CN104202803B - An energy-saving MAC protocol communication method based on wireless sensor network - Google Patents

Abstract

The present invention belongs to the field of wireless sensor network communication, and in particular, relates to an energy-saving MAC protocol communication method based on a wireless sensor network, comprising: a new node records the wake-up time offset value of a neighboring node by maintaining the wake-up schedule of the neighboring node; determining the wake-up time offset value of the new node according to the wake-up time offset value of the neighboring node; when the sending node sends data, querying the corresponding receiving node information in the wake-up schedule, and predicting the wake-up time of the receiving node. The present invention selects the offset value according to the wake-up time of the neighboring node, ensures that the nodes have different wake-up times, and can effectively reduce the energy consumption caused by idle listening and save energy by accurately predicting the wake-up time of the receiving node.

Description

An energy-saving MAC protocol communication method based on wireless sensor network

technical field

The invention relates to the field of communication, in particular to an energy-saving MAC protocol communication method based on a wireless sensor network.

Background technique

A wireless sensor network (Wireless Sensor Network, WSN) is a wireless network composed of a large number of stationary or moving sensors in a self-organizing and multi-hop manner to cooperatively perceive, collect, process and transmit the perceived objects in the geographical area covered by the network. Information.

During the use of the sensor network, some sensor nodes fail due to energy exhaustion or environmental factors, and some nodes are added to the network (new nodes) in order to make up for the failed nodes and increase the monitoring accuracy. In this way, the number of nodes in the sensor network It increases or decreases dynamically, so that the topology of the network changes dynamically accordingly.

In wireless sensor networks, the wake-up methods of nodes are as follows:

(1) Full wake-up mode: In this mode, all nodes in the wireless sensor network wake up at the same time to detect and track targets in the network. Although high tracking accuracy can be obtained in this mode, the network energy At the expense of huge consumption.

(2) Random wake-up mode: In this mode, the nodes in the wireless sensor network wake up randomly with a given wake-up probability p.

(3) The wake-up mode is selected by the prediction mechanism: in this mode, the nodes in the wireless sensor network selectively wake up the nodes that have a greater benefit to the tracking accuracy according to the needs of the tracking task, and predict the next moment of the target through the obtained information. state, and wake up the node.

(4) Task cycle wake-up mode: In this mode, the nodes in the wireless sensor network are periodically in the wake-up state. Nodes in this working mode can coexist with nodes in other working modes and assist nodes in other working modes to work .

In a wireless sensor network, the Media Access Control (MAC) protocol is at the bottom of the wireless sensor network protocol, and it is mainly used for fair and effective sharing of the communication medium between sensor nodes, which has a great impact on the performance of the sensor network. It is one of the key network protocols to ensure the effective communication of wireless sensor networks.

In the related art, based on the asynchronous MAC layer protocol initiated by the receiving end, the node maintains a fixed wake-up schedule of neighboring nodes, which brings large energy consumption during continuous idle listening, which is not conducive to energy saving.

Contents of the invention

The purpose of the present invention is to provide an energy-saving MAC protocol communication method based on a wireless sensor network to solve the above problems.

In an embodiment of the present invention, a wireless sensor network-based energy-saving MAC protocol communication method is provided, including:

The new node records the wake-up time offset value of the neighbor node by maintaining the wake-up schedule of the neighbor node;

Determine the wake-up time offset value of the new node according to the wake-up time offset value of the neighbor node, the formula is as follows:

In the formula, O _w (i) is the wake-up time offset value of the receiving node i, O _w is the wake-up time offset value of the new node, t(i, j) is the difference between the wake-up time of two nodes i and j, where i , j The wake-up time of the two nodes is within the shortest wake-up interval among all nodes;

When the sending node sends data, query the corresponding receiving node information in the wake-up schedule, and predict the wake-up time of the receiving node. The prediction formula is as follows:

t _remain (i)=T _wakeup (i)-(t _c -O _w (i))%T _wakeup (i)

In the formula, t _remain (i) is the remaining time of receiving node i’s next wake-up time, T _wakeup (i) is the wake-up interval of node i, t _c is the current time of sending node, O _w (i) is the wake-up bias of receiving node i transfer value.

