CN104507156B - For the time synchronization improved method based on IEEE 1588PTP mechanism of wireless network - Google Patents

Abstract

The present invention is a kind of time synchronization improved method based on 1588 PTP mechanism of IEEE for wireless network.This method is characterized in：In the case where deferring to 1588 PTP temporal information packet switch mechanism of IEEE, during the packet switch of time synchronization, intercept and intercept and capture temporal information packet when other adjacent nodes and host node are swapped according to IEEE1588 PTP mechanism, to realize it is a kind of from-from synchronization mechanism.The program is the extension synchronized to 1588 PTP MS master-slave of IEEE, more time information can be obtained, using from-information redundancy obtained in synchronization mechanism, make in the method for using linear regression from node more acurrate to clock offset and the estimation of frequency drift reliable, so as to weaken principal and subordinate path asymmetry, influence caused by the inaccurate factor of timestamp, to realize high-precision, highly reliable time synchronization in the wireless network.

Description

For the time synchronization improved method based on IEEE 1588PTP mechanism of wireless network

Technical field

The present invention relates to the communications field more particularly to it is a kind of for wireless network based on IEEE 1588PTP mechanism when Between synchronous improved method.

Background technology

Wireless sense network (WSNs, Wireless Sensor Networks) is the low power consumption node by largely cooperating The wireless network of composition, each node have limited computing capability, wireless communication ability and sensing capability.It is controlled by introducing Actuator, wireless sensor and actor network (WSANs, Wireless Sensor Actuator Networks), which refers to, has nothing Line traffic control executes function, is suitable for a kind of special wireless sense network of process monitoring and control.Due to wireless sensing actuator net The local clock of network node is interrupted by internal crystal oscillator to be counted to realize, brilliant by the initial timer time difference of node and inside Frequency departure variation shaken etc., the clock in network between each node is asynchronous.The time synchronization of WSAN is to instigate in WSAN to own Or part of nodes possesses identical time reference, seeks to the clock alignment for being distributed in each node (synchronization onwards are come).

Time synchronization (Time Synchronization) technology is the important support technology of wireless sensing actor network. Particularly, mutually coordinated extremely important between automatic workflow, it is desirable that associated biography in industrial automation system Sensor node can preferably execute synchronous data collection, and associated actuator node can harmoniously carry out control operation, therefore WSAN has higher requirement to the precision and reliability of time synchronization, is higher than average family and commercial wireless network system.Such as The data fusion of multisensor, target positioning and monitoring, distributed beams are molded array and control, and TDMA communication scheduling is based on The battery energy-saving etc. of sleep scheduling, all to time synchronization high requirement, therefore, time synchronization is special in many applications of WSAN Unimportant, importance is embodied in three aspects：Step determine data whether accurate and effective, determine that the performance of control system is good It is bad, determine that overall performance of network is good and bad (such as channel utilization, handling capacity, network lifecycle etc.).

Currently used method for synchronizing time has：NTP methods, RBS methods, TPSN methods and FTSP methods etc..Wherein, net Network time protocol (NTP) is a kind of typical master-slave synchronisation method, by NTP's mainly for traditional IP-based internet Client (i.e. from clock) is initiated, and sends the synchronization request for also having local time stamp T1 to ntp server (i.e. master clock) first Packet, server record this packet receiving time T2 after receiving the request bag.Then server is replied to client at the T3 moment and is rung It should wrap, and T3 timestamps are attached in the response bag.When client receives the response bag, receiving time stamp T4 is recorded.Visitor The timestamp information T1, T2, T3 and T4 that family end is obtained from the exchange can calculate the deviation between master-salve clock, to Deadline adjust with it is synchronous.RBS is a kind of method for synchronizing time put forward for wireless sensor and actor networks, and this method is based on One-to-All Broadcast mechanism effectively overcomes operation processing delay and medium access delay (such as CSMA/CA exponential backoffs calculation of transmitting terminal The delay of method) influence to synchronization accuracy, reached certain precision, reliability is higher, but its calculation amount and synchronization overhead compared with Greatly, energy consumption is higher.For TPSN methods based on two-way pairs of synchrone mechanism, synchronous effect is higher, the precision higher than RBS, but right The dependence of host node is larger, limited reliability.And FTSP methods are flooded broadcast formula Time synchronization algorithm, are then based on minimum two Multiplication carries out the estimation of clock skew, although One-to-All Broadcast so that the method for synchronization is simple, least square method needs a large amount of wide Multicast data and higher calculation amount, therefore more communication bandwidth and computing resource can be expended.FTSP methods there are the problem of master If：For the big network of density, flooded broadcast can be sent in the burst for forming a large amount of broadcast data packet, cause the several of collision Rate is very high, consumes node energy and Internet resources.

With the extensive use of distributed network TT&C system, for based on wired local Ethernet (Ethernet) TT&C system, IEEE (Institute of Electrical and Electronics Engineers) were issued in 2002 Accurate time synchronization protocol (Precision Time Protocol) standard, code name IEEE 1588, full name be that " network is surveyed The precision interval clock synchronous protocol standard of amount and control system ", abbreviation PTP.New version has been formulated in 2008 again IEEE1588v2 agreements.IEEE 1588 is a more complicated master-slave synchronisation method, similar to NTP, is to pass through master-salve clock The data packet with timestamp information is exchanged to synchronize.Theoretically, when timestamp is accurate enough (when as used hardware based Between stab technology), IEEE 1588PTP can provide the exact time synchronization of sub- Millisecond, this is with high accuracy more more than NTP etc., And communication loan and computing resource consumption it is relatively low, this make it be suitable for Industry Control, measure etc. times harshness application, therefore Current international real-time ethernet all uses a cores of the IEEE 1588 as its system.

IEEE1588 puts forward for wired local Ethernet, it is assumed that the realization journey of these three hypothesis there are three it Degree directly determines the precision of time synchronization.These three hypothesis are：

(1) symmetric path and principal and subordinate's transmission delay are equal.It requires data packet by host node to the transmission time from node It is equal by the transmission time from node to host node with data packet

(2) clock skew is constant during temporal information packet switch.The hypothesis requires relatively stable nodal clock oscillation The exchange of device and faster packet switch time, the data packet with timestamp were happened in the time of one section of very little, with ensure from The clock skew of clock is during this period of time changeless.Equivalently, this assumes to be also the steady of nodal clock oscillator Qualitative and precision hypothesis, it is desirable that oscillator has higher quality.

(3) accurate time label.Assuming that main and subordinate node can precisely measure out their transmissions or received data packet Time.

In practical applications, due to the transmission of the high-speed of Ethernet and cable signal be affected by the external environment it is weaker, it is false If (1) can preferably meet with (2), in the case of less concern power supply and equipment cost, may be used in ethernet device High quality crystal oscillator and hardware meet condition (2) and (3).

But these hypothesis may not necessarily be met well in the wireless network.This shows that, by battery powered, hardware is set Standby and environment influences the limitation of (such as temperature), and the crystal oscillator precision of radio node is limited, and drift is apparent.Very due to wireless channel decline Greatly, the problems such as being more susceptible to the electromagnetic interference of external environment and hidden node compared with wire channel, it is easy to be formed between principal and subordinate Transmission delay is asymmetric.Therefore the IEEE 1588PTP of standard can not be suitable for wireless sensing actor network well.

Invention content

The present invention is directed at least solve the technical problems existing in the prior art, especially innovatively propose a kind of for nothing The time synchronization improved method based on IEEE 1588PTP mechanism of gauze network.

In order to realize the above-mentioned purpose of the present invention, the present invention provides a kind of for wireless network based on IEEE The time synchronization improved method of 1588PTP mechanism, it is critical that including the following steps：

Step 1, it is handed over by the startup host node of host node cycle and from the temporal information packet for carrying timestamp between node It changes；

Step 2, it is several from node one by one with host node carry out temporal information packet switch, it is a certain from node not with host node Carry out temporal information packet switch when, should from node holding intercept pattern, and intercept and capture it is other it is adjacent between node and host node with wide The time synchronization information packet that broadcast mode swaps；

Step 3, it is carried out from node by the adjacent timestamp from the time synchronization information packet of node and host node of intercepting and capturing Linear regression optimizes, and obtains this from the frequency deviation of clock of node and the estimated value of frequency drift, and inclined using the clock obtained The estimated value of difference and frequency drift realizes time synchronization to being adjusted from nodal clock.

