Node synchronization method for wireless ad hoc network and communication node

Abstract

The invention discloses a node synchronization method for a wireless ad hoc network and a communication node. The node synchronization method comprises the following steps: searching a frame synchronization signal according to a preset mode; in response to the searched frame synchronization signal sent by the temporary synchronization node, receiving a broadcast message sent by the temporary synchronization node; judging whether the temporary synchronization node is a father node of the temporary synchronization node based on the network configuration information; in response to the fact that the temporary synchronization node is not the father node of the temporary synchronization node, determining a channel used by the father node of the temporary synchronization node for sending a broadcast time slot based on the network configuration information; and searching a frame synchronization signal on a channel used by the parent node for sending the broadcast time slot, and receiving a corresponding broadcast message after the frame synchronization signal is searched until the sending node of the broadcast message is determined to be the parent node of the parent node or an exit condition is met. By using the method, the node can be quickly synchronized to the specified father node, so that the network connection can be quickly established, and the stability of the wireless ad hoc network connection is improved.

Description

Technical Field

[0001] The present application relates to the field of wireless communication technology, and in particular, to a node synchronization method and a communication node for a wireless ad hoc network. Background Art

[0002] A wireless ad hoc network is a network composed of multiple communication nodes. It does not need to be deployed in advance. Each communication node needs to be self-organized to connect into a communication network. Therefore, a wireless ad hoc network has great flexibility.

[0003] Wireless ad hoc networks usually operate in unlicensed frequency bands, and the use of unlicensed frequency bands does not require a license. There are many communication protocols such as Wi-Fi, Bluetooth and other technologies that use unlicensed frequency bands as communication frequency bands. Therefore, the communication nodes of wireless ad hoc networks are easily interfered by other devices, making the wireless environment of wireless ad hoc networks relatively uncontrollable. In addition, due to the different geographical locations of various communication nodes in the wireless ad hoc network, the interference conditions of each communication node are also different, and the wireless environment is quite different. Since the resources of unlicensed frequency bands are limited, the frequency resources need to be coordinated between the various communication nodes within the wireless ad hoc network to avoid mutual interference between the communication nodes in the wireless ad hoc network. In such an application scenario, if the node is not connected to a node with better link quality, it is easy to be disconnected or frequently switched, resulting in unstable network connection, thereby affecting the communication quality of the wireless ad hoc network. Summary of the invention

[0004] One object of the present application is to provide a node synchronization method for a wireless ad hoc network, so that each node can quickly synchronize with a designated node corresponding to the node, thereby quickly establishing a network connection and improving the stability of the wireless ad hoc network node connection. Another object of the present application is to improve the anti-interference ability of the node and avoid mutual interference between nodes in the wireless ad hoc network.

[0005] In one aspect of the present application, a node synchronization method for a wireless ad hoc network is provided, wherein the wireless ad hoc network includes multiple nodes, and the method includes: searching for frame synchronization signals sent by other nodes in a preset manner during their broadcast time slots; in response to searching for a frame synchronization signal sent by a temporary synchronization node, receiving a broadcast message sent by the temporary synchronization node, wherein the broadcast message includes a sending node identifier, and the sending node identifier is a node identifier of the node that sends the broadcast message; judging whether the temporary synchronization node is its parent node based on network configuration information, wherein the network configuration information includes parent-child relationship configuration information of nodes in the wireless ad hoc network and broadcast time slot channel configuration information of nodes; in response to the temporary synchronization node not being its parent node, determining a channel used by its parent node for sending broadcast time slots based on the network configuration information; and searching for a frame synchronization signal on the channel used by its parent node for sending broadcast time slots, and receiving a broadcast message sent by the node that sends the frame synchronization signal after searching for the frame synchronization signal, until it is determined that the sending node of the broadcast message is its parent node or an exit condition is met.

[0006] In some embodiments, the frequency channel used by each of the nodes to send broadcast time slots changes cyclically based on a system frequency hopping sequence.

[0007] In some embodiments, the frequency channel used by each of the nodes to send broadcast time slots changes cyclically based on a system frequency hopping sequence of the same length.

[0008] In some embodiments, the frequency channel used by each of the nodes for sending broadcast time slots changes at fixed time intervals based on a system frequency hopping sequence, and the fixed time intervals take frames as time units.

[0009] In some embodiments, after determining that the sending node of the broadcast message is its parent node, it also includes: judging whether it is configured as a relay state; in response to being configured as a relay state, determining the channel used by its own sending broadcast time slot based on the broadcast time slot channel configuration information; using the determined channel to send a frame synchronization signal and a broadcast message on its own sending broadcast time slot.

[0010] In some embodiments, the broadcast time slot channel configuration information includes a frequency hopping offset of the master node and each node configured as a relay for sending broadcast time slots.

[0011] In this embodiment, determining the channel used by the sending broadcast time slot of its own parent node based on the network configuration information includes: determining the channel used by the sending broadcast time slot of the parent node based on the system frequency hopping sequence, the channel of the sending broadcast time slot of the temporary synchronization node, the frequency hopping offset of the sending broadcast time slot of the temporary synchronization node, and the frequency hopping offset of the sending broadcast time slot of the parent node.

