Self-adaptive dense access method and system based on time frame extension

Abstract

The invention discloses a self-adaptive dense access method and system based on time frame extension, and mainly solves the problems of high access overhead and high calculation complexity in the prior art. The implementation scheme comprises the following steps: a network access node constructs and broadcasts a control frame; the nodes which do not access the network check the broadcast control frame and initiate a time slot segmentation request; the network access node performs time slot segmentation according to the number of time slot segmentation requests after waiting for timeout of the timer, that is, the network access node actively segments the time slot to the non-network access node for use; the network access node initiates a time slot segmentation response after time slot segmentation; and the nodes which are not accessed to the network check the time slot segmentation response to complete dense access. According to the method, global information does not need to be obtained, a time frame structure does not need to be adjusted, the interaction process of the protocol does not depend on a specific time frame structure, the whole access process is only driven by the network access node to be completed, the calculation complexity is reduced, and the cost is reduced. The method can be used for ensuring the access capability of the node in a dense scene on the premise that the frame format of the mobile ad hoc network is not modified.

Description

Technical Field

[0001] The present invention belongs to the field of wireless communication technology, and further relates to a method and system for adaptive node access, which can be used in a mobile self-organizing network to ensure the access capability of nodes in dense scenarios without modifying the frame format. Background Art

[0002] Different from traditional wireless ad hoc networks, highly dynamic ad hoc network scenarios have the characteristics of fast changes in network topology. Some areas of the network are densely distributed with nodes, while others are sparsely distributed. Link time slot resources are shared by all nodes in the local topology. The existing access protocol allocates the entire time frame to each node in the network in units of time slots, thereby completing 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 the local topology is greater than the number of available time slots in the time frame, resulting in some nodes having no time slots available and being unable to access the network. Reducing the time slot length can increase the number of available time slots in the time frame to accommodate the access of 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 can directly increase the number of available time slots, but the nodes in the network are not always densely distributed. There are also many areas with sparse nodes in highly dynamic scenarios. Increasing the number of time slots in the time frame will cause many time slots in the sparse areas of the network to be wasted.

[0003] T. Deng designed a global resource allocation strategy in his paper “Global Resource Allocation for High Throughput and Low Delay in High-Density VANETs”. The strategy reduces the number of wasted time slots through a time slot exchange mechanism. At the same time, a weight allocation mechanism is designed for data packets to measure their importance. This allows the method to achieve a higher overall network throughput in scenarios with densely distributed nodes. However, it requires obtaining global information about nodes, which results in a high overhead.

[0004] Patent document with application number CN103096327B discloses an adaptive time slot allocation method based on TDMA, which meets the access needs of nodes by dynamically adjusting the frame length when the node perceives the change of node density. This method brings additional overhead because after the frame length is modified, the node needs to inform the neighboring nodes by broadcasting and wait for a time frame period to receive the response from the neighboring nodes.

[0005] Most of the existing research on dense node access is based on IEEE 802.11p. The improvements to the protocol can be divided into three categories: modifying the ratio of control channels to service channels, increasing the transmission of data packets by simplifying the interaction of control packets, and dynamically allocating channel resources to nodes. Since the protocol needs to divide a channel into seven channels by frequency, including one control channel and six service channels, these studies need to make full use of the existing seven channel resources and combine time slot frequency allocation resources to complete dense node access, which is relatively complex. Summary of the invention

[0006] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and propose an adaptive dense access method and system based on time frame extension 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] In order to achieve the above purpose, the technical idea of ​​the present invention is to actively split the occupied time slots in a dense scenario and allocate them to the non-networked nodes to complete access through active probing of the networked nodes; in a sparse scenario, actively recycle the idle time slots due to the node leaving, avoid time slot waste, and improve 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, comprising:

[0010] The access node constructs and broadcasts the control frame;

[0011] The node not in the network checks the broadcast control frame and initiates a time slot split request;

[0012] After the waiting timer of the access node times out, the time slot is split according to the number of time slot split requests;

[0013] The access node initiates a time slot split response after the time slot is split;

[0014] The node not connected to the network checks the time slot split response and completes the dense access.

