KR101690157B1

KR101690157B1 - Packet processing method based on wave and user terminal using the same

Info

Publication number: KR101690157B1
Application number: KR1020150136571A
Authority: KR
Inventors: 조봉관; 류상환
Original assignee: 한국철도기술연구원
Priority date: 2015-09-25
Filing date: 2015-09-25
Publication date: 2017-01-09

Abstract

Disclosed herein is a user terminal for performing a packet processing method and a packet processing method based on WAVE (Wireless Access in Vehicular Environments). A WAVE-based packet processing method according to an embodiment of the present invention includes: (a) a first terminal is selected based on a competition for acquiring a data transmission right of a first control channel interval (CCH) (B) after the end of the first control channel period and the end of the first service channel period (SCH), the first terminal transmits the first control channel period And transmitting remaining data that can not be transmitted in the control channel period.

Description

[0001] WAVE BASED PACKET PROCESSING METHOD AND USER DEVICE USING THE SAME [0002] BACKGROUND OF THE INVENTION [0003]

The present invention relates to a WAVE (Wireless Access for Vehicular Environment) based packet processing method and a user terminal using the same.

WAVE (Wireless Access in Vehicular Environments) is an ITS (Intelligent Transportation System) environment in which changes can be extreme and information can be exchanged in a short period of time. It is a technology that enables wireless communication between devices and is being applied to railway communication.

WAVE packets of WAVE-based railway communications are data about the services that are transmitted between trains or between trains and railroads.

Single PHY WAVE, which is the simplest structure of WAVE, performs communication by exchanging control channel (CCH) and service channel (SCH) alternately. This is according to IEEE 1609.4, and IEEE 1609.4 defines a WAVE MAC layer that provides multi-channel alternation in WAVE. Here, the WAVE is arranged to alternately listen to the CCH (Control Channel) and the SCH (Service Channel) in 50 ms channel intervals, and the beginning of each channel includes a guard interval (4 ms).

However, as the first control channel (CCH) period ends and the first control channel (SCH) is changed, the data transmission of the terminal that acquired the transmission right in the first control channel period fails or the backoff process is interrupted And a contention process for acquiring a transmission right is performed again in the second control channel period, which is inefficient in data packet transmission.

Accordingly, there is a need for an efficient packet processing method for a plurality of user terminals.

On the other hand, Korean Patent No. 10-1418991 (entitled " frame transmitting apparatus and method in WAVE-based vehicle communication system ") discloses that in a vehicle communication system, when a frame received from an upper layer is an emergency frame, Enhanced Distributed Channel Access) and provides a transmission opportunity through EDCA contention when a frame received from an upper layer is a general frame, not an emergency frame.

It is an object of some embodiments of the present invention to provide a packet processing method for a plurality of user terminals in a WAVE communication and a user terminal using the same.

It is to be understood, however, that the technical scope of the present invention is not limited to the above-described technical problems, and other technical problems may be present.

According to an aspect of the present invention, there is provided a method for processing a wireless access in vehicles (WAVE) based packet, the method comprising: (a) acquiring a data transmission right of a first control channel interval (CCH) The first terminal transmitting data as the first terminal is selected based on competition for the first terminal; (b) after the end of the first control channel interval and after the end of the first service channel interval (SCH), the remaining data that the first terminal can not transmit in the first control channel period .

In addition, the WAVE-based packet processing method according to an embodiment of the present invention includes: (a) when the first control channel period ends during the contention period of the first control channel interval (CCH), the WAVE- Pausing; And activating the paused backoff counter by the first terminal according to the start of the second control channel interval after the end of the first service channel interval (SCH).

In addition, a user terminal performing a WAVE-based packet processing method according to an embodiment of the present invention includes a communication unit transmitting and receiving data of the user terminal, the user terminal performing a WAVE-based packet processing method; A memory for storing a packet processing program of the user terminal; And a processor for executing the packet processing program.

At this time, as the user terminal is selected based on the competition for acquiring the data transmission right of the first control channel interval (CCH) according to the execution of the packet processing program, the processor transmits the data to the communication unit And transmits remaining data that the user terminal has failed to transmit in the first control channel period, according to the start of the second control channel period after the end of the first control channel period and the end of the first service channel period (SCH) Through a communication unit.

