CN111642004A - Cooperative communication transmission protocol based on critical data in WBAN - Google Patents

Abstract

A cooperative communication transmission protocol based on key data in WBAN relates to the technical field of communication, and is characterized in that data sensed by sensor nodes are classified by adopting a mutual information standard, and data transmission is allowed only when a mutual information value is smaller than a preset threshold value. The invention has the beneficial effects that: the average energy consumption of the sensor nodes is effectively reduced, and the service life of the network is greatly prolonged.

Description

A Collaborative Communication Transmission Protocol Based on Key Data in WBAN

technical field

The invention belongs to the technical field of communication, in particular to a cooperative communication transmission protocol based on key data in WBAN.

Background technique

Maximizing network lifetime is one of the main research challenges for WBANs. In WBAN, the health data measured by sensor nodes are often similar or close, which do not contain abnormal emergency medical information. However, a large amount of power is wasted when sensor nodes continuously transmit normal data in the body, resulting in shortened network lifetime.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to provide a cooperative communication transmission protocol based on key data in WBAN, so as to solve the problem that the nature of collected data is not considered in WBAN cooperative communication, which leads to redundant data transmission and reduces network life.

The technical solution adopted by the present invention to solve the above technical problems is: a cooperative communication transmission protocol based on key data in WBAN, the WBAN system is composed of n sensor nodes, m relay nodes and a coordinator, and the communication transmission protocol includes The following three stages:

1. Network initialization: At the beginning of network initialization, the coordinator broadcasts an initial message to the entire network, notifying the location of all sensor nodes and relay nodes, and assigning unique ID information to each sensor node; all sensor nodes store these location information , and broadcast an information packet consisting of network location, energy status and ID information to relay nodes, through this method, all sensor nodes update their position and energy status information to relay nodes and coordinators;

2. Transmission path selection: Calculate the mutual information value of the sensing data of the sensor node. Only when the mutual information value of the sensing data of the sensor node is less than the predetermined threshold TH _H , the establishment of a communication link is allowed. In this case:

(1) If the mutual information value of the data sensed by the sensor node is greater than the predetermined threshold TH _L , the data sensed by the sensor node is normal data, and a transmission link is directly established between the sensor node and the coordinator. The time slot of the address is allocated to the sensor node to avoid data conflict;

(2) If the mutual information value of the sensing data of the sensor node is less than the predetermined threshold TH _L , the data sensed by the sensor node is the key data, and a communication link is created between the sensor node and the corresponding relay node, and the communication process is as follows: The relay node is selected by the relay selection algorithm, and the data sensed by the sensor node is first transmitted to the selected relay node, and then forwarded by the relay node to the coordinator;

3. Data transmission stage: After the transmission path is established, it enters the data transmission stage. During this period, the coordinator allocates time slots based on time division multiple access to the sensor nodes and relay nodes. If the data is normal, the sensor nodes will be in the scheduled time The sensor node sends the sensed data to the coordinator; if it is critical data, the cooperative transmission path is adopted, and the sensor node first sends the sensed data to the selected relay node, and then the relay node forwards the collected data to the The coordinator, finally, aggregates the data from the sensor nodes and relay nodes at the coordinator using data merging techniques.

The method for calculating the mutual information MI(D _x ,D _y ) of the sensor node sensing data in the second stage of the present invention is:

Among them, _Dx and _Dy represent the scanning data set of sensor nodes in consecutive time slots tx and ty, _x and _y are discrete random variables in _Dx and _Dy , which are used to refer to the data collected by sensor nodes, D Is the abbreviation of DataSet. p(D _x , _Dy ) is the joint probability distribution function of D _x and _Dy , and p(D _x ) and p(D _y ) are the marginal probability distribution functions of D _x and _Dy , respectively.

The relay selection algorithm in the second stage of the present invention is: calculate the cost function C(i,j) of the i-th sensor node to select the j-th relay node by the following formula, and select the relay node with the smallest cost function value. carry out data transmission;

where i∈(1,2,...,n), j∈(1,2,...m), d(i,j) represents the transmission distance between sensor node i and potential relay node j, E(i) represents the remaining energy of sensor node i, and the relay node with the smallest cost function value is selected for data transmission.

