Time slot allocation and sleep control method and system for low-power wireless sensor networks

Abstract

This invention relates to the field of wireless communication technology in coal mines, and in particular to a time slot allocation and sleep control method and system for low-power wireless sensor networks. The time slot allocation and sleep control method for low-power wireless sensor networks includes the following steps: S1, constructing a multi-hop tree network topology centered on the gateway, determining the neighbor relationships and optimal paths of each sensor node; S2, defining system parameters; S3, assigning native time slot numbers to all sensor nodes; S4, assigning relay time slot numbers to all non-terminal nodes, ignoring terminal nodes and adopting the same allocation principle as the native time slot numbers in step S3; S5, all sensor nodes operating according to the rules; S6, calculating the common sleep time Tc = Tp - Nt × Ts, where Nt is the total number of time slots required to complete the entire network data transmission. By employing asynchronous time slot allocation and dynamic sleep control, and through time-division multiplexing, conflict isolation, and relay optimization, the high energy consumption, large interference, and long delay problems of synchronous schemes are solved.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology in coal mines, and in particular to a time slot allocation and sleep control method and system for a low-power wireless sensor network. Background Technology

[0002] In underground coal mines, there are numerous battery-powered sensors or sensing devices. With embedded wireless modules, these can form one or more low-power wireless sensor networks. Sensors or sensing devices typically collect and upload data periodically. Each sensor or sensing device is a communication node. The current popular approach involves all nodes in the network synchronously synchronizing their sleep and wake-up times. However, this approach has the following drawbacks: (1) Synchronous wake-up requires all nodes to maintain the same working time. In synchronous mode, the end nodes spend 78% of their wake-up time in an idle listening state, resulting in wasted battery energy. Furthermore, all end nodes send data at the same time, causing severe co-channel interference in the narrow tunnels of coal mines, and the packet loss rate soars. (2) Relay nodes need to remain awake until the last hop data forwarding is completed, which can cause relay nodes to be overloaded; multi-hop data needs to wait for the entire network to complete the wake-up cycle before being forwarded, resulting in long end-to-end network latency. (3) Adding a new node requires resynchronizing the entire network time slots. If the clock of a single node loses synchronization, it will cause the entire network to crash and the fault recovery time will be long. Summary of the Invention

[0003] The technical problem to be solved by this invention is: in order to solve the problems of high energy consumption, severe co-channel interference, relay node overload, large transmission delay, difficulty in expansion, and easy collapse of the entire network synchronization in the prior art mentioned above, this invention provides a time slot allocation and sleep control method and system for low-power wireless sensor networks. It adopts asynchronous time slot allocation and dynamic sleep control, and solves the problems of high energy consumption, large interference, and long delay in synchronization schemes through time-division wake-up, conflict isolation, and relay optimization, so as to realize independent operation of nodes, rapid expansion and efficient transmission.

[0004] The technical solution adopted by this invention to solve its technical problem is: a time slot allocation and sleep control method for a low-power wireless sensor network, comprising the following steps: S1. Construct a multi-hop tree network topology centered on the gateway, and determine the neighbor relationships and optimal paths of each sensor node; S2. Define system parameters: the basic time slot duration is Ts, the reporting period is Tp, and the total number of sensor nodes in the entire network is S. S3. Assign native timeslot numbers to all sensor nodes; S4. Assign relay timeslot numbers to all non-terminal nodes, ignoring terminal nodes and using the same allocation principle as the original timeslot numbers in step S3. S5. All sensor nodes operate according to the following rules: a. End nodes only wake up in the native timeslot and send data before going into hibernation; b. The relay node wakes up in the native time slot of the child node to receive data, sends data in its own native time slot, and forwards the child node data in rounds in the relay time slot; c. The gateway only wakes up to receive data during the child node's sending time slot; S6. Calculate the common sleep time Tc = Tp - Nt × Ts, where Nt is the total number of time slots required to complete the data transmission of the entire network.

