MAC layer directional link perception and maintenance method and system for highly dynamic ad hoc networks

Abstract

This invention discloses a MAC layer directional link awareness and maintenance method and system for highly dynamic ad hoc networks, mainly addressing the problems of slow directional link awareness and high data transmission packet loss rate in existing technologies under highly dynamic scenarios. The implementation scheme includes two parts: link awareness and maintenance of neighbor-occupied time slot sub-links and link awareness and maintenance of neighbor links. The awareness and maintenance of all neighbor-occupied time slot sub-links is based on a cross-time slot packet reception feedback mechanism. Nodes record the transmission status of time slot sub-links and provide rapid packet reception feedback in data time slots, enabling neighboring nodes to obtain cross-time slot link quality awareness. The link awareness and maintenance of all neighbor links is based on link failure time prediction. This invention can accelerate the directional link awareness speed and quickly track adjacent topology changes in highly dynamic scenarios, increasing the data transmission reliability of the MAC protocol in highly dynamic ad hoc network scenarios. It can be used in mobile ad hoc networks with directional antennas.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, and specifically relates to a method for directional link sensing and maintenance, which can be used in mobile ad hoc networks based on directional antennas to ensure that directional links can still communicate effectively and reliably under high dynamic conditions, thereby reducing the packet loss rate of link transmission. Background Technology

[0002] In the context of flight ad hoc networks with high dynamic and large-capacity service transmission requirements, directional antennas are widely used in flight ad hoc networks because they have longer transmission distances, stronger anti-interference capabilities, and can better utilize space resources to improve network capacity, compared to traditional omnidirectional antennas.

[0003] However, due to the narrow beam angle and stringent beam alignment requirements of directional antennas, high-speed relative movement between nodes can easily lead to beam misalignment in directional communication with neighboring nodes, causing communication interruptions between nodes. This also interferes with the normal communication of other directional links, increasing the network packet loss rate. Furthermore, rapid node movement means constantly changing adjacency topology; frequent directional link failures caused by neighbor node removal can result in the loss of a large number of data packets over a period of time. Therefore, understanding and quickly identifying changes in directional link status and maintaining them accordingly is crucial for directional MAC protocols to track adjacency topology changes, maintain directional link transmission quality, and achieve reliable service transmission in highly dynamic scenarios.

[0004] The paper (FM-MAC: A Multi-Channel MAC Protocol for FANETs with Directional Antenna) addresses the link interruption problem caused by the high mobility of UAVs by proposing a resource reservation scheme based on mobility prediction. This scheme avoids link interruptions by predicting the mobility of UAVs; specifically, for data packet nodes that need to be transmitted on the service channel (SCH), it estimates their transmission time and proposes a judgment formula that considers the position and velocity of the source and target nodes, as well as the maximum coverage distance and angle of the directional antenna, to predict whether the link will exceed the communication range. However, this scheme only considers one type of directional link failure—whether the currently transmitted object will move out of the beam communication range in the next transmission time—and does not comprehensively consider all possible directional link failures. Instead, it avoids interference by increasing physical resources, thus reducing the reliability of directional link transmission.

[0005] The paper (Adaptive Communication Protocols in Flying Ad Hoc Network) proposes a PPMAC method, which assumes periodic, collision-free location information broadcasting and uses this to predict neighbor node movement for directional link scheduling. To ensure reliable link transmission, location information is sent directionally before transmitting data packets so that receiving nodes can perform beam alignment. Reliable link transmission is guaranteed through the interaction of RTS, CTS, and WTS information. While this method can guarantee reliable transmission of directional links, it introduces significant overhead during link establishment, and its cautious link collision avoidance methods lead to low link utilization. Therefore, it is not suitable for long-distance transmission scenarios using directional antennas and can easily cause a decrease in network throughput.

[0006] In his graduation thesis, "Research on Time Division Multiple Access Protocol in Purely Directed Adaptive Networks," Wang Jinjie proposed a "link distance" calculation formula to quantify inter-link interference. The "link distance" is defined using the inter-link distance and beam difference within the same time slot. His method periodically collects link state information, calculates the "link distance," predicts potentially interfering links, and makes corresponding adjustments. Furthermore, to accelerate maintenance, the paper proposes a strategy to assist in beam switching within service time slots. However, this method, in order to obtain link transmission quality information, sends empty packets even when there is no service. The link-aware approach, which characterizes link quality by statistically analyzing packet loss rates using fixed-length empty packets, causes additional interference to other directional links transmitting at the same time, leading to a decline in link transmission quality. Simultaneously, fixed-period link failure detection cannot quickly track adjacent topology changes, and the MAC protocol still suffers from limited adaptability to highly dynamic scenarios. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of the prior art by proposing an efficient directional link awareness and maintenance method for MAC layer in highly dynamic ad hoc networks, thereby improving the speed of directional awareness of adjacency relationships and increasing the reliability of directional data transmission in highly dynamic ad hoc networks.