The data merging method at the coordinator of the present invention is:

和

分别表示S_iD和R_jD通信链路上传输的信号，S_iD表示第i个传感器节点与协调器之间的链路，R_jD表示第j个中继节点与协调器之间的路径，i∈(1,2,...n)，j∈(1,2,…,m)，α和β分别是这两个通信链路的权重，比率α/β反映了通信链路的质量，并刻画了信道阴影效应对传输信道的影响，当选择中继节点时，该比率可以表示为距离的函数：where y _D represents the combined output signal on the coordinator,

and

represent the signals transmitted on the communication links of S _i D and R _j D respectively, S _i D represents the link between the ith sensor node and the coordinator, and R _j D represents the link between the j th relay node and the coordinator path, i∈(1,2,...n), j∈(1,2,...,m), α and β are the weights of the two communication links, respectively, and the ratio α/β reflects the communication chain The quality of the path and the influence of the channel shadow effect on the transmission channel are described. When selecting a relay node, the ratio can be expressed as a function of distance:

和

有关。where α/β is related to the transmission distance

and

related.

The value of the ratio α/β according to the present invention is 2.

The beneficial effects of the present invention are as follows: the present invention avoids the transmission of redundant data by considering the mutual information value between sensor sensing data, and transmits key data by means of relay cooperation, ensuring reliable data transmission at the same time. , prolonging the life of the network; in addition, the present invention considers the cost function based on the remaining energy of the sensor node and the transmission distance when selecting the relay node, so that the energy consumption of the sensor node is balanced; finally, the simulation experiment proves that the present invention can be effective. The average energy consumption of sensor nodes is greatly reduced, thereby greatly extending the network life.

Description of drawings

1 is a schematic diagram of a WBAN network model of the present invention;

FIG. 2 is a schematic flowchart of a cooperative communication transmission protocol of the present invention;

Fig. 3 is the network life comparison diagram of two kinds of protocols in the simulation experiment of the present invention;

Fig. 4 is the analysis and comparison diagram of the residual energy of the network life of two protocols in the simulation test of the present invention;

FIG. 5 is an analysis and comparison diagram of the path loss performance of the two protocols in the simulation experiment of the present invention.

Detailed ways

The specific embodiments (embodiments) of the present invention will be described below with reference to the accompanying drawings, so that those skilled in the art can better understand the present invention.

The invention proposes a cooperative communication data protocol based on key data. When the data collected by the sensor is the key data, the data is transmitted to the coordinator through cooperative communication to ensure timely and reliable data transmission; when the data collected by the sensor is When the data is normal, it can be directly transmitted by the sensor node to the coordinator; when the data collected by the sensor is redundant data, it is not allowed to send the data. Specifically divided into three stages: initialization stage, transmission path selection stage and data transmission stage. The overall communication process is shown in Figure 2.

1. Network initialization

At the beginning of network initialization, the coordinator broadcasts an initial message to the whole network, notifying the location of all sensor nodes and relay nodes, and assigning unique ID information to each sensor node. Then, all sensor nodes store these locations and broadcast packets consisting of network location, energy status and ID information to relay nodes. In this way, all sensor nodes can provide relay nodes and coordinators with status information updates on their positions and energies.

2. Transmission path selection

The key data-based cooperative communication transmission strategy of the present invention aims to prolong network life and maintain communication link quality. Therefore, only when the mutual information value of the sensor sensing data is less than the predetermined threshold TH _H , the establishment of the communication link is allowed. The data sensed by the sensor can be directly transmitted to the coordinator, or can be collected by the relay node and forwarded to the coordinator. If the mutual information value of the sensor sensing data is greater than the predetermined threshold TH _L , a transmission link is directly established between the sensor node and the coordinator. The coordinator assigns time-division multiple access (TDMA)-based time slots to sensor nodes to avoid data collisions.

If the mutual information value of the sensor sensing data is smaller than the predetermined threshold TH _L , a communication link is established between the sensor node and the corresponding relay node. The communication process is that the data sensed by the sensor node is first transmitted to the body surface relay node, and then forwarded by the relay node to the coordinator.

The method for calculating the mutual information MI(D _x ,D _y ) of the sensor node sensing data is:

Among them, _Dx and _Dy represent the scanning data set of sensor nodes in consecutive time slots tx and ty, _x and _y are discrete random variables in _Dx and _Dy , which are used to refer to the data collected by sensor nodes, p (D _x , _Dy ) is the joint probability distribution function of D _x and _Dy , and p(D _x ) and p(D _y ) are the marginal probability distribution functions of D _x and _Dy , respectively.

Consider a WBAN system with two candidate relay nodes. In order to balance the energy consumption of all sensor nodes, a relay selection algorithm is used to select relay nodes in each round of data transmission. The algorithm is:

where the ith sensor node selects the cost function C(i,j) of the jth relay node, i∈(1,2,...,n), j∈(1,2,...m), d(i,j) represents the transmission distance between sensor node i and potential relay node j, E(i) represents the remaining energy of sensor node i, and the relay node with the smallest cost function value is selected for data transmission.

