KR100831172B1 - Beacon scheduling method in communication network system - Google Patents

Abstract

A beacon scheduling method in a communication network system is disclosed. This method is a method of determining when the top and child coordinators transmit beacons in a communication network system in which a top coordinator and child coordinators transmit beacons at regular intervals. First, a tree is formed by a top coordinator. After connecting the highest and child coordinators to the configured tree, the beacon transmission time of the child coordinators is calculated within an inactive period in the beacon period of the highest coordinator.

According to this method, the beacon transmission timings of the child coordinators are all different, and each active period is configured immediately after the transmission time of each coordinator so that the beacon transmission intervals and the active periods of the child coordinators do not overlap. Accordingly, collision between beacons generated in the child coordinator or collisions with data transmitted by devices connected to other coordinators by the beacons transmitted by the coordinators can be prevented.

Communication, Network, Coordinator, Beacon, Scheduling

Description

Beacon scheduling method in communication network system

1 is a diagram illustrating an active section and an inactive section in a beacon period of a conventional coordinator.

2 is a diagram illustrating a conventional beacon scheduling method of a plurality of coordinators.

3 is a view showing a region in which beacons of conventional coordinators overlap.

4 illustrates beacon transmission scheduling superimposed by conventional coordinators.

5 is a view showing overlapping active sections of conventional coordinators.

6 is a diagram illustrating a transmission zone overlapping an overlapping active section of conventional coordinators.

7 is a flowchart illustrating an execution process of a beacon scheduling method in a communication network system according to an embodiment of the present invention.

8 illustrates a tree structure of coordinators configured for implementing a beacon scheduling method in a communication network system according to an embodiment of the present invention.

9 is a view illustrating a beacon transmission time of a plurality of coordinators in a beacon scheduling method in a communication network system according to an embodiment of the present invention.

10 is a flowchart illustrating an initialization process of a coordinator when child coordinators are connected to a tree in a beacon scheduling method in a communication network system according to an embodiment of the present invention.

11 is a flowchart illustrating a process of allowing a higher coordinator when a lower coordinator attempts to connect in a beacon scheduling method in a communication network system according to an embodiment of the present invention.

12 is a flowchart illustrating a process of processing a request for a tree number usable by a lower coordinator in a beacon scheduling method in a communication network system according to an embodiment of the present invention.

13 is a diagram illustrating a tree structure before expansion when there is a tree expansion request in a beacon scheduling method in a communication network system according to an embodiment of the present invention;

FIG. 14 is a diagram illustrating a tree structure expanded dynamically after processing of a tree extension request in a beacon scheduling method in a communication network system according to an exemplary embodiment of the present invention. FIG.

<Explanation of symbols for the main parts of the drawings>

100,110,211,221 ... Beacon 101 ... Beacon interval (cycles)

102,111,112,212,222 ... active interval 103 ... inactive interval

104 Competitive Sector (CAP) 105 Competitive Free Sector (CFP)

200 ... Top Coordinator (PANC) 210,220 ... Child Coordinator (C1, C2)

230 ... Overlapping section of beacon transmission area 310 ... Device (N)

320 ... Overlap of Beacon Transmission Area and Data Transmission Area

401 ... 413 Beacon transmission point ... 421-433 ... Active section

441 ... tree depth 1 442 ... tree depth 2

443 ... tree depth 3

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beacon scheduling method in a communication network system employed in the field of wireless communication network technology. In particular, the present invention relates to a communication capable of preventing collision between beacons and data between beacons and data occurring in different coordinators. A beacon scheduling method in a network system.

According to the ZigBee network topology, each node in the network is divided into a top coordinator, a child coordinator, and a device.

A plurality of devices are connected to one coordinator, and the node selects one of the beacons of the coordinator transmitted to the coordinator to connect to the coordinator. The coordinator transmits a beacon to nodes connected to the coordinator, and the nodes may synchronize with and communicate with the coordinator. The highest coordinator refers to the node located at the top of the tree structure and manages the entire tree, and the tree structure can be spread by the node connected to the coordinator acting as the lower coordinator.

