An Adaptive Dense Access Method and System Based on Time-Frame Spreading

Abstract

This invention discloses an adaptive dense access method and system based on time frame extension, mainly addressing the problems of high access overhead and computational complexity in existing technologies. The implementation scheme includes: a network-joining node constructs and broadcasts a control frame; non-network-joining nodes check the broadcast control frame and initiate a time slot allocation request; the network-joining node waits for a timer to expire and then performs time slot allocation based on the number of time slot allocation requests, i.e., the network-joining node actively allocates time slots to non-network-joining nodes; the network-joining node initiates a time slot allocation response after time slot allocation; and non-network-joining nodes check the time slot allocation response to complete dense access. This invention does not require obtaining global information or adjusting the time frame structure, and the protocol interaction process does not depend on a specific time frame structure. The entire access process is driven solely by the network-joining node, reducing computational complexity and overhead. It can be used in mobile ad hoc networks to ensure node access capability in dense scenarios without modifying the frame format.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, and further relates to an adaptive node access method and system, which can be used in mobile ad hoc networks to ensure the access capability of nodes in dense scenarios without modifying the frame format. Background Technology

[0002] Unlike traditional wireless ad hoc networks, highly dynamic ad hoc networks are characterized by rapidly changing network topologies, with some areas densely populated with nodes and others sparsely populated. Link time slot resources are shared by all nodes within a local topology. Existing access protocols allocate entire time frames to nodes in the network on a time slot basis to facilitate node access. However, for a given time frame structure, the number of time slots in a frame is fixed. In highly dynamic scenarios, the number of nodes in a local topology may exceed the number of available time slots in a time frame, resulting in some nodes having no available time slots and being unable to access the network. Reducing the time slot length can increase the number of available time slots in a time frame to accommodate more nodes, but the clock accuracy of physical devices is limited, and the time frame length cannot be reduced indefinitely. Increasing the time frame length directly increases the number of available time slots, but nodes in a network are not always densely packed; highly dynamic scenarios also have many sparsely populated areas, and increasing the number of time slots in a time frame would lead to many time slots being wasted in these sparse areas.

[0003] In his paper "Global Resource Allocation for High Throughput and LowDelay in High-Density VANETs", T. Deng designed a global resource allocation strategy. This strategy reduces the number of wasted time slots through a time slot switching mechanism and designs a weight allocation mechanism for data packets to measure their importance. In scenarios with dense node distribution, this method achieves high overall network throughput, but it incurs significant overhead due to the need to obtain global information about the nodes.

[0004] Patent document with application number CN103096327B discloses an adaptive time slot allocation method based on TDMA, which dynamically adjusts the frame length to meet the access requirements of nodes when they sense changes in node density. However, this method incurs additional overhead because after the frame length is modified, the node needs to inform its neighboring nodes by broadcasting and wait for a time frame period to receive a response from the neighboring nodes.

[0005] Existing research on dense node access is largely based on IEEE 802.11p, and its improvements to this protocol can be categorized into three types: modifying the ratio of control channels to service channels, increasing data packet transmission by simplifying control packet interaction, and dynamically allocating channel resources to nodes. Since this protocol requires dividing a channel into seven channels based on frequency, including one control channel and six service channels, these studies all need to fully utilize the existing seven channel resources and jointly allocate time slot frequency resources to achieve dense node access, resulting in high complexity. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the prior art by proposing an adaptive dense access method and system based on time frame extension, so as to avoid time slot waste, improve the utilization rate of time slot resources, and enhance the access capability of nodes in dense scenarios without modifying the time frame structure.

[0007] To achieve the above objectives, the technical approach of this invention is to proactively partition occupied time slots and allocate them to non-networked nodes in dense scenarios through active probing by already connected nodes, enabling them to complete access; and to proactively reclaim idle time slots due to node departures in sparse scenarios, thereby avoiding time slot waste and improving the utilization rate of time slot resources. The technical solution includes the following:

[0008] Technical Solution 1:

[0009] An adaptive dense access method based on time frame extension includes:

[0010] The network entry node constructs and broadcasts control frames;

[0011] Unconnected nodes check broadcast control frames and initiate time slot division requests;

[0012] After the waiting timer expires, the network node performs time slot division based on the number of time slot division requests.

