CN103929799A - Wireless sensor network MAC transmission method applied to bridge monitoring - Google Patents

Abstract

The invention relates to a wireless sensor network MAC transmission method applied to bridge monitoring. An MPMC-MAC protocol is combined with the type of data received by nodes and information sending frequency of the nodes to distribute priorities to the nodes, and channel distribution is carried out on the nodes according to the priorities and channel conditions so that it can be guaranteed that a node with a high priority sends the data preferentially. When information needs to be transmitted again due to the fact that channel collision occurs or node communication is interfered, a channel redistribution technique is adopted. According to the technique, channels are distributed to the nodes again according to the priority of the nodes, remaining energy of the nodes and retransmission times, and fairness of channel distribution is guaranteed. Additionally, according to the method, the active cycle of the nodes and the duration of a sleep cycle are adjusted dynamically so that energy can be saved, and time delay of transmission is reduced.

Description

A kind of wireless sensor network MAC transmission method that is applied to bridge monitoring

Technical field

The present invention relates to a kind of wireless sensor network MAC transmission method that is applied to bridge monitoring, belong to wireless sensor network technology field.

Background technology

In today of rapid urban, in city, be a mass of different types of rridges.And the hill start of Shang Qiao and lower bridge and the place such as turn round are all the places that takes place frequently of traffic accident, will monitor to avoid to the key area of bridge the generation of accident herein accordingly.Wireless sensor network as one can perception the instrument of real time information around on bridge monitoring, play an important role.And MAC agreement is the basic agreement that affects wireless sensor network overall performance, the MAC protocol for wireless sensor networks that designs a kind of applicable bridge monitoring has real meaning.

MAC protocol for wireless sensor networks is divided three classes by channel dispatch mode at present: the MAC agreement based on competitive channel mode, the MAC agreement of the MAC agreement based on scheduling channel mode and comprehensive above-mentioned two kinds of tactful hybrid modes.The agreement of competitive way realizes simple, can meet preferably the variation of number of nodes and offered load.But node sends data, need to monitor also competitive channel, excessive monitoring and competition can reduce channel utilization and expend unnecessary energy, as S-MAC (Sensor-MAC, S-MAC) and T-MAC (Timeout-MAC, T-MAC).When offered load is larger, their monitoring and competitive channel can cause channel confliction, affect network real-time.And the agreement of scheduling formula realizes complexity, and expansion is bad, as EM-MAC (Efficient Multichannel MAC, EM-MAC) and DMAC (Data gathering tree-based MAC, DMAC).The mode of their fixed allocation time slots causes channel utilization not high, and affects the expansion of network.Hybrid protocol has carried out the combination of competition with scheduling, and the overall performance of network is improved.ZMAC in hybrid protocol (Zebra MAC, ZMAC) is used the mode access channel of csma (Carrier Sense Multiple Access, CSMA) when network traffics are low, can improve channel utilization.When high flow capacity, adopt the mode of time division multiplexing (Time Division Multiple Access, TDMA) to reduce conflict.Starting stage agreement needs clock synchronous, and under conflict mode, this node can only transmit data in limited time slot, has increased time delay.HyMAC (Hybrid MAC, HyMAC) is applicable to have the wireless sensor network application of data acquisition tree structure.But agreement, not according to the dynamic adjustment of offered load, affects real-time.The MAC agreement of IEEE802.15.4MAC definition is also a kind of MAC agreement of hybrid mode, and it will be divided into two stages the work period under the state of superframe, i.e. channel competition access phase and channel contention free period.This mode is comparatively flexible, but its network throughput is little, is not suitable for the communication of big data quantity.These agreements are not all suitable for the wireless sensor network of bridge monitoring.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, the invention provides a kind of wireless sensor network MAC transmission method that is applied to bridge monitoring.

