A method for dynamic frequency selection in a mobile ad hoc network

Abstract

The application discloses a kind of mobile ad hoc network's dynamic frequency selection method, comprising the following steps: step 1, generating control node, selecting a control node in subnet, the node is responsible for network frequency switching command issue;Step 2, each node maintains a local channel interference frequency quality set, each node periodically broadcasts its own frequency quality set to one-hop node;Step 3, the frequency quality set received by surrounding one-hop neighbor node and its own frequency quality set are made intersection operation, form new frequency quality set;Step 4, by exchanging frequency set, make all nodes in the network generate a common frequency quality set, and under the command of control node, all nodes in the network switch working frequency.The application can improve the communication quality between mobile ad hoc network nodes, increase the throughput of network, and reduce the interference to surrounding communication equipment by periodically detecting the channel quality of multiple frequency points and selecting a frequency band with minimum interference.

Description

Technical Field

[0001] This invention relates to the field of mobile communication technology, and in particular to a dynamic frequency selection method for mobile ad hoc networks. Background Technology

[0002] With the development of mobile communications, spectrum resources are becoming increasingly scarce, and co-channel and adjacent-channel interference are becoming more severe. Operating a communication system in a frequency band with severe electromagnetic interference can lead to a decrease in the received signal-to-noise ratio, an increase in the bit error rate, and a reduction in network throughput. Therefore, the ability of a communication system to dynamically select communication frequencies is of great significance.

[0003] Dynamic Frequency Selection (DFS) is currently widely used in Wi-Fi technology. However, if two adjacent access points (APs) operate on the same frequency, it can cause severe interference. For example... Figure 1 As shown, when terminal 1 is communicating with AP1, AP2 operates on the same frequency as AP1. While terminal 1 is communicating with AP1, AP2 is also transmitting wireless signals, causing co-channel interference for terminal 1 and resulting in reception failure. Since both AP1 and terminal 1 are running the DFS mechanism, they can select a suitable frequency from a set of predefined frequencies for communication.

[0004] In Wi-Fi's Depth-First-Served (DFS) mechanism, access nodes are within the one-hop range of the access point (AP) node. However, when multi-hop links exist in the network, Wi-Fi's DFS mechanism exhibits several shortcomings, especially in mobile ad hoc network scenarios. For example, in mobile ad hoc networks, due to the mobility of nodes, the DFS mechanism is used more frequently to avoid interference with other communication devices. Furthermore, in mobile ad hoc networks, nodes are located in different locations, resulting in different channel detection results for different frequency points for each node, making it impossible to generate a communication frequency applicable to all nodes based on a specific node. Inter-node communication often involves multi-hop links; when a communication node is outside the first hop, Wi-Fi's DFS mechanism cannot control nodes outside the first hop, and cannot adjust the communication frequency in a timely manner when interference occurs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a dynamic frequency selection method for mobile ad hoc networks. By periodically detecting the channel quality of multiple frequency points, a frequency band with the least interference is selected, which can improve the communication quality between mobile ad hoc network nodes, increase the network throughput, and reduce interference to surrounding communication equipment.

[0006] To address the aforementioned technical problems, this invention provides a dynamic frequency selection method for mobile ad hoc networks, comprising the following steps:

[0007] Step 1: Generate a control node. Select a control node in the subnet. This node is responsible for issuing frequency switching commands for the network.

[0008] Step 2: Each node maintains a local frequency quality set of channel interference conditions, and each node periodically broadcasts its frequency quality set to the one-hop node;

[0009] Step 3: The surrounding one-hop neighbor nodes perform an intersection operation between the received frequency quality set and their own frequency quality set to form a new frequency quality set;

[0010] Step 4: By exchanging frequency sets, all nodes in the network generate a common frequency quality set, and under the command of the control node, all nodes in the network switch their working frequencies in a unified manner.

[0011] Preferably, in step 1, the methods for generating control nodes include the specified method and the automatic generation method.

