Method for realizing centerless ad hoc network dynamic frequency selection based on TDMA (Time Division Multiple Access) system

Abstract

The invention discloses a method for realizing centerless ad hoc network dynamic frequency selection based on a TDMA (Time Division Multiple Access) system, which relates to the field of ad hoc network communication, and comprises the following steps of: S1, dividing time into periodic frames through the TDMA system, and dividing the frames into a plurality of time slots, so that each mobile station can only transmit signals according to the specified time slot in each frame; s2, binding different operations with different time slots to avoid influence on execution of different operations; s3, after the nodes are powered on, networking is carried out according to frequency point conditions in a frequency band range; s4, scanning the frequency points after networking succeeds, and storing background noise information of the frequency points; and S5, when the bottom noise of the current frequency point is abnormal, searching the frequency point with the best bottom noise information and switching the frequency. According to the technical scheme provided by the invention, the frequency hopping and DFS technologies are fused, the concept of master and slave nodes is removed, the current electromagnetic environment can be monitored and analyzed in real time, and the optimal working frequency point is dynamically selected, so that the interference influence is reduced.

Description

Technical Field

[0001] The invention relates to the field of ad hoc network communication, and in particular to a method for realizing dynamic frequency selection of a centerless ad hoc network based on a TDMA system. Background Art

[0002] Ad hoc network, that is, wireless self-organizing network, realizes node interconnection through mutual coordination and relay forwarding between nodes. In the field of ad hoc network communication, it is crucial to ensure the efficient and stable transmission of information in complex electromagnetic environments. When electromagnetic waves propagate in free space, if the selected working frequency encounters spectrum congestion or other signal interference, not only will the communication quality be significantly reduced, but in severe cases it may even cause the interruption of the communication link, which greatly limits the application scope and reliability of ad hoc networks.

[0003] In order to achieve the anti-interference effect, the prior art has developed a variety of anti-interference strategies, such as frequency hopping anti-interference technology and spread spectrum anti-interference technology, but this method also has some shortcomings. For example, frequency hopping anti-interference technology can avoid interference from interference signals by quickly changing the transmission frequency of wireless communication equipment, thereby achieving a strong anti-interference ability, but it may reduce a certain transmission rate. Spread spectrum anti-interference technology can expand wireless communication signals to a wider frequency band, reduce the signal strength on the unit frequency band, thereby reducing the impact of interference. Although it has strong anti-interference and anti-interception capabilities, it occupies a large bandwidth. Therefore, in view of the limitations of the above-mentioned technologies, a method that can quickly and flexibly realize dynamic frequency selection is needed, and the present invention solves this technical problem. Summary of the invention

[0004] The present invention provides a method for realizing dynamic frequency selection of a centerless self-organizing network based on a TDMA system, aiming to solve the technical problems corresponding to the background technology.

[0005] To achieve the above purpose, the present application proposes a method for realizing dynamic frequency selection of a centerless ad hoc network based on a TDMA system, comprising the following steps:

[0006] S1. Through the TDMA system, time is divided into periodic frames, and the frames are divided into several time slots, so that each mobile station can only transmit signals in the specified time slots in each frame;

[0007] S2. Bind different operations to different time slots to avoid affecting the execution of different operations;

[0008] S3. After the node is powered on, networking is performed according to the frequency points within the frequency band;

[0009] S4. After the network is successfully established, scan the frequency points and save the background noise information of the frequency points;

[0010] S5. When the background noise of the current frequency is abnormal, find the frequency with the best background noise information and switch the frequency.

[0011] Furthermore, the step S3 includes the following steps:

[0012] S31, after the node is powered on, first traverse all frequency points within the frequency band;

[0013] S32. If other nodes or subnets are found on one of the frequency points, the network is formed at a fixed frequency;

[0014] S33. If no other nodes or subnets are found, continue frequency hopping to search for valid signals.

