Communication networking and tag node rapid access method for UWB positioning in tunnels

Abstract

The present invention discloses a UWB-based communication networking and tag node rapid access method in a tunnel. Anchor nodes are deployed along the tunnel at linear intervals. An anchor node and the tag nodes located within its signal coverage range form a UWB-based communication subnet. Time slot management in the superframe of the communication subnet is divided into macro slots and micro slots. A complete task allocation is completed in a macro slot, and a macro slot contains at least one micro slot. When a tag node transitions from the communication subnet of one anchor node to the communication subnet of another anchor node, the anchor node of the communication subnet where the tag node is located actively allocates the macro slot and micro slot of the neighboring anchor node to the tag node through negotiation with the neighboring anchor node. The tag node does not need to move to the communication subnet of the neighboring anchor node and then apply for a time slot. The tag node can be online all the time as long as it enters the network once. The present invention improves the efficiency, real-time performance and reliability of communication, and also increases the density and real-time performance of tag nodes.

Description

Technical Field

[0001] The present invention relates to the technical field of UWB positioning communication, and in particular to a communication network suitable for UWB positioning in a tunnel without satellite positioning signals and a method for quickly accessing communication for a located tag node. Background Art

[0002] In recent years, tunnel construction technology and equipment have advanced rapidly, placing higher demands on construction safety, personnel, and equipment management. Tunnel construction has increased the need for positioning of construction personnel and mobile equipment. However, tunnels lack satellite positioning signals, making it impossible to use Global Navigation Satellite Systems (GNSS) such as GPS (Global Positioning System), BDS (Beidou Navigation Satellite System), and GLONASS. Therefore, unlike ground-based personnel and equipment, GNSS positioning and navigation cannot be employed, requiring the development of independent and self-organizing positioning solutions. UWB positioning methods can achieve centimeter-level positioning accuracy and are easy to deploy, meeting the positioning requirements of tunnel construction. Double-side two-way ranging (DS-TWR) is a time-of-flight (TOF)-based ranging method commonly used for ranging in UWB communications. DS-TWR uses multiple communications between two nodes, with the transmission and reception timestamps included in the communication messages. Using a specific algorithm, the time of flight of the electromagnetic wave between the two nodes is calculated. Multiplying this time by the speed of light yields the distance between the two nodes. During the DS-TWR communication process, the Phase Difference of Arrival (PDOA) method is used to measure the angle between the two nodes, so that the coordinate position of the measured node is determined based on the distance and angle to achieve positioning.

[0003] During positioning, the PDOA method, which measures the angle between a node's dual antennas and those of other nodes, does not require the node to transmit UWB messages; it merely monitors UWB messages from other nodes. However, a single DS-TWR ranging measurement requires four communication data packet exchanges between the anchor node and the tag node. To improve ranging accuracy, these four communications have strict return time requirements, requiring pre-planning of the DS-TWR transmission time slots to ensure that the transmission time error is within a certain range. All tag nodes in the same space share the communication bandwidth of that space. If tag node access to anchor nodes is not controlled, when a tag node is transmitting data, other nodes are likely to also transmit data, causing radio signal collisions and communication failure. A single DS-TWR communication requires four data packet exchanges. Data packets occupy the channel for a very short time (calculated as 1.2 milliseconds based on a maximum packet length of 127 bytes and a data rate of 850 Kbps. At a higher transmission rate of 6.8 Mbps, the channel occupancy time is only 150 microseconds). After receiving the data, nodes need time to process it. If all four ranging communications are allocated to a single time slot, a significant portion of the time slot will be idle, resulting in a significant waste of communication time. To improve communication efficiency, fully utilize channel resources, and reduce mutual interference, it is necessary to manage the communication process between tag nodes and anchor nodes and allocate communication time slots more accurately.

[0004] In order to reduce the time it takes for label nodes to access the anchor node communication subnet, it is necessary to make full use of the data exchange mechanism between multiple anchor nodes in the tunnel to implement the pre-allocation and immediate release of time slots for label nodes between two adjacent anchor nodes. This will improve the utilization of time slots, accommodate more label nodes, reduce competition with other nodes, and avoid wasting time slots and computing resources. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings and deficiencies of the existing technology and provide a communication networking and tag node rapid access method suitable for UWB positioning in tunnels. The tag node applies to join the nearest anchor node communication subnet based on its location, and is pre-assigned to other adjacent anchor nodes based on its location, thereby reducing the process of applying to join the anchor node communication subnet and achieving rapid access to the anchor node. In the communication time slot design, two levels of time slots are designed: macro time slot (MacroTime Slot) and micro time slot (Micro Time Slot). A macro time slot contains at least one micro time slot, and its micro time slot numbers are not necessarily continuous, so as to reduce idle time and increase the density of positioning tag nodes.