[0013] The node entering the network initiates a time slot division response after the time slot division;

[0014] Unconnected nodes check time slot segmentation responses to complete dense access.

[0015] Technical Solution 2:

[0016] An adaptive dense access system based on time frame extension includes:

[0017] The time slot table module is used to record the occupancy status of each multiframe by the current node and its neighboring nodes.

[0018] The neighbor table module is used to record the ID and hop count of each neighbor node and to count the number of neighbor nodes.

[0019] The time frame bit mode module is used to record the position of the current node in each multiframe in the superframe in a bit manner;

[0020] The timer module is used by the network access node to set the time slot division timeout after broadcasting a data frame containing probe information, and to trigger the time slot division algorithm after the timeout.

[0021] The perception scheduling module is used to trigger active probing and drive the timer module to work when the incoming node perceives that the number of neighboring nodes has reached a critical point and the number of multiframes of the current node is greater than 1.

[0022] The access module is used for non-network nodes to determine whether to send a time slot division request after sensing the active probing of network nodes, and to determine whether to complete the access after receiving the time slot division response.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] First, this invention addresses the characteristics of highly dynamic self-organizing networks where the local topology changes rapidly and nodes are sometimes dense and sometimes sparse. By having nodes actively probe the network and allocate time slots to nodes not yet joining, this invention improves the access capability of nodes in highly dynamic scenarios and increases the overall network throughput.

[0025] Second, the entire time slot division and recycling process of this invention is driven only by the network access node. Compared with the prior art, this invention does not need to obtain global information or adjust the time frame structure. The protocol interaction process does not depend on a specific time frame structure, which reduces the complexity of access and improves its universality. Attached Figure Description

[0026] Figure 1 This is the overall flowchart of Embodiment 1 of the adaptive dense access method based on time frame extension of the present invention;

[0027] Figure 2 yes Figure 1 The network-connected node constructs a control frame sub-flowchart containing probe information in the control time slot;

[0028] Figure 3 This is a diagram of the general time frame format used in Embodiment 1 of the present invention;

[0029] Figure 4 yes Figure 1 Sub-flowchart of time slot segmentation in the process

[0030] Figure 5 This is a block diagram of Embodiment 2 of the adaptive dense access system based on time frame extension of the present invention;

[0031] Figure 6 This is a simulation curve of the number of network nodes changing over time according to the present invention;

[0032] Figure 7 This is a simulation curve of the throughput as a function of load according to the present invention. Detailed Implementation

[0033] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0034] Terminology Explanation:

[0035] The “time slot” described in this example includes control time slots and data time slots, wherein m control time slots can constitute a control time frame and m data time slots can constitute a data time frame.

[0036] The "multiframe" described in this example consists of one control time frame and n-1 data time frames, such as... Figure 3 As shown.

[0037] The “superframe” described in this example refers to the structure that nodes spontaneously construct in dense scenarios. A superframe consists of several multiframes, and nodes that have not yet joined the network complete the network access by occupying a multiframe in the superframe.

[0038] The “time frame bit mode” described in this example is a binary bit group used to describe the position of the multiframe occupied by the current node in the superframe. For a superframe structure containing 4 multiframes, if the current node occupies all the multiframes, the bit mode is represented as 1111. If the current node only occupies the first 2 multiframes in the superframe, the bit mode is represented as 1100.

[0039] Example 1: Adaptive Dense Access Method Based on Time Frame Spread

[0040] Reference Figure 1 The technical solution in this example includes the following two parts:

[0041] Nodes already in the network actively probe and, in dense scenarios, proactively divide the already occupied time slots and allocate them to nodes not yet in the network to enable them to complete the access process.

[0042] In sparse scenarios, idle time slots due to node departures are proactively reclaimed for use by the current node, thereby improving the current node's access capability.

[0043] The implementation steps include the following:

[0044] Step 1: The network node constructs a control frame.

[0045] The control frame includes a node ID, control slot location, current node's time frame bit mode, probe flag, and time slot partitioning request timeout. When the probe flag is set to 1, the current control frame is said to "contain time slot partitioning probe information." The node entering the network initiates the adaptive dense access process by broadcasting the control frame containing this probe information.