[0015] Further, the step S4 includes the following steps:

[0016] S41. After the network is successfully established, the node will periodically traverse all frequency points and record the background noise information of the frequency points;

[0017] S42, save the background noise information of all frequencies, and send the background noise information to the reference node of clock synchronization, that is, the ssid node;

[0018] S43. After the current SSID node is powered off, the network will automatically bootstrap the node with the smallest node number as the SSID node.

[0019] Furthermore, the step S5 includes the following steps:

[0020] S51. When a node finds that the background noise of the current frequency is abnormal, it will search for all the frequencies within the range and find the frequency with the smallest background noise based on its background noise information;

[0021] S52, selecting different frequency switching modes according to whether the node is an SSID node;

[0022] S53, after sending the frequency cutting information through the ID field for multiple frame periods, the frequency is automatically cut, and the information of the abnormal frequency point of the background noise is saved;

[0023] S54: If the system loses step after switching the frequency, the system starts from the frequency hopping process after power-on, and enters the network at a fixed frequency after detecting the networking information during the frequency hopping process.

[0024] S55. If the network is re-entered after being out of sync, it is necessary to pay attention to the abnormal frequency information. When the background noise is restored, the SSID node is informed to delete the abnormal information.

[0025] Further, when the node in step S51 is an ssid node, the frequency switching method is as follows:

[0026] S521. Collect the background noise information of all nodes and select the frequency point with the smallest background noise in the entire network. After receiving the frequency switching information of the SSID node, all other nodes will synchronously follow the frequency switching in the entire network.

[0027] Furthermore, if the node in step 1 is not an SSID node, the frequency switching method is as follows:

[0028] S522, when the SSID node receives the frequency switching information of the node, if it is determined that the frequency switching information meets the noise floor requirement of the entire network, the entire network synchronously follows the frequency switching;

[0029] S523, if not satisfied, remove the current working frequency and the frequency received from other nodes, then recalculate the noise floor, find the frequency with the best noise floor, and synchronize the frequency cutting of the whole network. Meanwhile, record the abnormal frequency and node information, and remove the frequency when selecting the best frequency later until the noise floor of the frequency is normal.

[0030] Furthermore, the calculation process of the background noise in step S523 is as follows:

[0031] S5231, all nodes periodically scan the background noise of each frequency point;

[0032] S5232, sending the background noise information of all frequencies to the SSID node via network communication;

[0033] S5233, SSID node compares the noise floor values ​​received at each frequency point, and selects the optimal frequency point according to the difference in noise floor value and the size of the optimal signal-to-noise ratio.

[0034] Furthermore, the method of selecting the optimal frequency is as follows:

[0035] If the noise floor of the current frequency differs from the best noise floor among all the frequencies by a certain value, and the optimal signal-to-noise ratio of the current frequency is less than a certain value, it is necessary to switch to the best frequency, that is, the frequency with the best noise floor;

[0036] If the bit error rate of the current frequency is greater than a certain value and the best frequency has a better noise floor than the current frequency, the frequency needs to be cut.

[0037] Furthermore, the process of step S2 is as follows:

[0038] S21, allocating time slot IDs according to different processing events;

[0039] S22, the corresponding event operation must be performed in the current time slot, and the execution order must be executed from the beginning in the order of the time slot ID;

[0040] S23. If the last processed event times out, resulting in missing the current time slot, the missed event is stopped, and further execution of the event is stopped, and the corresponding event is continued to be executed in the next cycle.

[0041] The technical effects of the present invention are as follows:

[0042] (1) This solution integrates frequency hopping and DFS technology and eliminates the concept of master-slave nodes. It can sense the noise floor of the frequency point in real time, select the frequency point with the best noise floor information and switch the frequency, so as to dynamically select the optimal working frequency point to minimize the impact of electromagnetic interference;

[0043] (2) This solution can analyze the collected information and use the frequency with the least interference and the best channel quality for communication. It can also select the best frequency for communication according to the actual situation, realizing dynamic adjustment of the frequency selection strategy, thereby ensuring the continuity and stability of communication while taking into account the transmission efficiency.

