CN117956591B - Dynamic network time slot allocation method based on directional antenna and network simulation system - Google Patents
Dynamic network time slot allocation method based on directional antenna and network simulation system Download PDFInfo
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Abstract
The invention relates to a dynamic network time slot allocation method based on a directional antenna and a network simulation system; the method comprises the following steps: neighbor discovery, frame reservation and data transmission are carried out between nodes in the dynamic ad hoc network based on a time division multiple access protocol of directional beams; carrying out power level negotiation and time slot reservation confirmation among nodes in a neighbor discovery period; the method comprises the steps of carrying out re-linking and time slot confirmation between nodes in a frame reservation period; data transmission between nodes is carried out in a data transmission period to negotiate power and reserve time slots; in the dynamic Ad hoc network data transmission process, the service quality of each node data transmission size, transmission time delay and service priority is guaranteed; and respectively carrying out time slot allocation according to the priority of the neighbor nodes from the packets with high priority to the packets with low priority through the established node list based on the different priority groups so as to meet the output transmission service requirements among the nodes. The invention improves the network service quality and the anti-interference capability.
Description
Technical Field
The present invention relates to the field of dynamic wireless network technologies and network simulations, and in particular, to a dynamic network time slot allocation method and a network simulation system based on a directional antenna.
Background
The mobile self-organizing network Ad Hoc network is a wireless network without centers, self-organizing and multi-hop, two nodes can communicate with each other only in the communication range, and compared with a wired fixed network, the Ad Hoc network has small channel bandwidth and low data transmission rate. The Ad Hoc network utilizing the channel multiple access control MAC protocol can improve the channel utilization rate and the network throughput, meet the index requirements of service delay, packet loss rate and the like in an unmanned aerial vehicle Ad Hoc network scene, and ensure the real-time requirements of wired or emergency service.
The network simulation technology is to utilize a simulation platform to build a network node model, a device model, a network link model and the like to simulate the flow of a real network, obtain the actual running condition of the network, the load condition of each device in the network and the like to analyze the performance of the real network. OPNET is currently mainstream network simulation software, and hierarchical simulation mode is adopted, so that from the perspective of a network level, the OPNET provides three modeling mechanisms, namely, from the bottom layer to the upper layer: process models, node models, and network models, the OPNET can describe network characteristics in detail using this hierarchical simulation approach.
In the specific application of the unmanned aerial vehicle communication network, channel resources are often obtained according to the size of traffic, nodes which are important in transmitted information, such as transmitting nodes and central nodes in the network, are not concerned, although the traffic is small, the functions of the nodes in the network are different, the data amount required to be transmitted is different, and the requirements on time delay are inconsistent.
Disclosure of Invention
In view of the above analysis, the present invention aims to disclose a dynamic network time slot allocation method and a network simulation system for a directional antenna; the method effectively solves the problems of large control overhead, route interruption and the like faced by node movement and the like in a large-scale network, and improves the service quality and the anti-interference capability of the network.
The invention discloses a dynamic network time slot allocation method based on a directional antenna, which comprises the following steps:
Step S1, neighbor discovery, frame reservation and data transmission are carried out among nodes in a dynamic ad hoc network based on a time division multiple access protocol of a directional beam;
Carrying out power level negotiation and time slot reservation confirmation among nodes in a neighbor discovery period; the method comprises the steps of carrying out re-linking and time slot confirmation between nodes in a frame reservation period; data transmission between nodes is carried out in a data transmission period to negotiate power and reserve time slots;
step S2, in the dynamic ad hoc network data transmission process, carrying out service quality assurance comprising the data transmission size, the transmission time delay and the service priority of each node;
And respectively carrying out time slot allocation according to the priority of the neighbor nodes from the packets with high priority to the packets with low priority through the established node list based on the different priority groups so as to meet the output transmission service requirements among the nodes.