[0015] Technical solution 2:

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

[0017] The time slot table module is used to record the occupation of each multiframe by the current node and neighboring nodes;

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

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

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

[0021] The perception scheduling module is used to trigger active detection and drive the timer module to work when the network node perceives that the number of neighbor nodes has reached a critical value and the number of multiframes of the current node is greater than 1;

[0022] The access module is used for the non-networked node to determine whether to send a time slot split request after sensing the active probe of the networked node, and to determine whether to complete the access after receiving the time slot split response.

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

[0024] First, in view of the characteristics of high-dynamic self-organizing networks in which the local topology structure changes rapidly and the nodes are sometimes dense and sometimes sparse, the present invention improves the access capability of nodes in high-dynamic scenarios and improves the throughput of the entire network by actively probing the connected nodes and splitting time slots to the non-connected nodes.

[0025] Second, the entire time slot segmentation and recovery process of the present invention is only driven by the network access node. Compared with the prior art, the present invention does not need to obtain global information or adjust the time frame structure. The interaction process of the protocol does not depend on a specific time frame structure, which reduces the complexity of access and improves its universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a general flow chart 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 access node constructs a control frame sub-flowchart containing the probe information in the control time slot;

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

[0029] Figure 4 yes Figure 1 Sub-flowchart for performing time slot segmentation in

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

[0031] Figure 6 It is a simulation curve diagram of the number of network access nodes changing with time according to the present invention;

[0032] Figure 7 It is a simulation curve diagram of throughput changing with load of the present invention. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0034] Terminology Note:

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

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

[0037] The "superframe" described in this example refers to a structure that nodes construct spontaneously in a dense scenario. A superframe is composed of several multiframes. Nodes that are not connected to the network complete network access by occupying a multiframe in the superframe.

[0038] The "time frame bit pattern" 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 network-accessing node occupies all multiframes, the bit pattern is represented as 1111. If the current node only occupies the first 2 multiframes in the superframe, the bit pattern is represented as 1100.

[0039] Embodiment 1: Adaptive dense access method based on time frame extension

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

[0041] The nodes that have joined the network conduct active probing, and in dense scenarios, they actively split the occupied time slots and allocate them to the nodes that have not joined the network to enable them to complete access;

[0042] In sparse scenarios, the idle time slots due to node departure are actively recovered for use by the current node, thereby improving the access capacity of the current node.

[0043] The implementation steps include the following:

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

[0045] The control frame includes the node ID, the control time slot position, the time frame bit pattern of the current node, the probe flag, and the time slot split request timeout. When the probe flag is set to 1, the current control frame is called "containing time slot split probe information", and the access node starts the adaptive dense access process by broadcasting the control frame of the probe information.

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

[0047] 1.1) Assume that the number of multiframes in the current superframe is m, the number of time slots in the time frame is n, and the number of multiframes occupied by the access node is m 1 , the network access node calculates the critical value:

[0048] 1.2) The node entering the network compares the number of neighbor nodes N and the critical value L:

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

[0050] Otherwise, it indicates that the time slots in the current multiframe are not fully utilized by the current node and each neighboring node. The network-entering node will set the probe flag of the control frame to 0, and consider that there are idle time slot resources and recycle the time slots, and execute step 1.4)

[0051] 1.3) The network-entering 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, and the time slot split request timer is set, and the timer timeout period is written into the control frame.

