Communication networking and label node quick access method for UWB positioning in tunnel

Abstract

The invention discloses a UWB positioning communication networking and label node fast access method in a tunnel, anchor nodes are deployed along the tunnel according to a linear interval, one anchor node and label nodes positioned in a signal coverage range of the anchor node form a UWB positioning communication subnet, time slot management in a superframe of the communication subnet is divided into a macro time slot and a micro time slot, and the macro time slot and the micro time slot are distributed in the same time slot. One time of complete task distribution is completed in one macro time slot, and one macro time slot comprises at least one micro time slot; when a label node transits from a communication subnet of one anchor node to a communication subnet of another anchor node, the anchor node of the communication subnet where the label node is located actively allocates a macro time slot and a micro time slot of a neighbor anchor node to the label node by negotiating with the neighbor anchor node. The label node does not need to apply for a time slot after moving to a communication subnet of a neighbor anchor node, and the label node can be always online as long as the label node accesses the network once. According to the method, the communication efficiency, the real-time performance and the reliability are improved, and the density and the real-time performance of the label nodes are also improved.

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 fast access communication of a located tag node. Background Art

[0002] In recent years, tunnel construction technology and equipment have been developing rapidly, and higher requirements have been put forward for construction safety, construction personnel, and equipment management. In tunnel construction, the positioning requirements for construction personnel and construction mobile equipment have increased, but there is no satellite positioning signal in the tunnel, and the global navigation satellite system (GNSS) such as GPS (Global Positioning System), BDS (Beidou Navigation Satellite System) and GLONASS cannot be applied. Therefore, GNSS positioning and navigation cannot be used like ground personnel and equipment, and only independent and self-organizing positioning solutions can be developed. The UWB positioning method can achieve centimeter-level positioning accuracy and is easy to deploy, which can meet the positioning needs in tunnel construction. Double side two-way ranging (DS-TWR) is a ranging method based on time of flight (TOF), which is often used for ranging in UWB communication. DS-TWR uses multiple communications between two nodes, and attaches timestamps of the sending and receiving times in the communication message. According to a certain algorithm, the flight time of the electromagnetic wave between the two nodes can be calculated, and the distance between the two nodes can be obtained by multiplying it with the speed of light. During the DS-TWR communication process, the Phase Difference of Arrival (PDOA) method is used to measure the angle between two nodes, so that the coordinate position of the measured node is determined according to the distance and angle to achieve positioning.

[0003] During the positioning process, the PDOA method that measures the angle between the dual antennas of this node and other nodes does not require this node to transmit UWB messages, but only needs to monitor the UWB messages of other nodes. However, one DS-TWR ranging requires four communication data packet exchanges between the anchor node and the tag node. In order to improve the ranging accuracy, the transmission time of the four communications has strict return time requirements. It is necessary to pre-plan the transmission time slot of DS-TWR to ensure that the transmission time error is within a certain range. All tag nodes in the same space share the communication bandwidth of the space. If the tag node's access to the anchor node is not controlled, when a tag node is sending data, other nodes are likely to send data, causing communication radio signal conflicts and communication failures. A DS-TWR communication requires four data packet exchanges. The data packet occupies the channel for a very short time (calculated as 1.2ms based on the maximum data packet length of 127B and the data transmission rate of 850Kbps. If a higher transmission rate of 6.8Mbps is selected, the channel occupancy time is only 150us). After receiving the data, the node needs to spend a certain amount of time to process it. If the four ranging communications are allocated to one time slot, the time slot will be idle for a long time, resulting in a large amount of communication time wasted. In order to improve communication efficiency, make full use of channel resources, and reduce mutual interference, it is necessary to manage the communication process between the tag node and the anchor node and allocate the communication time slot 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 realize the pre-allocation of time slots and immediate release of time slots for label nodes between two adjacent anchor nodes, thereby improving the utilization of time slots, accommodating more label nodes, reducing competition with other nodes, and avoiding 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 prior art, and to provide a communication networking and tag node rapid access method suitable for UWB positioning in a tunnel. According to the position of the tag node, an application is made to join the communication subnet of the nearest anchor node, and the tag node is pre-allocated to other adjacent anchor nodes according to the position of the tag node, thereby reducing the process of applying to join the communication subnet of the anchor node and realizing rapid access to the anchor node. In the design of the communication time slot, two levels of time slots are designed: macro time slot and micro time slot. A macro time slot contains at least one micro time slot, and the micro time slot numbers are not necessarily continuous, so as to reduce idle time and improve the density of positioning tag nodes.

