KR100889216B1 - The backoff time decision method and The channel access method in wireless sensor network - Google Patents

Abstract

The present invention relates to a method for determining a backoff time in a wireless sensor network, a method of accessing a channel using the same, and a computer-readable recording medium recording a program for realizing each method. To determine the backoff time for data transmission (channel access) to have different Gaussian distributions for each priority, and to adjust the determined backoff time according to the channel state to access the channel. A method of determining a backoff time in a sensor network, a channel access method using the same, and a computer-readable recording medium recording a program for realizing each method are provided.

To this end, the present invention, in the method for determining the backoff time in the wireless sensor network, initializing the number of backoff performed, the number of channel access attempts, and the backoff length setting parameters, the priority of the transmission target data Setting a Gaussian function by selecting a predetermined average value and a variance value according to the identified priority, and determining a random backoff time in a backoff time interval using the set Gaussian function. Steps.

Wireless Sensor Networks, IEEE 802.15.4, MAC, Channel Access, Backoff Time, Priority, Gaussian Distribution, QoS, Channel Status

Description

The backoff time determination method and the channel access method using the same in the wireless sensor network

The present invention relates to a method for determining a backoff time in a wireless sensor network, a method of accessing a channel using the same, and a computer-readable recording medium recording a program for realizing each method. To determine the backoff time for data transmission (channel access) to have different Gaussian distributions for each priority, and to adjust the determined backoff time according to the channel state to access the channel. A method for determining a backoff time in a sensor network, a channel access method using the same, and a computer-readable recording medium having recorded thereon a program for realizing each method.

Recently, the Wireless Sensor Network (WSN), which is being standardized, refers to a network that wirelessly delivers specific information collected by sensors provided between nodes to external devices. A representative protocol used in such a wireless sensor network is a media access control (MAC) protocol for guaranteeing data transmission quality (Qos) proposed in "IEEE 802.15.4" (hereinafter referred to as "IEEE 802.15.4 protocol"). There is this.

1 is a hierarchical diagram of a known IEEE 802.15.4 protocol.

As shown in FIG. 1, the IEEE 802.15.4 protocol is structured as a MAC layer 11 in which wireless channel access control is performed and a physical layer 12 in which data communication is performed. In addition, since the IEEE 802.15.4 protocol structure shown in FIG. 1 is a well-known and common technology, a detailed description thereof will be omitted.

The IEEE 802.15.4 protocol does not define a standard for the upper layer 13 (aka application layer) of the MAC layer 11, and it is recommended that developers independently design modules corresponding to the layer. have.

2 is a frame structure diagram defined in a known IEEE 802.15.4 protocol.

The IEEE 802.15.4 protocol uses a super frame as shown in FIG. 2 for channel access control.

The super frame is divided into an active section and an inactive section, and the active section is a contention access period (CAP) section, which is a channel access section based on a data transmission competition between nodes, and a non-competition based data transmission between nodes. It is divided into a CFP (Contention Free Period) section, which is a channel access section.

The size of the super frame is determined by a period of a beacon message transmitted by a sync node or the like on the wireless sensor network, and the beacon period is set by a network manager.

Each node listens to a beacon message periodically generated in the wireless sensor network to synchronize its beacon with the corresponding beacon, and then performs data communication with other nodes on the active period of the super frame.

In addition, each node uses a "Slotted Aloha" (aka "Slotted CSMA / CA") for channel access on the active period, preferably the CAP period. Here, the slotted Aloha scheme is a wireless communication protocol that randomly performs communication by dividing a packet transmission time point into a slot unit.

3 is a flowchart illustrating a slotted Aloha operation used in a known IEEE 802.15.4 protocol.

First, each node on the wireless sensor network has a number of backoffs (NB) (hereinafter referred to as "NB"), a channel access attempt (CW) (hereinafter referred to as "CW"), The default value of the backoff length setting variable BE (hereinafter referred to as "BE") is initialized to "0", "2" and "macMinBE", respectively (301). Here, "macMinBE" represents the "minimum BE value" preset in advance for channel access in the wireless sensor network.

Then, each node determines a backoff time by generating a random variable having a uniform distribution in the interval [0, 2 ^BE -1], which is a backoff time interval (302). Here, the backoff time indicates the channel access order of the node.

