JP7281039B2 - Body area network communication method - Google Patents

Description

The present invention is an ad-hoc network such as a body area network (IEEE802.15.6, hereinafter sometimes abbreviated as BAN), which is a network within a range of several meters around the human body. More specifically, in an ad-hoc network such as a BAN, it monitors whether neighboring BANs are using the same communication channel, and uses the same communication channel. number of sensor nodes (hereinafter sometimes abbreviated as nodes) in its own network and the number of detected peripheral BAN nodes using the same channel If it has connected the maximum number of nodes, it does not transfer the communication channel and keeps the same communication channel, and if it does not have the maximum number of nodes connected, it follows the procedure to transfer the communication channel. , a body area network communication system characterized by transitioning to another communication channel.

BAN is one of the ad-hoc networks, and generally has a hub and multiple nodes that measure and wirelessly transmit data to the hub, and the communication distance between the hub and nodes is at most several meters on the channel set when the BAN is established. to send and receive signals. Although the communicable distance is only a few meters at most, there is a possibility of interference between BANs using the same channel. Even if a vacant channel is confirmed among the specified 40 channels and a BAN is established at the time of initial setup, other users operating on the same channel may approach as the user moves.
In particular, when a large number of BANs on the same channel approach each other, it is necessary to quickly and efficiently avoid the interference of all BANs.
Even in standards such as Smart BAN and IEEE 802.15.6, there is no provision for measures to avoid interference caused by such BAN movement, and it currently depends on the implementation.

As a method to avoid interference in the BAN, Non-Patent Document 1 detects each other's network IDs, subtracts the other party's ID from its own ID, and if the value is "plus and odd" or "negative and even" A method has been proposed in which the own channel is not switched, and if the number is "plus and even" or "minus and odd", the channel is switched. In this method, the BANs to be channel-switched are randomly selected by computation using the network ID, so the priority of channel switching for all target BANs is the same. However, in an actual system, 1. The number of nodes connected to a BAN differs depending on the BAN;2. Since the quality of service (Quality of Service, hereinafter sometimes abbreviated as QoS) of data transmitted by connected nodes differs depending on the BAN, priority should be given to the BAN that should switch channels. is desired.

As another method for avoiding interference in BANs, in Patent Document 1, when two BANs operating on the same channel are close to each other, is it possible to achieve both by changing communication behavior such as active period/inactive period? A method has been proposed in which a determination is made as to whether or not the two are compatible, and if it is determined that compatibility is not possible, a BAN for channel switching is determined based on the number of nodes and the duty cycle of both. This method is effective as a one-to-one interference avoidance method when there are two BANs operating on the same channel, but when there are many BANs operating on the same channel, one-to-one interference Avoidance operations need to be performed multiple times, and there remains a problem in terms of quick and efficient interference avoidance.

Tatsuya Kikuchi, Teruhisa Ninomiya, 'Study of Interference Avoidance Method for Cooperative Operation Using NW-ID', Institute of Electronics, Information and Communication Engineers Technical Report (IEICE Technical Report) 113(85), 13-18, 2013-06 -17

Japanese Patent Publication No. 2017-526269

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in the prior art, and to provide a communication system that allows all BANs to quickly and efficiently avoid interference even when a plurality of BANs operating on the same channel are close to each other. and

In the body area network communication method of the present invention for achieving such an object, when an interference state occurs due to the proximity of a plurality of BANs establishing a network on the same channel, each BAN is an interference avoidance target. It is characterized by detecting the number of nodes connected to the BAN that is, and if the number of own nodes is larger, the current channel is held, and if the number of nodes is the same or smaller, it shifts to another channel. and

The method of detecting the number of nodes connected to a BAN that is subject to interference avoidance is to receive C-beacon signals broadcast from the BAN at predetermined time intervals, and to obtain Duty Cycle information that indicates the occupancy rate of nodes in the BAN. A value may be used.

The method of detecting the number of nodes connected to a BAN that is subject to interference avoidance consists of a C-beacon signal in a new format that adds a bit string indicating the number of connected nodes to the conventional C-beacon signal broadcast from the BAN. However, the value of the number of connected nodes included in the new C beacon signal may be used.

In the body area network communication method of the present invention for achieving such an object, when an interference state occurs due to the proximity of a plurality of BANs establishing a network on the same channel, each BAN is an interference avoidance target. Detects the number of nodes communicating with the highest QoS among the nodes connected to the BAN that If it is larger, the current channel is retained, and if the number of QoS nodes is the same or smaller, it shifts to another channel.