[0008] To achieve the above objectives, the technical solution of the present invention includes:

[0009] I. An efficient directional link-aware maintenance method for highly dynamic ad hoc networks at the MAC layer, including link-aware maintenance of all neighbor-occupied time slot sublinks and link-aware maintenance of all neighbor links;

[0010] The aforementioned awareness and maintenance of all neighbor-occupied time slot sub-links is based on a cross-time slot packet reception feedback mechanism.

[0011] The link awareness maintenance of all neighboring links is based on link failure time prediction.

[0012] Preferably, the sensing and maintenance of neighbor-occupied time slot sublinks based on a cross-time slot packet reception feedback mechanism includes:

[0013] 2a) The node records the link transmission status to each neighbor node within one frame and adds it to the link transmission record table for that neighbor;

[0014] 2b) When a node arrives at a transmission time slot, it first sends a maintenance packet to provide feedback on the historical packet reception status of the receiving node in this time slot, and then sends the service data packet;

[0015] 2c) When a node arrives at a receive time slot, it receives a maintenance packet containing neighbor packet reception feedback information, and based on this feedback information, it perceives the link quality of the time slot that the node is transmitting to that neighbor, including:

[0016] Confirm the feedback information for this node based on the maintenance package;

[0017] By comparing the packet transmission and reception records of the link, the transmission quality perception of the time slot sub-link is obtained;

[0018] Update the LastRcvFeedback field of the most recently received feedback slot for this node to the current slot in the local link transmission record table;

[0019] 2d) For all time slot sublinks that are perceived to be of poor quality, the node waits for the nearest scheduling time slot to adjust the time slot allocation and complete the maintenance of the time slot sublinks of its neighbors.

[0020] Preferably, the link-aware maintenance based on link failure time prediction for all neighboring links includes:

[0021] 3a) Nodes periodically exchange their own position and velocity information during fixed duty time slots to obtain an initial one-hop neighbor table and determine the beam direction for directional link transmission;

[0022] 3b) When a node receives location and speed information from a neighbor, it adjusts the beam pointing according to the latest neighbor's location and predicts the link failure time Δt and failure type for that neighbor.

[0023] 3c) When a node updates the predicted link failure time Δt or the time slot resource occupancy status, it adaptively adjusts the link maintenance time slot T for that neighbor. p ;

[0024] 3d) Nodes in link maintenance time slot T p It sends its own location and speed information to maintain the link until the neighbor link fails when Δt is reached. Depending on the failure type, it cancels the directional link time slot occupation or deletes the neighbor, thus completing the maintenance of the entire life cycle of the neighbor link.

[0025] II. A MAC layer-oriented link-aware maintenance system for highly dynamic ad hoc networks, including:

[0026] The time-slot sub-link quality feedback module is used to record the link transmission status to neighboring nodes within one frame and to provide feedback on historical packet reception information when sending maintenance packets.

[0027] The time slot sub-link quality awareness module is used to receive maintenance packets containing neighbor packet reception feedback information, and to perceive the link quality of the time slot sent by this node to that neighbor based on the packet reception feedback information;

[0028] The time slot sublink maintenance module is used to adjust the time slot allocation for all time slot sublinks that are perceived to have poor quality in the most recent scheduling time slot, and to complete the maintenance of the time slot sublinks of the neighbors.

[0029] The neighbor link failure time prediction module is used to predict the link failure time Δt and failure type for that neighbor after receiving the neighbor's location and speed information.

[0030] The neighbor link maintenance module is used to adaptively adjust the link maintenance time slot T for neighbors after the predicted link failure time Δt is updated. p and in link maintenance time slot T p It sends its own location and speed information for link maintenance;

[0031] The neighbor link failure handling module is used to cancel the directional link time slot occupation or delete the neighbor when a neighbor link fails, based on the failure type, thus completing the maintenance of the neighbor link throughout its entire lifecycle.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] Firstly, this invention employs a fast cross-timeslot link packet reception feedback mechanism, which can effectively detect poor link quality caused by inter-group interference in directional multiplexed links and unpredictable external interference, and improves the detection speed of timeslot sub-link quality for actual data transmission, thereby enhancing the reliability of directional data transmission in ad hoc networks under highly dynamic conditions.

[0034] Secondly, this invention improves the speed of adjacency relationship orientation perception by predicting link failure time, and adaptively adjusts the timing of neighbor link failure maintenance based on real-time time slot resource occupancy information, starting from the orientation link failure type, thereby reducing the overhead of orientation link perception and maintenance.