[0046] like Figure 2 As shown, the steps for an incoming node to construct the control frame in a control time slot include:

[0047] 1.1) Assuming the number of multiframes in the current superframe is m, the number of time slots in the current frame is n, and the number of multiframes occupied by the network access node is m1, calculate the critical value for the network access node:

[0048] 1.2) The incoming node compares the number of neighboring nodes N with the threshold value L:

[0049] If N≥L, it indicates that the time slots in the current multiframe are fully utilized by the current node and all neighboring nodes. At this time, the node entering the network believes that there may be nodes in the network that have not yet entered the network, and executes step 1.3).

[0050] Otherwise, it indicates that the time slots in the current multiframe are not being fully utilized by the current node and its neighboring nodes. The new node will set the probe flag of the control frame to 0 and assume that there are idle time slot resources, and will reclaim the time slots, proceeding to step 1.4).

[0051] 1.3) The incoming node determines whether the number of multiframes occupied by the current node in the superframe is greater than 1:

[0052] If the number of multiframes occupied by the current node is greater than 1, the probe flag in the control frame is set to 1, the time slot division request timer is set, and the timer timeout is written into the control frame.

[0053] Otherwise, set the probe flag in the control frame to 0;

[0054] 1.4) Network access nodes perform time slot reclamation:

[0055] 1.4.1) The incoming node traverses all multiframes and occupied idle multiframes in the current superframe:

[0056] When a node enters the network, it traverses each bit of the frame bit pattern and skips bits that are 1.

[0057] For each bit that is 0 in the time frame bit mode, the incoming node queries the time slot table to check whether the multiframe corresponding to the current bit is occupied by a neighboring node:

[0058] If it is not occupied, the network node will mark the corresponding multiframe in the time slot table as occupied;

[0059] Otherwise, the incoming node skips the corresponding multiframe;

[0060] 1.4.2) Modify the current frame bit mode according to the position of the newly occupied multiframe in the superframe:

[0061] When a node enters the network, it traverses each bit of the frame bit pattern and skips bits that are 1.

[0062] For each bit in the time frame bit mode that is 0, check whether the multiframe corresponding to the current bit has been marked by the network entry node:

[0063] If marked, the incoming node sets the current bit in the time frame bit mode to 1;

[0064] Otherwise, the new node skips the current bit;

[0065] 1.5) The node entering the network will write its own node ID, the position of the control time slot it occupies, and the time frame bit mode into the control frame, and obtain the control frame as shown in Table 1, thus completing the construction of the control frame.

[0066] Table 1 Control Frame Format

[0067]

[0068] Step 2: The network entry node broadcasts a control frame.

[0069] The node entering the network broadcasts the control frame constructed in step one to each neighboring node, thereby informing them of the time slot division probe information and initiating the adaptive dense access process.

[0070] Step 3: Unconnected nodes check broadcast control frames.

[0071] 3.1) After receiving a broadcast control frame, a node that has not yet joined the network checks the "probe flag" field of the control frame:

[0072] If the probe flag in the control frame is 0, it is considered that the control frame does not contain probe information for time slot division. The non-networked node ignores the control frame and terminates the process.

[0073] Otherwise, it is assumed that the control frame contains probing information for time slot division, and step 3.2 is executed;

[0074] 3.2) Unconnected nodes check whether the current control time slot is occupied by other neighboring nodes within a two-hop range:

[0075] If the current control time slot is occupied by other neighboring nodes within two hops, the non-networked node terminates the process to avoid time slot occupation conflicts.

[0076] Otherwise, proceed to step 3.3);

[0077] 3.3) Comparison of time slot division request timeout T0 and current time T in the control frame for nodes not yet connected to the network:

[0078] If T0≤T, the time slot allocation request is considered to have timed out, and the process is terminated for nodes that have not yet joined the network.

[0079] Otherwise, proceed to step four.

[0080] Step 4: Nodes not yet connected to the network initiate time slot allocation requests.

[0081] The non-network-joined node constructs a time slot division request, which includes the ID of the current non-network-joined node and the ID of the network-joined node in the broadcast control frame in step two, as shown in Table 2.

[0082] Table 2 Time Slot Allocation Request Format

[0083] Current unregistered node ID (7 bits) Network access node ID (7 bits)

[0084] Nodes not yet on the network send the constructed time slot allocation request to nodes already on the network via unicast.