[0006] To achieve the above objectives, the present invention provides a technical solution: a method for UWB positioning communication networking and tag node rapid access in a tunnel, comprising:

[0007] Anchor nodes are deployed at linear intervals along the tunnel. Anchor nodes communicate and locate tag nodes via UWB. Anchor nodes communicate with each other via wired or wireless networks. An anchor node and tag nodes located within its signal coverage form a UWB-based communication subnet. The MAC layer protocol for UWB based on IEEE 802.15.4 is used, and a dynamic superframe structure is proposed based on this protocol. This structure consists of an active period and an inactive period. The active period consists of a beacon frame, a non-contention access phase (CFP), and a contention access phase (CAP). During the active period, anchor nodes first broadcast a Beacon frame, followed by a CFP, and finally a CAP.

[0008] The time slot management in the superframe of the communication subnet is divided into macro time slots and micro time slots. A complete task is assigned in a macro time slot. A macro time slot contains at least one micro time slot. These micro time slots are not necessarily consecutive. The number of micro time slots in the macro time slot and their position in the superframe are selected according to the timing requirements of the communication task to be completed.

[0009] When a tagged node transitions from one anchor node's communication subnet to another, the anchor node in the communication subnet where the tagged node is located negotiates with neighboring anchor nodes and proactively allocates the neighboring anchor node's macro and micro time slots to the tagged node. This eliminates the need for the tagged node to move to the neighboring anchor node's communication subnet and then apply for a time slot. The tagged node can remain online after just one network access. The tagged node actively applies for the first network access in the CAP. After that, during normal communication, it passively receives the macro and micro time slots allocated by the anchor node. If the anchor node does not receive communication frames from the tagged node for a long time, it releases its time slot.

[0010] Furthermore, the active periods of adjacent anchor nodes do not overlap, and time-sharing communication between anchor nodes and different tag nodes is achieved through time division multiple access (TDMA); the active periods of anchor nodes separated by one position can overlap, and simultaneous communication of different communication subnets is achieved through space division multiple access (SDMA), thereby improving the density of tag nodes and the real-time performance of communication.

[0011] Furthermore, the spacing between anchor nodes is lengthened, but it is necessary to ensure that at any location of the tag node there is at least one anchor node that can communicate with it, that is, the UWB communication distance of the tag node must be greater than half the spacing between anchor nodes; the anchor nodes can be installed on one side wall, both sides wall, or the top of the construction tunnel, and the superframe transmission time between adjacent anchor nodes is allocated according to TDMA time sharing. The communication cycle of the anchor nodes is set. Anchor node K is in the superframe state in the time interval [t1, t1+1], and starts sending Beacon frames at time t1, and continues to communicate for the preset time. In the time interval [t1+1, t1+2], it is in the non-superframe state and does not send UWB communication signals; while anchor nodes K-1 and anchor node K+1 are in the superframe state in the time interval [t1+1, t1+2]. These two nodes start sending Beacon frames at time t1+1 second. Due to their different spatial positions, the UWB signals will not interfere with each other, thereby achieving SDMA;

[0012] When the label node is at position a in the tunnel, it first detects the Beacon frame in the superframe of the anchor node. If two Beacon frames are detected in sequence within the duration of the two Beacon frames, it indicates that it is in the cross-coverage range of two adjacent anchor nodes. At this time, the label node selects the anchor node with larger signal strength to join, and the label node applies for the macro time slot and micro time slot of the CFP time interval in the CAP time interval of the superframe; when the label node is at position b in the tunnel, it is already in the transition area of ​​the anchor node. At this time, the anchor node K-1 negotiates with the anchor node K for the macro time slot and micro time slot for the label node through WIFI or other communication methods. The anchor node K-1 informs the label node of the applied time slot during the normal CFP communication process with the label node. After that, the label node can communicate with the anchor node K in the CFP time slot. The label node can also immediately apply to the anchor node K-1 to release the time slot it occupies. If the label node does not actively apply to release the time slot occupied by the anchor node K-1, then after a period of time, the label node does not communicate with the anchor node K-1, and the anchor node K-1 believes that the label node is no longer in the communication subnet it manages, and actively releases the CFP time slot occupied by the label node. Similarly, if the label node does not communicate with the anchor node to which it is assigned CFP, it will also actively clear the CFP time slot it occupies in its time slot allocation data table. After the label node enters the tunnel, once it applies for a communication subnet of an anchor node, if the data in the established time slot allocation data table is not lost due to a failure, it does not need to apply for a CFP time slot through competition in the CAP again. Otherwise, it needs to apply for a CFP time slot of the current anchor node's communication subnet in the CAP again.

[0013] Furthermore, a star topology is adopted in the communication subnet of each anchor node. The macro time slot of the anchor node broadcasting the Beacon frame occupies one micro time slot. A bilateral two-way ranging (DS-TWR) between the anchor node and the tag node includes four UWB communications. The entire communication consists of four positioning communication frames: the request frame (Poll frame), the response frame (Resp frame), the last frame (Final frame), and the confirmation frame (Ack frame). These frames occupy four micro time slots numbered i, i+3, i+6, and i+9, respectively. i is a possible micro time slot number. The other time slots between the four micro time slots (such as i+1 and i+2) can arrange ranging communications or other functional communications of other tag nodes.

