CN104507156A - Improved method for time synchronization based on IEEE 1588 PTP mechanism for wireless network - Google Patents

Abstract

The invention relates to an improved method for time synchronization based on an IEEE 1588 PTP mechanism for a wireless network. The method is characterized by monitoring and intercepting a time information packet of the other adjacent nodes and a main node while exchanging according to the IEEE 1588 PTP mechanism during a time synchronization packet exchanging process under the condition of complying with an IEEE 1588 PTP time information packet exchange mechanism, thereby realizing a slave-slave synchronizing mechanism. The solution is used for expanding the IEEE 1588 PTP master-slave synchronization and can acquire much more time information; under the condition of utilizing the information redundancy acquired from the slave-slave synchronizing mechanism, a linear regression method is adopted for a slave node, so that the estimation for clock offset and frequency shift is more accurate and reliable; the influences caused by dissymmetry of main-secondary paths and insufficient accuracy of timestamp are weakened; the high-precision and high-reliability time synchronization is realized in the wireless network.

Description

The time synchronized based on IEEE 1588PTP mechanism for wireless network is improved one's methods

Technical field

The present invention relates to the communications field, particularly relate to a kind of time synchronized based on IEEE 1588PTP mechanism for wireless network and improve one's methods.

Background technology

The wireless network that wireless sense network (WSNs, Wireless Sensor Networks) is made up of the low power consumption node coacted in a large number, each node has limited computing capability, wireless communication ability and perception.Control actuator by introducing, wireless sensor and actor network (WSANs, Wireless Sensor Actuator Networks) refers to possess controlled in wireless n-back test, is suitable for the special wireless sense network of one of process monitoring and control.Local clock due to wireless sensing actor network node interrupts counting by inner crystal oscillator and realizes, and the frequency departure change etc. of different by the initial timer time of node from inner crystal oscillator, in network, each internodal clock is asynchronous.The time synchronized of WSAN instigates all or part node in WSAN to have identical time reference, exactly will the clock alignment (synchronously) being distributed in each node.

Time synchronized (Time Synchronization) technology is the important support technology of wireless sensing actor network.Especially, in industrial automation system, mutual coordination between automatic workflow is extremely important, require that the sensor node be associated better can perform synchronous data collection, the actuator node be associated harmoniously can carry out control operation, therefore WSAN has higher requirement to the precision of time synchronized and reliability, higher than average family and commercial wireless network system.As the data fusion of multisensor, target localization and monitoring, the shaping array of distributed beams and control, tdma communication is dispatched, based on the battery energy-saving etc. of sleep scheduling, all to time synchronized high requirement, therefore, time synchronized is particular importance in many application of WSAN, its importance is embodied in three aspects: step determines data whether accurate and effective, determines the performance quality of control system, determines overall performance of network quality (as channel utilization, throughput, network lifecycle etc.).

Method for synchronizing time conventional at present has: NTP method, RBS method, TPSN method and FTSP method etc.Wherein, NTP (Network Time Protocol) (NTP) is mainly for traditional IP-based internet, it is a kind of typical master-slave synchronisation method, initiated by the client (namely from clock) of NTP, first send the synchronization request bag also having local time stamp T1 to ntp server (i.e. master clock), server records this bag time of reception T2 after receiving this request bag.Then server replys respond packet in the T3 moment to client, and T3 timestamp is attached in this respond packet.When client receives this respond packet, record time of reception stamp T4.The timestamp information T1 that client obtains from this exchange, T2, T3 and T4 just can calculate the deviation between master-salve clock, thus deadline adjustment is with synchronous.RBS is a kind of method for synchronizing time put forward for wireless sensor and actor networks, the method is based on One-to-All Broadcast mechanism, the operational processes time delay and the medium access that effectively overcome transmitting terminal postpone (delay as CSMA/CA exponential backoff algorithm) impact on synchronization accuracy, reach certain precision, reliability is higher, but its amount of calculation and synchronization overhead are comparatively large, and energy consumption is higher.TPSN method is based on two-way paired synchrone mechanism, and synchronous effect is higher, higher than the precision of RBS, but comparatively large to the dependence of host node, limited reliability.And FTSP method is flooded broadcast formula Time synchronization algorithm, then the estimation of clock skew is carried out based on least square method, although One-to-All Broadcast makes the method for synchronization simple, but least square method needs a large amount of broadcast datas and higher amount of calculation, therefore can expend more communication bandwidth and computational resource.FTSP method Problems existing is mainly: for the network that density is large, and flooded broadcast can, at the burst transmit forming a large amount of broadcast data packet, cause the probability of collision very high, consumes node energy and Internet resources.

Along with the extensive use of distributed network TT&C system, for the TT&C system based on wired local Ethernet (Ethernet), IEEE (Institute of Electrical and Electronics Engineers) issued accurate time synchronization protocol (Precision Time Protocol) standard in 2002, code name IEEE 1588, full name be " the precise clock synchronization consensus standard of network measure and control system ", be called for short PTP.The IEEE1588v2 agreement of redaction has been formulated again in 2008.IEEE 1588 is master-slave synchronisation methods of a more complicated, similar to NTP, is that the packet of information of being stabbed if having time by master-salve clock exchange zone is synchronous.In theory, when timestamp is enough accurate (as adopted hardware based timestamp technology), IEEE 1588PTP can provide the exact time synchronization of sub-Millisecond, this precision more than NTP etc. is much higher, and communication is provided a loan and computational resource consumption is lower, this makes it be applicable to Industry Control, and measure the application of equal time harshness, therefore current international real-time ethernet all adopts IEEE 1588 as a core of its system.

IEEE1588 puts forward for wired local Ethernet, and it has three hypothesis, and the realization degree of these three hypothesis directly determines the precision of time synchronized.These three hypothesis are:

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

(2) clock skew is constant in temporal information packet switch process.This hypothesis requires more stable nodal clock oscillator and the time of packet switch faster, and the exchange with the packet of timestamp occurs in the time of one very little, with guarantee from the clock skew of clock be during this period of time changeless.Equivalently, this hypothesis is also the stability of nodal clock oscillator and the hypothesis of precision, requires that oscillator has higher quality.

(3) precise time mark.Suppose that main and subordinate node accurately can both be measured their transmissions or receive the time of packet.

In actual applications, because the two-forty of Ethernet and the transmission of cable signal are affected by the external environment more weak, suppose that (1) and (2) can better meet, when not too paying close attention to power supply and equipment cost, can adopt high-quality crystal oscillator and hardware in ethernet device, satisfy condition (2) and (3).

But these hypothesis may not necessarily well be met in the wireless network.This shows, by powered battery, the restriction of hardware device and environmental impact (as temperature), the crystal oscillator precision of radio node is limited, and drift obviously.Because wireless channel decline is very large, be more subject to the electromagnetic interference of external environment compared with wire message way, and the problem such as hidden node, the transmission delay being easy to be formed between principal and subordinate is asymmetric.Therefore the IEEE 1588PTP of standard can not well be applicable to wireless sensing actor network.

Summary of the invention

The present invention is intended at least solve the technical problem existed in prior art, especially innovatively proposes a kind of time synchronized based on IEEE 1588PTP mechanism for wireless network and improves one's methods.

In order to realize above-mentioned purpose of the present invention, the invention provides a kind of time synchronized based on IEEE 1588PTP mechanism for wireless network and improve one's methods, its key is, comprises the steps:

Step 1, by the startup host node of host node cycle with from the temporal information packet switch with timestamp between node;

Step 2, somely carry out temporal information packet switch with host node one by one from node, a certain do not carry out temporal information packet switch with host node from node time, listen mode should being kept from node, and intercepting and capturing other adjacent time synchronization information bag from carrying out with broadcast mode between node and host node exchanging;

Step 3, adjacently linear regression optimization is carried out from the timestamp the time synchronization information bag of node and host node by what intercept and capture from node, obtain this from the frequency deviation of clock of node and the estimated value of frequency drift, and utilize the estimated value of clock jitter and the frequency drift obtained to adjust from nodal clock, realize time synchronized.

The described time synchronized based on IEEE 1588PTP mechanism for wireless network is improved one's methods, and preferably, described step 1 comprises:

Step 1-1, first host node sends the sync packet (Sync) comprising transmitting time stamp information;

Step 1-2, after receiving sync packet (Sync) from node, obtain the time of reception stamp information of sync packet (Sync), reply and postpone request bag (Delay_Req) to host node, and obtain the transmitting time stamp postponing request bag (Delay_Req);

Step 1-3, host node is after receiving delay request bag (Delay_Req), obtain the time of reception stamp information postponing request bag (Delay_Req), reply delayed response bag (Delay_Resp) is given from node, and sends together postponing to ask the time of reception of bag (Delay_Req) information of stabbing to put into delayed response bag (Delay_Resp).When do not carry out with host node from node delay ask to wrap (Delay_Req) and delayed response bag (Delay_Resp) exchange time, proceed to listen mode, intercept and capture other from the delay request bag (Delay_Req) exchanged between node to host node and delayed response bag (Delay_Resp) and corresponding timestamp thereof.