Further, in step S1, it includes:
Step S101, during neighbor discovery, a pair of nodes with directional antennas forming a direct communication condition complete power level negotiation of communication and reservation confirmation of communication time slots through three-way handshake;
step S102, during the frame reservation period, linking again according to the appointed time slot and the appointed direction, and carrying out time slot confirmation;
step S103, data transmission among nodes is carried out in reserved time slots and negotiated time slots among data transmission.
Further, the three-way handshake during neighbor discovery includes:
1) A first handshake; node 1 as handshake initiator broadcasts handshake request information to potential neighbors with the maximum transmitting power of the transceiver of the node; the handshake request information comprises identifier information of the node 1;
2) A second handshake; node 2 as a handshake responder listens for broadcasted handshake request information; if no information is received, node 2 discards the handshake; if the node 1 is determined to be a potential neighbor after receiving the information and obtaining the identifier of the node 1, the node 2 broadcasts handshake response information to the node 1; the power level of the broadcasted handshake response information is determined according to the power of the handshake response information broadcasted by the node 1 received by the node 2;
The handshake response information comprises identifier information of the node 1, identifier information of the node 2, transmitting power, consent information and idle time slot information of the node;
3) A third handshake; node 1 monitors handshake response information returned by node 2; if no information is received, node 1 discards the handshake; if the information is successfully received, after the node 1 calculates the intersection time with the node 2, the handshake confirmation information is broadcasted to the node 2 for the node 2 to confirm handshake; the power level of the broadcasted handshake acknowledgement information is determined according to the transmitting power in the handshake acknowledgement information broadcasted by the node 2;
The handshake confirmation information includes identifier information of the node 1, identifier information of the node 2, transmission power, and node intersection time.
Further, in the second handshake, after the node 2 determines that the node 1 is a potential neighbor, re-evaluating the neighbor relation between the node 2 and the node 1 according to two conditions to make a frame reservation; wherein,
Case (1) node 1 and node 2 detected each other at a previous time and have agreed to reconfirm their connection and make a reservation at a future time;
Case (2) node 1 and node 2 have never previously detected each other or have previously detected each other but cannot agree on the time to re-guarantee connection and make a frame reservation.
Further, in the third handshake, the node intersection time determination procedure in case (2) includes:
1) Node 1 first calculates a selected set of rendezvous times, n_free com, where n_free com＝N_free1&N_free2; where n_free 1 is the available time slot for node 1; n_free 2 is the free time slot of node 2 obtained by the second handshake node 1;
2) Node 1 transmits a response message to node 2; the response message includes identifier information of node 1, identifier information of node 2, transmit power, and selected rendezvous time set n_free com;
3) Node 2 waits for a response message from node 1; if no response message is received, node 2 considers that node 1 does not agree to establish a connection; otherwise, if the node 2 successfully receives the response message, the node 2 knows that the node 1 confirms the frame reservation, the node 1 starts the frame reservation flow, and the valid period of the frame reservation appointed between the two nodes is reached until the two nodes detect the other side again.
Further, in step S2, a priority queue is designed for each neighbor, and a priority is set for each node to meet the requirements of data volume, time delay, service priority and the like transmitted by each node;
When the neighbor discovery stage receives a neighbor node request, extracting priority queue information and node priority information, grouping node priorities, placing nodes with the same priority in the same group, forming a node list based on different priority groups, respectively performing time slot allocation according to the groups with high priority to the groups with low priority, and entering the next time slot allocation waiting when all nodes in the final network are circulated.
Further, step S2 includes:
Step S201, a frame reservation stage receives a neighbor node broadcast request, extracts priority information of the request, and adds the priority information into a priority packet queue;
Step S202, judging the priority level, carrying out priority time slot allocation on the task with the highest priority level, and updating a time slot list;
step S203, node time slot allocation is carried out on all nodes in the priority group, and then node time slot allocation is carried out on the next priority group.
The invention also discloses a directional antenna dynamic Ad hoc network simulation system built by using the OPNET network simulation platform; adopting a modeling mechanism of OPNET to perform network simulation of the dynamic network time slot allocation method based on the directional antenna; and carrying out simulation verification on the network access time, network delay and network quality of the protocol through the network topology design, node design and process design of the channel access protocol.