The time synchronization improved method based on IEEE 1588PTP mechanism for wireless network, it is preferred that institute Stating step 1 includes：

Step 1-1, host node send the synchronous package (Sync) for including sending time stamp information first；

Step 1-2, after node receives synchronous package (Sync), the receiving time for obtaining synchronous package (Sync) stabs information, Delay request bag (Delay_Req) is replied to host node, and obtains the sending time stamp of delay request bag (Delay_Req)；

Step 1-3, host node obtain delay request bag (Delay_ after receiving delay request bag (Delay_Req) Req receiving time) stabs information, and reply delay response bag (Delay_Resp) is given from node, and delay request bag (Delay_ Req receiving time stamp information) is put into delay response bag (Delay_Resp) to be sent together.When from node not with host node into Row delay request bag (Delay_Req) and delay response bag (Delay_Resp) exchange when, be transferred to the pattern of intercepting, intercept and capture other from The delay request bag (Delay_Req) that is exchanged between node and host node and delay response bag (Delay_Resp) and its it is corresponding when Between stab.

The time synchronization improved method based on IEEE 1588PTP mechanism for wireless network, it is preferred that institute Stating step 1 includes：

Step 1A, host node send a synchronous package (Sync) to all from node, startup time synchronization with broadcast mode Process；

Step 1B, host node is using local clock as reference, and the sending time for obtaining synchronous package (Sync) stabs t1, and by the time T1 additions are stabbed in synchronous package (Sync)；

Step 1C in a receive mode from node waits the synchronous package (Sync) to be received；

Step 1D, from node after receiving the synchronous package (Sync) that host node is sent, to be ginseng from node local clock According to obtaining the receiving time of the synchronous package (Sync) at once, be denoted as timestamp t2；

Step 1E parses the data in received synchronous package (Sync) from node, obtains timestamp information therein t1。

The time synchronization improved method based on IEEE 1588PTP mechanism for wireless network, it is preferred that institute Stating step 2 includes：

Step 2A, host node are transferred to reception pattern, and preparing to receive will be by the delay request bag (Delay_ that is returned from node Req it) wraps；

Step 2B is transferred to sending mode from node, is ready for sending delay request bag (Delay_Req) message to main section Point, and enter the wireless channel contention process of MAC mechanism defineds；

Step 2C sends the Delay_ with broadcast mode if obtaining the right to use of wireless channel from node to host node Req packets, and t3 is stabbed using the sending time for, as reference, obtaining delay request bag (Delay_Req) from node local clock, by the time Stamp t3 is attached to as timestamp in delay request bag (Delay_Req)；

Step 2D, host node is after receiving delay request bag (Delay_Req), using host node local clock as reference, The receiving time for obtaining the delay request bag (Delay_Req) at once, is denoted as timestamp t4；Host node is transferred to sending mode, will Timestamp t4 is attached in delay request bag (Delay_Req), with broadcast mode send delay request bag (Delay_Req) to from Node；After being sent completely, host node is transferred to reception pattern；

Step 2E receives delay request bag (Delay_Req) from node, and timestamp t4 is parsed；

Step 2F is transferred to from node if failing to obtain the right to use of wireless channel from node and intercepts reception pattern, intercept simultaneously It intercepts and captures the delay request bag (Delay_Req) that other adjacent nodes are sent out and the delay with timestamp t4 that host node is sent out is rung (Delay_Resp) should be wrapped to be intercepted and captured；When intercepting and capturing delay request bag (Delay_Req), to be ginseng from the local clock of node According to the receiving time of acquisition delay request bag (Delay_Req) is denoted as timestamp t5；Intercepting and capturing delay response bag (Delay_ Resp after), the timestamp t4 postponed in response bag (Delay_Resp) is parsed；

Step 2G, the slave node of the right to use for obtaining wireless channel are abandoned after completing step 2C, 2D and 2E The right to use, be transferred to step 2F intercepts pattern；

Step 2H, the slave node of the right to use for not obtaining wireless channel are transferred to step 2B after completing step 2F Sending mode, competition use the wireless channel right to use, the delay request bag (Delay_Req) of oneself is sent to host node；

The packet switch of step 2I, host node terminate mechanism, when it is all from node with host node complete packet switch after, or The exchange of any time information report is not listened in setting time threshold value, then host node thinks that epicycle synchronously completes, and terminates current Packet switch process waits for next round to arrive synchronizing cycle, is transferred to step 1-1；

Step 2J terminates mechanism from the packet switch of node, when it is all from node with host node complete packet switch after, or It does not listen to the exchange of any time information report in a period of time threshold value, then thinks that the packet switch that epicycle synchronizes is complete from node At exiting reception from node and intercept pattern.

The time synchronization improved method based on IEEE 1588PTP mechanism for wireless network, it is preferred that institute Stating step 3 includes：

Step 3A, the t1 that packet switch obtains between node and host node, t2, t3, t4 timestamps and one group are by intercepting The t4 [k] and t5 [k] timestamp that packet switch obtains between obtained other neighbors k and host node, wherein k are k-th of adjoining Point, if certain possesses N number of neighbors from node, k={ 1,2 ... N }, N is positive integer, should at most be obtained from node by intercepting The time deviation from nodal clock is estimated using linear regression optimization method to { t4 [k], t5 [k] } timestamp to N；Reference IEEE 1588PTP modes obtain one about the functional relation between clock jitter and transmission delay from t1, t2, t3 and t4 Formula；

Step 3B intercepts the N of acquisition to obtaining N number of letter about between deviation and transmission delay in { t4 [k], t5 [k] } Number relational expression；

Step 3C solves above-mentioned N+1 functional relation with least square method, obtains the optimal of clock jitter Estimated value.

Step 3D, after obtained clock jitter optimal estimation value, from the calculated frequency drift from nodal clock of node, Obtain the estimated value of clock jitter and frequency drift；

Step 3E, it is real to being adjusted from nodal clock using obtained clock jitter and frequency drift estimated value Existing time synchronization.

The time synchronization improved method based on IEEE 1588PTP mechanism for wireless network, it is preferred that institute Stating temporal information packet switch includes：

Step 101：In time point TA, host node starts to send Sync temporal information packets with broadcast mode, and obtaining should The sending time t1 of Sync packets, and t1 is put into Sync packets and is sent together；

Step 102：In time point TB, which reaches from node, it is each from node with local from clock For reference, the receiving time of Sync packets is obtained, since the local of each node is not consistent from clock, so when the reception of Sync packets Between the value stabbed not yet, therefore be denoted as t2 [i] between the reception of the Sync packets of node i, and so on；

Step 103：In time point TC, through after a period of time processing delay and medium contention process, obtained from node i The right to use of medium replys Delay_Req temporal information packets, the Delay_ in the time point t3 [i] from node to host node Req packets are also sent with broadcast mode, can also be intercepted and received by adjacent node；

Step 104：In time point TD, the Delay_Req temporal information packets that are sent out from node i reach host node and each adjacent Node, host node obtain the time that Delay_Req packets reach host node using master clock as reference, are denoted as t4 [i], and wherein i is indicated The Delay_Req packets come from node i, it is adjacent from node respectively since clock is reference, to obtain the arrival of Delay_Req packets respectively from section The time of point, it is denoted as t5 [i] respectively；

Step 105：In time point TE, host node connects after processing delay after a period of time what is obtained in step 104 It receives timestamp t4 [i] and is put into a Delay_Resp temporal information packet, and the Delay_Resp times are sent with broadcast mode and are believed Breath packet to all from node, including from node i；

Step 106：In time point TF, which reaches from node, it is each from node from this Timestamp information t4 [i] is extracted in Delay_Resp packets；

Step 107, in time point TG, another right to use for obtaining medium from node k, at the time point from node T3 [k] replys Delay_Req temporal information packets to host node, which is also sent with broadcast mode, can also be by phase Neighbors is intercepted and is received；

Step 108, in time point TH, the Delay_Req temporal information packets that are sent out from node k reach host node and each adjacent Node, host node obtain the time that Delay_Req packets reach host node, are denoted as t4 [k], wherein k tables using master clock as reference Show that the Delay_Req packets come from node k；It is adjacent from node using respectively since clock is reference, obtain the arrival of Delay_Req packets respectively from The time of node is denoted as t5 [k] respectively；

