Time slot allocation and dormancy control method and system for low-power wireless sensor network

Abstract

The invention relates to the technical field of coal mine underground wireless communication, in particular to a time slot distribution and dormancy control method and system of a low-power-consumption wireless sensor network. The invention discloses a time slot allocation and dormancy control method for a low-power-consumption wireless sensor network, and the method comprises the following steps: S1, constructing a multi-hop tree network topology which takes a gateway as a center, and determining the neighborhood relation and the optimal path of each sensing node; s2, defining system parameters; s3, distributing native time slot numbers for all the sensing nodes; s4, distributing relay time slot numbers for all non-tail-end nodes, ignoring the tail-end nodes during distribution, and adopting a distribution principle which is the same as the original time slot number in the step S3; s5, all the sensing nodes work according to rules; and S6, the common dormancy time Tc = Tp-Nt * Ts is calculated, and Nt is the total time slot number required for completing data transmission of the whole network. Asynchronous time slot allocation and dynamic dormancy control are adopted, and the problems of high energy consumption, large interference and long delay of a synchronization scheme are solved through time-sharing awakening, conflict isolation and relay optimization.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless communication 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 Art

[0002] Underground in coal mines, there are numerous battery-powered sensors or sensing devices. After being implanted with wireless modules, they can form one or more low-power wireless sensor networks. Sensors or sensing devices typically collect and upload sensor data periodically. Each sensor or sensing device is a communication node. The current popular approach is to synchronize all nodes in a network to sleep and wake up, which has the following drawbacks: (1) Synchronous wake-up requires all nodes to maintain the same working time. In the synchronous mode, the end nodes are in the idle listening state for 78% of the wake-up time, resulting in battery energy waste. In addition, all end nodes send data at the same time, causing serious co-frequency interference in the narrow tunnels of the coal mine, and the packet loss rate soars. (2) Relay nodes need to remain awake until the last hop of data forwarding is completed, which causes relay node overload; multi-hop data needs to wait for the entire network wake-up cycle to complete before being forwarded uniformly, resulting in long end-to-end delay in the network; (3) Newly added nodes need to resynchronize the time slots of the entire network. The loss of synchronization of a single node clock will cause the synchronization of the entire network to collapse, and the fault recovery time is long. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: in order to solve the problems of high energy consumption, serious co-frequency interference, relay node overload, large transmission delay, difficulty in capacity expansion, and easy collapse of full network synchronization in the existing technology in the above-mentioned background technology, a time slot allocation and sleep control method and system for a low-power wireless sensor network are provided. Asynchronous time slot allocation and dynamic sleep control are adopted, and through time-sharing wake-up, conflict isolation and relay optimization, the problems of high energy consumption, large interference and long delay of the synchronization scheme are solved, so as to realize independent operation of nodes, rapid capacity expansion and efficient transmission.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a time slot allocation and sleep control method for a low-power wireless sensor network, comprising the following steps: S1. Build a multi-hop tree network topology centered on the gateway to determine the neighbor relationship and optimal path 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 time slot numbers to all sensor nodes; S4. Allocate relay time slot numbers to all non-end nodes, ignoring the end nodes and using the same allocation principle as the original time slot number in step S3; S5. All sensor nodes work according to the following rules: a. The end node only sleeps after waking up and sending data in its native time slot; b. The relay node wakes up in the child node's native time slot to receive data, sends data in its own native time slot, and forwards the child node's data in the relay time slot in turn; c. The gateway wakes up and receives data only 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 data transmission across the entire network.

[0005] For battery-powered sensor networks in 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 the cumulative energy consumption caused by multi-hop forwarding. Relay nodes dynamically adjust their working hours based on the amount of data from child nodes to avoid idle monitoring. Time slot isolation under a single channel across the entire network greatly reduces the packet loss rate in the multipath interference environment of coal mine tunnels.