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

[0054] 1.4) The access node reclaims the time slot:

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

[0056] The access node traverses each bit of the frame bit pattern and skips the bits that are 1;

[0057] For each bit that is 0 in the time frame bit pattern, the access 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 access node marks the corresponding multiframe in the time slot table as occupied;

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

[0060] 1.4.2) Modify the time frame bit pattern of the newly occupied multiframe according to its position in the superframe:

[0061] The access node traverses each bit of the frame bit pattern and skips the bits that are 1;

[0062] For each bit that is 0 in the time frame bit pattern, check whether the multiframe corresponding to the current bit is marked by the access node:

[0063] If it is marked, the network-entering node sets the current bit in the time frame bit pattern to 1;

[0064] Otherwise, the network-entering node skips the current bit;

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

[0066] Table 1 Control frame format

[0067]

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

[0069] The access node sends the control frame constructed in step 1 to each neighbor node by broadcasting, completes the notification of time slot splitting trial information, and starts the process of adaptive dense access.

[0070] Step 3: The node not connected to the network checks the broadcast control frame.

[0071] 3.1) After receiving the broadcast control frame, the non-networked node checks the "probe identifier" 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 the probe information of time slot segmentation, and the node not in the network ignores the control frame and terminates the process;

[0073] Otherwise, it is considered that the control frame contains the time slot segmentation probe information, and step 3.2 is executed;

[0074] 3.2) The node not in the network checks whether the current control time slot is occupied by other neighboring nodes within the two-hop range:

[0075] If the current control time slot is occupied by other neighboring nodes within the two-hop range, the node not connected to the network terminates the process to avoid time slot occupation conflicts;

[0076] Otherwise, go to step 3.3);

[0077] 3.3) The node not in the network compares the time slot split request timeout T in the control frame 0 With the current time T:

[0078] If T 0 ≤T, the time slot splitting request is considered to have timed out, and the node that has not joined the network terminates the process;

[0079] Otherwise, go to step 4.

[0080] Step 4: The node not connected to the network initiates a time slot splitting request.

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

[0082] Table 2 Time slot split request format

[0083] The node ID that is not currently connected to the network (7 bits) Network access node id (7bit)

[0084] The non-networked node sends the constructed time slot splitting request to the networked node in a unicast manner.

[0085] Step 5: The network-entering node waits for the timer to time out and counts the time slot splitting requests.

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

[0087] 5.1) The network-entering node performs different operations according to whether the time slot split request timer it sets has timed out:

[0088] If the time slot split request timer has timed out, go to step 5.2)

[0089] Otherwise, the node entering the network waits until the timer times out;

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

[0091] If c>0, the network access node records the node ID of each node that initiates the time slot split request and executes step 6;

[0092] Otherwise, there is no non-network node requesting to split the time slot, and the network node terminates the process.

[0093] Step 6: The network access node performs time slot division.

[0094] Existing methods for dense node access include: global resource allocation strategy, dynamic modification of time frame length, multi-channel resource allocation and other methods. Among them, the global resource allocation strategy requires the central node to uniformly calculate the resource allocation results, which is not suitable for distributed scenarios; dynamic modification of time frame length requires informing the time frame modification information to all nodes in the network to ensure the clock synchronization of the entire network, which has a large overhead; multi-channel resource allocation requires the joint time and frequency domains, which has a high complexity; the present invention adopts a time slot segmentation method to limit the interactive process of dense node access to the networked nodes and the non-networked nodes, and completes the 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 access node defines the number of time slot splits n that can be processed, and assigns n to the number of time slot split requests c counted in step 5;

[0097] 6.2) The network-entering node traverses each bit in the time frame bit pattern and counts the number of bits in the time frame bit pattern that are 1 as the number of multiframes m occupied by the current node in the superframe;

[0098] 6.3) The node entering the network compares the size relationship between n+1 and m:

[0099] If n+1>m, it means that the existing multiframes of the networked node are not enough to be split to all requesting nodes. The current node ignores the excess time slot split requests and assigns n to m-1, that is, the current node can only process the time slot split requests of m-1 nodes that are not networked.

[0100] Otherwise, it means that before the time slot split timer times out, all time slot split requests received by the access node can be processed by time slot splitting;

[0101] 6.4) The network access node divides m by n+1 to obtain the average occupied multiframe number avg;

[0102] 6.5) The access node performs time slot segmentation by bit operation, traverses each bit from the lowest bit of the current time frame bit pattern and counts the bits with 1 in the time frame bit pattern. When the count reaches avg, the time frame bit pattern is segmented to obtain a set of time frame bit patterns.