[0014] After the time synchronization between the tag node and the anchor node is completed in the Beacon frame, CFP communication is immediately carried out. The time synchronization error between each tag node should be small, which is conducive to reducing the interference of UWB signals between time slots. In addition, if the communication fails in CFP, it can be communicated again through competition in CAP, and there is no need to wait for the next superframe to carry out CFP communication, which improves the reliability and real-time performance of communication. The micro-time slot only sends one communication frame, and multiple communication frames are sent back and forth and managed by the macro time slot. A macro time slot contains at least one micro time slot, and the micro time slots occupied by each tag node can be discontinuous. The Beacon frame is a broadcast frame sent by the anchor node and only occupies one micro time slot. A DS-TWR communication between the tag node and the anchor node is completed in CFP. The four positioning communication frames required for ranging, namely Poll frame, Resp frame, Final frame and Ack frame, occupy four micro time slots respectively and are managed by one macro time slot. Since ranging calculation and MCU access to the UWB transceiver require time, To improve communication efficiency, these four mini-slots are not consecutive but separated by three mini-slots. The Poll, Resp, Final, and Ack frames occupy mini-slots numbered i, i+3, i+6, and i+9, respectively. Here, i is the mini-slot number of the Poll frame, the first communication frame of the DS-TWR communication. This fixes the time intervals between these four communication frames. When the time difference between these time intervals is less than the preset microseconds, higher ranging accuracy is achieved. The macroslots in the CAP use a length of two mini-slots to ensure that the tag node and the anchor node can communicate back and forth once. The storage table for slot allocation is called the slot allocation table. In this table, the anchor node needs to store the slot allocations of all tag nodes in its communication subnet, while the tag node only needs to store a few of its own occupied slots. Both the anchor node and the tag node use the IEEE short address and PAN-ID address, which are 4 bytes in total, of which the short address and PAN-ID address are both 2 bytes.

[0015] Furthermore, in the four UWB communications between the anchor node and the tag node for positioning, since the length of each positioning communication frame is short, other data communication functions are enclosed in these communication frames, that is, other communication data frames and positioning data frames are merged into composite data frames to improve communication efficiency; the composite data frame is implemented using the frame type reserved in the MAC frame control field of IEEE802.15.4. The first byte of the composite data frame payload is the first function number. The length of the first function number and its related data content is fixed, followed by the second function number. The second function number and the content after it are consistent with the standard IEEE802.15.4 application layer protocol. The content length of the second function number is variable. Like the standard IEEE802.15.4, the total length of the first and second functions is marked in the physical frame header and is less than 128 bytes.

[0016] Furthermore, in terms of energy management of anchor nodes and tag nodes, an asymmetric energy management design is adopted, as follows:

[0017] The anchor node has a continuous power source and is always in working state; the tag node is powered by a battery, works during the active period, and is in sleep state during the inactive period; when the tag node is in sleep state, it is awakened by a pre-set clock and enters the active state, waiting for the Beacon frame from the anchor node. After receiving the Beacon frame, it first performs clock synchronization, superframe and working parameter updates, and then waits for its own macro slot and micro slot, completing the ranging and positioning tasks in the macro slot. If there are no other tasks to be completed, it immediately enters sleep state. Before entering sleep state, it configures the wake-up clock interrupt according to the start time of the next superframe (slightly in advance of the start time); if it still needs to communicate in the CAP, it completes the communication task of the CAP before entering sleep state.

[0018] Furthermore, taking into full consideration the interrupt response time of the microcontroller unit (MCU), the communication time between the MCU and the UWB transceiver, and the interrupt program execution time, a basic time unit Tb (such as 100 microseconds) is defined. Other time parameters are based on this basic time unit, thereby simplifying the configuration of key time parameters, including the duration of the micro-slot Tmicro being an integer multiple of Tb (such as 15Tb), the MCU waking up from sleep 2Tb earlier than the arrival time of the Beacon frame, and the clock synchronization accuracy of the anchor node and the tag node being configured to be 0.01Tb (if Tb is 100 microseconds, the clock synchronization accuracy is achieved according to 1 microsecond).

[0019] Furthermore, the workflow of the anchor node is as follows:

[0020] The anchor node performs time synchronization via wired or wireless means, allocates the time period of the Active state according to the location where it is installed in the tunnel, and stores it in the EEPROM of the anchor node. After power-on, the time synchronization is completed, and then it is determined in Step 501 whether it is in the Active state. If it is not in the Active state, it enters Step 502 to complete other tasks, including time synchronization, and then enters Step 503 to transfer the state in the Active time slot or the Inactive time slot according to the running time, and then returns to Step 501. If Step 501 is in the Active state at this time, then Enter Step 510 to determine the sub-state of the Active state, and enter Step 511, Step 512 and Step 513 according to the Beacon sub-state, CFP sub-state and CAP sub-state respectively; send a Beacon frame in Step 511; complete the CFP macro-slot and mini-slot communication in the time slot sequence in Step 512; complete the CAP macro-slot and mini-slot communication in the time slot sequence in Step 513; after completing Step 511, Step 512 and Step 513, enter Step 503 to complete the possible state transition, that is, transfer from one mini-slot to the next mini-slot, and then return to Step 501.

