MAC (Media Access Control) layer directional link sensing maintenance method and system for high-dynamic ad hoc network

Abstract

The invention discloses an MAC (Media Access Control) layer directional link sensing maintenance method and system for a high-dynamic ad hoc network, and mainly solves the problems of low directional link sensing speed and high data transmission packet loss rate in a high-dynamic scene in the prior art. According to the implementation scheme, the method comprises two parts of link sensing maintenance of neighbor occupied time slot sub-links and link sensing maintenance of neighbor links, the sensing maintenance of all the neighbor occupied time slot sub-links is carried out based on a cross-time slot packet receiving feedback mechanism, namely, nodes record the transmission conditions of the time slot sub-links, and the nodes record the transmission conditions of the time slot sub-links. Fast packet receiving condition feedback is carried out in a data time slot, so that the neighbor node obtains cross-time-slot link quality perception; the link perception maintenance of all neighbor links is carried out based on link failure time prediction. According to the method, the directional link sensing speed can be increased, the adjacent topology change can be quickly tracked in the high-dynamic scene, the data transmission reliability of the MAC protocol in the high-dynamic ad hoc network scene is improved, and the method can be used for the mobile ad hoc network of the directional antenna.

Description

Technical Field

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

[0002] Faced with flying ad hoc networking scenarios with high-dynamic and large-capacity business transmission requirements, directional antennas are widely used in flying ad hoc networks because of their long transmission distance, strong anti-interference ability, and ability to better utilize space resources to improve network capacity compared to traditional omnidirectional antennas.

[0003] However, due to the narrow beam angle of directional antennas and the strict beam alignment conditions, the high-speed relative movement between nodes can easily lead to misalignment of the directional communication beam with neighboring nodes, interruption of communication between nodes, and interference with the normal communication of other directional links, resulting in an increase in the network packet loss rate. In addition, the rapid movement of nodes means that the node adjacency topology is constantly changing, and frequent failures of directional links caused by the removal of neighboring nodes will also cause a large number of data packets to be lost over a period of time. Therefore, how to face the various causes of poor quality and disconnection of directional links, quickly perceive and identify changes in the state of directional links, and perform maintenance accordingly is particularly important for the directional MAC protocol to track changes in the adjacency topology in highly dynamic scenarios, maintain the transmission quality of directional links, and achieve reliable service transmission.

[0004] The paper (FM-MAC: A Multi-Channel MAC Protocol for FANETs with Directional Antenna) proposes a resource reservation scheme based on mobility prediction to solve the link interruption problem caused by the high mobility of UAVs. This scheme avoids link interruption by predicting the mobility of UAVs, that is, for the data packet nodes that need to be transmitted on the service channel SCH, the transmission time is estimated, and a judgment formula that takes into account the position and speed of the source node and the target node, as well as the maximum coverage distance and angle of the directional antenna is proposed to predict whether the link will exceed the communication range. This scheme only considers whether the current transmission object will move out of the beam communication range in the next transmission time, which is a directional link failure situation. It does not fully consider the directional link failure situation, but avoids interference by increasing physical resources, thereby 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 conflict-free location information broadcasts, and predicts the movement of neighboring nodes to perform directional link scheduling. To ensure reliable transmission of the link, the location information is sent in a directional manner before transmitting the data packet so that the receiving node can perform beam alignment, and the link transmission is guaranteed to be reliable through the interaction of RTS, CTS and WTS information. Although this method can ensure the reliable transmission of directional links, it introduces a lot of overhead in the process of establishing the link. Its cautious link conflict avoidance method will lead to low link utilization, so it is not suitable for long-distance transmission scenarios using directional antennas, and it is easy to cause a decrease in network throughput.