[0006] To achieve the above purpose, the technical solution provided by the present invention is: a communication network and tag node rapid access method for UWB positioning in a tunnel, including: Anchor nodes are deployed along the tunnel at linear intervals. Anchor nodes communicate and locate with tag nodes through UWB. Anchor nodes communicate with each other through wired or wireless communication. An anchor node and tag nodes located within its signal coverage form a UWB positioning communication subnet. The MAC layer protocol of UWB based on IEEE 802.15.4 is adopted. Based on this protocol, a dynamic superframe structure is proposed, which 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. In the active period, the anchor node first broadcasts the Beacon frame, followed by the CFP, and finally the 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. These micro time slots are not necessarily continuous. The number of micro time slots in the macro time slot and the position in the superframe are selected according to the timing requirements of the communication task to be completed. When a label 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 label node is located negotiates with the neighboring anchor node and actively allocates the macro time slot and micro time slot of the neighboring anchor node to the label node. The label node does not need to move to the communication subnet of the neighboring anchor node and then apply for the time slot. The label node can be online all the time as long as it enters the network once. Among them, the label node actively applies for the first time it enters the network in CAP, and then passively receives the macro time slot and micro time slot information allocated by the anchor node during normal communication. If the anchor node does not receive the communication frame of the label node for a long time, its time slot will be released.

[0007] Furthermore, the activity periods of adjacent anchor nodes do not overlap, and time-division multiple access (TDMA) is used to realize time-sharing communication between anchor nodes and different tag nodes; the activity periods of anchor nodes separated by one position can overlap, and space division multiple access (SDMA) is used to realize simultaneous communication of different communication subnets, thereby improving the density of tag nodes and the real-time performance of communication.

[0008] Furthermore, the distance 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 of the distance between anchor nodes; the anchor nodes can be installed on one side wall or both sides of the wall or the top of the tunnel, and the adjacent anchor nodes allocate the superframe transmission time according to the TDMA time-sharing, and set the communication cycle of the anchor nodes. Anchor node K is in the superframe state in the [t1, t1+1] time interval, starts sending Beacon frames at t1, and continues to communicate for the preset time. In the [t1+1, t1+2] time interval, 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 [t1+1, t1+2] time interval. These two nodes start sending Beacon frames at t1+1 seconds. Due to their different spatial positions, UWB signals will not interfere with each other, thereby 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 two Beacon frames, it means that it is in the cross-coverage range of two adjacent anchor nodes. At this time, the label node selects the anchor node with greater signal strength to join, and the label node applies for the allocation of macro time slots and micro time slots in 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, anchor node K-1 negotiates with anchor node K for macro time slots and micro time slots for the label node through WIFI or other communication methods. 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 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, then 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, the label node does not communicate with the anchor node to which it is assigned CFP, and it also actively clears 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 the CFP time slot again through competition in the CAP, otherwise it needs to re-apply for the CFP time slot of the communication subnet of the current anchor node in the CAP.

[0009] Furthermore, 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 a micro time slot, and 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, namely the request frame, the Poll frame, the response frame, the last frame, and the confirmation frame, namely the Ack frame, which occupy 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 (such as i+1, i+2) can arrange the ranging communication of other tag nodes or the communication 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 in CAP through competition, 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 slot 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, and the four positioning communication frames required for ranging, namely the 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 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, which occupy four micro-time slots numbered i, i+3, i+6 and i+9 respectively. At this time, i is the micro-time slot number of the first communication frame of the DS-TWR communication, namely, the Poll frame. In this way, the time interval between the four communication frames is fixed. When the time difference between these time intervals is less than the preset microseconds, it has a higher ranging accuracy. The macro time slot in CAP adopts a length of 2 micro-time 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 requires to store several occupied time slots of itself. 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.

[0010] 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 entrained 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, and the first byte of the composite data frame payload is the first function number, and the length of the first function number and the data content related to it is fixed, followed by the second function number, and the second function number and its subsequent content are consistent with the standard IEEE802.15.4 application layer protocol, and 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.

[0011] Furthermore, 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 to enter the active state, waiting for the Beacon frame of 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 time slot and micro time slot, completes the ranging and positioning tasks in the macro time slot, and immediately enters the sleep state if there are no other tasks to be completed. Before entering the sleep state, the wake-up clock interrupt is configured according to the start time of the next superframe (slightly in advance of a certain start time); if communication is still required in the CAP, it enters the sleep state after completing the communication task of the CAP.

