阅读说明：本技术 动态环境下的wban间信道分配方法 (Method for allocating channels between WBANs (white-light-emitting networks) in dynamic environment ) 是由 陈昱欣 郭坤祺 王晨阳 胡效康 于 2021-06-28 设计创作，主要内容包括：本发明公开了动态环境下的WBAN间信道分配方法,根据无线体域网工作时的受干扰状况sink为传感器节点分配信道；根据多个无线体域网的动态环境,服务中心为无线体域网sink分配传输信道；根据无线体域网距离服务中心的距离,调整无线体域网sink的发射功率。该方法充分考虑了干扰,针对多无线体域网共存干扰问题提出相应的解决方案,提高了数据传输的可靠性,节约了能耗。(The invention discloses a method for allocating channels among WBAN (work group area networks) in a dynamic environment, which allocates channels for sensor nodes according to an interfered condition sink when a wireless body area network works; according to the dynamic environments of a plurality of wireless body area networks, a service center allocates a transmission channel for a sink of the wireless body area network; and adjusting the transmitting power of the sink of the wireless body area network according to the distance between the wireless body area network and the service center. The method fully considers the interference, provides a corresponding solution for the problem of the coexistence interference of the multi-wireless body area network, improves the reliability of data transmission and saves energy consumption.)

1. The method for allocating the channels among the WBAN in the dynamic environment is characterized in that in the communication process from the sensor nodes on the first layer to the sink node, when only one wireless body area network exists in the environment, the channels are allocated by using a TDMA mode according to the priority of each node, the sensor nodes are prevented from generating interference with each other when communicating to the sink node, if the sensor nodes are in the same priority, the sink randomly allocates time slots for the sensor nodes, and records the received signal strength from each sensor node.

2. The WBAN-to-WBAN channel allocation method according to claim 1, wherein when a plurality of wireless body area networks exist in the same narrow environment, first,whether the target wireless body area network is interfered is judged by the target wireless body area network, and the judging method comprises the following steps: when the distance D between the sink of the two parties is less than four times of the maximum communication radius R of the sensor and the duration T is more than T_thJudging that the two wireless body area networks generate interference; then, sink nodes of different wireless body area networks which generate interference exchange the time slot distribution tables and the signal intensity of sensor nodes thereof mutually, and superframe synchronization is realized.

3. The method of allocating WBAN channels according to claim 2, further comprising determining whether a sink node operating in a same time slot is interfered, wherein the determining comprises: calculating the signal to interference plus noise ratio (SINR) of communication in the same time slot, judging whether the corresponding sink node is interfered, and if the SINR is not interfered, judging whether the sink node is interfered<SINR_thIf so, interference is generated, at the moment, a time slot is added after the current time slot by the sink nodes of the two parties, and the two sink nodes are randomly distributed with a sequence; otherwise, no interference is generated, and the sink of the two parties can carry out communication work in the same time slot.

4. The method of WBAN channel assignment in a dynamic environment of claim 3, wherein the SINR isWherein sigma²Representing additive white Gaussian noise, S_iI represents external interference for the received power of the ith sink node.

5. The method of allocating WBAN-to-WBAN channels in a dynamic environment according to claim 1, further comprising: in the communication process from the sink node at the second layer to the service center, the sink node communicates with the service center at the 2.4Ghz frequency band by adopting a CSMA/CA mode, and interference among the sink nodes is judged under the condition that:

when the distance between the two sinks is larger than or equal to R' + R, no interference is judged, the two sinks are allowed to use the same channel at the moment, the transmission of the wireless body area network related to the two sinks triggers the carrier sensing of the service center receiver, the service center randomly allocates channels for the sinks, and the two sinks can transmit information at the same time.

And when the distance between the two sink is smaller than R' + R, judging that interference is generated, at the moment, firstly calculating the shortest channel path between the service center and each sink, performing channel allocation by adopting a CSMA/CA mode under the shortest channel path, and maintaining the channel stability by adopting a binary exponential back-off algorithm.

6. The method of WBAN-to-WBAN channel assignment in a dynamic environment according to claim 5, wherein the shortest channel path is calculated by dijkstra method as follows:

setting G (V, E) as a weighted directed graph, dividing a sink set V into two groups A and B, listing the sink already allocated to a channel into a set A, listing the sink not allocated to the channel into a set B, sequentially adding the sink in the B into the A according to the ascending order of the shortest path length, simultaneously removing the sink from the B until all the sinks in the B are traversed, and in the adding process, always keeping the shortest path length from a service center to each sink in the A not more than the shortest path length from the service center to any sink in the B;

each sink corresponds to a distance E, the distance E of the sink in A refers to the shortest path length from a service center to the sink vertex, and the distance of the sink in B refers to the current shortest path length from the service center to the sink through sinnk in A as a relay.