[0012] In this embodiment, determining the channel used by one's own sending broadcast time slot based on the broadcast time slot channel configuration information includes: determining the channel used by one's own sending broadcast time slot based on the system frequency hopping sequence, the channel of the parent node's sending broadcast time slot, the frequency hopping offset of the parent node's sending broadcast time slot, and one's own sending broadcast time slot's frequency hopping offset.

[0013] In some embodiments, the network configuration information is included in a broadcast message and is broadcast in the wireless ad hoc network via a global broadcast method.

[0014] In a second aspect of the present disclosure, a communication node of a wireless ad hoc network is provided, comprising a processor and a non-transitory storage medium storing computer-executable instructions, wherein the computer-executable instructions can be executed by the processor to perform the steps and functions in each embodiment of the above method.

[0015] The above is an overview of the present application, which may be simplified, summarized, and omitted in detail. Therefore, those skilled in the art should recognize that this section is only illustrative and is not intended to limit the scope of the present application in any way. This summary section is neither intended to determine the key features or essential features of the claimed subject matter, nor is it intended to be used as an auxiliary means to determine the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other features of the present application will be more fully understood through the following description and the attached claims in conjunction with the accompanying drawings. It is understood that these drawings only depict several embodiments of the present application and should not be considered as limiting the scope of the present application. By using the accompanying drawings, the present application will be more clearly and detailed.

[0017] Figure 1 A schematic diagram of the topological structure of the wireless ad hoc network disclosed in the present invention is shown;

[0018] Figure 2 A frame structure that can be used to implement the node synchronization method for a wireless ad hoc network disclosed in the present invention is shown;

[0019] Figure 3 The configuration mode of the broadcast time slot in the frame structure of each node is exemplarily shown;

[0020] Figure 4 A schematic diagram of a channel configuration for sending broadcast time slots is exemplarily shown;

[0021] Figure 5 A schematic diagram showing mapping each element of a single system frequency hopping sequence to multiple system frequency hopping sequences is shown;

[0022] Figure 6A schematic diagram showing the channel allocation results of multiple system frequency hopping sequences;

[0023] Figure 7 A node synchronization method 100 for a wireless ad hoc network according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the present disclosure will be described in detail below in conjunction with the accompanying drawings. In the accompanying drawings, similar symbols generally represent similar components unless the context otherwise indicates. The illustrative embodiments described in the detailed description, drawings and claims are not intended to be limiting. Other embodiments may be adopted and other changes may be made without departing from the spirit or scope of the subject matter of the present application. It is understood that various aspects of the content of the present application generally described in the present application and illustrated in the accompanying drawings may be configured, replaced, combined, and designed in a variety of different configurations, all of which clearly constitute part of the content of the present application.

[0025] To facilitate understanding by those skilled in the art, Figure 1 FIG. 1 shows a schematic diagram of the topological structure of the wireless ad hoc network disclosed in the present invention. Figure 1 As shown, the wireless ad hoc network includes multiple communication nodes, and these communication nodes all have wireless transceiver functions. For the sake of simplicity, "communication node" is referred to as "node" in this disclosure. "Node" can be a communication device, or a communication unit or module in a device. Each node in the wireless ad hoc network can be distinguished by a node identifier, that is, in a wireless ad hoc network, each node has a unique node identifier. A node in the wireless ad hoc network can use a suitable channel to send or receive wireless signals in a specified time domain according to the configuration. In this disclosure, a channel represents a frequency interval with a certain bandwidth, and a channel can be represented by a center frequency, or by a pre-compiled channel number. In general, two different channels do not overlap in frequency and / or in time domain to avoid mutual interference.

[0026] In the present disclosure, in a wireless ad hoc network, based on whether the node needs to determine the time reference by receiving the frame synchronization signal sent by other nodes in the wireless ad hoc network, the nodes of the wireless ad hoc network can be generally divided into master nodes and slave nodes. The master node can determine the time reference by its own clock, or by receiving the synchronization signal of the external network (for example, the synchronization signal sent by the external network device or other wireless ad hoc network) or the clock signal (for example, the clock sent by the GPS, Beidou satellite system), and periodically sends the frame synchronization signal. The slave node needs to determine the time reference by the frame synchronization signal sent by other nodes in the wireless ad hoc network, and the slave node can be further divided into a relay slave node and a terminal slave node. After the relay slave node is synchronized with the parent node, it also periodically sends a frame synchronization signal for other slave nodes to search. The terminal slave node does not send a frame synchronization signal. A slave node can be configured as a relay state as needed. When the slave node is configured as a relay state, it is a relay slave node, and when it is configured as a non-relay state, it is a terminal slave node. In the present disclosure, the number of master nodes is 1, and the number of slave nodes can be 1 or more. Figure 1 The topology structure of a wireless ad hoc network is shown as an example. Figure 1 In the example, node 1 is the master node, and nodes 2-8 are slave nodes. Nodes 3, 4, 6, and 8 are configured as relay slave nodes, and nodes 2, 5, and 7 are configured as terminal slave nodes.

