cordless communication network step by step.
The satellite time service system such as GPS, the Big Dipper is utilized to carry out the Time Synchronizing of cordless communication network, need integrated timing signal receiving equipment within network nodes, increase the cost of network node, and when satellite time transfer signal is interfered or under the scene that signal strength signal intensity is more weak, Network Synchronization precision can not ensure.
IEEE1588 (Digital reference service accurate clock synchronous protocol) time service is utilized to carry out the Time Synchronizing of cordless communication network, need external stable clock source, increase the cost of cordless communication network and realize difficulty, simultaneously this kind of scheme needs the stability of reliable and stable clock transfer network guarantee time synchronized, is difficult to realize for cordless communication network.
Another kind of is that the deadline is step by step synchronous by setting up hierarchical relationship between the node of cordless communication network.This kind of Time Synchronizing is by selecting clock tracing source node, and present node only carries out time synchronized with the tracing source node selected.
When frequency departure between cordless communication network interior joint is larger, to cause between node low-order-modulated also cannot proper communication, now node cannot receive the time synchronization information of clock tracing node, therefore can not ensure completing smoothly of cordless communication network time synchronized.And the difference on the frequency between node can cause the difference of clock timing speed, influence time synchronization accuracy.
Summary of the invention
The object of this invention is to provide a kind of cordless communication network clock synchronizing method and relevant apparatus, to solve in existing method for synchronizing time because difference on the frequency between cordless communication network interior joint clock causes more greatly correctly resolving the not high problem of timing tracking accuracy that wireless signal and difference on the frequency cause.
According to technical scheme provided by the invention, clock self-synchronization method in described cordless communication network is: there is not tracking synchronized relation between network node, each node sends respective synchronizing sequence according to the frequency of self, all nodal test and resolve adjacent node send synchronizing sequence, receiving node can estimate the difference on the frequency obtained between sending node according to the correlation of synchronizing sequence, and completes the calibration of local clock frequency in accordance with the following methods:
Nodal test and resolve obtain adjacent node send synchronizing sequence after, the difference on the frequency obtained between sending node can be estimated according to the correlation of synchronizing sequence, if difference on the frequency is less than predetermined threshold value, then local clock frequency is not adjusted; Otherwise, according to the clock frequency of sending node, local clock frequency upwards or is downwards adjusted Delta, the difference on the frequency after making adjustment between this node and sending node reduces, after adjustment after a while, the clock frequency in whole net will remain within certain difference on the frequency scope; The frequency adjusted value that described Delta is default frequency adjusted value or calculates based on requency sampling fjlter.
Described synchronizing sequence is used for nodal test wireless signal, and receiving node can estimate the difference on the frequency obtained between sending node according to the correlation of synchronizing sequence.This synchronizing sequence should have good correlation, is easy to node and correctly resolves; And send on fixing frequency domain position, be convenient to the fast detecting of node.
Described difference on the frequency scope needs correctly can to resolve between support node the wireless signal of most primary channel.
Use the relative synchronization that the cordless communication network of the method for the invention still can keep under without the scene of external clock reference in network between clock, interconnecting of guarantee network, the advantage of the method is:
1) do not need integrated extra receiving system within network nodes, the cost of network node can be saved;
2) do not rely on satellite time service system, avoid the problem because use scenes and signal disturbing cause;
3) do not rely on external clock source, reduce and realize cost and complexity;
4) motor synchronizing agreement relies on normal data transmission between node completely, does not rely on extra clock transfer network.
Accompanying drawing explanation
Fig. 1 is wireless communication network topology structure.Wherein line represents that the wireless signal between node covers mutually; (t, f) represents time and the frequency of node.
Fig. 2 is the structural representation of network node.
Fig. 3 is the synchronous handling process of distributed frequency.
Fig. 4 is distributed frequency Synchronization Example.The selected clock tracing source of node k-1 is shown in figure; F represents the frequency of each node.
Fig. 5 selects source to follow the tracks of handling process.
Fig. 6 is that handling process is selected in clock tracing source.
Fig. 7 selects source to follow the tracks of Synchronization Example.Show node k-1 in figure to network.
Embodiment
Below in conjunction with accompanying drawing and concrete case study on implementation, technical scheme of the present invention is described.