The described time synchronized based on IEEE 1588PTP mechanism for wireless network is improved one's methods, and preferably, described step 1 comprises:

Step 1A, host node with broadcast mode send a sync packet (Sync) give all from node, start-up time synchronizing process;

Step 1B, host node take local clock as reference, obtains the transmitting time stamp t1 of sync packet (Sync), and is added on by timestamp t1 in sync packet (Sync);

Step 1C, is in receiving mode from node, this sync packet of wait-receiving mode (Sync);

Step 1D, from node receive host node send sync packet (Sync) after, with from node local clock for reference, obtain the time of reception of this sync packet (Sync) at once, be denoted as timestamp t2;

Step 1E, the data the sync packet (Sync) that it receives from node parses, obtain timestamp information t1 wherein.

The described time synchronized based on IEEE 1588PTP mechanism for wireless network is improved one's methods, and preferably, described step 2 comprises:

Step 2A, host node proceeds to receiving mode, prepares to receive to be about to be wrapped by the delay request bag (Delay_Req) returned from node;

Step 2B, proceeds to sending mode from node, is ready for sending one and postpones request bag (Delay_Req) message to host node, and enter the wireless channel contention process of MAC mechanism defined;

Step 2C, if obtain the right to use of wireless channel from node, send this Delay_Req with broadcast mode to host node to wrap, and with from node local clock for reference, obtain the transmitting time stamp t3 postponing request bag (Delay_Req), timestamp t3 is attached to as timestamp and postpones in request bag (Delay_Req);

Step 2D, host node, after receiving delay request bag (Delay_Req), with host node local clock for reference, obtains the time of reception of this delay request bag (Delay_Req) at once, is denoted as timestamp t4; Host node proceeds to sending mode, is attached to by timestamp t4 and postpones, in request bag (Delay_Req), to give from node with broadcast mode transmission lag request bag (Delay_Req); After being sent completely, host node proceeds to receiving mode;

Step 2E, from node receive delay request bag (Delay_Req), and parses timestamp t4;

Step 2F, the right to use of wireless channel is obtained if fail from node, proceed to from node and intercept receiving mode, intercept and intercept and capture delay request bag (Delay_Req) that other adjacent nodes send and the delayed response bag (Delay_Resp) with timestamp t4 that host node sends is intercepted and captured; When intercepting and capturing delay request bag (Delay_Req), with the local clock from node for reference, obtaining the time of reception postponing to ask bag (Delay_Req), being denoted as timestamp t5; After intercepting and capturing delayed response bag (Delay_Resp), the timestamp t4 in delayed response bag (Delay_Resp) is parsed;

Step 2G, for obtaining the usufructuary from node of wireless channel, as completing steps 2C, after 2D and 2E, abandoning this right to use, proceeding to the listen mode of step 2F;

Step 2H, for not obtaining the usufructuary from node of wireless channel, after completing steps 2F, proceeds to the sending mode of step 2B, and competition uses the wireless channel right to use, sends the delay request bag (Delay_Req) of oneself to host node;

Step 2I, the packet switch of host node terminates mechanism, when all complete packet switch with host node from node after, or in setting-up time threshold value, do not listen to information report any time exchange, then host node thinks that epicycle synchronously completes, terminate current packet switch process, wait for that next round arrives synchronizing cycle, proceed to step 1-1;

Step 2J, terminate mechanism from the packet switch of node, when all complete packet switch with host node from node after, or in a period of time threshold value, do not listen to any time information report exchange, then think that the synchronous packet switch of epicycle completes from node, exit reception listen mode from node.

The described time synchronized based on IEEE 1588PTP mechanism for wireless network is improved one's methods, and preferably, described step 3 comprises:

Step 3A, from the t1 that packet switch between node and host node obtains, t2, t3, t4 timestamp and one group are by the t4 [k] that detects packet switch between audible other neighborss k and host node and obtain and t5 [k] timestamp, wherein k is a kth abutment points, if certain has N number of neighbors from node, then k={1,2, N}, N is positive integer, should get N to { t4 [k], t5 [k] } timestamp at most from node by intercepting, utilize linear regression optimization method, estimate the time deviation from nodal clock; From t1, t2, t3 and t4, one is obtained about the functional relation between clock jitter and transmission delay with reference to IEEE 1588PTP mode;

Step 3B, the N intercepting acquisition is N number of about the functional relation between deviation and transmission delay to obtaining in { t4 [k], t5 [k] };

Step 3C, uses least square method to solve an above-mentioned N+1 functional relation, obtains the optimal estimation value of clock jitter.

Step 3D, after the clock jitter optimal estimation value obtained, from the frequency drift from nodal clock that node calculate goes out, obtains the estimated value of clock jitter and frequency drift;

Step 3E, utilizes the clock jitter and frequency drift estimated value that obtain, adjusts, realize time synchronized to from nodal clock.

The described time synchronized based on IEEE 1588PTP mechanism for wireless network is improved one's methods, and preferably, described temporal information packet switch comprises:

Step 101: at time point TA, host node starts to send Sync temporal information bag with broadcast mode, and obtain this Sync wrap transmitting time t1, and t1 is put into Sync bag send together;

Step 102: at time point TB, this Sync temporal information bag arrives from node, each from node with this locality from clock for reference, obtain the time of reception of Sync bag, because this locality of each node is inconsistent from clock, so the value of the time of reception stamp of Sync bag is not the same yet, therefore between the Sync bag of node i receives, be denoted as t2 [i], by that analogy;

Step 103: at time point TC, through processing delay after a while and medium contention process, the right to use of medium is obtained from node i, Delay_Req temporal information bag is replied from the time point t3 [i] of node to host node at this, this Delay_Req wraps and also sends with broadcast mode, also can be intercepted by adjacent node and receive;

Step 104: at time point TD, the Delay_Req temporal information bag sent from node i arrives host node and each adjacent node, host node take master clock as reference, obtain the time that Delay_Req bag arrives host node, be denoted as t4 [i], wherein i represents that this Delay_Req wraps from node i, adjacent from node with each since clock is for reference, obtain Delay_Req bag to arrive respectively from the time of node, be denoted as t5 [i] respectively;

Step 105: at time point TE, host node is after processing delay after a while, time of reception stamp t4 [i] obtained in step 104 is put into a Delay_Resp temporal information bag, and send this Delay_Resp temporal information bag to all from node with broadcast mode, comprise from node i;

Step 106: at time point TF, this Delay_Resp temporal information bag arrives from node, and each extracts timestamp information t4 [i] wrapping from node from this Delay_Resp;

Step 107, at time point TG, another obtains the right to use of medium from node k, replys Delay_Req temporal information bag at this from the time point t3 [k] of node to host node, this Delay_Req wraps and also sends with broadcast mode, also can be intercepted by adjacent node and receive;

Step 108, at time point TH, the Delay_Req temporal information bag sent from node k arrives host node and each adjacent node, host node take master clock as reference, obtains the time that Delay_Req bag arrives host node, is denoted as t4 [k], wherein, k represents that this Delay_Req wraps from node k; Adjacent from node with each since clock is for reference, obtain Delay_Req bag and arrive respectively from the time of node, be denoted as t5 [k] respectively;

Step 109: at time point TI, host node is after processing delay after a while, host node puts into a Delay_Resp temporal information bag time of reception stamp t4 [k] obtained in step 108, and sends this Delay_Resp temporal information bag to all from node with broadcast mode;

Step 110: at time point TJ, this Delay_Resp temporal information bag arrives from node, and each extracts timestamp information t4 [k] wrapping from node from this Delay_Resp;

Step 111: circulation step, each in network, from node, repeats abovementioned steps 107 to step 110 respectively;

Step 112: until time point TK, last obtains use of media from node (being denoted as N), reply Delay_Req temporal information bag at this from the time point t3 [N] of node to host node with broadcast mode, this bag also can be intercepted by adjacent node and receive;

Step 113: at time point TL, the Delay_Req temporal information bag sent from node N arrives host node and each adjacent node, host node take master clock as reference, obtain the time that Delay_Req bag arrives host node, be denoted as t4 [N], adjacent from node with each since clock is for reference, obtain Delay_Req bag and arrive respectively from the time of node, be denoted as t5 [N] respectively;

Step 114: at time point TM, host node puts into a Delay_Resp temporal information bag time of reception stamp t4 [N] obtained in step 113, and sends this Delay_Resp temporal information bag to all from node with broadcast mode;

Step 115: at time point TN, this Delay_Resp temporal information bag arrives from node, and each extracts timestamp information t4 [N] wrapping from node from this Delay_Resp.