1 is a diagram illustrating an active section and an inactive section in a beacon period of a conventional coordinator.

Referring to FIG. 1, this indicates a beacon interval, an active section, and an inactive section managed by one coordinator. The beacon interval (period) 101 includes an active period 102 for devices to transmit and receive data and an inactive period 103 for entering a sleep state to minimize energy consumption. The active period 102 is a contention free period in which a specific device transmits data without contention between a contention access period (CAP) 104 and a device, in which devices connected to the coordinator transmit data through contention. Period: CFP) 105. The coordinator periodically transmits the beacon 100 to inform the devices of the beacon interval (period) 101, the active period 102, and information about a device to transmit data in the competition free period 105.

2 is a diagram illustrating a conventional beacon scheduling method of a plurality of coordinators.

Referring to FIG. 2, this indicates a beacon transmission section and an active section for each coordinator in a network in which a highest coordinator and a child coordinator exist. The highest coordinator initially sets the size of the beacon period 101 and the active period 102 and informs the nodes connected to it through the beacon 100. The child coordinator operates as a device in the active section 111 of the highest coordinator, transmits and receives data with the highest coordinator, determines the transmission time of the beacon 110 in the inactive section 103 of the highest coordinator, and sets its own beacon ( 110) After transmission, data is transmitted / received with the devices connected to it in the active section 112.

3 and 4 are diagrams illustrating regions in which beacons of conventional coordinators overlap and beacon transmission scheduling overlapped by coordinators, respectively.

Referring to FIG. 3, this shows a network to which the highest coordinator 200 and child coordinators C1 210 and C2 220 are connected. FIG. 4 illustrates a time and an active period in which each coordinator transmits a beacon in the network environment of FIG. 3.

After the active section 111 of the highest coordinator 200 ends, in the inactive section 103, the child coordinator C1 210 selects a random time to transmit the beacon 211 and uses the active section 212. The coordinator C2 220 also transmits its beacon 221 in the inactive section 103 and uses the active section 222. At this time, when the beacon transmission times 211 and 221 of the two coordinators C1 and C2 are the same, beacons collide with each other in the section 230 where the transmission zones overlap. In FIG. 3, reference numeral 310 denotes a device.

5 and 6 illustrate overlapping active sections of conventional coordinators and transmission zones overlapping the overlapping active sections, respectively.

Referring to FIG. 5, this means that the beacon 211 of the C1 210 and the beacon 221 of the C2 220 that are child coordinators of the highest coordinator 200 do not collide with each other, but the active period of the C1 210 may be 212 and the active period 222 of the C2 220 overlaps.

In FIG. 6, when device N 310 is a device connected to the coordinator C1 210, a device in the active section 212 of the coordinator C1 210 at the time when the coordinator C2 220 transmits a beacon. When the N 310 transmits data to the coordinator C1 210, an overlap section 320 is generated. In this case, beacons and data collide with each other.

The present invention has been made to solve the above problems in the prior art, without beacons transmitted from coordinators constituting a network collide with each other, or data transmitted from devices connected to other coordinators. An object of the present invention is to provide a beacon scheduling method in a communication network system capable of stably transmitting beacons of all coordinators.

In order to achieve the above object, a beacon scheduling method in a communication network system according to an aspect of the present invention,

A beacon scheduling method in a communication network system that determines when the top and bottom coordinators transmit a beacon in a communication network system in which a top (parent) coordinator and a bottom (child) coordinators transmit beacons at regular intervals.

a) constructing a tree by the highest level coordinator;

b) coupling said top and bottom coordinators to said constructed tree; And

c) calculating a beacon transmission time of the lower coordinators within an inactive period in the beacon period of the highest coordinator.

Here, the method further includes the step b)) initializing the coordinator after the step b).

And after step c), d) managing the tree by a higher coordinator.

