CN101282335A - Method for snooping and sleeping low-load wireless sensor network MAC layer - Google Patents

Abstract

The present invention discloses a low load wireless sensor network MAC layer monitoring and resenting method comprising synchronous scheduling list phase of establishing node and node normal work phase of adopting EmMAC work mechanism; the node starts the radio frequency to detect channel in the normal work phase when arouses the timer to trigger, if the transmitting node is to transmit the data, so the transmitting node must waken before the EmMAC period; the EmMAC work mechanism divides the MAC layer into CSMA delamination and EmMAC delamination; the present invention uses synchronous sleep arousing mechanism, short preamble packet, fake preamble domain mechanism and two stage channel carrier to monitor through the whole network node so as to reduce the free time of the node and increase the sleep time; synchronously, the scheduling list only records the left time domain of the node and leads all kinds of low consumption technologies such as collision avoidance, overtime work, overhearing avoidance and so on when receives the data so as to greatly improve the energy saving ration of the present invention and achieve the design object of ultra-low-power.

Description

The low-load wireless sensor network MAC layer dormancy monitoring method

Technical field:

The present invention relates to a kind of low-load wireless sensor network MAC layer dormancy monitoring method.

Background technology:

The low-load wireless sensor network technology has rapid networking, flexible, and is not subjected to the advantage of cable network constraint, and it can be applicable to fields such as urgent search, disaster relief, environmental monitoring, is with a wide range of applications.But, the energy consumption problem is but limiting the development of low-load wireless sensor network technology always, how to save the node power consumption, particularly improves the energy utilization efficiency of MAC layer, thereby prolong the life span of network, be the key issue in the wireless sensor network practical application always.Since radio not only under transmission and receiving mode consumed energy maximum, and under idle pulley, also make and move costliness because of the more energy of consumption rate.Therefore, the main direction of studying of most of existing low-power consumption MAC agreements is switches of managing radio radio frequency how accurately, makes radio be in sleep state as far as possible, thereby saves energy.

At present, efficient generally all is competitive agreement than higher low-power consumption agreement, and one of them is to use the agreement of channel sample, is representative with the LPL agreement; Another one then is to use the agreement of time scheduling, is representative with the S-MAC agreement.

The basic thought of LPL agreement is: by the length that increases preamble field recipient's cost is transferred to the sender.The recipient is the open wireless electricity periodically, thereby data on the horizon are sampled, and whether the detection introduction possesses or exist, if detect an introduction, it can be monitored up to the beginning label arrival always and receive data again; If do not detect introduction, radio will be closed once more up to sampling next time.The weak point of LPL agreement is: 1, transmit leg needs the multiple preamble field also slightly longer than the LPL cycle of sending, and therefore will expend the more energy; 2, it can not merge cross-talk and some power-saving technologies such as avoids.Because above-mentioned two defectives, so the LPL agreement can only be controlled at energy consumption in the scope, can not finish the important task of super low-power consumption.

Another kind of agreement is that the main thought of S-MAC (Schedules MAC) agreement is by making node periodically monitor and sleep and reduce listening period, making the operation of radio frequency low duty ratio, thereby reach purpose of energy saving.After waking up and come, when channel idle, adopt node RTS/CTS/DATA/ACK mechanism to communicate flow process; Each node is broadcasted the schedule information of oneself to neighbours, neighbor node with identical scheduling will form a virtual cluster, and the boundary node between several bunches will write down two or more scheduling, dispatch list that has write down the schedule information of each neighbor node of each node maintenance of while, periodic their scheduling of renewal mutually is to prevent long clock drift.The weak point of S-MAC agreement is: 1, because sleep work duty cycle is subjected to the restriction of various aspects, so it can not reach the requirement of super low-power consumption; 2, the consumption imbalance of energy between node.

As further optimization and improvement that the LPL agreement is carried out, though WiseMAC agreement and SP agreement can be used very short preamble field in sending part divided data bag, save the energy of transmit leg greatly, but, because not only there is the clock drift problem in it, and invalid to broadcast packet, so the energy-efficient performance of the improvement of its suitable degree in the bursty data environment is than higher, and quite different in other environment, still be difficult to reach the requirement of super low-power consumption.