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

[0104] 6.7) In the n+1 groups of time frame bit patterns, the bit pattern corresponding to the current multiframe with the bit position of 1 is used as the new time frame bit pattern used by the networked nodes after the time slot division, and the remaining n groups of time frame bit patterns are used as the time frame bit patterns used by the non-networked nodes after the time slot division.

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

[0106] The network-entering node matches the n groups of time frame bit patterns obtained in step 6 with the node ID recorded in step 5, obtains the node ID and the time frame bit pattern group, and constructs a time slot segmentation response frame as shown in Table 3.

[0107] Table 3 Time slot split response frame

[0108] Node 1 id (7 bits) Node 1 frame bit pattern (4 bits) Node 2id (7 bits) Node 2 frame bit pattern (4 bits) …… ……

[0109] The networked node informs the non-networked nodes of the time slot splitting response frame by broadcasting.

[0110] Step 8: The node not connected to the network checks the time slot split response.

[0111] After receiving the broadcast time slot split response frame, the node not connected to the network checks whether its current node ID is already in the response frame:

[0112] If not, it means that the networked node has not performed time slot division on the current node, and the node that has not entered the network terminates the process;

[0113] Otherwise, the node not in the network obtains the time frame bit pattern corresponding to the current node ID in the time slot division response frame, and completes the access by occupying the multiframe represented by the time frame bit pattern in the superframe.

[0114] Embodiment 2, adaptive dense access system based on time frame extension,

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

[0116] The time slot table module is used to record the occupation of each multiframe by the current node and neighboring nodes;

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

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

[0119] A timer module is used for setting a time slot splitting timeout after the network access node broadcasts a data frame containing a probe message, and triggering the network access node to check the number of time slot splitting requests after the timeout;

[0120] The perception scheduling module is used to trigger active detection and drive the timer module to work when the network access node perceives that the number of neighbor nodes has reached a critical value and the number of multiframes occupied by them is greater than 1;

[0121] The access module is used for the non-networked node to determine whether to send a time slot split request after sensing the active probe of the networked node, and to determine whether to complete the access after receiving the time slot split response.

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

[0123] The perception scheduling module 5 of the network access node obtains the number of neighbor nodes by querying the neighbor table module 2. After the number of neighbor nodes reaches a critical value, the frame bit pattern module 3 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 the neighbor nodes. At the same time, a timeout time is set in the timer module 4, and waits for timeout;

[0124] After receiving the probe frame, the access module 6 of the non-networked node queries the neighbor table module 2 to obtain the IDs of each neighbor node within its two-hop range, and queries the time slot table module 1 to obtain the time slots occupied by each neighbor node, and then determines whether there is a node among these neighbor nodes that occupies the control time slot in the probe frame: if not, the non-networked node sends a time slot split request; otherwise, the non-networked node ignores the received probe frame;

[0125] After the timer module 4 of the networked node times out, it counts the number of time slot split requests received: if the number is 0, no subsequent processing is performed; otherwise, the time slot splitting algorithm is triggered to perform time slot splitting, and a time slot splitting response frame is constructed according to the result of the time slot splitting, and is notified to the non-networked node in a broadcasting manner;

[0126] After receiving the time slot division response frame, the access module 6 of the non-networked node determines whether its node id exists in the time slot division response frame: if it exists, the non-networked node obtains the time frame bit pattern corresponding to its node id in the time slot division response frame, and completes the access by occupying the complex frame represented by the time frame bit pattern in the superframe; otherwise, the non-networked node needs to wait for the subsequent probe frame to re-access.

[0127] The effect of the present invention is further described below in conjunction with simulation experiments:

[0128] 1. Simulation experiment conditions:

[0129] The software platform of the simulation experiment is: windows10 operating system, Exata7.2.0.