Also, a user terminal performing a WAVE-based packet processing method according to an embodiment of the present invention includes a communication unit for transmitting / receiving back-off counter information; A memory for storing a packet processing program of the user terminal; A processor for executing the program; The processor executes the packet processing program.

At this time, when the first control channel period ends during the contention period of the first control channel interval (CCH), the backoff counter of the user terminal is temporarily stopped based on the information received through the communication unit, The user terminal activates the paused backoff counter based on the information received through the communication unit according to the start of the second control channel period after the end of the service channel period (SCH).

The MPDU of the user terminal in which the residual data is generated in the first control channel period is generated and the MPDU of the user terminal in the second control channel period It is efficient in data packet processing by omitting the competition process and transmitting the residual data with priority.

In addition, according to any one of the tasks of the present invention, the backoff is stopped for the user terminal that has generated the remaining backoff in the first control channel period, the remaining backoff is stopped in the second control channel, So that it is efficient in data packet processing.

1 is a diagram for explaining a typical WAVE communication method.
2 is a simplified block diagram of a user terminal performing a WAVE-based packet processing method according to an embodiment of the present invention.
3 is a diagram for explaining generation of residual data of a user terminal according to an exemplary embodiment of the present invention.
4A and 4B illustrate an MP packet data unit (MPDU) of a user terminal according to an exemplary embodiment of the present invention.
FIG. 5 is a flowchart illustrating a WAVE-based packet processing method of a user terminal in which residual data occurs as a transmission time of a first channel section ends according to an embodiment of the present invention.
6 is a simplified block diagram of a user terminal performing a WAVE-based packet processing method according to another embodiment of the present invention.
7 is a diagram for explaining an occurrence of a residual backoff according to an embodiment.
8 is a flowchart illustrating a WAVE-based packet processing method for processing a residual backoff counter according to another exemplary embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another part in between . Also, when an element is referred to as "including" an element, it is to be understood that the element may include other elements as well as other elements, And does not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

The following examples are intended to further illustrate the present invention and are not intended to limit the scope of the present invention. Accordingly, the same scope of the invention performing the same function as the present invention will also fall within the scope of the present invention.

Prior to explanation, FIG. 1 is a diagram for explaining a typical WAVE communication method.

The structure of WAVE which is designed to be suitable for road traffic is as follows. The simplest structure is Single PHY WAVE, and the control channel (CCH) and service channel (SCH) .

In the IEEE 1609.4 standard, as shown in FIG. 1, a control channel (CCH) and a service channel (SCH) are alternately listened at a 50 ms channel interval, and the beginning of each channel includes a guard interval (4 ms).

Meanwhile, the EDCA defined in IEEE 802.11p may be applied to the railway traffic to classify the traffic using the control channel (CCH) and the traffic using the service channel (SCH) as follows.

Specifically, as the traffic using the control channel (CCH), there may be traffic for control, for example, a WSA. Also, the traffic using the service channel (SCH) may include traffic related to safety, and traffic for railway communication.

However, if there are a plurality of users to transmit data in a control channel (CCH) interval, the UE performs contention for data transmission in a control channel (CCH) period and transmits data after the contention is completed.

However, since the control channel (CCH) has a limited time and performs communication with the service channel (SCH) alternately, a problem occurs as the control channel (CCH) period ends.

For example, when the data transmission of the user who has acquired the transmission right is not completed due to the end of the control channel (CCH) period, the residual data is generated, and the remaining data of the corresponding user on the next control channel (CCH) There is a problem that a separate contention must be performed to acquire the transmission right of the corresponding user.

Also, if the backoff process of the contention process is not completed due to the end of the control channel (CCH) period, a residual backoff occurs, and a problem of having to compete again in the control channel (CCH) have.

Accordingly, the present invention provides a WAVE communication-based packet processing method for solving the problem caused by termination of a control channel (CCH) period.

Hereinafter, a method of performing a WAVE-based packet processing method and a user terminal will be described in detail with reference to the drawings.

2 is a simplified block diagram of a user terminal performing a WAVE-based packet processing method according to an embodiment of the present invention.