3. Data transfer stage

After the transmission path is established, the data transmission phase is entered. During this period, the coordinator assigns TDMA-based time slots to sensor nodes and relay nodes. The sensor node sends the sensed data to the coordinator within the scheduled time; if the cooperative transmission path is adopted, the sensor node first sends the sensed data to the selected relay node, and then the relay node sends the collected data forwarded to the coordinator. Finally, the data from sensor nodes and relay nodes is aggregated at the coordinator using data merging techniques.

The data merging scheme collected at the coordinator can be expressed as:

Among them, y _D represents the combined output signal on the coordinator, y _SD and y _RD represent the signals transmitted on the S _i D and R _j D communication links, respectively, and S _i D represents the communication between the ith sensor node and the coordinator. Link, R _j D represents the path between the jth relay node and the coordinator, i∈(1,2,...,n), j∈(c,w), j is the body surface relay node On the human body, c and w represent the chest and wrist, respectively, and α and β are the weights of these two communication links, respectively. The ratio α/β reflects the quality of the communication link and characterizes the effect of channel shadowing on the transmission channel. When choosing a relay node, this ratio can be expressed as a function of distance:

和

有关。为了使y_D最大化，协调器采用固定比率合并方案，其最佳比率值为2。where α/β is related to the transmission distance

and

related. To maximize y _D , the coordinator adopts a fixed-ratio merging scheme with an optimal ratio value of 2.

Simulation and Performance Evaluation

(1) Simulation environment

The cooperative communication transmission protocol based on key data proposed by the present invention is simulated, and compared with the cooperative communication strategy based on two relays in the related WBAN, and the comparative analysis is carried out from the aspects of network life, network residual energy and path loss, etc. .

The communication transmission protocol of the present invention is simulated on the MATLAB platform, and its detailed parameter settings are shown in Table 1.

Table 1 Simulation parameter settings

(2) Analysis of simulation results

In the simulation, sensor nodes and relay nodes are placed in predetermined positions, and the coordinator is fixed at the center of the human body, such as at the waist. It is assumed that the number of sensor nodes is limited to 6, while the body surface relay node is 2 and the coordinator is 1. Sensor nodes are used to monitor physiological parameters such as glucose and insulin levels and transmit sensed data simultaneously on both direct and relay data transmission paths in a cooperative manner to reduce packet loss. When the mutual information value is less than a predetermined threshold, a data transmission link is established. The relay node is used for cooperative transmission, which can ensure that the sensor node has multiple transmission links at the same time.

FIG. 3 is a comparison diagram of the network life of two protocols in the simulation experiment of the present invention. It can be seen from FIG. 3 that the stable period of the communication transmission protocol of the present invention is about 11,000 cycles, while the stable period of the cooperative communication strategy based on two relays is about 11,000 cycles. for 4100 cycles. Likewise, the present invention can achieve longer network lifetimes, approximately 12,800 cycles, compared to only 4250 cycles for a cooperative communication strategy based on two relays. The reason for this result is that compared with the static two-relay-based cooperative communication strategy, the relay selection technique based on the cost function of the present invention guarantees a longer network lifetime, because the proposed relay node selection method can At the same time, the transmission distance and remaining energy state information of each sensor node are considered to balance the energy consumption of sensor nodes in each cycle. In addition, the present invention enables sensor nodes to avoid redundant data transmission, thereby prolonging the stabilization period and network lifetime.

FIG. 4 is an analysis and comparison diagram of the remaining energy of the network lifetime of the two protocols in the simulation test of the present invention, and FIG. 4 shows the state of the remaining network energy in each cycle of the two communication protocols. Compared with the average energy consumption per cycle of 2.1 mJ based on the cooperative communication strategy of two relays, the average energy consumption per cycle of the present invention is lower, about 0.7 mJ. This is because the present invention can reduce redundant power consumption by prohibiting the transmission of continuously sensed redundant data, and the relay selection algorithm based on the remaining energy of the sensor node and the transmission distance further considers the energy consumption of the node, while the A cooperative communication strategy of two relays requires sending all sensed data, resulting in higher energy waste. In addition, the network residual energy based on the two-relay cooperative communication strategy ends at zero after 4100 cycles, because in the two-relay cooperative communication strategy, the relay node always forwards the received information and consumes rapidly The remaining energy of the node is reduced, which reduces the stability period of the network.