Further, the establishment process of the directional antenna dynamic Ad hoc network simulation system comprises a network layer modeling process, a node layer modeling process and a process layer modeling process.
Further, in the modeling process, the method comprises the following steps:
1) Setting a simulation network area, arranging mobile nodes, priority levels of the nodes, and moving tracks and maximum moving speeds of the nodes in the network layer modeling process;
2) In the modeling process of the node layer, a protocol stack of the node model comprises a network layer, a data link layer and an application layer; wherein,
The network layer adopts an AODV protocol;
the data link layer adopts a time division multiple access protocol based on directional beams of the scheme;
The application layer uses an OPNET original simple_source module to simulate the ad hoc network to carry out packet sending at a fixed packet sending rate and time interval;
In the process layer modeling process, a finite state machine of a time division multiple access protocol based on directional beams is designed, wherein the states of the finite state machine comprise an initialization state, an idle state, a neighbor discovery state and a message broadcasting state; wherein,
The initialization state is used for initializing various state variables and global variables and reading simulation attributes and parameters;
an idle state for staying in this state when the simulation process does not need to do any action;
the message broadcasting state is used for broadcasting self state information to surrounding nodes after the nodes access the network;
And the neighbor discovery state discovery is implemented by broadcasting information of the neighbor nodes and three-way handshake flow.
The invention can realize one of the following beneficial effects:
The invention discloses a dynamic network time slot allocation method and a network simulation system for a directional antenna, which are used for designing a dynamic Ad Hoc network dynamic time slot allocation method based on the directional antenna, dividing a channel into a plurality of time slots according to the direction of a time axis, and allocating nodes in the network to one or more time slots for message transmission; designing a time slot allocation scheme based on priority, and using network multi-service transmission requirements by adding node priority information; based on OPNET network simulation software, dynamic time slot allocation protocol modeling of a directional antenna dynamic Ad hoc network based on OPNET is designed, a network topology structure is built for network simulation, and network load and time delay are required in an unmanned aerial vehicle Ad hoc network scene.
Drawings
The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, like reference numerals being used to refer to like parts throughout the several views.
Fig. 1 is a flow chart of a dynamic network time slot allocation method based on directional antennas in an embodiment of the present invention;
fig. 2 is a priority assignment flow chart in an embodiment of the invention.
Detailed Description
Preferred embodiments of the present application are described in detail below with reference to the attached drawing figures, which form a part of the present application and are used in conjunction with embodiments of the present application to illustrate the principles of the present application.
One embodiment of the present invention discloses a dynamic network time slot allocation method based on directional antennas, as shown in fig. 1, comprising:
Step S1, neighbor discovery, frame reservation and data transmission are carried out among nodes in a dynamic ad hoc network based on a time division multiple access protocol of a directional beam;
Carrying out power level negotiation and time slot reservation confirmation among nodes in a neighbor discovery period; the method comprises the steps of carrying out re-linking and time slot confirmation between nodes in a frame reservation period; data transmission between nodes is carried out in a data transmission period to negotiate power and reserve time slots;
step S2, in the dynamic ad hoc network data transmission process, carrying out service quality assurance comprising the data transmission size, the transmission time delay and the service priority of each node;
And respectively carrying out time slot allocation according to the priority of the neighbor nodes from the packets with high priority to the packets with low priority through the established node list based on the different priority groups so as to meet the output transmission service requirements among the nodes.
Specifically, the node in this embodiment is a ground node or an airborne node equipped with a directional beam antenna to obtain a high channel gain; in an ad hoc network, communications occur in three dimensions, between ground nodes and airborne nodes, between ground nodes at different altitudes, and between airborne nodes flying at different altitudes.
Based on the time division multiple access protocol of directional beams, a channel is divided into a plurality of time slots according to the time axis direction, and in a TDMA mode, nodes in a network can be allocated to one or more time slots to transmit information so as to meet bandwidth information required by the nodes.