[0085] Step 5: The network node waits for the timer to expire and counts the time slot division requests.

[0086] The timer is a module set by the network access node when constructing the control frame to trigger a specific event after a certain period of time. Its function is to trigger the network access node to count the number of time slot division requests after the timeout.

[0087] 5.1) The network access node performs different operations based on whether its configured time slot division request timer has expired:

[0088] If the time slot division request timer has expired, proceed to step 5.2.

[0089] Otherwise, the node will wait indefinitely until the timer expires;

[0090] 5.2) The network node counts the number c of all received time slot division requests from the start of timer setting to timer expiration, and determines whether c is greater than 0:

[0091] If c > 0, the network entry node records the node IDs of each node that initiated the time slot division request and proceeds to step six.

[0092] Otherwise, if there are no unregistered nodes requesting a time slot, the process will terminate for the registered nodes.

[0093] Step six: The network access node performs time slot division.

[0094] Existing methods for dense node access include global resource allocation strategies, dynamic modification of time frame length, and multi-channel resource allocation. Among these, the global resource allocation strategy requires a central node to uniformly calculate the resource allocation result, which is not suitable for distributed scenarios; dynamic modification of time frame length requires informing all nodes in the network of the time frame modification information to ensure network clock synchronization, which incurs significant overhead; and multi-channel resource allocation requires joint time and frequency domain analysis, which is highly complex. This invention adopts a time slot segmentation method to limit the interaction process of dense node access to nodes between nodes that have joined the network and those that have not, thereby completing dense node access in a distributed manner with low overhead and low complexity.

[0095] Reference Figure 4 The implementation of this step includes the following:

[0096] 6.1) The network node defines the number of time slot divisions n that can be processed, and assigns n the number of time slot division requests c counted in step five;

[0097] 6.2) The network node traverses each bit in the time frame bit mode and counts the number of bits that are 1 in the time frame bit mode, which is used as the number of multiframes m occupied by the current node in the superframe.

[0098] 6.3) Compare the size relationship between the n+1 and m of the incoming nodes:

[0099] If n+1>m, it means that the existing multiframes of the network-connected node are insufficient to be allocated to all requesting nodes. The current node ignores the excess time slot allocation requests and assigns n to m-1. That is, the current node can only process the time slot allocation requests of m-1 non-network-connected nodes.

[0100] Otherwise, it means that before the time slot division timer expires, all time slot division requests received by the network node can be processed through time slot division.

[0101] 6.4) The network node divides m and n+1 to obtain the average number of multiframes occupied (avg);

[0102] 6.5) The network access node performs time slot division using bitwise operations. Starting from the least significant bit of the current time frame bit pattern, it iterates through each bit and counts the bits that are 1 in the time frame bit pattern. When the count reaches avg, the time frame bit pattern is divided to obtain a set of time frame bit patterns.

[0103] 6.6) Reset the count and repeat step 6.5) until n+1 groups of time frame bit patterns are obtained;

[0104] 6.7) In the n+1 group of time frame bit modes, the bit mode with the current multiframe corresponding to a bit of 1 is used as the new time frame bit mode for the network-entering node after time slot division, and the remaining n groups of time frame bit modes are used as the time frame bit modes for the nodes that have not yet entered the network after time slot division.

[0105] Step 7: The node entering the network initiates a time slot division response.

[0106] The network node matches the n sets of time frame bit patterns obtained in step six with the node ID recorded in step five to obtain the node ID and time frame bit pattern group, and constructs the time slot division response frame as shown in Table 3.

[0107] Table 3 Time Slot Division Response Frames

[0108] Node 1 ID (7 bits) Node 1 frame bit mode (4 bits) Node 2 ID (7 bits) Node 2 frame bit mode (4-bit) …… ……

[0109] The nodes joining the network broadcast time slot division response frames to the nodes that have not yet joined the network.

[0110] Step 8: Non-networked nodes check time slot division response.

[0111] After receiving the broadcast time-slot segmentation response frame, a node that has not yet joined the network checks whether its current node ID is already in the response frame:

[0112] If not, it means that the node joining the network has not performed time slot division for the current node, and the process of the non-joining node is terminated.

[0113] Otherwise, nodes not yet connected to the network obtain the time frame bit mode corresponding to the current node ID in the time slot division response frame, and complete the access by occupying the multiframe represented by the time frame bit mode in the superframe.

