An Energy Adaptive Cooperative Transmission Method in a Radio Frequency Energy Harvesting Body Area Network

Abstract

The present invention discloses an energy - adaptive cooperative transmission method in a radio - frequency energy - harvesting body area network, which includes: multiple sensors respectively send messages, the central node counts the message correct reception rate, and divides the multiple sensors into remote sensors and cooperative sensors; multiple remote sensors respectively send messages, the cooperative sensors count the correct reception rate of the cooperative sensors themselves when the multiple remote sensors send messages, and upload the correct reception rate of the messages sent by the multiple remote sensors to the central node; the central node selects the optimal cooperative sensor for each remote sensor, and allocates data upload time slots for each sensor; the remote sensors send messages within the allocated time slots; the cooperative sensors upload the received messages to the central node within the allocated time slots; wherein, the message sent by each remote sensor is uploaded by its corresponding optimal cooperative sensor. The cooperative transmission method provided by the present invention can improve the probability that the message is successfully received by the central node.

Description

Technical Field

[0001] The present invention belongs to the field of communication technologies, and particularly relates to an energy - adaptive cooperative transmission method in a radio - frequency energy - harvesting body area network. Background Art

[0002] A body area network can detect the health status information of a human body in real - time over a relatively long period of time, and has good application prospects in multiple fields such as medical treatment, education, military, and entertainment. For multiple sensor nodes that need to be worn for a long time, frequent battery replacement will reduce the quality of user experience. When charging, the health status cannot be detected, and a large number of discarded batteries will cause environmental pollution. Radio - frequency energy - harvesting technology can provide a battery - free solution in a body area network environment with a low data transmission volume. However, the available energy obtained by sensors through energy harvesting is strictly limited. How to use limited energy to maximize the quality of network service is an important problem to be solved.

[0003] When sensors collect radio - frequency energy, nodes closer to the central node can collect more energy, and the energy required for uploading messages is less than that of distant nodes. Therefore, close - range nodes can be used as potential cooperative nodes for relaying and forwarding data messages. Summary of the Invention

[0004] The purpose of the present invention is to provide an energy - adaptive cooperative transmission method in a radio - frequency energy - harvesting body area network. By reasonably dividing remote sensors and cooperative sensors, and using cooperative sensors to relay and forward the data of remote sensors, the probability that a message is successfully received by the central node can be increased.

[0005] The technical solution provided by the present invention is as follows:

[0006] An energy - adaptive cooperative transmission method in a radio - frequency energy - harvesting body area network, comprising:

[0007] Multiple sensors respectively send messages, the central node counts the message correct reception rate, and divides the multiple sensors into remote sensors and cooperative sensors;

[0008] Multiple remote sensors respectively send messages, the cooperative sensors count the correct reception rate of the cooperative sensors themselves when the multiple remote sensors send messages, and upload the correct reception rates of the multiple remote sensors sending messages to the central node; the central node selects the optimal cooperative sensor for each remote sensor and allocates data upload time slots for each sensor;

[0009] The remote sensors send messages within the allocated time slots; the cooperative sensors upload the received messages to the central node within the allocated time slots;

[0010] Among them, the messages sent by each of the remote sensors are uploaded by their corresponding optimal cooperative sensors.

[0011] Preferably, the energy - adaptive cooperative transmission method in the radio - frequency energy - harvesting body area network further includes:

[0012] The central node divides time into continuous super - frames, and each super - frame includes an energy - harvesting period, a scheduling period, and a data - uploading period;

[0013] During the energy - harvesting period, the central node broadcasts radio - frequency energy, and the sensor nodes collect radio - frequency energy and store it in the built - in capacitors;

[0014] During the scheduling period, the sensors receive the scheduling messages broadcast by the central node;

[0015] Among them, the scheduling messages include: the information of the optimal cooperative sensors of the remote sensors, and the data - uploading time slots allocated to each sensor;

[0016] During the data - uploading period, the sensors upload the information messages collected.