2, a user terminal 100 that performs a WAVE-based packet processing method according to an embodiment of the present invention includes a memory 110, a processor 120, a packet data unit generation unit 122, a communication unit 130, .

The memory 110 stores a packet processing program.

The processor 120 executes a packet processing program stored in the memory.

In particular, the processor 120 processes the residual data of the user terminal that has not been transmitted due to the termination of the first channel interval (CCH) through the packet processing program.

The processor 120 determines that the first terminal is selected based on the competition for acquiring the data transmission right of the first control channel interval (CCH) according to the execution of the program, And transmits remaining data that the first terminal fails to transmit in the first control channel period, through the communication unit, according to the start of the second control channel period after the end of the first control channel period and the end of the first service channel period (SCH) send.

The processor 120 may generate a MAC packet data unit (MPDU) including a frame check sequence (FCS) as data to be transmitted by the first terminal. At this time, the MPDU may be generated through the packet data unit generation unit 122 in the processor 120.

The processor 120 records information on the time required for transmission of the MPDU in a duration field of the MPDU and divides the time into a first MSDU and a second MSDU based on a time period during which the first control channel duration is maintained , And generates a first MPDU and a second MPDU for the first MSDU and the second MSDU.

The processor 120 may transmit the first MPDU during the first control channel period and transmit the second MPDU as the residual data.

The first MPDU and the second MPDU may each include a preamble, and the FCS may be included in the second MPDU.

The first MPDU and the second MPDU may include a preamble, a MAC header, transmission data, and an FCS, respectively.

If an error occurs in the transmission of the first MPDU, the MPDU before the division can be transmitted without performing the transmission of the second MPDU.

3 is a view for explaining a WAVE-based packet processing method of a user terminal in which residual data is generated as a first control channel period ends according to an embodiment of the present invention.

Referring to FIG. 3, the first control channel period includes a guard interval period 201 and a transmission opportunity interval 202.

The guard interval interval 201 is a time sub-interval for accurately distinguishing the first control channel interval according to frequent changes of the first control channel interval (CCH) and the first service channel interval (SCH). The user terminal can not transmit data in the corresponding interval 203. [

The transmission opportunity interval 202 is a period in which data of the user terminal can be transmitted substantially in the first control channel period.

The transmission opportunity interval 202 includes a period of DIFS (Distributed Inter Frame Space) 204 for avoiding a collision with a plurality of user terminal shared media, and a competition among a plurality of user terminals And a data transmission interval 206 in which the selected user terminal transmits data, but it is not limited thereto.

The DIFS (Distributed Inter Frame Space) 204, the contention interval 205, and the data transmission interval 206 included in the transmission opportunity interval 202 are repeated until the first control channel ends, Can be performed.

The remaining data 209 may be generated due to the incomplete data transmission of the user terminal that has acquired the transmission opportunity as the predetermined usage time of the first control channel period is terminated and changed to the first service channel period.

To process the residual data 209, the user terminal generates an MP packet data unit (MPDU).

The MPDU including the residual data 207 is transmitted in the second control channel period.

At this time, the corresponding MPDU is preferentially transmitted without a contention process (steps 203 to 205 of FIG. 2) for acquiring the transmission right of the corresponding user in the second control channel period. This will be described in detail later with reference to FIGS. 3A to 3B.

4A and 4B are diagrams for explaining a MAC packet data unit (MPDU) of a user terminal according to an embodiment of the present invention.

4A illustrates a structure of a single MacPacket Data Unit (MPDU) generated to transmit the residual data of a user terminal according to an example.

An MPDU for separating and transmitting data and residual data in a physical layer based on a time during which a first control channel section is maintained when residual data of a selected first terminal is generated based on competition among a plurality of user terminals, The MPDU may be designed to include a MAC header 303 and a frame check sequence (FCS) 304 in the remaining data transmission portion.

At this time, since the receiver must receive the data and the residual data twice, the preamplifier 305 according to the data and the preamble 306 according to the residual data must be transmitted twice.

At this time, a time including all transmission times of the data and the remaining data may be input to the duration field of the MAC header 303. [

4B is an example of a divided MPDU (Mac Packet Data Unit) generated to transmit the residual data of the user terminal according to an example.