Further, before the new node records the wake-up time offset value of the neighbor node by maintaining the wake-up schedule of the neighbor node, it also includes:

Continuously monitor the duration of the initial maximum wake-up interval of the node, and when receiving the beacon frame sent by the neighbor node, send an empty data frame with the wake-up status flag bit of the requesting node;

When the sending node receives an empty data frame with a flag bit, embed the wake-up interval of the node in the sent ACK frame;

The new node receives the ACK frame returned by the neighbor node during the continuous monitoring time, and maintains a wake-up schedule of the neighbor node after the monitoring ends.

Further, the method further includes: when the difference between the actual wake-up time of the receiving node and the predicted wake-up time of the sending node is greater than an error threshold, re-requesting information about the wake-up time of the receiving node.

Further, the method also includes: before the sending node sends data each time, detecting the number of data packets waiting to be transmitted in the buffer queue, calculating the level of the number of data packets waiting to be transmitted according to the number of data packets waiting to be transmitted, and adapting to the level according to the number of data packets waiting to be transmitted Change the wakeup interval of a node.

Further, according to the level of the number of data packets waiting to be transmitted, the wake-up interval of the node is adaptively changed, including:

When the level of the number of data packets waiting to be transmitted is changed compared to the previous data transmission, the flag bit and the level of the number of data packets waiting to be transmitted are embedded in the pre-sent data frame; wherein the flag bit is used to notify the receiving node The number of data packets waiting to be transmitted is embedded in the data frame, and the number of data packets waiting to be transmitted is obtained by the following formula:

In the formula, ρ _wait (i) is the level of the number of data packets that node i is waiting to transmit, N _wait (i) is the number of data packets that node i is waiting to transmit, n _threshold is the load factor of the sending node, and ρ _threshold is the load factor of the receiving node;

When the node receives the data frame with the flag bit, update the sum of the number of data packets waiting to be transmitted in the child node. When the data frame with the flag bit is not received, keep the number of data packets waiting to be transmitted unchanged; wherein, The sum of the levels of the number of data packets waiting to be transmitted in the child nodes is obtained by the following formula:

In the formula, ρ _wait is the sum of the number of data packets waiting to be transmitted in child nodes, ρ _wait (i) is the number of data packets waiting for node i to transmit, and s is the number of child nodes;

The receiving node dynamically changes the wake-up interval; the condition for dynamically changing the wake-up interval is the change of the adjustment factor, and the related formula is as follows:

In the formula, μ is the adjustment factor, ρ _wait is the sum of the number of data packets waiting to be transmitted in the child nodes, ρ _threshold is the load factor of the receiving node, T _tmp is the wake-up interval calculated by the node, T _{init_wakeup} is the initial maximum wake-up interval of the node, T _wakeup is the wakeup interval of the node, and T _min is the minimum wakeup interval of the node.

Further, the method further includes: keeping the wake-up interval unchanged when the adjustment factor does not change.

Further, the method further includes: when the sending node receives the wake-up beacon frame of the receiving node, switching to a sleep state until the next wake-up time of the receiving node and retransmitting data.

Compared with the prior art, the wireless sensor network-based energy-saving MAC protocol communication method provided by the embodiment of the present invention ensures that nodes have different wake-up times by selecting the offset value according to the wake-up time of neighboring nodes, and accurately predicts the reception The wake-up time of the node can effectively reduce the energy consumption caused by idle listening and save energy.

Description of drawings

Fig. 1 shows the flow chart of a kind of energy-saving MAC protocol communication method based on wireless sensor network of the present invention;

Fig. 2 shows a schematic diagram of the working process of a wireless sensor network-based energy-saving MAC protocol communication method of the present invention;

FIG. 3 shows a schematic diagram of an energy-saving MAC protocol communication method based on a wireless sensor network according to the present invention, and a schematic diagram of a new node joining the network initialization stage.

detailed description

The present invention will be described in further detail below through specific implementation examples and in conjunction with the accompanying drawings.

