A method for supporting the TSCH mode of wireless sensor networks and improving the determinacy of burst traffic

Abstract

The present invention belongs to the field of wireless sensor networks and relates to a scheduling method that supports the TSCH mode of wireless sensor networks and improves the certainty of burst traffic. The method includes: a MAC layer that uses a combination of time division multiple access and frequency division multiple access to divide communication resources, thereby allocating corresponding communication resources for nodes in the wireless sensor network; an access mode that uses time synchronization and time slot channel hopping between nodes in the wireless sensor network; a link monitoring mechanism based on scheduling block utilization to monitor node links in the wireless sensor network; and a PID-based time-varying periodic scheduling strategy based on the monitoring results of the node links, adjusting the PID scheduling control time according to the frequency of sending and receiving data packets. The present invention can more accurately select the PID scheduling period based on the scheduling block utilization to reasonably allocate node communication resources, thereby improving the wireless sensor network's ability to cope with burst traffic and supporting low-power communication in the TSCH mode.

Description

Technical Field

[0001] The invention belongs to the field of wireless sensor networks and relates to a method for supporting a TSCH mode of a wireless sensor network and improving the certainty of burst traffic. Background Art

[0002] Currently, resource-constrained wireless sensor networks face two major problems when conducting inter-node communication: one is the problem of nodes being unable to handle bursts of traffic in a timely manner. When faced with bursts of traffic, if the communication resources (cells) between nodes cannot be replenished in time, it often causes data loss and network delays. This requires regulating surplus cells to cope with the bursts of traffic generated in a short period of time; the other is the problem of wasted communication resources when the node communication traffic is low. When the inter-node traffic decreases to a certain level, if the number of cells is not reduced in time, communication resources will be wasted.

[0003] Existing standard protocols using the traditional Minimal Scheduling Function (MSF) scheduling method waste communication resources when allocating cells. When allocating cell resources, a cell is added when utilization is high, and a cell is removed when utilization is low. This can sometimes result in a high cell idle rate. Furthermore, nodes wait too long to invoke the MSF when the number of cells is low. The MSF is only invoked once every 32 cells are counted. This delay, especially when the number of cells is low, impacts real-time network communication. Summary of the Invention

[0004] In order to solve the problems of network delay, data packet loss and communication resource waste caused by burst traffic, improve the real-time and accuracy of link monitoring, reduce transmission delay and packet loss rate, and improve the efficiency of communication resource utilization, the present invention proposes a method that supports the TSCH mode of wireless sensor networks and improves the certainty of burst traffic, which specifically includes the following steps:

[0005] The MAC layer uses a combination of time division multiple access and frequency division multiple access to divide communication resources and allocate corresponding communication resources for nodes in the wireless sensor network;

[0006] The nodes in the wireless sensor network use a time synchronization and time slot channel hopping access mode;

[0007] The node links of wireless sensor networks are monitored using a link monitoring mechanism based on scheduling block usage.

[0008] According to the monitoring results of node links, a PID-based time-varying periodic scheduling strategy is used to schedule communication resources.

[0009] Beneficial effects of the present invention:

[0010] 1. The present invention divides communication resources by combining TDMA and FDMA to avoid mutual interference of signals between nodes, thereby increasing the anti-interference ability of communication. At the same time, the nodes of the wireless sensor network adopt time synchronization and time slot channel hopping access mode, which broadens the transmission channel in the frequency domain, reduces data conflicts and energy waste caused by channel occupancy, reduces node communication consumption, and greatly enhances the reliability of communication between wireless devices.

[0011] 2. The present invention monitors the usage rate of cells arranged by the node over a period of time, reflects the burst traffic based on the usage rate, and more accurately determines the usage status of communication resources, thereby improving the real-time performance and accuracy of link monitoring.

[0012] 3. This invention uses usage to determine whether a traffic burst has occurred. When a traffic burst occurs, the burst will fully occupy all allocated extra cells. This shortens the next PID scheduling call time to once every n time slot frames. This allows for faster adaptation to traffic bursts, more efficient utilization of communication resources, and resolves the issues of traffic bursts and wasted idle resources in wireless network communications.