In addition, LPL, follow-on WiseMAC, all before proposing, the 802.15.4 standard formulates with agreement such as S-MAC, popular at that time radio frequency chip is the CC1000 of chipcon company, these classical agreements also fail to go up realization at the radio frequency chip (as CC2420, CC2430 etc.) of supporting the 802.15.4 standard.The CC2420 chip is the radio frequency chip of bag level, microcontroller can not obtain the visit of byte level, thereby it is influential to time synchronized, can not be as the CC1000 radio frequency chip that belongs to byte control, thereby node if find the destination address receive be not oneself just can close the data packet byte that radio frequency does not receive the back, finish cross-talk effectively with this and avoid.Simultaneously, because the radio frequency transmission rate of CC2420 is than CC1000 height, therefore concerning agreement, the accessible time, still less in order to deal with burst data, it is more effective that agreement must design.

Summary of the invention:

The technical problem to be solved in the present invention is that a kind of low-load wireless sensor network MAC layer dormancy monitoring method of super low-power consumption is provided.

Technical solution of the present invention is, a kind of low-load wireless sensor network MAC layer dormancy monitoring method with following content is provided: it comprises that following two stages are that new node is set up isochronous schedules table stage and node normal work stage in advance: described new node is set up the isochronous schedules table in advance and is referred to, the node that adds this network after first node of wireless sensor network reaches all need be provided with an emission timer and a synchronized wake-up timer, the cycle of described emission timer and synchronized wake-up timer is the EmMAC cycle, the triggered time of described emission timer needs than synchronized wake-up timer time in advance, and the similar trigger triggered time of all nodes is identical in the network, preamble field in this phase transmission node emission is pseudo-long preambles territory, and the length in described pseudo-long preambles territory slightly is longer than the EmMAC cycle; Described node normal work stage refers to that node property synchronizing cycle of the whole network is waken up, so that receive data or change sleep over to, and finishes the transmission data and keeps all node synchronizing functions; What described node normal work stage adopted is EmMAC working mechanism; Described EmMAC working mechanism refers to synchronized model MAC mechanism, it comprise the CSMA layering that can finish basic transmitting-receiving packet function and can finish synchronously, EmMAC layering that incidentally function and supporting produces preamble packet mechanism and bottom channel monitoring, retransmission mechanism; Described CSMA layering comprises the CSMA agreement of finishing channel-monitoring and finishes conflict is avoided, timeout treatment and cross-talk are avoided function RTS/CTS mechanism and ripe wireless technology such as NAV mechanism; Described node uses short preamble field when operate as normal; The length of described short preamble field is omited the channel-monitoring time long and that cover receiving node than listening period.

After adopting above step and content, compared with prior art, the present invention has the following advantages:

1, the node periodic synchronous is waken up and is slept, and transmitting node adopts short preamble field when operate as normal:

The present invention utilizes the MAC head definition of 802.15.4, propose and realized pseudo-long preambles territory, and set up the isochronous schedules table in advance by new node, thereby property synchronizing cycle that realizes the whole network node is waken up and is slept, in other words, the receiving node that the free of data bag will send in the whole network when waking up as long as do not receive short preamble field and then transfer sleep immediately to, thereby reduced the idle listening period of node, increased the length of one's sleep of node.Simultaneously, what transmitting node used when operate as normal is short preamble field, this weak point preamble field is less than 16 bytes, default value is 4 bytes, can generate automatically by the CC2420 radio frequency, the energy of receiving node has not only been saved in the employing of above measure, has saved the energy of transmitting node again, has reached the purpose of super low-power consumption of the present invention;

2, propose and realize EmMAC working mechanism and dual mode maintain synchronization:

Propose and realized that EmMAC working mechanism is the EmMAC agreement in the node normal work stage among the present invention, EmMAC mechanism makes the MAC layer comprise EmMAC layering and CSMA layering, and two layerings make mechanism structure clear.Because the definition of the MAC layer packet header type field that is proposed, make the EmMAC layering can finish synchronously and function incidentally, thereby utilize special-purpose sync packet and utilize incidentally this dual mode of broadcast packet to carry out synchronous maintenance, in other words, it can make node regularly send sync packet and correct clock drift to reach the synchronous requirement of all node times in the network, and incidentally function be meant sending node in broadcast data packet incidentally with sync packet in the same schedule information, effectively reduced the transmission number of times of sync packet, thereby reduced the energy expense that sends controlling packet, reached the requirement of super low-power consumption.