The method of detecting the number of QoS nodes in a BAN that is subject to interference avoidance consists of adding a bit string indicating the number of QoS nodes to the C-beacon signal from the BAN to form a C-beacon signal in a new format, and generating a new C-beacon signal. It is also possible to use the value of the number of QoS nodes included in .

A BAN that has decided to shift to another channel by comparing the number of nodes or the number of QoS nodes uses the Interference Mitigation bit, which indicates that the channel is being shifted in the C beacon signal, during the shift operation, It is also possible to notify the BAN that it is in the transition operation.

A BAN that has decided to shift to another channel by comparing the number of nodes or the number of QoS nodes generates a C-beacon signal in a new format in which a bit string indicating the destination channel number is added to the C-beacon signal during the shift operation. It may be configured to notify the surrounding BANs to which channel it is in transition operation.

According to the present invention, even when a plurality of BANs operating on the same channel approach each other and cause interference, all BANs can quickly and efficiently avoid interference.

Conceptual diagram of interference between BANs The figure which shows the basic structure and function of the radio|wireless transmission/reception part of the hub of BAN. Diagram showing configurations of C channel information bit string signal, D channel information bit string signal, C beacon signal, and D beacon signal of BAN FIG. 4 illustrates a procedure for determining channel hold/move according to the first embodiment; Diagram showing BAN's C-beacon signal format for estimating the number of connected nodes Diagram showing the structure of the new C beacon signal format including information on the number of connected nodes Diagram showing an example of how to decide where to move a channel A diagram showing the structure of a new C-beacon signal format including destination channel information A diagram showing the configuration of a new C beacon signal format including information on the number of connected nodes and destination channel information FIG. 4 illustrates a procedure for determining channel hold/move according to a second embodiment; Diagram showing the structure of the new C-beacon signal format including information on the number of QoS nodes The figure which shows the simulation test result regarding the Example of this invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals, and their description may be omitted.

FIG. 1 is a diagram conceptually explaining the occurrence of an interference state when a plurality of BANs approach each other and avoidance of interference by the communication system of the present invention. In FIG. 1, the BAN 100 monitors the BANs existing in its vicinity at predetermined time intervals by receiving C-beacons broadcast from the BANs in the vicinity. BAN110 and BAN120 are approaching BAN100, BAN100 and BAN120 are communicating with the hub and node on the same channel 1, and BAN110 is communicating with the hub and node on different channel 2.
BAN100 detects the number of connected nodes of BAN120 together, compares the number of connected nodes of itself and the number of connected nodes of BAN120, and if the number of nodes of BAN120 is larger than the number of nodes of itself, or the number of nodes is the same , when the BAN 100 detects that the BAN 120 approaches within a predetermined range, it shifts to another channel (other than 1 and 2) that is not used in the vicinity.

FIG. 2 is a diagram showing an outline of an information communication system in BAN. The radio transmitting/receiving section 3 of the hub performs data communication with its own nodes by means of a D-channel information bit string signal 310 from a data channel (D-channel) transmitting/receiving device 31, and the information received from each node is shown in the figure as an information bit string. is sent to the higher-level components of the hub not shown.
The channel used for data transmission/reception is set by confirming an empty channel from among the 40 specified channels when the BAN is established.
The radio transmitting/receiving unit 3 of the hub transmits information such as which channel is used by its own BAN to communicate with the nodes, the number of nodes, etc. in the C channel information bit string signal 300 from the control channel (C channel) transmitting/receiving device 30. is notified to the surrounding BANs by the C beacon signal 301, and by receiving the C beacon signals of the surrounding BANs, is there a BAN in the surroundings that has established communication with the node on the same channel as itself? It is possible to obtain information such as whether or not, if any, how many exist, and the number of those nodes.

FIG. 3 schematically shows a timing chart of the C beacon signal 301 and the D channel information bit string signal 310. The C beacon signal 301 is notified from the radio transmitting/receiving unit 3 of the hub to the peripheral BANs at predetermined time intervals. The D beacon signal 311 is transmitted and received within its own BAN at the timing of transmission and reception between the hub and node within its own BAN.