As shown in fig. 2, time is divided into several frames, a first subframe is used for neighbor discovery, a second subframe is used for two nodes to reconfirm connection discovered in the neighbor discovery process, and information storage is performed, and a third subframe is data transmission, and each frame is divided into several slots.
Each subframe is divided into a plurality of periods. Each time slot during neighbor discovery/reservation consists of a plurality of small time slots. In both the neighbor discovery period and the reservation period, a three-way handshake is required to perform power level negotiation and reservation confirmation. The three information contents used in neighbor discovery are different from those used in reservation. Let n mini-slots be the first subframe and r mini-slots be the second subframe. The values of n and r may be different and may be configured at the time of network configuration. The third subframe has M slots.
Specifically, in step S1, the method includes:
Step S101, during neighbor discovery, a pair of nodes with directional antennas forming a direct communication condition complete power level negotiation of communication and reservation confirmation of communication time slots through three-way handshake;
step S102, during the frame reservation period, linking again according to the appointed time slot and the appointed direction, and carrying out time slot confirmation;
step S103, data transmission among nodes is carried out in reserved time slots and negotiated time slots among data transmission.
More specifically, the method comprises the steps of,
A pair of nodes with directional antennas communicate directly if the line connecting them is contained in both the current transmit beam of one node and the current receive beam of the other node. Two nodes must direct beams to each other at the same time and must be in complementary transmit/receive modes (i.e., one node transmits and the other node receives).
In an ad hoc network, such as an unmanned aerial vehicle, communication takes place in three dimensions, communication takes place between ground nodes and airborne nodes, communication takes place between ground nodes of different altitudes and between airborne nodes flying at different altitudes, in order to formalize this condition, provision is made forAndThe transmit and receive directions of the two nodes, respectively, for a narrow beam antenna, communication between the two nodes requires that the two beams point in opposite directions and are in complementary transmit/receive modes, namely:
in this embodiment, the scanning of the node is defined as a sequence comprising the pointing and pattern of the directional antennas. The sequence minimally covers the entire search volume by the area formed by the intersection of the volume and the width ω beam centered on each pointing direction.
In each scan, the nodes scan in a predetermined order. During scanning, the node transmits a broadcast to a designated direction for each antenna beam. While listening, the node waits for broadcast in the designated direction of each antenna beam. If the listening node receives a broadcast, it will respond to its own broadcast in a direction for a short time interval and will wish to receive a receipt.
When making a neighbor node selection to establish communication, the node may detect all potential neighbors in one direction sequence scan, but typically requires multiple scans to find them. The lower and upper limits of the number of scans required for all nodes in the network to find all their potential neighbors depend on the characteristics of the achievable network map and the node selection algorithm that the nodes use to select, scan, monitor. The present scheme uses a deterministic pattern selection algorithm. The initialization parameters for each node are N and j, where j e {0,..n-1 } (its unique identifier) and N are the maximum number of nodes in the network that can be detected by each other if the two nodes are within reach, at most, only log 2 N scans.
Specifically, the three-way handshake during neighbor discovery includes:
1) A first handshake; node 1 as handshake initiator broadcasts handshake request information to potential neighbors with the maximum transmitting power of the transceiver of the node;
2) A second handshake; node 2 as a handshake responder listens for broadcasted handshake request information; if no information is received, node 2 discards the handshake; if the node 1 is determined to be a potential neighbor after receiving the information and obtaining the identifier of the node 1, the node 2 broadcasts handshake response information to the node 1; the power level of the broadcasted handshake response information is determined according to the power of the handshake response information broadcasted by the node 1 received by the node 2;
The handshake response comprises identifier information of the node 1, identifier information of the node 2, transmitting power, consent information and idle time slot information of the node;
The node idle time slot information is a binary vector n_free 2, the dimension is m×r, m is the number of subframes reserved by the frame, and r is the number of mini time slots of the second subframe.
