WO2016111505A1

WO2016111505A1 - Method and apparatus for dynamically adjusting ccat in near field communication system

Info

Publication number: WO2016111505A1
Application number: PCT/KR2016/000004
Authority: WO
Inventors: 김이고르; 강현덕; 고광진; 송명선; 오진형; 최재익
Original assignee: 한국전자통신연구원
Priority date: 2015-01-05
Filing date: 2016-01-04
Publication date: 2016-07-14

Abstract

The present invention relates to a method and an apparatus for dynamically adjusting a CCA threshold (CCAT) in wireless nodes for increasing the reuse of space and entire network efficiency through more intelligent carrier sensing, in a near field communication system and the like operating in infrastructure and ad hoc modes.

Description

Method and Apparatus for Dynamic CAT Adjustment in Near Field Communication System

The present invention relates to a channel access method and apparatus in a short range wireless communication system, and more particularly, to a method and apparatus for dynamically adjusting a CCA threshold (CCAT) in a short range wireless communication system.

In general, in a short range wireless transmission system, a station (STA) must perform a clear channel assessment (CCA), which is a 7 mechanism used to determine the state of a channel before accessing the channel. The channel may be busy or idle due to transmission or collision of another station (STA). Carrier sense (CS) includes PCS (Physical Carrier Sense) and VCS (Virtual Carrier Sense).

In the VCS, the transmitter and the receiver exchange Request To Send (RTS) and Clear To Send (CTS) for medium reservation before actual data transmission. After receiving an RTS or CTS frame, all other nodes establish a Network Allocation Vector (NAV), which is the time when the station (STA) cannot access the medium because it is considered busy due to other data transmissions.

PCS is the receiver's ability to detect and decode the preamble of a radio frame. To detect and decode the preamble of the radio frame, the receiver sets a CCA Threshold (CCAT). If the received signal level is greater than CCAT, the medium is in use. In practice, the CCAT is fixed at a preset value and does not change. This can result in severe resource underutilization and poor spatial reuse.

FIG. 1 is a diagram for describing a general scenario according to three access points (APs) and stations (STAs) distributed in respective cells. An example of a scenario with improved space reuse when CCAT is adjusted is described.

First, CCAT of AP1 is set to CCAT ₁ covering the STA2 and STA3 with the PCS range of R1. STA2 and STA3 are associated with AP2 and SP3, respectively. If STA2 or STA3 transmits data to their respective serving APs, it means that AP1 will not interfere with ongoing transmissions from STA2 or STA3, but meanwhile it is in a state where it cannot transmit data.

This problem is generally related to the exposed node problem. In a given scenario, AP1 is exposed, and this exposure causes severe performance degradation. Also, given the fact that a significant amount of traffic is sent in the downlink direction, the streams at STA1 and STA6 may experience long delays. Clearly, the PCS range of R1 significantly reduces the aggregate capacity of such an exemplary network.

If AP1 updates the CCAT value to CCAT ₂ (CCAT ₂ > CCAT ₁ ), the PCS range shrinks to R2, which is enough to allow simultaneous transmission from AP1 and STA2 / STA3 in each cell. These CCAT updates can significantly improve the space reuse of such networks and increase their utilization. Simultaneous transmission of STA3 or STA2 is still received at AP1, but AP1 ignores this because the power level of the signals is lower than CCAT ₂ . However, AP1 treats these signals as interference. This increases the tradeoff between space reuse improvement and the amount of interference. Dynamic CCAT coordination algorithms are needed to counter this tradeoff.

Accordingly, the present invention has been made to solve the above-described problem, and an object of the present invention is to provide more intelligent carrier sensing in a short range wireless communication system operating in an infrastructure and ad hoc mode. The present invention provides a method and apparatus for dynamically adjusting CCA Threshold (CCAT) in wireless nodes to increase space reuse and overall network efficiency.

Technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following descriptions.