Considering that in the prior art, a node maintains a fixed wake-up schedule of neighboring nodes, which causes a large energy consumption during continuous idle listening, an embodiment of the present invention provides a HELD-MAC (High energy efficiency MAC) based on a wireless sensor network. and Low delay-Media Access Control, energy-efficient low-delay media media access control) protocol.

Referring to Figs. 1 to 3, Fig. 1 shows a flowchart of a wireless sensor network-based energy-saving MAC protocol communication method of the present invention; Fig. 2 shows a wireless sensor network-based energy-saving MAC protocol communication method of the present invention Schematic diagram of the working process of the method; FIG. 3 shows a schematic diagram of an energy-saving MAC protocol communication method based on a wireless sensor network in the present invention, and a schematic diagram of a new node joining the network initialization stage.

In order to solve the above problems, the idea of the present invention is to select an offset value according to the wake-up time of the neighbor nodes when the new node joins the network, so as to ensure that the wake-up time is different from that of the neighbor nodes. By predicting the wake-up time of the receiving node, when the sending node has data transmission, it wakes up at Tcd time in advance according to the predicted wake-up time of the receiving node, so as to wait for receiving the wake-up beacon frame. Specifically include:

Step S102, the new node records the wake-up time offset value of the neighbor node by maintaining the wake-up time table of the neighbor node;

Step S104, determine the wake-up time offset value of the new node according to the wake-up time offset value of the neighbor node, the formula is as follows:

In the formula (1), O _w (i) is the wake-up time offset value of the receiving node i, O _w is the wake-up time offset value of the new node, t(i, j) is the difference between the wake-up time of the two nodes i and j , the wake-up time of the two nodes must be within the shortest wake-up interval among all nodes;

Step S106, when the sending node sends data, query the corresponding receiving node information in the wake-up schedule, and predict the wake-up time of the receiving node, the prediction formula is as follows:

t _remain (i)=T _wakeup (i)-(t _c -O _w (i))%T _wakeup (i) (2)

In formula (2), t _remain (i) is the remaining time of receiving node i’s next wake-up time, T _wakeup (i) is the wake-up interval of node i, t _c is the current time of sending node, O _w (i) is receiving node i The wake-up offset value.

In this embodiment, the wake-up interval should be understood as the interval between two wake-ups, and the wake-up time should be understood as the wake-up moment, that is, the moment of wake-up.

The HELD-MAC protocol provided in this embodiment, through formula (1), selects the offset value according to the wake-up time of neighboring nodes, which ensures that the nodes have different wake-up times, and accurately predicts the wake-up time of the receiving node through formula (2) , which can effectively reduce energy consumption caused by idle listening and save energy.

In this embodiment, at the initial stage when a new node joins the network, before the new node records the wake-up time offset value of the neighbor node by maintaining the wake-up schedule of the neighbor node, it also includes:

Continuously monitor the duration of the initial maximum wakeup interval T _{init_wakeup} of the node. During the monitoring process, when receiving the beacon frame sent by the neighbor node, send an empty data frame with the request node wakeup status flag;

When the sending node receives an empty data frame with a flag bit, it embeds the wakeup interval T _wakeup of the node in the sent ACK frame (the last wakeup time of the node is T _last , the current time of the node is T _cur );

The new node receives the ACK frame returned by the neighbor node during the continuous monitoring time, and maintains a wake-up schedule of the neighbor node after the monitoring ends.

When the related technologies predict the wake-up time, there will be different degrees of error. The error is not only caused by clock drift, but also the operating system and hardware delay will also bring obvious prediction errors. In order to effectively solve this problem, the HELD provided by this embodiment -MAC protocol introduces prediction error threshold E _threshold , when the difference between the actual wake-up time of the receiving node and the predicted wake-up time of the sending node is greater than the error threshold, the node re-requests the information of the wake-up time of the receiving node according to the method in the above initialization phase. The value range of the error threshold E _threshold may be 0-20 ms.