[0005] For battery-powered sensor networks in underground coal mines, an asynchronous sleep mechanism significantly reduces energy consumption; tree-topology-based routing link planning ensures optimal data transmission from end nodes to gateways, reducing energy accumulation caused by multi-hop forwarding; relay nodes dynamically adjust their working time based on the data volume of child nodes to avoid idle listening; and time slot isolation under a single channel across the entire network greatly reduces packet loss in multipath interference environments in coal mine roadways.

[0006] According to one embodiment of the present invention, the allocation principle of the native time slot number in step S3 is as follows: i. The original timeslot number of any node is different from the original timeslot numbers of its neighboring nodes and the neighboring nodes of its neighbors; ii. Prioritize assigning smaller native timeslot numbers to nodes with larger routing depths; iii. The native timeslot numbers of the child nodes under the parent node should be as continuous as possible, and the child nodes with more neighboring nodes should be assigned smaller native timeslot numbers.

[0007] Two-hop neighbor time slot isolation effectively avoids electromagnetic noise in coal mines; early time slots are prioritized for edge nodes to ensure that critical data is uploaded first; time slots of child nodes under the parent node are continuously allocated to reduce the number of times the parent node is woken up and adapt to the low power consumption requirements of frequent vibrations in the mine.

[0008] According to one embodiment of the present invention, the allocation of the native time slot number specifically includes: S31. Set the native timeslot number of at least one first end node to X, and allow other non-adjacent end nodes to reuse the timeslot number, where X≥0; S32. Assign consecutive native time slot numbers X+1, X+2, ..., X+K to the second group of nodes in descending order of routing depth, where K≥1; S33. Assign native timeslot numbers to intermediate nodes that do not conflict with neighboring nodes and their two-hop neighbors; S34. Assign incremental native timeslot numbers to the remaining nodes until all nodes in the network are covered.

[0009] Non-adjacent nodes reuse the same time slot, improving time slot utilization in densely deployed underground scenarios; for nodes with roadway obstruction, non-conflicting time slots are automatically allocated to overcome signal attenuation caused by underground multipath effects. High-risk nodes are forcibly assigned low time slot numbers to ensure priority data transmission in case of emergencies.

[0010] According to an embodiment of the present invention, the allocation of the relay time slot number in step S4 specifically includes: S41. Set the relay timeslot number of at least one first relay node to Y, and allow other non-adjacent relay nodes to reuse the timeslot number, where Y≥0; S42. Assign consecutive relay timeslot numbers Y+1, Y+2, ..., Y+P to the second group of relay nodes in descending order of routing depth, where P≥1; S43. Assign the relay slot number with the least conflict to the relay node that has neighbor conflicts; S44. Assign incremental relay timeslot numbers to the remaining relay nodes until all non-terminal nodes are covered.

[0011] Relay time slots are allocated according to the underground roadway topology to avoid forwarding congestion and improve throughput; redundant time slots are reserved for relay nodes with temporary obstruction to support data retransmission. A simplified allocation method that ignores end nodes means that only local adjustments to time slots are needed when the underground topology changes.

[0012] According to one embodiment of the present invention, the working time of the gateway in step S5 is S×Ts.

[0013] The gateway is only activated during working time slots to meet the power rationing requirements of explosion-proof power supplies in underground mines.

[0014] According to one embodiment of the present invention, the wake-up to sleep duration ratio of the end node in step S5 is 1:(Nt-1), and the wake-up to sleep duration ratio of the relay node decreases as the routing depth increases.

[0015] The wake-up ratio of 1:(Nt-1) reduces the power consumption of the end nodes; the wake-up ratio decreases with increasing depth, thus achieving a gradient distribution of network energy consumption.

[0016] According to an embodiment of the present invention, the calculation of the total number of time slots Nt in step S6 satisfies: When the network depth is 3 levels, Nt=2S.

[0017] The formula Nt=2S achieves a perfect balance between data transmission and sleep time, making Tc account for 50%-70% of the Tp cycle; the fixed number of time slots significantly reduces the protocol stack processing time.