First, to summarize the features of the present invention, a dynamic clear channel assessment threshold (CCAT) adjustment method in a station and an access point for short-range wireless communication according to an aspect of the present invention for achieving the above object, trial frame or regular frame Determining a type of a transmission target frame with any one of; Setting a CCAT retry sequence including a sequence of CCAT and a retry number according to the determined type of the transmission target frame; And controlling transmission of the transmission target frame according to the CCAT retry sequence.

The transmission ratio between the trial frame and the regular frame is preset to n: m, where n <m (n, m is a real number).

The setting of the CCAT retry sequence includes setting the CCAT within a predetermined range from a predetermined current optimal CCAT (CCATcur).

In the dynamic CCAT adjustment method, when the transmission target frame is transmitted according to the CCAT retry sequence, the CCATcur is updated based on statistics of successful and failed transmissions for each CCAT value and statistics on channel access time. It further comprises the step.

The updating of the CCATcur includes updating a Carrier Sense (CS) window having lower and upper boundaries for the CCAT about the updated CCATcur.

Repetitively at predetermined update intervals, the type of the transmission target frame is determined, the CCAT retry sequence is set, and the transmission of the transmission target frame is controlled.

The setting of the CCAT retry sequence may include randomly selecting a trial frame from a CS (Carrier Sense) window having a lower boundary (CCATlow) and an upper boundary (CCATup) about a current optimal CCAT (CCATcur). And determining the CCAT retry sequence including the number of retries for each frame transmission in the order of CCATrand, CCATcur, and CCATlow when the value CCATrand is greater than the CCATcur.

The setting of the CCAT retry sequence may include randomly selecting a trial frame from a CS (Carrier Sense) window having a lower boundary (CCATlow) and an upper boundary (CCATup) about a current optimal CCAT (CCATcur). And determining the CCAT retry sequence including the number of retries of each frame transmission in the order of the CCATcur, the CCATrand, and the CCATlow when the value CCATrand is selected as the CCATcur or less than the CCATcur.

For the regular frame, the CCATcur, CCATnext and CCATlow order, respectively, based on a CS (Carrier Sense) window having a lower boundary (CCATlow) and an upper boundary (CCATup) around a current optimal CCAT (CCATcur). Determining the CCAT retry sequence including the retry number of frame transmissions, wherein the CCATnext is a CCAT that achieves the highest throughput in retransmission after the CCATcur.

In addition, the dynamic clear channel assessment threshold (CCAT) adjusting device in a station and an access point for short-range wireless communication according to another aspect of the present invention includes a frame transmission manager for determining a type of a transmission target frame as either a trial frame or a regular frame. ; And a physical carrier sensing manager configured to set a CCAT retry sequence including a CCAT and a retry number sequence according to the determined type of the transmission target frame, wherein the frame transmission manager is configured to transmit the CCAT retry sequence according to the CCAT retry sequence. It is characterized by controlling the transmission of the target frame.

The physical carrier sensing manager may set the CCAT within a predetermined range from a predetermined current optimal CCAT (CCATcur).

When the transmission target frame is transmitted according to the CCAT retry sequence, the dynamic CCAT adjusting device updates the CCATcur based on statistics of channel access time and statistics of successful and failed transmission for each CCAT value. It further includes a channel access manager.

The channel access manager updates a carrier sense window (CS) having lower and upper boundaries for the CCAT around the updated CCATcur.

Repeated at predetermined update intervals, the type of the transmission target frame is determined, the CCAT retry sequence is set, and the transmission of the transmission target frame is controlled.

The physical carrier sensing manager randomly selects CCAT for the trial frame from a CS (Carrier Sense) window having a lower boundary (CCATlow) and an upper boundary (CCATup) around a current optimal CCAT (CCATcur). When (CCATrand) is larger than the CCATcur, the CCAT retry sequence including the number of retries of each frame transmission may be determined in the order of the CCATrand, the CCATcur, and the CCATlow.

The physical carrier sensing manager randomly selects CCAT for the trial frame from a CS (Carrier Sense) window having a lower boundary (CCATlow) and an upper boundary (CCATup) around a current optimal CCAT (CCATcur). When (CCATrand) is less than or equal to the CCATcur, the CCAT retry sequence including the number of retries of each frame transmission may be determined in the order of the CCATcur, the CCATrand, and the CCATlow.