3, various Low-power Technology have been merged in EmMAC working mechanism inside:

The CSMA layering comprises the CSMA agreement of finishing channel-monitoring and finishes RTS/CTS mechanism and the NAV mechanism that conflict is avoided, timeout treatment and cross-talk are avoided function; As long as RTS/CTS mechanism makes receiving node receive short preamble field and RTS bag, just can distinguish the address, and make corresponding filtration treatment, guaranteed that non-receiving node in time enters sleep; And the employing of NAV mechanism is NVA virtual carrier monitoring technique, node only need be broadcasted the dispatch list of oneself, does not have boundary node and virtual cluster, does not need the dispatch list of maintenance of neighbor node, therefore make the present invention well finish conflict and avoid, timeout treatment and cross-talk such as avoid at function.

In sum, the present invention saves the energy expense in MAC layer data receiving course and the process of transmitting, reduce the conflict probability of happening, improve the usefulness of node competition, make the free time of node greatly reduce, greatly increase the length of one's sleep, saved huge control and maintenance costs, save the node more resources, finally reached super low-power consumption design object of the present invention.

Above-mentioned new node is set up the isochronous schedules table stage in advance and is comprised passive sub, sub and finish sub initiatively;

The step of above-mentioned passive sub is as follows:

Step a: node is opened radio frequency always, and EmMAC cycle of passive wait is so that can receive the sync packet that neighbor node sends;

Step b: if receive sync packet during this period, set up dispatch list according to the information of sync packet so, enter behind the dispatch list of broadcasting oneself then and finish sub; If never receive sync packet then node changes initiatively sub over to;

The step of above-mentioned active sub is as follows:

Step a: send the pseudo-long preambles territory that a time span slightly is longer than the EmMAC cycle earlier, and then a request of broadcast transmission sync packet, and wait for a set time;

Step b: if during this period of time receive sync packet, then the information according to sync packet is provided with dispatch list, enters behind the dispatch list of broadcasting oneself then and finishes sub, if during this period of time do not receive sync packet, send the request sync packet once more, repeating step b.

Step c: when the quantity that sends the request sync packet reaches a threshold value, just think that the whole network node all do not set up dispatch list, thereby use the schedule information that presets that dispatch list is set; Just do not received sync packet if reach threshold value, then set up dispatch list, the dispatch list of back broadcasting oneself has been set successfully, and entered and finish sub according to the information of sync packet;

The above-mentioned sub of finishing refers to that each node has set an emission timer and a synchronized wake-up timer synchronous with the whole network, set up dispatch list, and broadcasted oneself dispatch list to neighbor node, enter normal EmMAC working mechanism, but the node operate as normal.

As a kind of improvement of the present invention, described pseudo-long preambles territory refers to that preamble field is to be formed by a plurality of packet combinations, and the length of preamble field must be slightly longer than the EmMAC cycle; The implementation method that adopts is in advance a preamble packet to be packed in the buffering area of CC2420 radio frequency chip, just constantly sends order to CC2420 then and sends same preamble packet, rather than reload new bag; In the DSN field of the MAC head that in 802.15.4, defines, actual be used have only 7bit, its highest order is not used; The highest order of described DSN is to represent that this bag was preamble packet at 1 o'clock; The highest order of described DSN is to represent that this bag was the general data bag at 0 o'clock.Described pseudo-long preambles territory is formed by a plurality of packet combinations can solve the problem that CC2420 radio frequency chip preamble field is restricted to the longest 16 bytes; And the buffering that in advance data is packaged into the CC2420 radio frequency chip is in order to reduce the time that packet is written into, and carries required energy thereby further save because of packet.In addition, the present invention can utilize the highest order of DSN to identify the bag type, if promptly the highest order of DSN is 1, represents that then this bag is a preamble packet, is that 0 expression is the general data bag.