(First embodiment)
The first embodiment of the present invention will be specifically described with reference to FIGS. 4, 5, 6, 7 and 8. FIG.
FIG. 4 shows that approaching BANs monitor BANs existing around themselves, evaluate the number of detected BAN nodes, and determine whether they should maintain the same communication channel without transferring the communication channel, or another It shows the procedure for deciding whether to move to a communication channel.
step one
C beacon signals 301 from peripheral BANs are searched at predetermined time intervals to monitor peripheral BANs.
step 2
When a peripheral BAN is detected, it is determined from the C beacon signal 301 whether or not its own BAN and peripheral BAN are on the same channel. go to step 3.
step 3
Detects the number of nodes connected to the peripheral BAN from the C beacon signal 301 of the peripheral BAN using the same channel, compares it with the number of connected nodes of its own, and if the number of nodes of its own is larger, it uses itself. Hold the channel that is being used, return to step 1 to continue monitoring the peripheral BAN, and proceed to step 4 if the number of nodes is equal or smaller.
step 4
Notifies the surrounding BAN that the channel is in operation, notifies the destination channel number, etc., transfers the channel currently used by itself to another channel, returns to step 1 after the transfer, and returns to the peripheral continue to monitor for bans.

Regarding the determination of "whether or not there is a BAN on the same channel" in step 2 of FIG. 4, the channel configuration of the ETSI BAN (ETSI TS 103 325 V1.1.1 (see 2015-04)) can be monitored using the C-beacon signal 301.
As shown in FIG. 3, the radio transmitting/receiving unit 3 of the hub transmits information indicating which channel is used by its own BAN to communicate with the node in the C beacon signal 301 whose signal configuration is shown in FIG. D-ch Channel Number (400)” is notified to the surrounding BANs, and by receiving the C beacon 301 signal of the surrounding BANs, is there a BAN communicating with the node on the same channel as yourself? It is possible to check how many there are, if any, and so on.

As a mechanism for "detecting the number of connected nodes" in step 3 of FIG. 4, for example, the number of connected nodes can be estimated from the Duty Cycle (410) included in the C beacon signal 301 shown in FIG. That is, when 2 bits of Duty Cycle are '00', the occupancy rate of Scheduled Access Period (SAP) in the data channel is 0 to 25%, '01' is 25% to 50%, and '10' is When it is 50% or more and less than 75%, when it is '11' it is 75% or more. It determines that the number of nodes is large, and if its own occupancy rate is small, it determines that the number of nodes is small.

As a mechanism for "detecting the number of connected nodes" in step 3 of FIG. 4, it is also possible to construct a C beacon signal 500 in a new format containing information on the number of connected nodes, as shown in FIG. That is, the number of connected nodes can be detected by constructing a C beacon signal in which a bit (4 bits) indicating the number of connected nodes is newly inserted into the C beacon signal of the ETSI BAN. It can be realized by adding a new 4 bits (510) indicating the number of connected nodes after the Time Stamp and increasing the 1 bit Reserved bit (520) by 4 bits to 5 bits for byte alignment.

As for the "channel transfer procedure" in step 4 of FIG. 4, the transfer destination can be selected at random from available channels, but as shown in FIG. It is also possible to migrate the channel spacing where is the furthest apart to a channel that bisects as evenly as possible. In FIG. 7, if there are four channels currently in use, namely channels 1, 2, 14, and 20, the interval between adjacent in-use channels is the shortest between channels 2 and 14. , and the channel 8 located in the middle can be selected as the new destination channel.

When switching to another channel (other than 1 and 2) that is not used in the vicinity, it is possible to notify that the channel is being switched by the C beacon signal. For example, in ETSI BAN, by setting the Interference Mitigation bit (420) in the C beacon signal shown in Fig. 5 to '1', it is reported that the channel is being shifted. As a result, surrounding BANs using the same channel can be used as a basis for determining whether or not their own BAN should switch channels.
Each BAN detects the Interference Mitigation bit (420) from each other and determines whether or not it should switch channels, so even if interference occurs in 3 or more BANs, Interference avoidance operations can be performed sequentially.
For example, even if it is detected in step 2 of FIG. 4 or step 2 of FIG. 10 to be described later that the surrounding BAN is using the same channel as itself, the Interference Mitigation bit (420) indicates that the BAN is in the process of channel migration. is recognized, the interference avoidance operation can be sequentially performed without causing confusion by returning to step 1 without proceeding to step 3.

Also, as shown in FIG. 8, the C beacon signal format is extended to create a C beacon 700 of a new format that includes destination channel information, and a destination channel (710) is provided in the C beacon signal to If the channel number of the BAN can be described, it is possible to notify the channel number of the transition destination, and it is possible to prevent the BANs that are simultaneously performing channel transition from shifting to the channel with the same number.
In the specific example of FIG. 8, since 710 is 6 bits, Reserved (720) is increased by 2 bits and expanded to 3 bits in order to achieve byte alignment.