The physical carrier sensing manager, based on the CS (Carrier Sense) window having a lower boundary (CCATlow) and an upper boundary (CCATup) around the current optimal CCAT (CCATcur), the CCATcur, CCATnext And the CCAT retry sequence including the retry number of each frame transmission in the CCATlow order, wherein the CCATnext may be a CCAT that achieves the highest throughput in retransmission after the CCATcur.

According to the CCA Threshold (CCAT) dynamic adjustment method and apparatus in the wireless nodes of the short-range wireless communication system according to the present invention, more intelligent carrier sensing can increase space reuse and overall network efficiency. By allowing data transmission of potentially exposed nodes even when interfering transmissions are in progress, it is possible to alleviate exposed node problems and significantly increase overall network utilization and performance.

It also provides a simple and effective solution for the dynamic adjustment of CCAT to cope with space reuse and interference tradeoffs. It operates in a distributed way and does not require centralized management. It can provide an open loop solution without additional overhead and modifications to existing infrastructure and standards. That is, it does not require any modification to existing network configuration and hardware, and can be easily employed in both infrastructure and ad hoc networks.

FIG. 1 is a diagram for describing a general scenario according to three access points (APs) and stations (STAs) distributed in respective cells.

2 is a block diagram illustrating a CCAT dynamic adjustment device according to an embodiment of the present invention.

3 exemplarily illustrates a carrier sense (CS) window sliding concept according to an embodiment of the present invention.

4 is a flowchart illustrating a concept of a CCAT adjustment method in a CCAT dynamic adjustment device according to an embodiment of the present invention.

5 is a flowchart of analyzing a CCAT retry sequence for a trial frame in a CCAT dynamic adjustment device according to an embodiment of the present invention.

6 is a flowchart of analyzing a CCAT retry sequence for a regular frame in a CCAT dynamic adjustment device according to an embodiment of the present invention.

7 is a view for explaining an example of an implementation method of a CCAT dynamic adjustment device according to an embodiment of the present invention.

Hereinafter, some embodiments of the present invention will be described in detail through exemplary drawings. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are assigned to the same components as much as possible even though they are shown in different drawings. In addition, in describing the embodiments of the present invention, if it is determined that the detailed description of the related well-known configuration or function interferes with the understanding of the embodiments of the present invention, the detailed description thereof will be omitted.

In describing the components of the embodiments of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are only for distinguishing the components from other components, and the nature, order or order of the components are not limited by the terms. In addition, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

First, in the present invention, a station (STA) is a physical layer (media) for the medium access control (MAC) and the wireless medium (medium) conforming to the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard. layer) Any functional medium that includes an interface. The station STA may include a processor and a transceiver, and may further include a user interface and a display device. A processor refers to a unit designed to generate a frame to be transmitted through a wireless network or to process a frame received through a wireless network, and performs various functions for controlling a station (STA). A transceiver is a unit that is functionally connected to a processor and is designed to transmit and receive a frame through a wireless network for a station (STA).

In the present invention, a station includes a wireless transmit / receive unit (WTRU), a user equipment (UE), a user terminal (UT), an access terminal (AT), a mobile station , MS), a mobile terminal, a subscriber unit, a subscriber station (SS), a wireless device, a mobile subscriber unit, etc., It may include some or all of them. The terminal may be, for example, a desktop computer, a laptop computer, a tablet PC, a wireless phone, a mobile phone, a smart phone that can communicate with each other. ), Smart watch, smart glass, e-book reader, portable multimedia player (PMP), portable game console, navigation device, digital camera, digital multimedia broadcasting (DMB) Player, digital audio recorder, digital audio player, digital picture recorder, digital picture player, digital video recorder, digital video player It may include an electronic device capable of wireless communication such as a digital video player.

Also, in the present invention, the access point (AP) is a centralized controller, a base station (BS), a radio access station, a node B, a node B, an evolved node B, an MMR ( may refer to a mobile multihop relay (BS) -BS, a base transceiver system (BTS), a site controller, or the like, and may include some or all of their functions.