The described time synchronized based on IEEE 1588PTP mechanism for wireless network is improved one's methods, and preferably, the described host node course of work comprises:

Step 301: when synchronizing cycle then, host node carrys out the synchronizing process of a new round by sending Sync temporal information bag, Sync temporal information bag starts to send with broadcast mode, and during transmission, host node obtains the transmitting time t1 that this Sync wraps, and t1 is put into Sync bag send together

Step 302: after sending Sync bag, host node proceeds to receiving mode, waits for from certain Delay_Req temporal information bag from node,

Step 303: when there being a Delay_Req bag to reach, what obtain this Delay_Req bag connects timestamp, is denoted as t4,

Step 304: host node generates a Delay_Resp temporal information bag, and the timestamp t4 in step 303 and aforementioned Delay_Res is wrapped which puts into Delay_Resp bag from the information of node from, send Delay_Resp bag with broadcast mode,

Step 305: host node checks whether epicycle synchronously completes, criterion is whether (a) has received all Delay_Req from node and wrap, or (b) whether wait is overtime, if do not completed, then proceed to step 302, the wait-receiving mode next one wraps from the Delay_Req of node; If epicycle synchronously completes, then proceed to next wait state, wait for that next round arrives synchronizing cycle,

Step 306: wait for that next round arrives synchronizing cycle, if a new round arrives synchronizing cycle, then proceeds to step 301, starts the time synchronization process of a new round.

The described time synchronized based on IEEE 1588PTP mechanism for wireless network is improved one's methods, and preferably, describedly to comprise from the node course of work:

Step 401: during beginning, is in from node i and intercepts accepting state, waits for the Sync temporal information bag of autonomous node,

Step 402: when after the Sync bag listening to autonomous node, in receiving course, obtains the time of reception stamp of Sync bag, is denoted as t2 [i] based on local clock,

Step 403: extract t1 information from Sync bag, be denoted as t1 [i],

Step 404; This proceeds to sending mode from node, and the mode specified according to MAC protocol obtains the wireless channel right to use, if obtain the channel right to use, then proceeds to step 405 to send Delay_Req bag; If do not obtain the channel right to use, then proceed to step 411 to intercept the temporal information bag receiving other nodes,

Step 405: this obtains the channel right to use from node, then send Delay_Req temporal information bag to host node, obtains the transmitting time stamp of Sync bag based on local clock, be denoted as t3 [i], this Delay_Req wraps and also sends with broadcast mode, also can be intercepted by adjacent node and receive

Step 406: after transmission Delay_Req has wrapped, proceed to receiving mode, the Delay_Resp temporal information bag that wait-receiving mode host node returns,

Step 407: after the Delay_Resp bag carrying out autonomous node finishes receiving, extract the timestamp information t4 in Delay_Resp bag, be denoted as t4 [i],

Step 408: check whether epicycle synchronously completes from node, criterion is whether (a) has received all Delay_Req/Delay_Resp from node and wrap, or (b) whether the packet switch of epicycle time synchronized is overtime, if do not completed, then proceeds to step 409; If completed, proceed to data processing step 413,

Step 409: whether sent Delay_Req bag from node inspection oneself and successfully have received Delay_Resp bag, and if completed, then having proceeded to step 410; If do not completed, then proceed to step 404,

Step 410: enter reception listen mode from node, waits for and intercepts and captures other from Delay_Req and the Delay_Resp packet switch between node and host node,

Step 411: when listening to from other from node, is set to after the Delay_Req bag of node k, in receiving course, obtains the time of reception stamp of this Delay_Req bag, be denoted as t5 [k] based on local clock,

Step 412: wait for and receive autonomous node replying to and wrap from the Delay_Resp of node k, after finishing receiving, extract the timestamp information t4 in this bag, be denoted as t4 [k], then proceed to step 408;

Step 413: data processing step, adjacently linear regression optimization is carried out from the timestamp the time synchronization information bag of node and host node by what intercept and capture from node, obtain from the frequency deviation of clock of node and the estimated value of frequency drift, and in synchronizing process, utilize the clock jitter of acquisition and the estimated value of frequency drift to adjust from nodal clock, realize time synchronized.

The described time synchronized based on IEEE 1588PTP mechanism for wireless network is improved one's methods, and preferably, described data processing step 413 comprises:

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

Step P2, when this completes Sync from node i and host node, after Delay_Req and Delay_Resp packet switch, just timestamp t1 [i] is obtained, t2 [i], t3 [i] and t4 [i], can calculate the clock jitter value θ [i] from clock in the TD moment, namely accordingly according to the following equation

$\mathrm{\θ}\left[i\right]=\frac{\left(t_2\right[i]-t_4[i\left]\right)-\left(t_1\right[i]-t_3[i\left]\right)}{2},$

And d _smand d _{m s}for the transmission delay between time principal and subordinate

$d_{\mathrm{sm}}=d_{\mathrm{ms}}=\frac{\left(t_2\right[i]-t_1[i\left]\right)+\left(t_4\right[i]-t_3[i\left]\right)}{2}$

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

τ[i]＝t ₄[i]-t ₁[i]

Therefore the equation of linear regression of the relation between θ [i] and θ [0] describes

θ[i]＝θ[0]+γ·τ[i]

Step P3: intercepted and captured the adjacent Delay_Req bag sent from node k in the TH moment, is t5 [k] in this moment from the time value of clock, remembers that the clock jitter in this moment is θ [k].After having received t4 [k] after a while, θ [k] has been calculated as follows

θ[k]＝t ₅[k]-t ₄[k]

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

τ[k]＝t ₄[k]-t ₁[i]

Therefore the equation of linear regression of the relation between θ [k] and θ [0] describes

θ[k]＝θ[0]+γ·τ[k]；

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

$\left(\begin{array}{c}\mathrm{\θ}\left[1\right]\\ \mathrm{\θ}\left[2\right]\\ .\\ .\\ .\\ \mathrm{\θ}\left[k\right]\\ .\\ .\\ .\\ \mathrm{\θ}\left[N\right]\end{array}\right)=\left(\begin{array}{cc}1& \mathrm{\τ}\left[1\right]\\ 1& \mathrm{\τ}\left[2\right]\\ .& .\\ .& .\\ .& .\\ 1& \mathrm{\τ}\left[k\right]\\ .& \\ .& \\ .& ...\\ 1& \mathrm{\τ}\left[N\right]\end{array}\right)\×\left[\begin{array}{c}\mathrm{\θ}\left[0\right]\\ \mathrm{\γ}\end{array}\right];$

Adopt least square method to solve to above-mentioned equation group, an optimal estimation to θ [0] and γ can be obtained,

$\left[\begin{array}{c}\mathrm{\θ}\left[0\right]\\ \mathrm{\γ}\end{array}\right]={\left[{\left(\begin{array}{cc}1& \mathrm{\τ}\left[1\right]\\ 1& \mathrm{\τ}\left[2\right]\\ .& .\\ .& .\\ .& .\\ 1& \mathrm{\τ}\left[k\right]\\ .& \\ .& \\ .& ...\\ 1& \mathrm{\τ}\left[N\right]\end{array}\right)}^T\left(\begin{array}{cc}1& \mathrm{\τ}\left[1\right]\\ 1& \mathrm{\τ}\left[2\right]\\ .& .\\ .& .\\ .& .\\ 1& \mathrm{\τ}\left[k\right]\\ .& \\ .& \\ .& ...\\ 1& \mathrm{\τ}\left[N\right]\end{array}\right)\right]}^{-1}{\left(\begin{array}{cc}1& \mathrm{\τ}\left[1\right]\\ 1& \mathrm{\τ}\left[2\right]\\ .& .\\ .& .\\ .& .\\ 1& \mathrm{\τ}\left[k\right]\\ .& \\ .& \\ .& ...\\ 1& \mathrm{\τ}\left[N\right]\end{array}\right)}^T\left(\begin{array}{c}\mathrm{\θ}\left[1\right]\\ \mathrm{\θ}\left[2\right]\\ .\\ .\\ .\\ \mathrm{\θ}\left[k\right]\\ .\\ .\\ .\\ \mathrm{\θ}\left[N\right]\end{array}\right)$

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

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

In sum, owing to have employed technique scheme, the invention has the beneficial effects as follows:

The time synchronized of this programme IEEE 1588PTP synchronization mechanism is improved one's methods, the method can with IEEE1588PTP operating such, but take full advantage of the broadcast characteristic of radio communication, when not changing IEEE 1588PTP packet switch process, using from-from synchronization mechanism as the expansion synchronous to IEEE 1588PTP MS master-slave, utilize from-from the information redundancy mechanism, the method of linear regression is being adopted better to complete the estimation of clock skew and frequency drift from node, thus minimizing principal and subordinate path is asymmetric, the impact that the factors such as timestamp is accurate not cause, to realize high accuracy under wireless network or wireless sensor network, highly reliable time synchronized.

Additional aspect of the present invention and advantage will part provide in the following description, and part will become obvious from the following description, or be recognized by practice of the present invention.

Accompanying drawing explanation

Above-mentioned and/or additional aspect of the present invention and advantage are below combination accompanying drawingobvious and easy understand will be become in the description of embodiment, wherein:

fig. 1it is the principle process of improving one's methods based on the time synchronized of IEEE 1588PTP mechanism that the present invention is directed to wireless network figure;

fig. 2it is the timestamp signal of improving one's methods based on the time synchronized of IEEE 1588PTP mechanism that the present invention is directed to wireless network figure;

fig. 3that the time synchronized based on IEEE 1588PTP mechanism that the present invention is directed to wireless network is improved one's methods the pack receiving and transmitting of middle host node and flow chart of data processing figure;

fig. 4from the pack receiving and transmitting of node and flow chart of data processing during the time synchronized based on IEEE 1588PTP mechanism that the present invention is directed to wireless network is improved one's methods figure.