[0006] In his graduation thesis "Research on Time Division Multiple Access Protocol in Pure Directional Self-Organizing Networks", Wang Jinjie proposed a "link distance" calculation formula to quantify the interference between links, where the "link distance" is defined by the distance between links and the beam difference in the same time slot. The method periodically collects link status information, calculates the "link distance" to predict the links that may be interfered and makes corresponding adjustments. In addition, in order to speed up maintenance, the article also proposes a strategy to assist in beam switching in the service time slot. In order to obtain link transmission quality information, this method sends empty packets even when there is no business. The link perception method that characterizes the link quality by sending empty packets of fixed length and statistical packet loss rate will cause additional interference to other directional links transmitting at the same time, resulting in a decrease in link transmission quality. At the same time, fixed-period link failure detection cannot quickly track changes in adjacent topology, and there is still the problem of limited adaptability of the MAC protocol to high-dynamic scenarios. Summary of the invention

[0007] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and to propose an efficient MAC layer directional link perception and maintenance method for highly dynamic self-organizing networks, so as to improve the directional perception speed of adjacency relationships and increase the reliability of directional data transmission in self-organizing networks under highly dynamic conditions.

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

[0009] 1. An efficient directional link awareness maintenance method for MAC layer in highly dynamic ad hoc networks, including link awareness maintenance for all neighbor occupied time slot sub-links and link awareness maintenance for all neighbor links;

[0010] The perception and maintenance of all neighbor-occupied time slot sub-links is performed based on a cross-time slot packet receiving feedback mechanism;

[0011] The link-aware maintenance of all neighbor links is performed based on the prediction of link failure time.

[0012] Preferably, the performing perception maintenance on the neighbor occupied time slot sub-link based on the cross-time slot packet receiving feedback mechanism includes:

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

[0014] 2b) When a node reaches a sending time slot, it first sends a maintenance packet to the receiving node of this time slot to provide feedback on the historical packet receiving situation, and then sends the service data packet;

[0015] 2c) When the node reaches the receiving time slot, it receives a maintenance packet containing the neighbor's packet receiving feedback information, and perceives the link quality of the node's sending time slot to the neighbor based on the packet receiving feedback information, including:

[0016] Confirm the feedback information of this node according to the maintenance package;

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

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

[0019] 2d) The node waits for the nearest scheduled time slot to adjust the time slot allocation for all time slot sub-links that it perceives to have poor quality, and completes the time slot sub-link maintenance for its neighbors.

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

[0021] 3a) The node periodically exchanges its own position and speed information in the fixed service time slot to obtain the initial one-hop neighbor table and determine the beam pointing for directional link transmission;

[0022] 3b) When a node receives the position and velocity information of a neighbor, it adjusts the beam pointing according to the latest neighbor position and predicts the link failure time Δt and failure type for the neighbor;

[0023] 3c) 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 the neighbor p ;

[0024] 3d) The node is in the link maintenance time slot T p The link maintenance is performed by sending its own position and speed information until the neighbor link fails at Δt. The directional link time slot occupancy is canceled or the neighbor is deleted according to the failure type, thus completing the maintenance of the entire life cycle of the neighbor link.

[0025] 2. MAC layer directional link perception and 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 the neighboring node within one frame time and provide historical packet reception information feedback when sending maintenance packets;

[0027] The time slot sub-link quality perception module is used to receive the maintenance packet containing the neighbor's packet reception feedback information, and perceive the link quality of the time slot sent by the node to the neighbor according to the packet reception feedback information;

[0028] The time slot sub-link maintenance module is used to adjust the time slot allocation of all time slot sub-links with poor quality perceived in the nearest scheduling time slot, and complete the time slot sub-link maintenance of the neighbors;

[0029] A neighbor link failure time prediction module is used to predict the link failure time Δt and failure type of the neighbor after receiving the neighbor position speed information;

[0030] Neighbor link maintenance module, used to adaptively adjust the link maintenance time slot T for neighbors after the predicted link failure time Δt is updated p , and in the link maintenance time slot T p Send its own position and speed information for link maintenance;

[0031] The neighbor link failure processing module is used to cancel the directional link time slot occupation or delete the neighbor according to the failure type when the neighbor link fails, so as to complete the maintenance of the entire life cycle of the neighbor link.

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

[0033] Firstly, the present invention can effectively perceive the poor link quality caused by interference between directional multiplexing link groups and unpredictable external interference through a fast cross-time slot link packet reception feedback mechanism, and improve the perception speed of the time slot sub-link quality of actual data transmission, thereby enhancing the reliability of directional data transmission in self-organizing networks under high dynamic conditions.