[0017] Preferably, during the data - uploading period, the central node uses a time - division multiplexing mechanism to divide time slots and allocates the divided time slots to the sensors, and the sensors upload messages within the allocated time slots.

[0018] Preferably, the central node divides the multiple sensors into remote sensors \(Q = [a_1,a_2,\cdots,a\) t and cooperative sensors \(R = [b_1,b_2,\cdots,b\) k according to the correct reception rate of the messages uploaded by the sensors to the central node;

[0019] Among them, for a i the correct reception rate of the message uploaded to the central node is less than or equal to \(p\) ＊ , for b j the correct reception rate of the message uploaded to the central node is greater than \(p\) ＊ ; \(p\) ＊ is the set threshold of the correct reception rate of the messages uploaded by the sensors to the central node.

[0020] Preferably, the cooperative sensor \(b\) j counts the probability that it can correctly receive the message sent by the remote sensor when the remote sensor sends a message, and obtains the message correct - reception rate matrix of the cooperative sensor \(b\) j itself j

[0021] Each cooperative sensor uploads the packet correct reception rate matrix to the central node, and the central node obtains the packet correct reception rate matrices of all cooperative sensors:

[0022]

[0023] where p ij (i = 1, 2..., t; j = 1, 2..., k) represents the probability that cooperative sensor b j correctly receives the packet sent by remote sensor a i . The central node needs to simultaneously count the packet correct reception rate when receiving the remote sensor and obtain a one-dimensional matrix P c = {p 1c , p 2c ,..., p tc}, where p ic represents the probability that the central node receives the data packet when remote sensor a i uploads the data packet.

[0024] Preferably, the method for the central node to select the optimal cooperative sensor for the remote sensor includes:

[0025] Setting the constraint condition for obtaining the optimal cooperative matrix as:

[0026] and

[0027] Obtaining the optimal cooperative matrix according to the constraint condition:

[0028]

[0029] where f ij = 1 or 0, when f ij = 1, it means that cooperative sensor b j is the optimal cooperative sensor for remote sensor a i ;

[0030] In the formula, l i represents the length of the packet forwarded by remote sensor a i , is the maximum data packet length that cooperative sensor b j can forward.

[0031] Preferably, the energy - adaptive cooperative transmission method in the radio - frequency energy - harvesting body area network further includes: Before uploading the packet, the cooperative sensor selects the optimal transmission power and uploads the packet using the optimal transmission power.

[0032] Preferably, the method for the cooperative sensor to select the optimal transmission power is as follows:

[0033] The cooperative sensor starts from the highest transmission power, gradually reduces the transmission power of the message, and counts the probability that the message is successfully received by the central node for each transmission power. When the message success acceptance rate is within the threshold interval [p ＊ , p ＊ +δ], the cooperative sensor selects the current transmission power as the optimal transmission power;

[0034] where δ represents the error threshold of the message acceptance rate.

[0035] The beneficial effects of the present invention are as follows:

[0036] The energy - adaptive cooperative transmission method in the radio - frequency energy - harvesting body area network provided by the present invention, based on the comprehensive scheduling of the central node, maximally utilizes the energy collected by all sensors as much as possible, and further improves the probability that the central node correctly receives messages through the cooperative transmission method, and can effectively improve the quality of network service. Description of the Drawings

[0037] Figure 1 is a flowchart of the energy - adaptive cooperative transmission method in the radio - frequency energy - harvesting body area network according to the present invention.

[0038] Figure 2 is a schematic diagram of the network structure according to the present invention.

[0039] Figure 3 is a schematic diagram of the super - frame division structure according to the present invention. Detailed Embodiments

[0040] The following further describes the present invention in detail with reference to the drawings, so that those skilled in the art can implement it according to the description in the specification.