[0012] Preferably, in the designated method, a certain node is manually configured as a control node, and other nodes are ordinary nodes.

[0013] Preferably, in the automatic generation method, after the node network is completed, the node with the smallest node number is designated as the control node based on the routing information.

[0014] Preferably, in step 2, a frequency quality set is formed based on the frequency bandwidth and frequency quality, and the entire frequency band is divided into N(f1,f2,f3,…,f…). N Given a fixed bandwidth, the finer the granularity of frequency band division, the more concentrated frequency points there are. The physical layer scans the energy level of each sub-band to classify the quality of the sub-bands into four levels, as shown in Table 1.

[0015] Number of bits occupied 2 2 2 …… 2 2 Test results 0 2 3 …… 1 2

[0016] In the test results, 0 indicates that the frequency is unavailable, 1 indicates that the frequency is available but of average quality, 2 indicates that the frequency is available and of good quality, and 3 indicates that the frequency is available and of very good quality.

[0017] Preferably, in step 2, after the network is completed or after receiving the frequency switching message from the control node, the protocol layer configures the physical layer to perform a frequency detection task, the physical layer feeds back the detection results to the protocol layer, and the protocol layer forms a frequency quality set after obtaining the results.

[0018] Preferably, in step 3, each node periodically sends its own frequency set exchange message, with a period of T. FQS The FGS message carries its own frequency quality set. After receiving the FQS message from the surrounding one-hop neighbor node, the node performs an intersection operation with the local frequency quality set according to the content of the message to form a new frequency quality set.

[0019] Preferably, in step 3, the frequency-quality intersection operation is defined as: (fx1 ,f x2 …,f xi ,…f xn )∩(f y1 ,f y2 …,f yi ,…f yi )=(f z1 ,f z2 …,f zi …f zn ), where f zi equal to f xi and f yi The minimum value is i = [1, n]. Assuming the local frequency quality set is (f1, f2, f3), the frequency quality set in the received FQS message is (3, 2, 1), and the local frequency quality set is (2, 2, 1), then the updated local frequency quality set is (3, 2, 1) ∩ (2, 2, 1) = (2, 2, 1).

[0020] Preferably, in step 4, the control node periodically sends a frequency switching message FS, with a period of T. FS The FS message is flooded across the entire network. After receiving the FS message, all nodes forward the message. At the start of the superfn superframe, they switch to the dst_frq frequency and initialize the local frequency quality set. The protocol layer reconfigures the frequency detection task for the physical layer. The physical layer feeds back the detection results to the protocol layer, forming a new local frequency quality set.

[0021] Preferably, the FS message carries the target frequency for the handover and the time of the handover frequency.

[0022] The beneficial effects of this invention are as follows: the frequency set propagation mechanism based on FQS messages overcomes the shortcomings of channel results detected by specific nodes in the network being applicable to all nodes; the network-wide propagation mechanism based on FS messages can meet the needs of multi-hop nodes to adjust communication frequencies simultaneously; by adjusting the period of FGS and FS messages, the needs of mobile ad hoc networks to frequently adjust communication frequencies can be met; and the mechanism based on automatic election of control nodes can meet the damage resistance of mobile ad hoc networks and improve network robustness. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of communication interference in existing technologies.

[0024] Figure 2 This is a schematic diagram of the FQS message frame structure of the present invention.

[0025] Figure 3 This is a schematic diagram of the FS message frame structure of the present invention.

[0026] Figure 4This is a schematic diagram of the control nodes generated by the automatic generation method of the present invention.

[0027] Figure 5 This is a schematic diagram of the method flow of the present invention. Detailed Implementation

[0028] like Figure 5 As shown, a dynamic frequency selection method for mobile ad hoc networks includes the following steps:

[0029] Step 1: Generate a control node. Select a control node in the subnet. This node is responsible for issuing frequency switching commands for the network.