[0034] Secondly, the present invention improves the directional perception speed of adjacency relationships by predicting link failure time, and adaptively adjusts the timing of neighbor link failure maintenance based on the directional link failure type and real-time time slot resource occupancy information to reduce the directional link perception maintenance overhead.

[0035] Third, the present invention combines active link failure prediction and passive link quality feedback to comprehensively identify and respond to various link failure and interference situations, providing a basis for rapid transmission link adjustment and adjacent topology maintenance, enabling nodes to quickly track adjacent topology changes, while improving data transmission reliability, that is, reducing transmission packet loss rate, and increasing the adaptability of the MAC protocol in highly dynamic self-organizing network scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a general flow chart for realizing the method of the present invention;

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

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

[0039] Figure 4 This is a comparison diagram of link failure perception time in the same scenario simulated by the present invention and the traditional periodic perception method;

[0040] Figure 5 This is a comparison chart of link transmission packet loss rates at different mobile speeds simulated using the present invention and the traditional periodic sensing method. DETAILED DESCRIPTION

[0041] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only embodiments of a part of the present invention, not all embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without creative work should all belong to 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. Each node in the self-organizing network has equal status, has exactly the same physical capabilities and executes the same protocol suite. At the MAC layer, each node independently recognizes neighbor relationships and negotiates channel resource allocation based on information interaction with neighbors.

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

[0044] In the data time slot, the sending node occupying this time slot uses a directional antenna to send, and its neighboring node uses a directional antenna to receive it. The sending node first sends a short maintenance packet for link perception, and then sends a data packet. The link resources occupied by sending the maintenance packet are the overhead of this solution.

[0045] Reference Figure 1 The MAC layer directional link perception maintenance method for highly dynamic ad hoc networks proposed in this example is optimized based on the TDMA protocol, including link perception maintenance of all neighbor-occupied time slot sub-links and link perception maintenance of all neighbor links. The implementation steps include the following figure:

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

[0047] The node is powered on and, by interacting with neighbor information, adds the nodes within the communication range of the node to the initial one-hop neighbor table, and considers the node as a neighbor of the node.

[0048] Step 2: Nodes allocate time slots.

[0049] The node negotiates and allocates time slot resources for all neighbor nodes according to the interference conditions of the directional links in the scheduling time slot: one or more conflict-free time slots are allocated to each link between neighbor nodes for directional data transmission, and an initial time slot occupancy table is generated.

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

[0051] In this example, the link L between node i and neighbor j is ij Take this as an example to describe the steps:

[0052] 1. The perception and maintenance of the neighbor-occupied time slot sub-link based on the cross-time slot packet receiving feedback mechanism includes:

[0053] Step 3.1a) The node records the link transmission status to the neighbor node within one frame time and adds it to the link transmission record table of the neighbor:

[0054] The link transmission record table is indexed by the neighbor node ID, and contains the packet sending record SendSituation[] and the packet receiving record RcvSituation[] for all transmission time slots occupied by the neighbor, as well as the feedback confirmed time slot MaxSlotConfirmed field and the most recently received feedback time slot LastRcvFeedback field. 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 , the sending node i records the packet sending situation in the packet sending record field SendSituation(j, T k ) in the receiving node j; the receiving node j records the packet receiving situation in the packet receiving record field RcvSituation(i,T k )middle;

[0058] For the two types of records, if the record already exists in the table, the current record directly overwrites the previous frame time slot T k -1 The transmission record of the link is only retained for one frame time.

[0059] Step 3.2a) When node i reaches the sending time slot, it first sends a maintenance packet to provide historical packet receiving status feedback to the receiving node j of 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 receiving situation records RcvSituation(j,S)[] for the neighbor, as shown in Table 2.

[0061] Table 2 Link maintenance package format

[0062]

[0063] In the table, RcvSituation(j,S)[] is the packet receiving status of all time slot sublinks that have not been confirmed by neighbor j in the previous frame time, and S is the total number of packets allocated to the link from the maxSlotConfirmed time to the current time. The receiving time slot set of RcvSituation(j,S)[] is sent in the maintenance packet to ensure the link The packet reception status of all time slots is fed back to the link sending node j.