[0041] As Figures 1-3 shown, the present invention provides an energy - adaptive cooperative transmission method in a radio - frequency energy - harvesting body area network. Through the cooperative transmission of cooperative sensors (nodes) in the network, the overall network efficiency is effectively improved. The central node classifies sensors according to the message arrival rate of the received sensors, and uses sensors with surplus available energy as potential cooperative sensors (nodes) to assist remote sensors (nodes) in forwarding data messages. The specific steps are as follows:

[0042] S110. The central node divides the super - frame and allocates time slots

[0043] As Figure 3As shown, time is divided into continuous superframes, and each superframe includes three parts: an energy harvesting period, a scheduling period, and a data uploading period. During the energy harvesting period, the central node broadcasts radio frequency energy, and the sensor harvests the radio frequency energy and stores it in a capacitor. During the scheduling period, the sensor receives the scheduling message broadcast by the central node. During the data uploading period, the sensor uploads the sensed information message. During the data uploading period of the superframe, the central node uses a time division multiplexing mechanism to divide the time slot resources and allocates the divided time slots to the sensors. The sensors can upload data messages only within the allocated time slots.

[0044] S120. Classification of sensors (nodes)

[0045] Due to the different distances between the sensors and the central node, there are certain differences in the energy harvesting efficiency. The sensors closer to the central node can harvest more energy and require less energy when uploading messages. These close-range sensors can act as relay nodes to cooperate in forwarding the messages of the long-range sensors. The central node is responsible for selecting the optimal relay node to forward the data messages of the long-range sensors during cooperative transmission according to the real-time network state. The specific process is as follows:

[0046] The sensor first uses all available energy to upload the message, and the central node counts the correct reception rate of the message.

[0047] The central node divides the sensors into two major categories: remote sensors Q = [a1, a2,..., a t and cooperative sensors R = [b1, b2,..., b k based on the correct reception rate of the messages uploaded by the sensors, where t + k = n. For a i The probability that the message sent is received by the central node is not greater than the threshold p ＊ , and for b j The probability that the message sent is received by the central node is greater than the threshold p ＊ ; p ＊ Is the set threshold for the correct reception rate of the messages uploaded by the sensors to the central node.

[0048] The central node records the message acceptance rate of the remote sensors to obtain a one-dimensional matrix P c = {p 1c , p 2c ,..., p tc}, where p ic Represents the probability that the central node receives the data message when the remote sensor a i uploads it.

[0049] S130. The cooperative node adjusts the transmission power

[0050] The cooperative sensor gradually reduces the transmission power of the message starting from the highest transmission power, and counts the probability that the message is successfully received by the central node at each transmission power. When the message success acceptance rate is within the threshold interval [p ＊ , p ＊ + δ], the cooperative sensor selects the current transmission power as the subsequent data transmission power; where δ represents the error threshold of the message acceptance rate.

[0051] S140. The cooperative node detects the message success arrival rate of the remote node

[0052] The cooperative sensor counts the probability that it can correctly receive the data message when each remote sensor sends the data message. For the cooperative sensor b j , a one-dimensional matrix is obtained

[0053] Each cooperative sensor uploads the obtained message correct acceptance rate matrix to the central node, and the central node obtains the matrix:

[0054] where p ij (i = 1, 2..., t; j = 1, 2..., k) represents the probability that the cooperative sensor b i can correctly receive the message when the remote sensor a j sends the message.

[0055] S150. The central node formulates a cooperation plan and adjusts the time slot allocation

[0056] The central node selects the optimal cooperative sensor for the remote sensor to complete the forwarding of the data message to improve the message success arrival rate; the maximum data message length that the cooperative sensor can forward is where is the maximum data message length that the cooperative sensor b j can forward; where E j , R, p rx , are the energy available for cooperative forwarding, data transmission rate, receiving power, and sending power respectively. To maximize the network throughput, the central node needs to obtain the optimal cooperation matrix where f ij = 1 or 0. When f ij = 1, it means that the cooperative sensor b j will act as a cooperative node to forward the data message of the remote sensor a i .