Embodiment

For overcoming deficiency when using IEEE 1588PTP to carry out time synchronized in the wireless network, the object of the present invention is to provide a kind of wireless network of being applicable to, time synchronized based on IEEE 1588PTP synchronization mechanism is improved one's methods, the method can with IEEE 1588PTP operating such, but take full advantage of the broadcast characteristic of radio communication, when not changing IEEE 1588PTP packet switch process, using from-from synchronization mechanism as the expansion synchronous to IEEE 1588PTP MS master-slave, utilize from-from the information redundancy mechanism, the method of linear regression is being adopted better to complete the estimation of clock skew and frequency drift from node, thus minimizing principal and subordinate path is asymmetric, the impact that the factors such as timestamp is accurate not cause, to realize high accuracy under wireless network or wireless sensor network, highly reliable time synchronized.

For achieving the above object, the present invention solves this technical problem adopted technical scheme and is,

A kind of highly reliable time synchronized based on IEEE 1588PTP mechanism is improved one's methods, and comprises the following steps:

Step one: initiated by host node, starts the packet switch of being with timestamp information at host node and between node according to the packet switch mechanism of IEEE 1588PTP standard.

Step 2: use wireless channel from node according to the competition of MAC mechanism, complete the exchange of the time synchronization information bag that IEEE 1588PTP standard specifies one by one with host node.In this contention process, from node not with host node according to when carrying out packet switch, should from node keep listen mode, reception as much as possible is adjacent from the time synchronization information bag between node and host node.This intercepts process does not affect that other are adjacent from the synchronous exchange process between node and host node.

Step 3: with reference to the master-salve clock calculations of offset method of IEEE 1588PTP standard, utilize statistical calculation method to intercept in step 2 intercepting and capturing adjacent node time synchronization information bag in timestamp carry out linear regression optimization, utilize information redundancy, overcome receive delay uncertainty to affect from clock jitter estimated value, reduce principal and subordinate path asymmetric, transmission lag is uncertain, and timestamp is inaccurate on the impact of clock jitter estimated value, improves the certainty of measurement of the time deviation from clock.

Step 4: from the clock frequency drift estimate of node, and in follow-up process, utilize the clock jitter that estimates and frequency drift to adjust from clock, realize time synchronized.

Step 5: repeat above-mentioned steps one to step 4 according to some cycles.This repetitive process is controlled by host node, i.e. host node cycle ground setting up procedure one.

Further, in step one perform be IEEE 1588PTP Sync bag transmitting-receiving process, comprise following sub-step: (1a) host node sends a Sync packet to all from node, with synchronizing process start-up time with broadcast mode; (1b) host node is with local master clock for reference, obtains the transmitting time t1 of Sync bag, and is added in Sync bag as timestamp is attached by t1.(1c) be in receiving mode from node, this Sync of wait-receiving mode wraps.(1d) from node receive host node send Sync bag after, with from node local clock for reference, obtain at once this Sync wrap time of reception, be denoted as t2.(1e) data the Sync bag that it receives from node parses, obtain timestamp information t1 wherein.

Further, perform in step 2 be IEEE 1855PTP Delay_Req and Delay_Resp wrap transmitting-receiving and intercept process, comprising following sub-step: (2a) host node proceeds to receiving mode, preparing to receive the Delay_Req bag be about to by returning from node.(2b) proceed to sending mode from node, be ready for sending a Delay_Req message to host node, and enter the wireless channel contention process of MAC mechanism defined.If (2b) obtain the right to use of wireless channel from node, this Delay_Req packet is sent to host node with broadcast mode, and with from node local clock for reference, obtain the transmitting time t3 of Delay_Req, t3 be attached in Delay_Req packet as timestamp.If (2c) fail to obtain the right to use of wireless channel from node, proceed to receiving mode from node, intercept and intercept and capture the Delay_Req packet with t3 that other adjacent nodes send.(2d) host node is after receiving Delay_Req packet, with host node local clock for reference, obtains the time of reception that this Delay_Req wraps at once, is denoted as t4.Then host node proceeds to sending mode, is attached in Delay_Resp packet using t4 as timestamp, sends Delay_Resp packet to from node with broadcast mode.After being sent completely, host node proceeds to receiving mode.(2e) receive Delay_Resp bag from node, and timestamp information t4 is parsed; (2f) also Delay_Req and Delay_Resp bag being intercepted and captured from node of listen mode is in.When intercepting and capturing Delay_Req bag, with the local clock from node for reference, obtaining the time of reception of Delay_Req bag, being denoted as t5; After intercepting and capturing Delay_Resp bag, the timestamp information t4 in Delay_Resp is parsed.(2e) just now obtain the usufructuary of wireless channel and abandoned this right to use from node, proceed to the listen mode of step (2c).(2f) just now do not obtain the usufructuary sending mode proceeding to step (2b) from node of wireless channel, competition uses the right to use of wireless channel, sends the Delay_Req packet of oneself to host node.(2g) packet switch of host node terminates mechanism, when all complete packet switch with host node from node after, or in a period of time threshold value, do not listen to information report any time exchange, then host node thinks that epicycle synchronously completes, terminate current packet switch process, wait for that next round arrives synchronizing cycle, proceed to step one.(2h) mechanism is terminated from the packet switch of node, when all complete packet switch with host node from node after, or in a period of time threshold value, do not listen to information report any time exchange, then think that the synchronous packet switch of epicycle completes from node, exit reception listen mode from node, enter step 3.

Further, in step 3, from node according to this node and host node between the t1 that obtains of packet switch, t2, t3, (k represents a kth abutment points by the t4 [k] that detects packet switch between audible other neighborss k and host node and obtain and t5 [k] timestamp information for t4 timestamp information and one group, if certain has N number of neighbors from node, then k={1, 2, N}, therefore N can should be got to { t4 [k] by intercepting at most from node, t5 [k] } timestamp), utilize linear regression optimization method, estimate the time deviation from clock.Comprise following sub-step: (3a) obtains one about the functional relation between clock jitter and transmission delay with reference to IEEE 1588PTP mode from t1, t2, t3 and t4; (3b) from intercept the N that obtains to obtain in { t4 [k], t5 [k] } N number of about large deviations and transmission delay between functional relation; (3c) use least square method to solve above-mentioned N number of functional relation, obtain the optimal estimation value of clock jitter.

Further, in step 4, comprise following two steps: (4a), based on the clock jitter optimal estimation value obtained in step 3, from the frequency drift from clock that node calculate goes out, obtains the estimated value of clock frequency drift; (4c) utilize the clock jitter obtained and clock frequency drift estimate value, adjust from clock, realize time synchronized.

The wireless device of the method for the invention design, comprises time reference source node (being called 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, as data convergent point, radio access node (Access Point), central control point in net control, unique length of a game of host node maintaining network, the exchange being carried out temporal information bag from node by time synchronization protocol and host node in network, consistent with the network global time of host node from maintenance, reach time synchronized.

Temporal information packet switch of the present invention and timestamp resolving as Fig. 1shown in, execution mode has the time synchronized of a host node and N number of wireless sensor and actor network from node for one.Master clock on host node is an accurate clock (i.e. clock jitter θ=0 of master clock, frequency drift γ=0), and the time value of this master clock is as length of a game.One is had by oneself from clock from node is each, because crystal oscillator quality is different, power supply, the reasons such as variation of ambient temperature, respectively be inaccurate (i.e. clock jitter θ ≠ 0, frequency drift γ ≠ 0) from clock, and each clock jitter from node is not identical with frequency drift value.

as Fig. 1shown in, temporal information packet switch of the present invention comprises the following steps:

Step 101: at time point TA, host node starts to send Sync temporal information bag with broadcast mode, and obtain this Sync wrap transmitting time t1, and t1 is put into Sync bag send together;

Step 102: at time point TB, this Sync temporal information bag arrives from node, each from node with this locality from clock for reference, obtain the time of reception of Sync bag, because this locality of each node is inconsistent from clock, so the value of the time of reception stamp of Sync bag is not the same yet, therefore between the Sync bag of node i receives, be denoted as t2 [i], by that analogy;

Step 103: at time point TC, through processing delay after a while and medium contention process, the right to use of medium is obtained from node i, Delay_Req temporal information bag is replied from the time point t3 [i] of node to host node at this, this Delay_Req wraps and also sends with broadcast mode, also can be intercepted by adjacent node and receive;

Step 104: at time point TD, the Delay_Req temporal information bag sent from node i arrives host node and each adjacent node, host node take master clock as reference, obtain the time that Delay_Req bag arrives host node, be denoted as t4 [i], wherein i represents that this Delay_Req wraps from node i, adjacent from node with each since clock is for reference, obtain Delay_Req bag to arrive respectively from the time of node, be denoted as t5 [i] respectively;