[0035] Third, this invention combines proactive link failure prediction with passive link quality feedback to comprehensively identify and address various link failure and interference scenarios, providing a foundation for rapid transmission link adjustment and adjacency topology maintenance. This enables nodes to quickly track changes in adjacency topology, while improving data transmission reliability and reducing packet loss rate, thus increasing the adaptability of the MAC protocol in highly dynamic ad hoc network scenarios. Attached Figure Description

[0036] Figure 1 This is a flowchart illustrating the overall implementation of the method of the present invention;

[0037] Figure 2 This is a schematic diagram of the time slot frame structure and packet transmission structure;

[0038] Figure 3 This is a functional block diagram of the system of the present invention;

[0039] Figure 4 This is a comparison chart of link failure detection time in the same scenario simulated using the present invention and the traditional periodic sensing method;

[0040] Figure 5 This is a comparison chart of link transmission packet loss rates at different movement speeds, simulated using the present invention and traditional periodic sensing methods. Detailed Implementation

[0041] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the protection scope of the present invention.

[0042] The working scenario of this example is a self-organizing network composed of highly mobile nodes equipped with directional antennas. In this self-organizing network, each node is equal in status, has the same physical capabilities, and executes the same protocol suite. At the MAC layer, each node independently recognizes its adjacency relationship and negotiates and allocates channel resources based on its interaction with its neighbors.

[0043] The link-state-aware maintenance technology proposed in this invention can be selectively embedded into the original MAC layer TDMA protocol in a functional manner. The basic principle of this protocol is to divide the time axis into non-overlapping time frames, and further divide each time frame into multiple time slots, allocating different time slots for communication to different nodes. One time slot frame structure used in this example is as follows: Figure 2As shown, a frame consists of multiple equally spaced time slots, including one scheduling time slot for time slot resource allocation and adjustment, and the rest are data time slots, which are allocated to each node and its neighboring nodes for data transmission.

[0044] In a data time slot, the transmitting node occupying the time slot uses a directional antenna to transmit, and its neighboring nodes use directional antennas to receive it. The transmitting node first sends a short maintenance packet to perform link awareness, and then sends data packets. The link resources occupied by sending the maintenance packet are the overhead of this scheme.

[0045] Reference Figure 1 The MAC layer-oriented link-aware maintenance method for highly dynamic ad hoc networks proposed in this example is based on the TDMA protocol and is optimized. It includes link-aware maintenance of all neighbor-occupied time slot sublinks and link-aware maintenance of all neighbor links. The implementation steps are shown in the figure below:

[0046] Step 1: The node performs neighbor discovery.

[0047] The node powers on and, through communication with its neighbors, adds nodes within its communication range to the initial one-hop neighbor table, considering these nodes as its neighbors.

[0048] Step 2: Nodes allocate time slots.

[0049] A node negotiates and allocates time slot resources with all its neighboring nodes during the scheduling time slot based on the interference conditions of the directional link: it allocates one or more conflict-free time slots for directional data transmission on the link between each neighboring node, and generates an initial time slot occupancy table.

[0050] Step 3: The node performs directional data transmission in a loop according to the time slot occupancy table, and simultaneously performs link awareness maintenance on all neighboring time slot sub-links and on all neighboring links.

[0051] This example uses the link L between node i and its neighbor j. ij For example, the steps are described as follows:

[0052] 1. The aforementioned sensing and maintenance of neighbor-occupied time-slot sublinks based on a cross-time-slot packet reception feedback mechanism includes:

[0053] Step 3.1a) The node records the link transmission information to its neighboring node within one frame and adds it to the link transmission record table for that neighbor:

[0054] The link transmission record table is indexed by the neighbor node ID. It contains the packet sending record SendSituation[] and packet receiving record RcvSituation[] for all transmission time slots occupied by the neighbor, as well as the MaxSlotConfirmed field for the confirmed feedback time slot and the LastRcvFeedback field for the most recently received feedback time slot. The structure is shown in Table 1.

[0055] Table 1. Link Transmission Record Table Format

[0056]

[0057] In the transmission time slot T of node i to j k Sending node i records the packet sending status in the SendSituation(j, T) field of the link transmission record table for neighbor j. k In the link transmission record table for neighbor i, the receiving node j records the packet reception status in the packet reception record field RcvSituation(i,T). k )middle;

[0058] For both types of records, if the record already exists in the table, the current record directly overwrites the previous frame's time slot T. k -1 The transmission record, i.e., the link transmission record, is only retained for one frame.

[0059] Step 3.2a) When node i arrives at the transmission time slot, it first sends a maintenance packet to provide feedback on the historical packet reception status of the receiving node j in this time slot, and then sends the service data packet:

[0060] The maintenance packet format includes: the LastRcvFeedback field in the local link transmission record table and all packet reception records for that neighbor, RcvSituation(j,S)[], as shown in Table 2.

[0061] Table 2 Link Maintenance Packet Format

[0062]

[0063] In the table, RcvSituation(j,S)[] represents the packet reception status of all time slot sub-links that were not acknowledged by neighbor j within the previous frame time, and S is the total number of packets allocated to links from the maxSlotConfirmed time to the current time. The set of receive time slots, sent in the maintenance packet as RcvSituation(j,S)[], is used to ensure the link. All packet reception status in all time slots is fed back to the link sending node j.