[0057] Among them, the central node determines whether each of the cooperative nodes needs to forward the packets sent by other nodes. When a cooperative node needs to forward a packet, it determines which remote node's packet to forward. When formulating a cooperation strategy, each remote node selects at most one cooperative node to forward the packet, and the sum of the lengths of the packets forwarded by the remote nodes cannot exceed the maximum packet length that the remote nodes themselves can forward. On this basis, the maximum value of the throughput improvement is obtained. Therefore, the constraint conditions for obtaining the optimal cooperation matrix are set as follows:

[0058]

[0059] In the formula, p ic represents the probability that the packet sent by the remote sensor a i can be successfully received by the central node. q * represents the probability that the packet sent by the cooperative sensor can be successfully received by the central node. p ij represents the probability that the packet sent by the remote sensor a i can be successfully received by the cooperative sensor b j ; l i represents the length of the packet forwarded by the remote sensor a i .

[0060] In one embodiment, in order to obtain the solution of the cooperation matrix based on a lower computational complexity, the payoff matrix is first initialized where, v ij =q*p ij -p ic . Then, the data in the payoff matrix V is traversed from large to small. When traversing to the data v ij , if the constraint condition 1 ij and the constraint condition 2 still hold when f is set to 1, then f ij is assigned a value of 1; otherwise, it is assigned a value of 0. After the traversal is completed, an optimal solution of the cooperation matrix based on the greedy strategy can be obtained.

[0061] The central node allocates available time slots for data upload of all the sensors in the scheduling packet. The time slot allocation information and the cooperative transmission information are both packed in the scheduling packet and broadcast to the sensors during the scheduling period. For the case where f ij =1, the upload time slot of the cooperative sensor is allocated after the upload time slot of the remote sensor to ensure that the optimal cooperative sensor uploads after receiving all the packets of its corresponding remote sensors, so as to ensure the upload efficiency of the packets.

[0062] Since the remote sensor can be received by both the cooperative sensor and the central node when uploading a message, and the message uploaded by the remote sensor can be forwarded to the central node by its optimal cooperative sensor. If the central node fails to receive the message successfully when the remote sensor uploads the message, then it can successfully receive the previously unreceived message when the cooperative sensor forwards it, thus increasing the probability of the central node successfully receiving the message.

[0063] S160. The sensor completes data upload and cooperative transmission

[0064] After the sensor receives the scheduling message, it uploads the data message sensed by itself to the central node within the time slot allocated by the central node. For the case where the cooperative sensor b j forwards the data message of the remote sensor a i (at this time, the cooperative sensor b j is the optimal sensor of the remote sensor a i ), the cooperative sensor b j listens to the channel and receives the message in the time slot when the remote sensor a i sends data. After successfully receiving the message, the cooperative sensor b j forwards the received message within the time slot allocated to itself.

[0065] Although the embodiments of the present invention have been disclosed as above, they are not limited to only the applications listed in the specification and the embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated and described examples here.

Claims

1. A collaborative transmission method with energy adaptation in a radio frequency energy harvesting body area network, characterized in that Including: Multiple sensors respectively send messages, the central node statistically calculates the correct reception rate of the messages, and divides the multiple sensors into remote sensors and cooperative sensors; Multiple remote sensors respectively send messages, the cooperative sensors statistically calculate the correct reception rate of the cooperative sensors themselves when the multiple remote sensors send messages, and upload the correct reception rate of the messages sent by the multiple remote sensors to the central node; the central node selects the optimal cooperative sensor for each of the remote sensors, and allocates data upload time slots for each sensor; The remote sensors send messages within the allocated time slots; The cooperative sensors upload the received messages to the central node within the allocated time slots; Wherein, the message sent by each remote sensor is uploaded by its corresponding optimal cooperative sensor; The method for the central node to select the optimal cooperative sensor for the remote sensors includes: Setting the constraint condition for obtaining the optimal cooperation matrix as: and Obtaining the optimal cooperation matrix according to the constraint condition: Among them, f ij = 1 or 0, when f ij = 1, it means that the cooperative sensor b j is the optimal cooperative sensor for the remote sensor a i ; Where, l i represents the length of the message forwarded by the remote sensor a i , and is the maximum data message length that the cooperative sensor b j can forward. p ij (i = 1, 2,..., t; j = 1, 2,..., k) represents the probability that the cooperative sensor b j correctly receives the message sent by the remote sensor a i . p ic represents the probability that the central node receives the message when the remote sensor a i uploads the data message; q * represents the probability that the message sent by the cooperative sensor can be successfully received by the central node.