Further, after step d), e) expanding the tree by the higher coordinator.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and similar reference numerals are used for similar parts throughout the specification.

In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

Now, a beacon scheduling method in a communication network system according to an embodiment of the present invention will be described with reference to the drawings.

7 is a flowchart illustrating an execution process of a beacon scheduling method in a communication network system according to an embodiment of the present invention.

7, the beacon scheduling method in the communication network system according to an embodiment of the present invention, the highest coordinator and the child coordinators in the communication network system that transmits the beacon every certain period of the top and child coordinators to beacon In the beacon scheduling method in the communication network system for determining the time of transmission, a tree is first constructed by the highest coordinator (step S711). Such a tree configuration will be described in detail later with reference to FIG. 8. When the tree is constructed in this way, the top and bottom (child) coordinators are connected to the constructed tree (step S712). Here, when the child coordinators are connected to the tree in this way, the coordinators go through an initialization process, which will be described later with reference to FIG. 10.

When the connection of the highest and child coordinators to the tree is completed by the above, the beacon transmission time of the child coordinators is calculated within the inactive period in the beacon period of the highest coordinator (step S713). Here, the calculation of the beacon transmission time point will be described in detail with reference to FIGS. 8 and 9.

As described above, when the beacon transmission time for each coordinator is calculated, each coordinator transmits the beacon according to the beacon transmission time.

On the other hand, the beacon scheduling method according to the embodiment of the present invention is completed by the calculation of the beacon transmission time as described above, but preferably, the step of managing the tree by the higher coordinator (step S714) and also the higher coordinator thereafter. Further comprising the step of expanding the tree (step S715). Such tree management and expansion will be described in detail with reference to FIGS. 11, 12, 13, and 14.

8 is a diagram illustrating a tree structure of coordinators configured for implementing a beacon scheduling method in a communication network system according to an embodiment of the present invention.

Referring to FIG. 8, coordinators form a tree structure for implementing a beacon scheduling method in a communication network system according to an exemplary embodiment of the present invention. That is, the highest coordinator C01 and the child coordinators C02, C03, C04, C05, C06, C07, C08, C09, C10, C11, C12, and C13 form a tree structure. Here, the tree structure is configured by one software program, and does not mean any hardware structure. That is, if the tree information and the tree number of the top coordinator (C01) are designated, and the tree numbers (C02 to C13) of the child coordinators are given accordingly, as shown in FIG. 8 (this is represented as a figure for the sake of understanding). The tree structure is automatically configured by the software program.

8 shows a tree structure completed by the coordinator when the maximum tree depth value is 3 and the maximum number of children is 3.

At this time, all coordinators store the tree information, the position information of the parent coordinator in the tree and its own position information. Here, the tree information includes the maximum depth of the tree (hereinafter referred to as "maximum tree depth") and the maximum number of child coordinators (hereinafter referred to as "maximum number of children"). The "tree number" is the order determined by the depth first search (DFS) method in the completed tree.

In FIG. 8, the coordinator belonging to the tree depth 1 (441) is the highest coordinator C01, the coordinators belonging to the tree depth 2 (442) are C02, C06, and C10, and the coordinators belonging to the tree depth 3 (443) are C03, C04, and C05. , C07, C08, C09, C11, C12, C13. In addition, the tree numbers of the coordinators C01, C02, C03, C04, C05, C06, C07, C08, C09, C10, C11, C12, and C13 are 1, 2, 3, 4, 5, 6, 7 , 8, 9, 10, 11, 12, 13

FIG. 10 is a flowchart illustrating an initialization process of a coordinator when child coordinators are connected to a tree in a beacon scheduling method in a communication network system according to an exemplary embodiment of the present invention.

10, first, it is determined whether the corresponding coordinator is the highest coordinator (step S501). Here, the top coordinator is incorporated into the network as one general coordinator, but if another coordinator is not present through the scan, the top coordinator becomes the top coordinator.

