CN117998458A - Wireless body area network MAC method based on priority scheduling - Google Patents
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Abstract
The invention discloses a wireless body area network MAC method based on priority scheduling, which can divide data into three types according to the characteristics of different data generated in the practical application of the wireless body area network: emergency data, periodic data, general data. Wherein the emergency data comprises random data, such data typically being associated with vital sign abnormality reports or medical emergency situations, such as arrhythmia emergency alert signals, or other medical conditions requiring immediate response. Periodic data includes periodic collection from sensors. The invention improves the superframe structure, simplifies the control difficulty, reduces the control overhead, makes the superframe more easily adapt to network changes, and ensures more flexible and reliable data transmission; optimizing the sensor node category and the sensor node priority setting strategy, and effectively relieving the collision problem during data transmission; by optimizing the time slot allocation strategy, the duty ratio of the sensor node is reduced, the energy loss is reduced, and the overall network performance and the system service quality of the wireless body area network are improved.
Description
Technical Field
The invention relates to the technical field of wireless communication, in particular to a wireless body area network efficient MAC protocol based on priority scheduling.
Background
A wireless body area network (Wireless BodyArea Network, WBAN) is an advanced wireless communication technology designed specifically for personal health monitoring and data transmission. The system consists of a coordinator and a plurality of wearable or implantable sensor nodes, wherein the sensor nodes can collect various physiological data such as heart rate, blood pressure, body temperature and the like, and the collected data is forwarded to the coordinator for further analysis and diagnosis by doctors. The main advantages of WBAN include its low interference with user activity, high data accuracy and real-time, and great contribution to personal health management and telemedicine. In addition, WBAN also exhibits a broad application potential in the fields of sports training, military monitoring, entertainment, and the like. Through wireless technology, the WBAN provides a flexible, efficient and continuous health monitoring system for users.
In wireless body area networks, the Medium Access Control (MAC) protocol is located between the physical layer and the network layer, which has a decisive role in the overall performance of the WBAN. As a key technology in wireless body area networks, the MAC protocol is responsible for scheduling and controlling the transmission of data packets in the network, ensuring reliable and efficient communication. The wireless body area network data transmission method and the wireless body area network data transmission system ensure the reliability and the high efficiency of the data transmission through the functions of managing the data transmission time, solving the data packet conflict, distributing the network resources and the like. Thus, the MAC protocol is critical to improve the overall performance and user experience of the WBAN.
The proposal of the IEEE 802.15.6 standard has a significant impact on the study of MAC protocols in wireless body area networks. The standard is designed specifically for WBAN, providing a comprehensive set of communication specifications, including detailed specifications for the MAC protocol. These regulations take into account WBAN specific requirements such as low power consumption, high data transmission efficiency, reliability and support for emergency medical data transmission. The formulation of the IEEE 802.15.6 standard provides a clear framework and direction for research and development of the MAC protocol, which promotes the development and application of WBAN technology.
Nevertheless, existing wireless body area network MAC protocols still suffer from a number of deficiencies. First, these protocols lack flexibility in handling high-priority and low-priority data streams, making efficient resource allocation difficult. For example, emergency medical data and conventional health monitoring data are often treated equally, resulting in unnecessary delays that may be encountered in emergency data transmission. Second, existing protocols are not generally optimized for node energy consumption, resulting in reduced device battery life, frequent battery replacement or charging is particularly inconvenient in telemedicine and long-term health monitoring scenarios. Furthermore, conventional MAC protocols fail to accommodate network loading and environmental dynamics, which is particularly evident in multi-user, high-density deployment environments. Therefore, a new MAC protocol is urgently needed, which can effectively manage the energy consumption of the device while ensuring the timely transmission of the emergency data, and adapt to the change of the network conditions so as to improve the overall performance of the WBAN system.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a wireless body area network efficient MAC protocol based on priority scheduling, which aims to improve the performance of the wireless body area network in terms of throughput, energy consumption, time delay and the like, and fully ensures the real-time performance and reliability of the transmission of emergency data.