The present invention proposes a kind of clock self-synchronization method of cordless communication network, utilize the method when cordless communication network is without external clock source, can realize the synchronous of network clocking, keep network to be normally communicated with.
In the present invention, other nodes within the coverage of the wireless signal that node sends are called the adjacent node of this node.Wherein, described node includes but are not limited to the radio communication devices such as via node, base station equipment, mobile terminal.
In the present invention, clock synchronous comprises Frequency Synchronization and time synchronized.
The present invention is the clock synchronizing method proposing the calibration of a kind of distributed frequency on the basis of existing wireless communications network method for synchronizing time.There is not tracking synchronized relation between network node, the synchronizing sequence that all nodes send according to adjacent node carries out Frequency Synchronization.
In cordless communication network, each node sends respective synchronizing sequence according to the frequency of self.All nodal test and resolve the synchronizing sequence that adjacent node sends, receiving node obtains the difference on the frequency between sending node according to the correlation estimation of synchronizing sequence, and completes the frequency calibration of local clock according to the method preset.
Wherein, described synchronizing sequence is used for nodal test wireless signal, and receiving node can estimate the difference on the frequency obtained between sending node according to the correlation of synchronizing sequence, do not limit concrete implementation.This synchronizing sequence should have good correlation, is easy to node and correctly resolves; And send on fixing frequency domain position, be convenient to the fast detecting of node.
The calibration that the described method according to presetting completes local clock frequency refers to: after nodal test resolving obtains the synchronizing sequence that adjacent node sends, the difference on the frequency obtained between sending node is estimated according to synchronizing sequence, if difference on the frequency is less than predetermined threshold value, then local clock frequency is not adjusted; Otherwise, according to the clock frequency of sending node, local clock frequency upwards or is downwards adjusted Delta, difference on the frequency after adjustment between this node and sending node reduces, namely the Frequency Synchronization between node is realized, after adjustment after a while, the clock frequency in whole net will remain within certain difference on the frequency scope.The frequency adjusted value that Delta is default frequency adjusted value or calculates based on requency sampling fjlter.
Wherein, described difference on the frequency scope needs correctly can to resolve between support node the wireless signal of most primary channel.
The enterprising line time synchronous adjustment on the basis that described distributed frequency is synchronous, can ensure correctly can receive time synchronization information between node, and ensures that the clock timing speed difference between node is less, improves the stability of time synchronized.
As shown in Figure 1, be wireless communication network topology structure, the present invention will be described in detail for this topological structure, but be not limited thereto.
Other nodes within the wireless signal coverage that node sends, are called the adjacent node of this node, represent the neighbouring relations between node in figure with line.Can transceiving data mutually between adjacent node, then can not receive and dispatch mutually between nonneighbor node.Such as, the adjacent node of figure interior joint 1 has node 2 and node 4, and node 3 is not the adjacent node of node 1.
Figure 2 shows that the structure of the present embodiment interior joint equipment.Node device structure is only to be resolved the implementation case and illustrates, does not form constraint to the present invention.Node device is at least by antenna, synchronizing sequence processing module, frequency synchronization module, time synchronized module, tracing management module composition.
Wherein, node adopts omnidirectional antenna, and node can send to any direction and can receive wireless signal from any direction.The antenna type of node is only and is explained and illustrated the implementation case, also can use the antenna equipment of the other types such as directional antenna, not form constraint to the present invention.
Synchronizing sequence processing module is for generating the synchronizing sequence that node needs to send and the synchronizing sequence detecting adjacent node transmission.
Frequency synchronization module is used for Frequency Synchronization
Time synchronized module is used for time synchronized.
Tracing management module is used for selection and the clock Synchronization Control in clock tracing source.
Figure 3 shows that the handling process that distributed frequency is synchronous:
1) node sends respective synchronizing sequence with the frequency of self.
2) node receiving slot continue detect adjacent node send synchronizing sequence, resolved detection to synchronizing sequence and obtain the difference on the frequency between sending node according to the correlation estimation of synchronizing sequence.
3) compare the clock frequency of local clock frequency and sending node, if difference on the frequency is greater than predetermined scope, then the clock frequency based on sending node upwards or downwards adjusts local frequency; Otherwise, remain unchanged.
4) in network, all nodes are after distributed frequency is after a while synchronous, and the frequency of whole net can remain within the scope of certain difference on the frequency.