Specifically, in the second handshake process, after the node 2 receives the information and obtains the identifier of the node 1, according to the received power rcv 1,1 of the broadcast signal of the receiving node 1, the transmitting power trn 1 of the node 2 is calculated, if trn 1＞trnmax, the node 2 considers that a neighbor relation cannot be established with the node 1, and if trn 1＜trnmax, the node 2 continues the handshake.
The transmit power trn 1＝(rcv1,1 -T) + VCSManginPower of the node 2, where T is the antenna gain of the node 2, and VCSManginPower is a configuration parameter considering attenuation and other factors.
Determining that node 1 is a potential neighbor; node 2 will begin to establish a future rendezvous period with the potential neighbor; the future rendezvous time period is used for node 2 to evaluate the relationship of the two nodes.
In the handshake, the node 2 reevaluates the neighbor relation of the node 2 and the node 1 according to two conditions to carry out frame reservation; wherein,
Case (1) node 1 and node 2 detected each other at a previous time and have agreed to reconfirm their connection and make a reservation at a future time;
Case (2) node 1 and node 2 have never previously detected each other or have previously detected each other but cannot agree on the time to re-guarantee connection and make a frame reservation.
Node 2 will indicate in the consent information field indicating consent or non-consent whether it is case (1) or case (2);
after establishing the future rendezvous time with node 1, node 2 sends handshake reply information to node 1 at transmit power trn 1.
The handshake response information includes identifier information of the node 1, identifier information of the node 2, transmitting power, consent information and an idle time slot available binary vector n_free 2, where the dimension is mxr, m is a subframe number capable of being reserved by a frame, and r is a mini time slot number of the second subframe.
3) A third handshake; node 1 monitors handshake response information returned by node 2; if no information is received, node 1 discards the handshake; if the information is successfully received, after the node 1 calculates the intersection time with the node 2, the handshake confirmation information is broadcasted to the node 2 for the node 2 to confirm handshake; the power level of the broadcasted handshake acknowledgement information is determined according to the transmitting power in the handshake acknowledgement information broadcasted by the node 2;
The handshake confirmation information includes identifier information of the node 1, identifier information of the node 2, transmission power, and node intersection time.
In the third handshake, in case (1), node 1 agrees to the previous protocol and acknowledges with node 2 that they will make frame reservations at the protocol convergence time set.
In the third handshake, in case (2), the node intersection time determination procedure includes:
1) Node 1 first calculates a selected set of rendezvous times, n_free com, where n_free com＝N_free1&N_free2, where n_free 1 is the available time slot for node 1; n_free 2 is the free slot of node 2 obtained by the second handshake;
2) Node 1 transmits a response message to node 2 at transmit power trn 1; the response message includes identifier information of node 1, identifier information of node 2, transmit power trn 1, and selected rendezvous time set n_free com;
3) Node 2 waits for a response message from node 1; if no response message is received, node 2 considers that node 1 does not agree to establish a connection; otherwise, if the node 2 successfully receives the response message, the node 2 knows that the node 1 confirms the frame reservation, the node 1 starts the frame reservation flow, and the valid period of the frame reservation appointed between the two nodes is reached until the two nodes detect the other side again.
So far, the description of the three-way handshake is completed.
In the neighbor discovery process, two nodes detect each other and agree on a rendezvous time, during which the two nodes will guarantee connection again and check whether reservation can be completed. When the opposite side is re-detected and reserved, the two nodes only need to point to each other in the reserved sub-time slot according to the direction appointed by the neighbor discovery, if the two nodes find the opposite side in the direction in the method, the next sub-time slot in the next frame or the neighbor discovery time is required to be reserved.
In step S2, a priority queue is designed for each neighbor, and a priority is set for each node, so as to meet the requirements of data volume, time delay, service priority and the like transmitted by each node;
When the neighbor discovery stage receives a neighbor node request, extracting priority queue information and node priority information, grouping node priorities, placing nodes with the same priority in the same group, forming a node list based on different priority groups, respectively performing time slot allocation according to the groups with high priority to the groups with low priority, and entering the next time slot allocation waiting when all nodes in the final network are circulated.