In the determination, if the coordinator is the highest coordinator, the highest coordinator determines its beacon interval (period), the length of the active and inactive sections, the maximum tree depth, and the maximum number of children (step S502). At this time, the tree depth and the tree number of the highest coordinator become 1 (step S503). For this purpose, the relationship as shown in Equation 1 below must be satisfied.

On the other hand, if it is not the highest coordinator in the determination step S501, the child coordinator receives the maximum tree depth, the maximum number of children, the higher and the own tree number from the highest coordinator after accessing the highest coordinator (step S504). That is, when the child coordinators C02, C06, and C10 are connected, the highest coordinator C01 is a beacon interval, an active section length, tree information (maximum tree depth 3, maximum number of children 3) and its tree number 1 and the tree number of child coordinators. For 2, 6, and 10, respectively.

In this way, when information is transmitted from the highest coordinator to the child coordinator, the child coordinator stores the information received from the parent coordinator, and calculates its tree depth through the tree information and its tree number (step S505). Then, it is determined whether the calculated tree depth is smaller than the maximum tree depth (step S506). If the tree depth calculated in this determination is not less than the maximum tree depth (ie, greater than or equal to), then the initialization process ends. If the tree depth calculated in the determination step S506 is smaller than the maximum tree depth, the tree number of the coordinator which can be connected to the lower coordinator is calculated (step S507), and the lower tree number is managed (step S508).

Hereinafter, the coordinator will determine a method for determining a beacon transmission time and data transmission and reception.

FIG. 9 is a view illustrating beacon transmission time of a plurality of coordinators in a beacon scheduling method in a communication network system according to an exemplary embodiment of the present invention.

Referring to FIG. 9, this shows a beacon transmission time and an active period for each coordinator in the tree structure of the coordinator created in FIG. 8.

The beacon transmission points for the coordinators C01, C02, C03, C04, C05, C06, C07, C08, C09, C10, C11, C12, and C13 in FIG. 8 are respectively 401, 402, 403, 404, 405 in FIG. , 406, 407, 408, 409, 410, 411, 412, 413, and the active periods of the coordinators are 421, 422, 423, 424, 425, 426, 427, 428, 429, 430, 431, 432, 433, respectively. to be. Here, the lengths of the active sections of all coordinators are the same. In addition, all coordinators have respective active sections immediately following the beacon transmission point, as shown.

In FIG. 9, each coordinator calculates an offset value from the beacon transmission point 401 of the highest coordinator to its beacon transmission point, which is calculated by the information of the tree and its position in the tree. This calculation is made possible by the following equation.

(Tree number -1) x length of active section
In addition, in FIG. 9, each coordinator must be awake in the active section of the parent coordinator to communicate with its parent coordinator, and the starting point of the active section of the parent coordinator is calculated by Equation 2 with the tree number of the parent coordinator.

delete

For example, in FIG. 8, in the case of coordinator C06, data is transmitted and received with C01 in the active section 421 of the coordinator C01, and the device and data including the child coordinators C07, C08, and C09 are transmitted in their active section 426. Send and receive

As described above, according to the method of the embodiment of the present invention, the beacon transmission time points of the child coordinators are all different, and each active period is configured immediately after the transmission time point of each coordinator. The active sections do not overlap. Therefore, a collision between beacons generated in different coordinators or a beacon transmitted by coordinators as in the related art is prevented from colliding with data transmitted by devices connected to other coordinators. Thus, the beacons of all coordinators can be transmitted stably.

Hereinafter, a method of managing a tree by the coordinator will be described.

In the method according to the embodiment of the present invention, the coordinator may connect the coordinator as the maximum number of children to the child coordinator when the calculated tree depth is smaller than the maximum tree depth, and the tree depth is greater than the maximum number of children and when the tree depth is equal to the maximum tree depth. In the case of connecting many coordinators, it can be connected after requesting permission from the parent coordinator.

All coordinators maintain information about the tree number of the child coordinator connected to them. In addition, the changed information about the tree number to be managed is transmitted to the higher coordinator, the top coordinator manages the information about the tree number of the child coordinator connected to all coordinators.