In order to solve the problem that the MAC protocol in the related art cannot dynamically change the node wake-up interval under the dynamic load condition of the network, resulting in a higher data transmission collision rate and a larger data transmission delay, the HELD- MAC protocol, also includes:

Before sending data each time, the sending node detects the number of data packets waiting to be transmitted in the buffer queue, (if there are data packets waiting to be transmitted in addition to the data packets transmitted this time), it is calculated according to the number of data packets waiting to be transmitted N _wait (i) The level of the number of data packets waiting to be transmitted ρ _wait (i), adaptively changes the wake-up interval of the node according to the level of the number of data packets waiting to be transmitted.

In this embodiment, the wake-up interval of the node is adaptively changed according to the level of the number of data packets waiting to be transmitted, specifically including:

When the level of the number of data packets waiting to be transmitted is changed compared to the previous data transmission, the flag bit and the level of the number of data packets waiting to be transmitted are embedded in the pre-sent data frame; wherein the flag bit is used to notify the receiving node The number of data packets waiting to be transmitted is embedded in the data frame, and the number of data packets waiting to be transmitted is obtained by formula (3):

In the formula (3), ρ _wait (i) is the level of the number of data packets that node i is waiting to transmit, N _wait (i) is the number of data packets that node i is waiting to transmit, n _threshold is the load factor of the sending node, and ρ _threshold is the load of the receiving node factor;

The receiving node dynamically maintains the sum _ρwait of the number of data packets waiting to be transmitted in the child node. The larger the value of _ρwait , the more data packets waiting to be transmitted in the child node. It is updated when the node receives a data frame with a flag bit The sum ρ _wait of the number of data packets waiting to be transmitted in the child node, when the data frame with the flag bit is not received, the number of data packets waiting to be transmitted remains unchanged; wherein, the sum of the number of data packets waiting to be transmitted in the child node Obtained from formula (4):

(4) In the formula, ρ _wait is the sum of the number of data packets waiting to be transmitted in the child nodes, ρ _wait (i) is the number of data packets waiting for node i to transmit, and s is the number of child nodes;

The receiving node dynamically changes the wake-up interval; the condition for dynamically changing the wake-up interval is that the adjustment factor (μ value) changes, and when the adjustment factor (μ value) does not change, the wake-up interval remains unchanged. The relevant formulas are as follows: (5), (6 ), (7):

In formulas (5), (6), and (7), μ is the adjustment factor, ρ _wait is the sum of the number of data packets waiting to be transmitted in the child nodes, ρ _threshold is the load factor of the receiving node, and T _tmp is the wake-up time of the node after calculation interval, T _{init_wakeup} is the initial maximum wakeup interval of the node, T _wakeup is the wakeup interval of the node, and T _min is the minimum wakeup interval of the node, which is calculated according to the remaining energy of the node.

The larger the value of μ, the more data packets waiting to be transmitted in the child node; the load factor n _threshold of the sending node in the formula (3) and the load factor of the receiving node in the formula (5), ρ _threshold , can be adjusted according to the application Packet transmission delay tolerance adjustment, if the transmission delay tolerance is large, you can increase its value appropriately, otherwise, you can decrease its value.

The HELD-MAC protocol provided in this embodiment detects the number of data packets waiting to be transmitted in the buffer queue before the sending node sends data each time, calculates the number level of data packets waiting to be transmitted according to the number of data packets waiting to be transmitted, and calculates the number level of data packets waiting to be transmitted according to the The quantity level adaptively changes the wake-up interval of the node, and realizes that the receiving node can adaptively change the node wake-up interval according to the network load status, so that the receiving node still has a different wake-up time after changing the wake-up interval, thereby ensuring a relatively high load under high load conditions. Low data transmission delay and data transmission collision rate, at the same time, the node can adaptively change the minimum wake-up interval of the node according to the estimated remaining energy, ensuring that the node will not shut down prematurely due to frequent data forwarding, prolonging the survival of the network Period, which enhances the stability of the network.