As another kind of improvement the of the present invention, the form of described sync packet and request sync packet is:

MAC layer packet header

Territory remaining time (2byte)

CRC(2byte)

RTS bag in the described RTS/CTS mechanism and CTS bag also have territory remaining time of two bytes.Territory remaining time of sync packet, request sync packet, RTS bag and subsidiary two bytes of CTS bag can be used to refer to the time that node also needs busy channel, promptly can handle broadcast packet as sync packet simultaneously thereby better finish incidentally function, further save power consumption of the present invention.

The type field in above-mentioned MAC layer packet header is divided into two sections, the bag type of the high 4bit sign CSMA layering of type field, the bag type of the low 4bit sign EmMAC layering of type field.

The step that above-mentioned node normal phase sends data is:

Step a, emission timer trigger, if there are data to send, change step b; Otherwise, transfer accepting state to Deng waking the timer triggering synchronously up;

Step b: open radio frequency, beginning is the channel carrier sense of 1～8 stochastical sampling window for the first time; If the passage free time is changeed step c, otherwise change steps d;

Step c: send preamble packet, and carry out the channel carrier sense of 8～24 stochastical sampling windows for the second time, if the passage free time, commentaries on classics step e, otherwise change steps d;

Steps d: close radio frequency, enter sleep and wait for repeating transmission;

Step e: send packet;

Step f, transmission finish, and send the data success to network layer or application layer report;

The above-mentioned step of stating node normal phase reception data is:

Step a:, then enter transmit status if the emission timer has data to send when triggering; When if the free of data bag sends, then the wake-up waiting time triggers to back synchronized wake-up timer, and starting radio frequency, to begin sampling window be 1 channel monitoring; If the channel sky closes, then close radio frequency and enter sleep; If channel busy is then changeed step b;

Step b: wait for that receiving preamble packet finishes; If wait for that the reception preamble packet is overtime, then close radio frequency and enter sleep; If it is not overtime that preamble packet receives when finishing, then change step c;

Step c: receive packet, and to its processing of classifying.If receive packet, then notify the upper strata, and close radio frequency and enter sleep; If what receive is broadcast packet or sync packet, then utilize synchronizing information corrigendum dispatch list, close radio frequency then, enter sleep.

Description of drawings:

Fig. 1 is that low-load wireless sensor network starts triphasic flow chart

Fig. 2 is the pseudo-long preambles of an EmMAC mechanism territory work schematic diagram.

Fig. 3 is a MAC rough schematic of 802.15.4 agreement regulation

Fig. 4 is an EmMAC mechanism structure sketch.

Fig. 5 is the MAC package head format of EmMAC module.

Fig. 6 is an EmMAC mechanism works schematic diagram.

Fig. 7 is EmMAC transmission flow figure.

Fig. 8 is that EmMAC receives flow chart.

Specific embodiment:

The invention will be further described below in conjunction with the drawings and specific embodiments:

The present invention realizes on the hardware platform of MSP430+CC2420, operating frequency is 4MHz, and low-load wireless sensor network MAC layer dormancy monitoring method of the present invention at first will make new node set up the isochronous schedules table in the specific implementation in wireless sensor network, described isochronous schedules table refers to sync packet, incidentally wrap, territory remaining time of packet and its ACK bag, the time of i.e. next one sleep, its meaning is to inform that neighbor node also needs busy channel how long promptly to be equivalent to preengage the whole message of channel and sends the needed time, and each receiving node is being received sync packet or incidentally will adjust the correlation of two wake-up timer of oneself according to this thresholding rapidly behind the bag that it is synchronous to reach each node with the method.In the present invention, new node is set up the isochronous schedules table in advance and is referred in the described wireless sensor network, the node that adds this network after first node of wireless sensor network reaches all is provided with an emission timer and a synchronized wake-up timer, and the cycle of described emission timer and synchronized wake-up timer is the EmMAC cycle, the triggered time of described emission timer needs than synchronized wake-up timer time in advance, and the similar trigger triggered time of interior all nodes of network is identical; As shown in Figure 2, set up node isochronous schedules table in the stage at wireless sensor network, the preamble field of transmitting node emission is pseudo-long preambles territory, that is to say that transmitting node uses " pseudo-long preambles territory " to replace the function in long preambles territory, the long preambles territory is not to be generated automatically by the CC2420 radio frequency chip, but combine by a plurality of preamble packet, and in fact preamble packet is exactly packet, so the long preambles territory is called pseudo-long preambles territory, the implementation method that adopt in pseudo-long preambles territory is in advance a preamble packet to be packed in the buffering area of CC2420 radio frequency chip, just constantly send order then and send same preamble packet, rather than reload new bag to CC2420; In the DSN field of the MAC head that in 802.15.4, defines, actual be used have only 7bit, its highest order is not used, therefore this specific embodiment utilizes this bit-identify bag type, if promptly the highest order of DSN is 1, represent that then this bag is a preamble packet, be that 0 expression is the general data bag.Set up in advance in the isochronous schedules table stage at new node, because each neighbor node might be at each section monitor channel of waking up in the time, can receive preamble field and receive the packet of preamble field back in order to guarantee neighbor node, the preamble field length of transmitting node must be that cycle of described emission timer and synchronized wake-up timer is slightly long than the EmMAC cycle, therefore, in this specific embodiment, the time that the length in the pseudo-long preambles of the present invention territory is set to cover 512ms, the time of 512ms described here refers to the EmMAC cycle; According to the length in pseudo-long preambles territory, the MAC layer can calculate the number of preamble packet.