[0030] Step 2: Each node maintains a local frequency quality set of channel interference conditions, and each node periodically broadcasts its frequency quality set to the one-hop node;

[0031] Step 3: The surrounding one-hop neighbor nodes perform an intersection operation between the received frequency quality set and their own frequency quality set to form a new frequency quality set;

[0032] Step 4: By exchanging frequency sets, all nodes in the network generate a common frequency quality set, and under the command of the control node, all nodes in the network switch their working frequencies in a unified manner.

[0033] The dynamic frequency selection technology solution for mobile ad hoc networks can be divided into two parts: between nodes and within nodes.

[0034] Inside the node:

[0035] Step 1: Create Control Nodes. Node roles are divided into two categories: control nodes and ordinary nodes. Ordinary nodes are controlled by the control nodes and their operating frequency bands are adjusted periodically. The creation of control nodes mainly involves two methods: designated method and automatic generation method. Designated method: A specific node is manually configured as the control node, and other nodes are ordinary nodes. Automatic generation method: After the node network is formed, the node with the smallest node number is designated as the control node based on routing information. This solution can use either the designated method or the automatic generation method depending on the actual situation.

[0036] Step 2: Configure the frequency quality set. A frequency quality set is created based on the frequency bandwidth and frequency quality, such as... Figure 2 As shown, the entire frequency band is divided into N(f1,f2,f3,…,f…). N Given a fixed bandwidth, the finer the granularity of frequency band division, the more concentrated frequency points there are. The physical layer scans the energy level of each sub-band to classify its quality into four levels, as shown in Table 1.

[0037] Table 1 Quality Classification of Sub-bands

[0038] Number of bits occupied 2 2 2 …… 2 2 Test results 0 2 3 …… 1 2

[0039] In the test results, 0 indicates that the frequency is unavailable, 1 indicates that the frequency is available but of average quality, 2 indicates that the frequency is available and of good quality, and 3 indicates that the frequency is available and of very good quality.

[0040] Step 3: Formation of Node Frequency Quality Set. After the network is completed, or after receiving a frequency switching message from the control node, the protocol layer configures the physical layer to perform a frequency detection task. The physical layer feeds back the detection results to the protocol layer, which then forms its own new frequency quality set after receiving the results.

[0041] Inter-node: Mobile ad hoc network nodes mainly achieve frequency quality set exchange and frequency switching by sending messages.

[0042] Step 1: Each node periodically sends its own Frequency Quality Set (FQS) message, with a period of T. FQS FGS messages carry their own frequency quality set. GFS messages are not forwarded; their propagation is limited to their one-hop neighbor nodes. For example... Figure 2 The format diagram of the FGS message is shown in Table 2, and its contents are shown in Table 2.

[0043] Table 2 Contents of FGS Messages

[0044] src_addr Message source node freq_n Quality of band n

[0045] Step 2: After receiving the FQS message from its one-hop neighbor, the node performs an intersection operation with its local frequency quality set based on the message content, forming a new frequency quality set. Definition of frequency quality set intersection operation: (f x1 ,f x2 …,f xi ,…f xn )∩(f y1 ,f y2 …,f yi ,…f yi )=(f z1 ,f z2 …,f zi …f zn ), where f zi equal to f xi and f yi The minimum value is i = [1, n]. Assuming the local frequency quality set is (f1, f2, f3), the frequency quality set in the received FQS message is (3, 2, 1), and the local frequency quality set is (2, 2, 1), then the updated local frequency quality set is (3, 2, 1) ∩ (2, 2, 1) = (2, 2, 1).

[0046] Step 3: The control node periodically sends a Frequency Switch (FS) message, with a period of T. FS FS messages are flooded across the network, and nodes forward them upon receipt. The FS message carries the target frequency and the time of the switchover, such as... Figure 3 The image shows the format of an FS message.

[0047] Table 3 describes the FS message format. src_addr is the address of the control node, dst_freq is the target frequency, seq is the message sequence number used to control message flooding and prevent duplicate forwarding, and superfn is the superframe number for switching frequencies. Since all nodes in this scheme have the same time, they can switch frequencies simultaneously starting from the superfn superframe.