[0021] Furthermore, the workflow of the label node is as follows:

[0022] After the tag node is powered on, it enters Step 601 and listens to the Beacon frame of the anchor node. When the Beacon frame is listened to, the superframe information of the anchor node is updated, including the PAN-ID address and MAC short address (ie, IEEE short address) of the anchor node, time synchronization information, superframe structure information, Active and Inactive period periods and mini-slot width, and then enters Step 602. In Step 602, it is determined whether the anchor node has been added. If it has been added, it enters Step 611, otherwise it enters Step 603; in Step 603, it is determined whether it is in the CAP state according to the CAP time specified in the superframe structure; if it has not entered the CAP period, it continues to wait; if it has passed the CAP period, it enters Step 607 and enters the sleep state; if it is already in the CAP period, it applies for CF from the anchor node. P time slot, including macro time slot and micro time slot, and wait for one time slot, then enter Step 605 to determine whether it has received confirmation from the anchor node. If not, return to Step 603 to continue applying for CFP time slot. If the tag node applies for CFP time slot, it enters Step 606, in which it registers and updates the macro time slot and micro time slot and their related parameters; if the tag node already has a time slot allocated by the anchor node, it will transfer to Step 611 after the judgment in Step 602, in which DS-TWR communication is completed; then enter Step 612, in which other tasks of the tag node are completed, including neighbor node reserved time slot and time slot allocation table update, and then enter the Sleep state in Step 607 to achieve energy saving, and wake up through the clock interrupt before the next Beacon frame arrives.

[0023] Furthermore, the anchor node includes a first UWB communication module, a first MCU module, a UPS power module, a WIFI communication module and a first other functional module; the tag node includes a second UWB communication module, a second MCU module, a battery power module and a second other functional module; the first UWB communication module and the second UWB communication module are responsible for completing the UWB communication function, including positioning communication between the anchor node and the tag node, uploading sensor data of the tag node and issuing commands to the anchor node; the UPS power module provides continuous power supply to the anchor node, and the tag node is powered by the battery of the battery power module; the WIFI communication module completes the anchor node. WiFi communication between nodes, and communication between anchor nodes can also be achieved through wired Ethernet or optical fiber communication included in the first other functional module; the second other functional module realizes the sensing and measurement function; the first MCU module and the second MCU module of the anchor node and the tag node realize the application layer and MAC layer protocols of UWB communication, read the data packet transmission and reception time and phase parameters in the first UWB communication module and the second UWB communication module, thereby realizing ranging and angle measurement, and thus realizing the positioning function; the UWB transceiver adopts DW1000, the MCU of the tag node adopts STM32L072, and the MCU of the anchor node adopts STM32H750. The MCU and DW1000 communicate using the SPI interface, and respond to the transmission and reception events of DW1000 using interrupt mode.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] 1. The present invention makes full use of the narrow and long tunnel characteristics. The tag node adopts a communication time slot pre-allocation mechanism between different anchor nodes. That is, the tag node passively receives the macro time slot and micro time slot information allocated by the anchor node, thereby improving communication efficiency.

[0026] 2. The present invention swaps the front and back positions of CFP and CAP in the IEEE802.15.4 superframe, reducing the active time of the tag node and benefiting energy saving. It also allows unfinished communications in CFP to be resumed in CAP, improving the real-time and reliability of communication.

[0027] 3. Adopting a dynamic superframe structure and introducing a hierarchical time slot management mechanism of macroslots and microslots improves the utilization of time slots in the superframe and can increase the density and real-time performance of tag nodes.

[0028] 4. Integrate communication and positioning, and design a composite data frame structure to improve the utilization rate and payload ratio of communication frames. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the anchor node structure diagram.

[0030] Figure 2 This is the label node structure diagram.

[0031] Figure 3 This is the distribution diagram of anchor nodes and label nodes in the tunnel.

[0032] Figure 4 Schematic diagram of a superframe structure with macro slots and micro slots.

[0033] Figure 5 Schematic diagram of the time slot allocation table.

[0034] Figure 6 This is the anchor node workflow diagram.

[0035] Figure 7 This is the label node workflow diagram.

[0036] Figure 8 A diagram showing the composite data frame type and data payload structure. DETAILED DESCRIPTION

[0037] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0038] This embodiment discloses a communication network and tag node rapid access method suitable for UWB positioning in tunnels, the details of which are as follows:

[0039] See also Figure 1 and Figure 2As shown, the anchor node includes a first UWB communication module M101, a first MCU module M102, a UPS power module M103, a WIFI communication module M104 and a first other function module M105; the tag node includes a second UWB communication module M111, a second MCU module M112, a battery power module M113 and a second other function module M114; the first UWB communication module M101 and the second UWB communication module M111 are responsible for completing the UWB communication function, including positioning communication between the anchor node and the tag node, uploading sensor data of the tag node and issuing commands to the anchor node, etc.; the UPS power module M103 provides continuous power supply to the anchor node, and the tag node is powered by the battery of the battery power module M113; the WIFI communication The communication module M104 completes the WIFI communication between the anchor nodes, and the communication between the anchor nodes can also be achieved through the wired Ethernet or optical fiber communication included in the first other functional module M105; the second other functional module M114 realizes functions such as sensor measurement (such as inertial sensors, etc.); the first MCU module M102 and the second MCU module M112 of the anchor node and the tag node implement the application layer and MAC layer protocols of UWB communication, read the data packet transmission and reception time and phase parameters in the first UWB communication module M101 and the second UWB communication module M111, thereby realizing distance measurement and angle measurement, thereby realizing the positioning function; the UWB transceiver adopts DW1000, the MCU of the tag node adopts STM32L072, and the MCU of the anchor node adopts STM32H750. The MCU and DW1000 communicate using the SPI interface, and respond to the transmission and reception events of DW1000 using interrupt mode.