New node is set up the isochronous schedules table stage in advance and is comprised passive sub, sub and finish sub initiatively among the present invention; The step of described passive sub is as follows:

Step a: node is opened radio frequency always, and EmMAC cycle of passive wait is so that can receive the sync packet that neighbor node sends;

Step b: if receive sync packet during this period, set up dispatch list according to the information of sync packet so, enter behind the dispatch list of broadcasting oneself then and finish sub; If never receive sync packet then node changes initiatively sub over to.

In this specific embodiment, because before wireless sensor network is set up first node isochronous schedules table, the node that wireless sensor network has not also been set up dispatch list is that node is not received sync packet, so the present invention's node when implementing enters initiatively sub by passive sub, as shown in Figure 1, the step of described active sub is as follows:

Step a: send the pseudo-long preambles territory that a time span slightly is longer than the EmMAC cycle earlier, and then a request of broadcast transmission sync packet, and wait for a set time;

Step b: if during this period of time receive sync packet, then the information according to sync packet is provided with dispatch list, enters behind the dispatch list of broadcasting oneself then and finishes sub, if during this period of time do not receive sync packet, send the request sync packet once more, repeating step b;

Step c: when the quantity that sends the request sync packet reaches a threshold value, just think that the whole network node all do not set up dispatch list, thereby use the schedule information that presets that dispatch list is set; Just do not received sync packet if reach threshold value, then set up dispatch list, the dispatch list of back broadcasting oneself has been set successfully, and entered and finish sub according to the information of sync packet.

In the present invention, the described sub of finishing refers to that each node has set an emission timer and a synchronized wake-up timer synchronous with the whole network, has set up dispatch list, and has broadcasted the dispatch list of oneself to neighbor node, enter normal EmMAC working mechanism, but the node operate as normal.

In this specific embodiment, what node adopted in normal work stage among the present invention is EmMAC working mechanism, EmMAC working mechanism is the title that the applicant defines, its Chinese meaning is synchronized model MAC mechanism, as shown in Figure 4, this mechanism is divided into CSMA layering and EmMAC layering with the MAC layer, and basic transmitting-receiving packet function is finished in the CSMA layering, comprise by the CSMA agreement and finish channel-monitoring, by RTS/CTS mechanism and NAV mechanism finish conflict avoid, timeout treatment and cross-talk avoid function.EmMAC layering utilization EmMAC agreement is finished synchronously, function incidentally, and supports to produce preamble packet mechanism and bottom channel monitoring, retransmission mechanism.