[0044] (3) This solution does not distinguish between master and slave roles, i.e. master nodes and slave nodes. All nodes can quickly sense interference and select the best frequency point for frequency switching without waiting for the decision of the central node, thus maximizing the use of bandwidth.

[0045] (4) This solution is based on the TDMA system, which enables each mobile station to transmit signals only in the designated time slot within each frame. Therefore, under the conditions of timing and synchronization, the base station can receive the signals of each mobile station in each time slot without interfering with each other, thereby avoiding affecting the execution of different operations and ensuring the normal operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0047] Figure 1 It is a flowchart of the present invention.

[0048] Figure 2 It is a schematic diagram of the time slot ID and processing events of the present invention.

[0049] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0052] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of the features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0053] See also Figure 1 , Figure 2 A method for realizing dynamic frequency selection of a centerless ad hoc network based on a TDMA system comprises the following steps:

[0054] S1. Through the TDMA system, time is divided into periodic frames, and the frames are divided into several time slots, so that each mobile station can only transmit signals in the specified time slots in each frame;

[0055] S2. Bind different operations to different time slots to avoid affecting the execution of different operations;

[0056] S3. After the node is powered on, networking is performed according to the frequency points within the frequency band;

[0057] S4. After the network is successfully established, scan the frequency points and save the background noise information of the frequency points;

[0058] S5. When the background noise of the current frequency is abnormal, find the frequency with the best background noise information and switch the frequency.

[0059] TDMA system means that on a broadband wireless carrier, time is divided into periodic frames, and each frame is divided into several time slots. The frames or time slots do not overlap each other. Each time slot is a communication channel allocated to one user. According to certain time slot allocation principles, the system enables each mobile station to transmit signals (burst signals) to the base station only in the designated time slot in each frame. Under the conditions of timing and synchronization, the base station can receive the signals of each mobile station in each time slot without interfering with each other.

[0060] Further, step S3 includes the following steps:

[0061] S31, after the node is powered on, first traverse all frequency points within the frequency band;

[0062] S32. If other nodes or subnets are found on one of the frequency points, the network is formed at a fixed frequency;

[0063] S33. If no other nodes or subnets are found, continue frequency hopping to search for valid signals.

[0064] The effective signals are those whose information is relatively regular and can be interpreted.

[0065] Further, step S4 includes the following steps:

[0066] S41. After the network is successfully established, the node will periodically traverse all frequency points and record the background noise information of the frequency points;

[0067] S42, save the background noise information of all frequencies, and send the background noise information to the reference node of clock synchronization, that is, the ssid node;

[0068] S43. After the current SSID node is powered off, the network will automatically bootstrap the node with the smallest node number as the SSID node.

[0069] Among them, the SSID node is a clock-aligned node and is unique in the entire network. If there are multiple clock nodes in the entire network, the clocks of each node will be out of sync, resulting in network abnormality.

[0070] Further, step S5 includes the following steps:

[0071] S51. When a node finds that the background noise of the current frequency is abnormal, it will search for all the frequencies within the range and find the frequency with the smallest background noise based on its background noise information;

[0072] S52, selecting different frequency switching modes according to whether the node is an SSID node;

[0073] S53, after sending the frequency cutting information through the ID field for multiple frame periods, the frequency is automatically cut, and the information of the abnormal frequency point of the background noise is saved;

[0074] S54: If the system loses step after switching the frequency, the system starts from the frequency hopping process after power-on, and enters the network at a fixed frequency after detecting the networking information during the frequency hopping process.

[0075] S55. If the network is re-entered after being out of sync, it is necessary to pay attention to the abnormal frequency information. When the background noise is restored, the SSID node is informed to delete the abnormal information.