[0064] Step 3.3a) When a node arrives at a receive time slot, it receives a maintenance packet containing neighbor packet reception feedback information, and based on the packet reception feedback information, it perceives the link quality of the time slot for which it transmits to that neighbor, including:

[0065] 3.3a-1) Confirm the feedback information of this node based on the maintenance package:

[0066] Node j obtains the value R of the LastRcvFeedback field from the neighbor based on the received neighbor maintenance packet. z Then it is assumed that the neighbor has confirmed R. z Previously, this node provided feedback on the neighbor's packet receiving status;

[0067] Update the MaxSlotConfirmed field value in the local link transmission record table to R. z And delete in R z All packet reception records for that neighbor in the previous time slot are recorded to ensure that packet reception information is not repeatedly fed back.

[0068] 3.3a-2) By comparing the packet transmission and reception records of the link, the transmission quality perception of the time slot sub-link is obtained:

[0069] Node j uses its local timeslot table to look up all the timeslots allocated to links since the last time slot LastRcvFeedback was received. The set of sending time slots S' is then used to find the packet sending records of these time slot sub-links SendSituation(i,S')[] based on the link transmission record table for the neighbor i;

[0070] Node j obtains the packet reception status feedback RcvSituation(j,S)[] of neighbor i based on the maintenance packet received from neighbor i, and compares the packet sending record SendSituation(i,S')[] of the time slot sublink with the packet receiving record RcvSituation(j,S)[] fed back by the neighbor:

[0071] If a packet sending record exists in a certain time slot, but the packet receiving feedback from neighboring nodes does not contain a packet receiving record for that time slot, i.e., time slot k∈(S′-S), then the sub-link of that time slot is considered to be... It has expired; record the time slot of the expiration.

[0072] Otherwise, it is assumed that during this period, all nodes j transmit time slot sublinks to i. Feedback was received that packet loss rate was used as the standard for measuring the quality of time slot sub-links. The packet loss rate LR of each time slot in set S was calculated and compared with the set packet loss rate threshold LR. thres Compare and determine the transmission quality of the time slot sub-links:

[0073] If LR > LR thres If the time slot is not in good quality or has failed, then the time slot is recorded.

[0074] Conversely, if the transmission of the gapped sub-link is considered reliable at this time, no adjustment is made;

[0075] 3.3a-3) In the local link transmission record table, the LastRcvFeedback field of the node is updated to the current time slot, indicating that the node last received feedback from the neighbor in the LastRcvFeedback time slot.

[0076] At this point, node j obtains the transmission quality statistics of the time slot sub-links previously sent by node i through the feedback across time slots, and believes that node j can perceive the transmission quality of all time slot sub-links to neighbor i, and the perception speed does not exceed one frame duration.

[0077] Step 3.4a) For all time slot sublinks that are perceived to have poor quality, regardless of whether the interference is caused by movement or other external interference, the node adopts a cautious link maintenance strategy. First, it cancels the transmission of the failed time slot sublink, and then adjusts the allocation of time slot sublinks in the nearest scheduling time slot to complete the quality maintenance of the neighbor's time slot sublinks.

[0078] In the network, a node performs link L between node i and node j on all time slot sublinks occupied by its neighbors, following steps 3.1a) to 3.4a) above. ij The same operation is used to perform awareness maintenance on each time slot sub-link, thereby increasing the reliability of directional data transmission in ad hoc networks under highly dynamic conditions.

[0079] II. The aforementioned perception-based maintenance of neighbor links based on link failure time prediction includes:

[0080] Step 3.1b) Periodic mobile information interaction.

[0081] Nodes periodically exchange their location and velocity information with their neighbors during fixed duty slots. To determine the beam direction θ of the neighbor, and to perform directional data transmission in the data time slot occupied by the neighbor according to the beam direction θ.

[0082] Step 3.2b) When a node receives the location and speed information of a neighbor, it adjusts the beam pointing according to the latest neighbor's location and predicts the link failure time Δt and failure type for that neighbor.

[0083] 3.2b-1) Solve for the link failure time Δt of the neighbor using the following formula:

[0084]

[0085] Among them, P s and V s P represents the position and velocity of the source node. d and V d These represent the bits of the destination node.

[0086] Position and speed, R max θ and θ represent the maximum coverage distance and beam angle of the directional antenna, respectively. This formula indicates that the neighbor link is expected to break down after a future Δt.