[0027] Figure 1 In the example, an arrow from one node to another node indicates the synchronization relationship between the two nodes. When there is an arrow from node i to node j, it indicates that node j continuously receives the frame synchronization signal sent by node i to maintain frame synchronization with node i, thereby maintaining synchronization with the wireless ad hoc network. Node i is the parent node of node j, and node j is the child node of node i. Here, i and j are the node numbers. For example Figure 1 In the figure, nodes 2, 3, 6 and 7 are synchronized with the wireless ad hoc network by continuously receiving the frame synchronization signal sent by node 1. Node 1 is the parent node of nodes 2, 3, 6 and 7, and nodes 2, 3, 6 and 7 are the child nodes of node 1. Node 4 is synchronized with the wireless ad hoc network by continuously receiving the frame synchronization signal sent by node 3. Node 3 is the parent node of node 4, and node 4 is the child node of node 3, and so on. It should be pointed out that Figure 1 The wireless ad hoc network topology structure formed by the synchronization relationship of the multiple nodes shown is only exemplary, and the method disclosed in the present invention does not impose any restrictions on the specific topology structure of the wireless ad hoc network formed by the multiple nodes. In addition, the continuous reception mentioned in the continuous reception refers to maintaining the receiving state, not to continuous reception in time, because the received frame synchronization signal itself is not continuously distributed in the time domain. Usually, this reception is periodic reception.

[0028] also, Figure 1 The wireless ad hoc network shown also includes a network control center (not shown in the figure), which is used to control the network locally or globally, for example, to set system parameters (including frame period, system frequency hopping sequence, etc.), to allocate physical resources to nodes, etc. It should be understood that in specific implementation, the network control center can be integrated into the node or can be a separate device. It can be implemented in software, hardware, or a combination of hardware and software.

[0029] In the present disclosure, nodes perform actions such as sending and receiving wireless signals based on their frame structures to achieve synchronization of nodes and coordinate communication between nodes. Figure 2 A frame structure that can be used to implement the node synchronization method for wireless ad hoc networks disclosed in the present invention is shown. Figure 2 As shown, the wireless physical resources can be divided into multiple frames in terms of time. The start time and end time of the frame define the frame boundary. From the start to the end of the frame is a frame period, and the frame is repeated continuously with the same frame period. The frame period can be a fixed value, but it can also be dynamically or semi-statically configured as needed. For example, the frame period can be switched at an agreed time. Different nodes in a wireless ad hoc network can have different frame structures, but the frame boundaries of each node are aligned with each other in time, so the frame period of each node is the same.

[0030] Each frame of a node may include multiple time slots. Depending on the function of the time slot, the time slots may be divided into different types, such as broadcast time slots (BR) time slots, data time slots, and access time slots. Broadcast time slots are used to carry frame synchronization signals and broadcast messages. Frame synchronization signals may be used to provide time references. Nodes obtain time references and determine the time boundaries of frames by searching for frame synchronization signals. Before the synchronization of the ad hoc network is obtained, nodes usually search for frame synchronization signals continuously in the time domain of one to multiple frame cycles. In addition, considering factors such as transceiver switching, there may be a certain gap between adjacent time slots (not shown in the figure). Equivalently, the gap required for this transceiver switching may also be defined as a part of the time slot itself. In terms of design, the lower limit of the length of the gap depends on the consideration of the distance between the two nodes with the longest distance in the area covered by the ad hoc network. Exemplarily, a broadcast message may include one or more information blocks, each of which includes information type and information content. In order to distinguish information blocks of the same type contained in different broadcast messages, the information block may also include a sequence number, and different sequence numbers correspond to different information blocks. Different information types can be defined as needed to achieve different functions. Broadcast messages may include control information, which is used to control wireless ad hoc networks or nodes. The control information can be organized in the form of information blocks. Normally, messages sent on wireless communication networks will be sent after data packaging of the specific information to be sent, that is, the message sent will include a message header and message content. The message header will set relevant information fields according to the communication scenario, which may include all or part of the information such as frame number, sequence number, session type, check bit, sender ID, receiver ID, etc. Usually, the same message content, sent by the same node at different times, may have different message headers. Similarly, the message headers may also be different when sent by different nodes.

[0031] Each node performs wireless signal transmission and reception in the time slot assigned to it. The time slot type, number, position, length, channel and other parameters of the node's frame structure can be pre-configured or dynamically configured according to different needs. For the same time interval, different nodes can be assigned different types of time slots. For example, in the corresponding time domains in the frame of the two broadcast time slots BR1 and BR2 of a certain relay slave node, for the master node, it can be configured as the master node's broadcast time slot BR1 and access time slot. The time slot configuration of a node in its frame period is called the frame structure of the node.

[0032] The frame structure of the master node includes at least one broadcast time slot for sending frame synchronization signals and broadcast messages. After the master node is powered on, it can send frame synchronization signals and broadcast messages in its broadcast time slot according to the configuration. In some embodiments, the frame structure of the master node may include only one broadcast time slot for sending frame synchronization signals and broadcast messages. In other embodiments, the frame structure of the master node may include two or more broadcast time slots for sending frame synchronization signals and broadcast messages. Increasing the number of frame synchronization signals sent by the master node within one frame period can increase the probability of the slave node searching for the frame synchronization signal sent by the master node and increase the flexibility of the time slot position for relaying the frame synchronization signal sent by the slave node.

[0033] The frame structure of the relay slave node contains at least two broadcast time slots, one of which is used to receive frame synchronization signals and broadcast messages sent by the master node or other relay slave nodes, and the other broadcast time slots are used to send frame synchronization signals and broadcast messages. The end slave node does not need to send frame synchronization signals and broadcast messages, and its frame structure can contain only one broadcast time slot for receiving frame synchronization signals and broadcast messages sent by the master node or relay slave node.