[0114] Example 2: Adaptive Dense Access System Based on Time Frame Spread

[0115] Reference Figure 5 This example includes a time slot table module 1, a neighbor table module 2, a time frame bit mode module 3, a timer module 4, a sensing and scheduling module 5, and an access module 6. Among them:

[0116] The time slot table module is used to record the occupancy status of each multiframe by the current node and its neighboring nodes.

[0117] The neighbor table module is used to record the ID and hop count of each neighbor node and to count the number of neighbor nodes.

[0118] The time frame bit mode module is used to record the position of the current node in each multiframe in the superframe in a bit manner;

[0119] The timer module is used by the network access node to set the time slot division timeout after broadcasting a data frame containing probe information, and to trigger the network access node to check the number of time slot division requests after the timeout.

[0120] The perception scheduling module is used to trigger active probing and drive the timer module to work when the incoming node perceives that the number of neighboring nodes has reached a critical point and the number of multiframes occupied by them is greater than 1.

[0121] The access module is used for non-network nodes to determine whether to send a time slot division request after sensing the active probing of network nodes, and to determine whether to complete the access after receiving the time slot division response.

[0122] The working principle of the above module is as follows:

[0123] The sensing and scheduling module 5 of the network node obtains the number of neighboring nodes by querying the neighbor table module 2. After the number of neighboring nodes reaches the critical point, it queries the frame bit mode module 3 to obtain the number of multiframes occupied by the current node. When the number of multiframes occupied by the current node is greater than 1, it triggers an active probe, broadcasts a probe frame to the neighboring nodes, and sets a timeout in the timer module 4 to wait for the timeout.

[0124] After receiving a probe frame, the access module 6 of the non-network node queries the neighbor table module 2 to obtain the IDs of each neighbor node within its two-hop range, and at the same time queries the time slot table module 1 to obtain the time slots occupied by each neighbor node. Then it determines whether any of these neighbor nodes has occupied the control time slot in the probe frame: if not, the non-network node sends a time slot division request; otherwise, the non-network node ignores the received probe frame.

[0125] After the timer module 4 of the network-joining node times out, it counts the number of received time slot division requests: if the number is 0, no further processing is performed; otherwise, the time slot division algorithm is triggered to perform time slot division, and a time slot division response frame is constructed based on the time slot division result and broadcast to the non-network-joining nodes.

[0126] After receiving the time slot division response frame, the access module 6 of the non-network node determines whether its node ID exists in the time slot division response frame. If it exists, the non-network node obtains the time frame bit mode corresponding to its node ID in the time slot division response frame and completes the access by occupying the multiframe represented by the time frame bit mode in the superframe. Otherwise, the non-network node needs to wait for the subsequent probe frame to re-access.

[0127] The effects of this invention will be further illustrated below with simulation experiments:

[0128] 1. Simulation experimental conditions:

[0129] The software platform for the simulation experiment was Windows 10 operating system and Exata 7.2.0.

[0130] The simulation parameter settings are shown in Table 4.

[0131] Table 4 Simulation Parameters

[0132]

[0133]

[0134] 2. Simulation content and result analysis:

[0135] Simulation 1: In the above scenario, both the present invention and the traditional TDMA protocol are used to statistically analyze the node network entry time and construct a curve showing the change in the number of network-entering nodes over time. The results are as follows: Figure 6 . Figure 6 The entire network access process is divided into three stages. The first stage is the node competition for network access, which starts from the beginning of the simulation and ends at about 0.8s. The second stage is the first time slot division stage, which starts from 0.8s and ends at about 1.6s. The third stage is the second time slot division stage, which starts after 1.6s and ends at the end of the simulation.

[0136] from Figure 6 As can be seen, the node network access status in the three stages is as follows:

[0137] In the first phase, all nodes compete to join the network. Since a time frame contains only 32 time slots, a maximum of 32 nodes can complete the network entry process. Thereafter, the critical node count for all nodes joining the network is set to 32.

[0138] In the second phase, all nodes that joined the network in the first phase are allocated time slots to idle nodes so that idle nodes can join the network. Since 32 nodes completed joining the network in the first phase, these 32 nodes will allocate time slots to 32 nodes that have not yet joined the network in the second phase. At the end of the second phase, the number of nodes that have joined the network reaches 64, and thereafter the threshold value for each node joining the network will be set to 64.