[0064] Step 3.3a) When the node reaches the receiving time slot, it receives a maintenance packet containing the neighbor's packet receiving feedback information, and perceives the link quality of the node's sending time slot to the neighbor based on the packet receiving feedback information, which includes:

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

[0066] Node j obtains the value R of the LastRcvFeedback field in the neighbor's feedback based on the neighbor maintenance packet received. z , then the neighbor is considered to have confirmed R z The node previously 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 the z All the packet receiving records of the neighbor before the time are recorded to ensure that the packet receiving information is not fed back repeatedly.

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

[0069] Node j searches the local time slot table for all nodes assigned to the link since the last feedback time slot LastRcvFeedback was received. The sending time slot set S', and then according to the link transmission record table of neighbor i, find the packet sending records SendSituation(i,S')[] of these time slot sub-links;

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

[0071] If there is a packet sending record in a time slot but there is no packet receiving record in the packet receiving feedback of the neighboring node, that is, the time slot k∈(S′-S), then the sublink of the time slot is considered Expired, record the expiration time slot;

[0072] Otherwise, it is considered that all nodes j send time slot sublinks to i during this period The packet loss rate is used as the standard to measure the quality of the time slot sub-link. The packet loss rate LR of each time slot in the set S is calculated and compared with the set packet loss rate threshold LR. thres Compare and judge the transmission quality of the time slot sub-link:

[0073] If LR>LR thres , then the sub-link quality of this time slot is considered to be poor or failed, and the time slot is recorded;

[0074] Otherwise, it is considered that the sub-link transmission is reliable at this time slot, and no adjustment is made;

[0075] 3.3a-3) The LastRcvFeedback field of the node's most recently received feedback timeslot in the local link transmission record table is updated to the current timeslot, indicating that the neighbor feedback was most recently received in the LastRcvFeedback timeslot.

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

[0077] Step 3.4a) For all time slot sub-links that are perceived to have poor quality, the node adopts a cautious link maintenance strategy, regardless of whether it is caused by inter-link interference of simultaneous slot transmissions due to mobility or other external interference. It first cancels the failed time slot sub-link transmission, and then adjusts the time slot sub-link allocation in the nearest scheduled time slot to complete the time slot sub-link quality maintenance for the neighbors.

[0078] The nodes in the network perform the L operation on all the time slot sub-links occupied by their neighbors according to the above steps 3.1a) to 3.4a) with the link L between node i and node j. ij The same operation completes the perception and maintenance of each time slot sub-link to increase the reliability of directional data transmission in the self-organizing network under high dynamic conditions.

[0079] 2. The perceptual maintenance of neighbor links based on link failure time prediction includes:

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

[0081] Nodes periodically communicate their location and speed information with neighbors during fixed service time slots. To determine the beam pointing θ to the neighbor, and perform directional data transmission according to the beam pointing θ in the data time slot occupied by the neighbor.

[0082] Step 3.2b) When the node receives the neighbor position and velocity information, it adjusts the beam pointing according to the latest neighbor position and predicts the link failure time Δt and failure type for the neighbor.

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

[0084]

[0085] Among them, P s and V s represents the position and velocity of the source node, P d and V d The destination nodes are represented by

[0086] Position and speed, R max and θ represent the maximum coverage distance and beam angle of the directional antenna, respectively. This formula indicates that it is expected that the neighbor link will be disconnected after Δt in the future;

[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 subject to the maximum transmission distance R in the first clause of the formula max If there is no constraint, 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 failure of the neighbor link;

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

[0091] 3.3b-1) The node queries the slot occupancy table for the period Δt from the current moment forward:

[0092] If the transmission time slot to the neighbor cannot be found within the Δt time, the node cannot actively maintain the location and speed information of the node to the neighbor before the expected link failure time arrives, and jumps to step 3.4b);

[0093] Otherwise, find the first transmission time slot to the neighbor, and record it as the fastest adjustment time t for the neighbor link according to the current time slot occupancy l , and find the closest link failure time t′ loss =t now +Δt transmission time slot, recorded as the last adjustment time t for the neighbor link r ;

