Low-conflict multiple access method oriented to long delay characteristic of underwater acoustic network

Abstract

The invention discloses a low-conflict multiple access method oriented to the long delay characteristic of an underwater acoustic network, and belongs to the technical field of network communication. The method comprises the following steps that: nodes in a cluster initialize own time slot number and time slot length; the cluster head broadcasts the control frame twice; after receiving the control frame, the intra-cluster node determines the number and the number of time slots of the intra-cluster node and sends an access request in the corresponding time slot; the cluster head responds after receiving the access request; and the nodes in the cluster complete access. According to the invention, by introducing the double control frames and the priority-based multi-access mechanism, the access waiting time of the nodes in the long-delay underwater acoustic network is reduced, and the access delay and conflict probability are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of network communication, and particularly relates to a low-collision multiple access method for long delay characteristics of an underwater acoustic network. Background Art

[0002] Underwater acoustic networks are used to connect multiple underwater fixed or mobile nodes, establish data channels, and complete network information sharing and data distribution. Related technologies are playing an increasingly important role in military and civilian fields such as ocean monitoring, ocean navigation, ocean disaster relief, and ocean production.

[0003] Underwater acoustic networks rely on underwater acoustic communication links to establish data channels. The main characteristics of underwater acoustic channels are low data transmission rate and long propagation delay (about 1500 m / s). In recent years, in order to improve the success rate of networking cooperation and working efficiency among nodes, many studies have been conducted on multiple access methods for underwater acoustic networks, among which the node clustering method is the most prominent. However, directly applying the clustering mode to underwater acoustic networks will have the disadvantages of long waiting time for node multiple access and low utilization rate of link resources. Especially in scenarios with frequent dynamic access requirements (such as large-scale underwater networks or multi-mobile node cooperation tasks), the access delay problem will be further exacerbated, seriously affecting the overall performance and response ability of the network. Therefore, there is an urgent need for a low-collision multiple access method that fully considers the characteristics of underwater acoustic network channels. Summary of the Invention

[0004] In view of this, the present invention provides a low-collision multiple access method for long delay characteristics of an underwater acoustic network. This method fully considers the long delay characteristics of the underwater acoustic communication network and the requirements of node dynamic access, and reduces the access waiting time of in-cluster nodes, and reduces the access delay and collision probability by introducing a double control frame and a multiple access mechanism.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A low-collision multiple access method for long delay characteristics of an underwater acoustic network, which is applied to an underwater acoustic network with a clustering structure. Each cluster has a cluster head, and the in-cluster nodes of each cluster are time-synchronized, and includes the following steps:

[0007] Step 1, each in-cluster node initializes the number and length of time slots of its own TDMA frame;

[0008] Step 2, the cluster head broadcasts a control frame twice in its own cluster at the start time and another fixed time of each TDMA frame, and the content of the control frames broadcast twice in the same TDMA frame is exactly the same;

[0009] Step 3, after receiving the control frame, the in-cluster node determines the number and number of its time slots, and sends an access request in the corresponding time slot;

[0010] Step 4: After receiving the access request, the cluster head carries a response message in the control frame broadcast in the next TDMA frame. The response message is used to allocate data time slot numbers for the nodes, and the nodes that have not been allocated data time slot numbers fail to access.

[0011] Step 5: After receiving the response message, the nodes within the cluster that have successfully accessed complete the access, and the nodes that have failed to access return to Step 3 to continue the access.

[0012] Further, the control frame includes the position information of the cluster head, random access resource information, and response message.

[0013] Further, in Step 3, the nodes within the cluster send an access request only once within the same TDMA frame, that is, if a node within the cluster has already sent an access request for the control frame broadcast for the first time, it will not reply when receiving the control frame broadcast for the second time.

[0014] Further, in Step 3, determine its own number and sequence number of time slots. The specific method is as follows:

[0015] Step 301: Allocate a type weight value to the node, where: the weight of the relay node is a n = 0.9, and the weight of the ordinary node a n = 0.5;

[0016] Step 302: Allocate a service weight value to the node, where: the weight of the fault alarm is b n = 0.9, the weight of the control instruction is b n = 0.8, the weight of the processing result is b n = 0.5, the weight of the status information is b n = 0.3, and the weight of the original data is b n = 0.2;

[0017] Step 303: Allocate a historical access success rate weight value to the node according to the historical access success rate; assume that the historical access success rate of the node is c0, then the historical access success rate weight value is c n = 1 - c0;

[0018] Step 304: Allocate an energy status weight value to the node; assume that the current energy status percentage of the node is d0, then the energy status weight value is d n = d0;

[0019] Step 305: Calculate s according to the type weight value, service weight value, historical access success rate weight value, and energy status weight value of the node n = a n + b n + c n + dn , round up s n to obtain the number of time slots selected by the node in this access;

[0020] Step 306, determine the access time slot number selected by the node by means of random selection.