[0012] 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 execution time of the interrupt program, a basic time unit Tb (such as 100 microseconds) is defined, and other time parameters are based on the 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 (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 according to 0.01Tb (if Tb is 100 microseconds, the clock synchronization accuracy is implemented according to 1 microsecond).

[0013] Further, the workflow of the anchor node is as follows: The anchor node performs time synchronization by 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 micro-slot communication in the order of time slots in Step 512; complete the CAP macro-slot and micro-slot communication in the order of time slots in Step 513; after completing Step 511, Step 512 and Step 513, enter Step 503 to complete possible state transfer, that is, transfer from one micro-slot to the next micro-slot, and then return to Step 501.

[0014] Furthermore, the workflow of the label node is as follows: After the tag node is powered on, it enters Step 601 and monitors the Beacon frame of the anchor node. When the Beacon frame is monitored, 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 time period and mini-time 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 to the anchor node for CF P time slot, including macro time slot and micro time slot, and wait for a time slot, then enter Step 605 to determine whether the anchor node is confirmed. If not, return to Step 603 to continue to apply for CFP time slot. If the tag node applies for CFP time slot, enter Step 606, and register and update macro time slot and micro time slot and related parameters in Step 606; if the tag node already has a time slot allocated by the anchor node, it will turn to Step 611 after judging in Step 602, and complete DS-TWR communication in Step 611; then enter Step 612, and complete other tasks of the tag node in Step 612, including neighbor node reserved time slot and time slot allocation table update, and then enter Sleep state in Step 607 to achieve energy saving, and wake up through clock interrupt before the next Beacon frame arrives.

[0015] 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, 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 measurement function; the first MCU module and the second MCU module of the anchor node and the tag node implement the application layer and MAC layer protocols of UWB communication, read the data packet receiving and sending time and phase parameters in the first UWB communication module and the second UWB communication module, so as to realize ranging 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 receiving and sending events of DW1000 by interrupt mode.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The present invention makes full use of the narrow and long characteristics of the tunnel. 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 the communication efficiency.

[0017] 2. The present invention exchanges the front and back positions of CFP and CAP in the IEEE802.15.4 superframe, which reduces the activity time of the tag node and is beneficial to energy saving; it is also beneficial that the unfinished communication in CFP can be communicated again in CAP, thereby improving the real-time and reliability of communication.

[0018] 3. A dynamic superframe structure is adopted, and a hierarchical time slot management mechanism of macro time slots and micro time slots is introduced to improve the utilization of time slots in the superframe, which can increase the density and real-time performance of tag nodes.

[0019] 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

[0020] Figure 1 This is the anchor node structure diagram.

[0021] Figure 2 It is a label node structure diagram.

[0022] Figure 3 This is the distribution diagram of anchor nodes and label nodes in the tunnel.

[0023] Figure 4 Schematic diagram of a superframe structure with macro time slots and micro time slots.

[0024] Figure 5 Schematic diagram of the time slot allocation table.

[0025] Figure 6 This is the anchor node workflow diagram.

[0026] Figure 7 This is a label node workflow diagram.

[0027] Figure 8 A schematic diagram of a composite data frame type and data payload structure table. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0029] This embodiment discloses a communication network and tag node fast access method suitable for UWB positioning in a tunnel, and the specific situation is as follows: 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 realized through the wired Ethernet or optical fiber communication contained in the first other functional module M105; the second other functional module M114 realizes the functions such as sensor measurement (such as inertial sensor, 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 receiving and sending time and phase parameters in the first UWB communication module M101 and the second UWB communication module M111, so as to realize the 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 receiving and sending events of DW1000 using interrupt mode.

[0030] See also Figure 3As shown in the figure, the anchor nodes are arranged at equal intervals along the tunnel, and the anchor nodes can communicate with each other via WIFI, Ethernet or optical fiber. In order to save costs, the distance between the anchor nodes is as long as possible, but it is necessary to ensure that at least one anchor node can communicate with the tag node at any position, that is, the UWB communication distance of the tag node must be greater than half of the distance between the anchor nodes. The anchor nodes can be installed on one side wall or both sides of the construction tunnel or on the top of the tunnel. Each anchor node and the tag nodes located within its signal coverage range form a UWB positioning communication subnet. The transmission time of superframes is allocated between adjacent anchor nodes according to TDMA (time division multiple access). For example, the communication cycle of the anchor node is designed to be 2 seconds. The anchor node K is in the superframe state in the time interval [t1, t1+1], and starts sending Beacon frames at t1, and continues to communicate 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 the anchor nodes K-1 and K+1 are in the superframe state in the time interval [t1+1, t1+2]. These two nodes start sending Beacon frames at 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).

