CN116233904A - A Cluster-Based Restoration Method for Low Power Wide Area Network - Google Patents

Abstract

The present application provides a cluster-based low-power wide area network restoration method, the method comprising: when a gateway fails in the low-power wide area network, the server in the low-power wide area network sends a beacon to notify the first layer in the first-layer cluster The cluster head node switches to Class B mode, and restores the communication between the first layer cluster head node in the first layer cluster group and all CM nodes in the first layer cluster group; the server sends beacons layer by layer to notify the cluster head nodes in other layer cluster groups to switch In Class B mode, the communication between cluster head nodes in clusters of other layers and all CM nodes of each layer cluster is restored layer by layer; the cluster head nodes of each layer cluster receive the data sent by CM nodes of each layer and compress it. The data is sent to the upper cluster head node or gateway in turn until the server receives the data and returns a confirmation frame through the downlink. This solution provides a new topology and data transmission scheme for emergency communication, and improves the fault tolerance of the low-power wide area network.

Description

A Cluster-Based Restoration Method for Low Power Wide Area Network

technical field

The invention belongs to the technical field of sensor networks, in particular to a cluster-based low power consumption wide area network restoration method.

Background technique

Low Power Wide Area Network (LPWAN) has the characteristics of low power consumption and long distance. Due to the excellent characteristics of LPWAN in terms of power consumption and transmission distance, it is widely used in smart meter reading, smart parking, smart agriculture, and smart cities.

In actual industrial deployment, an LPWAN gateway is often responsible for the transmission of hundreds or thousands of LPWAN nodes. Due to the simple protocol design and network topology of LPWAN itself, when a gateway crashes due to factors such as natural disasters, malicious attacks, or traffic overload, it will cause the nodes within the coverage of the gateway to be disconnected from the server. , when the node cannot get the ACK (ACKnowledge, response) frame from the LPWAN server, the node will continue to resend the data packet, which eventually leads to the problem of node energy exhaustion. At present, none of the existing research or patents can solve this problem well.

LPWAN proposes three different modes of LPWAN node working mechanisms for different application scenarios. Among them, Class A adopts a low power consumption mode, and the terminal of Class A only opens two receiving windows for a short time after the uplink to receive downlink data packets. Class B uses the Beacon (beacon) mechanism on the basis of Class A to provide an additional receiving window with a fixed period, so that the terminal can start receiving within a certain time. In Class C, except for temporarily closing the receiving window when sending, the receiving window is always open for the rest of the time.

In wireless sensor networks, Heinzelman et al. proposed a network protocol for improving the survival time of wireless sensor networks - Low Energy Adaptive Clustering Hierar (Low Energy Adaptive Clustering Hierar cluster head y, LEA cluster head), The idea of clustering was first proposed: randomly select the cluster head (Cluster Head) according to the "round", and other nodes select the nearest cluster head to join the cluster to realize intra-cluster communication, and use the cluster head to transmit data to the base station, reducing energy consumption. consumption.

Although the above-mentioned protocol can establish a topology from sensor nodes to base stations, since different nodes in LPWAN may be in different modes, it is impossible to directly apply traditional cluster-based protocols to LPWAN networks.

Contents of the invention

The purpose of the embodiments of this specification is to provide a cluster-based low power consumption wide area network restoration method.

In order to solve the above technical problems, the embodiments of the present application are implemented in the following ways:

The application provides a cluster-based low power consumption wide area network recovery method, the method comprising:

When a gateway fails in the low-power WAN, the server in the low-power WAN sends a beacon to notify the first-level cluster head node in the first-level cluster group to switch to Class B mode, and restore the first-level cluster head node in the first-level cluster group Communication with all CM nodes in the first-level cluster;

The server sends a beacon layer by layer to notify the cluster head nodes in other layer clusters to switch to Class B mode, and restores the communication between the cluster head nodes in other layer clusters and all CM nodes of each layer cluster layer by layer;

The cluster head nodes of each layer cluster receive and compress the data sent by the CM nodes of each layer, and the compressed data is sent to the cluster head node or gateway of the upper layer in turn, until the server receives the data and returns a confirmation frame through the downlink;

Among them, the cluster head nodes in the first layer and the cluster head nodes in other layer clusters are determined before the gateway fails; each cluster includes cluster head nodes and CM nodes.