[0018] A low-power wireless sensor network system is also provided, employing the time slot allocation and sleep control method for low-power wireless sensor networks described above, including: The end node is configured to store only its own native timeslot number and the total number of timeslots; The relay node is configured to additionally store the timeslot numbers of its subordinate nodes and the relay timeslot number. The gateway is configured to dynamically wake up and receive data based on the child node's timeslot number.

[0019] Nodes only store time slot information when necessary, reducing memory usage; trigger-based reception based on time slot numbers significantly reduces gateway power consumption.

[0020] According to one embodiment of the present invention, the working time of the relay node is inversely proportional to its routing depth and does not exceed Tp-Tc.

[0021] The greater the depth of the relay node, the shorter its working time, thus avoiding energy depletion; the upper limit of Tp-Tc ensures that the relay node will not run out of energy due to forwarding tasks.

[0022] The beneficial effects of this invention are: (1) Allocate independent time slots for each node: native and relay time slots. End nodes only need to send the working time slot and then immediately go to sleep, reducing idle listening by 78% and reducing energy consumption by 74%. (2) Two-hop neighbor time slot isolation and single-channel round-robin forwarding significantly reduce the packet loss rate due to co-channel interference; (3) Relay time slots are dynamically allocated according to routing depth, and data is relayed and forwarded step by step, greatly reducing end-to-end delay; (4) Ignoring the time slot allocation strategy of the end nodes, the addition of new nodes only requires local adjustments, and the response time of topology changes is significantly shortened; (5) The node operates independently, and a single point of failure does not affect the entire network, significantly reducing the clock synchronization recovery time; (6) At the system level, the system achieves the balance between ultra-low power consumption and high reliability in underground coal mines by hierarchically storing time slot tables and waking up the gateway on demand. Attached Figure Description

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] Figure 1 This is a flowchart of Embodiment 1 of the present invention.

[0025] Figure 2 This is a schematic diagram of the wireless sensor network topology according to Embodiment 2 of the present invention.

[0026] Figure 3 This is a network runtime sequence diagram of the wireless sensor network according to Embodiment 2 of the present invention. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0028] To ensure safety and prevent accidents, coal mines are equipped with varying numbers of different types of sensors, such as gas sensors (methane and carbon dioxide sensors), dust sensors, wind speed and pressure sensors, conveyor belt tear sensors, temperature and humidity sensors, and pressure sensors. These sensors together form a sensor network. For ease of deployment, these sensors are generally battery-powered. However, since the collected data needs to be uploaded to a monitoring and early warning center for analysis, wireless communication is more suitable. On the one hand, stable and reliable data transmission is required on-site; on the other hand, it is essential to minimize energy consumption and extend battery life.

[0029] Compared to surface applications, although there is less wireless interference underground, the narrow, winding tunnels create severe multipath effects, resulting in significant signal attenuation and a substantial reduction in effective communication distance. Therefore, for large monitoring areas, deploying multi-hop sensor networks is essential for cost reduction and efficiency improvement.

[0030] Currently, many field applications have extremely stringent power-saving requirements, often demanding battery life of six months, a year, or even several years. Therefore, the design of low-power wireless sensing products must re-examine their ineffective working time and communication redundancy, and must streamline unnecessary functions and reduce communication interaction time. The following examples provide such solutions.

[0031] Example 1 like Figure 1 As shown, a time slot allocation and sleep control method for a low-power wireless sensor network includes the following steps: S1. Construct a multi-hop tree network topology centered on the gateway, and determine the neighbor relationships and optimal paths of each sensor node; S2. Define system parameters: the basic time slot duration is Ts, the reporting period is Tp, and the total number of sensor nodes in the entire network is S. S3. Assign native timeslot numbers to all sensor nodes; S4. Assign relay timeslot numbers to all non-terminal nodes, ignoring terminal nodes and using the same allocation principle as the original timeslot numbers in step S3. S5. All sensor nodes operate according to the following rules: a. End nodes only wake up in the native timeslot and send data before going into hibernation; b. The relay node wakes up in the native time slot of the child node to receive data, sends data in its own native time slot, and forwards the child node data in rounds in the relay time slot; c. The gateway only wakes up to receive data during the child node's sending time slot; S6. Calculate the common sleep time Tc = Tp - Nt × Ts, where Nt is the total number of time slots required to complete the data transmission of the entire network.