As shown in Figure 5, in order to keep CSMA module and the EmMAC module independence when the pack processing, present embodiment is divided into two sections with the type field in MAC layer packet header, and the high 4bit of type field is used to represent the bag type of CSMA module, and the low 4bit of the type field is used for the bag type of EmMAC layering.As shown in Figure 3, it is the preamble field bag that the highest order of the DSN in present embodiment EmMAC module MAC packet header is set to 1 this bag of expression, constantly repeat to send that preamble packet at first then, up to sending required preamble packet number, then send out the synchronization request bag, determine that still all nodes all do not have scheduling, then dispatch list is set with the schedule information 512ms that presets, as shown in Figure 3, what simultaneously the highest order setting of the DSN field in EmMAC module MAC packet header is designated that preamble packet is set to promptly that 0 expression sends out is normal packet, and the dispatch list of broadcasting oneself.Next second node adds network, then can receive the sync packet of first node by above-mentioned passive sub, and according to the scheduling tabular value of first node the dispatch list of oneself is set.

In this specific embodiment, as shown in Figure 6, black rectangle represents that the synchronized wake-up timer triggers the channel-monitoring period after node is waken up, and what described transmitting node used when operate as normal is short preamble field; The length of described short preamble field is omited the channel-monitoring time long and that cover receiving node than listening period, thereby guarantees that receiving node can monitor the channel busy state, and receives the packet of preamble field back.As shown in Figure 6, sending node must be waken up and handle and finish being written into of channel carrier sense for the first time and preamble packet before the triggering of synchronized wake-up timer and beginning Channel Detection of neighbor node in advance if will send data.Present embodiment is provided with a synchronized wake-up timer and an emission timer for by the way each node, joins wireless sensor network after setting up good oneself dispatch list.Node is slept in a period of time simultaneously, closes its radio in sleep.Regularly trigger second every 512ms, wake node up and open the radio frequency monitor channel, all nodes are got identical sleep and wakeup time.

As shown in Figure 7, EmMAC of the present invention working mechanism is defined in an EmMAC and only sends a bag in the cycle, and the passage free time is confirmed in carrier sense for the first time, then calls physical layer interface, begins to send preamble packet.Battery has fired begins to carry out the channel carrier sense second time.If the passage free time, then begin to send data block; If passage is busy, then wait for the next round repeating transmission.If it is busy that passage is confirmed in the carrier sense first time, then close radio frequency, entering sleep and waiting for repeating transmission.Have only the node of the success of carrier sense for the first time just can enter carrier sense for the second time.

As shown in Figure 7, the step of node normal phase transmission data of the present invention is:

Step a, emission timer trigger, if there are data to send, change step b; Otherwise, transfer accepting state to Deng waking the timer triggering synchronously up;

Step b: open radio frequency, beginning is the channel carrier sense of 1～8 stochastical sampling window for the first time; If the passage free time is changeed step c, otherwise change steps d;

Step c: send preamble packet, and carry out the channel carrier sense of 8～24 stochastical sampling windows for the second time, if the passage free time, commentaries on classics step e, otherwise change steps d;

Steps d: close radio frequency, enter sleep and wait for repeating transmission;

Step e: send packet;

Step f, transmission finish, and send the data success to network layer or application layer report.

As shown in Figure 9, the step of node normal phase reception data of the present invention is:

Step a:, then enter transmit status if the emission timer has data to send when triggering; If the free of data bag sends, then the wake-up waiting time triggers to back synchronized wake-up timer, and starting radio frequency, to begin sampling window be 1 channel monitoring; If the channel sky closes, then close radio frequency and enter sleep; If channel busy is then changeed step b;

Step b: wait for that receiving preamble packet finishes; If wait for that the reception preamble packet is overtime, then close radio frequency and enter sleep; If it is not overtime that preamble packet receives when finishing, then change step c;

Step c: receive packet, and to its processing of classifying.If receive packet, then notify the upper strata, and close radio frequency and enter sleep; If what receive is broadcast packet or sync packet, then utilize synchronizing information corrigendum dispatch list, close radio frequency then, enter sleep.

And in this specific embodiment, the transmission flow of described node is: the emission timer triggers, and sends because of data are arranged, and opens radio frequency, and beginning is the channel carrier sense of 1～8 stochastical sampling window for the first time, may have 3 kinds of situations during monitoring.Situation is 1.: passage is busy, closes radio frequency, entering sleep and waiting for and retransmitting.Situation is 2.: the passage free time, send preamble field, and its length is slightly longer than listening period, carry out the channel carrier sense of 8～24 stochastical sampling windows for the second time after sending, record the passage free time again, then send packet, send and finish, send the data success to network layer or application layer report; Situation is 3.: it is busy to record passage in the second time in the channel carrier sense, closes radio frequency, entering sleep and waiting for and retransmitting.