11 is a flowchart illustrating a process of allowing a higher coordinator when a lower coordinator attempts to connect in a beacon scheduling method in a communication network system according to an embodiment of the present invention.

Referring to FIG. 11, when the lower coordinator requests a connection, the upper coordinator first determines whether there is a tree number available among the managed tree numbers (lower tree numbers assigned to each coordinator by the initialization process of the coordinator connected to the tree). (Step S601). In this determination, if there is a tree number available, a tree number is assigned to the lower coordinator (step S602), and the changed information is notified to the higher coordinator of the assigned tree number (step S603). Then, it is determined whether the higher coordinator is the highest coordinator (step S604), and if the highest coordinator is terminated, the connection is terminated, and if not, the changed information is notified to the higher coordinator (step S605).

On the other hand, if there is no tree number available in step S601, it is determined whether or not it is the highest coordinator (step S606). In this determination, if the user is the highest coordinator, the connection of the lower coordinator is not allowed (step S607), and if the user is not the highest coordinator, the tree number available to the upper coordinator is requested (step S608). Then, it is judged whether or not the tree number is allowed (step S609), and if not allowed, the connection of the lower coordinator is not allowed (step S607). If the tree number is accepted in the step S609, the upper coordinator manages the allowed tree number (step S610), and assigns the tree number to the lower coordinator (step S611).

12 is a flowchart illustrating a process of processing a request for a tree number usable in a lower coordinator in a beacon scheduling method in a communication network system according to an exemplary embodiment of the present invention.

Referring to FIG. 12, when requesting a tree number usable in a lower coordinator, first, the upper coordinator checks whether there is a tree number available among the managed tree numbers (lower tree numbers assigned to the coordinator by the initialization process of the coordinator connected to the tree). It determines (step S801). In this determination, if there is a tree number available, a tree number is assigned to the lower coordinator (step S802), and the changed information is notified to the higher coordinator of the assigned tree number (step S803). Then, it is determined whether the higher coordinator is the highest coordinator (step S804), and if the highest coordinator is terminated, the program is terminated, and if it is not the highest coordinator, the changed information is notified to its own high coordinator (step S805).

On the other hand, if there is no tree number available in step S801, it is determined whether or not it is the highest coordinator (step S806). In this determination, if it is the highest coordinator, it sends a request failure message to the lower coordinator (step S807), and if it is not the highest coordinator, it requests again the tree number available to its upper coordinator (step S808). Then, it is determined whether or not the tree number is allowed (step S809), and if not, a request failure message is sent to the lower coordinator (step S807). If the tree number is accepted in the determination of step S809, the allowed coordinator manages the allowed tree number in the upper coordinator (step S810), and assigns the tree number to the lower coordinator (step S811).

13 and 14 schematically show a processing procedure when there is a request to expand a tree in a beacon scheduling method in a communication network system according to an embodiment of the present invention, and FIG. 13 shows a tree structure before a tree is expanded. FIG. 14 is a view showing a tree structure which is fluidly expanded.

Referring to FIG. 13, this is a tree managed by the highest coordinator C01 when the maximum tree depth and the maximum number of children are three, and the coordinators C02 and C10 may have up to three child coordinators, but only one coordinator is connected to each other.

At this time, the coordinators C02 and C10 inform the upper node (coordinator) of 4, 5, 12, and 13 that are not used among the lower tree numbers. Accordingly, it can be seen that the tree number 4, 5, 12, 13 is not used for C01, the highest coordinator.

Referring to FIG. 14, when a new coordinator requests a connection to coordinator C06 in FIG. 13, C06 may not exceed its maximum number of children (ie, 3), and thus request a tree number from a parent coordinator C01. Coordinator C01 allocates 5 to C06 among tree numbers 4, 5, 12, and 13 that can be used among the tree numbers below its own. Then, C01 informs the coordinator C02, which is the parent node of tree number 5, to prevent the use of tree number 5 in C02.