The wireless body area network MAC method based on priority scheduling comprises the following steps:
(1) Sensor node classification
According to the characteristic that different data are generated in the practical application of the wireless body area network, the data can be divided into three types: emergency data, periodic data, general data. Wherein the emergency data comprises primarily random data, such data typically being associated with vital sign abnormality reports or medical emergency situations, such as arrhythmia emergency alert signals, or other medical conditions requiring immediate response. The periodic data includes stable medical metrics such as heart beat, blood pressure, etc. collected from the sensors on a periodic basis. Common data refers to non-urgent information that is less time sensitive, such data mainly including daily health monitoring data such as activity tracking, sleep quality recording, and regular health status updates that do not require immediate feedback.
Firstly, classifying sensor nodes according to data types collected by sensors, wherein emergency data, periodic data and common data correspond to A, B, C types respectively, the type A sensor node has highest emergency degree, the type A sensor node is ensured to timely and reliably transmit data to a coordinator, the type B sensor node is inferior in type C sensor node, the type C sensor node has delay tolerance, the reliability requirement is lower, and a certain amount of data packet loss can be accepted.
Because the wireless body area network is applied to the field of medical health monitoring, when the physical health of a patient has sudden conditions, such as heart beat acceleration, blood pressure rise and the like, the data are ensured to be timely and accurately transmitted to the coordinator so as to avoid misleading doctors to carry out wrong evaluation on the physical state of the patient and cause serious consequences. In order to ensure reliable transmission of data under emergency, the invention sets different thresholds for the sensor nodes according to the data types collected by the sensor nodes, such as pulse low threshold of 50bpm, pulse high threshold of 120bpm, respiratory rate low threshold of 11 times/min, respiratory high threshold of 20 times/min and the like in general, and can also specifically adjust the high and low thresholds of the sensor nodes according to the physical condition of a patient. If the data collected by the sensor node is higher than the high threshold value or lower than the low threshold value of the sensor node, the physical condition of the patient is indicated, the emergency degree of the sensor node is improved by one grade, and the B type is adjusted to the A type or the C type is adjusted to the B type, so that the reliable transmission of the data is ensured.
(2) Superframe structure
The IEEE 802.15.6 standard divides the superframe structure into 9 phases, which are respectively a beacon phase 1, an exclusive access phase 1, a random access phase 1, a management access phase 1, an exclusive access phase 2, a random access phase 2, a management access phase 2, a beacon phase 2 and a contention access phase, wherein the access phases are staggered, and the control difficulty of the protocol is increased.
The invention improves the super frame structure of IEEE 802.15.6 to 4 stages, namely a beacon stage (B), a contention access stage (CAP), a non-contention access stage (CFP) and a sleep stage (IP), wherein the beacon stage is responsible for clock synchronization, network initialization and other functions. In the contention access stage, the class-C sensor node preemptively uses a contention mode to preempt channels and send data, and in the non-contention access stage, the coordinator allocates time slots to class-A and class-B sensor nodes to ensure that the data is transmitted without delay. In the sleep stage, the node enters a sleep state, reducing energy consumption. In each stage, if there is no sensor node of the corresponding class to transmit data, the stage length may be set to 0.
(3) Priority setting of sensor nodes
For the same kind of sensor nodes, the higher the priority, the greater the opportunity to obtain the transmission data. The invention fully considers the data type, sampling rate, data packet length and buffer occupation condition of the sensor node to dynamically adjust the priority of the sensor node, wherein the priority of the sensor node is calculated by the following formula:
Wherein Priority represents the sensor node Priority; nodeType denotes a sensor node class, whose possible values are A, B, C for priorities 7, 6, 5 in IEEE 802.15.6, respectively; BOS represents the occupation condition of the buffer zone of the sensor node, and is calculated by the ratio of the size of the data packet of the current buffer zone of the sensor node to the total capacity of the buffer zone, so that the higher the BOS value of the sensor node is, the higher the priority of the sensor node is; lambda t indicates the traffic generation rate of the sensor node, P size indicates the length of the data packets, and low traffic and small size data packets will cause an increase in their transmission priority in order to ensure that the network will not become congested by handling a large number of large size data packets, in emergency situations, such as medical monitoring or security systems, where timely transmission of small amounts of critical data is far more important than transmission of large amounts of non-urgent data.