[0006] According to one embodiment of the present invention, the principle for allocating native time slot numbers in step S3 is: i. The native time slot number of any node is different from the native time slot number of its neighbor node and the neighbor node of its neighbor; ii. Prioritize assigning smaller native time slot numbers to nodes with large routing depth; iii. The native time slot numbers of the child nodes under the parent node should be as continuous as possible, and the child nodes with more neighbor nodes should be assigned smaller native time slot numbers.

[0007] Two-hop neighbor time slot isolation effectively avoids electromagnetic noise in coal mines; early time slots are allocated to edge nodes first to ensure that key 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 wakes up, adapting to the low power consumption requirements of frequent vibrations underground.

[0008] According to one embodiment of the present invention, the allocation of the native time slot number specifically includes: S31. Set the native time slot number of at least one first end node to X, and allow other non-adjacent end nodes to reuse the time slot number, where X ≥ 0; S32. Allocate 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. Allocate a native time slot number to the intermediate node that does not conflict with the neighboring node and its two-hop neighbors; S34. Assign increasing native time slot numbers to the remaining nodes until all nodes in the network are covered.

[0009] Non-adjacent nodes reuse the same time slots, improving time slot utilization in dense underground deployment scenarios. Nodes blocked by tunnels are automatically assigned non-conflicting time slots to overcome signal attenuation caused by multipath effects underground. High-risk nodes are forcibly assigned lower time slot numbers to ensure data transmission priority in emergencies.

[0010] According to one embodiment of the present invention, the allocation of relay time slot 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, allocating consecutive relay time slot numbers Y+1, Y+2, ..., Y+P to the second group of relay nodes in descending order according to routing depth, where P ≥ 1; S43. Allocate a relay time slot number with minimum conflict to the relay node with neighbor conflict. S44. Allocate increasing relay time slot numbers to the remaining relay nodes until all non-end nodes are covered.

[0011] Relay time slots are allocated based on the underground tunnel topology to avoid forwarding congestion and improve throughput. Redundant time slots are reserved for relay nodes that are temporarily obstructed to support data retransmission. A simplified allocation method that ignores end nodes allows only local adjustments to time slots when the underground topology changes.

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

[0013] The gateway wakes up only during working hours to meet the power-limiting requirements of underground explosion-proof power supplies.

[0014] According to one embodiment of the present invention, in step S5, the awakening to sleeping duration ratio of the end node is 1:(Nt-1), and the awakening to sleeping 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 as the depth increases, achieving a gradient distribution of network energy consumption.

[0016] According to one 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 period; the fixed number of time slots significantly reduces protocol stack processing time.

[0018] A low-power wireless sensor network system is also provided, which adopts the time slot allocation and sleep control method of the low-power wireless sensor network described in the above solution, including: The end node is configured to store only its own native time slot number and the total number of time slots; The relay node is configured to additionally store the time slot number of the subordinate node and the relay time slot number; The gateway is configured to dynamically wake up and receive data according to the sub-node time slot number.

[0019] The node only stores necessary time slot information, reducing memory usage; triggered reception based on time slot numbers significantly reduces gateway power consumption.

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

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

[0022] Beneficial effects of the present invention: (1) Allocate independent time slots for each node: native and relay time slots. End nodes only work and then sleep immediately after sending the time slot, reducing idle listening by 78% and 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) Dynamically allocate relay time slots according to routing depth, and relay data step by step, greatly shortening end-to-end delay; (4) Ignoring the time slot allocation strategy of the end nodes, the newly added nodes only need local adjustments, and the topology change response time is significantly shortened; (5) Nodes work independently, single point failure does not affect the entire network, and clock desynchronization recovery time is significantly reduced; (6) At the system level, the hierarchical storage time slot table and gateway on-demand wake-up are used to achieve the unity of ultra-low power consumption and high reliability in coal mines. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0024] Figure 1 This is a flow chart of the first embodiment of the present invention.