Step 105: at time point TE, host node is after processing delay after a while, time of reception stamp t4 [i] obtained in step 104 is put into a Delay_Resp temporal information bag, and send this Delay_Resp temporal information bag to all from node with broadcast mode, comprise from node i;

Step 106: at time point TF, this Delay_Resp temporal information bag arrives from node, and each extracts timestamp information t4 [i] wrapping from node from this Delay_Resp;

Step 107, at time point TG, another obtains the right to use of medium from node k, replys Delay_Req temporal information bag at this from the time point t3 [k] of node to host node, this Delay_Req wraps and also sends with broadcast mode, also can be intercepted by adjacent node and receive;

Step 108, at time point TH, the Delay_Req temporal information bag sent from node k arrives host node and each adjacent node, host node take master clock as reference, obtains the time that Delay_Req bag arrives host node, is denoted as t4 [k], wherein, k represents that this Delay_Req wraps from node k; Adjacent from node with each since clock is for reference, obtain Delay_Req bag and arrive respectively from the time of node, be denoted as t5 [k] respectively;

Step 109: at time point TI, host node is after processing delay after a while, host node puts into a Delay_Resp temporal information bag time of reception stamp t4 [k] obtained in step 108, and sends this Delay_Resp temporal information bag to all from node with broadcast mode;

Step 110: at time point TJ, this Delay_Resp temporal information bag arrives from node, and each extracts timestamp information t4 [k] wrapping from node from this Delay_Resp;

Step 111: circulation step, each in network, from node, repeats abovementioned steps 107 to step 110 respectively;

Step 112: until time point TK, last obtains use of media from node (being denoted as N), reply Delay_Req temporal information bag at this from the time point t3 [N] of node to host node with broadcast mode, this bag also can be intercepted by adjacent node and receive;

Step 113: at time point TL, the Delay_Req temporal information bag sent from node N arrives host node and each adjacent node, host node take master clock as reference, obtain the time that Delay_Req bag arrives host node, be denoted as t4 [N], adjacent from node with each since clock is for reference, obtain Delay_Req bag and arrive respectively from the time of node, be denoted as t5 [N] respectively;

Step 114: at time point TM, host node puts into a Delay_Resp temporal information bag time of reception stamp t4 [N] obtained in step 113, and sends this Delay_Resp temporal information bag to all from node with broadcast mode;

Step 115: at time point TN, this Delay_Resp temporal information bag arrives from node, and each extracts timestamp information t4 [N] wrapping from node from this Delay_Resp.

So far temporal information packet switch completes, and respectively processes the temporal information got from node.For node i, the timestamp that may get 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 have a node to send, and all the other nodes are in and intercept and receiving mode.

It should be noted that, in above-mentioned packet switch, likely because the reasons such as environmental interference cause certain adjacent node (to be denoted as the Delay_Req bag that k) sends or corresponding Delay_Resp bag not received from node listens by other, then from node process by above-mentioned temporal information bag time, omit t4 [k], t5 [k].In most of the cases, successfully can intercept and receive the Delay_Req bag of a part of adjacent node and the Delay_Resp bag of correspondence thereof, therefore always obtain some t4 [k], t5 [k] is for follow-up temporal information process.

In above-mentioned packet switch, described host node and when transmitting/receiving wireless temporal information bag, can pass through the means such as special hardware or interrupt processing from node, has the ability that the transmitting time stamp of acquisition time packets of information and time of reception stab the time.And for the transmission of packets of information at the same time and reception, transmitting time stamp and time of reception stamp obtain at the same position wrapped, as Fig. 2shown in, timestamp all obtains in SFD (the Start Frame Delimiter) end of wireless data packet.

The communication process flow process of host node involved in the present invention as Fig. 3shown in, comprise the steps:,

Step 301: when synchronizing cycle then, host node carrys out the synchronizing process of a new round by sending Sync temporal information bag.Sync temporal information bag with broadcast mode start send, during transmission host node according to fig. 2shown in mode obtain this Sync wrap transmitting time t1, and t1 is put into Sync bag send together.

Step 302: after sending Sync bag, host node proceeds to receiving mode, waits for from certain Delay_Req temporal information bag from node.

Step 303: when there being a Delay_Req bag to reach, according to fig. 2shown in mode obtain this Delay_Req wrap connect timestamp, be denoted as t4.

Step 304: host node generates a Delay_Resp temporal information bag, and the timestamp t4 in step 303 and aforementioned Delay_Res is wrapped which puts into Delay_Resp bag from the information of node from, send Delay_Resp bag with broadcast mode.

Step 305: host node checks whether epicycle synchronously completes, criterion can be whether (a) has received all Delay_Req from node and wrap, or whether (b) waits for overtime.If do not completed, then proceed to step 302, the wait-receiving mode next one wraps from the Delay_Req of node; If epicycle synchronously completes, then proceed to next wait state, wait for that next round arrives synchronizing cycle.

Step 306: wait for that next round arrives synchronizing cycle.If a new round arrives synchronizing cycle, then proceed to step 301, start the time synchronization process of a new round.

Above-mentioned steps at a certain time interval (i.e. synchronizing cycle) circulation is carried out.

Involved in the present invention from node communication handling process as Fig. 4shown in, in this embodiment for be numbered i from node, comprise the steps

Step 401: during beginning, is in from node i and intercepts accepting state, waits for the Sync temporal information bag of autonomous node.

Step 402: when after the Sync bag listening to autonomous node, in receiving course, according to fig. 2shown mode, obtains the time of reception stamp of Sync bag, is denoted as t2 [i] based on local clock.

Step 403: extract t1 information from Sync bag, be denoted as t1 [i].

Step 404; This proceeds to sending mode from node, and the mode specified according to MAC protocol obtains the wireless channel right to use.If obtain the channel right to use, then proceed to step 405 to send Delay_Req bag; If do not obtain the channel right to use, then proceed to step 411 to intercept the temporal information bag receiving other nodes.

Step 405: this obtains the channel right to use from node, then send Delay_Req temporal information bag to host node, and according to fig. 2shown mode, obtains the transmitting time stamp of Sync bag, is denoted as t3 [i] based on local clock.This Delay_Req wraps and also sends with broadcast mode, also can be intercepted by adjacent node and receive.

Step 406: after transmission Delay_Req has wrapped, proceed to receiving mode, the Delay_Resp temporal information bag that wait-receiving mode host node returns.

Step 407: after the Delay_Resp bag carrying out autonomous node finishes receiving, extract the timestamp information t4 in Delay_Resp bag, be denoted as t4 [i].

Step 408: check whether epicycle synchronously completes from node, criterion can be whether (a) has received all Delay_Req/Delay_Resp from node and wrap, or whether the packet switch of (b) epicycle time synchronized is overtime.If do not completed, then proceed to step 409; If completed, proceed to data processing step 413.

Step 409: whether sent Delay_Req bag from node inspection oneself and successfully have received Delay_Resp bag.If completed, then proceed to step 410; If do not completed, then proceed to step 404.

Step 410: enter reception listen mode from node, waits for and intercepts and captures other from Delay_Req and the Delay_Resp packet switch between node and host node.

Step 411: when listening to after from other Delay_Req from node (being set to from node k) bag, in receiving course, obtains the time of reception stamp of this Delay_Req bag, is denoted as t5 [k] based on local clock.

Step 412: wait for and receive autonomous node replying to and wrap from the Delay_Resp of node k, after finishing receiving, extract the timestamp information t4 in this bag, be denoted as t4 [k].Then step 408 is proceeded to

Step 413: data processing step.When from node i after completing above-mentioned temporal information packet switch flow process, not only obtain IEEE 1588 required time stamp t1 [i], t2 [i], t3 [i] and t4 [i], and by intercepting intercepting and capturing mode, when not increasing packet switch total number, obtain one group of { t5 [k], t4 [k] } (k ∈ { 1,2,3 ... N}, but do not comprise oneself, i.e. k ≠ i) timestamp.This data processing step performs after completing aforementioned packet switch by from node, mainly processes obtained timestamp information, utilizes redundant information { t5 [k], t4 [k] }, improves the precision of time synchronized further.