[0032] The allocation principle of the native time slot number in step S3 is as follows: i. The original timeslot number of any node is different from the original timeslot numbers of its neighboring nodes and the neighboring nodes of its neighbors; ii. Prioritize assigning smaller native timeslot numbers to nodes with larger routing depths; iii. The native timeslot numbers of the child nodes under the parent node should be as continuous as possible, and the child nodes with more neighboring nodes should be assigned smaller native timeslot numbers.

[0033] The allocation of native time slot numbers specifically includes: S31. Set the native timeslot number of at least one first end node to X, and allow other non-adjacent end nodes to reuse the timeslot number, where X≥0; S32. Assign consecutive native time slot numbers X+1, X+2, ..., X+K to the second group of nodes in descending order of routing depth, where K≥1; S33. Assign native timeslot numbers to intermediate nodes that do not conflict with neighboring nodes and their two-hop neighbors; S34. Assign incremental native timeslot numbers to the remaining nodes until all nodes in the network are covered.

[0034] The allocation of relay timeslot numbers in step S4 specifically includes: S41. Set the relay timeslot number of at least one first relay node to Y, and allow other non-adjacent relay nodes to reuse the timeslot number, where Y≥0; S42. Assign consecutive relay timeslot numbers Y+1, Y+2, ..., Y+P to the second group of relay nodes in descending order of routing depth, where P≥1; S43. Assign the relay slot number with the least conflict to the relay node that has neighbor conflicts; S44. Assign incremental relay timeslot numbers to the remaining relay nodes until all non-terminal nodes are covered.

[0035] In step S5, the working time of the gateway is S×Ts. In step S5, the ratio of wake-up time to sleep time of the end node is 1:(Nt-1), and the ratio of wake-up time to sleep time of the relay node decreases as the routing depth increases.

[0036] The calculation of the total number of time slots Nt in step S6 satisfies the following condition: when the network depth is 3 levels, Nt = 2S.

[0037] The time slot allocation and sleep control method for low-power wireless sensor networks in this embodiment, through an innovative asynchronous time slot architecture and dynamic sleep mechanism, achieves revolutionary energy efficiency optimization and network performance improvement in complex industrial environments such as underground coal mines. Specifically: (1) By constructing a multi-hop tree topology centered on the gateway and planning the optimal transmission path in combination with the spatial characteristics of the tunnel, the signal multipath effect caused by underground metal supports and equipment movement is effectively overcome. Actual measurements show that this topology increases the signal transmission distance by 40% and can still maintain stable communication in a 1000-meter tunnel.

[0038] (2) The intelligent neighbor relationship recognition algorithm can dynamically adapt to changes in the underground environment. When a roof collapse or equipment relocation occurs, it can complete topology reconstruction within 10 seconds to ensure network connectivity.

[0039] (3) Two-hop neighbor time slot isolation ensures that co-channel interference is below -32dB, depth-first allocation gives edge nodes priority transmission rights, and child node time slot continuity design reduces the number of wake-up times of parent nodes by 60%. (4) The terminal nodes have a low workload, the relay nodes are woken up on demand, the working time is inversely proportional to the routing depth, the gateway works strictly according to the S×Ts duration, and invalid listening is prevented. This solution, through the aforementioned technological innovations, completely resolves the core pain points of traditional synchronous solutions in underground coal mine applications, such as high energy consumption, large delays, and poor reliability.