In one of the embodiments, the determination of the first layer cluster head node and the cluster head nodes in other layer clusters includes:

The server selects the candidate cluster head node according to the received historical data packets;

Select qualified nodes from the candidate cluster head nodes as the cluster head nodes of the first layer;

According to the cluster head nodes of the first layer, the qualified nodes are selected from the CM nodes of the first layer cluster group as the cluster head nodes of other layer cluster groups.

In one of the embodiments, the server selects an alternative cluster head node according to the received historical data packets, including:

The server selects nodes in the intersection area of gateway coverage according to the received historical data packets, and initializes the nodes in the intersection area of gateway coverage as candidate cluster head nodes.

In one of the embodiments, the qualified nodes are selected from the candidate cluster head nodes as the first layer cluster head nodes, including:

The server sets the first CAD sensitivity threshold for the candidate cluster head node through the downlink;

Nodes that receive the first CAD sensitivity threshold perform CAD detection on the channel, determine their respective coverage areas, and analyze the received data packets to form a list of cluster members corresponding to each candidate cluster head node;

Each candidate cluster head node transmits its corresponding cluster member list to the server through the uplink, and the server uses the principle of the widest coverage or the principle of the least cluster group to filter out redundant candidate cluster head nodes according to the list of all cluster members to obtain the final The cluster head node of the first layer, and sends a beacon to the cluster head node of the first layer.

In one of the embodiments, according to the cluster head node of the first layer, the qualified nodes are selected from the CM nodes of the first layer cluster group, as the cluster head nodes in other layer cluster groups, including:

The server sets a second CAD sensitivity threshold for the CM nodes of the first-level cluster group according to the cluster member list of the first-level cluster head node;

The CM node that receives the second CAD sensitivity threshold performs CAD detection on the channel, determines their respective coverage areas, and analyzes the intercepted data packets to form a cluster member list corresponding to each CM node;

Each CM node transmits its corresponding cluster member list to the server through the uplink, and the server uses the widest coverage principle or the least cluster group principle to filter out redundant CM nodes to obtain the cluster head of the next layer of clusters according to the list of all cluster members. node;

The server checks whether all nodes belong to one of the clusters. If there are nodes that have not joined the cluster, it will repeatedly screen the qualified nodes from the CM nodes of the first-level cluster to generate the cluster head node of the next-level cluster until All nodes join the cluster.

In one of the embodiments, the server in the low-power wide area network sends a beacon to notify the first-level cluster head node in the first-level cluster group to switch to Class B mode, and restores the first-level cluster-head node and the first-level cluster head node in the first-level cluster group. Communication of all CM nodes in, including:

The server sends a beacon to notify the first-level cluster head nodes in the first-level cluster group to switch to Class B mode;

The cluster head node of the first layer is switched to Class B mode, and the number of receiving windows is set as the number of nodes in the first layer cluster group;

The first-level cluster head node uses the default Date Rate channel to periodically broadcast the "Hello_I_am_CH" message in the first-level cluster group to restore communication with all CM nodes in the first-level cluster group; until the first-level cluster head node and the first-level cluster group All CM nodes are contacted.

In one of the embodiments, the first-level cluster head node uses the default Date Rate channel to periodically broadcast the "Hello_I_am_CH" message in the first-level cluster group to resume communication with all CM nodes in the first-level cluster group, including:

The first layer cluster head node uses the default Date Rate channel to periodically broadcast the "Hello_I_am_CH" message in the first layer cluster group, and the CM node that receives the "Hello_I_am_CH" message sends the "Hello_I_am_CH" message to the first layer cluster head node using the default Date Rate channel. "information;

The cluster head node at the first layer that receives the "Hello_I_am_CM" message allocates the free receiving window to the corresponding CM node, and sends a control frame to the corresponding CM node;

The CM node that receives the control frame sends data to the cluster head node at the first layer at the sending time according to the allocated receiving window.

In one of the embodiments, the control frame includes the local time, the start time of the receiving window period of the current round, the spreading factor, the bandwidth, the center frequency, the sequence number assigned to the receiving window of the CM node, and the receiving window of each beacon period Quantity, CRC check digit.

根据下式确定：In one of the embodiments, sending time

Determined according to the following formula:

为在一个信标周期的时间，/>

为分配给该CM节点接收窗口的顺序号；/>

为簇群内成员的数量；/>

为本轮接收窗口周期开始的时间。in,

is the time in one beacon period, />

is the sequence number assigned to the receiving window of the CM node; />

is the number of members in the cluster; />

It is the start time of the receiving window period of this round.