Referring to FIG. 4B, when residual data of the selected first terminal is generated based on competition among a plurality of user terminals, the MSDU (MAC Service Data Unit) is divided based on the time during which the first control channel section is maintained, MPDUs are created independently for the MSDUs that are not included in the MPDU.

At this time, a single MPDU described in FIG. 4A may also be generated.

The first MS selected based on the competition among the plurality of MSs determines a first MSDU with respect to the transmittable data based on the time during which the first control channel duration is maintained, The second MSDU can be divided.

At this time, a first MPDU and a second MPDU may be generated for each of the first MSDU and the second MSDU, and may be designed to include a preamble, a MAC header, transmission data, and an FCS, respectively.

Referring to FIG. 4B, in the MAC header 307 of the first MPDU, information on the time required for transmission of data that can be transmitted can be recorded based on a time during which the first control channel section is maintained. Information on the time required to transmit the remaining data may be recorded in the MAC header 309 of the second MPDU

At this time, information on the time taken to transmit both the data and the remaining data may be recorded in the MAC header 303 of the MPDU including the first MPDU and the second MPDU.

That is, the first MPDU includes data that can be transmitted during a period during which the control channel interval is maintained, and includes a preamble, a MAC header, and an FCS.

Also, the second MPDU includes residual data that can not be transmitted during a time period during which the control channel interval is maintained, and includes a preamble, a MAC header, and an FCS.

Referring to FIG. 4A, the transmittable data is Data1 (301), which is configured as a first MPDU. The first MPDU may be transmitted on the first control channel.

Thereafter, the first MPDU is configured and the remaining data is referred to as Data2 (302), thereby configuring a second MPDU. And the second MPDU may transmit in the second control channel.

At this time, since the receiver must receive the first MPDU for the data and the second MPDU for the residual data, the preamble 305 of the first MPDU and the preamble 306 of the second MPDU must be transmitted twice .

Here, the FCS 308 of the first MPDU may be used to determine an error for the first MPDU.

If an error due to the transmission of the first MPDU in the first control channel is not generated, the second MPDU may be transmitted in the second control channel.

When an error occurs in the first control channel period due to the transmission of the first MPDU, the second MPDU is not transmitted in the second control channel, .

In other words, the first MPDU is configured such that the first MPDU is configured independently of the first MSDU (MAC Service Data Unit), which is transmittable data, based on the total data to be transmitted by the first user terminal, will be.

The first MPDU is transmitted during the first control channel period, and whether the first MPDU is erroneous may affect the second MPDU transmission in the second control channel period.

The second MPDU is configured to be independent of the second MSDU, which is the remaining data exceeding the transmittable time, based on the time during which the first control channel section is maintained, out of the total data to be transmitted by the first user terminal.

One or more of the first MPDU and the second MPDU may be designed to include an FCS.

For example, when the first MPDU includes the FCS, it can check the error of the first MPDU. If there is an error of the first MPDU, the second MPDU may not be transmitted in the second control channel period. At this time, it may be designed to transmit the pre-division MPDU.

FIG. 5 is a flowchart illustrating a WAVE-based packet processing method of a user terminal in which residual data occurs as a transmission time of a first channel section ends according to an embodiment of the present invention.

The WTRU-based packet processing method according to an embodiment of the present invention is a method in which a first terminal is selected based on competition for acquiring a data transmission right of a first control channel interval (CCH) 1 terminal transmits data (S601)

At this time, in step S601, an MPDU (MAC packet data unit) including a frame check sequence (FCS) is generated as data to be transmitted by the first mobile station. Information about the time required for transmission of the MPDU is stored in a Duration field of the MPDU. Dividing the MSDU into a first MSDU and a second MSDU based on a time during which a first control channel section is maintained; generating a first MPDU second MPDU for a first MSDU and a second MSDU; 1 MPDU for a first control channel period.

The first MPDU and the second MPDU may be designed to include a preamble, a MAC header, transmission data, and an FCS, respectively. In this case, the error detection is performed during transmission of the first MPDU, and whether or not the second MPDU is transmitted may be determined according to whether the error is detected.

