A cross-layer optimized data transmission scheduling method for body area networks

Abstract

The present invention discloses a cross-layer optimized body area network data transmission scheduling method, comprising: setting message transmission power according to the category of data messages uploaded by sensors; wherein the categories of the data messages include: periodic data, event-triggered data and emergency data; the transmission power of the emergency data is greater than the transmission power of the periodic data and the transmission power of the event-triggered data; the sensor uploads the corresponding message to a central node according to the set transmission power; the central node monitors the residual energy value of each sensor node in the body area network in real time, and determines whether each sensor node has a potential relay node; if a sensor node has a potential relay node, the optimal relay node is selected from the potential relay nodes as the collaborative node of the sensor; the sensor node sends the message to its corresponding collaborative node, and the collaborative node forwards the received message to the central node.

Description

Technical Field

[0001] The present invention belongs to the field of communication technology, and in particular relates to a cross-layer optimized body area network data transmission scheduling method. Background Art

[0002] Body area networks (BANs) have experienced rapid growth in recent years, providing a highly effective means for monitoring potential illnesses, health status, and the condition of athletes. However, due to the wearable nature of BAN sensors, they are typically miniaturized, resulting in very limited battery capacity. The failure of a single node can significantly impact network performance, and frequent battery resets can also degrade user experience. Maximizing network lifespan while ensuring quality of service has become a critical technical challenge that needs to be addressed. Summary of the Invention

[0003] The purpose of the present invention is to provide a cross-layer optimized body area network data transmission scheduling method, which can effectively improve the comprehensive energy efficiency of sensor nodes and increase the network life span.

[0004] The technical solution provided by the present invention is:

[0005] A cross-layer optimized body area network data transmission scheduling method, comprising:

[0006] Set the message transmission power according to the type of data message uploaded by the sensor;

[0007] The data message categories include: periodic data, event-triggered data, and emergency data; the transmission power of the emergency data is greater than the transmission power of the periodic data and the transmission power of the event-triggered data;

[0008] The sensor uploads the corresponding message to the central node according to the set transmission power;

[0009] The central node monitors the remaining energy value of each sensor node in the body area network in real time and determines whether each sensor node has a potential relay node; if a sensor node has a potential relay node, the central node selects the best relay node from the potential relay nodes as the cooperative node of the sensor;

[0010] The sensor node sends a message to its corresponding cooperation node, and the cooperation node forwards the received message to the central node.

[0011] Preferably, the transmission power of the emergency data is set to the maximum data transmission power.

[0012] Preferably, the transmission power of the periodic data and event-triggered data is set as the reference data transmission power;

[0013] The reference data transmission power is calculated using the following formula:

[0014]

[0015] Where R is the data transmission rate, B is the noise bandwidth, and P i is the data transmission power of the sensor node, γ ci P is the signal-to-noise ratio of the message sent by the central node received by the sensor node, c is the data transmission power of the central node, L i is the length of the data message to be uploaded by the sensor node, and Φ is the expected minimum correct reception rate of the message.

[0016] Preferably, the cross-layer optimized body area network data transmission scheduling method further includes: if the confirmation message received by the sensor node does not contain confirmation information for its own uploaded message, determining whether the message needs to be retransmitted by the following method:

[0017] If the message type is event-triggered data or urgent data, the message needs to be retransmitted;

[0018] If the message type is periodic data, calculate the weight of the monitoring value in the message if Greater than the weight threshold The message needs to be retransmitted;

[0019] in:

[0020]

[0021] Where, ψ is the deviation of the monitoring value, v min and m max are the maximum and minimum values ​​of the normal range of monitoring data, respectively, v δ is the deviation threshold, is the successful reception rate of the first M periodic data messages uploaded by the sensor, λ1 and λ2 are the weights of the deviation and reception rate, and λ1+λ2=1.

[0022] Preferably, if the message type is periodic data, the transmission power when the message is retransmitted for the tth time is set to:

[0023]

[0024] in, is the sensor node n i The benchmark data transmission power, is the basic step size of power adjustment, P max is the maximum data transmission power.