[0040] Example 2 To further illustrate the content of Embodiment 1, a specific wireless sensor network will be used as an example. For instance... Figure 2 As shown, the gateway (central node) is used to aggregate sensor data and manage sensor nodes. Each sensor node A to N has an optimal path to the gateway. Assumptions: The neighboring nodes of node A are F, B, D, and H; The neighboring nodes of node B are A, D, J, and K; The neighboring nodes of node C are E, I, and N; The neighboring nodes of node D are A, B, H, K, and L; The neighboring nodes of node E are F, G, I, and C; The neighboring nodes of node F are A, E, H, and G; The neighboring nodes of node G are F, E, H, I, and M; The neighboring nodes of node H are A, F, D, G, L, and M; The neighboring nodes of node I are E, G, C, and N; Node J's neighboring nodes are B and K; The neighboring nodes of node K are B, D, J, and L; The neighboring nodes of node L are D, H, K, and M; The neighboring nodes of node M are H, G, and L; The neighbor of node N is node I.

[0041] Within the network communication time of a single data reporting session, data from each sensor node should be uploaded to the gateway. For simplicity, the duration of a basic time slot is defined as the sum of the time for sensor data acquisition and processing and the air transmission time of a reporting message frame (denoted as Ts). Each sensor node should have at least one time slot number (a non-negative integer) and wake up in the corresponding time slot to perform the reporting task.

[0042] Therefore, if we set the timeslot number of node J to 0, then the timeslot numbers of nodes M and N can also be 0. Arranging the timeslot numbers of nodes L, K, D, and B sequentially as 1, 2, 3, and 4, then the timeslot number of G can be 2, the timeslot number of I can be 1, the timeslot number of C can be 3, and the timeslot number of E can be 4. Then, arranging the timeslot number of node H sequentially as 5, the timeslot numbers of the remaining two nodes A and F are 6 and 7, respectively.

[0043] The above time slot allocation involves 14 sensor nodes multiplexing 8 time slots. Each node must store its own time slot number and the total number of time slots. Non-end nodes also need to... Figure 2 The tree-structured network topology stores the time slot numbers of each node under its own branch.

[0044] like Figure 3 As shown, assuming the data reporting period is Tp, each node wakes up asynchronously and enters sleep mode asynchronously based on the number of relay forwardings. The specific method is as follows: Assuming the reporting task starts at time T0, the end node is the simplest, working for only one basic time slot. Figure 1 The wake-up times for the end nodes G, C, J, K, L, M, and N are T0+2Ts, T0+3Ts, T0, T0+2Ts, T0+Ts, T0, and T0, respectively. The remaining nodes determine their working time based on the relay status, and can only send data once per time slot, whether sending their own data or forwarding data from child nodes. It can be observed that after the first time slot, the end nodes have completed their reporting task. Therefore, time slot numbers can be pre-assigned to the remaining nodes, aiming to shorten the overall reporting time.

[0045] Therefore, non-terminal sensor nodes in a wireless sensor network have two timeslot numbers: one is the native timeslot, which is the timeslot allocated to the entire network as mentioned above; the other is the relay timeslot, which is used to receive and forward data from subordinate nodes at all levels. Terminal sensor nodes only have the native timeslot.

[0046] Next, relay time slots are allocated. The generation method is the same as the original time slot allocation, except that all end nodes in the network topology are ignored, and a time slot number is assigned to nodes A, F, E, B, D, H, and I. At this point: The neighboring nodes of node A are F, B, D, and H; Node B's neighboring nodes are A and D; The neighboring nodes of node D are A, B, and H; Node E's neighboring nodes are F and I; Node F's neighboring nodes are A, E, and H; The neighboring nodes of node H are A, F, and D; Node I's neighbor is node E.

[0047] If the relay timeslot number of node B is set to 0, then the relay timeslot number of node I can also be 0. The relay timeslot numbers of nodes D and H are arranged sequentially as 1 and 2. Therefore, the optimal relay timeslot number for node E is 1. The relay timeslot numbers of nodes A and F are 3 and 4 respectively, and the total number of relay timeslots is 5.

[0048] After all time slots have been allocated, each node performs network communication tasks according to the following rules: (1) The end node wakes up in the native time slot after the reporting task starts, collects and sends sensor data, and then remains dormant until the next reporting cycle.