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

[0095] If the link fails due to the prediction that the neighbor will move out of the communication range, 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 the failure of a neighbor can be quickly detected;

[0096] If the link failure is caused by beam misalignment between the predicted neighbor and the neighbor, the link maintenance time slot T p =t l , perform link maintenance on the neighbor in the next transmission time slot, so that the neighbor can adjust the beam as quickly as possible and maintain link stability;

[0097] Step 3.4b) The node is in the link maintenance time slot T p Send its own position and speed information to perform link maintenance until the neighbor link fails at Δt. According to the failure type, cancel the directional link time slot occupation or delete the neighbor, completing the maintenance of the entire life cycle of the neighbor link:

[0098] 3.4b-1) Before the predicted link failure time Δt of the neighbor arrives, the node needs to actively maintain the link in the link maintenance time slot T obtained in 3.3b) p Send its own position and speed information to perform link maintenance. To maintain the neighbor link, due to the continuous update of link failure time prediction and time slot occupancy, the node checks whether the current time slot is a link maintenance time slot in each sending time slot to the neighbor. p :

[0099] If the link maintenance time slot T p , then the location and speed information of this node is added to the maintenance packet sent in this time slot Perform maintenance on this neighbor link;

[0100] Otherwise, the location and speed information of the node is not added to the maintenance package, and the initial periodic link maintenance is maintained.

[0101] 3.4b-2) When the predicted link failure time Δt for the neighbor is reached, the time slot is occupied or the neighbor is deleted according to the link failure type:

[0102] If the neighbor moves out of the communication range, all directional time slots to the node are stopped, and when no packet is received from the node in a certain receiving time slot, the neighbor deletion process is immediately executed, that is, the neighbor is deleted from the one-hop neighbor table to track the neighbor topology changes in a timely manner;

[0103] If the beam is misaligned 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 scheduled time slot to re-establish the directional link.

[0104] Each node in the network executes the L between node i and node j according to the above steps 3.1b) to 3.4b) for all its neighbor links. ij The same operation is performed to complete the perception and maintenance of each neighbor link, so as to improve the directional perception speed of the node's adjacency relationship in a highly dynamic situation.

[0105] Reference Figure 3 This example provides a MAC layer directional link perception and maintenance system for highly dynamic self-organizing networks, including: a time slot sub-link quality feedback module 1, a time slot sub-link quality perception module 2, a time slot sub-link maintenance module 3, a neighbor link failure time prediction module 4, a neighbor link maintenance module 5 and a neighbor link failure processing module 6. Among them, the time slot sub-link quality feedback module 1, the time slot sub-link quality perception module 2, and the time slot sub-link maintenance module 3 are used to complete the node's perception and maintenance of the occupied time slot sub-link; the neighbor link failure time prediction module 4, the neighbor link maintenance module 5 and the neighbor link failure processing module 6 are used to complete the node's link perception and maintenance of the neighbor link,

[0106] The working principle of the time slot sub-link quality feedback module 1, the time slot sub-link quality perception module 2 and the time slot sub-link maintenance module 3 to complete the perception and maintenance of the occupied time slot sub-link by the node is as follows:

[0107] The time slot sub-link quality feedback module 1 records the link transmission status to the neighbor node within one frame time, and feeds back the historical packet receiving information to the time slot sub-link quality perception module 2 of the neighbor node by sending a maintenance packet. The time slot sub-link quality perception module 2 receives the maintenance packet containing the neighbor packet receiving feedback information, and perceives the link quality of the time slot sent by this node to the neighbor based on the packet receiving feedback information: if there is a time slot sub-link with poor quality, the time slot number is transmitted to the time slot sub-link maintenance module 3 to adjust the time slot allocation of the time slot sub-link with poor quality, and complete the time slot sub-link maintenance for the neighbor; otherwise, the time slot sub-link quality feedback module and the time slot sub-link 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 processing module 6 complete the link perception maintenance of the node to the neighbor link, and its 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 of the neighbor; 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 the link maintenance time slot T pThe path failure time prediction module 4 sends its own position speed information to the neighbor node; the neighbor link failure time prediction module 4 and the neighbor link maintenance module 5 are executed alternately according to the time slot occupancy table, and the link failure time Δt is transmitted to the neighbor link failure processing module 6, so that when the neighbor link fails, the directional link time slot occupancy is canceled or the neighbor is deleted according to the failure type, thereby completing the maintenance of the entire life cycle of the neighbor link.