Step 109：In time point TI, host node is after processing delay after a period of time, and host node in step 108 obtaining The receiving time stamp t4 [k] obtained is put into a Delay_Resp temporal information packet, and sends the Delay_Resp with broadcast mode Temporal information packet is to all from node；

Step 110：In time point TJ, which reaches from node, it is each from node from this Timestamp information t4 [k] is extracted in Delay_Resp packets；

Step 111：Circulation step, it is each from node in network, abovementioned steps 107 are repeated respectively to step 110；

Step 112：Until time point TK, the last one obtains use of media from node (being denoted as N), this from node Time point t3 [N] replys Delay_Req temporal information packets to host node with broadcast mode, which can also be intercepted by adjacent node And it receives；

Step 113：In time point TL, the Delay_Req temporal information packets that are sent out from node N reach host node and each adjacent Node, host node obtains the time that Delay_Req packets reach host node, is denoted as t4 [N] using master clock as reference, adjacent from section Point is using respectively since clock is reference, acquisition Delay_Req packets reach respectively from the time of node, are denoted as t5 [N] respectively；

Step 114：In time point TM, the receiving time stamp t4 [N] obtained in step 113 is put into one by host node Delay_Resp temporal information packets, and the Delay_Resp temporal informations packet is sent to all from node with broadcast mode；

Step 115：In time point TN, which reaches from node, it is each from node from this Timestamp information t4 [N] is extracted in Delay_Resp packets.

The time synchronization improved method based on IEEE 1588PTP mechanism for wireless network, it is preferred that institute Stating the host node course of work includes：

Step 301：When synchronizing cycle then, host node pass through send Sync temporal informations packet synchronizing come a new round Journey, Sync temporal information packets start to send with broadcast mode, and host node obtains the sending time t1 of the Sync packets when transmission, and will T1 is put into Sync packets and sends together,

Step 302：After having sent Sync packets, host node is transferred to reception pattern, waits for from some from the Delay_ of node Req temporal information packets,

Step 303：When reaching there are one Delay_Req packets, obtain the Delay_Req packets connects timestamp, is denoted as t4,

Step 304：Host node generate a Delay_Resp temporal information packet, and the timestamp t4 in step 303 with And which aforementioned Delay_Res packets be put into Delay_Resp packets from the information of node from, and Delay_ is sent with broadcast mode Resp packets,

Step 305：Host node check epicycle synchronization whether completes, criterion be (a) whether have been received it is all from The Delay_Req packets of node, or (b) wait for whether time-out is transferred to step 302, waits to be received next if do not completed From the Delay_Req packets of node；If epicycle synchronization has been completed, it is transferred to next wait state, next round is waited for synchronize Period arrives,

Step 306：It waits for next round to arrive synchronizing cycle, if a new round arrives synchronizing cycle, is transferred to step 301, starts The time synchronization process of a new round.

The time synchronization improved method based on IEEE 1588PTP mechanism for wireless network, it is preferred that institute It states from the node course of work and includes：

Step 401：It when beginning, is in from node i and intercepts reception state, wait for the Sync temporal informations for carrying out autonomous node Packet,

Step 402：After listening to the Sync packets for carrying out autonomous node, in receive process, obtained based on local clock The receiving time of Sync packets is stabbed, and t2 [i] is denoted as,

Step 403：T1 information is extracted from Sync packets, is denoted as t1 [i],

Step 404；This is transferred to sending mode from node, and the wireless channel right to use is obtained according to mode as defined in MAC protocol, If obtaining the channel right to use, step 405 is transferred to send Delay_Req packets；If not obtaining the channel right to use, Be transferred to step 411 with intercept receive other nodes temporal information packet,

Step 405：This obtains the channel right to use from node, then sends Delay_Req temporal information packets, base to host node The sending time stamp of Sync packets is obtained in local clock, is denoted as t3 [i], which is also sent with broadcast mode, also may be used To be intercepted and be received by adjacent node,

Step 406：After the completion of sending Delay_Req packets, it is transferred to reception pattern, the Delay_ for waiting host node to be received to return Resp temporal information packets,

Step 407：After the Delay_Resp packets for carrying out autonomous node finish receiving, the time in Delay_Resp packets is extracted Information t4 is stabbed, t4 [i] is denoted as,

Step 408：From node check epicycle synchronization whether complete, criterion be (a) whether have been received it is all from The Delay_Req/Delay_Resp packets of node, or (b) whether the packet switch of epicycle time synchronization is overtime, if do not completed, Then it is transferred to step 409；Data processing step 413 is transferred to if being completed,

Step 409：Check oneself whether be transmitted across Delay_Req packets and be properly received Delay_Resp from node Packet, if be completed, is transferred to step 410；If do not completed, it is transferred to step 404,

Step 410：Enter reception from node and intercept pattern, waits for the Delay_ for intercepting and capturing other between node and host node Req and Delay_Resp packet switch,

Step 411：When listening to from other from node, it is set as after the Delay_Req packets of node k, in receive process In, the receiving time stamp of the Delay_Req packets is obtained based on local clock, is denoted as t5 [k],

Step 412：It waits for and receives carrying out autonomous node and replying to Delay_Resp packets from node k, after finishing receiving, carry The timestamp information t4 in the packet is taken, t4 [k] is denoted as, is then transferred to step 408；

Step 413：Data processing step, from node by the adjacent time synchronization information packet from node and host node of intercepting and capturing In timestamp carry out linear regression optimization, obtain from the frequency deviation of clock of node and the estimated value of frequency drift, and same Realize that the time is same to being adjusted from nodal clock using the estimated value of the clock jitter of acquisition and frequency drift during step Step.

The time synchronization improved method based on IEEE 1588PTP mechanism for wireless network, it is preferred that institute Stating data processing step 413 includes：

Clock jitter from clock at the TA moment is denoted as θ [0] by step P1, and θ [0] is unknown-value, this moment from clock when Between value be approximately t2 [i], the time value of master clock is t1 [i]=t1；

Step P2 completes Sync from node i and host node when this and is just obtained after Delay_Req and Delay_Resp packet switch Obtained timestamp t1 [i], t2 [i], t3 [i] and t4 [i], can calculate according to the following equation accordingly the TD moment slave clock when Clock deviation θ [i], i.e.,

And d_smAnd d_{m s}For the transmission delay between time principal and subordinate

From the perspective of master clock, the time difference τ [i] between TD the and TA moment is

τ [i]=t₄[i]-t₁[i]

Therefore the relationship between θ [i] and θ [0] is described with an equation of linear regression

θ [i]=θ [0]+γ τ [i]

Step P3：Intercepted and captured the adjacent Delay_Req packets sent out from node k at the TH moment, the moment from clock when Between value be t5 [k], remember the moment clock jitter be θ [k].After having received t4 [k] later, θ [k] calculates as follows

θ [k]=t₅[k]-t₄[k]

From the perspective of master clock, the time difference τ [k] between TH the and TA moment is

τ [k]=t₄[k]-t₁[i]

Therefore the relationship between θ [k] and θ [0] is described with an equation of linear regression

θ [k]=θ [0]+γ τ [k]；

Step P4 repeats step P3, obtains multiple above-mentioned equations, as follows with matrix description

Above-mentioned equation group is solved using least square method, an optimal estimation to θ [0] and γ can be obtained,

In above formula, subscript T representing matrix transposition, -1 representing matrix of subscript is inverted.

Step P5, clock correction, by clock jitter and the optimal estimation value Γ of frequency drift for the correction to clock.

In conclusion by adopting the above-described technical solution, the beneficial effects of the invention are as follows：

The time synchronization improved method of this programme IEEE 1588PTP synchronization mechanisms, this method can be marked with IEEE1588PTP Standard is compatible, but takes full advantage of the broadcast characteristic of wireless communication, in the case where not changing IEEE 1588PTP packet switch processes, Using from-from synchronization mechanism as the extension synchronized to IEEE 1588PTP MS master-slave, using from-from the information redundancy in mechanism, The estimation of clock skew and frequency drift is more preferably completed using the method for linear regression from node, it is not right to reduce principal and subordinate path Claim, is influenced caused by the factors such as timestamp is inaccurate, to realize high-precision under wireless network or wireless sensor network, Highly reliable time synchronization.

The additional aspect and advantage of the present invention will be set forth in part in the description, and will partly become from the following description Obviously, or practice through the invention is recognized.