[0021] Furthermore, in step 4, after the cluster head receives the access request from the nodes in the cluster, it judges the access priority of the nodes according to the number of time slots applied by the nodes in the cluster. When allocating data time slots for the nodes, it preferentially allocates data time slots to the nodes with high priority.

[0022] The beneficial effects of the present invention are as follows:

[0023] (1) The present invention adopts a dual control frame mechanism to provide access guidance for the nodes that have been waiting at the beginning of the frame and the nodes that have missed the initial control frame respectively. This mechanism can solve the problem of node waiting delay caused by the nodes missing the control frame. Even if the nodes miss the initial control information frame, they can still complete the access attempt within this frame period, thus reducing the node waiting time.

[0024] (2) The present invention adopts a multi-access request mechanism based on priority. Among them, the nodes with higher priority can select multiple time slots for access attempts, while the nodes with lower priority only select fewer time slots for access attempts and do not need to wait for the feedback of the first access. The cluster head automatically ignores the remaining access requests of the nodes that have successfully accessed, reduces resource waste, and ensures the efficient utilization of access resources. Even after an access conflict, the nodes can quickly attempt a second access, avoiding the delay of waiting for the next frame period, and improving the access success rate and resource utilization rate. Description of the Drawings

[0025] Figure 1 is a schematic diagram of the clustered network used in the present invention.

[0026] Figure 2 is a flowchart of an embodiment of the present invention.

[0027] Figure 3 is a schematic diagram of the timing of sending a control frame and a random access frame under the dual control frame mechanism.

[0028] Figure 4 is a schematic diagram of the timing of sending a control frame and a random access frame under the multi-access request mechanism based on priority. Detailed Embodiments

[0029] The following further elaborates on the specific embodiments of the present invention in conjunction with the drawings.

[0030] A low-collision multiple access method for the long time delay characteristics of an underwater acoustic network is applied to, such as Figure 1The underwater acoustic network with a clustering structure is shown, where each cluster has a cluster head, and the nodes within each cluster maintain time synchronization.

[0031] This method divides all the nodes in the underwater acoustic network into different clusters according to certain rules. The cluster head node in each cluster broadcasts control frame 1 and control frame 2 carrying access resource information in a fixed time slot of each frame. When a node receives the control frame, it is the case that after the nodes within the cluster receive the control frame broadcast by the cluster head, they determine the number of access time slots according to their own and the priorities of the services to be transmitted and send access requests in the corresponding time slots. The cluster head receiving the node access request means that the cluster head makes an overall judgment on whether the node access is successful according to the access requests of multiple nodes and broadcasts the access result in the next round of control frame.

[0032] Specifically, it includes the following steps:

[0033] Step 1, each node within each cluster initializes the number and length of time slots of its TDMA frame;

[0034] Step 2, the cluster head broadcasts the control frame twice within its own cluster at the start time and another fixed time of each TDMA frame. The content of the control frame broadcast twice in the same TDMA frame is exactly the same; the control frame contains the position information of the cluster head, random access resource information, and response messages.

[0035] Step 3, after receiving the control frame, the nodes within the cluster determine their own number and numbering of time slots and send access requests in the corresponding time slots; the specific method is as follows:

[0036] Step 301, assign a type weight value to the node, where: the weight of the relay node is a n = 0.9, and the weight of the ordinary node is a n = 0.5;

[0037] Step 302, assign a service weight value to the node, where: the weight of the fault alarm is b n = 0.9, the weight of the control instruction is b n = 0.8, the weight of the processing result is b n = 0.5, the weight of the status information is b n = 0.3, the weight of the original data is b n = 0.2;

[0038] Step 303, assign a historical access success rate weight value to the node according to the historical access success rate; assume that the historical access success rate of the node is c0, then the historical access success rate weight value is c n = 1 - c0;

[0039] Step 304, assign an energy state weight value to the node; assume that the current energy state percentage of the node is d0, then the energy state weight value is dn = d0;

[0040] Step 305: Calculate s according to the type weight value, service weight value, historical access success rate weight value, and energy state weight value of the node n = a n + b n + c n + d n , round s n upward to obtain the number of time slots selected by the node in this access;

[0041] Step 306: Determine the time slot number of the node by means of random selection.