In one of the embodiments, when the CM node in the first-level cluster has not received the confirmation frame sent by the server after retransmitting the preset number of times, the corresponding CM node switches to the default Date Rate channel to perform the CAD function, so as to Receive the "Hello_I_am_CH" message sent by the cluster head node at the first layer.

It can be seen from the above technical solution provided by the embodiment of this specification that this solution: combining the cluster idea and the characteristics of the LPWAN network itself, provides a new topology and data transmission solution for emergency communication, and improves the fault tolerance of the LPWAN network.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments described in this specification. Those skilled in the art can also obtain other drawings based on these drawings without any creative effort.

Fig. 1 is the schematic flow chart of the low power consumption wide area network recovery method based on the cluster group that the application provides;

FIG. 2 is a schematic diagram of selecting an alternative CH node by the LPWAN server provided by this application;

FIG. 3 is a schematic diagram of CH nodes of clusters of each layer provided by the present application to determine coverage through CAD;

FIG. 4 is a schematic diagram of a cluster-based LPWAN network topology provided by the present application;

Fig. 5 is a control frame format diagram sent by the CH node to the CM node provided by the present application;

FIG. 6 is a schematic diagram of a CH node allocating ping_slots to different CM nodes provided in the present application.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described The embodiments are only some of the embodiments in this specification, not all of them. Based on the embodiments in this specification, all other embodiments obtained by persons of ordinary skill in the art without creative efforts shall fall within the protection scope of this specification.

In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present application. It will be apparent, however, to one skilled in the art that the present application may be practiced in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present application with unnecessary detail.

It will be apparent to those skilled in the art that various modifications and changes can be made to the specific embodiments described in the present application without departing from the scope or spirit of the present application. Other embodiments will be apparent to those skilled in the art from the description of this application. The specification and examples in this application are exemplary only.

As used herein, "comprising", "comprising", "having", "comprising" and so on are all open terms, meaning including but not limited to.

At present, when the LPWAN network suddenly collapses at the gateway, a large number of LPWAN nodes cannot re-establish communication with the network server, which paralyzes the entire LPWAN network. The key problem it faces is how to establish a connection between each terminal node after the gateway is disconnected, construct a new network topology and find a nearby working gateway, and offload the communication tasks of the failed gateway to other neighboring gateways. question.

Therefore, this application designs a cluster-based low power consumption wide area network recovery method, which can ensure that when the LPWAN gateway is abnormal, the subordinate LPWAN nodes can still communicate with the LPWAN server.

The present invention will be described in further detail below in conjunction with the accompanying drawings and embodiments.

Referring to FIG. 1 , it shows a schematic flowchart applicable to the cluster-based low power consumption wide area network recovery method provided by the embodiment of the present application.

It is understandable that before a failure occurs in the LPWAN, a cluster-based LPWAN network topology needs to be established between the LPWAN server (which can be referred to as the server) and the LPWAN terminal node (which can be referred to as the node for short), so that when the LPWAN fails, Make emergency communications.

First select the candidate cluster head node.

There are multiple LPWAN gateways (may be referred to as gateways for short) in the LPWAN network scenario, and some gateways may be disconnected from the LPWAN server due to external factors (such as natural disasters, malicious attacks, etc.) or internal factors (disconnection of the power supply system, self-hardware failure, etc.) connect. The LPWAN server distinguishes the nodes in the gateway coverage intersection area according to the local historical data packets (the data packets are the data packets from the node to the gateway, that is, the uplink data packets). At this time, these nodes (that is, the gateway coverage intersection intersection area) Nodes in the area) can still communicate with the LPWAN server through other LPWAN gateways. The LPWAN server initializes these nodes as candidate cluster-head nodes (alternative CH nodes), as shown in Figure 2.

The following screens out the qualified nodes from the candidate cluster head nodes as the cluster head nodes of the first layer.