[0076] In Ad Hoc Network communications, "out-of-sync" refers to the deviation of time synchronization of nodes in the network, which causes them to fail to send or receive data correctly within the predetermined time window. Out-of-sync occurs when the local clock of a node is not synchronized with other nodes or reference clocks in the network. This may be due to the instability of the clock crystal, clock offset caused by node movement, communication delays or network congestion.

[0077] Further, when the node in step S51 is an ssid node, the frequency switching method is as follows:

[0078] S521. Collect the background noise information of all nodes and select the frequency point with the smallest background noise in the entire network. After receiving the frequency switching information of the SSID node, all other nodes will synchronously follow the frequency switching in the entire network.

[0079] Furthermore, if the node in step 1 is not an SSID node, the frequency switching method is as follows:

[0080] S522, when the SSID node receives the frequency switching information of the node, if it is determined that the frequency switching information meets the noise floor requirement of the entire network, the entire network synchronously follows the frequency switching;

[0081] S523, if not satisfied, remove the current working frequency and the frequency received from other nodes, then recalculate the noise floor, find the frequency with the best noise floor, and synchronize the frequency cutting of the whole network. Meanwhile, record the abnormal frequency and node information, and remove the frequency when selecting the best frequency later until the noise floor of the frequency is normal.

[0082] Furthermore, the calculation process of the background noise in step S523 is as follows:

[0083] S5231, all nodes periodically scan the background noise of each frequency point;

[0084] S5232, sending the background noise information of all frequencies to the SSID node via network communication;

[0085] S5233, SSID node compares the noise floor values ​​received at each frequency point, and selects the optimal frequency point according to the difference in noise floor value and the size of the optimal signal-to-noise ratio.

[0086] Furthermore, the method of selecting the optimal frequency is as follows:

[0087] If the noise floor of the current frequency differs from the best noise floor among all the frequencies by a certain value, and the optimal signal-to-noise ratio of the current frequency is less than a certain value, it is necessary to switch to the best frequency, that is, the frequency with the best noise floor;

[0088] If the bit error rate of the current frequency is greater than a certain value and the best frequency has a better noise floor than the current frequency, the frequency needs to be cut.

[0089] In this embodiment, when the noise floor of the current frequency differs from the best noise floor among the frequencies by at least 10db, and the optimal signal-to-noise ratio is less than 16, the frequency is switched accordingly (under normal conditions, if the optimal signal-to-noise ratio is less than about 16, it can be considered that the anti-interference ability is poor, so it is necessary to switch to a better frequency; optimal signal-to-noise ratio: the best signal-to-noise ratio among the nodes within the synchronization range). Or when the bit error is greater than 20, and the noise floor of the best node is more than 1db better than that of the current node. (When a bit error occurs, it is considered that the current frequency has generated interference, so as long as the noise floor of any frequency is better than the current frequency, it can be switched)

[0090] Furthermore, the process of step S2 is as follows:

[0091] S21, allocating time slot IDs according to different processing events;

[0092] S22, the corresponding event operation must be performed in the current time slot, and the execution order must be executed from the beginning in the order of the time slot ID;

[0093] S23. If the last processed event times out, resulting in missing the current time slot, the missed event is stopped, and further execution of the event is stopped, and the corresponding event is continued to be executed in the next cycle.

[0094] Timeslot ID is a concept used in Time Division Multiple Access (TDMA) communication systems to identify specific time periods divided in the time domain. In a TDMA system, the entire spectrum is divided into multiple timeslots, each of which can be used to transmit one or more data packets, frames, or information units. Timeslot ID is a unique identifier assigned to each timeslot. It allows devices in the system to identify and distinguish between different timeslots, so they know when to send or receive data.

[0095] It takes 3ms of idle time slots (including GAP) for the self-organizing network device to switch to the frequency point for detecting the background noise, detect the background noise, and then switch to the working frequency point. Therefore, it is necessary to first confirm whether there are enough time slots for the background noise detection operation after the network is established.