7. The WBAN-to-WBAN channel assignment method according to claim 5, wherein the binary exponential back-off algorithm is specifically designed as follows:

s1, determining basic back-off time, and regarding end-to-end round-trip time 2t as the basic back-off time;

s2, defining a parameter k which is min [ collision times, 10], wherein k is related to the collision times, and the larger the collision times are, the larger the value of k is, and the maximum value of k is not more than 10;

s3, taking a discrete integer set [0,1,2, … …, (2)^k-1)]R, the waiting time delay is r times2 rt;

and S4, when the number of times of collision is more than 10, randomly selecting a number from [0,1,2, … … and 1023] as a value of r.

8. The WBAN-to-WBAN channel allocation method according to claim 5, wherein in the communication from the sink node of the second layer to the service center, the method further comprises controlling the transmission power of the sink node to improve channel multiplexing and throughput.

9. The method of WBAN-to-WBAN channel assignment in a dynamic environment according to claim 8, wherein the method of controlling the sink node transmit power comprises: the service center compares the received signal strength of the wireless body area network sink with the expected received signal strength to obtain an offset value e, and controls the corresponding wireless body area network sink transmitting power through a discrete incremental PID algorithm:

Δu(k)＝K_p(e(k)-e(k-1))+K_ie(k)+K_d(e(k)-2e(k-1)+e(k-2))

K_p、K_i、K_drespectively representing a proportional term, a differential term and an integral term, e (k-i) represents the signal intensity deviation received by the previous i rounds, and delta u (k) is the transmission power of the next round of controlling the sink.

Technical Field

The invention belongs to the technical field of wireless communication, and particularly relates to a method for allocating channels among WBANs (wireless broadband access networks) in a dynamic environment.

Background

In recent years, with the continuous development of the technology level, wireless sensor networks are increasingly applied to daily life, and one important application field is medical science and medical care. A Wireless Body Area Network (Wireless Body Area Network) is a special-purpose sensor Network composed of a plurality of Wireless sensors in the range of human Body, which connects different medical sensors to clothes, Body surface or human Body, monitors the health conditions of human Body such as heartbeat, blood pressure and blood sugar in real time, and reports abnormal data to related personnel and mechanisms in time once the data are abnormal.

As a health product with low cost and high effectiveness, the wireless body area network can effectively relieve the current situation of shortage of public medical resources in the society. With the help of the emerging technology, real-time physiological information of human bodies can be obtained, particularly for patients suffering from diseases such as Alzheimer disease, Parkinson disease, cardiovascular diseases and the like, and the monitoring of real-time physiological data is of great help to the physical health of the patients. Wireless body area networks may also be deployed in retirement homes to monitor the daily activities of the elderly to prevent accidents.

Most of the wireless body area network technologies work in the ISM (Industrial Scientific Medical) frequency band, which is common in all countries, however, there are many devices working in the frequency band, and the number of channels orthogonal to each other in the ISM frequency band is very limited, so that the wireless body area network and other devices working in the frequency band or wireless body area networks equipped to other people can work on the same channel with a high probability. In addition, because each user individual of the wireless body area network is in continuous motion, the high mobility and the irregularity enable the uncertainty of the co-channel interference mitigation between the wireless body area networks, the uncertainty causes the uncertainty of the interference between the wireless body area networks, and a greater challenge is brought to the coexistence problem.

Disclosure of Invention

In view of the above background problems, the present invention provides a method for channel allocation in a moving state of a wireless body area network, which enables a sink node of the wireless body area network to formulate a corresponding transmission strategy according to shared information, and can effectively reduce interference between wireless body area networks operating at the same frequency.

Aiming at the dynamic scene of the coexistence of multiple groups of wireless body area networks, the channels are allocated to different body area networks through cooperative scheduling, so that the effectiveness and reliability of data transmission can be effectively improved, and the energy consumption of nodes is effectively reduced.

The invention aims to allocate channels for a wireless body area network in a moving state. The method is mainly realized by the following scheme:

the communication of the wireless body area network is divided into three layers, wherein the first layer is communication between a sensor node and a sink node, the second layer is communication between the sink node and a service center, and the third layer is communication between the service center and institutions such as hospitals.