[0034] For the sake of convenience, in the frame structure of each node, the broadcast time slot used to send the frame synchronization signal and the broadcast message is called the send broadcast time slot of the node, and the broadcast time slot used to receive the frame synchronization signal and the broadcast message is called the receive broadcast time slot of the node. It can be understood that the send broadcast time slot of one node can overlap with the receive broadcast time slot of another node in time.

[0035] Figure 2 The example shows that the node frame structure includes two broadcast time slots, which are represented by BR1 and BR2 respectively. However, it should be pointed out that Figure 2 The frame structure shown is merely exemplary, and the present disclosure does not limit the number of broadcast time slots contained in a frame.

[0036] for Figure 1 The wireless ad hoc network shown, Figure 3 The configuration of the broadcast time slot in the frame structure of each node is exemplarily shown. Figure 3 In the figure, the subscript TX indicates that the node sends (Transmit, TX) signals in the broadcast time slot, and the subscript RX indicates that the node receives (Receive, RX) signals. Figure 3In the example shown, BR1 and BR2 in the frame structure of node 1 are both sending broadcast time slots; BR1 in the frame structure of node 4 and node 6 is a sending broadcast time slot, and BR2 is a receiving broadcast time slot; BR1 in the frame structure of node 3 and node 8 is a receiving broadcast time slot, and BR2 is a sending broadcast time slot; BR1 in the frame structure of node 2 and node 5 is a receiving broadcast time slot, and BR2 in the frame structure of node 7 is a receiving broadcast time slot. It should be pointed out that although Figure 3 It is shown that the BR1 time slot is located at the starting position of the frame structure of each node, but this is only exemplary. The BR1 time slot can be set to have a certain time offset from the starting position of the frame structure as needed.

[0037] In some implementations, different nodes can set the numbering sequence of the broadcast time slots in their frame structures and the start time of the frames as needed. For example, for node 6, it obtains synchronization by receiving the frame synchronization signal sent by node 1 in the BR2 time slot. It can set the time slot number in its frame structure to BR1, and use the start time of the time slot as the start of its frame, and set the time slot number corresponding to the BR1 time slot of node 1 to BR2. However, those skilled in the art will appreciate that this implementation is different from Figure 3 The frame structures shown are only different in form, and the two are essentially the same. For the sake of simplicity, in this disclosure, for the same time interval, broadcast time slots of different nodes are represented by the same number, that is, broadcast time slots of different nodes with the same number correspond to the same time interval.

[0038] According to the present disclosure, multiple nodes can simultaneously send signals in the broadcast time slot of the same time domain. When there are two sending nodes that are close to each other, a node that receives signals in the broadcast time slot may receive signals from both sending nodes at the same time. Since the number of channels is limited, if the two nodes use the same channel to send signals, it may cause greater interference, making it difficult for the receiving node to synchronize. In order to solve the above interference problem, the present disclosure further proposes a frequency hopping method, which can avoid interference between signals sent simultaneously by multiple nodes in the broadcast time slot of the same time domain based on the limited number of channels.

[0039] According to the frequency hopping method disclosed in the present invention, when the master node and the relay slave node send signals in a broadcast time slot, the frequency channel used by each node changes based on the system frequency hopping sequence associated with the broadcast time slot.

[0040] In the present disclosure, the system frequency hopping sequence is a channel sequence associated with a specific time slot of a node of the wireless ad hoc network, and the node derives the channel of the corresponding time slot based on the system frequency hopping sequence. The system frequency hopping sequence can be pre-configured for each node, or generated by a network control center and dynamically configured for each node. In some embodiments, in the same time period, all nodes of the wireless ad hoc network use the same system frequency hopping sequence in the broadcast time slot. In some embodiments, in order to prevent tracking or improve communication confidentiality, the wireless ad hoc network can also have different system frequency hopping sequences in the same time period. Each node configures a system frequency hopping sequence for a transmission broadcast time slot. Therefore, the system frequency hopping sequences configured by different nodes in different broadcast time slots may be different. For the sake of convenience, the number of system frequency hopping sequences associated with the broadcast time slots of each node in the wireless ad hoc network can be expressed as K, K≥1, then the kth system frequency hopping sequence can be expressed as the channel sequence f k,0 , f k,1 , …, f k,N-1 , where 0≤k≤K-1, the length of the K system frequency hopping sequences is N, f k,n (n=0, 1, ..., N-1) is the nth element of the kth system frequency hopping sequence.

[0041] It should be noted that in the present disclosure, the channel used by the node's broadcast time slot changes based on the system frequency hopping sequence associated with the time slot, which means that the channel used by the node to send signals in the broadcast time slot is derived from the system frequency hopping sequence associated with the broadcast time slot configured for the node.

[0042] In some embodiments, the channel used by the node to send signals in the broadcast time slot changes at fixed time intervals based on the system frequency hopping sequence. The fixed time interval uses frames as time units, that is, the fixed time interval is a positive integer multiple of the frame period.