In this specific embodiment, the reception flow process of described node is: the emission timer triggers, and the free of data bag sends, and the node wake-up waiting time triggers to back synchronized wake-up timer, and to begin sampling window be 1 channel monitoring to automated radio frequency then; May there be 3 kinds of situations during monitoring.Situation is 1.: the channel sky closes, and closes radio frequency, enters sleep; Situation is 2.: channel busy receives preamble packet.Time of reception does not surpass 8ms, then receives packet.If what receive is the clear data bag, the notice upper strata is closed radio frequency and is entered sleep after then receiving; If what receive is broadcast packet or sync packet, then utilize synchronizing information corrigendum dispatch list, close radio frequency then and enter sleep.Situation is 3.: the time of reception of preamble packet surpasses 8ms, closes radio frequency and enters sleep.

As shown in Figure 5, the high 4bit of MAC layer packet header type field is used for representing the bag type of CSMA layering in this process, the low 4bit of type field is used to represent the bag type of EmMAC layer, the present invention by the broadcast transmission special use sync packet or utilize broadcast packet incidentally remove clock drift, because of type field identification of broadcast bag, needn't be that 0xFFFF points out it is broadcast packet with destination address again, and destination address is 2 bytes just, the same with the schedule information word length, just in time be used as this node territory remaining time, finish incidentally function, promptly can handle broadcast packet as sync packet simultaneously.

Sync packet form in this specific embodiment is:

02H

Keep (1byte)

Source address (2byte)

Destination address (2byte)

00AAH

CRC (2byte)

Wherein 00AAH is thresholding remaining time.

In this concrete enforcement, the broadcast packet incidentally form of synchronizing information is:

00

Keep (1byte)

Source address (2byte)

0 0AAH

DATA

CRC (2byte)

Wherein 00AAH is thresholding remaining time.

Claims (7)

1, a kind of low-load wireless sensor network MAC layer dormancy monitoring method, it comprises following two stages:

1), new node is set up the isochronous schedules table stage in advance;

2), node normal work stage;

Described new node is set up the isochronous schedules table in advance and is referred to, the node that adds this network after first node of wireless sensor network reaches all need be provided with an emission timer and a synchronized wake-up timer, the cycle of described emission timer and synchronized wake-up timer is the EmMAC cycle, the triggered time of described emission timer needs than synchronized wake-up timer time in advance, and the similar trigger triggered time of all nodes is identical in the network, preamble field in this phase transmission node emission is pseudo-long preambles territory, and the length in described pseudo-long preambles territory slightly is longer than the EmMAC cycle;

Described node normal work stage refers to that node property synchronizing cycle of the whole network is waken up, so that receive data or change sleep over to, and finishes the transmission data and keeps all node synchronizing functions;

What described node normal work stage adopted is EmMAC working mechanism; Described EmMAC working mechanism refers to synchronized model MAC mechanism, it comprise the CSMA layering that can finish basic transmitting-receiving packet function and can finish synchronously, EmMAC layering that incidentally function and supporting produces preamble packet mechanism and bottom channel monitoring, retransmission mechanism; Described CSMA layering comprises the CSMA agreement of finishing channel-monitoring and finishes RTS/CTS mechanism and the NAV mechanism that conflict is avoided, timeout treatment and cross-talk are avoided function; Described transmitting node uses short preamble field when operate as normal; The length of described short preamble field is omited the channel-monitoring time long and that cover receiving node than listening period.