Thereafter, when the backoff time arrives (after waiting for the backoff time), each node performs a Clear Channel Assessment (CCA) by the "CW value" for channel access (303). Here, the CCA refers to a process of checking whether the channel is currently busy or idle.

As a result of performing the CCA, when the channel is not in the idle state, each node performs the backoff time determination process. When the channel is in the idle state, each node decreases the "CW value" by "1". If the channel is in the idle state as a result of performing the CCA again, data (packets) are transmitted (304, 305, 306, 307).

On the other hand, if the channel is busy as a result of re-executing the CCA, each node increases the "NB value" by "1" and increases the "BE value" by "1" and a preset "maximum BE value". The "BE value" is adjusted as the smaller of ["aMaxBE"] (308).

Then, each node waits for channel access while adjusting the " NB value " and " BE value " and when the adjusted (incremented) " NB value " exceeds " macMaxCSMABackoffs " It is regarded as a data transmission failure. Here, "macMaxCSMABackoffs" is a variable for determining data transmission failure when the number of backoffs is exceeded a predetermined number of times to prevent the backoff from continuing (309 and 310).

As described above, the prior art uses a method of adjusting variables such as "CW", "NB", "BE", etc. to ensure data transmission of the node.

Particularly, in the prior art, data transmission quality (QoS) is guaranteed by distinguishing high priority data from low priority data and differently setting the value of the variable according to each priority.

In other words, the "CW value" is set as a value other than "2" in a method commonly used in the prior art. For example, in the prior art, by setting the "CW value" to a higher value for data having a higher priority and a "CW value" to a smaller value for data having a lower priority, the high priority data is transmitted. This allows nodes to succeed in channel access more quickly.

However, according to the related art, the number of data transmission priorities according to the type of service provided by the nodes, the number of nodes, and the like is different depending on the state and the situation of each wireless sensor network. The problem is how much the value needs to be adjusted. That is, in the prior art, there is a problem in which it is not clear how to change the "CW value" and the like on each wireless sensor network to improve the network performance.

In addition, there is a problem that is incompatible when applying the prior art as described above in the state where a product [node] is released in the market in accordance with the standardization of the IEEE 802.15.4 protocol. That is, in order to apply the prior art to the wireless sensor network, there is a problem in that the hardware of the node needs to be changed substantially.

Therefore, there is an urgent need for an algorithm capable of efficiently supporting data transmission priorities and data transmission quality in various cases regardless of the state of the wireless sensor network while maintaining compatibility with the known IEEE 802.15.4 protocol specification.

Accordingly, the present invention has been proposed in order to solve the above problems and meet the above requirements, and provides a data transmission (channel access) method having a different Gaussian distribution for each data transmission priority. A method for determining a backoff time in a wireless sensor network, a channel access method using the same, and each method for determining an off time and accessing a channel by adjusting the determined backoff time according to a channel state It is an object of the present invention to provide a computer-readable recording medium that records a program for realization.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned above can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

In accordance with an aspect of the present invention, a method for determining a backoff time in a wireless sensor network includes: initializing a number of backoffs, a number of channel access attempts, and a backoff length setting variable; Determining a priority of the gaussian, setting a Gaussian function by selecting a predetermined average value and a variance value according to the identified priorities, and using the set Gaussian function, a random backoff time ( backoff time).

The method may further include resetting the Gaussian function by increasing the mean value and the variance value by the corresponding backoff time interval increase as the channel is not accessed after determining the backoff time. .

Meanwhile, the present invention provides a function of initializing the number of backoff executions, the number of channel access attempts, and the backoff length setting variable to a node connected to the wireless sensor network, a function of checking the priority of data to be transmitted, and the identified priority. To realize a function of setting a Gaussian function by selecting a predetermined average value and a variance value according to the ranking, and determining a random backoff time in a backoff time interval using the set Gaussian function. A computer readable recording medium having recorded a program is provided.

In addition, the present invention, the program for further realizing the function of resetting the Gaussian function by increasing the mean value and the variance value by the increment of the back off time interval, as the channel is not accessed after determining the back off time. Provide a computer readable recording medium having recorded thereon.