[0096] The working cycle of networking equipment is generally in ms (milliseconds), which can be generally divided into 10ms, 20ms, 30ms and other frame lengths that increase in multiples of 10. The granularity of operations such as transmission, reception and background noise detection performed by networking equipment is in units of 0.5ms.

[0097] When the system is idle, the frequency is switched, the noise floor is detected, and the frequency is switched back to the working frequency. Each operation must strictly meet the timing requirements, so the operation and time slot binding method is used here to prevent abnormalities after the interrupt is lost. Lost interrupt: All executed tasks need to be completed within the current operation granularity (0.5ms). If this time is exceeded, the execution of the next 0.5ms event will be affected.

[0098] See also Figure 2 In this embodiment, the event operation with the corresponding number must be performed in the current 0.5ms, and the execution order must be executed sequentially starting from 1. If the current 0.5ms is missed due to a timeout problem, the missed event will be stopped, and the execution of the previous event will be stopped. The corresponding event will be executed again in the next detection cycle to avoid affecting other operations.

[0099] In this embodiment, when the time slot ID is 1, it is necessary to determine whether to perform subsequent frequency cutting operations (because it is necessary to reserve a time slot to detect the noise floor of the current working frequency, the remaining frequencies are detected once every frame length period); when frequency cutting is required, when the time slot ID is 2, switch to the new frequency and configure VGA; when the time slot ID is 3, it is necessary to turn off frequency cutting; when the time slot ID is 4, it is necessary to wait for 0.5ms to detect the noise floor of the frequency; when the time slot ID is 4, it is necessary to switch back to the working frequency and configure VGA; when the time slot ID is 6, it is necessary to record the noise floor information and turn off the frequency cutting enable.

[0100] Frequency Switching Enable generally refers to a function that allows the system to dynamically change the operating frequency of wireless devices based on specific conditions or requirements during operation. This function is essential to avoid interference, improve spectrum utilization, and optimize communication performance.

[0101] It can be seen from the above embodiments that the present application aims to fundamentally solve the problem of decreased communication effect caused by interference of working frequency points in self-organizing network communication, and ensure that the communication process is always in the best state by combining frequency hopping and dynamic spectrum optimization strategy. During the construction and operation stage of the self-organizing network, the present invention cleverly utilizes the idle time slots of the system to implement an efficient and periodic frequency band scanning and intelligent screening mechanism to achieve a comprehensive evaluation and optimization of all potential working frequency points within the entire frequency band. During the scanning process, the system will collect and process key information such as the signal strength and noise level of each frequency point in real time.

[0102] On this basis, the present invention further removes the centralized strategy, that is, the roles of all nodes are consistent, and the loss of any node will not affect the dynamic frequency selection function. The system will intelligently select the optimal working frequency for switching based on the current communication needs, network environment changes, and real-time evaluation results of candidate frequencies. This process not only ensures that the working frequency is always kept in the best state, effectively resists the impact of external interference on communication effects, but also greatly improves the flexibility and robustness of the communication system.

[0103] The above description is only an exemplary embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for realizing dynamic frequency selection in a centerless ad hoc network based on a TDMA system, characterized in that: The following steps are involved: S1. Through the TDMA system, time is divided into periodic frames, and the frames are divided into several time slots, so that each mobile station can only transmit signals in the specified time slots in each frame; S2. Bind different operations to different time slots to avoid affecting the execution of different operations; S3. After the node is powered on, networking is performed according to the frequency points within the frequency band; S4. After the network is successfully established, scan the frequency points and save the background noise information of the frequency points; S5. When the background noise of the current frequency is abnormal, find the frequency with the best background noise information and switch the frequency.

2. The method for realizing dynamic frequency selection in a centerless ad hoc network based on a TDMA system according to claim 1, characterized in that: The step S3 comprises the following steps: S31, after the node is powered on, first traverse all frequency points within the frequency band; S32. If other nodes or subnets are found on one of the frequency points, the network is formed at a fixed frequency; S33. If no other nodes or subnets are found, continue frequency hopping to search for valid signals.