[0043] In some embodiments, the channel sequence used by a node to send a signal in a broadcast time slot in its frame structure in a frequency hopping manner changes cyclically according to a fixed channel sequence period, and the channel sequence within a channel sequence period is a cyclic shift of the system frequency hopping sequence associated with the broadcast time slot. To facilitate understanding by those skilled in the art, an example is given below. Assume that the system frequency hopping sequence associated with the kth broadcast time slot for sending a signal in the frame structure of the node is f k,0 , f k,1 , …, f k,N-1 , which uses channel f in the broadcast time slot of the nth frame k,n1 , the channel used in the broadcast time slot changes at a fixed interval of 2 frames, then the channel used in the broadcast time slot in the (n+2)th frame is f k,(n1+1)mod N , the channel used by the broadcast time slot in the (n+2m)th frame is f k,(n1+m)mod N, where 0≤n1≤N-1, m is a positive integer, and "mod" represents a modulo operation. For a mod b (where a and b are both positive integers), the result is the remainder of a divided by b. The channel sequence used by a node to send a signal in a broadcast time slot in its frame structure obtained by the above method is a cyclic sequence.

[0044] In order to avoid conflicts caused by different nodes using the same channel to send signals in the same time domain, each broadcast time slot for sending signals of each node is associated with a frequency hopping offset, which indicates the offset of the channel sequence used by the node when sending signals in the broadcast time slot relative to the channel sequence used by the designated broadcast time slot of the reference node. The designated broadcast time slot is a broadcast time slot in the frame structure of the reference node, which can be pre-configured for each node of the wireless ad hoc network, or adjusted by the control center as needed.

[0045] It should be noted that the length of the system frequency hopping sequence associated with the broadcast time slot for sending signals of a node should be the same as the length of the system frequency hopping sequence associated with the designated broadcast time slot of the reference node corresponding to the frequency hopping offset associated with the broadcast time slot. Even if the same system frequency hopping sequence is used in a wireless ad hoc network, by setting different frequency hopping offsets for the broadcast time slots used to send signals of different nodes, different nodes can use different channels to send signals in the broadcast time slots in the same time domain, thus effectively avoiding signal interference between nodes. A wireless ad hoc network can select a node as a reference node as needed, so the reference node can be a master node or a slave node.

[0046] Since the channel sequence used by the reference node's designated broadcast time slot is a reference for other nodes to determine the channel sequence used to send signals in their broadcast time slots based on their frequency hopping offsets, the reference node's designated broadcast time slot may have no frequency hopping offset, or its frequency hopping offset may be set to 0 by default.

[0047] Since the relative value of the frequency hopping offset of each node obtained by selecting different nodes as the reference node does not change, there is no substantial difference in which node is selected as the reference node. Considering the ease of implementation, the main node is usually used as the reference node. Therefore, in the following text, unless otherwise specified, the main node is used as the reference node.

[0048] In some embodiments, in order to simplify the system implementation, only the same system frequency hopping sequence or multiple system frequency hopping sequences of the same length are used in the wireless ad hoc network. At this time, if the master node is a reference node, the first broadcast time slot of the master node is a designated broadcast time slot. For the master node, if it uses two or more broadcast time slots to send signals in a frame period, each broadcast time slot may also be associated with a frequency hopping offset, which indicates the offset of the channel sequence used by the master node when sending signals in the broadcast time slot relative to the channel sequence used in the first broadcast time slot of the master node. At this time, the frequency hopping offset associated with the transmission broadcast time slot of the slave node is the offset of the channel sequence used in the broadcast time slot relative to the channel sequence used in the first broadcast time slot of the master node. Optionally, the master node uses the broadcast time slot with the smallest time slot number in the frame period as the first broadcast time slot. However, it should be noted that the position of the first broadcast time slot can be set as needed, for example, the broadcast time slot with the largest time slot number in the frame period can also be used as the first broadcast time slot.

[0049] The broadcast message sent by the master node in its broadcast time slot includes the frequency hopping offset associated with the broadcast time slot sent by the master node and / or the relay slave node in the wireless ad hoc network.

[0050] The relay slave node receives the broadcast message and learns the difference between the frequency hopping offset associated with the broadcast time slot of the node that sends the broadcast message and the frequency hopping offset associated with its own broadcast time slot.

[0051] Figure 4 A schematic diagram showing an exemplary channel configuration for sending broadcast time slots is shown. Figure 4 Each node uses Figure 3 The frame structure configuration shown in the figure, after the nodes are synchronized, the topology of the wireless ad hoc network is as follows Figure 1 As shown in the figure, node 1 is the master node, nodes 3, 4, 6, and 8 are configured as relay slave nodes, and nodes 2, 5, and 7 are configured as terminal slave nodes. Figure 4 In the wireless ad hoc network, each node uses the same system frequency hopping sequence, which can be expressed as a channel sequence "f1, f2, f3, f4, f5, f6". Node 1 sends signals in both the first broadcast time slot BR1 and the second broadcast time slot BR2 in its frame structure. Each broadcast time slot used to send signals by each node in the wireless ad hoc network is associated with a frequency hopping offset, which indicates the offset of the channel sequence used when sending signals in its associated broadcast time slot relative to the channel sequence used by the master node in the first broadcast time slot in its frame structure. At this time, the frequency hopping offsets of BR1 and BR2 in the master node's frame structure are 0 and 2, respectively, the frequency hopping offsets of BR1 of nodes 4 and 6 in their frame structures are 3 and 1, respectively, and the frequency hopping offsets of BR2 of nodes 3 and 8 in their frame structures are 4 and 0, respectively.