On the other hand, another method of the present invention, in the channel access method in the wireless sensor network, the number of backoff performed (hereinafter referred to as "NB value"), the number of channel access attempts (hereinafter referred to as "CW" value) and backoff length setting Initializing a variable (hereinafter, referred to as "BE value"), setting a Gaussian function by selecting a predetermined average value and a dispersion value according to the priority of the data to be transmitted, and determining a corresponding backoff time; As the determined backoff time arrives, performing a Clear Channel Assessment (CCA) as much as the "CW" value. As a result of performing the CCA, when the channel is in an idle state, the data is transmitted. When the channel is busy, the " Adjusting the NB value "and" BE value ", and waiting for channel access while adjusting the" NB value "and" BE value ", and as the determined backoff time interval ends, Mean and variance Appointed and a step of performing the re CCA After recrystallization the back-off time.

Meanwhile, the present invention relates to a node connected to the wireless sensor network, the number of backoffs performed (hereinafter referred to as "NB value"), the number of channel access attempts (hereinafter referred to as "CW" value), and the backoff length setting variable (hereinafter referred to as "BE"). Value "), a function of setting a Gaussian function by selecting a preset average value and a variance value according to the priority of the data to be transmitted, and determining a corresponding backoff time, and the determined backoff time arrives. As a result, a function of performing a Clear Channel Assessment (CCA) as much as the "CW" value, and as a result of performing the CCA, transmits the data when the channel is in the idle state, and transmits the data when the channel is busy. A function of adjusting the "BE value", and waiting for channel access while adjusting the "NB value" and "BE value", and adjusts the average value and the variance value of the Gaussian function as the interval of the determined backoff time ends. The backoff time It provides a computer readable recording medium having a program for realizing the function of the re CCA After recrystallization computer.

As described above, the present invention has an effect of ensuring different quality of service (QoS) for each data transmission priority in the wireless sensor network.

In addition, the present invention has an effect that the average delay time of the data to be transmitted on the wireless sensor network can be adjusted by having a different Gaussian distribution for each data transmission priority.

In addition, the present invention has the effect of adjusting the transmission rate of the data to be transmitted on the wireless sensor network by setting the difference between the average value and the dispersion value of each data transmission priority differently.

In addition, since the present invention can set and use various Gaussian functions having different average and variance values according to the number of nodes, the number of data transmission priorities, etc. It can be effective.

In addition, the present invention can be applied to the wireless sensor network without changing the hardware of the node, and there is an effect that can support the compatibility with the known IEEE 802.15.4 protocol.

The above objects, features, and advantages will become more apparent from the detailed description given hereinafter with reference to the accompanying drawings, and accordingly, those skilled in the art to which the present invention pertains may share the technical idea of the present invention. It will be easy to implement. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

4 is a diagram illustrating an embodiment of a backoff time determination algorithm according to the present invention.

In the present invention, for example, a Gaussian function is used to generate the backoff time so that the backoff time for data transmission (channel access) has a different Gaussian distribution for each data transmission priority.

As shown in FIG. 4, each node on the wireless sensor network according to the present invention may apply any Gaussian function among Gaussian functions having different characteristics according to the priority [data transmission priority] of data (packet) to be transmitted. Decide whether to choose.

"인 가우시안 함수와 평균이 "m_L", 분산이 "

"인 가우시안 함수가 되며, 상기 가우시안 함수 중 어느 하나의 가우시안 함수를 사용해 해당 데이터 전송 우선순위에 따른 백오프 시간을 결정한다. 여기서, 데이터 전송 우선순위가 상대적으로 더 높은 데이터에 대해서는 상기 평균이 "m_H", 분산이 "

"인 가우시안 함수를 사용하고, 데이터 전송 우선순위가 상대적으로 더 낮은 데이터에 대해서는 상기 평균이 "m_L", 분산이 "

"인 가우시안 함수를 사용한다.For example, when two data transmission priorities are set on a wireless sensor network, each Gaussian function corresponding to each data transmission priority has an average of "m _H " and a variance of ".

Gaussian function with "m _L " and variance "

Is a Gaussian function, and a Gaussian function of either of the Gaussian functions is used to determine the backoff time according to the corresponding data transmission priority. For the data having a relatively higher data transmission priority, the average is " m _H ", dispersion"

For data with a Gaussian function of ", where the data transfer priority is relatively lower, the mean is " m _L "

Use a Gaussian function.