[0139] In the third phase, the remaining 36 idle nodes will initiate time slot allocation requests to the 64 nodes already in the network to complete their network access.

[0140] Through three stages, this invention enables 100 nodes to access the network in dense scenarios via time slot division, while the traditional TDMA protocol can only guarantee that each time slot is allocated to a single node, ultimately limiting the number of nodes that can join the network to 32. Compared to the traditional TDMA protocol, this invention increases the number of nodes that can join the network by 68.

[0141] Simulation 2: In the above scenario, both the present invention and the traditional TDMA protocol were used. Different load conditions were applied to statistically analyze the network throughput as a function of load intensity. The results are as follows: Figure 7 .

[0142] from Figure 7It is evident that the traditional TDMA protocol can only guarantee network access for 32 nodes, meaning only 32% of the service load injected into 100 nodes can be used for node transmission. Furthermore, among the 32 nodes already in the network, only 32% of their load destination nodes have also successfully joined the network; the remaining load is discarded due to the lack of neighbors. In this scenario, the throughput is only 10.24% of the total load. With an available link speed of 20Mbps, the link utilization rate is at most only 20%.

[0143] This invention ensures that all 100 nodes in the network can access the network through time slot division, and that both the origin and destination nodes can be reached. The overall network throughput can reach 14.37 Mbps, and the link utilization rate reaches 71.85%.

[0144] The above results demonstrate that the adaptive dense access method of the present invention can ensure rapid access for nodes in node-dense scenarios. Compared with the traditional TDMA protocol, it has higher throughput and link utilization under both light and heavy load conditions.

[0145] The above description is merely two specific examples of the present invention and does not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and details without departing from the principles and structure of the present invention. However, these modifications and changes based on the concept of the present invention are still within the scope of protection of the claims of the present invention.

[0146] It should be noted that the step numbers in the specification and claims of this invention are only for the purpose of clearly describing the embodiments of this invention and facilitating understanding, and their order is not limited.

Claims

1. An adaptive dense access method based on time frame extension, characterized in that: The network entry node constructs and broadcasts control frames; Unconnected nodes check broadcast control frames and initiate time slot division requests; After the network access node waits for the timer to expire, it performs time slot partitioning based on the number of time slot partitioning requests, including: 4a) After the time slot division timer expires, the network node counts the number of time slot division requests received before the timer expires; 4b) Determine whether to perform time slot division based on the number of time slot division requests: If the number of time slot allocation requests received by the network node is greater than 0, it will be considered that the node distribution is dense, and time slot allocation will be performed, dividing the existing time frame bit patterns into several groups. The implementation includes: 4b1) The number n of time slot division requests received by the network node before the time slot division timer expires; 4b2) The network node traverses each bit in the time frame bit mode and counts the number of bits that are 1 in the time frame bit mode, which is used as the number of multiframes m occupied by the current node in the superframe. 4b3) Compare the size relationship between n+1 and m of the incoming nodes: If n+1 is larger, it means that the existing multiframes of the network-connected node are insufficient to be allocated to all requesting nodes. The current node ignores the excess time slot allocation requests and assigns n to m-1. That is, the current node can only process the time slot allocation requests of m-1 non-network-connected nodes. Otherwise, it means that before the time slot division timer expires, all time slot division requests received by the network node can be processed through time slot division. 4b4) The network node divides m and n+1 to obtain the average number of multiframes occupied (avg); 4b5) The network access node performs time slot division by bit operation. Starting from the least significant bit of the current time frame bit pattern, it traverses each bit and counts the bits that are 1 in the time frame bit pattern. When the count reaches avg, the time frame bit pattern is divided to obtain a set of time frame bit patterns. 4b6) Reset the count, continue step 4b5) until the n+1th group of time frame bit mode is obtained; 4b7) In the n+1 group of time frame bit modes, the bit mode with the current multiframe corresponding to the bit with the bit set to 1 is used as the new time frame bit mode used by the network entry node after time slot division, and the remaining n time frame bit modes are used as the time frame bit modes used by the nodes that have not entered the network after time slot division. Otherwise, it is assumed that the current node distribution is not dense, and time slot division is not performed; The node entering the network initiates a time slot division response after the time slot division; Unconnected nodes check time slot division responses to complete dense access; The network access node performs time slot division based on the number of time slot division requests after the waiting timer expires.