Description of the drawings

The above-mentioned and/or additional aspect and advantage of the present invention will become in the description from combination following accompanying drawings to embodiment Obviously and it is readily appreciated that, wherein：

Fig. 1 is principle of the present invention for the time synchronization improved method based on IEEE 1588PTP mechanism of wireless network Flow chart；

Fig. 2 is time of the present invention for the time synchronization improved method based on IEEE 1588PTP mechanism of wireless network Stab schematic diagram；

Fig. 3 is the present invention for main section in the time synchronization improved method based on IEEE 1588PTP mechanism of wireless network The pack receiving and transmitting and flow chart of data processing figure of point；

Fig. 4 is that the present invention is directed in the time synchronization improved method based on IEEE 1588PTP mechanism of wireless network from section The pack receiving and transmitting and flow chart of data processing figure of point.

Specific implementation mode

When to overcome the shortcomings of to use IEEE 1588PTP to carry out time synchronization in the wireless network, the purpose of the present invention exists It is a kind of suitable for wireless network in providing, based on the time synchronization improved method of IEEE 1588PTP synchronization mechanisms, this method Can be compatible with IEEE 1588PTP standards, but the broadcast characteristic of wireless communication is taken full advantage of, do not changing IEEE 1588PTP In the case of packet switch process, using from-from synchronization mechanism as the extension synchronized to IEEE 1588PTP MS master-slave, using from-from Information redundancy in mechanism more preferably completes the estimation of clock skew and frequency drift in the method for using linear regression from node, It to reduce principal and subordinate path asymmetry, is influenced caused by the factors such as timestamp is inaccurate, in wireless network or wireless to pass High-precision, highly reliable time synchronization are realized under sensor network.

In order to achieve the above objectives, the present invention solve the technical problem the technical scheme adopted is that

A kind of highly reliable time synchronization improved method based on IEEE 1588PTP mechanism, includes the following steps：

Step 1：Initiated by host node, host node and between node according to the packet switching exchange of IEEE 1588PTP standards System starts the packet switch with timestamp information.

Step 2：Wireless channel is used from node according to the competition of MAC mechanism, completes IEEE 1588PTP with host node one by one The exchange of time synchronization information packet as defined in standard.During this contention, from node not with host node according to carrying out packet friendship When changing, pattern, the adjacent time synchronization information between node and host node of reception as much as possible should be intercepted from node holding Packet.This is intercepted process and has no effect on other adjacent synchronous exchange processes between node and host node.

Step 3：With reference to the master-salve clock calculations of offset method of IEEE 1588PTP standards, statistical calculation method pair is utilized The timestamp intercepted in step 2 in the time synchronization information packet of the adjacent node of intercepting and capturing carries out linear regression optimization, utilizes letter Redundancy is ceased, overcoming reception to postpone uncertainty, principal and subordinate path is asymmetric, and transmission postpones on from the influence of clock jitter estimated value, reducing Uncertain, timestamp inaccuracy influences clock estimation of deviation value, improves the measurement accuracy from the time deviation of clock.

Step 4：From the clock frequency drift estimate of node, and during subsequent using the clock jitter estimated and Frequency drift realizes time synchronization to being adjusted from clock.

Step 5：According to some cycles repeat the above steps one arrive step 4.The repetitive process is controlled by host node, i.e., main Node is periodically turned on step 1.

Further, what is executed in step 1 is the transmitting-receiving process of the Sync packets of IEEE 1588PTP, including following several Sub-steps：(1a) host node sends a Sync data packet to all from node, to start time synchronization mistake with broadcast mode Journey；(1b) host node obtains the sending time t1 of Sync packets, and using t1 as the attached addition of timestamp using local master clock as reference In Sync packets.(1c) in a receive mode, waits the Sync packets to be received from node.(1d) is receiving host node hair from node After the Sync packets sent, as reference, to obtain the receiving time of the Sync packets at once from node local clock, be denoted as t2.(1e) from Node parses the data in received Sync packets, obtains timestamp information t1 therein.

Further, what is executed in step 2 is the transmitting-receiving of IEEE 1855PTP Delay_Req and Delay_Resp packets With intercept process, including following sub-step：(2a) host node is transferred to reception pattern, and prepare reception will be by returning from node Delay_Req packets.(2b) is transferred to sending mode from node, is ready for sending a Delay_Req message to host node, and enter The wireless channel contention process of MAC mechanism defineds.(2b) is if obtain the right to use of wireless channel from node, with broadcast mode Send the Delay_Req data packets to host node, and using from node local clock as reference, when obtaining the transmission of Delay_Req Between t3, be attached to t3 as timestamp in Delay_Req data packets.(2c) from node if fail to obtain the use of wireless channel Power, is transferred to reception pattern from node, intercepts and intercept and capture the Delay_Req data packets with t3 that other adjacent nodes are sent out. (2d) host node is after receiving Delay_Req data packets, using host node local clock as reference, obtains the Delay_ at once The receiving time of Req packets, is denoted as t4.Then host node is transferred to sending mode, and Delay_Resp is attached to using t4 as timestamp In data packet, Delay_Resp data packets are sent to from node with broadcast mode.After being sent completely, host node is transferred to reception mould Formula.(2e) receives Delay_Resp packets from node, and timestamp information t4 is parsed；(2f) is in the slave section for pattern of intercepting Point also intercepts and captures Delay_Req and Delay_Resp packets.When intercepting and capturing Delay_Req packets, with from the local clock of node For reference, the receiving time of Delay_Req packets is obtained, t5 is denoted as；It, will be in Delay_Resp after intercepting and capturing Delay_Resp packets Timestamp information t4 is parsed.The slave node that (2e) obtained the right to use of wireless channel just now abandons the use Power, be transferred to step (2c) intercepts pattern.The slave node that (2f) did not obtained the right to use of wireless channel just now is transferred to step (2b) Sending mode, competition using wireless channel the right to use, the Delay_Req data packets of oneself are sent to host node.(2g) is main The packet switch of node terminates mechanism, when it is all complete packet switch with host node from node after, or in a period of time threshold value The exchange of any time information report is not listened to, then host node thinks that epicycle synchronously completes, and terminates current packet switch process, under waiting One wheel synchronizing cycle arrive, be transferred to step 1.(2h) terminates mechanism from the packet switch of node, when it is all from node with host node it is complete It after packet switch, or does not listen to the exchange of any time information report in a period of time threshold value, then thinks that epicycle is same from node The packet switch of step has been completed, and is exited reception from node and is intercepted pattern, enters step three.

Further, in step 3, from node according to this node and host node between packet switch obtained t1, t2, T3, t4 timestamp information and one group by the t4 [k] that packet switch obtains between other neighbors k intercepted and host node and T5 [k] timestamp information (k represents k-th of abutment points, if certain possesses N number of neighbors from node, k={ 1,2 ... N }, therefore From node can N at most should be got to { t4 [k], t5 [k] } timestamp by intercepting), using linear regression optimization method, estimate Count out the time deviation from clock.Including following sub-step：(3a) with reference to IEEE 1588PTP modes from t1, t2, t3 and One is obtained in t4 about the functional relation between clock jitter and transmission delay；(3b) is from the N obtained is intercepted to { t4 [k], t5 [k] } in obtain it is N number of about large deviations and transmission delay between functional relation；(3c) uses least square method Above-mentioned N number of functional relation is solved, the optimal estimation value of clock jitter is obtained.

Further, in step 4, including following two steps：(4a) is optimal based on the clock jitter obtained in step 3 Estimated value obtains the estimated value of clock frequency drift from the calculated frequency drift from clock of node；Obtained by (4c) is utilized Clock jitter and clock frequency drift estimate value realize time synchronization to being adjusted from clock.

The wireless device of the method for the invention design, including time reference source node (being referred to as host node), wireless network Node, wireless sensor node and wireless actuator node (being referred to as from node).

Host node is generally the central apparatus of network, such as data convergent point, radio access node (Access Point), control Central control point in network processed, host node safeguard that unique length of a game of network, the slave node in network pass through time synchronization Agreement carries out exchanging for temporal information packet with host node, and from keeping consistent with the network global time of host node, it is same to reach the time Step.

Temporal information packet switch and the timestamp resolving of the present invention is as shown in Figure 1, embodiment has one with one A host node and N number of for the time synchronization of the wireless sensor and actor network of node.Master clock on host node is one A accurate clock (i.e. clock jitter θ=0 of master clock, frequency drift γ=0), when the time value of the master clock is as the overall situation Between.From node respectively there are one from clock, since crystal oscillator quality is different, power supply, the reasons such as variation of ambient temperature, respectively simultaneously from clock Inaccurate (i.e. clock jitter θ ≠ 0, frequency drift γ ≠ 0), and each from the clock jitter of node and frequency drift value not phase Together.