"와 "

"의 값이 서로 동일하고 각 평균값 중 "m_H"가 "m_L"보다 작다면, 데이터 전송 우선순위가 높은 데이터가 평균적으로 더 짧은 백오프 시간을 갖게 된다. 따라서 본 발명에서는 데이터 전송 우선순위가 높아 평균 백오프 시간이 짧은 데이터가 채널에 접근할 확률이 더 높아지고 채널에 접근하는 시간도 더 짧아지게 할 수 있으므로, 각각의 데이터 전송 우선순위에 따른 QoS를 서로 다르게 결정할 수 있는 것이다.In the Gaussian functions proposed in the present invention, each variance value,

"Wow "

If the values of "are equal to each other and" m _H "of each average value is smaller than" m _L ", data having a higher data transmission priority has a shorter backoff time on average. Thus, in the present invention, data transmission priority The higher the data, the shorter the average backoff time is, the more likely it is to access the channel and the shorter the time to access the channel. Therefore, the QoS of each data transmission priority can be determined differently.

That is, in the present invention, by setting the average value "m" of the Gaussian function differently according to the data transmission priority, the average delay time of the data to be transmitted on the wireless sensor network can be adjusted, and the average value difference of each data transmission priority is different. By setting the and variance values differently, the transmission speed of data to be transmitted on the wireless sensor network can also be adjusted. In addition, in the present invention, since various Gaussian functions having different average and variance values may be set and used according to the number of nodes, the number of data transmission priorities, and the like, the data transmission of the nodes may be efficiently supported regardless of the state of the wireless sensor network. Can be.

Meanwhile, in the known IEEE 802.15.4 protocol, when the channel cannot be used (accessed) after the backoff time is determined, the "BE value" is increased by "1" to increase the backoff time in the interval [0, 2 ^BE -1]. Decide again. For example, when a node fails to access a channel, the backoff time is distributed over a wide interval so that data transmission collision does not occur.

Accordingly, the present invention also changes the average value and the variance value of the Gaussian function as the backoff time interval becomes wider [0, 2 ^BE- 1] interval. That is, in the present invention, the following equation (1) is used to calculate the mean and variance of the Gaussian function according to the increase of the "BE value".

"만큼의 백오프 시간 구간이 증가하게 되며, 이에 상기 백오프 시간 구간 증가분만큼 평균값과 분산값을 증가시키면 공지의 IEEE 802.15.4 프로토콜과 호환성을 갖으면서 노드의 채널 접근 실패 시에 백오프 시간을 넓은 구간에 분산시켜 데이터 전송 충돌이 일어나지 않도록 할 수 있는 것이다.As can be seen from the above [Equation 1], when the "BE value" is increased to "1" in the present invention "

"Increases the backoff time interval, and increasing the average value and the variance value by the backoff time interval increase increases the backoff time when the node fails to access the channel while being compatible with the known IEEE 802.15.4 protocol. It can be distributed over a wide interval to prevent data transmission collisions.

On the other hand, the present invention also defines a data structure to know the data transmission priority on the wireless sensor network. This will be described in detail with reference to FIG. 5 as follows.

5 is a data structure diagram according to the present invention.

The data structure defined in the known IEEE 802.15.4 protocol includes frame control, sequence number, addressing fields, security header, data payload, And FCS, which is a well-known and common technology, and thus a separate description of each item will be omitted.

In the present invention, as shown in Figure 5, for compatibility with the known IEEE 802.15.4 protocol Frame Control (Frame Control), Sequence Number (Address Sequence), Addressing fields, Security Header (Security Header) The data is structured with a data payload and an FCS, but a new command frame identifier can be set to specify the data transmission priority.

FIG. 6 is a table for explaining a command frame identifier shown in the present invention.

As shown in FIG. 6, in the present invention, the "0x01 to 0x09" portion of the command frame identifier is used to transmit and receive an existing command, and the data transmission priority [MAC frame priority] is used using the remaining portion, for example, the "0x0a to 0xff" portion. ] Is specified.

Next, a method of determining a backoff time and a channel access method in the wireless sensor network according to the present invention will be described in detail with reference to FIG. 7.