2. The energy adaptive cooperative transmission method in the radio frequency energy harvesting body area network according to claim 1, wherein Also including: The central node divides time into continuous superframes, and each superframe includes an energy harvesting period, a scheduling period, and a data upload period; During the energy harvesting period, the central node broadcasts radio frequency energy, and the sensor nodes harvest the radio frequency energy and store it in the built-in capacitor; During the scheduling period, the sensors receive the scheduling messages broadcast by the central node; Wherein, the scheduling messages include: the optimal cooperative sensor information of the remote sensors, and the data upload time slots allocated to each sensor; During the data upload period, the sensors upload the collected information messages.

3. The collaborative transmission method with energy adaptation in the radio frequency energy harvesting body area network according to claim 2, wherein During the data upload period, the central node divides the time slots using a time division multiplexing mechanism, and allocates the divided time slots to the sensors, and the sensors upload the messages within the allocated time slots.

4. The collaborative transmission method with energy adaptivity in the RF energy harvesting body area network according to claim 3, wherein The central node divides the multiple sensors into remote sensors Q = [a1, a2,..., a t and cooperative sensors R = [b1, b2,..., b k according to the correct reception rate of the messages uploaded by the sensors to the central node; Among them, for a i the correct reception rate of the message uploaded to the central node is less than or equal to p ＊ , for b j the correct reception rate of the message uploaded to the central node is greater than p ＊ ; p ＊ is the threshold of the correct reception rate of the message uploaded by the set sensor to the central node.

5. The method for energy - adaptive cooperative transmission in a radio - frequency energy - harvesting body area network according to claim 3 or 4, characterized in that Cooperative sensor b j When the remote sensor sends a message, b j The probability that it can correctly receive the message itself, obtaining the cooperative sensor b j Message correct reception rate matrix Each cooperative sensor uploads the message correct reception rate matrix to the central node, and the central node obtains the message correct reception rate matrices of all cooperative sensors: where p ij (i = 1, 2..., t; j = 1, 2..., k) represents the probability that the collaborative sensor b j correctly receives the message sent by the remote sensor a i The central node needs to simultaneously count the message correct acceptance rate when receiving the remote sensor and obtain a one-dimensional matrix P c ={p 1c , p 2c , …, p tc}, where p ic represents the probability that the central node receives the data message uploaded by the remote sensor a i .

6. The collaborative transmission method with energy adaption in the RF energy harvesting body area network according to claim 5, wherein Also including: Before uploading the messages, the cooperative sensors select the optimal transmission power and upload the messages using the optimal transmission power.

7. The collaborative transmission method with energy adaptivity in the radio frequency energy harvesting body area network according to claim 6, characterized in that, The method for the cooperative sensors to select the optimal transmission power is: The collaborative sensor starts from the highest transmission power, gradually reduces the transmission power of the message, and counts the probability that the message is successfully received by the central node at each transmission power. When the successful reception rate of the message is within the threshold range [p ＊ , p ＊ +δ], the collaborative sensor selects the current transmission power as the optimal transmission power; Wherein, δ represents the error threshold of the message acceptance rate.

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