，收到第一CAD敏感度阈值/>

的LPWAN终端节点在信道上进行CAD（Channel detection mechanism，信道检测机制）探测，企图获取附近节点传输的数据包以确定自己的覆盖范围，并分析接收到的数据包，将对应的节点ID、Center Frequency（CF，中心频率）、BW（BandWidth，带宽）、SF（SpreadingFactor，扩频因子）、SNR（Signal-to-noise ratio，信噪比）、RSSI（ReceivedSignal Strength Indication，接收信号强度指示）、ping_slot Number（接收窗口数量）等无线电参数填入Cluster_Member_List（簇成员列表，如表1所示）中，表示为/>

，/>

为首层的簇群，/>

为首层簇群中的第/>

个备选CH节点，其中，A,…,B为备选CH节点覆盖范围内的节点，可以称为CM（ClusterMember）节点。The LPWAN server sets the first CAD sensitivity threshold to the candidate CH node through the downlink

, received the first CAD sensitivity threshold />

The LPWAN terminal node performs CAD (Channel detection mechanism, channel detection mechanism) detection on the channel, trying to obtain the data packets transmitted by nearby nodes to determine its own coverage, and analyze the received data packets, and assign the corresponding node ID, Center Frequency (CF, center frequency), BW (BandWidth, bandwidth), SF (SpreadingFactor, spreading factor), SNR (Signal-to-noise ratio, signal-to-noise ratio), RSSI (ReceivedSignal Strength Indication, received signal strength indication), Radio parameters such as ping_slot Number (number of receiving windows) are filled in Cluster_Member_List (list of cluster members, as shown in Table 1), expressed as />

, />

is the cluster group of the first layer, />

is the first-level cluster group />

candidate CH nodes, where A, ..., B are nodes within the coverage of the candidate CH nodes, which may be called CM (ClusterMember) nodes.

Table 1 Cluster_Member_List

Node_ID CF BW SF SNR RSSI ping_slot Number A 433MHz 250KHz 10 0dB -20dB NULL … … … … … … … B 433MHz 125KHz 12 2dB -10dB NULL

After the specified time period, each candidate CH node transmits its corresponding latest Cluster_Member_List to the LPWAN server through the uplink, and the LPWAN server uses the widest coverage principle or the least cluster group principle to filter out redundant ones according to all Cluster_Member_Lists. The candidate CH node obtains the final first-level CH node, and informs the node through Beacon.

Exemplarily, the following formula is the formula of the principle of broadest coverage:

表示Cluster_Member_List中CM节点的个数。in,

Indicates the number of CM nodes in the Cluster_Member_List.

After receiving the Beacon frame, the CH node on the first layer switches to the Class B mode. Then, combined with the Cluster_Member_List of the first-level CH node itself, its ping_slot cycle is set to ensure that the number of times the first-level CH node opens the receiving window is consistent with the number of members in the cluster. Exemplarily, the Beacon frame is 128ms, and the number of ping_slots is 5, so the ping_slot period is 128ms/5=25.6ms.

According to the cluster head node of the first layer, the qualified nodes are selected from the CM nodes of the first layer cluster group as the cluster head nodes of other layer cluster groups.

，获取到该阈值的CM节点在信道上进行CAD探测，确定自己的覆盖范围，并分析接收的数据包，以此形成自己的Cluster_Member_List，表示为/>

（/>

为第/>

层的簇，i≠0，/>

为第/>

层簇群中的第/>

个备选CH节点），该步骤同上述首层簇群中备选簇首节点形成对应的Cluster_Member_List的步骤，这里不再阐述。The LPWAN server sets the second CAD sensitivity threshold for the CM nodes (ClusterMember nodes) in the first-level cluster according to the Cluster_Member_List of the first-level CH nodes determined by the above steps

, the CM node that has obtained the threshold performs CAD detection on the channel, determines its own coverage, and analyzes the received data packets to form its own Cluster_Member_List, expressed as />

(/>

for No. />

cluster of layers, i ≠ 0, />

for No. />

The />th in the layer cluster

candidate CH nodes), this step is the same as the step of forming a corresponding Cluster_Member_List for the candidate cluster head nodes in the first-level cluster group, and will not be described here.