In wireless sensor networks, an efficient data retransmission mechanism is an important aspect that needs to be considered in real sensor networks. The increase in network load and the simultaneous transmission of multiple adjacent nodes will cause data transmission conflicts, and transmission failure requires data retransmission. In the HELD-MAC protocol provided in this embodiment, when the sending node receives the wake-up beacon frame of the receiving node, it switches to the sleep state until the receiving node wakes up next time to retransmit the data, that is, when the sending node needs data retransmission, When a transmission conflict is detected, the node immediately switches to the sleep state, intelligently chooses when to wake up and retransmit data, and realizes efficient energy utilization. Figure 2 illustrates the prediction-based data retransmission mechanism of the HELD-MAC protocol. As shown in Figure 2, if the sending node S receives the wake-up beacon frame of the receiving node R instead of the confirmation frame of data transmission, the S node will think that the data transmission failed or the confirmation frame transmission failed, and the S node immediately switches to the sleep state until The receiving node retransmits data at the next wake-up time, and the method reduces energy consumption by reducing the waiting time for the receiving node to wake up.

The HELD-MAC protocol provided by the present invention predicts the wake-up time of the node by dynamically maintaining the wake-up schedule of the neighbor nodes, and the node adaptively changes the wake-up interval of the node according to the network load situation, while ensuring that the nodes still have different The wake-up interval has obvious advantages in data transmission delay, energy consumption, network throughput, and transmission collision.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (7)

1. a kind of energy-efficient MAC protocols communication means based on wireless sensor network, it is characterised in that including：

The wakeup time table that new node passes through maintenance of neighbor node, records the wakeup time deviant of neighbor node；

Wakeup time deviant according to neighbor node determines the wakeup time deviant of new node, and formula is as follows：

In formula, O_wI () is the wakeup time deviant of receiving node i, O_wIt is the wakeup time deviant of new node, t (i, j) is I, j two waking up nodes moment difference, wake-up moment of wherein i, j two node are in the most short time of Wakeup interval in all nodes It is interior；

When sending node sends data, corresponding receiving node information in the wakeup time table is inquired about, and predict reception section The wakeup time of point, predictor formula is as follows：

t_remain(i)=T_wakeup(i)-(t_c-O_w(i)) %T_wakeup(i)

In formula, t_remainI () is that receiving node i wakes up remaining time at moment, T next time_wakeupI () is node i Wakeup interval, t_cFor Sending node current time, O_wI () is the wake-up deviant of receiving node i.

2. a kind of energy-efficient MAC protocols communication means based on wireless sensor network according to claim 1, its feature exists Before, new node marks the wakeup time deviant of record neighbor node by the wakeup time of maintenance of neighbor node, also include：

The duration of node initial maximum Wakeup interval is persistently monitored, when the beacon frame of neighbor node transmission is received, band is sent There is the empty data frame of request waking up nodes state flag bit；

When sending node receives the empty data frame with flag bit, the Wakeup interval of embedded node in the ACK frames for sending；

New node receives the ACK frames of neighbor node return in lasting listening period, and a neighbours are safeguarded after monitoring terminates Waking up nodes timetable.

3. a kind of energy-efficient MAC protocols communication means based on wireless sensor network according to claim 2, its feature exists In also including：

When the actual wakeup time of receiving node is more than error threshold with the difference of the wakeup time of sending node prediction, again Ask the information of receiving node wakeup time.

4. a kind of energy-efficient MAC protocols communication means based on wireless sensor network according to claim 1,2 or 3, its It is characterised by, also includes：

Before sending node sends data every time, detect buffering queue awaiting transmission data packet number, according to etc. it is waiting for transmission Data packet number is calculated and waits transmission packet quantitative levels, according to wait transmission packet quantitative levels adaptively changing node Wakeup interval.