Next, according to the start of the second control channel period after the end of the first control channel period and the end of the first service channel period (SCH), the first terminal transmits remaining data that can not be transmitted in the first control channel period S602)

At this time, the second MPDU can be transmitted as the remaining data.

Here, when an error occurs in the transmission of the first MPDU, the MPDU before the division can be transmitted without performing the transmission of the second MPDU.

6 is a simplified block diagram of a user terminal performing a WAVE-based packet processing method according to another embodiment of the present invention.

6, a user terminal 100 that performs a WAVE-based packet processing method according to another embodiment of the present invention includes a memory 110, a processor 120, a back-off-in-signal processing unit 124, 130).

The memory 110 stores a packet processing program.

The processor 120 executes a packet processing program stored in the memory.

In particular, when a residual backoff occurs through the packet processing program, the processor 120 stops the corresponding backoff counter and performs activation for the paused backoff in the second control channel period.

When the first control channel period ends during the contention period of the first control channel period (CCH), the processor 120 pauses the backoff counter of the first terminal and, after the end of the first service channel period (SCH) In accordance with the start of the second control channel period, the first terminal activates the paused backoff counter.

Processor 120 may pause the backoff counter based on carrier sense information (PHY-CCA.indication) that the physical layer transmits to the MAC layer.

Processor 120 may activate the paused backoff counter based on the carrier sense information (PHY-CCA.indication) transmitted by the physical layer to the MAC layer according to the start of the second control channel period.

At this time, the back-off process can be stopped and activated through the back-off processing unit 124 in the processor 120.

The communication unit 130 temporarily suspends the backoff counter and transmits and receives interlayer information to activate the backoff counter.

7 is a diagram for explaining an occurrence of a residual backoff according to an embodiment.

Referring to FIG. 7, as the predetermined transmission time of the first control channel period ends, the competition process for a plurality of terminals is not completed in the contention period (Contention) 505, and the remaining backoff counter 507 is generated .

That is, it is possible to stop the backoff for the user terminal that has generated the residual backoff in the first control channel period, and activate the remaining backoff that is stopped in the second control channel period to perform the competition process.

8 is a flowchart illustrating a WAVE-based packet processing method for processing a residual backoff counter according to another exemplary embodiment of the present invention.

The method for processing a packet based on WAVE according to an embodiment of the present invention includes: when a first control channel period ends during a contention period of a first control channel interval (CCH) OFF counter is temporarily stopped (S701).

At this time, the physical layer can suspend the backoff counter based on the carrier sense information (PHY-CCA.indication) transmitted to the MAC layer.

Next, in accordance with the start of the second control channel period after the end of the first service channel period (SCH), the first terminal activates the paused backoff counter (S702).

At this time, according to the start of the second control channel period, the physical layer can activate the paused backoff counter based on the carrier sense information (PHY-CCA.indication) transmitted to the MAC layer.

The user terminal 100 that performs the WAVE-based packet processing method of the present invention includes the memory 110, the processor 120, and the communication unit 130, And the back-off counter processing unit 124 as shown in FIG.

That is, the user terminal 100 performs the data packet program stored in the memory and transmits the remaining data generated due to the end of the first channel section, the remaining data generated by the data unit generating unit 122 and the back-off counter processing unit 124, Off < / RTI >

One embodiment of the present invention may also be embodied in the form of a recording medium including instructions executable by a computer, such as program modules, being executed by a computer. Computer readable media can be any available media that can be accessed by a computer and includes both volatile and nonvolatile media, removable and non-removable media. In addition, the computer-readable medium can include both computer storage media and communication media. Computer storage media includes both volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Communication media typically includes any information delivery media, including computer readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave, or other transport mechanism.

While the methods and systems of the present invention have been described in connection with specific embodiments, some or all of those elements or operations may be implemented using a computer system having a general purpose hardware architecture.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

It is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. .

100: user terminal
110: Memory
120: Processor
122:
130:

Claims

1. A packet processing method based on WAVE (wireless access in and well environments)
(a) transmitting, by the first terminal, data as the first terminal is selected based on competition for acquiring a data transmission right of the first control channel interval (CCH);
(b) after the end of the first control channel interval and after the end of the first service channel interval (SCH), the remaining data that the first terminal can not transmit in the first control channel period Gt; WAVE < / RTI > based packet processing method.