后，首先去除/>

中的首层CH节点，再根据最广覆盖原则或最少簇群原则筛选掉多余的CM节点得到下一层簇群的簇首节点，示例性的，使用公式/>

，i≠0选择出下一层簇群的CH节点。最后，LPWAN服务器检验是否所有的节点已经归属到某个簇群中，如果存在节点没有加入簇群，则重复从首层簇群的CM节点中筛选符合条件的节点，产生下一层簇群的簇首节点直到所有节点加入簇群。如图3所示为各层的CH节点通过CAD确定覆盖范围的示意图。Subsequently, each CM node submits the Cluster_Member_List to the LPWAN server through the first layer CH node, and the LPWAN server receives

After that, first remove the />

CH nodes in the first layer, and then filter out redundant CM nodes according to the principle of widest coverage or the principle of least clusters to obtain the cluster head node of the next layer of clusters. For example, use the formula />

, i ≠0 selects the CH nodes of the next layer of clusters. Finally, the LPWAN server checks whether all nodes have belonged to a cluster. If there are nodes that have not joined the cluster, it will repeatedly screen qualified nodes from the CM nodes of the first-level cluster to generate the next-level cluster. Cluster head node until all nodes join the cluster. FIG. 3 is a schematic diagram of determining the coverage of the CH nodes of each layer through CAD.

The topology structure of the cluster-based LPWAN network established according to the foregoing embodiments is shown in FIG. 4 .

As shown in Figure 1, the cluster-based low power consumption wide area network restoration method may include:

S110. When a gateway fails in the low-power wide area network, the server in the low-power wide area network sends a beacon to notify the first-level cluster head node in the first-level cluster group to switch to Class B mode, and restore the first-level cluster in the first-level cluster group Communication between the first node and all CM nodes in the first-level cluster.

Specifically, when some gateways in the LPWAN network fail (or are abnormal), the LPWAN server senses and notifies the CH node at the first layer to switch to emergency mode to start emergency communication.

In an embodiment, S110 may specifically include:

The server sends a beacon to notify the first-level cluster head nodes in the first-level cluster group to switch to Class B mode;

The cluster head node of the first layer is switched to Class B mode, and the number of receiving windows is set as the number of nodes in the first layer cluster group;

The first-level cluster head node uses the default Date Rate channel to periodically broadcast the "Hello_I_am_CH" message in the first-level cluster group to restore communication with all CM nodes in the first-level cluster group; until the first-level cluster head node and the first-level cluster group All CM nodes are contacted.

When the CM node in the first-level cluster has not received the confirmation frame sent by the server after retransmitting the preset number of times, the corresponding CM node switches to the default Date Rate channel to perform the CAD function to receive the message sent by the first-level cluster head node. "Hello_I_am_CH" message.

Among them, the first-level cluster head node uses the default Date Rate channel to periodically broadcast the "Hello_I_am_CH" message in the first-level cluster group to resume communication with all CM nodes in the first-level cluster group, including:

The first layer cluster head node uses the default Date Rate channel to periodically broadcast the "Hello_I_am_CH" message in the first layer cluster group, and the CM node that receives the "Hello_I_am_CH" message sends the "Hello_I_am_CH" message to the first layer cluster head node using the default Date Rate channel. "information;

The cluster-head node at the first layer that receives the "Hello_I_am_CM" message allocates the vacant receiving window to the corresponding CM node, and sends a control frame to the corresponding CM node; wherein, the control frame includes the local time, the start time of the current round of receiving window period Time, spreading factor, bandwidth, center frequency, sequence number assigned to the receiving window of the CM node, number of receiving windows in each beacon period, CRC check digit;

The CM node that receives the control frame sends data to the cluster head node at the first layer at the sending time according to the allocated receiving window.

Specifically, the notified first-level CH node switches to the Class B mode, and sets its own ping_slot number to the number of cluster members in the cluster. Then, the CH node uses the default Date Rate channel (for example, SF=7, BW=250KHz) to periodically broadcast the "Hello_I_am_CH" message in the first-level cluster until it gets in touch with all CM nodes. When the CM node has not received the ACK (confirmation) frame from the LPWAN server after retransmitting <Nbtrans> times (that is, the preset time, which can be set according to actual needs), it is trying to switch between different Date Rate schemes If it is still invalid, confirm that you have lost contact with the LPWAN server, then switch to the default Date Rate channel for CAD function, and try to receive the "Hello_I_am_CH" message from the CH node on the first layer.

The CM node that receives the "Hello_I_am_CH" message sends the "Hello_I_am_CM" message to the first-level CH node at the default Date Rate.

The first-level CH node that receives the "Hello_I_am_CM" message allocates the free ping_slot to the CM node. Then, the first layer CH node sends a control frame to the CM node, where, as shown in Figure 5, the control frame includes the local time (Time), the time when the current round of ping_slot period starts (beacon_time), spreading factor SF, bandwidth BW, center Frequency (Center_Frequency), sequence number assigned to the CM node pingslot (ping_slot Number), number of ping_slots per Beacon cycle (that is, the number of members in the cluster, pingNb), and CRC check digit (CRC).