Of the present invention being achieved through the following technical solutions:

A wireless sensor network MAC transmission method that is applied to bridge monitoring, is characterized in that: comprise the steps:

(1), when data communication, adopt priority distribute data; Implementation step is as follows:

The first step: carry out Data classification according to the entrained sensor type of node, different data are divided three classes; The temperature data recording with the node of temperature sensor, the lower L that is made as of its urgency level ₁; The bridge recording with the node of acceleration transducer is to vibration frequency data, and its priority is made as M ₁; The bridge key point displacement data recording with the node of displacement transducer, its priority is made as H ₁; Generate three class data priorities;

Second step: according to node transmission frequency, node is divided into two classes; Adopt a kind of improved minimum distance classification algorithm; This sorting algorithm is directly found out maximum and the minimum value of node transmission times, the basic point using them as classification; By node transmission times in the classification cycle, be divided into high priority H ₂, low priority is made as L ₂, generated two quefrency priority;

The 3rd step: in conjunction with data type priority and frequency priority, can obtain six priority levels, that is: H ₁h ₂, M ₁h ₂, H ₁l ₂, M ₁l ₂, L ₁h ₂, L ₁l ₂; They are corresponded to P from high to low successively ₁to P ₆six priority class.

The 4th step: the priority of each node is packaged into priority command frame; Priority command frame is sent after sending beacon frame by aggregation node;

The 5th step: node is received the priority command frame of oneself is used this priority in this classification cycle;

(2) when channel allocation, adopt New Data Channel Scheduling Algorithms, its key step is as follows:

The first step: the priority that each node sends according to aggregation node judges own operable channel set;

Second step: node is random in spendable channel set selects a channel to communicate; This time the both sides of communication are by approximately establishing a capital on this channel and communicate by letter in advance;

The 3rd step: if this time communicate by letter successfully, the channel of communication next time is still selected at random in this set; And the duration of knot modification activity periods and sleep cycle at this moment, guarantee the real-time of perception information;

The 4th step: when transmission data are unsuccessful, data are retransmitted.During re-transmission, channel is reallocated; Be provided with a variable α _m, α _mthe priority P that represents node m _mwith its dump energy E _leftthe ratio of long-pending and number of retransmissions S; Work as α _m>=1 o'clock, this node obtained good channel not enough, random selective channel in the original channel set distributing still when retransmit next time; Work as α _mduring < 1, this node can the good channel of behaviour in service, from good channel set, selects at random a channel to retransmit;

The 5th step: if node is still failed in channel set re-transmission preferably, abandon retransmitting; Communicate by letter next time.

The step of the activity periods of described dynamic knot modification and the duration of sleep cycle is specially:

The first step: determine parameters exact value in this work period, as T _activerepresent the duration of activity periods, T' _activethe duration of the activity periods of representative within the next work period.Parameter M _totaland M _currentmessage queue total capacity and queue current residual amount in their difference representation node internal memories.In addition, in this agreement, also set two variable T _limitwith Δ t, when initial, T _limit=0.4T _active, Δ t=0.1T _active;

Second step: find in this work period the time point of the perception events E finally occurring;

The 3rd step: the time point of perception events and set parameter are compared;

The 4th step: if 1. time point is at T _limitwithin, at T _limitdo not have perception events to occur outward; Be described the morning that perception events occurs, and the data of generation are also less.The duration that can reduce activity periods in the upper work period to be once to save energy, concrete adjust as shown in the formula:

$T_{\mathrm{active}}^{\&prime;}=T_{\mathrm{active}}-\frac{M_{\mathrm{current}}}{M_{\mathrm{total}}}\&CenterDot;T_{\mathrm{limit}}$

If 2. time point is at T _limitoutside, within Δ t, not illustrating that perception events is just in time in activity periods, the work period is constant next time;

If 3. time point is within Δ t, illustrate that activity periods may be not enough.Likely can miss some perception events, need to extend the activity periods duration in this cycle and next work period.The duration of this activity periods, the activity periods duration of next cycle and the Δ t of next cycle adjust as shown in the formula:

T _active＝T _active+Δt

$T_{\mathrm{active}}^{\&prime;}=T_{\mathrm{active}}+(1+\frac{M_{\mathrm{total}}-M_{\mathrm{current}}}{M_{\mathrm{total}}})\&CenterDot;\mathrm{\&Delta;t}$

$\mathrm{\&Delta;t}=\left(\frac{T_{\mathrm{active}}-T_{\mathrm{limit}}}{T_{\mathrm{active}}}\right)\&CenterDot;\frac{M_{\mathrm{current}}}{M_{\mathrm{total}}}\&CenterDot;T_{\mathrm{limit}}.$

Beneficial effect of the present invention: compared with prior art, the present invention, according to the particular surroundings of bridge monitoring, provides a kind of multipriority multi channel MAC protocol for wireless sensor networks.This agreement adopts the cycle of activity of dynamic knot modification and the duration of sleep cycle to reduce to postpone, and saves energy.The sorting algorithm adopting in agreement is applicable to the node priority classification under bridge monitoring environment, guarantees that the node of high priority can obtain better channel resource.Agreement provided by the invention has higher throughput, lower network delay, and because node energy is saved in the minimizing of conflict; It is applicable to long-term bridge real-time monitoring system.

Accompanying drawing explanation

Fig. 1 dynamically adjusts schematic diagram.

Fig. 2 is classification cycle schematic diagram.

Fig. 3 is protocol channels distribution schematic diagram.

Fig. 4 is that aggregation node sends priority command frame flow chart.

Fig. 5 is ordinary node selective channel flow chart.

Embodiment

Below in conjunction with accompanying drawing, the present invention is further described.The place, gateway of bridge is the location that traffic accident takes place frequently, and its feature is climb and fall, need to be to dealing automobile speed limit and freight weight limit.Because road conditions are complicated, increased the risk that traffic accident occurs.The place, gateway that wireless sensor node is arranged in to bridge, responds in real time, forms the wireless sensor network of a Real-Time Monitoring.Node can carry multiple sensors, pressure sensor for example, and laser velocimeter transducer and temperature sensor are collected the weight of car, the temperature on speed and road surface simultaneously.

The present invention has designed a kind of data type of combination node reception and the priority algorithm that node sends information frequency.This algorithm be take one hour as a classification cycle, and the sensor type of installing by recognition node is released the data type in node.Within the classification cycle, record each node and to aggregation node, send the number of times of data, according to transmission times, classify and form priority with combination of data types.In the classification cycle, comprise a plurality of work periods and a computing cycle, as shown in Figure 2.In computing cycle, no longer more new node sends the information of data number of times, and all classified calculating are carried out in computing cycle.The final precedence information generating is encapsulated in command frame, by aggregation node transmission after next beacon frame sends, guarantees that each node knows its precedence information when the new classification cycle starts.The concrete implementation step of this algorithm is as follows:

The first step: carry out Data classification according to the entrained sensor type of node, different data are divided three classes.For example, the temperature data recording with the node of temperature sensor, the lower L that is made as of its urgency level ₁; The member temperature data that record with the node of fiber-optic grating sensor, the lower L that is made as of its urgency level ₁; The bridge recording with the node of acceleration transducer is to vibration frequency data, and its priority is made as M ₁; The bridge key point displacement data recording with the node of displacement transducer, its priority is made as H ₁.

Second step: classify according to node transmission frequency.Because the magnitude of traffic flow is continuous, so also will consider the transmission frequency of last classification cycle node when node transmission frequency is classified.By all nodes, the transmission times in the classification cycle is designated as data set D to be sorted to this agreement; Set E _irepresent the transmission times of the i node in this classification cycle; E ' _irepresent the last corresponding transmission times of classification cycle of i node; μ _ithe factor is adjusted in representative, and it is E ' _ibe multiplied by weights with the ratio of each cycle transmission times mean value before, this agreement is set as 0.5 again; The transmission times N of each node _ias shown in the formula:

$N_i=(E_i,{\mathrm{\&mu;}}_i\&CenterDot;E_i^{\&prime;}),{\mathrm{\&mu;}}_i=\frac{n\&CenterDot;E_i^{\&prime;}}{\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}{E}_j}*0.5,n=\mathrm{0,1},...,t$

Concrete steps are as follows:

(1): obtain the maximum E in data set D to be sorted _maxwith minimum value E _min, and calculate E _maxcorresponding vector value N _maxand E _mincorresponding vector value N _min.