[0031] See also Figure 3 As shown in FIG. 1 , when the labeled node enters the tunnel and is at position a in the tunnel (labeled as labeled 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 indicates that it is in the cross coverage range of two adjacent anchor nodes. At this time, the labeled node selects the anchor node with larger signal strength to join. The labeled node applies for the allocation of macro slots and micro slots in the CFP time interval in the CAP time interval of the superframe (see Figure 4 When the label node is in Figure 3 When the label node is at position b (marked as label 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 label node through WIFI or other communication methods. 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 anchor node K in CFP time slots. At the same time, the label node can also immediately apply to 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 anchor node K-1, then after a period of time, the label node does not communicate with anchor node K-1, then 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, the label 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 label node in its time slot allocation table (see Figure 5After 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 table is not lost due to a fault, it does not need to apply for a CFP time slot again through competition in the CAP. Otherwise, it needs to apply for a CFP time slot of the communication subnet of the current anchor node in the CAP again.

[0032] See also Figure 4As shown, according to the requirements of tunnel UWB positioning, the existing superframe structure of IEEE802.15.4 is modified, and a dynamic superframe structure is proposed, which consists of an active period (Activeperiod) and an inactive period (Inactive period). The active period consists of three parts: a beacon frame, a non-contention access period (Contention free period, CFP), and a contention access period (Contention access period, CAP); different from the IEEE802.15.4 standard, the CFP stage of the present invention is before the CAP stage, which reduces the requirements for node clock synchronization. The active periods between adjacent anchor nodes (such as the Kth anchor node and the K+1th anchor node) do not overlap, and the time-division communication between anchor nodes and different tag nodes is realized through TDMA (Time division multiple access); the active periods between anchor nodes separated by one position (such as the K-1th anchor node and the K+1th anchor node) can overlap, and the simultaneous communication of different communication subnets is realized through SDMA (Space division multiple access), which improves the density of tag nodes and the real-time performance of communication. During the active period, the anchor node first broadcasts the Beacon frame, then the CFP time period, and finally the CAP time period. 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 is smaller, 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 in CAP through competition, without waiting for the next superframe to carry out CFP communication, which improves the reliability and real-time performance of communication. A major difference from the IEEE802.15.4 standard is the adoption of a dual-layer time slot mechanism of macro time slots and micro time slots. A micro time slot only sends one communication frame, while multiple communication frames are sent back and forth and managed through a 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, 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 frames, Resp frames, Final frames, and Ack frames, occupy four micro-time slot frames respectively and are managed by one macro-time slot. Since ranging calculation and MCU access to the UWB transceiver require time, in order to improve communication efficiency, these four micro-time slots are not continuous, but differ by three micro-time slot intervals, namely Poll frames, Resp frames, Final frames, and Ack frames, respectively. Occupies 4 micro-time slots numbered i, i+3, i+6, and i+9. At this time, i is the micro-time slot number of the first communication frame (i.e., Poll frame) of this DS-TWR communication. In this way, the time intervals between these 4 communication frames are fixed. When the time difference between these time intervals is less than 400 microseconds, it has higher ranging accuracy. At the same time, it can reduce the redundant idle time between communication frames caused by the transmission of 4 DS-TWR communication frames in one time slot or multiple consecutive time slots in the general superframe structure. The two-layer time slot structure of macro time slots and micro time slots improves the communication efficiency. See. Figure 4 As shown, the macro slot in CAP uses 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 which the anchor node needs to store the time slot allocation of all label nodes in its communication subnet, while the label node only needs to store a few occupied time slots of itself. Figure 5 In the table, the anchor node number column is not needed for the anchor node, but the tag node needs this column because the tag node can be in the communication subnet of two anchor nodes at the same time. Both the anchor node and the tag node use the IEEE short address (2 bytes) and PAN-ID address (2 bytes), a total of 4 bytes.