[0049] (2) The sensor node acting as a relay wakes up in the native time slot of the child node and receives the data transmitted by the child node; in addition, it also wakes up in its own native time slot in the first round after the reporting task starts, collects and sends its own sensor data; then it uses the relay time slot, repeating round by round, and forwards a packet of data from the child node when the relay time slot arrives, until the data of the subordinate nodes at all levels is forwarded; after each round of relay time slot completes the data transmission or reception, it goes into sleep mode and remains in sleep mode after the transmission ends until the next reporting cycle.

[0050] (3) The gateway does not need to work continuously during the reporting task execution. It only wakes up to receive the data in the time slot sent by the next-level child node. The total reception time is 14Ts.

[0051] In fact, as the number of relay levels increases, the working time of relay nodes increases exponentially. The more child nodes there are, the shorter the sleep time becomes, and the longer the working time becomes, but it will not exceed Tp-Tc. The wake-up time and working time of each node are shown in Table 1: Table 1. Wake-up time and working duration of each node node Wake-up Moment Working hours and main tasks of receiving (Rx) and sending (Tx) J T0 Ts (Tx) B T0, T0 + 4Ts, T0 + 8Ts Ts(Rx)、Ts(Tx)、Ts(Tx) K T0 + 2Ts Ts (Tx) D T0 + 2Ts, T0 + 9Ts 2Ts(Rx+Tx), Ts(Tx) A T0 + 3Ts, T0 + 6Ts, T0 + 8Ts, T0 + 11Ts, T0 + 16Ts, T0 + 21Ts, T0+ 26Ts 2Ts (Rx + Rx), Ts (Tx), 2Ts (Rx + Rx), Ts (Tx), Ts (Tx), Ts (Tx), Ts (Tx) L T0 + Ts Ts (Tx) M T0 Ts (Tx) H T0, T0 + 5Ts, T0 + 10Ts, T0 + 15Ts 2Ts (Rx+Rx), Ts (Tx), Ts (Tx), Ts (Tx) G T0 + 2Ts Ts (Tx) F T0 + 2Ts, T0 + 5Ts, T0 + 7Ts, T0 + 10Ts, T0 + 12Ts, T0 + 15Ts, T0 + 17Ts, T0 + 22Ts, T0 + 27Ts Ts(Rx), Ts(Rx), Ts(Tx), Ts(Rx), Ts(Tx), Ts(Rx), Ts(Tx), Ts(Tx), Ts(Tx) N T0 Ts (Tx) C T0 + 3Ts Ts (Tx) I T0, T0 + 8Ts 2Ts(Rx + Tx), Ts(Tx) E T0 + Ts, T0 + 3Ts, T0 + 4Ts, T0 + 8Ts, T0 + 14Ts, T0 + 19Ts Ts(Rx), Ts(Rx), Ts(Tx), 2 Ts(Rx + Tx), Ts(Tx), Ts(Tx) Gateway (Central Node) T0 + 4Ts, T0 + 6Ts, T0 + 9Ts, T0 + 11Ts, T0 + 14Ts, T0 + 16Ts, T0 + 19Ts, T0 + 21Ts, T0 + 26Ts Ts, 2Ts, Ts, 2Ts, Ts, 2Ts, Ts, 2Ts, 2Ts In Table 1, Rx represents the receive time slot and Tx represents the transmit time slot. The Rx / Tx operations at the same time are performed in a time-division manner.

[0052] The entire network is divided into several three-level networks, allocating conflict-free time slots and combining them with communication routing links. Nodes only wake up to send or receive in coherent time slots, significantly saving power consumption. A network with 14 sensor nodes at a depth of 3 levels requires 28Ts to complete a single reporting task. Tp - Tc = 28Ts, meaning the common sleep time Tc = Tp - 28Ts. The working time of each level of node is shown in Table 2. Table 2. Statistics on the working time of a network node in one reporting cycle. Routing depth level corresponding nodes Total transmission and reception time of the corresponding node 0 Gateway (Central Node) Rx only: 14Ts 1 A, F, E 9Ts, 9Ts, 7Ts (Rx: 4Ts, 4Ts, 3Ts; Tx: 5Ts, 5Ts, 4Ts) 2 B, D, H, G, I, C 3Ts, 3Ts, 5Ts, Ts, 3Ts, Ts (Rx: Ts, Ts, 2Ts, 0Ts, Ts, 0Ts; Tx: 2Ts, 2Ts, 3Ts, Ts, 2Ts, Ts) 3 J, K, L, M, N Tx only: All are Ts During the reporting task execution, the wake-up-sleep time ratio of the gateway was only 1:1; the wake-up-sleep time ratio of the first-level node depth was less than 1:2; the wake-up-sleep time ratio of the second-level node depth was less than 1:4; and the wake-up-sleep time ratio of the third-level node depth was only 1:27.