(4) Time slot allocation strategy
For the class-C sensor node, the CSMA/CA mechanism is adopted to compete for accessing the channel in the competition access stage, the higher the priority of the sensor node is, the smaller the corresponding competition window is, and the higher the probability of success of competition is. For the A-type and B-type sensor nodes, the distributed time slots are sequentially obtained according to the descending order of the priorities of the sensor nodes based on a TDMA mechanism in a non-competitive access stage, if no sensor node needs to send data, the sleep stage is entered, the sensor node enters a sleep state, and the energy consumption is reduced.
The specific implementation method of the wireless body area network high-efficiency MAC protocol based on priority scheduling comprises the following steps: in the beacon stage, the coordinator broadcasts a beacon frame to the sensor nodes of the wireless body area network to realize node synchronization; the sensor node collects patient data according to the sampling rate of the sensor node, analyzes whether the data is in the range of the threshold value of the sensor node, dynamically adjusts the node type, and stores the data to be transmitted into a sensor node buffer area; the sensor node which needs to send data sends a request frame to the coordinator, wherein the request frame comprises information such as the type of the sensor node, the sampling rate, the length of a data packet, the occupation condition of a buffer area and the like and is used for judging the priority by the coordinator; if the data is the data sent by the class-C sensor node, the data is directly sent after the channel is determined to be idle based on a random back-off algorithm and a collision avoidance mechanism by combining a CSMA/CA mechanism with the self priority to access the channel in the contention access stage, if the coordinator receives the data, a confirmation signal is returned to finish data transmission, and if the sensor node does not receive the confirmation signal for a long time, a retransmission mechanism is started; if the data is the data sent by the class A or class B sensor nodes, the coordinator allocates a special time slot for each sensor node in a non-competitive access stage based on a TDMA mechanism according to the priority of the sensor node, and returns an allocation result to the class A and class B sensor nodes; after receiving the return information, the class A and class B sensors enter a sleep state, and data transmission is performed when the time slot allocated is reached; and after receiving the data, the coordinator returns a confirmation signal, the sensor node receives the confirmation signal, the data transmission is completed, and the coordinator enters a sleep state until the beacon period is ended.
Compared with the prior art, the invention improves the super frame structure based on the IEEE 802.15.6MAC protocol, simplifies the control difficulty, reduces the control cost, makes the control cost more easily adapt to network changes, and ensures more flexible and reliable data transmission; optimizing the sensor node type and the sensor node priority setting strategy, distributing appointed data transmission stages for the sensor nodes of different types, effectively relieving the collision problem during data transmission, enhancing the transmission and processing capacity of emergency data and improving the reliability of the wireless body area network; by optimizing the time slot allocation strategy, the duty ratio of the sensor node is effectively reduced, and the energy loss is reduced, so that the overall network performance and the system service quality of the wireless body area network are improved.
Drawings
Fig. 1 is a topology of a wireless body area network in an embodiment of the invention
Fig. 2 is a superframe structure diagram of a wireless body area network according to an embodiment of the present invention
Fig. 3 is a flow chart of a wireless body area network efficient MAC protocol based on priority scheduling in an embodiment of the invention
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in fig. 1, the network of the embodiment of the invention adopts a star topology structure, and comprises 1 coordinator and a plurality of sensor nodes, wherein the coordinator is generally a personal portable terminal device, such as a smart watch, a smart phone and the like, which is convenient to charge, and the plurality of sensor nodes are distributed on the surface or in the body of a human body, and only a battery can be used as a power supply and the energy is difficult to supplement, such as a heart rate monitor, a blood pressure sensor, a blood sugar monitor, a body temperature sensor, a sleep monitor and the like.
Firstly, setting a threshold value and a class for each sensor node, generally, setting a heart rate monitor and a blood pressure sensor in a normal threshold value as a class B sensor node, setting a blood glucose monitor, a body temperature sensor and a sleep monitor as a class C sensor node, if the sensor node data exceeds the threshold value, improving the corresponding sensor node class, and naturally, setting the sensor node class individually according to the requirement of the physical condition of a patient, wherein the sensor node class can be adjusted to be higher if the patient has hypertension, and the diabetes patient can set the blood glucose monitor as a class B or class A sensor node.