(2): the vector value N that obtains all node transmission times _i.

(3): calculate N _iwith N _maxand N _minthe vectorial Euclidean distance d of two _imaxand d _imin.

(4): compare d _imaxwith d _iminif, d _imax>d _imin, N _ibelong to high transmission frequency H ₂class.If d _imax<d _imin, N _ibelong to low transmission frequency L ₂class.If d _imax=d _imin, N _ibelong to the class of current negligible amounts in two classifications.

The 3rd step: in agreement provided by the invention, node can be divided into two classes according to this algorithm.It is H that the node that transmission times is many is established its priority ₂, the node priority that transmission times is few is L ₂.Itself and data type priority are before combined, can obtain six priority levels, that is: H ₁h ₂, M ₁h ₂, H ₁l ₂, M ₁l ₂, L ₁h ₂, L ₁l ₂.For sake of clarity, they are corresponded to from P ₁to P ₆six priority class.

The 4th step: priority is packaged into priority command frame.

The 5th step: judge whether to send beacon frame.If send, send immediately priority command frame.If do not send beacon frame, after priority command frame being inserted into the position that sends beacon frame in buffer queue, wait is sent.

In addition, in the present invention's design, for node channel allocation aspect, provide channel dispatch strategy.Because viaduct periphery has a lot of office buildings and residential building, the channel that the local channel of the IEEE802.11 agreement that the Wireless Communication Equipment in these buildings is used and this agreement are used has overlapping.Use the general power of the network equipment of 802.11 agreements larger, can cause the local channel of this agreement to disturb.The channel distribution of MPMC-MAC agreement is copied the channel distribution method of IEEE802.15.4 standard, has 16 channels in 2.4G frequency range, concrete distribution as shown in Figure 3.In order to guarantee the real-time arrival of high-priority data, according to node priority, carry out channel allocation herein.Channel is divided into four set by channel number, is shown below:

C ₁＝{CH _x|x∈N}，x＝{x|11≤x≤24}-{16,20}

C ₂＝{CH _y|y∈N}，y＝{y|11≤y≤24}

C ₃＝{CH _z|z∈N}，z＝{z|11≤z≤26}

C4＝{CH _p|p∈N}，p＝{16,20,25,26}

C ₁the channel of set is all to have with IEEE802.11 agreement the channel overlapping, and the possibility that produces channel confliction in interference range is relatively large.C ₄the channel of set is not to be subject to the channel that other agreements are disturbed, and is difficult for producing conflict.The specific implementation step of channel dispatch strategy is as follows:

The first step: node monitor channel.

Second step: the information of having judged whether sends to node.If no, returning to the first step continues to monitor.If have, judge information type.

The 3rd step: if node reception is general data information, deposited in reception buffer queue.If priority command frame, extracts precedence information.

The 4th step: if there is P ₅, P ₆the node request of priority is in the communication of scheduling access phase, from C ₁in set, with meaning it, distribute an initial channel.If there is P ₃, P ₄the node request of priority is in the communication of scheduling access phase, from C ₂in set, with meaning it, distribute an initial channel.If there is P ₁, P ₂the node request of priority is in the communication of scheduling access phase, from C ₃in set, be an initial channel of its distribution at random.The node of high priority has higher probability to communicate by letter on the measured channel of matter like this, and the initial channel with lowest priority node can only be general channel.They jump at random next channel of distribute of set after communication once, then continue communication.