As shown in Figure 1, the temporal information packet switch of the present invention includes the following steps：

Step 101：In time point TA, host node starts to send Sync temporal information packets with broadcast mode, and obtaining should The sending time t1 of Sync packets, and t1 is put into Sync packets and is sent together；

Step 102：In time point TB, which reaches from node, it is each from node with local from clock For reference, the receiving time of Sync packets is obtained, since the local of each node is not consistent from clock, so when the reception of Sync packets Between the value stabbed not yet, therefore be denoted as t2 [i] between the reception of the Sync packets of node i, and so on；

Step 103：In time point TC, through after a period of time processing delay and medium contention process, obtained from node i The right to use of medium replys Delay_Req temporal information packets, the Delay_ in the time point t3 [i] from node to host node Req packets are also sent with broadcast mode, can also be intercepted and received by adjacent node；

Step 104：In time point TD, the Delay_Req temporal information packets that are sent out from node i reach host node and each adjacent Node, host node obtain the time that Delay_Req packets reach host node using master clock as reference, are denoted as t4 [i], and wherein i is indicated The Delay_Req packets come from node i, it is adjacent from node respectively since clock is reference, to obtain the arrival of Delay_Req packets respectively from section The time of point, it is denoted as t5 [i] respectively；

Step 105：In time point TE, host node connects after processing delay after a period of time what is obtained in step 104 It receives timestamp t4 [i] and is put into a Delay_Resp temporal information packet, and the Delay_Resp times are sent with broadcast mode and are believed Breath packet to all from node, including from node i；

Step 106：In time point TF, which reaches from node, it is each from node from this Timestamp information t4 [i] is extracted in Delay_Resp packets；

Step 107, in time point TG, another right to use for obtaining medium from node k, in the time point t3 from node [k] replys Delay_Req temporal information packets to host node, which is also sent with broadcast mode, can also be adjacent Node is intercepted and is received；

Step 108, in time point TH, the Delay_Req temporal information packets that are sent out from node k reach host node and each adjacent Node, host node obtain the time that Delay_Req packets reach host node, are denoted as t4 [k], wherein k tables using master clock as reference Show that the Delay_Req packets come from node k；It is adjacent from node using respectively since clock is reference, obtain the arrival of Delay_Req packets respectively from The time of node is denoted as t5 [k] respectively；

Step 109：In time point TI, host node is after processing delay after a period of time, and host node in step 108 obtaining The receiving time stamp t4 [k] obtained is put into a Delay_Resp temporal information packet, and sends the Delay_Resp with broadcast mode Temporal information packet is to all from node；

Step 110：In time point TJ, which reaches from node, it is each from node from this Timestamp information t4 [k] is extracted in Delay_Resp packets；

Step 111：Circulation step, it is each from node in network, abovementioned steps 107 are repeated respectively to step 110；

Step 112：Until time point TK, the last one obtains use of media from node (being denoted as N), this from node Time point t3 [N] replys Delay_Req temporal information packets to host node with broadcast mode, which can also be intercepted by adjacent node And it receives；

Step 113：In time point TL, the Delay_Req temporal information packets that are sent out from node N reach host node and each adjacent Node, host node obtains the time that Delay_Req packets reach host node, is denoted as t4 [N] using master clock as reference, adjacent from section Point is using respectively since clock is reference, acquisition Delay_Req packets reach respectively from the time of node, are denoted as t5 [N] respectively；

Step 114：In time point TM, the receiving time stamp t4 [N] obtained in step 113 is put into one by host node Delay_Resp temporal information packets, and the Delay_Resp temporal informations packet is sent to all from node with broadcast mode；

Step 115：In time point TN, which reaches from node, it is each from node from this Timestamp information t4 [N] is extracted in Delay_Resp packets.

So far temporal information packet switch is completed, and is respectively handled the temporal information got since node.With node i For, the timestamp that may be got has t1, t2 [i], t3 [i], t4 [i] and t4 [k], t5 [k], wherein k ∈ 1,2,3, ... N }, and k ≠ i；

According to above-mentioned embodiment, in given time range, only sent there are one node, and remaining node In intercepting and reception pattern.

It is worth noting that, in above-mentioned packet switch, it is possible to cause certain adjacent node (note due to environmental disturbances etc. Make Delay_Req packets k) sent out or corresponding Delay_Resp packets do not intercepted and received from node by other, then from Node omits t4 [k], t5 [k] when processing is by above-mentioned temporal information packet.In most cases, successfully it can intercept and connect The Delay_Req packets of a part of adjacent node and its corresponding Delay_Resp packets are received, therefore always obtains some t4 [k], T5 [k] is handled for subsequent temporal information.

In above-mentioned packet switch, the host node and can be in transmitting/receiving wireless temporal information packet from node can be by special With means such as hardware device or interrupt processings, there is the sending time stamp and receiving time stamp time for obtaining temporal information packet Ability.And sending and receiving for packet at the same time, sending time stamp and receiving time stamp are in the same of packet Position is obtained, as shown in Fig. 2, timestamp is at the SFD of wireless data packet (Start Frame Delimiter) end It obtains.

The communication process flow of host node according to the present invention is as shown in figure 3, include the following steps：,

Step 301：When synchronizing cycle then, host node pass through send Sync temporal informations packet synchronizing come a new round Journey.Sync temporal information packets start to send with broadcast mode, and host node obtains the Sync packets according to mode shown in Fig. 2 when transmission Sending time t1, and t1 is put into Sync packets and is sent together.

Step 302：After having sent Sync packets, host node is transferred to reception pattern, waits for from some from the Delay_ of node Req temporal information packets.

Step 303：When reaching there are one Delay_Req packets, the Delay_Req packets are obtained according to mode shown in Fig. 2 Timestamp is connect, t4 is denoted as.

Step 304：Host node generate a Delay_Resp temporal information packet, and the timestamp t4 in step 303 with And which aforementioned Delay_Res packets be put into Delay_Resp packets from the information of node from, and Delay_ is sent with broadcast mode Resp packets.

Step 305：Host node checks whether epicycle synchronization is completed, and criterion can be whether (a) has been received institute There are the Delay_Req packets from node, or (b) whether waiting is overtime.If do not complete, be transferred to step 302, wait it is to be received under One Delay_Req packet from node；If epicycle synchronization has been completed, it is transferred to next wait state, waits for next round Synchronizing cycle arrives.

Step 306：Next round is waited for arrive synchronizing cycle.If a new round arrives synchronizing cycle, it is transferred to step 301, is started The time synchronization process of a new round.

Above-mentioned steps (i.e. synchronizing cycle) cycle progress at a certain time interval.

It is according to the present invention from node communication process flow as shown in figure 4, in this embodiment with number be i slave section For point, include the following steps

Step 401：It when beginning, is in from node i and intercepts reception state, wait for the Sync temporal informations for carrying out autonomous node Packet.

Step 402：After listening to the Sync packets for carrying out autonomous node, in receive process, according to mode shown in Fig. 2, base The receiving time stamp of Sync packets is obtained in local clock, is denoted as t2 [i].

Step 403：T1 information is extracted from Sync packets, is denoted as t1 [i]

Step 404；This is transferred to sending mode from node, and the wireless channel right to use is obtained according to mode as defined in MAC protocol. If obtaining the channel right to use, step 405 is transferred to send Delay_Req packets；If not obtaining the channel right to use, Step 411 is transferred to intercept the temporal information packet for receiving other nodes.

Step 405：This obtains the channel right to use from node, then sends Delay_Req temporal information packets to host node, and According to mode shown in Fig. 2, the sending time stamp of Sync packets is obtained based on local clock, is denoted as t3 [i].The Delay_Req packets It is sent, can also be intercepted and received by adjacent node with broadcast mode.

Step 406：After the completion of sending Delay_Req packets, it is transferred to reception pattern, the Delay_ for waiting host node to be received to return Resp temporal information packets.

Step 407：After the Delay_Resp packets for carrying out autonomous node finish receiving, the time in Delay_Resp packets is extracted Information t4 is stabbed, t4 [i] is denoted as.