[0025] Preferably, if the message type is event-triggered data or emergency data, the transmission power is set to:

[0026]

[0027] in, is the sensor node n i The benchmark data transmission power, is the basic step size of power adjustment, P max is the maximum data transmission power, θ is the weight associated with the message category, ∈(0, 1).

[0028] Preferably, the method for determining whether each sensor node has a potential relay node is:

[0029] The central node calculates the sensor node n i The expected survival time T i , n i Sensor node n j When acting as a relay node, relay node n j The survival time T′ j , and n i With n j After relay collaboration i Survival time T ij ;

[0030] If there is a relay node n j Satisfy T′ j >T i , and T ij Greater than T i , then n j n i Potential relay nodes;

[0031] in:

[0032]

[0033]

[0034]

[0035] Where, E i is the sensor node n i The remaining energy value, L i is the sensor node n i The length of the data packet to be uploaded, R is the data transmission rate, is the benchmark data transmission power, E j is the sensor node nj The remaining energy value, L j n j The length of the data packet to be uploaded, H is the length of the data packet that has been uploaded. j As a set of sensor nodes that forward messages in the cooperative node, L k is the sensor node n in H k The periodic data message length, P r is the data receiving power of the sensor node; Sensor n i To n j The transmission power required to achieve the desired minimum correct message reception rate Φ when sending data.

[0036] Preferably, the optimal relay node is selected by the following judgment conditions:

[0037]

[0038] Among them, T is Sensor n s Acts as a relay node to forward n i The message of sensor n i The expected survival time, T s is the sensor node n s Acts as a relay node to forward n i The message of sensor n s The expected survival time, G i Represents the set of potential relay nodes.

[0039] Preferably, the central node divides the superframe structure into a beacon period, a contention-free period, an acknowledgement period, and a contention access period;

[0040] Wherein, the contention-free period is divided into a plurality of time slots;

[0041] During the beacon period, the central node broadcasts a beacon message, which includes the duration of each period in the current superframe structure and the time slot allocated to the sensor node in the contention access period;

[0042] The sensor node uploads periodic data messages to the central node in the allocated time slot;

[0043] During the confirmation period, the central node broadcasts a confirmation message;

[0044] The sensor node uploads event-triggered data messages, emergency data messages, and data messages that need to be retransmitted during the contention access period.

[0045] The beneficial effects of the present invention are:

[0046] The cross-layer optimized body area network data transmission scheduling method provided by the present invention adaptively adjusts the transmission power of sensor nodes based on the message type, effectively improving the survival time of sensor nodes while ensuring the differentiated transmission quality requirements of heterogeneous data; and further improves the network survival time and the overall network throughput through point-to-point collaborative transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a flow chart of the cross-layer optimized body area network data transmission scheduling method according to the present invention.

[0048] Figure 2 Schematic diagram of the network structure in an embodiment of the present invention.

[0049] Figure 3 Schematic diagram of the superframe division structure of the present invention.

[0050] Figure 4 This is a schematic diagram of data retransmission according to the present invention.

[0051] Figure 5 This is a schematic diagram of the point-to-point collaborative transmission described in the present invention. DETAILED DESCRIPTION

[0052] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0053] like Figure 1 As shown, the present invention provides a cross-layer optimized body area network data transmission scheduling method, which improves energy efficiency and sensor node survival time on the basis of ensuring data transmission quality through adaptive power adjustment of sensor nodes in the network. The central node monitors the energy distribution and changes in the network and allocates potential collaborative relay nodes to low-energy sensor nodes, further improving the network survival time. The specific implementation process is as follows.

[0054] S110: The central node divides the superframe and allocates time slots

[0055] like Figure 2 As shown, the network of this embodiment includes a central node and three sensor nodes n1, n2 and n3, which respectively collect body temperature information, heart rate information and body surface humidity information. The central node is responsible for the division of superframe structure and the allocation of time slot resources. Figure 3As shown, the superframe structure is divided into a beacon period (BP), a contention-free period (CFP), an acknowledgment period (AP) and a contention access period (CBP), wherein the CFP period is further divided into multiple time slots based on the TDMA mechanism, and the BP and AP periods are both occupied by the central node separately. The sensor nodes compete for channels for data communication based on the CSMA / CD mechanism during the CBP period.