In the first layer of communication, a reasonable and effective method needs to be found to allocate appropriate working channels to each wireless body area network in a scene, so that the total throughput rate of communication among nodes is improved, radio interference on the nodes is reduced, and the network performance is improved. Meanwhile, in the second layer of communication, power control on sink sending power is considered while channels are distributed, long-term, stable and efficient work of nodes is facilitated, reusability and throughput rate of network space channels are improved, network energy consumption is reduced, and personal damage caused by overheating is avoided.

Interference suffered by the wireless body area network in the first layer of communication mainly comes from the inside and the outside of the wireless body area network, wherein the interference from the outside of the wireless body area network can come from other wireless body area networks or from devices working in the same frequency band with the wireless body area network, such as Bluetooth, WiFi and the like. According to the ieee802.15.6 protocol introduced in 2012, it divides QoS into 7 priorities: 1 (lowest priority) to 7 (highest priority).

When only one wireless body area network exists in the environment, the channels are distributed by using a TDMA mode according to the priority of each node, and the sensor nodes are prevented from generating interference with each other when communicating to the sink. If the sensor nodes are in the same priority, the sink randomly allocates time slots for the sensor nodes, and records the received signal strength from each sensor node.

When there are multiple wireless body area networks in the same narrow environment, first, the target wireless body areaThe method for judging whether the network is interfered or not comprises the following steps: when the distance D between the sink of the two parties is less than four times of the maximum communication radius R of the sensor and the duration T is more than T_thAnd judging that the two wireless body area networks generate interference. Wherein T is_thIs a quantitative threshold, generally takenT_MAPIs the duration, N, of the MAP segment in the superframe structure_SThe number of the sensor nodes in the current single body area network. Then, when the interference between the wireless body area networks is mostly generated in a short distance without object blocking, the transmission loss LS of the free space is mainly considered to be 32.45+20 × log (f) +20 × log (d), where the unit of the transmission frequency f is MHz and the unit of the transmission distance d is km. Sink nodes of different wireless body area networks which generate interference exchange the time slot distribution tables and the signal intensity of sensor nodes thereof mutually, thereby realizing superframe synchronization.

Wherein, whether the sink node working in the same time slot is interfered or not needs to be judged, and the method comprises the following steps: and calculating the signal to interference plus noise ratio (SINR) of communication in the same time slot, and judging whether the corresponding sink node is interfered or not. If the SINR is<SINR_thIf so, interference is generated, a time slot is added after the working time slot of the sensor node which is currently communicated by the sink of the two parties, and the two nodes are randomly distributed with a sequence; otherwise, no interference is generated, and the sink of the two parties can carry out communication work in the same time slot.

Wherein the signal to interference plus noise ratioWherein sigma²Representing additive white Gaussian noise, S_iI represents external interference for the received power of the ith sink node.

In the second layer of communication, the sink communicates with the service center in a 2.4Ghz frequency band by adopting a CSMA/CA mode. Because the second layer communication adopts a CSMA/CA mode, when a large number of users of the wireless body area network exist, the performance of a wireless channel is reduced, information communication among the users can generate collision, and therefore the network throughput is reduced, and the energy efficiency is also reduced.

The following two conditions exist between the coexisting sink nodes:

a. no interference: the distance between the two sinks is greater than or equal to R' + R. This is the minimum distance that allows two sinks to use the same channel without causing interference independent of the client distribution. Where R' represents a maximum distance from the sink within which simultaneous transmission of the sinks of other body area networks will trigger carrier sensing by the service centre receiver. Transmissions from the sink or the body area network associated with the sink will trigger carrier sensing by the service centre receiver. Two sinks can transmit information simultaneously.

b. Interference is generated: the distance between the two sinks is less than R' + R. The service center will not be able to correctly determine the source of the received transmission. Two sinks cannot transmit information simultaneously.

If the condition a is met, the service center randomly allocates channels to the N wireless body area networks, if the condition b is met, the shortest channel path between the service center and each sink is firstly calculated, and the channels are allocated in a CSMA/CA mode under the shortest channel path. The shortest channel path is calculated by the dijkstra method as follows:

setting G (V, E) as a weighted directed graph, dividing a sink set V into two groups A and B, listing the sink already allocated to a channel into a set A, listing the sink not allocated to the channel into a set B, sequentially adding the sink in the B into the A according to the ascending order of the shortest path length, simultaneously removing the sink from the B until all the sinks in the B are traversed, and in the adding process, always keeping the shortest path length from a service center to each sink in the A not more than the shortest path length from the service center to any sink in the B;

each sink corresponds to a distance E, the distance E of the sink in A refers to the shortest path length from the service center to the sink vertex, and the distance of the sink in B refers to the current shortest path length from the service center to the sink via the sink in A as a relay.