5. a kind of energy-efficient MAC protocols communication means based on wireless sensor network according to claim 4, its feature exists In, according to wait transmission packet quantitative levels adaptively changing node Wakeup interval, specifically include：

Before data are sent compared to the last time, transmission packet quantitative levels are waited when changing, by flag bit and described Transmission packet quantitative levels are waited to be embedded into the data frame of pre- transmission；Wherein, the flag bit is used to notify receiving node The wait transmission packet quantitative levels of change are embedded with data frame, the wait transmission packet quantitative levels are asked by following formula ：

${\mathrm{\&rho;}}_{\mathrm{wait}}\left(i\right)=\left\{\begin{array}{cc}0,& N_{\mathrm{wait}}\left(i\right)<n_{\mathrm{threshold}1}\\ 1,& {n_{\mathrm{threshold}1}\&le;N}_{\mathrm{wait}}\left(i\right)<{\mathrm{\&rho;}}_{\mathrm{threshold}2}\\ 2,& {n_{\mathrm{threshold}2}\&le;N}_{\mathrm{wait}}\left(i\right)\end{array}\right.$

In formula, ρ_waitI () is that node i waits transmission packet quantitative levels, N_waitI () is the number-of-packets waiting for transmission such as node i Amount, n_thresholdIt is sending node load factor, ρ_thresholdIt is receiving node load factor；

Child nodes awaiting transmission data packet number grade is updated when node receives the data frame with the flag bit Summation, when the data frame with the flag bit is not received, remains waiting for transmission packet quantitative levels constant；Wherein, child The summation of child node awaiting transmission data packet number grade is tried to achieve by following formula：

${\mathrm{\&rho;}}_{\mathrm{wait}}=\underset{i=1}{\overset{s}{\mathrm{\&Sigma;}}}{\mathrm{\&rho;}}_{\mathrm{wait}}\left(i\right)$

In formula, ρ_waitIt is the summation of child nodes awaiting transmission data packet number grade, ρ_waitI () is the numbers to be transmitted such as node i According to bag quantitative levels, s is the number of child nodes；

Receiving node dynamically changes Wakeup interval；Wherein, dynamic changes the condition of Wakeup interval for Dynamic gene changes, related public Formula is as follows：

$\mathrm{\&mu;}=\left\{\begin{array}{cc}0,& {\mathrm{\&rho;}}_{\mathrm{wait}}<{\mathrm{\&rho;}}_{\mathrm{threshold}1}\\ 1,& {\mathrm{\&rho;}}_{\mathrm{threshold}1}\&le;{\mathrm{\&rho;}}_{\mathrm{wait}}<{\mathrm{\&rho;}}_{\mathrm{threshold}2}\\ 2,& {\mathrm{\&rho;}}_{\mathrm{threshold}2}\&le;{\mathrm{\&rho;}}_{\mathrm{wait}}<{\mathrm{\&rho;}}_{\mathrm{threshold}3}\\ 3,& {\mathrm{\&rho;}}_{\mathrm{threshold}3}\&le;{\mathrm{\&rho;}}_{\mathrm{wait}}\end{array}\right.$

$T_{\mathrm{tmp}}={\left(\frac{1}{2}\right)}^{\mathrm{\&mu;}}\&CenterDot;T_{\mathrm{init}\_\mathrm{wakeup}}$

$T_{\mathrm{wakeup}}=\left\{\begin{array}{cc}{T}_{\min },& T_{\mathrm{tmp}}<T_{\min }\\ T_{\mathrm{tmp}},& T_{\min }\&le;T_{\mathrm{tmp}}<T_{\mathrm{init}\_\mathrm{wakeup}}\\ T_{\mathrm{init}\_\mathrm{wakeup}},& T_{\mathrm{tmp}}\&GreaterEqual;T_{\mathrm{init}\_\mathrm{wakeup}}\end{array}\right.$

In formula, μ is Dynamic gene, ρ_waitIt is the summation of child nodes awaiting transmission data packet number grade, ρ_thresholdTo connect Receive the node load factor, T_tmpWakeup interval after being calculated for node, T_{init_wakeup}It is node initial maximum Wakeup interval, T_wakeup It is the Wakeup interval of node, T_minIt is node minimum Wakeup interval.

6. a kind of energy-efficient MAC protocols communication means based on wireless sensor network according to claim 5, its feature exists In also including：Keep Wakeup interval constant when Dynamic gene does not change.

7. a kind of energy-efficient MAC protocols communication means based on wireless sensor network according to claim 6, its feature exists In also including：

When sending node receives the wake-up beacon frame of receiving node, sleep state is converted to until next time receiving node is called out The time of waking up retransmits data.