[0013] 4. The present invention uses the ratio of the number of cells used in the statistical period to the number of cells allocated in the statistical period to calculate the utilization rate of the cells arranged by the node over a period of time, and uses a PID control algorithm to process the utilization rate, the number of cells in the current time slot frame, and the additional cells to calculate the number of cells that need to be added in the next round, thereby realizing the regulation of the number of cells to adapt to burst traffic.

[0014] 5. The present invention introduces an extra cell, that is, adding 1 after calculating the required cell formula. When the number of cells is relatively large, the extra cell can help the node control the cell utilization rate at a reasonable level. When the number of cells is low, the extra cell can weaken the decision of low utilization on the cell, so that when the actual usage of the node in a time slot frame is less than or equal to 1 cell, there are 2 cells in the time slot frame; when the actual usage of the node in a time slot frame is less than or equal to 2 cells, there are 3 cells in the time slot frame, so as to cope with possible communication traffic growth or small traffic fluctuations. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of a scheduling method that supports the TSCH mode of a wireless sensor network and improves the certainty of burst traffic according to the present invention;

[0016] Figure 2 Schematic diagram of the PID-based time-varying periodic scheduling strategy mechanism of the present invention. DETAILED DESCRIPTION

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0018] The embodiment of the present invention utilizes a monitoring mechanism based on scheduling block usage rate in combination with a suitable PID resource scheduling algorithm, which is more suitable for wireless sensor networks, can more reasonably utilize communication resources, and solve the problems of burst traffic and idle resource waste in wireless network communications.

[0019] The present invention proposes a method for supporting the TSCH mode of wireless sensor networks and improving the certainty of burst traffic, such as Figure 1 , specifically including the following steps:

[0020] 101. The MAC layer uses a combination of time division multiple access and frequency division multiple access to divide communication resources and allocate corresponding communication resources for nodes in the wireless sensor network;

[0021] In an embodiment of the present invention, the MAC layer divides communication resources using a method combining time division multiple access and frequency division multiple access, including: time division multiple access uses different time slots to distinguish nodes, that is, the data of the nodes are transmitted on different time slots, thereby avoiding mutual interference of signals between nodes; frequency division multiple access uses different channels to distinguish nodes, and the data of the nodes are transmitted on different channels, thereby avoiding mutual interference of signals between nodes; and network resources are divided into a series of communication resources and allocated to specific node links in the wireless sensor network in accordance with the combination of time division multiple access and frequency division multiple access.

[0022] The MAC layer uses a combination of TDMA and FDMA to divide communication resources, including:

[0023] (1) Each cycle is divided into multiple time slots on the time axis. A certain number of time slots constitutes a time slot frame. The position number of a time slot in the time slot frame is called the time slot offset. Different channels are divided in the frequency domain, and the channel number is called the channel deviation.

[0024] (2) A table determined by time slot offset and channel deviation is the communication resource of the node, which is allocated to the link for communication.

[0025] 102. The nodes in the wireless sensor network adopt the access mode of time synchronization and time slot channel hopping;

[0026] In this embodiment of the present invention, the TSCH mode is adopted. This mode uses precise time synchronization for time-slot communication, significantly reducing unnecessary waiting time for wireless devices. The TSCH mode also uses frequency hopping technology to broaden the transmission channel in the frequency domain, reducing data conflicts and energy waste caused by channel occupancy, and significantly enhancing the reliability of communication between wireless devices.

[0027] In order to ensure time synchronization and time slot channel hopping, when a new node joins the network, it will listen to the network broadcast information and synchronize time with the entire network. After joining the network, neighboring nodes periodically exchange data frames to complete time synchronization.

[0028] Specifically, nodes in the network use a time synchronization and time-slot channel hopping access mode to reduce node communication consumption and increase communication anti-interference capabilities: when a new node joins the network, it listens to the EB (enhanced beacon) packets periodically broadcast from existing nodes to synchronize time with the entire network; after the node successfully joins the network, it needs to further adopt the device-to-device time synchronization mechanism to maintain accurate synchronization.