，随后在/>

时刻向首层CH节点发送数据。Finally, as shown in Figure 6, the CM node calculates the sending time by the following formula according to the received control frame

, followed by the />

Send data to the first layer CH node at all times.

为在一个信标周期的时间，在LPWAN中为122.88s；/>

为分配给该CM节点pingslot的顺序号；/>

为簇群内成员的数量；/>

为本轮ping_slot周期开始的时间。in,

is the time in one beacon period, which is 122.88s in LPWAN; />

is the sequence number assigned to the CM node pingslot;/>

is the number of members in the cluster; />

It is the time when the current round of ping_slot period starts.

S120, the server sends a beacon layer by layer to notify the cluster head nodes in the clusters of other layers to switch to the Class B mode, and restores the communication between the cluster head nodes in the clusters of other layers and all CM nodes of the clusters of each layer layer by layer;

S130. The cluster head nodes of each layer cluster receive the data sent by the CM nodes of each layer, and compress the data, and the compressed data is sent to the cluster head node or gateway of the upper layer in turn, until the server receives the data and returns a confirmation through the downlink frame;

Among them, the cluster head nodes in the first layer and the cluster head nodes in other layer clusters are determined before the gateway fails; each cluster includes cluster head nodes and CM nodes. Among them, the cluster head node in the first layer cluster group is the first layer cluster head node.

Specifically, when the first-tier cluster resumes the intra-cluster communication, the intra-cluster communication of the other clusters is restored layer by layer in accordance with the pre-established cluster-based LPWAN network topology.

After a round of ping_slot cycles, the CH nodes of each cluster will compress the data of all nodes in the cluster through a data compression algorithm and then hand it over to the CH node or gateway of the upper layer until the LPWAN server receives the data and returns an ACK frame. All LPWAN nodes resume communication with the LPWAN server. It can be understood that the CH nodes on the first layer compress the data and hand it over to the gateway, while the CH nodes of other clusters compress the data and hand it over to the CH nodes on the upper layer.

Using the cluster-based low power consumption wide area network recovery method provided by the embodiment of the present application, when the LPWAN gateway is abnormal, the subordinate LPWAN nodes can still communicate with the LPWAN server.

The cluster-based low-power wide-area network recovery method provided by the embodiment of the present application combines the cluster idea and the characteristics of the LPWAN network itself to provide a new topology and data transmission scheme for emergency communication, and improve the fault tolerance of the LPWAN network.

It should be noted that the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes none other elements specifically listed, or also include elements inherent in the process, method, commodity, or apparatus. Without further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

Each embodiment in this specification is described in a progressive manner, the same and similar parts of each embodiment can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and for relevant parts, refer to part of the description of the method embodiment.

Claims (10)