Specifically, as shown in fig. 2, step S2 includes:
Step S201, a frame reservation stage receives a neighbor node broadcast request, extracts priority information of the request, and adds the priority information into a priority packet queue;
Step S202, judging the priority level, carrying out priority time slot allocation on the task with the highest priority level, and updating a time slot list;
1) Judging whether the current priority is highest; if yes, the time slot is allocated according to the node request, if not, the highest priority node is continuously searched;
2) After the time slot is allocated to the request node, updating a time slot allocation list; 3) Judging whether the priority grouping is distributed completely, if not, returning to the step 2) for the next node, and distributing time slots according to the request of the node; if yes, entering the next step;
step S203, node time slot allocation is carried out on all nodes in the priority group, and then node time slot allocation is carried out on the next priority group.
In step S203, the allocation procedure of steps 1) -3) may be repeated upon entering the slot allocation of the next priority packet.
The embodiment of the invention comprises a directional antenna dynamic Ad hoc network simulation system built by using an OPNET network simulation platform; and carrying out network topology design, node design and process design of a channel access protocol through a modeling mechanism of OPNET, and carrying out simulation verification of network access time, network delay and network quality of the protocol.
The OPNET software adopts a three-layer modeling mechanism, namely a network layer, a node layer and a process layer, wherein the network layer consists of a subnet, nodes and communication links, the setting of the network layer describes the topological structure of the network, the node layer consists of functional entities and data streams between the functional entities, and the node layer simulates the communication flow of communication nodes. The process layer consists of a process model, and the process behavior is realized by a programming language.
Specifically, the establishment process of the directional antenna dynamic Ad hoc network simulation system comprises a network layer modeling process, a node layer modeling process and a process layer modeling process.
More specifically, the modeling process includes:
1) Setting a simulation network area, arranging mobile nodes, priority levels of the nodes, and moving tracks and maximum moving speeds of the nodes in the network layer modeling process;
Specifically, a simulation network area of 6 km×6 km is selected, 50 mobile nodes are arranged in the simulation network area, the maximum movement speed of the nodes is set to be 10 m/h according to a certain movement track, and the priority level of part of the nodes is set.
2) In the modeling process of the node layer, a protocol stack of the node model comprises a network layer, a data link layer and an application layer; wherein,
The network layer adopts an AODV protocol;
the data link layer adopts a time division multiple access protocol based on directional beams of the scheme;
The application uses the OPNET original simple_source module to simulate ad hoc network to perform packet sending at fixed packet sending rate and time interval.
3) In the process layer modeling process, a finite state machine of a time division multiple access protocol based on directional beams is designed, wherein the states of the finite state machine comprise an initialization state, an idle state, a neighbor discovery state and a message broadcasting state; wherein,
The initialization state is used for initializing various state variables and global variables and reading simulation attributes and parameters;
an idle state for staying in this state when the simulation process does not need to do any action;
the message broadcasting state is used for broadcasting self state information to surrounding nodes after the nodes access the network;
And the neighbor discovery state discovery is implemented by broadcasting information of the neighbor nodes and three-way handshake flow.
Compared with the prior art, the technical proposal which is conceived by the invention can obtain the following
The beneficial effects are that:
according to the invention, through improving the standard wireless model in the OPNET, and constructing the wireless mobile node based on the improved wireless model, the unmanned aerial vehicle ad hoc network is constructed, so that the network has larger load capacity and lower end-to-end delay under a high-speed dynamic motion state.
The present invention is not limited to the above-mentioned embodiments, and any changes or substitutions that can be easily understood by those skilled in the art within the technical scope of the present invention are intended to be included in the scope of the present invention.