In addition, when a new coordinator requests a connection to the coordinator C11 in FIG. 13, C11 requests a tree number from the upper node C10 because its tree depth is equal to the maximum tree depth (ie, 3). Then, the coordinator C10 allocates C11, which is not used among its lower tree numbers, to C11, and informs C01, the higher coordinator, of this information.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

As described above, in the beacon scheduling method in the communication network system according to the embodiment of the present invention, the beacon transmission timings of the child coordinators are all different, and each active period is configured immediately after the transmission time of each coordinator. Therefore, the beacon transmission section and the active section of the child coordinators do not overlap. Therefore, a collision between beacons generated in different coordinators or a beacon transmitted by coordinators as in the related art is prevented from colliding with data transmitted by devices connected to other coordinators. As a result, beacons of all coordinators can be transmitted stably, and data transmission efficiency can be increased.

Claims (24)

A beacon scheduling method in a communication network system that determines when the top and bottom coordinators transmit a beacon in a communication network system in which a top (parent) coordinator and a bottom (child) coordinators transmit beacons at regular intervals. a) constructing a tree by the highest level coordinator; b) coupling said top and bottom coordinators to said constructed tree; And c) calculating a beacon transmission time of the lower coordinators within an inactive period in the beacon period of the highest coordinator. The method of claim 1, And b ') initiating a coordinator after step b). The method of claim 1, And after step c), d) managing the tree by a higher coordinator. The method of claim 3, After step d), e) expanding the tree by a higher coordinator. The method of claim 2, wherein b ') initializing the coordinator comprises: b'-1) determining whether the corresponding coordinator is the highest coordinator; b'-2) if the coordinator is the highest coordinator, determining tree information and a tree number of the highest coordinator; b'-3) calculating the tree depth of the child coordinator using the tree information and the tree number of the highest coordinator if the highest coordinator in step b'-1); b'-4) determining whether the calculated tree depth is smaller than the maximum tree depth; And b'-5) if the calculated tree depth is smaller than the maximum tree depth, calculating and managing a tree number of coordinators that can be connected to a lower coordinator. The method of claim 5, In step b'-2), the tree information of the highest coordinator includes a maximum tree depth and the maximum number of children in the beacon scheduling method in a communication network system. The method of claim 5, Beacon scheduling in the communication network system, characterized in that the beacon interval (period), the length of the active and inactive intervals of the highest coordinator is determined together with the determination of the tree information and the tree number of the highest coordinator in step b'-2). Way. The method of claim 5, The beacon scheduling method of the communication network system, characterized in that the tree number of the highest coordinator is determined in step b'-2). The method of claim 8, A beacon scheduling method in a communication network system, characterized in that to satisfy the following mathematical relationship as a condition that the tree number of the highest coordinator becomes 1.