[0087] 3.2b-2) Determine the link failure type based on the constraints of the above formula for solving the link failure time Δt:

[0088] If the predicted link failure time Δt is affected by the maximum transmission distance R in the first clause of the formula... max If the constraint is met, then the neighbor link failure type is considered to be the neighbor moving out of the communication range of this node, that is, it is predicted that the neighbor will move out of the communication range of this node after Δt, resulting in the neighbor link failure;

[0089] If the predicted link failure time Δt is constrained by the directional antenna beam angle θ in the second formula, then the neighbor link failure type is considered to be beam misalignment between the neighbor and this node, that is, it is predicted that the neighbor will be beam misalignment between the neighbor and this node after Δt, resulting in the neighbor link failure.

[0090] Step 3.3b) When the predicted link failure time Δt or time slot resource occupancy is updated, the node adaptively adjusts the link maintenance time slot T for that neighbor. p .

[0091] 3.3b-1) Nodes query the time slot occupancy table for the time interval Δt from the current time:

[0092] If a transmission slot to a neighbor cannot be found within the time interval Δt, the node will be unable to actively maintain its position and velocity information to the neighbor before the expected link failure time arrives, and will proceed to step 3.4b).

[0093] Otherwise, find the first transmission time slot for that neighbor, and denote it as the fastest adjustment time t for the link to that neighbor under the current time slot occupancy. l And find the closest time to the predicted link failure time t′. loss =t now The transmission time slot of +Δt is denoted as the last adjustment time t for that neighbor link. r ;

[0094] 3.3b-2) Determine the link maintenance slot T for this neighbor based on the link failure type. p :

[0095] If the link failure is predicted to be caused by a neighbor moving out of the communication range, then the link maintenance time slot T... p =t r Link maintenance is performed in the last transmission time slot before the link fails, so that it can be quickly detected once a neighbor fails.

[0096] If the link failure is predicted to be caused by beam misalignment between the link and its neighbor, then the link maintenance time slot T... p =t l In the next transmission slot for that neighbor, link maintenance is performed to enable it to perform beam adjustment as soon as possible and maintain link stability.

[0097] Step 3.4b) Nodes in link maintenance time slot T p It sends its own location and velocity information for link maintenance until a neighboring link fails when Δt is reached. Depending on the failure type, it cancels the directional link time slot occupation or deletes the neighbor, thus completing the maintenance of the neighboring link for its entire lifecycle.

[0098] 3.4b-1) Before the predicted link failure time Δt for the neighbor arrives, the node needs to proactively use the link maintenance time slot T obtained in 3.3b). p The node sends its own location and velocity information to maintain the link to its neighbor. Due to the continuous updates to link failure time prediction and time slot occupancy issues, the node checks whether the current time slot is the link maintenance time slot T in each time slot it sends information to the neighbor. p :

[0099] If it is the link maintenance time slot T p Then, the position and velocity information of this node will be added to the maintenance packet sent in this time slot. Maintain this neighbor link;

[0100] Otherwise, do not add the node's location and speed information to the maintenance package, and maintain the initial periodic link maintenance.

[0101] 3.4b-2) Upon reaching the predicted link failure time Δt for that neighbor, the neighbor is either occupied or deleted based on the link failure type:

[0102] If a neighbor moves out of the communication range, all directional time slot transmissions to that node will be stopped. If no packets are received from that node in a certain receiving time slot, the neighbor deletion process will be executed immediately, that is, the neighbor will be deleted from the one-hop neighbor table in order to track the adjacency topology changes in a timely manner.

[0103] If the beam is out of alignment with the neighbor, all directional time slot occupancy will be cancelled in the time slot occupancy table, and beam discovery will be performed again in the scheduling time slot to re-establish the directional link.

[0104] Each node in the network performs the following steps on all its neighbor links, following steps 3.1b) to 3.4b), to execute the link L between node i and j. ij The same operation is used to complete the perception and maintenance of each neighbor link, so as to improve the speed of adjacency relationship orientation perception of nodes under highly dynamic conditions.

[0105] Reference Figure 3 This example provides a MAC layer-oriented link-aware maintenance system for highly dynamic ad hoc networks, comprising: a time-slot sublink quality feedback module 1, a time-slot sublink quality awareness module 2, a time-slot sublink maintenance module 3, a neighbor link failure time prediction module 4, a neighbor link maintenance module 5, and a neighbor link failure handling module 6. The time-slot sublink quality feedback module 1, time-slot sublink quality awareness module 2, and time-slot sublink maintenance module 3 are used to perform node awareness and maintenance of occupied time-slot sublinks; the neighbor link failure time prediction module 4, neighbor link maintenance module 5, and neighbor link failure handling module 6 are used to perform node link awareness and maintenance of neighbor links.