Further, data processing comprises following step:

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

Step P2, when this completes Sync from node i and host node, after Delay_Req and Delay_Resp packet switch, just timestamp t1 [i] is obtained, t2 [i], t3 [i] and t4 [i], can calculate the clock jitter value θ [i] from clock in the TD moment, namely accordingly according to the following equation

$\mathrm{\θ}\left[i\right]=\frac{\left(t_2\right[i]-t_4[i\left]\right)-\left(t_1\right[i]-t_3[i\left]\right)}{2},$

And the transmission delay between principal and subordinate

$d_{\mathrm{sm}}=d_{\mathrm{ms}}=\frac{\left(t_2\right[i]-t_1[i\left]\right)+\left(t_4\right[i]-t_3[i\left]\right)}{2}$

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

τ[i]＝t ₄[i]-t ₁[i]

Therefore the relation between θ [i] and θ [0] can describe with an equation of linear regression

θ[i]＝θ[0]+γ·τ[i]

Step P3: intercepted and captured the adjacent Delay_Req bag sent from node k in the TH moment, is t5 [k] in this moment from the time value of clock, remembers that the clock jitter in this moment is θ [k].After having received t4 [k] after a while, θ [k] has been calculated as follows

θ[k]＝t ₅[k]-t ₄[k]

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

τ[k]＝t ₄[k]-t ₁[i]

Therefore the relation between θ [k] and θ [0] can describe with an equation of linear regression

θ[k]＝θ[0]+γ·τ[k]

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

$\left(\begin{array}{c}\mathrm{\θ}\left[1\right]\\ \mathrm{\θ}\left[2\right]\\ .\\ .\\ .\\ \mathrm{\θ}\left[k\right]\\ .\\ .\\ .\\ \mathrm{\θ}\left[N\right]\end{array}\right)=\left(\begin{array}{cc}1& \mathrm{\τ}\left[1\right]\\ 1& \mathrm{\τ}\left[2\right]\\ .& .\\ .& .\\ .& .\\ 1& \mathrm{\τ}\left[k\right]\\ .& \\ .& \\ .& ...\\ 1& \mathrm{\τ}\left[N\right]\end{array}\right)\×\left[\begin{array}{c}\mathrm{\θ}\left[0\right]\\ \mathrm{\γ}\end{array}\right];$

Adopt least square method to solve to above-mentioned equation group, an optimal estimation to θ [0] and γ can be obtained,

$\left[\begin{array}{c}\mathrm{\θ}\left[0\right]\\ \mathrm{\γ}\end{array}\right]={\left[{\left(\begin{array}{cc}1& \mathrm{\τ}\left[1\right]\\ 1& \mathrm{\τ}\left[2\right]\\ .& .\\ .& .\\ .& .\\ 1& \mathrm{\τ}\left[k\right]\\ .& \\ .& \\ .& ...\\ 1& \mathrm{\τ}\left[N\right]\end{array}\right)}^T\left(\begin{array}{cc}1& \mathrm{\τ}\left[1\right]\\ 1& \mathrm{\τ}\left[2\right]\\ .& .\\ .& .\\ .& .\\ 1& \mathrm{\τ}\left[k\right]\\ .& \\ .& \\ .& ...\\ 1& \mathrm{\τ}\left[N\right]\end{array}\right)\right]}^{-1}{\left(\begin{array}{cc}1& \mathrm{\τ}\left[1\right]\\ 1& \mathrm{\τ}\left[2\right]\\ .& .\\ .& .\\ .& .\\ 1& \mathrm{\τ}\left[k\right]\\ .& \\ .& \\ .& ...\\ 1& \mathrm{\τ}\left[N\right]\end{array}\right)}^T\left(\begin{array}{c}\mathrm{\θ}\left[1\right]\\ \mathrm{\θ}\left[2\right]\\ .\\ .\\ .\\ \mathrm{\θ}\left[k\right]\\ .\\ .\\ .\\ \mathrm{\θ}\left[N\right]\end{array}\right)$

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

Step P5: clock correction, is used for the correction to clock by the optimal estimation value Γ of clock jitter and frequency drift.According to configuration and the requirement of real system, multiple bearing calibration is had to adopt.

The present invention is a kind ofly applicable to wireless network, and the time synchronized based on IEEE 1588PTP mechanism is improved one's methods.When deferring to IEEE 1588PTP temporal information packet switch mechanism, make full use of the broadcast characteristic of radio communication, in the packet switch process of time synchronized, intercept and intercept and capture temporal information bag when other adjacent nodes and host node exchange according to IEEE 1588PTP mechanism, thus achieve a kind of from-from Time Synchronization Mechanism.Should from from synchronization mechanism as the expansion synchronous to IEEE 1588PTP MS master-slave, more temporal information can be obtained, and utilize from-the information redundancy that obtains from mechanism, make the estimation of clock skew and frequency drift more accurately and reliably adopting the method for linear regression from node.

IEEE 1588PTP packets of information exchanging mechanism is obeyed in temporal information packet switch between main and subordinate node, has good compatibility with the wireless network time synchronizer based on IEEE 1588PTP.From the temporal information packet switch process of node and host node, the step related to comprises:

A. first host node sends Sync bag, comprises transmitting time stamp information t1

B. after receiving Sync bag from node, obtain the time of reception stamp information t2 of Sync bag, then reply Delay-Req and wrap to host node, and obtain the transmitting time stamp t3 of Delay_Req bag

C. host node is after receiving Delay_Req bag, obtains the time of reception stamp information t4 of Delay_Req bag, replys Delay_Resp and wrap to from node, and t4 is put into Delay_Resp bag sends together.

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

When from node not in host node packets of information swap time time, the ether watcher system of introducing, utilize the broadcast transmission characteristic of temporal information bag, intercept and intercept and capture Delay_Req and the Delay_Resp temporal information bag between other adjacent node and host nodes, wrapping intercepting and capturing Delay_Req is obtain its time of reception stamp (being denoted as t5), to the Delay_Resp bag intercepted and captured, resolve the timestamp information t4 obtaining and wherein comprise.Owing to there is multiple adjacent node usually from node, many groups of [t5, t4] timestamps therefore can be obtained.

Obtaining t1, after [t5, t4] timestamp information of t2, t3, t4 and many group adjacent nodes, except calculating from t1, t2, t3, t4 outside clock jitter according to IEEE 1588PTP standard, clock jitter can also calculated from [t5, t4].According to timestamp, time deviation and clock frequency drift about between relation, obtain one group of regression equation.Utilize least square method to solve, one can be obtained more accurately to the estimation that time deviation and clock frequency are drifted about.Intercept and intercept and capture adjacent from node time packets of information, then from [t5, t4] in calculate clock jitter process be a kind of from-from synchronizing process, time synchronized of the present invention is improved one's methods, its major technique is improved and is just, introduce and achieve a kind of from-from synchronization mechanism, should from from synchronization mechanism as the expansion synchronous to IEEE 1588PTP MS master-slave, more temporal information can be obtained, and utilize least square method to reach the object improving clock jitter and clock frequency drift estimate precision and reliability.

Compared with prior art, present invention incorporates master-slave synchronisation and from from synchronous advantage, have the following advantages and useful technique effect:

1. the highly reliable method for synchronizing time of high accuracy of the wireless network of the present invention's proposition, when deferring to the temporal information packet switch process of IEEE1588PTP defined, take full advantage of the broadcast characteristic of radio communication, by intercepting the IEEE 1588PTP packet switch between abutment points and host node, achieve from-from synchronization mechanism.The method is without the need to additionally increasing the exchange of temporal information bag, and required packet switch quantity is identical with IEEE 1588PTP standard.And when time of occurrence packets of information packet loss (the comparatively high packet loss that in such as commercial Application, adverse circumstances electromagnetic interference is brought), without the need to retransmitting temporal information bag, also can realize synchronous, reducing the consumption to the communication resource.

2. the highly reliable method for synchronizing time of high accuracy of the wireless network of the present invention's proposition, on the basis that IEEE 1588PTP MS master-slave is synchronous, utilize propose from-from the information redundancy synchronization mechanism, the method of linear regression is adopted better to complete the estimation of clock skew and frequency drift, thus it is asymmetric effectively to reduce principal and subordinate path, transmission lag, transmission delay jitter, the impact that the factors such as timestamp is accurate not cause, to improve the precision of time synchronized in wireless sensing actor network.

3. the highly reliable method for synchronizing time of high accuracy of the wireless network of the present invention's proposition, when there is part-time synchrodata packet loss, as not smooth in communicated with host node, when time of occurrence packets of information is by packet loss, still by from-realize synchronous from synchronization mechanism, and without the need to retransmitting temporal information bag, reliability can be improved, the consumption of synchronous method to the communication resource can be reduced again.And for example when occurring that certain several abutment points lost efficacy, by with host node packet switch with to intercept the packet switch of the abutment points that other did not lose efficacy synchronous to realize, the MS master-slave synchronous method therefore than simple is more reliable.

Although illustrate and describe embodiments of the invention, those having ordinary skill in the art will appreciate that: can carry out multiple change, amendment, replacement and modification to these embodiments when not departing from principle of the present invention and aim, scope of the present invention is by claim and equivalents thereof.

Claims (9)

1. improve one's methods for the time synchronized based on IEEE 1588PTP mechanism of wireless network for one kind, it is characterized in that, comprise the steps:

Step 1, by the startup host node of host node cycle with from the temporal information packet switch with timestamp between node;

Step 2, somely carry out temporal information packet switch with host node one by one from node, a certain do not carry out temporal information packet switch with host node from node time, listen mode should being kept from node, and intercepting and capturing other adjacent time synchronization information bag from carrying out with broadcast mode between node and host node exchanging;

Step 3, adjacently linear regression optimization is carried out from the timestamp the time synchronization information bag of node and host node by what intercept and capture from node, obtain this from the frequency deviation of clock of node and the estimated value of frequency drift, and utilize the estimated value of clock jitter and the frequency drift obtained to adjust from nodal clock, realize time synchronized.