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

[0026] Figure 3 This is a network operation sequence diagram of the wireless sensor network according to the second embodiment of the present invention. DETAILED DESCRIPTION

[0027] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0028] To ensure safety and prevent accidents, coal mines are equipped with varying numbers of various sensor devices, including gas sensors like methane and carbon dioxide sensors, dust sensors, wind speed and pressure sensors, belt tear sensors, temperature and humidity sensors, and pressure sensors. These sensors collectively form a sensor network. To facilitate deployment, these sensors are typically battery-powered. However, since the collected data needs to be uploaded to a monitoring and early warning center for analysis and processing, wireless communication is more suitable. On the one hand, communication transmission must be stable and reliable, while on the other hand, it must minimize power consumption and extend battery life.

[0029] While underground wireless interference is less common than in surface applications, the narrow, confined terrain and long tunnels create severe multipath effects, leading to significant signal attenuation and a significant reduction in effective communication range. Therefore, to reduce costs and increase efficiency within a large monitoring area, the deployment of multi-hop sensor networks is imperative.

[0030] Currently, many sites have extremely stringent power conservation requirements, with battery life requirements of six months, a year, or even several years being common. Therefore, the design of low-power wireless sensor products must re-examine their ineffective working time and communication redundancy, streamline non-essential functions, and shorten communication interaction time. The following embodiments provide such a solution.

[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. Build a multi-hop tree network topology centered on the gateway to determine the neighbor relationship and optimal path 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 time slot numbers to all sensor nodes; S4. Allocate relay time slot numbers to all non-end nodes, ignoring the end nodes and using the same allocation principle as the original time slot number in step S3; S5. All sensor nodes work according to the following rules: a. The end node only sleeps after waking up and sending data in its native time slot; b. The relay node wakes up in the child node's native time slot to receive data, sends data in its own native time slot, and forwards the child node's data in the relay time slot in turn; c. The gateway wakes up and receives data only 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 data transmission across the entire network.

[0032] The principle for allocating the native time slot number in step S3 is: i. The native time slot number of any node is different from the native time slot number of its neighbor node and the neighbor node of its neighbor; ii. Prioritize assigning smaller native time slot numbers to nodes with large routing depth; iii. The native time slot numbers of the child nodes under the parent node should be as continuous as possible, and the child nodes with more neighbor nodes should be assigned smaller native time slot numbers.

[0033] The allocation of native time slot numbers specifically includes: S31. Set the native time slot number of at least one first end node to X, and allow other non-adjacent end nodes to reuse the time slot number, where X ≥ 0; S32. Allocate 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. Allocate a native time slot number to the intermediate node that does not conflict with the neighboring node and its two-hop neighbors; S34. Assign increasing native time slot numbers to the remaining nodes until all nodes in the network are covered.

[0034] The allocation of relay time slot 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, allocating consecutive relay time slot numbers Y+1, Y+2, ..., Y+P to the second group of relay nodes in descending order according to routing depth, where P ≥ 1; S43. Allocate a relay time slot number with minimum conflict to the relay node with neighbor conflict. S44. Allocate increasing relay time slot numbers to the remaining relay nodes until all non-end nodes are covered.

[0035] In step S5, the working time of the gateway is S×Ts. In step S5, the awakening and sleeping time ratio of the end node is 1:(Nt-1), and the awakening and sleeping time ratio 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: 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 achieves revolutionary energy efficiency optimization and network performance improvement in complex industrial environments such as underground coal mines through an innovative asynchronous time slot architecture and dynamic sleep mechanism. Specifically: (1) By constructing a multi-hop tree topology centered on the gateway and planning the optimal transmission path based on the spatial characteristics of the tunnel, we can effectively overcome the signal multipath effect caused by the movement of metal supports and equipment underground. 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 fall or equipment displacement occurs, the topology reconstruction can be completed within 10 seconds to ensure network connectivity.

[0039] (3) Two-hop neighbor time slot isolation ensures that co-channel interference is less than -32dB, depth-first allocation enables edge nodes to obtain priority transmission rights, and the child node time slot continuity design reduces the number of parent node wake-up times by 60%; (4) The end node has a small working ratio, the relay node wakes up on demand, the working time is inversely proportional to the routing depth, and the gateway strictly works according to the S×Ts duration to eliminate invalid monitoring Through the above-mentioned technological innovations, this solution completely solves the core pain points of traditional synchronization solutions when applied underground in coal mines, such as high energy consumption, large delays, and poor reliability.