[0040] See also Figure 3As shown, anchor nodes are evenly spaced throughout the tunnel, communicating with each other via Wi-Fi, Ethernet, or fiber optics. To save costs, the spacing between anchor nodes is maximized, but it is essential that at any given tag node, there is at least one anchor node capable of communicating with it. This means that the UWB communication range of a tag node must be greater than half the spacing between anchor nodes. Anchor nodes can be installed on one or both sides of a construction tunnel, or on the tunnel roof. Each anchor node and the tag nodes within its signal coverage area form a UWB positioning communication subnet. Adjacent anchor nodes allocate superframe transmission time according to TDMA (time division multiple access) time division. For example, the communication cycle of the anchor nodes is designed to be 2 seconds. Anchor node K is in the superframe state in the time interval [t1, t1+1], starts sending Beacon frames at time t1, and continues communication for 1 second. In the time interval [t1+1, t1+2], it is in the non-superframe state and does not send UWB communication signals; while anchor nodes K-1 and anchor node K+1 are in the superframe state in the time interval [t1+1, t1+2]. These two nodes start sending Beacon frames at time t1+1 second. Because they are in different spatial positions, the UWB signals will not interfere with each other, thereby realizing SDMA (space division multiplexing).

[0041] See also Figure 3 As shown in the figure, when the tagged node enters the tunnel and is at position a in the tunnel (labeled as tagged node 7a), it first detects the Beacon frame in the superframe of the anchor node. If two Beacon frames are detected in sequence within the duration of the two Beacon frames, it means that it is in the cross coverage range of two adjacent anchor nodes. At this time, the tagged node selects the anchor node with larger signal strength to join. The tagged node applies for the allocation of macro slots and micro slots in the CFP time interval of the superframe in the CAP time interval (see Figure 4 As shown). When the label node is Figure 3 When the tag node is at position b (marked as tag node 7b), it is already in the transition area of ​​the anchor node. At this time, anchor node K-1 negotiates with anchor node K for macro time slots and micro time slots for the tag node through WIFI or other communication methods. Anchor node K-1 informs the tag node of the time slot it has applied for during the normal CFP communication process with the tag node. After that, the tag node can communicate with anchor node K in the CFP time slot. At the same time, the tag node can also immediately apply to anchor node K-1 to release the time slot it occupies. If the tag node does not actively apply to release the time slot occupied by anchor node K-1, then after a period of time, the tag node does not communicate with anchor node K-1, then anchor node K-1 believes that the tag node is no longer in the communication subnet it manages, and actively releases the CFP time slot occupied by the tag node. Similarly, the tag node does not communicate with the anchor node to which it is assigned CFP, and also actively releases the CFP time slot occupied by the tag node in its time slot allocation table (see Figure 5After a tag node enters a tunnel and applies for a communication subnet of an anchor node, it does not need to apply for a CFP time slot again through competition in the CAP unless the data in the established time slot allocation table is lost due to a fault. Otherwise, it needs to apply for a CFP time slot in the communication subnet of the current anchor node again in the CAP.