2 is a block diagram illustrating a CCAT dynamic adjustment device 100 according to an embodiment of the present invention. The CCAT dynamic adjustment device 100 may be provided in an access point (AP).

Referring to FIG. 2, the CCAT dynamic adjustment device 100 according to an embodiment of the present invention includes a channel access manager 110, a physical carrier sensing manager 120, and It includes a frame transmission manager (130).

The channel access manager 110 is a main functional block for controlling the operation of the Clear Channel Assessment (CCA) Threshold (CCAT) dynamic adjustment algorithm of the present invention. The channel access manager 110 is connected to the physical carrier sensing manager 120 and the frame transmission manager 130 through an appropriate interface. The physical carrier sensing manager 120 and the frame transmission manager 130 are connected through an appropriate interface, and the frame transmission manager 130 interacts with the physical carrier sensing manager 120 with respect to the type of frame currently being transmitted.

The physical carrier sensing manager 120 generates a CCAT retry sequence. The frame transmission manager 130 controls data frame transmission and retransmission according to the CCAT retry sequence.

In the present invention, frames transmitted through a transmitter under the control of the frame transmission manager 130 are classified into a trial frame for a CCAT test and a regular frame for normal data transmission. The main purpose of trial frames is to test different CCAT values that can potentially improve performance. Regular frames and trial frames are transmitted using different CCAT settings. Since the number of trial frames transmitted during the update interval T _u should be less than the number of regular frames to prevent performance attenuation due to frequent CCAT adjustments, the transmission ratio between trial frames and regular frames is n: m It is preset to n <m where n and m are real.

The frame transmission manager 130 interacts with the physical carrier sensing manager 120 in relation to the type of frame currently being transmitted. It is also assumed that the same data frame can be transmitted with different CCAT values. To this end, the physical carrier sensing manager 120 generates a CCAT retry sequence including a sequence of CCAT and a retry number. Retransmission of data frames in different CCATs helps to ensure that the CCATs are optimal.

The channel access manager 110 may determine the frame transmission success probability based on the statistics of successful and unsuccessful transmissions for each CCAT value and channel access time based on reception of ACK frames received through a receiver. The channel access delay and the like can be analyzed based on the statistics. Based on this, the channel access manager 110 estimates the theoretically achievable throughput, and theoretically selects the CCAT having the maximum throughput as the CCATcur (current optimal CCAT) for the next update interval T _u .

As described above, the receiver sets the CCAT to detect and decode the preamble of the radio frame. If the signal level received from the receiver is greater than CCAT, the medium is in use. If the signal level to be received is less than CCAT, the ACK frame is not received. As shown in FIG. 1, setting a larger CCAT reduces coverage, and setting a smaller CCAT increases coverage. That is, CCAT is the basis of the signal level that can be received by the receiver.

3 exemplarily illustrates a carrier sense (CS) window sliding concept according to an embodiment of the present invention. The channel access manager 110 may perform CS window sliding in the following manner.

Referring to FIG. 3, parameter d represents the minimum value at which the CCAT can be updated. CCATmin and CCATmax represent possible minimum and maximum values of CCAT values. CCATlow and CCATup represent the lower and upper bounds of the CS window. In the given example the CS window size W is set to 4d, for example. CCATcur is placed in the center of the CS window and represents the current optimal threshold.

When the threshold CCATcur is updated based on measurements made during the previous update interval T _u (i-1), the CS window moves down (small) or top (high) so that the updated new CCATcur is centered in the CS window. Move (slid). In exceptional cases, the CS window may approach CCATmin or CCATmax, where the CS window size W may be smaller than 4d.

4 is a flowchart illustrating a concept of a CCAT adjustment method in the CCAT dynamic adjustment device 100 according to an embodiment of the present invention.

Referring to FIG. 4, first, all tuning parameters are initially initialized to a predetermined initial value (S110). Initial values of CCATcur and CCATlow are set to CCATmin. The update interval T _u is chosen at a predetermined value so that the algorithm can respond quickly to sudden network changes.