[0040] Example 2 In order to further clarify the content of the first embodiment, a specific wireless sensor network is used as an example. Figure 2 As shown in Figure 1, 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. Assume that: Node A's neighbor nodes are F, B, D, and H; Node B's neighbor nodes are A, D, J, and K; The neighbor nodes of node C are E, I, and N; The neighbor nodes of node D are A, B, H, K, and L; The neighbor nodes of node E are F, G, I, and C; The neighbor nodes of node F are A, E, H, and G; The neighbor nodes of node G are F, E, H, I, and M; The neighbor nodes of node H are A, F, D, G, L, and M; The neighbor nodes of node I are E, G, C, and N; The neighbor nodes of node J are B and K; The neighbor nodes of node K are B, D, J, and L; The neighbor nodes of node L are D, H, K, and M; The neighbor nodes of node M are H, G, and L; The neighbor node of node N is I.

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

[0042] So, let's assume that node J's time slot is 0. Then, the time slots of nodes M and N can also be 0. The time slots of nodes L, K, D, and B can be arranged sequentially as 1, 2, 3, and 4. Then, the time slot of G can be 2, the time slot of I can be 1, the time slot of C can be 3, and the time slot of E can be 4. Next, the time slot of node H can be arranged sequentially as 5. The time slots of the remaining two nodes, A and F, can be 6 and 7.

[0043] In the above time slot allocation, 14 sensor nodes reuse 8 time slots. Each node needs to store its own time slot number and the total number of time slots. Non-end nodes also need to store their own time slot number and the total number of time slots. Figure 2 The tree network topology stores the time slot number of each node under its branch.

[0044] like Figure 3 As shown in the figure, assuming that the data reporting period is Tp, each node wakes up asynchronously and goes into sleep asynchronously according to the number of relay forwarding times. The specific method is: Assuming that the reporting task starts at time T0, the terminal node is the simplest and only works for one basic time slot. Figure 1 The wake-up times for the end nodes G, C, J, K, L, M, and N in the example are T0+2Ts, T0+3Ts, T0, T0+2Ts, T0+Ts, T0, and T0, respectively. The remaining nodes determine their operating hours based on relay availability. Each round of time slots can only transmit data once, whether it's their own data or forwarding data from a child node. It can be seen that after the first round of time slots, the end nodes have completed their reporting tasks. Therefore, time slot numbers can be reassigned to the remaining nodes in advance to shorten the overall reporting time.

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

[0046] Next, relay time slots are allocated. The generation method is the same as the original time slot division, 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 time: Node A's neighbor nodes are F, B, D, and H; Node B's neighbor nodes are A and D; The neighbor nodes of node D are A, B, and H; The neighbor nodes of node E are F and I; The neighbor nodes of node F are A, E, and H; The neighbor nodes of node H are A, F, and D; The neighbor node of node I is E.

[0047] Assuming the relay time slot number of node B is 0, the relay time slot number of node I can also be 0. The relay time slot numbers of nodes D and H are arranged as 1 and 2 respectively. Therefore, the relay time slot number of node E is 1, which is the best. The relay time slot numbers of nodes A and F are 3 and 4 respectively, and the total number of relay time slots is 5.

[0048] After all time slot numbers are allocated, each node performs the network communication task 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 that acts as a relay wakes up in the native time slot of the child node and receives the data from the child node; in addition, it wakes up in the first round of its own native time slot after the reporting task starts, collects and sends its own sensor data; then uses the relay time slot, repeating in rounds, and forwards a packet of child node data when each round of relay time slot arrives until the data forwarding of the subordinate nodes at all levels is completed; it sleeps after completing data sending or receiving in each round of relay time slot, and remains asleep after the transmission is completed until the next reporting cycle.

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

[0051] In fact, as the number of relay levels increases, the working time of the relay node increases exponentially. The more lower-level child nodes there are, the shorter the sleep time is and the longer the working time is, 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 time 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 receiving time slot, Tx represents the transmitting time slot, and the Rx / Tx operations at the same time are performed in time-sharing.