Step 408：Check whether epicycle synchronization is completed from node, criterion can be whether (a) has been received institute There are the Delay_Req/Delay_Resp packets from node, or (b) whether the packet switch of epicycle time synchronization is overtime.If not complete At being then transferred to step 409；Data processing step 413 is transferred to if being completed.

Step 409：Check oneself whether be transmitted across Delay_Req packets and be properly received Delay_Resp from node Packet.If be completed, it is transferred to step 410；If do not completed, it is transferred to step 404.

Step 410：Enter reception from node and intercept pattern, waits for the Delay_ for intercepting and capturing other between node and host node Req and Delay_Resp packet switch.

Step 411：Other are come from from node (after being set as from the Delay_Req packets of node k), in receive process when listening to In, the receiving time stamp of the Delay_Req packets is obtained based on local clock, is denoted as t5 [k].

Step 412：It waits for and receives carrying out autonomous node and replying to Delay_Resp packets from node k, after finishing receiving, carry The timestamp information t4 in the packet is taken, t4 [k] is denoted as.Then it is transferred to step 408

Step 413：Data processing step.It after completing above-mentioned temporal information packet switch flow, is not only obtained when from node i 1588 required times of IEEE stamp t1 [i], t2 [i], t3 [i] and t4 [i], and by intercepting intercepting and capturing mode, do not having In the case of increasing packet switch total number, obtain one group { t5 [k], t4 [k] } (k ∈ { 1,2,3 ... N }, but do not include from Oneself, i.e. k ≠ i) timestamp.The data processing step from node after completing aforementioned packet switch by executing, mainly to being obtained Timestamp information handled, using redundancy { t5 [k], t4 [k] }, further increase the precision of time synchronization.

Further, data processing includes following steps：

Step P1：Clock jitter from clock at the TA moment is denoted as θ [0], θ [0] is unknown-value, this moment from clock Time value is approximately t2 [i], and the time value of master clock is t1 [i]=t1.

Step P2 completes Sync from node i and host node when this and is just obtained after Delay_Req and Delay_Resp packet switch Obtained timestamp t1 [i], t2 [i], t3 [i] and t4 [i], can calculate according to the following equation accordingly the TD moment slave clock when Clock deviation θ [i], i.e.,

Transmission delay between principal and subordinate

From the perspective of master clock, the time difference τ [i] between TD the and TA moment is

τ [i]=t₄[i]-t₁[i]

Therefore the relationship between θ [i] and θ [0] can be described with an equation of linear regression

θ [i]=θ [0]+γ τ [i]

Step P3：Intercepted and captured the adjacent Delay_Req packets sent out from node k at the TH moment, the moment from clock when Between value be t5 [k], remember the moment clock jitter be θ [k].After having received t4 [k] later, θ [k] calculates as follows

θ [k]=t₅[k]-t₄[k]

From the perspective of master clock, the time difference τ [k] between TH the and TA moment is

τ [k]=t₄[k]-t₁[i]

Therefore the relationship between θ [k] and θ [0] can be described with an equation of linear regression

θ [k]=θ [0]+γ τ [k]

Step P4 repeats step P3, can obtain multiple above-mentioned equations, as follows with matrix description

Above-mentioned equation group is solved using least square method, an optimal estimation to θ [0] and γ can be obtained,

In above formula, subscript T representing matrix transposition, -1 representing matrix of subscript is inverted.

Step P5：Clock correction, by clock jitter and the optimal estimation value Γ of frequency drift for the correction to clock.Root According to the configuration and requirement of real system, may be used there are many bearing calibration.

The present invention be it is a kind of be suitable for wireless network, the time synchronization improved method based on IEEE 1588PTP mechanism. In the case where deferring to IEEE 1588PTP temporal information packet switch mechanism, make full use of the broadcast characteristic of wireless communication, when Between during synchronous packet switch, intercept and intercept and capture other adjacent nodes and handed over according to IEEE 1588PTP mechanism with host node Temporal information packet when changing, to realize it is a kind of from-from Time Synchronization Mechanism.It should be used as from from synchronization mechanism to IEEE The extension that 1588PTP MS master-slave synchronizes, can obtain more temporal informations, and using superfluous from the-information obtained in mechanism It is remaining, make in the method for using linear regression from node more acurrate to clock offset and the estimation of frequency drift reliable.

IEEE 1588PTP packet exchanging mechanisms are obeyed in temporal information packet switch between main and subordinate node, with based on The wireless network time synchronizer of IEEE 1588PTP has compatibility well.From the temporal information packet of node and host node In exchange process, the step of being related to, includes：

A. host node sends Sync packets first, including sending time stamp information t1

B. after node receives Sync packets, the receiving time for obtaining Sync packets stabs information t2, then replys Delay-Req It wraps to host node, and obtains the sending time stamp t3 of Delay_Req packets

C. for host node after receiving Delay_Req packets, the receiving time for obtaining Delay_Req packets stabs information t4, replys Delay_Resp packets are put into t4 in Delay_Resp packets and send together to from node.

The transmission of three above temporal information packet is carried out according to broadcast mode.

When from node not in host node swap time packet, ether watcher system is introduced, temporal information packet is utilized Broadcast transmission characteristic, intercept and intercept and capture Delay_Req the and Delay_Resp times between other adjacent nodes and host node and believe Breath packet is to obtain its receiving time to stab (being denoted as t5) to intercepting and capturing Delay_Req packets, and to the Delay_Resp packets of intercepting and capturing, parsing obtains Take timestamp information t4 wherein included.Due to from node usually have multiple adjacent nodes, can obtain it is multigroup [t5, T4] timestamp.

T1, t2, t3 are being obtained, after [t5, t4] timestamp information of t4 and multigroup adjacent node, in addition to according to IEEE 1588PTP standards are calculated from t1, t2, t3, t4 outside clock jitter, can also calculate clock jitter from [t5, t4].It presses According to timestamp, the relationship between time deviation and clock frequency drift has obtained one group of regression equation.It is asked using least square method Solution, you can obtain an estimation more accurately drifted about to time deviation and clock frequency.Intercept and intercept and capture it is adjacent from node when Between packet, the process that clock jitter is then calculated from [t5, t4] be it is a kind of from-from synchronizing process, it is of the present invention Time synchronization improved method, major technique improvement be that, introduce and realize it is a kind of from-from synchronization mechanism, should be from from same Step mechanism can obtain more temporal informations, and utilize least square as the extension synchronized to IEEE 1588PTP MS master-slave Method achievees the purpose that improve clock jitter and clock frequency drift estimate precision and reliability.

Compared with prior art, present invention incorporates master-slave synchronisations with from from synchronous advantage, has the following advantages and has The technique effect of benefit：

1. the highly reliable method for synchronizing time of the high-precision of wireless network proposed by the present invention is deferring to IEEE1588PTP institutes In the case of defined temporal information packet switch process, the broadcast characteristic of wireless communication is taken full advantage of, by intercepting abutment points IEEE 1588PTP packet switch between host node, realize from-from synchronization mechanism.This method increases time letter without additional The exchange of packet is ceased, required packet switch quantity is identical as IEEE 1588PTP standards.And in time of occurrence packet packet loss In the case of (for example adverse circumstances electromagnetic interference is caused compared with high packet loss in commercial Application), it is not necessarily to re-transmission time packet, Also it can realize synchronization, reduce the consumption to the communication resource.

2. the highly reliable method for synchronizing time of the high-precision of wireless network proposed by the present invention, in IEEE 1588PTP MS master-slave On the basis of synchronization, utilize proposed from-from the information redundancy in synchronization mechanism, more preferably completed using the method for linear regression The estimation of clock skew and frequency drift sends and postpones so as to effectively reduce principal and subordinate path asymmetry, transmission delay jitter, It is influenced caused by the factors such as timestamp is inaccurate, to improve the precision of time synchronization in wireless sensing actor network.

3. is there is the same step number of part-time in the highly reliable method for synchronizing time of the high-precision of wireless network proposed by the present invention When according to packet loss, such as communicated with host node it is unsmooth, when time of occurrence packet is by packet loss, remain to by from-from synchronization mechanism reality It now synchronizes, without re-transmission time packet, reliability can be improved and reduce consumption of the synchronous method to the communication resource. It, can be by with host node packet switch and intercepting the packets of the abutment points that other do not fail for another example when there is certain several abutment points failure It exchanges to realize synchronization, therefore more relatively reliable than simple MS master-slave synchronous method.