Next, before every frame transmission attempt, frame transmission manager 130 may determine what type of frame is to be transmitted based on the n: m ratio.

When the transmission target frame is a trial frame (S120), the physical carrier sensing manager 120 may set the CCAT retry sequence by selecting the CCAT as shown in FIG. 5 (S130) (S140).

When the transmission target frame is a regular frame (S120), the physical carrier sensing manager 120 may set a CCAT retry sequence as shown in FIG. 6 (S140).

In setting the CCAT retry sequence, a CCAT sequence is set in a predetermined range, that is, the CS window range, from the current optimal CCAT (CCATcur) predetermined in the previous update interval, and the number of retries for each CCAT is set. Set it.

5 is a flowchart of resolving a CCAT retry sequence for a trial frame in the CCAT dynamic adjustment device 100 according to an embodiment of the present invention.

First, when the transmission target frame is a trial frame (S120), when the transmission target frame is ready to transmit through the transmitter (Tx) (S210), the physical carrier sensing manager 120 is random from the CS window [CCATlow, CCATup] To output the selected value (CCATrand) (S220). At this time, the retry sequence of CCAT is different according to the selected value.

If the selected CCATrand value is larger than the current optimal CCATcur (S230), the physical carrier sensing manager 120 sets the CCAT retry sequence to {CCATrand (r1), CCATcur (r2), CCATlow (r3)} (S240). ). First, it means that CCAT is set to CCATrand before frame transmission. If the frame is still not delivered to the station STA within the first number of transmission attempts r1, the CCAT is set to CCATcur. If the frame is not delivered within the second number of transmission attempts r2, finally, the CCAT is set to CCATlow and the frame may be retransmitted at the third number of transmission attempts r3. The retry numbers r1, r2, and r3 can be selected such that the sum of the values r1 + r2 + r3 is equal to the maximum retry limit (R).

On the other hand, when the CCATrand selected in S230 is less than or equal to CCATcur, the physical carrier sensing manager 120 sets the CCAT retry sequence to {CCATcur (r1), CCATrand (r2), CCATlow (r3)} (S250). Here, the retry sequence is set differently because setting CCATrand at the initial position for all trial frames can lead to suboptimal performance. For example, if the current CCAT setting is optimal, setting CCATrand smaller than CCATcur in the initial position for trial frames will cause unnecessary carrier sensing increase and performance reduction. Again, the same maximum retry limit (R) applies.

6 is a flowchart of resolving a CCAT retry sequence for a regular frame in the CCAT dynamic adjustment device 100 according to an embodiment of the present invention.

First, when the transmission target frame is a regular frame (S120), when the transmission target frame is ready to transmit through the transmitter (Tx) (S310), the physical carrier sensing manager 120, the CCAT retry sequence {CCATcur ( r1), CCATnext (r2), and CCATlow (r3)} (S320). Here, CCATnext represents a CCAT in which a station (STA) achieves the highest throughput in retransmission after CCATcur. The channel access manager 110 may determine the CCATnext based on statistics related to frame transmission and failure, channel access time, and the like. Again, the same maximum retry limit (R) applies.

On the other hand, if the CCAT retry sequence is set for the frame as described above (S140), it is transmitted to the frame transmission manager 130. The frame transmission manager 130 controls transmission and retransmission for the corresponding frame according to the CCAT retry sequence.

During transmission and retransmission of such a frame, in FIG. 4, the channel access manager 110 collects and updates statistics of successful transmission and failed transmission for each CCAT values (S150). The decision about frame delivery is based on the reception of ACK frames. Frame error rate statistics are not used as the sole condition for whether or not CCAT is optimal. For example, in the case of an exposed node problem, an exposed node may achieve a low packet error rate but may exhibit low throughput performance due to frequent backoff. To estimate the theoretically possible throughput, channel access manager 110 records channel access time statistics. The channel access time is defined as the time interval from when the frame reaches the head of the transmission queue to the actual transmission.

In FIG. 4, when the timer Tu expires (S160), the statistics collected during the last measurement interval and the statistics collected for a long term up to a certain interval prior to the smoothing of the temporary results. Processing using moving average or other techniques.