The method according to claim 1,
The step (a)
(MPDU) including a frame check sequence (FCS) as data to be transmitted by the first terminal, and transmits information about a time required for transmission of the MPDU to a duration field of the MPDU Recording;
Dividing into a first MSDU (MAC service data unit) and a second MSDU based on a time during which the first control channel section is maintained; And
Generating a first MPDU and a second MPDU for the first MSDU and the second MSDU; And
And transmitting the first MPDU during the first control channel period,
The step (b)
And transmits the second MPDU as the residual data.

3. The method of claim 2,
Wherein the first MPDU and the second MPDU each include a preamble,
And the FCS is included in the second MPDU.

3. The method of claim 2,
Wherein the first MPDU and the second MPDU each include a preamble, a MAC header, transmission data, and an FCS, respectively.

5. The method of claim 4,
Wherein when the error occurs in the transmission of the first MPDU in step (a), the step (b) transmits the MPDU before the division without performing the transmission of the second MPDU.

A WAVE-based packet processing method,
(a) pausing a backoff counter of a first terminal when the first control channel period ends during a contention period of a first control channel interval (CCH);
(b) activating the paused backoff counter by the first terminal in response to initiation of a second control channel period after termination of a first service channel interval (SCH). .

The method according to claim 6,
Wherein the step (a) temporarily suspends the backoff counter based on carrier sense information (PHY-CCA.indication) transmitted by the physical layer to the MAC layer.

The method according to claim 6,
Wherein the step (b) activates the paused backoff counter based on carrier sense information (PHY-CCA.indication) transmitted by the physical layer to the MAC layer according to the start of the second control channel period. WAVE based packet processing method.

A user terminal for performing a WAVE-based packet processing method,
A communication unit for transmitting and receiving data of the user terminal;
A memory for storing a packet processing program of the user terminal; And
And a processor for executing the packet processing program,
Wherein the processor, upon execution of the packet processing program,
The user terminal transmits data through the communication unit as the user terminal is selected based on the competition for acquiring the data transmission right of the first control channel interval (CCH)
The control unit transmits remaining data that the user terminal can not transmit in the first control channel period to the communication unit through the communication unit according to the start of the second control channel period after the end of the first control channel period and the end of the first service channel period User terminal.

10. The method of claim 9,
The processor
(MPDU) including a frame check sequence (FCS) as data to be transmitted by the user terminal, and information on a time required for transmission of the MPDU is recorded in a duration field of the MPDU In addition,
A first MSDU (MAC service data unit) and a second MSDU based on a time when the first control channel section is maintained,
Generates a first MPDU and a second MPDU for the first MSDU and the second MSDU,
Transmitting the first MPDU during the first control channel period,
And transmits the second MPDU as the residual data.

11. The method of claim 10,
Wherein the first MPDU and the second MPDU each include a preamble and the FCS is included in the second MPDU.

11. The method of claim 10,
Wherein the first MPDU and the second MPDU comprise a preamble, a MAC header, transmission data, and an FCS, respectively.

13. The method of claim 12,
The processor
And to transmit the MPDU before the division without performing the transmission of the second MPDU when an error occurs in the transmission of the first MPDU.

A user terminal for performing a WAVE-based packet processing method,
A communication unit for transmitting and receiving back-off counter information;
A memory for storing a packet processing program of the user terminal;
A processor for executing the program;
Wherein the processor, upon execution of the packet processing program,
When the first control channel period ends during the contention period of the first control channel interval (CCH), the backoff counter of the user terminal is temporarily stopped based on the information received through the communication unit,
Wherein the user terminal activates the paused backoff counter based on information received through the communication unit according to the start of a second control channel period after the end of the first service channel period (SCH).

15. The method of claim 14,
The processor
Wherein the physical layer suspends the backoff counter based on carrier sense information (PHY-CCA.indication) transmitted by the physical layer to the MAC layer.

15. The method of claim 14,
The processor
And activates the paused backoff counter based on carrier sense information (PHY-CCA.indication) transmitted by the physical layer to the MAC layer upon initiation of the second control channel period.