Although an embodiment of the present invention has been shown and described, it will be understood by those skilled in the art that：Not In the case of being detached from the principle of the present invention and objective a variety of change, modification, replacement and modification can be carried out to these embodiments, this The range of invention is limited by claim and its equivalent.

Claims (8)

1. a kind of time synchronization improved method based on 1588 PTP mechanism of IEEE for wireless network, which is characterized in that packet Include following steps：

Step 1, by host node cycle start host node and between node carry timestamp temporal information packet switch；

Step 2, several to carry out temporal information packet switch with host node one by one from node, it is not carried out from node with host node a certain When temporal information packet switch, should from node holding intercept pattern, and intercept and capture it is other it is adjacent between node and host node with broadcaster The time synchronization information packet that formula swaps；

Step 3, the adjacent timestamp from the time synchronization information packet of node and host node of intercepting and capturing is carried out from node linear Regression optimization obtains this from the frequency deviation of clock of node and the estimated value of frequency drift, and using the clock jitter obtained and The estimated value of frequency drift realizes time synchronization to being adjusted from nodal clock；

The temporal information packet switch includes：

Step 101：In time point TA, host node starts to send Sync temporal information packets with broadcast mode, and obtains the Sync packets Sending time t1, and t1 is put into Sync packets and is sent together；

Step 102：In time point TB, which reaches from node, each to be joined from node from clock with local According to the receiving time of acquisition Sync packets, since the local of each node is not consistent from clock, so the receiving time stamp of Sync packets Value not yet, therefore be denoted as t2 [i] between the reception of the Sync packets of node i, and so on；

Step 103：In time point TC, through after a period of time processing delay and medium contention process, obtain medium from node i The right to use, the time point t3 [i] from node to host node reply Delay_Req temporal information packets, the Delay_Req packets Also it is sent, can also be intercepted and received by adjacent node with broadcast mode；

Step 104：In time point TD, the Delay_Req temporal information packets sent out from node i reach host node and each adjacent segments Point, host node obtain the time that Delay_Req packets reach host node using master clock as reference, are denoted as t4 [i], wherein i is indicated should Delay_Req packets come from node i, it is adjacent from node respectively since clock is reference, to obtain the arrival of Delay_Req packets respectively from node Time, be denoted as t5 [i] respectively；

Step 105：In time point TE, host node is after processing delay after a period of time, when the reception obtained in step 104 Between stamp t4 [i] be put into a Delay_Resp temporal information packet, and the Delay_Resp temporal information packets are sent with broadcast mode To all from node, including from node i；

Step 106：In time point TF, which reaches from node, each from node from the Delay_ Timestamp information t4 [i] is extracted in Resp packets；

Step 107, in time point TG, another right to use for obtaining medium from node k, in the time point t3 [k] from node Delay_Req temporal information packets are replied to host node, which is also sent with broadcast mode, can also be by adjacent segments Point is intercepted and is received；

Step 108, in time point TH, the Delay_Req temporal information packets sent out from node k reach host node and each adjacent segments Point, host node obtain the time that Delay_Req packets reach host node, are denoted as t4 [k], wherein k is indicated using master clock as reference The Delay_Req packets come from node k；It is adjacent from node respectively since clock is reference, to obtain the arrival of Delay_Req packets respectively from section The time of point, it is denoted as t5 [k] respectively；

Step 109：In time point TI, host node is after the processing delay after a period of time, and host node in step 108 obtaining Receiving time stamp t4 [k] is put into a Delay_Resp temporal information packet, and sends the Delay_Resp times with broadcast mode Packet is to all from node；

Step 110：In time point TJ, which reaches from node, each from node from the Delay_ Timestamp information t4 [k] is extracted in Resp packets；

Step 111：Circulation step, it is each from node in network, abovementioned steps 107 are repeated respectively to step 110；

Step 112：Until time point TK, the last one obtains use of media from node (being denoted as N), in the time from node Point t3 [N] replys Delay_Req temporal information packets to host node with broadcast mode, which can also be intercepted and connect by adjacent node It receives；

Step 113：In time point TL, the Delay_Req temporal information packets sent out from node N reach host node and each adjacent segments Point, host node obtains the time that Delay_Req packets reach host node, is denoted as t4 [N] using master clock as reference, adjacent from node Using respectively since clock is reference, acquisition Delay_Req packets reach respectively from the time of node, are denoted as t5 [N] respectively；

Step 114：In time point TM, the receiving time stamp t4 [N] obtained in step 113 is put into a Delay_ by host node Resp temporal information packets, and the Delay_Resp temporal informations packet is sent to all from node with broadcast mode；

Step 115：In time point TN, which reaches from node, each from node from the Delay_ Timestamp information t4 [N] is extracted in Resp packets.

2. the time synchronization improvement side based on 1588 PTP mechanism of IEEE according to claim 1 for wireless network Method, which is characterized in that the step 1 includes：

Step 1-1, host node send the synchronous package (Sync) for including sending time stamp information first；

Step 1-2, after node receives synchronous package (Sync), the receiving time for obtaining synchronous package (Sync) stabs information, replys Postpone request bag (Delay_Req) to host node, and obtains the sending time stamp of delay request bag (Delay_Req)；

Step 1-3, host node obtain delay request bag (Delay_Req) after receiving delay request bag (Delay_Req) Receiving time stabs information, and reply delay response bag (Delay_Resp) is given from node, and delay request bag (Delay_Req) Receiving time stamp information is put into delay response bag (Delay_Resp) to be sent together；When not postponed from node with host node Request bag (Delay_Req) and delay response bag (Delay_Resp) exchange when, be transferred to the pattern of intercepting, intercept and capture other from node with The delay request bag (Delay_Req) and delay response bag (Delay_Resp) that are exchanged between host node and its corresponding timestamp.

3. the time synchronization improvement side based on 1588 PTP mechanism of IEEE according to claim 2 for wireless network Method, which is characterized in that the step 1 includes：

Step 1A, host node send a synchronous package (Sync) to all from node, startup time synchronization process with broadcast mode；

Step 1B, host node is using local clock as reference, and the sending time for obtaining synchronous package (Sync) stabs t1, and by timestamp t1 Addition is in synchronous package (Sync)；

Step 1C in a receive mode from node waits the synchronous package (Sync) to be received；

Step 1D, from node after receiving the synchronous package (Sync) that host node is sent, as reference, to be stood from node local clock The receiving time for obtaining the synchronous package (Sync) is carved, timestamp t2 is denoted as；

Step 1E parses the data in received synchronous package (Sync) from node, obtains timestamp information t1 therein.

4. the time synchronization improvement side based on 1588 PTP mechanism of IEEE according to claim 2 for wireless network Method, which is characterized in that the step 2 includes：

Step 2A, host node are transferred to reception pattern, and preparing to receive will be by the delay request bag (Delay_Req) that is returned from node Packet；

Step 2B is transferred to sending mode from node, is ready for sending delay request bag (Delay_Req) message to host node, And enter the wireless channel contention process of MAC mechanism defineds；

Step 2C sends the Delay_Req with broadcast mode if obtaining the right to use of wireless channel from node to host node Packet, and t3 is stabbed using the sending time for, as reference, obtaining delay request bag (Delay_Req) from node local clock, by timestamp T3 is attached to as timestamp in delay request bag (Delay_Req)；

Step 2D, host node is after receiving delay request bag (Delay_Req), using host node local clock as reference, at once The receiving time for obtaining the delay request bag (Delay_Req), is denoted as timestamp t4；Host node is transferred to sending mode, by the time Stamp t4 is attached in delay request bag (Delay_Req), is given from section with broadcast mode transmission delay request bag (Delay_Req) Point；After being sent completely, host node is transferred to reception pattern；

Step 2E receives delay request bag (Delay_Req) from node, and timestamp t4 is parsed；

Step 2F is transferred to from node if failing to obtain the right to use of wireless channel from node and intercepts reception pattern, intercept and intercept and capture The delay response bag with timestamp t4 that the delay request bag (Delay_Req) and host node that other adjacent nodes are sent out are sent out (Delay_Resp) it is intercepted and captured；When intercepting and capturing delay request bag (Delay_Req), using the local clock from node as reference, The receiving time for obtaining delay request bag (Delay_Req), is denoted as timestamp t5；Intercepting and capturing delay response bag (Delay_Resp) Afterwards, the timestamp t4 postponed in response bag (Delay_Resp) is parsed；

Step 2G, the slave node of the right to use for obtaining wireless channel, after completing step 2C, 2D and 2E, abandoning this makes With power, be transferred to step 2F intercepts pattern；

Step 2H, the slave node of the right to use for not obtaining wireless channel are transferred to the transmission of step 2B after completing step 2F Pattern, competition use the wireless channel right to use, the delay request bag (Delay_Req) of oneself are sent to host node；

The packet switch of step 2I, host node terminate mechanism, when it is all complete packet switch with host node from node after, or setting The exchange of any time information report is not listened in threshold value of fixing time, then host node thinks that epicycle synchronously completes, and terminates current packet and hands over It changes process, waits for next round to arrive synchronizing cycle, be transferred to step 1-1；

Step 2J terminates mechanism from the packet switch of node, when it is all complete packet switch with host node from node after, or one The exchange of any time information report is not listened in section time threshold, then thinks that the packet switch that epicycle synchronizes has been completed from node, Reception, which is exited, from node intercepts pattern.