In this way, the frame transmission success probability based on the statistics of successful and unsuccessful transmissions for each CCAT value, and the channel access delay based on the statistics on the channel access time are smoothed. Using this, the channel access manager 110 can estimate the theoretically achievable throughput. Accordingly, the channel access manager 110 may select the CCAT having the maximum theoretical throughput as the CCATcur for the next Tu (S170). The CS window also slides by the same value when the newly updated CCATcur is increased or decreased. By sliding the range of possible CCATs, the channel access manager 110 can control to obtain the necessary statistics in real time and make intelligent selection of the most optimal CCAT under given conditions.

7 is a view for explaining an example of an implementation method of the CCAT dynamic adjustment device 100 according to an embodiment of the present invention. CCAT dynamic adjustment device 100 according to an embodiment of the present invention may be made of hardware, software, or a combination thereof. For example, the CCAT dynamic adjustment device 100 may be implemented with a computing system 1000 as shown in FIG. 7.

The computing system 1000 may include at least one processor 1100, a memory 1300, a user interface input device 1400, a user interface output device 1500, a storage 1600, and a network connected through a bus 1200. It may include an interface 1700. The processor 1100 may be a central processing unit (CPU) or a semiconductor device that executes processing for instructions stored in the memory 1300 and / or the storage 1600. The memory 1300 and the storage 1600 may include various types of volatile or nonvolatile storage media. For example, the memory 1300 may include a read only memory (ROM) 1310 and a random access memory (RAM) 1320.

Thus, the steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, software module, or a combination of the two executed by the processor 1100. The software module resides in a storage medium (ie, memory 1300 and / or storage 1600), such as RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs. You may. An exemplary storage medium is coupled to the processor 1100, which can read information from and write information to the storage medium. In the alternative, the storage medium may be integral to the processor 1100. The processor and the storage medium may reside in an application specific integrated circuit (ASIC). The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.

As described above, in the CCA Threshold (CCAT) dynamic coordination apparatus 100 in the wireless nodes of the short-range wireless communication system according to the present invention, space reuse and overall network efficiency can be increased by more intelligent carrier sensing. By allowing data transmission of potentially exposed nodes even when interfering transmissions are in progress, it is possible to alleviate exposed node problems and significantly increase overall network utilization and performance. It also provides a simple and effective solution for the dynamic adjustment of CCAT to cope with space reuse and interference tradeoffs. It operates in a distributed way and does not require centralized management. It can provide an open loop solution without additional overhead and modifications to existing infrastructure and standards. That is, it does not require any modification to existing network configuration and hardware, and can be easily employed in both infrastructure and ad hoc networks.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention.

Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

Claims

In a method for adjusting a dynamic clear channel assessment threshold (CCAT) in a station and an access point for near field communication,

Determining a type of a transmission target frame as either a trial frame or a regular frame;

Setting a CCAT retry sequence including a sequence of CCAT and a retry number according to the determined type of the transmission target frame; And

Controlling transmission of the transmission target frame according to the CCAT retry sequence

Dynamic CCAT adjustment method comprising a.
The method of claim 1,

The transmission rate between the trial frame and the regular frame is preset to n: m, n <m (n, m is a real number) characterized in that the dynamic CCAT adjustment method.
The method of claim 1,

Setting the CCAT retry sequence,

Setting the CCAT within a predetermined range from a predetermined current optimal CCAT (CCATcur)

Dynamic CCAT adjustment method comprising a.
The method of claim 3,

When the transmission target frame is transmitted according to the CCAT retry sequence, updating the CCATcur based on statistics of channel access time and statistics of successful and failed transmission for each CCAT value;

Dynamic CCAT adjustment method further comprises.
The method of claim 4, wherein

Updating the CCATcur,

Updating a carrier sense window having a lower and upper boundary for the CCAT around the updated CCATcur

Dynamic CCAT adjustment method comprising a.
The method of claim 1,

And repetitively determining the type of the transmission target frame, setting the CCAT retry sequence, and controlling transmission of the transmission target frame repeatedly at predetermined update intervals.
The method of claim 1,