[0042] See also Figure 4As shown in the figure, based on the requirements of tunnel UWB positioning, the existing superframe structure of IEEE802.15.4 is modified to propose a dynamic superframe structure, which consists of an active period and an inactive period. The active period consists of three parts: a beacon frame, a contention free period (CFP), and a contention access period (CAP). Unlike the IEEE802.15.4 standard, the CFP phase of the present invention precedes the CAP phase, which reduces the requirements for node clock synchronization. The active periods of adjacent anchor nodes (e.g., anchor nodes K and K+1) do not overlap, enabling time-division multiple access (TDMA) to enable time-sharing communication between anchor nodes and different tag nodes. The active periods of anchor nodes separated by one position (e.g., anchor nodes K-1 and K+1) can overlap, enabling simultaneous communication across different communication subnets using SDMA (Space Division Multiple Access), improving tag node density and real-time communication. During the active period, anchor nodes first broadcast Beacon frames, followed by the CFP period, and finally the CAP period. After time synchronization between the tag node and anchor node is completed in the Beacon frame, CFP communication immediately commences. This minimizes time synchronization errors between tag nodes, helping to reduce UWB signal interference between time slots. Furthermore, if communication fails during CFP, communication can be resumed through contention in the CAP, eliminating the need to wait for the next superframe for CFP communication, improving communication reliability and real-time performance. A major difference from the IEEE802.15.4 standard is the adoption of a dual-layer time slot mechanism of macro slots and micro slots. A micro slot only sends a communication frame once, while multiple communication frames are sent back and forth and managed through a macro slot. A macro slot contains at least one micro slot, and the micro slots occupied by each tag node can be discontinuous, which is very flexible.Beacon frames are broadcast frames sent by anchor nodes and only occupy one micro-time slot. A DS-TWR communication between a tag node and an anchor node is completed in the CFP time period. The four positioning communication frames required for ranging, namely Poll frame, Resp frame, Final frame and Ack frame, occupy four micro-time slot frames respectively and are managed by one macro-time slot. Since ranging calculation and MCU access to UWB transceiver require time, in order to improve communication efficiency, these four micro-time slots are not continuous, but are separated by three micro-time slot intervals, namely Poll frame, Resp frame, Final frame and Ack frame, respectively. The four mini-slots numbered i, i+3, i+6, and i+9 are occupied. Here, i is the mini-slot number of the first communication frame (i.e., the Poll frame) of this DS-TWR communication. This fixes the time intervals between these four communication frames. When the time difference between these time intervals is less than 400 microseconds, higher ranging accuracy is achieved. This also reduces the extra idle time between communication frames caused by transmitting four DS-TWR communication frames in a single time slot or across multiple consecutive time slots in the common superframe structure. The dual-layer structure of macroslots and mini-slots improves communication efficiency. (See [1] for details.) Figure 4 As shown in Figure 2, the macro slot in CAP uses a length of 2 micro slots to ensure that the tag node and the anchor node can communicate back and forth once. Figure 5 A storage table for time slot allocation is given, called the time slot allocation table. In the time slot allocation table, the anchor node needs to store the time slot allocation of all tag nodes in its communication subnet, while the tag node only needs to store a few occupied time slots of its own. Figure 5 In the table, the anchor node number column is not required for anchor nodes, but it is required for tag nodes because tag nodes can be in the communication subnets of two anchor nodes at the same time. Both anchor nodes and tag nodes use IEEE short addresses (2 bytes) and PAN-ID addresses (2 bytes), totaling 4 bytes.

[0043] See also Figure 6As shown in the figure, the anchor node's workflow is as follows: The anchor node synchronizes time via Wi-Fi or other means. The time period for the Active state is assigned based on its installation location in the tunnel and stored in the anchor node's EEPROM. After powering on, the anchor node completes time synchronization (Step 500). Then, in Step 501, it determines whether it is in the Active state. If not, it proceeds to Step 502, completing other tasks such as time synchronization. It then proceeds to Step 503, transitioning between the Active period and the Inactive period based on the running time, and then returns to Step 501. If Step 501 indicates the Active state, it proceeds to Step 510, determining the Active state's substate. Based on the Beacon, CFP, and CAP substates, it proceeds to Steps 511, 512, and 513, respectively. In Step 511, a Beacon frame is sent; in Step 512, CFP macroslot and minislot communications are completed in sequence; and in Step 513, CAP macroslot and minislot communications are completed in sequence. After completing Step 511, Step 512, and Step 513, the process proceeds to Step 503, completes possible state transitions (from one mini-time slot to the next mini-time slot), and then returns to Step 501.

[0044] See also Figure 7As shown in Figure 6, the tag node's workflow is as follows: After powering on, the tag node proceeds to Step 601, listening for anchor node Beacon frames. Upon receiving a Beacon frame, the node updates the anchor node's superframe information, including the anchor node's PAN-ID address and short MAC address (i.e., IEEE short address), time synchronization information, superframe structure information, active and inactive period periods, mini-slot width, and so on. The node then proceeds to Step 602. In Step 602, the node determines whether it has joined the anchor node. If so, the node proceeds to Step 611; otherwise, the node proceeds to Step 603. In Step 603, determine whether it is in the CAP state according to the CAP time specified in the superframe structure; if it has not entered the CAP period, continue waiting; if it has passed the CAP period, enter Step 607 and enter the sleep state; if it is already in the CAP period, apply for a CFP time slot (including macro time slots and micro time slots) from the anchor node and wait for one time slot, then enter Step 605 to determine whether it has received confirmation from the anchor node. If not, return to Step 603 and continue to apply for a CFP time slot. If the tag node applies for a CFP time slot, enter Step 606, and register and update the macro time slot and micro time slot and their related parameters in Step 606. If the tag node already has a time slot allocated by the anchor node, it will proceed to Step 611 after the judgment in Step 602. In Step 611, the DS-TWR ranging communication is completed; then it proceeds to Step 612, in which other tasks of the tag node are completed, including neighbor node reserved time slots and time slot allocation table updates, etc. Then, it enters the Sleep state in Step 607 to achieve energy saving and wakes up through the clock interrupt before the next Beacon frame arrives.

[0045] See also Figure 8 As shown, the present invention is backward compatible with the existing IEEE802.15.4 MAC frame structure. A new frame type (composite data frame, which is a special composite communication frame) is added to the original MAC frame to implement the positioning communication content required by the present invention. The newly added composite data frame is implemented by using the frame type reserved in the MAC frame control field, and 101b is used to identify the composite data frame. The first byte of the composite data frame payload is the first function number. The length of the first function number and the data content related to it is fixed. It is followed by the second function number. The second function number and the content after it are consistent with the application layer protocol of the standard IEEE802.15.4. The content length of the second function number is variable. Like the standard IEEE802.15.4, the total length of the first and second functions is identified in the physical frame header and is less than 128 bytes. Figure 8 The relevant function numbers and byte numbers of the positioning communication frame and time slot management frame are given in the figure, which can meet the needs of tunnel positioning.