[0110] The following is a further explanation of the effect of this example combined with the simulation experiment results:

[0111] 1. Simulation conditions

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

[0113] The software platform of the simulation experiment is: windows11 operating system, Exata7.2.0.

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

[0115] 2. Simulation content and result analysis:

[0116] Simulation 1: In the above scenario, a node movement path that experiences multiple link disconnections is set. The method of the present invention and the traditional periodic link perception method are used to simulate the moment when the node and its surrounding nodes perceive the link disconnection, and the difference between the moment and the actual physical link disconnection moment is calculated. The results are as follows: Figure 4 shown.

[0117] from Figure 4It can be seen that in 14 link failures, the link failure perception time of the link perception technology proposed by the present invention has been steadily reduced compared to the traditional periodic perception method, and the average link failure perception time has dropped to 1 / 4 of the traditional periodic perception method. This is because the traditional periodic perception method requires two superframe times to perceive the link failure, while the present invention adopts a cross-time slot packet feedback mechanism to reduce the perception time of the time slot sub-link state to within one frame, greatly reducing the link failure perception time. At the same time, since the present aspect adopts neighbor link perception based on link failure time prediction, it can adapt to a variety of link failure scenarios. Therefore, in the 14 statistics, the variance of the link perception time using the present invention is also smaller than that using the traditional periodic perception method. It shows that the present invention can not only effectively improve the directional link perception speed, but also can quickly track adjacent topology changes in high dynamic scenarios, and improve the adaptability of the MAC protocol in high dynamic scenarios.

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

[0119] from Figure 5 It can be seen that when the moving speed is 150m / s, the transmission packet loss rate using the periodic link perception and maintenance method is 11.6%, and the transmission packet loss rate using the present invention is 2.7%. This is because node movement will cause link disconnection or link quality deterioration. The MAC protocol using the periodic link perception and maintenance method cannot perceive the link status in time, and continuous data transmission will cause a large number of data packets to be lost. The present invention can effectively perceive the poor link quality caused by interference between directional multiplexing link groups and external interference through the link packet feedback mechanism across time slots, and adjust the failed time slots in time. Therefore, the use of the directional link perception and maintenance technology of the present invention can reduce the transmission packet loss rate to 1 / 5 of the traditional periodic perception 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 transmission packet loss.

[0120] In summary, the present invention is a MAC layer link perception and maintenance method that can quickly perceive neighbor link status, track adjacent topology changes, and maintain directional link transmission reliability in a highly dynamic self-organizing network scenario.

[0121] It should be noted that the step numbers in the specification and claims of the present invention are only for a clear description of the implementation scheme of the present invention to facilitate understanding, and the order of the step numbers is not limited.

Claims

1. A MAC layer directional link perception and maintenance method for a highly dynamic ad hoc network, characterized in that: include: Link awareness maintenance of all neighbor-occupied time slot sub-links and link awareness maintenance of all neighbor links; The perception and maintenance of all neighbor-occupied time slot sub-links is performed based on a cross-time slot packet receiving feedback mechanism; The link-aware maintenance of all neighbor links is performed based on the prediction of link failure time.

2. The method according to claim 1, characterized in that The sensing and maintenance of the neighbor-occupied time slot sub-link based on the cross-time slot packet receiving feedback mechanism includes: 2a) The node records the link transmission status of each neighbor node within one frame time and adds it to the link transmission record table of the neighbor; 2b) When a node reaches a sending time slot, it first sends a maintenance packet to the receiving node of this time slot to provide feedback on the historical packet receiving situation, and then sends the service data packet; 2c) When the node reaches the receiving time slot, it receives a maintenance packet containing the neighbor's packet receiving feedback information, and perceives the link quality of the node's sending time slot to the neighbor based on the packet receiving feedback information, including: Confirm the feedback information of this node according to the maintenance package; By comparing the link packet transmission and reception records, the transmission quality perception of the time slot sub-link is obtained; Update the LastRcvFeedback field of the node's most recently received feedback time slot in the local link transmission record table to the current time slot; 2d) The node adjusts the time slot allocation for all time slot sub-links that are perceived to have poor quality in the nearest scheduled time slot to complete the time slot sub-link maintenance for its neighbors.