[0052] Starting from the nth frame, the channels used by the master node to send signals on the first broadcast time slot BR1 of each frame are f1, f2, f3, f4, f5, f6, f1, f2, f3, f4, f5, f6, ... in a system frequency hopping sequence. The channels used by the master node to send signals on the second broadcast time slot BR2 of each frame are f3, f4, f5, f6, f1, f2, f3, f4, f5, f6, f1, f2, ... in a system frequency hopping sequence, but the frequency hopping offset relative to the channel sequence of BR1 is 2.

[0053] The following is an example of node 3, which is similar to the situation for other slave nodes. Node 3 uses the broadcast time slot BR2 in its frame structure to send signals. Starting from the nth frame, the channels used by the master node to send signals on the first broadcast time slot BR1 of each frame are f1, f2, f3, f4, f5, f6, f1, f2, f3, f4, f5, f6, ... in a system frequency hopping sequence. The frequency hopping offset of node 3 in BR2 is 4, so starting from the nth frame, the channels used by node 3 to send signals on BR2 are f5, f6, f1, f2, f3, f4, f5, f6, f1, f2, f3, f4, ... in a system frequency hopping sequence. Figure 4 The frequency channels used by each node to send signals in the broadcast time slot from the nth frame to the n+2th frame are shown.

[0054] In the case where there are multiple system frequency hopping sequences, each channel of a single system frequency hopping sequence can be first mapped to each channel of the system frequency hopping sequence used by each node in sequence, and then based on the case of a single system frequency hopping sequence, the channel sequence used by each node for sending broadcast time slots is obtained, and then the obtained channel sequence based on the single system frequency hopping sequence is replaced with the corresponding channel sequence according to the established mapping relationship. The following is an explanation of the case of two system frequency hopping sequences, and the case of more system frequency hopping sequences is similar.

[0055] The system frequency hopping sequence 1 is represented as "A, B, C, D, E, F", and the system frequency hopping sequence 2 is represented as "G, H, I, J, K, L". Each element of each system frequency hopping sequence represents a channel. Without loss of generality, let Figure 3 Nodes 1, 3, and 4 use system frequency hopping sequence 1, and nodes 6 and 8 use system frequency hopping sequence 2.

[0056] First, each element of a single system frequency hopping sequence is mapped to each system frequency hopping sequence. The mapping relationship is as follows: Figure 5 As shown, for the system frequency hopping sequence 1, the mapping relationship 1 is f1→A, f2→B, ..., f6→F; for the system frequency hopping sequence 2, the mapping relationship 2 is f1→G, f2→H, ..., f6→L.

[0057] Then, based on the single system frequency hopping sequence "f1, f2, f3, f4, f5, f6", according to the frequency hopping offset of the broadcast time slot of each node, the channel allocation of the broadcast time slot of each node is obtained, that is, Figure 4 Results shown.

[0058] Then, for each node, the channel allocation result obtained based on a single system frequency hopping sequence is replaced with the channel of system frequency hopping sequence 1 or system frequency hopping sequence 2 according to the corresponding mapping relationship 1 or mapping relationship 2. After the above replacement, the final channel allocation is as follows: Figure 6 shown.

[0059] The slave node searches for the frame synchronization signal sent by other nodes, then receives the broadcast message sent by the same node in the broadcast time slot where the frame synchronization signal is located, and determines the position of the broadcast time slot in the frame according to the content of the broadcast message, so as to determine the frame boundary. After determining the frame boundary, synchronization with the node that sent the frame synchronization signal is achieved, and since the frame boundaries of each node are aligned with each other in time, it can also be considered that synchronization with the wireless ad hoc network is achieved.

[0060] Although the slave node can synchronize with the wireless ad hoc network by searching for frame synchronization signals sent by other nodes, due to the differences in the wireless environment of the wireless ad hoc network, the frame synchronization signal first searched by the slave node is not necessarily sent by the node with better wireless channel quality. If the slave node continues to synchronize with the node, it may easily lead to unstable connection. In order to solve the above problem, the present disclosure proposes a node synchronization method for a wireless ad hoc network, so that a node can quickly synchronize to a parent node designated for the node.

[0061] The node synchronization method for a wireless ad hoc network according to an embodiment of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0062] Figure 7 A node synchronization method 100 for a wireless ad hoc network according to an embodiment of the present disclosure is shown. The method 100 is executed by a slave node. Using the method, the slave node can quickly synchronize with its parent node, thereby quickly completing the deployment of the wireless ad hoc network. Specifically, the method 100 includes the following steps:

[0063] In step 110, the slave node searches for frame synchronization signals sent by other nodes in the broadcast time slots in a preset manner.

[0064] In this step, "other nodes" can be master nodes or other slave nodes that have been synchronized. Before a slave node synchronizes with its parent node, it is in an unsynchronized state. It can search for frame synchronization signals in a preset manner, for example, it can search for frame synchronization signals in a fixed channel; it can also search for frame synchronization signals in a certain channel within a time period. If it is not found, it will search for frame synchronization signals in another channel within the next time period. This process continues until the frame synchronization signal is found or the search state is exited.

[0065] In step 120, in response to searching for a frame synchronization signal sent by the temporary synchronization node, the slave node receives a broadcast message sent by the temporary synchronization node.

[0066] For the sake of identification, the node sending the frame synchronization signal searched by the slave node is called a temporary synchronization node. Since the frame synchronization signal is sent through the broadcast time slot, and the frame synchronization signal and the broadcast message are sent in the same broadcast time slot, after the slave node searches for the frame synchronization signal, it can further receive the broadcast message sent by the temporary synchronization node.