[0029] 103. Monitoring node links in a wireless sensor network using a link monitoring mechanism based on scheduling block usage;

[0030] In an embodiment of the present invention, when the nodes of the wireless sensor network communicate in a time slot frame, the utilization rate of the communication resources in the first few time slot frames is calculated (the ratio of the number of cells used in the statistical period to the time when the minimum scheduling function is called each time within the current time, that is, the utilization rate of the cells arranged by the node over a period of time).

[0031] The variable optimized for PID scheduling, or link monitoring, is the ratio of two counters, NumCellUsed (number of cells used during the statistical period) and NumCellElapsed (number of cells allocated during the statistical period), each time the Minimal Scheduling Function (MSF) is called from network synchronization to the current time. This ratio represents the utilization rate of cells scheduled by the node over a period of time, and is used to determine the number of cells that need to be added or deleted by each neighboring node.

[0032] In this embodiment of the present invention, each time the negotiation node monitors the usage of MAX_NUM_CELLS (32) cells, it calls the PID scheduling function to calculate the cell usage during this period and determine the number of cells that each neighboring node needs to add or delete. If the PID detects a high usage rate, it controls the addition of cells in the time slot frame; if the PID detects a low usage rate, it controls the reduction of cells in the time slot frame and reserves a certain proportion of cells to prevent a sudden increase in communication demand.

[0033] Specifically, when nodes in a wireless sensor network communicate, the traffic is initialized to normal traffic according to an existing protocol. According to the monitoring mechanism for normal traffic, the utilization rate of the communication resources is calculated based on the time period in which 4N communication resources are allocated. If the calculated utilization rate is 100%, it is determined to be burst traffic. According to the monitoring mechanism for burst traffic, the utilization rate of the communication resources is calculated based on every N communication resources. Taking N=8 as an example, the traditional mechanism calculates the utilization rate once after 32 communication resources. Once the calculated utilization rate is 100%, it means that all the current communication resources are occupied. It is determined that the current traffic is burst traffic, which can shorten the monitoring time, can more quickly and accurately judge the usage status of the communication resources, and improve the real-time and accuracy of link monitoring.

[0034] For example, when the utilization rate is 100%, the burst traffic will occupy all the allocated additional cells. At this time, the calling time of the next PID scheduling is shortened to once every n time slot frames. In this way, scheduling can be started every n time slot frames when cells are urgently needed to be added. Here, n is a positive integer, for example, it can be 1, 2, 3, etc. In this embodiment, 2 time slot frames are preferably taken. Here, 1 time slot frame corresponds to 4 communication resources as an example; when the utilization rate is less than 100%, the calling time of the next PID scheduling is set to once every N communication resources. Here, N can be set to 32 cells, that is, MSF will reset the reset counter MAX_NUM_CELLS to 32 counting mode after the next scheduling instruction is issued.

[0035] 104. According to the monitoring results of the node links, a PID-based time-varying periodic scheduling strategy is used to schedule communication resources.

[0036] In order to respond faster to burst traffic, allocate cells in a timely manner, and improve network accuracy, the present invention adopts a PID time-varying periodic scheduling strategy:

[0037] When burst traffic occurs, the number of communication resources is adjusted through PID scheduling until the number of communication resources meets the burst traffic demand;

[0038] When the number of communication resources reaches the traffic demand, the number of communication resources is adjusted through PID scheduling to control the utilization rate of the communication resources within the first range within n time slot frames;

[0039] When the traffic demand for communication resources decreases, that is, when the utilization rate of communication resources is lower than the second range, the idle communication resources are recovered through PID scheduling, and the utilization rate of communication resources is adjusted to be within the first range;

[0040] When the data packet sending rate fluctuates, that is, when the utilization rate of communication resources is in the second range, the fluctuation trend is evaluated. If it is an accidental fluctuation, there is no need to issue a PID scheduling command. Otherwise, the PID scheduling command is reissued to adjust the amount of communication resources through PID scheduling.

[0041] The above-mentioned scheduling strategy of this embodiment can achieve the effect of reducing errors and delays caused by burst traffic and reducing the waste of communication resources.

[0042] It can be understood that the first range and the second range are both values between 0 and 1. For example, the first range can be 75%, and the second range can be 30%. Those skilled in the art can make appropriate adjustments to the first range and the second range to ensure that the first range is larger than the second range and conforms to the actual usage occupancy.