[0033] See also Figure 6As shown, the specific workflow of the anchor node is as follows: the anchor node performs time synchronization through WIFI and other 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 (i.e., Step 500), 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 such as 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, it enters Step 510 to determine the sub-state of the Active state, and enters Step 511, Step 512 and Step 513 according to the Beacon sub-state, CFP sub-state and CAP sub-state respectively. In Step 511, a Beacon frame is sent; in Step 512, CFP macro time slot and micro time slot communication are completed in the order of time slots; in Step 513, CAP macro time slot and micro time slot communication are completed in the order of time slots. After completing Step 511, Step 512 and Step 513, enter Step 503, complete possible state transfer (transfer from one mini-time slot to the next mini-time slot) and then return to Step 501.

[0034] See also Figure 7As shown in FIG. 1 , the specific workflow of the tag node is as follows: after the tag node is powered on, it is in Step 601, monitoring the anchor node Beacon frame. When the Beacon frame is monitored, the superframe information of the anchor node is updated, including the anchor node PAN-ID address and MAC short address (ie, IEEE short address), time synchronization information, superframe structure information, Active and Inactive period cycles, mini-slot width, etc., and then enters Step 602. In Step 602, it is determined whether the anchor node has been added. If so, it enters Step 611, otherwise it enters 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 to wait; 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 a time slot, then enter Step 605 to determine whether the anchor node confirms it. If not, return to Step 603 to continue applying for a CFP time slot. If the tag node applies for a CFP time slot, enter Step 606 to register and update 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 proceed to Step 611 after judging in Step 602, in which 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., and 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.

[0035] 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, and the length of the first function number and the data content related to it is fixed. It is followed by the second function number, and the second function number and the content thereafter 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 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.

[0036] 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 equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for fast access of UWB-based communication networks and tag nodes in tunnels, characterized in that: include: Anchor nodes are deployed along the tunnel at linear intervals. Anchor nodes communicate and locate with tag nodes through UWB. Anchor nodes communicate with each other through wired or wireless communication. An anchor node and tag nodes located within its signal coverage form a UWB positioning communication subnet. The MAC layer protocol of UWB based on IEEE 802.15.4 is adopted. Based on this protocol, a dynamic superframe structure is proposed, which 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. In the active period, the anchor node first broadcasts the Beacon frame, followed by the CFP, and finally the 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. These micro time slots are not necessarily continuous. The number of micro time slots in the macro time slot and the position in the superframe are selected according to the timing requirements of the communication task to be completed. When a label 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 label node is located negotiates with the neighboring anchor node and actively allocates the macro time slot and micro time slot of the neighboring anchor node to the label node. The label node does not need to move to the communication subnet of the neighboring anchor node and then apply for the time slot. The label node can be online all the time as long as it enters the network once. Among them, the label node actively applies for the first time it enters the network in CAP, and then passively receives the macro time slot and micro time slot information allocated by the anchor node during normal communication. If the anchor node does not receive the communication frame of the label node for a long time, its time slot will be released.

2. The method for rapid access of UWB positioning communication network and tag nodes in a tunnel according to claim 1, characterized in that: The active periods of adjacent anchor nodes do not overlap, and time-division multiple access (TDMA) is used to realize 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 realize simultaneous communication of different communication subnets, thereby improving the density of tag nodes and the real-time performance of communication.

3. The method for rapid access of UWB positioning communication network and tag node in a tunnel according to claim 2, characterized in that: The distance between anchor nodes is lengthened, but it is necessary to ensure that at least one anchor node can communicate with the tag node at any position, that is, the UWB communication distance of the tag node must be greater than half of the distance between anchor nodes; the anchor nodes can be installed on one side wall or both sides of the construction tunnel or on the top of the tunnel. The superframe transmission time is allocated between adjacent anchor nodes according to the TDMA time-sharing method. 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 seconds. Due to their different spatial positions, UWB signals will not interfere with each other, thereby 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 two Beacon frames, it means that it is in the cross-coverage range of two adjacent anchor nodes. At this time, the label node selects the anchor node with greater signal strength to join, and the label node applies for the allocation of macro time slots and micro time slots in 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, anchor node K-1 negotiates with anchor node K for macro time slots and micro time slots for the label node through WIFI or other communication methods. 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 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, then 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, the label node does not communicate with the anchor node to which it is assigned CFP, and it also actively clears 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 the CFP time slot again through competition in the CAP, otherwise it needs to re-apply for the CFP time slot of the communication subnet of the current anchor node in the CAP.