2. The method according to claim 1, characterized in that: The network access node constructs and broadcasts control frames, including: The node entering the network writes the node ID (7 bits), control time slot (5 bits), time frame bit mode (4 bits), probe identifier (1 bit), and time slot segmentation request timeout time (16 bits) into the control frame to complete the construction of the control frame. During the control time slot, the newly joined node sends the constructed control frame to its neighboring nodes via broadcast.

3. The method according to claim 1, characterized in that: The non-network-connected node checks the broadcast control frame and initiates a time slot division request, including: After receiving a control frame containing probe information, a node that has not yet joined the network determines whether the current time slot is occupied by other neighboring nodes within a two-hop range: If the current time slot is not occupied by other neighboring nodes within two hops, a time slot allocation request containing the current node ID is sent to the incoming node via unicast. Otherwise, abandon the request to split a time slot to avoid time slot conflicts.

4. The method according to claim 1, characterized in that, The network access node initiates a time slot division response after time slot division, including: The network access node constructs a time slot division response frame based on the time slot division result. The time slot division response frame consists of several groups of responses, each group of responses is 11 bits in size, of which the response node ID occupies 7 bits and the response node time frame bit mode occupies 4 bits. The nodes joining the network broadcast the constructed time-slot division response frames to the nodes not joining the network.

5. The method according to claim 1, characterized in that, The non-network-connected nodes check the time slot segmentation response to complete dense access, including: After receiving the time slot division response, nodes that have not yet joined the network check whether their current node ID exists in the time slot division response: If the current node ID exists in the time-slot division response frame, the current node completes dense access by occupying the multiframe of the time-frame bit mode corresponding to the current node ID in the time-slot division response frame; Otherwise, the current node fails to connect and waits for control frames from subsequent nodes joining the network before attempting to connect again.

6. An adaptive dense access system based on time frame extension, comprising: The time slot table module is used to record the occupancy status of each multiframe by the current node and its neighboring nodes. The neighbor table module is used to record the ID and hop count of each neighbor node and to count the number of neighbor nodes. The time frame bit mode module is used to record the position of the current node in each multiframe in the superframe in a bit manner; The timer module is used by the network-joining node to set a timeout period for time slot division after broadcasting a data frame containing probe information, and to trigger the time slot division algorithm after the timeout. After the timeout, the timer module counts the number of received time slot division requests: if the number is 0, no further processing is performed; otherwise, the time slot division algorithm is triggered to perform time slot division, and a time slot division response frame is constructed based on the result of the time slot division and broadcast to the non-network-joining nodes. The perception and scheduling module is used by the network node to trigger active probing and drive the timer module when it senses that the number of neighboring nodes has reached a critical point and the number of multiframes of the current node is greater than 1. Specifically, it obtains the number of neighboring nodes by querying the neighbor table module. After the target reaches the critical point, the time frame mode module is queried to obtain the number of multiframes occupied by the current node. When the number of multiframes occupied by the current node is greater than 1, an active probe is triggered, and a probe frame is broadcast to neighboring nodes. At the same time, a timeout period is set in the timer module, and the node waits for the timeout to expire. The access module is used to determine whether to send a time slot division request after a non-network node senses an active probe from a network node, and to determine whether to complete the access after receiving a time slot division response. Specifically, upon receiving a probe frame, the node obtains the IDs of all neighboring nodes within its two-hop range by querying the neighbor table module, and simultaneously queries the time slot table module to obtain the time slots occupied by each neighboring node. Then, it determines whether any of these neighboring nodes has occupied the control time slot in the probe frame: if not, the non-networked node issues a time slot division request; otherwise, the non-networked node ignores the received probe frame. Upon receiving a time slot division response frame, the access module determines whether its node ID exists in the time slot division response frame: if it does, the non-networked node obtains the time frame bit pattern corresponding to its node ID in the time slot division response frame and completes access by occupying the multiframe represented by that time frame bit pattern in the superframe; otherwise, the non-networked node needs to wait for subsequent probe frames to re-access.

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