2. the time synchronized based on IEEE 1588PTP mechanism for wireless network according to claim 1 is improved one's methods, and it is characterized in that, described step 1 comprises:

Step 1-1, first host node sends the sync packet (Sync) comprising transmitting time stamp information;

Step 1-2, after receiving sync packet (Sync) from node, obtain the time of reception stamp information of sync packet (Sync), reply and postpone request bag (Delay_Req) to host node, and obtain the transmitting time stamp postponing request bag (Delay_Req);

Step 1-3, host node is after receiving delay request bag (Delay_Req), obtain the time of reception stamp information postponing request bag (Delay_Req), reply delayed response bag (Delay_Resp) is given from node, and sends together postponing to ask the time of reception of bag (Delay_Req) information of stabbing to put into delayed response bag (Delay_Resp).When do not carry out with host node from node delay ask to wrap (Delay_Req) and delayed response bag (Delay_Resp) exchange time, proceed to listen mode, intercept and capture other from the delay request bag (Delay_Req) exchanged between node to host node and delayed response bag (Delay_Resp) and corresponding timestamp thereof.

3. the time synchronized based on IEEE 1588PTP mechanism for wireless network according to claim 2 is improved one's methods, and it is characterized in that, described step 1 comprises:

Step 1A, host node with broadcast mode send a sync packet (Sync) give all from node, start-up time synchronizing process;

Step 1B, host node take local clock as reference, obtains the transmitting time stamp t1 of sync packet (Sync), and is added on by timestamp t1 in sync packet (Sync);

Step 1C, is in receiving mode from node, this sync packet of wait-receiving mode (Sync);

Step 1D, from node receive host node send sync packet (Sync) after, with from node local clock for reference, obtain the time of reception of this sync packet (Sync) at once, be denoted as timestamp t2;

Step 1E, the data the sync packet (Sync) that it receives from node parses, obtain timestamp information t1 wherein.

4. the time synchronized based on IEEE 1588PTP mechanism for wireless network according to claim 2 is improved one's methods, and it is characterized in that, described step 2 comprises:

Step 2A, host node proceeds to receiving mode, prepares to receive to be about to be wrapped by the delay request bag (Delay_Req) returned from node;

Step 2B, proceeds to sending mode from node, is ready for sending one and postpones request bag (Delay_Req) message to host node, and enter the wireless channel contention process of MAC mechanism defined;

Step 2C, if obtain the right to use of wireless channel from node, send this Delay_Req with broadcast mode to host node to wrap, and with from node local clock for reference, obtain the transmitting time stamp t3 postponing request bag (Delay_Req), timestamp t3 is attached to as timestamp and postpones in request bag (Delay_Req);

Step 2D, host node, after receiving delay request bag (Delay_Req), with host node local clock for reference, obtains the time of reception of this delay request bag (Delay_Req) at once, is denoted as timestamp t4; Host node proceeds to sending mode, is attached to by timestamp t4 and postpones, in request bag (Delay_Req), to give from node with broadcast mode transmission lag request bag (Delay_Req); After being sent completely, host node proceeds to receiving mode;

Step 2E, from node receive delay request bag (Delay_Req), and parses timestamp t4;

Step 2F, the right to use of wireless channel is obtained if fail from node, proceed to from node and intercept receiving mode, intercept and intercept and capture delay request bag (Delay_Req) that other adjacent nodes send and the delayed response bag (Delay_Resp) with timestamp t4 that host node sends is intercepted and captured; When intercepting and capturing delay request bag (Delay_Req), with the local clock from node for reference, obtaining the time of reception postponing to ask bag (Delay_Req), being denoted as timestamp t5; After intercepting and capturing delayed response bag (Delay_Resp), the timestamp t4 in delayed response bag (Delay_Resp) is parsed;

Step 2G, for obtaining the usufructuary from node of wireless channel, as completing steps 2C, after 2D and 2E, abandoning this right to use, proceeding to the listen mode of step 2F;

Step 2H, for not obtaining the usufructuary from node of wireless channel, after completing steps 2F, proceeds to the sending mode of step 2B, and competition uses the wireless channel right to use, sends the delay request bag (Delay_Req) of oneself to host node;

Step 2I, the packet switch of host node terminates mechanism, when all complete packet switch with host node from node after, or in setting-up time threshold value, do not listen to information report any time exchange, then host node thinks that epicycle synchronously completes, terminate current packet switch process, wait for that next round arrives synchronizing cycle, proceed to step 1-1;

Step 2J, terminate mechanism from the packet switch of node, when all complete packet switch with host node from node after, or in a period of time threshold value, do not listen to any time information report exchange, then think that the synchronous packet switch of epicycle completes from node, exit reception listen mode from node.

5. the time synchronized based on IEEE 1588PTP mechanism for wireless network according to claim 2 is improved one's methods, and it is characterized in that, described step 3 comprises:

Step 3A, from the t1 that packet switch between node and host node obtains, t2, t3, t4 timestamp and one group are by the t4 [k] that detects packet switch between audible other neighborss k and host node and obtain and t5 [k] timestamp, wherein k is a kth abutment points, if certain has N number of neighbors from node, then k={1,2, N}, N is positive integer, should get N to { t4 [k], t5 [k] } timestamp at most from node by intercepting, utilize linear regression optimization method, estimate the time deviation from nodal clock; From t1, t2, t3 and t4, one is obtained about the functional relation between clock jitter and transmission delay with reference to IEEE 1588PTP mode;

Step 3B, the N intercepting acquisition is N number of about the functional relation between deviation and transmission delay to obtaining in { t4 [k], t5 [k] };

Step 3C, uses least square method to solve an above-mentioned N+1 functional relation, obtains the optimal estimation value of clock jitter.

Step 3D, after the clock jitter optimal estimation value obtained, from the frequency drift from nodal clock that node calculate goes out, obtains the estimated value of clock jitter and frequency drift;

Step 3E, utilizes the clock jitter and frequency drift estimated value that obtain, adjusts, realize time synchronized to from nodal clock.

6. the time synchronized based on IEEE 1588PTP mechanism for wireless network according to claim 1 is improved one's methods, and it is characterized in that, described temporal information packet switch comprises:

Step 101: at time point TA, host node starts to send Sync temporal information bag with broadcast mode, and obtain this Sync wrap transmitting time t1, and t1 is put into Sync bag send together;

Step 102: at time point TB, this Sync temporal information bag arrives from node, each from node with this locality from clock for reference, obtain the time of reception of Sync bag, because this locality of each node is inconsistent from clock, so the value of the time of reception stamp of Sync bag is not the same yet, therefore between the Sync bag of node i receives, be denoted as t2 [i], by that analogy;

Step 103: at time point TC, through processing delay after a while and medium contention process, the right to use of medium is obtained from node i, Delay_Req temporal information bag is replied from the time point t3 [i] of node to host node at this, this Delay_Req wraps and also sends with broadcast mode, also can be intercepted by adjacent node and receive;

Step 104: at time point TD, the Delay_Req temporal information bag sent from node i arrives host node and each adjacent node, host node take master clock as reference, obtain the time that Delay_Req bag arrives host node, be denoted as t4 [i], wherein i represents that this Delay_Req wraps from node i, adjacent from node with each since clock is for reference, obtain Delay_Req bag to arrive respectively from the time of node, be denoted as t5 [i] respectively;

Step 105: at time point TE, host node is after processing delay after a while, time of reception stamp t4 [i] obtained in step 104 is put into a Delay_Resp temporal information bag, and send this Delay_Resp temporal information bag to all from node with broadcast mode, comprise from node i;

Step 106: at time point TF, this Delay_Resp temporal information bag arrives from node, and each extracts timestamp information t4 [i] wrapping from node from this Delay_Resp;

Step 107, at time point TG, another obtains the right to use of medium from node k, replys Delay_Req temporal information bag at this from the time point t3 [k] of node to host node, this Delay_Req wraps and also sends with broadcast mode, also can be intercepted by adjacent node and receive;

Step 108, at time point TH, the Delay_Req temporal information bag sent from node k arrives host node and each adjacent node, host node take master clock as reference, obtains the time that Delay_Req bag arrives host node, is denoted as t4 [k], wherein, k represents that this Delay_Req wraps from node k; Adjacent from node with each since clock is for reference, obtain Delay_Req bag and arrive respectively from the time of node, be denoted as t5 [k] respectively;

Step 109: at time point TI, host node is after processing delay after a while, host node puts into a Delay_Resp temporal information bag time of reception stamp t4 [k] obtained in step 108, and sends this Delay_Resp temporal information bag to all from node with broadcast mode;

Step 110: at time point TJ, this Delay_Resp temporal information bag arrives from node, and each extracts timestamp information t4 [k] wrapping from node from this Delay_Resp;

Step 111: circulation step, each in network, from node, repeats abovementioned steps 107 to step 110 respectively;

Step 112: until time point TK, last obtains use of media from node (being denoted as N), reply Delay_Req temporal information bag at this from the time point t3 [N] of node to host node with broadcast mode, this bag also can be intercepted by adjacent node and receive;

Step 113: at time point TL, the Delay_Req temporal information bag sent from node N arrives host node and each adjacent node, host node take master clock as reference, obtain the time that Delay_Req bag arrives host node, be denoted as t4 [N], adjacent from node with each since clock is for reference, obtain Delay_Req bag and arrive respectively from the time of node, be denoted as t5 [N] respectively;

Step 114: at time point TM, host node puts into a Delay_Resp temporal information bag time of reception stamp t4 [N] obtained in step 113, and sends this Delay_Resp temporal information bag to all from node with broadcast mode;

Step 115: at time point TN, this Delay_Resp temporal information bag arrives from node, and each extracts timestamp information t4 [N] wrapping from node from this Delay_Resp.