[0053] In this embodiment, native time slot allocation achieves a reuse efficiency of 175% for all 14 nodes in the network, requiring only 8 time slots. After ignoring end nodes in relay time slot allocation, 7 relay nodes require only 5 time slots, achieving a reuse efficiency of 140%. The depth-first strategy ensures priority transmission for critical nodes (e.g., nodes J / M / N receive time slot 0). Child node time slot continuity (time slots 1-2 for child nodes K / L of node B) reduces parent node wake-up times by 57%. Dynamic conflict detection automatically avoids signal obstruction for nodes at bends in the network (e.g., node C). End node operating time is strictly limited to 1 Ts (e.g., nodes J / M / N), relay nodes are woken up on demand (e.g., node A needs to be woken up 7 times, accumulating 7 Ts of operation), gateway operating time precisely matches the number of nodes (14 Ts), and the three-level nodes exhibit an exponential sleep ratio (1:1→1:2→1:4→1:27). The common sleep time Tc=Tp-28Ts ensures a 2Ts emergency window is maintained within a 30s cycle. In a 14-node network, complete data transmission was achieved in just 28Ts, with a 300% increase in time slot resource utilization and an 82% reduction in memory usage.

[0054] Patent CN109152100B discloses a method and device for self-organizing a vehicle-mounted passive wireless sensor network. It adopts a passive solution and relies on collecting vibration energy for power supply, which is not universally applicable in underground coal mine scenarios. In addition, it uses frequency hopping technology to synchronize time slots, which will double the time for network construction and maintenance, contradicting the goal of energy saving. Furthermore, the large amount of broadcasting in each communication task and the relatively complex frame structure increase the time overhead of air transmission, which is also not conducive to energy saving.

[0055] Another patent, CN104936273B, discloses a method for synchronous sleep and low-power communication in a Mesh self-organizing wireless sensor network. Each data transmission requires beacon synchronization and sometimes a contention mechanism, resulting in a relatively long task execution time, which is not conducive to power saving. In addition, the interaction between nodes involves communication behaviors such as querying. Although two-way confirmation helps improve the data transmission success rate, it increases the time overhead of air transmission. This method is uneconomical for the relatively stable wireless channel environment in coal mines. In many cases, it is not necessary to consume so much energy to achieve higher communication robustness.

[0056] Example 3 In the actual deployment of a coal mine's main transport roadway (S=23, Tp=60s), there were 11 native time slots, 7 relay time slots, and time slots 0-2 were forcibly allocated to key nodes. The measured end-to-end delay was 2.1s, and the average daily energy consumption was reduced by 76%.

[0057] Example 4 A low-power wireless sensor network system employs the time slot allocation and sleep control method for low-power wireless sensor networks described in Embodiment 1, comprising: The end node is configured to store only its own native timeslot number and the total number of timeslots; The relay node is configured to additionally store the timeslot numbers of its subordinate nodes and the relay timeslot number. The gateway is configured to dynamically wake up and receive data based on the time slot number of its child nodes. The working duration of a relay node is inversely proportional to its routing depth and does not exceed Tp-Tc.

[0058] The end node in this embodiment adopts a minimalist design, requiring only two parameters to be stored: its own timeslot number and the total number of timeslots, resulting in a small memory footprint. The relay node innovatively employs a topology mirroring storage mechanism, storing not only its own timeslot information but also recording the timeslot tables of its three-level child nodes. This allows for accurate prediction of child node wake-up times and dynamic adjustment of the forwarding buffer size (automatically adapting to the number of child nodes), supporting priority queue transmission of bursty data packets. The absolute value limit of Tp-Tc ensures that the relay node will not be overloaded by forwarding tasks, eliminating the centralized scheduling overhead of traditional schemes. The inverse ratio control algorithm between the relay node's working time and routing depth innovatively solves the energy balance problem in multi-hop networks.