[0056] The heterogeneous data (messages) uploaded by the sensor nodes include three categories: periodic data, event-triggered data, and emergency data.

[0057] Among them, periodic data is data uploaded according to a fixed cycle, and event-triggered data or emergency data is classified and triggered by the application according to business needs.

[0058] In this embodiment, event-triggered data refers to: a body temperature exceeding 39°C or below 35°C, a heart rate below 50°C or above 110°C, and a body surface humidity exceeding 75°C. Emergency data refers to: a body temperature exceeding 40°C or below 34°C, and a heart rate below 40°C or above 120°C. Event-triggered data and emergency data messages must not be triggered repeatedly within ten minutes.

[0059] The sensor node uploads periodic data in the time slot allocated to itself during the CFP period, and uploads event-triggered data and emergency data during the CBP period.

[0060] During the BP period, the central node broadcasts a beacon message that includes the duration of each period in the current superframe and the sensor node to which each time slot in the CFP period is assigned. In this embodiment, the central node assigns the first, second, and third time slots to n1, n2, and n3, respectively.

[0061] During the AP period, the central node broadcasts a confirmation message to confirm the message received during the CFP period. Based on the confirmation message, the sensor can determine whether the message uploaded during the CFP period is successfully received by the central node.

[0062] S120, the sensor evaluates the channel status and calculates the reference transmission power

[0063] When the sensors n1, n2 and n3 receive the beacon message broadcast by the central node during the BP period, they detect the signal-to-noise ratio γ of the received signal. ci The value of , and after taking the derivative of the following formula, use Newton's bisection method to find the power corresponding to the zero value As a reference transmission power;

[0064]

[0065] Among them, R, B and Pi are the data transmission rate, noise bandwidth and data transmission power of the central node, L i is the length of the data message that the sensor wants the node to upload, P c is the data transmission power of the central node, Φ is the expected minimum correct reception rate of the message, and in this embodiment, Φ is set to 0.98.

[0066] S130, sensor adjusts transmission power based on data type

[0067] Urgent data has the highest priority, and the initial transmission power (non-retransmission) is set to the maximum transmission power P max =0.1mW;

[0068] The initial power of event-triggered data and periodic data is set to the calculated baseline transmission power.

[0069] S140: When a message is lost, the sensor evaluates whether retransmission is required.

[0070] If the confirmation message received by the sensor node does not contain confirmation information for its own uploaded message, the message is lost and it is necessary to evaluate whether the message needs to be retransmitted.

[0071] If the message type is event-triggered data or urgent data, the message needs to be retransmitted.

[0072] For periodic data, according to the pre-set reasonable range [v min , m max ] (In this embodiment, the reasonable ranges of body temperature, heart rate and body surface humidity are [35,37], [60,100] and [40,80] respectively) and the actual value v are used to calculate the deviation ψ of the data.

[0073]

[0074] Among them, v δ is a preset deviation threshold;

[0075] Further weighting of data Perform calculations,

[0076]

[0077] Where, is the successful reception rate of the first M periodic messages uploaded by the sensor, λ1 and λ2 are the weights of the deviation and acceptance rate, λ1+λ2=1; when Greater than the preset weight threshold When the message is lost, it will be re-uploaded during the CBP period. Otherwise, no processing will be done on the lost message.