[0106] The working principle of the time slot sublink quality feedback module 1, time slot sublink quality perception module 2, and time slot sublink maintenance module 3 in completing the perception and maintenance of occupied time slot sublinks by nodes is as follows:

[0107] The time-slot sublink quality feedback module 1 records the link transmission status to neighboring nodes within one frame and feeds back historical packet reception information to the time-slot sublink quality perception module 2 of neighboring nodes by sending maintenance packets. The time-slot sublink quality perception module 2 receives the maintenance packet containing neighbor packet reception feedback information and perceives the link quality of the time slots transmitted by this node to the neighbor based on the packet reception feedback information: if there is a time-slot sublink with poor quality, the time slot number is transmitted to the time-slot sublink maintenance module 3 to adjust the time slot allocation for the time-slot sublink with poor quality and complete the time-slot sublink maintenance for the neighbor; otherwise, the time-slot sublink quality feedback module and the time-slot sublink quality perception module continue to be executed alternately according to the time slot occupancy table.

[0108] The neighbor link failure time prediction module 4, the neighbor link maintenance module 5, and the neighbor link failure handling module 6 complete the link awareness maintenance of the node on the neighbor links. Their working principle is as follows:

[0109] After receiving the neighbor's location and speed information, the neighbor link failure time prediction module 4 predicts the link failure time Δt and failure type for that neighbor; it then transmits the predicted link failure time Δt to the neighbor link maintenance module 5 to adaptively adjust the link maintenance time slot T for the neighbor. p and in link maintenance time slot T pThe path failure time prediction module 4 sends its own location and speed information to neighboring nodes; the neighbor link failure time prediction module 4 and the neighbor link maintenance module 5 execute alternately according to the time slot occupancy table, and transmit the link failure time Δt to the neighbor link failure processing module 6, so that when a neighbor link fails, the directional link time slot occupancy can be canceled or the neighbor can be deleted according to the failure type, thus completing the maintenance of the entire life cycle of the neighbor link.

[0110] The following section provides further explanation of the effectiveness of this example, based on simulation results:

[0111] 1. Simulation conditions

[0112] The simulation experiment application platform is: a 20-core Intel i7 12700H 64-bit CPU with a main frequency of 2.7GHz and 16GB of memory.

[0113] The software platform for the simulation experiment was Windows 11 operating system and Exata 7.2.0.

[0114] The network scenario in the simulation experiment is 30 nodes randomly and evenly distributed in a 100km×100km space. Each node is equipped with a directional antenna with a beamwidth of 15° and a directional communication distance of 20km. Each node is configured with a one-hop Poisson traffic flow with a traffic generation interval of 0.1ms.

[0115] 2. Simulation content and result analysis:

[0116] Simulation 1: In the above scenario, a node movement path experiencing multiple link disconnections is set up. The time when the node and its surrounding nodes perceive the link disconnection is simulated using both the method of this invention and the traditional periodic link sensing method. The difference between the time of perception and the actual physical link disconnection is calculated. The results are as follows: Figure 4 As shown.

[0117] from Figure 4As can be seen, in 14 link failures, the link failure detection time proposed in this invention is consistently reduced compared to the traditional periodic detection method, with the average link failure detection time decreasing to 1 / 4 of the traditional periodic detection method. This is because the traditional periodic detection method requires two superframes to detect a link failure, while this invention, by employing a cross-timeslot packet reception feedback mechanism, reduces the detection time of the timeslot sub-link status to within one frame, greatly reducing the link failure detection time. Furthermore, since this invention uses neighbor link detection based on link failure time prediction, it can adapt to various link failure scenarios. Therefore, in the 14 statistical tests, the variance of the link detection time using this invention is also smaller than that using the traditional periodic detection method. This indicates that this invention not only effectively improves the speed of directional link detection but also can quickly track adjacent topology changes in highly dynamic scenarios, improving the adaptability of the MAC protocol in highly dynamic scenarios.

[0118] Simulation 2: In the above scenario, a random waypoint movement model is set up for all nodes. The method of this invention and the traditional periodic link-aware maintenance method are used respectively to simulate the packet loss rate of service transmission in the network at different movement speeds. The results are as follows: Figure 5 .

[0119] from Figure 5 It can be seen that at a moving speed of 150 m / s, the packet loss rate using the periodic link-aware maintenance method is 11.6%, while the packet loss rate using the present invention is 2.7%. This is because node movement can lead to link disconnection or deterioration of link quality. The MAC protocol using the periodic link-aware maintenance method cannot detect the link status in a timely manner, and continuous data transmission will result in the loss of a large number of data packets. However, the present invention, through a cross-timeslot link packet reception feedback mechanism, can effectively detect poor link quality caused by interference between directional multiplexed link groups and external interference, and adjust the failed time slots in a timely manner. Therefore, the directional link-aware maintenance technology of the present invention can reduce the packet loss rate to 1 / 5 of the traditional periodic sensing and maintenance method, indicating that the present invention can effectively enhance the data transmission reliability of the MAC protocol in high dynamic scenarios and reduce packet loss.

[0120] In summary, this invention is a MAC layer link awareness and maintenance method that can quickly perceive the status of neighboring links, track adjacent topology changes, and maintain the reliability of directional link transmission in highly dynamic self-organizing network scenarios.