[0048] Table 3 FS Message Format Table

[0049] src_addr Message source node dst_frq Switching target frequency seq Serial Number superfn Superframe number for switching frequency

[0050] Step 4: After receiving the FS message, all nodes switch to the dst_frq frequency at the start of the superfn superframe, and initialize the local frequency quality set. The protocol layer reconfigures the frequency detection task for the physical layer, and the physical layer feeds back the detection results to the protocol layer to form a new local frequency quality set.

[0051] Explanation of the convergence problem of the frequency-mass set of all nodes in the network:

[0052] By periodically sending FQS messages across the entire network, nodes can achieve a shared optimal frequency set for the entire network, meaning that the local frequency quality sets of all nodes will converge to the same value. Let T be the local frequency quality set of node i. i The common frequency quality set T was completed through FQS messages exchanged between nodes. p =T1∩T2∩T3∩…T n-1 ∩T n In this operation, after several cycles, the FQS message for every node in the entire network is the same: T. p Assume the maximum hop count of the network is X, node A and node B are separated by X hops, the frequency-quality intersection calculation for nodes A and B requires X hops, and the FQS message sending period for nodes is T. FQS Then T is required. FQS *Time X completes the frequency quality set intersection calculation. Since the hop distance between other nodes is less than X, the time to complete the frequency band set union calculation is less than T. FQS *X, the minimum T required for the entire network to complete one round of public frequency quality set computation. FQS *X time.

[0053] Regarding the period T for the control node to send FS messages FS Selection instructions: After all nodes in the network have completed the convergence of the frequency quality set, the control node needs to send an FS message to notify the entire network. Assume that the single-hop propagation delay is Y, and the time required to propagate X hops is X*Y.

[0054] Then T FS It should be greater than X*Y+T FQS *X.

[0055] Node internal configuration process:

[0056] Depending on the application scenario, certain solution parameters need to be determined. The parameters for this implementation process are shown in Table 4:

[0057] Table 4 Implementation Process Parameter Table

[0058] Network scale 6 <![CDATA[FQS message transmission period (T FQS )]]> 2s Maximum number of hops in communication (X) 6 Single-hop propagation delay (Y) 1s Superframe length 1000ms <![CDATA[FS message transmission period (T FS )]]> 20s Operating frequency band [1000M, 1500M] Subbandwidth 50M Number of frequency points 10 <![CDATA[Maintenance value of the seq field of the FS message (M seq )]]> Initialize to 0

[0059] Step 1: Control node generation. The scheme includes both automatic generation and specified generation methods. This scheme uses the automatic generation method, such as... Figure 4 As shown, the network has 6 nodes. After the network is set up, all nodes exchange routing information and determine that node 1 has the smallest address, thus becoming the control node. Alternatively, if a designation method is used, a specific node is designated as the control node during network setup, while the other nodes are ordinary nodes.

[0060] Step 2: Start the timers. The control node needs to periodically send FQS and FS messages; therefore, the control node's protocol layer needs to start FQS and FS message timers. Ordinary nodes need to periodically send FQS messages; therefore, the ordinary node's protocol layer needs to start an FQS message timer. After network formation is complete, start the FQS message timer and set the period to 2 seconds. After confirming that this node is the control node, start the FS message timer and set the period to 20 seconds.

[0061] Step 3: Confirm the frequency quality set details, as shown in Table 5. The working frequency band is distributed in [1000M, 1500M], the sub-band width is 50M, and there are 10 working center frequencies available for switching.

[0062] Table 5. Detailed Table of Frequency Quality Set

[0063] bandwidth M 50 50 50 50 50 50 50 50 50 50

[0064] The physical layer classifies the detection results of each frequency point into four levels: 0 represents that the frequency is unusable, 1 represents that the frequency is usable but of average quality, 2 represents that the frequency is usable and of good quality, and 3 represents that the frequency is usable and of very good quality.