2, low-load wireless sensor network MAC layer dormancy monitoring method according to claim 1 is characterized in that: described new node is set up the isochronous schedules table stage in advance and is comprised passive sub, sub and finish sub initiatively;

The step of described passive sub is as follows:

Step a: node is opened radio frequency always, and EmMAC cycle of passive wait is so that can receive the sync packet that neighbor node sends;

Step b: if receive sync packet during this period, set up dispatch list according to the information of sync packet so, enter behind the dispatch list of broadcasting oneself then and finish sub; If never receive sync packet then node changes initiatively sub over to;

The step of described active sub is as follows:

Step a: send the pseudo-long preambles territory that a time span slightly is longer than the EmMAC cycle earlier, and then a request of broadcast transmission sync packet, and wait for a set time;

Step b: if during this period of time receive sync packet, then the information according to sync packet is provided with dispatch list, enters behind the dispatch list of broadcasting oneself then and finishes sub, if during this period of time do not receive sync packet, send the request sync packet once more, repeating step b;

Step c: when the quantity that sends the request sync packet reaches a threshold value, just think that the equal end of the whole network node sets up dispatch list, thereby use the schedule information that presets that dispatch list is set; Just do not received sync packet if reach threshold value, then set up dispatch list, the dispatch list of back broadcasting oneself has been set successfully, and entered and finish sub according to the information of sync packet;

The described sub of finishing refers to that each node has set an emission timer and a synchronized wake-up timer synchronous with the whole network, set up dispatch list, and, enter normal EmMAC working mechanism, but node operate as normal to the dispatch list of neighbor node broadcasting oneself.

3, low-load wireless sensor network MAC layer dormancy monitoring method according to claim 1 and 2 is characterized in that: described pseudo-long preambles territory refers to that preamble field is formed by a plurality of packet combinations, and the length of preamble field must be slightly longer than the EmMAC cycle; The implementation method that adopts is in advance a preamble packet to be packed in the buffering area of CC2420 radio frequency chip, just constantly sends order to CC2420 then and sends same preamble packet, rather than reload new bag; In the DSN field of the MAC head that in 802.15.4, defines, actual be used have only 7bit, its highest order is not used; The highest order of described DSN is to represent that this bag was preamble packet at 1 o'clock; The highest order of described DSN is to represent that this bag was the general data bag at 0 o'clock.

4, low-load wireless sensor network MAC layer dormancy monitoring method according to claim 1 and 2 is characterized in that: the form of described sync packet and request sync packet is:

MAC layer packet headerTerritory remaining time (2byte) CRC(2byte)

RTS bag in the described RTS/CTS mechanism and CTS bag also have territory remaining time of two bytes.

5, low-load wireless sensor network MAC layer dormancy monitoring method according to claim 4, it is characterized in that: the type field in described MAC layer packet header is divided into two sections, the bag type of the high 4bit sign CSMA layering of type field, the bag type of the low 4bit sign EmMAC layering of type field.

6, low-load wireless sensor network MAC layer dormancy monitoring method according to claim 1 is characterized in that: the step that described node normal phase sends data is:

Step a, emission timer trigger, if there are data to send, change step b; Otherwise, transfer accepting state to Deng waking the timer triggering synchronously up;

Step b: open radio frequency, beginning is the channel carrier sense of 1～8 stochastical sampling window for the first time; If the passage free time is changeed step c, otherwise change steps d;

Step c: send short preamble packet, and carry out the channel carrier sense of 8～24 stochastical sampling windows for the second time, if the passage free time, commentaries on classics step e, otherwise change steps d;

Steps d: close radio frequency, enter sleep and wait for repeating transmission;

Step e: send packet;

Step f, transmission finish, and send the data success to network layer or application layer report.

7, low-load wireless sensor network MAC layer dormancy monitoring method according to claim 1 is characterized in that: the step that described node normal phase receives data is:

Step a:, then enter transmit status if the emission timer has data to send when triggering; When if the free of data bag sends, then the wake-up waiting time triggers to back synchronized wake-up timer, and starting radio frequency, to begin sampling window be 1 channel monitoring; If the channel sky closes, then close radio frequency and enter sleep; If channel busy is then changeed step b;

Step b: wait for that receiving preamble packet finishes; If wait for that the reception preamble packet is overtime, then close radio frequency and enter sleep; If it is not overtime that preamble packet receives when finishing, then change step c;

Step c: receive packet, and to its processing of classifying.If receive packet, then notify the upper strata, and close radio frequency and enter sleep; If what receive is broadcast packet or sync packet, then utilize synchronizing information corrigendum dispatch list, close radio frequency then, enter sleep.

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