[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, the present invention and the traditional TDMA protocol are used respectively to count the node access time and construct a curve of the number of nodes accessing the network 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 network access stage, 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 from 1.6s to the end of the simulation.

[0136] from Figure 6 It can be seen that the nodes are connected to the network in three stages, including:

[0137] In the first stage, all nodes compete to join the network. Since a time frame contains only 32 time slots, only 32 nodes can join the network at most. After that, the critical number of nodes for all nodes joining the network is set to 32.

[0138] In the second stage, all nodes that joined the network in the first stage split time slots to idle nodes so that idle nodes can join the network. Since 32 nodes joined the network in the first stage, in the second stage, these 32 nodes that joined the network will split time slots to 32 nodes that have not joined the network. At the end of the second stage, the number of nodes that joined the network reached 64, and the critical value of each node that joined the network will be set to 64.

[0139] In the third stage, the remaining 36 idle nodes will initiate time slot splitting requests to the 64 nodes that have joined the network to complete the network entry.

[0140] After three stages, the present invention realizes the access of 100 nodes in dense scenarios by time slot segmentation, while the traditional TDMA protocol can only ensure that each time slot is allocated to a single node, and the number of nodes finally connected to the network can only reach 32. Compared with the traditional TDMA protocol, the present invention increases the number of nodes connected to the network by 68.

[0141] Simulation 2: In the above scenario, the present invention and the traditional TDMA protocol are used respectively, and different loads are used to calculate the curve of the throughput of the entire network as a function of load intensity. The results are as follows: Figure 7 .

[0142] from Figure 7It can be seen that the traditional TDMA protocol can only ensure that 32 nodes complete network access, and only 32% of the service load injected into 100 nodes can be used for node transmission. Among the 32 nodes that have been connected to the network, only 32% of the destination nodes of their loads have completed network access. The remaining loads will be discarded due to the non-existence of neighbors. In this scenario, the throughput is only 10.24% of the total load. When the available link is 20Mbps, the maximum link utilization is only 20%.

[0143] The present invention ensures that all 100 nodes in the entire network can access the network through time slot segmentation, both the original node and the destination node can be reached, the throughput of the entire network can reach 14.37Mbps, and the link utilization rate reaches 71.85%.

[0144] The above results show that the adaptive dense access method of the present invention can ensure fast access of nodes in node-dense scenarios, and has higher throughput and link utilization in both light and heavy load situations compared to the traditional TDMA protocol.

[0145] The above descriptions are only two specific examples of the present invention and do not constitute any limitation to the present invention. It is obvious that for professionals in this field, after understanding the content and principles of the present invention, it is possible to make various modifications and changes in form and details without departing from the principles and structures of the present invention. However, these modifications and changes based on the ideas 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 the present invention are only for a clear description of the implementation scheme of the present invention to facilitate understanding, and the order of the step numbers is not limited.

Claims

1. An adaptive dense access method based on time frame extension, characterized in that: The access node constructs and broadcasts the control frame; The node not in the network checks the broadcast control frame and initiates a time slot split request; After the waiting timer of the access node times out, the time slot is split according to the number of time slot split requests; The access node initiates a time slot split response after the time slot is split; The node not connected to the network checks the time slot split response and completes the dense access.

2. The method according to claim 1, characterized in that: The access node constructs and broadcasts a control frame, including: The node entering the network writes the node ID (7 bits), the control time slot (5 bits), the time frame bit pattern (4 bits), the probe flag (1 bit), and the time slot split request timeout (16 bits) into the control frame to complete the construction of the control frame. The node entering the network sends the constructed control frame to the neighboring nodes by broadcasting in the control time slot.

3. The method according to claim 1, characterized in that: The non-networked node checks the broadcast control frame and initiates a time slot splitting request, including: After receiving the control frame containing the probe information, the non-networked node determines whether the current time slot is occupied by other neighboring nodes within two hops: If the current time slot is not occupied by other neighboring nodes within the two-hop range, a time slot splitting request containing the current node ID is sent to the network-entering node via unicast; Otherwise, the time slot splitting request is abandoned to avoid time slot conflict.