[0078] In this embodiment, for three sensors, v δ are 1, 10 and 5 respectively; M is set to 10 frames, λ1 and λ2 are both 0.5, Both are 0.3. Figure 4 As shown in the figure, the three sensors all uploaded a data packet in the time slot corresponding to the CFP of the current frame. The body temperature value uploaded by n1 is 37.2, the heart rate value uploaded by n2 is 110, and the humidity value uploaded by n3 is 70. Among them, the packets uploaded by n1 and n2 are lost, while the packet uploaded by n3 is correctly received by the central node. The confirmation messages received by n1 and n2 from the AP do not contain confirmation information for their own data, so they need to evaluate whether to retransmit the data. The data weight calculated by n1 is 0.1, so no data retransmission is performed. The weight calculated by n2 is 0.5, so the data needs to be retransmitted and the data is re-uploaded in the CBP stage.

[0079] S150, the sensor adjusts the transmission power when retransmitting data

[0080] For periodic data, the power used during the t-th retransmission is:

[0081]

[0082] For event-triggered data and urgent data, the power used during the tth retransmission is:

[0083]

[0084] in, is the benchmark data transmission power, is the basic step size of power adjustment, P max is the maximum data transmission power, θ is the weight associated with the message category. If the message category is event-triggered data, θ∈(0, 1) is the weight associated with the message category, which is set by the application based on the category and importance of the message.

[0085] In this embodiment, Set to / 10; such as Figure 4 As shown, n2 retransmits periodic data with a weight of 0.5 in the CBP phase, and the power used is For n3, the value of θ is 1, and the event-triggered data generated in the CBP phase, the power used by n3 when retransmitting after data loss is

[0086] S160, the central node formulates and adjusts the collaborative transmission strategy

[0087] The uploaded message of the sensor node includes its own residual energy value. The central node calculates the residual energy value of the sensor node n at the end of each superframe. i Expected survival time:

[0088]

[0089] Among them, E i is the sensor node n i The remaining energy value of sensor node n; At the same time, the central node will calculate j (j≠i) assists the sensor node n i Relay node n when forwarding data j Survival time:

[0090]

[0091] And the sensor node n i Lifetime after relay collaboration:

[0092]

[0093] Among them, H is the j As a set of sensor nodes that forward messages as cooperative nodes, L k is the periodic data message length of the sensor node in H, P r is the data receiving power of the sensor node;

[0094] T′ j and T ij Both are greater than T i When n j Can be used as n i The central node will select the best potential relay node as n i The optimal relay node judgment condition is:

[0095]

[0096] Among them, T is Sensor n s Acts as a relay node to forward n i The message of sensor n i The expected survival time, T s is the sensor node n s Acts as a relay node to forward n i The message of sensor n s The expected survival time, G i Represents the set of potential relay nodes.

[0097] As the energy distribution in the network changes, when the current optimal relay node consumes too much energy and is no longer the optimal option, the central node will be adjusted to a low-energy node n in real time. i Replace the new relay cooperation node.

[0098] like Figure 5 As shown, in the initial state, n1, n2 and n3 all send data directly to the central node, and n1 consumes energy faster. 12 When T′2 and T′2 are both greater than T1, the central node assigns n2 to n1 as a relay node. When n1 sends periodic data, it will reduce the transmission power and use power Send a message, By calculation After obtaining the data, n1 sends the data to n2, which then forwards it to the central node. As the energy of n2 is consumed, when n3 becomes the optimal relay node, the central nodes adjust the cooperation strategy and assign n3 to n1 as the relay node. n1 adjusts the power and sends the data to n3.

[0099] The cross-layer optimized body area network data transmission scheduling method provided by the present invention can effectively improve the comprehensive energy efficiency and survival time of sensor nodes by adaptively adjusting the data transmission power; and further improve the survival time of the network through the relay transmission of mutual cooperation between sensor nodes.