Further, as shown in FIG. 9, it is also possible to expand the C beacon signal format and configure a C beacon signal 1000 of a new format that includes information on the number of connected nodes and destination channel information. If Number of Nodes (1003) and Destination Channel (1004) can be provided in the C beacon signal, and the bit (4 bits) indicating the number of connected nodes and the destination channel number (6 bits) can be described in the C beacon signal, the As a mechanism for "detecting the number of connected nodes" in Step 4, Step 3, Number of Nodes (1003) can be used and at the same time, it is possible to prevent the BAN that is performing channel migration from shifting to the same numbered channel.
In the specific example of FIG. 9, since the total of 1003 and 1004 is 10 bits, PHY version (1001) is set to 3 bits and MAC version (1002) is set to 3 bits for byte alignment.

(Second embodiment)
A second embodiment of the present invention will be specifically described with reference to FIGS. 10 and 11. FIG.
In the first embodiment, the method of determining whether to hold or shift the channel used by itself depending on the number of nodes connected to the BAN has been described. is also possible.
As described above, BAN 100 monitors BANs existing in its vicinity at predetermined time intervals. In the example shown in FIG. Recognize that the hub and node are communicating on the same channel 1.
At this time, BAN100 detects the number of QoS nodes of BAN120 and compares the number of QoS nodes of its own with the number of QoS nodes of BAN120. . If equal or less, BAN 100 moves to another channel (other than 1 and 2) not in use in the surroundings.

FIG. 10 shows the procedure for determining whether the communication channel itself should not be migrated and the same communication channel should be maintained, or whether the communication channel should be migrated to another communication channel.
step one
C beacon signals 301 from peripheral BANs are searched at predetermined time intervals to monitor peripheral BANs.
step 2
When a peripheral BAN is detected, it is determined from the C beacon signal 301 whether or not its own BAN and peripheral BAN are on the same channel. go to step 3.
step 3
Detect the number of QoS nodes of the surrounding BAN from the C beacon signal 301 of the surrounding BAN using the same channel, compare it with the number of own QoS nodes, and if the number of own QoS nodes is larger than the number of QoS nodes of the surrounding BAN It retains the channel it is using and returns to step 1 to continue monitoring the peripheral BANs.If the number of QoS nodes of itself is equal to or smaller than the number of QoS nodes of the peripheral BANs, it proceeds to step 4.
step 4
Notifies the surrounding BAN that the channel is in operation, notifies the destination channel number, etc., transfers the channel currently used by itself to another channel, returns to step 1 after the transfer, and returns to the peripheral continue to monitor for bans.

As a mechanism for detecting the number of QoS nodes of each BAN in the second embodiment, for example, a new bit "Number of High QoS 910" (4 bits) indicating the number of QoS nodes is inserted into the C beacon of the ETSI BAN. 11, a new format C-beacon signal 900 containing QoS node number information can be constructed.
In communication between nodes and hubs, QoS is classified into 4 stages from lowest level 0 to highest level 3, and the number of nodes communicating at highest level 3 is a new C beacon format "Number of High QoS 910" 4 bits are added to the reserved bit (920), which was 1 bit, to make it 5 bits.

In the first and second embodiments, only BAN120 is using the same channel as BAN100 around BAN100. , the BAN with the largest number of connected nodes (or the largest number of QoS nodes) among the BANs approaching within a predetermined range retains the current channel without performing channel migration, and other BANs all perform channel migration, and until there are no more BANs on the same channel, the BAN with the smallest number of connected nodes (or the smallest number of QoS nodes) at that point performs channel migration. The body area network communication method of the present invention makes it possible for all related BANs to recognize the communication status of many BANs using the same channel. Quick and efficient interference avoidance becomes possible.

In addition, in order to detect an approaching BAN in advance and effectively implement the interference avoidance operation of the present invention, it is necessary to set the reaching distance of the C beacon larger than the reaching distance of the D beacon. It is considered appropriate to make the beacon reachable distance about two to three times the D beacon reachable distance.