Claims (4)
1. A method for dynamic network slot allocation based on directional antennas, comprising:
Step S1, neighbor discovery, frame reservation and data transmission are carried out among nodes in a dynamic ad hoc network based on a time division multiple access protocol of a directional beam;
Carrying out power level negotiation and time slot reservation confirmation among nodes in a neighbor discovery period; the method comprises the steps of carrying out re-linking and time slot confirmation between nodes in a frame reservation period; data transmission between nodes is carried out in a data transmission period to negotiate power and reserve time slots;
step S2, in the dynamic ad hoc network data transmission process, carrying out service quality assurance comprising the data transmission size, the transmission time delay and the service priority of each node;
through the established node list based on different priority groups, respectively performing time slot allocation according to the priority of the neighbor nodes from the high-priority packet to the low-priority packet so as to meet the output transmission service requirements among the nodes;
In step S1, it includes:
Step S101, during neighbor discovery, a pair of nodes with directional antennas forming a direct communication condition complete power level negotiation of communication and reservation confirmation of communication time slots through three-way handshake;
step S102, during the frame reservation period, linking again according to the appointed time slot and the appointed direction, and carrying out time slot confirmation;
step S103, data transmission among nodes is carried out in reserved time slots and negotiated time slots among data transmission;
The three-way handshake during neighbor discovery includes:
1) A first handshake; node 1 as handshake initiator broadcasts handshake request information to potential neighbors with the maximum transmitting power of the transceiver of the node;
2) A second handshake; node 2 as a handshake responder listens for broadcasted handshake request information; if no information is received, node 2 discards the handshake; if the node 1 is determined to be a potential neighbor after receiving the information and obtaining the identifier of the node 1, the node 2 broadcasts handshake response information to the node 1; the power level of the broadcasted handshake response information is determined according to the power of the handshake response information broadcasted by the node 1 received by the node 2;
The handshake response comprises identifier information of the node 1, identifier information of the node 2, transmitting power, consent information and idle time slot information of the node;
The node idle time slot information is a binary vector N_free 2, the dimension is m×r, m is the number of subframes capable of being reserved by a frame, and r is the number of mini time slots of a second subframe;
In the second handshake process, after the node 2 receives the information and obtains the identifier of the node 1, according to the received power rcv 1,1 of the broadcast signal of the receiving node 1, calculating the transmitting power trn 1 of the node 2, if trn 1>trnmax, the node 2 considers that a neighbor relation cannot be established with the node 1, and if trn 1<trnmax, the node 2 continues the handshake;
Wherein, the transmitting power trn 1＝(rcv1,1 -T) + VCSManginPower of the node 2, wherein T is the antenna gain of the node 2, VCSManginPower is a configuration parameter considering factors such as attenuation, trn max is the maximum value of the transmitting power of the node 2;
determining that node 1 is a potential neighbor; node 2 will begin to establish a future rendezvous period with the potential neighbor; the future convergence time period is used for the node 2 to evaluate the relationship of the two nodes;
in the handshake, the node 2 reevaluates the neighbor relation of the node 2 and the node 1 according to two conditions to carry out frame reservation; wherein,
Case-node 1 and node 2 detected each other at some previous time and have agreed to reconfirm their connection and make reservations at some future time;
The two nodes 1 and 2 never detect each other before or detect each other before but cannot agree on the time for re-ensuring connection and making frame reservation;
Node 2 will indicate in the consent information field indicating consent or disagreement whether it is case one or case two;
after establishing the future rendezvous time with node 1, node 2 sends handshake reply information to node 1 at transmit power trn 1;
3) A third handshake; node 1 monitors handshake response information returned by node 2; if no information is received, node 1 discards the handshake; if the information is successfully received, after the node 1 calculates the intersection time with the node 2, the handshake confirmation information is broadcasted to the node 2 for the node 2 to confirm handshake; the power level of the broadcasted handshake acknowledgement information is determined according to the transmitting power in the handshake acknowledgement information broadcasted by the node 2;
The handshake confirmation information comprises identifier information of the node 1, identifier information of the node 2, transmitting power and node intersection time;
in the third handshake, in case node 1 agrees to the previous protocol and acknowledges with node 2 that they will make frame reservations at the protocol convergence time set;
In the third handshake, in case two, the node intersection time determination procedure includes:
1) Node 1 first calculates a selected set of rendezvous times, n_free com, where n_free com＝N_free1&N_free2, where n_free 1 is the available time slot for node 1; n_free 2 is the free slot of node 2 obtained by the second handshake;
2) Node 1 transmits a response message to node 2 at transmit power trn 1; the response message includes identifier information of node 1, identifier information of node 2, transmit power trn 1, and selected rendezvous time set n_free com;
3) Node 2 waits for a response message from node 1; if no response message is received, node 2 considers that node 1 does not agree to establish a connection; otherwise, if the node 2 successfully receives the response message, the node 2 knows that the node 1 confirms the frame reservation, the node 1 starts the frame reservation flow, and the valid period of the frame reservation appointed between the two nodes is reached until the two nodes detect the other side again.