[0121] It should be noted that the step numbers in the specification and claims of this invention are only for the purpose of clearly describing the embodiments of this invention and facilitating understanding, and their order is not limited.

Claims

1. A MAC layer directional link-aware maintenance method for highly dynamic self-organizing networks, characterized in that, include: Link-aware maintenance of all neighbor-occupied time slot sub-links and link-aware maintenance of all neighbor links; The awareness and maintenance of all neighbor-occupied time slot sublinks is based on a cross-time slot packet reception feedback mechanism, including: 2a) The node records the link transmission status to each neighbor node within one frame and adds it to the link transmission record table for that neighbor; 2b) When a node arrives at a transmission time slot, it first sends a maintenance packet to provide feedback on the historical packet reception status of the receiving node in this time slot, and then sends the service data packet; 2c) When a node arrives at a receive time slot, it receives a maintenance packet containing neighbor packet reception feedback information, and based on this feedback information, it perceives the link quality of the time slot that the node is transmitting to that neighbor, including: Confirm the feedback information for this node based on the maintenance package; By comparing the packet transmission and reception records of the link, the transmission quality perception of the time slot sub-link is obtained; Update the LastRcvFeedback field of the most recently received feedback slot for this node to the current slot in the local link transmission record table; 2d) For all time slot sublinks that are perceived to have poor quality, the node adjusts the time slot allocation in the nearest scheduling time slot to complete the maintenance of the time slot sublinks of its neighbors; The link-aware maintenance of all neighboring links is based on link failure time prediction and includes: 3a) Nodes periodically exchange their own position and velocity information during fixed duty time slots to obtain an initial one-hop neighbor table and determine the beam direction for directional link transmission; 3b) When a node receives the location and speed information of its neighbor, it adjusts the beam pointing according to the latest neighbor's location and predicts the link failure time for that neighbor. and failure type; 3c) Nodes during the predicted link failure time When the time slot resource occupancy status is updated, the link maintenance time slot for that neighbor is adaptively adjusted. ; 3d) Nodes in link maintenance time slots It sends its own location and speed information for link maintenance until it reaches its destination. When a neighbor link fails, depending on the failure type, cancel the directional link time slot occupation or delete the neighbor, thus completing the maintenance of the entire lifecycle of the neighbor link.

2. The method according to claim 1, characterized in that, Step 2a) The node records the link transmission status to each neighbor node within one frame and adds it to the link transmission record table for that neighbor. This is implemented as follows: Each node records the packet transmission and reception details of each neighbor node's transmission time slot in the link transmission record table for that neighbor: If there is no corresponding record in the table, then add this information to the link transmission record table of that neighbor. If a record already exists in the table, the current record will directly overwrite the transmission record of the previous frame in this time slot, meaning that the link transmission record is only retained for one frame. The link transmission record table is indexed by the neighbor node ID and contains records of all transmitted and received packets in all transmission slots occupied by that neighbor, as well as the MaxSlotConfirmed field for confirmed feedback slots and the LastRcvFeedback field for the most recently received feedback slot.

3. The method according to claim 1, characterized in that, The maintenance packet mentioned in step 2b) includes: the LastRcvFeedback field in the local link transmission record table and all records of packet reception to the neighbor. The record is the packet reception status of all time slot sub-links that were not confirmed by the neighbor in the previous frame time, that is, the packet reception status of the local node to the neighbor's time slot sub-links from the maxSlotConfirmed time to the current time.

4. The method according to claim 1, characterized in that, Step 2c) involves confirming the feedback information of this node based on the maintenance package, which is implemented as follows: The node obtains the value R of the LastRcvFeedback field from the neighbor based on the received neighbor maintenance packet. z Then it is assumed that the neighbor has confirmed R. z Previously, this node provided feedback on the neighbor's packet receiving status; Update the MaxSlotConfirmed field value in the local link transmission record table to R. z And delete in R z All packet reception records for that neighbor in the time slot prior to this time.

5. The method according to claim 1, characterized in that, Step 2c) Obtain the transmission quality awareness of the time slot sub-link by comparing the link's transmitted and received packet records. This is implemented as follows: 2c1) The node uses its local timeslot table to find the set of all the time-slot sub-links that sent data to the neighbor since the last time slot LastRcvFeedback was received, and then uses the link transmission record table for the neighbor to find the packet transmission records of these time-slot sub-links. 2c2) Based on the received maintenance packet, obtain the neighbor's packet reception status for the above-mentioned time slot sub-link set, and compare the packet sending records of the time slot sub-links found in 2c1) with the packet receiving records returned by the neighbor: If a packet sending record exists in a certain time slot but no packet receiving record exists in the packet receiving feedback of the neighboring node, then the sub-link of that time slot is considered to have failed, and the time slot is recorded. Otherwise, proceed to step 2c3); 2c3) Using packet loss rate as the standard for measuring the quality of time slot sub-links, calculate the packet loss rate LR of each time slot sub-link and compare it with the set packet loss rate threshold LR. thres Compare and determine the link transmission quality: If LR > LR thres If the time slot is not in good quality or has failed, then the time slot is recorded. Otherwise, the transmission of the gap sub-link is considered reliable at this time, and no adjustment is made.