Path loss is a crucial performance parameter when studying signal power attenuation from sensor nodes to coordinators. Figure 5 shows the path loss performance versus network lifetime for two cooperative communication transmission strategies. As can be seen from FIG. 5 , compared with the cooperative communication strategy based on two relays, the present invention can significantly reduce the overall communication distance and thus obtain a smaller path loss. Furthermore, the cooperative communication strategy based on two relays significantly reduces the path loss in the first 4000 cycles because the number of surviving sensor nodes decreases rapidly, while in the present invention, no sensor nodes die after nearly 11,000 cycles. It can be seen from this that the protocol of the present invention has better reliability and network lifetime.

Claims (5)

1. Cooperative data-based communication transport protocol in a WBAN, characterized by: the WBAN system consists of n sensor nodes, m relay nodes and a coordinator, and the communication transmission protocol comprises the following three stages:

   firstly, network initialization: the method comprises the following steps that when network initialization is started, a coordinator broadcasts an initial message to the whole network, informs the positions of all sensor nodes and relay nodes, and assigns unique ID information to each sensor node; all the sensor nodes store the position information and broadcast information packets consisting of network positions, energy states and ID information to the relay nodes, and through the mode, all the sensor nodes update the position and energy state information of the sensor nodes and provide the updated position and energy state information to the relay nodes and the coordinator;

   secondly, selecting a transmission path: calculating mutual information value of the sensing data of the sensor nodes only when the mutual information value of the sensing data of the sensor nodes is less than a predetermined threshold value TH_HOnly allows the establishment of a communication link, in which case:

   (1) if the mutual information value of the sensing data of the sensor nodes is larger than a preset threshold value TH_LIf the data sensed by the sensor nodes are normal data, a transmission link is directly established between the sensor nodes and the coordinator, and the coordinator allocates time slots based on time division multiple access to the sensor nodes to avoid data collision;

   (2) if the mutual information value of the sensing data of the sensor nodes is less than the predetermined threshold TH_LIf the data sensed by the sensor node is the key data, a communication link is created between the sensor node and the corresponding relay node, and the communication flow is as follows: selecting a relay node through a relay selection algorithm, transmitting data sensed by a sensor node to the selected relay node, and forwarding the data to a coordinator through the relay node;

   thirdly, data transmission stage: after a transmission path is established, a data transmission stage is entered, during which the coordinator allocates time slots based on time division multiple access to the sensor nodes and the relay nodes, and if the data are normal data, the sensor nodes send the sensed data to the coordinator within scheduled time; if the data is the key data, a cooperative transmission path is adopted, the sensor node firstly sends the sensed data to the selected relay node, then the relay node forwards the collected data to the coordinator, and finally, the data from the sensor node and the relay node are aggregated at the coordinator by adopting a data merging technology.
2. 2. A cooperative data-based communication transport protocol in a WBAN according to claim 1, wherein: calculating mutual information MI (D) of sensor node sensing data in the second stage_x,D_y) The method comprises the following steps:

   

   wherein D is_xAnd D_yRepresenting successive time slots t_xAnd t_yScan data set of inner sensor node, x, y are D_x、D_yThe discrete random variable in (1) is used to refer to the data collected by the sensor node, p (D)_x,D_y) Is D_xAnd D_yOf the joint probability distribution function, p (D)_x) And p (D)_y) Are each D_xAnd D_yThe edge probability distribution function of (1).
3. 3. A cooperative data-based communication transport protocol in a WBAN according to claim 1, wherein: the relay selection algorithm in the second stage is as follows: calculating a cost function C (i, j) of selecting a jth relay node by an ith sensor node through the following formula, and selecting the relay node with the minimum cost function value for data transmission;

   

   wherein i belongs to (1,2,...., n), j belongs to (1,2,..., m), d (i, j) represents the transmission distance between the sensor node i and the potential relay node j, and E (i) represents the residual energy of the sensor node i, and the relay node with the minimum cost function value is selected for data transmission.
4. 4. A cooperative data-based communication transport protocol in a WBAN according to claim 1, wherein: the data merging method at the coordinator comprises the following steps:

   

   wherein, y_DRepresenting the combined output signal at the coordinator,

   

   and

   

   respectively represent S_iD and R_jD signals transmitted over communication links, S_iD represents a link between the ith sensor node and the coordinator, R_jD denotes the path between the j-th relay node and the coordinator, i ∈ (1,2,. n., j ∈ (1,2, …, m), α and β are the weights of the two communication links, respectively, the ratio α/β reflects the quality of the communication links and characterizes the effect of channel shadowing on the transmission channel, which ratio can be expressed as a function of distance when selecting a relay node:

   

   wherein α/β is related to transmission distance

   

   And

   

   it is related.
5. 5. The cooperative data-based communication transport protocol in a WBAN according to claim 4, wherein: the value of the ratio alpha/beta is 2.

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