4. The method according to claim 1, characterized in that: After the access node waits for the timer to time out, the access node performs time slot division according to the number of time slot division requests, including: 4a) After the time slot splitting timer times out, the network-entering node counts the number of time slot splitting requests received before the timer times out; 4b) Determine whether to perform time slot segmentation according to the number of time slot segmentation requests: If the number of time slot split requests received by the network-entering node is greater than 0, it will be considered that the nodes are densely distributed and time slot splitting will be performed to divide the existing time frame bit patterns into several groups; Otherwise, it is considered that the current node distribution is not dense and time slot segmentation is not performed.

5. The method according to claim 1, characterized in that The network access node initiates a time slot split response after the time slot is split, including: The access node constructs a time slot division response frame according to the result of the time slot division. The time slot division response frame consists of several groups of responses. The size of each group of responses is 11 bits, of which the response node ID occupies 7 bits and the response node frame bit pattern occupies 4 bits. The networked node informs the non-networked nodes of the constructed time slot splitting response frame by broadcasting.

6. The method according to claim 1, characterized in that The non-networked node checks the time slot splitting response and completes the dense access, including: After receiving the time slot split response, the non-networked node checks whether the current node ID exists in the time slot split response: If the current node ID exists in the time slot splitting response frame, the current node completes the dense access by occupying the multiframe of the time frame bit pattern corresponding to the current node ID in the time slot splitting response frame; Otherwise, the current node fails to access and waits for the control frame of the subsequent node to access the network and tries to access again.

7. The method according to claim 4, characterized in that The time slot segmentation in 4b) is performed to divide the existing time frame bit pattern into several groups, which is implemented by: 4b1) The network-entering node counts the number n of time slot split requests received before the time slot split timer times out; 4b2) The network-entering node traverses each bit in the time frame bit pattern and counts the number of bits in the time frame bit pattern that are 1 as the number m of multiframes occupied by the current node in the superframe; 4b3) The node entering the network compares the size relationship between n+1 and m: If n+1 is larger, it means that the existing multiframes of the connected node are not enough to split to all requesting nodes. The current node ignores the excess time slot split requests and assigns n to m-1, that is, the current node can only process the time slot split requests of m-1 nodes that are not connected to the network; Otherwise, it means that before the time slot split timer times out, all time slot split requests received by the access node can be processed by time slot splitting; 4b4) The network access node divides m by n+1 to obtain the average occupied multiframe number avg; 4b5) The access node performs time slot segmentation by bit operation, traverses each bit starting from the lowest bit of the current time frame bit pattern and counts the bits with bits being 1 in the time frame bit pattern. When the count reaches avg, the time frame bit pattern is segmented to obtain a set of time frame bit patterns; 4b6) Reset the count and continue step 4b5) until n+1 sets of time frame bit patterns are obtained; 4b7) In the n+1 groups of time frame bit patterns, the bit pattern corresponding to the current multiframe with the bit position of 1 is used as the new time frame bit pattern used by the networked nodes after the time slot division, and the remaining n time frame bit patterns are used as the time frame bit patterns used by the non-networked nodes after the time slot division.

8. An adaptive dense access system based on time frame extension, comprising: The time slot table module is used to record the occupation of each multiframe by the current node and neighboring nodes; The neighbor table module is used to record the ID and hop count information of each neighbor node and count the number of neighbor nodes; The time frame bit pattern module is used to record the position of each multiframe occupied by the current node in the superframe in a bit manner; The timer module is used for the network access node to set the timeout period of the time slot division after broadcasting the data frame containing the probe information, and trigger the time slot division algorithm after the timeout period; The perception scheduling module is used to trigger active detection and drive the timer module to work when the network node perceives that the number of neighbor nodes has reached a critical value and the number of multiframes of the current node is greater than 1; The access module is used for the non-networked node to determine whether to send a time slot split request after sensing the active probe of the networked node, and to determine whether to complete the access after receiving the time slot split response.

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