Collisions may be detected due to the presence of multiple wireless body area networks, and to reduce the probability of re-collisions, a random time may be waited and then transmitted using CSMA methods. In order to ensure that the backoff is kept stable, a binary exponential backoff algorithm is adopted, and the algorithm process is as follows:

1. a basic back-off time is determined, typically considering the end-to-end round-trip time 2t as the basic back-off time.

2. A parameter k is defined as min [ collision number, 10], where k is related to the collision number, and the larger the collision number is, the larger the value of k is, and the maximum value does not exceed 10.

3. Taking a random number r as a discrete integer set [0,1,2, … …, (2)^k-1)]Is a basic back-off time r times, i.e. 2 rt.

4. And when the number of collisions is more than 10, randomly selecting a number from [0,1,2, … … and 1023] as a value of r.

Considering the change of the distance between the wireless body area network and the service center in the moving process, when the distance is close, if the original transmitting power is still kept, the energy consumption of the sink is increased, and meanwhile, the interference to other wireless body area networks is generated. Therefore, the service center compares the received signal strength of the wireless body area network sink with the expected received signal strength to obtain an offset value e, and controls the corresponding wireless body area network sink to transmit power through a discrete incremental PID algorithm:

Δu(k)＝K_p(e(k)-e(k-1))+K_ie(k)+K_d(e(k)-2e(k-1)+e(k-2))

K_p、K_i、K_drespectively representing a proportional term, a differential term and an integral term, e (k-i) represents the signal intensity deviation received by the previous i rounds, and delta u (k) is the transmission power of the next round of controlling the sink.

The invention has the beneficial effects that:

the channel allocation scheme fully considers the problems of interference, power control and the like, provides a corresponding solution for the problem of channel allocation of the multi-wireless body area network, improves the reliability of data transmission and saves energy consumption.

Drawings

FIG. 1 is a three-level scene graph;

FIG. 2 is a diagram of a multiple wireless body area network coexistence scenario;

FIG. 3 is a diagram of time slots before and after channel allocation;

fig. 4 is 14 channels divided by IEEE at 2.4Ghz band.

Detailed Description

The invention provides a method for allocating channels among WBAN (white blood pressure and volume area networks) in a dynamic environment, wherein the sink allocates channels for sensor nodes according to the interference condition when a wireless body area network works; according to the dynamic environments of a plurality of wireless body area networks, a service center allocates a transmission channel for a sink of the wireless body area network; and adjusting the transmitting power of the sink of the wireless body area network according to the distance between the wireless body area network and the service center. The method fully considers the interference, provides a corresponding solution for the problem of the coexistence interference of the multi-wireless body area network, improves the reliability of data transmission and saves energy consumption.

For convenience of description, according to the RPGM mobility model, the wireless body area network may be considered as a circle with a radius R, the sink node is located at the center of the circle, and the sensor nodes are distributed in the circle and move regularly around the sink.

When only one wireless body area network exists in the environment, the channels are distributed by using a TDMA mode according to the priority of each node, and the sensor nodes are prevented from generating interference with each other when communicating to the sink. If the sensor nodes are in the same priority, the sink randomly allocates time slots for the sensor nodes, and records the received signal strength from each sensor node.

When the distance D between the sink of the two parties is more than four times of the maximum communication radius R of the sensor and the duration T is more than T_thAnd judging that the two wireless body area networks generate interference. Sink nodes of different wireless body area networks which generate interference mutually exchange time slot distribution tables and signal strength of sensor nodes of the sink nodes.

And calculating the signal to interference plus noise ratio (SINR) of communication in the same time slot, and judging whether the corresponding sink node is interfered or not. If the SINR is<SINR_thIf so, interference is generated, a time slot is added after the time slot by the sink of the two parties, and the two nodes are randomly distributed with a sequence; otherwise, no interference is generated, and the sink and the corresponding of the two parties can carry out communication work in the same time slot.

In the second layer of communication, the sink communicates with the service center in a 2.4Ghz frequency band by adopting a CSMA/CA mode.

The following two situations exist between the coexisting sink nodes: no interference and interference generation. If no interference exists, the service center randomly allocates channels for the interference, and if the interference occurs, the CSMA/CA mode is adopted for channel allocation. Because a plurality of wireless body area networks exist, collision can be detected, and in order to reduce the probability of re-collision, a binary exponential back-off algorithm is adopted to avoid collision and re-generation of collision.