Then, as shown in fig. 2, the superframe structure of the wireless body area network in the embodiment of the present invention is respectively a beacon stage (B), a contention access stage (CAP), a non-contention access stage (CFP), and a sleep stage (IP), where the beacon stage is responsible for clock synchronization, initializing the network, and other functions. In the contention access stage, the class-C sensor node has priority contention access channels based on a CSMA/CA mechanism in combination with the self node, and the mechanism is simple and flexible to realize, but when the network is congested, data collision is easy to cause, frequent data retransmission and loss are caused, network delay is increased, and the reliability of the wireless body area network is reduced. In the non-competitive access stage, the class A and class B sensor nodes only transmit data in the allocated time slots, and only one sensor node transmits data in each time slot, so that collision does not occur, the reliability of data transmission is ensured, but the method needs time synchronization between a coordinator and the sensor nodes, and the energy consumption is increased. The sleep stage is entered after the data transfer of the sensor node is completed until the end of the beacon period.
Fig. 3 is a specific flowchart of a wireless body area network efficient MAC protocol based on priority scheduling in an embodiment of the present invention.
Step 1: in the beacon stage, the coordinator broadcasts a beacon frame to the wireless body area network to realize node synchronization.
Step 2: the sensor node dynamically adjusts the self category according to the type of the collected data and the relation between the numerical value and the threshold value, and stores the data to be transmitted into a sensor node buffer area.
Step 3: the sensor node with data to be sent requests a request frame to be sent to the coordinator, wherein the request frame comprises information such as the category of the sensor node, the sampling rate, the length of a data packet, the occupation condition of a buffer area and the like.
Step 4: after receiving the request frame, the coordinator calculates the priority of the sensor node according to the following formula according to the information of the request frame:
The Priority represents a Priority of the sensor node, nodeType represents a class of the sensor node, possible values of A, B, C respectively correspond to priorities 7, 6 and 5 in IEEE 802.15.6, bos represents an occupation condition of a buffer area of the sensor node, the occupation condition is calculated by a ratio of a data packet size of a current buffer area of the sensor node to a total capacity of the buffer area, lambda t represents a flow generation rate of the sensor node, and P size represents a length of the data packet.
Step 5: the coordinator returns a priority calculation result to the C sensor node and allows the C sensor node to transmit data based on a CSMA/CA mechanism contention channel in a contention access stage; if the sensor nodes are the class A and the class B sensor nodes, the coordinator allocates exclusive time slots for the sensor nodes in the non-competitive access stage according to the descending order of the priorities of the sensor nodes and returns allocation results to the class A and the class B sensor nodes.
Step 6: if the sensor node is the C-type sensor node, the channel is accessed based on a CSMA/CA mechanism and combined with own priority to compete, the CSMA/CA mechanism comprises a monitoring channel, a random back-off algorithm, a collision avoidance mechanism, an acknowledgement mechanism and a retransmission mechanism, the higher the priority of the sensor node is, the smaller the competition window of the random back-off algorithm is, the higher the probability of successful node competition is, and the data transmission is effectively managed in the wireless body area network through the mechanisms so as to reduce the collision and improve the stability and the efficiency of the network.
Step 7: if the sensor node is the A-type or B-type sensor node, data is sent in a dedicated time slot of a non-competitive access stage allocated by the coordinator, and the rest of time enters a sleep state so as to reduce energy consumption.
Step 8: after the coordinator successfully receives the data, an acknowledgement frame is returned to the sender.
Step 9: and after receiving the confirmation frame returned by the coordinator, the sender of the sensor node indicates that the data transmission is finished and enters a sleep state until the beacon period is finished, and if the confirmation frame is not received for a long time, a retransmission mechanism is started.
In summary, compared with the prior art, the method of the embodiment has the following advantages and beneficial effects:
(1) The invention optimizes the super frame structure of the MAC protocol, simplifies the control difficulty, reduces the control overhead, ensures that the super frame structure can adapt to network changes, and ensures that the data transmission is more flexible.
(2) According to the invention, the sensor node type and the sensor node priority setting strategy are optimized, the designated data transmission stage is allocated for different sensor node types, so that the collision problem during data transmission is effectively relieved, the priority degree of emergency data is improved, the transmission and processing capacity of a wireless body area network to the emergency data is enhanced, the state of the sensor node is fully considered, the problem of data loss caused by overflow of a sensor node buffer area is avoided, and the reliability of data transmission is improved.