4. The method for rapid access of UWB positioning communication network and tag nodes in a tunnel according to claim 3, characterized in that: In the communication subnet of each anchor node, a star topology is adopted; the macro time slot of the anchor node broadcasting Beacon frame occupies a micro time slot, and a bilateral two-way ranging DS-TWR between the anchor node and the tag node includes 4 UWB communications. The entire communication consists of 4 positioning communication frames, namely the request frame, the Poll frame, the response frame, the last frame, and the confirmation frame, namely the Ack frame, which occupy 4 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 4 micro time slots can arrange the ranging communication of other tag nodes or the communication 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 the tag nodes 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 in CAP through competition, 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 slot occupied by each tag node can be discontinuous; the Beacon frame is a broadcast frame sent by the anchor node and occupies only one micro time slot; a DS-TWR communication between the tag node and the anchor node is completed in the CFP, and the four positioning communication frames required for ranging, namely the 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 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, which occupy four micro-time slots numbered i, i+3, i+6 and i+9 respectively. At this time, i is the micro-time slot number of the first communication frame of this DS-TWR communication, namely the Poll frame. In this way, the time interval between these four communication frames is fixed. When the time difference between these time intervals is less than the preset microseconds, it has a higher ranging accuracy. The macro time slot in CAP adopts a length of 2 micro-time 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 requires to store several occupied time slots of itself. Both the anchor node and the tag node use 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.

5. The method for rapid access of UWB positioning communication network and tag nodes in a tunnel according to claim 4, characterized in that: 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 entrained in these communication frames, that is, other communication data frames are merged with the positioning communication frames 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 its subsequent content 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.

6. The method for rapid access of UWB positioning communication network and tag nodes in a tunnel according to claim 5, 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 to enter the active state, waiting for the Beacon frame of 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 time slot and micro time slot, completes the ranging and positioning tasks in the macro time slot, and immediately enters the sleep state if there are no other tasks to be completed. Before entering the 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 the sleep state after completing the communication task of the CAP.

7. The method for rapid access of UWB positioning communication network and tag nodes in a tunnel according to claim 6, characterized in that: Taking full account of the interrupt response time of the microcontroller MCU, the communication time between the MCU and the UWB transceiver, and the execution time of the interrupt program, a basic time unit Tb is defined, and 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.

8. The method for fast access of UWB positioning communication network and tag node in tunnel according to claim 7, characterized in that: The workflow of the anchor node is as follows: The anchor node performs time synchronization by 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 micro-slot communication in the order of time slots in Step 512; complete the CAP macro-slot and micro-slot communication in the order of time slots in Step 513; after completing Step 511, Step 512 and Step 513, enter Step 503 to complete possible state transfer, that is, transfer from one micro-slot to the next micro-slot, and then return to Step 501.

9. The method for fast access of UWB positioning communication network and tag node in tunnel according to claim 8, characterized in that: The workflow of the label node is as follows: After the tag node is powered on, it is in Step 601, monitoring the Beacon frame of the anchor node. When the Beacon frame is monitored, the superframe information of the anchor node is updated, including the PAN-ID address and MAC short address of the anchor node, i.e., the IEEE short address, time synchronization information, superframe structure information, Active and Inactive time periods and mini-slot width, and then enters Step 602, in which it is determined whether the anchor node has been added. If so, it enters Step 611, otherwise it enters Step 603; In step 603, it is determined whether the device is in the CAP state according to the CAP time specified in the superframe structure; if the device has not entered the CAP period, it continues to wait; if the device 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 a CFP time slot from the anchor node, including a macro time slot and a micro time slot, and waits for a time slot, then enters Step 605 to determine whether it has been confirmed by the anchor node. If not, it returns to Step 603 to continue applying for a CFP time slot. If the tag node applies for a 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 turn to Step 611 after judging in Step 602, in which the DS-TWR communication is completed; then it enters Step 612, in which other tasks of the tag node are completed, including neighbor node reserved time slots and time slot allocation table updates, and then enters the Sleep state in Step 607 to achieve energy saving, and wakes up through a clock interrupt before the next Beacon frame arrives.

10. The method for rapid access of UWB positioning communication network and tag nodes in a tunnel according to claim 9, 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, sensor data uploading of the tag node and issuing of anchor node commands; 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 realized through the wired Ethernet or optical fiber communication contained in the first other functional module (M105); the second other functional module (M114) realizes the sensing 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 receiving and sending time and phase parameters in the first UWB communication module (M101) and the second UWB communication module (M111), thereby realizing the distance measurement and angle measurement, and realizing the positioning function accordingly; 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 receiving and sending events of DW1000 using interrupt mode.

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