[0046] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for fast accessing UWB-based communication networks and tag nodes in tunnels, characterized in that: include: Anchor nodes are deployed at linear intervals along the tunnel. Anchor nodes communicate and locate tag nodes via UWB. Anchor nodes communicate with each other via wired or wireless methods. An anchor node and the tag nodes located within its signal coverage form a UWB positioning communication subnet. A dynamic superframe structure is proposed, consisting of an active period and an inactive period. The active period consists of a beacon frame, a non-contention access phase (CFP), and a contention access phase (CAP). During the active period, anchor nodes first broadcast a Beacon frame, followed by a CFP, and finally a CAP. The time slot management in the superframe of the communication subnet is divided into macro time slots and micro time slots. A complete task allocation is completed in a macro time slot. A macro time slot contains at least one micro time slot, and these micro time slots are not necessarily consecutive. When a tagged node transitions from one anchor node's communication subnet to another, the anchor node in the tagged node's communication subnet negotiates with neighboring anchor nodes to proactively allocate the neighbor's macro and micro time slots to the tagged node. This eliminates the need for the tagged node to move to the neighbor's communication subnet and then apply for a time slot. The tagged node only needs to be online once. The tagged node actively applies for network access on the CAP for the first time. Thereafter, during normal communication, it passively receives macro and micro time slot information allocated by the anchor node. If the anchor node does not receive communication frames from the tagged node for a long period of time, it releases its time slot. The active periods of adjacent anchor nodes do not overlap, and time-division multiple access (TDMA) is used to achieve time-sharing communication between anchor nodes and different tag nodes. The active periods of anchor nodes separated by one position can overlap, and space division multiple access (SDMA) is used to achieve simultaneous communication in different communication subnets, thereby improving the density of tag nodes and the real-time performance of communication. It is necessary to ensure that at any location of the tag node there is at least one anchor node that can communicate with it, that is, the UWB communication distance of the tag node must be greater than half the distance between the anchor nodes; the anchor nodes can be installed on one side wall, both sides wall or the top of the construction tunnel, and the superframe transmission time between adjacent anchor nodes is allocated according to the TDMA time sharing. The communication cycle of the anchor nodes is set. Anchor node K is in the superframe state in the time interval [t1, t1+1], and starts sending Beacon frames at time t1, and continues to communicate for the preset time. In the time interval [t1+1, t1+2], it is in the non-superframe state and does not send UWB communication signals; anchor nodes K-1 and anchor node K+1 are in the superframe state in the time interval [t1+1, t1+2]. These two nodes start sending Beacon frames at time t1+1 second. Due to their different spatial positions, the UWB signals will not interfere with each other, thus realizing SDMA; When the label node is at position a in the tunnel, it first detects the Beacon frame in the superframe of the anchor node. If two Beacon frames are detected in sequence within the duration of the two Beacon frames, it indicates that it is in the cross-coverage range of two adjacent anchor nodes. At this time, the label node selects the anchor node with larger signal strength to join, and the label node applies for the macro time slot and micro time slot of the CFP time interval in the CAP time interval of the superframe; when the label node is at position b in the tunnel, it is already in the transition area of ​​the anchor node. At this time, the anchor node K-1 negotiates with the anchor node K for the macro time slot and micro time slot for the label node through WIFI or other communication methods. The anchor node K-1 informs the label node of the applied time slot during the normal CFP communication process with the label node. After that, the label node can communicate with the anchor node K in the CFP time slot. The labeled node can also immediately request the release of its occupied time slot from anchor node K-1. If the labeled node does not proactively request the release of its occupied time slot at anchor node K-1, then after a period of time, if the labeled node does not communicate with anchor node K-1, anchor node K-1 will assume that the labeled node is no longer in the communication subnet it manages and proactively release the CFP time slot occupied by the labeled node. Similarly, if the labeled node does not communicate with the anchor node to which it is assigned CFP, it will proactively clear the CFP time slot it occupies from its time slot allocation data table. After entering the tunnel, once the labeled node has applied for a communication subnet of an anchor node, if the data in the established time slot allocation data table has not been lost due to a fault, it does not need to apply for a CFP time slot through competition in the CAP again. Otherwise, it needs to re-apply for a CFP time slot in the communication subnet of the current anchor node in the CAP. In the communication subnet of each anchor node, a star topology is adopted; The macro time slot of the anchor node broadcasting the Beacon frame occupies one micro time slot. A bilateral two-way ranging (DS-TWR) between the anchor node and the tag node includes four UWB communications. The entire communication consists of four positioning communication frames: the request frame (Poll frame), the response frame (Resp frame), the last frame (Final frame), and the confirmation frame (Ack frame). These four micro time slots occupy the four micro time slots numbered i, i+3, i+6, and i+9 respectively, where i is a possible micro time slot number. The other time slots between the four micro time slots can arrange ranging communications of other tag nodes or communications of other functions. After the time synchronization between the tag node and the anchor node is completed in the Beacon frame, CFP communication is immediately carried out. The time synchronization error between each tag node should be small, which is conducive to reducing the interference of UWB signals between time slots. In addition, if the communication fails in CFP, it can also communicate again through competition in CAP, without waiting for the next superframe to carry out CFP communication, which improves the reliability and real-time performance of communication. The micro-time slot only sends one communication frame, and multiple communication frames are sent back and forth through the macro time slot for management. A macro time slot contains at least one micro time slot, and the micro time slots occupied by each tag node can be discontinuous. The Beacon frame is a broadcast frame sent by the anchor node and only occupies one micro time slot. A DS-TWR communication between the tag node and the anchor node is completed in CFP. The four positioning communication frames required for ranging, namely Poll frame, Resp frame, Final frame and Ack frame, occupy four micro time slots respectively and are managed by one macro time slot. Since ranging calculation and MCU access to the UWB transceiver require time To improve communication efficiency, these four micro-slots are not continuous, but are separated by three micro-slot intervals. The Poll frame, Resp frame, Final frame, and Ack frame occupy the four micro-slots numbered i, i+3, i+6, and i+9, respectively. Here, i is the micro-slot number of the first communication frame of the DS-TWR communication, namely the Poll frame. This fixes the time intervals between the four communication frames. When the time difference between these time intervals is less than the preset microseconds, higher ranging accuracy is achieved. The macro slot in the CAP uses a length of two micro-slots to ensure that the tag node and the anchor node can communicate back and forth once. The storage table for time slot allocation is called the time slot allocation table. In this time slot allocation table, the anchor node needs to store the time slot allocation of all tag nodes in its communication subnet, while the tag node only needs to store a few of its own occupied time slots. Both the anchor node and the tag node use the IEEE short address and PAN-ID address, a total of 4 bytes, of which the short address and PAN-ID address are both 2 bytes. In the four UWB communications between the anchor node and the tag node for positioning, since the length of each positioning communication frame is short, other data communication functions are enclosed in these communication frames, that is, other communication data frames are merged with the positioning communication frame into a composite data frame to improve communication efficiency.