FIG. 7 is a flowchart illustrating a method for determining a backoff time and a channel access method according to the present invention. / CA].

First, each node on the wireless sensor network sets the default value of the number of backoffs (NB), the number of channel access attempts (CW), and the backoff length setting variable (BE; Backoff Exponent), respectively. Initialize to "2" and "macMinBE" (701). Here, "macMinBE" represents the "minimum BE value" preset in advance for channel access in the wireless sensor network.

Then, each node checks the priority (data transmission priority) of the data (packet) to be transmitted on the wireless sensor network (702). In this case, each node should check the priority of the command frame identifier included in the data for data to be received from another node and relay to another node, and transmit the corresponding data in the priority order. For the newly generated data on the application layer, the priority received from the application layer on the MAC layer is checked and recorded in the command frame identifier of the corresponding data.

Thereafter, each node sets the Gaussian function by selecting the corresponding average value ["m _k "] and variance value ["v _k "] according to the checked priority (703). Here, the average value and the variance value of the Gaussian function may use a corresponding value previously determined for each data transmission priority by an administrator or the like on the wireless sensor network.

Then, each node determines (generates) a random backoff time in the interval [0, 2 ^BE −1], which is the backoff time interval, using the set Gaussian function. As described above, the backoff time determined by the present invention has a Gaussian distribution having different average and variance values for each data transmission priority.

Next, after determining the backoff time as described above, a method of accessing the channel using the node will be described.

Thereafter, when the determined backoff time arrives (after waiting for the backoff time), each node performs a Clear Channel Assessment (CCA) by as much as the "CW value" for channel access (705). Here, the CCA refers to a process of checking whether the channel is currently busy or idle.

As a result of performing the CCA, when the channel is in the idle state, each node decreases the " CW value " by " 1 " and re-performs the CCA again and transmits data when the channel is in the idle state as a result of the CCA re-execution ( 706, 707, 708, 709).

On the other hand, when the channel is busy as a result of the CCA execution or re-execution, each node increases the "NB value" by "1" and increases the "BE value" by "1" and the preset "maximum BE". The "BE value" is adjusted as the smaller of the value "[" aMaxBE "] (710).

Then, that is, each node waits for channel access while adjusting the "NB value" and "BE value", and the adjusted (increased) "NB value" is set to "macMaxCSMABackoffs" (also called "backoff performance limit times"). If exceeded, it is considered to be a data transmission failure (711, 712), and if all the backoff time intervals have ended when the adjusted (incremented) "NB value" does not exceed "macMaxCSMABackoffs" (also called "backoff performance limit count"). In order to change the backoff time interval according to the adjusted (increased) "BE value", the average value and the variance value of the set Gaussian function are adjusted using Equation 1 (713 and 714). Here, "macMaxCSMABackoffs" is a variable for determining a data transmission failure when the number of times of performing the backoff exceeds a certain number of times so that the backoff does not continue.

Thereafter, each node adjusts the average value and the variance of the Gaussian function as described above, waits for the backoff time to arrive after determining the random backoff time again in the interval [0, 2 ^BE −1].

On the other hand, the method of the present invention as described above can be written in a computer program. And the code and code segments constituting the program can be easily inferred by a computer programmer in the art. In addition, the written program is stored in a computer-readable recording medium (information storage medium), and read and executed by a computer to implement the method of the present invention. The recording medium may include any type of computer readable recording medium.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

1 is a hierarchy diagram of a known IEEE 802.15.4 protocol,

2 is a frame structure diagram defined in a known IEEE 802.15.4 protocol,

3 is a flowchart illustrating a slotted Aloha operation used in a known IEEE 802.15.4 protocol.

4 is an exemplary explanatory diagram for illustrating a backoff time determination algorithm according to the present invention;

5 is a data structure diagram according to the present invention;

FIG. 6 is a table for explaining a command frame identifier (Command Frame Identifier) according to the present invention.

7 is a flowchart illustrating a method of determining a backoff time and a channel access method according to the present invention.