6. The method according to claim 1, characterized in that, In step 3b), the node predicts the link failure time of its neighbors. And failure types, the implementation of which includes the following: 3b1) Solve for the link failure time of the neighbor using the following formula. : ， in, and Indicates the position and velocity of the source node. and These represent the position and velocity of the destination node, respectively. and These represent the maximum coverage distance and beam angle of the directional antenna, respectively. 3b2) Solve for the link failure time based on the above. The constraints of the formula determine the type of link failure: If the predicted link failure time Subject to the maximum transmission distance in the first clause of the formula If there is a constraint, the neighbor link failure type is considered to be the neighbor moving out of the communication range of this node; If the predicted link failure time Subject to the second rule of the formula: directional antenna beam angle If constrained, the neighbor link failure type is considered to be beam misalignment between the neighbor and the current node.

7. The method according to claim 1, characterized in that, Step 3c) The node determines the link failure time based on the predicted link failure time. Based on real-time time slot resource occupancy, adaptively adjust the timing of link maintenance for neighbors. Its implementation includes the following: 3c1) Querying nodes from the current time forward Time slot occupancy table within a given time period: If in If a transmission slot to a neighbor cannot be found within the specified time, the node will be unable to proactively maintain its position and velocity information with its neighbor before the expected link failure time arrives, and will proceed to step 3d). Otherwise, find the first transmission time slot for that neighbor and record it as the fastest adjustment time for the link to that neighbor under the current time slot occupancy. And find the closest time to the predicted link failure time. The transmission time slot is recorded as the last adjustment time for that neighbor link. ; 3c2) Determine the link maintenance time slot for the neighbor based on the link failure type. : If the link failure is predicted to be caused by a neighbor moving out of the communication range, then the link maintenance time slot... Link maintenance is performed in the last transmission slot before the link fails, so that it can be quickly detected once a neighbor fails. If the link failure is predicted to be caused by beam misalignment between the predictor and neighbor, then the link maintenance time slot... In the next transmission slot for that neighbor, link maintenance is performed to enable beam adjustment as soon as possible and maintain link stability.

8. The method according to claim 1, characterized in that: In step 3d), the node obtains the link maintenance opportunity. It then sends its own location and speed information for link maintenance, based on the predicted link failure time of its neighbors. Before arrival, check if the current transmission time slot is a link maintenance time slot. : If it is a link maintenance time slot Then, the position and velocity information of this node will be added to the maintenance packet sent in this time slot. , This neighbor link is maintained. Otherwise, do not add the node's location and speed information to the maintenance package, and maintain the initial periodic link maintenance; In step 3d), the node cancels the directional link time slot occupation or deletes the neighbor based on the failure type, which is done when the predicted link failure time for that neighbor is reached. At that time, based on the link failure type, time slots are occupied or neighbors are deleted: If a neighbor moves out of the communication range, all directional time slot transmissions to that node will be stopped. If no packets are received from that node in a certain receiving time slot, the neighbor deletion process will be executed immediately, that is, the neighbor will be deleted from the one-hop neighbor table in order to track the adjacency topology changes in a timely manner. If the beam is out of alignment with the neighboring beam, all directional time slots are cancelled, beam discovery is performed again in the scheduling time slot, and the directional link is re-established.

9. A MAC layer directional link-aware maintenance system for highly dynamic ad hoc networks, comprising: The time-slot sub-link quality feedback module is used to record the link transmission status to neighboring nodes within one frame and to provide feedback on historical packet reception information when sending maintenance packets. The time slot sub-link quality awareness module is used to receive maintenance packets containing neighbor packet reception feedback information, and to perceive the link quality of the time slot sent by this node to that neighbor based on the packet reception feedback information; The time slot sublink maintenance module is used to adjust the time slot allocation for all time slot sublinks that are perceived to have poor quality in the most recent scheduling time slot, and to complete the maintenance of the time slot sublinks of the neighbors. The neighbor link failure time prediction module is used to predict the link failure time for that neighbor after receiving the neighbor's location and speed information. and failure type; The neighbor link maintenance module is used to monitor predicted link failure times. After the update, the link maintenance slots for neighbors are adaptively adjusted. and in the link maintenance time slot It sends its own location and speed information for link maintenance; The neighbor link failure handling module is used to cancel the directional link time slot occupation or delete the neighbor when a neighbor link fails, based on the failure type, thus completing the maintenance of the neighbor link throughout its entire lifecycle.

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