2. The method for communication networking and tag node rapid access for UWB positioning in a tunnel according to claim 1, characterized in that: In terms of energy management of anchor nodes and tag nodes, an asymmetric energy management design is adopted, as follows: The anchor node has a continuous power source and is always in working state; the tag node is powered by a battery, works during the active period, and is in sleep state during the inactive period; when the tag node is in sleep state, it is awakened by a pre-set clock and enters the active state, waiting for the Beacon frame from the anchor node. After receiving the Beacon frame, it first performs clock synchronization, superframe and working parameter updates, and then waits for its own macro slot and micro slot, completing the ranging and positioning tasks in the macro slot. If there are no other tasks to be completed, it immediately enters sleep state. Before entering sleep state, according to the start time of the next superframe, the wake-up clock interrupt is configured in advance; if communication is still required in the CAP, it will enter sleep state after completing the communication task of the CAP.

3. The method for communication networking and tag node rapid access for UWB positioning in a tunnel according to claim 2, characterized in that: Taking into full consideration the interrupt response time of the microcontroller MCU, the communication time between the MCU and the UWB transceiver, and the interrupt program execution time, a basic time unit Tb is defined. Other time parameters are based on this basic time unit, thereby simplifying the configuration of key time parameters, including the duration of the micro-time slot Tmicro being an integer multiple of Tb, the MCU waking up from sleep 2Tb earlier than the arrival time of the Beacon frame, and the clock synchronization accuracy of the anchor node and the tag node being configured according to 0.01Tb.

4. The method for communication networking and tag node rapid access for UWB positioning in a tunnel according to claim 3, characterized in that: The anchor node includes a first UWB communication module (M101), a first MCU module (M102), a UPS power module (M103), a WIFI communication module (M104) and a first other functional module (M105); the tag node includes a second UWB communication module (M111), a second MCU module (M112), a battery power module (M113) and a second other functional module (M114); the first UWB communication module (M101) and the second UWB communication module (M111) are responsible for completing UWB communication functions, including positioning communication between the anchor node and the tag node, uploading sensor data of the tag node and issuing commands to the anchor node; the UPS power module (M103) provides continuous power supply to the anchor node, and the tag node is powered by the battery of the battery power module (M113). Power supply; the WIFI communication module (M104) completes the WIFI communication between the anchor nodes, and the communication between the anchor nodes can also be achieved through the wired Ethernet or optical fiber communication included in the first other functional module (M105); the second other functional module (M114) realizes the sensing and measurement function; the first MCU module (M102) and the second MCU module (M112) of the anchor node and the tag node realize the application layer and MAC layer protocols of the UWB communication, read the data packet transmission and reception time and phase parameters in the first UWB communication module (M101) and the second UWB communication module (M111), thereby realizing distance measurement and angle measurement, thereby realizing the positioning function; the UWB transceiver adopts DW1000, the MCU of the tag node adopts STM32L072, and the MCU of the anchor node adopts STM32H750. The MCU and DW1000 communicate using the SPI interface, and respond to the transmission and reception events of the DW1000 using an interrupt mode.

Images