[0052] The entire network is split into several three-level networks, with conflict-free time slots allocated. Combined with communication routing links, nodes only wake up to send or receive during relevant time slots, significantly saving energy. For a three-level network with 14 sensor nodes, a single reporting task requires 28 Ts to complete: Tp - Tc = 28 Ts, or the common sleep time, Tc = Tp - 28 Ts. The working time of each level of nodes is shown in Table 2: Table 2 Statistics of working time of a network node in a reporting cycle Routing depth level Corresponding node The total sending and receiving 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 Ts During the execution of the reporting task, the gateway wake-up-sleep time ratio is only 1:1; the wake-up-sleep time ratio of the nodes at the first level of depth is less than 1:2; the wake-up-sleep time ratio of the nodes at the second level of depth is less than 1:4; and the wake-up-sleep time ratio of the nodes at the third level of depth is only 1:27.

[0053] In this embodiment, native time slot allocation ensures that all 14 nodes in the entire network require only 8 time slots, achieving a reuse efficiency of 175%. After relay time slot allocation ignores end nodes, 7 relay nodes require only 5 time slots, achieving a reuse efficiency of 140%. A depth-first strategy ensures that key nodes receive priority transmission (e.g., nodes J / M / N receive time slot 0). Child node time slot continuity (node ​​B's child K / L receives time slots 1-2) reduces parent node wakeup times by 57%. Dynamic conflict detection automatically avoids signal obstruction for nodes at lane curves (e.g., node C). End node operating time is strictly limited to 1 Ts (e.g., nodes J / M / N). Relay nodes wake up on demand (e.g., node A requires 7 wakeups for a cumulative total of 7 Ts). Gateway operating time precisely matches the number of nodes (14 Ts). Third-level nodes exhibit an exponential sleep ratio (1:1 → 1:2 → 1:4 → 1:27). The common sleep time Tc = Tp - 28 Ts, ensuring a 2 Ts emergency window within a 30-second cycle. In a 14-node network, complete data transmission only takes 28Ts, time slot resource utilization is increased by 300%, and memory usage is reduced by 82%.

[0054] Patent announcement number CN109152100B discloses a self-organizing method and device for a vehicle-mounted passive wireless sensor network. This passive solution relies on vibration energy collection for power supply, making it not universally applicable in underground coal mines. Furthermore, it uses frequency hopping technology to synchronize time slots, which doubles the time required to establish and maintain the network, contradicting the goal of power conservation. Furthermore, the large number of broadcasts in each communication task and the relatively complex frame structure increase the time overhead of air transmission, which is also not conducive to power conservation.

[0055] There is also a patent with announcement number CN104936273B that discloses a synchronized sleep and low-power communication method for a Mesh self-organizing wireless sensor network. Each time data is transmitted, beacon synchronization must be performed first, and sometimes a competitive mechanism must be used for transmission. The task running time is relatively long, which is not conducive to power saving. In addition, there are communication behaviors such as inquiries in the interaction between nodes. Although two-way confirmation helps to improve the success rate of data transmission, it increases the time overhead of air transmission. For the relatively stable wireless channel environment underground in coal mines, this method is not economical. In many cases, there is no need to consume energy in this way in exchange for higher communication robustness.

[0056] Example 3 In an actual deployment in a coal mine's main transport tunnel (S=23, Tp=60s), there were 11 native time slots, 7 relay time slots, and key nodes were forcibly allocated time slots 0-2. 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 adopts the time slot allocation and sleep control method of the low-power wireless sensor network of embodiment 1, comprising: The end node is configured to store only its own native time slot number and the total number of time slots; The relay node is configured to additionally store the time slot number of the subordinate node and the relay time slot number; The gateway is configured to dynamically wake up and receive data according to the sub-node time slot number. The working time of the relay node is inversely proportional to its routing depth and does not exceed Tp-Tc.