The method of claim 1, In step b), the connection of the child coordinators to the tree is made by the child (lower) coordinator requesting the top (higher) coordinator to access the lower coordinator or requesting a tree number. Beacon scheduling method in. The method of claim 10, When the child (child) coordinator requests a connection to the top (parent) coordinator, 11-1) determining whether there is a tree number available among the managed tree numbers; 11-2) if there is a tree number available, assigning the tree number to the lower coordinator; 11-3) notifying the higher coordinator of the assigned tree number changed information; 11-4) determining whether the higher coordinator is the highest coordinator; 11-5) A method of scheduling beacons in a communication network system, the method comprising: terminating the connection if the highest coordinator and notifying the higher coordinator of the changed information if the highest coordinator is not. The method of claim 11, 11-6) if there is no tree number available in step 11-1), determining whether it is the highest coordinator; 11-7) in the determination of step 11-6), disallowing connection of the lower coordinator if the self is the highest coordinator; 11-8) in the determination of step 11-6), requesting a tree number available to the higher coordinator if the self is not the highest coordinator; 11-9) after the request, determining whether the tree number is allowed; 11-10) disallowing connection of the lower coordinator if the tree number is not allowed in the determination of step 11-9); And 11-11) If the tree number is allowed in the determination of step 11-9), the higher coordinator manages the allowed tree number and assigns the tree number to the lower coordinator. Scheduling Method. The method of claim 10, When the child (child) coordinator requests a tree number from the top (parent) coordinator, 13-1) determining whether there is a tree number available among the managed tree numbers; 13-2) if there is a tree number available in the determination, assigning the tree number to the lower coordinator; 13-3) notifying the higher coordinator of the allocated tree number to the changed information; 13-4) determining whether the higher coordinator is the highest coordinator; And 13-5) The method of the beacon scheduling in the communication network system comprising the step of terminating the program if the highest coordinator in step 13-4), and informs the higher coordinator of the changed information if not the highest coordinator. The method of claim 13, 13-6) if there is no tree number available in the determination of step 13-1), determining whether it is the highest coordinator; 13-7) transmitting the request failure message to the lower coordinator if the self is the highest coordinator in the determination; 13-8) requesting an available tree number from its higher coordinator if it is not the highest coordinator in the determination of step 13-6); 13-9) after the request, determining whether the tree number is allowed; 13-10) if the tree number is not granted in the determination of step 13-9), sending a request failure message to the lower coordinator; And 13-11) If the tree number is allowed in the determination of step 13-9), the higher coordinator manages the allowed tree number, and further includes assigning the tree number to the lower coordinator. Scheduling Method. The method of claim 1, In step c), the coordinator calculates the beacon transmission time point by calculating an offset value from the beacon transmission time point of the highest coordinator to the beacon transmission time point of any child coordinator. Beacon scheduling method. The method of claim 15, The calculation of the offset value is calculated by the information of the tree and its position in the tree, the calculation is performed by the following equation. (Tree number -1) x length of active section The method of claim 1, Beacon scheduling method in a communication network system, characterized in that the length of the active period of all coordinators to be equal for the calculation of the beacon transmission time of the coordinators in step c). The method of claim 1, For calculating the beacon transmission timing of the coordinators in step c), wherein all coordinators have respective active sections immediately following each beacon transmission timing. The method of claim 3, In the communication network system, all coordinators manage information on the tree number of the lower coordinator connected to the higher coordinator and transmit changed information on the tree number managed to the higher coordinator. Beacon scheduling method. The method of claim 3, Beacon scheduling method in a communication network system, characterized in that for the tree management by the upper coordinator, the highest coordinator manages information on the tree number of the child coordinator connected to all coordinators. The method of claim 4, wherein the expansion of the tree by the higher coordinator, 21-1) the lower coordinator notifying the higher coordinator of the tree number which is not used among its lower tree numbers; 21-2) when the new coordinator requests to connect to the lower coordinator having the maximum number of children, the lower coordinator requests a tree number from his upper coordinator; And 21-3) A beacon scheduling method in a communication network system comprising assigning an arbitrary tree number that can be used by a higher coordinator to a lower coordinator requesting the tree number according to the request. . The method of claim 21, wherein after step 21-3) 21-4) The upper coordinator further informs the other lower coordinator, which is the parent node of the tree number assigned by the higher coordinator, to prevent the coordinator from using the allocated tree number. Beacon scheduling method in a network system. The method of claim 4, wherein the expansion of the tree by the higher coordinator, 23-1) the lower coordinator notifying the higher coordinator of the tree number that is not used among its lower tree numbers; 23-2) when the new coordinator requests to connect to the lower coordinator having the maximum tree depth, the lower coordinator requests a tree number from the coordinator which is his upper node; And 23-3) A beacon scheduling method in a communication network system comprising the step of assigning a tree number which is not used among its lower tree numbers to a lower coordinator requesting the tree number according to the request. The method of claim 23, wherein after step 23-3) 23-4) Beacon scheduling method in a communication network system further comprising the step of notifying the tree coordinator allocation information as described above.

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