5. the time synchronization improvement side based on 1588 PTP mechanism of IEEE according to claim 2 for wireless network Method, which is characterized in that the step 3 includes：

Step 3A, the t1 that packet switch obtains between node and host node, t2, t3, t4 timestamps and one group are obtained by intercepting Other neighbors k and host node between the obtained t4 [k] of packet switch and t5 [k] timestamp, wherein k is k-th of abutment points, if Certain possesses N number of neighbors from node, then k={ 1,2 ... N }, and N is positive integer, at most should get N pairs by intercepting from node { t4 [k], t5 [k] } timestamp estimates the time deviation from nodal clock using linear regression optimization method；With reference to IEEE 1588 PTP modes obtain one about the functional relation between clock jitter and transmission delay from t1, t2, t3 and t4；

Step 3B, the N for intercepting acquisition are closed to obtaining N number of function about between deviation and transmission delay in { t4 [k], t5 [k] } It is formula；

Step 3C solves N+1 functional relation with least square method, obtains the optimal estimation value of clock jitter；

Step 3D after obtained clock jitter optimal estimation value, from the calculated frequency drift from nodal clock of node, is obtained The estimated value of clock jitter and frequency drift；

Step 3E realizes the time using obtained clock jitter and frequency drift estimated value to being adjusted from nodal clock It is synchronous.

6. the time synchronization improvement side based on 1588 PTP mechanism of IEEE according to claim 1 for wireless network Method, which is characterized in that the host node course of work includes：

Step 301：When synchronizing cycle then, host node by sending Sync temporal informations packet come the synchronizing process of a new round, Sync temporal information packets start to send with broadcast mode, and host node obtains the sending time t1 of the Sync packets when transmission, and by t1 It is put into Sync packets and sends together,

Step 302：After having sent Sync packets, host node is transferred to reception pattern, when waiting for from some from the Delay_Req of node Between packet,

Step 303：When reaching there are one Delay_Req packets, obtain the Delay_Req packets connects timestamp, is denoted as t4,

Step 304：Host node generates a Delay_Resp temporal information packet, and timestamp t4 in step 303 and preceding It states Delay_Res packets to be put into Delay_Resp packets from the information of node from which, Delay_Resp is sent with broadcast mode Packet,

Step 305：Host node checks whether epicycle synchronization is completed, and it is all from node that criterion is whether (a) has been received Delay_Req packets, or (b) wait for whether time-out, if do not complete, be transferred to step 302, wait to be received next from section The Delay_Req packets of point；If epicycle synchronization has been completed, it is transferred to next wait state, waits for next round synchronizing cycle It arrives,

Step 306：It waits for next round to arrive synchronizing cycle, if a new round arrives synchronizing cycle, is transferred to step 301, starts new one The time synchronization process of wheel.

7. the time synchronization improvement side based on 1588 PTP mechanism of IEEE according to claim 1 for wireless network Method, which is characterized in that described to include from the node course of work：

Step 401：It when beginning, is in from node i and intercepts reception state, wait for the Sync temporal information packets for carrying out autonomous node,

Step 402：After listening to the Sync packets for carrying out autonomous node, in receive process, Sync packets are obtained based on local clock Receiving time stamp, be denoted as t2 [i],

Step 403：T1 information is extracted from Sync packets, is denoted as t1 [i],

Step 404；This is transferred to sending mode from node, and the wireless channel right to use is obtained according to mode as defined in MAC protocol, if The channel right to use is obtained, then is transferred to step 405 to send Delay_Req packets；If not obtaining the channel right to use, it is transferred to Step 411 receives the temporal information packet of other nodes to intercept,

Step 405：This obtains the channel right to use from node, then sends Delay_Req temporal information packets to host node, based on this The sending time that ground clock obtains Sync packets is stabbed, and t3 [i] is denoted as, which is also sent with broadcast mode, can also be by Adjacent node is intercepted and is received,

Step 406：After the completion of sending Delay_Req packets, it is transferred to reception pattern, the Delay_Resp for waiting host node to be received to return Temporal information packet,

Step 407：After the Delay_Resp packets for carrying out autonomous node finish receiving, the timestamp letter in Delay_Resp packets is extracted T4 is ceased, t4 [i] is denoted as,

Step 408：Check whether epicycle synchronization is completed from node, it is all from node that criterion is whether (a) has been received Delay_Req/Delay_Resp packets, or (b) whether the packet switch of epicycle time synchronization overtime, if do not completed, turns Enter step 409；Data processing step 413 is transferred to if being completed,

Step 409：Check oneself whether be transmitted across Delay_Req packets and be properly received Delay_Resp packets from node, If be completed, it is transferred to step 410；If do not completed, it is transferred to step 404,

Step 410：Enter reception from node and intercept pattern, waits for the Delay_Req for intercepting and capturing other between node and host node With Delay_Resp packet switch,

Step 411：When listening to from other from node, it is set as after the Delay_Req packets of node k, in receive process, base The receiving time stamp of the Delay_Req packets is obtained in local clock, is denoted as t5 [k],

Step 412：It waits for and receives carrying out autonomous node and replying to Delay_Resp packets from node k, after finishing receiving, extraction should Timestamp information t4 in packet is denoted as t4 [k], is then transferred to step 408；

Step 413：Data processing step, from node by the adjacent from the time synchronization information packet of node and host node of intercepting and capturing Timestamp carries out linear regression optimization, obtains from the frequency deviation of clock of node and the estimated value of frequency drift, and synchronizing In journey time synchronization is realized to being adjusted from nodal clock using the estimated value of the clock jitter of acquisition and frequency drift.

8. the time synchronization improvement side based on 1588 PTP mechanism of IEEE according to claim 1 for wireless network Method, which is characterized in that the data processing step 413 includes：

Clock jitter from clock at the TA moment is denoted as θ [0] by step P1, and θ [0] is unknown-value, this moment from the time value of clock It is approximately t2 [i], the time value of master clock is t1 [i]=t1；

Step P2 completes Sync from node i and host node when this and is just obtained after Delay_Req and Delay_Resp packet switch Timestamp t1 [i], t2 [i], t3 [i] and t4 [i], the clock that can be calculated according to the following equation accordingly in the slave clock at TD moment are inclined Difference θ [i], i.e.,

And d_smAnd d_msFor the transmission delay between time principal and subordinate

From the perspective of master clock, the time difference τ [i] between TD the and TA moment is

τ [i]=t₄[i]-t₁[i]

Therefore the relationship between θ [i] and θ [0] is described with an equation of linear regression

θ [i]=θ [0]+γ τ [i]

Step P3：The adjacent Delay_Req packets sent out from node k are intercepted and captured at the TH moment, at the moment from the time value of clock For t5 [k], remember that the clock jitter at the moment is θ [k].After having received t4 [k] later, θ [k] calculates as follows

θ [k]=t₅[k]-t₄[k]

From the perspective of master clock, the time difference τ [k] between TH the and TA moment is

τ [k]=t₄[k]-t₁[i]

Therefore the relationship between θ [k] and θ [0] is described with an equation of linear regression

θ [k]=θ [0]+γ τ [k]；

Step P4 repeats step P3, obtains multiple equations, as follows with matrix description

Above-mentioned equation group is solved using least square method, an optimal estimation to θ [0] and γ can be obtained,

In above formula, subscript T representing matrix transposition, -1 representing matrix of subscript is inverted；

Step P5, clock correction, by clock jitter and the optimal estimation value Γ of frequency drift for the correction to clock.