[0042] The nodes within the cluster send an access request only once within the same TDMA frame. That is, if a node within the cluster has already sent an access request for the first broadcast control frame, it will not reply when receiving the second broadcast control frame.

[0043] Step 4: After receiving the access request, the cluster head determines the access priority of the node according to the number of time slots applied for by the nodes within the cluster, and carries a response message in the control frame broadcast in the next TDMA frame; the response message is used to allocate data time slot numbers for the nodes, and the nodes that have not been allocated data time slot numbers fail to access; when allocating data time slots for the nodes, high-priority nodes are preferentially allocated data time slots.

[0044] Step 5: After receiving the response message, the nodes within the cluster that have successfully accessed complete the access, and the nodes that have failed to access return to Step 3 to continue the access.

[0045] This method reduces the access waiting time of nodes in a long-delay underwater acoustic network and reduces the access delay and collision probability by introducing a dual control frame and a priority-based multiple access mechanism.

[0046] The following is a more specific example:

[0047] A low-collision multiple access method for the long-delay characteristics of an underwater acoustic network, as Figure 2 shown, this method includes the following steps:

[0048] Step 1: Establish a clustered network as Figure 1 shown.

[0049] Step 1a: Divide the underwater acoustic network according to certain rules, and the subsequent management unit after division is called a cluster.

[0050] Step 1b: Map each node to the cluster according to certain rules, and the underwater acoustic communication coverage or the placement space can be pre-clustered.

[0051] Step 1c: According to certain rules, for each elected cluster head, usually a node with composite communication means is selected as the cluster head, such as a surface ship, a wave boat, a buoy or an unmanned underwater vehicle with underwater acoustic and radio, satellite communication links.

[0052] Step 1d: Each cluster node ensures time synchronization, initializes the number of time slots and the length of time slots in the TDMA frame. The time synchronization method can adopt pre-time calibration, synchronization signal broadcast, delay compensation, etc.

[0053] Step 2: The cluster head broadcasts control frame 1.

[0054] Step 2a: The cluster head broadcasts control frame 1 at the start time of each frame. As shown in, where T is the total duration of a TDMA frame, T is the control frame, T is the access time slot, T is the data time slot, T is the transmission delay of data in the underwater acoustic channel. Control frame 1 contains the position information of the cluster head and the random access resources within the frame. Figure 3 shown, where, T S is the total duration of a TDMA frame, T BEACON is the control frame, T RA is the access time slot, T DATA is the data time slot, T P is the transmission delay of data in the underwater acoustic channel. Control frame 1 contains the position information of the cluster head and the random access resources within the frame.

[0055] Step 3: The node receives control frame 1.

[0056] Step 3a: The node calculates the number of access time slots according to its own and the priority of the information to be transmitted.

[0057] Step 3b: The node determines the list of time slot numbers for sending access requests according to the calculated number of access time slots.

[0058] Step 3c: The node sends an access request in the corresponding time slot according to the number and number of time slots it selects.

[0059] Step 4: The cluster head broadcasts control frame 2.

[0060] The cluster head broadcasts control frame 2 at a fixed time of each frame. As shown in, control frame 2 contains the position information of the cluster head and the reserved random access resources within the frame. Figure 3 shown, control frame 2 contains the position information of the cluster head and the reserved random access resources within the frame.

[0061] Step 5: The cluster head receives the access request of the node.

[0062] Step 5a: The cluster head comprehensively judges whether the node accesses successfully and sends a response message in the next control frame 1. As shown in Figure 4 shown.

[0063] Step 5b: If the node accesses successfully, it sends a success message; otherwise, it sends an access failure message.

[0064] Step 6: The node receives control frame 2.

[0065] Step 6a, the node determines whether it has missed control frame 1. If it has missed control frame 1, it executes Step 6b and Step 6c. If it has already executed Step 3, it will not reply anymore.

[0066] Step 6b, the node calculates the number of access time slots according to its own and the priority of the information to be transmitted.