Setting the CCAT retry sequence,

For the trial frame, a value (CCATrand) that randomly selects CCAT from a CS (Carrier Sense) window having a lower boundary (CCATlow) and an upper boundary (CCATup) around a current optimal CCAT (CCATcur) is greater than that of the CCATcur. If greater, determining the CCAT retry sequence including the number of retries for each frame transmission in the order of CCATrand, CCATcur, and CCATlow

Dynamic CCAT adjustment method comprising a.
The method of claim 1,

Setting the CCAT retry sequence,

For the trial frame, a value (CCATrand) that randomly selects CCAT from a CS (Carrier Sense) window having a lower boundary (CCATlow) and an upper boundary (CCATup) around a current optimal CCAT (CCATcur) is less than or equal to the CCATcur. Determining, by the CCATcur, the CCATrand and the CCATlow, the CCAT retry sequence including the number of retries for each frame transmission.

Dynamic CCAT adjustment method comprising a.
The method of claim 1,

For the regular frame, the CCATcur, CCATnext and CCATlow order, respectively, based on a CS (Carrier Sense) window having a lower boundary (CCATlow) and an upper boundary (CCATup) around a current optimal CCAT (CCATcur). Determining the CCAT retry sequence including the retry number of frame transmission,

Wherein the CCATnext is a CCAT that achieves the highest throughput in retransmission after the CCATcur.
In a dynamic clear channel assessment threshold (CCAT) coordination apparatus in a station and an access point for near field communication,

A frame transmission manager for determining a type of a transmission target frame as either a trial frame or a regular frame; And

A physical carrier sensing manager configured to set a CCAT retry sequence including a sequence of CCAT and a retry number according to the determined type of the transmission target frame;

And the frame transmission manager controls the transmission of the transmission target frame according to the CCAT retry sequence.
The method of claim 10,

And a transmission ratio between the trial frame and the regular frame is preset to n: m, wherein n < m (n, m is a real number).
The method of claim 10,

And the physical carrier sensing manager sets the CCAT within a predetermined range from a predetermined current optimal CCAT (CCATcur).
The method of claim 12,

When the transmission target frame is transmitted according to the CCAT retry sequence, the channel access manager updating the CCATcur based on statistics of channel access time and statistics of successful and failed transmission for each CCAT value.

Dynamic CCAT adjusting device further comprises.
The method of claim 13,

And the channel access manager updates a carrier sense window having a lower and upper boundary for the CCAT around the updated CCATcur.
The method of claim 10,

And repetitively determining the type of the transmission target frame, setting the CCAT retry sequence, and controlling the transmission of the transmission target frame repeatedly at predetermined update intervals.
The method of claim 10,

The physical carrier sensing manager,

For the trial frame, a value (CCATrand) that randomly selects CCAT from a CS (Carrier Sense) window having a lower boundary (CCATlow) and an upper boundary (CCATup) around a current optimal CCAT (CCATcur) is greater than that of the CCATcur. If large, determining the CCAT retry sequence including the number of retries of each frame transmission in the order of CCATrand, CCATcur, and CCATlow.
The method of claim 10,

The physical carrier sensing manager,

For the trial frame, a value (CCATrand) that randomly selects CCAT from a CS (Carrier Sense) window having a lower boundary (CCATlow) and an upper boundary (CCATup) around a current optimal CCAT (CCATcur) is less than or equal to the CCATcur. And determine the CCAT retry sequence including the number of retries of each frame transmission in the order of CCATcur, CCATrand and CCATlow.
The method of claim 10,

The physical carrier sensing manager,

For the regular frame, the CCATcur, CCATnext and CCATlow order, respectively, based on a CS (Carrier Sense) window having a lower boundary (CCATlow) and an upper boundary (CCATup) around a current optimal CCAT (CCATcur). Determine the CCAT retry sequence including the retry number of frame transmissions, wherein the CCATnext is a CCAT that achieves the highest throughput in retransmission after the CCATcur.