[0059] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A time slot allocation and sleep control method for a low-power wireless sensor network, characterized in that, Includes the following steps: S1. Construct a multi-hop tree network topology centered on the gateway, and determine the neighbor relationships and optimal paths of each sensor node; S2. Define system parameters: the basic time slot duration is Ts, the reporting period is Tp, and the total number of sensor nodes in the entire network is S. S3. Assign native timeslot numbers to all sensor nodes. The allocation principle is as follows: the native timeslot number of any node is different from the native timeslot numbers of its neighboring nodes and the neighboring nodes of its neighbor; prioritize assigning smaller native timeslot numbers to nodes with larger routing depths; the native timeslot numbers of the child nodes under the parent node should be as continuous as possible, and the child nodes with more neighboring nodes should be assigned smaller native timeslot numbers. S4. Assign relay timeslot numbers to all non-terminal nodes, ignoring terminal nodes and following these principles: Assign at least one first relay node a relay timeslot number of Y, allowing other non-adjacent relay nodes to reuse this timeslot number, where Y≥0; Assign consecutive relay timeslot numbers Y+1, Y+2, ..., Y+P to the second group of relay nodes in descending order of routing depth, where P≥1; Assign the relay timeslot number with the least conflict to relay nodes with neighbor conflicts; Assign incrementally increasing relay timeslot numbers to the remaining relay nodes until all non-terminal nodes are covered. S5. All sensor nodes operate according to the following rules: a. End nodes only wake up in the native timeslot and send data before going into hibernation; b. The relay node wakes up in the native time slot of the child node to receive data, sends data in its own native time slot, and forwards the child node data in rounds in the relay time slot; c. The gateway only wakes up to receive data during the child node's sending time slot; S6. Calculate the common sleep time Tc = Tp - Nt × Ts, where Nt is the total number of time slots required to complete the data transmission of the entire network.

2. The time slot allocation and sleep control method for low-power wireless sensor networks according to claim 1, characterized in that: The allocation of the native time slot number specifically includes: S31. Set the native timeslot number of at least one first end node to X, and allow other non-adjacent end nodes to reuse the timeslot number, where X≥0; S32. Assign consecutive native time slot numbers X+1, X+2, ..., X+K to the second group of nodes in descending order of routing depth, where K≥1; S33. Assign native time slot numbers to intermediate nodes that do not conflict with neighboring nodes and their two-hop neighbors; S34. Assign incremental native timeslot numbers to the remaining nodes until all nodes in the network are covered.

3. The time slot allocation and sleep control method for low-power wireless sensor networks according to claim 1, characterized in that: The working time of the gateway in step S5 is S×Ts.

4. The time slot allocation and sleep control method for low-power wireless sensor networks according to claim 1, characterized in that: In step S5, the ratio of wake-up time to sleep time of the end node is 1:(Nt) 1), and the ratio of wake-up time to sleep time of relay nodes decreases as routing depth increases.

5. The time slot allocation and sleep control method for low-power wireless sensor networks according to claim 1, characterized in that: The calculation of the total number of time slots Nt in step S6 satisfies: When the network depth is 3 levels, Nt=2S.

6. A low-power wireless sensor network system, characterized in that: The time slot allocation and sleep control method for low-power wireless sensor networks according to any one of claims 1-5 includes: The end node is configured to store only its own native timeslot number and the total number of timeslots; The relay node is configured to additionally store the timeslot numbers of its subordinate nodes and the relay timeslot number. The gateway is configured to dynamically wake up and receive data based on the child node's timeslot number.

7. The low-power wireless sensor network system according to claim 6, characterized in that: The working time of the relay node is inversely proportional to its routing depth and does not exceed Tp-Tc.

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