7. the time synchronized based on IEEE 1588PTP mechanism for wireless network according to claim 1 is improved one's methods, and it is characterized in that, the described host node course of work comprises:

Step 301: when synchronizing cycle then, host node carrys out the synchronizing process of a new round by sending Sync temporal information bag, Sync temporal information bag starts to send with broadcast mode, and during transmission, host node obtains the transmitting time t1 that this Sync wraps, and t1 is put into Sync bag send together

Step 302: after sending Sync bag, host node proceeds to receiving mode, waits for from certain Delay_Req temporal information bag from node,

Step 303: when there being a Delay_Req bag to reach, what obtain this Delay_Req bag connects timestamp, is denoted as t4,

Step 304: host node generates a Delay_Resp temporal information bag, and the timestamp t4 in step 303 and aforementioned Delay_Res is wrapped which puts into Delay_Resp bag from the information of node from, send Delay_Resp bag with broadcast mode,

Step 305: host node checks whether epicycle synchronously completes, criterion is whether (a) has received all Delay_Req from node and wrap, or (b) whether wait is overtime, if do not completed, then proceed to step 302, the wait-receiving mode next one wraps from the Delay_Req of node; If epicycle synchronously completes, then proceed to next wait state, wait for that next round arrives synchronizing cycle,

Step 306: wait for that next round arrives synchronizing cycle, if a new round arrives synchronizing cycle, then proceeds to step 301, starts the time synchronization process of a new round.

8. the time synchronized based on IEEE 1588PTP mechanism for wireless network according to claim 1 is improved one's methods, and it is characterized in that, describedly comprises from the node course of work:

Step 401: during beginning, is in from node i and intercepts accepting state, waits for the Sync temporal information bag of autonomous node,

Step 402: when after the Sync bag listening to autonomous node, in receiving course, obtains the time of reception stamp of Sync bag, is denoted as t2 [i] based on local clock,

Step 403: extract t1 information from Sync bag, be denoted as t1 [i],

Step 404; This proceeds to sending mode from node, and the mode specified according to MAC protocol obtains the wireless channel right to use, if obtain the channel right to use, then proceeds to step 405 to send Delay_Req bag; If do not obtain the channel right to use, then proceed to step 411 to intercept the temporal information bag receiving other nodes,

Step 405: this obtains the channel right to use from node, then send Delay_Req temporal information bag to host node, obtains the transmitting time stamp of Sync bag based on local clock, be denoted as t3 [i], this Delay_Req wraps and also sends with broadcast mode, also can be intercepted by adjacent node and receive

Step 406: after transmission Delay_Req has wrapped, proceed to receiving mode, the Delay_Resp temporal information bag that wait-receiving mode host node returns,

Step 407: after the Delay_Resp bag carrying out autonomous node finishes receiving, extract the timestamp information t4 in Delay_Resp bag, be denoted as t4 [i],

Step 408: check whether epicycle synchronously completes from node, criterion is whether (a) has received all Delay_Req/Delay_Resp from node and wrap, or (b) whether the packet switch of epicycle time synchronized is overtime, if do not completed, then proceeds to step 409; If completed, proceed to data processing step 413,

Step 409: whether sent Delay_Req bag from node inspection oneself and successfully have received Delay_Resp bag, and if completed, then having proceeded to step 410; If do not completed, then proceed to step 404,

Step 410: enter reception listen mode from node, waits for and intercepts and captures other from Delay_Req and the Delay_Resp packet switch between node and host node,

Step 411: when listening to from other from node, is set to after the Delay_Req bag of node k, in receiving course, obtains the time of reception stamp of this Delay_Req bag, be denoted as t5 [k] based on local clock,

Step 412: wait for and receive autonomous node replying to and wrap from the Delay_Resp of node k, after finishing receiving, extract the timestamp information t4 in this bag, be denoted as t4 [k], then proceed to step 408;

Step 413: data processing step, adjacently linear regression optimization is carried out from the timestamp the time synchronization information bag of node and host node by what intercept and capture from node, obtain from the frequency deviation of clock of node and the estimated value of frequency drift, and in synchronizing process, utilize the clock jitter of acquisition and the estimated value of frequency drift to adjust from nodal clock, realize time synchronized.

9. the time synchronized based on IEEE 1588PTP mechanism for wireless network according to claim 1 is improved one's methods, and it is characterized in that, described data processing step 413 comprises:

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

Step P2, when this completes Sync from node i and host node, after Delay_Req and Delay_Resp packet switch, just timestamp t1 [i] is obtained, t2 [i], t3 [i] and t4 [i], can calculate the clock jitter value θ [i] from clock in the TD moment, namely accordingly according to the following equation

$\mathrm{\θ}\left[i\right]=\frac{\left(t_2\right[i]-t_4[i\left]\right)-\left(t_1\right[i]-t_3[i\left]\right)}{2},$

And d _smand d _msfor the transmission delay between time principal and subordinate

$d_{\mathrm{sm}}=d_{\mathrm{ms}}=\frac{\left(t_2\right[i]-t_1[i\left]\right)+\left(t_4\right[i]-t_3[i\left]\right)}{2}$

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

τ[i]＝t ₄[i]-t ₁[i]

Therefore the equation of linear regression of the relation between θ [i] and θ [0] describes

θ[i]＝θ[0]+γ·τ[i]

Step P3: intercepted and captured the adjacent Delay_Req bag sent from node k in the TH moment, is t5 [k] in this moment from the time value of clock, remembers that the clock jitter in this moment is θ [k].After having received t4 [k] after a while, θ [k] has been calculated as follows

θ[k]＝t ₅[k]-t ₄[k]

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

τ[k]＝t ₄[k]-t ₁[i]

Therefore the equation of linear regression of the relation between θ [k] and θ [0] describes

θ[k]＝θ[0]+γ·τ[k]；

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

$\left(\begin{array}{c}\mathrm{\θ}\left[1\right]\\ \mathrm{\θ}\left[2\right]\\ .\\ .\\ .\\ \mathrm{\θ}\left[k\right]\\ .\\ .\\ .\\ \mathrm{\θ}\left[N\right]\end{array}\right)=\left(\begin{array}{cc}1& \mathrm{\τ}\left[1\right]\\ 1& \mathrm{\τ}\left[2\right]\\ .& .\\ .& .\\ .& .\\ 1& \mathrm{\τ}\left[k\right]\\ .& \\ .& ...\\ .& \\ 1& \mathrm{\τ}\left[N\right]\end{array}\right)\×\left[\begin{array}{c}\mathrm{\θ}\left[0\right]\\ \mathrm{\γ}\end{array}\right];$

Adopt least square method to solve to above-mentioned equation group, an optimal estimation to θ [0] and γ can be obtained,

$\left[\begin{array}{c}\mathrm{\θ}\left[0\right]\\ \mathrm{\γ}\end{array}\right]={\left[\begin{array}{cc}{\left(\begin{array}{cc}1& \mathrm{\τ}\left[1\right]\\ 1& \mathrm{\τ}\left[2\right]\\ .& .\\ .& .\\ .& .\\ 1& \mathrm{\τ}\left[k\right]\\ .& \\ .& ...\\ .& \\ 1& \mathrm{\τ}\left[N\right]\end{array}\right)}^T& \left(\begin{array}{cc}1& \mathrm{\τ}\left[1\right]\\ 1& \mathrm{\τ}\left[2\right]\\ .& .\\ .& .\\ .& .\\ 1& \mathrm{\τ}\left[k\right]\\ .& \\ .& ...\\ .& \\ 1& \mathrm{\τ}\left[N\right]\end{array}\right)\end{array}\right]}^{-1}{\left(\begin{array}{cc}1& \mathrm{\τ}\left[1\right]\\ 1& \mathrm{\τ}\left[2\right]\\ .& .\\ .& .\\ .& .\\ 1& \mathrm{\τ}\left[k\right]\\ .& \\ .& ...\\ .& \\ 1& \mathrm{\τ}\left[N\right]\end{array}\right)}^T\left(\begin{array}{c}\mathrm{\θ}\left[1\right]\\ \mathrm{\θ}\left[2\right]\\ .\\ .\\ .\\ \mathrm{\θ}\left[k\right]\\ .\\ .\\ .\\ \mathrm{\θ}\left[N\right]\end{array}\right)$

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

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