[0067] The broadcast message includes a sending node identifier, which is a node identifier of a node that sends the broadcast message, so that nodes that receive the broadcast message can learn the sender of the broadcast message.

[0068] In step 130, the slave node determines whether the temporary synchronization node is its parent node based on the network configuration information.

[0069] The network configuration information includes the parent-child relationship configuration information of the nodes in the wireless ad hoc network, and the parent-child relationship configuration information indicates the parent node of each node. The slave node can determine its parent node based on the parent-child relationship configuration information. The parent-child relationship configuration information can be dynamically generated by the network control center based on the wireless channel quality measurement results reported in advance by the node. In some application scenarios, such as in situations where the mobility of the slave node is low, the parent-child relationship configuration information can also be pre-set in each node based on factors such as the location where the slave node is deployed and the expected communication traffic. The present disclosure does not limit the configuration method and process of the parent-child nodes.

[0070] The network configuration information also includes the broadcast time slot channel configuration information of the node, and the broadcast time slot channel configuration information includes the frequency hopping offset of the transmission broadcast time slot of the master node and each slave node configured as a relay state. The frequency hopping offset of the transmission broadcast time slot indicates the offset of the channel sequence used by the transmission broadcast time slot relative to the channel sequence used by the designated broadcast time slot of the reference node.

[0071] The network configuration information can be statically configured to each node in advance, or can be dynamically generated by the network control center according to the network status, and then broadcast in the wireless ad hoc network through a global broadcast. In some embodiments, the network configuration information is included in the broadcast message.

[0072] In this step, the slave node can determine the identifier of its parent node according to the network configuration information, and judge whether the sending node identifier is the identifier of its parent node, and thus judge whether the node sending the broadcast message is its parent node.

[0073] If the sending node identifier is the identifier of its own parent node, it means that the slave node has achieved synchronization with its own parent node. If the sending node identifier is not the identifier of its own parent node, it means that the slave node has not achieved synchronization with its own parent node, and then continue to execute step 140.

[0074] In step 140, in response to the temporary synchronization node not being its parent node, the slave node determines the channel used by its parent node for sending broadcast time slots based on the network configuration information.

[0075] After the slave node determines that the temporary synchronization node is not its parent node, it can determine the channel of the sending broadcast time slot of its parent node by combining the channel used by the sending broadcast time slot where the temporary synchronization node sends the frame synchronization signal and the network configuration information. Specifically, based on the broadcast time slot channel configuration information in the network configuration information, the frequency hopping offset of the sending broadcast time slot where the temporary synchronization node sends the frame synchronization signal and the frequency hopping offset of the sending broadcast time slot of its parent node can be determined, so that the frequency hopping offset of the channel of the sending broadcast time slot of its parent node relative to the channel of the sending broadcast time slot where the temporary synchronization node sends the frame synchronization signal can be obtained, and the channel of the sending broadcast time slot where the temporary synchronization node sends the frame synchronization signal has been obtained through search, therefore, based on the above information, the channel of the sending broadcast time slot of its parent node can be determined.

[0076] In step 150, the slave node searches for a frame synchronization signal on the frequency channel used by its own parent node to send broadcast time slots until it determines that the sending node of the broadcast message is its own parent node or an exit condition is met.

[0077] After determining the channel on which its parent node sends the broadcast time slot, the slave node can search for the frame synchronization signal sent by its parent node on the channel.

[0078] In some cases, the parent node of a slave node may access the network later than the slave node. In this case, the slave node needs to change the search channel frame by frame according to the channel switching mode of its parent node until it finds its own parent node.

[0079] In some cases, the frame synchronization signal searched by the slave node may not be sent by its parent node. At this time, after the slave node determines that it is not its parent node by receiving the broadcast message, it will re-determine the channel of the parent node and continue searching until it finds its own parent node.

[0080] After searching for the frame synchronization signal, the broadcast message sent by the same node in the time slot where the frame synchronization signal is located is received. Based on the sending node identifier in the broadcast message, it can be determined whether the sending node of the broadcast message is its parent node. After determining that the sending node of the broadcast message is its parent node, synchronization with its parent node is achieved.

[0081] In some cases, a slave node may not be able to search for its parent node due to various reasons. To avoid abnormal situations, the search can be terminated when an exit condition is met. The exit condition can be set according to the specific situation. For example, the exit condition can be "the parent node has not been searched after a preset time."

[0082] In some embodiments, after step 150, method 100 further includes the following steps 160-162.

[0083] In step 160, the slave node determines whether it is configured as a relay state.

[0084] In step 161, in response to being configured as a relay state, the channel used by the broadcast time slot to send the broadcast time slot is determined based on the broadcast time slot channel configuration information.

[0085] As described above, the broadcast time slot channel configuration information includes the frequency hopping offsets of the master node and each slave node configured as a relay state for sending broadcast time slots. If a slave node determines that it is configured as a relay state, it can determine the channel of its own sending broadcast time slot based on the frequency hopping offset of the sending broadcast time slot of its parent node in the broadcast time slot channel configuration information and its own frequency hopping offset of the sending broadcast time slot, as well as the channel of the broadcast time slot in which it receives the frame synchronization signal from the parent node.

[0086] In step 162, the frame synchronization signal and the broadcast message are transmitted in the own transmission broadcast time slot using the determined channel.