[0100] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A cross-layer optimized body area network data transmission scheduling method, characterized in that: include: Set the message transmission power according to the type of data message uploaded by the sensor; The data message categories include: periodic data, event-triggered data, and emergency data; the transmission power of the emergency data is greater than the transmission power of the periodic data and the transmission power of the event-triggered data; The sensor uploads the corresponding message to the central node according to the set transmission power; The central node monitors the remaining energy value of each sensor node in the body area network in real time and determines whether each sensor node has a potential relay node; if a sensor node has a potential relay node, the central node selects the best relay node from the potential relay nodes as the cooperative node of the sensor; The sensor node sends the message to its corresponding cooperation node, and the cooperation node forwards the received message to the central node; Setting the transmission power of the periodic data and event-triggered data as the reference data transmission power; The reference data transmission power is calculated using the following formula: Where R is the data transmission rate, B is the noise bandwidth, and P i is the data transmission power of the sensor node, γ ci P is the signal-to-noise ratio of the message sent by the central node to the sensor node. c is the data transmission power of the central node, L i is the length of the data message to be uploaded by the sensor node, Φ is the expected minimum correct reception rate of the message; The method to determine whether each sensor node has a potential relay node is: The central node calculates the sensor node n i The expected survival time T i , n i Sensor node n j When acting as a relay node, relay node n j Survival time T′ j , and n i With n j After relay collaboration i Survival time T ij ; If there is a relay node n j Satisfy T′ j >T i , and T ij Greater than T i , then n j n i Potential relay nodes; in: Where, E i is the sensor node n i The remaining energy value, L i is the sensor node n i The length of the data packet to be uploaded, R is the data transmission rate, is the benchmark data transmission power, E j is the sensor node n j The remaining energy value, L j n j The length of the data packet to be uploaded, H is the length of the data packet that has been uploaded. j As a set of sensor nodes that forward messages in the cooperative node, L k is the sensor node n in H k The periodic message length, P r is the data receiving power of the sensor node; Sensor n i To n j The transmission power required to achieve the desired minimum correct message reception rate Φ when sending data; Select the optimal relay node based on the following judgment conditions; Among them, T is Sensor n s Acts as a relay node to forward n i The message of sensor n i The expected survival time, T s is the sensor node n s Acts as a relay node to forward n i The message of sensor n s The expected survival time, G i Represents the set of potential relay nodes.

2. The cross-layer optimized body area network data transmission scheduling method according to claim 1, characterized in that: The transmission power of the emergency data is set to the maximum data transmission power.

3. The cross-layer optimized body area network data transmission scheduling method according to claim 2, characterized in that: Also includes: If the confirmation message received by the sensor node does not contain confirmation information for its own uploaded message, it determines whether the message needs to be retransmitted by the following method: If the message type is event-triggered data or urgent data, the message needs to be retransmitted; If the message type is periodic data, the weight w of the monitoring value in the message is calculated. If W is greater than the weight threshold The message needs to be retransmitted; in: Where, ψ is the deviation of the monitoring value, v min and v max are the maximum and minimum values ​​of the normal range of monitoring data, respectively, v δ is the deviation threshold, is the successful reception rate of the first M periodic data messages uploaded by the sensor, λ1 and λ2 are the weights of the deviation and reception rate, and λ1+λ2=1.

4. The cross-layer optimized body area network data transmission scheduling method according to claim 3, characterized in that: If the message type is periodic data, the transmission power setting for the tth retransmission message is: in, is the sensor node n i The benchmark data transmission power, is the basic step size of power adjustment, P max is the maximum data transmission power.

5. The cross-layer optimized body area network data transmission scheduling method according to claim 3 or 4, characterized in that: If the message type is event-triggered data or emergency data, the transmission power setting for the tth retransmission message is: in, is the sensor node n i The benchmark data transmission power, is the basic step size of power adjustment, P max is the maximum data transmission power, θ is the weight associated with the message category, θ∈(0,1).

6. The cross-layer optimized body area network data transmission scheduling method according to claim 5, characterized in that: The central node divides the superframe structure into beacon period, contention-free period, confirmation period and contention access period; Wherein, the contention-free period is divided into a plurality of time slots; During the beacon period, the central node broadcasts a beacon message, which includes the duration of each period in the current superframe structure and the time slot allocated to the sensor node in the contention access period; The sensor node uploads periodic data messages to the central node in the allocated time slot; During the confirmation period, the central node broadcasts a confirmation message; The sensor node uploads event-triggered data messages, emergency data messages, and data messages that need to be retransmitted during the contention access period.

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