The 5th step: judge whether information sends successfully.If success, according to the time of origin of perception events, dynamic knot modification activity periods and sleep cycle duration, the real-time of assurance perception information; If failure, retransmits.

The 6th step: determine variable α _m.In order to guarantee the reasonable utilization of retransfer channel, the present invention has used the retransfer channel distribution method based on priority.Be provided with in the method a variable α _m, α _mthe priority P that represents node m _mwith its dump energy E _leftthe ratio of long-pending and number of retransmissions S, be shown below:

${\mathrm{\&alpha;}}_m=\frac{P_m\&CenterDot;E_{\mathrm{left}}}{S}$

The 7th step: according to α _mselective channel set, therefrom selects retransfer channel.Work as α _m>=1 o'clock, this node obtained good channel not enough, random selective channel in the original channel set distributing still when retransmit next time.Work as α _mduring < 1, this node can the good channel of behaviour in service, at random from C ₄in set, select a channel to retransmit.If node is at C ₄the channel of set retransmits still failed, abandons this bag.

The step of the activity periods of described dynamic knot modification and the duration of sleep cycle is specially:

The first step: determine parameters exact value in this work period, as T _activerepresent the duration of activity periods, T' _activethe duration of the activity periods of representative within the next work period.Parameter M _totaland M _currentmessage queue total capacity and queue current residual amount in their difference representation node internal memories.In addition, in this agreement, also set two variable T _limitwith Δ t, when initial, T _limit=0.4T _active, Δ t=0.1T _active;

Second step: find in this work period the time point of the perception events E finally occurring;

The 3rd step: the time point of perception events and set parameter are compared;

The 4th step: if 1. time point is at T _limitwithin, at T _limitdo not have perception events to occur outward; Be described the morning that perception events occurs, and the data of generation are also less.The duration that can reduce activity periods in the upper work period to be once to save energy, concrete adjust as shown in the formula:

$T_{\mathrm{active}}^{\&prime;}=T_{\mathrm{active}}-\frac{M_{\mathrm{current}}}{M_{\mathrm{total}}}\&CenterDot;T_{\mathrm{limit}}$

If 2. time point is at T _limitoutside, within Δ t, not illustrating that perception events is just in time in activity periods, the work period is constant next time;

If 3. time point is within Δ t, illustrate that activity periods may be not enough.Likely can miss some perception events, need to extend the activity periods duration in this cycle and next work period.The duration of this activity periods, the activity periods duration of next cycle and the Δ t of next cycle adjust as shown in the formula:

T _active＝T _active+Δt

$T_{\mathrm{active}}^{\&prime;}=T_{\mathrm{active}}+(1+\frac{M_{\mathrm{total}}-M_{\mathrm{current}}}{M_{\mathrm{total}}})\&CenterDot;\mathrm{\&Delta;t}$

$\mathrm{\&Delta;t}=\left(\frac{T_{\mathrm{active}}-T_{\mathrm{limit}}}{T_{\mathrm{active}}}\right)\&CenterDot;\frac{M_{\mathrm{current}}}{M_{\mathrm{total}}}\&CenterDot;T_{\mathrm{limit}}.$

Claims (2)

1. a wireless sensor network MAC transmission method that is applied to bridge monitoring, is characterized in that: comprise the steps:

(1), when data communication, adopt priority distribute data; Implementation step is as follows:

The first step: carry out Data classification according to the entrained sensor type of node, different data are divided three classes; The temperature data recording with the node of temperature sensor, the lower L that is made as of its urgency level ₁; The bridge recording with the node of acceleration transducer is to vibration frequency data, and its priority is made as M ₁; The bridge key point displacement data recording with the node of displacement transducer, its priority is made as H ₁; Generate three class data priorities;

Second step: according to node transmission frequency, node is divided into two classes; Adopt a kind of improved minimum distance classification algorithm; This sorting algorithm is directly found out maximum and the minimum value of node transmission times, the basic point using them as classification; By node transmission times in the classification cycle, be divided into high priority H ₂, low priority is made as L ₂, generated two quefrency priority;

The 3rd step: in conjunction with data type priority and frequency priority, can obtain six priority levels, that is: H ₁h ₂, M ₁h ₂, H ₁l ₂, M ₁l ₂, L ₁h ₂, L ₁l ₂; They are corresponded to P from high to low successively ₁to P ₆six priority class.