3. The method according to claim 1, characterized in that: The link-aware maintenance of all neighbor links based on link failure time prediction includes: 3a) The node periodically exchanges its own position and speed information in the fixed service time slot to obtain the initial one-hop neighbor table and determine the beam pointing for directional link transmission; 3b) When a node receives the neighbor's position and speed information, it adjusts the beam pointing according to the latest neighbor's position and predicts the link failure time Δt and failure type for the neighbor; 3c) 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 the neighbor p ; 3d) The node is in the link maintenance time slot T p The network sends its own position and speed information to perform link maintenance until the neighbor link fails at Δt. According to the failure type, the directional link time slot occupancy is canceled or the neighbor is deleted, thus completing the maintenance of the entire life cycle of the neighbor link.

4. The method according to claim 2, characterized in that: Step 2a) The node records the link transmission status of each neighbor node within one frame time and adds it to the link transmission record table of the neighbor. The implementation includes the following: During the transmission time slot of each neighbor node, the node records the packet sending and receiving status of the time slot in the link transmission record table of the neighbor node: If there is no corresponding record in the table, add the information to the link transmission record table of the neighbor. If there is already a record in the table, the current record will directly overwrite the transmission record of the previous frame and time slot, that is, the link transmission record will only retain one frame time; The link transmission record table uses the neighbor node ID as an index, and includes the records of receiving and sending packets of all transmission time slots occupied by the neighbor, as well as the MaxSlotConfirmed field of the feedback confirmed time slot and the LastRcvFeedback field of the most recently received feedback time slot.

5. The method according to claim 2, characterized in that: The maintenance package described in step 2b) includes: the LastRcvFeedback field in the local link transmission record table and all packet reception records for the neighbor, which record is the packet reception status of all time slot sub-links that have not been confirmed by the neighbor within the previous frame time, that is, the time slot sub-link packet reception status of this node for the neighbor from the maxSlotConfirmed moment to the current moment.

6. The method according to claim 2, characterized in that In step 2c), the feedback information of the node is confirmed according to the maintenance package, and its implementation includes the following: The node obtains the value R of the LastRcvFeedback field in the neighbor's feedback based on the neighbor maintenance packet received. z , then the neighbor is considered to have confirmed R z The node previously 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 the z All timeslot packet reception records about the neighbor before time.

7. The method according to claim 2, characterized in that: Step 2c) obtains the transmission quality perception of the time slot sub-link by comparing the link packet sending and receiving records, which is implemented as follows: 2c1) The node searches for all the sending time slot sub-link sets of the neighbor since the last feedback time slot LastRcvFeedback was received according to the local time slot table, and then searches for the packet sending records of these time slot sub-links according to the link transmission record table of the neighbor; 2c2) Obtain the neighbor's feedback on the packet receiving status of the above-mentioned time slot sub-link set according to the received maintenance packet, and compare the time slot sub-link packet sending record found in 2c1) with the packet receiving record fed back by the neighbor: If there is a packet sending record in a time slot but there is no packet receiving record in the packet receiving feedback of the neighboring node, it is considered that the sub-link of this time slot has failed and the time slot is recorded; Otherwise, execute step 2c3); 2c3) Using the packet loss rate as a measure of the quality of the time slot sub-link, the packet loss rate LR of each time slot sub-link is calculated and compared with the set packet loss rate threshold LR. thres Compare and judge the link transmission quality: If LR>LR thres , then the sub-link quality of this time slot is considered to be poor or failed, and the time slot is recorded; Otherwise, it is considered that the sub-link transmission in this slot is reliable and no adjustment is made.