[0087] After determining the channel for sending the broadcast time slot, the slave node configured in the relay state uses the channel to send the frame synchronization signal and the broadcast message in its own broadcast time slot.

[0088] Through the method 100 of the present disclosure, a slave node can quickly synchronize with a designated parent node.

[0089] In the present disclosure, in addition to network configuration information, control information such as frame period, node frame structure, system frequency hopping sequence, node type, reference node, and designated broadcast time slot of reference node can be pre-configured to each node.

[0090] In order to dynamically manage the wireless ad hoc network to meet different needs, in some embodiments, one or more of the above control information can also be dynamically adjusted by the control center as needed and sent to each node via a global broadcast.

[0091] The global broadcast referred to in the present disclosure means that the master node sends specific information through a broadcast message, and the relay slave node that receives the broadcast message further sends the specific information in its broadcast message, so that all slave nodes that can receive the broadcast message in the entire network can receive this specific information. The master node can achieve global broadcast of the specific information by setting the information type of the information block to "global broadcast" and the information content to the specific information that needs to be broadcast globally. It should be pointed out that the above method is only an exemplary method for achieving global broadcast, and global broadcast can also be achieved by other methods. The present disclosure does not impose any restrictions on the global broadcast method, as long as similar functions can be achieved.

[0092] The present disclosure also provides a communication device for a wireless ad hoc network, comprising a processor and a non-transitory storage medium storing computer executable instructions, wherein the computer executable instructions can be executed by the processor to perform various steps and functions in various embodiments of the node synchronization method 100 for a wireless ad hoc network.

[0093] A person of ordinary skill in the art can understand and implement other changes to the disclosed embodiments by reading the specification and drawings, the content of the invention and the claims of the present disclosure, and they all fall within the scope of protection of the claims of the present disclosure without departing from the essence of the claims of the present disclosure. In the claims, the wording "comprising" does not exclude other elements and steps, and the words "one" and "an" do not exclude the plural. In the actual application of the present application, a part may perform the functions of multiple technical features cited in the claims. Any figure marks in the claims should not be construed as limiting the scope.

Claims

1. A node synchronization method for a wireless ad hoc network, characterized in that: The wireless ad hoc network includes a plurality of nodes, and the method includes: Searching for frame synchronization signals sent by other nodes in their broadcast time slots in a preset manner; In response to searching for a frame synchronization signal sent by a temporary synchronization node, receiving a broadcast message sent by the temporary synchronization node, the broadcast message including a sending node identifier, the sending node identifier being a node identifier of a node sending the broadcast message; Determine whether the temporary synchronization node is its parent node based on network configuration information, wherein the network configuration information includes parent-child relationship configuration information of nodes in the wireless ad hoc network and broadcast time slot channel configuration information of the nodes; In response to the temporary synchronization node not being its parent node, determining a channel used by its parent node for sending broadcast time slots based on network configuration information; and It searches for the frame synchronization signal on the channel used by its parent node to send broadcast time slots, and after searching for the frame synchronization signal, receives the broadcast message sent by the node that sent the frame synchronization signal, until it determines that the sending node of the broadcast message is its parent node or the exit condition is met.

2. The method according to claim 1, characterized in that The frequency channel used by each of the nodes to send broadcast time slots changes cyclically based on a system frequency hopping sequence.

3. The method according to claim 2, characterized in that The frequency channel used by each of the nodes for sending broadcast time slots changes cyclically based on a system frequency hopping sequence of the same length.

4. The method according to claim 2, characterized in that: The frequency channel used by each of the nodes for sending broadcast time slots changes at fixed time intervals based on a system frequency hopping sequence, and the fixed time intervals take frames as time units.

5. The method according to claim 2, characterized in that: After determining that the sending node of the broadcast message is its parent node, the method further includes: Determine whether it is configured as a relay; In response to being configured as a relay state, determining a channel used by the broadcast time slot to be sent based on the broadcast time slot channel configuration information; The determined channel is used to send a frame synchronization signal and a broadcast message in its own broadcast transmission time slot.

6. The method according to claim 5, characterized in that The broadcast time slot channel configuration information includes the frequency hopping offset of the broadcast time slot sent by the master node and each node configured as a relay state.

7. The method according to claim 6, characterized in that The channels used by the parent node to send broadcast time slots based on network configuration information include: The channel used by the parent node's broadcast time slot is determined based on the system frequency hopping sequence, the channel of the temporary synchronization node's broadcast time slot, the frequency hopping offset of the temporary synchronization node's broadcast time slot, and the frequency hopping offset of the parent node's broadcast time slot.

8. The method according to claim 6, characterized in that Determining the channel used for sending the broadcast time slot based on the broadcast time slot channel configuration information includes: The channel used by the parent node's broadcast time slot is determined based on the system frequency hopping sequence, the channel of the parent node's broadcast time slot, the frequency hopping offset of the parent node's broadcast time slot, and the frequency hopping offset of the parent node's broadcast time slot.

9. The method according to claim 1, characterized in that: The network configuration information is included in a broadcast message and is broadcast in the wireless ad hoc network in a global broadcast manner.

10. A communication node of a wireless ad hoc network, comprising a processor and a non-transitory storage medium storing computer executable instructions, characterized in that: The computer executable instructions may be executed by the processor to perform the method of any one of claims 1 to 9.

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