Figure 4 shows that the concrete scene that a kind of distributed frequency is synchronous.Described scene is only and is explained and illustrated the present invention, does not form constraint to the present invention.In this scenario, for node K, distributed frequency is synchronously described.The selected clock tracing source of node K-1, all not selected clock tracing source of all the other nodes.The difference on the frequency scope preset is Δ f, and default Adjustment precision is delta.
When node K receives the synchronizing sequence of adjacent node transmission, be f according to the correlation estimation of the synchronizing sequence difference on the frequency obtained between sending node
d=abs (f
k-f
t), if f
d> Δ f, then adjusting local clock frequency is:
f
k＝(f
k-((f
k-f
t)/(abs(f
k-f
t)))*delta)；
When node K-1 receives the synchronizing sequence of node K transmission, be f according to the correlation estimation of the synchronizing sequence difference on the frequency obtained between node K
d=abs (f
k-1-f
k), if f
d> Δ f, then adjust frequency into:
f
k-1＝(f
k-1-(f
k-1-f
k)/(abs(f
k-1-f
k)))*delta)；
When node K-2 receives the synchronizing sequence of node K transmission, be f according to the correlation estimation of the synchronizing sequence difference on the frequency obtained between node K
d=abs (f
k-2-f
k), if f
d> Δ f, then adjust frequency into:
f
k-2＝(f
k-2-((f
k-2-f
k)/(abs(f
k-2-f
k)))*delta)；
Figure 5 shows that and select the synchronous handling process of source tracking time:
1) node periodically sends the clock information of self at time-frequency location selected separately;
2) node in selected clock tracing source receives the clock information of adjacent node, and now node is in tracking mode.If this clock information is from clock tracing source node, then carry out time synchronized according to clock information, otherwise judge the whether selected clock tracing source of the sending node of this clock information, if the not selected clock tracing source of sending node, directly abandons this clock information, otherwise judge that whether the main controlled node that main controlled node that sending node is corresponding is corresponding with this node is identical, if the same directly abandon this clock information, otherwise perform step 3, carry out the network integration;
3) select the good node of clock quality between two main controlled nodes, if main controlled node clock quality corresponding to sending node is better, then this node abandons former clock tracing source, selects sending node to be clock tracing source, otherwise abandons this clock information; If two main controlled node clock qualities are identical, select the node that between two main controlled nodes, node ID is less, if the ID of main controlled node corresponding to sending node is less, then this node abandons former clock tracing source, select sending node to be clock tracing source, otherwise abandon this clock information;
4) node in not selected clock tracing source receives the clock information of adjacent node, and now node is in non-tracking mode, and clock information is saved in this locality, uses with during alternative clock tracing source;
5) node being in pre-tracking mode receives the clock information of adjacent node, if receive the clock information that self-clock follows the tracks of node in advance, then carries out tracking according to clock information synchronous; If node selected clock tracing source followed the tracks of in advance by clock, then the tracking mode upgrading this node is tracking mode.
Wherein, described clock information comprises node ID in the present embodiment, node enters net state, node jumping figure, clock quality, the time, frequency, clock tracing nodal information.
Described main controlled node refers to that this node only externally provides clock information, and the clock tracing source node of this node is oneself.
Handling process is selected as shown in Figure 6 in described clock tracing source, and this clock tracing source system of selection is only and is explained and illustrated the present embodiment, does not form constraint to the present invention.
Through after a period of time, node receives and records the clock information of adjacent node, and carries out the selection of tracing source node according to the clock information received.
1) there is the adjacent node in selected clock tracing source:
A) adjacent node selecting jumping figure minimum is as clock tracing source.This selection mode can ensure that the clock tracing source node jumping figure of nodal distance network is minimum, can effectively reduce the impact of accumulated error on clock synchronization accuracy;
B) there is multiple jumping figure and be all minimum adjacent node, the node selecting clock quality best is as clock tracing source.This selection mode can improve clock synchronization accuracy;
C) there is multiple clock quality and be all best adjacent node, the node selecting node ID minimum is as clock tracing source.This mode can improve efficiency of selection.