8. The method according to claim 3, characterized in that In step 3b), the node predicts the link failure time Δt and failure type of its neighbor, which is implemented as follows: 3b1) Solve the neighbor's link failure time Δt using the following formula: Among them, P s and V s represents the position and velocity of the source node, P d and V d denote the location and velocity of the destination node, R max and θ represent the maximum coverage distance and beam angle of the directional antenna, respectively; 3b2) Determine the link failure type according to the constraint conditions of the above formula for solving the link failure time Δt: If the predicted link failure time Δt is subject to the maximum transmission distance R in the first clause of the formula max If there is no restriction, 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 Δt is constrained by the directional antenna beam angle θ in the second formula, the neighbor link failure type is considered to be the beam misalignment between the neighbor and the local node.

9. The method according to claim 3, characterized in that: Step 3c) The node adaptively adjusts the link maintenance timing T for the neighbor according to the predicted link failure time Δt and the real-time time slot resource occupancy. p , which is implemented as follows: 3c1) The node queries the time slot occupancy table within Δt time from the current moment: If the transmission time slot to the neighbor cannot be found within the Δt time, the node cannot actively maintain the location and speed information of the node to the neighbor before the expected link failure time arrives, and jumps to step 3d); Otherwise, find the first transmission time slot to the neighbor, and record it as the fastest adjustment time t for the neighbor link according to the current time slot occupancy l , and find the closest link failure time t′ loss =t now +Δt transmission time slot, recorded as the last adjustment time t for the neighbor link r ; 3c2) Determine the link maintenance time slot T for the neighbor based on the link failure type p : If the link fails due to the predicted neighbor moving out of the communication range, 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 the failure of a neighbor can be quickly detected; If the link failure is caused by beam misalignment between the predicted neighbor and the neighbor, the link maintenance time slot T p =t l , perform link maintenance on the neighbor in the next transmission time slot so that it can adjust the beam as quickly as possible and maintain link stability.

10. The method according to claim 3, characterized in that: In step 3d), the node obtains the link maintenance opportunity T p After that, it sends its own position and speed information for link maintenance. Before the predicted link failure time Δt of the neighbor arrives, it checks whether the current sending time slot is the link maintenance time slot T p : If the link maintenance time slot T p , then the location and speed information of this node is added to the maintenance packet sent in this time slot Perform maintenance on this neighbor link. Otherwise, the location and speed information of the node is not added to the maintenance package, and the initial periodic link maintenance is maintained. In step 3d), the node cancels the directional link time slot occupation or deletes the neighbor according to the failure type, which is to occupy the time slot or delete the neighbor according to the link failure type when the predicted link failure time Δt of the neighbor is reached: If the neighbor moves out of the communication range, stop sending all directional time slots to the node, and immediately execute the neighbor deletion process when no packet is received from the node in a certain receiving time slot, that is, delete the neighbor in the one-hop neighbor table to track the neighbor topology changes in time; If the beam with the neighbor is misaligned, all directional time slots are canceled, beam discovery is performed again in the scheduled time slot, and the directional link is re-established.

11. A MAC layer directional link perception and 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 the neighboring node within one frame time and provide historical packet reception information feedback when sending maintenance packets; The time slot sub-link quality perception module is used to receive the maintenance packet containing the neighbor's packet reception feedback information, and perceive the link quality of the time slot sent by the node to the neighbor according to the packet reception feedback information; The time slot sub-link maintenance module is used to adjust the time slot allocation of all time slot sub-links with poor quality perceived in the nearest scheduling time slot, and complete the time slot sub-link maintenance of the neighbors; A neighbor link failure time prediction module is used to predict the link failure time Δt and failure type of the neighbor after receiving the neighbor position speed information; Neighbor link maintenance module, used to adaptively adjust the link maintenance time slot T for neighbors after the predicted link failure time Δt is updated p , and in the link maintenance time slot T p Send its own position and speed information for link maintenance; The neighbor link failure processing module is used to cancel the directional link time slot occupation or delete the neighbor according to the failure type when the neighbor link fails, so as to complete the maintenance of the entire life cycle of the neighbor link.

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