Considering the change of the distance between the wireless body area network and the service center in the moving process, when the distance is close, if the original transmitting power is still kept, the energy consumption of the sink is increased, and meanwhile, the interference to other wireless body area networks is generated. Therefore, the service center compares the received signal strength of the wireless body area network sink with the expected received signal strength to obtain an offset value e, and performs transmission power control on the corresponding wireless body area network sink through a discrete incremental PID algorithm:

Δu(k)＝K_p(e(k)-e(k-1))+K_ie(k)+K_d(e(k)-2e(k-1)+e(k-2))

K_p、K_i、K_drespectively representing a proportional term, a differential term and an integral term, e (k-i) represents the signal intensity deviation received by the previous i rounds, and delta u (k) is the transmission power of the next round of controlling the sink.

The invention will be further explained with reference to the drawings.

As shown in fig. 1, the communication structure of the wireless body area network may be divided into three layers, where the first layer is communication between the sensor node and the sink, the second layer is communication between the sink and the service center, and the third layer is communication between the service center and an organization such as a hospital.

When only one wireless body area network exists in the environment, the channels are distributed according to the priorities of the nodes by using a TDMA mode, and the priorities are shown in the table 1, so that the sensor nodes are prevented from generating interference with each other when communicating to the sink. If the sensor nodes are in the same priority, the sink randomly allocates time slots for the sensor nodes, and records the received signal strength from each sensor node.

Table 1ieee802.15.6 priority

When a plurality of wireless body area networks exist in the same narrow environment, as shown in fig. 2, the method for determining whether the target wireless body area network is interfered includes: when the distance D between the sink of the two parties is more than four times of the maximum communication radius R of the sensor and the duration T is more than T_thAnd judging that the two wireless body area networks generate interference. In the case of a short distance without object blocking, the interference between wireless body area networks is mostly generated, and the transmission loss LS of the free space is mainly considered to be 32.45+20 × log (f) +20 × log (d), where the unit of the transmission frequency f is MHz and the unit of the transmission distance d is km. Sink nodes of different wireless body area networks which generate interference mutually exchange time slot distribution tables and signal strength of sensor nodes of the sink nodes.

The method for judging whether the sink nodes working in the same time slot are interfered or not comprises the following steps: and calculating the signal to interference plus noise ratio (SINR) of communication in the same time slot, and judging whether the corresponding sink node is interfered or not. If the SINR is<SINR_thIf so, interference is generated, a time slot is added after the time slot by the sink of the two parties, and the two nodes are randomly distributed with a sequence; otherwise, no interference is generated, and the sink of the two parties can carry out communication work in the same time slot correspondingly.

The time slot channels before and after the reallocation are shown in fig. 3.

In the second layer communication, as shown in fig. 4, the IEEE working group only divides the 2.4Ghz band into 14 channels, wherein the truly orthogonal channels are only 3, and the rest channels are all partially overlapped. Because the second layer communication adopts a CSMA/CA mode, when a large number of users of the wireless body area network exist, the performance of a wireless channel is reduced, information communication among the users can generate collision, and therefore the network throughput is reduced, and the energy efficiency is also reduced.

The existing sink nodes have two situations, namely no interference and interference generation, if no interference exists, the service center randomly allocates channels for the sink nodes, and if interference is generated, the CSMA/CA mode is adopted for channel allocation. Because a plurality of wireless body area networks exist, collision can be detected, and in order to reduce the probability of re-collision, a binary exponential back-off algorithm is adopted to avoid collision and re-generation of collision.

Considering the change of the distance between the wireless body area network and the service center in the moving process, when the distance is close, if the original transmitting power is still kept, the energy consumption of the sink is increased, and meanwhile, the interference to other wireless body area networks is generated. Therefore, the service center compares the received signal strength of the wireless body area network sink with the expected received signal strength to obtain an offset value e, and performs transmission power control on the corresponding wireless body area network sink through a discrete incremental PID algorithm:

Δu(k)＝K_p(e(k)-e(k-1))+K_ie(k)+K_d(e(k)-2e(k-1)+e(k-2))

the above-listed series of detailed descriptions are merely specific illustrations of possible embodiments of the present invention, and they are not intended to limit the scope of the present invention, and all equivalent means or modifications that do not depart from the technical spirit of the present invention are intended to be included within the scope of the present invention.