Claims (13)

A method for determining backoff time in a wireless sensor network, Initializing the number of backoff executions, the number of channel access attempts, and the backoff length setting variable; Checking the priority of the data to be transmitted; Setting a Gaussian function by selecting a preset average value and a variance value according to the checked priorities; And Determining a random backoff time in a backoff time interval using the set Gaussian function Method for determining a backoff time in a wireless sensor network comprising a. The method of claim 1, Resetting the Gaussian function by increasing the mean value and the variance value by the corresponding backoff time interval increase as the channel is not accessed after determining the backoff time. The method of determining a backoff time in a wireless sensor network further comprising. The method according to claim 1 or 2, The transmission target data, And a command frame identifier (ID) for indicating the priority of corresponding data. The method of claim 3, wherein Checking the priority of the transmission target data, The method of determining a backoff time in a wireless sensor network according to claim 1, wherein the data received from another node and relayed to another node are checked by checking the priority of the command frame identifier included in the data. The method of claim 3, wherein Checking the priority of the transmission target data, For the data generated by the node itself, the priority of the data received from the internal application layer is checked to confirm the priority of the corresponding data, and the priority is recorded in the command frame identifier of the corresponding data. How time is determined. The method according to claim 1 or 2, Setting the Gaussian function, A method of determining a backoff time in a wireless sensor network, characterized in that a corresponding Gaussian function is set by selecting a corresponding average value smaller than an average value of other data priorities as the checked data has a higher priority. . On a node connected to a wireless sensor network, A function of initializing the number of backoff executions, the number of channel access attempts, and the backoff length setting variable; A function of confirming priority of transmission target data; Setting a Gaussian function by selecting a preset mean value and a variance value according to the checked priority; And A function of determining a random backoff time in a backoff time interval using the set Gaussian function A computer-readable recording medium having recorded thereon a program for realizing this. The method of claim 7, wherein After determining the backoff time, as the channel is not accessed, a function of resetting the Gaussian function by increasing the mean value and the variance value by the corresponding backoff time interval increase. A computer-readable recording medium that records a program for further realization. In the channel access method in the wireless sensor network, Initializing the number of backoff executions (hereinafter referred to as "NB value"), the number of channel access attempts (hereinafter referred to as "CW" value) and the backoff length setting variable (hereinafter referred to as "BE value"); Determining a corresponding backoff time by setting a Gaussian function by selecting a predetermined average value and a dispersion value according to the priority of the data to be transmitted; Performing the Clear Channel Assessment (CCA) as much as the "CW" value as the determined backoff time arrives; As a result of performing the CCA, transmitting the data when the channel is in the idle state, and adjusting the "NB value" and the "BE value" when the channel is busy; And Waiting for channel access while adjusting the " NB value " and " BE value ", and after determining the backoff time by adjusting the average value and the variance value of the Gaussian function, Re-executing the CCA Channel access method in a wireless sensor network comprising a. The method of claim 9, Adjusting the "NB value" and the "BE value", Wherein the "NB value" is increased by a predetermined value, and the "BE value" is adjusted as a smaller value between a value of increasing the "BE value" by a predetermined value and a preset "maximum BE value". Channel approach in sensor networks. The method according to claim 9 or 10, Adjusting the mean and variance of the Gaussian function, And a mean value and a variance value of a corresponding Gaussian function when the determined backoff time interval ends and the adjusted "NB value" does not exceed a preset number of backoff execution limits. Channel approach at. The method of claim 11, The wireless sensor, characterized in that it is regarded as a data transmission failure while waiting for channel access while adjusting the "NB value" and "BE value", when the adjusted "NB value" exceeds a preset backoff execution limit. Channel approach on the network. On a node connected to a wireless sensor network, A function of initializing the number of backoff executions (hereinafter referred to as "NB value"), the number of channel access attempts (hereinafter referred to as "CW" value) and the backoff length setting variable (hereinafter referred to as "BE value"); Selecting a preset average value and a variance value according to the priority of the transmission target data to set a Gaussian function to determine a corresponding backoff time; Performing the Clear Channel Assessment (CCA) as much as the "CW" value as the determined backoff time arrives; As a result of performing the CCA, transmitting the data when the channel is in the idle state and adjusting the "NB value" and the "BE value" when the channel is busy; And Waiting for channel access while adjusting the " NB value " and " BE value ", and after determining the backoff time by adjusting the average value and the variance value of the Gaussian function, Re-execution of the CCA A computer-readable recording medium having recorded thereon a program for realizing this.

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