(3) The invention optimizes the time allocation strategy, effectively reduces the duty ratio of the nodes and reduces the energy loss, thereby improving the overall network performance and the system service quality of the wireless body area network.
Claims (7)
1. The wireless body area network MAC method based on priority scheduling is characterized by comprising the following steps: step 1: in the beacon stage, the coordinator broadcasts a beacon frame to the wireless body area network to realize node synchronization;
Step 2: the sensor node dynamically adjusts the self category according to the type of the collected data and the relation between the numerical value and the threshold value, and stores the data to be transmitted into a sensor node buffer area;
Step 3: a sensor node request frame with data to be sent is sent to a coordinator, and the request frame comprises sensor node types, sampling rate, data packet length and occupation condition information of a buffer area;
Step 4: after receiving the request frame, the coordinator calculates the priority of the sensor node according to the following formula according to the information of the request frame:
The Priority represents the Priority of the sensor node, nodeType represents the class of the sensor node, possible values of A, B, C respectively correspond to priorities 7, 6 and 5 in IEEE 802.15.6, BOS represents the occupation condition of a buffer zone of the sensor node, the occupation condition is calculated by the ratio of the size of a data packet of the current buffer zone of the sensor node to the total capacity of the buffer zone, lambda t represents the flow generation rate of the sensor node, and P size represents the length of the data packet;
Step 5: the coordinator returns a priority calculation result to the C sensor node and allows the C sensor node to transmit data based on a CSMA/CA mechanism contention channel in a contention access stage; if the sensor nodes are the class A and the class B sensor nodes, the coordinator allocates exclusive time slots for the sensor nodes in a non-competitive access stage according to the descending order of the priorities of the sensor nodes and returns allocation results to the class A and the class B sensor nodes;
Step 6: if the sensor node is the C-type sensor node, the CSMA/CA mechanism is based on the CSMA/CA mechanism and is combined with the priority to compete for accessing the channel, the CSMA/CA mechanism comprises a monitoring channel, a random back-off algorithm, a collision avoidance mechanism, a confirmation mechanism and a retransmission mechanism, the higher the priority of the sensor node is, the smaller the competition window of the random back-off algorithm is, the higher the probability of successful node competition is, the data transmission is effectively managed in the wireless body area network through the mechanisms, the collision is reduced, and the network stability and efficiency are improved;
step 7: if the sensor node is the A-type or B-type sensor node, transmitting data in a dedicated time slot of a non-competitive access stage allocated by the coordinator, and entering a sleep state in the rest time to reduce energy consumption;
Step 8: after the coordinator successfully receives the data, returning an acknowledgement frame to the sender;
Step 9: and after receiving the confirmation frame returned by the coordinator, the sender of the sensor node indicates that the data transmission is finished and enters a sleep state until the beacon period is finished, and if the confirmation frame is not received for a long time, a retransmission mechanism is started.
2. The wireless body area network MAC method based on priority scheduling according to claim 1, wherein the data are classified into three categories according to characteristics of different data generated in the wireless body area network practical application: emergency data, periodic data, general data;
The sensor nodes are classified according to the data types collected by the sensors, and emergency data, periodic data and common data correspond to A, B, C types respectively, wherein the type A sensor node has highest emergency degree, the sensor nodes are ensured to transmit data to the coordinator, the type B sensor node is inferior, the type C sensor node has delay tolerance and lower reliability requirement, and a certain amount of data packets are received to be lost;
Setting different thresholds for the sensor nodes according to the types of data acquired by the sensor nodes; if the data collected by the sensor node is higher than the high threshold value or lower than the low threshold value of the sensor node, the physical condition of the patient is indicated, the emergency degree of the sensor node is improved by one level, and the data is adjusted to be A type or B type from B type or C type so as to ensure the reliable transmission of the data.