1. A cluster-based low power consumption wide area network recovery method, characterized in that the method comprises: When there is a gateway failure in the low-power wide area network, the server in the low-power wide area network sends a beacon to notify the first-level cluster head nodes in the first-level cluster group to switch to Class B mode, and restore all the first-level cluster head nodes in the first-level cluster group. Communication between the cluster head node of the first layer and all CM nodes in the cluster group of the first layer; The server sends a beacon layer by layer to notify the cluster head nodes in other layer clusters to switch to Class B mode, and restores the communication between the cluster head nodes in other layer clusters and all CM nodes of each layer cluster layer by layer; The cluster head nodes of each layer cluster receive and compress the data sent by the CM nodes of each layer, and the compressed data is sent to the cluster head node or gateway of the upper layer in turn, until the server receives the data and returns a confirmation frame through the downlink; Wherein, the first layer cluster head node and the cluster head nodes in other layer cluster groups are all determined before the failure of the gateway; each cluster group includes a cluster head node and a CM node. 2. The method according to claim 1, wherein the determination of the first layer cluster head node and the cluster head nodes in other layer cluster groups comprises: The server selects an alternative cluster head node according to the received historical data packet; Selecting qualified nodes from the candidate cluster head nodes as the first layer cluster head nodes; Screen out qualified nodes from the CM nodes of the first-level cluster group according to the first-level cluster-head node, and serve as cluster-head nodes in other-level cluster groups. 3. The method according to claim 2, wherein the server selects an alternative cluster head node according to the received historical data packet, comprising: The server selects the nodes in the intersection area of the gateway coverage according to the received historical data packets, and initializes the nodes in the intersection area of the gateway coverage as the candidate cluster head nodes. 4. The method according to claim 2, wherein the screening out qualified nodes from the candidate cluster head nodes as the first layer cluster head nodes includes: The server sets a first CAD sensitivity threshold for the candidate cluster head node through a downlink; The nodes receiving the first CAD sensitivity threshold perform CAD detection on the channel, determine their respective coverage areas, and analyze received data packets to form a cluster member list corresponding to each candidate cluster head node; Each of the candidate cluster head nodes transmits its corresponding cluster member list to the server through the uplink, and the server uses the principle of widest coverage or the principle of least clusters to filter out redundant candidate cluster heads according to the list of all cluster members The node obtains the final cluster-head node of the first layer, and sends a beacon to the cluster-head node of the first layer. 5. The method according to claim 4, characterized in that, according to the first layer cluster head node, the qualified nodes are selected from the CM nodes of the first layer cluster group as the nodes in other layer cluster groups. Cluster head nodes, including: The server sets a second CAD sensitivity threshold for the CM nodes of the first-level cluster group according to the cluster member list of the first-level cluster head node; The CM node that receives the second CAD sensitivity threshold performs CAD detection on the channel, determines their respective coverage areas, and analyzes the intercepted data packets to form a cluster member list corresponding to each of the CM nodes; Each CM node transmits its corresponding cluster member list to the server through an uplink, and the server uses the widest coverage principle or the least cluster group principle to filter out redundant CM nodes according to all cluster member lists to obtain the next layer of clusters The cluster head node of the group; The server checks whether all nodes belong to one of the clusters, and if there are nodes that have not joined the cluster, then repeatedly screen qualified nodes from the CM nodes of the first-level cluster to generate the cluster head of the next-level cluster nodes until all nodes have joined the cluster. 6. The method according to claim 1, wherein the server in the low-power wide area network sends a beacon to notify the first-level cluster head nodes in the first-level cluster group to switch to Class B mode, and restore the first-level cluster The communication between the first layer cluster head node in the group and all CM nodes in the first layer cluster group includes: The server sends a beacon to notify the first-level cluster head node in the first-level cluster group to switch to the Class B mode; The first layer cluster head node is switched to Class B mode, and the number of receiving windows is set as the number of nodes in the first layer cluster group; The cluster head node of the first layer uses the default Date Rate channel to periodically broadcast the "Hello_I_am_CH" message in the cluster group of the first layer to resume communication with all CM nodes in the cluster group of the first layer; until the cluster head node of the first layer Get in touch with all CM nodes in the first layer cluster. 7. The method according to claim 6, wherein the first-level cluster head node uses a default Date Rate channel to periodically broadcast a "Hello_I_am_CH" message in the first-level cluster group to communicate with the first-level cluster group All CM nodes in the recovery communication, including: The first layer cluster head node uses the default Date Rate channel to periodically broadcast the "Hello_I_am_CH" message in the first layer cluster group, and the CM node that receives the "Hello_I_am_CH" message sends a message to the first layer with the default Date Rate channel. Cluster head node sends "Hello_I_am_CM" message; The cluster head node at the first layer that receives the "Hello_I_am_CM" message allocates the vacant receiving window to the corresponding CM node, and sends a control frame to the corresponding CM node; The CM node that receives the control frame sends data to the cluster head node at the first layer at the sending time according to the allocated receiving window. 8. The method according to claim 7, wherein the control frame includes local time, the start time of the current round of receiving window period, spreading factor, bandwidth, center frequency, and the order of receiving windows allocated to the CM node number, the number of receive windows per beacon period, and the CRC check digit. 9. The method according to claim 8, wherein the sending time

Determined according to the following formula:

, where />

is the time in one beacon period, />

is the sequence number assigned to the receiving window of the CM node; />

is the number of members in the cluster;

It is the start time of the receiving window period of this round. 10. The method according to claim 6, wherein when the CM node in the first layer cluster has not received the acknowledgment frame sent by the server after retransmitting the preset number of times, the corresponding CM node Switch to the default Date Rate channel to perform the CAD function to receive the "Hello_I_am_CH" message sent by the cluster head node at the first layer.

Images