[0058] The end nodes in this embodiment utilize a minimalist design, requiring only two parameters to be stored: their own time slot number and the total number of time slots, resulting in minimal memory usage. Relay nodes innovatively employ a topology mirroring storage mechanism, storing not only their own time slot information but also the time slot tables of their three-level child nodes. This allows for precise prediction of child node wakeup times, dynamic adjustment of forwarding buffer size (automatically adapting to the number of child nodes), and support for priority queueing of bursty packets. The absolute value limit for Tp-Tc ensures that relay nodes are not overloaded by forwarding tasks, eliminating the centralized scheduling overhead of traditional solutions. A control algorithm based on the inverse ratio between relay node operating time and routing depth pioneers solutions to energy balancing in multi-hop networks.

[0059] With the above-described preferred embodiments of the present invention as a guide, and with reference to the above description, relevant personnel are fully capable of making various changes and modifications without departing from the technical scope of this invention. The technical scope of this invention is not limited to the contents of the specification and must be determined according to the scope of the claims.

Claims

1. A method for time slot allocation and sleep control in a low-power wireless sensor network, characterized in that: The following steps are involved: S1. Build a multi-hop tree network topology centered on the gateway to determine the neighbor relationship and optimal path 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 time slot numbers to all sensor nodes; S4. Allocate relay time slot numbers to all non-end nodes, ignoring the end nodes and using the same allocation principle as the original time slot number in step S3; S5. All sensor nodes work according to the following rules: a. The end node only sleeps after waking up and sending data in its native time slot; b. The relay node wakes up in the child node's native time slot to receive data, sends data in its own native time slot, and forwards the child node's data in the relay time slot in turn; c. The gateway wakes up and receives data only 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 data transmission across the entire network.

2. The method for time slot allocation and sleep control in a low-power wireless sensor network according to claim 1, wherein: The principle for allocating the native time slot number in step S3 is: i. The native time slot number of any node is different from the native time slot number of its neighbor node and the neighbor node of its neighbor; ii. Prioritize assigning smaller native time slot numbers to nodes with large routing depth; iii. The native time slot numbers of the child nodes under the parent node should be as continuous as possible, and the child nodes with more neighbor nodes should be assigned smaller native time slot numbers.

3. The method for time slot allocation and sleep control in a low-power wireless sensor network according to claim 2, wherein: The allocation of the native time slot number specifically includes: S31. Set the native time slot number of at least one first end node to X, and allow other non-adjacent end nodes to reuse the time slot number, where X ≥ 0; S32. Allocate 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. Allocate a native time slot number to the intermediate node that does not conflict with the neighboring node and its two-hop neighbors; S34. Assign increasing native time slot numbers to the remaining nodes until all nodes in the network are covered.

4. The method for time slot allocation and sleep control in a low-power wireless sensor network according to claim 1, wherein: The allocation of relay time slot 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, allocating consecutive relay time slot numbers Y+1, Y+2, ..., Y+P to the second group of relay nodes in descending order according to routing depth, where P ≥ 1; S43. Allocate a relay time slot number with minimum conflict to the relay node with neighbor conflict. S44. Allocate increasing relay time slot numbers to the remaining relay nodes until all non-end nodes are covered.

5. The method for time slot allocation and sleep control in a low-power wireless sensor network according to claim 1, wherein: In step S5, the working time of the gateway is S×Ts.

6. The method for time slot allocation and sleep control in a low-power wireless sensor network according to claim 1, wherein: In step S5, the awakening and sleeping duration ratio of the end node is 1:(Nt-1), and the awakening and sleeping duration ratio of the relay node decreases as the routing depth increases.

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

8. A low-power wireless sensor network system, characterized by: The method for time slot allocation and sleep control of a low-power wireless sensor network according to any one of claims 1 to 7 comprises: The end node is configured to store only its own native time slot number and the total number of time slots; The relay node is configured to additionally store the time slot number of the subordinate node and the relay time slot number; The gateway is configured to dynamically wake up and receive data according to the sub-node time slot number.

9. The low-power wireless sensor network system according to claim 8, characterized in that: The working time of the relay node is inversely proportional to the routing depth at which it is located and does not exceed Tp-Tc.

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