[0043] The PID scheduling includes calculating the expected number of cells to be allocated in the next round according to the number of cells in the current time slot frame, the number of cells used in the statistical period, and the number of cells allocated in the statistical period; calculating the number of cells to be added in the next round based on the expected number of cells to be allocated in the next round in combination with the PID control algorithm; when the number of cells to be added in the next round exceeds a first threshold, performing a cell addition operation; when the number of cells to be added in the next round exceeds the opposite of a second threshold and is less than the first threshold, keeping the current cells unchanged; and when the number of cells to be added in the next round is less than the second threshold, performing a cell reduction operation.

[0044] In this embodiment, two thresholds are used to control the cell increase and decrease operations. Compared with the traditional technology, the conditions for increasing and decreasing the PID cell in this embodiment are changed to: when u t The cell can be added only when it increases above the set second threshold c. t The cell can be reduced only when the number of cells decreases to below the negative number of the first threshold -d.

[0045] In a preferred embodiment of the present invention, when c is 0.4 and d is -1, the method can obtain better results.

[0046] The expected number of cells to be allocated in the next round is calculated as follows:

[0047] r t =C n ×C U ÷C E +EL

[0048] Where r t Indicates the expected number of cells to be allocated in the next round, C n The number of cells in the current time slot frame, C U Indicates the value of the counter NumCellsUsed, which is the number of cells used in the statistical period. E Indicates the value of the counter NumCellsElapsed, which is the number of cells allocated during the statistical period; EL indicates the additional cells added.

[0049] In order to cope with sudden or fluctuating traffic, the present invention will introduce an additional cell in any case, that is, add an additional EL after calculating the required cell formula. In this embodiment, EL = 1. When the number of cells is relatively large, the additional cell can help the node control the cell utilization rate at a reasonable utilization level. When the number of cells is low, the additional cell can weaken the decision of low utilization on the cell, so that when the actual usage of the node in a time slot frame is less than or equal to 1 cell, there are 2 cells in the time slot frame; when the actual usage of the node in a time slot frame is less than or equal to 2 cells, there are 3 cells in the time slot frame, so as to cope with possible communication traffic growth or small traffic fluctuations.

[0050] Therefore, the number of cells that need to be increased in the next round is expressed as:

[0051]

[0052] e t =r t -C n

[0053] Among them, u t is the number of cells that need to be added in the next round, e t K is the error between the expected number of cells and the current number of cells. P , K i , K d They are the P, I, and D coefficients of PID scheduling, r t Indicates the expected number of cells to be allocated in the next round, Cn The number of cells in the current time slot frame. This embodiment uses a PID-based time-varying periodic scheduling strategy, with the period size dynamically adjusted based on the frequency of sending and receiving data packets. This addresses the issues of large fluctuations in cell utilization when facing bursty or fluctuating traffic, and the long cell addition period when facing bursty traffic. Furthermore, cells can be promptly reclaimed when traffic is low, saving communication resources and improving network performance.

[0054] Figure 2 This is a schematic diagram of the time-varying periodic scheduling strategy mechanism based on PID of the present invention, as shown in FIG. Figure 2 As shown in the figure, in this mechanism, the parameters are initialized first, and the value of the counter NumCellsUsed is the number of cells used in the statistical period C U =0, the value of the counter NumCellsElapsed is the number of communication resources C allocated during the statistical period E = 0, let the time period for monitoring communication resources under the normal traffic monitoring mechanism be a = 32; here we assume a = 4N, that is, one time slot frame occupies 4 communication resources, a total of 8 time slot frames, and the utilization rate is calculated once after 32 cells; if the time period of a communication resource in a time slot frame is 0, then it is determined whether the communication resource is used. If it is used, let C U =C U +1, and let C E =C E +1; otherwise, only C E =C E +1; Judgment C E Has it exceeded a? If not, continue the above process until all a communication resources are used. If it has exceeded, calculate the utilization rate of communication resources in this cycle K = C U / C E According to the size of the usage rate, it can be determined whether the current stage is a burst traffic phase, so as to adjust the monitoring mechanism for burst traffic and speed up the monitoring time. Here, the usage rate is calculated once in 2 time slot frames as an example, that is, the usage rate is calculated once after 8 cells. At this time, it is also necessary to perform iterative calculations according to the PID formula to determine whether the PID output exceeds the threshold. If it exceeds the threshold, 6p negotiation is used to increase or decrease the number of cells, so that C U =0, C E =0; otherwise, directly set C U =0, C E =0 ends the process.