[0067] Step 6c, the node sends an access request in the corresponding time slot according to the number of time slots and the time slot number it has selected.

[0068] Step 7, the cluster head receives the access request of the node, and the process is the same as Step 5.

[0069] In summary, the present invention is based on a clustered network mode, introduces a dual control frame mechanism and a multiple access mechanism, and reduces the access delay and collision probability.

[0070] The above is only a specific example of the present invention and does not constitute any limitation to the present invention. Obviously, for professionals in the field, after understanding the content and principle of the present invention, various modifications and changes in form and details may be made without departing from the principle and structure of the present invention. However, these corrections and changes based on the idea of the present invention are still within the protection scope of the claims of the present invention.

[0071] The beneficial effects of the present invention are as follows: The dual control frame mechanism provides access guidance for the nodes that have been waiting at the beginning of the frame and the nodes that have missed the initial control frame respectively, reducing the access waiting delay of the nodes. At the same time, in the multi-access request mechanism based on priority, different numbers of attempted access time slots are allocated according to the node and service priorities, and the access overall processing of the cluster head node reduces the waste of access resources, improves the node access success rate and resource utilization rate.

[0072] It should be noted that the step numbers in the description and claims of the present invention are only for clearly describing the implementation scheme of the present invention and facilitating understanding, and the order of the numbers is not limited.

Claims

1. A low-collision multiple access method for long time-delay characteristics of underwater acoustic networks, characterized in that, Applied to an underwater acoustic network with a clustering structure, each cluster has a cluster head, and the nodes within each cluster maintain time synchronization, including the following steps: Step 1, each node within the cluster initializes the number of time slots and the length of time slots of its TDMA frame; Step 2, at the start time of each TDMA frame and another fixed time, the cluster head broadcasts a control frame twice within its own cluster, and the content of the control frames broadcast twice in the same TDMA frame is exactly the same; Step 3, after receiving the control frame, the nodes within the cluster determine the number and number of their time slots, and send an access request in the corresponding time slot; Step 4, after receiving the access request, the cluster head carries a response message in the control frame broadcast in the next TDMA frame. The response message is used to allocate a data time slot number for the node, and the nodes that do not receive the allocated data time slot number fail to access; Step 5, after receiving the response message, the nodes that succeed in accessing complete the access, and the nodes that fail to access return to Step 3 to continue the access.

2. The low-collision multiple access method for long time-delay characteristics of an underwater acoustic network according to claim 1, wherein The control frame includes the position information of the cluster head, random access resource information, and response message.

3. A low-collision multiple access method for long time-delay characteristics of an underwater acoustic network according to claim 1, characterized in that In Step 3, the nodes within the cluster only send an access request once within the same TDMA frame, that is, if a node within the cluster has sent an access request for the control frame broadcast for the first time, it will not reply when receiving the control frame broadcast for the second time.

4. A low-collision multiple access method for long time-delay characteristics of an underwater acoustic network according to claim 1, characterized in that In Step 3, to determine the number and number of its time slots, the specific method is as follows: Step 301: Assign type weight values to nodes, where: the weight of a relay node is a n = 0.9, and the weight a of an ordinary node n = 0.5; Step 302, assign service weight values to the nodes, where: the weight of the fault alarm is b n = 0.9, the weight of the control instruction is b n = 0.8, the weight of the processing result is b n = 0.5, the weight of the status information is b n = 0.3, the weight of the original data is b n = 0.2; Step 303: Assign a historical access success rate weight value to the node according to the historical access success rate; assuming that the historical access success rate of the node is c0, the historical access success rate weight value is c n = 1 - c0; Step 304, assign an energy state weight value to the node; assume that the current energy state percentage of the node is d0, then the energy state weight value is d n = d0; Step 305: Calculate s according to the type weight value, service weight value, historical access success rate weight value, and energy state weight value of the node n = a n + b n + c n + d n , round up s n to obtain the number of time slots selected by the node in this access; Step 306, use a random selection method to determine the access time slot number selected by the node.

5. The low-collision multiple access method for long time-delay characteristics of an underwater acoustic network according to claim 1, characterized in that In Step 4, after receiving the access request from the nodes within the cluster, the cluster head judges the access priority of the nodes according to the number of time slots applied by the nodes within the cluster. When allocating data time slots for the nodes, it preferentially allocates data time slots to the nodes with high priority.

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