[0065] Step 4: Configure frequency detection tasks for the physical layer. After network deployment is complete, or after receiving a frequency switching message from the control node, the frequency information to be detected is configured to the physical layer through the interface agreed upon by the protocol layer and the physical layer. After obtaining the relevant parameters, the physical layer executes the frequency detection task.

[0066] Step 5: Forming a frequency quality set. The physical layer feeds back the channel sounding results to the protocol layer through the interface agreed upon by the physical layer and the protocol. After obtaining the relevant data, the protocol layer divides the channel quality into four levels to form a frequency quality set.

[0067] Inter-node interaction process:

[0068] Step 1: The node sends an FQS message. After the FQS message timer expires, the node forms an FQS message based on its local frequency quality set and broadcasts it to its one-hop neighbors.

[0069] Step 2: The node receives the FQS message, performs an intersection operation between the frequency quality set in the FQS message and its own local frequency quality set, and forms a new local frequency quality set.

[0070] Taking 1025M, 1075M, and 1125M frequency points as examples, assuming the local frequency quality set is (2, 1, 3), the neighbor frequency quality sets (2, 3, 3), (3, 2, 3), and (1, 1, 3) are obtained by receiving FQS messages from neighboring nodes. Through a parallel operation, (2, 1, 3)∩(2, 3, 3)∩(3, 2, 3)∩(1, 2, 3)=(1, 1, 3), forming a new local frequency quality set (1, 1, 3). After the next FQS message timer expires, (1, 1, 3) is broadcast to a one-hop neighbor via an FQS message.

[0071] Step 3: Repeat Step 1 and Step 2 until all nodes have the same local frequency quality set, forming a network-wide common frequency quality set. This set contains the common optimal frequency point of all nodes in the network.

[0072] Taking 1025M, 1075M, and 1125M frequency points as examples, as shown in Table 6, after multiple rounds of FQS message sending and receiving, the local frequency quality set of all nodes is (1, 1, 3).

[0073] Table 6 shows the node frequency quality set for 1025MHz, 1075MHz, and 1125MHz frequency points.

[0074]

[0075]

[0076] Step 4: The control node sends an FS message. In this implementation, after the FS message timer of node 1 expires, it selects an optimal frequency fn from the local frequency set. In the FS message, the src_addr field is 1, the dst_frq field is fn, the superfn field is the current superframe + maximum communication hop count / superframe length, and the seq field is M. seq M seq Increment the value by 1. Send an FS message to the entire network.

[0077] Step 5: When a node receives an FS message, it uses the seq field to determine whether the FS message is the latest message.

[0078] 1. If it is the latest news, forward the FS message. Using the dst_frq and fn fields in the FS message, the node switches its operating frequency to fn at the dst_fn superframe moment. At the same time, a new round of frequency detection task is started.

[0079] 2. If it is an old message, discard it.

[0080] This invention relates to a dynamic frequency selection method for mobile ad hoc network (MAN) communication. This method ensures that the MAN operates in a relatively clean electromagnetic interference frequency band and can adjust the network's operating frequency in real time based on the current spectrum interference situation, giving the MAN a certain degree of anti-interference capability. The method first selects a control node in the subnet, which is responsible for issuing frequency switching commands. Each node maintains a frequency quality set based on local channel interference. Each node periodically broadcasts its frequency quality set to its one-hop neighbor nodes. The receiving one-hop neighbor nodes intersect their own frequency quality set with the received one-hop neighbor's set to form a new frequency quality set. Through mutual exchange of frequency quality sets, all nodes in the network generate a common frequency quality set, and under the command of the control node, all nodes in the network uniformly switch their operating frequencies.

[0081] Mobile ad hoc networks (MAVs) operating on fixed frequencies may interfere with surrounding communication equipment, or vice versa, leading to degraded communication quality. By periodically detecting channel quality at multiple frequency points and selecting the frequency band with minimal interference, the communication quality between MAV nodes can be improved, network throughput increased, and interference to surrounding communication equipment reduced.