When interference between BANs occurs, the method of randomly determining the BAN to be channel-shifted and the priority based on the number of nodes connected to the BAN and the number of QoS nodes of the present invention are used. For the method, simulation tests were conducted to study the time required to complete the channel transition to avoid interference.
The conditions of the simulation test are as follows. Considering transmission line errors, etc., the time required to complete the channel transition is set to 100 msec between D beacons, and all nodes within the BAN correctly receive D beacons. was the average time to
BAN number: Minimum value 2, Poisson distribution (λ = 8)
Number of nodes: minimum 1, maximum 16, Gaussian distribution (mean 2, variance 2)
Number of QoS nodes: minimum value 0, maximum value 3, Gaussian distribution (average 0, variance 2)
Number of bits of D-beacon: 264bit
D-beacon interval: 100msec
SNR: 11.4dB
Number of trials: 10000 times

The results of the simulation test are shown in FIG.
In FIG. 12, the horizontal axis indicates the number of BANs in the interference state, and the vertical axis indicates the time required for channel transition to avoid the interference state. , A method of randomly determining a BAN to be channel-shifted by the communication method of the present invention (A and B in the figure) that determines the BAN to be channel-shifted according to the priority based on the number of QoS nodes ( It can be seen that channel migration can be completed more efficiently and quickly than in C).

INDUSTRIAL APPLICABILITY The present invention can be used as a communication method for avoiding the interference state that occurs when a plurality of BANs approach each other in a BAN, which is a network within a range of several meters around the human body.

3 Hub wireless transmitter/receiver 30 C-channel transmitter/receiver 31 D-channel transmitter/receiver 100 BAN
110 BAN
120 BAN
300 C channel information bit string signal 301 C beacon signal 310 D channel information bit string signal 311 D beacon signal 500 New format C beacon signal containing connected node number information 700 New format C beacon signal containing destination channel information 900 New format C beacon signal containing QoS node number information 1000 New format C beacon signal containing connected node number information and destination channel information

Claims (8)

When interference occurs due to the proximity of multiple body area networks (BANs) in which hubs and nodes establish a network on the same channel, the wireless transmission/reception units of the hubs in each BAN are subject to mutual interference avoidance. Detects the number of nodes connected to the BAN, and if the number of nodes in its own BAN is larger, it retains the current channel, and if the number of nodes is equal or smaller , it is used next to it. A body area network communication system characterized by avoiding interference by shifting a channel interval that is the furthest between adjacent channels to another channel that is equally divided into two channels as much as possible . The method of detecting the number of nodes connected to a BAN that is subject to interference avoidance uses the value of Duty Cycle information, which indicates the occupancy rate of nodes in the BAN, in the C beacon signal broadcast from the BAN. The body area network communication system of claim 1, wherein: A method for detecting the number of nodes connected to a BAN that is subject to interference avoidance is to configure a C beacon signal of a new format by adding a bit string indicating the number of connected nodes to the C beacon signal broadcast from the BAN, 2. The body area network communication system according to claim 1, wherein the number of connected nodes included in the new C-beacon signal is used. A BAN in which the wireless transmission/reception units of hubs in each BAN are subject to mutual interference avoidance when interference occurs due to the proximity of multiple BANs in which the hub and node establish a network on the same channel. Detects the number of nodes communicating with the highest QoS (number of QoS nodes) among the nodes connected to the A body area characterized in that, if the number is equal or smaller , the channel spacing that is the furthest between adjacently used channels is transferred to another channel that bisects as evenly as possible. Network communication method. A method for detecting the number of QoS nodes of a BAN that is subject to interference avoidance is to configure a C beacon signal of a new format by adding a bit string indicating the number of QoS nodes to the C beacon signal broadcast from the BAN, and 5. The body area network communication system according to claim 4, wherein the value of the number of QoS nodes included in a C beacon signal is used. The radio transmitter/receiver of the hub in the BAN that has decided to shift to another channel uses the Interference Mitigation bit in the C beacon signal, which indicates that the channel is being shifted, to neighboring BANs during the shift operation. 5. The body area network communication system according to claim 1 or 4, characterized in that the body area network communication system according to claim 1 or 4, characterized in that it notifies that its own BAN is in transition operation. The radio transmitting/receiving unit of the hub in the BAN that has decided to shift to another channel constructs a new format C beacon signal by adding a bit string indicating the shift destination channel number to the C beacon signal during the shift operation, 5. The body area network communication system according to claim 1 or claim 4, wherein said C beacon signal informs surrounding BANs to which channel the own BAN is in transition operation. A new format in which the radio transmitting/receiving unit of the hub in the BAN that has decided to shift to another channel adds a bit string indicating the destination channel number and the number of connected nodes of its own BAN to the C beacon signal during the transition operation. The C beacon signal is configured to notify the surrounding BANs of the number of connected nodes of its own BAN and to which channel its own BAN is in transition operation by means of the C beacon signal, A body area network communication system according to claim 1 or claim 4.

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