2. The method for directional antenna based dynamic network slot allocation as recited in claim 1, wherein,
In step S2, a priority queue is designed for each neighbor, and a priority is set for each node, so as to meet the requirements of data volume, time delay, service priority and the like transmitted by each node;
When the neighbor discovery stage receives a neighbor node request, extracting priority queue information and node priority information, grouping node priorities, placing nodes with the same priority in the same group, forming a node list based on different priority groups, respectively performing time slot allocation according to the groups with high priority to the groups with low priority, and entering the next time slot allocation waiting when all nodes in the final network are circulated.
3. The method for directional antenna based dynamic network slot allocation as recited in claim 1, wherein,
The step S2 includes:
Step S201, a frame reservation stage receives a neighbor node broadcast request, extracts priority information of the request, and adds the priority information into a priority packet queue;
Step S202, judging the priority level, carrying out priority time slot allocation on the task with the highest priority level, and updating a time slot list;
step S203, node time slot allocation is carried out on all nodes in the priority group, and then node time slot allocation is carried out on the next priority group.
4. A directional antenna dynamic Ad hoc network simulation system built by using an OPNET network simulation platform is characterized in that,
The OPNET network simulation platform adopts a three-layer modeling mechanism, namely a network layer, a node layer and a process layer, wherein the network layer consists of a subnet, nodes and communication links, the setting of the network layer describes the topological structure of the network, the node layer consists of functional entities and data streams between the functional entities, and the node layer simulates the communication flow of communication nodes; the process layer consists of a process model, and the process behavior is realized by a programming language;
performing network simulation of the directional antenna-based dynamic network time slot allocation method according to any one of claims 1 to 3 by using an OPNET modeling mechanism; simulation verification is carried out on network access time, network delay and network quality of the protocol through network topology design, node design and process design of the channel access protocol;
The establishment process of the directional antenna dynamic Ad hoc network simulation system comprises a network layer modeling process, a node layer modeling process and a process layer modeling process;
in the modeling process, the method comprises the following steps:
1) Setting a simulation network area, arranging mobile nodes, priority levels of the nodes, and moving tracks and maximum moving speeds of the nodes in the network layer modeling process;
2) In the modeling process of the node layer, a protocol stack of the node model comprises a network layer, a data link layer and an application layer; wherein,
The network layer adopts an AODV protocol;
the data link layer adopts a time division multiple access protocol based on directional beams of the scheme;
The application uses an OPNET original simple_source module to simulate the ad hoc network to carry out packet sending at a fixed packet sending rate and time interval;
In the process layer modeling process, a finite state machine of a time division multiple access protocol based on directional beams is designed, wherein the states of the finite state machine comprise an initialization state, an idle state, a neighbor discovery state and a message broadcasting state; wherein,
The initialization state is used for initializing various state variables and global variables and reading simulation attributes and parameters;
an idle state for staying in this state when the simulation process does not need to do any action;
the message broadcasting state is used for broadcasting self state information to surrounding nodes after the nodes access the network;
And the neighbor discovery state discovery is implemented by broadcasting information of the neighbor nodes and three-way handshake flow.
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