Claims

1. A dynamic frequency selection method for mobile ad hoc networks, characterized in that, Includes the following steps: Step 1: Create a control node. Select a control node in the subnet. This node is responsible for issuing frequency switching commands for the network. Step 2: Each node maintains a local frequency quality set of channel interference conditions, and each node periodically broadcasts its frequency quality set to the one-hop node; Step 3: The surrounding one-hop neighbor nodes perform an intersection operation between the received frequency quality set and their own frequency quality set to form a new frequency quality set; Step 4: By exchanging frequency sets, all nodes in the network generate a common frequency quality set, and under the command of the control node, all nodes in the network switch their working frequencies in a unified manner.

2. The dynamic frequency selection method for mobile ad hoc networks as described in claim 1, characterized in that, In step 1, the methods for generating control nodes include the specified method and the automatic generation method.

3. The dynamic frequency selection method for mobile ad hoc networks as described in claim 2, characterized in that, In the designated method, a certain node is manually configured as the control node, and other nodes are ordinary nodes.

4. The dynamic frequency selection method for mobile ad hoc networks as described in claim 2, characterized in that, In the automatic generation method, after the node network is completed, the node with the smallest node number is designated as the control node based on the routing information.

5. The dynamic frequency selection method for mobile ad hoc networks as described in claim 1, characterized in that, In step 2, a frequency quality set is formed based on the frequency bandwidth and frequency quality, and the entire frequency band is divided into N(f1,f2,f3,…,f…). N Given a fixed bandwidth, the finer the granularity of frequency band division, the more concentrated frequency points there are. The physical layer scans the energy level of each sub-band to classify the quality of the sub-bands into four levels, as shown in Table 1. In the test results, 0 indicates that the frequency is unavailable, 1 indicates that the frequency is available but of average quality, 2 indicates that the frequency is available and of good quality, and 3 indicates that the frequency is available and of very good quality.

6. The dynamic frequency selection method for mobile ad hoc networks as described in claim 1, characterized in that, In step 2, after the network is completed or after receiving the frequency switching message from the control node, the protocol layer configures the physical layer to perform a frequency detection task. The physical layer feeds back the detection results to the protocol layer, and the protocol layer forms a frequency quality set after obtaining the results.

7. The dynamic frequency selection method for mobile ad hoc networks as described in claim 1, characterized in that, In step 3, each node periodically sends its own frequency set exchange message with a period of TFQS. The FGS message carries its own frequency quality set. After receiving the FQS message from the surrounding one-hop neighbor node, the node performs an intersection operation with the local frequency quality set according to the content of the message to form a new frequency quality set.

8. The dynamic frequency selection method for mobile ad hoc networks as described in claim 7, characterized in that, In step 3, the frequency-quality intersection operation is defined as: (f x1 ,f x2 …,f xi ,…f xn )∩(f y1 ,f y2 …,f yi ,…f yi )=(f z1 ,f z2 …,f zi …f zn ), where f zi equal to f xi and f yi The minimum value is i = [1, n]. Assuming the local frequency quality set is (f1, f2, f3), the frequency quality set in the received FQS message is (3, 2, 1), and the local frequency quality set is (2, 2, 1), then the updated local frequency quality set is (3, 2, 1) ∩ (2, 2, 1) = (2, 2, 1).

9. The dynamic frequency selection method for mobile ad hoc networks as described in claim 1, characterized in that, In step 4, the control node periodically sends a frequency switching message FS, with a period of T. FS The FS message is flooded across the entire network. After receiving the FS message, all nodes forward the message. At the start of the superfn superframe, they switch to the dst_frq frequency and initialize the local frequency quality set. The protocol layer reconfigures the frequency detection task for the physical layer, and the physical layer feeds back the detection results to the protocol layer to form a new local frequency quality set.

10. The dynamic frequency selection method for mobile ad hoc networks as described in claim 9, characterized in that, The FS message carries the target frequency for the handover and the time of the handover.

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