[0055] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A scheduling method supporting TSCH mode of wireless sensor networks and improving the certainty of burst traffic, characterized in that: The specific steps include: The MAC layer uses a combination of time division multiple access and frequency division multiple access to divide communication resources and allocate corresponding communication resources for nodes in the wireless sensor network; The nodes in the wireless sensor network use a time synchronization and time slot channel hopping access mode; The node links of wireless sensor networks are monitored using a link monitoring mechanism based on scheduling block usage. According to the monitoring results of node links, a PID-based time-varying periodic scheduling strategy is used to schedule communication resources; When burst traffic occurs, the number of communication resources is adjusted through PID scheduling until the number of communication resources meets the burst traffic demand; When the number of communication resources reaches the traffic demand, the number of communication resources is adjusted through PID scheduling to control the utilization rate of the communication resources within the first range within n time slot frames; When the traffic demand for communication resources decreases, that is, when the utilization rate of communication resources is lower than the second range, the idle communication resources are recovered through PID scheduling, and the utilization rate of communication resources is adjusted to be within the first range; When the data packet sending rate fluctuates, that is, when the utilization rate of the communication resources is within the second range, the fluctuation trend is evaluated. If it is an accidental fluctuation, there is no need to issue a PID scheduling command. Otherwise, the PID scheduling command is reissued to adjust the amount of communication resources through PID scheduling. The PID scheduling includes calculating the expected number of cells to be allocated in the next round according to the number of cells in the current time slot frame, the number of cells used in the statistical period, and the number of cells allocated in the statistical period; calculating the number of cells to be added in the next round based on the expected number of cells to be allocated in the next round in combination with the PID control algorithm; when the number of cells to be added in the next round exceeds a first threshold, performing a cell addition operation; when the number of cells to be added in the next round exceeds the opposite of a second threshold and is less than the first threshold, keeping the current cells unchanged; and when the number of cells to be added in the next round is less than the second threshold, performing a cell reduction operation; The number of cells that need to be added in the next round is expressed as: e t =r t -C n r t =C n ×C U ÷C E +THE Among them, u t is the number of cells that need to be added in the next round, e t K is the error between the expected number of cells and the current number of cells. P , K i , K d They are the P, I, and D coefficients of PID scheduling, r t Indicates the expected number of cells to be allocated in the next round, C n The number of cells in the current time slot frame; C U Indicates the value of the counter NumCellsUsed, which is the number of cells used in the statistical period. E represents the value of the counter NumCellsElapsed, that is, the number of cells allocated in the statistical period; EL represents the additionally added cells, and the number of the additionally added cells EL≥1.

2. A scheduling method supporting a wireless sensor network TSCH mode and improving burst traffic determinism according to claim 1, characterized in that: The MAC layer uses a method combining time division multiple access and frequency division multiple access to divide communication resources, including: time division multiple access uses different time slots to distinguish nodes, that is, the data of the nodes are transmitted on different time slots, thereby avoiding mutual interference of signals between nodes; frequency division multiple access uses different channels to distinguish nodes, and the data of the nodes are transmitted on different channels, thereby avoiding mutual interference of signals between nodes; according to the combination of time division multiple access and frequency division multiple access, network resources are divided into a series of communication resources and allocated to specific node links in the wireless sensor network.

3. The scheduling method according to claim 1, which supports the TSCH mode of wireless sensor networks and improves the certainty of burst traffic, is characterized in that: The method for monitoring the node links of the wireless sensor network using a link monitoring mechanism based on the scheduling block usage rate includes initializing the traffic to normal traffic when the nodes of the wireless sensor network communicate, calculating the usage rate of the communication resources according to the time period of allocating 4N communication resources according to the monitoring mechanism of normal traffic, and if the calculated usage rate is 100%, it is judged to be burst traffic, and calculating the usage rate of the communication resources according to the monitoring mechanism of burst traffic based on every N communication resources.

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