3. The method for realizing dynamic frequency selection in a centerless ad hoc network based on a TDMA system according to claim 1, characterized in that: The step S4 comprises the following steps: S41. After the network is successfully established, the node will periodically traverse all frequency points and record the background noise information of the frequency points; S42, save the background noise information of all frequencies, and send the background noise information to the reference node of clock synchronization, that is, the ssid node; S43. After the current SSID node is powered off, the network will automatically bootstrap the node with the smallest node number as the SSID node.

4. The method for realizing dynamic frequency selection in a centerless ad hoc network based on a TDMA system according to claim 1, characterized in that: The step S5 comprises the following steps: S51. When a node finds that the background noise of the current frequency is abnormal, it will search for all the frequencies within the range and find the frequency with the smallest background noise based on its background noise information; S52, selecting different frequency switching modes according to whether the node is an SSID node; S53, after sending the frequency cutting information through the ID field for multiple frame periods, the frequency is automatically cut, and the information of the abnormal frequency point of the background noise is saved; S54, if the step is lost after the frequency switching, the frequency hopping process after power-on is started, and the network is accessed at a fixed frequency after the networking information is detected during the frequency hopping process; S55. If the network is re-entered after being out of sync, it is necessary to pay attention to the abnormal frequency information. When the background noise is restored, the SSI D node is informed to delete the abnormal information.

5. The method for realizing dynamic frequency selection of centerless ad hoc network based on TDMA system according to claim 4, characterized in that: When the node in step S51 is an ssi d node, the frequency switching method is as follows: S521. Collect the background noise information of all nodes and select the frequency point with the smallest background noise in the entire network. After receiving the frequency switching information of the SSID node, all other nodes will synchronously follow the frequency switching in the entire network.

6. The method for realizing dynamic frequency selection in a centerless ad hoc network based on a TDMA system according to claim 4, characterized in that: If the node in step 1 is not an SSI d node, the frequency switching method is as follows: S522, when the SSID node receives the frequency switching information of the node, if it is determined that the frequency switching information meets the noise floor requirement of the entire network, the entire network synchronously follows the frequency switching; S523, if not satisfied, remove the current working frequency and the frequency received from other nodes, then recalculate the noise floor, find the frequency with the best noise floor, and synchronize the frequency cutting of the whole network. Meanwhile, record the abnormal frequency and node information, and remove the frequency when selecting the best frequency later until the noise floor of the frequency is normal.

7. The method for realizing dynamic frequency selection in a centerless ad hoc network based on a TDMA system according to claim 6, characterized in that: The calculation process of the background noise in step S523 is as follows: S5231, all nodes periodically scan the background noise of each frequency point; S5232, sending the background noise information of all frequencies to the SSI D node via network communication; S5233, the ssi d node compares the noise floor values ​​received at each frequency point, and selects the optimal frequency point based on the difference in noise floor values ​​and the size of the optimal signal-to-noise ratio.

8. The method for realizing dynamic frequency selection in a centerless ad hoc network based on a TDMA system according to claim 7, characterized in that: The method for selecting the optimal frequency is as follows: If the noise floor of the current frequency differs from the best noise floor among all the frequencies by a certain value, and the optimal signal-to-noise ratio of the current frequency is less than a certain value, it is necessary to switch to the best frequency, that is, the frequency with the best noise floor; If the bit error rate of the current frequency is greater than a certain value and the best frequency has a better noise floor than the current frequency, the frequency needs to be cut.

9. The method for realizing dynamic frequency selection in a centerless ad hoc network based on a TDMA system according to claim 1, characterized in that: The process of step S2 is as follows: S21, allocating time slot IDs according to different processing events; S22, the corresponding event operation must be performed in the current time slot, and the execution order must be executed from the beginning in the order of the time slot ID; S23. If the last event processed times out, resulting in missing the current time slot, the missed event is stopped, and further execution of the event is stopped, and the corresponding event is continued to be executed in the next cycle.

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