2) there is not the adjacent node in selected clock tracing source:
A) comprising the node selecting clock quality best in this node and known adjacent node, if the node that existence anduniquess clock quality is best, then performing step c, otherwise perform step b;
B) be all from multiple clock quality the node selecting node ID minimum best node, because the ID in network between each node is not the same, a unique node can be selected surely, perform step c;
If the node c) selected is present node, then select self as clock tracing node, and the state upgrading this node follow the tracks of node state for selected; Otherwise what select is adjacent node, then the clock information following the tracks of this adjacent node carries out time synchronized, and the state upgrading this node is pre-tracking mode.
3) there is not adjacent node: select self as clock tracing source node, namely select certainly as main controlled node.
Figure 7 shows that a concrete scene selecting source to follow the tracks of.In scene shown in Fig. 7, node K-1 is in tracking mode, and all the other nodes are all in non-tracking mode.For node K, follow the tracks of handling process to selecting source and be explained and illustrated.
Node K is in non-tracking mode, when receiving the clock information of adjacent node transmission, clock information is kept at this locality, uses with during alternative clock tracing source.
Node K, based on receiving and the clock information stored, judges to only have node K-1 to be in tracking mode in adjacent node, selects node K-1 as its clock tracing source, and arranges oneself state for tracking mode; Simultaneously according to the clock t of the clock information adjustment self of node K-1
k=t
k-1;
If node K-1 is also in non-tracking mode, then all adjacent nodes of node K are all in non-tracking mode.Based on receiving and the clock information stored, judge that the adjacent node that clock quality is all High comprises node K-1 and node K+1, therefore the node K-1 selecting node ID minimum is as clock tracing source, and upgrading this node is pre-tracking mode, when again receive the clock information of K-1 node and node K-1 be in tracking mode time, upgrade this node for tracking mode.
When the node K in selected clock tracing source receives the clock information of node K+1, judge that clock information is from non-clock tracing source node, directly abandons.
In sum, the present invention proposes a kind of distributed clock frequency calibration steps of node, overall procedure is: each node sends respective synchronizing sequence with the frequency of self to eating dishes without rice or wine, when after the node parses in network to the synchronizing sequence of other nodes, the difference on the frequency between sending node is obtained according to the correlation estimation of synchronizing sequence, if difference on the frequency is less than predetermined scope, then do not carry out clock frequency adjustment, otherwise upwards or downwards adjust delta, the clock frequency through whole network after a while can be stabilized within the scope of certain difference on the frequency.The method, under the prerequisite of cordless communication network without external clock source, can keep the synchronous of network clocking by the motor synchronizing of clock between cordless communication network interior joint, and then ensures interconnecting of network.
Claims (4)
1. the clock self-synchronization method in cordless communication network, it is characterized in that: between network node, there is not tracking synchronized relation, each node sends respective synchronizing sequence according to the frequency of self, all nodal test and resolve adjacent node send synchronizing sequence, receiving node can estimate the difference on the frequency obtained between sending node according to the correlation of synchronizing sequence, and completes the calibration of local clock frequency in accordance with the following methods:
Nodal test and resolve obtain adjacent node send synchronizing sequence after, the difference on the frequency obtained between sending node can be estimated according to the correlation of synchronizing sequence, if difference on the frequency is less than predetermined threshold value, then local clock frequency is not adjusted; Otherwise, according to the clock frequency of sending node, local clock frequency upwards or is downwards adjusted Delta, the difference on the frequency after making adjustment between this node and sending node reduces, after adjustment after a while, the clock frequency in whole net will remain within certain difference on the frequency scope; The frequency adjusted value that described Delta is default frequency adjusted value or calculates based on requency sampling fjlter.
2. the clock self-synchronization method in cordless communication network as claimed in claim 1, it is characterized in that, described synchronizing sequence is used for nodal test wireless signal, and receiving node can estimate the difference on the frequency obtained between sending node according to the correlation of synchronizing sequence.
3. the clock self-synchronization method in cordless communication network as claimed in claim 2, is characterized in that, described synchronizing sequence sends on fixing frequency domain position, is convenient to the fast detecting of node.
4. the clock self-synchronization method in cordless communication network as claimed in claim 1, is characterized in that, described difference on the frequency scope needs correctly can to resolve between support node the wireless signal of most primary channel.
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| CN105491656A (en) * | 2015-10-12 | 2016-04-13 | 山东大学（威海） | Light-weight time synchronization method oriented to large-scale ad hoc network |
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Application publication date: 20150715 |