3. The wireless body area network MAC method based on priority scheduling of claim 1, wherein the super frame structure of IEEE 802.15.6 is improved, and is reorganized into 4 phases, namely a beacon phase B, a contention access phase CAP, a non-contention access phase CFP, and a sleep phase IP, wherein the beacon phase is responsible for clock synchronization, and initializing the network; in the contention access stage, the class-C sensor node preemptively uses a contention mode to preempt channels and send data, and in the non-contention access stage, the coordinator allocates time slots to class-A and class-B sensor nodes to ensure that the data is transmitted without delay; in the sleep stage, the node enters a sleep state, so that energy consumption is reduced; in each stage, if no sensor node of the corresponding class needs to transmit data, the stage length is set to 0.
4. The wireless body area network MAC method based on priority scheduling of claim 1, wherein for similar sensor nodes, the higher their priority, the greater the chance of getting transmitted data; the priority of the sensor node is dynamically adjusted by fully considering the data type, sampling rate, data packet length and occupation condition of the buffer zone of the sensor node, and the priority of the sensor node is calculated by the following formula:
Wherein Priority represents the sensor node Priority; nodeType denotes a sensor node class, whose possible values are A, B, C for priorities 7, 6, 5 in IEEE 802.15.6, respectively; BOS represents the occupation condition of the buffer zone of the sensor node, and is calculated by the ratio of the size of the data packet of the current buffer zone of the sensor node to the total capacity of the buffer zone, so as to avoid data loss caused by overflow of the buffer zone of the sensor node, and the higher the BOS value of the sensor node, the higher the priority of the BOS value; lambda t indicates the traffic generation rate of the sensor node, P size indicates the length of the data packets, and low traffic and small size data packets will cause an increase in their transmission priority in order to ensure that the network will not become congested by handling a large number of large size data packets, in emergency situations, such as medical monitoring or security systems, where timely transmission of small amounts of critical data is far more important than transmission of large amounts of non-urgent data.
5. The wireless body area network MAC method based on priority scheduling according to claim 1, wherein, for a class C sensor node, a CSMA/CA mechanism is adopted to contend for access to a channel in a contention access phase, the higher the priority of the sensor node, the smaller the corresponding contention window, and the greater the probability of contention success; for the sensor nodes of the A type and the B type, the allocated time slots are sequentially obtained according to the descending order of the priorities of the sensor nodes based on a TDMA mechanism in a non-competitive access stage, if no sensor node needs to send data, the sleep stage is entered, the sensor node enters a sleep state, and the energy consumption is reduced.
6. The wireless body area network MAC method based on priority scheduling of claim 1, wherein in a beacon phase, the coordinator broadcasts a beacon frame to sensor nodes of the wireless body area network to realize node synchronization; the sensor node collects patient data according to the sampling rate of the sensor node, analyzes whether the data is in the range of the threshold value of the sensor node, dynamically adjusts the node type, and stores the data to be transmitted into a sensor node buffer area; the sensor node which needs to send data sends a request frame to the coordinator, wherein the request frame comprises the category of the sensor node, the sampling rate, the length of a data packet and the occupation condition of a buffer area and is used for judging the priority by the coordinator; if the data is the data sent by the class-C sensor node, the data is directly sent after the channel is determined to be idle based on a random back-off algorithm and a collision avoidance mechanism by combining a CSMA/CA mechanism with the self priority to access the channel in the contention access stage, if the coordinator receives the data, a confirmation signal is returned to finish data transmission, and if the sensor node does not receive the confirmation signal for a long time, a retransmission mechanism is started; if the data is the data sent by the sensor node of the class A or the class B, the coordinator allocates a special time slot for each sensor node in a non-competitive access stage based on a TDMA mechanism according to the priority of the sensor node, and returns an allocation result to the sensor node of the class A and the class B; after receiving the return information, the class A and class B sensors enter a sleep state, and data transmission is performed when the time slot allocated is reached; and after receiving the data, the coordinator returns a confirmation signal, the sensor node receives the confirmation signal, the data transmission is completed, and the coordinator enters a sleep state until the beacon period is ended.
7. The priority scheduling based wireless body area network MAC method as claimed in claim 2, wherein the emergency data comprises random data, such data being related to vital sign abnormality reports or medical emergencies, arrhythmia emergency alert signals, or other medical conditions requiring immediate response; the periodic data comprises medical indexes of heartbeat and stable blood pressure collected from the sensor periodically; common data refers to non-urgent information that is less time sensitive, including daily health monitoring data, activity tracking, sleep quality recording, and regular health updates that do not require immediate feedback.
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