The 4th step: the priority of each node is packaged into priority command frame; Priority command frame is sent after sending beacon frame by aggregation node;

The 5th step: node is received the priority command frame of oneself is used this priority in this classification cycle;

(2) when channel allocation, adopt New Data Channel Scheduling Algorithms, its key step is as follows:

The first step: the priority that each node sends according to aggregation node judges own operable channel set; Second step: node is random in spendable channel set selects a channel to communicate; This time the both sides of communication are by approximately establishing a capital on this channel and communicate by letter in advance;

The 3rd step: if this time communicate by letter successfully, the channel of communication next time is still selected at random in this set; And the duration of knot modification activity periods and sleep cycle at this moment, guarantee the real-time of perception information;

The 4th step: when transmission data are unsuccessful, data are retransmitted.During re-transmission, channel is reallocated; Be provided with a variable α _m, α _mthe priority P that represents node m _mwith its dump energy E _leftthe ratio of long-pending and number of retransmissions S; Work as α _m>=1 o'clock, this node obtained good channel not enough, random selective channel in the original channel set distributing still when retransmit next time; Work as α _mduring < 1, this node can the good channel of behaviour in service, from good channel set, selects at random a channel to retransmit;

The 5th step: if node is still failed in channel set re-transmission preferably, abandon retransmitting; Communicate by letter next time.

2. a kind of wireless sensor network MAC transmission method that is applied to bridge monitoring according to claim 1, is characterized in that: the step of the activity periods of described dynamic knot modification and the duration of sleep cycle is specially:

The first step: determine parameters exact value in this work period, as T _activerepresent the duration of activity periods, T' _activethe duration of the activity periods of representative within the next work period.Parameter M _totaland M _currentmessage queue total capacity and queue current residual amount in their difference representation node internal memories.In addition, in this agreement, also set two variable T _limitwith Δ t, when initial, T _limit=0.4T _active, Δ t=0.1T _active;

Second step: find in this work period the time point of the perception events E finally occurring;

The 3rd step: the time point of perception events and set parameter are compared;

The 4th step: if 1. time point is at T _limitwithin, at T _limitdo not have perception events to occur outward; Be described the morning that perception events occurs, and the data of generation are also less.The duration that can reduce activity periods in the upper work period to be once to save energy, concrete adjust as shown in the formula:

$T_{\mathrm{active}}^{\&prime;}=T_{\mathrm{active}}-\frac{M_{\mathrm{current}}}{M_{\mathrm{total}}}\&CenterDot;T_{\mathrm{limit}}$

If 2. time point is at T _limitoutside, within Δ t, not illustrating that perception events is just in time in activity periods, the work period is constant next time;

If 3. time point is within Δ t, illustrate that activity periods may be not enough.Likely can miss some perception events, need to extend the activity periods duration in this cycle and next work period.The duration of this activity periods, the activity periods duration of next cycle and the Δ t of next cycle adjust as shown in the formula:

T _active＝T _active+Δt

$T_{\mathrm{active}}^{\&prime;}=T_{\mathrm{active}}+(1+\frac{M_{\mathrm{total}}-M_{\mathrm{current}}}{M_{\mathrm{total}}})\&CenterDot;\mathrm{\&Delta;t}$

$\mathrm{\&Delta;t}=\left(\frac{T_{\mathrm{active}}-T_{\mathrm{limit}}}{T_{\mathrm{active}}}\right)\&CenterDot;\frac{M_{\mathrm{current}}}{M_{\mathrm{total}}}\&CenterDot;T_{\mathrm{limit}}.$